Nano-silica modified organic composite grouting material for micro-fracture water plugging

Abstract

The invention discloses a nano-silica modified organic composite grouting material for micro-fracture water plugging. The nano-silica modified organic composite grouting material comprises the following raw materials: rice husk, citric acid, p-xylene, a polymerization inhibitor, an acrylic emulsion, acrylamide, a retarder, triethanolamine, a cross-linking agent, a coupling agent, an initiator, sodium carbonate and water. Inorganic nano-modified silicon dioxide is prepared from environment-friendly raw materials, fatty alcohol and a silane coupling agent are used for composite modification, the compatibility with organic materials is improved, modified silicon dioxide and acrylic emulsion are subjected to in-situ polymerization, submicron particles are dispersed in the acrylic emulsion, and the nano-modified silicon dioxide is prepared. The inorganic-organic nano modified composite grouting material with high compressive strength, excellent toughness and good permeability is prepared. By combining the respective performance advantages of organic materials and inorganic materials, the problems of brittleness of the inorganic materials and low strength of the organic materials are greatly improved, and the material can be widely applied to micro-crack grouting, water proofing and leaking stoppage in various fields.

Description

Technical Field

[0001] The invention belongs to the field of grouting waterproofing and leak plugging, and relates to a nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging and a preparation method thereof. Background Art

[0002] Grouting is the main means of preventing and controlling water leakage in the grouting field. At present, inorganic grouting materials are more commonly used, including cement, ultrafine cement, water glass, cement-fly ash and other grouting materials. These grouting materials are widely used in the field of grouting waterproofing and plugging. However, these grouting materials have a relatively large particle size and cannot be injected into micron-level cracks. They are also brittle and prone to repeated leakage in the later stage. Polymer grouting materials have better toughness and better pourability than inorganic grouting materials, but their strength cannot guarantee the grouting effect. Summary of the invention

[0003] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a nano-silica modified organic composite grouting material for micro-crack water plugging. The inorganic grouting materials currently used have insufficient permeability and cannot effectively grout and plug tiny cracks in various fields, while the organic grouting materials are insufficient in strength and their environmental protection needs to be improved. The present invention uses modified nano-silica to prepare inorganic-organic composite grouting materials, and uses environmentally friendly rice husks as raw materials to prepare silica, which can solve the problems of micro-crack waterproofing and plugging, material environmental protection problems, and resource recycling, thereby achieving sustainable development.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0005] A nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging comprises the following raw materials: rice husk, citric acid, p-xylene, polymerization inhibitor, acrylic emulsion, acrylamide, retarder, triethanolamine, cross-linking agent, coupling agent, initiator, sodium carbonate and water.

[0006] The present invention also includes the following technical features:

[0007] Specifically, the polymerization inhibitor is one or more of hydroquinone, p-tert-butylcatechol, and p-benzoquinone.

[0008] Specifically, the cross-linking agent is one or more of NN methylenebisacrylamide, ethylene glycol acrylate, and dimethylaminoethyl methacrylate.

[0009] Specifically, the coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane.

[0010] Specifically, the initiator is one or more of ammonium persulfate, potassium persulfate, and sodium persulfate.

[0011] Specifically, the retarder is one or more of potassium ferrocyanide, diphenylamine, and copper cyclopentaneate.

[0012] Specifically, the monomers used in the acrylic emulsion are isooctyl acrylate, styrene, dimethylaminoethyl methacrylate, vinyl triisopropoxy silane, ε-caprolactone and mercaptopropanol.

[0013] The method for preparing the nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging comprises the following steps:

[0014] Step 1: Mix rice husk, citric acid and water, heat the mixture to 50-65° C. with a magnetic stirrer, continue stirring for 25-35 minutes, wash three times with water to remove acid, and then dry for 2-3 hours to form a calcined product;

[0015] Step 2: using an electric furnace to heat the rice husk obtained in step 1 to 300-400° C. and carbonize for 10-20 min, and then calcining in a muffle furnace at 550° C., 600° C., 650° C. and 700° C. for 30-35 min, respectively, to obtain white powdery silicon dioxide;

[0016] Step 3: Mix the white powdered silica obtained in step 2 with the long-chain fatty alcohol and place in a high-pressure reactor to maintain the pressure at 2×10 5 ~6×10 5 Pa, react at 500-800°C for 100-170 min, and after the reaction is completed, fatty alcohol-modified nano-silicon dioxide is obtained;

[0017] Step 4: Mix the modified silica obtained in step 3 with a coupling agent and p-xylene, add 0.1% to 0.3% of a polymerization inhibitor to prevent the coupling agent from self-polymerizing, heat to 100° C. with a shear stirrer and continue stirring for 80 to 110 minutes;

[0018] Step 5: After filtering, washing with p-xylene three times to remove the inhibitor, drying at 100° C. for 1 to 1.5 hours, grinding with a mortar for 20 to 30 minutes, and grinding the silica particles to a particle size of 25 to 45 μm to obtain surface-modified silica;

[0019] Step 6: Mix the initiator and water, stir until clear and use as the initiator solution for later use; mix high-purity sodium carbonate and water and use as the buffer solution for later use;

[0020] Step 7: Isooctyl acrylate, styrene, dimethylaminoethyl methacrylate, vinyl triisopropoxysilane, ε-caprolactone and mercaptopropanol are stirred and mixed to obtain a mixed monomer, and a portion of the mixed monomer and deionized water are added to a four-necked flask equipped with a condenser, a mechanical stirrer, and a tetrafluoro constant pressure dropping funnel. The mixture is heated and stirred in a water bath, and the temperature is raised to 70-80° C., and the remaining mixed monomer and initiator solution are added dropwise, and nitrogen is introduced at the same time. After reacting for 2 hours, the temperature is lowered, and the material is filtered through a 300-mesh filter to obtain an acrylic emulsion;

[0021] Step 8: Add the surface-modified silica obtained in step 5 to the buffer solution of step 6, and carry out in-situ free radical solution polymerization with the acrylic emulsion of step 7: add water and surface-modified silica to a flask, adjust the water bath temperature to 95°C, and after the flask is filled with nitrogen, maintain a slow nitrogen flow until the solution temperature reaches 95°C; pour all the buffer solution, 10wt% mixed monomer and 10wt% initiator solution into the flask under mechanical stirring at 500-600rpm, and pre-emulsify for 15-20min; add the remaining mixed monomer and initiator dropwise to the flask at a rate of 6 drops / 60 seconds and 1 drop / 60 seconds, respectively; continue the reaction for 1-2h to ensure the reaction is complete;

[0022] Step 9: The reaction is maintained at 95° C. and 500-700 rpm for 35-40 min; then cooled to room temperature and discharged to obtain a nano-silicon dioxide modified acrylic emulsion;

[0023] Step 10: Evenly mix the modified acrylic emulsion, acrylamide, crosslinking agent, triethanolamine and water, and continue stirring for 15 to 25 minutes. Then, add the initiator and retarder, and stir for 5 to 10 minutes. When the curing reaction is completed, a nano-modified acrylic inorganic-organic composite grouting material for micro-crack water plugging is obtained.

[0024] Specifically, in step 1, the mass ratio of rice husk, citric acid and water is 1:1:15 to 1:1.5:20;

[0025] In step 3, the mass ratio of white powdered silicon dioxide to long-chain fatty alcohol is 1:0.2 to 1:0.9;

[0026] In step 4, the mass ratio of modified silica to coupling agent and p-xylene is 1:1:20 to 1:1.2:23;

[0027] In step 6, the mass ratio of the initiator to water is 1:100 to 1:160; the mass ratio of sodium carbonate to water is 1:95 to 1:110;

[0028] In step 7, the mass ratio of isooctyl acrylate, styrene, dimethylaminoethyl methacrylate, vinyl triisopropoxy silane, ε-caprolactone and mercaptopropanol is (30-50): (25-40): (20-35): (35-50): (10-15): (2-6).

[0029] Specifically, in step 10, the proportions of the modified acrylic emulsion, acrylamide, crosslinking agent, triethanolamine, water, initiator and retarder are calculated by weight, wherein water is 100 parts, the modified acrylic emulsion is 10 parts, acrylamide is 70 parts, the crosslinking agent is 0.9 parts, the triethanolamine is 5 parts, the initiator is 3 parts, and the retarder is 0.05-1 parts.

[0030] Compared with the prior art, the present invention has the following technical effects:

[0031] The grouting material for micro-crack water plugging of the invention combines the performance advantages of organic materials and inorganic materials, prepares inorganic nano-modified silica with environmentally friendly raw materials, uses fatty alcohol and silane coupling agent to carry out composite modification on the inorganic nano-modified silica, improves the compatibility with organic materials, carries out in-situ polymerization with homemade acrylic emulsion, disperses the modified silica in the acrylic emulsion as submicron particles, and prepares an inorganic-organic nano-modified composite grouting material with high compressive strength, excellent toughness and good permeability; the prepared inorganic-organic composite grouting material greatly improves the brittleness of inorganic materials and the low strength of organic materials, is suitable for tunnel construction, deformation joints and cracks of subway stations, settlement post-casting strips, crack water plugging in coal mines, deformation joints of villa basements, hollow walls, and wall crack seepage; all cracks only need to be grouted once, and the process is completed in one step, providing a certain technical idea for micro-crack grouting waterproofing and leak plugging in various fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the synthesis mechanism of micro-fracture water-plugging material.

[0033] Figure 2 It is the elongation at break of each embodiment and comparative example.

[0034] Figure 3 It is the compressive strength of each embodiment and comparative example.

[0035] Figure 4 It is the setting time of each embodiment and comparative example. DETAILED DESCRIPTION

[0036] The present invention provides a nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging. At present, inorganic-organic composite has become the future research and development direction of grouting modified materials. Among them, nano-modified organic-inorganic composite materials combine the advantages of inorganic materials (such as rigidity and thermal stability) and organic polymers (such as flexibility, ductility and processability), which can greatly improve the performance of grouting materials. There are three main forms of waterproof plugging mechanism. The first is bonding, such as epoxy resin adhesives, and the second is filling, such as cement-based inorganic grouting materials. The third is expansion plugging, such as polyurethane-type foaming materials.

[0037] Nano-silica has a large specific surface area. As a filler, it can significantly increase the specific surface area. Polymers can contact with silica and improve the agglomeration of nano-silica. Introducing nano-silica into the material system can improve the hardness, mechanical properties, wear resistance, corrosion resistance, heat resistance and hydrophobicity of the system.

[0038] At present, acrylic emulsion is various, and the grouting material used in the present invention requires good water resistance, compressive strength and storage stability during construction, which requires acrylic emulsion to have excellent flexibility, high purity and narrow molecular weight distribution. Therefore, the long-chain monomer with good flexibility, the rigid structure of polyphenyl rings and the monomer with functionality are introduced to meet the above performance requirements. Wherein the monomer used by acrylic emulsion is isooctyl acrylate, styrene, dimethylaminoethyl methacrylate, vinyl triisopropoxysilane, ε-caprolactone and mercaptopropanol, and the acrylic emulsion synthesized with these monomers can give the material excellent flexibility, strength, hardness, water resistance and storage stability, and the synthetic acrylic emulsion has a narrow molecular weight distribution, and the PDI is very small, and the viscosity of the system is reduced synchronously, and the purity can reach the highest, and solution polymerization can be carried out with nano silicon dioxide better to form a more homogeneous grouting material.

[0039] The present invention uses rice husk as raw material, calcines it into rice husk ash (RHA), obtains silicon dioxide, and performs surface modification on silicon dioxide to improve its surface agglomeration. The most commonly used surface modification method is the silane coupling agent modification method. The coupling agent needs to be hydrolyzed before reacting with nano silicon dioxide, but in this process, the hydrolysis product may undergo self-condensation, hindering the reaction with the surface hydroxyl group and affecting the modification effect. The alcohol ester modification method is to react with the hydroxyl group on the surface of silicon dioxide with a fatty alcohol under high temperature and high pressure, remove water molecules, and replace the hydroxyl group on the surface of silicon dioxide with an alkoxy group. The advantage of using alcohol modification is that the modifier fatty alcohol is cheap, easy to synthesize and easy to control in structure.

[0040] The present invention adopts a composite modification method. First, under high temperature and high pressure conditions, a fatty alcohol is used to react with the hydroxyl group on the surface of nano-silicon dioxide to change the surface wettability of the silicon dioxide; then a silane coupling agent is used for chemical modification to improve its surface properties to the greatest extent. The two-step modification maximizes the compatibility of nano-silicon dioxide with organic materials. First, a fatty alcohol is used to modify the nano-silicon dioxide. Under high temperature and high pressure, the activity of the hydroxyl group on the surface of the nano-silicon dioxide is increased to the maximum, so that it can play the maximum role when it is subsequently modified with the silane coupling agent, and the self-condensation of the hydrolysis product is reduced, so that the surface modification effect is optimal.

[0041] Silica particles are in-situ polymerized with acrylic emulsion through silicon-oxygen bonds to form modified acrylic emulsion, which is then free radical solution polymerized with various monomers to form an inorganic-organic composite grouting material with the characteristics of high strength, high toughness and high specific surface area.

[0042] Rice husk is a natural raw material and agricultural waste that can be used as an alternative biomass silicon source. It contains 65-75% organic matter and 15-20% inorganic matter, of which 95-98% of the inorganic matter is composed of water and amorphous silica. Therefore, rice husk is an ideal biomass source of silica. The global rice husk resources are abundant, with about 600 million tons of rice husk produced each year, and China produces 50 million tons each year, but the utilization rate of rice husk is very low. Most of the rice husks are discarded as waste or used as low-grade fuel, causing environmental pollution. The development and utilization of rice husk resources, the realization of their added value, and the transformation of waste into treasure are of great practical significance to promote the efficient recycling of rice husk resources.

[0043] In summary, combining the current waterproofing and plugging mechanism and the performance advantages of nano-inorganic and organic composite materials, an inorganic-organic nano-modified composite grouting material is developed to combine the advantages of the two, so that the modified nano-silicon dioxide is dispersed in the organic material at the submicron level. The nano-modified inorganic-organic composite material has good environmental protection, low cost, one-time construction and long-term use, high compressive strength, good toughness, strong penetration ability, high bonding strength, and high expansion rate. It is of great significance for grouting waterproofing and plugging of tiny cracks in various fields and the recycling of resources.

[0044] The nano-silica modified organic composite grouting material for micro-crack water plugging of the present invention comprises the following raw materials: rice husk, citric acid, p-xylene, polymerization inhibitor, acrylic emulsion, acrylamide, retarder, triethanolamine, crosslinking agent, coupling agent, initiator, high-purity sodium carbonate, and water. The polymerization inhibitor is one or more of hydroquinone, p-tert-butylcatechol, and p-benzoquinone. The crosslinking agent is one or more of NN methylenebisacrylamide, ethylene glycol acrylate, and dimethylaminoethyl methacrylate. The coupling agent is one or more of γ-aminopropyltriethoxysilane (KH550, silane coupling agent), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560, silane coupling agent), and γ-methacryloyloxypropyltrimethoxysilane (KH570, silane coupling agent). The initiator is one or more of ammonium persulfate, potassium persulfate, and sodium persulfate. The retarder is one or more of potassium ferrocyanide, diphenylamine and copper cyclohexane. The monomers used in the acrylic emulsion are isooctyl acrylate, styrene, dimethylaminoethyl methacrylate, vinyl triisopropoxysilane, ε-caprolactone and mercaptopropanol.

[0045] The preparation method of the nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging is as follows: Figure 1 As shown, the following steps are included:

[0046] Step 1: Mix rice husk, citric acid and water in a mass ratio of (1:1:15 to 1:1.5:20), heat the mixture to 50 to 65° C. using a magnetic stirrer, and continue stirring for 25 to 35 minutes, wash the rice husk pretreated with citric acid three times with water to remove the acid, and then dry for 2 to 3 hours to form a calcined product;

[0047] Step 2: using an electric furnace to heat the rice husk obtained in step 1 to 300-400° C. and carbonize for 10-20 min, and then calcining in a muffle furnace at 550° C., 600° C., 650° C. and 700° C. for 30-35 min, respectively, to obtain white powdery silicon dioxide;

[0048] Step 3: The white powdered silicon dioxide obtained in step 2 was mixed with the long-chain fatty alcohol in a mass ratio of (1:0.2 to 1:0.9), placed in a high-pressure reactor, and the pressure was maintained at 2×10 5 ~6×10 5 Pa, react at 500-800°C for 100-170 minutes, and obtain fatty alcohol-modified nano-silicon dioxide after the reaction is completed; wherein the long-chain fatty alcohol is one or more of tridecanol: CHOH, tetradecanol: CHOH and pentadecanol: CHOH.

[0049] Step 4: The modified silica obtained in step 3 is mixed with a coupling agent and p-xylene in a mass ratio of (1:1:20 to 1:1.2:23), and then 0.1% to 0.3% of an inhibitor is added to prevent the coupling agent from self-polymerizing, and the mixture is heated to 100° C. with a shear stirrer and stirred for 80 to 110 minutes;

[0050] Step 5: After filtering, washing with p-xylene three times to remove the inhibitor, drying at 100° C. for 1 to 1.5 hours, grinding with a mortar for 20 to 30 minutes, and grinding the silica particles to a particle size of 25 to 45 μm to obtain surface-modified silica;

[0051] Step 6: Mix the initiator and water in a mass ratio of (1:100-1:160), stir until clear and use as an initiator solution for standby; mix high-purity sodium carbonate and water in a mass ratio of (1:95-1:110) and use as a buffer solution for standby;

[0052] Step 7: isooctyl acrylate, styrene, dimethylaminoethyl methacrylate, vinyl triisopropoxysilane, ε-caprolactone and mercaptopropanol are stirred and mixed in proportion to obtain a mixed monomer, wherein the mass ratio of isooctyl acrylate, styrene, dimethylaminoethyl methacrylate, vinyl triisopropoxysilane, ε-caprolactone and mercaptopropanol is (30-50): (25-40): (20-35): (35-50): (10-15): (2-6), a portion of the mixed monomer and deionized water are added to a four-necked flask with a condenser, a mechanical stirrer and a tetrafluoro constant pressure dropping funnel, heated in a water bath and stirred, the temperature was raised to 70-80° C., the remaining mixed monomer and the initiator solution prepared in step 6 were added dropwise, nitrogen was introduced at the same time, the reaction was continued for 2 hours, the temperature was lowered, and the material was filtered through a 300-mesh filter to obtain an acrylic emulsion;

[0053] Step 8: adding the surface modified silica obtained in step 5 to the buffer solution of step 6, and performing in-situ free radical solution polymerization with the acrylic emulsion of step 7: adding water and surface modified silica (1wt%, 2wt%, 3wt%, 4wt% and 5wt%) to a four-necked flask respectively, adjusting the water bath temperature to 95°C, and after the four-necked flask is filled with nitrogen, maintaining a slow nitrogen flow until the solution temperature reaches 95°C; pouring all the buffer solution, 10wt% mixed monomer, i.e. acrylic emulsion, and 10wt% initiator solution into the four-necked flask under mechanical stirring at 500-600rpm, and pre-emulsifying for 15-20min; adding the remaining mixed monomer, i.e. acrylic emulsion and initiator, dropwise into the four-necked flask at a rate of 6 drops / 60 seconds and 1 drop / 60 seconds, respectively; continuing the reaction for 1-2h to ensure the complete reaction;

[0054] Step 9: The reaction is maintained at 95° C. and 500-700 rpm for 35-40 min; then cooled to room temperature and discharged to obtain a nano-silicon dioxide modified acrylic emulsion;

[0055] Step 10: Evenly mix the modified acrylic emulsion, acrylamide, crosslinking agent, triethanolamine and water in a predetermined ratio, continue stirring for 15 to 25 minutes, then add the measured initiator and retarder, stir for 5 to 10 minutes, and the curing reaction is completed to obtain the nano-modified acrylic inorganic-organic composite grouting material for micro-crack water plugging. Among them, the proportions of modified acrylic emulsion, acrylamide, crosslinking agent, triethanolamine, water, initiator and retarder are calculated by weight, wherein water is 100 parts, modified acrylic emulsion is 10 parts, acrylamide is 70 parts, crosslinking agent is 0.9 parts, triethanolamine is 5 parts, initiator is 3 parts, and retarder is 0.05 to 1 part.

[0056] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0057] Embodiment 1:

[0058] This embodiment provides a nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging and a preparation method thereof, comprising the following steps:

[0059] Step 1: Rice husk (40 g) and citric acid (40 g) were mixed with 600 mL of water. The mixture was heated to 50° C. with a magnetic stirrer and stirred for 25 min. The rice husk pretreated with citric acid was washed three times with water to remove the acid and then dried for 2 hours to form a calcined product.

[0060] Step 2: The rice husk was heated to 400°C and carbonized for 10 min using an electric furnace, and then calcined in a muffle furnace at 550°C, 600°C, 650°C and 700°C for 30 min, respectively, to obtain white powdery silica.

[0061] Step 3: The white powdered silica obtained in step 2 was mixed with the long-chain fatty alcohol in a mass ratio of (1:0.2) and placed in a high-pressure reactor, maintaining the pressure at 2×10 5 Pa, react at 500°C for 100 min, and after the reaction is completed, fatty alcohol-modified nano-silica can be obtained.

[0062] Step 4: Add 5.0 g of silica and 5.0 g of γ-methacryloxypropyltrimethoxysilane (KH570, silane coupling agent) to 160 mL of p-xylene, and then add 0.08 g of inhibitor hydroquinone to prevent self-polymerization of γ-methacryloxypropyltrimethoxysilane (KH570, silane coupling agent), heat to 100° C. with a shear stirrer and continue stirring for 110 minutes.

[0063] Step 5: After filtering, wash with p-xylene three times to remove the inhibitor, dry at 100° C. for 1 hour, grind with a mortar for 25 minutes, and the particle size of the ground silica particles is 25 to 45 μm to obtain surface-modified silica.

[0064] Step 6: Dissolve the initiator sodium persulfate (0.12 g) in 30 g of water and stir until clear as an initiator solution for later use; dissolve anhydrous sodium carbonate (0.10 g) in 30 g of water and use as a buffer solution for later use.

[0065] Step 7: 30 g of isooctyl acrylate, 25 g of styrene, 20 g of dimethylaminoethyl methacrylate, 35 g of vinyl triisopropoxy silane, 10 g of ε-caprolactone and 2 g of mercaptopropanol are stirred and mixed in proportion to obtain a mixed monomer, and part of the monomers and deionized water are added to a four-necked flask with a condenser, a mechanical stirrer, and a tetrafluoro constant pressure dropping funnel, and water bath heating and stirring are started. The temperature is raised to 70-80°C, and the remaining monomers and initiator solution, i.e., sodium persulfate solution, are added dropwise, and nitrogen is introduced at the same time. After reacting for 2 hours, the temperature is lowered, and the material is filtered through a 300-mesh filter to obtain a modified acrylic emulsion.

[0066] Step 8: Add the surface modified silica obtained in step 5 to the buffer solution and perform in-situ free radical solution polymerization with the acrylic emulsion obtained in step 7. Add water (60g) and surface modified silica (1wt%) to a four-necked flask respectively, adjust the water bath temperature to 95°C, and after the four-necked flask is filled with nitrogen, maintain a slow nitrogen flow until the solution temperature reaches 95°C. Under mechanical stirring at 500rpm, pour all the buffer solution, 10wt% monomer and 10wt% sodium persulfate solution into the four-necked flask and pre-emulsify for 15min. Add the remaining monomer and sodium persulfate dropwise to the four-necked flask at a rate of 6 drops / 60 seconds and 1 drop / 60 seconds, respectively. Continue the reaction for 1h to ensure the reaction is complete.

[0067] Step 9: The reaction was maintained at 95° C. and 500 rpm for 35 min, and then cooled to room temperature and discharged to obtain a nano-silicon dioxide modified acrylic emulsion.

[0068] Step 10: Mix the modified acrylic emulsion, acrylamide, dimethylaminoethyl methacrylate, triethanolamine and water in a predetermined proportion, stir continuously for 15 minutes, then add measured sodium persulfate and potassium ferrocyanide, stir for 5 minutes, and the curing reaction is completed to obtain a nano-modified acrylic inorganic-organic composite grouting material for micro-crack water plugging.

[0069] Embodiment 2:

[0070] This embodiment provides a nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging and a preparation method thereof, comprising:

[0071] Step 1: Rice husk (40 g) and citric acid (60 g) were mixed with 800 mL of water. The mixture was heated to 55° C. with a magnetic stirrer and stirred for 25 min. The rice husk pretreated with citric acid was washed three times with water to remove the acid and then dried for 2.5 hours to form a calcined product.

[0072] Step 2: The rice husk was heated to 400°C and carbonized for 10 min using an electric furnace, and then calcined in a muffle furnace at 550°C, 600°C, 650°C and 700°C for 30 min, respectively, to obtain white powdered silica.

[0073] Step 3: The white powdered silica obtained in step 2 was mixed with the long-chain fatty alcohol in a mass ratio of (1:0.5), placed in a high-pressure reactor, and the pressure was maintained at 4×10 5 Pa, react at 590 ° C for 110 minutes, and then the fatty alcohol-modified nano-silica can be obtained.

[0074] Step 4: Add 5.0 g of silica and 5.0 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560, silane coupling agent) to 160 mL of p-xylene, and then add 0.08 g of p-tert-butylcatechol to prevent self-polymerization of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560, silane coupling agent), heat to 100°C with a shear stirrer and continue stirring for 110 minutes.

[0075] Step 5: After filtering, wash with p-xylene three times to remove the inhibitor, dry at 100° C. for 1 hour, grind with a mortar for 23 minutes, and the particle size of the ground silica particles is 25 to 45 μm to obtain surface-modified silica.

[0076] Step 6: Dissolve potassium persulfate (0.12 g) in 28 g of water and stir until clear as an initiator solution; dissolve anhydrous sodium carbonate (0.10 g) in 30 g of water as a buffer solution.

[0077] Step 7: 32 g of isooctyl acrylate, 28 g of styrene, 25 g of dimethylaminoethyl methacrylate, 37 g of vinyl triisopropoxy silane, 13 g of ε-caprolactone and 3 g of mercaptopropanol are stirred and mixed in proportion to obtain a mixed monomer, and part of the monomers and deionized water are added to a four-necked flask with a condenser, a mechanical stirrer, and a tetrafluoro constant pressure dropping funnel. Water bath heating and stirring are started, and the temperature is raised to 70-80°C. The remaining monomers and potassium persulfate solution are started to be added dropwise, and nitrogen is introduced at the same time. After reacting for 2 hours, the temperature is lowered, and the material is filtered through a 300-mesh filter to obtain a modified acrylic emulsion.

[0078] Step 8: Add the surface modified silica obtained in step 5 to the buffer solution and perform in-situ free radical solution polymerization with the acrylic emulsion obtained in step 7. Add water (60g) and surface modified silica (2wt%) to a four-necked flask respectively, adjust the water bath temperature to 95°C, and after the four-necked flask is filled with nitrogen, maintain a slow nitrogen flow until the solution temperature reaches 95°C. Under mechanical stirring at 560rpm, pour all the buffer solution, 10wt% monomer and 10wt% potassium persulfate solution into the four-necked flask and pre-emulsify for 15min. Add the remaining monomer and potassium persulfate dropwise to the four-necked flask at a rate of 6 drops / 60 seconds and 1 drop / 60 seconds, respectively. Continue the reaction for 1h to ensure the reaction is complete.

[0079] Step 9: The reaction was maintained at 95° C. and 550 rpm for 38 min, and then cooled to room temperature and discharged to obtain a nano-silicon dioxide modified acrylic emulsion.

[0080] Step 10: Mix the modified acrylic emulsion, acrylamide, NN methylenebisacrylamide, triethanolamine and water in a predetermined proportion, continue stirring for 16 minutes, then add measured potassium persulfate and potassium ferrocyanide, stir for 8 minutes, and the curing reaction is completed to obtain a nano-modified acrylic inorganic-organic composite grouting material for micro-crack water plugging.

[0081] Embodiment 3:

[0082] This embodiment provides a nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging and a preparation method thereof, comprising:

[0083] Step 1: Rice husk (40 g) and citric acid (50 g) were mixed with 650 mL of water. The mixture was heated to 60° C. with a magnetic stirrer and stirred for 25 min. The rice husk pretreated with citric acid was washed three times with water to remove the acid and then dried for 3 hours to form a calcined product.

[0084] Step 2: The rice husk was heated to 400°C and carbonized for 10 min using an electric furnace, and then calcined in a muffle furnace at 550°C, 600°C, 650°C and 700°C for 30 min, respectively, to obtain white powdered silica.

[0085] Step 3: The white powdered silica obtained in step 2 was mixed with the long-chain fatty alcohol in a mass ratio of (1:0.5), placed in a high-pressure reactor, and the pressure was maintained at 2.8×10 5 Pa, react at 600°C for 130min, and after the reaction is completed, fatty alcohol-modified nano-silica can be obtained.

[0086] Step 4: Add 5.0 g of silica and 5.0 g of γ-aminopropyltriethoxysilane (KH550, silane coupling agent) to 160 mL of p-xylene, and then add 0.08 g of p-benzoquinone to prevent self-polymerization of γ-aminopropyltriethoxysilane (KH550, silane coupling agent), heat to 100°C with a shear stirrer and continue stirring for 120 minutes.

[0087] Step 5: After filtering, wash with p-xylene three times to remove the inhibitor, dry at 100°C for 1.1 hours, grind with a mortar for 30 minutes, and the particle size of the ground silica particles is 25-45 μm to obtain surface-modified silica.

[0088] Step 6: Dissolve ammonium persulfate (0.12 g) in 35 g of water, stir until clear and use as an initiator solution; dissolve anhydrous sodium carbonate (0.10 g) in 30 g of water and use as a buffer solution.

[0089] Step 7: 31 g of isooctyl acrylate, 38 g of styrene, 29 g of dimethylaminoethyl methacrylate, 46 g of vinyltriisopropoxysilane, 13 g of ε-caprolactone and 5 g of mercaptopropanol are stirred and mixed in proportion to obtain a mixed monomer. Part of the monomers and deionized water are added to a four-necked flask with a condenser, a mechanical stirrer and a tetrafluoro constant pressure dropping funnel. Water bath heating and stirring are started. The temperature is raised to 70-80°C, and the remaining monomers and initiator solution are added dropwise. Nitrogen is introduced at the same time. After reacting for 2 hours, the temperature is lowered, and the material is filtered through a 300-mesh filter to obtain a modified acrylic emulsion.

[0090] Step 8: Add the surface modified silica obtained in step 5 to the buffer solution and perform in-situ free radical solution polymerization with the acrylic emulsion obtained in step 7. Add water (60g) and surface modified silica (3wt%) to a four-necked flask respectively, adjust the water bath temperature to 95°C, and after the four-necked flask is filled with nitrogen, maintain a slow nitrogen flow until the solution temperature reaches 95°C. Under mechanical stirring at 500rpm, pour all the buffer solution, 10wt% monomer and 10wt% ammonium persulfate solution into the four-necked flask and pre-emulsify for 15min. Add the remaining monomer and ammonium persulfate dropwise to the four-necked flask at a rate of 6 drops / 60 seconds and 1 drop / 60 seconds, respectively. Continue the reaction for 1h to ensure the reaction is complete.

[0091] Step 9: The reaction was maintained at 95° C. and 500 rpm for 38 min, and then cooled to room temperature and discharged to obtain a nano-silicon dioxide modified acrylic emulsion.

[0092] Step 10: Evenly mix the modified acrylic emulsion, acrylamide, ethylene glycol acrylate, triethanolamine and water in a predetermined proportion, and continue stirring for 15 minutes. Then, add measured amounts of ammonium persulfate and copper cyclohexaneate, and stir for 9 minutes. After the curing reaction is completed, a nano-modified acrylic inorganic-organic composite grouting material for microcrack water plugging is obtained.

[0093] Embodiment 4:

[0094] This embodiment provides a nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging and a preparation method thereof, comprising:

[0095] Step 1: Rice husk (40 g) and citric acid (55 g) were mixed with 680 mL of water. The mixture was heated to 65° C. with a magnetic stirrer and stirred for 29 min. The rice husk pretreated with citric acid was washed three times with water to remove the acid and then dried for 2 hours to form a calcined product.

[0096] Step 2: The rice husk was heated to 400°C and carbonized for 10 min using an electric furnace, and then calcined in a muffle furnace at 550°C, 600°C, 650°C and 700°C for 30 min, respectively, to obtain white powdered silica.

[0097] Step 3: The white powdered silica obtained in step 2 was mixed with the long-chain fatty alcohol in a mass ratio of (1:0.9), placed in a high-pressure reactor, and the pressure was maintained at 6×10 5 Pa, react at 800°C for 160min, and after the reaction is completed, fatty alcohol-modified nano-silica can be obtained.

[0098] Step 4: Add 5.0 g of silica, 2.0 g of γ-methacryloxypropyltrimethoxysilane (KH570, silane coupling agent) and 3.0 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560, silane coupling agent) to 160 mL of p-xylene, and then add 0.05 g of hydroquinone and 0.03 g of p-tert-butylcatechol to prevent the coupling agent from self-polymerization, heat to 100°C with a shear mixer and continue stirring for 110 minutes.

[0099] Step 5: After filtering, wash with p-xylene three times to remove the inhibitor, dry at 100° C. for 1.5 hours, grind with a mortar for 20 minutes, and the particle size of the ground silica particles is 25 to 45 μm to obtain surface-modified silica.

[0100] Step 6: Dissolve sodium persulfate (0.10 g) and potassium persulfate (0.02 g) in 30 g of water, stir until clear and use as an initiator solution; dissolve anhydrous sodium carbonate (0.10 g) in 30 g of water and use as a buffer solution.

[0101] Step 7: 40 g of isooctyl acrylate, 35 g of styrene, 30 g of dimethylaminoethyl methacrylate, 38 g of vinyltriisopropoxysilane, 15 g of ε-caprolactone and 3 g of mercaptopropanol are stirred and mixed in proportion to obtain a mixed monomer, and part of the monomers and deionized water are added to a four-necked flask with a condenser, a mechanical stirrer and a tetrafluoro constant pressure dropping funnel, and water bath heating and stirring are started. The temperature is raised to 70-80°C, and the remaining monomers and initiator solution are added dropwise, and nitrogen is introduced at the same time. After reacting for 2 hours, the temperature is lowered, and the material is filtered through a 300-mesh filter to obtain a modified acrylic emulsion.

[0102] Step 8: Add the surface modified silica obtained in step 5 to the buffer solution and perform in-situ free radical solution polymerization with the acrylic emulsion obtained in step 7. Add water (60g) and surface modified silica (4wt%) to a four-necked flask respectively, adjust the water bath temperature to 95°C, and after the four-necked flask is filled with nitrogen, maintain a slow nitrogen flow until the solution temperature reaches 95°C. Under mechanical stirring at 500rpm, pour all the buffer solution, 10wt% monomer and 10wt% sodium persulfate and potassium persulfate solution into the four-necked flask and pre-emulsify for 16min. Add the remaining monomer and sodium persulfate and potassium persulfate dropwise to the four-necked flask at a rate of 6 drops / 60 seconds and 1 drop / 60 seconds, respectively. Continue the reaction for 1.2h to ensure the reaction is complete.

[0103] Step 9: The reaction was maintained at 95° C. and 590 rpm for 35 min, and then cooled to room temperature and discharged to obtain a nano-silicon dioxide modified acrylic emulsion.

[0104] Step 10: Evenly mix the modified acrylic emulsion, acrylamide, dimethylaminoethyl methacrylate, triethanolamine and water in a predetermined proportion, and continue stirring for 17 minutes. Then, add measured sodium persulfate, potassium persulfate and diphenylamine, and stir for 10 minutes. After the curing reaction is completed, a nano-modified acrylic inorganic-organic composite grouting material for micro-crack water plugging is obtained.

[0105] Embodiment 5:

[0106] This embodiment provides a nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging and a preparation method thereof, comprising:

[0107] Step 1: Rice husk (40 g) and citric acid (50 g) were mixed with 670 mL of water. The mixture was heated to 62° C. with a magnetic stirrer and stirred for 30 min. The rice husk pretreated with citric acid was washed three times with water to remove the acid and then dried for 3 hours to form a calcined product.

[0108] Step 2: The rice husk was heated to 400°C and carbonized for 16 min using an electric furnace, and then calcined in a muffle furnace at 550°C, 600°C, 650°C and 700°C for 33 min, respectively, to obtain white powdered silica.

[0109] Step 3: The white powdered silica obtained in step 2 was mixed with the long-chain fatty alcohol in a mass ratio of (1:0.7), placed in a high-pressure reactor, and the pressure was maintained at 5×10 5 Pa, react at 680°C for 140min, and after the reaction is completed, fatty alcohol-modified nano-silica can be obtained.

[0110] Step 4: Add 5.0 g of silica and 5.0 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560, silane coupling agent) to 140 mL of p-xylene, then add 0.03 g of p-benzoquinone and 0.05 g of p-tert-butylcatechol to prevent self-polymerization of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560, silane coupling agent), heat to 100°C with a shear stirrer and continue stirring for 100 min.

[0111] Step 5: After filtering, wash with p-xylene three times to remove the inhibitor, dry at 100°C for 1 hour, grind with a mortar for 30 minutes, and the particle size of the ground silica particles is 25-45 μm to obtain surface-modified silica.

[0112] Step 6: Dissolve sodium persulfate (0.12 g) in 35 g of water, stir until clear and use as an initiator solution; dissolve anhydrous sodium carbonate (0.10 g) in 37 g of water and use as a buffer solution.

[0113] Step 7: 32 g of isooctyl acrylate, 38 g of styrene, 34 g of dimethylaminoethyl methacrylate, 43 g of vinyltriisopropoxysilane, 14 g of ε-caprolactone and 5 g of mercaptopropanol are stirred and mixed in proportion to obtain a mixed monomer, and part of the monomers and deionized water are added to a four-necked flask with a condenser, a mechanical stirrer and a tetrafluoro constant pressure dropping funnel, and water bath heating and stirring are started. The temperature is raised to 70-80°C, and the remaining monomers and initiator solution are added dropwise, and nitrogen is introduced at the same time. After reacting for 2 hours, the temperature is lowered, and the material is filtered through a 300-mesh filter to obtain a modified acrylic emulsion.

[0114] Step 8: Add the surface modified silica obtained in step 5 to the buffer solution and perform in-situ free radical solution polymerization with the acrylic emulsion obtained in step 7. Add water (60g) and surface modified silica (5wt%) to a four-necked flask respectively, adjust the water bath temperature to 95°C, and after the four-necked flask is filled with nitrogen, maintain a slow nitrogen flow until the solution temperature reaches 95°C. Under mechanical stirring at 600rpm, pour all the buffer solution, 10wt% monomer and 10wt% sodium persulfate solution into the four-necked flask and pre-emulsify for 15min. Add the remaining monomer and sodium persulfate dropwise to the four-necked flask at a rate of 6 drops / 60 seconds and 1 drop / 60 seconds, respectively. Continue the reaction for 1.5h to ensure the reaction is complete.

[0115] Step 9: The reaction was maintained at 95° C. and 500 rpm for 40 min, and then cooled to room temperature and discharged to obtain a nano-silicon dioxide modified acrylic emulsion.

[0116] Step 10: Evenly mix the modified acrylic emulsion, acrylamide, ethylene glycol acrylate, triethanolamine and water in a predetermined proportion, and continue stirring for 18 minutes. Then, add measured amounts of sodium persulfate, potassium ferrocyanide and copper cyclopentaneate, and stir for 5 minutes. After the curing reaction is completed, a nano-modified acrylic inorganic-organic composite grouting material for micro-crack water plugging is obtained.

[0117] Comparative Example 1:

[0118] This comparative example provides a composite grouting material and a preparation method thereof. The comparative example does not perform fatty alcohol-modified nano-silica, and specifically comprises the following steps:

[0119] Step 1: Rice husk (40 g) and citric acid (40 g) were mixed with 600 mL of water. The mixture was heated to 50° C. with a magnetic stirrer and stirred for 25 min. The rice husk pretreated with citric acid was washed three times with water to remove the acid and then dried for 2 hours to form a calcined product.

[0120] Step 2: The rice husk was heated to 400°C and carbonized for 10 min using an electric furnace, and then calcined in a muffle furnace at 550°C, 600°C, 650°C and 700°C for 30 min, respectively, to obtain white powdery silica.

[0121] Step 3: Add 5.0 g of silica and 5.0 g of γ-methacryloxypropyltrimethoxysilane (KH570, silane coupling agent) to 160 mL of p-xylene, and then add 0.08 g of hydroquinone to prevent self-polymerization of γ-methacryloxypropyltrimethoxysilane (KH570, silane coupling agent), heat to 100° C. with a shear stirrer and continue stirring for 110 minutes.

[0122] Step 4: After filtering, wash with p-xylene three times to remove the inhibitor, dry at 100° C. for 1 hour, grind with a mortar for 25 minutes, and the particle size of the ground silica particles is 25 to 45 μm to obtain surface-modified silica.

[0123] Step 5: Dissolve sodium persulfate (0.12 g) in 30 g of water. Dissolve anhydrous sodium carbonate (0.10 g) in 30 g of water and prepare as a buffer solution.

[0124] Step 6: 30 g of isooctyl acrylate, 25 g of styrene, 20 g of dimethylaminoethyl methacrylate, 35 g of vinyltriisopropoxysilane, 10 g of ε-caprolactone and 2 g of mercaptopropanol are stirred and mixed in proportion to obtain a mixed monomer, and part of the monomers and deionized water are added to a four-necked flask with a condenser, a mechanical stirrer, and a tetrafluoro constant pressure dropping funnel, and water bath heating and stirring are started. The temperature is raised to 70-80°C, and the remaining monomers are added dropwise while nitrogen is introduced. After reacting for 2 hours, the temperature is lowered, and the material is filtered through a 300-mesh filter to obtain a modified acrylic emulsion.

[0125] Step 7: Add the surface modified silica obtained in step 4 to the buffer solution and perform in-situ free radical solution polymerization with the acrylic emulsion obtained in step 6. Add water (60g) and surface modified silica (1wt%) to a four-necked flask respectively, adjust the water bath temperature to 95°C, and after the four-necked flask is filled with nitrogen, maintain a slow nitrogen flow until the solution temperature reaches 95°C. Under mechanical stirring at 500rpm, pour all the buffer solution, 10wt% monomer and 10wt% sodium persulfate solution into the four-necked flask and pre-emulsify for 15min. Add the remaining monomer and sodium persulfate dropwise to the four-necked flask at a rate of 6 drops / 60 seconds and 1 drop / 60 seconds, respectively. Continue the reaction for 1h to ensure the reaction is complete.

[0126] Step 8: The reaction was maintained at 95° C. and 500 rpm for 35 min, and then cooled to room temperature and discharged to obtain a nano-silicon dioxide modified acrylic emulsion.

[0127] Step 9: Evenly mix the modified acrylic emulsion, acrylamide, dimethylaminoethyl methacrylate, triethanolamine and water in a predetermined proportion, and continue stirring for 15 minutes. Then, add the measured sodium persulfate and potassium ferrocyanide, and stir for 5 minutes. After the curing reaction is completed, a composite grouting material is obtained.

[0128] Comparative Example 2:

[0129] This comparative example provides a composite grouting material and a preparation method thereof. The comparative example does not perform fatty alcohol-modified nano-silica and does not add a silane coupling agent. The comparative example specifically comprises the following steps:

[0130] Step 1: Rice husk (40 g) and citric acid (40 g) were mixed with 600 mL of water. The mixture was heated to 50° C. with a magnetic stirrer and stirred for 25 min. The rice husk pretreated with citric acid was washed three times with water to remove the acid and then dried for 2 hours to form a calcined product.

[0131] Step 2: Use an electric furnace to heat the rice husk to 400°C and carbonize for 10 minutes, then calcine in a muffle furnace at 550°C, 600°C, 650°C and 700°C for 30 minutes respectively, grind in a mortar for 30 minutes, and the ground silica particles have a particle size of 25-45 μm to obtain white powdery modified silica.

[0132] Step 3: Dissolve sodium persulfate (0.12 g) in 30 g of water. Dissolve anhydrous sodium carbonate (0.10 g) in 30 g of water and prepare as a buffer solution.

[0133] Step 4: 30 g of isooctyl acrylate, 25 g of styrene, 20 g of dimethylaminoethyl methacrylate, 35 g of vinyl triisopropoxy silane, 10 g of ε-caprolactone and 2 g of mercaptopropanol are stirred and mixed in proportion to obtain a mixed monomer, and part of the monomers and deionized water are added to a four-necked flask with a condenser, a mechanical stirrer, and a tetrafluoro constant pressure dropping funnel, and water bath heating and stirring are started. The temperature is raised to 70-80°C, and the remaining monomers are added dropwise while nitrogen is introduced. After reacting for 2 hours, the temperature is lowered, and the material is filtered through a 300-mesh filter to obtain a modified acrylic emulsion.

[0134] Step 5: Add the modified silica obtained in step 2 to the buffer solution and perform in-situ free radical solution polymerization with the acrylic emulsion obtained in step 4. Add water (60g) and surface modified silica (1wt%) to a four-necked flask respectively, adjust the water bath temperature to 95°C, and after the four-necked flask is filled with nitrogen, maintain a slow nitrogen flow until the solution temperature reaches 95°C. Under mechanical stirring at 500rpm, pour all the buffer solution, 10wt% monomer and 10wt% sodium persulfate solution into the four-necked flask and pre-emulsify for 15min. Add the remaining monomer and sodium persulfate dropwise to the four-necked flask at a rate of 6 drops / 60 seconds and 1 drop / 60 seconds, respectively. Continue the reaction for 1h to ensure the reaction is complete.

[0135] Step 6: The reaction was maintained at 95° C. and 500 rpm for 35 min, and then cooled to room temperature and discharged to obtain a nano-silicon dioxide modified acrylic emulsion.

[0136] Step 7: Evenly mix the modified acrylic emulsion, acrylamide, dimethylaminoethyl methacrylate, triethanolamine and water in a predetermined proportion, and continue stirring for 15 minutes. Then, add the measured sodium persulfate and potassium ferrocyanide, and stir for 5 minutes. After the curing reaction is completed, a composite grouting material is obtained.

[0137] Figure 2 is the elongation at break of each embodiment and comparative example, from Figure 2 It can be seen that the elongation at break of Examples 1 to 5 prepared by the present invention is all above 800%, among which the elongation at break of Example 3 is the largest, reaching 940%, and the performance is the best at this time; however, the elongations at break of Comparative Examples 1 and Comparative Examples 2 prepared using traditional processes are 623% and 657%, respectively, which are reduced by a maximum of 34% compared with the materials prepared by the present invention; the grouting material prepared by the present invention has excellent toughness.

[0138] Figure 3 is the compressive strength of each embodiment and comparative example, from Figure 3 It can be seen that the compressive strengths of Examples 1 to 5 prepared by the present invention are all above 10 MPa, among which Example 3 has the largest compressive strength, which can reach 16 MPa; however, Comparative Examples 1 and Comparative Examples 2 prepared by traditional processes have compressive strengths of 6 MPa and 8 MPa, respectively. Compared with the materials prepared by the present invention, the compressive strengths are obviously insufficient, and deformation and fracture will occur under greater surrounding rock pressure.

[0139] Figure 4 is the setting time of each embodiment and comparative example, from Figure 4It can be seen that the setting time of Comparative Examples 1 and 2 is longer than that of the five embodiments prepared by the present invention, and they are not suitable for use in working conditions requiring rapid solidification. At the same time, the slow reaction rate may affect the early strength of the material, resulting in poor grouting reinforcement effect. In summary, the grouting material prepared by the present invention has great advantages in resistance to deformation, toughness and setting time.

Claims

1. A nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging, characterized in that: The invention comprises the following raw materials: rice husk, citric acid, p-xylene, polymerization inhibitor, acrylic emulsion, acrylamide, retarder, triethanolamine, cross-linking agent, coupling agent, initiator, sodium carbonate and water.

2. The nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging according to claim 1, characterized in that: The polymerization inhibitor is one or more of hydroquinone, p-tert-butylcatechol and p-benzoquinone.

3. The nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging according to claim 1, characterized in that: The cross-linking agent is one or more of NN methylene bisacrylamide, ethylene glycol acrylate, and dimethylaminoethyl methacrylate.

4. The nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging according to claim 1, characterized in that: The coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane.

5. The nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging according to claim 1, characterized in that: The initiator is one or more of ammonium persulfate, potassium persulfate and sodium persulfate.

6. The nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging according to claim 1, characterized in that: The retarder is one or more of potassium ferrocyanide, diphenylamine and copper naphthenate.

7. The nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging according to claim 1, characterized in that: The monomers used in the acrylic emulsion are isooctyl acrylate, styrene, dimethylaminoethyl methacrylate, vinyl triisopropoxy silane, ε-caprolactone and mercaptopropanol.

8. The method for preparing the nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Mix rice husk, citric acid and water, heat the mixture to 50-65° C. with a magnetic stirrer, continue stirring for 25-35 minutes, wash three times with water to remove acid, and then dry for 2-3 hours to form a calcined product; Step 2: using an electric furnace to heat the rice husk obtained in step 1 to 300-400° C. and carbonize for 10-20 min, and then calcining in a muffle furnace at 550° C., 600° C., 650° C. and 700° C. for 30-35 min, respectively, to obtain white powdery silicon dioxide; Step 3: Mix the white powdered silica obtained in step 2 with the long-chain fatty alcohol and place in a high-pressure reactor to maintain the pressure at 2×10 5 ~6×10 5 Pa, react at 500-800°C for 100-170 min, and after the reaction is completed, fatty alcohol-modified nano-silicon dioxide is obtained; Step 4: Mix the modified silica obtained in step 3 with a coupling agent and p-xylene, add 0.1% to 0.3% of a polymerization inhibitor to prevent the coupling agent from self-polymerizing, heat to 100° C. with a shear stirrer and continue stirring for 80 to 110 minutes; Step 5: After filtering, washing with p-xylene three times to remove the inhibitor, drying at 100° C. for 1 to 1.5 hours, grinding with a mortar for 20 to 30 minutes, and grinding the silica particles to a particle size of 25 to 45 μm to obtain surface-modified silica; Step 6: Mix the initiator and water, stir until clear and use as the initiator solution for later use; mix high-purity sodium carbonate and water and use as the buffer solution for later use; Step 7: Isooctyl acrylate, styrene, dimethylaminoethyl methacrylate, vinyl triisopropoxysilane, ε-caprolactone and mercaptopropanol are stirred and mixed to obtain a mixed monomer, and a portion of the mixed monomer and deionized water are added to a four-necked flask equipped with a condenser, a mechanical stirrer, and a tetrafluoro constant pressure dropping funnel. The mixture is heated and stirred in a water bath, and the temperature is raised to 70-80° C., and the remaining mixed monomer and initiator solution are added dropwise, and nitrogen is introduced at the same time. After reacting for 2 hours, the temperature is lowered, and the material is filtered through a 300-mesh filter to obtain an acrylic emulsion; Step 8: Add the surface-modified silica obtained in step 5 to the buffer solution of step 6, and carry out in-situ free radical solution polymerization with the acrylic emulsion of step 7: add water and surface-modified silica to a flask, adjust the water bath temperature to 95°C, and after the flask is filled with nitrogen, maintain a slow nitrogen flow until the solution temperature reaches 95°C; pour all the buffer solution, 10wt% mixed monomer and 10wt% initiator solution into the flask under mechanical stirring at 500-600rpm, and pre-emulsify for 15-20min; add the remaining mixed monomer and initiator dropwise to the flask at a rate of 6 drops / 60 seconds and 1 drop / 60 seconds, respectively; continue the reaction for 1-2h to ensure the reaction is complete; Step 9: The reaction is maintained at 95° C. and 500-700 rpm for 35-40 min; then cooled to room temperature and discharged to obtain a nano-silicon dioxide modified acrylic emulsion; Step 10: Evenly mix the modified acrylic emulsion, acrylamide, crosslinking agent, triethanolamine and water, and continue stirring for 15 to 25 minutes. Then, add the initiator and retarder, and stir for 5 to 10 minutes. When the curing reaction is completed, a nano-modified acrylic inorganic-organic composite grouting material for micro-crack water plugging is obtained.

9. The method for preparing the nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging according to claim 8, characterized in that: In the step 1, the mass ratio of rice husk, citric acid and water is 1:1:15 to 1:1.5:20; In step 3, the mass ratio of white powdered silicon dioxide to long-chain fatty alcohol is 1:0.2 to 1:0.9; In step 4, the mass ratio of modified silica to coupling agent and p-xylene is 1:1:20 to 1:1.2:23; In step 6, the mass ratio of the initiator to water is 1:100 to 1:160; the mass ratio of sodium carbonate to water is 1:95 to 1:110; In step 7, the mass ratio of isooctyl acrylate, styrene, dimethylaminoethyl methacrylate, vinyl triisopropoxy silane, ε-caprolactone and mercaptopropanol is (30-50): (25-40): (20-35): (35-50): (10-15): (2-6).

10. The method for preparing the nano-silicon dioxide modified organic composite grouting material for micro-crack water plugging according to claim 8, characterized in that: In step 10, the proportions of the modified acrylic emulsion, acrylamide, crosslinking agent, triethanolamine, water, initiator and retarder are calculated by weight, wherein water is 100 parts, the modified acrylic emulsion is 10 parts, acrylamide is 70 parts, the crosslinking agent is 0.9 parts, the triethanolamine is 5 parts, the initiator is 3 parts, and the retarder is 0.05-1 parts.

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