Coal mine underground gas extraction hole sealing material and preparation method thereof

Abstract

The application discloses a kind of coal mine underground gas extraction hole sealing material and preparation method thereof, and the hole sealing material includes composite silicate material, composite nanometer material and surfactant;Composite silicate material includes three components A, B, C;Component A is selected from montmorillonite, bentonite;Component B is selected from zeolite, diatomite;Component C is selected from metakaolin, calcined clay.Composite nanometer material includes nanometer silicon dioxide, sheet nanometer clay and functional nanometer additive;Functional nanometer additive is selected from nanometer aluminum hydroxide, nanometer magnesium hydroxide, nanometer tin oxide antimony.Alkaline silicate material, composite nanometer material and surfactant are dispersed in deionized water to form uniform and stable slurry;Slurry is sent into spray drying tower, and microsphere powder is formed after atomization, and the product is obtained after collecting microsphere powder and sieving.The long-term stability and flame retardant performance of the material are significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology for mining, specifically, it relates to a sealing material for underground gas extraction in coal mines and its preparation method. Background Technology

[0002] Gas drainage is a core technology for preventing gas disasters, and the sealing quality of gas drainage boreholes is a key factor determining drainage efficiency and lifespan. Currently, commonly used sealing materials are mainly cement-based mortar and organic polyurethane materials.

[0003] Cement mortar is low in cost and high in strength, but it shrinks and cracks after hardening, making it unable to seal the crescent-shaped fracture zone at the top of the borehole, and it is difficult to adapt to the deformation caused by coal seam mining. Polyurethane materials, although expansive, have exothermic reactions, large shrinkage rates, poor permeability, and cannot be used for secondary sealing of fractures that develop later. In addition, existing materials generally suffer from poor water retention, weak impermeability, and insufficient environmental friendliness, resulting in rapid decay of gas extraction concentration and low borehole utilization.

[0004] Chinese invention patent CN113636789A discloses a sealing material mainly composed of silicates, nano-oxides, and surfactants. When mixed with water in a certain proportion, it forms a slurry for sealing. When used, the gel-like substance formed by the sealing material with water has thixotropic properties and can deform synchronously with the coal seam, sealing the gas leakage channel and increasing the gas extraction concentration. However, the material still has the following defects: (1) The stability under long-term extraction negative pressure and changes in ground stress needs to be improved; (2) The nano-oxides have a single function, mainly playing the role of adjusting the interlayer spacing, without giving the material additional safety or structural enhancement functions; (3) The uniformity of powder mixing in the preparation process depends on physical stirring, and the nanoparticles are prone to agglomeration; (4) It depends on specific silicate minerals (such as high-purity montmorillonite), and the raw material cost is high and the source is limited. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a sealing material for underground gas extraction in coal mines and a method for preparing the same, so as to at least improve the long-term stability and flame retardancy of the sealing material.

[0006] To solve the above technical problems, according to one aspect of the present invention, a sealing material for underground gas drainage in coal mines is provided, comprising the following components by mass percentage: 80.0% ~ 98.0% composite silicate materials, 1.0% ~ 15.0% composite nanomaterials and 0.5% ~ 5.0% surfactants; The composite silicate material includes component A, component B, and component C; component A is selected from at least one of montmorillonite and bentonite; component B is selected from at least one of zeolite and diatomaceous earth; and component C is selected from at least one of metakaolinite and calcined clay. The composite nanomaterial includes nano-silica, layered nano-clay, and functional nano-additives; the layered nano-clay is selected from at least one of nano-mica, vermiculite, and kaolin flakes; the functional nano-additives are selected from at least one of nano-aluminum hydroxide, nano-magnesium hydroxide, and nano-tin antimony oxide.

[0007] As a preferred embodiment, the composite silicate material has a mass ratio of component A, component B and component C of (5~8): (1~3): (1~2).

[0008] In a preferred embodiment, the mass ratio of nano-silica, layered nano-clay, and functional nano-additives in the composite nanomaterial is (6~10): (3~5): (1~3).

[0009] In a preferred embodiment, the specific surface area of ​​the nano-silica is 150 m². 2 / g~300 m 2 / g, with a particle size of 10 nm to 50 nm.

[0010] In a preferred embodiment, the aspect ratio of the layered nanoclay is 20 to 100, and the layer thickness is 1 nm to 20 nm.

[0011] In a preferred embodiment, the surfactant is a compound cationic surfactant system composed of ester-based gemini quaternary ammonium salt and chitosan quaternary ammonium salt in a mass ratio of (3~5):1.

[0012] In a preferred embodiment, the surfactant is an amphiphilic block copolymer.

[0013] In a preferred embodiment, the surfactant is a compound of alkyl glycoside and sodium lignosulfonate in a mass ratio of (5~7):(3~5).

[0014] According to another aspect of the present invention, a method for preparing the above-described sealing material for underground gas drainage in coal mines is provided, comprising: Step 1: Disperse the composite silicate material, composite nanomaterial and surfactant in deionized water to form a uniform and stable slurry; Step 2: The slurry is fed into the spray drying tower. The inlet air temperature is set to 180~220℃ and the outlet air temperature is controlled at 80~110℃. After the slurry is atomized by the atomizer, it forms microsphere powder. The microsphere powder is collected and sieved to obtain the product.

[0015] In a preferred embodiment, in step one, the solid content of the slurry is controlled at 20%~40% (w / w).

[0016] This invention significantly improves the long-term stability and flame-retardant properties of sealing materials through the synergistic effect of composite silicate materials, composite nanomaterials, and surfactants. The composite silicate material provides a basic gel network, water retention and impermeability, and structural flexibility, which can be adjusted synchronously with coal seam deformation; the composite nanomaterials construct a dense barrier layer, enhance mechanical strength, and impart excellent flame-retardant properties; the surfactants achieve uniform particle dispersion, reduce agglomeration, and enhance interfacial bonding and thixotropic flow properties. The synergistic effect of these three components makes the material less prone to cracking, water loss, or leakage under long-term negative pressure and geostress disturbances, significantly improving the flame-retardant rating and ensuring long-term stable gas extraction concentration, thus achieving long-term, safe, and efficient sealing. Detailed Implementation

[0017] The coal mine underground gas extraction sealing material provided by a typical embodiment of the present invention includes composite silicate material, composite nanomaterial and surfactant.

[0018] The contents of the above components by mass percentage are: 80.0% ~ 98.0% composite silicate material, 1.0% ~ 15.0% composite nanomaterial, and 0.5% ~ 5.0% surfactant.

[0019] For example, the sealing material for underground gas extraction in coal mines provided in this embodiment includes: 80.0% composite silicate material, 15.0% composite nanomaterial, and 5.0% surfactant; or 98.0% composite silicate material, 1.0% composite nanomaterial, and 1.0% surfactant; or 95.0% composite silicate material, 4.5% composite nanomaterial, and 0.5% surfactant.

[0020] The composite silicate material includes component A, component B and component C.

[0021] Component A is selected from at least one of montmorillonite and bentonite; component B is selected from at least one of natural zeolite, artificial zeolite, and diatomaceous earth; and component C is selected from at least one of metakaolinite and calcined clay.

[0022] Component A possesses strong hydration swelling properties and high water retention, forming a layered gel network upon contact with water. This provides basic thixotropy and self-healing capabilities, adapting to micro-deformations in coal seams and reducing gas leakage from fractures. Component B has a porous structure and high adsorption capacity, enhancing the material's water retention, impermeability, and structural stability, inhibiting long-term water loss shrinkage, and improving slurry fluidity and injectability. Component C provides active silica-alumina components, participating in the hydration reaction, strengthening the gel network's density and mechanical strength, improving the material's resistance to aging and negative pressure erosion, and significantly enhancing long-term stability.

[0023] In composite silicate materials, component A provides a flexible gel matrix, component B enhances water retention, impermeability, and structural support, and component C is used to strengthen strength and durability. The material after the three components are combined has the characteristics of low shrinkage, high water retention, strong adhesion, deformation resistance, and aging resistance, effectively sealing cracks and adapting to mining deformation, significantly improving long-term sealing stability.

[0024] In a preferred embodiment, the mass ratio of component A, component B and component C is (5~8): (1~3): (1~2), for example: 5:1:1, 5:3:2, 6:2:1, 7:3:1, 8:1:1, 8:3:2, etc.

[0025] The composite nanomaterial comprises nano-silica, layered nano-clay, and functional nano-additives. The layered nano-clay is selected from at least one of nano-mica, vermiculite, and kaolin flakes; the functional nano-additives are selected from at least one of nano-aluminum hydroxide, nano-magnesium hydroxide, and nano-tin antimony oxide.

[0026] Among them, nano-silica, with its high specific surface area and small particle size, can fill the pores of silicate gel, constructing a dense nanoscale barrier network to improve the material's density, strength, and impermeability; it also enhances interfacial bonding and reduces particle agglomeration. Layered nanoclay, with its high aspect ratio and thin layered structure, can form a barrier layer within the material, extending the gas permeation path and significantly improving impermeability and gas barrier properties; its lamellar slip properties enhance the material's flexibility and resistance to deformation. Functional nano-additives, upon thermal decomposition, absorb heat, release water of crystallization, and form a dense carbon layer, significantly improving the material's flame retardancy, smoke suppression, and thermal stability, reducing the risk of downhole fires; they also enhance the material's thermal stability and mechanical properties.

[0027] Nano-silica provides a dense framework, layered clay constructs a barrier, and functional nano-additives impart flame-retardant safety performance; after compounding, the flame-retardant performance of the material is significantly improved (LOI≥35%), with high density, strong impermeability and gas barrier, and stable structure. It is not easy to break down and leak gas under long-term negative pressure, while meeting the downhole flame-retardant safety requirements.

[0028] In a preferred embodiment, the mass ratio of the nano-silica, the layered nano-clay, and the functional nano-additive is (6~10): (2~5): (1~3), for example: 6:3:1, 7:4:2, 7:2:1, 9:5:1, 10:5:3, etc.

[0029] The specific surface area of ​​the nano-silica is 150 m². 2 / g~300 m 2 / g, with a particle size of 10 nm to 50 nm.

[0030] Limiting the specific surface area of ​​nano-silica ensures its high dispersibility, strong filling capacity, and high reactivity: too small a particle size leads to agglomeration, while too large a particle size results in low filling efficiency; too low a specific surface area leads to weak interfacial bonding and insufficient pore filling, while too high a specific surface area leads to water absorption and agglomeration, affecting flowability. This parameter range achieves optimal filling densification and interfacial enhancement effects.

[0031] The aspect ratio of the layered nanoclay is 20 to 100, and the layer thickness is 1 nm to 20 nm.

[0032] By limiting the aspect ratio and layer thickness of the layered nanoclay, a continuous, uniform, and highly barrier-resistant layered network can be formed: if the aspect ratio is too low, the barrier effect is poor; if it is too high, it is prone to stacking and agglomeration; if the layer is too thick, the flexibility is poor and it is prone to cracking; if it is too thin, dispersion is difficult. This parameter range takes into account barrier efficiency, structural flexibility, and dispersion stability.

[0033] The surfactant provided in this embodiment can be a compound system or a single structural type.

[0034] Among them, the compound cationic surfactant system is composed of ester-based gemini quaternary ammonium salt and chitosan quaternary ammonium salt in a mass ratio of (3~5):1.

[0035] For example, the mass ratio of ester-based gemini quaternary ammonium salt to chitosan quaternary ammonium salt is 3:1, 4:1, 5:1, etc.

[0036] The preferred ester-based gemini quaternary ammonium salts are biodegradable gemini quaternary ammonium salts synthesized using natural fatty acids or rosin acid as hydrophobic groups. Specific examples include: laurate-based gemini quaternary ammonium salts, stearate-based gemini quaternary ammonium salts, or oleate-based gemini quaternary ammonium salts.

[0037] Specific examples of chitosan quaternary ammonium salts include at least one of hydroxypropyl chitosan quaternary ammonium salt and carboxymethyl chitosan quaternary ammonium salt.

[0038] Compound surfactant systems can also be mixtures of alkyl glycosides and sodium lignosulfonate, with a mass ratio of (5~7):(3~5). For example: 5:3, 5:5, 6:4, 6:5, 7:5, etc.

[0039] The surfactant with a single structural type is an amphiphilic block copolymer, specifically selected from at least one of the following compounds: polydimethyldiallylammonium chloride-b-polyethylene glycol (PDMDAAC-b-PEG), polyacrylamide-b-polyethylene glycol (PAM-b-PEG), and polyquaternium-10-b-polyethylene glycol. The number-average molecular weight of the above copolymers is preferably between 2000 and 10000.

[0040] Single-structure surfactants can also be polyoxyethylene-polyoxypropylene-polyoxyethylene or polyacrylic acid-b-polyethylene glycol.

[0041] Surfactants, through wetting, dispersing, emulsifying, and solubilizing effects, achieve uniform dispersion of composite silicates and composite nanoparticles in water, inhibit nanoparticle aggregation, and improve slurry stability, flowability, and thixotropy. Simultaneously, they adsorb onto the particle surface, enhancing the interfacial bonding between silicates and nanomaterials, and improving the density and adhesion strength of the gel network. Different types of surfactants are suitable for different working conditions, further optimizing the material's water retention, impermeability, and biodegradability, achieving highly efficient synergy with inorganic-organic systems.

[0042] Another typical embodiment of the present invention provides a method for preparing the above-mentioned coal mine underground gas drainage sealing material, including the following steps.

[0043] Step 1: Slurry preparation and in-situ compounding.

[0044] Composite silicate materials, composite nanomaterials, and surfactants are dispersed in deionized water to form a uniform and stable slurry. During this process, the composite nanoparticles and surfactants undergo in-situ adsorption and binding with the surface of the silicate material particles in the liquid phase.

[0045] In this step, the material is dispersed in a high-speed shear disperser at a speed of 3000~8000 rpm for 30~60 minutes to form a uniform and stable suspension slurry. The solid content of the suspension slurry is controlled at 20%~40% (w / w).

[0046] Step 2: Spray drying.

[0047] The slurry is fed into a spray drying tower, with the inlet air temperature set at 180~220℃ and the outlet air temperature controlled at 80~110℃. After the slurry is atomized by the atomizer, the moisture evaporates rapidly, forming hollow spherical or near-spherical microsphere powder.

[0048] Step 3: Collection and Packaging.

[0049] Collect the dried powder from the bottom of the spray drying tower, pass it through a 75μm sieve, and the residue should be ≤5%. After passing the test, seal it in moisture-proof packaging to obtain the finished sealing material.

[0050] During on-site sealing, the sealing material provided by this invention is mixed with water at a water-to-solid ratio of (4-6):1 in a mixer and stirred for 3-5 minutes until a uniform, viscous, gel-like slurry without dry powder is formed. The slurry is then injected into the sealing section of the gas extraction borehole using a grouting pump or manual injection. Upon encountering moisture in the coal seam within the borehole, the slurry further hydrates and expands, filling the annular space of the borehole and penetrating surrounding micro-fractures to form a non-shrinking, highly adhesive, and tight seal.

[0051] The technical solutions claimed in this invention will be further described below through some embodiments. However, the embodiments and comparative examples are for explaining the implementation schemes of this invention and do not exceed the scope of the subject matter of this invention. The scope of protection of this invention is not limited by the embodiments. Unless otherwise specified, the materials and reagents used in this invention can be obtained from commercially available products in the art.

[0052] The detection methods used in the following examples and comparative examples are all performed in accordance with the relevant national standards, as detailed below: pH value: determined according to GB / T 5211.6-2020; Material stability: After the material is mixed with water and solids according to the water-solid ratio, it is left to stand at room temperature for 7 days to observe whether it separates into layers or bleeds. Determination of residue on sieves: GB / T 21524-2008, applicable to various inorganic powder materials (including silicates, nano oxides, etc.), using dry sieving or wet sieving methods; Water retention: The water loss rate after 7 days of open storage at room temperature was determined according to GB / T 45002-2024. Limiting oxygen index (LOI): determined according to GB / T 2406.2-2009; Gas extraction concentration: determined according to AQ / T 1019-2006 standard; Marsh funnel viscosity: determined according to GB / T 1723 Coating viscosity test method; Surface resistivity: determined according to GB / T 31838.2-2019; Simulated fracture plugging efficiency: A self-made fracture model was used, and the gas leakage rate was tested after the slurry was injected. Example 1

[0053] The composite silicate material consists of montmorillonite, zeolite, and metakaolin in a mass ratio of 70:20:10. The composite nanomaterial consists of nano-silica, nano-mica sheets, and nano-aluminum hydroxide in a mass ratio of 70:20:10. The surfactant consists of laurate-based gemini quaternary ammonium salt and hydroxypropyl chitosan quaternary ammonium salt in a mass ratio of 4:1.

[0054] In this embodiment, the mass percentage contents of the composite silicate material, the composite nanomaterial, and the surfactant are 88.0%, 10.0%, and 2.0%, respectively.

[0055] Step 1: Weigh the composite silicate material, composite nanomaterial and surfactant according to the above formula, add them together to deionized water, and disperse them in a high-speed shear disperser at 6000 rpm for 40 minutes to form a uniform and stable suspension slurry.

[0056] Step 2: The above slurry is conveyed to a spray drying tower, with the inlet air temperature set at 200℃ and the outlet air temperature at 95℃. After the slurry is atomized by the atomizer, the moisture evaporates rapidly, resulting in hollow spherical composite microsphere powder.

[0057] Step 3: Collect the dried powder, pass it through a 75μm standard sieve, and control the residue on the sieve to be ≤5%. After passing the test, seal and moisture-proof package to obtain the finished sealing material.

[0058] In use, the sealing material provided in this embodiment is mixed with water at a water-to-solid ratio of 5:1 in a mixer and stirred for 4 minutes until a uniform, viscous, gel-like slurry without dry powder is formed. The slurry is then injected into the sealing section of the gas extraction borehole using a grouting pump or manual injection.

[0059] Testing revealed that the pH value of the material obtained in this embodiment was 10, and its gel stability (after 7 days in a 60°C constant temperature chamber) was: no stratification and no water seepage; its water retention (after 7 days of open storage at room temperature) was < 5%; and its gas extraction concentration was ≥ 80% after 2 months. Example 2

[0060] The composite silicate material is made of bentonite, diatomaceous earth, and calcined clay in a mass ratio of 75:15:10. The composite nanomaterial is made of nano-silica, nano-vermiculite flakes, and nano-magnesium hydroxide in a mass ratio of 60:30:10. The surfactant is a PEO-PPO-PEO block copolymer (molecular weight approximately 6000).

[0061] In this embodiment, the mass percentage contents of the composite silicate material, the composite nanomaterial, and the surfactant are 92.0%, 6.5%, and 1.5%, respectively.

[0062] Step 1: Weigh the composite silicate material, composite nanomaterial and surfactant according to the above formula, add them together to deionized water, and disperse them in a high-speed shear disperser at 6000 rpm for 40 minutes to form a uniform and stable suspension slurry.

[0063] Step 2: The above slurry is conveyed to a spray drying tower, with the inlet air temperature set at 200℃ and the outlet air temperature at 95℃. After the slurry is atomized by the atomizer, the moisture evaporates rapidly, resulting in hollow spherical composite microsphere powder.

[0064] Step 3: Collect the dried powder, pass it through a 75μm standard sieve, and control the residue on the sieve to be ≤5%. After passing the test, seal and moisture-proof package to obtain the finished sealing material.

[0065] In use, the sealing material provided in this embodiment is mixed with water at a water-to-solid ratio of 4:1 in a mixer and stirred for 4 minutes until a uniform, viscous, gel-like slurry without dry powder is formed. The slurry is then injected into the sealing section of the gas extraction borehole using a grouting pump or manual injection.

[0066] Testing revealed that the material obtained in this embodiment has a pH value of 10.5, excellent gel thixotropy (it forms a gel when left to stand, and the viscosity decreases significantly after stirring); water retention (water loss rate after 7 days of open storage at room temperature) < 4%; and a gas extraction concentration ≥ 85% after 2 months. Example 3

[0067] The composite silicate material consists of montmorillonite, zeolite, and metakaolin in a mass ratio of 70:15:15. The composite nanomaterial consists of nano-silica, nano-kaolin flakes, and nano-tin antimony oxide in a mass ratio of 70:20:10. The surfactant consists of alkyl glycosides and sodium lignosulfonate in a mass ratio of 6:4.

[0068] In this embodiment, the mass percentage contents of the composite silicate material, the composite nanomaterial, and the surfactant are 82.0%, 15.0%, and 3.0%, respectively.

[0069] Step 1: Weigh the composite silicate material, composite nanomaterial and surfactant according to the above formula, add them together to deionized water, and disperse them in a high-speed shear disperser at 6000 rpm for 40 minutes to form a uniform and stable suspension slurry.

[0070] Step 2: The above slurry is conveyed to a spray drying tower, with the inlet air temperature set at 200℃ and the outlet air temperature at 95℃. After the slurry is atomized by the atomizer, the moisture evaporates rapidly, resulting in hollow spherical composite microsphere powder.

[0071] Step 3: Collect the dried powder, pass it through a 75μm standard sieve, and control the residue on the sieve to be ≤5%. After passing the test, seal and moisture-proof package to obtain the finished sealing material.

[0072] In use, the sealing material provided in this embodiment is mixed with water at a water-to-solid ratio of 6:1 in a mixer and stirred for 4 minutes until a uniform, viscous, gel-like slurry without dry powder is formed. The slurry is then injected into the sealing section of the gas extraction borehole using a grouting pump or manual injection.

[0073] Testing revealed that the material obtained in this embodiment has a pH value of 9.8, good slurry fluidity (Marsh funnel viscosity 45s), water retention (water loss rate after 7 days of open storage at room temperature) < 6%, and a gas extraction concentration ≥ 75% after 2 months.

[0074] Comparative Example 1 This comparative example uses commercially available ordinary silicate cement-based sealing material.

[0075] Weigh commercially available 42.5 grade ordinary Portland cement and water according to a water-to-solid ratio of 0.6:1. Mix them in a cement mortar mixer at 200 rpm for 3 minutes to form a uniform slurry. Immediately pour the slurry into a standard mold and cure it for 28 days at room temperature (20±2℃) and relative humidity >90%.

[0076] Testing revealed that the material has a linear shrinkage rate of ≥ 0.8% over 28 days; it has no ability to penetrate and seal existing fractures; the gas extraction concentration dropped to < 30% after 2 months due to cracking; and the material is a rigid solidified material that cannot adapt to coal seam deformation.

[0077] Comparative Example 2 This comparative example uses sodium-based montmorillonite, nano-silica, and sodium dodecylbenzenesulfonate, a traditional anionic surfactant, with mass percentages of 95%, 4%, and 1%, respectively. The water-to-solid ratio is 5:1 during use.

[0078] Sodium montmorillonite, nano-silica, and sodium dodecylbenzenesulfonate were first dry-mixed in a three-dimensional mixer for 30 minutes. Then, the mixed dry powder was added to water and stirred in a paddle mixer at 300 rpm for 10 minutes to form a slurry, which was then allowed to stand to gel.

[0079] Testing revealed that the material exhibits poor gel stability, is prone to dehydration and shrinkage (7-day water loss rate > 15%), has a loose gel structure and low cohesion, maintains a gas extraction concentration of approximately 60% over 2 months, and uses non-biodegradable surfactants.

[0080] Comparative Example 3 This comparative example does not include any composite nanomaterials. A composite silicate material composed of montmorillonite and zeolite in a 1:1 mass ratio is used, and the surfactant is sodium dodecylbenzenesulfonate (SDBS), a single-type anionic surfactant.

[0081] The mass percentage content of the composite silicate material and the surfactant is 94.0% and 6.0%, respectively.

[0082] The preparation method is the same as in Example 1. The water-to-solid ratio used is 5:1.

[0083] Testing revealed that the material exhibited poor gel density and a porous structure; its simulated fracture plugging efficiency was <60%; it was easily broken down by airflow under negative pressure during extraction; and its gas extraction concentration maintenance rate was <50% over two months.

[0084] The scope of protection claimed by this invention is not limited to the specific embodiments described above. For those skilled in the art, this invention can have various modifications and alterations. Any modifications, improvements, and equivalent substitutions made within the concept and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A sealing material for underground gas extraction in coal mines, characterized in that, The components include the following percentages by mass: 80.0% ~ 98.0% composite silicate materials, 1.0% ~ 15.0% composite nanomaterials, and 0.5% ~ 5.0% surfactants; The composite silicate material includes component A, component B, and component C; component A is selected from at least one of montmorillonite and bentonite; component B is selected from at least one of zeolite and diatomaceous earth; and component C is selected from at least one of metakaolinite and calcined clay. The composite nanomaterial includes nano-silica, layered nano-clay, and functional nano-additives; the layered nano-clay is selected from at least one of nano-mica, vermiculite, and kaolin flakes; the functional nano-additives are selected from at least one of nano-aluminum hydroxide, nano-magnesium hydroxide, and nano-tin antimony oxide.

2. The sealing material for underground gas extraction in coal mines according to claim 1, characterized in that, The composite silicate material has a mass ratio of (5~8): (1~3): (1~2) for components A, B, and C.

3. The sealing material for underground gas extraction in coal mines according to claim 1 or 2, characterized in that, In the composite nanomaterial, the mass ratio of nano-silica, layered nano-clay, and functional nano-additives is (6~10):(2~5):(1~3).

4. The sealing material for underground gas extraction in coal mines according to claim 3, characterized in that, The specific surface area of ​​the nano-silica is 150 m². 2 / g~300 m 2 / g, with a particle size of 10 nm to 50 nm.

5. The sealing material for underground gas extraction in coal mines according to claim 4, characterized in that, The aspect ratio of the layered nanoclay is 20 to 100, and the layer thickness is 1 nm to 20 nm.

6. The sealing material for underground gas extraction in coal mines according to claim 1, characterized in that, The surfactant is a compound cationic surfactant system, composed of ester-based gemini quaternary ammonium salt and chitosan quaternary ammonium salt in a mass ratio of (3~5):

1.

7. The sealing material for underground gas extraction in coal mines according to claim 1, characterized in that, The surfactant is an amphiphilic block copolymer.

8. The sealing material for underground gas extraction in coal mines according to claim 1, characterized in that, The surfactant is a compound of alkyl glycoside and sodium lignosulfonate, with a mass ratio of (5~7):(3~5).

9. The method for preparing the sealing material for underground gas drainage in coal mines according to any one of claims 1-8, characterized in that, include: Step 1: Disperse the composite silicate material, composite nanomaterial and surfactant in deionized water to form a uniform and stable slurry; Step 2: The slurry is fed into the spray drying tower. The inlet air temperature is set to 180~220℃ and the outlet air temperature is controlled at 80~110℃. After the slurry is atomized by the atomizer, it forms microsphere powder. The microsphere powder is collected and sieved to obtain the product.

10. The method for preparing sealing material for underground gas drainage in coal mines according to claim 9, characterized in that: In step one, the solid content of the slurry is controlled at 20%~40% (w / w).