Fire-retardant heat-sensitive self-crosslinking hydrogel fire extinguishing agent and preparation method thereof

Abstract

The present application relates to the technical field of fire-fighting materials, and particularly relates to a fire-resistant heat-sensitive self-crosslinking hydrogel fire extinguishing agent and a preparation method thereof. In view of the limited fire resistance effect of the existing hydrogel fire extinguishing agent, especially for high-temperature fire sources, the existing hydrogel fire extinguishing agent is difficult to achieve good fire resistance effect, the present application discloses a fire-resistant heat-sensitive self-crosslinking hydrogel fire extinguishing agent, in terms of mass percentage of each component: arylsulfonyl carboxymethyl cellulose: 0.05-1%; first thickening agent: 0.1-2%; second thickening agent: 0.1-2%; surfactant: 0.3-3%; first fire retardant: 0.5-5%; second fire retardant: 0.5-5%; and the rest is a solvent. The above-mentioned fire-resistant heat-sensitive self-crosslinking hydrogel fire extinguishing agent can be used for rapid extinguishing and afterglow inhibition of high-temperature (<=700 DEG C) fire sources. And good fire resistance effect is achieved.

Description

Technical Field

[0001] This invention relates to the field of fire protection materials technology, and in particular to a fire-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent and its preparation method. Background Technology

[0002] In recent years, with the rapid development of industrialization and urbanization, various fire accidents have occurred frequently, especially high-temperature fire scenarios such as catastrophic wildfires, oil fires, and chemical fires, posing a severe challenge to traditional fire extinguishing technologies. Currently, commonly used fire extinguishing agents mainly include water-based extinguishing agents, foam extinguishing agents, dry powder extinguishing agents, and gaseous extinguishing agents, but these traditional fire extinguishing materials all have significant limitations in practical applications. For example, traditional fluorinated foams contain substances such as perfluorooctane sulfonic acid (PFOS), which have persistent organic pollutant characteristics and cause long-term environmental damage.

[0003] Hydrogel fire extinguishing agents, as a new type of fire extinguishing agent, mainly extinguish fires by absorbing heat and cooling down due to their high water content. They have the advantages of being environmentally friendly and precise in extinguishing fires. However, their fire-retardant effect is limited, especially for high-temperature fire sources, where existing hydrogel fire extinguishing agents are difficult to achieve good fire-retardant effects. Summary of the Invention

[0004] In view of the above analysis, the present invention aims to provide a heat-sensitive self-crosslinking hydrogel fire extinguishing agent and its preparation method, in order to solve at least one of the following problems: the fire-retardant effect of existing hydrogel fire extinguishing agents is limited, especially for high-temperature fire sources, existing hydrogel fire extinguishing agents are difficult to achieve good fire-retardant effect; or for oil or organic solvent fires, existing hydrogel fire extinguishing agents have limited adsorption and flame-retardant effects.

[0005] In a first aspect, the present invention discloses a flame-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent, comprising the following components by mass percentage: arylsulfonated carboxymethyl cellulose: 0.05–1%; first thickener: 0.1–2%; second thickener: 0.1–2%; surfactant: 0.3–3%; first flame retardant: 0.5–5%; second flame retardant: 0.5–5%; the remaining components are solvents.

[0006] Specifically, the first thickener is selected from one or more of hydroxyethyl cellulose, methyl cellulose, and polyvinyl alcohol;

[0007] The second thickener is selected from one or more of carboxymethyl cellulose, hydroxypropyl cellulose, and polyacrylamide.

[0008] The surfactant is selected from one or more of α-alkenylsulfonic acid, sodium dodecyl sulfate, Tween, and Span.

[0009] The first flame retardant is selected from phosphorus-based flame retardants or nitrogen-based flame retardants;

[0010] The second flame retardant is selected from nano-metal oxides.

[0011] Preferably, the first flame retardant is ammonium polyphosphate, and the second flame retardant is nano-silica; the mass ratio of the nano-silica to the ammonium polyphosphate is 1.0:(1.0-2.0).

[0012] Further, the mass ratio of the arylsulfonated carboxymethyl cellulose: the first thickener: the second thickener is (0.5-1.0):(1.0-2.0):(1.0-2.0).

[0013] It is worth noting that the preparation method of the arylsulfonated carboxymethyl cellulose includes: mixing carboxymethyl cellulose with an acid-binding agent under nitrogen atmosphere and stirring to dissolve; adding arylsulfonyl chloride solution dropwise under temperature control; after the reaction is completed, concentrating under reduced pressure, pulping, filtering and vacuum drying to obtain arylsulfonated carboxymethyl cellulose.

[0014] Secondly, this invention discloses a method for preparing the above-mentioned flame-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent, comprising the following steps:

[0015] Step 1: Under nitrogen atmosphere, carboxymethyl cellulose is mixed with an acid-binding agent and stirred to dissolve; under temperature control, arylsulfonyl chloride solution is added dropwise. After the reaction is completed, the mixture is concentrated under reduced pressure, pulped, filtered and dried under vacuum to obtain arylsulfonated carboxymethyl cellulose.

[0016] Step 2: Mix the first thickener, the second thickener, arylsulfonated carboxymethyl cellulose and solvent, stir under controlled temperature, then add the surfactant, the first flame retardant and the second flame retardant in sequence, stir until uniformly dispersed, and cool to room temperature to obtain the flame-retardant heat-sensitive self-adhesive hydrogel fire extinguishing agent.

[0017] Specifically, in step 1, the mass-to-volume ratio of carboxymethyl cellulose, acid-binding agent, and arylsulfonyl chloride is (10.0–25.0) g : (80–100) mL : (2.0–4.0) g.

[0018] In step 1, the temperature control conditions are -5 to 25°C, the arylsulfonyl chloride solution is added dropwise, the reaction temperature is -5 to 25°C, and the reaction time is 8 to 24 hours; and / or,

[0019] In step 2, the temperature control conditions are 39–46°C, and the stirring time under these conditions is 2–5 hours.

[0020] Thirdly, this invention discloses the application of the above-mentioned flame-retardant heat-sensitive self-crosslinking hydrogel fire extinguishing agent in rapid fire suppression and reignition inhibition in high-temperature fire scenarios.

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

[0022] 1. This invention discloses a flame-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent composed of arylsulfonated carboxymethyl cellulose, a first thickener, a second thickener, a surfactant, a first flame retardant, a second flame retardant, and a solvent. The arylsulfonated carboxymethyl cellulose, by introducing lipophilic functional groups such as p-toluenesulfonyl groups, possesses a hydrophilic-hydrophobic bifunctional structure, exhibiting both lipophilic and water solubility. The first thickener has good water solubility. Therefore, the first thickener and the arylsulfonated carboxymethyl cellulose can exert a good synergistic effect, making it suitable for both non-oil-based and oil-based or organic solvent-based fire sources. By using two different types of cellulose—the first and second thickeners—a good thickening effect can be achieved, ensuring the formation of a dense gel network structure, enabling the slow release of the first and second flame retardants, continuously exerting a flame-retardant effect in the fire scene, and significantly reducing the risk of reignition. The fire-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent provided by this invention is suitable for rapid extinguishing and reignition suppression of high-temperature fires, and also provides excellent fire-retardant properties.

[0023] 2. In this invention, the first flame retardant and the second flame retardant are used in combination to achieve a synergistic flame retardant effect. The first flame retardant decomposes, absorbs heat and cools down, and releases inert gas to dilute oxygen. The second flame retardant forms an amorphous glassy layer at high temperature, which isolates oxygen and heat transfer, effectively achieving the flame retardant effect. Compared with traditional halogenated flame retardants, this compound system does not contain heavy metals or toxic and harmful substances.

[0024] 3. This invention uses the addition of surfactants to increase the compatibility of the flame retardant compound system and effectively exert the flame retardant effect of the flame retardant.

[0025] 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

[0026] 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.

[0027] Figure 1 The 1H NMR spectrum of p-toluenesulfonated carboxymethyl cellulose;

[0028] Figure 2(a) is a SEM image of the extinguishing agent prepared in Example 1 before phase change;

[0029] Figure 2 (b) is a SEM image of the fire extinguishing agent prepared in Example 1 after phase change;

[0030] Figure 3 (a) shows the fire extinguishing agent used in Example 1, applied to a wooden block.

[0031] Figure 3 (b) in the diagram is a schematic diagram of ignition using a cartridge flamethrower;

[0032] Figure 3 (c) in the diagram is a schematic diagram of the extinguishing agent after it has been completely ignited;

[0033] Figure 3 (d) in the diagram represents the complete ignition of the extinguishing agent and the subsequent cleaning up of the ash produced during combustion;

[0034] Figure 4 (a) in the figure shows water being sprinkled on the wooden block in Comparative Example 6;

[0035] Figure 4 (b) shows the burning of the wood block after 4 minutes of continuous flame spraying. 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] To address the limited fire-retardant effect of existing hydrogel fire extinguishing agents, especially against high-temperature fire sources, this invention discloses a fire-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent, comprising the following components by mass percentage: arylsulfonated carboxymethyl cellulose: 0.05–1%; first thickener: 0.1–2%; second thickener: 0.1–2%; surfactant: 0.3–3%; first flame retardant: 0.5–5%; second flame retardant: 0.5–5%; the remaining components are solvents.

[0038] The fire-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent provided by this invention is suitable for rapid extinguishing and reignition suppression of high-temperature (≤700℃) fire sources. Furthermore, it achieves excellent fire-retardant effects for fire sources with temperatures of 1300–1500℃ emitted by cartridge flamethrowers.

[0039] The thermosensitive self-crosslinking hydrogel fire extinguishing agent exhibits temperature-responsive characteristics, with a critical phase transition temperature ranging from 30°C to 150°C. When the temperature of the fire extinguishing agent is below 129.5°C, the viscosity of the solution is very low. Therefore, the thermosensitive self-crosslinking hydrogel fire extinguishing agent can be easily sprayed onto the fire point using fire-fighting equipment for fire extinguishing. Due to the high temperature at the fire scene, the temperature of the hydrogel rises. When the temperature exceeds the critical temperature, the viscosity increases significantly. Above 129.5°C, the temperature rise causes the solution to transform into a non-flowing hydrogel, achieving rapid adhesion, rapid cooling, and fire source encapsulation for fire extinguishing and flame retardancy.

[0040] The arylsulfonated carboxymethyl cellulose is selected from p-toluenesulfonated carboxymethyl cellulose, benzenesulfonated carboxymethyl cellulose, and naphthalenesulfonated carboxymethyl cellulose. By introducing lipid-soluble functional groups such as p-toluenesulfonyl group, the arylsulfonated carboxymethyl cellulose has a hydrophilic-hydrophobic bifunctional structure, which is both lipid-soluble and water-soluble, and is therefore suitable for oil or organic solvent-based ignition sources.

[0041] The preparation method of the arylsulfonated carboxymethyl cellulose includes: mixing carboxymethyl cellulose with an acid-binding agent under nitrogen atmosphere and stirring to dissolve; adding arylsulfonyl chloride solution dropwise under controlled temperature (-5 to 25)℃, wherein the mass-volume ratio of carboxymethyl cellulose, acid-binding agent and arylsulfonyl chloride is (10.0 to 25.0) g: (80 to 100) mL: (2.0 to 4.0) g, and reacting at a reaction temperature of (-5 to 25)℃ for 8 to 24 hours, followed by vacuum concentration, pulping, filtration and vacuum drying to obtain arylsulfonated carboxymethyl cellulose.

[0042] Taking the preparation of p-toluenesulfonated carboxymethyl cellulose as an example, under nitrogen atmosphere, carboxymethyl cellulose and an acid-binding agent are mixed and stirred to dissolve. Under controlled temperature (-5 to 25)℃, p-toluenesulfonyl chloride solution is added dropwise. The mass-volume ratio of carboxymethyl cellulose, acid-binding agent, and p-toluenesulfonyl chloride is (10.0 to 25.0) g: (80 to 100) mL: (2.0 to 4.0) g. Under reaction temperature (-5 to 25)℃, after reacting for 8 to 24 hours, the mixture is concentrated under reduced pressure, pulped, filtered, and dried under vacuum to obtain p-toluenesulfonated carboxymethyl cellulose.

[0043] Taking the preparation of benzenesulfonated carboxymethyl cellulose as an example, the preparation method is the same as that for the preparation of p-toluenesulfonated carboxymethyl cellulose, except that benzenesulfonyl chloride solution is added dropwise under controlled temperature (-5 to 25)℃.

[0044] Taking the preparation of naphthalenesulfonated carboxymethyl cellulose as an example, the preparation method is the same as that for the preparation of p-toluenesulfonated carboxymethyl cellulose, except that naphthalenesulfonyl chloride solution is added dropwise under controlled temperature (-5~25)℃.

[0045] The first thickener is selected from one or more of hydroxyethyl cellulose, methyl cellulose, and polyvinyl alcohol; the hydroxyethyl cellulose used in this invention has a viscosity of 3000-4000 mPa, such as 3000 mPa, 3500 mPa, or 4000 mPa; the methyl cellulose has a viscosity of 4500-5500 mPa, such as 4500 mPa, 5000 mPa, or 5500 mPa; and the polyvinyl alcohol has a viscosity of 900-1100 mPa, such as 900 mPa, 1000 mPa, or 1100 mPa.

[0046] The first thickener has good water solubility and can form a moderately entangled network in aqueous solution, ensuring good fluidity of the extinguishing agent at room temperature, while rapidly forming a high-strength gel at high temperatures; a dense polymer film is formed on the gel surface, locking moisture in the gel structure and delaying moisture evaporation. On the other hand, the flame-retardant, heat-sensitive, self-crosslinking hydrogel extinguishing agent provided by this invention uses arylsulfonated carboxymethyl cellulose, which is both fat-soluble and water-soluble, while the first thickener has good water solubility. Therefore, the first thickener and arylsulfonated carboxymethyl cellulose can exert a good synergistic effect, making it suitable for both non-oil-based and oil-based or organic solvent-based fire sources.

[0047] The second thickener is selected from one or more of carboxymethyl cellulose, hydroxypropyl cellulose, and polyacrylamide. The carboxymethyl cellulose used in this invention has a viscosity of 4500–5500 mPa, such as 4500 mPa, 5000 mPa, or 5500 mPa; the hydroxypropyl cellulose has a viscosity of 4500–5500 mPa, such as 4500 mPa, 5000 mPa, or 5500 mPa; and the polyacrylamide has a viscosity of 3000–4000 mPa, such as 3000 mPa, 3500 mPa, or 4000 mPa. The second thickener has high viscosity, enabling the slow release of the flame retardant and providing continuous flame retardant action in a fire, significantly reducing the risk of reignition.

[0048] Because different cellulose structures form different gel networks during the crosslinking process, the combination of arylsulfonated carboxymethyl cellulose with two different celluloses, namely the first thickener and the second thickener, can ensure the formation of a dense gel network structure, achieve slow release of flame retardant, and continuously exert flame retardant effect in the fire scene, greatly reducing the risk of reignition.

[0049] The arylsulfonated carboxymethyl cellulose accounts for 0.05-1.0% of the mass of the extinguishing agent, such as 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.50%, 0.55%, 0.60%, 0.65%, 0.70%, 0.75%, 0.80%, 0.90%, or 1.0%, preferably 0.1-0.2%.

[0050] The first thickener accounts for 0.1% to 2% of the mass of the extinguishing agent, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, or 2.0%, preferably 0.2% to 0.4%.

[0051] The second thickener constitutes 0.1-2% of the extinguishing agent by mass, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, or 2.0%, preferably 0.2-0.4%.

[0052] The combined use of the first and second thickeners can optimize the construction of the gel network through synergistic effects, forming a stable and uniform three-dimensional network structure. This ensures rapid cross-linking response when heated and improves the overall flexibility and mechanical strength of the gel, avoiding structural defects that may be caused by a single thickener.

[0053] The mass ratio of the arylsulfonated carboxymethyl cellulose, the first thickener, and the second thickener is (0.5–1.0, e.g., 0.5, 1.0): (1.0–2.0, e.g., 1.0, 1.5, 2.0): (1.0–2.0, e.g., 1.0, 1.5, 2.0), preferably 0.5:1.0:1.0. This ensures that the system reaches the critical gel concentration at high temperatures, forming a dense three-dimensional network structure to achieve effective fire extinguishing against high-temperature fire sources. Simultaneously, it exhibits high fluidity at low temperatures, ensuring ease of operation when spraying or sprinkling the extinguishing agent, while also promoting uniform dispersion of the flame retardant and maximizing its flame-retardant effect.

[0054] The surfactant can be anionic, such as α-alkenylsulfonic acid or sodium dodecyl sulfate; or nonionic, such as Tween or Span; or amphoteric surfactant; preferably α-alkenylsulfonic acid; the surfactant accounts for 0.3-3.0% of the mass of the fire extinguishing agent, for example 0.3%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 2.0%, 2.5%, 3.0%, preferably 0.4-0.6%; the addition of the surfactant can increase the compatibility of the flame retardant compound system, and can also effectively reduce surface tension and maintain gel stability.

[0055] The first flame retardant is selected from phosphorus-based flame retardants, such as ammonium polyphosphate, melamine polyphosphate, and phosphate esters; or nitrogen-based flame retardants; when the first flame retardant is ammonium polyphosphate, the ammonium polyphosphate decomposes to produce phosphoric acid and ammonia, phosphoric acid promotes carbonization, and ammonia dilutes the oxygen concentration;

[0056] The second flame retardant is selected from nano metal oxides, such as nano silica and nano alumina; the second flame retardant forms an amorphous glassy layer at high temperature, which isolates oxygen and heat transfer. On the other hand, the nanoscale size effect of the nano metal oxide enhances the mechanical strength of the gel.

[0057] Specifically, the first flame retardant accounts for 0.5% to 5.0% of the mass of the extinguishing agent, such as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 2.0%, 2.5%, 3.0%, 3.4%, 3.5%, 3.6%, 3.7%, 4.0%, 4.5%, 5.0%, preferably 0.8% to 1.5%.

[0058] The second flame retardant accounts for 0.5% to 5.0% of the mass of the extinguishing agent, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 2.0%, 2.5%, 3.0%, 3.4%, 3.5%, 3.6%, 3.7%, 4.0%, 4.5%, 5.0%, preferably 0.8% to 1.5%.

[0059] Preferably, the first flame retardant is ammonium polyphosphate, and the second flame retardant is nano-silica;

[0060] The mass ratio of nano-silica to ammonium polyphosphate is 1.0g:(1.0-2.0)g, such as 1.0g:1.0g, 1.0g:1.5g, 1.0g:2.0g; preferably 1.0g:1.0g. When nano-silica and ammonium polyphosphate are compounded at 1.0g:1.0g, the synergistic flame-retardant effect of the two can be maximized, the negative impact on the performance of the substrate can be minimized, and the optimal balance between cost and efficiency can be achieved. It can also improve dispersion compatibility and optimize char quality. The improvement of char quality can improve the fire-retardant effect of the fire extinguishing agent. The equal proportion of the two flame retardants allows them to fully leverage their respective advantages, forming a dual flame retardant mechanism in both the condensed and gas phases. On the one hand, they complement each other, covering a wider range of combustion inhibition pathways. For example, the first flame retardant decomposes, absorbs heat, and cools down, releasing inert gases to dilute oxygen, while the second flame retardant forms an amorphous glassy layer at high temperatures, isolating oxygen and heat transfer. On the other hand, the equal proportions ensure uniform dispersion in the gel system, avoiding imbalances in flame retardant efficiency caused by excessively high or low local concentrations. This results in a stable and efficient flame retardant barrier, significantly extending the flame retardant time of the material and reducing the risk of reignition.

[0061] The solvent is deionized water, an ethanol-water mixture, or other polar solvents, with deionized water being the preferred solvent.

[0062] This invention discloses the application of a flame-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent in rapid fire suppression and reignition inhibition in high-temperature fire scenarios; the high-temperature fire scenarios include:

[0063] Flammable liquid fires (oils, organic solvents);

[0064] Electrical fires (lithium battery, data center);

[0065] Fires involving solid combustible materials (forests, urban buildings);

[0066] Chemical fire (leaking of flammable chemicals).

[0067] The fire-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent provided by this invention has the core working principle of forming a heat-sensitive, self-crosslinking hydrogel by arylsulfonated carboxymethyl cellulose, a first thickener, and a second thickener. The controlled release of the fire extinguishing agent is achieved by utilizing the temperature sensitivity of arylsulfonated carboxymethyl cellulose, the first thickener, and the second thickener. Specifically, under normal or low temperature conditions, the molecular chains of arylsulfonated carboxymethyl cellulose, the first thickener, and the second thickener in the hydrogel remain in an extended state, enabling them to absorb a large amount of water and swell, forming a porous gel with a three-dimensional network structure. At this time, the first flame retardant and the second flame retardant are stably encapsulated in the gel network. When the ambient temperature rises to the critical phase transition temperature, the molecular chain structure of the arylsulfonated carboxymethyl cellulose, the first thickener, and the second thickener in the hydrogel undergoes drastic changes, rapidly dehydrating and shrinking, and carbonizing to form a carbon layer. The network pores close, thereby releasing the first and second flame retardants loaded inside. Taking the compound of nano-silica and ammonium polyphosphate as a flame retardant as an example, the ammonium polyphosphate decomposes upon heating to produce phosphoric acid and metaphosphoric acid, further catalyzing the dehydration and carbonization of cellulose. The nano-silica is uniformly dispersed in the carbon layer, further improving the density and strength of the carbon layer, making the carbon layer denser. It can not only insulate heat and oxygen but also prevent the release of flammable gases and slow down the heating rate of the material.

[0068] Taking the fire extinguishing agent prepared in Example 1 as an example, the SEM image before phase change is as follows: Figure 2 As shown in (a), the hydrogel system exhibits dispersed, loosely aggregated particles with clear boundaries and a uniform microstructure, representing the initial stable state morphology of the material; the SEM images after the phase transition are shown in Figure (a). Figure 2 As shown in (b), the hydrogel system evolves into a distinct network structure with complex pore morphology and significant surface fusion. The flame retardant forms a dotted support structure, reflecting the microstructural reshaping and morphological transformation caused by combustion.

[0069] This invention discloses a method for preparing a flame-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent, comprising the following steps:

[0070] Step 1: Under nitrogen atmosphere, carboxymethyl cellulose is mixed with an acid-binding agent and stirred to dissolve; under temperature control, arylsulfonyl chloride solution is added dropwise. After the reaction is completed, the mixture is concentrated under reduced pressure, pulped, filtered and dried under vacuum to obtain arylsulfonated carboxymethyl cellulose.

[0071] Step 2: Mix the first thickener, the second thickener, arylsulfonated carboxymethyl cellulose and solvent, stir under controlled temperature, then add the surfactant, the first flame retardant and the second flame retardant in sequence, stir until uniformly dispersed, and cool to room temperature to obtain the flame-retardant heat-sensitive self-adhesive hydrogel fire extinguishing agent.

[0072] The general formula for the chemical reaction in step 1 is:

[0073]

[0074] in

[0075] The preferred formulation of this invention is p-toluenesulfonyl.

[0076] Specifically, in step 1, the acid-binding agent is pyridine, triethylamine, diisopropylethylamine, or 4-dimethylaminopyridine, preferably pyridine. Pyridine has good solubility for cellulose and combines with the HCl generated in the reaction to form pyridine hydrochloride, so no additional neutralizing agent is needed.

[0077] In step 1, the mass-to-volume ratio of carboxymethyl cellulose, acid-binding agent, and aryl sulfonyl chloride (such as p-toluenesulfonated carboxymethyl cellulose, benzenesulfonated carboxymethyl cellulose, and naphthalenesulfonated carboxymethyl cellulose) is (10.0–25.0) g : (80–100) mL : (2.0–4.0) g. Controlling this range ensures that the cellulose is fully dissolved, maintains reaction efficiency, suppresses side reactions while precisely controlling the degree of cellulose acylation, and effectively simplifies the post-processing flow.

[0078] Specifically, in step 1, the mass-to-volume ratio of carboxymethyl cellulose, acid-binding agent, and arylsulfonyl chloride is (10.0–25.0, e.g., 10.0, 15.0, 18.0, 20.0, 25.0) g : (80–100, e.g., 80, 85, 90, 95, 100) mL : (2.0–4.0, e.g., 2.0, 2.5, 3.0, 3.5, 4.0) g.

[0079] Preferably, in step 1, the mass-to-volume ratio of carboxymethyl cellulose, acid-binding agent, and arylsulfonyl chloride is 10.0g:100mL:2.0g.

[0080] In step 1, the mass concentration of the arylsulfonyl chloride solution is (0.1-0.5) g / mL. The advantage of controlling it within this range is that it can reduce operational risks while ensuring reaction efficiency and reducing side reactions.

[0081] In step 1, the temperature control temperature is (-5 to 25)℃, such as (0 to 10)℃, (2 to 12)℃, or (-1 to 9)℃. The temperature control temperature of (-5 to 25)℃ can ensure a stable reaction process and reduce the generation of by-products through precise temperature control, while avoiding the safety risks caused by excessively high temperature leading to a rapid increase in reaction temperature, or the slow reaction rate and surge in energy consumption caused by excessively low temperature. Among them, 0℃ to 10℃ is the preferred temperature control range.

[0082] The solvent for the aryl sulfonyl chloride solution in step 1 is anhydrous acetonitrile, dichloromethane, tetrahydrofuran, or dimethyl sulfoxide.

[0083] The reaction time in step 1 is 8 to 24 hours, such as 8 hours, 10 hours, 11 hours, 11.5 hours, 12 hours, 13 hours, 14 hours, 16 hours, 18 hours, 20 hours, and 24 hours. If the reaction time is too long, it will lead to a surge in energy consumption, and if it is too short, it will result in a large amount of raw material residue due to insufficient reaction. The preferred reaction time is 12 to 18 hours.

[0084] The solvent used in the pulping process in step 1 is acetone or ethyl acetate, preferably acetone; the volume ratio of the solvent used for pulping to the volume of cellulose is 1.0 g: (50.0~100) mL; insufficient solvent will result in residual byproducts such as pyridine in the product, while excessive use will cause solvent waste and increase the cost of subsequent waste liquid treatment; the preferred amount of pulping solvent is 1.0 g: 50.0 mL.

[0085] In step 1, the vacuum drying temperature is set at 50℃ to 80℃. The advantage of this temperature range is that it controls the temperature to prevent product degradation while ensuring drying efficiency. The drying time is 8 to 12 hours.

[0086] The mass-to-volume ratio of the first thickener, the second thickener, arylsulfonated carboxymethyl cellulose, the surfactant, the first flame retardant, the second flame retardant, and the solvent is (0.75-7.1)g : (0.75-7.1)g : (0.35-3.6)g : (1.5-10.0)g : (3.4-14.0)g : (3.4-14.0)g : (190-333)mL;

[0087] Specifically, the mass-to-volume ratio of the first thickener, the second thickener, arylsulfonated carboxymethyl cellulose, the surfactant, the first flame retardant, the second flame retardant, and the solvent is (0.75-7.1, e.g., 0.75, 0.8, 0.9, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 6.0, 7.1) g : (0.75-7.1, e.g., 0.75, 0.80, 0.9, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 6.0, 7.1) g : (0.35-3.6, e.g., 0.35, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, ... 2.0, 2.5, 3.0, 3.6) g: (1.5-10.0, e.g., 1.5, 2.0, 3.0, 5.0, 6.0, 8.0, 10.0) g: (3.4-14.0, e.g., 3.4, 3.5, 4.0, 5.0, 7.0, 10.0, 12.0, 14.0) g: (3.4-14.0, e.g., 3.4, 3.5, 4.0, 5.0, 7.0, 10.0, 12.0, 14.0) g: (190-333, e.g., 190, 200, 210, 220, 230, 240, 250, 260, 280, 300, 320, 330, 333) mL;

[0088] Preferably, the mass-volume ratio of the first thickener, the second thickener, arylsulfonated carboxymethyl cellulose, the surfactant, the first flame retardant, the second flame retardant, and the solvent is 1.0g:1.0g:0.5g:1.5g:3.4g:3.4g:333mL.

[0089] The temperature control in step 2 is (39-46)℃, such as (39-44)℃, (40-45)℃, or (41-46)℃. The advantage of this temperature range is that precise temperature control promotes thorough and uniform mixing of the components, avoiding gel denaturation due to excessively high temperatures or reduced efficiency due to excessively low temperatures. The preferred temperature is 40-45℃.

[0090] The stirring time under temperature control in step 2 is 2 to 5 hours, such as 2 hours, 2.5 hours, 3 hours, 4 hours, and 5 hours. The preferred stirring time under temperature control is 3 hours.

[0091] In step 2, after adding the surfactant, the stirring time is 1 to 3 hours; after adding the first flame retardant, the stirring time is 2 to 4 hours; after adding the second flame retardant, the stirring time is 2 to 4 hours. If the stirring time is too long, energy consumption will increase significantly and waste will result; if it is too short, it will be difficult to achieve uniform stirring.

[0092] In step 2, the formation process and principle of the thermosensitive self-crosslinking hydrogel are based on the synergistic effect of chemical crosslinking and physical action: the sulfonyl group of arylsulfonated carboxymethyl cellulose undergoes an esterification reaction with the cellulose hydroxyl group, forming irreversible chemical crosslinking points; the alkenyl group of α-alkenylsulfonic acid undergoes free radical polymerization with the cellulose molecular chain, further strengthening the network structure; nano-silica forms hydrogen bonds with cellulose through surface hydroxyl groups, and utilizes the nanoscale size effect to enhance the mechanical strength and temperature resistance of the gel. As the temperature increases, the pre-constructed crosslinking sites in the system accelerate the reaction, increasing the gel network density.

[0093] The flame-retardant test results show that when the critical temperature is reached, the gel transforms from a sol state into a solid state with high water retention and adhesion, achieving "thermal self-crosslinking" characteristics. This allows it to quickly solidify and adhere to the surface of the burning material in a high-temperature fire environment, exerting efficient heat insulation, cooling, and flame-retardant effects. In Examples 1-7, the extinguishing agents all exhibited excellent flame-retardant effects (flame-retardant time 6-10 minutes); Comparative Examples 1-6, due to the lack of key components, resulted in a significantly shortened flame-retardant time (1-3 minutes), especially Comparative Example 6 (pure water), which had almost no flame-retardant effect.

[0094] The fire extinguishing experiment results showed that the extinguishing agents in Examples 1-7 had an extinguishing time of approximately 12-28 seconds, with no reignition. The extinguishing times of Comparative Examples 1-6 were significantly longer, and all of them exhibited reignition. Among them, Comparative Example 6 (pure water) had an extinguishing time of >180 seconds and experienced violent reignition.

[0095] In the following specific embodiments, the p-toluenesulfonated carboxymethyl cellulose used in step 2 was prepared by referring to the method in step 1; the other raw materials and solvents in steps 1 and 2 were all from commercially available products.

[0096] Example 1

[0097] Step 1: 10.0 g of carboxymethyl cellulose and 100 mL of pyridine were added to a reaction flask. After purging with nitrogen, the mixture was stirred until dissolved. A 2 g solution of p-toluenesulfonyl chloride (dissolved in 20 mL of anhydrous acetonitrile) was slowly added dropwise at 0–10 °C, and the reaction was allowed to proceed for 12 hours. The pyridine was removed by concentration under reduced pressure. The residue was slurried with 100 mL of acetone for 30 min, filtered under reduced pressure, and washed with 500 mL of acetone. The filter cake was dried under vacuum at 50 °C for 10 hours to obtain 10.5 g of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC), which was a pale yellow powder. ¹H-NMR (400 MHz, DMSO-d6) δ 9.11–9.12 (d, 1H), δ 8.60 (s, 1H), δ 7.43–7.49 (m, 2H), δ 7.10–7.12 (d, 1H).

[0098] Step 2: Add 1.00g of hydroxyethyl cellulose, 1.00g of carboxymethyl cellulose, 0.50g of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC), and 333mL of deionized water to a reaction flask, and stir at 40-45℃ for 3 hours. Add 1.50g of α-alkenyl sulfonic acid (AOS) and stir for 2 hours. Add 3.40g of ammonium polyphosphate (APP), stir for 3 hours, then add 3.40g of nano-silica, stir for 3 hours, and cool to room temperature to obtain a heat-sensitive self-colloidal hydrogel fire extinguishing agent.

[0099] Example 2

[0100] Step 1: Add 20.0 g of carboxymethyl cellulose and 100 mL of triethylamine to a reaction flask. After purging with nitrogen, stir until dissolved. Slowly add 3 g of p-toluenesulfonyl chloride solution (dissolved in 50 mL of anhydrous dichloromethane) at a controlled temperature of -5℃ to 5℃, and react for 12 hours. Concentrate under reduced pressure to remove triethylamine. Pulverize the residue with 300 mL of acetone for 60 min, filter under reduced pressure, and wash with 1000 mL of acetone. Dry the filter cake under vacuum at 50℃ for 10 hours to obtain 18.5 g of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC) as a pale yellow powder.

[0101] Step 2: Add 1.00g of hydroxyethyl cellulose, 2.00g of carboxymethyl cellulose, 0.80g of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC), and 200mL of deionized water to a reaction flask, and stir at 40-45℃ for 2 hours. Add 3.00g of sodium dodecyl sulfate and stir for 5 hours. Add 3.50g of ammonium polyphosphate (APP) in batches, and stir for 3 hours. Then add 3.50g of nano-silica and stir for 6 hours. Cool to room temperature to obtain a heat-sensitive self-colloidal hydrogel fire extinguishing agent.

[0102] Example 3

[0103] Step 1: 25.0 g of carboxymethyl cellulose and 100 mL of N,N-isopropylethylamine were added to a reaction flask. After purging with nitrogen, the mixture was stirred until dissolved. A p-toluenesulfonyl chloride solution (3.5 g, dissolved in 60 mL of anhydrous dichloromethane) was slowly added dropwise at a controlled temperature of 10–25 °C, and the reaction was allowed to proceed for 14 hours. 800 mL of ethyl acetate was added to induce crystallization. The crystals were filtered, and the resulting solid was slurried with 350 mL of ethyl acetate for 75 min. The mixture was then filtered under reduced pressure and washed with 1200 mL of ethyl acetate. The filter cake was dried under vacuum at 55 °C for 12 hours to obtain 22.3 g of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC) as a pale yellow powder.

[0104] Step 2: Add 1.30g of carboxymethyl cellulose, 2.30g of hydroxyethyl cellulose, 0.65g of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC), and 230mL of deionized water to a reaction flask. Stir at 41-46℃ for 2.2 hours. Add 3.30g of sodium dodecyl sulfate and stir for 5.2 hours. Add 6.25g of melamine polyphosphate in batches and stir for 3.2 hours. Then add 6.25g of nano-silica and stir for 6.2 hours. Cool to room temperature to obtain a heat-sensitive self-adhesive hydrogel fire extinguishing agent.

[0105] Example 4

[0106] Step 1: Add 18.0 g of carboxymethyl cellulose and 85 mL of N,N-dimethylaniline to a reaction flask. After purging with nitrogen, stir until dissolved. Slowly add 2.8 g of p-toluenesulfonyl chloride solution (dissolved in 48 mL of anhydrous dichloromethane) at a controlled temperature of 20–25 °C, and react for 11.5 hours. Concentrate under reduced pressure to remove N,N-dimethylaniline. Pulverize the residue with 280 mL of acetone for 58 min, filter under reduced pressure, and wash with 1050 mL of acetone. Dry the filter cake under vacuum at 48 °C for 9.5 hours to obtain 16.8 g of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC) as a pale yellow powder.

[0107] Step 2: Add 2.50g of hydroxyethyl cellulose, 2.50g of hydroxypropyl methyl cellulose, 1.25g of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC), and 190mL of deionized water to a reaction flask, and stir at 39-44℃ for 4 hours. Add 2.10g of sodium dodecylbenzenesulfonate and stir for 3 hours. Add 5.25g of ammonium polyphosphate (APP) in batches, and stir for 4 hours. Then add 5.25g of alumina and stir for 3 hours. Cool to room temperature to obtain a heat-sensitive self-colloidal hydrogel fire extinguishing agent.

[0108] Example 5

[0109] The preparation method of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC) is the same as step 1 of Example 1.

[0110] 0.75 g of hydroxyethyl cellulose, 0.75 g of carboxymethyl cellulose, 0.35 g of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC), and 333 mL of deionized water were added to a reaction flask and stirred at 40–45 °C for 3 hours. 10.00 g of α-alkenyl sulfonic acid (AOS) was added and stirred for 2 hours. 14.00 g of ammonium polyphosphate (APP) was added and stirred for 3 hours. Then, 14.00 g of nano-silica was added and stirred for 3 hours. The mixture was then cooled to room temperature to obtain a heat-sensitive self-colloidal hydrogel fire extinguishing agent.

[0111] Example 6

[0112] The preparation method of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC) is the same as step 1 of Example 1.

[0113] 4.12 g of hydroxyethyl cellulose, 4.12 g of carboxymethyl cellulose, 2.06 g of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC), and 333 mL of deionized water were added to a reaction flask and stirred at 40–45 °C for 3 hours. 1.50 g of α-olefin sulfonic acid (AOS) was added and stirred for 2 hours. 3.40 g of ammonium polyphosphate (APP) was added and stirred for 3 hours. Then, 3.40 g of nano-silica was added and stirred for 3 hours. The mixture was then cooled to room temperature to obtain a thermosensitive self-colloidal hydrogel fire extinguishing agent.

[0114] Example 7

[0115] The preparation method of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC) is the same as step 1 of Example 1.

[0116] 7.01 g of hydroxyethyl cellulose, 7.01 g of carboxymethyl cellulose, 3.505 g of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC), and 333 mL of deionized water were added to a reaction flask and stirred at 40–45 °C for 3 hours. 1.50 g of α-olefin sulfonic acid (AOS) was added and stirred for 2 hours. 3.40 g of ammonium polyphosphate (APP) was added and stirred for 3 hours. Then, 3.40 g of nano-silica was added and stirred for 3 hours. The mixture was then cooled to room temperature to obtain a heat-sensitive self-colloidal hydrogel fire extinguishing agent.

[0117] Comparative Example 1

[0118] The preparation method of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC) is the same as step 1 of Example 1.

[0119] Add 1.00 g of hydroxyethyl cellulose, 1.00 g of carboxymethyl cellulose, and 333 mL of deionized water to a reaction flask, and stir at 40–45 °C for 3 hours. Add 1.50 g of α-alkenyl sulfonic acid (AOS) and stir for 2 hours. Add 3.40 g of ammonium polyphosphate (APP), stir for 3 hours, then add 3.40 g of nano-silica, stir for 3 hours, and cool to room temperature to obtain a heat-sensitive self-colloidal hydrogel fire extinguishing agent.

[0120] Comparative Example 2

[0121] The preparation method of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC) is the same as step 1 of Example 1.

[0122] 1.00 g of hydroxyethyl cellulose, 0.50 g of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC), and 333 mL of deionized water were added to a reaction flask and stirred at 40–45 °C for 3 hours. 1.50 g of α-olefin sulfonic acid (AOS) was added and stirred for 2 hours. 3.40 g of ammonium polyphosphate (APP) was added and stirred for 3 hours. Then, 3.40 g of nano-silica was added and stirred for 3 hours. The mixture was cooled to room temperature to obtain a heat-sensitive self-colloidal hydrogel fire extinguishing agent.

[0123] Comparative Example 3

[0124] The preparation method of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC) is the same as step 1 of Example 1.

[0125] 1.00 g of hydroxyethyl cellulose, 0.50 g of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC), and 333 mL of deionized water were added to a reaction flask and stirred at 40–45 °C for 3 hours. 1.50 g of α-olefin sulfonic acid (AOS) was added and stirred for 2 hours. 3.40 g of ammonium polyphosphate (APP) was added and stirred for 3 hours. Then, 3.40 g of nano-silica was added and stirred for 3 hours. The mixture was cooled to room temperature to obtain a heat-sensitive self-colloidal hydrogel fire extinguishing agent.

[0126] Comparative Example 4

[0127] The preparation method of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC) is the same as step 1 of Example 1.

[0128] 1.00 g of hydroxyethyl cellulose, 1.00 g of carboxymethyl cellulose, 0.50 g of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC), and 333 mL of deionized water were added to a reaction flask and stirred at 40–45 °C for 3 hours. Then, 3.40 g of ammonium polyphosphate (APP) was added and stirred for 3 hours. Next, 3.40 g of nano-silica was added and stirred for another 3 hours. The mixture was then cooled to room temperature to obtain a heat-sensitive self-colloidal hydrogel fire extinguishing agent.

[0129] Comparative Example 5

[0130] The preparation method of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC) is the same as step 1 of Example 1.

[0131] 1.00 g of hydroxyethyl cellulose, 1.00 g of carboxymethyl cellulose, 0.50 g of p-toluenesulfonated carboxymethyl cellulose (Tosyl-CMC), and 333 mL of deionized water were added to a reaction flask and stirred at 40–45 °C for 3 hours. 1.50 g of α-olefin sulfonic acid (AOS) was added and stirred for 2 hours. 3.40 g of ammonium polyphosphate (APP) was added, and after stirring for 3 hours, the mixture was cooled to room temperature to obtain a heat-sensitive self-colloidal hydrogel fire extinguishing agent.

[0132] Comparative Example 6

[0133] Use 333 mL of deionized water as the water-based fire extinguishing agent.

[0134] Experimental Example 1

[0135] Simulated burning wood construction:

[0136] Timber selection and pretreatment: Dry pine wood (moisture content ≤12%), with no bark or cracks on the surface to ensure even burning.

[0137] Dimensions: 100±5mm in length and width, 20mm in thickness.

[0138] Arrangement: Place the wooden blocks flat on the experimental table (stainless steel table).

[0139] Ignition source: Cartridge-type gas flamethrower.

[0140] Flame-retardant test:

[0141] Under environmental conditions of 29℃ air temperature and wind speed of 3-7 m / s, thirteen identical wooden blocks, each 100±5 mm in length and width and 20 mm in thickness (50±5 mm for each ignition point), were prepared and placed on a stainless steel experimental table. A cartridge-type flamethrower was used as the ignition source. After applying the extinguishing agent to the wooden blocks, the flamethrower nozzle was held directly over the center of the blocks and continuously sprayed until the extinguishing agent was completely burned. The thickness of the heat-sensitive self-crosslinking hydrogel extinguishing agent applied was 3-5 mm; in Comparative Example 6, 10 mL of water was used. The flame-retardant time after the extinguishing agent had completely burned was recorded.

[0142] Experimental results:

[0143] like Figure 3 As shown, after continuous spraying for 10 minutes, the center of the wood block coated with the heat-sensitive self-adhesive hydrogel fire extinguishing agent of Example 1 (the area covered by hydrogel) did not burn, the flame retardant time was ≥10 minutes, and the wood block remained intact.

[0144] The water-sprayed wood blocks ignited after about 1 minute, and the fire was intense. After 4 minutes of spraying, the wood blocks were burning as follows: Figure 4 As shown in (b) of the diagram.

[0145] The flame-retardant times of the extinguishing agents in Examples 1-7 and Comparative Examples 1-6 are shown in Table 1:

[0146] Table 1. Fire-retardant time of extinguishing agents in Examples 1-7 and Comparative Examples 1-6

[0147] sample Fire arresting time Remark Example 1 ≥10min Achieve effective fire resistance Example 2 8min Achieve effective fire resistance Example 3 9min Achieve effective fire resistance Example 4 7min Achieve effective fire resistance Example 5 6min Achieve effective fire resistance Example 6 8min Achieve effective fire resistance Example 7 9min Achieve effective fire resistance Comparative Example 1 2min arylsulfonated carboxymethyl cellulose Comparative Example 2 3min Free of primary thickener Comparative Example 3 3min Free of secondary thickener Comparative Example 4 2min Surfactant-free Comparative Example 5 3min Without nano-silica Comparative Example 6 1min pure water

[0148] Discussion of experimental results:

[0149] Experimental results show that the flame-retardant properties of the thermosensitive self-crosslinking hydrogel fire extinguishing agent are closely related to the synergistic effect of its components. In Examples 1-7, the fire extinguishing agent formulations containing arylsulfonated carboxymethyl cellulose, a first thickener, a second thickener, a surfactant, a first flame retardant, and a second flame retardant all exhibited excellent flame-retardant effects (flame-retardant time 6-10 minutes), with Example 1 showing the best performance (≥10 minutes). In contrast, Comparative Examples 1-6, lacking one of the following: arylsulfonated carboxymethyl cellulose, a first thickener, a second thickener, a surfactant, or nano-silica, resulted in a significantly shortened flame-retardant time (1-3 minutes), especially Comparative Example 6 (pure water), which showed almost no flame-retardant effect.

[0150] Experimental Example 2

[0151] Simulated construction of burning wood piles:

[0152] Timber selection and pretreatment: Dry pine wood (moisture content ≤12%), conforming to GB / T1931-2009 "Method for Determination of Moisture Content of Timber", with no bark or cracks on the surface to ensure uniform burning.

[0153] Dimensions: Diameter 50±5mm, Length 500±50mm (Refer to GB / T17658-2018 "Standard Wooden Sticks for Flammability Test").

[0154] Arrangement method: "Cross-grid stacking method" (according to Appendix A of GB / T 16172-2007): 4 pieces of wood per layer, placed orthogonally, stacked for a total of 5 layers, with a total height of approximately 300mm. The gap between layers is 20±2mm to ensure uniform ventilation.

[0155] Ignition source: Standard cellulose cotton sheet (GB / T 5454-1997 "Test for Burning Performance of Textiles"), placed at the center of the bottom of the pile.

[0156] Fire extinguishing experiment:

[0157] Under environmental conditions of 29°C and wind speed of 3–7 m / s, thirteen identical stacks of wood were constructed. Each stack consisted of 20 pieces of pine wood, each 500 ± 50 mm long and approximately 50 ± 5 mm in diameter, with a moisture content of 10%–12%. These were arranged in five layers on angle iron supports, and standard cellulose cotton sheets were used as ignition plates. The extinguishing agents described in Examples 1–7 and Comparative Examples 1–6 were used to extinguish the fires, and the extinguishing time and reignition events were recorded.

[0158] Experimental results:

[0159] The extinguishing time of the heat-sensitive self-adhesive hydrogel fire extinguishing agent in Example 1 was approximately 12 seconds, with no reignition observed. In contrast, Comparative Example 6 (pure water) extinguished the fire in >180 seconds, resulting in violent reignition.

[0160] The extinguishing time and reignition situation in Examples 1-7 and Comparative Examples 1-6 are shown in Table 1:

[0161] Table 1. Extinguishing time and reignition status of Examples 1-7 and Comparative Examples 1-6

[0162] sample Firefighting time reignition situation Example 1 12s none Example 2 18s none Example 3 15s none Example 4 22s none Example 5 28s none Example 6 20s none Example 7 16s none Comparative Example 1 ＞60s reignition Comparative Example 2 45s reignition Comparative Example 3 50s reignition Comparative Example 4 ＞60s reignition Comparative Example 5 40s reignition Comparative Example 6 ＞180s violent reignition

[0163] Discussion of experimental results:

[0164] Experimental results show that the heat-sensitive self-adhesive hydrogel fire extinguishing agent exhibits excellent fire extinguishing performance. Specifically, the fire extinguishing agent in Example 1 can rapidly extinguish a standard timber stack fire within 12 seconds, with a fire-retardant time ≥10 minutes. This invention can be widely applied to various scenarios such as forest fires and building fires.

[0165] 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 flame-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent, characterized in that, By mass percentage of each component: p-Toluenesulfonated carboxymethyl cellulose: 0.05~1%; First thickener: 0.1~2%; Second thickener: 0.1~2%; Surfactant: 0.3~3%; First flame retardant: 0.5~5%; Second flame retardant: 0.5~5%; The remaining components are solvents; The first thickener is selected from one or more of hydroxyethyl cellulose, methyl cellulose, and polyvinyl alcohol; The second thickener is selected from one or more of carboxymethyl cellulose, hydroxypropyl cellulose, and polyacrylamide; The first flame retardant is selected from phosphorus-based flame retardants or nitrogen-based flame retardants; The second flame retardant is selected from nano-metal oxides.

2. The flame-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent according to claim 1, characterized in that, The surfactant is selected from one or more of α-olefin sulfonic acid, sodium dodecyl sulfate, Tween, and Span.

3. The flame-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent according to claim 2, characterized in that, The first flame retardant is ammonium polyphosphate, and the second flame retardant is nano-silica; the mass ratio of the nano-silica to the ammonium polyphosphate is 1.0:(1.0-2.0).

4. The flame-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent according to any one of claims 1-3, characterized in that, The mass ratio of p-toluenesulfonated carboxymethyl cellulose: first thickener: second thickener is (0.5~1.0):(1.0~2.0):(1.0~2.0).

5. The flame-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent according to claim 4, characterized in that, The method for preparing p-toluenesulfonated carboxymethyl cellulose includes: mixing carboxymethyl cellulose with an acid-binding agent under nitrogen atmosphere and stirring to dissolve; adding aryl sulfonyl chloride solution dropwise under temperature control; after the reaction is completed, concentrating under reduced pressure, pulping, filtering and vacuum drying to obtain p-toluenesulfonated carboxymethyl cellulose.

6. A method for preparing a flame-retardant, heat-sensitive, self-crosslinking hydrogel fire extinguishing agent according to any one of claims 1-5, comprising the following steps: Step 1: Under nitrogen atmosphere, carboxymethyl cellulose and acid-binding agent are mixed and stirred to dissolve; under temperature control, aryl sulfonyl chloride solution is added dropwise. After the reaction is completed, the mixture is concentrated under reduced pressure, pulped, filtered and dried under vacuum to obtain p-toluenesulfonated carboxymethyl cellulose. Step 2: Mix the first thickener, the second thickener, p-toluenesulfonated carboxymethyl cellulose and solvent, stir under controlled temperature, then add the surfactant, the first flame retardant and the second flame retardant in sequence, stir until uniformly dispersed, and cool to room temperature to obtain the flame-retardant heat-sensitive self-adhesive hydrogel fire extinguishing agent.

7. The preparation method according to claim 6, characterized in that, In step 1, the mass-to-volume ratio of carboxymethyl cellulose, acid-binding agent, and arylsulfonyl chloride is (10.0~25.0) g: (80~100) mL: (2.0~4.0) g.

8. The preparation method according to claim 7, characterized in that, In step 1, the temperature control conditions are -5 to 25°C, the arylsulfonyl chloride solution is added dropwise, the reaction temperature is -5 to 25°C, and the reaction time is 8 to 24 hours; and / or, In step 2, the temperature control condition is 39~46℃, and the stirring time under the temperature control condition is 2~5 hours.

9. The application of the fire-retardant heat-sensitive self-crosslinking hydrogel fire extinguishing agent according to any one of claims 1-5 or the fire-retardant heat-sensitive self-crosslinking hydrogel fire extinguishing agent obtained by the preparation method according to any one of claims 6-8 in the rapid extinguishing and reignition suppression of high-temperature fire scenarios.

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