Coal mine spraying air leakage stopping material and preparation method thereof

Abstract

This invention discloses a coal mine spray-applied air-sealing material and its preparation method, which is composed of component A: polymeric MDI and component B: polyol, catalyst, foam stabilizer, foaming agent, filler, flame retardant, and long-lasting reinforcing agent. The long-lasting reinforcing agent is a waxy film-forming material coated with crystalline inorganic salt, and the particle size is controlled to be 100-300 μm by shear granulation or fluidized bed coating granulation. This invention solves the problem of exothermic reaction and can achieve self-repair.

Description

Technical Field

[0001] This invention belongs to the field of mine safety and fireproof materials technology, specifically relating to a material suitable for spraying and sealing air leaks in coal mines and its preparation method. Background Technology

[0002] The underground ventilation system in coal mines is the lifeline for ensuring safe production. Its stability and effectiveness directly affect the safety of underground workers and production efficiency. However, due to complex coal seam geological conditions, mining pressure, and aging roadway support structures, cracks and air leakage channels often appear in underground roadways, goafs, and sealed walls, leading to major safety hazards such as airflow short-circuiting, gas accumulation, and spontaneous combustion of coal. These air leaks in underground roadways, goafs, and sealed walls have long been considered "hidden killers" of mine safety, easily triggering spontaneous combustion of coal and seriously threatening production safety. Air leakage sealing technology is an important technique for preventing and extinguishing fires by disrupting the oxygen supply conditions for spontaneous combustion of coal. It mainly includes methods such as constructing sealed walls and spraying air leakage sealing coatings. Spraying air leakage sealing technology has received widespread attention.

[0003] Currently, the main material used for spraying is concrete. However, sprayed concrete has drawbacks: long curing time, high rebound rate, large transportation volume of cement, sand, and other materials, cumbersome spraying procedures, high equipment requirements, inconvenient operation, and a tendency to crack after curing, affecting its airtightness. Traditional sealing materials are no longer sufficient to meet the increasingly complex and demanding requirements of mining environments. Therefore, sprayed polymer materials, as an efficient and convenient solution, rapidly form a dense, high-strength elastic sealing layer on the leaking surface through spraying, effectively sealing air leakage channels, improving the ventilation network, and playing an irreplaceable role in preventing coal mine gas and fire accidents.

[0004] Patent CN 116285918B discloses a flame-retardant coal mine spray-applied sealing material, which consists of two components. Component A is mainly composed of water glass (inorganic binder), combined with a catalyst and modified nano-calcium carbonate. Component B is mainly composed of polymeric MDI (organic reactant), combined with polyether, modified illite (functional filler), and a foam stabilizer. In application, components A and B are mixed, and through the synergistic effect of the gel curing of the inorganic materials and the polymerization and foaming reaction of the organic materials, a solidified body with flame retardancy, antistatic properties, and a certain mechanical strength is quickly formed. However, after the material cures, it forms a cross-linked network. Once internal microcracks or damage occur due to mine pressure or vibration, its performance (such as sealing and strength) will permanently decline and cannot be automatically repaired. The material's lifespan depends entirely on its initial strength and toughness, and its long-term reliability faces challenges in the dynamically changing downhole environment.

[0005] Patent CN 102432994B discloses a polyurethane-based flame-retardant and antistatic multi-nano component foam material and its preparation method. This method introduces various nanomaterials as functional fillers into a polyurethane raw material system (isocyanate, polyether polyol). Through the dispersion and compounding of nanomaterials in the matrix, the final foam material possesses both flame-retardant and antistatic properties. However, this method utilizes the large specific surface area and heat capacity of nanomaterials to absorb and buffer the heat released during the polyurethane polymerization reaction. However, nanomaterials suffer from problems such as easy agglomeration and failure, insufficient functional durability, difficulty in quality control, and high production costs.

[0006] Therefore, developing a new type of coal mine air-sealing material with low heat release and self-healing function can not only help improve mine operation safety, but also extend the service life after spraying and reduce the number of subsequent sprayings, thus effectively improving production efficiency.

[0007] Patent CN 104909636B discloses a biomimetic self-healing material for sealing leaks in coal mines. This material consists of three parts: a fast-setting and expanding material (such as a cement-based material), microcapsules containing a healing agent, and a catalyst. The catalyst used (especially expensive metal-organic catalysts such as Grubbs) is prone to premature deactivation under the humid and highly alkaline conditions (cement environment) underground. The preparation and dispersion of the self-healing material requires complex production processes and strict quality control, increasing material costs and construction complexity. Furthermore, this healing method relies on the free flow of the healing agent within the crack. Underground coal dust and accumulated water may block or contaminate the crack, hindering the flow of the healing agent and its contact with the catalyst, leading to repair failure.

[0008] Wu Mingyue et al. from Shandong University of Science and Technology published a paper titled "Preparation and Performance Study of Self-Repairing Spray Material for Coal Mine Leakage Sealing." Their research focused on the central issue of sealing cracks in coal mine leakage sealing spray materials using the mineralization ability of microorganisms. They screened a carbonate mineralizing bacterium, studied the effects of different external environments on its growth and enzyme activity, and optimized the bacterial growth conditions. Furthermore, they prepared an inorganic cementitious material as a coating material for the bacteria, and used this material to prepare a biocapsule. This biocapsule showed a certain effect on improving the performance of cement-based materials and promoting crack healing. While this technology can be applied to cement-based coal mine leakage sealing spray materials, it cannot be directly applied to novel polymeric materials because the presence of polyols and catalysts in the components is detrimental to microbial survival.

[0009] Therefore, there is an urgent need for a coal mine spray sealing material that generates low heat, can be repeatedly triggered for repair, is friendly to the substrate, is more adaptable to the underground environment, and is cost-controllable. Summary of the Invention

[0010] Addressing the shortcomings of existing technologies for spray-applied air-sealing materials in coal mines, the inventors unexpectedly discovered, while conducting targeted research on reducing heat generation and extending the lifespan of materials through self-repair, that adding crystalline inorganic salts coated with a waxy material of suitable melting point range to the material not only allows for the storage of crystalline inorganic salts within the air-sealing material while utilizing the hydrophobic properties of the wax, but also enables the waxy coating to absorb heat during the phase change reaction, reducing the risk of combustion. Simultaneously, the waxy film-forming material encapsulating the crystalline inorganic salts, after melting, exposes and disperses the crystalline inorganic salts within the solidified coating surface. When internal micro-cracks or damage occur due to mine pressure or vibration, in the high-humidity environment of the mine, the crystalline inorganic salts hydrate and expand upon contact with moisture, or undergo a hydration reaction, filling the cracks and achieving repair, thus extending the lifespan of the spray-applied air-sealing material.

[0011] This invention is achieved through the following means:

[0012] This invention provides a coal mine spray sealing material, which contains a long-lasting reinforcing agent prepared from crystalline inorganic salts coated with a waxy film-forming material.

[0013] Firstly, the coal mine spray sealing material provided by the present invention is composed of the following components:

[0014] Component A: Polymerized MDI (polymethylene polyphenyl polyisocyanate);

[0015] Component B: polyol, catalyst, foam stabilizer, foaming agent, filler, flame retardant, and long-lasting reinforcing agent, wherein the long-lasting reinforcing agent is a crystalline inorganic salt coated with a waxy film-forming material.

[0016] Furthermore, the polyol is at least one of polyether polyol and polyester polyol;

[0017] Furthermore, the catalyst is at least one of triethylenediamine, dimethylcyclohexylamine, stannous octoate, and dibutyltin dilaurate; further, the foam stabilizer is at least one of polyether-modified siloxane foam stabilizer, allyl polyether-modified foam stabilizer, bio-based polyether silicone copolymer foam stabilizer, and polyurethane foam stabilizer; further, the foaming agent is water; further, the filler is at least one of calcium carbonate, talc, and quartz powder; further, the flame retardant is at least one of ammonium polyphosphate, melamine, and expandable graphite.

[0018] Furthermore, in the long-lasting reinforcing agent, the waxy film-forming material and the crystalline inorganic salt are in a weight ratio of 0.1-1:1, preferably 0.4-0.6. If the amount of waxy film-forming material is too low, a continuous coating with a certain thickness cannot be formed, leading to hydration of the crystalline inorganic material during storage. If the amount of waxy film-forming material is too high, on the one hand, the heat generated by the sprayed sealing material is insufficient to completely melt the waxy material, exposing all the crystalline inorganic salt; on the other hand, it cannot be evenly dispersed in the polyol system of component B, resulting in uneven cooling of different parts of the sprayed sealing material.

[0019] Furthermore, the long-acting enhancer accounts for 5%–20% of component B by mass.

[0020] Furthermore, the particle size of the long-lasting reinforcing agent is 100-300μm, preferably 150-250μm. The long-lasting reinforcing agent with a suitable particle size can be uniformly dispersed in the polyol system and exert its best performance during spraying operations.

[0021] Furthermore, the waxy film-forming material is at least one of paraffin wax, microcrystalline wax, oxidized polyethylene wax, montmorillonite wax, and Fischer-Tropsch wax, preferably microcrystalline wax or montmorillonite wax. The melting temperature of microcrystalline wax is 60-90℃ and the melting temperature of montmorillonite wax is 70-90℃. This melting temperature is higher than room temperature (20-30℃) and significantly lower than the reaction temperature of the sprayed air-sealing material (≤140℃), which satisfies the storage requirements and allows the material to melt and expose the crystalline inorganic matter during operation.

[0022] Furthermore, the crystalline inorganic salt is at least one of anhydrous sodium sulfate, calcium sulfoaluminate, and magnesium oxide, preferably anhydrous sodium sulfate, which is a widely available, inexpensive, and cost-effective basic chemical raw material. Moreover, when anhydrous sodium sulfate (Na₂SO₄) is converted to sodium sulfate decahydrate (Na₂SO₄·10H₂O), its volume expands by approximately 3 to 4 times; this expansion pressure characteristic can provide a sealing effect.

[0023] Secondly, the present invention also provides a method for preparing component B of a coal mine spray-applied air-sealing material, comprising the following steps:

[0024] S1, Preparation of Long-Lasting Enhancer

[0025] Crystalline inorganic salt powder is mixed with waxy film-forming materials and then granulated by shearing or fluidized bed coating.

[0026] Preparation of S2 and B components

[0027] Mix the polyol, catalyst, foam stabilizer, and filler at a low speed of 50-500 rpm for 10 minutes; add the long-lasting reinforcing agent from S1 and mix at a low speed for 10 minutes; finally add the foaming agent and mix for 3-5 minutes, then immediately vacuum degas for 5-10 minutes and seal the package.

[0028] Furthermore, the long-acting reinforcing agent is prepared by shear granulation as follows:

[0029] S1. Place the crystalline inorganic salt into a high-efficiency wet granulation machine;

[0030] S2. Heat the waxy film-forming material to a molten state, spray it online into the crystalline inorganic material, and start stirring at 100-500 rpm and cutting at 3000-5000 rpm for high-shear granulation for 10-20 minutes.

[0031] S3. The material prepared in S2 is sieved through an air jet sieve to obtain a long-lasting reinforcing agent.

[0032] Furthermore, the preparation of the long-acting reinforcing agent via fluidized bed coating and granulation is as follows:

[0033] S1. Place the crystalline inorganic salt into a fluidized bed granulator and preheat it with hot air at 65-85℃.

[0034] S2. Heat the waxy film-forming material to a molten state, and coat it with powder by spraying it from the top, then condense and coat it on the surface of the inorganic salt; the air inlet volume is 3-20 m³ / h, the atomization pressure is 0.3-0.6 MPa, the nozzle diameter is 0.5-1.2 mm, and the liquid flow rate is 5-15 g / min;

[0035] S3. The material prepared in S2 is sieved through an air jet sieve to obtain a long-lasting reinforcing agent.

[0036] The beneficial effects of this invention are as follows:

[0037] 1. Reduced the exothermic reaction problem of air-sealing materials sprayed in coal mines.

[0038] The long-lasting reinforcing agent provided by this invention, which consists of a waxy material with a specific melting point coating crystalline inorganic salts, absorbs heat when the polymerization reaction occurs during spraying operations, as the waxy coating melts. Simultaneously, the released crystalline inorganic salts undergo a crystallization transformation process (such as the conversion of anhydrous sodium sulfate to sodium sulfate decahydrate), which also absorbs some of the heat.

[0039] 2. It achieves active blocking and penetration, forming a denser and stronger protective layer.

[0040] During the spraying process, the hydration of inorganic salts causes expansion. The micro-pressure generated by this expansion drives the unsolidified reaction slurry, allowing it to penetrate and fill the tiny pores in the cracks more fully, thus achieving a tighter physical bond with the sprayed surface.

[0041] 3. After spraying, it has self-healing capabilities in the humid environment of a coal mine.

[0042] After the material has cured, if new microcracks are generated due to stress or other reasons, the exposed anhydrous sodium sulfate will expand again after encountering water, automatically sealing the new cracks and giving the material a continuous self-healing function.

[0043] 4. The selected materials are widely available and inexpensive, and the preparation process has significant advantages in performance.

[0044] The key materials selected in this invention, namely waxy film-forming materials and crystalline inorganic salts, are widely available and inexpensive bulk chemical products. The processes involved, such as melt coating and sieving, are mature and simple. By optimizing and controlling the particle size of the coated microparticles within the range of 100-300 μm, their dispersibility in the polyol system of component B is effectively improved, preventing agglomeration and sedimentation, and ensuring the uniform distribution of functional components within the spraying area. This allows the cooling and expansion effects to be performed uniformly and reliably. Attached Figure Description

[0045] Figure 1 Example 1: Trend chart of sample reaction temperature test

[0046] Figure 2 Comparative Example 1: Trend chart of sample reaction temperature

[0047] Figure 3 Schematic diagram of reaction temperature uniformity testing device Detailed Implementation

[0048] The following description illustrates exemplary embodiments of the present invention, including various details to aid understanding, and should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the invention. Similarly, for clarity and brevity, descriptions of well-known functions, operations, and structures are omitted in the following description.

[0049] Unless otherwise defined, the technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art. While similar or identical methods and materials may be applied in experimental or practical applications, the present invention describes materials and methods hereinafter. In case of conflict, the definitions included herein shall prevail.

[0050] Example 1: Preparation of Component B of Coal Mine Sprayed Air Leakage Sealing Material

[0051] 1. Formula

[0052]

[0053] Note: The long-acting reinforcing agent is added in excess according to the sieving yield to ensure that the amount of long-acting reinforcing agent material with the required particle size meets the final formulation dosage requirements. The amount of long-acting reinforcing agent listed in the formulation table is the content of the final product.

[0054] 2. Preparation process

[0055] S1. Preparation of long-lasting reinforcing agent (shear granulation method)

[0056] 1. Place 500-mesh anhydrous sodium sulfate into a high-efficiency granulator and start stirring at 300 rpm.

[0057] 2. Heat the microcrystalline wax to 95±5℃ until it is completely melted. Using an online spray nozzle with a diameter of 0.8mm and an atomization pressure of 0.4-0.6MPa, spray it evenly onto the surface of the tumbling anhydrous sodium sulfate. Stir at 300rpm and cutter at 4000rpm, and granulate under high shear for 15min. After granulation, discharge the material and cool it to room temperature.

[0058] 3. Use an air jet screen to screen the cooled material from step 2. Use a screen with a mesh size of 60 mesh and 100 mesh to select material with a particle size between 60-100 mesh (particle size 150-250μm).

[0059] Preparation of S2 and B components

[0060] 1. Premixed:

[0061] In the reactor, add polyether polyol, triethylenediamine, dibutyltin dilaurate, polyether-modified siloxane foam stabilizer, calcium carbonate, and ammonium polyphosphate in sequence. Start stirring and stir at a low speed of 200 rpm for 10 minutes to ensure that all components are mixed evenly.

[0062] 2. Add a long-lasting enhancer:

[0063] Add the long-lasting reinforcing agent prepared in S1 to the above mixture, and continue stirring at a low speed of 200 rpm for 10 minutes to ensure that the reinforcing agent is uniformly dispersed in the polyol system without agglomeration.

[0064] 3. Add foaming agent:

[0065] Add foaming agent water and stir quickly at 200 rpm for 3 minutes.

[0066] 4. Degassing and Packaging:

[0067] After processing, vacuum is applied, and degassing is performed for 8 minutes at a vacuum level of -0.095 MPa. After degassing, component B is sealed and packaged to obtain the final product.

[0068] Examples 2-3: Preparation of Component B of Leak-Sealing Materials with Different Doses of Waxy Film-Forming Material

[0069] 1. Formula

[0070]

[0071] 2. Preparation process

[0072] Same as Example 1.

[0073] Example 4: Preparation of Component B of Fluidized Bed Coated Granulated Coal Mine Spraying and Leak-Sealing Material

[0074] 1. Formula

[0075] Same as Example 1.

[0076] 2. Preparation process

[0077] S1. Preparation of long-lasting reinforcing agents (fluidized bed coating and granulation method)

[0078] 1. Place anhydrous sodium sulfate in the fluidized bed material silo, turn on the equipment, and introduce 75℃ hot air to fluidize the material.

[0079] 2. Heat the microcrystalline wax to 95±5℃ until it is completely melted, then turn on the fluidized bed top spray coating. The control parameters are as follows: air volume 10m³ / h, atomization pressure 0.5MPa, nozzle diameter 0.8mm, spray flow rate 10g / min. After the powder coating is completed, turn off the heating and blow air until the material reaches room temperature.

[0080] 3. Use an air jet screen to screen the cooled material from step 2. Use a screen with a mesh size of 60 mesh and 100 mesh to select material with a particle size between 60-100 mesh (particle size 150-250μm).

[0081] Preparation of S2 and B components

[0082] The S2 B component was prepared in the same manner as in Example 1.

[0083] Example 5: Preparation of Component B of Coal Mine Sprayed Leak-Sealing Material Containing Fine-Particle Long-Lasting Reinforcing Agent

[0084] 1. Formula

[0085] Same as Example 1.

[0086] 2. Preparation process

[0087] S1. Preparation of long-lasting reinforcing agent (shear granulation method)

[0088] 1. Place 500-mesh anhydrous sodium sulfate into a high-efficiency granulator and start stirring at 500 rpm.

[0089] 2. Heat the microcrystalline wax to 95±5℃ until it is completely melted. Using an online spray nozzle (0.6mm) and atomization pressure (0.8MPa), spray it evenly onto the surface of the tumbling anhydrous sodium sulfate. Stir at 500rpm and cutter at 5000rpm, and granulate under high shear for 20 minutes. After granulation, discharge the material and cool it to room temperature.

[0090] 3. Use an air jet screen to screen the cooled material from step 2. Use 80 mesh and 150 mesh screens to select materials with a particle size between 80-150 mesh (particle size 100-180μm).

[0091] Preparation of S2 and B components

[0092] 1. Premixed:

[0093] In the reactor, add polyether polyol, triethylenediamine, dibutyltin dilaurate, polyether-modified siloxane foam stabilizer, calcium carbonate, and ammonium polyphosphate in sequence. Start stirring and stir at a low speed of 100 rpm for 10 minutes to ensure that all components are mixed evenly.

[0094] 2. Add a long-lasting enhancer:

[0095] Add the long-lasting reinforcing agent prepared in S1 to the above mixture, and continue stirring at a low speed of 100 rpm for 10 minutes to ensure that the reinforcing agent is uniformly dispersed in the polyol system without agglomeration.

[0096] 3. Add foaming agent:

[0097] Add foaming agent water and stir quickly at 200 rpm for 4 minutes.

[0098] 4. Degassing and Packaging:

[0099] After processing, vacuum is applied, and degassing is performed at a vacuum level of -0.08 MPa for 9 minutes. After degassing, component B is sealed and packaged to obtain the final product.

[0100] Example 6 Preparation of Component B of Coal Mine Sprayed Air Leakage Sealing Material Containing Coarse-grained Long-lasting Reinforcing Agent

[0101] 1. Formula

[0102] Same as Example 1.

[0103] 2. Preparation process

[0104] S1. Preparation of long-lasting reinforcing agent (shear granulation method)

[0105] 1. Place 500-mesh anhydrous sodium sulfate into a high-efficiency granulator and start stirring at 100 rpm.

[0106] 2. Heat the microcrystalline wax to 95±5℃ until it is completely melted. Using an online spray nozzle (1.2mm) and atomization pressure (0.4MPa), spray it evenly onto the surface of the tumbling anhydrous sodium sulfate. Stir at 100rpm and cutter at 3000rpm, and granulate under high shear for 12 minutes. After granulation, discharge the material and cool it to room temperature.

[0107] 3. Use an air jet screen to screen the cooled material from step 2. Use a screen with a mesh size of 50 mesh or 100 mesh to select material with a particle size between 50-100 mesh (particle size 150-300μm).

[0108] Preparation of S2 and B components

[0109] 1. Premixed:

[0110] In the reactor, add polyether polyol, triethylenediamine, dibutyltin dilaurate, polyether-modified siloxane foam stabilizer, calcium carbonate, and ammonium polyphosphate in sequence. Start stirring and stir at a low speed of 450 rpm for 10 minutes to ensure that all components are mixed evenly.

[0111] 2. Add a long-lasting enhancer:

[0112] Add the long-lasting reinforcing agent prepared in S1 to the above mixture, and continue stirring at a low speed of 450 rpm for 10 minutes to ensure that the reinforcing agent is uniformly dispersed in the polyol system without agglomeration.

[0113] 3. Add foaming agent:

[0114] Add foaming agent water and stir quickly at 500 rpm for 5 minutes.

[0115] 4. Degassing and Packaging:

[0116] After processing, vacuum is applied, and degassing is performed at a vacuum level of -0.09 MPa for 10 minutes. After degassing, component B is sealed and packaged to obtain the final product.

[0117] Comparative Example 1: Preparation of Component B of Coal Mine Sprayed Air Leakage Sealing Material without Long-Lasting Reinforcing Agent

[0118] 1. Formula

[0119] Note: The long-acting reinforcing agent is fed in excess in proportion according to the sieving yield to ensure that the amount of long-acting reinforcing agent material with the required particle size meets the final formulation dosage requirements.

[0120] 2. Preparation process

[0121] 1. Premixed:

[0122] In the reactor, add polyether polyol, triethylenediamine, dibutyltin dilaurate, polyether-modified siloxane foam stabilizer, calcium carbonate, and ammonium polyphosphate in sequence. Start stirring and stir at a low speed of 200 rpm for 10 minutes to ensure that all components are mixed evenly.

[0123] 2. Add foaming agent:

[0124] Add foaming agent water and stir quickly at 200 rpm for 3 minutes.

[0125] 3. Degassing and Packaging:

[0126] After processing, vacuum is applied, and degassing is performed for 8 minutes at a vacuum level of -0.095 MPa. After degassing, component B is sealed and packaged to obtain the final product.

[0127] Comparative Example 2: Preparation of Component B of Coal Mine Sprayed Air Leakage Sealing Material Containing but Not Coated with Long-Lasting Reinforcing Agent

[0128] 1. Formula

[0129]

[0130] 2. Preparation process

[0131] S1. Preparation of long-lasting enhancer (physical mixing only)

[0132] 1. The microcrystalline wax is pulverized at a low temperature, with the temperature controlled at ≤30℃, and then passed through an 80-mesh sieve.

[0133] 2. Place the pulverized microcrystalline wax and anhydrous sodium sulfate into a hopper mixer and mix at a speed of 15 rpm for 30 minutes.

[0134] Preparation of S2 and B components

[0135] 1. Premixed:

[0136] In the reactor, add polyether polyol, triethylenediamine, dibutyltin dilaurate, polyether-modified siloxane foam stabilizer, calcium carbonate, and ammonium polyphosphate in sequence. Start stirring and stir at a low speed of 200 rpm for 10 minutes to ensure that all components are mixed evenly.

[0137] 2. Add a long-lasting enhancer:

[0138] Add the long-lasting reinforcing agent mixture prepared in S1 to the above mixture, and continue stirring at a low speed of 200 rpm for 10 minutes.

[0139] 3. Add foaming agent:

[0140] Add foaming agent water and stir quickly at 200 rpm for 3 minutes.

[0141] 4. Degassing and Packaging:

[0142] After processing, vacuum is applied, and degassing is performed for 8 minutes at a vacuum level of -0.095 MPa. After degassing, component B is sealed and packaged to obtain the final product.

[0143] Experiment 1 Performance Testing

[0144] According to industry standard AQ 1088-2011 "Technical Conditions for Polymer Materials Used for Spraying and Sealing Air Leaks in Coal Mines" Representative batches of samples were tested; adhesion was determined according to section 7.1 of GB / T16777-2008; and air permeability was determined according to GB / T10655-2003.

[0145] Component A, the polymerized MDI, is a commercially available product (such as Wanhua MDI-50). Component B is the product prepared in each example or comparative example.

[0146] Test results:

[0147] in conclusion:

[0148] After the samples prepared in each example were compared with commercially available component A for spraying performance testing, the test results all met industry safety requirements. Furthermore, the highest reaction temperature and air permeability of the samples containing the long-acting enhancer (including Comparative Example 2) were significantly lower than those of Comparative Example 1; the adhesion of the coated long-acting enhancer was higher than that of Comparative Example 1 and Comparative Example 2, demonstrating the beneficial effects of the long-acting enhancer's active sealing and penetration in this invention.

[0149] Experimental Example 2: Test of Reaction Temperature Uniformity

[0150] Based on the industry standards AQ 1088-2011 "Technical Conditions for Polymer Materials Used for Spraying and Sealing Air Leaks in Coal Mines" and AQ 1116-2020 "General Safety Technical Specifications for Polymer Materials Used for Reinforcement, Water Blocking, Filling and Spraying in Coal Mines," reaction temperature uniformity tests were conducted. Component A, the polymerized MDI, was a commercially available product (such as Wanhua MDI-50). Component B consisted of the products prepared in Example 1, Comparative Examples 1 and 2.

[0151] Nine sets of temperature probes were set up for each test. The probes were arranged in a 3x3 grid within the reaction chamber, with a minimum spacing of 4 cm between each set. The nine calibrated thermocouple temperature probes were connected to a data acquisition instrument, and each thermocouple was numbered. The probes were then placed in the reaction chamber to continuously record temperature values. After the test, the highest value of each temperature probe was recorded, and the difference between the highest and lowest values ​​was compared.

[0152] See the attached diagram in the instruction manual for details. Figure 1 — Figure 3 .

[0153] Test results:

[0154] Conclusion: The above experimental results show that the sample in Example 1 has the smallest temperature difference, and in the temperature trend graph, the temperature values ​​of the nine temperature probes are close, and the curves basically overlap. Comparative Example 1 has a larger temperature difference because it does not contain a long-lasting reinforcing agent, while Comparative Example 2 has a smaller temperature difference because the long-lasting reinforcing agent was not effectively coated, which may lead to premature hydration of crystalline inorganic salts or uneven dispersion of waxy coating materials.

[0155] Test Example 3: Anti-aging Performance Test

[0156] Anti-aging tests were conducted in accordance with section 5.6 of AQ1116-2020 "General Safety Technical Specification for Polymer Materials Used for Reinforcement, Water Blocking, Filling and Spraying in Coal Mines" and GB / T18244.

[0157] According to the test requirements, after each group of test samples were sprayed and cured, the samples were placed in an environment of (80±2)℃ for 168 hours, and then placed in a square oscillator (oscillation frequency 10HZ) and relative humidity RH75%±10 for 24 hours before the adhesion and air permeability were measured.

[0158] Test results:

[0159]

[0160] in conclusion:

[0161] After the anti-aging performance test, the adhesion of the sample in Example 1 showed almost no decrease, and the air permeability showed almost no increase. This is significantly better than the sample in Comparative Example 1, which does not contain a long-lasting reinforcing agent, and the sample in Comparative Example 2, which contains a long-lasting reinforcing agent but is not coated.

Claims

1. A coal mine spray-applied air-sealing material, characterized in that, It is composed of the following components: Component A: Polymerized MDI; Component B: polyol, catalyst, foam stabilizer, foaming agent, filler, flame retardant, and long-lasting reinforcing agent, wherein the long-lasting reinforcing agent is a crystalline inorganic salt coated with a waxy film-forming material.

2. The coal mine spray-applied air-sealing material according to claim 1, characterized in that, The polyol is at least one of polyether polyol and polyester polyol; The catalyst is at least one of triethylenediamine, dimethylcyclohexylamine, stannous octoate, and dibutyltin dilaurate; The foam stabilizer is at least one of the following: polyether-modified siloxane foam stabilizer, allyl polyether-modified foam stabilizer, bio-based polyether silicone copolymer foam stabilizer, and polyurethane foam stabilizer. The foaming agent is water; The filler is at least one of calcium carbonate, talc, and quartz powder; The flame retardant is at least one of ammonium polyphosphate, melamine, and expandable graphite.

3. The coal mine spray-applied air-sealing material according to claim 1, characterized in that, The waxy film-forming material and the crystalline inorganic salt in the long-lasting reinforcing agent are in a weight ratio of 0.1 to 1:

1.

4. The coal mine spray-applied air-sealing material according to claim 1, characterized in that, The long-acting enhancer accounts for 5%–20% of the mass of component B.

5. The coal mine spray-applied air-sealing material according to claim 1, characterized in that, The particle size of the long-acting reinforcing agent is 100-300μm.

6. The coal mine spray-applied air-sealing material according to claim 1, characterized in that, The waxy film-forming material is at least one of the following: paraffin wax, microcrystalline wax, oxidized polyethylene wax, montmorillonite wax, and Fischer-Tropsch wax.

7. The coal mine spray-applied air-sealing material according to claim 1, characterized in that, The crystalline inorganic salt is at least one of anhydrous sodium sulfate, calcium sulfoaluminate, and magnesium oxide.

8. A method for applying component B of a coal mine spray-applied air-sealing material as described in claim 1, characterized in that, Includes the following steps: S1, Preparation of Long-Lasting Enhancer Crystalline inorganic salt powder is mixed with waxy film-forming materials and then granulated by shearing or fluidized bed coating. Preparation of S2 and B components Mix the polyol, catalyst, foam stabilizer, filler, and flame retardant at a low speed of 50-500 rpm for 10 minutes; add the long-lasting reinforcing agent from S1 and mix at a low speed for 10 minutes; finally add the foaming agent and mix for 3-5 minutes, then immediately vacuum degas for 5-10 minutes and seal the package.

9. The method for preparing component B of the coal mine air-sealing material according to claim 8, characterized in that, The long-acting reinforcing agent is prepared by shear granulation as follows: S1. Place the crystalline inorganic salt into a high-efficiency wet granulation machine; S2. Heat the waxy film-forming material to a molten state, spray it online into the crystalline inorganic material, and start stirring at 100-500 rpm and cutting at 3000-5000 rpm for high-shear granulation for 10-20 minutes. S3. The material prepared in S2 is sieved through an air jet sieve to obtain a long-lasting reinforcing agent.

10. The method for preparing component B of the coal mine leak-sealing material according to claim 8, characterized in that, The preparation of the long-acting reinforcing agent by fluidized bed coating and granulation is as follows: S1. Place the crystalline inorganic salt into a fluidized bed granulator and preheat it with hot air at 65-85℃. S2. Heat the waxy film-forming material to a molten state, and coat it with powder by spraying it from the top, then condense and coat it on the surface of the inorganic salt; the air inlet volume is 3-20 m³ / h, the atomization pressure is 0.3-0.6 MPa, the nozzle diameter is 0.5-1.2 mm, and the liquid flow rate is 5-15 g / min; S3. The material prepared in S2 is sieved through an air jet sieve to obtain a long-lasting reinforcing agent.

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