Fire preventing and extinguishing material for mine and preparation method of fire preventing and extinguishing material

Abstract

The invention relates to the technical field of fire extinguishing materials, and provides a fire preventing and extinguishing material for a mine and a preparation method thereof. The invention discloses a fire preventing and extinguishing material for mines. The building material is prepared from the following raw materials in parts by weight: 30 to 40 parts of sulphoaluminate cement, 20 to 25 parts of acid-activated coal gangue, 5 to 10 parts of bentonite-based composite phase change body, 3 to 5 parts of hollow glass beads, 0.5 to 1 part of polypropylene fiber, 3 to 4 parts of chitosan-acrylic acid copolymer, 1 to 2 parts of foaming agent, 2 to 3 parts of expanded graphite, 1 to 3 parts of zinc borate, 2 to 4 parts of nano silicon dioxide and 260 to 320 parts of water. According to the fire preventing and extinguishing material for the mine, the performance stability in fire preventing and extinguishing of high-temperature fire disasters and the storage stability in the storage process are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fire extinguishing materials, and in particular to a fire extinguishing material for mines and a preparation method thereof. Background Art

[0002] As key locations for the extraction of coal and other mineral resources, mine safety is paramount. However, mine fires remain a major threat to mine safety. Mine fires not only destroy large quantities of coal, resulting in significant economic losses, but also generate high temperatures, toxic and hazardous gases, and smoke, seriously threatening the lives of underground workers. They can even trigger secondary disasters such as gas explosions, further expanding the scope of the accident. Therefore, the development of efficient and reliable mine fire extinguishing materials is of great practical significance for preventing and controlling the occurrence of mine fires and ensuring safe mine production.

[0003] However, the existing fire-fighting materials for mines have many limitations in practical applications. Taking certain gel materials as an example, this type of material has good heat insulation and oxygen isolation properties at room temperature and can effectively prevent the spread of fire. However, in high-temperature environments, gel materials are prone to dehydration. As water is lost, the structure of the gel is gradually destroyed, and its heat insulation and oxygen isolation functions are also lost. Therefore, this type of gel material may only be suitable for the prevention and control of coal spontaneous combustion in low-temperature environments. In the early stages of coal spontaneous combustion, the temperature is relatively low, and the gel material can play a better role. However, as the coal spontaneous combustion develops, the temperature rises, and the gel material cannot maintain good fire extinguishing performance, making it difficult to meet the fire prevention and extinguishing needs of high-temperature fires. In addition to unstable performance at high temperatures, the lack of stability of existing fire-fighting materials is also reflected in other aspects. Some fire-fighting materials are prone to physical or chemical changes during storage, resulting in a decrease in their performance. Based on this, the present invention proposes a fire-fighting material for mines and a preparation method thereof. Summary of the Invention

[0004] The present invention proposes a fire-proofing and extinguishing material for mines and a preparation method thereof, which improves the problem that existing fire-proofing and extinguishing materials for mines are easily dehydrated and structurally damaged in high-temperature environments, resulting in loss of heat insulation and oxygen isolation properties, and improves the performance stability of the material in high-temperature fire prevention and extinguishing; it also improves the problem that existing fire-proofing and extinguishing materials are prone to physical or chemical changes during storage, resulting in performance degradation, and improves the storage stability and comprehensive fire-proofing and extinguishing performance of the material.

[0005] The technical solutions of the present invention are as follows: In a first aspect, the present invention provides a fire extinguishing material for mines, which is composed of the following raw materials in parts by weight: 30-40 parts of sulfoaluminate cement, 20-25 parts of acid-activated coal gangue, 5-10 parts of bentonite-based composite phase change agent, 3-5 parts of hollow glass microspheres, 0.5-1 part of polypropylene fiber, 3-4 parts of chitosan-acrylic acid copolymer, 1-2 parts of foaming agent, 2-3 parts of expanded graphite, 1-3 parts of zinc borate, 2-4 parts of nano-silicon dioxide and 260-320 parts of water.

[0006] As a further technical solution, the preparation method of the acid-activated coal gangue includes drying the coal gangue at 100-110°C for 2-3 hours and then crushing it to 200 mesh, mixing the crushed coal gangue with a 10% volume concentration of sulfuric acid solution at a solid-liquid ratio of 1g:3-4mL, stirring at a temperature of 80±2°C and 180-220rpm for 2-3 hours, vacuum filtration separation, and washing, placing the acid-washed coal gangue in a muffle furnace, heating it to 560-600°C at 5°C / min, calcining it at a constant temperature for 50-70 minutes, naturally cooling it to room temperature, and grinding it to a particle size of ≤50μm.

[0007] As a further technical solution, the preparation method of the bentonite-based composite phase-shifted product includes: mixing bentonite, anhydrous sodium sulfate and water; ultrasonically dispersing for 30-40 minutes to form a uniform suspension; transferring the suspension to a constant temperature reactor, stirring at 60°C±1°C and 400-500 rpm for 3-4 hours; centrifuging, taking the precipitate and vacuum drying it at 70-80°C for 10-12 hours, and grinding the dried material and passing it through a 200-mesh sieve to obtain the product.

[0008] As a further technical solution, the weight ratio of the bentonite, anhydrous sodium sulfate and water is 3-4:1-2:20-30.

[0009] As a further technical solution, the preparation method of the chitosan-acrylic acid copolymer includes: adding chitosan to an acetic acid solution with a volume concentration of 2%-3%, stirring at 500-600 rpm for 20-30 minutes, heating to 50-55°C to accelerate dissolution to form a chitosan solution; adding acrylic acid monomer dropwise to the chitosan solution at a rate of 1 mL / min, and simultaneously adding potassium persulfate initiator to react, cooling to room temperature, and adjusting the pH to 7±0.2; and spray drying to obtain the product.

[0010] As a further technical solution, the usage ratio of the chitosan, acetic acid solution, acrylic acid monomer and potassium persulfate is 50-60 g: 900-1100 mL: 140-160 g: 2-3 g.

[0011] As a further technical solution, the reaction is carried out under nitrogen protection, 200-300 rpm, and 60°C±1°C for 3-4 hours.

[0012] As a further technical solution, the inlet air temperature of the spray drying is 170-180°C, the outlet air temperature is 80-90°C, and the atomization pressure is 0.2-0.3 MPa.

[0013] As a further technical solution, the foaming agent includes a cement foaming agent and a silicone resin foam stabilizer in a weight ratio of 1:0.2-0.5.

[0014] In a second aspect, the present invention provides a method for preparing a fire extinguishing material for a mine, comprising the steps of: (1) Add sulphoaluminate cement, acid-activated coal gangue, nano-silica, zinc borate and expanded graphite to half of the water in sequence, and stir at 700-800 rpm for 10-15 minutes to form a uniform slurry; (2) Add chitosan-acrylic acid copolymer, adjust the stirring speed to 400-500 rpm, and continue for 5-10 minutes; pre-mix polypropylene fiber and hollow glass microspheres and add them, stirring at 500-600 rpm for 3-5 minutes; add bentonite-based composite phase change agent and stir at a low speed of 300-400 rpm for 2-4 minutes; (3) Add the foaming agent and the remaining weight of water, and stir at 200-300 rpm for 15-20 minutes.

[0015] The working principle and beneficial effects of the present invention are: The present invention introduces acid-activated gangue into mine fire prevention and extinguishing materials, replacing traditional unactivated gangue. Impurities on the gangue surface are removed through the acid washing process, exposing more active sites, significantly improving its surface activity, and enhancing the interfacial bonding between the gangue and the cement matrix, making the internal structure of the material more compact and effectively improving the compressive strength of the material. The calcination process promotes the formation of a porous structure within the gangue, which not only increases the specific surface area of ​​the material, but also improves the adsorption capacity for oxygen and combustible gases, enhancing the chemical resistance. Furthermore, the porous structure itself has good thermal stability, can buffer temperature stress in high-temperature environments, and reduce cracks in the material caused by uneven thermal expansion.

[0016] Furthermore, acid-activated gangue possesses both gelling and adsorption properties, acting synergistically with other components within the material system. Its gelling activity contributes to the formation of a stable material framework, while its adsorption function effectively adsorbs and immobilizes the inhibitor components, ensuring their uniform dispersion within the material and improving the material's thermal stability and performance. Without acid activation (as in Comparative Examples 1 and 2), the material framework becomes loose, the inhibitor components are unevenly dispersed, and thermal stability is significantly degraded.

[0017] This invention utilizes bentonite and anhydrous sodium sulfate to prepare a bentonite-based composite phase-change material for use in mine fire extinguishing materials, replacing conventional bentonite. This material exhibits unique phase-change energy storage properties. Under high-temperature conditions, the phase-change material undergoes a phase transition and absorbs heat, effectively buffering thermal stresses and preventing dehydration and cracking caused by excessive temperatures, significantly improving the material's high-temperature stability. Conventional bentonite lacks this phase-change energy storage capacity (as shown in Comparative Example 3) and is unable to regulate temperature through phase-change heat absorption. This results in the material being susceptible to dehydration and cracking at high temperatures, resulting in reduced storage stability. Furthermore, the bentonite-based composite phase-change material acts as a structural stabilizer within the material system. Uniformly dispersed throughout the material, it modulates the material's internal stress distribution through a phase-change process during temperature fluctuations, mitigating cracking caused by differences in thermal expansion coefficients. Furthermore, the composite phase-change material interacts with other inorganic-organic components within the material to form a stable structural system, enhancing the material's overall strength and stability. If there is no bentonite-based composite phase changer in the material (such as Comparative Example 4), the material loses its thermal management ability, water evaporates quickly, the structure collapses, and the synergistic reinforcement effect of the inorganic-organic components is also weakened.

[0018] The present invention also synthesized a chitosan-acrylic acid copolymer and applied it to mine fire extinguishing materials, replacing other polymers such as sodium alginate. Chitosan-acrylic acid copolymer has excellent film-forming properties, forming a dense protective film on the material surface, effectively preventing the penetration of oxygen and combustible gases and improving the material's resistance to chemical reactions. Furthermore, the active groups in its molecular structure exhibit chelation, forming stable chelates with metal ions and other substances in the inhibitor, enabling sustained release of the inhibitor and prolonging the duration of the resistance. When sodium alginate replaces the chitosan-acrylic acid copolymer (as in Comparative Example 5), the lack of these film-forming and chelating properties reduces the sustained release of the inhibitor, weakening the fiber-matrix interfacial adhesion and resulting in reduced material performance. It also acts as an interfacial binder within the material system, forming a good interfacial bond with components such as polypropylene fibers and hollow glass microspheres, enhancing the adhesion between the fibers and the matrix and improving the overall strength and toughness of the material. This interfacial bonding helps maintain the structural integrity of the material when subjected to external forces or temperature fluctuations, reducing the initiation and propagation of cracks.

[0019] In the present invention, expanded graphite and zinc borate are used in combination to exert a synergistic flame retardant effect. Expanded graphite can rapidly expand at high temperatures to form a dense thermal insulation layer, effectively preventing heat transfer and oxygen diffusion, acting as a physical barrier. Zinc borate decomposes at high temperatures to produce non-combustible gases, diluting the concentration of combustible gases. At the same time, its decomposition products cover the surface of the material, acting as a chemical flame retardant. The two work synergistically, preventing the spread of fire through physical barriers and suppressing the combustion reaction through chemical flame retardancy, significantly improving the material's resistance to fire. If zinc borate is used in place of expanded graphite (as in Comparative Example 6), relying solely on the chemical flame retardant effect of zinc borate alone, without the physical barrier effect of expanded graphite, the resistance rate decreases significantly and the high-temperature mass loss rate is high. DETAILED DESCRIPTION

[0020] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. It should be noted that the cement foaming agent model in the present invention is LG-2258, produced by Shandong Yousuo Chemical Technology Co., Ltd.; the silicone resin foam stabilizer model is YT-MPS, purchased from Dongying Yitong Chemical Co., Ltd.; polypropylene fiber, length 6mm, diameter 15-48μm, purchased from Shandong Jinhongyao Engineering Materials Co., Ltd.;.

[0021] Example 1 This embodiment provides a fire extinguishing material for mines, which is composed of the following raw materials in parts by weight: 35 parts of sulphoaluminate cement, 22 parts of acid-activated coal gangue, 8 parts of bentonite-based composite phase change, 4 parts of hollow glass microspheres, 0.8 parts of polypropylene fiber, 3.5 parts of chitosan-acrylic acid copolymer, 1.5 parts of foaming agent, 2.5 parts of expanded graphite, 2 parts of zinc borate, 3 parts of nano-silicon dioxide, and 290 parts of water; The preparation method of acid-activated coal gangue includes drying the coal gangue at 105°C for 2.5 hours and then crushing it to 200 mesh, mixing the crushed coal gangue with a 10% sulfuric acid solution at a solid-liquid ratio of 1g:3.5mL, stirring at 80°C and 200rpm for 2.5 hours, separating by vacuum filtration, washing, placing the acid-washed coal gangue in a muffle furnace, heating it to 580°C at 5°C / min, calcining it at a constant temperature for 60 minutes, naturally cooling it to room temperature, and grinding it to an average particle size of 40μm. The preparation method of the bentonite-based composite phase-shifter comprises: mixing bentonite, anhydrous sodium sulfate, and water; ultrasonically dispersing the mixture at a power of 500 W and a frequency of 40 kHz for 35 minutes to form a uniform suspension; transferring the suspension to a thermostatic reactor and stirring the mixture at 60° C. and 450 rpm for 3.5 hours; centrifuging the mixture at 8000 rpm for 10 minutes, vacuum drying the precipitate at 75° C. for 11 hours, grinding the dried mixture, and passing it through a 200-mesh sieve to obtain the obtained product; the weight ratio of bentonite, anhydrous sodium sulfate, and water is 3.5:1.5:25; The preparation method of chitosan-acrylic acid copolymer includes: adding 55g of chitosan to 1000mL of acetic acid solution with a volume concentration of 2.5%, stirring at 550rpm for 25min, heating to 52°C to accelerate dissolution to form a chitosan solution; adding 150g of acrylic acid monomer dropwise to the chitosan solution at a rate of 1mL / min, and adding 2.5g of potassium persulfate initiator at the same time, reacting for 3.5h at 250rpm and 60°C under nitrogen protection, cooling to room temperature, and slowly adding 10% NaOH solution to neutralize and adjust the pH to 7; controlling the inlet air temperature to 175°C, the outlet air temperature to 85°C, and the atomization pressure to 0.25MPa for spray drying to obtain the product; The foaming agent comprises a cement foaming agent and a silicone resin foam stabilizer in a weight ratio of 1:0.3; The preparation method of the fire extinguishing material for mines comprises the following steps: (1) Sulphoaluminate cement, acid-activated coal gangue, nano-silica, zinc borate, and expanded graphite were added to half the weight of water in sequence and stirred at 750 rpm for 12 minutes to form a uniform slurry; (2) Add chitosan-acrylic acid copolymer, adjust the stirring speed to 450 rpm, and continue for 8 minutes; pre-mix polypropylene fiber and hollow glass microspheres and add them, stirring at 550 rpm for 45 minutes; add bentonite-based composite phase change agent and stir at a low speed of 350 rpm for 3 minutes; (3) Add cement foaming agent, silicone resin foam stabilizer and remaining water, and stir at 250 rpm for 18 minutes.

[0022] Example 2 This embodiment provides a fire extinguishing material for mines, which is composed of the following raw materials in parts by weight: 30 parts of sulphoaluminate cement, 20 parts of acid-activated coal gangue, 5 parts of bentonite-based composite phase variant, 3 parts of hollow glass microspheres, 0.5 parts of polypropylene fiber, 3 parts of chitosan-acrylic acid copolymer, 1 part of foaming agent, 2 parts of expanded graphite, 1 part of zinc borate, 2 parts of nano-silicon dioxide, and 260 parts of water; The preparation method of acid-activated coal gangue includes drying the coal gangue at 100°C for 2 hours and then crushing it to 200 mesh, mixing the crushed coal gangue with a 10% sulfuric acid solution by volume at a solid-liquid ratio of 1g:3mL, stirring at a temperature of 80°C and 180rpm for 2 hours, separating by vacuum filtration, washing, placing the acid-washed coal gangue in a muffle furnace, heating it to 560°C at a rate of 5°C / min, calcining it at a constant temperature for 50 minutes, naturally cooling it to room temperature, and grinding it to an average particle size of 40μm. The preparation method of the bentonite-based composite phase-shifter includes: mixing bentonite, anhydrous sodium sulfate, and water; ultrasonically dispersing the mixture at a power of 500 W and a frequency of 40 kHz for 30 minutes to form a uniform suspension; transferring the suspension to a thermostatic reactor and stirring at 60°C and 400 rpm for 3 hours; centrifuging the mixture at 8000 rpm for 10 minutes, vacuum drying the precipitate at 70°C for 10 hours, grinding the dried material, and passing it through a 200-mesh sieve to obtain the obtained product; the weight ratio of bentonite, anhydrous sodium sulfate, and water is 3:1:20. The preparation method of chitosan-acrylic acid copolymer includes: adding 50g of chitosan to 900mL of 2% acetic acid solution, stirring at 500rpm for 20min, heating to 50°C to accelerate dissolution to form a chitosan solution; adding 140g of acrylic acid monomer dropwise to the chitosan solution at a rate of 1mL / min, and adding 2g of potassium persulfate initiator at the same time, reacting under nitrogen protection, 200rpm, and 60°C for 3h, cooling to room temperature, and slowly adding 10% NaOH solution to neutralize and adjust the pH to 7; controlling the inlet air temperature to 170°C, the outlet air temperature to 80°C, and the atomization pressure to 0.2MPa for spray drying to obtain the product; The foaming agent comprises a cement foaming agent and a silicone resin foam stabilizer in a weight ratio of 1:0.2; The preparation method of the fire extinguishing material for mines comprises the following steps: (1) Add sulphoaluminate cement, acid-activated coal gangue, nano-silica, zinc borate and expanded graphite to half of the water in sequence and stir at 700 rpm for 10 min to form a uniform slurry; (2) Add chitosan-acrylic acid copolymer, adjust the stirring speed to 400 rpm, and continue for 5 minutes; pre-mix polypropylene fiber and hollow glass microspheres and add them, stirring at 500 rpm for 3 minutes; add bentonite-based composite phase change agent and stir at a low speed of 300 rpm for 2 minutes; (3) Add cement foaming agent, silicone resin foam stabilizer and remaining water, and stir at 200 rpm for 15 minutes.

[0023] Example 3 This embodiment provides a fire extinguishing material for mines, which is composed of the following raw materials in parts by weight: 40 parts of sulphoaluminate cement, 25 parts of acid-activated coal gangue, 10 parts of bentonite-based composite phase variant, 5 parts of hollow glass microspheres, 1 part of polypropylene fiber, 4 parts of chitosan-acrylic acid copolymer, 2 parts of foaming agent, 3 parts of expanded graphite, 3 parts of zinc borate, 4 parts of nano-silicon dioxide, and 320 parts of water; The preparation method of acid-activated coal gangue includes drying the coal gangue at 110°C for 3 hours and then crushing it to 200 mesh, mixing the crushed coal gangue with a 10% sulfuric acid solution at a solid-liquid ratio of 1g:4mL, stirring at 80°C and 220rpm for 3 hours, vacuum filtration separation, washing, placing the acid-washed coal gangue in a muffle furnace, heating it to 600°C at 5°C / min, calcining it at a constant temperature for 70 minutes, naturally cooling it to room temperature, and grinding it to an average particle size of 40μm. The preparation method of the bentonite-based composite phase-shifter includes: mixing bentonite, anhydrous sodium sulfate, and water; ultrasonically dispersing the mixture at a power of 500 W and a frequency of 40 kHz for 40 minutes to form a uniform suspension; transferring the suspension to a thermostatic reactor and stirring at 60°C and 500 rpm for 4 hours; centrifuging the mixture at 8000 rpm for 10 minutes, vacuum drying the precipitate at 80°C for 12 hours, grinding the dried material, and passing it through a 200-mesh sieve to obtain the obtained product; the weight ratio of bentonite, anhydrous sodium sulfate, and water is 4:2:30. The preparation method of chitosan-acrylic acid copolymer includes: adding 60g of chitosan to 1100mL of 3% acetic acid solution, stirring at 600rpm for 30min, heating to 55°C to accelerate dissolution to form a chitosan solution; adding 160g of acrylic acid monomer dropwise to the chitosan solution at a rate of 1mL / min, and adding 3g of potassium persulfate initiator at the same time; reacting under nitrogen protection, 300rpm, and 60°C for 4h, cooling to room temperature, and slowly adding 10% NaOH solution to neutralize and adjust the pH to 7; controlling the inlet air temperature to 180°C, the outlet air temperature to 90°C, and the atomization pressure to 0.3MPa for spray drying to obtain the product; The foaming agent comprises a cement foaming agent and a silicone resin foam stabilizer in a weight ratio of 1:0.5; The preparation method of the fire extinguishing material for mines comprises the following steps: (1) Sulphoaluminate cement, acid-activated coal gangue, nano-silica, zinc borate, and expanded graphite were added to half the weight of water in sequence and stirred at 800 rpm for 15 min to form a uniform slurry; (2) Add chitosan-acrylic acid copolymer, adjust the stirring speed to 500 rpm, and continue for 10 minutes; pre-mix polypropylene fiber and hollow glass microspheres and add them, stirring at 600 rpm for 5 minutes; add bentonite-based composite phase change agent and stir at a low speed of 400 rpm for 4 minutes; (3) Add cement foaming agent, silicone resin foam stabilizer and remaining water, and stir at 300 rpm for 20 minutes.

[0024] Example 4 This embodiment provides a fire extinguishing material for mines, which is composed of the following raw materials in parts by weight: 30 parts of sulphoaluminate cement, 25 parts of acid-activated coal gangue, 5 parts of bentonite-based composite phase variant, 5 parts of hollow glass microspheres, 0.5 parts of polypropylene fiber, 4 parts of chitosan-acrylic acid copolymer, 1 part of foaming agent, 3 parts of expanded graphite, 1 part of zinc borate, 4 parts of nano-silicon dioxide, and 260 parts of water; The preparation method of acid-activated coal gangue includes drying the coal gangue at 110°C for 2 hours and then crushing it to 200 mesh, mixing the crushed coal gangue with a 10% sulfuric acid solution at a solid-liquid ratio of 1g:4mL, stirring at a temperature of 80°C and 220rpm for 2 hours, separating by vacuum filtration, washing, placing the acid-washed coal gangue in a muffle furnace, heating it to 600°C at a rate of 5°C / min, calcining it at a constant temperature for 50 minutes, naturally cooling it to room temperature, and grinding it to an average particle size of 40μm. The preparation method of the bentonite-based composite phase-shifter includes: mixing bentonite, anhydrous sodium sulfate, and water; ultrasonically dispersing the mixture at a power of 500 W and a frequency of 40 kHz for 40 minutes to form a uniform suspension; transferring the suspension to a thermostatic reactor and stirring at 60°C and 400 rpm for 4 hours; centrifuging the mixture at 8000 rpm for 10 minutes, vacuum drying the precipitate at 70°C for 12 hours, grinding the dried material, and passing it through a 200-mesh sieve to obtain the obtained product; the weight ratio of bentonite, anhydrous sodium sulfate, and water is 3:2:20. The preparation method of chitosan-acrylic acid copolymer includes: adding 60g of chitosan to 900mL of 3% acetic acid solution, stirring at 500rpm for 30min, heating to 50°C to accelerate dissolution to form a chitosan solution; adding 160g of acrylic acid monomer dropwise to the chitosan solution at a rate of 1mL / min, and adding 2g of potassium persulfate initiator at the same time, reacting under nitrogen protection, 300rpm, and 60°C for 3h, cooling to room temperature, and slowly adding 10% NaOH solution to neutralize and adjust the pH to 7; controlling the inlet air temperature to 180°C, the outlet air temperature to 80°C, and the atomization pressure to -0.3MPa for spray drying to obtain the product; The foaming agent comprises a cement foaming agent and a silicone resin foam stabilizer in a weight ratio of 1:0.2; The preparation method of the fire extinguishing material for mines comprises the following steps: (1) Add sulphoaluminate cement, acid-activated coal gangue, nano-silica, zinc borate and expanded graphite to half the weight of water in sequence and stir at 700 rpm for 15 min to form a uniform slurry; (2) Add chitosan-acrylic acid copolymer, adjust the stirring speed to 400 rpm, and continue for 10 minutes; pre-mix polypropylene fiber and hollow glass microspheres and add them, stirring at 500 rpm for 5 minutes; add bentonite-based composite phase change agent and stir at a low speed of 300 rpm for 4 minutes; (3) Add cement foaming agent, silicone resin foam stabilizer and remaining water, and stir at 200 rpm for 20 minutes.

[0025] Comparative Example 1 In Comparative Example 1, the acid-activated coal gangue was replaced by unactivated coal gangue with an average particle size of 40 μm. The rest was the same as in Example 1, and the preparation steps were the same as in Example 1.

[0026] Comparative Example 2 In Comparative Example 2, acid-activated coal gangue was not added, and the rest was the same as in Example 1, and the preparation steps were the same as in Example 1.

[0027] Comparative Example 3 In Comparative Example 3, the bentonite-based composite phase variant was replaced with bentonite with a particle size of 200 meshes, and the rest was the same as in Example 1, and the preparation steps were the same as in Example 1.

[0028] Comparative Example 4 In Comparative Example 4, no bentonite-based composite phase-modified substance was added, and the rest was the same as in Example 1, and the preparation steps were the same as in Example 1.

[0029] Comparative Example 5 In Comparative Example 5, the chitosan-acrylic acid copolymer was replaced with sodium alginate, and the rest was the same as in Example 1, and the preparation steps were the same as in Example 1.

[0030] Comparative Example 6 In Comparative Example 6, the expanded graphite was replaced by zinc borate, and the rest was the same as in Example 1, and the preparation steps were the same as in Example 1.

[0031] Test Example 1: The following tests were conducted on the fire extinguishing materials for mines prepared in Examples 1-4 and Comparative Examples 1-6: Compressive strength: The material was made into 100×100×20mm test blocks. After curing for 7 days, the test was carried out in accordance with GB / T 17671-2021 "Test method for strength of cement mortar"; Inhibition performance: Refer to MT / T 700-2019 "General Technical Requirements for Inhibitors for Coal Mine Fire Prevention" to test the inhibition rate at a coal temperature of 100°C; High-temperature dehydration and structural stability test: Referring to the crack resistance test method in GB / T 23439-2017 "Concrete Expansion Agent", the material was made into 100×100×20mm test blocks. After curing for 7 days, it was placed in a 200℃ constant temperature box and heated for 1 hour. After cooling, the mass loss rate was measured and the surface cracks were observed; Storage stability test: refer to GB / T 50082-2009 "Test method for long-term properties and durability of ordinary concrete" for accelerated aging; (1) Dry-wet cycle: The specimen was dried in a 50°C oven for 12 hours, then immersed in water for 12 hours. After 10 cycles, the compressive strength retention rate was tested. (2) High temperature and high humidity storage: The material is sealed and stored in an environment of 40°C and 90% humidity for 30 days, and the slurry fluidity (slump) and foaming ratio are tested.

[0032] The results are shown in Table 1 below: Table 1

[0033] Combined with the above content, it can be seen that the performance in Example 1 is the best. The compressive strength and retardation rate of the unactivated coal gangue in Comparative Example 1 are significantly lower than those in Example 1, and the high-temperature mass loss rate increases by 65%. This is because the surface activity of the unactivated coal gangue is low, and it is impossible to remove impurities and calcinate to form a porous structure through acid washing, resulting in weak interfacial bonding with the cement matrix and decreased retardation performance. The compressive strength and retardation rate of the acid-free activated coal gangue in Comparative Example 2 are further reduced, and the crack density is the highest. This is because the acid-activated coal gangue has both gelling activity and adsorption function, and its absence leads to a loose material skeleton, uneven dispersion of the retardation components, and significant deterioration of thermal stability. In Comparative Example 3, bentonite replaces the composite phase changer, and the high-temperature mass loss rate and crack density increase significantly, and the storage stability decreases. This is because ordinary bentonite lacks phase change energy storage capacity and cannot absorb heat through phase change to buffer temperature stress, resulting in dehydration and cracking of the material at high temperature. Comparative Example 4 has no bentonite-based composite phase changer, with the lowest compressive strength and retardation rate and the highest high-temperature mass loss rate. This is because the lack of composite phase variants causes the material to lose its thermal management ability, resulting in rapid evaporation of water and structural collapse, while weakening the synergistic reinforcement effect of inorganic-organic components. In Comparative Example 5, sodium alginate replaces chitosan-acrylic acid copolymer, and the resistance rate is slightly lower than that of Example 1, and the high-temperature crack density increases. This is because chitosan-acrylic acid copolymer has both film-forming properties and chelating effects, and its absence leads to a decrease in the slow-release ability of the inhibitor and a weakening of the fiber-matrix interface adhesion. In Comparative Example 6, zinc borate replaces expanded graphite, and the resistance rate decreases significantly, and the high-temperature mass loss rate is higher. This is because the high-temperature expansion characteristics of expanded graphite can form a dense thermal insulation layer, while single zinc borate only provides chemical flame retardancy and lacks physical barrier effect.

[0034] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A fire extinguishing material for mines, characterized in that: The invention is composed of the following raw materials in parts by weight: 30-40 parts of sulphoaluminate cement, 20-25 parts of acid-activated coal gangue, 5-10 parts of bentonite-based composite phase variant, 3-5 parts of hollow glass microspheres, 0.5-1 part of polypropylene fiber, 3-4 parts of chitosan-acrylic acid copolymer, 1-2 parts of foaming agent, 2-3 parts of expanded graphite, 1-3 parts of zinc borate, 2-4 parts of nano-silicon dioxide and 260-320 parts of water.

2. A fire extinguishing material for mines according to claim 1, characterized in that: The preparation method of the acid-activated coal gangue comprises drying the coal gangue at 100-110° C. for 2-3 hours and then crushing it to 200 mesh; mixing the crushed coal gangue with a 10% sulfuric acid solution by volume at a solid-liquid ratio of 1 g:3-4 mL; stirring at a temperature of 80±2° C. and 180-220 rpm for 2-3 hours; separating by vacuum filtration; washing; placing the acid-washed coal gangue in a muffle furnace, heating it to 560-600° C. at a rate of 5° C. / min, calcining it at a constant temperature for 50-70 minutes, naturally cooling it to room temperature, and grinding it to a particle size of ≤50 μm.

3. A fire extinguishing material for mines according to claim 1, characterized in that: The preparation method of the bentonite-based composite phase-shifted product comprises: mixing bentonite, anhydrous sodium sulfate and water; performing ultrasonic dispersion for 30-40 minutes to form a uniform suspension; transferring the suspension to a constant temperature reactor, stirring at 60°C±1°C and 400-500 rpm for 3-4 hours; performing centrifugal separation, vacuum drying the precipitate at 70-80°C for 10-12 hours, and grinding the dried material and passing it through a 200-mesh sieve to obtain the product.

4. The fire extinguishing material for mines according to claim 3, wherein the weight ratio of the bentonite, anhydrous sodium sulfate and water is 3-4:1-2:20-30.

5. The fire extinguishing material for mines according to claim 1, characterized in that: The preparation method of the chitosan-acrylic acid copolymer comprises: adding chitosan to an acetic acid solution with a volume concentration of 2%-3%, stirring at 500-600 rpm for 20-30 minutes, heating to 50-55°C to accelerate dissolution to form a chitosan solution; dripping acrylic acid monomer into the chitosan solution at a rate of 1 mL / min, simultaneously adding potassium persulfate initiator to react, cooling to room temperature, adjusting the pH to 7±0.2; and spray drying to obtain the product.

6. A fire extinguishing material for mines according to claim 5, characterized in that: The usage ratio of the chitosan, acetic acid solution, acrylic acid monomer and potassium persulfate is 50-60 g: 900-1100 mL: 140-160 g: 2-3 g.

7. A fire extinguishing material for mines according to claim 5, characterized in that: The reaction is carried out under nitrogen protection, 200-300 rpm, and 60°C±1°C for 3-4 hours.

8. The fire extinguishing material for mines according to claim 5, characterized in that: The inlet air temperature of the spray drying is 170-180° C., the outlet air temperature is 80-90° C., and the atomization pressure is 0.2-0.3 MPa.

9. The fire extinguishing material for mines according to claim 1, characterized in that: The foaming agent comprises a cement foaming agent and a silicone resin foam stabilizer in a weight ratio of 1:0.2-0.

5.

10. A method for preparing a fire extinguishing material for mines according to any one of claims 1 to 9, characterized in that the steps include: (1) Add sulphoaluminate cement, acid-activated coal gangue, nano-silica, zinc borate and expanded graphite to half of the water in sequence, and stir at 700-800 rpm for 10-15 minutes to form a uniform slurry; (2) Add chitosan-acrylic acid copolymer, adjust the stirring speed to 400-500 rpm, and continue for 5-10 minutes; pre-mix polypropylene fiber and hollow glass microspheres and add them, stirring at 500-600 rpm for 3-5 minutes; add bentonite-based composite phase change agent and stir at a low speed of 300-400 rpm for 2-4 minutes; (3) Add the foaming agent and the remaining weight of water, and stir at 200-300 rpm for 15-20 minutes.

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