A mine gas sealing material and a preparation method thereof

Abstract

A mine gas hole sealing material and a preparation method thereof belong to the technical field of hole sealing materials. The mine gas hole sealing material is composed of the following components in percentage by mass: 87.56~90.46% of superfine silicate cement, 0.25~0.55% of cellulose ether, 2.7~5.3% of an expanding agent, 0.15~0.20% of a water reducing agent, 1.0~1.8% of a defoaming agent, and 4.0~7.2% of a composite coagulation adjusting agent; the composite coagulation adjusting agent is composed of sodium citrate and tartaric acid in a mass ratio of 1:0.7~1.5; the preparation steps are as follows: (1) uniformly mixing sodium citrate and tartaric acid in a mass ratio to obtain the composite coagulation adjusting agent; (2) uniformly mixing the cellulose ether, the expanding agent, the water reducing agent, the defoaming agent, and the composite coagulation adjusting agent to obtain component A; and (3) uniformly mixing the superfine silicate cement and component A to obtain the mine gas hole sealing material. The mine gas hole sealing material has a high expansion rate, a high compressive strength, and a short setting time.

Description

Technical Field

[0001] This invention belongs to the field of sealing material technology, specifically relating to a mine gas sealing material and its preparation method. Background Technology

[0002] In the coal mining industry, gas drainage and blasting operations are core components for ensuring safe production and improving mining efficiency. The performance of sealing materials directly affects the success or failure of these operations and the safety of miners. Statistics show that gas leaks caused by poor-quality sealing materials account for a significant proportion of coal mine safety accidents, resulting not only in huge economic losses but also threatening the lives and health of miners. As coal mining depths increase, underground geological conditions become increasingly complex, with soft and fractured coal seams and significantly higher gas pressure and content, placing higher demands on sealing materials.

[0003] Traditional cement-based sealing materials have revealed many shortcomings in practical applications. For example, their slow setting speed makes sealing construction time-consuming, affecting the overall progress of coal mining. More importantly, cement is prone to shrinkage and water separation during the setting process, which can create pores and cracks inside the sealing hole, severely weakening the seal and significantly increasing the risk of gas leakage. This not only reduces gas drainage efficiency but can also lead to gas accumulation and cause major gas explosions.

[0004] While organic materials can compensate for some of the shortcomings of cement-based materials in pore sealing, their chemical reaction processes are intense and difficult to control. An excessively fast reaction rate can prevent the material from fully filling the pore space, while a reaction rate that is too slow will affect the construction progress. Furthermore, unstable reactions can lead to inconsistent pore sealing quality, increasing uncertainty and safety hazards during construction. Existing pore sealing materials also suffer from low expansion rates, low compressive strength, and long setting times. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a mine gas sealing material and its preparation method. The mine gas sealing material of the present invention has a high expansion rate, high compressive strength and short setting time.

[0006] To achieve the above objectives, the present invention provides a mine gas sealing material, which, by mass percentage, is composed of the following components: 87.56-90.46% ultrafine silicate cement, 0.25-0.55% cellulose ether, 2.7-5.3% expansion agent, 0.15-0.20% water-reducing agent, 1.0-1.8% defoamer, and 4.0-7.2% composite setting regulator; the composite setting regulator is composed of sodium citrate and tartaric acid in a mass ratio of 1:0.7-1.5.

[0007] The aforementioned mine gas sealing material, by mass percentage, comprises the following components: 88.08-90.18% ultrafine silicate cement, 0.32-0.36% cellulose ether, 3.1-4.2% expansion agent, 0.16-0.19% water-reducing agent, 1.1-1.4% defoamer, and 4.5-6.4% composite setting regulator. The water-reducing agent is a polycarboxylate-based high-performance water-reducing agent.

[0008] The composite setting regulator is composed of sodium citrate and tartaric acid in a mass ratio of 1:0.75~1.25. The synergistic effect of sodium citrate and tartaric acid achieves "graded regulation" of the cement hydration rate through a dual mechanism of "strong complexation-weak complexation" and "macromolecule adsorption-small molecule filling," thus delaying setting while ensuring compressive strength. The composite setting regulator, through the synergistic effect of sodium citrate and tartaric acid complexation, enables adjustable setting time while ensuring a 28-day compressive strength ≥45MPa, resolving the "retardation-strength" contradiction of traditional materials. The small molecules of tartaric acid fill the pores, working with the expansion agent to inhibit shrinkage and ensure a linear increase in the expansion rate.

[0009] The citrate ions in sodium citrate can form stable complexes with calcium ions released during cement hydration, reducing the concentration of free calcium ions in the solution, inhibiting the early crystallization of ettringite and calcium hydroxide, and delaying the initial setting rate of cement. Citrate ions adhere to the surface of cement particles through chemical adsorption, forming a hydrophilic adsorption layer that hinders interparticle contact and hydration reaction rates. The hydroxyl and carboxyl groups of tartaric acid can form weaker complexes with calcium ions, and the hydroxyl groups in its molecular structure can form hydrogen bonds with the hydroxyl groups on the surface of cement particles, enhancing the stability of the adsorption layer. Tartaric acid inhibits the hydration of tricalcium aluminate, delaying the hydration rate during the high-exothermic stage and preventing setting time fluctuations caused by localized overheating. The tricarboxylic acid structure of sodium citrate and the dicarboxylic acid structure of tartaric acid form a strong-weak complex pair. Sodium citrate rapidly complexes a large number of calcium ions, reducing the initial hydration rate; tartaric acid continuously replenishes the complexation effect, maintaining the stability of calcium ion concentration in the solution during the middle and later stages, avoiding "late-stage retarding failure" caused by excessive early complexation of a single component. The combination of sodium citrate and tartaric acid has lower solubility and can suppress the effective concentration of calcium ions for a longer period of time, thus prolonging the retarding effect.

[0010] Excessive tartaric acid leads to excessively delayed setting time and affects strength development. Besides complexing calcium ions, tartaric acid can also adsorb onto the surface of cement particles to form a protective film. Excessive tartaric acid significantly delays the hydration induction period, resulting in excessively long setting time and reduced compressive strength. Insufficient tartaric acid results in insufficient adsorption and retarding effects, failing to form a dual "complexation-adsorption" regulatory mechanism with sodium citrate. This leads to a decrease in the precision of the composite setting regulator's control over cement hydration, especially with temperature fluctuations, resulting in unstable setting time. When tartaric acid is insufficient, the complexing effect of sodium citrate dominates, leading to uneven charge distribution on the surface of cement particles, fluctuating water-reducing agent dispersion, and, in cases of ultrafine cement with a large specific surface area, the problem of "rapid slump loss over time" may occur.

[0011] The mass ratio of the defoamer to the expanding agent is 1:1.5~5.3; their synergistic effect allows the expansion stress to be effectively transferred to the entire structure, improving compressive strength and achieving an expansion rate greater than 2%, thus achieving the effect of non-shrinkage in mine gas sealing materials. The expanding agent is a UEA expanding agent, and the defoamer is a polyether defoamer; the expanding agent generates micro-expansion by producing ettringite crystals, compensating for shrinkage and increasing density; the defoamer, by disrupting the elasticity of the foam film and accelerating liquid film drainage, promptly eliminates larger bubbles generated during the expansion process, preventing the aggregation of larger bubbles from weakening the expansion pressure transmission efficiency. The defoamer eliminates larger bubbles, reducing surface defects and strength loss; the expanding agent added to the cement expands in volume when the cement sets and hardens, compensating for shrinkage, generating prestress for tensioning steel bars, and fully filling the cement gaps. Adding a certain amount of expanding agent causes volume expansion, compensating for the shrinkage value of the material itself and preventing shrinkage cracking. The expanding agent forms uniformly distributed micropores inside the cement through a chemical reaction, compensating for shrinkage and increasing density. Because ordinary cement-based materials exhibit shrinkage, they cannot be used in the field of mine gas sealing. The shrinkage rate of ordinary cement-based materials after 24 hours of solidification is 0.03~0.06%, and the shrinkage rate after 28 days is 1.5~2%, with the shrinkage slowing down significantly after 28 days. Therefore, when the expansion rate of the mine gas sealing material is greater than 2%, it indicates that the mine gas sealing material has achieved the technical effect of no shrinkage.

[0012] Excessive expansion agent, while increasing the peak expansion rate, can cause delayed expansion, disrupting the material's "expansion-strength coordinated development" mechanism. This leads to internal stress concentration, cracks, or reduced structural strength, affecting the long-term stability of the sealing layer. Insufficient expansion agent results in inadequate expansion efficiency, causing volume shrinkage after curing, leading to drying shrinkage and leakage, affecting sealing performance and increasing the risk of gas leakage. Excessive defoamer has an overly strong water-reducing effect, causing excessive dilution or reduced viscosity, affecting curing rate and adhesion. Insufficient defoamer prevents effective bubble elimination, increasing internal porosity, reducing density and compressive strength, leading to leakage channels in the sealing material and weakening the sealing effect of gas extraction.

[0013] Preferably, the mass ratio of defoamer to expander is 1:3.1~3.5; this ratio ensures that the expansion rate of the expander and the defoaming efficiency of the defoamer are optimally matched, avoiding the generation of new bubbles due to excessive expansion or the inhibition of effective expansion due to excessive defoaming; thus improving compressive strength and forming an optimal dual compaction effect of expansion and defoaming.

[0014] The cellulose ether is at least one of hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and carboxymethyl cellulose. When added to mortar, the cellulose ether dissolves in water and, due to its surface activity, promotes the uniform dispersion of the cementitious material in the system. Simultaneously, as a protective colloid, it "encapsulates" the solid particles, forming a lubricating film on their outer surface. This lubricating film not only makes the mortar system more stable but also improves the fluidity of the mortar during mixing and enhances its smoothness during construction. Furthermore, mixing the cellulose ether into cement can effectively control the cement's setting time and increase its initial strength.

[0015] Preferably, the cellulose ether is composed of carboxymethyl cellulose and hydroxypropyl methyl cellulose in a mass ratio of 1:3~5. This formulation design improves the initial compressive strength and durability of the sealing layer through charge balance and molecular structure complementarity, achieving a performance balance of "high suspension-low flow resistance-slow water loss" in the sealing material.

[0016] Carboxymethyl cellulose (CMC) provides a strong thickening effect through its anionic properties, while hydroxypropyl methyl cellulose (HMC) exhibits excellent water retention due to its nonionic structure. When combined, they maintain slurry fluidity while reducing water evaporation, ensuring thorough cement hydration. The high viscosity of CMC and the thixotropic properties of HMC result in anti-settling properties in a static state, while CMC suspends solid particles and reduces friction in a dynamic state. The lubricating film effect of HMC enhances the smoothness of grouting. The nonionic properties of HMC resist interference from metal ions in mine water, while CMC remains stable in alkaline cement environments. Their synergistic effect ensures the stability of the performance of mine gas sealing materials. CMC enhances interfacial adhesion by complexing with calcium ions on cement particle surfaces through its carboxyl groups, while HMC forms a hydration film through its hydroxyl groups, delaying shrinkage cracking and jointly improving the initial compressive strength and durability of the sealing layer. The anionic groups of CMC compete with sodium citrate / tartaric acid for adsorption, and HMC delays the peak hydration exothermic reaction.

[0017] Excessive carboxymethyl cellulose leads to excessively viscous slurry, abnormally prolonged setting time, and reduced compressive strength; insufficient carboxymethyl cellulose causes particle sedimentation and stratification, decreased water retention, and insufficient compressive strength. Excessive hydroxypropyl methyl cellulose increases the risk of gelation and hinders strength development; insufficient hydroxypropyl methyl cellulose results in excessively rapid water evaporation, poor leveling properties, and failure of anti-sagging.

[0018] The particle size distribution of the ultrafine silicate cement is as follows: 19-21% by mass for particles ≤ 0.2µm and ≤ 0.3µm, 29-31% by mass for particles < 0.3µm and ≤ 1.0µm, and 49-51% by mass for particles < 1.0µm and ≤ 5.0µm; the specific surface area of ​​the ultrafine silicate cement is 1490-1510 m². 2 / kg, preferred specific surface area of ​​ultrafine silicate cement: 1500m² 2 / kg.

[0019] Ultrafine silicate cement has good permeability, and the prepared slurry has good fluidity and diffusion. Utilizing its good particle distribution and flexural and compressive strength, it can achieve a significant increase in compressive strength. At the same time, the setting time can be adjusted according to the usage requirements to fully meet the requirements of actual application scenarios.

[0020] According to another aspect of the present invention, a method for preparing the above-mentioned mine gas sealing material is also provided, comprising the following steps:

[0021] (1) Sodium citrate and tartaric acid are mixed in a mass ratio to obtain a composite coagulation regulator;

[0022] (2) Mix the cellulose ether, expanding agent, water reducing agent, defoamer and composite setting regulator to obtain component A;

[0023] (3) Mix ultrafine silicate cement with component A to obtain a mine gas sealing material.

[0024] The mixing operation in step (1) is crucial to ensuring the uniform dispersion of the composite setting agent; otherwise, it will affect the stability of the material properties, leading to uncontrollable material properties and seriously threatening mine safety. The premixing operation is the core process to ensure the uniform dispersion of sodium citrate and tartaric acid at the molecular level, which directly affects the airtightness and durability of the sealing layer.

[0025] The mixing in step (2) ensures that the additives are evenly dispersed and avoids local agglomeration when directly mixed with ultrafine silicate cement.

[0026] The ultrafine silicate cement in step (3) has a high specific surface area, which can enhance hydration activity and react with setting regulator to form a dense structure; premixing the auxiliary materials before combining them with the cement can prevent cellulose ether from encapsulating the cement particles and hindering hydration.

[0027] The specific operation of mixing in step (3) is as follows: after measuring the ultrafine silicate cement and component A with a screw weigher, add them to a twin-shaft mixer with a diameter > 500 mm and a length > 3500 mm, and mix at a rate of 100 r / min for 45~50 min; during the mixing process, open the air box at the bottom of the mixer and turn on the Roots blower to suspend the material and make it fully homogenized.

[0028] The mine gas sealing material is packaged using a rotary packaging machine, with each bag weighing 25kg. The packaging bags are triple-layered laminated valve bags to prevent the material from becoming damp and solidifying. When stored in a dry, ventilated, waterproof, and moisture-proof environment, the unopened shelf life is 6 months.

[0029] According to another aspect of the present invention, the application of the above-mentioned mine gas sealing material or the mine gas sealing material prepared according to the above method in the field of mine gas sealing is also provided, comprising the following steps:

[0030] First, measure the mine gas sealing material and water at a weight ratio of 1:0.33 and then use a low-speed mechanical stirrer at 400~600rpm to avoid introducing air. Before stirring, add water to the stirring container, and while stirring, add the mine gas sealing material. Stir thoroughly for 3~5 minutes until the mixture is completely uniform and free of lumps. Then let the stirred material stand for 1~2 minutes to expel as much air as possible introduced during stirring, and then stir for another 1~2 minutes. Use the material within 20 minutes.

[0031] Compared with the prior art, the beneficial effects of this invention are:

[0032] 1. The mine gas sealing material of this application has a high expansion rate, high compressive strength, and short setting time; ultrafine silicate cement can increase the density of hydration products, thus giving it high compressive strength; the composite setting regulator achieves adjustable setting time through the synergistic effect of sodium citrate and tartaric acid complexation; the addition of the expansion agent gives it a high expansion rate. The expansion rate of this application reaches 2.5~3.7%, indicating that the mine gas sealing material prepared by this application does not shrink. The 1-hour compressive strength of this application reaches 7~11 MPa, the 4-hour compressive strength reaches 19~23 MPa, and the 1-day compressive strength reaches 27~32 MPa.

[0033] 2. The defoamer and expanding agent in this application work synergistically to effectively transfer expansion stress to the entire structure, thereby improving compressive strength.

[0034] 3. Carboxymethyl cellulose and hydroxypropyl methyl cellulose work synergistically through charge balance and complementary molecular structures to jointly enhance the initial compressive strength of the sealing layer. Detailed Implementation

[0035] Example 2 is the preferred embodiment of the present invention. The present invention will be further described below with reference to specific embodiments and comparative examples.

[0036] The chemical additives used in the embodiments and comparative examples of this invention are all commercially available, and the specific information is as follows:

[0037] Ultrafine silicate cement: purchased from Shandong Donghua Technology Co., Ltd.;

[0038] Hydroxyethyl cellulose: purchased from Jinan Zhunying International Trade Co., Ltd.;

[0039] Hydroxypropyl methylcellulose: purchased from Jinan Zhunying International Trade Co., Ltd.;

[0040] Carboxymethyl cellulose: purchased from Jinan Zhunying International Trade Co., Ltd.;

[0041] UEA swelling agent: purchased from Shandong Ruiyuan Biotechnology Co., Ltd.;

[0042] Polycarboxylate superplasticizer: purchased from Zibo Pengmiao New Material Technology Co., Ltd.;

[0043] Polyether defoamer: purchased from Zibo Pengmiao New Material Technology Co., Ltd.;

[0044] Sodium citrate: purchased from Shandong Kunteng Chemical Co., Ltd.;

[0045] Tartaric acid: purchased from Shandong Sanyi New Materials Co., Ltd.

[0046] Example 1

[0047] A mine gas sealing material is composed of the following components by mass percentage: 88.9% ultrafine silicate cement, 0.35% hydroxyethyl cellulose, 4% UEA expanding agent, 0.15% polycarboxylate-based high-performance water-reducing agent, 1.1% defoamer, 3% sodium citrate, and 2.5% tartaric acid; the specific surface area of ​​the ultrafine silicate cement is 1500 m². 2 / kg;

[0048] The preparation method uses the following steps:

[0049] (1) Sodium citrate and tartaric acid are mixed in a mass ratio to obtain a composite coagulation regulator;

[0050] (2) Mix the cellulose ether, expanding agent, water reducing agent, defoamer and composite setting regulator to obtain component A;

[0051] (3) Mix ultrafine silicate cement with component A to obtain a mine gas sealing material.

[0052] Example 2

[0053] A mine gas sealing material is composed of the following components by mass percentage: 89.25% ultrafine silicate cement, 0.35% hydroxyethyl cellulose, 4.1% UEA expanding agent, 0.2% polycarboxylate-based high-performance water-reducing agent, 1.1% defoamer, 2.6% sodium citrate, and 2.4% tartaric acid; the specific surface area of ​​the ultrafine silicate cement is 1500 m². 2 / kg;

[0054] The preparation method uses the following steps:

[0055] (1) Sodium citrate and tartaric acid are mixed in a mass ratio to obtain a composite coagulation regulator;

[0056] (2) Mix the cellulose ether, expanding agent, water reducing agent, defoamer and composite setting regulator to obtain component A;

[0057] (3) Mix ultrafine silicate cement with component A to obtain a mine gas sealing material.

[0058] Example 3

[0059] A mine gas sealing material is composed of the following components by mass percentage: 88.28% ultrafine silicate cement, 0.36% hydroxyethyl cellulose, 4.2% UEA expanding agent, 0.16% polycarboxylate-based high-performance water-reducing agent, 1.2% defoamer, 2.4% sodium citrate, and 3.4% tartaric acid; the specific surface area of ​​the ultrafine silicate cement is 1500 m². 2 / kg;

[0060] The preparation method uses the following steps:

[0061] (1) Sodium citrate and tartaric acid are mixed in a mass ratio to obtain a composite coagulation regulator;

[0062] (2) Mix the cellulose ether, expanding agent, water reducing agent, defoamer and composite setting regulator to obtain component A;

[0063] (3) Mix ultrafine silicate cement with component A to obtain a mine gas sealing material.

[0064] Example 4

[0065] A mine gas sealing material is composed of the following components by mass percentage: 88.17% ultrafine silicate cement, 0.07% carboxymethyl cellulose, 0.28% hydroxypropyl methyl cellulose, 5.3% UEA expanding agent, 0.18% polycarboxylate-based high-performance water-reducing agent, 1.1% defoamer, 2.8% sodium citrate, and 2.1% tartaric acid; the specific surface area of ​​the ultrafine silicate cement is 1500 m². 2 / kg;

[0066] The preparation method uses the following steps:

[0067] (1) Sodium citrate and tartaric acid are mixed in a mass ratio to obtain a composite coagulation regulator;

[0068] (2) Mix the cellulose ether, expanding agent, water reducing agent, defoamer and composite setting regulator to obtain component A;

[0069] (3) Mix ultrafine silicate cement with component A to obtain a mine gas sealing material.

[0070] Example 5

[0071] A mine gas sealing material is composed of the following components by mass percentage: 88.08% ultrafine silicate cement, 0.35% hydroxyethyl cellulose, 5.3% UEA expanding agent, 0.17% polycarboxylate-based high-performance water-reducing agent, 1.0% defoamer, 3% sodium citrate, and 2.1% tartaric acid; the specific surface area of ​​the ultrafine silicate cement is 1500 m². 2 / kg;

[0072] The preparation method uses the following steps:

[0073] (1) Sodium citrate and tartaric acid are mixed in a mass ratio to obtain a composite coagulation regulator;

[0074] (2) Mix the cellulose ether, expanding agent, water reducing agent, defoamer and composite setting regulator to obtain component A;

[0075] (3) Mix ultrafine silicate cement with component A to obtain a mine gas sealing material.

[0076] Example 6

[0077] A mine gas sealing material is composed of the following components by mass percentage: 90.18% ultrafine silicate cement, 0.08% carboxymethyl cellulose, 0.24% hydroxypropyl methyl cellulose, 3.6% UEA expanding agent, 0.2% polycarboxylate-based high-performance water-reducing agent, 1.2% defoamer, 2% sodium citrate, and 2.5% tartaric acid; the specific surface area of ​​the ultrafine silicate cement is 1500 m². 2 / kg;

[0078] The preparation method uses the following steps:

[0079] (1) Sodium citrate and tartaric acid are mixed in a mass ratio to obtain a composite coagulation regulator;

[0080] (2) Mix the cellulose ether, expanding agent, water reducing agent, defoamer and composite setting regulator to obtain component A;

[0081] (3) Mix ultrafine silicate cement with component A to obtain a mine gas sealing material.

[0082] Example 7

[0083] A mine gas sealing material is composed of the following components by mass percentage: 90.46% ultrafine silicate cement, 0.25% hydroxyethyl cellulose, 3.1% UEA expanding agent, 0.19% polycarboxylate-based high-performance water-reducing agent, 1% defoamer, 2% sodium citrate, and 3% tartaric acid; the specific surface area of ​​the ultrafine silicate cement is 1500 m² / g. 2 / kg;

[0084] The preparation method uses the following steps:

[0085] (1) Sodium citrate and tartaric acid are mixed in a mass ratio to obtain a composite coagulation regulator;

[0086] (2) Mix the cellulose ether, expanding agent, water reducing agent, defoamer and composite setting regulator to obtain component A;

[0087] (3) Mix ultrafine silicate cement with component A to obtain a mine gas sealing material.

[0088] Example 8

[0089] A mine gas sealing material is composed of the following components by mass percentage: 89.34% ultrafine silicate cement, 0.06% carboxymethyl cellulose, 0.3% hydroxypropyl methyl cellulose, 4.2% UEA expanding agent, 0.2% polycarboxylate-based high-performance water-reducing agent, 1.4% defoamer, 2% sodium citrate, and 2.5% tartaric acid; the specific surface area of ​​the ultrafine silicate cement is 1490 m². 2 / kg;

[0090] The preparation method uses the following steps:

[0091] (1) Sodium citrate and tartaric acid are mixed in a mass ratio to obtain a composite coagulation regulator;

[0092] (2) Mix the cellulose ether, expanding agent, water reducing agent, defoamer and composite setting regulator to obtain component A;

[0093] (3) Mix ultrafine silicate cement with component A to obtain a mine gas sealing material.

[0094] Example 9

[0095] A mine gas sealing material is composed of the following components by mass percentage: 87.56% ultrafine silicate cement, 0.55% hydroxyethyl cellulose, 2.7% UEA expanding agent, 0.19% polycarboxylate-based high-performance water-reducing agent, 1.8% defoamer, 3.6% sodium citrate, and 3.6% tartaric acid; the specific surface area of ​​the ultrafine silicate cement is 1510 m². 2 / kg;

[0096] The preparation method uses the following steps:

[0097] (1) Sodium citrate and tartaric acid are mixed in a mass ratio to obtain a composite coagulation regulator;

[0098] (2) Mix the cellulose ether, expanding agent, water reducing agent, defoamer and composite setting regulator to obtain component A;

[0099] (3) Mix ultrafine silicate cement with component A to obtain a mine gas sealing material.

[0100] Comparative Example 1

[0101] The mine gas sealing material described in this comparative example is the same as that in Example 2, except that the sodium citrate content in this comparative example is 3.5% and the tartaric acid content is 1.4%.

[0102] Comparative Example 2

[0103] The mine gas sealing material described in this comparative example is the same as that in Example 2, except that the sodium citrate content in this comparative example is 1.6% and the tartaric acid content is 3.3%.

[0104] Comparative Example 3

[0105] The mine gas sealing material described in this comparative example is the same as that in Example 2, except that the UEA expanding agent in this comparative example is 3.3% and the polyether defoamer is 1.3%.

[0106] Comparative Example 4

[0107] The mine gas sealing material described in this comparative example is the same as that in Example 2, except that the UEA expanding agent in this comparative example is 4% and the polyether defoamer is 0.6%.

[0108] Comparative Example 5

[0109] The mine gas sealing material described in this comparative example is the same as that in Example 2, except that the carboxymethyl cellulose in this comparative example is 0.05% and the hydroxypropyl methyl cellulose is 0.3%.

[0110] Comparative Example 6

[0111] The mine gas sealing material described in this comparative example is the same as that in Example 2, except that the carboxymethyl cellulose in this comparative example is 0.1% and the hydroxypropyl methyl cellulose is 0.25%.

[0112] Comparative Example 7

[0113] The composition of the mine gas sealing material described in this comparative example is the same as that in Example 2, the only difference being the preparation method using the following steps:

[0114] (1) Mix cellulose ether, swelling agent, water-reducing agent, defoamer, sodium citrate and tartaric acid to obtain component A;

[0115] (2) Mix ultrafine silicate cement with component A to obtain a mine gas sealing material.

[0116] Comparative Example 8

[0117] The composition of the mine gas sealing material described in this comparative example is the same as that in Example 2, the only difference being that the preparation method uses the following steps:

[0118] Ultrafine silicate cement, cellulose ether, expanding agent, water-reducing agent, defoamer, sodium citrate, and tartaric acid are mixed to obtain a mine gas sealing material.

[0119] Performance testing

[0120] The performance of the mine gas sealing materials prepared in the examples and comparative examples was tested, and the specific test results are shown in Table 1.

[0121] The setting time of the mine gas sealing material was tested according to GB / T1346-2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement".

[0122] The compressive strength of the gas sealing material for mining shall be tested in accordance with GB / T17671-2021 "Test for Strength of Cement Mortar".

[0123] The expansion rate of the mine gas sealing material was tested in accordance with NB / T10123-2018 "Technical Conditions for Sealing Drill Holes in Coal Mine Gas Drainage".

[0124] Table 1 Performance test results of the examples and comparative examples

[0125] .

[0126] The expansion rate of this application reaches 2.5-3.7%, indicating that the mine gas sealing material prepared by this application does not shrink. The compressive strength of this application reaches 7-11 MPa in 1 hour, 19-23 MPa in 4 hours, and 27-32 MPa in 1 day. The mine gas sealing material of this application has a high expansion rate, high compressive strength, and short setting time.

[0127] The prolonged initial setting time in Comparative Example 1 indicates a slower setting rate and reduced compressive strength, suggesting that insufficient tartaric acid may lead to inadequate retarding effect, affecting early strength development. Comparative Example 2 shows that excessive tartaric acid inhibits cement hydration, resulting in excessively delayed setting time and reduced compressive strength. Example 2, however, exhibits superior setting time and higher compressive strength.

[0128] The results of Comparative Example 3 show that when the defoamer is excessive, the water-reducing effect is too strong, leading to a prolonged initial setting time. The results of Comparative Example 4 show that when the mass ratio of defoamer to expanding agent is too high, insufficient defoamer results in ineffective bubble elimination, reducing compressive strength. The results of Comparative Examples 5 and 6 show that when the mass ratio of carboxymethyl cellulose to hydroxypropyl methyl cellulose exceeds the range specified in this application, it leads to a prolonged initial setting time and a reduced compressive strength. Example 2, however, exhibits a superior setting time and higher compressive strength.

[0129] The results of Comparative Example 7 show that when sodium citrate and tartaric acid are not premixed, a molecularly uniformly dispersed "strong-weak complex system" cannot be formed, resulting in excessively high local sodium citrate concentrations. This leads to rapid complexation of a large number of calcium ions, delaying the hydration induction period, prolonging the initial setting time, and causing uneven dispersion of tartaric acid, which cannot compensate for strength through the "adsorption-filling" mechanism. The synergistic regulation of the composite setting regulator on the expanding agent fails, and the micro-expansion force generated by the expanding agent is reduced due to uneven bubble distribution. The results of Comparative Example 8 show that ultrafine cement directly contacts cellulose ether, forming a coating layer that hinders hydration. At the same time, the lack of premixing of the setting regulator and defoamer causes cellulose ether to coat cement particles, reducing the hydration reaction rate. The expanding agent and defoamer cannot act synchronously, and the large bubbles generated during the expansion process are not eliminated in time, resulting in a decrease in expansion rate and compressive strength. Example 2, however, exhibits a better expansion rate and higher compressive strength.

[0130] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art can make changes or modifications to the disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A gas sealing material for mining, characterized in that, By mass percentage, it consists of the following components: 87.56~90.46% ultrafine silicate cement, 0.25~0.55% cellulose ether, 2.7~5.3% expansive agent, 0.15~0.20% water-reducing agent, 1.0~1.8% defoamer, and 4.0~7.2% composite setting regulator; the composite setting regulator is composed of sodium citrate and tartaric acid in a mass ratio of 1:0.7~1.5; the mass ratio of defoamer to expansive agent is 1:1.5~5.

3.

2. The mine gas sealing material according to claim 1, characterized in that, By mass percentage, it consists of the following components: 88.08~90.18% ultrafine silicate cement, 0.32~0.36% cellulose ether, 3.1~4.2% expansion agent, 0.16~0.19% water-reducing agent, 1.1~1.4% defoamer, and 4.5~6.4% composite setting regulator.

3. The mine gas sealing material according to claim 1, characterized in that: The composite coagulation regulator is composed of sodium citrate and tartaric acid in a mass ratio of 1:0.75~1.

25.

4. The mine gas sealing material according to claim 1, characterized in that: The mass ratio of the defoamer to the expanding agent is 1:3.1~3.

5.

5. The mine gas sealing material according to claim 1, characterized in that: The cellulose ether is at least one of hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and carboxymethyl cellulose.

6. A mine gas sealing material according to claim 1 or 5, characterized in that: The cellulose ether is composed of carboxymethyl cellulose and hydroxypropyl methyl cellulose in a mass ratio of 1:3 to 5.

7. The mine gas sealing material according to claim 1, characterized in that: The particle size distribution of the ultrafine silicate cement is as follows: 19-21% by mass for particles ≤ 0.2µm and ≤ 0.3µm, 29-31% by mass for particles < 0.3µm and ≤ 1.0µm, and 49-51% by mass for particles < 1.0µm and ≤ 5.0µm; the specific surface area of ​​the ultrafine silicate cement is 1490-1510 m². 2 / kg.

8. A method for preparing a mine gas sealing material according to any one of claims 1 to 7, characterized in that, Includes the following steps: (1) Sodium citrate and tartaric acid are mixed in a mass ratio to obtain a composite coagulation regulator; (2) Mix the cellulose ether, expanding agent, water reducing agent, defoamer and composite setting regulator to obtain component A; (3) Mix ultrafine silicate cement with component A to obtain a mine gas sealing material.

9. The method for preparing a mine gas sealing material according to claim 8, characterized in that: The specific operation of mixing in step (3) is to add ultrafine silicate cement and component A to a twin-shaft mixer with a diameter > 500 mm and a length > 3500 mm after measuring with a screw weigher, and mix at a rate of 100 r / min for 45~50 min; during the mixing process, open the air box at the bottom of the mixer and turn on the Roots blower to suspend the material and make it fully homogenized.