Temperature-pH double-response type hydrogel, preparation method and fire extinguishing agent thereof

Abstract

The invention relates to a temperature-pH double-response type hydrogel, a preparation method and a fire extinguishing agent thereof, belongs to the technical field of hydrogel fire extinguishing agents, and solves the problems of poor environmental adaptability, single response, high after-combustion rate and the like of a hydrogel fire extinguishing agent in the prior art. The temperature-pH double-response type hydrogel disclosed by the invention is prepared by the following steps: by taking ammonium persulfate as an initiator and pure water as a solvent, controlling the molar ratio of N-isopropylacrylamide (NIPAM) to maleic anhydride (MAH), so as to generate an intermediate product; and pure water is used as a solvent, the intermediate product reacts with melamine, and then separation and purification are performed, so that the obtained final product is relatively high in yield and has temperature and pH dual responsiveness.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrogel and fire extinguishing agent, and particularly relates to a temperature-pH dual-responsive hydrogel, a preparation method and a fire extinguishing agent thereof. BACKGROUND

[0002] Lithium ion battery fire has the characteristics of fast heat runaway speed, high temperature and strong toxicity. Due to internal short circuit, overcharge or mechanical damage, a chain heat release reaction is triggered, and electrolyte and electrode material decompose to generate a large amount of flammable gas (such as H2 and CO) and toxic fluoride (such as HF), resulting in jet fire (temperature can reach more than 800℃) and explosion risk. In the fire, the electrolyte (such as LiPF6) decomposes to generate acidic gas HF, forming a strong corrosive environment, not only accelerating the corrosion of metal parts, but also causing chemical burns to rescue personnel. When extinguishing the fire, water reacts with HF to further release heat and intensify the strong corrosive environment, and although the use of sodium bicarbonate and other alkaline extinguishing agents can neutralize the acid, it may cause local pH fluctuations due to incomplete reaction. Therefore, lithium ion battery fire prevention and control needs to focus on high temperature, toxic gas and acid-base corrosion, and adopt targeted fire extinguishing strategies to reduce secondary harm.

[0003] Temperature-sensitive hydrogel fire extinguishing agent has shown significant advantages in lithium ion battery fire. Its intelligent temperature-sensitive characteristics overcome the shortcomings of high viscosity and poor flowability of traditional hydrogels at room temperature. When lithium ion battery thermal runaway causes high-temperature fire, temperature-sensitive hydrogel, based on its critical transition temperature (LCST) characteristics, rapidly changes from low-viscosity sol state to high-viscosity gel state in a high-temperature environment, achieving rapid adhesion and covering the fire source, and 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, while inhibiting the flame through oxygen isolation and plugging, thereby improving the efficiency of fire extinguishing. Compared with traditional fire extinguishing agents, temperature-sensitive hydrogel has both intelligent responsiveness and high efficiency, providing an innovative solution for new energy fire prevention and control.

[0004] However, temperature-sensitive hydrogel and its fire extinguishing agent have the risk of reignition and cannot cope with the acid gas corrosion phenomenon generated during the burning process. SUMMARY

[0005] In view of the above analysis, the present application aims to provide a temperature-pH dual-responsive hydrogel, a preparation method and a fire extinguishing agent thereof, to solve the problems of poor environmental adaptability, single response and high reignition rate of existing hydrogel fire extinguishing agents, and to meet the rapid response requirements of lithium battery fire with high temperature and strong acidity.

[0006] In one aspect, the present application provides a temperature-pH dual-responsive hydrogel, the general formula of which is:

[0007] Wherein 100 < n < 1000.

[0008] Further, the temperature-pH dual responsive hydrogel is prepared by controlling the molar ratio of N-isopropyl acrylamide and maleic anhydride, copolymerizing them in water to generate an intermediate product, and then reacting the intermediate product with melamine in pure water as a solvent.

[0009] Further, the minimum response temperature of the temperature-pH dual responsive hydrogel is 38℃.

[0010] Further, the temperature-pH dual responsive hydrogel responds at a pH of 3-4.

[0011] In another aspect, the application discloses a preparation method of the temperature-pH dual responsive hydrogel, and the preparation method comprises the following steps:

[0012] S1-1: N-isopropyl acrylamide, maleic anhydride and water are fully mixed, then an initiator is added to generate a polymerization reaction, and after a period of time, the product is separated and purified to obtain an intermediate product A 0.5 ;

[0013] S1-2: The intermediate product A 0.5 is dissolved in pure water, melamine is added, and after stirring for a certain time, a crude product solution of A is obtained.

[0014] S1-3: The crude product solution of A is filtered, then the temperature is increased, so that the hydrogel of product A is precipitated, and the temperature-pH dual responsive hydrogel is obtained.

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

[0016] Further, in step S1-1, the amount of initiator is 0.05%-1% of the sum of the moles of N-isopropyl acrylamide and maleic anhydride.

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

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

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

[0020] In another aspect, the application discloses a temperature-pH dual responsive hydrogel fire extinguishing agent, which comprises the temperature-pH dual responsive hydrogel.

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

[0022] 1. The temperature-pH dual-responsive hydrogel disclosed by the present application is prepared by copolymerizing N-isopropyl acrylamide and maleic acid, and then introducing melamine into the molecular chain by reaction with the carboxyl group, wherein the main chain of the molecule is a -C-C- chain, the side chain is an isopropyl amide bond (-CONH-CH(CH3)2) and an amino acid zwitterion (-COO - -NH3 + ), the hydrophilic group is an amide group (-CONH-), an amino acid zwitterion (-COO - -NH3 + ), the hydrophobic group is an isopropyl group (-CH(CH3)2), and the pH-sensitive group is an amino acid zwitterion (-COO - -NH3 + ). The hydrogel not only has temperature response characteristics (transformation from sol to gel state at high temperature to achieve rapid coverage and cooling). By introducing a pH-sensitive group (such as a carboxyl group or an amino group), even if the battery surface temperature drops below the LCST in the later stage of fire extinguishing, the release of acidic gases such as HF in the fire environment can still be dynamically responded to, and the gel is formed.

[0023] 2. The temperature-pH dual-responsive hydrogel disclosed by the present application contains a melamine cationic group, which can generate non-combustible gases such as ammonia and nitrogen at high temperature, and can dilute combustible gases, thereby having a fire-retardant effect. In particular, when the hydrogel is used in combination with a phosphate flame retardant, the phosphate acts as an acid source, the hydrogel acts as a carbon source, and the melamine acts as a gas source, and the three work together to produce the effect of intumescent flame retardant, and the fire-retardant effect is stronger.

[0024] 3. In the preparation method of the temperature-pH dual-responsive hydrogel disclosed by the present application, ammonium persulfate is used as an initiator, pure water is used as a solvent, and the molar ratio of N-isopropyl acrylamide (NIPAM) to maleic anhydride (MAH) is controlled to make the intermediate product A 0.5 ; then, pure water is used as a solvent, A 0.5 reacts with melamine, and then the final product A is obtained after separation and purification, which not only has a high yield, but also has temperature and pH dual responsiveness.

[0025] 4. The temperature-pH dual-responsive hydrogel disclosed by the present application has strong fluidity at room temperature, which is convenient for transportation and spraying.

[0026] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of the present invention will be described in the following description, and some advantages will become apparent from the description or be learned through practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0028] Figure 1 middle, Figure 1 a. Figure 1 b. Figure 1 c shows the states 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 shows N-isopropylacrylamide and A1 0.5 The infrared contrast spectrum of Figure 3 b is Figure 3 a500cm -1 to 2000cm -1 Amplified comparison spectrum.

[0031] Figure 4 middle, Figure 4 a shows sample A1 0.5 , A1, infrared contrast spectra of melamine, Figure 4 b is Figure 4 a500cm -1 to 2000cm -1 Amplified comparison spectrum.

[0032] Figure 5a The NMR image of N-isopropylacrylamide (NIPAM) is shown. Figure 5b for Figure 5a A magnified NMR image of 0-7ppm.

[0033] Figure 6a Sample A1 is shown 0.5 The NMR images of Figure 6b for Figure 6a A magnified NMR image of 0-7ppm.

[0034] Figure 7a The nuclear magnetic chart of sample A1 is shown, Figure 7b For Figure 7a The nuclear magnetic amplification chart in 0-7ppm.

[0035] Figure 8 In, Figure 8 a, Figure 8 b, Figure 8 c respectively show the pictures after extinguishing of comparative example 1, comparative example 4 and example 1 DETAILED DESCRIPTION

[0036] The preferred embodiments of the present application will be described in detail below with reference to the drawings, wherein the drawings constitute a part of this application and are used to explain the principles of the embodiments of the present application, but are not used to limit the scope of the present application.

[0037] The existing fire extinguishing agents such as traditional hydrogel, chemical foam and dry powder fire extinguishing agent have the problems of poor environmental adaptability, single response and high rekindling rate, and especially cannot meet the rapid response requirement of lithium battery fire.

[0038] It is found in the research that when the existing hydrogel fire extinguishing agent is used to treat lithium battery fire, the rekindling problem and acid gas corrosion phenomenon are prone to occur. It is known through in-depth research that due to the high temperature and strong acidity characteristics of lithium battery fire, the existing hydrogel can only wrap the battery, and cannot neutralize the acid gas such as HF, so it cannot reduce the corrosion hazard; when the temperature of the battery surface decreases, there is a risk of spraying acid gas and rekindling, at this time, continuing to spray the temperature-sensitive hydrogel cannot form a gel on the surface of the battery (especially the acid gas spraying port), and the ability of the fire extinguishing agent to prevent the battery from rekindling decreases.

[0039] Based on this, the application discloses a temperature-pH dual response hydrogel fire extinguishing agent and a preparation method thereof, the fire extinguishing agent takes pure water as a solvent and is used as a main component of the fire extinguishing agent; temperature-pH dual response hydrogel, a pH stabilizer and a water-soluble flame retardant are sequentially dissolved to obtain the temperature-pH dual response hydrogel fire extinguishing agent. The fire extinguishing agent can be applied to class A and class B fires, and in particular, the fire extinguishing agent can also be applied to lithium ion battery fires. The temperature-pH dual response hydrogel in the fire extinguishing agent not only has temperature response characteristics (transformation from sol to gel state at high temperature to realize rapid covering and cooling), but also can dynamically respond to the release of acidic gases such as HF in the fire environment to form a gel even when the surface temperature of the battery drops below the LCST in the later stage of fire extinguishing. The alkaline functional component in the fire extinguishing agent can effectively neutralize harmful acidic substances such as HF and maintain the stability of the gel structure. This dual response mechanism not only solves the problem that traditional fire extinguishing agents cannot continuously cover and cool, but also overcomes the defects that ordinary hydrogels cannot chemically neutralize and respond to acidic gases, realizes the synergistic effect of physical cooling, oxygen isolation and chemical neutralization, and provides an efficient and safe comprehensive fire extinguishing solution for lithium ion battery fires.

[0040] The temperature-pH dual response hydrogel fire extinguishing agent provided by the application contains, in mass percentage, 2wt%-4wt% of temperature-pH dual response hydrogel, 2wt%-4wt% of a pH stabilizer, 2wt%-9wt% of a water-soluble flame retardant and 83wt%-94wt% of pure water.

[0041] The temperature-pH dual response hydrogel fire extinguishing agent provided by the application contains, in mass percentage, 2wt%-4wt% of temperature-pH dual response hydrogel, 2wt%-4wt% of a pH stabilizer, 2wt%-9wt% of a water-soluble flame retardant and 83wt%-94wt% of pure water.

[0042] Specifically, the application synthesizes a temperature-pH dual response hydrogel, and the temperature-pH dual response hydrogel is used in combination with a pH buffer, a flame retardant and water, so that the temperature-pH dual response hydrogel is suitable for the high temperature, rekindling and toxic gas of lithium ion battery fires and other multiple challenges, and provides an innovative solution for new energy fire prevention and control.

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

[0044] wherein 100 < n < 1000.

[0045] It should be noted that if the value of n is too small, the polymer molecular chains cannot be intertwined 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 large, making it difficult to transport and spray the fire extinguishing agent in the pipeline. The inventors have found that when 100 < n < 1000, the temperature and pH dual responsiveness and the convenience of transportation and use can be simultaneously considered.

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

[0047] It should be noted that the polymer molecule is sensitive to pH, which is the result of the action of the pH-sensitive group under acidic conditions. The pH-sensitive group is an 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 + ion in the system increases, the hydrophilicity of the carboxylate decreases, and the polymer molecules gradually precipitate, eventually forming a flocculent gel material.

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

[0049] The temperature-pH dual-responsive hydrogel disclosed in the present invention exhibits strong fluidity at room temperature, making it easy to transport and spray. Furthermore, at higher temperatures or acidic conditions, it can transform into a flocculent gel, forming a stable three-dimensional structure that combines dual temperature and pH responsiveness with high fire-extinguishing performance.

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

[0051] S1-1: After a certain molar ratio of N-isopropylacrylamide, maleic anhydride, and water are fully mixed; at 60°C, an initiator ammonium persulfate is added to cause a polymerization reaction; after a period of reaction, 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, and stir for a certain period of time to obtain a crude product solution of A.

[0053] S1-3: The crude product solution of A was filtered and then heated to 60° C. to precipitate the hydrogel of product A, thereby obtaining a 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 significantly influences the pH responsiveness and yield of the product. When the ratio is too high or too low, the polymer becomes less sensitive to weakly acidic conditions and the yield is low. An optimal NIPAM to MAH molar ratio is 8:1 to 2:1.

[0059] It should be noted that if the amount of ammonium persulfate used as the initiator in step S1-1 is too low, the molecular weight of the resulting polymer will be too high and the yield will be reduced. If the amount is too high, the molecular weight of the resulting polymer will be too low and gel formation will not occur. The appropriate initiator amount is 0.05% to 1% of the total molar amount of N-isopropylacrylamide and maleic anhydride.

[0060] It should be noted that the reaction 2 in S1-1 needs to strictly control the reaction temperature. When the reaction temperature is low, the initiator cannot work and the reaction will not occur, and when the reaction temperature is too high, it will cause explosive polymerization and cause the side reaction to intensify. The suitable reaction temperature is 50-80°C.

[0061] It should be noted that the reaction 2 in S1-1 needs to be carried out under the condition of inert gas such as nitrogen, argon, etc., otherwise the sulfate radical (SO4·) and hydroxyl radical (·OH) generated by the decomposition of ammonium persulfate will react with O2 to generate a low-activity peroxide radical (ROO·), which will affect the efficiency of the initiator and intensify the side reaction.

[0062] It should be noted that the product in S1-1 is separated and purified to obtain the intermediate product A 0.5 The specific operation is that the product is first filtered to remove the unreacted monomers and small molecules. Then the filtered product is washed with pure water for 3 times. Then the product is dissolved in pure water at room temperature (25°C±5°C) for the next reaction. If the temperature of the pure water used in the washing process is too low, the polymer will be dissolved, and if the temperature is too high, the polymer molecules will be excessively aggregated and difficult to be dissolved again. The suitable temperature of the washing water is 50-80°C.

[0063] It should be noted that the further polymerization reaction of melamine and the intermediate product A 0.5 in step S1-1 at room temperature is very necessary. First, A 0.5 Although it has certain temperature and pH dual responsiveness, it is an acidic substance and has certain limitations in actual use (such as not suitable for use with alkaline substances). Second, the reaction of melamine and the carboxyl group of A 0.5 will generate an amino acid zwitterion (-COO - -NH3 + ) structure, which will be protonated to generate a carboxylic acid (-COOH) structure under acidic conditions. With the decrease of pH value, the H + ion in the system increases, the hydrophilicity of the carboxylate decreases, and the pH responsiveness of the product can be enhanced, i.e. the pH responsiveness of the final product A is stronger than that of A 0.5 .

[0064] It should be noted that when the amount of melamine in S1-2 is too low, it cannot fully react with the carboxyl group in the molecular chain, and when the amount of melamine is too high, it will cause waste of melamine. The suitable amount of melamine is that the molar ratio of melamine to maleic anhydride is 1:10-2:1.

[0065] It should be noted that the reaction in S1-2 is preferably carried out at room temperature (25℃±5℃). Too high a temperature will cause the polymer molecules to precipitate, and too low a temperature will cause the reaction to be too slow. The stirring speed during the reaction is relatively slow 0.5 Inadequate contact and too fast stirring speed will cause the liquid to splash. The suitable stirring speed is 100-600r / min. In order to ensure complete reaction and avoid wasting time, the reaction time is preferably controlled at 4-36h.

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

[0067] The preparation method disclosed by the present application first uses ammonium persulfate as an initiator and pure water as a solvent to react N-isopropyl acrylamide (NIPAM) with maleic anhydride (MAH) to generate an intermediate product A 0.5 ; then uses pure water as a solvent to react A 0.5 with melamine, and then separates and purifies to obtain the final product A. A is a temperature-pH dual-responsive hydrogel that forms a flocculent gel under high temperature or acidic conditions. A also has certain flame retardant properties and can play a better flame retardant effect when compounded with a phosphate flame retardant.

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

[0069] It should be noted that the pH stabilizer not only enhances the stability of the fire extinguishing agent, so that it does not produce flocculation after long-term storage, but also neutralizes the acidic toxic gases generated by the burning material. The pH stabilizer B is one or more of sodium bicarbonate, aluminum hydroxide, sodium carbonate, and potassium carbonate. Preferably, it is sodium bicarbonate.

[0070] It should be noted that the water-soluble flame retardant can enhance the fire extinguishing effect of the fire extinguishing agent and also has a synergistic effect with the hydrogel: melamine is a N-based flame retardant that generates non-combustible gases such as ammonia and nitrogen at high temperatures, which can dilute combustible gases. In particular, when the hydrogel and the phosphate (a substance that generates acidic ions during combustion) are used together, the phosphate acts as an acid source, the hydrogel acts as a carbon source, and the melamine acts as a gas source, and the three work together to produce an intumescent flame retardant, making the fire extinguishing agent achieve better flame retardant effect. The 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. Preferably, it is an ammonium polyphosphate flame retardant.

[0071] One specific embodiment of the present application discloses a preparation method of a temperature-pH dual-responsive hydrogel fire extinguishing agent, which comprises the following steps:

[0072] (1) Dissolve a certain amount of temperature-pH dual-responsive hydrogel A in pure water, and fully dissolve;

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

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

[0075] The present application discloses a temperature-pH dual-responsive hydrogel fire extinguishing agent and a preparation method thereof. The fire extinguishing agent uses pure water as a solvent and is the main component of the fire extinguishing agent. The temperature-pH dual-responsive hydrogel, the pH stabilizer, and the water-soluble flame retardant are sequentially dissolved to obtain the temperature-pH dual-responsive hydrogel fire extinguishing agent. The 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 response characteristics (it changes from sol to gel state at high temperature to achieve rapid coverage and cooling), but also dynamically responds to the release of acidic gases such as HF in the fire environment even after the fire is extinguished, and forms a gel when the temperature of the battery surface drops below the LCST by introducing pH-sensitive groups (such as carboxyl or amino groups). The basic functional components in the fire extinguishing agent can effectively neutralize harmful acidic substances such as HF and maintain the stability of the gel structure. This dual-response mechanism not only solves the problem that traditional fire extinguishing agents cannot continuously cover and cool, but also overcomes the defects of ordinary hydrogels that cannot chemically neutralize and respond to acidic gases, achieving the synergistic effect of physical cooling, oxygen isolation, and chemical neutralization, and providing an efficient and safe comprehensive fire extinguishing solution for lithium ion battery fires.

[0076] The technical solutions of the present application are further explained and described in combination with specific embodiments.

[0077] Example 1

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

[0079] S1-1: In a three-necked flask, add N-isopropyl acrylamide 4.97g (0.044mol), maleic anhydride 1.08g (0.011mol), pure water (150g). Dissolve thoroughly at 200r / min. Increase temperature to 60℃, introduce nitrogen into the reaction system, keep nitrogen atmosphere and continue stirring. Add ammonium persulfate 0.14g, keep nitrogen atmosphere and start polymerization. Stop stirring after 2h and stop heating to obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride, and separate and purify the product to obtain A1 0.5 .

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

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

[0082] Example 2

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

[0084] S1-1: In a three-necked flask, add N-isopropyl acrylamide 4.97g (0.044mol), maleic anhydride 2.16g (0.022mol), pure water (180g). Dissolve thoroughly at 200r / min. Increase temperature to 60℃, introduce nitrogen into the reaction system, keep nitrogen atmosphere and continue stirring. Add ammonium persulfate 0.17g, keep nitrogen atmosphere and start polymerization. Stop stirring after 2h and stop heating to obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride, and separate and purify the product to obtain A2 0.5 .

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

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

[0087] Example 3

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

[0089] S1-1: In a three-necked flask, add N-isopropyl acrylamide 3.72 g (0.033 mol), maleic anhydride 3.24 g (0.033 mol), and pure water (180 g). Dissolve thoroughly at a rotation speed of 200 r / min. Increase the temperature to 60°C, and introduce nitrogen into the reaction system. Keep the nitrogen atmosphere and continue stirring. Add ammonium persulfate 0.17 g, keep the nitrogen atmosphere, and start the polymerization reaction. Stop stirring after 2 h, stop heating, and obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride. Separate and purify the product to obtain A3 0.5 .

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

[0091] S1-3: Filter the crude product solution of A3 to remove excess unreacted melamine. Then increase the temperature to 60°C, and the hydrogel of the product A3 will precipitate. Finally, obtain the temperature-pH dual-responsive hydrogel A3.

[0092] Example 4

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

[0094] S1-1: In a three-necked flask, add N-isopropyl acrylamide 2.48 g (0.022 mol), maleic anhydride 4.32 g (0.044 mol), and pure water (180 g). Dissolve thoroughly at a rotation speed of 200 r / min. Increase the temperature to 60°C, and introduce nitrogen into the reaction system. Keep the nitrogen atmosphere and continue stirring. Add ammonium persulfate 0.17 g, keep the nitrogen atmosphere, and start the polymerization reaction. Stop stirring after 2 h, stop heating, and obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride. Separate and purify the product to obtain A4 0.5 .

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

[0096] S1-3: Filter the crude product solution of A4 to remove excess unreacted melamine. Then increase the temperature to 60°C, and the hydrogel of the product A4 will precipitate. Finally, obtain the temperature-pH dual-responsive hydrogel A4.

[0097] Example 5

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

[0099] S1-1: In a three-necked flask, add N-isopropyl acrylamide 4.97 g (0.044 mol), maleic anhydride 0.54 g (0.0055 mol), and pure water (150 g). Dissolve thoroughly at a rotation speed of 200 r / min. Increase the temperature to 60°C, and introduce nitrogen into the reaction system. Keep the nitrogen atmosphere and continue stirring. Add ammonium persulfate 0.14 g, keep the nitrogen atmosphere, and start the polymerization reaction. Stop stirring after 2 h, stop heating, and obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride. Separate and purify the product to obtain A5 0.5 .

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

[0101] S1-3: Filter the crude product solution of A5 to remove excess unreacted melamine. Then increase the temperature to 60°C, and the hydrogel product A5 will precipitate. Finally, obtain the temperature-pH dual-responsive hydrogel A5.

[0102] Example 6

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

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

[0105] S1-1: In a three-necked flask, add N-isopropyl acrylamide 4.97 g (0.044 mol), maleic anhydride 1.08 g (0.011 mol), and pure water (150 g). Dissolve thoroughly at a rotation speed of 200 r / min. Increase the temperature to 60°C, and introduce nitrogen into the reaction system. Keep the nitrogen atmosphere and continue stirring. Add ammonium persulfate 0.14 g, keep the nitrogen atmosphere, and start the polymerization reaction. Stop stirring after 2 h, stop heating, and obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride. Separate and purify the product to obtain A1 0.5 .

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

[0107] S1-3: The crude product solution of A1 is filtered to remove excess unreacted melamine; the temperature is then raised to 60°C, and the hydrogel of product A1 precipitates, resulting in the final temperature-pH dual-responsive hydrogel A1.

[0108] (2) A1 (2 g) prepared is dissolved in pure water (90 g), and dissolved thoroughly;

[0109] (3) 2 g of sodium bicarbonate is added and dissolved thoroughly;

[0110] (4) 6 g of ammonium polyphosphate is added and dissolved thoroughly, resulting in a temperature-pH dual-responsive hydrogel fire extinguishing agent.

[0111] Example 7

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

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

[0114] S1-1: In a three-necked flask, N-isopropyl acrylamide 4.97 g (0.044 mol), maleic anhydride 2.16 g (0.022 mol), and pure water (180 g) are added. Dissolve thoroughly at a rotation speed of 200 r / min. Increase the temperature to 60°C, and introduce nitrogen into the reaction system to maintain a nitrogen atmosphere and continue stirring. Add 0.17 g of ammonium persulfate, maintain a nitrogen atmosphere, and start the polymerization reaction. After 2 h, stop stirring and heating to obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride, which is separated and purified to obtain A2 0.5 .

[0115] S1-2: The product A2 0.5 is dissolved in pure water, 2.8 g (about 0.022 mol) of melamine is added, and stirred at a rotation speed of 200 r / min for 12 h to fully react, obtaining a crude product solution of A2.

[0116] S1-3: The crude product solution of A2 is filtered to remove excess unreacted melamine; the temperature is then raised to 60°C, and the hydrogel of product A2 precipitates, resulting in the final temperature-pH dual-responsive hydrogel A2.

[0117] (2) A2 (2 g) prepared is dissolved in pure water (90 g), and dissolved thoroughly;

[0118] (3) 2 g of sodium bicarbonate is added and dissolved thoroughly;

[0119] (4) 6 g of ammonium polyphosphate is added and dissolved thoroughly, resulting in a temperature-pH dual-responsive hydrogel fire extinguishing agent.

[0120] Example 8

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

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

[0123] S1-1: In a three-necked flask, add N-isopropyl acrylamide 4.97g (0.044mol), maleic anhydride 1.08g (0.011mol), and pure water (150g). Dissolve thoroughly at a rotation speed of 200r / min. Increase the temperature to 60℃, and introduce nitrogen into the reaction system, keep the nitrogen atmosphere and continue stirring. Add ammonium persulfate 0.14g, keep the nitrogen atmosphere, and start the polymerization reaction. Stop stirring after 2h, stop heating, and obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride. Purify the product to obtain A1 0.5 .

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

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

[0126] (2) Dissolve A1 (1g) prepared separately in pure water (91g) and dissolve thoroughly;

[0127] (3) Add 2g of sodium bicarbonate and dissolve thoroughly;

[0128] (4) Add 6g of ammonium polyphosphate and dissolve thoroughly to obtain the temperature-pH dual-responsive hydrogel fire extinguishing agent.

[0129] Example 8

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

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

[0132] S1-1: In a three-necked flask, add N-isopropyl acrylamide 4.97g (0.044mol), maleic anhydride 1.08g (0.011mol), pure water (150g). Dissolve thoroughly at a rotation speed of 200r / min. Increase the temperature to 60℃, introduce nitrogen into the reaction system, keep the nitrogen atmosphere and continue stirring. Add ammonium persulfate 0.14g, keep the nitrogen atmosphere and start the polymerization reaction. Stop stirring after 2h and stop heating to obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride. Separate and purify the product to obtain A1 0.5 .

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

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

[0135] (2) Dissolve the prepared A1 (4g) in pure water (88g) respectively and dissolve thoroughly;

[0136] (3) Add 2g of sodium bicarbonate and dissolve thoroughly;

[0137] (4) Add 6g of ammonium polyphosphate and dissolve thoroughly to obtain the temperature-pH dual-responsive hydrogel fire extinguishing agent.

[0138] Example 10

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

[0140] (1) Prepare the temperature-pH dual-responsive hydrogel A1

[0141] S1-1: In a three-necked flask, add N-isopropyl acrylamide 4.97g (0.044mol), maleic anhydride 1.08g (0.011mol), pure water (150g). Dissolve thoroughly at a rotation speed of 200r / min. Increase the temperature to 60℃, introduce nitrogen into the reaction system, keep the nitrogen atmosphere and continue stirring. Add ammonium persulfate 0.14g, keep the nitrogen atmosphere and start the polymerization reaction. Stop stirring after 2h and stop heating to obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride. Separate and purify the product to obtain A1 0.5 .

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

[0143] S1-3: the crude product solution of A1 is filtered to filter out excess unreacted melamine; then warmed to 60℃, the hydrogel of product A1 will precipitate, finally to obtain temperature-pH dual responsive hydrogel A1.

[0144] (2) respectively dissolve A1 (2g) prepared in pure water (91g), fully dissolved;

[0145] (3) add 1g of sodium bicarbonate and fully dissolve;

[0146] (4) add 6g of ammonium polyphosphate and fully dissolve to obtain temperature-pH dual responsive hydrogel fire extinguishing agent.

[0147] Example 11

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

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

[0150] S1-1: add N-isopropyl acrylamide 4.97g (0.044mol), maleic anhydride 1.08g (0.011mol), pure water (150g) in a three-necked flask. Fully dissolved at 200 r / min. Increase the temperature to 60℃, blow nitrogen into the reaction system, keep the nitrogen atmosphere and continue to stir. Add 0.14g of ammonium persulfate, keep the nitrogen atmosphere, and start the polymerization reaction. Stop stirring after 2h, stop heating, and obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride, and then separate and purify the product to obtain A1 0.5 .

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

[0152] S1-3: the crude product solution of A1 is filtered to filter out excess unreacted melamine; then warmed to 60℃, the hydrogel of product A1 will precipitate, finally to obtain temperature-pH dual responsive hydrogel A1.

[0153] (2) respectively dissolve A1 (2g) prepared in pure water (88g), fully dissolved;

[0154] (3) add 4g of sodium bicarbonate and fully dissolve;

[0155] (4) Again add 6g of ammonium polyphosphate to fully dissolve, and obtain a temperature-pH dual-responsive hydrogel fire extinguishing agent.

[0156] Example 12

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

[0158] (1) Dissolve A1 (2g) prepared in Example 1 in pure water (93g) respectively, and fully dissolve;

[0159] (2) Again add 2g of sodium bicarbonate to fully dissolve;

[0160] (3) Again add 3g of ammonium polyphosphate to fully dissolve, and obtain a temperature-pH dual-responsive hydrogel fire extinguishing agent.

[0161] Example 13

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

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

[0164] S1-1: Add N-isopropyl acrylamide 4.97g (0.044mol), maleic anhydride 1.08g (0.011mol), and pure water (150g) in a three-necked flask. Fully dissolve at a stirring speed of 200r / min. Increase the temperature to 60℃, and introduce nitrogen into the reaction system to maintain a nitrogen atmosphere and continue stirring. Add ammonium persulfate 0.14g, maintain a nitrogen atmosphere, and start the polymerization reaction. Stop stirring after 2h, stop heating, and obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride. Purify the product to obtain A1 0.5 .

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

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

[0167] (2) Dissolve A1 (2g) prepared in Example 1 in pure water (93g) respectively, and fully dissolve;

[0168] (3) Again add 2g of sodium bicarbonate to fully dissolve;

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

[0170] Pure water

[0171] Comparative Example 2

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

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

[0174] S1-1: Add N-isopropyl acrylamide 4.97 g (0.044 mol), maleic anhydride 1.08 g (0.011 mol), and pure water (150 g) into a three-necked flask. Fully dissolve at a stirring speed of 200 r / min. Increase the temperature to 60°C, introduce nitrogen into the reaction system, and continue to stir under a nitrogen atmosphere. Add ammonium persulfate 0.14 g, maintain the nitrogen atmosphere, and start the polymerization reaction. Stop stirring after 2 h, stop heating, and obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride. Purify the product to obtain A1 0.5 .

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

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

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

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

[0179] Comparative Example 3

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

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

[0182] S1-1: In a three-necked flask, add N-isopropyl acrylamide 4.97g (0.044mol), maleic anhydride 1.08g (0.011mol), pure water (150g). Dissolve thoroughly at a rotation speed of 200r / min. Raise the temperature to 60℃, introduce nitrogen into the reaction system, keep the nitrogen atmosphere and continue stirring. Add ammonium persulfate 0.14g, keep the nitrogen atmosphere and start the polymerization reaction. Stop stirring after 2h and stop heating to obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride, separate and purify the product to obtain A1 0.5 .

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

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

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

[0186] (3) Add 6g of ammonium polyphosphate and fully dissolve to obtain the temperature-pH dual-responsive hydrogel fire extinguishing agent.

[0187] Comparative Example 4

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

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

[0190] S1-1: In a three-necked flask, add N-isopropyl acrylamide 4.97g (0.044mol), maleic anhydride 1.08g (0.011mol), pure water (150g). Dissolve thoroughly at a rotation speed of 200r / min. Raise the temperature to 60℃, introduce nitrogen into the reaction system, keep the nitrogen atmosphere and continue stirring. Add ammonium persulfate 0.14g, keep the nitrogen atmosphere and start the polymerization reaction. Stop stirring after 2h and stop heating to obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride, separate and purify the product to obtain A1 0.5 .

[0191] S1-2: Dissolve the product A1 0.5The product A1 is dissolved in pure water, melamine 1.4 g (about 0.011 mol) is added, and stirring is carried out at a rotation speed of 200 r / min for 12 h, and full reaction is obtained to obtain a crude product solution of A1.

[0192] S1-3: The crude product solution of A1 is filtered to filter out excess unreacted melamine; and then the temperature is increased to 60°C, and the hydrogel of the product A1 is precipitated, and finally a temperature-pH dual-responsive hydrogel A1 is obtained.

[0193] (2) The prepared A1 (2 g) is dissolved in pure water (90 g) and fully dissolved;

[0194] (3) 2 g of sodium bicarbonate is further added and fully dissolved;

[0195] (4) 2 g of water-soluble aluminum hydroxide is further added and fully dissolved to obtain a temperature-pH dual-responsive hydrogel fire extinguishing agent.

[0196] Comparative Example 5

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

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

[0199] S1-1: In a three-necked flask, N-isopropyl acrylamide 4.97 g (0.044 mol), maleic anhydride 1.08 g (0.011 mol), and pure water (150 g) are added. Fully dissolved at a rotation speed of 200 r / min. Increase the temperature to 60°C, and introduce nitrogen into the reaction system to maintain a nitrogen atmosphere and continue stirring. Add 0.14 g of ammonium persulfate, maintain a nitrogen atmosphere, and start the polymerization reaction. After 2 h, stop stirring and stop heating to obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride, and the product is separated and purified to obtain A1 0.5 .

[0200] S1-2: The product A1 0.5 is dissolved in pure water, melamine 1.4 g (about 0.011 mol) is added, and stirring is carried out at a rotation speed of 200 r / min for 12 h, and full reaction is obtained to obtain a crude product solution of A1.

[0201] S1-3: The crude product solution of A1 is filtered to filter out excess unreacted melamine; and then the temperature is increased to 60°C, and the hydrogel of the product A1 is precipitated, and finally a temperature-pH dual-responsive hydrogel A1 is obtained.

[0202] (2) The prepared A1 (2 g) is dissolved in pure water (93 g) and fully dissolved;

[0203] (3) 2 g of sodium bicarbonate is further added and fully dissolved;

[0204] (4) Again add 1g of water-soluble aluminum hydroxide to fully dissolve, to obtain a temperature-pH dual-responsive hydrogel fire extinguishing agent.

[0205] Comparative Example 6

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

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

[0208] S1-1: In a three-necked flask, add N-isopropyl acrylamide 4.97g (0.044mol), maleic anhydride 1.08g (0.011mol), and pure water (150g). Dissolve thoroughly at a rotation speed of 200r / min. Increase the temperature to 60℃, and introduce nitrogen into the reaction system, and continue to stir under a nitrogen atmosphere. Add ammonium persulfate 0.14g, maintain a nitrogen atmosphere, and start the polymerization reaction. Stop stirring after 2h, stop heating, and obtain the polymerization product of N-isopropyl acrylamide and maleic anhydride, and separate and purify the product to obtain A1 0.5 .

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

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

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

[0212] (3) Again add 2g of sodium bicarbonate to fully dissolve;

[0213] (4) Again add 4g of water-soluble aluminum hydroxide to fully dissolve, to obtain a temperature-pH dual-responsive hydrogel fire extinguishing agent.

[0214] 1. Characterization of hydrogel product

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

[0216] Figure 3 The infrared contrast spectrum of N-isopropyl acrylamide (NIPAM) and A1 0.5 is shown in Figure 2: 3500cm -1The stretching vibration peak of -OH in the carboxyl group on maleic acid is 1213 cm -1 The stretching vibration peak of -CO in the carboxyl group is at 1657cm; the stretching vibration peak of -C=O bond is at 1657cm -1 At the same time, both NIPAM and carboxyl groups contain -C=O bonds, and no difference can be seen in the infrared image, indicating that N-isopropylacrylamide and maleic acid have been successfully polymerized.

[0217] Figure 4 Display A1 0.5 , A1, melamine infrared spectrum comparison: melamine and A1 0.5 A1 obtained after the reaction has a more obvious stretching vibration peak of melamine. -1 The stretching vibration peak corresponding to the -NH bond is 1435 cm -1 The stretching vibration peaks of -CN bond are corresponding to these two peaks in A1 0.5 It is also reflected in the infrared spectrum, which is now more obvious; 801cm -1 The peak at 1400 cm corresponds to the out-of-plane bending vibration of the triazine ring. -1 The stretching vibration peak corresponding to -CH3 is 1303cm -1 The -CN- stretching vibration peak in the amide bond (-CONH-) is 1303 cm -1 The vibration peak of the methyl group in the isopropyl group is at 1657 cm-1, and the stretching vibration peak of the -C=O bond at other positions is at 1657 cm-1. -1 At 1650-1700cm -1 The -C=N- bond at the position overlaps. The infrared spectrum shows that melamine has already overlapped with A1 0.5 The reaction successfully generated A1.

[0218] Figure 5 shows the D2O H 1 The peaks at 5.78ppm, 5.68ppm, and 5.30ppm in the NMR spectrum show that the three H 1 Peak; The peak at 5.73 ppm shows H on -NH 1 Peak; The peak at 3.54ppm shows the H of -CH(CH3)2-CH- group 1 Peak; The peak at 0.73ppm shows the H of the -CH(CH3)2 -CH3 group 1 peak.

[0219] Figure 6 shows A1 0.5 D2O H 1 NMR, compared with the D2O H of N-isopropylacrylamide 1NMR spectrum, a new peak at 6.29 ppm corresponding to H on -COOH 1 Peak. It shows that N-isopropyl acrylamide and maleic acid are successfully polymerized.

[0220] Figure 7 shows the D2O H 1 NMR spectrum. Compared with A1 0.5 D2O H 1 NMR spectrum, a new peak at 6.29 ppm corresponding to H on -COOH 1 Peak disappears, a new peak at 5.49 ppm corresponding to -NH3 + H (spatial steric hindrance on the polymer molecular chain, delaying -NH3 + quickly exchange with D2O) 1 Peak. It shows that -NH2 successfully forms a stable amino acid zwitterion (-COO 0.5 -NH3 - ) structure with -COOH of A1 + , successfully generating A1 sample.

[0221] From the analysis of the test results of infrared and nuclear magnetic resonance, it can be seen that the intermediate product A1 0.5 and the final product A1 generated in Example 1 are successfully synthesized.

[0222] In addition, GPC analysis of A1 shows that the number average molecular weight Mn is approximately 4.16*10 5 , the polymer dispersion index PIN is 1.40, and the polymerization degree n is approximately 864.

[0223] 2, the influence of the molar ratio of N-isopropyl acrylamide and maleic anhydride on the pH response and yield of hydrogel

[0224] Examples 1-5 differ only in the ratio of N-isopropyl acrylamide and maleic anhydride, and the yield of the product and its state at pH 3-4 are shown in Table 1.

[0225] Table 1: Yield of products of Examples 1-5 and their state at pH 3-4, 10-11

[0226]

[0227]

[0228] As can be seen from Table 1, the yield of Examples 1, 2 and 5 is higher (more than 85%); white flocculent substances are produced at pH 3-4 in Examples 1, 2 and 5.

[0229] The reason for the analysis is as follows: the change of the pH-sensitive property of the hydrogel is mainly due to the different ionization of the pH-sensitive groups (amino, carboxyl) in different pH solutions, thereby showing its pH sensitivity. In this experiment, the product A generated contains the amino acid zwitterion (-COO - -NH3 + ) structure, and the carboxylate is protonated under acidic conditions to generate a carboxyl group (-COOH). The carboxyl group is pH-sensitive under acidic conditions, and therefore the pH sensitivity of the polymer mainly depends on the carboxyl content of the product A in S1-1. 0.5 For the copolymer of N-isopropyl acrylamide and maleic anhydride, as the content of maleic anhydride increases, the content of the carboxyl group (-COOH) in the copolymer increases: when the molar ratio of N-isopropyl acrylamide and maleic anhydride is 8:1 (Example 5), the influence of the amide bond (-CONH-) and the carboxyl group (-COOH) is equivalent, so the sample in Example 5 can generate flocculent gel material under acidic conditions (pH between 3 and 4) or alkaline conditions (pH between 10 and 11), and the polymer molecules are gradually precipitated. Continue to increase the molar ratio of maleic anhydride, the molar ratio of N-isopropyl acrylamide and maleic anhydride in Example 1 is 4:1, and the molar ratio of the two in Example 2 is 2:1, so the influence of the carboxyl group (-COOH) plays a leading role, and the polymer molecules are gradually precipitated under acidic conditions (pH between 3 and 4) in Example 1 and Example 2, and flocculent gel material is generated; under alkaline conditions, the carboxyl group is in a dissociated state and no gel is generated. Continue to increase the molar ratio of maleic anhydride, the molar ratio of N-isopropyl acrylamide and maleic anhydride in Example 3 is 1:1, and the molar ratio of the two in Example 2 is 1:2, and the content of the carboxyl group (-COOH) continues to increase, and the weak acidic conditions are insufficient to precipitate the polymer molecules, and the solution of the sample is clear and transparent; under alkaline conditions, the carboxyl group is in a dissociated state and no gel is generated.

[0230] Therefore, the ratio of N-isopropyl acrylamide and maleic anhydride seriously affects the pH response of the hydrogel and the yield of the product. After analysis, when the molar ratio of N-isopropyl acrylamide and maleic anhydride is 8:1 to 2:1, especially 4:1, the product can achieve pH response at pH between 3 and 4, and the yield of the product is relatively high.

[0231] 3. Temperature response test of the temperature-pH dual-responsive hydrogel prepared in Examples 1-5

[0232] The temperature response test method and results of the temperature-pH dual-responsive hydrogel prepared in Examples 1-5 are as follows:

[0233] The critical solution temperature (LCST) of the A1 sample is 49℃. 5g of A1 is dissolved in 100ml of pure water, and a picture of "Xinyuanqingcai" is placed below. The solution is transparent, as shown in Fig. a. The sample is placed in an oven at 60℃ for 10min, and then taken out and placed above the picture of "Xinyuanqingcai". A lot of flocculation is observed in the solution, as shown in Fig. b. Thus, the temperature-pH dual-responsive hydrogel A1 prepared in Example 1 can realize temperature response and generate gel at a higher temperature. Figure 2 Figure 2 The critical solution temperature (LCST) of the A1 sample is 49℃. 5g of A1 is dissolved in 100ml of pure water, and a picture of "Xinyuanqingcai" is placed below. The solution is transparent, as shown in Fig. a. The sample is placed in an oven at 60℃ for 10min, and then taken out and placed above the picture of "Xinyuanqingcai". A lot of flocculation is observed in the solution, as shown in Fig. b. Thus, the temperature-pH dual-responsive hydrogel A1 prepared in Example 1 can realize temperature response and generate gel at a higher temperature.

[0234] The critical solution temperature (LCST) of the A1 sample is 49℃. 5g of A1 is dissolved in 100ml of pure water, and a picture of "Xinyuanqingcai" is placed below. The solution is transparent, as shown in Fig. a. The sample is placed in an oven at 60℃ for 10min, and then taken out and placed above the picture of "Xinyuanqingcai". A lot of flocculation is observed in the solution, as shown in Fig. b. Thus, the temperature-pH dual-responsive hydrogel A1 prepared in Example 1 can realize temperature response and generate gel at a higher temperature.

[0235] The temperature-pH dual-responsive hydrogel prepared in the application can realize temperature response because the temperature sensitivity of poly-N-isopropylacrylamide-maleic anhydride is derived from the hydrophilic-hydrophobic reversible transformation of the molecular structure thereof at temperature change. At low temperature, the amide group (-CONH-) and the amino acid zwitterion (-COO - -NH3 + ) of the side chain of the molecule form hydrogen bonds with water molecules; the hydrophobic isopropyl group (-CH(CH3)2) around forms an ordered structure of water molecules (hydration layer), which makes the polymer chain hydrated and stretched, and dissolved in water; when the temperature is above the critical solution temperature (LCST), the thermal motion destroys the hydrogen bonds, and the hydrophobic isopropyl group (-CH(CH3)2) dominates, leading to the dehydration and collapse of the polymer and precipitation.

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

[0237] When the temperature is below the LCST, the amide group (-CONH-) and the amino acid zwitterion (-COO - -NH3 + ​) and water molecules form strong hydrogen bonds (exothermic process, ΔH < 0), which stabilizes the polymer in a dissolved state in water; water molecules form an ordered "iceberg structure" (hydration layer) around the hydrophobic isopropyl groups, resulting in a decrease in the entropy of the system (ΔS < 0). At this time, |ΔH| > |TΔS|, ΔG < 0, and the polymer dissolves in water.

[0238] When the temperature is equal to the LCST, the increase in temperature causes the thermal motion of water molecules to intensify, and the hydrogen bonds gradually break (endothermic process, ΔH > 0); the "iceberg structure" collapses, and the water molecules change from order to disorder (ΔS > 0), and the increase in entropy becomes the dominant factor. At the LCST, ΔH = TΔS, ΔG = 0, and the system reaches a critical state of dissolution and precipitation.

[0239] When the temperature is higher than the LCST, the water molecules completely separate from the polymer chains, and the entropy of the system is maximized (ΔS > 0), but the enthalpy cost of breaking the hydrogen bonds (ΔH > 0) cannot offset the entropy gain. TΔS > ΔH, ΔG > 0, the polymer chains dehydrate and aggregate, and phase separation occurs.

[0240] 4. pH response test of hydrogel

[0241] The pH response test method and results of the temperature-pH dual-responsive hydrogel prepared in Examples 1-5 of the present application are as follows:

[0242] About 2 / 3 of the water gel solution was added to the specimen bottle, and the concentration of the water gel was 2wt%. 0.1mol / L HCl solution was added to the water gel solution to create an acidic environment, 0.1mol / L NaOH solution was added to create an alkaline environment, and pure water was added as a neutral environment, and the pH was adjusted to 3.5, 10.5, and 7.0, respectively, to observe the state of the water gel solution.

[0243] Taking Example 1 as an example, the test results are as shown in Figure 1 . Figure 1 a indicates that the state of the water gel solution at pH = 7.0 is a colorless transparent liquid; Figure 1 b indicates that the state of the water gel solution at pH = 10.5 is a colorless transparent liquid; Figure 1 c indicates that the state of the water gel solution at pH = 3.5, where obvious white flocculent matter is produced. Thus, it is shown that the temperature-pH dual-responsive hydrogel A1 prepared in Example 1 can achieve pH response.

[0244] The change in the pH sensitivity of the hydrogel is mainly due to the different ionization of the pH-sensitive groups (amino, carboxyl) in different pH solutions, thereby showing its pH sensitivity. In this experiment, the product A contains zwitterions (-COO - -NH3 +) structure, the carboxylate group is protonated under acidic conditions to form a carboxyl group (-COOH), which is pH sensitive under acidic conditions. As the pH value decreases, the H + ions increase, the hydrophilicity of the carboxyl group decreases, and the polymer molecules gradually precipitate, eventually forming a flocculent gel material. The results of Examples 3 and 4 show that when the molar ratio of maleic anhydride in the comonomer is greater than 50%, the pH at 3-4 is not sufficient to cause precipitation, resulting in a flocculent gel.

[0245] 5. Effect of pH stabilizer and water-soluble flame retardant in fire extinguishing agent on its fire extinguishing performance

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

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

[0248] (2) Place the wood block in the middle of an iron disc with a diameter of 15 cm and a height of 5 cm, and place the disc in a stainless steel tray with dimensions of 100 cm * 60 cm * 5 cm to prevent the sprayed fire extinguishing agent from flying everywhere. Use an igniter to ignite the wood block, and the ignition time is 5 seconds with a flame height of 5 cm.

[0249] (3) Allow the wood block to burn for 20 seconds until it is fully burned. Use a water sprayer to spray the fire extinguishing agent at a flow rate of 100 ml / min.

[0250] (4) After the flame is completely extinguished, continue to spray the fire extinguishing agent for 5 seconds.

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

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

[0253] Table 2: Results of fire extinguishing agent tests

[0254] Sample Extinguishing time / s Rekindling time / s Remarks Example 6 11 No rekindling No black smoke produced Example 7 12 No rekindling No black smoke produced Comparative Example 1 35 55 Black smoke produced Comparative Example 2 23 No rekindling No black smoke produced Comparative Example 4 17 No rekindling No black smoke produced

[0255] As can be seen from Table 2, Comparative Example 1 (pure water) reignited after extinguishing the fire and produced a large amount of black smoke. Examples 6, 7, Comparative Examples 2 and 4 did not reignite and did not produce black smoke. In addition, Figure 8a, 8b, 8c respectively show the situation after fire extinguishing of Comparative Example 1, Comparative Example 4, Example 6. It can be seen that using pure water (Comparative Example 1) for fire extinguishing, the fire extinguishing time is the longest, and the fire rekindles, and it can be seen that Figure 8 a The whole is burned black, and the burning is serious. Using Comparative Example 4 for fire extinguishing, the fire extinguishing time is reduced, and the fire does not rekindle, and it can be seen that Figure 8 b The wood block is burned around, showing black, and the middle part shows white, which is not burned; the surface of the wood block can be seen white gelatinous material after fire extinguishing of the fire extinguishing agent and residues after gelatin evaporation; compared with Comparative Example 1, it can be seen that the fire extinguishing effect of Comparative Example 4 is improved. Using Example 6 for fire extinguishing, the fire extinguishing time continues to decrease, and the fire does not rekindle, and it can be seen that Figure 8 c The wood block is burned on both sides, showing black, and most of the middle part shows white, which is not burned; the surface of the wood block can be seen white gelatinous material after fire extinguishing of the fire extinguishing agent and a small amount of residues after gelatin evaporation; compared with Comparative Example 4, it can be seen that the fire extinguishing effect of Example 6 is further improved.

[0256] The reasons are as follows:

[0257] As shown in Table 2, Figure 8 It can be known that the fire extinguishing agent prepared in the present application can produce gel at high temperature, and the produced gel can play a role in isolating oxygen and reducing the discharge of flammable gas; the water gel and pH buffer in the fire extinguishing agent can neutralize the acidic gas (such as HF) produced by the combustion of the electrolyte, and prevent the generation of harmful gas and particulate matter.

[0258] Comparative Example 1 takes the longest time, which is because pure water can only rely on cooling and the generated water vapor to reduce the concentration of flammable gas to prevent combustion during the fire extinguishing process. The time taken by Comparative Example 2 is reduced by 34% compared with Comparative Example 1 (pure water), which shows that after adding the temperature-pH dual-responsive water gel, the fire extinguishing agent is sprayed on the surface of the burning object, and the produced water gel material plays a role in isolating combustion; however, the fire extinguishing time of Comparative Example 2 is greater than that of Comparative Example 4, Example 1 and Example 2, which is because there is no flame retardant added in Comparative Example 2. The fire extinguishing time of Example 6 is reduced by 69% compared with Comparative Example 1 (pure water), and the fire extinguishing time of Example 7 is reduced by 66% compared with Comparative Example 1 (pure water), and the fire extinguishing effect is good, which shows that the temperature-pH dual-responsive water gel cooperates with the flame retardant to make the fire extinguishing agent have good fire extinguishing effect. The fire extinguishing time of Example 6 is reduced by 51% compared with Comparative Example 4, which shows that although ammonium polyphosphate and water-soluble aluminum hydroxide are both water-soluble flame retardants, ammonium polyphosphate can also play a synergistic effect, and the flame retardant effect is stronger.

[0259] In addition, the inventors found that the pH buffer not only can be used to neutralize the acidic gas, but also can maintain the stability of the fire extinguishing agent. After placing the fire extinguishing agent prepared in Example 6 and Comparative Example 3 for a certain period of time, the fire extinguishing agent without adding sodium bicarbonate as the pH buffer reagent in Comparative Example 3 generated a white flocculent gel after 25 days, while the temperature-pH dual-responsive hydrogel fire extinguishing agent prepared in Example 6 did not flocculate after being placed for 6 months. This indicates that the pH buffer reagent can also prevent the flocculation of the hydrogel, thereby improving the stability of the fire extinguishing agent.

[0260] Through the above tests and analysis, it can be seen that the temperature-pH dual-responsive hydrogel fire extinguishing agent prepared by the present application can promote the generation of the gel state of the hydrogel due to the high temperature on the surface of the burning object or the generated acidic substances, thereby playing a role in blocking the combustible gas and preventing heat exchange; moreover, the pH buffer and the temperature-pH dual-responsive hydrogel can neutralize the acidic substances generated by burning, thereby reducing the generation of harmful gases; the pH buffer can also prevent the flocculation of the hydrogel, thereby improving the stability of the fire extinguishing agent; the addition of the flame retardant can play a role in capturing free radicals and can also generate a dense carbon layer, thereby playing a role in blocking the combustible gas and preventing heat exchange; the solvent in the solution is pure water, and the high latent heat of vaporization of pure water can play a good cooling effect. The temperature-pH dual-responsive hydrogel fire extinguishing agent of the present application can play a good fire extinguishing effect on the burning object generating acidic gas (such as a lithium battery) through the synergistic effect of the components.

[0261] 6, Effect of the amount of each component of the fire extinguishing agent on its fire extinguishing performance

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

[0263] Table 3 Fire extinguishing results of the fire extinguishing agents

[0264] Sample Extinguishing time / s Rekindling time / s Remarks Example 6 11 No rekindling No black smoke produced Example 8 21 No rekindling No black smoke produced Example 9 10 No rekindling No black smoke produced with slight obstruction of water outlet Example 10 14 No rekindling Little black smoke produced Example 11 11 No rekindling No black smoke produced Example 12 16 No rekindling No black smoke produced Example 13 11 No rekindling No black smoke produced Comparative Example 4 17 No rekindling No black smoke produced Comparative Example 5 22 No rekindling No black smoke produced Comparative Example 6 / / Obstruction of water outlet after 3 seconds of water spraying, unable to spray extinguishing agent

[0265] The amount of each component of the fire extinguishing agents of Examples 8-13 and Comparative Examples 4-7 is changed based on Example 6: in Example 8, the amount of hydrogel A1 is reduced by 50%, in Example 9, the amount of hydrogel A1 is increased by 100%; in Example 10, the amount of sodium bicarbonate is reduced by 50%, in Example 11, the amount of sodium bicarbonate is increased by 100%; in Example 12, the amount of ammonium polyphosphate is reduced by 50%, in Example 13, the amount of ammonium polyphosphate is increased by 50%. Compared with the sample in Comparative Example 4, in Comparative Example 5, the amount of aluminum hydroxide is reduced by 50%, and in Comparative Example 7, the amount of aluminum hydroxide is increased by 100%.

[0266] From Example 8 and Example 9, it can be seen that if the amount of temperature-pH dual responsive hydrogel is reduced by 50%, the fire extinguishing effect will become poor, because the barrier of the temperature-pH dual responsive hydrogel to heat and mass exchange is reduced, and the fire extinguishing effect of the fire extinguishing agent is reduced; if the amount of temperature-pH dual responsive hydrogel is increased by 100%, the viscosity of the fire extinguishing agent will increase, which may block the delivery pipeline or water outlet and hinder the fire extinguishing work.

[0267] From Example 10 and Example 11, it can be seen that if the amount of pH stabilizer sodium bicarbonate is reduced by 50%, the fire extinguishing effect will become poor, and a small amount of black smoke will be generated, which indicates that the reduction of the amount of sodium bicarbonate will reduce the neutralization ability of the fire extinguishing agent to acidic toxic gases; if the amount of pH stabilizer sodium bicarbonate is increased by 100%, the fire extinguishing time will not be shortened, and the fire extinguishing ability of the fire extinguishing agent will not be effectively improved.

[0268] From Example 12 and Example 13, it can be seen that if the amount of fire retardant ammonium polyphosphate is reduced by 50%, the fire extinguishing time will be prolonged, and the fire extinguishing ability of the fire extinguishing agent will be reduced, because the reduction of the amount of fire retardant will reduce the capture effect of free radicals and the ability to generate carbon layer, resulting in poor fire extinguishing effect of the fire extinguishing agent; if the amount of fire retardant ammonium polyphosphate is increased by 50%, the fire extinguishing time will not be shortened, and the fire extinguishing ability of the fire extinguishing agent will not be effectively improved.

[0269] From Comparative Example 5 and Comparative Example 6, it can be seen that if the amount of fire retardant soluble aluminum hydroxide is reduced by 50%, the fire extinguishing time will be prolonged, and the fire extinguishing ability of the fire extinguishing agent will be reduced; if the amount of soluble aluminum hydroxide is increased by 50%, a precipitate will be generated in the fire extinguishing agent, the water outlet will be blocked, and the fire extinguishing agent cannot be sprayed, which hinders the fire extinguishing work.

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

[0271] The above merely illustrates the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, which should be covered within the protection scope of the present application.

Claims

1. A temperature-pH dual responsive hydrogel, characterized in that, The general formula is: wherein 100 < n < 1000. 2.The temperature-pH dual-responsive hydrogel of claim 1, characterized in that, The intermediate product is prepared by controlling the molar ratio of N-isopropyl acrylamide and maleic anhydride, and then reacting the intermediate product with melamine in pure water as solvent. 3.The temperature-pH dual-responsive hydrogel of claim 1, wherein, The minimum response temperature of the temperature-pH dual-responsive hydrogel is 38℃. 4.The temperature-pH dual-responsive hydrogel of claim 1, wherein, The temperature-pH dual-responsive hydrogel responds when the pH is between 3 and 4.

5. The method for preparing a temperature-pH dual responsive hydrogel according to any one of claims 1-4, characterized in that, The preparation method comprises the following steps: S1-1: After mixing N-isopropyl acrylamide, maleic anhydride and water thoroughly, an initiator is added, a polymerization reaction occurs, and the product is separated and purified to obtain intermediate product A 0.5 ; S1-2: The intermediate product A 0.5 is dissolved in water, melamine is added, stirred for a certain time, and a crude product solution of A is obtained. S1-3: filtering the crude product solution of A, and then increasing the temperature to make the temperature-pH dual-responsive hydrogel of product A precipitate.

6. The production method according to claim 5, wherein The molar ratio of N-isopropyl acrylamide to maleic anhydride in step S1-1 is 8:1-2:

1.

7. The preparation method according to claim 5, characterized in that The amount of initiator used in step S1-1 is 0.05%-1% of the total moles of N-isopropyl acrylamide and maleic anhydride.

8. The preparation method according to claim 5, characterized in that The polymerization reaction temperature in S1-1 is 50-80℃, and the polymerization reaction is carried out under inert gas protection.

9. The preparation method according to claim 5, characterized in that In S1-2, the molar ratio of melamine to maleic anhydride is 1:10-2:1, and / or the reaction is carried out at room temperature; and / or the stirring speed is 100-600r / min, and the reaction time is 4-36h.

10. A temperature-pH dual responsive hydrogel extinguishing agent, characterized by, The fire extinguishing agent comprises the temperature-pH dual-responsive hydrogel of any one of claims 1-4 or the temperature-pH dual-responsive hydrogel prepared by the preparation method of any one of claims 5-9.

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