Preparation method of temperature response type hydrogel fire extinguishing agent

Abstract

The invention belongs to the field of novel fire extinguishing agents, and particularly relates to a preparation method of a temperature response type hydrogel fire extinguishing agent, which comprises the following steps: dissolving and uniformly mixing a temperature-sensitive agent, a flame retardant, a gelling agent and a cross-linking agent in water, and then adding an initiator to obtain a fire extinguishing aqueous solution; during fire extinguishing, an ignition point is heated to trigger the fire extinguishing water aqua to be gelatinized to cover the surface of a fire source, so that the effects of quickly cooling and isolating oxygen are achieved, and the fire extinguishing purpose is achieved. According to the hydrogel fire extinguishing agent, the gelation time can be adjusted by adjusting the concentration and temperature change of the flame retardant, the hydrogel fire extinguishing agent has very high flowability in a normal temperature state, resistance in a pipeline is reduced, the problem of pipeline blockage is further solved, and the hydrogel fire extinguishing agent has the advantages of being easy to prepare, convenient to use, high in fire extinguishing efficiency, resistant to after-combustion, low in smoke production rate, easy to clean after disasters and the like.

Description

Technical Field

[0001] The invention belongs to the field of novel fire extinguishing agents, and in particular relates to a method for preparing a temperature-responsive hydrogel fire extinguishing agent. Background Art

[0002] Fire is a very destructive and dangerous disaster. Once it occurs, it will pose a huge threat to the sustainable development of the national economy and ecological security. Fire extinguishing agents that efficiently suppress combustion play an irreplaceable role in preventing fires, ensuring personnel safety and improving fire extinguishing efficiency. With the advancement of science and technology and the enhancement of environmental awareness, the problems of traditional fire extinguishing agents such as dry powder, carbon dioxide, foam, etc. in terms of environmental protection, safety, and efficiency are becoming increasingly prominent. At present, water is still the most commonly used fire extinguishing agent, which has the advantages of low cost, environmental friendliness, and high specific heat capacity. However, water has strong fluidity and cannot reach the target position by floating with the wind. In addition, water has to pass through a high-temperature environment during the sprinkling process, causing part of the water to evaporate or directly gasify, which reduces the fire extinguishing efficiency in practical applications.

[0003] As a polymer material, hydrogel has excellent water retention, is safe and non-toxic, and can confine a large number of water molecules in its three-dimensional network space. At the same time, the adhesion of hydrogel enables it to stably adhere to the surface of other substances without falling off, and can be given flame retardant properties by modifying the polymer chain, copolymerizing with other hydrogels, and introducing flame retardants into the polymer network. In recent years, hydrogel has attracted widespread attention in the field of fire fighting as a new type of fire extinguishing material. However, due to its high viscosity and poor fluidity, it is easy to cause transportation difficulties during the fire fighting process, pipeline blockage and affect the spraying distance. It has certain limitations in the field of fire fighting and the fire fighting efficiency needs to be improved.

[0004] Therefore, developing a hydrogel fire extinguishing agent that can be flexibly delivered by adjusting the gelation temperature and time, has high fire extinguishing efficiency, resists re-ignition, and is easy to clean up after a disaster, so that it can effectively curb fires, is an urgent problem that needs to be solved at present. Summary of the invention

[0005] In view of the many deficiencies in the prior art, the present invention provides a method for preparing a temperature-responsive hydrogel fire extinguishing agent, and the specific steps are as follows: a temperature-sensitive agent, a flame retardant, a gelling agent, and a cross-linking agent are dissolved and mixed in water, and then an initiator is added to obtain a fire extinguishing agent solution, and when extinguishing a fire, the fire extinguishing agent is heated at the ignition point to trigger the gelation of the fire extinguishing agent and cover the surface of the fire source, which plays a role in rapid cooling and isolating oxygen, thereby achieving the purpose of extinguishing the fire. The hydrogel fire extinguishing agent can adjust the gelation time by adjusting the concentration and temperature change of the flame retardant, has strong fluidity at room temperature, reduces the resistance in the pipeline, and thus solves the problem of pipeline blockage, and has the advantages of simple preparation, easy use, high fire extinguishing efficiency, anti-reignition, low smoke production rate, and easy cleanup after the disaster.

[0006] The technical ideas of the present invention are as follows: The present invention uses a heat-induced cross-linked polymer and a thermosensitive agent to construct a composite hydrogel fire extinguishing agent. According to the Hofmeister sequence, a flame retardant containing a phosphate group is added to dehydrate the cellulose thermosensitive agent to control the sol-gel transition temperature, and then the sol state that flows at low temperatures is satisfied after being compounded with the heat-induced cross-linked polymer, which is convenient for transportation and storage and prevents pipeline blockage. At the same time, as the flame temperature increases, a high-viscosity gel state is formed at high temperature. After the water molecules in the composite hydrogel fire extinguishing agent are evaporated by heat, they form a barrier layer on the surface of the vegetation, inhibiting the transfer of the heat source and protecting the bottom combustibles from the influence of oxygen, thereby avoiding the occurrence of re-ignition.

[0007] The more specific technical solutions of the present invention are as follows: A method for preparing a temperature-responsive hydrogel fire extinguishing agent, the specific steps are as follows: (1) Dissolve the temperature-sensitive agent and flame retardant in water, heat and stir evenly, cool to room temperature, and place in a low temperature environment to obtain a clear and transparent suspension A; (2) dissolving the gelling agent and the cross-linking agent in the suspension A prepared in step (1) and stirring at room temperature for 0.5-12 h to obtain a solution B; (3) Add the initiator to the solution B prepared in step (2) and stir at room temperature for 0.5-6 h to obtain a temperature-responsive hydrogel fire extinguishing agent.

[0008] The temperature-responsive hydrogel fire extinguishing agent is heated at high temperature in the fire scene to form a hydrogel when in use, thereby achieving the purpose of extinguishing the fire.

[0009] Preferably, the temperature sensitive agent in step (1) includes one or more of methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, and hydroxypropyl methyl cellulose; the flame retardant includes one or more of ammonium polyphosphate, ammonium phosphate, diammonium hydrogen phosphate, sodium phosphate, disodium hydrogen phosphate, and phytic acid; the mass fraction of the temperature sensitive agent in the suspension A is 1-8wt%, and the concentration of the flame retardant is 0.01-0.05 mol / L.

[0010] If the mass fraction of the temperature-sensitive agent is too low, the viscosity of the product will be relatively low; if the mass fraction of the temperature-sensitive agent is too high, the fluidity of the product will be relatively low, but the prepared hydrogel fire extinguishing agent can form a hydrogel when used.

[0011] The higher the concentration of the flame retardant, the shorter the gelation time of the product hydrogel; however, too high a concentration of the flame retardant will lead to excessive salting out, making it impossible for the product to form a hydrogel by high temperature heating in a fire when in use.

[0012] More preferably, the mass fraction of the temperature sensitive agent in the suspension A is 2 wt %, at which point the viscosity and fluidity of the suspension A are optimal.

[0013] Preferably, in the heating and stirring in step (1), the heating temperature is 40-80°C, the stirring time is 0.2-5 h, the temperature of the low-temperature environment is 3-15°C, and the placement time in the low-temperature environment is 0.5-24 h, which can promote better hydration of the temperature sensitive agent.

[0014] Preferably, in step (2), the gelling agent comprises one or more of acrylamide, acrylic acid, sodium acrylate, and 2-acrylamide-2-methylpropanesulfonic acid; the cross-linking agent comprises one or more of N,N-methylenebisacrylamide, N-hydroxymethylacrylamide, diacetone acrylamide, and hydroxyethyl methacrylate; the mass fraction of the gelling agent in solution B is 1 wt%-15 wt%; and the mass fraction of the cross-linking agent in solution B is 0.05 wt%-11 wt%.

[0015] Preferably, in step (3), the initiator is a thermal initiator, and the thermal initiator includes one or more of potassium persulfate, ammonium persulfate, and sodium persulfate; the amount of the initiator accounts for 0.05-10 wt% of the final temperature-responsive hydrogel fire extinguishing agent.

[0016] Too high a dosage of gelling agent will reduce the viscoelasticity of the product hydrogel, while too low a dosage will result in an incomplete network structure. Too high a dosage of crosslinking agent will reduce the elasticity and water absorption of the product hydrogel, while too low a dosage will affect its stability. Too high a dosage of initiator will cause structural damage to the product hydrogel, while too low a dosage will result in an uneven internal structure, so the above dosage range is selected.

[0017] Preferably, the temperature-responsive hydrogel fire extinguishing agent prepared in step (3) can form a hydrogel by heating at 40-120° C. for 0.1-24 h.

[0018] The temperature-responsive hydrogel fire extinguishing agent prepared by the above method can adjust the gelation time by adjusting the concentration of the flame retardant and the temperature change. It has strong fluidity at room temperature, reduces the resistance in the pipeline, and thus solves the problem of pipeline blockage; it can improve the moisture absorption and water retention properties of the hydrogel fire extinguishing agent to prevent the occurrence of re-ignition; it can reduce the amount of hydrogel fire extinguishing agent used, improve the utilization rate of water, and make it easy to clean up the residues after the disaster.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) The temperature-sensitive agent in the temperature-responsive hydrogel fire extinguishing agent of the present invention promotes the free radical polymerization of acrylic acid and acrylamide-based gels, thereby improving the adhesion of the hydrogel fire extinguishing agent on the surface of combustibles.

[0020] (2) The flame retardant in the temperature-responsive hydrogel fire extinguishing agent of the present invention can improve the cross-linking degree of the hydrogel fire extinguishing agent. A large number of hydroxyl groups are introduced into the hydrogel fire extinguishing agent, which helps to form more hydrogen bonds and enhance its water absorption capacity. In addition, the flame retardant containing a phosphate group generates phosphoric acid at high temperature, which promotes the dehydration and carbonization of the temperature-sensitive agent and the gelling agent, thereby achieving the purpose of extinguishing the fire and avoiding the occurrence of re-ignition.

[0021] (3) The gelling agent added to the temperature-responsive hydrogel fire extinguishing agent of the present invention contains -COOH groups and -CONH 2 The group can fix water on the polymer chain through hydrogen bonds, giving the hydrogel fire extinguishing agent excellent chemical and thermal stability. Compared with other types of gelling agents, the selected gelling agent has a larger water absorption capacity, a longer water retention time, and a higher viscosity. The protective film formed with the temperature-sensitive agent and flame retardant is not easy to break, maintains a stable structure at high temperatures, and effectively covers the surface of combustibles to prevent re-ignition.

[0022] (4) The preparation method of the temperature-responsive hydrogel fire extinguishing agent proposed in the present invention, the gel network constructed by the thermosensitive agent and the flame retardant and the polyacrylic acid and polyacrylamide-based gel obtained by free radical polymerization are intertwined with each other, and the obtained composite hydrogel fire extinguishing agent has physical and chemical cross-linking effects, which can provide excellent water retention, flame retardancy and heat insulation. By forming a stable hydrogel protective film on the surface of the combustible material, the release of volatile gases is limited, thereby achieving the purpose of reducing the amount of fire extinguishing agent and improving the efficiency of the use of the fire extinguishing agent. In addition, it is difficult to achieve the expected fire extinguishing effect without any component in the present invention.

[0023] (5) The method for preparing the temperature-responsive hydrogel fire extinguishing agent proposed in the present invention can adjust the gelation time by adjusting the concentration of the flame retardant and the temperature change, so as to meet the sol state of flow at low temperature, facilitate transportation and storage, and solve the problem of pipeline blockage. At the same time, the heat released by the fire source is used to cause the sol-gel transition process, forming a highly adhesive hydrogel on the surface of the vegetation, making it difficult to reignite, thereby achieving the purpose of efficient fire extinguishing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The inverted picture and rheological diagram of the composite hydrogel fire extinguishing agent prepared in Examples 1-4 of the present invention are shown in FIG. in, Figure 1 a is an inverted picture of the composite hydrogel fire extinguishing agent. Figure 1 b is the lower critical solution temperature of the composite hydrogel fire extinguishing agent, Figure 1 cf are rheological diagrams of the composite hydrogel fire extinguishing agents of Examples 1-4, respectively; in the figure, 0.01 M, 0.02 M, 0.03 M and 0.04 M correspond to the concentrations of the flame retardant ammonium polyphosphate in the composite hydrogel fire extinguishing agents prepared in Examples 1, 2, 3 and 4, respectively.

[0025] Figure 2 The infrared spectra of the hydrogel (MC-APP-PAM) formed by the fire extinguishing agent prepared in Example 2 of the present invention, as well as polyacrylamide hydrogel (PAM), temperature-sensitive agent methyl cellulose (MC), flame retardant ammonium polyphosphate (APP), and gelling agent acrylamide (AM); wherein PAM is formed by free radical polymerization of gelling agent acrylamide, cross-linking agent N,N-methylenebisacrylamide and initiator ammonium persulfate.

[0026] Figure 3 This is a thermogravimetric analysis diagram of the composite hydrogel fire extinguishing agent prepared in Example 2 of the present invention.

[0027] Figure 4 The flame morphology changes of the composite hydrogel fire extinguishing agent prepared in Example 5 of the present invention, Comparative Example 1, Comparative Example 2 and Comparative Example 3 during the fire extinguishing process, in, Figure 4 a is the flame morphology change of the composite hydrogel fire extinguishing agent in Example 5 during the fire extinguishing process, Figure 4 b is the change of flame morphology during the fire extinguishing process of comparative example 1, Figure 4 c is the change of flame morphology during the fire extinguishing process of comparative example 2, Figure 4 d is the change in flame morphology during the fire extinguishing process of Comparative Example 3.

[0028] Figure 5 The thermal infrared imaging changes of the composite hydrogel fire extinguishing agent prepared in Example 5 of the present invention, Comparative Example 1, Comparative Example 2 and Comparative Example 3 during the fire extinguishing process, in, Figure 5 a is the thermal infrared imaging change of the composite hydrogel fire extinguishing agent in Example 5 during the fire extinguishing process, Figure 5 b is the change of thermal infrared imaging in the fire extinguishing process of comparative example 1, Figure 5 c is the change of thermal infrared imaging in the fire extinguishing process of comparative example 2, Figure 5 d is the change of thermal infrared imaging of comparative example 3 during the fire extinguishing process.

[0029] Figure 6 The temperature change diagram of the composite hydrogel fire extinguishing agent prepared in Example 5 of the present invention, Comparative Example 1, Comparative Example 2 and Comparative Example 3 during the fire extinguishing process is shown in FIG. in, Figure 6 a is a temperature change diagram of the composite hydrogel fire extinguishing agent in Example 5 during the fire extinguishing process, Figure 6 b is the temperature change diagram of comparative example 1 during the fire extinguishing process, Figure 6 c is the temperature change diagram of comparative example 2 during the fire extinguishing process, Figure 6 d is the temperature change diagram of comparative example 3 during the fire extinguishing process. DETAILED DESCRIPTION

[0030] The invention will be further explained below in conjunction with specific embodiments. The following embodiments are only applicable to further fully and clearly explain the invention. The cases described are only partial embodiments of the invention, not all embodiments. All other embodiments created based on this invention belong to the protection scope of this invention.

[0031] Example 1 A method for preparing a temperature-responsive hydrogel fire extinguishing agent, the specific steps are as follows: Methyl cellulose was dispersed in a 0.01 mol / L aqueous solution of ammonium polyphosphate (n<20, water solubility>0.9 g / mL). The mass concentration of methyl cellulose after dispersion was 2 wt%. The mixture was stirred at 500 rpm at 55°C for 1 h to mix the methyl cellulose and ammonium polyphosphate evenly. The obtained suspension was cooled to room temperature and then placed in a low temperature environment of 5°C for 2 h to completely hydrate the methyl cellulose, thereby obtaining a clear and transparent suspension A.

[0032] Acrylamide and N,N-methylenebisacrylamide were dissolved in suspension A to make the mass concentration of acrylamide 3 wt % and the mass concentration of N,N-methylenebisacrylamide 0.15 wt %, and the mixture was stirred at 800 rpm at room temperature for 1.5 h to obtain solution B.

[0033] After uniform dissolution, ammonium persulfate was added to solution B to make its mass concentration 0.14 wt%, and stirred at 800 rpm at room temperature for 30 min to obtain a temperature-responsive hydrogel fire extinguishing agent.

[0034] The obtained temperature-responsive hydrogel fire extinguishing agent can form a hydrogel by heating at 80°C for 18 min.

[0035] Example 2 A method for preparing a temperature-responsive hydrogel fire extinguishing agent, the specific steps are as follows: Methyl cellulose was dispersed in a 0.02 mol / L aqueous solution of ammonium polyphosphate (n<20, water solubility>0.9 g / mL), and the mass concentration of methyl cellulose after dispersion was 2 wt%. The mixture was stirred at 500 rpm at 55°C for 1 h to mix the methyl cellulose and ammonium polyphosphate evenly. The obtained suspension was cooled to room temperature and then placed in a low temperature environment of 5°C for 2 h to completely hydrate the methyl cellulose, thereby obtaining a clear and transparent suspension A.

[0036] Acrylamide and N,N-methylenebisacrylamide were dissolved in suspension A to make the mass concentration of acrylamide 3 wt % and the mass concentration of N,N-methylenebisacrylamide 0.15 wt %, and the mixture was stirred at 800 rpm at room temperature for 1.5 h to obtain solution B.

[0037] After uniform dissolution, ammonium persulfate was added to solution B to make its mass concentration 0.14 wt%, and stirred at 800 rpm at room temperature for 30 min to obtain a temperature-responsive hydrogel fire extinguishing agent.

[0038] The obtained temperature-responsive hydrogel fire extinguishing agent can form a hydrogel by heating at 80°C for 15 min.

[0039] Figure 2 The infrared spectra of the hydrogel (MC-APP-PAM) formed by the fire extinguishing agent prepared in Example 2 of the present invention, the polyacrylamide hydrogel (PAM), the temperature-sensitive agent methyl cellulose (MC), the flame retardant ammonium polyphosphate (APP) and the gelling agent acrylamide (AM), wherein PAM is formed by free radical polymerization of the gelling agent acrylamide, the cross-linking agent N,N-methylenebisacrylamide and the initiator ammonium persulfate.

[0040] It can be seen from the figure that the composite hydrogel fire extinguishing agent is -1 The characteristic peaks on the left and right are attributed to the stretching vibration of -OH and -NH, 1634 cm -1 The characteristic peak at 1455 cm-1 is attributed to the stretching vibration of C=O. -1 The characteristic peak at is attributed to -CONH 2 The CN group of 1075 cm -1 The characteristic peak at 986 cm-1 is attributed to the asymmetric stretching vibration of POP. -1 The characteristic peak at 3300 cm -1 The -OH stretching vibration peaks on the left and right indicate the formation of hydrogen bonds in the system, and the obvious shift of the -OH absorption band to lower wavenumbers means that the hydrogen bonding in the system is extremely strong, forming multi-molecular associations. The resulting composite hydrogel fire extinguishing agent has chemical and physical cross-linking effects, which can provide excellent flame retardancy and thermal insulation. When exposed to high-temperature flames, the fire extinguishing agent improves the fire extinguishing efficiency and prevents re-ignition by absorbing heat and releasing flame-retardant gases.

[0041] Figure 3 The thermogravimetric analysis diagram of the composite hydrogel fire extinguishing agent prepared in Example 2 of the present invention shows that the decomposition of the composite hydrogel fire extinguishing agent can be divided into three stages: the mass loss in the first stage (30-150°C) is mainly the removal of free water and bound water; the second stage (150-280°C) is the decomposition of the polyacrylamide side chain in the composite hydrogel fire extinguishing agent to produce NH 3 , ammonium polyphosphate is thermally decomposed into NH 3The mass loss in the third stage (280-800℃) is mainly due to the degradation of ammonium polyphosphate and the volatilization of degradation products, and the formation of complex phosphorus and oxides. Methylcellulose is cracked into small molecules, accompanied by the precipitation of volatile components. The main chain of polyacrylamide is depolymerized into imide, nitrile and CO. 2 , forming molten carbon, which is basically decomposed after 700℃.

[0042] Example 3 A method for preparing a temperature-responsive hydrogel fire extinguishing agent, the specific steps are as follows: Methyl cellulose was dispersed in a 0.03 mol / L aqueous solution of ammonium polyphosphate (n<20, water solubility>0.9 g / mL), and the mass concentration of methyl cellulose after dispersion was 2 wt%. The mixture was stirred at 500 rpm at 55°C for 1 h to mix the methyl cellulose and ammonium polyphosphate evenly. The obtained suspension was cooled to room temperature and then placed in a low temperature environment at 5°C for 2 h to completely hydrate the methyl cellulose, thereby obtaining a clear and transparent suspension A.

[0043] Acrylamide and N,N-methylenebisacrylamide were dissolved in suspension A to make the mass concentration of acrylamide 3 wt % and the mass concentration of N,N-methylenebisacrylamide 0.15 wt %, and the mixture was stirred at 800 rpm at room temperature for 1.5 h to obtain solution B.

[0044] After uniform dissolution, ammonium persulfate was added to solution B to make its mass concentration 0.14 wt%, and stirred at 800 rpm at room temperature for 30 min to obtain a temperature-responsive hydrogel fire extinguishing agent.

[0045] The obtained temperature-responsive hydrogel fire extinguishing agent can form a hydrogel by heating at 80°C for 13 min.

[0046] Example 4 A method for preparing a temperature-responsive hydrogel fire extinguishing agent, the specific steps are as follows: Methyl cellulose was dispersed in a 0.04 mol / L aqueous solution of ammonium polyphosphate (n<20, water solubility>0.9 g / mL), and the mass concentration of methyl cellulose after dispersion was 2 wt%. The mixture was stirred at 500 rpm at 55°C for 1 h to mix the methyl cellulose and ammonium polyphosphate evenly. The obtained suspension was cooled to room temperature and then placed in a low temperature environment of 5°C for 2 h to completely hydrate the methyl cellulose, thereby obtaining a clear and transparent suspension A.

[0047] Acrylamide and N,N-methylenebisacrylamide were dissolved in suspension A to make the mass concentration of acrylamide 3 wt % and the mass concentration of N,N-methylenebisacrylamide 0.15 wt %, and the mixture was stirred at 800 rpm at room temperature for 1.5 h to obtain solution B.

[0048] After uniform dissolution, ammonium persulfate was added to solution B to make its mass concentration 0.14 wt%, and stirred at 800 rpm at room temperature for 30 min to obtain a temperature-responsive hydrogel fire extinguishing agent.

[0049] The obtained temperature-responsive hydrogel fire extinguishing agent can form a hydrogel by heating at 80°C for 10 min.

[0050] Figure 1 The inverted picture and rheological diagram of the composite hydrogel fire extinguishing agent prepared in Examples 1-4 of the present invention, in which 0.01M, 0.02M, 0.03M and 0.04M correspond to the composite hydrogel fire extinguishing agents of Examples 1, 2, 3 and 4, respectively, wherein: Figure 1 a is the final coagulation state of the composite hydrogel fire extinguishing agent. The prepared composite hydrogel fire extinguishing agent is initially a colorless, transparent, uniform aqueous solution at ambient temperature. When the temperature rises, the hydrophobic group plays a major role, and a network structure is formed between the hydrogel molecules. Figure 1 a It can be seen that with the increase of flame retardant concentration, the hydrogel fire extinguishing agent gradually precipitates and "precipitates". Figure 1 b is the lower critical solution temperature (LCST) of the composite hydrogel fire extinguishing agent measured by rheology. It can be seen from the figure that the higher the concentration of the flame retardant containing phosphate groups, the lower the temperature required for the hydrophobic groups to play a major role. Figure 1 cf are the changes in the elastic modulus G′ and viscous modulus G″ of the hydrogel fire extinguishing agents of Examples 1-4 with temperature. As the temperature increases, the elastic modulus G′ increases faster, while the viscous modulus G″ increases more slowly, and the gel network structure in the system increases. When the temperature rises to LCST, the elastic modulus G′ and the viscous modulus G″ begin to intersect, and then the elastic modulus G′ is greater than G″, elastic deformation occurs, and the prepared composite hydrogel fire extinguishing agent is in a solid state.

[0051] Example 5 A method for preparing a temperature-responsive hydrogel fire extinguishing agent, the specific steps are as follows: Methyl cellulose was dispersed in a 0.01 mol / L aqueous solution of ammonium polyphosphate (n<20, water solubility>0.9 g / mL), and the mass concentration of methyl cellulose after dispersion was 1 wt%. The mixture was stirred at 500 rpm at 55°C for 1 h to mix the methyl cellulose and ammonium polyphosphate evenly. The obtained suspension was cooled to room temperature and then placed in a low temperature environment at 5°C for 2 h to completely hydrate the methyl cellulose, thereby obtaining a clear and transparent suspension A.

[0052] Acrylamide and N,N-methylenebisacrylamide were dissolved in suspension A to make the mass concentration of acrylamide 1.5 wt % and the mass concentration of N,N-methylenebisacrylamide 0.08 wt %, and the suspension was stirred at 800 rpm at room temperature for 1.5 h to obtain solution B.

[0053] After uniform dissolution, ammonium persulfate was added to solution B to make its mass concentration 0.07 wt%, and stirred at 800 rpm at room temperature for 30 min to obtain a temperature-responsive hydrogel fire extinguishing agent.

[0054] The obtained temperature-responsive hydrogel fire extinguishing agent can form a hydrogel by heating at 120°C for 6 min.

[0055] Example 6 A method for preparing a temperature-responsive hydrogel fire extinguishing agent, the specific steps are as follows: Methyl cellulose was dispersed in a 0.03 mol / L phytic acid aqueous solution, and the mass concentration of methyl cellulose after dispersion was 2 wt%. The mixture was stirred at 600 rpm at 60°C for 1 h to uniformly mix the methyl cellulose and phytic acid. After the obtained suspension was cooled to room temperature, it was placed in a low temperature environment of 5°C for 6 h to completely hydrate the methyl cellulose, and a clear and transparent suspension A was obtained.

[0056] Acrylamide and N,N-methylenebisacrylamide were dissolved in suspension A to make the mass concentration of acrylamide 6 wt % and the mass concentration of N,N-methylenebisacrylamide 0.3 wt %. The suspension was stirred at 1200 rpm at room temperature for 3 h to obtain solution B.

[0057] After uniform dissolution, potassium persulfate was added to solution B to make its mass concentration 0.3 wt%, and stirred at 1200 rpm at room temperature for 1 h to obtain a temperature-responsive hydrogel fire extinguishing agent.

[0058] The obtained temperature-responsive hydrogel fire extinguishing agent can form a hydrogel by heating at 75°C for 15 min.

[0059] Example 7 A method for preparing a temperature-responsive hydrogel fire extinguishing agent, the specific steps are as follows: Methyl cellulose was dispersed in a 0.05 mol / L sodium phosphate aqueous solution, and the mass concentration of the methyl cellulose after dispersion was 8 wt%. The mixture was stirred at 55°C for 30 min at a speed of 600 rpm to mix the methyl cellulose and the sodium phosphate evenly. After the obtained suspension was cooled to room temperature, it was placed in a low temperature environment of 5°C for 3 h to completely hydrate the methyl cellulose, and a clear and transparent suspension A was obtained.

[0060] Acrylamide and N,N-methylenebisacrylamide were dissolved in suspension A to make the mass concentration of acrylamide 3 wt % and the mass concentration of N,N-methylenebisacrylamide 0.3 wt %. The suspension was stirred at 700 rpm at room temperature for 1.5 h to obtain solution B.

[0061] After uniform dissolution, ammonium persulfate was added to solution B to make its mass concentration 0.3 wt%, and stirred at 700 rpm at room temperature for 1.5 h to obtain a temperature-responsive hydrogel fire extinguishing agent.

[0062] The obtained temperature-responsive hydrogel fire extinguishing agent can form a hydrogel by heating at 70°C for 16 min.

[0063] Example 8 A method for preparing a temperature-responsive hydrogel fire extinguishing agent, the specific steps are as follows: Methyl cellulose was dispersed in a 0.03 mol / L sodium phosphate aqueous solution, and the mass concentration of methyl cellulose after dispersion was 4 wt%. The mixture was stirred at 800 rpm at 60°C for 30 min to mix the methyl cellulose and sodium phosphate evenly. After the obtained suspension was cooled to room temperature, it was placed in a low temperature environment of 5°C for 3 h to completely hydrate the methyl cellulose, and a clear and transparent suspension A was obtained.

[0064] Acrylamide and N,N-methylenebisacrylamide were dissolved in suspension A to make the mass concentration of acrylamide be 1 wt % and the mass concentration of N,N-methylenebisacrylamide be 0.05 wt %, and the mixture was stirred at 700 rpm at room temperature for 1.5 h to obtain solution B.

[0065] After uniform dissolution, ammonium persulfate was added to solution B to make its mass concentration 0.05 wt%, and stirred at 700 rpm at room temperature for 1.5 h to obtain a temperature-responsive hydrogel fire extinguishing agent.

[0066] The obtained temperature-responsive hydrogel fire extinguishing agent can form a hydrogel by heating at 70°C for 10 min.

[0067] Example 9 A method for preparing a temperature-responsive hydrogel fire extinguishing agent, the specific steps are as follows: Methyl cellulose was dispersed in a 0.02 mol / L phytic acid aqueous solution, and the mass concentration of methyl cellulose after dispersion was 3 wt%. The mixture was stirred at 55°C for 1 h at a speed of 600 rpm to uniformly mix the methyl cellulose and phytic acid. After the obtained suspension was cooled to room temperature, it was placed in a low temperature environment of 5°C for 3 h to completely hydrate the methyl cellulose, and a clear and transparent suspension A was obtained.

[0068] Acrylamide and N,N-methylenebisacrylamide were dissolved in suspension A to make the mass concentration of acrylamide 15 wt % and the mass concentration of N,N-methylenebisacrylamide 11 wt %, and the mixture was stirred at 700 rpm at room temperature for 1.5 h to obtain solution B.

[0069] After uniform dissolution, ammonium persulfate was added to solution B to make its mass concentration 10 wt%, and stirred at 700 rpm at room temperature for 1.5 h to obtain a temperature-responsive hydrogel fire extinguishing agent.

[0070] The obtained temperature-responsive hydrogel fire extinguishing agent can form a hydrogel by heating at 80°C for 16 min.

[0071] Comparative Example 1 This comparative example prepares a fire extinguishing agent by referring to the preparation method provided in Example 5. The difference between this comparative example and Example 5 is that in the process of preparing the fire extinguishing agent, an equal mass of water is used to replace the temperature sensitive agent methyl cellulose used in Example 5. The rest of the raw material ratios and preparation methods are strictly consistent with those in Example 5.

[0072] Comparative Example 2 This comparative example prepares a fire extinguishing agent by referring to the preparation method provided in Example 5. The difference between this comparative example and Example 5 is that in the process of preparing the fire extinguishing agent, an equal mass of water is used to replace the flame retardant, gelling agent, crosslinking agent, and initiator used in Example 5. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 5.

[0073] Comparative Example 3 This comparative example is water.

[0074] Experimental example The temperature-responsive hydrogel fire extinguishing agent prepared in Example 5, Comparative Example 1, Comparative Example 2 and Comparative Example 3 was used to perform a performance test on extinguishing a 1A woodpile fire according to GB17835-2008 "Water-based Fire Extinguishing Agents". The woodpile used was built with 72 50×4×4 cm pine wood strips, with 6 strips per layer and 12 layers in total. The changes in the flame morphology during the entire process were captured using a camera and an infrared thermal imager, and the temperature changes and fire extinguishing time during the entire process were recorded using a temperature recorder. The entire fire extinguishing experiment process was divided into a pre-combustion stage, a free combustion stage, a fire extinguishing stage and a re-ignition stage.

[0075] like Figure 4-6As shown, at the beginning of combustion, the flame is mainly concentrated in the center of the woodpile, and then the flame begins to spread outward from the center. The temperature on the upper surface of the woodpile increases rapidly. The woodpile burns stably for about 200 seconds, and the flame area is the largest. As the woodpile continues to burn, a large amount of charcoal layer will form on the surface of the woodpile. After the temperature reaches 700°C, the fire extinguishing aqueous solution prepared in Example 5, Comparative Example 1, Comparative Example 2 and Comparative Example 3 is sprayed onto the woodpile fire. The flame area continues to shrink, the height decreases, and the temperature of the woodpile also decreases significantly. However, since the open flame is extinguished during the fire extinguishing process, the temperature inside the woodpile is still very high, and there is smoldering. With the evaporation of water and the accumulation of heat, Comparative Example 1, Comparative Example 2 and Comparative Example 3 rekindle within 10 minutes after the flame is extinguished ( Figure 5 b, c, d), but the hydrogel fire extinguishing agent formed by the fire extinguishing water solution of Example 5 using the high temperature heating of the fire scene did not re-ignite ( Figure 5 a). In the initial fire extinguishing process, the dosage of comparative example 1 was 6 L, and the cooling rate was 11.37℃ / s ( Figure 6 b); the dosage of comparative example 2 is 12 L, and the cooling rate is 9.39℃ / s ( Figure 6 c); the dosage of comparative example 3 is 10 L, and the cooling rate is 9.79℃ / s ( Figure 6 d); The amount of the hydrogel fire extinguishing agent in Example 5 is 6 L, and the cooling rate reaches 20.14°C / s ( Figure 6 a), which shows that the prepared composite hydrogel fire extinguishing agent has excellent fire extinguishing performance. After extinguishing the fire with the composite hydrogel fire extinguishing agent, it can be easily cleaned up without residue.

[0076] In Comparative Example 1, the lack of a temperature-sensitive agent not only caused a re-ignition and produced a lot of smoke, but also the fire extinguishing agent fell off on the surface of the woodpile. This shows that the free radical polymerization of acrylic acid and acrylamide-based gel in the hydrogel fire extinguishing agent requires the promotion of a temperature-sensitive agent to improve the adhesion of the hydrogel fire extinguishing agent on the surface of the woodpile. Compared with Example 5, the amount of fire extinguishing agent used in Comparative Example 2 is significantly increased, smoke is still produced after the fire is extinguished, the cooling rate is the lowest, and re-ignition occurs after the fire is extinguished. Compared with Example 5, the amount of fire extinguishing agent used in Comparative Example 3 is large, the cooling rate is low, and re-ignition occurs. The above results show that the fire extinguishing agent of the present invention requires the synergistic effect of a temperature-sensitive agent, a flame retardant and a gelling agent to effectively improve the fire extinguishing efficiency.

[0077] The technical features of the above-described embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The description of the above embodiments can be used to help understand the principles and methods of the present invention. However, the above embodiments are not exclusive and should not be construed as limiting the present invention. At the same time, for those of ordinary skill in the art, according to the principles and methods of the present invention, flexible changes can be made in the specific implementation methods and application scopes.

Claims

1. A method for preparing a temperature-responsive hydrogel fire extinguishing agent, characterized in that: The specific steps are as follows: (1) Dissolve the temperature-sensitive agent and flame retardant in water, heat and stir evenly, cool to room temperature, and place in a low temperature environment to obtain a clear and transparent suspension A; (2) dissolving the gelling agent and the cross-linking agent in the suspension A prepared in step (1) and stirring at room temperature for 0.5-12 h to obtain a solution B; (3) Add the initiator to the solution B prepared in step (2) and stir at room temperature for 0.5-6 h to obtain a temperature-responsive hydrogel fire extinguishing agent.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass fraction of the temperature sensitive agent in the suspension A is 1 wt%-8 wt%, and the concentration of the flame retardant is 0.01-0.05 mol / L.

3. The preparation method according to claim 1 or 2, characterized in that: The mass fraction of the temperature sensitive agent in the suspension A is 2 wt %.

4. The preparation method according to claim 1 or 2, characterized in that: The temperature sensitive agent includes one or more of methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, and hydroxypropyl methyl cellulose; the flame retardant includes one or more of ammonium polyphosphate, ammonium phosphate, diammonium hydrogen phosphate, sodium phosphate, disodium hydrogen phosphate, and phytic acid.

5. The preparation method according to claim 1, characterized in that: The heating and stirring in step (1) has a heating temperature of 40-80°C, a stirring time of 0.2-5 h, a temperature of the low-temperature environment of 3-15°C, and a placement time in the low-temperature environment of 0.5-24 h.

6. The preparation method according to claim 1, characterized in that: The gelling agent in step (2) includes one or more of acrylamide, acrylic acid, sodium acrylate, and 2-acrylamide-2-methylpropanesulfonic acid; the cross-linking agent includes one or more of N,N-methylenebisacrylamide, N-hydroxymethylacrylamide, diacetone acrylamide, and hydroxyethyl methacrylate.

7. The preparation method according to claim 1, characterized in that: In step (2), the mass fraction of the gelling agent in solution B is 1 wt%-15 wt%; the mass fraction of the cross-linking agent in solution B is 0.05 wt%-11 wt%.

8. The preparation method according to claim 1, characterized in that: In step (3), the amount of the initiator used accounts for 0.05-10 wt % of the final temperature-responsive hydrogel fire extinguishing agent.

9. The preparation method according to claim 1, characterized in that: In step (3), the initiator is a thermal initiator, and the thermal initiator includes one or more of potassium persulfate, ammonium persulfate, and sodium persulfate.

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