Polyurea grouting liquid, its preparation method and application in treating underwater expansion joint

Abstract

The application belongs to the technical field of underwater seepage prevention and structure repair materials for hydraulic engineering, and particularly relates to a polyurea grouting liquid, a preparation method thereof and application thereof in treating underwater expansion joints. The polyurea grouting liquid provided by the application comprises 40-50 parts of an isocyanate component, 30-35 parts of a double-flexible block chain diol, 15-20 parts of an amino-terminated polyether, 0.5-1 part of a composite catalyst and 1-2 parts of a silane coupling agent. The isocyanate component comprises isophorone diisocyanate and diphenyl methane diisocyanate. The double-flexible block chain diol is a triblock structure formed by polymerization of polypropylene glycol, polydimethylsiloxane and polyethylene oxide. The composite catalyst comprises bismuth octoate and triethylenediamine. The polyurea grouting liquid provided by the application has the comprehensive performance of high elasticity, deformation resistance, underwater strong adhesion, environmental protection and durability, and meets the long-acting seepage prevention and repair requirements of underwater expansion joints for hydraulic engineering, thereby providing core material support for safe and stable operation of hydraulic engineering.

Description

Technical Field

[0001] This invention belongs to the technical field of underwater seepage prevention and structural repair materials for water conservancy projects, specifically relating to a polyurea grouting liquid, its preparation method, and its application in treating underwater expansion joints. Background Technology

[0002] In water conservancy projects such as dams, sluices, pumping stations, tunnels, and others, underwater expansion joints are crucial for ensuring structural safety. Their core function lies in a dual adaptation: firstly, absorbing the expansion and shear deformation of the concrete structure caused by temperature changes, foundation settlement, and water pressure fluctuations, thus preventing cracking of the main structure; secondly, blocking water seepage channels, preventing seepage erosion of the main structure, and extending its service life. This places multiple stringent requirements on the grouting materials, requiring them to simultaneously possess high elasticity and deformation resistance, long-term underwater bonding performance, excellent water aging resistance, and environmental safety. Furthermore, the curing rate must match the on-site construction rhythm, balancing grout flowability and molding stability.

[0003] Currently, the grouting materials used for underwater expansion joint treatment in water conservancy projects are mainly divided into three major systems: epoxy resin, polyurethane, and traditional polyurea. Each system has its shortcomings in meeting the requirements of the working conditions: epoxy resin materials are rigid after curing, have poor resistance to deformation, and are prone to brittle cracking and failure during repeated deformation of the expansion joint. They can only be cured on dry substrates, and their underwater bonding strength is generally lower than 1.5 MPa, making them unsuitable for dynamic seepage prevention scenarios. Polyurethane grouting liquids have basic elasticity, but their water aging resistance is poor. Long-term underwater immersion can easily lead to hydrolysis and swelling, and their seepage prevention life is usually less than 8 years. Some products also contain volatile solvents and toxic catalysts, which do not meet the durability and environmental protection requirements of underwater environments in water conservancy projects. Traditional polyurea grouting liquids, relying on the stability of the urea bond structure, are superior to polyurethane in terms of aging resistance and elasticity, and are gradually becoming the preferred choice for underwater seepage prevention.

[0004] From the perspective of existing technology research and engineering application practice, a great deal of work has been carried out both domestically and internationally to optimize the performance of polyurea grouting fluids, and many related technical solutions have been disclosed. These technologies can adapt to the crack sealing needs in some humid environments. However, for the dynamic deformation and long-term seepage prevention conditions of underwater expansion joints, existing polyurea grouting fluids still cannot simultaneously achieve high elasticity, strong underwater adhesion, and environmental friendliness, which limits their application in underwater expansion joint conditions. Summary of the Invention

[0005] The purpose of this invention is to provide a polyurea grouting fluid, its preparation method, and its application in treating underwater expansion joints. The polyurea grouting fluid provided by this invention possesses a combination of high elasticity and deformation resistance, strong underwater adhesion, and environmentally friendly durability, meeting the long-term seepage prevention and repair needs of underwater expansion joints in water conservancy projects, and providing core material support for the safe and stable operation of water conservancy projects.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a polyurea grouting fluid, comprising the following components in parts by weight: The composition comprises 40-50 parts isocyanate, 30-35 parts dual flexible block diol, 15-20 parts amino-terminated polyether, 0.5-1 part composite catalyst, and 1-2 parts silane coupling agent; the isocyanate comprises isophorone diisocyanate (IPDI) and diphenylmethane diisocyanate (MDI); the dual flexible block diol is a triblock structure formed by polymerization of polypropylene glycol (PPG), polydimethylsiloxane (PDMS), and polyethylene oxide (PEO); the composite catalyst comprises bismuth octanoate and triethylenediamine.

[0007] Preferably, the mass ratio of isophorone diisocyanate to diphenylmethane diisocyanate is (6~8):(2~4); the NCO group content of isophorone diisocyanate is 29.5%~30.5%, and the NCO group content of diphenylmethane diisocyanate is 33.5%~34.5%.

[0008] Preferably, the degree of polymerization of the polypropylene glycol is 20-30, the degree of polymerization of the polydimethylsiloxane is 5-10, and the degree of polymerization of the polyethylene oxide is 2-3; the mass content of the polypropylene glycol segment in the dual flexible block glycol is 65%-80%, and the mass content of the polyethylene oxide segment is ≤10%; the number average molecular weight of the dual flexible block glycol is 2000-2500, and the hydroxyl value is 45-55 mgKOH / g.

[0009] Preferably, the terminal amino polyether is polyoxypropylene diamine; the number-average molecular weight of the terminal amino polyether is 1900~2100, the primary amino value is 56~60mgKOH / g, and the viscosity at 25℃ is 1000~1500mPa·s.

[0010] Preferably, the mass ratio of bismuth octoate to triethylenediamine is 1~2:1.

[0011] Preferably, the silane coupling agent is γ-aminopropyltriethoxysilane (KH-550).

[0012] This invention provides a method for preparing the polyurea grout described above, comprising the following steps: In a protective gas atmosphere, the isocyanate component and the dual flexible block diol are mixed and subjected to a prepolymerization reaction to obtain a modified isocyanate prepolymer. The modified isocyanate prepolymer, amino-terminated polyether, composite catalyst and silane coupling agent are mixed and subjected to a crosslinking reaction to obtain the polyurea grouting solution.

[0013] Preferably, the mixing method of the isocyanate component and the biflexible block diol is as follows: the biflexible block diol is heated to a first temperature, and the isocyanate component is added dropwise under stirring; the first temperature is 60~80℃, the stirring speed is 80~100 r / min, and the dropwise addition time is 30~40 min; after the dropwise addition is completed, the temperature is raised to a second temperature for the prepolymerization reaction, the second temperature is 60~80℃, the holding time of the prepolymerization reaction is 2~3 h, and the NCO group content of the reaction system is sampled and detected during the prepolymerization reaction. When the NCO group content of the reaction system reaches 8.5%~9.5%, the prepolymerization reaction is stopped, and the mixture is cooled to below 40℃ to obtain the modified isocyanate prepolymer.

[0014] Preferably, the temperature of the crosslinking reaction is ≤40℃; the prepolymerization reaction is carried out under stirring conditions, with a stirring speed of 80~100r / min and a stirring time of 20~30min.

[0015] This invention provides the application of the polyurea grouting fluid described in the above technical solution or the polyurea grouting fluid prepared by the preparation method described in the above technical solution in the treatment of underwater expansion joints.

[0016] This invention provides a polyurea grouting fluid comprising the following components in parts by weight: 40-50 parts isocyanate component, 30-35 parts dual flexible block diol, 15-20 parts amino-terminated polyether, 0.5-1 part composite catalyst, and 1-2 parts silane coupling agent; wherein the isocyanate component comprises isophorone diisocyanate (IPDI) and diphenylmethane diisocyanate (MDI); wherein the dual flexible block diol is a triblock structure formed by polymerization of polypropylene glycol (PPG), polydimethylsiloxane (PDMS), and polyethylene oxide (PEO); and wherein the composite catalyst comprises bismuth octanoate and triethylenediamine. This invention utilizes a dual-flexible block diol (also known as PPG-PDMS-PEO dual-flexible block diol) to modify the isocyanate component. The PPG segments in the dual-flexible block diol, due to their moderate hydrophilicity and strong hydrolysis resistance, form a "flexible support framework" within the polymer network, ensuring slurry flowability and long-term underwater stability. The PDMS segments in the dual-flexible block diol, with their excellent molecular chain flexibility, interweave within the network, enhancing the elastomer's tensile and deformation recovery capabilities, adapting to repeated displacements in expansion joints. The PEO segments in the dual-flexible block diol are exposed on the network surface, improving compatibility with damp concrete substrates through molecular-level hydrophilicity, laying the foundation for subsequent bonding. This invention also employs a compound isocyanate of IPDI and MDI. The aliphatic cycloaliphatic structure of IPDI endows the polymer network with excellent resistance to yellowing and water aging, preventing embrittlement during long-term underwater service. The aromatic structure of MDI enhances the -NCO reactivity, accelerating prepolymerization and crosslinking reactions, while simultaneously reducing raw material costs. This invention utilizes a composite catalyst of bismuth octanoate and triethylenediamine. Bismuth octanoate preferentially catalyzes the prepolymerization reaction, controlling the reaction rate to avoid localized overheating and crosslinking. Triethylenediamine specifically regulates the underwater crosslinking reaction rhythm, enabling the system to gel in 30 minutes and fully cure in 24 hours underwater at 25°C, maintaining curing stability within a water temperature range of 10-30°C, adapting to various underwater construction environments. This invention employs a silane coupling agent that undergoes a hydrolytic condensation reaction with the hydroxyl groups (-OH) of the concrete substrate to form covalent bonds at one end, and forms hydrogen bonds with the amino and ether bonds in the polyurea network at the other end. Combined with the hydrophilic adsorption of PEO segments, a dual interfacial bond of covalent and hydrogen bonds is constructed, resisting water erosion and ensuring long-term stable bond strength. The urea bond crosslinking network formed after the polymerization reaction of the polyurea grouting fluid provided by this invention possesses excellent water resistance and aging resistance. Combined with the deformation buffering capacity of the dual flexible segments, the cured polyurea elastomer can withstand shear deformation of ±10mm or more in underwater expansion joints, while leaving no heavy metal residues, meeting the environmental protection requirements of water conservancy projects.

[0017] Furthermore, in this invention, when the mass ratio of IPDI to MDI is 7:3, a dynamic balance between weather resistance, reactivity, and cost can be achieved.

[0018] In summary, compared with existing technologies, this invention utilizes the synergistic modification of PPG-PDMS-PEO dual flexible block diols, simultaneously introducing molecular-level hydrophilic segments, thus solving the imbalance between elasticity and adhesion at the molecular structure level. This invention addresses the existing technology's reliance on single-dosage principles of pure IPDI (high cost) or pure MDI (poor weather resistance); it employs a compound system of IPDI and MDI, balancing weather resistance, reactivity, and cost control. This invention addresses the existing technology's reliance on tin-based heavy metal catalysts, which poses a risk of water pollution; it uses a bismuth octoate-triethylenediamine composite environmentally friendly catalyst, leaving no heavy metal residue and allowing for precise control of the underwater curing rate. This invention addresses the existing technology's lack of optimization for the dynamic deformation of underwater expansion joints, resulting in poor construction adaptability; through component synergistic design, this invention achieves high elasticity and deformation resistance, strong underwater adhesion, and wide temperature range adaptability, specifically tailored for underwater expansion joint applications. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the preparation of the modified isocyanate prepolymer in this embodiment. Detailed Implementation

[0020] This invention provides a polyurea grouting fluid, comprising the following components in parts by weight: The composition comprises 40-50 parts isocyanate, 30-35 parts dual flexible block diol, 15-20 parts amino-terminated polyether, 0.5-1 part composite catalyst, and 1-2 parts silane coupling agent; the isocyanate comprises isophorone diisocyanate (IPDI) and diphenylmethane diisocyanate (MDI); the dual flexible block diol is a triblock structure formed by polymerization of polypropylene glycol (PPG), polydimethylsiloxane (PDMS), and polyethylene oxide (PEO); the composite catalyst comprises bismuth octanoate and triethylenediamine.

[0021] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0022] The polyurea grouting solution provided by this invention comprises 40-50 parts by weight of isocyanate component, and in the examples, it can be 45 parts. In this invention, the preferred mass ratio of isophorone diisocyanate to diphenylmethane diisocyanate is (6-8):(2-4), and in the examples, it can be 7:3. The purity of the isophorone diisocyanate is preferably ≥99.5%. The isophorone diisocyanate has an aliphatic alicyclic structure. The NCO group content of the isophorone diisocyanate is preferably 29.5%-30.5%. The purity of the diphenylmethane diisocyanate is ≥99%. The diphenylmethane diisocyanate has an aromatic structure. The NCO group content of the diphenylmethane diisocyanate is preferably 33.5%-34.5%. In this invention, the IPDI ensures that the polyurea grouting material has excellent resistance to yellowing, water aging and flexibility, making it suitable for long-term underwater service; MDI can improve the reactivity of the system and reduce the cost of raw materials. This invention uses a combination of IPDI and MDI to achieve a balance between weather resistance, reactivity and cost.

[0023] Based on the mass fraction of the isocyanate component, the polyurea grouting solution provided by the present invention comprises 30-35 parts of a dual flexible block glycol, which may be 32 parts in the examples. In the present invention, the dual flexible block glycol is a triblock structure of PPG, PDMS, and PEO. The degree of polymerization (n) of the polypropylene glycol is preferably 20-30. The degree of polymerization (n) of the polydimethylsiloxane is preferably 5-10, and the degree of polymerization (n) of the polyethylene oxide is preferably 2-3.

[0024] In this invention, the mass content of PPG segments in the dual flexible block diol is preferably 65%~80%, more preferably 68~75%, and even more preferably 70~73%; the mass content of PDMS segments in the dual flexible block diol is preferably 20%~30%, more preferably 23~27%, and even more preferably 24~25%; the mass content of PEO segments in the dual flexible block diol is preferably ≤10%, more preferably 1~8%, and even more preferably 5~6%. The sum of the mass contents of PPG segments, PDMS segments, and PEO segments is 100%. The mass contents of PPG segments, PDMS segments, and PEO segments in the dual flexible block diol are respectively the percentages of the mass of PPG segments, PDMS segments, and PEO segments relative to the total mass of the dual flexible block diol.

[0025] In this invention, the number-average molecular weight of the biflexible block diol is preferably 2000-2500. The hydroxyl value of the biflexible block diol is preferably 45-55 mgKOH / g. The moisture content of the biflexible block diol is preferably ≤0.1%.

[0026] In this invention, the dual flexible block diol comprises: PPG segments ensuring the fluidity of the grout during high-pressure grouting and improving underwater hydrolytic stability; PDMS segments imparting ultra-high flexibility and wide temperature range adaptability of 40~120℃ to the elastomer, resisting repeated deformation of expansion joints; and PEO segments achieving molecular-level hydrophilic modification, improving interfacial compatibility with damp concrete substrates. This invention constructs a flexible framework adapted to underwater working conditions through the synergistic use of PPG segments, PDMS segments, and PEO segments.

[0027] In this invention, the dual flexible block copolymer diol is a block copolymer diol formed from polypropylene glycol (PPG), polydimethylsiloxane (PDMS), and polyethylene oxide (PEO), which belongs to a type of organosilicon-modified polyether diol.

[0028] This invention does not impose any special requirements on the preparation method of the aforementioned flexible block copolymer. Conventional synthesis methods well-known to those skilled in the art can be used. In a specific embodiment of this invention, the preparation method of the flexible block copolymer may include the following steps: using hydroxyl-terminated polypropylene glycol (PPG) as a starting agent, reacting it with hydroxyl-terminated polydimethylsiloxane (PDMS) under the action of a catalyst to form a PPG-PDMS diblock copolymer, and then further reacting it with polyethylene oxide (PEO) to obtain a PPG-PDMS-PEO triblock copolymer. The raw materials (PPG, PDMS, PEO) used in the above synthesis method are all commercially available. The reaction conditions are conventional conditions in the field of polymer block copolymerization (such as temperature 80-120℃, reaction time 2-4 hours, nitrogen protection, etc.). Those skilled in the art can prepare the desired flexible block copolymer using synthesis methods well-known to them, based on the degree of polymerization of PPG, PDMS, and PEO, the molecular weight of the flexible block copolymer, and the hydroxyl value parameters. In addition, those skilled in the art can also directly entrust chemical companies with block polymer synthesis qualifications to customize and obtain the parameters (degree of polymerization of PPG, PDMS, and PEO, molecular weight of the dual flexible block diol, and hydroxyl value) as disclosed in this invention.

[0029] In this invention, the dual flexible block glycol can be a commercially available organosilicon-modified polyether glycol product, or it can be prepared by itself using conventional block copolymerization methods in the art, or it can be commissioned to a qualified chemical company for customization. Regardless of the source, the key parameters of the dual flexible block glycol should meet the following requirements: number average molecular weight of 2000~2500, hydroxyl value of 45~55 mgKOH / g, and moisture content ≤0.1%. Those skilled in the art can determine the molecular weight and distribution by gel permeation chromatography (GPC), determine the hydroxyl value by hydroxyl titration, and determine the moisture content by Karl Fischer method.

[0030] Based on the mass fraction of the isocyanate component, the polyurea grouting solution provided by the present invention comprises 15-20 parts, preferably 18 parts, of terminal amino polyether. In the present invention, the terminal amino polyether can be polyoxypropylene diamine. The number average molecular weight of the terminal amino polyether is preferably 1900-2100. The primary amino value of the terminal amino polyether is preferably 56-60 mgKOH / g. The viscosity of the terminal amino polyether at 25°C is preferably 1000-1500 mPa·s. The moisture content of the terminal amino polyether is preferably ≤0.1%. In the embodiments of the present invention, the terminal amino polyether can be Jeffamine D-2000. In the present invention, the terminal amino polyether acts as a chain extender and reacts with the modified isocyanate prepolymer to form a crosslinked network containing urea bonds, further enhancing the elasticity and mechanical strength of the material. At the same time, its polyether skeleton improves the compatibility of the system with the flexible chain segments, avoiding phase separation.

[0031] Based on the mass fraction of the isocyanate component, the polyurea grouting solution provided by the present invention includes 0.5 to 1 part of a composite catalyst, which may be 0.8 or 1 part in the examples. The mass ratio of bismuth octoate to triethylenediamine is preferably 1 to 2:1. In the present invention, the purity of bismuth octoate is preferably ≥98%. The purity of triethylenediamine is preferably ≥99%. Both bismuth octoate and triethylenediamine are heavy metal-free and environmentally friendly components. As a composite catalyst, they replace traditional tin-based catalysts, leaving no heavy metal residue and avoiding the risk of water pollution. The bismuth octoate regulates the prepolymerization reaction rate, and the triethylenediamine optimizes the underwater curing rhythm, synergistically achieving gelation in 30 minutes and complete curing in 24 hours in an underwater environment at 25°C, while maintaining a stable curing rate within a water temperature range of 10 to 30°C.

[0032] Based on the mass fraction of the isocyanate component, the polyurea grouting solution provided by this invention includes 1-2 parts of silane coupling agent, which may be 1.5 parts or 2 parts in the examples. The silane coupling agent may be γ-aminopropyltriethoxysilane (KH-550). The purity of KH-550 is preferably ≥98%, the boiling point is preferably 217-219℃, and the refractive index at 25℃ is preferably 1.418-1.420. The silane coupling agent works synergistically with the hydrophilic segments of PEO, forming a covalent bond with the hydroxyl groups of the concrete substrate at one end and a hydrogen bond complex with the polyurea molecular chain at the other end, constructing a "dual interface bond," significantly improving underwater bonding strength and long-term stability, and resisting water erosion of the bonding interface.

[0033] This invention provides a method for preparing the polyurea grout described above, comprising the following steps: In a protective gas atmosphere, the isocyanate component and the dual flexible block diol are mixed and subjected to a prepolymerization reaction to obtain a modified isocyanate prepolymer. The modified isocyanate prepolymer, amino-terminated polyether, composite catalyst and silane coupling agent are mixed and subjected to a crosslinking reaction to obtain the polyurea grouting solution.

[0034] This invention involves mixing an isocyanate component and a biflexible block diol in a protective gas atmosphere to undergo a prepolymerization reaction, yielding a modified isocyanate prepolymer. Prior to mixing, the biflexible block diol is preferably pre-dried. The pre-drying method preferably includes vacuum drying the biflexible block diol. The vacuum drying temperature is preferably 100-110°C, and the vacuum drying time is preferably 2-3 hours. Pre-drying is preferred to remove moisture from the biflexible block diol. The moisture content of the pre-dried biflexible block diol is preferably ≤0.1%. The isocyanate component is preferably subjected to a heat treatment, preferably at a temperature of 25-30°C for 1-1.5 hours. The heat treatment preferably involves allowing the isocyanate component to stand in a very stable environment. This protective treatment eliminates the influence of temperature fluctuations on the reaction.

[0035] In this invention, the protective gas can be nitrogen. The flow rate of the protective gas is preferably 0.5~1 L / min. The prepolymerization reaction is preferably carried out in a reactor equipped with a nitrogen protection device, a stirring device, and a temperature control device. The preferred method for mixing the isocyanate component and the biflexible block diol is to heat the biflexible block diol to a first temperature, and then add the isocyanate component dropwise while stirring. The first temperature is preferably 60~80℃, more preferably 70~75℃. The stirring speed is preferably 80~100 r / min. The dropwise addition time is preferably 30~40 min. After the dropwise addition is complete, the temperature is raised to a second temperature for the prepolymerization reaction. The second temperature is preferably 60~80℃, more preferably 70~80℃, and in the examples, it can be 70, 75, or 80℃. The holding time for the prepolymerization reaction is preferably 2~3 h, and in the examples, it can be 2.5 h. During the prepolymerization reaction, it is preferred to sample and detect the NCO group content of the reaction system, and the sampling time interval is preferably 25~30 min. When the NCO group content of the reaction system preferably reaches 8.5%~9.5%, the prepolymerization reaction is stopped, and the mixture is cooled to below 40°C to obtain the modified isocyanate prepolymer.

[0036] After obtaining the modified isocyanate prepolymer, the present invention mixes the modified isocyanate prepolymer, terminal amino polyether, composite catalyst, and silane coupling agent to carry out a crosslinking reaction to obtain the polyurea grouting liquid. In the present invention, the mixing preferably includes the following steps: premixing the terminal amino polyether, composite catalyst, and silane coupling agent to obtain a mixed chain extender system. Then, the modified isocyanate prepolymer and the mixed chain extender system are mixed. The premixing is carried out at room temperature. The premixing is carried out under stirring conditions, the stirring speed is preferably 80~100 r / min, and the stirring time is preferably 15~20 min.

[0037] In this invention, the temperature of the crosslinking reaction is ≤40℃. The stirring reaction is preferably carried out under stirring conditions, with a stirring speed preferably of 80~100 r / min and a stirring time preferably of 20~30 min. This invention controls the temperature of the crosslinking reaction to ≤40℃ to avoid localized overheating leading to excessive crosslinking. Stirring continues until the system has no obvious particles and a uniform color, thus obtaining the finished polyurea grouting solution.

[0038] In this invention, the preferred method for testing and storing the finished polyurea grout is to sample and test the initial viscosity of the finished product (at 25°C, controlled at 500~800 mPa·s, suitable for high-pressure grouting), and after passing the test, seal and package it, and store it in a cool and dry environment at 20~30°C for no more than 6 months.

[0039] This invention provides the application of the polyurea grouting fluid described in the above technical solution or the polyurea grouting fluid prepared by the preparation method described in the above technical solution in the treatment of underwater expansion joints.

[0040] In this invention, the polyurea grout is specifically designed for underwater expansion joint treatment. In a 25°C underwater environment, the gelation time is controllable to 30 minutes, and it reaches complete curing in 24 hours. After curing, the elastomer's elongation at break is ≥600%, the underwater bond strength with the concrete substrate is ≥3.5 MPa, and the performance retention rate after 50 ±10 mm shear cycles is ≥92%. Furthermore, it contains no heavy metal residue, meeting the core requirements of "high elasticity and deformation resistance, strong adhesion and seepage prevention, environmental friendliness and durability" for underwater expansion joints in water conservancy projects. It provides a high-performance material solution for long-term seepage prevention and repair of underwater expansion joints, possessing significant engineering application value and promising prospects for promotion.

[0041] The polyurea grouting fluid provided by this invention belongs to the category of chemical polyurea grouting fluid compositions. Its core working principle is based on the polymerization reaction mechanism of the isocyanate component modified with a dual flexible block glycol. Through the synergistic effect of each component, a highly elastic and strongly adhesive polyurea crosslinking network suitable for underwater expansion joint conditions is constructed. The specific principle is as follows: In this invention, the isocyanate component and the dual flexible block glycol can undergo a polymerization reaction, which is an addition reaction between the isocyanate group (-NCO) and the hydroxyl group (-OH), generating a urethane bond (-NHCOO-). No byproducts are generated, and the reaction is highly controllable. The specific reaction principle of the polymerization reaction between the isocyanate component and the dual flexible block glycol in this invention is as follows: ; Reactant description: The left-side dihydroxy-2-hydroxyl-2-flexible block diol is the core of functional modification. Through block connection, the PPG, PDMS, and PEO segments are structurally regular and can function independently. OCN-R-NCO represents IPDI-MDI compound isocyanate (mass ratio 7:3). R corresponds to isocyanate residues (alicyclic residues of IPDI and aromatic residues of MDI). The coefficient "2" in "OCN-R-NCO" means that the molar amount of isocyanate component is twice that of the 2-flexible block diol. The purpose is to keep the isocyanate in excess so that the prepolymer generated by the reaction retains active -NCO groups at both ends, so that it can react with the terminal amino polyether to form a polyurea cross-linked structure.

[0042] In this invention, the polyurea grouting solution forms a polyurea elastomer through a polymerization reaction involving a modified isocyanate prepolymer and an amino-terminated polyether under catalytic conditions at room temperature underwater, yielding a polyurea crosslinked elastomer. This reaction involves the addition of NCO to an amino group (-NH2), generating urea bonds (-NH-CO-NH-). The amino-terminated polyether acts as a chain extender, crosslinking with the modified prepolymer to form a three-dimensional network structure. The dual flexible block chains are randomly distributed within the network, imparting high elasticity to the material. Simultaneously, PEO segments and silane coupling agents participate in interfacial interactions, enhancing underwater adhesion.

[0043] The polyurea grout provided by this invention has an elongation at break of ≥600% after curing, an underwater bond strength of ≥3.5MPa, and a performance retention rate of ≥92% after shear deformation cycle, and can withstand the dynamic deformation of underwater expansion joints and water erosion for a long time.

[0044] The polyurea grouting solution provided by this invention replaces toxic tin-based catalysts, leaves no heavy metal residues, and meets the environmental protection standards for water conservancy projects. At the same time, the IPDI-MDI compound solution reduces the cost by more than 20% compared with pure IPDI-based products, and all components are industrially mature products with stable supply.

[0045] The polyurea grout provided by this invention has strong construction adaptability: the curing rate is less affected by water temperature, the underwater gel time is stable at 25~35min at 10~30℃, the grout viscosity (25℃, 500~800mPa·s) is suitable for high-pressure grouting, there are no flow or blockage problems, and it is compatible with existing polyurea construction equipment.

[0046] The polyurea grout provided by this invention has excellent long-term stability. It is a blend of aliphatic and aromatic isocyanates, combined with dual flexible chain segment protection, and has outstanding resistance to yellowing and water aging. Its underwater service life can reach more than 15 years, far exceeding that of traditional polyurethane grout (less than 8 years).

[0047] In summary, the PPG segments in the polyurea grout provided by this invention, due to their moderate hydrophilicity and strong hydrolysis resistance, form a "flexible support skeleton" in the polymer network, ensuring the grout's fluidity and long-term underwater stability. The PDMS segments, due to their excellent molecular chain flexibility, are interspersed in the network to enhance the elastomer's tensile and deformation recovery capabilities, adapting to the repeated displacement of expansion joints. A small number of PEO segments are exposed on the network surface, improving compatibility with damp concrete substrates through molecular-level hydrophilicity, laying the foundation for subsequent bonding.

[0048] The polyurea grout provided by this invention has an aliphatic cycloaliphatic structure of IPDI that endows the polymer network with excellent resistance to yellowing and water aging, avoiding embrittlement during long-term underwater service; the aromatic structure of MDI enhances the -NCO reactivity, accelerates the prepolymerization and crosslinking reaction, and reduces the cost of raw materials. The 7:3 ratio of the two achieves a dynamic balance between weather resistance, reactivity and cost.

[0049] The polyurea grout provided by this invention preferentially catalyzes the prepolymerization reaction of bismuth octoate, controls the reaction rate to avoid local overheating and crosslinking; triethylenediamine specifically regulates the underwater crosslinking reaction rhythm, so that the system gels in 30 minutes at 25°C underwater and is completely cured in 24 hours, and maintains curing stability in the water temperature range of 10~30°C, making it suitable for different underwater construction environments.

[0050] The polyurea grout provided by this invention has a silane coupling agent (KH-550) that undergoes a hydrolytic condensation reaction with the hydroxyl group (-OH) of the concrete substrate to form a covalent bond at one end and forms a hydrogen bond complex with the amino and ether bonds in the polyurea network at the other end. Combined with the hydrophilic adsorption of PEO segments, it constructs a dual interface bond of "covalent bond and hydrogen bond", resists water erosion, and ensures long-term stability of the bonding strength.

[0051] The urea bond crosslinking network formed by the polymerization reaction in the polyurea grout provided by this invention has excellent water resistance and aging resistance. Combined with the deformation buffering capacity of the dual flexible segments, the cured polyurea elastomer can withstand shear deformation of more than ±10mm in underwater expansion joints. At the same time, there is no heavy metal residue, which meets the environmental protection requirements of water conservancy projects.

[0052] To further illustrate the present invention, the technical solutions provided by the present invention are described in detail below with reference to embodiments, but these should not be construed as limiting the scope of protection of the present invention. Some of the materials used in the following embodiments and comparative examples are commercially available, specifically sourced as follows: IPDI: Covestro Polymers (China) Co., Ltd., model Desmodur® I, NCO content: 37.0~38.0%. MDI: Covestro Polymers (China) Co., Ltd., model Desmodur® 44V20, NCO content: 31.5%~32.5%. Terminal amino polyether: Huntsman Advanced Chemical Materials (Guangdong) Co., Ltd., model Jeffamine® D-2000. Composite catalyst: Guangzhou Yourun Synthetic Materials Co., Ltd., model CUCAT-HA02. Silane coupling agent: Nanjing Shuguang Chemical Group Co., Ltd., model KH-550, purity: ≥97%.

[0053] The PPG-PDMS-PEO dual flexible block copolymer used in the following examples and comparative examples has the following parameters: PPG segment degree of polymerization 25, PDMS segment degree of polymerization 8, PEO segment degree of polymerization 2, number average molecular weight of PPG-PDMS-PEO dual flexible block copolymer approximately 2200, hydroxyl value 50 mg KOH / g, and moisture content ≤0.1%. Those skilled in the art can prepare raw materials meeting the above parameters using conventional block copolymerization methods or through custom orders.

[0054] This preparation example provides a method for preparing PPG-PDMS-PEO dual flexible block diols, as detailed below: Under nitrogen protection, 100 parts by weight of terminal hydroxyl polypropylene glycol (PPG, degree of polymerization 25, molecular weight approximately 1500) were added to the reactor, and the mixture was heated to 100°C and vacuum dehydrated for 1 hour. The temperature was then lowered to 80°C, and 35 parts by weight of terminal hydroxyl polydimethylsiloxane (PDMS, degree of polymerization 8, molecular weight approximately 600) and 0.2 parts by weight of catalyst (dibutyltin dilaurate) were added. The mixture was stirred until homogeneous, and then heated to 90-110°C for 2-3 hours to obtain the PPG-PDMS diblock copolymer.

[0055] Add 8 parts by mass of polyethylene oxide (PEO, degree of polymerization 2, molecular weight approximately 100) to the above reaction system, and continue the reaction at 90-110℃ for 2-3 hours. After the reaction is completed, remove low-boiling substances by vacuum distillation to obtain the PPG-PDMS-PEO triblock copolymer diol.

[0056] The product obtained in this preparation example has a number average molecular weight of 2000-2500, a hydroxyl value of 45-55 mgKOH / g, and a moisture content of ≤0.1%.

[0057] Example 1 This embodiment provides a highly elastic polyurea grouting fluid for underwater expansion joints, comprising (by parts by weight): IPDI 31.5 parts, MDI 13.5 parts (mass ratio of the two is 7:3), PPG-PDMS-PEO dual flexible block diol 32 parts, amino-terminated polyether 18 parts, composite catalyst 0.8 parts, silane coupling agent KH-550 1.5 parts.

[0058] The method for preparing the high-elasticity polyurea grout provided in this embodiment includes the following steps: Weigh all raw materials according to the above proportions. Place the PPG-PDMS-PEO dual flexible block diol in a vacuum drying oven at 105℃ for 2.5 hours until the moisture content is ≤0.1%, and cool to room temperature for later use. Let the IPDI and MDI stand in a constant temperature environment at 28℃ for 1 hour in advance. Pretreated PPG-PDMS-PEO dual flexible block diol was added to a reactor equipped with nitrogen protection, temperature control and stirring device. Nitrogen gas (flow rate of 0.8 L / min) was introduced to replace the air 3 times, the temperature was raised to 75℃ and the stirring speed was 90 r / min. A mixture of IPDI and MDI was slowly added dropwise over a period of 35 minutes. After the addition was complete, the mixture was kept at a constant temperature of 75°C for 2.5 hours for prepolymerization. During this period, samples were taken every 30 minutes to detect the NCO content until the NCO content reached 9.0%. The reaction was then stopped and the mixture was cooled to below 40°C to obtain the modified isocyanate prepolymer. Add amino-terminated polyether to a mixing tank and stir at 90 r / min at room temperature. Then add composite catalyst and silane coupling agent in sequence and stir for 20 min until uniformly dispersed to obtain a mixed chain extension system. The modified isocyanate prepolymer was slowly added to the mixed chain extender system, stirred at room temperature for 25 minutes, and the system temperature was controlled not to exceed 40°C. The mixture was stirred until there were no obvious particles and the color was uniform, thus obtaining a high-elasticity polyurea grouting solution.

[0059] Example 2 This embodiment provides a highly elastic polyurea grouting fluid for underwater expansion joints, comprising (by parts by weight): IPDI 31.5 parts, MDI 13.5 parts (mass ratio of the two is 7:3), PPG-PDMS-PEO dual flexible block diol 32 parts, amino-terminated polyether 18 parts, composite catalyst 1 part, silane coupling agent KH-550 1.5 parts.

[0060] The preparation method of the high-elasticity polyurea grouting fluid provided in this embodiment is the same as that in Example 1, and the high-elasticity polyurea grouting fluid is obtained.

[0061] Example 3 This embodiment provides a highly elastic polyurea grout for underwater expansion joints, comprising (by weight): 31.5 parts IPDI, 13.5 parts MDI (in a weight ratio of 7:3), 32 parts PPG-PDMS-PEO dual flexible block diol, 18 parts amino-terminated polyether, 0.8 parts composite catalyst, and 2.0 parts silane coupling agent KH-550.

[0062] The preparation method of the high-elasticity polyurea grouting fluid provided in this embodiment is the same as that in Example 1, and the high-elasticity polyurea grouting fluid is obtained.

[0063] Example 4 This embodiment provides a highly elastic polyurea grouting fluid for underwater expansion joints, comprising (by parts by weight): IPDI 31.5 parts, MDI 13.5 parts (mass ratio of the two is 7:3), PPG-PDMS-PEO dual flexible block diol 32 parts, amino-terminated polyether 18 parts, composite catalyst 0.8 parts, silane coupling agent KH-550 1.5 parts.

[0064] The preparation method of the high-elasticity polyurea grouting fluid provided in this embodiment is basically the same as that in Example 1. The difference is that the temperature of the prepolymerization reaction is 80°C and the time for the prepolymerization reaction is 2 hours, so as to obtain the high-elasticity polyurea grouting fluid.

[0065] Comparative Example 1 This comparative example provides a polyurea grouting solution, comprising (by parts by weight): IPDI 31.5 parts, MDI 13.5 parts (mass ratio of the two is 7:3), PPG diol 32 parts, amino-terminated polyether 18 parts, composite catalyst 0.8 parts, silane coupling agent KH-550 1.5 parts.

[0066] The preparation method of the polyurea grouting fluid provided in this comparison is basically the same as that in Example 1, except that the PPG-PDMS-PEO dual flexible block chain diol used in Example 1 is replaced with PPG diol to obtain the polyurea grouting fluid.

[0067] Comparative Example 2 This comparative example provides a polyurea grouting solution, comprising (by parts by weight): IPDI 31.5 parts, MDI 13.5 parts (mass ratio of the two is 7:3), PPG-PDMS-PEO dual flexible block diol 32 parts, amino-terminated polyether 18 parts, dibutyltin dilaurate catalyst 0.8 parts, silane coupling agent KH-550 1.5 parts.

[0068] The preparation method of the polyurea grouting fluid provided in this comparative example is basically the same as that in the examples, except that the composite catalyst used in Example 1 is replaced with dibutyltin dilaurate catalyst to obtain the polyurea grouting fluid.

[0069] Comparative Example 3 This comparative example provides a polyurea grouting solution, comprising (by parts by weight): 45 parts IPDI (single isocyanate, no MDI), 32 parts PPG-PDMS-PEO dual flexible block diol, 18 parts amino-terminated polyether, 0.8 parts composite catalyst, and 1.5 parts silane coupling agent KH-550.

[0070] The preparation method of the polyurea grouting fluid provided in this comparative example is basically the same as that in Example 1, except that the mixture of IPDI and MDI used in Example 1 is replaced with IPDI to obtain the polyurea grouting fluid.

[0071] The formulations of the polyurea grouting solutions prepared in Examples 1-4 and Comparative Examples 1-3 are shown in Table 1.

[0072] Table 1. Mixing ratio of polyurea grout (kg / m³) 3 )

[0073] The core mechanical properties of the polyurea in Examples 1-4 and Comparative Examples 1-3 were determined using the following methods: 1. Elongation at break and tensile strength test The determination of elongation at break and tensile strength was performed according to GB / T 528-2009 "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber". The polyurea grouting solutions of Examples 1-4 and Comparative Examples 1-3 were poured into dumbbell-shaped standard molds, cured at 25°C for 24 hours, demolded, and then cured again under the same conditions for 7 days to obtain test specimens. Tensile tests were performed using a universal testing machine at a tensile rate of 500 mm / min, and the elongation at break and tensile strength were recorded. Five parallel specimens were prepared for each mix proportion, and the average value of the test results was taken. The difference between the result of a single specimen and the average value should be less than 5%; otherwise, the specimen must be prepared again and the test repeated.

[0074] 2. Underwater bond strength test Underwater bond strength was determined according to the shear bond strength test clause in GB / T 16777-2008 "Test Methods for Waterproof Coatings for Buildings". Concrete specimens with dimensions of 40mm × 40mm × 160mm were prepared and cured until the required strength was achieved. Grouting fluid was then evenly applied to the bonding surfaces of two concrete specimens, and the specimens were bonded together and placed in a 25℃ constant temperature water bath for 24 hours, followed by further underwater curing for 7 days. Shear loading tests were performed using a universal testing machine at a loading rate of 10mm / min. The maximum stress at shear failure was recorded as the underwater bond strength. Five parallel specimens were prepared for each mix design. The difference between the result of a single specimen and the average value should be less than 5%; otherwise, the test must be repeated.

[0075] 3. Retention rate test after 50 shear cycles The retention rate after 50 shear cycles was determined based on underwater bond strength testing. Bonded samples cured underwater for 7 days were subjected to ±10 mm shear deformation cycles using a mechanical testing machine, for a total of 50 cycles. After each cycle, the samples were placed in a 25℃ constant temperature water bath for another 24 hours, and their underwater bond strength was measured again. The formula for calculating the shear cycle retention rate is: Retention rate (%) = Bond strength before cycle / Bond strength after cycle × 100%. Five parallel samples were prepared for each mix design. The difference between the retention rate of a single sample and the average value should be less than 3%; otherwise, the test must be repeated.

[0076] The gel time of the polyurea grout in Examples 1-4 and Comparative Examples 1-3 was determined using the following method: The gel time was determined according to the gel time test method in HG / T 4574-2013 "Single-component polyurethane foam sealant", using the glass plate method. Take 20g of freshly mixed grout and quickly invert it onto the center of a clean 10cm×10cm glass plate. Immediately place the glass plate in a constant temperature environment of 25℃±1℃ and start a stopwatch. Every 1 minute, gently lift the grout with a 2mm diameter thin glass rod and observe the changes in the grout's state. When the grout shows no stringing and has an elastic paste-like consistency, the recorded time is the gel time. Three parallel samples were tested for each mix proportion. The difference between the result of a single sample and the average value should be less than 2 minutes; otherwise, the test must be repeated.

[0077] The viscosity values ​​of the polyurea grouting fluids from Examples 1-4 and Comparative Examples 1-3 were determined using the following methods: The viscosity of the grout at 25℃ shall be determined according to GB / T 2794-2013 "Determination of Viscosity of Adhesives". Take freshly mixed grout and pour it into the test container of the rotational viscometer within 5 minutes. Place the test container in a constant temperature bath at 25℃±1℃, select an appropriate rotor and speed, and record the viscosity value after the reading stabilizes. Three parallel samples shall be tested for each mix proportion. The difference between the result of a single sample and the average value should be less than 5%; otherwise, the test must be repeated.

[0078] The method for determining the mixed heavy metal residue (tin content) of Examples 1-4 and Comparative Examples 1-3 is as follows: The determination of heavy metal residues (tin content) was performed using inductively coupled plasma optical emission spectrometry (ICP-OES) derived from GB / T 3050-2000 "General Method for Determination of Chloride Content in Inorganic Chemical Products - Potentiometric Titration". 5g of polyurea elastomer sample cured for 7 days was taken, pulverized, digested, and then diluted to a 50mL volumetric flask. The tin content of the digest was detected using an ICP-OES spectrometer, with the instrument detection limit set at 0.01mg / kg. Three parallel samples were prepared for each formulation. The difference between the result of a single sample and the average value should be less than 0.01mg / kg; otherwise, the sample must be digested and measured again.

[0079] The underwater aging resistance of the polyurea grouting fluids in Examples 1-4 and Comparative Examples 1-3 was determined using the following methods: The underwater aging resistance retention rate was determined based on the elongation at break test. Dumbbell-shaped samples, cured for 7 days, were immersed in a 25°C deionized water bath for 168 hours. After immersion, the samples were removed, surface moisture was wiped off, and the elongation at break was immediately measured according to GB / T 528-2009 standard. Five parallel samples were prepared for each mix design. The difference between the retention rate of a single sample and the average value should be less than 5%; otherwise, the test must be repeated.

[0080] The core mechanical properties test results of the polyurea grouting fluids in Examples 1-4 and Comparative Examples 1-3 are shown in Table 2, and other test results are shown in Table 3.

[0081] Table 2 Test results of core mechanical properties of polyurea grout

[0082] Table 3 Other test results of polyurea grout

[0083] Analysis of the performance test prediction results shows that, in Examples 1-4 of this invention, the high-elasticity polyurea grouting fluid meets the requirements of ≥600% elongation at break, ≥3.6MPa underwater bond strength, and no detection of heavy metal tin after curing at 25℃ for 7 days. Simultaneously, it exhibits ≥92% retention rate after 50 shear cycles and ≥88% retention rate of underwater aging resistance, thus meeting the requirements for seepage prevention, deformation resistance, and long-term service of underwater expansion joints in hydraulic structures. In Example 2, increasing the amount of composite catalyst shortened the gel time of the grouting fluid from 28-32 min in Example 1 to 22-25 min, significantly improving curing efficiency and making it suitable for rapid construction scenarios such as emergency repairs. In Example 3, increasing the amount of silane coupling agent KH-550 had virtually no effect on the elongation at break and gel time of the grouting fluid, but increased the underwater bond strength to ≥4.0MPa, significantly enhancing the interfacial bonding performance. In Example 4, increasing the prepolymerization temperature and shortening the reaction time did not significantly affect the core mechanical properties of the grout, although the gel time was slightly shortened, which improved production efficiency while maintaining performance. In Comparative Example 1, without the addition of PPG-PDMS-PEO dual flexible block glycol, and instead using a single PPG glycol, the grout's elongation at break was only 450%~480%, the underwater bond strength decreased to 1.8~2.2 MPa, and the retention rate after 50 shear cycles was only 65%~70%, unable to withstand the repeated deformation of underwater expansion joints and failing to meet engineering application requirements. In Comparative Example 2, without the addition of a composite bismuth catalyst, and instead using a dibutyltin dilaurate catalyst, the mechanical properties of the grout were similar to those of the examples, but 0.05~0.1 mg / kg of tin residue was detected in the cured samples, which does not meet the application standards for environmentally friendly materials in water conservancy projects. In Comparative Example 3, instead of using a compound system of IPDI and MDI, a single IPDI was used as the isocyanate component. The core properties of the grout, such as elongation at break and underwater bonding strength, all decreased to varying degrees. At the same time, the raw material procurement cost increased by more than 20%, making it uneconomical for industrial-scale promotion.

[0084] As can be seen from the above embodiments, compared with the existing technology that uses a single flexible chain (polyether / polysiloxane) modification, the present invention uses a dual flexible block diol (also known as PPG-PDMS-PEO dual flexible block diol) for synergistic modification, simultaneously introducing molecular-level hydrophilic segments to solve the contradiction of "elasticity and underwater adhesion being mutually exclusive". Compared with the existing technology that uses a single raw material of pure IPDI or pure MDI, the present invention uses an IPDI-MDI compound system, which takes into account both weather resistance and cost controllability, while optimizing reaction activity. Compared with the existing technology that relies on tin-based heavy metal catalysts, the present invention uses a bismuth octoate-triethylenediamine composite environmentally friendly catalyst, which has no heavy metal residue and can precisely control the underwater curing rate. Compared with the existing technology that does not optimize for the dynamic deformation of underwater expansion joints, the present invention achieves triple working condition adaptability of high elasticity and deformation resistance, strong underwater adhesion, and wide temperature range adaptability through component synergistic design, filling the technical gap of polyurea grouting fluid for underwater expansion joints.

[0085] The polyurea grout provided by this invention exhibits a cured elongation at break ≥600%, underwater bond strength ≥3.5MPa, and performance retention ≥92% after shear deformation cycles, demonstrating long-term resistance to dynamic deformation of underwater expansion joints and water erosion. This invention balances environmental friendliness and cost-effectiveness: it replaces toxic tin-based catalysts, leaves no heavy metal residue, and meets environmental standards for water conservancy projects; the IPDI-MDI compound scheme reduces costs by more than 20% compared to pure IPDI-based products, and all components are industrially mature products with stable supply. The polyurea grout provided by this invention has strong construction adaptability: the curing rate is minimally affected by water temperature, with a stable gel time of 25-35 minutes underwater at 10-30℃; the grout viscosity (25℃, 500-800 mPa·s) is suitable for high-pressure grouting, eliminating flow and clogging issues, and is compatible with existing polyurea construction equipment. The polyurea grout provided by this invention has excellent long-term stability: the aliphatic and aromatic isocyanates are compounded together, and with the protection of double flexible segments, it has outstanding resistance to yellowing and water aging, and its underwater service life can reach more than 15 years, far exceeding that of traditional polyurethane grout (less than 8 years).

[0086] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A polyurea grouting solution, characterized in that, The components include the following parts by mass: The composition comprises 40-50 parts isocyanate, 30-35 parts dual flexible block diol, 15-20 parts amino-terminated polyether, 0.5-1 part composite catalyst, and 1-2 parts silane coupling agent; the isocyanate component includes isophorone diisocyanate and diphenylmethane diisocyanate; the dual flexible block diol is a triblock structure formed by the polymerization of polypropylene glycol, polydimethylsiloxane, and polyethylene oxide; the composite catalyst includes bismuth octanoate and triethylenediamine.

2. The polyurea grouting fluid according to claim 1, characterized in that, The mass ratio of isophorone diisocyanate to diphenylmethane diisocyanate is (6~8):(2~4); the NCO group content of isophorone diisocyanate is 29.5%~30.5%, and the NCO group content of diphenylmethane diisocyanate is 33.5%~34.5%.

3. The polyurea grouting fluid according to claim 1, characterized in that, The degree of polymerization of the polypropylene glycol is 20-30, the degree of polymerization of the polydimethylsiloxane is 5-10, and the degree of polymerization of the polyethylene oxide is 2-3; the mass content of the polypropylene glycol segment in the dual flexible block glycol is 65%-80%, and the mass content of the polyethylene oxide segment is ≤10%; the number average molecular weight of the dual flexible block glycol is 2000-2500, and the hydroxyl value is 45-55 mgKOH / g.

4. The polyurea grouting fluid according to claim 1, characterized in that, The terminal amino polyether is polyoxypropylene diamine; the number average molecular weight of the terminal amino polyether is 1900~2100, the primary amino value is 56~60mgKOH / g, and the viscosity at 25℃ is 1000~1500mPa·s.

5. The polyurea grouting fluid according to claim 1, characterized in that, The mass ratio of bismuth octanoate to triethylenediamine is 1~2:

1.

6. The polyurea grouting fluid according to claim 1, characterized in that, The silane coupling agent is γ-aminopropyltriethoxysilane.

7. The method for preparing the polyurea grout according to any one of claims 1 to 6, characterized in that, Includes the following steps: In a protective gas atmosphere, the isocyanate component and the dual flexible block diol are mixed and subjected to a prepolymerization reaction to obtain a modified isocyanate prepolymer. The modified isocyanate prepolymer, amino-terminated polyether, composite catalyst and silane coupling agent are mixed and subjected to a crosslinking reaction to obtain the polyurea grouting solution.

8. The preparation method according to claim 7, characterized in that, The mixing method of the isocyanate component and the biflexible block diol is as follows: the biflexible block diol is heated to a first temperature, and the isocyanate component is added dropwise under stirring; the first temperature is 60~80℃, the stirring speed is 80~100 r / min, and the dropwise addition time is 30~40 min; after the dropwise addition is completed, the temperature is raised to a second temperature for the prepolymerization reaction, the second temperature is 60~80℃, and the holding time of the prepolymerization reaction is 2~3 h. During the prepolymerization reaction, the NCO group content of the reaction system is sampled and detected. When the NCO group content of the reaction system reaches 8.5%~9.5%, the prepolymerization reaction is stopped, and the mixture is cooled to below 40℃ to obtain the modified isocyanate prepolymer.

9. The preparation method according to claim 7, characterized in that, The temperature of the crosslinking reaction is ≤40℃; the prepolymerization reaction is carried out under stirring conditions, with a stirring speed of 80~100r / min and a stirring time of 20~30min.

10. The application of the polyurea grouting fluid according to any one of claims 1 to 6 or the polyurea grouting fluid prepared by the preparation method according to any one of claims 7 to 9 in the treatment of underwater expansion joints.

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