Coal-based solid waste and polyurethane composite gel material and preparation method thereof

Abstract

The invention discloses a coal-based solid waste and polyurethane composite gel material and a preparation method thereof. The composite gel material comprises a hydrophilic polyurethane prepolymer, a compression-resistant reinforcing agent turbid liquid, a water-based cross-linking liquid and an alkali liquid containing fly ash, wherein the mass ratio of the hydrophilic polyurethane prepolymer to the compression-resistant reinforcing agent turbid liquid is 1: (0.1-0.3); the mass ratio of the aqueous crosslinking solution to the hydrophilic polyurethane prepolymer is 1: (10-20); the mass ratio of the hydrophilic polyurethane prepolymer to the lye containing the fly ash is 1: (0.5-1), and the flame-retardant hydrophilic polyurethane composite material has good compressive strength, good flame-retardant effect and low possibility of re-leakage, and has good application value.

Description

Technical Field

[0001] The present application belongs to the technical field of composite gel materials, and relates to a composite gel material of coal-based solid waste and polyurethane and a preparation method thereof. Background Art

[0002] Polyurethane (PU) materials have unique advantages in various reinforcement fields such as coal mining and major infrastructure projects such as highways, urban underground rail transit, and dam crack repair due to their adjustable viscosity and curing time, good adhesion, corrosion resistance, and high consolidated body strength. However, they also have problems such as low compressive strength and easy leakage, which limit their widespread application in the reinforcement field.

[0003] Gangue is waste rock produced during the coal mining and washing processes. The large-scale disposal of this solid waste can cause serious environmental pollution. As the largest solid waste produced during coal mining, its resource utilization is crucial for environmental protection. Existing research primarily uses gangue in power generation, lightweight aggregate for construction, and the production of refractory bricks. Furthermore, there have been some breakthroughs in the extraction of rare metals and the preparation of absorbing materials from gangue. However, exploration of high-value applications for gangue is relatively lacking.

[0004] Water-soluble polyurethane is generally a prepolymer formed by reacting a hydrophilic polyether polyol with an excess of isocyanate. Upon contact with water, this hydrophilic polyurethane prepolymer rapidly self-emulsifies, crosslinks with water, and solidifies into a water-insoluble gel while simultaneously releasing CO2 gas. This generated gas propels the slurry deeper into the crack, effectively expanding to block water and stop it with water. However, existing hydrophilic polyurethane prepolymers suffer from insufficient gel strength, limiting their application and poor flame retardancy. Summary of the Invention

[0005] In order to solve the above problems, the composite gel material of coal-based solid waste and polyurethane of the present invention contains at least four types of gels: the first type is a gel formed by the reaction of polyurethane prepolymer and water; the second type is a gel formed by the hydration reaction of coal-based solid waste with water or with water under the action of alkali, which is embedded in the gel formed by the reaction of polyurethane prepolymer and water; the third type is a hydrate and gel formed by the hydration reaction of fly ash, alkali and water, which enters the pores of the gel formed by the reaction of polyurethane prepolymer and water; the fourth type is sodium alginate distributed in the aqueous cross-linking liquid in the gel formed by the reaction of polyurethane prepolymer and water, which can react with calcium ions overflowing from coal gangue or fly ash to further cross-link to form a gel. Therefore, the present invention discloses a composite gel material of coal-based solid waste and polyurethane and a preparation method thereof.

[0006] One of the objectives of the present invention is to provide a composite gel material of coal-based solid waste and polyurethane, wherein the composite gel material is prepared by reacting the following raw materials: a hydrophilic polyurethane prepolymer, a compressive reinforcing agent suspension, an aqueous crosslinking liquid, and an alkaline solution containing fly ash; wherein the mass ratio of the hydrophilic polyurethane prepolymer to the compressive reinforcing agent suspension is 1:(0.1-0.3); the mass ratio of the aqueous crosslinking liquid to the hydrophilic polyurethane prepolymer is 1:(10-20); and the mass ratio of the hydrophilic polyurethane prepolymer to the alkaline solution containing fly ash is 1:(0.5-1).

[0007] The hydrophilic polyurethane prepolymer of the present invention contains many free isocyanate groups, which react easily with water. By utilizing this property, the polyurethane is immediately dispersed and emulsified upon contact with water, and rapidly reacts with water in situ to crosslink and solidify to form a water-insoluble gel, thereby achieving the purpose of water blocking and water stopping. In addition, the present invention also introduces a compressive enhancer suspension into the hydrophilic polyurethane prepolymer, wherein the coal-based solid waste can undergo a hydration reaction to form high-strength ettringite and CSH gel, thereby increasing the compressive strength of the polyurethane and reducing the shrinkage rate of the water-based polyurethane, thereby further improving the effect of the polyurethane while realizing the resource utilization of the coal-based solid waste. The gel formed by the reaction of polyurethane prepolymer and water produces and overflows carbon dioxide, forming pores within the polyurethane prepolymer. The present invention also introduces a hydrate formed by the hydration reaction of fly ash with alkali and water, which enters the pores of the gel. Finally, the sodium alginate in the aqueous crosslinking liquid distributed within the gel after the reaction of the polyurethane prepolymer and water can further crosslink with calcium ions overflowing from the coal gangue or fly ash to form a gel. The combined action of the four gels in the composite gel material of coal-based solid waste and polyurethane of the present invention yields a composite gel material of coal-based solid waste and polyurethane with further improved performance. Experimental results demonstrate that the composite gel material of the present invention is not susceptible to leakage.

[0008] As a preferred embodiment,

[0009] The preparation method of the hydrophilic polyurethane prepolymer comprises the following steps:

[0010] In a protective atmosphere, polyether polyol and isocyanate are mixed and then heated to react to obtain the hydrophilic polyurethane prepolymer;

[0011] Preferably, the polyether polyol is dehydrated at 110-120° C. for 1.5-2.5 hours before use;

[0012] The molar ratio of -NCO (isocyanate group (-NCO)) of the isocyanate to -OH of the polyether polyol is (5-8):1;

[0013] The temperature of the temperature-raising reaction is 75-82° C., and the reaction time is 2.5 h-3 h.

[0014] As a preferred embodiment,

[0015] The polyether polyol is selected from polyether polyols having a functionality of 3 and a molecular weight of about 4000-10000; preferably BD3-9000A;

[0016] The isocyanate is selected from diphenylmethane diisocyanate (MDI).

[0017] As a preferred embodiment,

[0018] The compressive strength enhancer suspension comprises modified fly ash, modified coal gangue and an organic solvent;

[0019] mixed liquid;

[0020] Preferably,

[0021] Modified fly ash Modified fly ash is fly ash modified with silane coupling agent;

[0022] The modified coal gangue is coal gangue modified by a silane coupling agent;

[0023] The organic solvent is ethyl acetate or methyl acetate;

[0024] The mass ratio of fly ash before modification to coal gangue before modification is 1:(1.2-1.5);

[0025] The mass ratio of modified fly ash to organic solvent is (1-2):100.

[0026] As a preferred embodiment,

[0027] The preparation method of modified coal gangue comprises the following steps:

[0028] The coal gangue is added to a water-alcohol mixed solution, and then a silane coupling agent is added. After the hydrolysis reaction, the mixture is vacuum dried and ground, and the coal gangue modified with the silane coupling agent with a particle size of 2-4 mm is selected;

[0029] The preparation method of modified fly ash comprises the following steps:

[0030] The fly ash is added into a water-alcohol mixed solution, and then a silane coupling agent is added, and after a hydrolysis reaction, the fly ash is vacuum dried and ground to obtain fly ash modified with the silane coupling agent;

[0031] Preferably,

[0032] The silane coupling agent is KH-550 or KH-560;

[0033] The hydroalcohol mixed solution is a mixed solution of water and ethanol, and the volume ratio of the two is 1:8-9;

[0034] The mass ratio of the coal gangue to the water-alcohol mixed solution is 1:(10-15);

[0035] The mass ratio of the fly ash to the water-alcohol mixed solution is 1:(10-15);

[0036] The mass ratio of the silane coupling agent to the water-alcohol mixed solution is 1:(40-50);

[0037] The hydrolysis reaction time is 50-60 min.

[0038] As a preferred embodiment,

[0039] The modified fly ash, modified coal gangue and organic solvent are uniformly mixed to obtain a compressive strengthening agent suspension.

[0040] As a preferred embodiment,

[0041] The aqueous cross-linking liquid includes sodium alginate and water, and the mass ratio of sodium alginate to water is 1:(100-150).

[0042] As a preferred embodiment,

[0043] The fly ash-containing alkali solution is a sodium hydroxide solution or a potassium hydroxide solution; preferably, the concentration of the fly ash-containing alkali solution is 2-4 mol / L.

[0044] The second aspect of the present invention is to provide a method for preparing a composite gel material of coal-based solid waste and polyurethane, comprising the following steps:

[0045] (1) uniformly mixing a hydrophilic polyurethane prepolymer and a compressive strength enhancing agent suspension to obtain a mixed slurry;

[0046] (2) adding 75% to 90% of the total volume of the aqueous cross-linking liquid to the mixed slurry and reacting for 1 to 3 minutes to form a primary gel;

[0047] (3) adding alkali solution containing fly ash and reacting for 1-2 hours;

[0048] (4) Add the remaining aqueous cross-linking liquid and continue the reaction until it is completely cured.

[0049] As a preferred embodiment,

[0050] The primary gel in step (2) is generated by the reaction of a hydrophilic polyurethane prepolymer with water, and releases CO gas to form pores;

[0051] The fly ash-containing alkali solution in step (3) reacts with the fly ash in the pores of the primary gel to generate ettringite and CSH gel, thereby enhancing the compressive strength;

[0052] The remaining aqueous cross-linking liquid in step (4) is cross-linked with calcium ions dissolved from the coal-based solid waste through sodium alginate to form a three-dimensional network structure to reduce shrinkage.

[0053] The specific reaction process is as follows:

[0054] The present invention adds a compressive enhancer suspension to the hydrophilic polyurethane prepolymer. The compressive enhancer suspension can reduce the viscosity of the hydrophilic polyurethane prepolymer to prevent it from being too high and difficult to grout; and can also introduce coal-based solid waste into the hydrophilic polyurethane prepolymer. After the mixed slurry of the hydrophilic polyurethane prepolymer and the compressive strength enhancing agent suspension is injected into an ordinary container, a partial volume of aqueous cross-linking liquid is first added to react, wherein the isocyanate groups in the hydrophilic polyurethane prepolymer react with water to cross-link and solidify into a water-insoluble primary gel, and the coal-based solid waste and the sodium alginate in the aqueous cross-linking liquid are fixed and dispersed in the above primary gel. During the formation of the above primary gel, CO2 gas is also released at the same time. The generated gas will push the slurry to continue to diffuse deep into the cracks. At the same time, the released CO2 gas will leave pores in the above primary gel due to diffusion, part of which overflows the primary gel and part remains in the primary gel; after the primary gel is formed, an alkali solution containing fly ash is added. The alkali solution containing fly ash does not contain water, and it basically does not react with the hydrophilic polyurethane prepolymer, but can enter the pores of the primary gel, and further reaction of fly ash and hydration reaction of the alkali solution; finally, the remaining aqueous cross-linking liquid is added to continue reacting with the hydrophilic polyurethane prepolymer, further increasing the gel degree of the hydrophilic polyurethane prepolymer gel, and further wrapping the alkali solution into the above-mentioned primary gel; since the alkali in the alkali solution is in excess relative to the fly ash, it can react with the fly ash to generate high-strength ettringite and CSH gel, etc. to fill the pores of the primary gel, and can further diffuse in the above-mentioned gel to slowly hydrate with the coal-based solid waste fixed in the primary gel (that is, the coal-based solid waste introduced into the primary gel from the compressive strength enhancer suspension), and also react with the hydrophilic polyurethane prepolymer to generate high-strength ettringite and CSH gel, etc. to fill the primary gel, thereby enhancing the compressive strength of the gel after the polyurethane prepolymer reacts with water, and reducing the shrinkage of the gel after the polyurethane prepolymer reacts with water. In addition, when the fly ash or coal gangue of the present invention reacts with water or with water under the action of alkali solution, some calcium ions will also be dissolved. These calcium ions can form a coordination effect with the sodium alginate molecular chain, thereby further cross-linking the sodium alginate in the gel formed by the reaction of the polyurethane prepolymer and water. It can also enhance the compressive strength of the gel formed by the reaction of the polyurethane prepolymer and water, and reduce the shrinkage of the gel formed by the reaction of the polyurethane prepolymer and water.

[0055] Beneficial effects:

[0056] The present invention realizes the resource utilization of coal-based solid waste and prepares modified polyurethane with better effect. The composite gel material of the present invention has good compressive strength, excellent flame retardant effect and is not easy to leak back, and has relatively good application value. DETAILED DESCRIPTION

[0057] Preparation Example 1

[0058] Raw material preparation:

[0059] A: The preparation method of the hydrophilic polyurethane prepolymer comprises the following steps:

[0060] In a protective atmosphere (nitrogen), a polyether polyol and an isocyanate are mixed and then heated to react to obtain the hydrophilic polyurethane prepolymer. The polyether polyol is dehydrated at 120°C for 2 hours before use. The molar ratio of -NCO (isocyanate group (-NCO)) of the isocyanate to -OH of the polyether polyol is 5:1. The temperature of the heated reaction is 82°C and the reaction time is 2.5 hours. The polyether polyol is selected from BD3-9000A (purchased from Jiangsu Bader Polyurethane Co., Ltd.) with a functionality of 3 and a molecular weight of approximately 9000. The isocyanate is selected from diphenylmethane diisocyanate (MDI).

[0061] B: The preparation method of modified coal gangue includes the following steps:

[0062] The coal gangue was added to a water-alcohol mixed solution (wherein the volume ratio of water to ethanol was 1:9), and then the silane coupling agent KH-550 was added, and the mass ratio of the silane coupling agent to the water-alcohol mixed solution was 1:50. After 50 minutes of hydrolysis reaction, the mixture was vacuum dried at 60°C for 12 hours and ground for 3 hours. The coal gangue modified with the silane coupling agent with a particle size of 2 mm was selected.

[0063] C: The preparation method of modified fly ash comprises the following steps:

[0064] The fly ash was added to a water-alcohol mixed solution (wherein the volume ratio of water to ethanol was 1:8), and then a silane coupling agent KH-550 was added, and the mass ratio of the silane coupling agent to the water-alcohol mixed solution was 1:50. After the hydrolysis reaction was carried out for 50 minutes, the fly ash was vacuum dried at 60°C for 12 hours and ground for 1 hour to obtain fly ash modified with the silane coupling agent.

[0065] D: The modified fly ash, modified coal gangue and organic solvent (ethyl acetate) are mixed evenly to obtain a compressive strength enhancer suspension.

[0066] E: Aqueous crosslinking liquid: Sodium alginate and water are evenly mixed to obtain an aqueous crosslinking liquid, wherein the mass ratio of sodium alginate to water is 1:100.

[0067] F: Alkali solution containing fly ash: fly ash, alkali and ethanol are uniformly mixed to obtain an alkali solution containing fly ash; wherein the mass ratio of fly ash to alkali is 1:8; the concentration of alkali in ethanol is 4 mol / L; and the alkali is potassium hydroxide.

[0068] Preparation Example 2

[0069] Raw material preparation:

[0070] A: The preparation method of the hydrophilic polyurethane prepolymer comprises the following steps:

[0071] In a protective atmosphere (nitrogen), a polyether polyol and an isocyanate are mixed and then heated to react to obtain the hydrophilic polyurethane prepolymer. The polyether polyol is dehydrated at 120°C for 2 hours before use. The molar ratio of -NCO (isocyanate group (-NCO)) of the isocyanate to -OH of the polyether polyol is 8:1. The temperature of the heated reaction is 75°C and the reaction time is 3 hours. The polyether polyol is selected from BD3-9000A (purchased from Jiangsu Bader Polyurethane Co., Ltd.) with a functionality of 3 and a molecular weight of approximately 9000. The isocyanate is selected from diphenylmethane diisocyanate (MDI).

[0072] B: The preparation method of modified coal gangue includes the following steps:

[0073] The coal gangue was added to a water-alcohol mixed solution (wherein the volume ratio of water to ethanol was 1:8), and then the silane coupling agent KH-560 was added, and the mass ratio of the silane coupling agent to the water-alcohol mixed solution was 1:40. After 60 minutes of hydrolysis reaction, the mixture was vacuum dried at 60°C for 12 hours and ground for 2 hours. The coal gangue modified with the silane coupling agent with a particle size of 4 mm was selected.

[0074] C: The preparation method of modified fly ash comprises the following steps:

[0075] The fly ash was added to a water-alcohol mixed solution (wherein the volume ratio of water to ethanol was 1:8), and then a silane coupling agent KH-560 was added, and the mass ratio of the silane coupling agent to the water-alcohol mixed solution was 1:40. After the hydrolysis reaction was carried out for 60 minutes, the fly ash was vacuum dried at 60°C for 12 hours and ground for 0.5 hours to obtain fly ash modified with the silane coupling agent.

[0076] D: The modified fly ash, modified coal gangue and organic solvent (methyl acetate) are mixed evenly to obtain a compressive strengthening agent suspension.

[0077] E: Aqueous crosslinking liquid: Sodium alginate and water are uniformly mixed to obtain an aqueous crosslinking liquid, wherein the mass ratio of sodium alginate to water is 1:150.

[0078] F: Alkali solution containing fly ash: fly ash, alkali and ethanol are uniformly mixed to obtain an alkali solution containing fly ash; wherein the mass ratio of fly ash to alkali is 1:4; the concentration of alkali in ethanol is 2 mol / L; and the alkali is sodium hydroxide.

[0079] Example 1

[0080] (1) A composite gel material of coal-based solid waste and polyurethane, the composite gel material being prepared by reacting the following raw materials: a hydrophilic polyurethane prepolymer, a compressive strength enhancing agent suspension, an aqueous crosslinking liquid, and an alkaline solution containing fly ash, wherein the raw materials prepared in Preparation Example 1 are used; wherein the mass ratio of the hydrophilic polyurethane prepolymer to the compressive strength enhancing agent suspension is 1:0.2; the mass ratio of the aqueous crosslinking liquid to the hydrophilic polyurethane prepolymer is 1:18; and the mass ratio of the hydrophilic polyurethane prepolymer to the alkaline solution containing fly ash is 1:0.8. The hydrophilic polyurethane prepolymer and the compressive strength enhancing agent suspension are first mixed uniformly to obtain a mixed slurry.

[0081] (2) The mixed slurry is injected into an ordinary container (an ordinary beaker in the present invention), and then an aqueous cross-linking liquid accounting for 90% of the total volume of the aqueous cross-linking liquid is added. After the aqueous cross-linking liquid is added and reacted for 1 minute, an alkali solution containing fly ash is added and reacted for 2 hours, and then the remaining aqueous cross-linking liquid is added to obtain a composite gel material of coal-based solid waste and polyurethane.

[0082] Example 2

[0083] (1) A composite gel material of coal-based solid waste and polyurethane, the composite gel material being prepared by reacting the following raw materials: a hydrophilic polyurethane prepolymer, a compressive strength enhancing agent suspension, an aqueous crosslinking liquid, and an alkaline solution containing fly ash, wherein the raw materials prepared in Preparation Example 1 are used; wherein the mass ratio of the hydrophilic polyurethane prepolymer to the compressive strength enhancing agent suspension is 1:0.3; the mass ratio of the aqueous crosslinking liquid to the hydrophilic polyurethane prepolymer is 1:12; and the mass ratio of the hydrophilic polyurethane prepolymer to the alkaline solution containing fly ash is 1:0.5. The hydrophilic polyurethane prepolymer and the compressive strength enhancing agent suspension are first mixed uniformly to obtain a mixed slurry.

[0084] (2) The mixed slurry is injected into an ordinary container (an ordinary beaker in the present invention), and then an aqueous cross-linking liquid accounting for 85% of the total volume of the aqueous cross-linking liquid is added. After the aqueous cross-linking liquid is added and reacted for 2 minutes, an alkali solution containing fly ash is added and reacted for 1.5 hours, and then the remaining aqueous cross-linking liquid is added to obtain a composite gel material of coal-based solid waste and polyurethane.

[0085] Example 3

[0086] (1) A composite gel material of coal-based solid waste and polyurethane, the composite gel material being prepared by reacting the following raw materials: a hydrophilic polyurethane prepolymer, a compressive strength enhancing agent suspension, an aqueous crosslinking liquid, and an alkaline solution containing fly ash, wherein the raw materials prepared in Preparation Example 2 are used; wherein the mass ratio of the hydrophilic polyurethane prepolymer to the compressive strength enhancing agent suspension is 1:0.25; the mass ratio of the aqueous crosslinking liquid to the hydrophilic polyurethane prepolymer is 1:10; and the mass ratio of the hydrophilic polyurethane prepolymer to the alkaline solution containing fly ash is 1:1. The hydrophilic polyurethane prepolymer and the compressive strength enhancing agent suspension are first mixed uniformly to obtain a mixed slurry.

[0087] (2) The mixed slurry is injected into an ordinary container (an ordinary beaker in the present invention), and then an aqueous cross-linking liquid accounting for 90% of the total volume of the aqueous cross-linking liquid is added. After the aqueous cross-linking liquid is added and reacted for 3 minutes, an alkali solution containing fly ash is added and reacted for 1.5 hours, and then the remaining aqueous cross-linking liquid is added to obtain a composite gel material of coal-based solid waste and polyurethane.

[0088] Example 4

[0089] (1) A composite gel material of coal-based solid waste and polyurethane, the composite gel material being prepared by reacting the following raw materials: a hydrophilic polyurethane prepolymer, a compressive strength enhancing agent suspension, an aqueous crosslinking liquid, and an alkaline solution containing fly ash, wherein the raw materials prepared in Preparation Example 2 are used; wherein the mass ratio of the hydrophilic polyurethane prepolymer to the compressive strength enhancing agent suspension is 1:0.1; the mass ratio of the aqueous crosslinking liquid to the hydrophilic polyurethane prepolymer is 1:15; and the mass ratio of the hydrophilic polyurethane prepolymer to the alkaline solution containing fly ash is 1:0.6. The hydrophilic polyurethane prepolymer and the compressive strength enhancing agent suspension are first mixed uniformly to obtain a mixed slurry.

[0090] (2) The mixed slurry is injected into an ordinary container (an ordinary beaker in the present invention), and then an aqueous cross-linking liquid accounting for 75% of the total volume of the aqueous cross-linking liquid is added. After the aqueous cross-linking liquid is added and reacted for 2 minutes, an alkali solution containing fly ash is added and reacted for 1 hour, and then the remaining aqueous cross-linking liquid is added to obtain a composite gel material of coal-based solid waste and polyurethane.

[0091] Comparative Example 1

[0092] The preparation method is basically the same as that of Example 1, with the only difference being that sodium alginate is not added to the aqueous cross-linking liquid, and an equal mass of pure water is used instead of sodium alginate.

[0093] Comparative Example 2

[0094] The preparation method is basically the same as that of Example 1, with the only difference being that alkali and fly ash are not added to the fly ash-containing alkali solution, and ethanol of equal mass is used instead of the alkali and fly ash.

[0095] Comparative Example 3

[0096] The preparation method is basically the same as that of Example 1, with the only difference being that fly ash is not added to the alkali solution containing fly ash, and an equal mass of ethanol is used instead of the fly ash.

[0097] Comparative Example 4

[0098] The preparation method is basically the same as that of Example 1, with the only difference being that modified fly ash and modified coal gangue are not added to the compressive enhancer suspension, and ethyl acetate of equal mass is used instead of the modified fly ash and modified coal gangue.

[0099] Test method:

[0100] Compressive strength test: According to GB / T 2567-2008, the composite gel materials prepared in Examples 1-4 and the composite gel materials prepared in Examples 1-4 were subjected to compressive strength tests after being sealed and placed at room temperature for 7 days.

[0101] Limiting oxygen index (LOI) test: According to GB / T 2406.2-2009, the limiting oxygen index (LOI) of the composite gel materials prepared in Examples 1-4 was tested using a critical oxygen index instrument;

[0102] Solidification shrinkage test: Cut the solidification body (i.e. the composite gel material prepared above) into 20.0mm×20.0mm×20.0mm size and weigh its mass m a , put it into 80℃ electric heating blast drying, take it out and weigh its mass every 1 hour, wait until it is constant weight, take it out and test its mass m b The formula for calculating the shrinkage rate of the solid body is as follows: R1=(m a -m b ) / m a .

[0103] Water absorption test for solids: Cut the solid sample into 20.0 mm x 20.0 mm x 20.0 mm squares, dry in an oven to constant weight, and record its mass m1. Maintain the temperature at 20°C and immerse in distilled water for 8 hours. Remove the sample every hour to drain the surface moisture and weigh it. Once the weight stabilizes, reweigh it and record its weight m2. The formula for calculating the water absorption of the solid is as follows: R2 = (m2 - m1) / m1.

[0104] The results of the above examples and comparative examples are shown in Table 1.

[0105] Table 1

[0106]

[0107]

[0108] From the comparison of the compressive strength of the composite gel material prepared in the example and the composite gel material after being sealed and placed at room temperature for 7 days, it can be seen that since the composite gel material prepared in the present invention contains water and alkali, a hydration reaction of fly ash, coal gangue and water will further occur during the subsequent standing process, thereby further increasing the compressive strength of the composite gel material.

[0109] From the limiting oxygen index of the composite gel material of coal-based solid waste and polyurethane prepared in the example, it can be seen that the composite gel material of the present invention has a good flame retardant effect.

[0110] The sealing principle of polyurethane gel material is mainly that NCO in the system reacts with water, and quickly solidifies to form a large amount of gel solidified body. Since the generated solidified body contains a large amount of water, it will inevitably dry out and shrink during use. If the shrinkage rate of the solidified body is large, repeated leakage may occur. The standard for testing repeated leakage is "solidified body water absorption rate > solidified body shrinkage rate". The water absorption rate of the composite gel of coal-based solid waste and polyurethane prepared in the embodiment of the present invention is greater than the solidified body shrinkage rate, indicating that the composite gel of coal-based solid waste and polyurethane prepared in the embodiment of the present invention will not experience repeated leakage when used, and the composite gel of coal-based solid waste and polyurethane of the present invention has a lower solidified body shrinkage rate than the control example. The smaller solidified body shrinkage rate helps to reduce the distance between the solidified body shrinkage and the bonding matrix, thereby improving the overall performance and durability of the material.

[0111] It can be seen from the results of Example 1 and Comparative Examples 1-4 that only under the joint action of the four gels in the composite gel material of coal-based solid waste and polyurethane of the present invention can a composite gel material of coal-based solid waste and polyurethane with further improved performance be obtained.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be understood by those skilled in the art that various modifications or variations made by those skilled in the art based on the technical solution of the present invention without creative effort are still within the scope of protection of the present invention.

Claims

1. A composite gel material of coal-based solid waste and polyurethane, characterized in that: The composite gel material includes: a hydrophilic polyurethane prepolymer, a compressive reinforcing agent suspension, an aqueous cross-linking liquid, and an alkaline solution containing fly ash; wherein the mass ratio of the hydrophilic polyurethane prepolymer to the compressive reinforcing agent suspension is 1:(0.1-0.3); the mass ratio of the aqueous cross-linking liquid to the hydrophilic polyurethane prepolymer is 1:(10-20); and the mass ratio of the hydrophilic polyurethane prepolymer to the alkaline solution containing fly ash is 1:(0.5-1).

2. The composite gel material of coal-based solid waste and polyurethane according to claim 1, characterized in that: The hydrophilic polyurethane prepolymer is prepared by mixing polyether polyol and isocyanate in a protective atmosphere and reacting them at elevated temperature; Wherein, the polyether polyol is selected from a group having a functionality of 3 and a molecular weight of 4000-10000; The molar ratio of -NCO of the isocyanate to -OH of the polyether polyol is (5-8):1; Preferably, the polyether polyol is dehydrated at 110-120° C. for 1.5-2.5 hours before use; The temperature of the temperature-raising reaction is 75-82° C., and the reaction time is 2.5 h-3 h.

3. The composite gel material of coal-based solid waste and polyurethane according to claim 2, characterized in that: The polyether polyol is BD3-9000A; The isocyanate is selected from diphenylmethane diisocyanate.

4. The composite gel material of coal-based solid waste and polyurethane according to claim 1, characterized in that: The compressive strength enhancer suspension comprises modified fly ash, modified coal gangue and an organic solvent; Among them, the mass ratio of fly ash before modification to coal gangue before modification is 1:(1.2-1.5); The mass ratio of modified fly ash to organic solvent is (1-2):100; The organic solvent is ethyl acetate or methyl acetate.

5. The composite gel material of coal-based solid waste and polyurethane according to claim 4, characterized in that: The preparation method of the fly ash and modified coal gangue modified by the silane coupling agent comprises: Adding coal gangue or fly ash to a water-alcohol mixed solution, then adding a silane coupling agent, performing a hydrolysis reaction, vacuum drying, and grinding to obtain modified coal gangue or fly ash; Preferably, The silane coupling agent is at least one of KH-550 and KH-560.

6. The composite gel material of coal-based solid waste and polyurethane according to claim 5, characterized in that: The hydroalcohol mixed solution is a mixed solution of water and ethanol, and the volume ratio of the two is 1:(8-9); The mass ratio of the coal gangue or fly ash to the water-alcohol mixed solution is 1:(10-15); The mass ratio of the silane coupling agent to the water-alcohol mixed solution is 1:(40-50); The hydrolysis reaction time is 50-60min; The grinding time is 1-3 hours, and the coal gangue is ground to a particle size of 2-4 mm.

7. The composite gel material of coal-based solid waste and polyurethane according to claim 1, characterized in that: The aqueous cross-linking liquid includes sodium alginate and water, and the mass ratio of sodium alginate to water is 1:(100-150).

8. The composite gel material of coal-based solid waste and polyurethane according to claim 1, characterized in that: The fly ash-containing alkali solution comprises fly ash, alkali and ethanol; wherein the mass ratio of fly ash to alkali is 1:(4-8); the concentration of alkali in ethanol is 2-4 mol / L; and the alkali is sodium hydroxide or potassium hydroxide.

9. The method for preparing the composite gel material of coal-based solid waste and polyurethane according to any one of claims 1 to 8, comprising the following steps: (1) uniformly mixing a hydrophilic polyurethane prepolymer and a compressive strength enhancing agent suspension to obtain a mixed slurry; (2) adding 75% to 90% of the total volume of the aqueous cross-linking liquid to the mixed slurry and reacting for 1 to 3 minutes to form a primary gel; (3) adding alkali solution containing fly ash and reacting for 1-2 hours; (4) Add the remaining aqueous cross-linking liquid and continue the reaction until it is completely cured.

10. The method for preparing a composite gel material of coal-based solid waste and polyurethane according to claim 9, characterized in that: The primary gel in step (2) is generated by the reaction of a hydrophilic polyurethane prepolymer with water, and releases CO gas to form pores; The fly ash-containing alkali solution in step (3) reacts with the fly ash in the pores of the primary gel to generate ettringite and CSH gel, thereby enhancing the compressive strength; The remaining aqueous cross-linking liquid in step (4) is cross-linked with calcium ions dissolved from the coal-based solid waste through sodium alginate to form a three-dimensional network structure to reduce shrinkage.

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