Temperature-pH dual-responsive hydrogel, preparation method and fire extinguishing agent thereof

Abstract

The present application relates to a kind of temperature-pH dual-response hydrogel, preparation method and extinguishing agent thereof, belong to hydrogel extinguishing agent technical field, solve the problems such as poor environmental adaptability, single response and high reburning rate of hydrogel extinguishing agent in prior art.The temperature-pH dual-response hydrogel disclosed in the present application uses ammonium persulfate as initiator, pure water as solvent, by controlling the molar ratio of N-isopropyl acrylamide (NIPAM) and maleic anhydride (MAH), so that the intermediate product is generated;Again, using pure water as solvent, by the reaction of intermediate product and melamine, then after separation and purification, the final product obtained not only has higher yield, but also has temperature and pH dual response.

Description

Technical Field

[0001] This invention relates to the fields of hydrogels and fire extinguishing agents, and in particular to a temperature-pH dual-responsive hydrogel, its preparation method, and its fire extinguishing agent. Background Technology

[0002] Lithium-ion battery fires are characterized by rapid thermal runaway, high temperatures, and high toxicity. A chain reaction of exothermic reactions triggered by internal short circuits, overcharging, or mechanical damage causes the electrolyte and electrode materials to decompose, producing large amounts of flammable gases (such as H2 and CO) and toxic fluorides (such as HF), resulting in jet flames (temperatures exceeding 800°C) and the risk of explosion. During the fire, the electrolyte (such as LiPF6) decomposes upon heating, generating acidic gases such as HF, creating a highly corrosive environment that not only accelerates the corrosion of metal components but also causes chemical burns to rescue personnel. During firefighting, the reaction of water with HF further releases heat and exacerbates the corrosive environment. While alkaline extinguishing agents such as sodium bicarbonate can neutralize the acidity, incomplete reactions may lead to localized pH fluctuations. Therefore, lithium-ion battery fire prevention and control should focus on addressing high temperatures, toxic gases, and acid / alkali corrosion, and employ targeted firefighting strategies to reduce secondary hazards.

[0003] Thermosensitive hydrogel fire extinguishing agents have demonstrated significant advantages in lithium-ion battery fires. Their intelligent thermosensitive properties overcome the shortcomings of traditional hydrogels, such as high viscosity and poor flowability at room temperature. When thermal runaway of lithium-ion batteries triggers high-temperature fires, the thermosensitive hydrogel, based on its critical transition temperature (LCST) characteristic, rapidly transforms from a low-viscosity sol state to a high-viscosity gel state under high-temperature conditions. This allows it to quickly adhere to and cover the fire source, forming a stable three-dimensional network structure. This characteristic enables it to efficiently extend the residence time of water, rapidly cool the battery, and block heat transfer. Simultaneously, it suppresses flames through oxygen isolation and sealing, thus improving fire extinguishing efficiency. Compared to traditional fire extinguishing agents, thermosensitive hydrogels combine intelligent responsiveness with high-efficiency fire extinguishing capabilities, providing an innovative solution for fire prevention and control in the new energy sector.

[0004] However, thermosensitive hydrogels and their extinguishing agents pose a risk of reignition and cannot cope with the corrosion caused by acidic gases generated during combustion. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a temperature-pH dual-response hydrogel, its preparation method, and its fire extinguishing agent, in order to solve the problems of poor environmental adaptability, single response, and high reignition rate of existing hydrogel fire extinguishing agents, and is particularly suitable for the rapid response requirements of lithium battery fires with high temperature and strong acidity characteristics.

[0006] On one hand, embodiments of the present invention provide a temperature-pH dual-responsive hydrogel, with the general formula:

[0007] 100 <n<1000。

[0008] Furthermore, the temperature-pH dual-responsive hydrogel is prepared by controlling the molar ratio of N-isopropylacrylamide and maleic anhydride, which are then copolymerized in water to generate an intermediate product; then, pure water is used as a solvent to react the intermediate product with melamine.

[0009] Furthermore, the lowest response temperature of the temperature-pH dual-responsive hydrogel is 38°C.

[0010] Furthermore, the temperature-pH dual-responsive hydrogel responds at a pH between 3 and 4.

[0011] On the other hand, the present invention discloses a method for preparing the temperature-pH dual-responsive hydrogel, the preparation method comprising the following steps:

[0012] S1-1: N-isopropylacrylamide, maleic anhydride, and water are thoroughly mixed; an initiator is added to initiate a polymerization reaction; after a period of reaction, the product is separated and purified to obtain intermediate product A. 0.5 ;

[0013] S1-2: The intermediate product A... 0.5 Dissolve in pure water, add melamine, stir for a certain time to obtain a crude product solution of A;

[0014] S1-3: Filter the crude product solution of A, then heat it to precipitate the hydrogel of product A, and obtain a temperature-pH dual-responsive hydrogel.

[0015] Furthermore, in step S1-1, the molar ratio of N-isopropylacrylamide to maleic anhydride is 8:1-2:1.

[0016] Furthermore, in step S1-1, the amount of initiator used is 0.05%-1% of the sum of the molar amounts of N-isopropylacrylamide and maleic anhydride.

[0017] Furthermore, the suitable reaction temperature in S1-1 is 50℃-80℃, and the polymerization reaction is carried out under inert gas protection conditions.

[0018] Furthermore, the molar ratio of melamine to maleic anhydride in S1-2 is 1:10-2:1.

[0019] Furthermore, the reaction in S1-2 is carried out at room temperature. The stirring speed is 100-600 r / min. The reaction time is 4-36 h.

[0020] On the other hand, the present invention discloses a temperature-pH dual-responsive hydrogel fire extinguishing agent, which includes the above-mentioned temperature-pH dual-responsive hydrogel.

[0021] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0022] 1. The temperature-pH dual-responsive hydrogel disclosed in this invention is produced by copolymerizing N-isopropylacrylamide and maleic acid, and then introducing melamine into the molecular chain through a reaction with carboxyl groups. The main molecular chain is a -CC- chain, and the side chains are isopropylamide bonds (-CONH-CH(CH3)2) and amino acid zwitterions (-COO). - -NH3 + ), in which the hydrophilic groups are amide groups (-CONH-) and amino acid zwitterions (-COO-). - -NH3 + The hydrophobic group is isopropyl (-CH(CH3)2), and the pH-sensitive group is an amino acid zwitterion (-COO). - -NH3 + This hydrogel not only exhibits temperature-responsive properties (transforming from a sol to a gel state at high temperatures, enabling rapid coverage and cooling), but also, by introducing pH-sensitive groups (such as carboxyl or amino groups), it can dynamically respond to the release of acidic gases such as HF in the fire environment and form a gel even in the later stages of fire suppression when the battery surface temperature drops below the LCST.

[0023] 2. The temperature-pH dual-responsive hydrogel disclosed in this invention contains melamine cationic groups, which generate non-flammable gases such as ammonia and nitrogen at high temperatures, thus diluting flammable gases and exhibiting flame-retardant effects. In particular, when used in combination with phosphate flame retardants, the phosphate acts as an acid source, the hydrogel as a carbon source, and the melamine as a gas source; the three work synergistically to produce an intumescent flame retardant, resulting in a stronger flame-retardant effect.

[0024] 3. In the temperature-pH dual-responsive hydrogel preparation method disclosed in this invention, ammonium persulfate is used as the initiator and pure water as the solvent. By controlling the molar ratio of N-isopropylacrylamide (NIPAM) to maleic anhydride (MAH), intermediate product A is generated. 0.5 Then, using pure water as a solvent, through A... 0.5 The final product A obtained by reacting with melamine and then separating and purifying it not only has a high yield, but also exhibits dual temperature and pH responsiveness.

[0025] 4. The temperature-pH dual-responsive hydrogel disclosed in this invention has strong fluidity at room temperature, making it easy to transport and spray.

[0026] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0027] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0028] Figure 1 middle, Figure 1 a, Figure 1 b、 Figure 1 c shows the state of the temperature-pH dual-responsive hydrogel A1 prepared in Example 1 at pH = 7.0, 10.5, and 3.5, respectively;

[0029] Figure 2 middle, Figure 2 a, Figure 2 b shows the state of the temperature-pH dual-responsive hydrogel A1 prepared in Example 1 before and after heating;

[0030] Figure 3 middle, Figure 3 a showed N-isopropylacrylamide and A1 0.5 Infrared contrast spectrum. Figure 3 b is Figure 3 500cm in a middle -1 up to 2000cm -1 Magnified comparison spectrum.

[0031] Figure 4 middle, Figure 4 a shows sample A1 0.5 Infrared contrast spectra of A1 and melamine. Figure 4 b is Figure 4 500cm in a middle -1 Up to 2000cm -1 Magnified comparison spectrum.

[0032] Figure 5a The NMR spectrum of N-isopropylacrylamide (NIPAM) is shown. Figure 5b for Figure 5a Magnified NMR images of 0-7 ppm.

[0033] Figure 6a Sample A1 is shown 0.5 The MRI scan, Figure 6b for Figure 6a Magnified NMR images of 0-7 ppm.

[0034] Figure 7a The NMR spectrum of sample A1 is shown. Figure 7b for Figure 7a Magnified NMR images of 0-7 ppm.

[0035] Figure 8 middle, Figure 8 a, Figure 8 b、 Figure 8 c shows images after fire extinguishing in Comparative Example 1, Comparative Example 4, and Example 1, respectively. Detailed Implementation

[0036] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0037] Existing fire extinguishing agents, such as traditional hydrogels, chemical foams, and dry powder fire extinguishing agents, have problems such as poor environmental adaptability, limited response, and high reignition rate, especially failing to meet the rapid response requirements for lithium battery fires.

[0038] The study found that using existing hydrogel fire extinguishing agents to treat lithium battery fires easily leads to reignition and acid gas corrosion. Further research revealed that due to the high temperature and strong acidity of lithium battery fires, existing hydrogels merely coat the battery and cannot neutralize acidic gases such as HF, thus failing to reduce corrosion damage. Furthermore, even when the battery surface temperature decreases, there is still a risk of acid gas spraying and reignition. Continuing to spray temperature-sensitive hydrogel at this point will not allow gel formation on the battery surface (especially at the acid gas spray nozzle), reducing the fire extinguishing agent's ability to prevent reignition.

[0039] Based on this, the present invention discloses a temperature-pH dual-responsive hydrogel fire extinguishing agent and its preparation method. The fire extinguishing agent uses pure water as a solvent and as its main component; a temperature-pH dual-responsive hydrogel, a pH stabilizer, and a water-soluble flame retardant are dissolved sequentially to obtain the temperature-pH dual-responsive hydrogel fire extinguishing agent. This fire extinguishing agent can be applied to Class A and Class B fires, and in particular, it can also be applied to lithium-ion battery fires. The temperature-pH dual-responsive hydrogel in the fire extinguishing agent not only has temperature-responsive characteristics (transforming from a sol to a gel state at high temperatures, achieving rapid coverage and cooling), but also, by introducing pH-sensitive groups (such as carboxyl or amino groups), can dynamically respond to the release of acidic gases such as HF in the fire environment and form a gel even in the later stages of fire extinguishing when the battery surface temperature drops below the LCST, through the introduction of pH-sensitive groups (such as carboxyl or amino groups). The alkaline functional components in the fire extinguishing agent effectively neutralize harmful acidic substances such as HF while maintaining the stability of the gel structure. This dual-response mechanism solves the problem that traditional extinguishing agents cannot provide continuous coverage and cooling, and overcomes the shortcomings of ordinary hydrogels in terms of chemical neutralization and response to acidic gases. It achieves a synergistic effect of physical cooling, oxygen isolation and chemical neutralization, providing an efficient and safe comprehensive fire extinguishing solution for lithium-ion battery fires.

[0040] The present invention provides a temperature-pH dual-response hydrogel fire extinguishing agent, which, by weight percentage, comprises 2wt%-4wt% temperature-pH dual-response hydrogel, 2wt%-4wt% pH stabilizer, 2wt%-9wt% water-soluble flame retardant, and 83wt%-94wt% pure water.

[0041] The temperature-pH dual-responsive hydrogel fire extinguishing agent of this invention exhibits synergistic effects among its components, providing excellent fire extinguishing for combustion products that generate acidic gases (such as lithium batteries). Containing a temperature-pH dual-responsive hydrogel, the high temperature on the surface of the burning material or the acidic substances produced can promote the formation of a gel state in the hydrogel, effectively blocking combustible gases and preventing heat exchange. Furthermore, the pH buffer and the temperature-pH dual-responsive hydrogel can neutralize the acidic substances generated during combustion, reducing the generation of harmful gases. The pH buffer also helps prevent hydrogel flocculation during long-term storage, improving the stability of the fire extinguishing agent. The addition of a flame retardant can capture free radicals and generate a dense char layer, further blocking combustible gases and preventing heat exchange. The solvent in the solution is pure water, whose high latent heat of vaporization provides a good cooling effect.

[0042] Specifically, this invention synthesizes a temperature-pH dual-responsive hydrogel and uses it in combination with pH buffers, flame retardants, and water, making it suitable for the multiple challenges of lithium-ion battery fires, such as high temperatures, reignition, and toxic gases, thus providing an innovative solution for fire prevention and control in the new energy sector.

[0043] A specific embodiment of the present invention discloses a temperature-pH dual-responsive hydrogel, the general formula of which is:

[0044] where 100 < n < 1000.

[0045] It should be noted that if the value of n is too small, the polymer molecular chains cannot entangle with each other under high temperature or acidic conditions, resulting in the inability to form a gel; if the value of n is too large, the polymer molecules are difficult to dissolve in water, and the solution viscosity is too high, making it difficult to transport and spray the fire extinguishing agent in the pipeline. The inventors found that when 100 < n < 1000, the temperature and pH dual-responsive properties and the convenience of transportation and use can be taken into account simultaneously.

[0046] It should be noted that the temperature sensitivity of the polymer molecule is the result of the combined action of hydrophilic and hydrophobic groups at different temperatures. The hydrophilic groups are amide groups (-CONH-), amine groups (-NH2), and amino acid zwitterions (-COO - -NH3 + ), and the hydrophobic group is isopropyl (-CH(CH3)2). At low temperatures, the hydrophilic groups on the molecular chain form hydrogen bonds with water molecules; an ordered water structure (hydration layer) is formed around the hydrophobic isopropyl (-CH(CH3)2), causing the polymer chain to hydrate and unfold and dissolve in water; when the temperature rises above the critical solution temperature (LCST), the thermal motion destroys the hydrogen bonds, and the hydrophobic isopropyl (-CH(CH3)2) dominates, resulting in the dehydration and collapse of the polymer and precipitation, forming a flocculent gel.

[0047] It should be noted that the pH sensitivity of the polymer molecule is the result of the action of pH-sensitive groups under acidic conditions. Among them, the pH-sensitive group is the amino acid zwitterion (-COO - -NH3 + ) structure. Under acidic conditions, the carboxylate (-COO - ) is protonated to form a carboxylic acid (-COOH) structure. As the pH value decreases, the H + ions in the system increase, the hydrophilicity of the carboxylate decreases, and the polymer molecules will gradually precipitate, eventually forming a flocculent gel substance.

[0048] It should be noted that the polymer molecule also contains a melamine cation group, which generates non-combustible gases such as ammonia and nitrogen at high temperatures, can dilute combustible gases, and has a flame retardant effect. In particular, when the hydrogel is compounded with a phosphate flame retardant, the phosphate acts as an acid source, the hydrogel acts as a carbon source, and melamine acts as a gas source, and the three cooperate to produce the effect of an intumescent flame retardant, and the flame retardant effect is stronger.

[0049] The temperature-pH dual-responsive hydrogel disclosed in this invention exhibits strong fluidity at room temperature, facilitating transport and spraying. Furthermore, under higher temperatures or acidic conditions, it can transform into a flocculent gel, forming a stable three-dimensional structure, thus possessing both temperature and pH responsiveness and high fire extinguishing performance.

[0050] A specific embodiment of the present invention discloses a method for preparing a temperature-pH dual-responsive hydrogel. It includes the following steps:

[0051] S1-1: N-isopropylacrylamide, maleic anhydride, and water are thoroughly mixed in a certain molar ratio; ammonium persulfate is added as an initiator at 60°C to initiate a polymerization reaction; after reacting for a period of time, the product is separated and purified to obtain intermediate product A. 0.5 ;

[0052] S1-2: Product A 0.5 Dissolve in pure water, add melamine, stir for a certain time to obtain a crude product solution of A.

[0053] S1-3: Filter the crude product solution of A, and then heat it to 60℃ to precipitate the hydrogel of product A, thus obtaining temperature-pH dual-responsive hydrogel A.

[0054] It should be noted that the following reaction occurs in step S1-1:

[0055]

[0056] The following reaction occurs in step S1-2:

[0057]

[0058] It should be noted that the molar ratio of N-isopropylacrylamide (NIPAM) to maleic anhydride (MAH) in step S1-1 has a significant impact on the pH responsiveness and yield of the product. When the ratio is too high or too low, the polymer becomes insensitive to weakly acidic conditions, and the yield is low. The suitable molar ratio of NIPAM to MAH is 8:1 to 2:1.

[0059] It should be noted that if the amount of ammonium persulfate initiator in step S1-1 is too low, the resulting polymer will have an excessively large molecular weight and a reduced yield; if the amount is too high, the resulting polymer will have an excessively low molecular weight and will not be able to form a gel. The suitable amount of initiator is 0.05%-1% of the sum of the molar amounts of N-isopropylacrylamide and maleic anhydride.

[0060] It should be noted that reaction 2 in S1-1 requires strict temperature control. At low temperatures, the initiator will not function and the reaction will not occur; at excessively high temperatures, explosive polymerization may occur, exacerbating side reactions. The suitable reaction temperature is 50℃-80℃.

[0061] It should be noted that reaction 2 in S1-1 must be carried out under inert gas conditions such as nitrogen and argon. Otherwise, the sulfate radicals (SO4-·) and hydroxyl radicals (·OH) produced by the decomposition of ammonium persulfate will react with O2 to generate peroxy radicals (ROO·) with low activity, which will affect the efficiency of the initiator and exacerbate the side reactions.

[0062] It should be noted that in S1-1, the product is separated and purified to obtain intermediate product A. 0.5 The specific procedure involves first filtering the product to remove unreacted monomers and small molecules. The filtered product is then washed three times with pure water. Finally, the product is dissolved in pure water at room temperature (25℃±5℃) for the next reaction step. If the temperature of the pure water used during washing is too low, the polymer will dissolve; if the temperature is too high, the polymer molecules will excessively aggregate, making re-dissolution difficult. The suitable temperature for the washing water is 50℃-80℃.

[0063] It should be noted that in S1-2, melamine is reacted with intermediate product A from step S1-1. 0.5 Further polymerization at room temperature is essential. First, A 0.5 Although it exhibits some temperature and pH responsiveness, it is an acidic substance, which limits its practical use (for example, it is not suitable for use with alkaline substances). Secondly, melamine and A... 0.5 The carboxyl group reaction will generate an amino acid zwitterion (-COO-). - -NH3 + The structure (-COOH) undergoes protonation under acidic conditions to form a carboxylic acid (-COOH) structure. As the pH decreases, the H+ in the system... + The increase in ions decreases the hydrophilicity of the carboxylate group, which enhances the pH responsiveness of the product; that is, the pH responsiveness of the final product A is greater than that of A. 0.5 We need to be stronger.

[0064] It should be noted that if the amount of melamine in S1-2 is too low, it cannot fully react with the carboxyl groups in the molecular chain; if the amount of melamine is too high, it will be wasted. The appropriate amount of melamine is a molar ratio of melamine to maleic anhydride of 1:10-2:1.

[0065] It should be noted that the reaction in S1-2 is best carried out at room temperature (25℃±5℃). Excessive temperature will cause polymer molecules to precipitate, while excessively low temperature will slow the reaction down. During the reaction, the stirring speed should be relatively slow for melamine and A... 0.5 Insufficient contact and excessive stirring speed will cause liquid splashing. The suitable magnetic stirrer speed is 100-600 r / min. To ensure complete reaction and avoid wasting time, the reaction time should be controlled between 4-36 h.

[0066] It should be noted that, in steps S1-3, to ensure product purity, after the hydrogel of product A precipitates, it is washed three times with pure water. The suitable temperature for the washing water is 50℃-80℃.

[0067] The preparation method disclosed in this invention first uses ammonium persulfate as an initiator and pure water as a solvent to react N-isopropylacrylamide (NIPAM) with maleic anhydride (MAH) to generate intermediate product A. 0.5 Then, using pure water as a solvent, through A... 0.5 The product reacts with melamine, followed by separation and purification, to obtain the final product A. A is a temperature-pH dual-responsive hydrogel that forms a flocculent gel under higher temperatures or acidic conditions. Simultaneously, A possesses certain flame-retardant properties; when combined with phosphate flame retardants, it can achieve even better flame-retardant effects.

[0068] A specific embodiment of the present invention discloses a temperature-pH dual-responsive hydrogel fire extinguishing agent, which comprises 2-3 wt% of the above-mentioned temperature-pH dual-responsive hydrogel, 2-3 wt% of sodium bicarbonate, 6-8 wt% of ammonium polyphosphate, and 86-90 wt% of pure water.

[0069] It should be noted that pH stabilizers not only enhance the stability of extinguishing agents, preventing flocculation after prolonged storage, but also neutralize acidic and toxic gases produced by the burning materials. pH stabilizer B is one or more of sodium bicarbonate, aluminum hydroxide, sodium carbonate, and potassium carbonate. Sodium bicarbonate is preferred.

[0070] It should be noted that water-soluble flame retardants can enhance the extinguishing effect of fire extinguishing agents and can also have a synergistic effect with hydrogels. Melamine is an N-series flame retardant that generates non-combustible gases such as ammonia and nitrogen at high temperatures, which can dilute flammable gases. In particular, when hydrogels and phosphates (substances that produce acidic ions upon combustion) are used in combination, the phosphates act as an acid source, the hydrogels act as a carbon source, and the melamines act as a gas source. The three work synergistically to produce the effect of an intumescent flame retardant, resulting in a better flame retardant effect for the fire extinguishing agent. Water-soluble flame retardant C is one or more of ammonium hypophosphite, ammonium polyphosphate, ammonium sulfate, monoammonium phosphate, diammonium phosphate, water-soluble magnesium hydroxide, and water-soluble aluminum hydroxide. Ammonium polyphosphate flame retardant is preferred.

[0071] A specific embodiment of the present invention discloses a method for preparing a temperature-pH dual-responsive hydrogel fire extinguishing agent, which includes the following steps:

[0072] (1) Dissolve a certain amount of temperature-pH dual-response hydrogel A in pure water until fully dissolved;

[0073] (2) Add a certain amount of pH stabilizer and dissolve it completely;

[0074] (3) Add a certain amount of water-soluble flame retardant and dissolve it completely to obtain a temperature-pH dual-response hydrogel fire extinguishing agent.

[0075] This invention discloses a temperature-pH dual-responsive hydrogel fire extinguishing agent and its preparation method. The fire extinguishing agent uses pure water as a solvent and as its main component. A temperature-pH dual-responsive hydrogel, a pH stabilizer, and a water-soluble flame retardant are dissolved sequentially to obtain the temperature-pH dual-responsive hydrogel fire extinguishing agent. This fire extinguishing agent can be applied to Class A and Class B fires, and in particular, it can also be applied to lithium-ion battery fires. The temperature-pH dual-responsive hydrogel in the fire extinguishing agent not only has temperature-responsive characteristics (transforming from a sol to a gel state at high temperatures, achieving rapid coverage and cooling), but also, by introducing pH-sensitive groups (such as carboxyl or amino groups), it can still dynamically respond to the release of acidic gases such as HF in the fire environment and form a gel even in the later stages of fire extinguishing when the battery surface temperature drops below the LCST, through the introduction of pH-sensitive groups (such as carboxyl or amino groups). The alkaline functional components in the fire extinguishing agent effectively neutralize harmful acidic substances such as HF while maintaining the stability of the gel structure. This dual-response mechanism solves the problem that traditional extinguishing agents cannot provide continuous coverage and cooling, and overcomes the shortcomings of ordinary hydrogels in terms of chemical neutralization and response to acidic gases. It achieves a synergistic effect of physical cooling, oxygen isolation and chemical neutralization, providing an efficient and safe comprehensive fire extinguishing solution for lithium-ion battery fires.

[0076] The technical solution of the present invention will be further explained below with reference to specific embodiments.

[0077] Example 1

[0078] A method for preparing a temperature-pH dual-responsive hydrogel, the specific steps of which are as follows:

[0079] S1-1: Add 4.97 g (0.044 mol) of N-isopropylacrylamide, 1.08 g (0.011 mol) of maleic anhydride, and 150 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.14 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A1. 0.5 .

[0080] S1-2: Transfer product A1 0.5 Dissolve in pure water, add 1.4 g of melamine (about 0.011 mol), stir at 200 r / min for 12 h to allow the reaction to proceed fully, and obtain a crude product solution of A1.

[0081] S1-3: Filter the crude product solution of A1 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A1 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A1.

[0082] Example 2

[0083] A method for preparing a temperature-pH dual-responsive hydrogel, the specific steps of which are as follows:

[0084] S1-1: Add 4.97 g (0.044 mol) of N-isopropylacrylamide, 2.16 g (0.022 mol) of maleic anhydride, and 180 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.17 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A2. 0.5 .

[0085] S1-2: Transfer product A2 0.5 Dissolve in pure water, add 2.8g of melamine (about 0.022mol), stir at 200r / min for 12h to allow the reaction to proceed fully, and obtain a crude product solution of A2.

[0086] S1-3: Filter the crude product solution of A2 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A2 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A2.

[0087] Example 3

[0088] A method for preparing a temperature-pH dual-responsive hydrogel, the specific steps of which are as follows:

[0089] S1-1: Add 3.72 g (0.033 mol) of N-isopropylacrylamide, 3.24 g (0.033 mol) of maleic anhydride, and 180 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.17 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A3. 0.5 .

[0090] S1-2: Transfer product A3 0.5 Dissolve in pure water, add 4.2g of melamine (about 0.033mol), stir at 200r / min for 12h to allow the reaction to proceed fully, and obtain a crude product solution of A3.

[0091] S1-3: Filter the crude product solution of A3 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A3 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A3.

[0092] Example 4

[0093] A method for preparing a temperature-pH dual-responsive hydrogel, the specific steps of which are as follows:

[0094] S1-1: Add 2.48 g (0.022 mol) of N-isopropylacrylamide, 4.32 g (0.044 mol) of maleic anhydride, and 180 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.17 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A4. 0.5 .

[0095] S1-2: Transfer product A4 0.5 Dissolve in pure water, add 5.6 g of melamine (about 0.044 mol), stir at 200 r / min for 12 h to allow the reaction to proceed fully, and obtain a crude product solution of A4.

[0096] S1-3: Filter the crude product solution of A4 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A4 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A4.

[0097] Example 5

[0098] A method for preparing a temperature-pH dual-responsive hydrogel, the specific steps of which are as follows:

[0099] S1-1: Add 4.97 g (0.044 mol) of N-isopropylacrylamide, 0.54 g (0.0055 mol) of maleic anhydride, and 150 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.14 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A5. 0.5 .

[0100] S1-2: Transfer product A5 0.5 Dissolve in pure water, add 0.7g of melamine (about 0.0055mol), stir at 200r / min for 12h to allow the reaction to proceed fully, and obtain a crude product solution of A5.

[0101] S1-3: Filter the crude product solution of A5 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A5 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A5.

[0102] Example 6

[0103] A method for preparing a temperature-pH dual-responsive hydrogel fire extinguishing agent, the specific steps of which are as follows:

[0104] (1) Preparation of temperature-pH dual-responsive hydrogel A1

[0105] S1-1: Add 4.97 g (0.044 mol) of N-isopropylacrylamide, 1.08 g (0.011 mol) of maleic anhydride, and 150 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.14 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A1. 0.5 .

[0106] S1-2: Transfer product A1 0.5 Dissolve in pure water, add 1.4 g of melamine (about 0.011 mol), stir at 200 r / min for 12 h to allow the reaction to proceed fully, and obtain a crude product solution of A1.

[0107] S1-3: Filter the crude product solution of A1 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A1 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A1.

[0108] (2) Dissolve the prepared A1 (2g) in pure water (90g) until fully dissolved;

[0109] (3) Add another 2g of sodium bicarbonate and dissolve it completely;

[0110] (4) Add 6g of ammonium polyphosphate and dissolve it completely to obtain a temperature-pH dual-response hydrogel fire extinguishing agent.

[0111] Example 7

[0112] A method for preparing a temperature-pH dual-responsive hydrogel fire extinguishing agent, the specific steps of which are as follows:

[0113] (1) Preparation of temperature-pH dual-responsive hydrogel A2

[0114] S1-1: Add 4.97 g (0.044 mol) of N-isopropylacrylamide, 2.16 g (0.022 mol) of maleic anhydride, and 180 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.17 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A2. 0.5 .

[0115] S1-2: Transfer product A2 0.5 Dissolve in pure water, add 2.8g of melamine (about 0.022mol), stir at 200r / min for 12h to allow the reaction to proceed fully, and obtain a crude product solution of A2.

[0116] S1-3: Filter the crude product solution of A2 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A2 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A2.

[0117] (2) Dissolve the prepared A2 (2g) in pure water (90g) until fully dissolved;

[0118] (3) Add another 2g of sodium bicarbonate and dissolve it completely;

[0119] (4) Add 6g of ammonium polyphosphate and dissolve it completely to obtain a temperature-pH dual-response hydrogel fire extinguishing agent.

[0120] Example 8

[0121] A method for preparing a temperature-pH dual-responsive hydrogel fire extinguishing agent, the specific steps of which are as follows:

[0122] (1) Preparation of temperature-pH dual-responsive hydrogel A1

[0123] S1-1: Add 4.97 g (0.044 mol) of N-isopropylacrylamide, 1.08 g (0.011 mol) of maleic anhydride, and 150 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.14 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A1. 0.5 .

[0124] S1-2: Transfer product A1 0.5 Dissolve in pure water, add 1.4 g of melamine (about 0.011 mol), stir at 200 r / min for 12 h to allow the reaction to proceed fully, and obtain a crude product solution of A1.

[0125] S1-3: Filter the crude product solution of A1 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A1 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A1.

[0126] (2) Dissolve the prepared A1 (1g) in pure water (91g) until fully dissolved;

[0127] (3) Add another 2g of sodium bicarbonate and dissolve it completely;

[0128] (4) Add 6g of ammonium polyphosphate and dissolve it completely to obtain a temperature-pH dual-response hydrogel fire extinguishing agent.

[0129] Example 9

[0130] A method for preparing a temperature-pH dual-responsive hydrogel fire extinguishing agent, the specific steps of which are as follows:

[0131] (1) Preparation of temperature-pH dual-responsive hydrogel A1

[0132] S1-1: Add 4.97 g (0.044 mol) of N-isopropylacrylamide, 1.08 g (0.011 mol) of maleic anhydride, and 150 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.14 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A1. 0.5 .

[0133] S1-2: Transfer product A1 0.5 Dissolve in pure water, add 1.4 g of melamine (about 0.011 mol), stir at 200 r / min for 12 h to allow the reaction to proceed fully, and obtain a crude product solution of A1.

[0134] S1-3: Filter the crude product solution of A1 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A1 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A1.

[0135] (2) Dissolve the prepared A1 (4g) in pure water (88g) until fully dissolved;

[0136] (3) Add another 2g of sodium bicarbonate and dissolve it completely;

[0137] (4) Add 6g of ammonium polyphosphate and dissolve it completely to obtain a temperature-pH dual-response hydrogel fire extinguishing agent.

[0138] Example 10

[0139] A method for preparing a temperature-pH dual-responsive hydrogel fire extinguishing agent, the specific steps of which are as follows:

[0140] (1) Preparation of temperature-pH dual-responsive hydrogel A1

[0141] S1-1: Add 4.97 g (0.044 mol) of N-isopropylacrylamide, 1.08 g (0.011 mol) of maleic anhydride, and 150 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.14 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A1. 0.5 .

[0142] S1-2: Transfer product A1 0.5Dissolve in pure water, add 1.4 g of melamine (about 0.011 mol), stir at 200 r / min for 12 h to allow the reaction to proceed fully, and obtain a crude product solution of A1.

[0143] S1-3: Filter the crude product solution of A1 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A1 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A1.

[0144] (2) Dissolve the prepared A1 (2g) in pure water (91g) until fully dissolved;

[0145] (3) Add another 1g of sodium bicarbonate and dissolve it completely;

[0146] (4) Add 6g of ammonium polyphosphate and dissolve it completely to obtain a temperature-pH dual-response hydrogel fire extinguishing agent.

[0147] Example 11

[0148] A method for preparing a temperature-pH dual-responsive hydrogel fire extinguishing agent, the specific steps of which are as follows:

[0149] (1) Preparation of temperature-pH dual-responsive hydrogel A1

[0150] S1-1: Add 4.97 g (0.044 mol) of N-isopropylacrylamide, 1.08 g (0.011 mol) of maleic anhydride, and 150 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.14 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A1. 0.5 .

[0151] S1-2: Transfer product A1 0.5 Dissolve in pure water, add 1.4 g of melamine (about 0.011 mol), stir at 200 r / min for 12 h to allow the reaction to proceed fully, and obtain a crude product solution of A1.

[0152] S1-3: Filter the crude product solution of A1 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A1 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A1.

[0153] (2) Dissolve the prepared A1 (2g) in pure water (88g) until fully dissolved;

[0154] (3) Add another 4g of sodium bicarbonate and dissolve it completely;

[0155] (4) Add 6g of ammonium polyphosphate and dissolve it completely to obtain a temperature-pH dual-response hydrogel fire extinguishing agent.

[0156] Example 12

[0157] A method for preparing a temperature-pH dual-responsive hydrogel fire extinguishing agent, the specific steps of which are as follows:

[0158] (1) Dissolve A1 (2g) prepared in Example 1 in pure water (93g) until fully dissolved;

[0159] (2) Add another 2g of sodium bicarbonate and dissolve it completely;

[0160] (3) Add 3g of ammonium polyphosphate and dissolve it completely to obtain a temperature-pH dual-response hydrogel fire extinguishing agent.

[0161] Example 13

[0162] A method for preparing a temperature-pH dual-responsive hydrogel fire extinguishing agent, the specific steps of which are as follows:

[0163] (1) Preparation of temperature-pH dual-responsive hydrogel A1

[0164] S1-1: Add 4.97 g (0.044 mol) of N-isopropylacrylamide, 1.08 g (0.011 mol) of maleic anhydride, and 150 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.14 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A1. 0.5 .

[0165] S1-2: Transfer product A1 0.5 Dissolve in pure water, add 1.4 g of melamine (about 0.011 mol), stir at 200 r / min for 12 h to allow the reaction to proceed fully, and obtain a crude product solution of A1.

[0166] S1-3: Filter the crude product solution of A1 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A1 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A1.

[0167] (2) Dissolve the prepared A1 (2g) in pure water (87g) until fully dissolved;

[0168] (3) Add another 2g of sodium bicarbonate and dissolve it completely;

[0169] (4) Add 9g of ammonium polyphosphate and dissolve it completely to obtain a temperature-pH dual-response hydrogel fire extinguishing agent.

[0170] Comparative Example 1: Pure Water

[0171] Comparative Example 2

[0172] A method for preparing a temperature-pH dual-responsive hydrogel fire extinguishing agent, the specific steps of which are as follows:

[0173] (1) Preparation of temperature-pH dual-responsive hydrogel A1

[0174] S1-1: Add 4.97 g (0.044 mol) of N-isopropylacrylamide, 1.08 g (0.011 mol) of maleic anhydride, and 150 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.14 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A1. 0.5 .

[0175] S1-2: Transfer product A1 0.5 Dissolve in pure water, add 1.4 g of melamine (about 0.011 mol), stir at 200 r / min for 12 h to allow the reaction to proceed fully, and obtain a crude product solution of A1.

[0176] S1-3: Filter the crude product solution of A1 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A1 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A1.

[0177] (2) Dissolve the prepared A1 (2g) in pure water (90g) until fully dissolved;

[0178] (3) Add 2g of sodium bicarbonate and dissolve it completely to obtain a temperature-pH dual-response hydrogel fire extinguishing agent.

[0179] Comparative Example 3

[0180] A method for preparing a temperature-pH dual-responsive hydrogel fire extinguishing agent, the specific steps of which are as follows:

[0181] (1) Preparation of temperature-pH dual-responsive hydrogel A1

[0182] S1-1: Add 4.97 g (0.044 mol) of N-isopropylacrylamide, 1.08 g (0.011 mol) of maleic anhydride, and 150 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.14 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A1. 0.5 .

[0183] S1-2: Transfer product A1 0.5 Dissolve in pure water, add 1.4 g of melamine (about 0.011 mol), stir at 200 r / min for 12 h to allow the reaction to proceed fully, and obtain a crude product solution of A1.

[0184] S1-3: Filter the crude product solution of A1 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A1 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A1.

[0185] (2) Dissolve the prepared A1 (2g) in pure water (90g) until fully dissolved;

[0186] (3) Add 6g of ammonium polyphosphate and dissolve it completely to obtain a temperature-pH dual-response hydrogel fire extinguishing agent.

[0187] Comparative Example 4

[0188] A method for preparing a temperature-pH dual-responsive hydrogel fire extinguishing agent, the specific steps of which are as follows:

[0189] (1) Preparation of temperature-pH dual-responsive hydrogel A1

[0190] S1-1: Add 4.97 g (0.044 mol) of N-isopropylacrylamide, 1.08 g (0.011 mol) of maleic anhydride, and 150 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.14 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A1. 0.5 .

[0191] S1-2: Transfer product A1 0.5Dissolve in pure water, add 1.4 g of melamine (about 0.011 mol), stir at 200 r / min for 12 h to allow the reaction to proceed fully, and obtain a crude product solution of A1.

[0192] S1-3: Filter the crude product solution of A1 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A1 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A1.

[0193] (2) Dissolve the prepared A1 (2g) in pure water (90g) until fully dissolved;

[0194] (3) Add another 2g of sodium bicarbonate and dissolve it completely;

[0195] (4) Add 2g of water-soluble aluminum hydroxide and dissolve it completely to obtain a temperature-pH dual-response hydrogel fire extinguishing agent.

[0196] Comparative Example 5

[0197] A method for preparing a temperature-pH dual-responsive hydrogel fire extinguishing agent, the specific steps of which are as follows:

[0198] (1) Preparation of temperature-pH dual-responsive hydrogel A1

[0199] S1-1: Add 4.97 g (0.044 mol) of N-isopropylacrylamide, 1.08 g (0.011 mol) of maleic anhydride, and 150 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.14 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A1. 0.5 .

[0200] S1-2: Transfer product A1 0.5 Dissolve in pure water, add 1.4 g of melamine (about 0.011 mol), stir at 200 r / min for 12 h to allow the reaction to proceed fully, and obtain a crude product solution of A1.

[0201] S1-3: Filter the crude product solution of A1 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A1 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A1.

[0202] (2) Dissolve the prepared A1 (2g) in pure water (93g) until fully dissolved;

[0203] (3) Add another 2g of sodium bicarbonate and dissolve it completely;

[0204] (4) Add 1g of water-soluble aluminum hydroxide and dissolve it completely to obtain a temperature-pH dual-response hydrogel fire extinguishing agent.

[0205] Comparative Example 6

[0206] A method for preparing a temperature-pH dual-responsive hydrogel fire extinguishing agent, the specific steps of which are as follows:

[0207] (1) Preparation of temperature-pH dual-responsive hydrogel A1

[0208] S1-1: Add 4.97 g (0.044 mol) of N-isopropylacrylamide, 1.08 g (0.011 mol) of maleic anhydride, and 150 g of pure water to a three-necked flask. Dissolve completely at 200 rpm. Raise the temperature to 60 °C, purge the reaction system with nitrogen gas, and continue stirring while maintaining the nitrogen atmosphere. Add 0.14 g of ammonium persulfate, maintain the nitrogen atmosphere, and begin the polymerization reaction. After 2 hours, stop stirring and heating to obtain the polymerization product of N-isopropylacrylamide and maleic anhydride. Separate and purify the product to obtain A1. 0.5 .

[0209] S1-2: Transfer product A1 0.5 Dissolve in pure water, add 1.4 g of melamine (about 0.011 mol), stir at 200 r / min for 12 h to allow the reaction to proceed fully, and obtain a crude product solution of A1.

[0210] S1-3: Filter the crude product solution of A1 to remove excess unreacted melamine; then heat to 60℃, and the hydrogel of product A1 will precipitate, finally obtaining temperature-pH dual-responsive hydrogel A1.

[0211] (2) Dissolve the prepared A1 (2g) in pure water (80g) until fully dissolved;

[0212] (3) Add another 2g of sodium bicarbonate and dissolve it completely;

[0213] (4) Add 4g of water-soluble aluminum hydroxide and dissolve it completely to obtain a temperature-pH dual-response hydrogel fire extinguishing agent.

[0214] 1. Characterization of hydrogel products

[0215] The infrared spectrum analysis and nuclear magnetic resonance analysis results of the temperature-pH dual-responsive hydrogel prepared in Example 1 of this invention are as follows:

[0216] Figure 3 The image shows N-isopropylacrylamide (NIPAM) and A1. 0.5 Infrared contrast spectrum: 3500cm -1The peak corresponds to the stretching vibration of the -OH group in the carboxyl group carried by maleic acid; 1213 cm⁻¹ -1 The stretching vibration peak corresponds to the -CO group in the carboxyl group; the stretching vibration peak of the -C=O bond is at 1657 cm⁻¹. -1 At this point, both NIPAM and the carboxyl group contain -C=O bonds, making them indistinguishable in the infrared spectrum. This indicates that N-isopropylacrylamide and maleic acid have been successfully polymerized.

[0217] Figure 4 The middle displays A1 0.5 Infrared contrast spectra of melamine, A1, and melamine: Melamine and A1 0.5 The resulting A1 layer showed a more pronounced stretching vibration peak of melamine. (3116 cm⁻¹) -1 The peak corresponding to the stretching vibration of the -NH bond is 1435 cm⁻¹. -1 The stretching vibration peaks corresponding to the -CN bond are located at A1. 0.5 It is also reflected in the infrared spectrum, and is now even more obvious; 801cm -1 The peak corresponds to the out-of-plane bending vibration of the triazine ring. In the infrared spectrum of A1, a peak at 1400 cm⁻¹ can also be seen. -1 The corresponding stretching vibration peak of -CH3 is 1303 cm⁻¹. -1 The peak corresponds to the -CN- stretching vibration of the amide bond (-CONH-), at 1303 cm⁻¹. -1 The peak corresponds to the vibration of the methyl group in isopropyl; other positions, such as the stretching vibration peak of the -C=O bond, are at 1657 cm⁻¹. -1 At a depth of 1650-1700 cm, it reacts with melamine. -1 The -C=N- bonds at this point overlap. Infrared spectroscopy reveals that melamine has already bonded with A1. 0.5 The reaction successfully produced A1.

[0218] Figure 5 shows the D2O H of N-isopropylacrylamide. 1 The NMR spectrum shows peaks at 5.78 ppm, 5.68 ppm, and 5.30 ppm, indicating the presence of three H atoms on CH2=CH-. 1 Peak; the peak at 5.73 ppm indicates H on -NH. 1 The peak at 3.54 ppm indicates the presence of the H atom in the -CH- group on -CH(CH3)2. 1 The peak at 0.73 ppm indicates the presence of the H atom of the -CH3 group on -CH(CH3)2. 1 peak.

[0219] Figure 6 shows A1 0.5 D2O H 1 NMR spectrum, compared to D2O H of N-isopropylacrylamide 1The NMR spectrum shows a new peak at 6.29 ppm, corresponding to the H+ on -COOH. 1 The peak indicates that N-isopropylacrylamide and maleic acid were successfully polymerized.

[0220] Figure 7 shows the D2O H of A1 1 NMR MRI. Compared to A1 0.5 D2O H 1 NMR spectrum, H corresponding to -COOH at 6.29 ppm 1 The peak disappears, and the corresponding -NH3 appears at 5.49 ppm. + (The steric hindrance in the polymer molecular chain delays -NH3) + H (rapid exchange with D2O) 1 Peak. Explanation - NH2 successfully interacts with A1. 0.5 -COOH forms a stable amino acid zwitterion (-COO-). - -NH3 + The structure was obtained, and the A1 sample was successfully generated.

[0221] Analysis of the infrared and nuclear magnetic resonance test results shows that the intermediate product A1 generated in Example 1... 0.5 Both the final product A1 and the final product were successfully synthesized.

[0222] Furthermore, GPC analysis of A1 yielded a number-average molecular weight Mn ≈ 4.16 * 10⁻⁶. 5 The polymer dispersion index PIN = 1.40 and the degree of polymerization n ≈ 864.

[0223] 2. Effect of the molar ratio of N-isopropylacrylamide and maleic anhydride on the pH response and yield of hydrogels

[0224] Examples 1-5 differ only in the ratio of N-isopropylacrylamide and maleic anhydride. The yield of the products and their pH values ​​between 3 and 4 are shown in Table 1.

[0225] Table 1. Yields of products from Examples 1-5 and their pH values ​​between 3-4 and 10-11.

[0226]

[0227]

[0228] As can be seen from Table 1, the yields of Examples 1, 2, and 5 are relatively high (greater than 85%); white flocculent matter is produced in Examples 1, 2, and 5 when the pH is between 3 and 4.

[0229] The reasons are analyzed as follows: The change in the pH-sensitive properties of the hydrogel is mainly due to the different ionization of pH-sensitive groups (amino and carboxyl groups) in solutions with different pH values, thus exhibiting its pH sensitivity. In this experiment, product A contains amino acid zwitterions (-COO-). - -NH3 + The structure involves the protonation of the carboxylate group under acidic conditions to form a carboxyl group (-COOH). The carboxyl group exhibits pH sensitivity under acidic conditions; therefore, the polymer's pH sensitivity primarily depends on product A in step S1-1. 0.5 The carboxyl content. For the copolymer of N-isopropylacrylamide and maleic anhydride, the carboxyl (-COOH) content in the copolymer increases with the increase of maleic anhydride content: when the molar ratio of N-isopropylacrylamide to maleic anhydride is 8:1 (Example 5), the effects of amide bond (-CONH-) and carboxyl group (-COOH) are comparable. Therefore, in the sample of Example 5, under acidic conditions (pH between 3 and 4) or alkaline conditions (pH between 10 and 11), polymer molecules will gradually precipitate out, and flocculent gel substances can be produced. The molar ratio of maleic anhydride was further increased. In Example 1, the molar ratio of N-isopropylacrylamide to maleic anhydride was 4:1, and in Example 2, it was 2:1. The influence of carboxyl groups (-COOH) played a dominant role. Therefore, in Examples 1 and 2, polymer molecules gradually precipitated under acidic conditions (pH between 3 and 4), producing flocculent gel substances. Under alkaline conditions, the carboxyl groups were in a dissociated state, and no gel was produced. The molar ratio of maleic anhydride was further increased. In Example 3, the molar ratio of N-isopropylacrylamide to maleic anhydride was 1:1, and in Example 2, it was 1:2. With the continued increase in the carboxyl group (-COOH) content, the weaker acidic conditions were insufficient to cause polymer molecules to precipitate, and the sample solution was clear and transparent. Under alkaline conditions, the carboxyl groups were in a dissociated state, and no gel was produced.

[0230] Therefore, the ratio of N-isopropylacrylamide to maleic anhydride significantly affects the pH response of the hydrogel and the yield of the product. Analysis shows that when the molar ratio of N-isopropylacrylamide to maleic anhydride is 8:1 to 2:1, especially 4:1, the product can achieve a pH response between pH 3 and 4, and the product yield is relatively high.

[0231] 3. Hydrogel Temperature Response Test

[0232] The temperature response testing methods and results of the temperature-pH dual-responsive hydrogels prepared in Examples 1-5 of this invention are as follows:

[0233] The critical dissolution temperature (LCST) of sample A1 was tested to be 49℃. When 5g of A1 was dissolved in 100ml of pure water, and an image of the words "Xinyuan Qingcai" was placed below it, the solution became transparent. Figure 2 As shown in Figure a. The sample was placed in a 60℃ oven for 10 minutes. After removing the sample, it was placed above an image of the "Xinyuan Qingcai" brand. Many flocculent substances were observed to form in the solution, such as... Figure 2 As shown in b. This demonstrates that the temperature-pH dual-responsive hydrogel A1 prepared in Example 1 can achieve a temperature response, producing gel at higher temperatures.

[0234] The method for testing the critical dissolution temperature, taking Example 1 as an example, involves adjusting the oven temperature. When the temperature is 48°C, placing the sample in the oven for 1 hour results in no change in the sample. When the temperature is 49°C, placing the sample in the oven for 1 hour results in the formation of flocculent matter in the solution. The critical dissolution temperature (LCST) of sample A1 was determined to be 49°C. Table 1 shows the LCSTs for Examples 1 to 5. It can be seen that as the proportion of maleic anhydride in the comonomer increases, the LCST increases. This is because the introduction of hydrophilic groups such as carboxyl groups or zwitterions of amino acids increases the proportion of hydrophilic groups and decreases the proportion of hydrophobic groups in the copolymer molecular chain, requiring a higher temperature for the copolymer to form a gel.

[0235] The hydrogel prepared in this invention exhibits temperature responsiveness because the thermosensitivity of poly(N-isopropylacrylamide-maleic anhydride) stems from the reversible hydrophilic-hydrophobic transition of its molecular structure upon temperature changes. At low temperatures, the amide groups (-CONH-) and zwitterions (-COO-) of the molecular side chains... - -NH3 + Hydrogen bonds are formed between the hydrophobic isopropyl group (-CH(CH3)2) and water molecules; an ordered structure of water molecules (hydration layer) is formed around the hydrophobic isopropyl group (-CH(CH3)2), which allows the polymer chain to hydrate and expand, and dissolve in water; when the temperature rises above the critical dissolution temperature (LCST), thermal motion breaks the hydrogen bonds, and the hydrophobic isopropyl group (-CH(CH3)2) becomes dominant, leading to polymer dehydration, collapse and precipitation.

[0236] The essence of this phase transition is determined by the competition between entropy (ΔS) and enthalpy (ΔH), and its phase transition process can be explained by the Gibbs free energy formula ΔG=ΔH-TΔS:

[0237] When the temperature is below LCST, the amide group (-CONH-) and the amino acid zwitterion (-COO-) are present. - -NH3 +The polymer forms strong hydrogen bonds with water molecules (an exothermic process, ΔH < 0), and this interaction stabilizes the polymer's solubility in water. Water molecules form an ordered "iceberg structure" (hydration layer) around the hydrophobic isopropyl group, leading to a decrease in system entropy (ΔS < 0). At this point, |ΔH| > |TΔS|, ΔG < 0, and the polymer dissolves in water.

[0238] When the temperature equals LCST, the increase in temperature intensifies the thermal motion of water molecules, and hydrogen bonds gradually break (endothermic process, ΔH>0); the "iceberg structure" collapses, and water molecules change from ordered to disordered (ΔS>0), with entropy increase becoming the dominant factor. At LCST, ΔH=TΔS, ΔG=0, and the system reaches the critical state of dissolution and precipitation.

[0239] When the temperature exceeds LCST, water molecules completely detach from the polymer chains, maximizing the system entropy (ΔS>0). However, the enthalpy cost of hydrogen bond breaking (ΔH>0) cannot offset the entropy gain. With TΔS>ΔH and ΔG>0, the polymer chains dehydrate and aggregate, resulting in phase separation.

[0240] 4. Hydrogel pH Response Test

[0241] The pH response testing methods and results of the temperature-pH dual-responsive hydrogels prepared in Examples 1-5 of this invention are as follows:

[0242] Add hydrogel solution to approximately 2 / 3 of the specimen bottle, with a hydrogel concentration of 2wt%. Add 0.1 mol / L HCl solution to create an acidic environment, add 0.1 mol / L NaOH solution to create an alkaline environment, and add pure water to create a neutral environment. Adjust the pH to 3.5, 10.5, and 7.0 respectively, and observe the state of the hydrogel solution.

[0243] Taking Example 1 as an example, the test results are as follows: Figure 1 As shown. Figure 1 'a' indicates that the hydrogel solution is a colorless and transparent liquid at pH 7.0. Figure 1 b indicates that the hydrogel solution is a colorless and transparent liquid at pH = 10.5; Figure 1 c indicates that the hydrogel solution is at pH = 3.5, where obvious white flocculent matter can be observed. This demonstrates that the temperature-pH dual-responsive hydrogel A1 prepared in Example 1 can achieve pH response.

[0244] The variation in the pH-sensitive properties of hydrogels is mainly due to the different ionization of pH-sensitive groups (amino and carboxyl groups) in solutions with different pH values, thus exhibiting their pH sensitivity. In this experiment, product A contains the amino acid zwitterion (-COO-). - -NH3 +The structure involves the protonation of the carboxylate group under acidic conditions to form a carboxyl group (-COOH). This carboxyl group exhibits pH sensitivity under acidic conditions. As the pH decreases, the H+ in the system... + As the number of ions increases, the hydrophilicity of the carboxyl groups decreases, causing polymer molecules to gradually precipitate and eventually form a flocculent gel. The results of Examples 3 and 4 indicate that when the molar ratio of maleic anhydride in the comonomer is greater than 50%, a pH of 3-4 is insufficient to induce precipitation and produce a flocculent gel.

[0245] 5. The influence of pH stabilizers and water-soluble flame retardants in fire extinguishing agents on their fire extinguishing performance.

[0246] To verify the performance of the fire extinguishing agent based on the temperature-pH dual-response hydrogel, the following method was used:

[0247] (1) Cut a 5cm*5cm*1.2cm wooden block and soak it in an electrolyte (1.0mol / L LiPF6 (lithium hexafluorophosphate) dissolved in EC (ethylene carbonate) and DMC (dimethyl carbonate) (volume ratio of 1:1) for 24h.

[0248] (2) Place the wooden block in the center of an iron disc with a diameter of 15cm and a height of 5cm, and place the disc in a stainless steel tray with a diameter of 100cm*60cm*5cm to prevent the extinguishing agent from splashing everywhere. Ignite the wooden block with an igniter for 5 seconds, and the flame height is 5cm.

[0249] (3) The wood block will spontaneously combust for 20 seconds, allowing it to burn completely. Use a water sprayer to apply extinguishing agent at a flow rate of 100 ml / min.

[0250] (4) After the flames are completely extinguished, continue spraying the extinguishing agent for 5 seconds.

[0251] (5) Place the sample for 30 minutes and observe whether the wood block reignites. If it reignites, extinguish it with pure water after burning for 600 seconds.

[0252] The experimental results of extinguishing agents in Examples 6 and 7, and Comparative Examples 1, 2, and 4 are shown in Table 2. Extinguishing time and reignition time are calculated from the start of spraying the extinguishing agent. The time when the flame is extinguished is recorded as the extinguishing time, and the time when reignition occurs is recorded as the reignition time.

[0253] Table 2 Results of Fire Extinguishing Agent Tests

[0254] sample Extinguishing time / s reignition time / s Remark Example 6 11 No reignition No black smoke produced Example 7 12 No reignition No black smoke produced Comparative Example 1 35 55 Black smoke is produced Comparative Example 2 23 No reignition No black smoke produced Comparative Example 4 17 No reignition No black smoke produced

[0255] As shown in Table 2, in Comparative Example 1 (pure water), reignition occurred after extinguishing the fire, producing a large amount of black smoke. In Examples 6, 7, Comparative Example 2, and 4, no reignition occurred and no black smoke was produced. Furthermore, Figure 8Images a, 8b, and 8c show the conditions after fire extinguishing in Comparative Example 1, Comparative Example 4, and Example 6, respectively. It is evident that using pure water (Comparative Example 1) resulted in the longest extinguishing time and subsequent reignition. Figure 8 The entire structure of component a was burned black and severely damaged. Using Comparative Example 4 for fire extinguishing reduced the extinguishing time and prevented reignition. Figure 8 The wooden block b was burned around the edges, turning black, while the center remained white and unburned. White gel-like substances from the extinguishing agent and residues after the gel evaporated were visible on the surface of the block. Compared to Comparative Example 1, Comparative Example 4 showed improved extinguishing effectiveness. Using Example 6 for fire extinguishing further reduced the extinguishing time and prevented reignition. Figure 8 The sides of the wooden block were burned and turned black, while most of the middle area was white and not burned. White gel-like substances and a small amount of gel residue after evaporation could be seen on the surface of the wooden block. Compared with Comparative Example 4, the fire extinguishing effect of Example 6 was further improved.

[0256] The reasons are analyzed as follows:

[0257] From Table 2, Figure 8 It is known that the fire extinguishing agent prepared by the present invention will produce gel at high temperature. The gel will isolate oxygen and reduce the emission of combustible gases. The hydrogel and pH buffer in the fire extinguishing agent will neutralize the acidic gases (such as HF) produced by the combustion of the electrolyte, preventing the generation of harmful gases and particulate matter.

[0258] Comparative Example 1 took the longest time to extinguish the fire. This is because pure water, during the extinguishing process, can only rely on cooling and the generated water vapor to reduce the concentration of combustible gases and prevent combustion. Comparative Example 2 extinguished the fire 34% faster than Comparative Example 1 (pure water), indicating that after adding the temperature-pH dual-response hydrogel, the hydrogel material produced when the extinguishing agent is sprayed onto the surface of the burning material plays a role in isolating combustion. However, the extinguishing time of Comparative Example 2 was longer than that of Comparative Example 4, Example 1, and Example 2 because no flame retardant was added in Comparative Example 2. The extinguishing time of Example 6 was 69% faster than that of Comparative Example 1 (pure water), and the extinguishing time of Example 7 was 66% faster than that of Comparative Example 1 (pure water), showing good extinguishing effects. This indicates that the extinguishing agent prepared by combining the temperature-pH dual-response hydrogel with a flame retardant has a good extinguishing effect. The extinguishing time of Example 6 was 51% faster than that of Comparative Example 4, indicating that although ammonium polyphosphate and water-soluble aluminum hydroxide are both water-soluble flame retardants, ammonium polyphosphate can also exert a synergistic effect, resulting in a stronger flame retardant effect.

[0259] Furthermore, the inventors discovered that pH buffers can not only neutralize acidic gases but also maintain and improve the stability of fire extinguishing agents. After the fire extinguishing agents prepared in Example 6 and Comparative Example 3 were left to stand for a certain period, the fire extinguishing agent in Comparative Example 3, without the addition of sodium bicarbonate as a pH buffer, formed a white flocculent gel after 25 days, while the temperature-pH dual-response hydrogel fire extinguishing agent prepared in Example 6 did not exhibit flocculation even after 6 months. This indicates that pH buffers can also prevent hydrogel flocculation, thereby improving the stability of the fire extinguishing agent.

[0260] The above experiments and analyses show that the temperature-pH dual-responsive hydrogel fire extinguishing agent prepared in this invention, due to the presence of temperature-pH dual-responsive hydrogel, allows the high temperature on the surface of the burning material or the acidic substances produced to promote the formation of a gel state in the hydrogel, thus blocking combustible gases and preventing heat exchange. Furthermore, the pH buffer and the temperature-pH dual-responsive hydrogel can neutralize the acidic substances generated during combustion, reducing the generation of harmful gases. The pH buffer also prevents hydrogel flocculation, improving the stability of the fire extinguishing agent. The addition of flame retardants can capture free radicals and generate a dense char layer, further blocking combustible gases and preventing heat exchange. The solvent in the solution is pure water, whose high latent heat of vaporization provides a good cooling effect. The synergistic effect of the components of the temperature-pH dual-responsive hydrogel fire extinguishing agent of this invention can effectively extinguish fires involving burning materials that produce acidic gases (such as lithium batteries).

[0261] 6. The effect of the dosage of each component of the extinguishing agent on its extinguishing performance

[0262] The test results of the extinguishing agents in Examples 6, 8-13 and Comparative Examples 4-7 are shown in Table 3.

[0263] Table 3 Extinguishing results of extinguishing agents

[0264] sample Extinguishing time / s reignition time / s Remark Example 6 11 No reignition No black smoke produced Example 8 21 No reignition No black smoke produced Example 9 10 No reignition No black smoke was produced, and the spray nozzles were slightly blocked. Example 10 14 No reignition A small amount of black smoke was produced. Example 11 11 No reignition No black smoke produced Example 12 16 No reignition No black smoke produced Example 13 11 No reignition No black smoke produced Comparative Example 4 17 No reignition No black smoke produced Comparative Example 5 22 No reignition No black smoke produced Comparative Example 6 / / The nozzle became blocked 3 seconds after water was sprayed, preventing the fire extinguishing agent from being sprayed.

[0265] Examples 8-13 and Comparative Examples 4-7 show variations in the amounts of each component of the fire extinguishing agent compared to Example 6: Example 8 reduced the amount of hydrogel A1 by 50%, and Example 9 increased the amount of hydrogel A1 by 100%; Example 10 reduced the amount of sodium bicarbonate by 50%, and Example 11 increased the amount of sodium bicarbonate by 100%; Example 12 reduced the amount of ammonium polyphosphate by 50%, and Example 13 increased the amount of ammonium polyphosphate by 50%. Compared to the sample proportions in Comparative Example 4, Comparative Example 5 reduced the amount of aluminum hydroxide by 50%, and Comparative Example 7 increased the amount of aluminum hydroxide by 100%.

[0266] As can be seen from Examples 8 and 9, reducing the amount of temperature-pH dual-response hydrogel by 50% will result in a poorer fire extinguishing effect. This is because the hydrogel barrier that prevents heat and material exchange during the fire extinguishing process is reduced, thus reducing the fire extinguishing effect of the fire extinguishing agent. Increasing the amount of temperature-pH dual-response hydrogel by 100% will result in an increase in the viscosity of the fire extinguishing agent, which may block the delivery pipeline or water nozzle during the fire extinguishing process, hindering the fire extinguishing work.

[0267] As can be seen from Examples 10 and 11, reducing the amount of pH stabilizer sodium bicarbonate by 50% will result in a poorer fire extinguishing effect and the production of a small amount of black smoke, indicating that reducing the amount of sodium bicarbonate will lead to a poorer neutralization ability of the fire extinguishing agent against acidic toxic gases; increasing the amount of pH stabilizer sodium bicarbonate by 100% will not shorten the fire extinguishing time, and the fire extinguishing ability of the fire extinguishing agent will not be effectively improved.

[0268] As can be seen from Examples 12 and 13, reducing the amount of flame retardant ammonium polyphosphate by 50% will lead to a longer extinguishing time and a reduced extinguishing ability of the extinguishing agent. This is because the reduced amount of flame retardant reduces the ability to capture free radicals and generate a char layer, resulting in a worse extinguishing effect. Increasing the amount of flame retardant ammonium polyphosphate by 50% will not shorten the extinguishing time, and the extinguishing ability of the extinguishing agent will not be effectively improved.

[0269] Comparative Examples 5 and 6 show that a 50% reduction in the amount of soluble aluminum hydroxide added as a flame retardant leads to a longer extinguishing time and a reduced extinguishing capacity of the extinguishing agent; a 50% increase in the amount of soluble aluminum hydroxide added leads to precipitation in the extinguishing agent, blockage of the nozzles, and inability to spray the extinguishing agent, thus hindering the fire extinguishing work.

[0270] In summary, the optimal ratio of the fire extinguishing agent is determined as follows: for the temperature-pH dual-response hydrogel, polymer product A1 is selected at a mass fraction of 2 wt%; for the pH stabilizer, sodium bicarbonate is selected at a mass fraction of 2 wt%; for the water-soluble flame retardant, ammonium polyphosphate is selected at a mass fraction of 6%; and for the solvent, pure water is selected at a mass fraction of 90%.

[0271] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A temperature-pH dual-responsive hydrogel, characterized in that, The general formula is: 100 <n<1000; The hydrogel is prepared by controlling the molar ratio of N-isopropylacrylamide to maleic anhydride, which are then copolymerized in water to generate an intermediate product; then, using pure water as a solvent, the intermediate product is reacted with melamine to obtain the final product.

2. The temperature-pH dual-responsive hydrogel according to claim 1, characterized in that, The temperature-pH dual-responsive hydrogel has a response temperature of 49°C.

3. The temperature-pH dual-responsive hydrogel according to claim 1, characterized in that, The temperature-pH dual-responsive hydrogel responds at pH 3.

5.

4. A method for preparing a temperature-pH dual-responsive hydrogel according to any one of claims 1-3, characterized in that, The preparation method includes the following steps: S1-1: After thoroughly mixing N-isopropylacrylamide, maleic anhydride, and water, an initiator is added to initiate a polymerization reaction. The product is then separated and purified to obtain intermediate product A. 0.5 The molar ratio of N-isopropylacrylamide to maleic anhydride is 8:1-2:

1. S1-2: The intermediate product A... 0.5 Dissolve in water, add melamine, stir for a certain time to obtain a crude product solution of A; the molar ratio of melamine to maleic anhydride is 1:10-2:1; S1-3: Filter the crude product solution of A, then heat it to precipitate the hydrogel of product A, and obtain a temperature-pH dual-responsive hydrogel.

5. The preparation method according to claim 4, characterized in that, In step S1-1, the molar ratio of N-isopropylacrylamide to maleic anhydride is 4:1-2:

1.

6. The preparation method according to claim 4, characterized in that, In step S1-1, the amount of initiator used is 0.05%-1% of the sum of the molar amounts of N-isopropylacrylamide and maleic anhydride.

7. The preparation method according to claim 4, characterized in that, The polymerization reaction temperature in S1-1 is 50℃-80℃, and the polymerization reaction is carried out under inert gas protection conditions.

8. The preparation method according to claim 4, characterized in that, In S1-2, the molar ratio of melamine to maleic anhydride is 1:10-1:1, and / or the reaction is carried out at room temperature; and / or the stirring speed is 100-600 r / min, and the reaction time is 4-36 h.

9. A temperature-pH dual-responsive hydrogel fire extinguishing agent, characterized in that, The extinguishing agent includes the temperature-pH dual-responsive hydrogel according to any one of claims 1-3 or the temperature-pH dual-responsive hydrogel obtained by the preparation method according to any one of claims 4-8.

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