An inorganic expandable cured foam material and its preparation method

Abstract

The present invention discloses an inorganic expandable cured foam material and a preparation method thereof. The inorganic expandable cured foam material is formed by mixing and expanding 20% - 30% of material A, 45% - 55% of material B and 20% - 30% of water. Material A is prepared from raw materials in the following weight percentages: 10% - 30% of fly ash, 10% - 30% of bentonite, 5% - 20% of calcium carbonate, and 40% - 60% of phosphate cement; Material B is prepared from raw materials in the following weight percentages: 15% - 25% of hydroxyethylidene diphosphonic acid, 1% - 10% of ammonium chloride, 1% - 5% of sodium phosphate, 0.1% - 0.8% of cocamidopropyl betaine, and 50% - 80% of water. The inorganic expandable cured foam material of the present invention has the characteristics of non-combustibility, almost no heat release, strong bonding and reinforcement ability, high compressive strength, controllable foaming multiple, etc., and has a very remarkable effect on preventing and controlling coal spontaneous combustion, and the operation process is simple, safe and low-cost.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of solidified foam, and particularly relates to an inorganic expandable solidified foam material and a preparation method thereof. Background Art

[0002] Coal is the main energy source in China. In the next quite long period, China will still maintain an energy structure dominated by coal. However, coal mining faces serious spontaneous combustion problems, which not only burn a large amount of coal resources, but also produce toxic and harmful gases, and even lead to a series of induced disasters such as gas explosions. Most mine fires in China occur in goafs, and the main reasons for ignition are serious air leakage in the goaf and slow working face advancing speed, resulting in the residual coal in the goaf being in the oxidation zone for a long time and spontaneous combustion. Accelerating the working face extraction speed and using sealing materials to block the air leakage channels in the goaf are currently the most effective and commonly used methods to prevent goaf spontaneous combustion. However, due to complex geological conditions, geological structures such as faults and folds cause the coal seam roof to be broken, restricting the extraction speed; at the same time, in order to control air leakage in the goaf, coal mines usually adopt technologies such as injecting water glass gel and injecting cement slurry, but there are certain defects and deficiencies, and the effect of plugging air leakage is not ideal.

[0003] In recent years, foam materials have attracted more and more attention from domestic and foreign scholars due to their good fluidity and permeability before curing, and excellent plugging and oxygen isolation characteristics after curing. However, existing inorganic foam plugging materials, such as the commonly used ordinary Portland cement-based solidified foam, have a slow curing speed, poor foam stability, low compressive strength, and are prone to cracking under the influence of mining-induced deformation of coal and rock strata, resulting in a decline in the air leakage prevention performance, and the effect of long-term prevention of coal spontaneous combustion is very limited. Organic foams, such as Roxul and Marisan, have problems such as large heat release, flammability, and high costs, which limit their large-scale popularization and application in coal mine sites.

[0004] CN114656276A proposes a nano self-expanding solidified foam fire prevention and extinguishing material, but this solidified foam material undergoes spontaneous foaming by the reaction of aluminum powder with alkaline cement to release hydrogen. This foaming method will produce flammable and explosive hydrogen, which has certain dangers and is not applicable in underground mines; CN107936218A proposes an elastic solidified foam material for underground goafs. This material uses the chain growth reaction of organic polyisocyanates and polyol compounds to obtain polyurethane foam, but this material is flammable, and the reaction is violently exothermic, which is extremely likely to cause coal spontaneous combustion; CN103964766A prepares solidified foam by mixing fly ash-cement slurry with water-based foam, but this material has a long setting time, unstable foam, is greatly affected by the environment, and the preparation process is complex, and it is not applicable to reinforce the broken roof of coal seams underground. Summary of the Invention

[0005] The object of the present invention is to provide an inorganic expanded solidified foam material. During the processing and use of this inorganic expanded solidified foam material, no harmful substances such as strong acids and strong alkalis are added or used. It has the advantages of being non-combustible, hardly generating heat, having strong bonding and reinforcement ability, high compressive strength, and controllable foaming multiple. When the foaming multiple is controlled to be 3 - 5 times, it can fill and reinforce the broken roof of the coal seam. When the foaming multiple > 10 times, it can quickly fill and plug leaks in a large space. At the same time, the effect of preventing coal spontaneous combustion of this material is very remarkable.

[0006] Another object of the present invention is to provide a preparation method of the above-mentioned inorganic expanded solidified foam material. The whole process has no harsh requirements for experimental environments such as high temperature and high pressure. The operation process is simple, safe, and low-cost, and can be industrially produced.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] In the first aspect, the present invention provides an inorganic expanded solidified foam material, which is made of raw materials with the following weight percentages: 20% - 30% of material A, 45% - 55% of material B, and 20% - 30% of water; wherein material A is prepared from raw materials with the following weight percentages: 10% - 30% of fly ash, 10% - 30% of bentonite, 5% - 20% of calcium carbonate, and 40% - 60% of phosphate cement; material B is prepared from raw materials with the following weight percentages: 15% - 25% of hydroxyethylidene diphosphonic acid, 1% - 10% of ammonium chloride, 1% - 5% of sodium phosphate, 0.1% - 0.8% of coconut amide propyl betaine, and 50% - 80% of water.

[0009] Preferably, the inorganic expanded solidified foam material is made of raw materials with the following weight percentages: 20% - 25% of material A, 45% - 55% of material B, and 25% - 30% of water; wherein material A is made of raw materials with the following weight percentages: 20% of fly ash, 20% of bentonite, 5% - 15% of calcium carbonate, and 45% - 55% of phosphate cement; wherein material B is made of raw materials with the following weight percentages: 24% - 32% of hydroxyethylidene diphosphonic acid, 1.8% of ammonium chloride, 1% of sodium phosphate, 0.2% of coconut amide propyl betaine, and 65% - 73% of water.

[0010] Preferably, the preparation process of material A is: weighing fly ash, bentonite, calcium carbonate, and phosphate cement respectively according to the ratio, and uniformly mixing them by ball milling to obtain material A.

[0011] Preferably, the fly ash is secondary fly ash, the particle size of the bentonite is 10 - 30 mesh, and the particle size of the calcium carbonate is 200 - 300 mesh.

[0012] Preferably, the ball milling speed is 100 - 300 r / min, and the ball milling time is 10 - 30 min.

[0013] Preferably, the preparation process of the B material is as follows:

[0014] 1) Weigh ammonium chloride, sodium phosphate and water respectively according to the ratio. At room temperature, dissolve ammonium chloride and sodium phosphate completely in water to obtain a uniform inorganic salt solution.

[0015] 2) Weigh hydroxyethane diphosphonic acid and cocoamidopropyl betaine respectively according to the ratio, add them into the above inorganic salt solution, and stir at room temperature until completely dispersed to obtain a uniform B material.

[0016] In a second aspect, the present invention also provides a preparation method of the above inorganic expandable cured foam material. The specific steps are as follows: First, stir and mix the A material and water evenly according to the ratio, then add the B material according to the ratio, and mix and stir at room temperature for 5 s to 15 s to obtain the inorganic expandable cured foam material; the foaming multiple, foaming rate and curing time are adjusted by adjusting the weight ratio of each component of the A material and the B material.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. In the present invention, fly ash, bentonite, calcium carbonate, and phosphate cement are ball-milled and blended. The calcium carbonate powder with smaller particle size adheres to fly ash and bentonite. Taking fly ash and bentonite as carriers, with their excellent emulsifying and dispersing properties in the solution, the foaming agent calcium carbonate powder is evenly dispersed in the solution, avoiding the problems of agglomeration and insufficient dispersion of the small-particle-size calcium carbonate powder in water, and improving the stability of the solution dispersion system; as a common and relatively inexpensive chemical substance, calcium carbonate is easily obtained in the market, which helps to reduce the cost of the inorganic expandable cured foam material; calcium carbonate is evenly dispersed in the A material solution. When the A material is mixed with the B material, it can react with hydroxyethane diphosphonic acid in the B material to generate inert gas carbon dioxide, thereby realizing the self-foaming of the material. At the same time, the carbon dioxide gas plays a role in diluting the oxygen concentration in the oxidation space of the residual coal in the goaf; cocoamidopropyl betaine reduces the interfacial tension and enhances the foam stability of spontaneous foaming, ensuring that the foam will not break before the material cures; the smaller the particle size of calcium carbonate, the faster the foaming reaction rate, and the larger the addition amount of calcium carbonate, the higher the foaming multiple of the material. By controlling the addition amount and particle size of calcium carbonate, the foaming multiple, foaming rate and cell structure of the cured foam can be adjusted to meet the needs of different use scenarios and purposes in the mine, such as for broken roof reinforcement or filling and plugging large spaces, etc.

[0019] The present invention uses phosphate cement as the main solidifying material, and fly ash and bentonite as auxiliary materials. The main component of phosphate cement is phosphate compounds. In an acidic environment, when phosphate cement starts to solidify, phosphate compounds begin to react with metal ions and gradually form a gelling product, which promotes the solidification of phosphate cement and forms a hard cement matrix. Among them, the commonly used metal ion is calcium ion, which comes from the added calcium salts, auxiliary materials, and calcium-containing minerals in the cement itself. The gelling product forms crystals in the cement matrix, fills the pores, and forms an interlocking structure with the particles, thereby increasing the strength and stability of the material. In addition, after the fly ash and bentonite particles are foamed, they fill the cell walls of the solidified foam, which is beneficial to improving the structural strength, stiffness, wear resistance, and flame retardancy of the solidified foam. The particle shape and surface characteristics of fly ash powder particles help to improve the mechanical properties of the material. The good heat resistance of fly ash improves the high-temperature resistance of the solidified foam and reduces the thermal expansion of the material; the excellent water retention property of bentonite improves the water retention ability of the solidified foam, making it have good fire extinguishing and cooling capabilities; at the same time, bentonite has a high barrier property, which can block the penetration of oxygen and improve the performance of the solidified foam in plugging and oxygen isolation.

[0020] 2. In the process of preparing Material B of the present invention, ammonium chloride and sodium phosphate are added to water in proportion and stirred at room temperature to obtain a uniform inorganic salt solution. Then, hydroxyethylidene diphosphonic acid is added to the above inorganic salt solution in proportion and stirred at room temperature until it is completely dissolved in the solution, and finally a uniform Material B is obtained. The dissolution of ammonium chloride in water is an endothermic reaction, which reduces the system temperature and absorbs the heat generated by the reaction of Material A, Material B, and water, thereby stabilizing the temperature of the reaction system. At the same time, the relatively high water-solid ratio and porosity of the inorganic foam material itself endow it with excellent heat insulation performance, so that the material exhibits almost no heat release characteristics (the temperature rise at the center of the reaction is less than 1°C); the phosphate ions in sodium phosphate are important components for the solidification of phosphate cement, and sodium phosphate and ammonium chloride can be used as inorganic salt adjuvants to promote the solidification reaction of phosphate cement. Hydroxyethylidene diphosphonic acid is a weak acid. On the one hand, it can react with calcium carbonate in Material A to generate carbon dioxide gas to form a self-foaming system. On the other hand, it provides an acidic condition for the solidification reaction of phosphate cement, accelerating the solidification reaction rate of phosphate cement, so that the material can achieve rapid solidification while self-foaming and obtain strength and stability, and finally form an expanded solidified foam material; by adjusting the component ratio of Material B, the solidification time of the self-foaming system can be adjusted to meet the needs of different use scenarios in mines.

[0021] 3. The present invention provides an inorganic expandable solidified foam material, which can adjust the foaming multiple, foaming rate and curing time according to different use scenarios and purposes. It can quickly fill and plug large spaces by drilling and grouting (foaming multiple > 10 times), or reinforce the broken roof of coal seams (foaming multiple 3 - 5 times) to improve the mining speed. It can also be sprayed upwards by high-pressure grouting. After the material foams, it can accumulate upwards, fill, bond and reinforce the broken coal and rock mass, and cover and wrap the surface of the coal and rock mass to plug air leakage or reinforce the roof. After the material coagulates and solidifies, it has a high foam porosity, can isolate oxygen, has heat insulation, and has a certain compressive strength and durability, preventing cracks from occurring in the material affected by mining and the development of secondary cracks in the coal and rock consolidation body to allow air to enter, which is beneficial to the efficient prevention and control of coal spontaneous combustion in mines. In addition, the inorganic expandable solidified foam material is non-toxic, harmless, low-cost, has a simple preparation method, is easy to operate, and has a very broad application prospect. Detailed Embodiments

[0022] The following further elaborates the present invention in detail with specific embodiments.

[0023] The raw materials used in the following embodiments are all commercially available products. The fly ash is secondary fly ash, the particle size of bentonite is 10 - 30 mesh, and the particle size of calcium carbonate is 200 - 300 mesh.

[0024] The A material used in the following embodiments is prepared according to the following steps: Weigh fly ash, bentonite, calcium carbonate and phosphate cement in proportion, and mix them evenly by ball milling to obtain the A material, where the ball milling speed is 100 - 300 r / min and the ball milling time is 10 - 30 min.

[0025] The B material used in the following embodiments is prepared according to the following steps: (1) Weigh ammonium chloride, sodium phosphate and water in proportion, add ammonium chloride and sodium phosphate to water, stir at room temperature for 5 min, and after completely dissolving in water, obtain a uniform inorganic salt solution; (2) Weigh hydroxyethane diphosphonic acid and cocamidopropyl betaine in proportion, add them to the above inorganic salt solution, stir at room temperature for 5 min, and after completely dispersing in the solution, finally obtain a uniform B material.

[0026] Example 1

[0027] An inorganic expandable solidified foam material is made from the following raw materials by weight percentage: 25% of A material, 50% of B material, and 25% of water. Among them, the A material is made from the following raw materials by weight percentage: 20% of fly ash, 20% of bentonite, 5% of calcium carbonate, and 55% of phosphate cement; among them, the B material is made from the following raw materials by weight percentage: 24% of hydroxyethane diphosphonic acid, 1.8% of ammonium chloride, 1% of sodium phosphate, 73% of water, and 0.2% of cocamidopropyl betaine.

[0028] In this embodiment, the preparation method of the inorganic expandable solidified foam material comprises the following specific steps:

[0029] First, add material A into water in proportion. After stirring and mixing evenly, then add material B in proportion and stir at room temperature for 5 s to 15 s to obtain the inorganic expandable solidified foam material.

[0030] Example 2

[0031] An inorganic expandable solidified foam material is made from the following raw materials by weight percentage: 25% of material A, 50% of material B, and 25% of water. Among them, material A is made from the following raw materials by weight percentage: 20% of fly ash, 20% of bentonite, 15% of calcium carbonate, and 45% of phosphate cement. Among them, material B is made from the following raw materials by weight percentage: 32% of hydroxyethylidene diphosphonic acid, 1.8% of ammonium chloride, 1% of sodium phosphate, 65% of water, and 0.2% of cocamidopropyl betaine.

[0032] The preparation method of the inorganic expandable solidified foam material in this embodiment is the same as that in Example 1.

[0033] Example 3

[0034] An inorganic expandable solidified foam material is made from the following raw materials by weight percentage: 25% of material A, 45% of material B, and 30% of water. Among them, material A is made from the following raw materials by weight percentage: 20% of fly ash, 20% of bentonite, 5% of calcium carbonate, and 55% of phosphate cement. Among them, material B is made from the following raw materials by weight percentage: 24% of hydroxyethylidene diphosphonic acid, 1.8% of ammonium chloride, 1% of sodium phosphate, 73% of water, and 0.2% of cocamidopropyl betaine.

[0035] The preparation method of the inorganic expandable solidified foam material in this embodiment is the same as that in Example 1.

[0036] Example 4

[0037] An inorganic expandable solidified foam material is made from the following raw materials by weight percentage: 25% of material A, 45% of material B, and 30% of water. Among them, material A is made from the following raw materials by weight percentage: 20% of fly ash, 20% of bentonite, 15% of calcium carbonate, and 45% of phosphate cement. Among them, material B is made from the following raw materials by weight percentage: 32% of hydroxyethylidene diphosphonic acid, 1.8% of ammonium chloride, 1% of sodium phosphate, 65% of water, and 0.2% of cocamidopropyl betaine.

[0038] The preparation method of the inorganic expandable solidified foam material in this embodiment is the same as that in Example 1.

[0039] Example 5

[0040] An inorganic expandable solidified foam material is made from raw materials in the following weight percentages: 20% of Material A, 55% of Material B, and 25% of water. Among them, Material A is made from raw materials in the following weight percentages: 20% of fly ash, 20% of bentonite, 5% of calcium carbonate, and 55% of phosphate cement. Among them, Material B is made from raw materials in the following weight percentages: 24% of hydroxyethane diphosphonic acid, 1.8% of ammonium chloride, 1% of sodium phosphate, 73% of water, and 0.2% of cocamidopropyl betaine.

[0041] In this example, the preparation method of the inorganic expandable solidified foam material is the same as that in Example 1.

[0042] Example 6

[0043] An inorganic expandable solidified foam material is made from raw materials in the following weight percentages: 20% of Material A, 55% of Material B, and 25% of water. Among them, Material A is made from raw materials in the following weight percentages: 20% of fly ash, 20% of bentonite, 15% of calcium carbonate, and 45% of phosphate cement. Among them, Material B is made from raw materials in the following weight percentages: 32% of hydroxyethane diphosphonic acid, 1.8% of ammonium chloride, 1% of sodium phosphate, 65% of water, and 0.2% of cocamidopropyl betaine.

[0044] In this example, the preparation method of the inorganic expandable solidified foam material is the same as that in Example 1.

[0045] The inorganic expandable solidified foam materials prepared in the above Examples 1-6 were tested for expansion ratio, maximum reaction temperature, and compressive strength with reference to the industry standard for polymer foaming materials for coal mine filling and sealing (AQ / T 1090-2020). The curing time of the material was tested by the touch rod method, that is, by pressing the surface of the inorganic expandable solidified foam material with the self-weight of a glass rod. The time from the start of foaming when Materials A and B were mixed to the time when the surface of the material was pressed and no deformation occurred was recorded as the curing time of the material. At the same time, the foaming and expansion time of the material was observed and recorded during the test, that is, the time from the start of foaming when Materials A and B were mixed to the time when the material no longer foamed and expanded. The specific data are shown in Table 1.

[0046] Table 1 Influence of different raw material ratios on the properties of inorganic expandable solidified foam materials

[0047]

[0048] As can be seen from Table 1, for the inorganic expandable solidified foam material of the present invention, its foaming multiple, foaming rate and curing time are adjustable, the reaction temperature rise is less than 1°C, the foaming and swelling time is 10 - 20 s, the foam curing time is 45 - 120 s, and the maximum compressive strength is 18.2 MPa. This is because after the A material, B material and water provided by the present invention are mixed, they can quickly react to generate inert gas carbon dioxide for self-foaming, generate stable and durable foam, and solidify and condense in a short time to form an inorganic expandable solidified foam material with relatively high strength.

[0049] The present invention utilizes the reaction of calcium carbonate and hydroxyethylidene diphosphonic acid to generate inert gas carbon dioxide to form a self-foaming system, and improves the strength through the solidification of fly ash, bentonite and phosphate cement. According to different usage scenarios and purposes, the foaming multiple, foaming rate and cell structure are adjusted by adjusting the content and particle size of the foaming agent calcium carbonate, and the curing time is adjusted by adjusting the content of hydroxyethylidene diphosphonic acid, ammonium chloride and sodium phosphate in the B material, and finally a multi-purpose inorganic expandable solidified foam material is formed.

[0050] The inorganic expandable solidified foam material of the present invention has the characteristics of non-combustibility, almost no heat release (the central reaction temperature rise is less than 1°C), strong bonding and reinforcement ability, large compressive strength, controllable foaming multiple, etc. When the foaming multiple is controlled to be 3 - 5 times, it can fill and reinforce the broken roof of the coal seam. When the foaming multiple is controlled to be >10 times, it can quickly fill and plug large spaces, meeting the requirements of the inorganic solidified foam for the reinforcement and support of the broken roof underground, the high-level filling, plugging and oxygen isolation in the goaf and other fire prevention and extinguishing needs. At the same time, the material has a very significant effect on preventing coal spontaneous combustion, the operation process is simple, safe and low-cost, greatly reducing the labor intensity of underground workers, and meeting the application requirements of the mine site.

[0051] Although the above embodiments give some implementation manners of the present invention, for those skilled in the art, without departing from the basic principles of the present invention, only making changes in the composition ratio and modification of the embodiments, replacing the same type of materials, etc., all belong to the scope of the claims of the present invention.

Claims

1. An inorganic expandable solidified foam material, characterized in that, It is made from raw materials with the following weight percentages: 20% - 30% of Material A, 45% - 55% of Material B, and 20% - 30% of water; wherein Material A is prepared from raw materials with the following weight percentages: 10% - 30% of fly ash, 10% - 30% of bentonite, 5% - 20% of calcium carbonate, and 40% - 60% of phosphate cement; Material B is prepared from raw materials with the following weight percentages: 15% - 25% of hydroxyethylidene diphosphonic acid, 1% - 10% of ammonium chloride, 1% - 5% of sodium phosphate, 0.1% - 0.8% of cocamidopropyl betaine, and 50% - 80% of water.

2. The inorganic expandable cured foam material according to claim 1, characterized in that, It is made from raw materials with the following weight percentages: 20% - 25% of Material A, 45% - 55% of Material B, and 25% - 30% of water; wherein Material A is made from raw materials with the following weight percentages: 20% of fly ash, 20% of bentonite, 5% - 15% of calcium carbonate, and 45% - 55% of phosphate cement; wherein Material B is made from raw materials with the following weight percentages: 24% - 32% of hydroxyethylidene diphosphonic acid, 1.8% of ammonium chloride, 1% of sodium phosphate, 0.2% of cocamidopropyl betaine, and 65% - 73% of water.

3. An inorganic expandable cured foam material according to claim 1 or 2, characterized in that, The preparation process of Material A is as follows: Weigh fly ash, bentonite, calcium carbonate, and phosphate cement respectively according to the proportion, and mix them evenly by ball milling to obtain Material A.

4. An inorganic expandable cured foam material according to claim 3, characterized in that, The fly ash is secondary fly ash, the particle size of the bentonite is 10 - 30 mesh, and the particle size of the calcium carbonate is 200 - 300 mesh.

5. An inorganic expandable cured foam material according to claim 3, characterized in that, The ball milling speed is 100 - 300 r / min, and the ball milling time is 10 - 30 min.

6. An inorganic expandable cured foam material according to claim 1 or 2, characterized in that, The preparation process of Material B is as follows: 1) Weigh ammonium chloride, sodium phosphate, and water respectively according to the proportion, and completely dissolve ammonium chloride and sodium phosphate in water at room temperature to obtain a uniform inorganic salt solution; 2) Weigh hydroxyethylidene diphosphonic acid and cocamidopropyl betaine respectively according to the proportion, add them into the above inorganic salt solution, and stir at room temperature until completely dispersed to obtain a uniform Material B.

7. A method for preparing the inorganic expandable cured foam material according to any one of claims 1 to 6, characterized in that, The specific steps are as follows: First, stir and mix Material A and water evenly according to the proportion, then add Material B according to the proportion, and mix and stir at room temperature for 5 s - 15 s to obtain an inorganic expansion type solidified foam material; the foaming multiple, foaming rate, and curing time are adjusted by adjusting the weight ratio of each component of Material A and Material B.

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