Modified polyurethane grouting material for plugging and preparation method thereof

Abstract

The application provides a modified polyurethane grouting material for plugging and a preparation method thereof, and relates to the field of waterproof plugging materials. The modified polyurethane grouting material comprises the following raw materials in parts by weight: 90-100 parts of modified polyurethane prepolymer, 5-15 parts of organic modified nanometer vermiculite, 5-20 parts of modified cellulose hydrogel microspheres, 5-12 parts of hydrogenated hydroxyl terminated nitrile rubber liquid, 1-5 parts of a curing agent, 10-25 parts of a solvent and 0.5-2 parts of a catalyst. The modified polyurethane prepolymer is prepared by the reaction of polytetrahydrofuran ether glycol and diphenyl methane diisocyanate, and the content of the functional group -NCO is 15%-25%. The modified polyurethane grouting material has low shrinkage of the formed unit body, dynamic repair function, excellent acid resistance and weather resistance, and high strength and high toughness.

Description

Technical Field

[0001] This invention relates to the field of leak-sealing and waterproofing materials, and more specifically, to a modified polyurethane grouting material for leak sealing and its preparation method. Background Technology

[0002] Polyurethane grouting material is widely used for waterproofing and sealing cracks, foundation reinforcement, and waterproofing treatment in construction, underground tunnels, water conservancy facilities, bridges, and culverts. Its main component is an isocyanate prepolymer made from polymeric polyols and polyisocyanates, containing an excess of unreacted isocyanate groups (-NCO). During construction, the grout is injected into the cracks using grouting equipment. The -NCO groups react chemically with the seeping water, generating urea bonds and releasing carbon dioxide gas. This causes the grout to rapidly expand and solidify, forming a foam-like solidified body that instantly seals the water flow channels, achieving rapid water stoppage.

[0003] Although polyurethane grouting materials have achieved significant results in the field of leak sealing, with the expansion of engineering practice and the increasing complexity of application environments, their inherent material defects and limitations have gradually become apparent, becoming a bottleneck restricting their application in high-standard, long-life projects. Existing technologies, whether water-soluble or oil-based polyurethane grouting materials, generally suffer from the following drawbacks:

[0004] 1. High volume shrinkage leads to the risk of secondary leakage, especially with oil-based polyurethane materials. The initial volume expansion of the solidified body depends on the CO2 gas generated during the reaction. In the later stages, the CO2 gas gradually escapes from the foam, and the natural shrinkage of the polymer body in a dry environment causes a significant reduction in the volume of the solidified body. This causes the solidified body to detach from the concrete crack wall, forming new gaps and resulting in secondary leakage.

[0005] 2. Poor resistance to chemical corrosion, especially prone to failure in acidic environments. Traditional polyurethane materials, particularly polyester polyols or grouting materials containing ester bonds, are susceptible to hydrolysis of ester bonds (-COO-) and urea bonds (-NH-CO-) in their molecular chains under acid and alkali catalysis, leading to molecular chain breakage. In areas with frequent acid rain or in acidic environments such as chemical workshops and basements, the mechanical strength of the solidified body will rapidly decline, the structure will become loose, and it will eventually lose its leak-sealing function.

[0006] 3. Insufficient elasticity and toughness, poor resistance to deformation: Traditional grouting materials have a high cross-linking density, resulting in high hardness but poor toughness and low elongation at break of the solidified body. When the building structure undergoes slight deformation due to temperature changes, foundation settlement, or external vibrations, the brittle solidified body cannot deform accordingly and is prone to cracking and breaking, thus forming leakage points again.

[0007] 4. Limited functionality and inability to cope with alternating wet and dry environments: Traditional grouting materials have a one-time reaction. Once cured, their volume is fixed. In environments with alternating wet and dry conditions (such as reservoir water level changes or seasonal rainfall), the material shrinks when drying and cannot expand again to fill the gaps created by shrinkage when water is introduced. This results in a performance degradation with each drying cycle, requiring repeated grouting repairs, increasing maintenance costs and construction difficulty.

[0008] To address the aforementioned issues, patent documents disclose the addition of a water-absorbing polymer to polyurethane grouting materials. During the foaming process, the polymer simultaneously absorbs water, accelerating the consolidation and expansion of the grouting material. This forms an elastic, solidified mixture of the water-absorbing polymer and polyurethane with a high water content, achieving dynamic filling of cracks and reducing the drying shrinkage rate of the solidified body. In a cyclically humid environment, it can repeatedly expand to self-seal cracks, achieving self-waterproofing and repair, and reducing secondary leakage. However, this grouting material still suffers from drawbacks such as poor acid resistance, insufficient elasticity, and insufficient toughness. Summary of the Invention

[0009] The purpose of this invention is to provide a modified polyurethane grouting material for sealing leaks, which forms a solid with low shrinkage, dynamic repair function, excellent acid resistance and weather resistance, and also has high strength and high toughness.

[0010] Another objective of this invention is to provide a method for preparing a modified polyurethane grouting material for sealing leaks, which is simple and efficient.

[0011] The technical problem solved by this invention is achieved by the following technical solution.

[0012] On one hand, embodiments of the present invention provide a modified polyurethane grouting material for sealing leaks, comprising the following raw materials by weight:

[0013] The mixture comprises 90-100 parts of modified polyurethane prepolymer, 5-15 parts of organically modified nano-vermiculite, 5-20 parts of modified cellulose hydrogel microspheres, 5-12 parts of hydrogenated hydroxyl-terminated butadiene-acrylonitrile rubber liquid, 1-5 parts of curing agent, 10-25 parts of solvent, and 0.5-2 parts of catalyst; the modified polyurethane prepolymer is prepared by reacting polytetrahydrofuran ether diol with diphenylmethane diisocyanate, and its functional group -NCO content is 15%-25%; the curing agent is a latent curing agent.

[0014] In some embodiments of the present invention, the preparation method of the modified polyurethane prepolymer includes the following steps: polytetrahydrofuran ether diol, hydroxyl-terminated polybutadiene, and trifunctional polyether polyol are vacuum dehydrated at 120°C and -0.095 MPa for 2 hours, cooled to 60°C, and then added to a reaction vessel. Diphenylmethane diisocyanate and 1,4-butanediol are then added to the reaction vessel, the temperature is raised to 85-90°C, and dibutyltin dilaurate is added. The reaction is carried out under nitrogen protection for 3 hours. When the -NCO content of the system reaches 15%-25%, the reaction is stopped. The temperature is then lowered to room temperature to obtain the modified polyurethane prepolymer.

[0015] In some embodiments of the present invention, the modified polyurethane comprises, by weight, the following raw materials: 80-90 parts of polytetrahydrofuran ether diol, 10-20 parts of hydroxyl-terminated polybutadiene, 5-10 parts of trifunctional polyether polyol, 35-40 parts of diphenylmethane diisocyanate, 1-5 parts of 1,4-butanediol, and 0.03-0.1 parts of dibutyltin dilaurate.

[0016] In some embodiments of the present invention, the preparation method of the organically modified vermiculite includes the following steps: drying nano-vermiculite at 100-105℃ for 3-4 hours; dispersing the dried nano-vermiculite at a mass concentration of 3-5% in a mixture of ethanol and water, dispersing at 7000-8000 rpm for 20-30 minutes to obtain a suspension; adding KH-550 silane coupling agent at 8-10% of the vermiculite mass to the mixture of ethanol and water, adding glacial acetic acid to adjust the pH to 4-5, stirring for 20-30 minutes to obtain a silane solution; adding the silane solution dropwise to the suspension, stirring and reacting at 65-70℃ for 4-5 hours; filtering, washing the filter cake to neutrality, vacuum drying the filter cake at 70-80℃ for 10-12 hours, grinding, and sieving to obtain organically modified nano-vermiculite.

[0017] In some embodiments of the present invention, the preparation method of the modified cellulose hydrogel microspheres includes the following steps: dissolving sodium carboxymethyl cellulose in deionized water to prepare an aqueous phase of 5-10%; dissolving Span-80 emulsifier in liquid paraffin to obtain an oil phase; adding the aqueous phase to the oil phase under stirring at 800-1000 rpm to form an emulsion; adding the modified polyurethane prepolymer dropwise to the emulsion, stirring and reacting for 1-2 hours, adding ethanol, filtering and collecting the microspheres, and washing to obtain the modified cellulose hydrogel microspheres.

[0018] In some embodiments of the present invention, the solvent is at least one selected from dimethyl carbonate, ethyl acetate, n-propyl acetate, and n-butyl acetate.

[0019] In some embodiments of the present invention, the catalyst is a formate of dibutyltin dilaurate and 1,4-diazabicyclo[2.2.2]octane in a mass ratio of 2:1.

[0020] On the other hand, embodiments of the present invention provide a method for preparing a modified polyurethane grouting material for sealing leaks, comprising the following steps:

[0021] S1, mix the modified polyurethane prepolymer, hydrogenated hydroxyl-terminated butadiene nitrile rubber liquid, and solvent, and stir until homogeneous;

[0022] S2, then add organically modified nano-vermiculite, and disperse at high speed under shear for 30-60 minutes;

[0023] S3, then add modified cellulose hydrogel microspheres and curing agent, stir at low speed until evenly mixed;

[0024] S4, then add the catalyst, stir evenly, seal and package to obtain the grouting material.

[0025] In some embodiments of the present invention, in step S2, the rotational speed of the high-speed shear dispersion is 5000-6000 rpm.

[0026] In some embodiments of the present invention, in step S3, the speed of low-speed stirring is 800-1000 rpm.

[0027] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0028] The modified polyurethane grouting material provided by this invention uses modified polyurethane prepolymer as the main raw material, combined with organic modified nano-vermiculite and modified cellulose hydrogel microspheres. The resulting aggregate has a low shrinkage rate, dynamic repair function, excellent acid resistance and weather resistance, and also possesses high strength and high toughness.

[0029] Specifically, the modified polyurethane utilizes a dual mechanism of chemical pre-expansion and physical intelligent re-expansion to solve the problem of secondary leakage caused by volume shrinkage after solidification in traditional polyurethane grouting materials. Secondly, the grouting material of this invention incorporates modified cellulose hydrogel microspheres, enabling it to sense moisture and respond with expansion, maintaining continuous sealing pressure on cracks during building cycles of wet and dry conditions and thermal expansion and contraction, achieving long-term leak sealing. Furthermore, the slight expansion generated by the latent curing agent's subsequent reaction precisely counteracts the chemical shrinkage of the polymer itself.

[0030] The modified polyurethane prepolymer provided by this invention is prepared by reacting polytetrahydrofuran ether diol with diphenylmethane diisocyanate. Its ether bonds and C / C backbone have extremely strong chemical stability. The nano-vermiculite sheets form a dense labyrinth structure in the matrix, which slows down the penetration rate of corrosive media and provides physical protection for the polyurethane matrix. Through the synergistic effect of the hydrolysis-resistant matrix and the nano-barrier, the prepolymer material can still maintain more than 90% of its mechanical properties in a strong acid environment with pH=3, which expands the application range and makes it suitable for harsh environments such as acid rain areas, chemical plants, and basements.

[0031] The tensile strength and elongation at break of the material are significantly improved. Its solidified body can adapt to slight deformation and vibration of the building structure and will not fail due to brittle fracture. It has extremely strong resistance to deformation and impact. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to specific embodiments.

[0034] This invention provides a modified polyurethane grouting material for sealing leaks, comprising the following raw materials by weight:

[0035] The mixture comprises 90-100 parts of modified polyurethane prepolymer, 5-15 parts of organically modified nano-vermiculite, 5-20 parts of modified cellulose hydrogel microspheres, 5-12 parts of hydrogenated hydroxyl-terminated butadiene-acrylonitrile rubber liquid, 1-5 parts of curing agent, 10-25 parts of solvent, and 0.5-2 parts of catalyst; the modified polyurethane prepolymer is prepared by reacting polytetrahydrofuran ether diol with diphenylmethane diisocyanate, and its functional group -NCO content is 15%-25%; the curing agent is a latent curing agent.

[0036] In some embodiments of the present invention, the preparation method of the modified polyurethane prepolymer includes the following steps: polytetrahydrofuran ether diol, hydroxyl-terminated polybutadiene, and trifunctional polyether polyol are vacuum dehydrated at 120°C and -0.095 MPa for 2 hours, cooled to 60°C, and then added to a reaction vessel. Diphenylmethane diisocyanate and 1,4-butanediol are then added to the reaction vessel, the temperature is raised to 85-90°C, a catalyst is added, and the reaction is carried out under nitrogen protection for 3 hours. When the -NCO content of the system reaches 15%-25%, the reaction is stopped; the temperature is then lowered to room temperature to obtain the modified polyurethane prepolymer.

[0037] Long-chain, linear polytetrahydrofuran ether diol (PTMG, Mn=2000) was selected as the main soft segment, whose regular ether bond structure provides excellent flexibility and hydrolysis resistance. Diphenylmethane diisocyanate (MDI) and 1,4-butanediol were selected as hard segments. MDI provides rigid benzene rings, imparting high strength to the material. The chain extender 1,4-butanediol (BDO), with its even-numbered carbon chains, facilitates the formation of a regular hydrogen bond network, enhancing the cohesive force in the hard segment region, thereby significantly improving the mechanical properties of the polyurethane matrix. A small amount of hydroxyl-terminated polybutadiene (HTPB) was added; its molecular backbone consists of saturated C-C and C=C bonds, making it extremely stable and exhibiting good hydrolysis and chemical corrosion resistance. Furthermore, the addition of HTPB effectively improves the material's toughness and low-temperature flexibility. A small amount (approximately 2%-5%) of trifunctional polyether polyol was added, which can form controllable crosslinking points in the polymer network, significantly improving the compressive strength, abrasion resistance, and solvent resistance of the polyurethane matrix material.

[0038] In some embodiments of the present invention, the modified polyurethane comprises, by weight, the following raw materials: 80-90 parts of polytetrahydrofuran ether diol, 10-20 parts of hydroxyl-terminated polybutadiene, 5-10 parts of trifunctional polyether polyol, 35-40 parts of diphenylmethane diisocyanate, 1-5 parts of 1,4-butanediol, and 0.03-0.1 parts of dibutyltin dilaurate.

[0039] In some embodiments of the present invention, the preparation method of the organically modified vermiculite includes the following steps: drying nano-vermiculite at 100-105℃ for 3-4 hours; dispersing the dried nano-vermiculite at a mass concentration of 3-5% in a mixture of ethanol and water, dispersing at 7000-8000 rpm for 20-30 minutes to obtain a suspension; adding KH-550 silane coupling agent at 8-10% of the vermiculite mass to the mixture of ethanol and water, adding glacial acetic acid to adjust the pH to 4-5, stirring for 20-30 minutes to obtain a silane solution; adding the silane solution dropwise to the suspension, stirring and reacting at 65-70℃ for 4-5 hours; filtering, washing the filter cake to neutrality, vacuum drying the filter cake at 70-80℃ for 10-12 hours, grinding, and sieving to obtain organically modified nano-vermiculite.

[0040] In some embodiments of the present invention, the preparation method of the modified cellulose hydrogel microspheres includes the following steps: dissolving sodium carboxymethyl cellulose in deionized water to prepare an aqueous phase of 5-10%; dissolving Span-80 emulsifier in liquid paraffin to obtain an oil phase; adding the aqueous phase to the oil phase under stirring at 800-1000 rpm to form an emulsion; adding the modified polyurethane prepolymer dropwise to the emulsion, stirring and reacting for 1-2 hours, adding ethanol, filtering and collecting the microspheres, and washing to obtain the modified cellulose hydrogel microspheres.

[0041] Adding modified cellulose hydrogel microspheres to a modified polyurethane matrix enables zero shrinkage and repeated self-healing of the polyurethane aggregate material. Secondly, the soft microspheres, as elastomers, can induce mechanisms such as crazing and shear banding when subjected to external forces, absorbing impact energy and improving the material's toughness. Furthermore, the shell of the microspheres can, to some extent, slow down the water penetration rate, facilitating deeper penetration of the slurry. Specifically, in a dry state, the microsphere shell protects the internal sodium carboxymethyl cellulose core, ensuring its stability within the hydrophobic polyurethane slurry. When the aggregate encounters water, water molecules slowly penetrate through the polyurethane shell, causing the internal sodium carboxymethyl cellulose core to rapidly absorb water and swell, generating significant expansion stress. This stress acts uniformly outward on the surrounding polyurethane matrix, precisely offsetting the volume reduction caused by polymer shrinkage and gas escape. When the environment becomes dry, water is slowly released from the microspheres, and the volume shrinks back. This process can be repeated upon subsequent contact with water. This physical process can be repeated, achieving the material's intelligent self-healing function.

[0042] The solvent is at least one selected from dimethyl carbonate, ethyl acetate, n-propyl acetate, and n-butyl acetate. The catalyst is a formate of dibutyltin dilaurate and 1,4-diazabicyclo[2.2.2]octane in a mass ratio of 2:1.

[0043] The latent curing agent is a ketimine or oxazolidinyl ether, formed by the condensation of ketones (such as methyl isobutyl ketone) and diamines (such as isophorone diamine IPDA, ethylenediamine). It does not react with the polyurethane prepolymer (-NCO) at room temperature, ensuring the stability of the slurry during storage and initial application. Upon contact with water, it rapidly hydrolyzes to generate a highly reactive primary amine (-NH2). The reaction rate of the primary amine with the -NCO group is extremely fast, much faster than the reaction between water and -NCO, rapidly triggering curing accompanied by slight volume expansion to counteract later shrinkage.

[0044] On the other hand, embodiments of the present invention provide a method for preparing a modified polyurethane grouting material for sealing leaks, comprising the following steps:

[0045] S1, mix the modified polyurethane prepolymer, hydrogenated hydroxyl-terminated butadiene nitrile rubber liquid, and solvent, and stir until homogeneous;

[0046] S2, then add organically modified nano-vermiculite, and shear disperse at high speed (5000-6000 rpm) for 30-60 min;

[0047] S3, then add modified cellulose hydrogel microspheres and curing agent, stir at low speed (800-1000 rpm) until mixed evenly;

[0048] S4, then add the catalyst, stir evenly, seal and package to obtain the grouting material.

[0049] During the mixing stage, the -NCO of the prepolymer reacts chemically with the hydroxyl groups (-OH) on the surface of the organically modified nano-vermiculite, the hydroxyl groups at the chain ends of hydrogenated nitrile butadiene rubber (HTBN), and the active groups on the shell of the cellulose microspheres, forming strong covalent bonds. This creates a three-dimensional interpenetrating network structure that combines rigidity and flexibility. This not only improves the interfacial compatibility between inorganic nanomaterials, organic elastomers, and the polyurethane matrix, preventing phase separation, but also enables effective stress transfer from the continuous phase to the dispersed phase, which is crucial for obtaining high-performance composite materials. Furthermore, the polyurethane hard segment region and the organically modified nano-vermiculite sheets form a hard segment network, providing strength and modulus. The polyurethane soft segment, the HTBN rubber phase, and the hydrogel microspheres form a flexible network, providing elasticity and toughness. The synergy between the rigid and flexible networks allows the rigid network to bear the main stress when the material is subjected to external forces, while the flexible network dissipates energy through deformation and viscous flow, thus simultaneously achieving high strength, high toughness, and high elasticity.

[0050] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0051] Example

[0052] 1. Prepare the raw materials for each modified polyurethane prepolymer according to the following proportions:

[0053] Modified polyurethane prepolymer A:

[0054] 80 parts of polytetrahydrofuran ether diol, 10 parts of hydroxyl-terminated polybutadiene, 5 parts of trifunctional polyether polyol, 35 parts of diphenylmethane diisocyanate, 1 part of 1,4-butanediol, and 0.03 parts of dibutyltin dilaurate.

[0055] Modified polyurethane prepolymer B:

[0056] 90 parts of polytetrahydrofuran ether diol, 20 parts of hydroxyl-terminated polybutadiene, 10 parts of trifunctional polyether polyol, 40 parts of diphenylmethane diisocyanate, 5 parts of 1,4-butanediol, and 0.1 parts of dibutyltin dilaurate.

[0057] Modified polyurethane prepolymer C:

[0058] 85 parts polytetrahydrofuran ether diol, 15 parts hydroxyl-terminated polybutadiene, 8 parts trifunctional polyether polyol, 38 parts diphenylmethane diisocyanate, 3 parts 1,4-butanediol, and 0.08 parts dibutyltin dilaurate.

[0059] Based on the above formulation, each modified polyurethane prepolymer was prepared according to the following steps:

[0060] Polytetrahydrofuran ether diol, hydroxyl-terminated polybutadiene, and trifunctional polyether polyol were vacuum dehydrated at 120°C and -0.095 MPa for 2 hours, cooled to 60°C, and then added to a reactor. Diphenylmethane diisocyanate and 1,4-butanediol were then added to the reactor, the temperature was raised to 90°C, a catalyst was added, and the reaction was carried out under nitrogen protection for 3 hours. When the -NCO content of the system reached 20%, the reaction was stopped. The mixture was then cooled to room temperature to obtain the modified polyurethane prepolymer.

[0061] 2. Prepare organically modified vermiculite using the following method:

[0062] Nano-vermiculite was dried at 105℃ for 3 hours to remove moisture. The dried nano-vermiculite was dispersed at a mass concentration of 5% in a mixture of ethanol and water (volume ratio 1:1) and dispersed at 8000 rpm for 20 minutes to obtain a suspension. KH-550 silane coupling agent (10% by mass of vermiculite) was added to the ethanol and water mixture (volume ratio 1:1), and glacial acetic acid was added to adjust the pH to 4-5. The mixture was stirred for 30 minutes to obtain a silane solution. The silane solution was added dropwise to the suspension, and the mixture was stirred at 65℃ for 5 hours. The mixture was filtered, the filter cake was washed until neutral, and the filter cake was vacuum dried at 70-80℃ for 12 hours. It was then ground and sieved to obtain organically modified nano-vermiculite. The volume ratio of the silane solution to the suspension was 1:1.

[0063] 3. Prepare modified cellulose hydrogel microspheres using the following method:

[0064] Sodium carboxymethyl cellulose was dissolved in deionized water to prepare a 10% aqueous phase; Span-80 emulsifier was dissolved in liquid paraffin to obtain an oil phase; the aqueous phase was added to the oil phase under stirring at 1000 rpm to form an emulsion; the modified polyurethane prepolymer was added dropwise to the emulsion, and the mixture was stirred for 2 hours. Ethanol was added, the microspheres were collected by filtration, and washed to obtain the modified cellulose hydrogel microspheres.

[0065] 4. Based on the raw material ratios in Table 1, prepare various modified polyurethane grouting materials:

[0066] Table 1. Amount of each raw material (parts by weight)

[0067]

[0068] In this study, modified polyurethane prepolymer A was used in groups 1-2, with dimethyl carbonate as the solvent; modified polyurethane prepolymer B was used in groups 3-4, with ethyl acetate as the solvent; and modified polyurethane prepolymer C was used in groups 3-4, with n-butyl acetate as the solvent. Ketoimine was used as the curing agent in groups 1-3, and oxazolidine was used as the curing agent in groups 4-6. All catalysts were mixtures of dibutyltin dilaurate and 1,4-diazabicyclo[2.2.2]octanecarbamate in a 2:1 mass ratio. Hydrogenated hydroxyl-terminated butadiene-acrylonitrile rubber liquid was purchased from Shandong Ruweng Chemical Co., Ltd., HTBN-1.

[0069] Based on the above proportions, the modified polyurethane grouting material is prepared according to the following steps:

[0070] S1, mix the modified polyurethane prepolymer, hydrogenated hydroxyl-terminated butadiene nitrile rubber liquid, and solvent, and stir until homogeneous;

[0071] S2, then add organically modified nano-vermiculite, and shear disperse at high speed (5000 rpm) for 30 min;

[0072] S3, then add modified cellulose hydrogel microspheres and curing agent, stir at low speed (1000 rpm) for 10 minutes, and mix evenly;

[0073] S4, then add the catalyst, stir evenly, seal and package to obtain the grouting material.

[0074] Comparative Example 1

[0075] The difference between this material and the first group of grouting materials in the examples is that nano-vermiculite is used instead of organically modified nano-vermiculite, and sodium carboxymethyl cellulose is used instead of modified cellulose hydrogel microspheres. The other raw materials and preparation methods are the same as those in the first group of grouting materials.

[0076] Comparative Example 2

[0077] The difference between this material and the first group of grouting materials in the examples is that nano-vermiculite is used instead of organically modified nano-vermiculite, while the other raw materials and preparation methods are the same as those in the first group of grouting materials.

[0078] Comparative Example 3

[0079] The difference between this material and the first group of grouting materials in the examples is that sodium carboxymethyl cellulose is used instead of modified cellulose hydrogel microspheres, while the other raw materials and preparation methods are the same as those in the first group of grouting materials.

[0080] Example of effect

[0081] Using the grouting materials of Examples 1-6 and Comparative Examples 1-3 as test objects, the tensile strength, repeated expansion rate, acid resistance, and water absorption rate of each grouting material were tested, and the results are shown in Table 2.

[0082] Tensile strength: Pour the grouting material into a flat mold, allowing it to foam freely and fully cure. Cut at least 5 valid specimens from the solidified plate using a standard dumbbell-shaped I-beam cutter; cure for 7 days under standard experimental conditions (23±2℃, 50±10%RH). Using a universal testing machine, clamp the specimens symmetrically in the fixtures and tensile them at a constant speed of 500 mm / min to test the tensile strength of each specimen. Test each group of grouting materials 3 times and take the average value.

[0083] Repeated expansion rate: (1) Initial expansion volume (V1) determination: Weigh 20g of slurry and place it in a 500mL graduated cylinder. Add 50mL of water and stir quickly to allow it to react and foam fully. After the reaction stops and cools to room temperature, read the volume of the solidified body in the graduated cylinder and record it as V1. Remove the solidified body from the graduated cylinder and wipe off the surface moisture. Place it in a forced-air drying oven and dry it at 60℃ for 48 hours until constant weight.

[0084] (2) Determination of the volume of secondary expansion (V2): Place the dried solidified body back into a 500mL graduated cylinder. Add enough water to completely submerge the solidified body. After soaking for 24 hours, read the volume of the secondary expansion of the solidified body and record it as V2.

[0085] (3) Cycle: Repeat steps 2 and 3 to perform 5 dry-wet cycles, and record the volume V5 of the solidified body in the 5th cycle.

[0086] The expansion retention rate after 5 cycles = (V5 / V1)*100%.

[0087] Acid resistance: Prepare a sulfuric acid solution with pH=3.0 using concentrated sulfuric acid and deionized water (simulating a strong acid rain environment).

[0088] Immersion test: Immerse dumbbell-shaped Type I samples (5 samples per group) completely in a sufficient amount of sulfuric acid solution with pH=3. Also, immerse 5 samples from each group in deionized water as a blank control. Seal the containers and immerse at 23°C for 7 days.

[0089] Testing and Calculation: Remove the sample, rinse gently with running water, and then blot dry with filter paper. Test the tensile strength of the sample after immersion.

[0090] Acid resistance strength retention rate (%) = (σ1 / σ0) * 100%, σ0: average tensile strength of the blank control group, σ1: average tensile strength of the acid immersion group.

[0091] Water absorption rate: The solidified body was prepared into a flat plate sample of 50mm×50mm×5mm, and the surface was polished smooth. It was dried in a drying oven at 50℃ for 24 hours, then removed and cooled to room temperature in a desiccator, and weighed to an accuracy of 0.1mg. This mass is recorded as m0.

[0092] Immerse the dried sample completely in a container filled with distilled water, ensuring that the sample does not contact each other or the container walls. After soaking for 168 hours, remove the sample and quickly absorb the surface moisture with filter paper (within 1 minute). Immediately weigh the sample at saturation and record it as m1.

[0093] Result calculation: Water absorption rate (W) a =[(m1-m0) / m0]*100%. Take 3 samples from each group for testing and calculate the average value.

[0094] Table 2

[0095]

[0096] Table 2 shows that the tensile strength of the grouting materials in Examples 1-6 is above 10 MPa, exhibiting excellent mechanical properties. Even after acid immersion, they maintain high tensile strength, indicating minimal impact of acid on the tensile strength and good acid resistance. After five cycles of wet-drying, the expansion retention rate of the grouting material is above 90%, meaning that while there is some volume shrinkage after drying, the modified cellulose hydrogel microspheres absorb water and expand upon secondary contact with water, offsetting the volume shrinkage during drying and reducing overall volume shrinkage. This, in turn, reduces the gap between the grouting material and the crack, minimizing secondary leakage. In contrast, the comparative example lacks the volume compensation from the expanded modified cellulose hydrogel microspheres, resulting in an expansion retention rate below 90%.

[0097] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A modified polyurethane grouting material for sealing leaks, characterized in that, By weight, it includes the following ingredients: 90-100 parts of modified polyurethane prepolymer, 5-15 parts of organic modified nano-vermiculite, 5-20 parts of modified cellulose hydrogel microspheres, 5-12 parts of hydrogenated hydroxyl-terminated butadiene-acrylonitrile rubber liquid, 1-5 parts of curing agent, 10-25 parts of solvent, and 0.5-2 parts of catalyst. The modified polyurethane prepolymer is prepared by reacting polytetrahydrofuran ether diol with diphenylmethane diisocyanate, and its functional group -NCO content is 15%-25%; The curing agent is a latent curing agent; The preparation method of the organically modified vermiculite includes the following steps: The nano-vermiculite was dried at 100-105℃ for 3-4 hours; Dry nano-vermiculite was dispersed in a mixture of ethanol and water at a mass concentration of 3-5% and dispersed at 7000-8000 rpm for 20-30 min to obtain a suspension. Add KH-550 silane coupling agent to a mixture of ethanol and water at 8-10% of the vermiculite mass, adjust the pH to 4-5 with glacial acetic acid, and stir for 20-30 minutes to obtain a silane solution. The silane solution was added dropwise to the suspension and stirred at 65-70℃ for 4-5 hours; the mixture was filtered, the filter cake was washed until neutral, the filter cake was vacuum dried at 70-80℃ for 10-12 hours, ground and sieved to obtain organically modified nano-vermiculite; The preparation method of the modified cellulose hydrogel microspheres includes the following steps: Dissolve sodium carboxymethyl cellulose in deionized water to prepare a 5-10% aqueous phase; Span-80 emulsifier was dissolved in liquid paraffin to obtain the oil phase; While stirring at 800-1000 rpm, the aqueous phase is added to the oil phase to form an emulsion; The modified polyurethane prepolymer was added dropwise to the emulsion, and the mixture was stirred for 1-2 hours. Ethanol was added, the microspheres were collected by filtration, and washed to obtain the modified cellulose hydrogel microspheres.

2. The modified polyurethane grouting material for sealing leaks according to claim 1, characterized in that, The preparation method of the modified polyurethane prepolymer includes the following steps: Polytetrahydrofuran ether diol, hydroxyl-terminated polybutadiene, and trifunctional polyether polyol were vacuum dehydrated at 120°C and -0.095 MPa for 2 hours, cooled to 60°C, and then added to a reactor. Diphenylmethane diisocyanate and 1,4-butanediol were then added to the reactor, and the temperature was raised to 85-90°C. Dibutyltin dilaurate was then added, and the reaction was carried out for 3 hours under nitrogen protection. When the -NCO content of the system reached 15%-25%, the reaction was stopped. The mixture was then cooled to room temperature to obtain the modified polyurethane prepolymer.

3. The modified polyurethane grouting material for sealing leaks according to claim 2, characterized in that, The modified polyurethane comprises the following raw materials by weight: 80-90 parts of polytetrahydrofuran ether diol, 10-20 parts of hydroxyl-terminated polybutadiene, 5-10 parts of trifunctional polyether polyol, 35-40 parts of diphenylmethane diisocyanate, 1-5 parts of 1,4-butanediol, and 0.03-0.1 parts of dibutyltin dilaurate.

4. The modified polyurethane grouting material for sealing leaks according to claim 1, characterized in that, The solvent is at least one of dimethyl carbonate, ethyl acetate, n-propyl acetate, and n-butyl acetate.

5. The modified polyurethane grouting material for sealing leaks according to claim 1, characterized in that, The catalyst is a formate of dibutyltin dilaurate and 1,4-diazabicyclo[2.2.2]octane, with a mass ratio of 2:

1.

6. A method for preparing a modified polyurethane grouting material for sealing leaks as described in any one of claims 1-5, characterized in that, Includes the following steps: S1, mix the modified polyurethane prepolymer, hydrogenated hydroxyl-terminated butadiene nitrile rubber liquid, and solvent, and stir until homogeneous; S2, then add organically modified nano-vermiculite, and disperse at high speed under shear for 30-60 minutes; S3, then add modified cellulose hydrogel microspheres and curing agent, stir at low speed until evenly mixed; S4, then add the catalyst, stir evenly, seal and package to obtain the grouting material.

7. The preparation method of the modified polyurethane grouting material for leak sealing according to claim 6, characterized in that, In step S2, the rotational speed of the high-speed shear dispersion is 5000-6000 rpm.

8. The preparation method of the modified polyurethane grouting material for sealing leaks according to claim 6, characterized in that, In step S3, the stirring speed is 800-1000 rpm.

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