Spraying polyurea material suitable for in-situ spray construction repair of underground pipeline and preparation method thereof

Abstract

This invention discloses a sprayable polyurea material and its preparation method suitable for in-situ spray repair of underground pipelines, belonging to the field of polymer materials and infrastructure repair technology. The material consists of two components, A and B, in a 1:1 volume ratio. Component A includes a bio-based terminal amine polyether, a specifically formulated amine chain extender, and functional additives; component B is a phosphorus-doped isocyanate prepolymer obtained through a two-step prepolymerization reaction of hexamethylene diisocyanate, 4,4'-(pentane-2,2-diyl)diphenol, and acetic acid phenylphosphine. This material innovatively introduces the flame-retardant element phosphorus in a covalent bond form, and, in conjunction with bio-based hydrophobic segments and a rigid benzene ring structure, achieves a bonding strength higher than 1.0 MPa on a damp substrate with a relative humidity ≥90%, a flame retardancy rating of UL94 V-0, high tensile strength and toughness, and excellent corrosion resistance and durability. This solves the core problems of traditional repair materials, such as poor adhesion on damp substrates, lack of flame retardancy, and limited structural reinforcement.

Description

Technical Field

[0001] This invention relates to the field of polymer materials and underground infrastructure repair technology, specifically to a sprayable polyurea material and its preparation method suitable for in-situ spraying repair of underground pipelines. Background Technology

[0002] Many of my country's underground water diversion pipelines, water conservancy culverts, and drainage pipelines have entered their aging service phase. These facilities are mostly constructed of concrete or reinforced concrete. During long-term service, they are subjected to multiple effects, including the load of the overlying soil, internal water pressure, water flow erosion, and corrosive media erosion. As a result, these pipelines (culverts) commonly suffer from defects such as leakage, cracking, corrosion thinning, and structural strength reduction. This not only leads to engineering safety accidents such as water leakage, pipe bursts, voids, and subsidence, but also poses fire hazards due to structural damage (such as the accumulation of methane gas in underground pipelines igniting upon contact with an open flame). These defects seriously threaten the safe operation of urban infrastructure and the safety of the surrounding environment. Therefore, reinforcing and repairing these underground pipelines (culverts) has become crucial to ensuring their long-term safe and stable operation.

[0003] Trenchless repair technology for underground pipelines (culverts) has gradually replaced traditional excavation repair methods and become the mainstream technology in the industry due to its advantages such as high construction efficiency, short cycle, low cost, and minimal impact on surface traffic and the surrounding environment. In-situ spraying, as a core branch of trenchless repair technology, constructs a complete inner lining layer by spraying repair materials onto the inner wall of old pipelines or culverts, achieving structural reinforcement and functional restoration. Its repair effect directly depends on the comprehensive performance of the spraying material.

[0004] Existing in-situ spraying materials are mainly divided into inorganic (such as cement mortar) and organic (such as epoxy resin, polyurethane, and polyurea). Inorganic cement mortar has high strength and can improve the load-bearing capacity of pipelines to a certain extent, but it has poor durability and weak impermeability. It is prone to secondary damage under the scouring and erosion of fluids inside the pipe, and its long-term repair effect is not good. Among organic materials, epoxy resin, polyurethane, and traditional polyurea have excellent durability and impermeability, but they have significant technical defects: First, they are sensitive to the humidity of the substrate. In the humid substrate environment common in underground pipelines, the adhesion is insufficient, and after curing, delamination and peeling are prone to occur. The adhesion weakens significantly during long-term service. Second, they lack flame retardant properties. Underground pipelines (culverts) are prone to accumulating methane, combustible dust, etc., in the confined space. Traditional polyurea is a flammable material. Once a fire occurs, it will accelerate the spread of fire and expand the disaster loss. Third, traditional organic spraying materials focus more on the repair of impermeability function and have limited effect on improving the load-bearing capacity of pipeline structures, making it difficult to meet the dual requirements of structural reinforcement and safety protection at the same time.

[0005] To improve the performance of polyurea materials, existing technologies mostly optimize their adhesion or corrosion resistance through modification. For example, the siloxane-modified polyurea material disclosed in Chinese invention patent CN113667086A can improve adhesion to cement mortar, but it still fails to solve the core problems of poor compatibility with damp substrates and lack of flame retardant function. It cannot meet the stringent requirements of underground pipelines (culverts) for repair materials that are "water-insensitive, flame-retardant and safe, and simultaneously provide structural reinforcement and impermeability." Therefore, developing a flame-retardant and water-desensitized polyurea material that maintains high-strength adhesion on damp substrates while possessing excellent flame retardant effects, structural reinforcement capabilities, and impermeability and corrosion resistance is of great significance for promoting the upgrading of trenchless repair technology for underground pipelines (culverts) and ensuring the safe operation of infrastructure. Summary of the Invention

[0006] The purpose of this invention is to provide a sprayable polyurea material suitable for in-situ spraying repair of underground pipelines, which solves the problems of traditional repair materials such as sensitivity to damp substrates, lack of flame retardant properties, and limited structural reinforcement effect, and meets the multiple functional requirements of in-situ spraying repair of underground pipelines.

[0007] The technical solution of the present invention: a sprayable polyurea material suitable for in-situ spraying repair of underground pipelines, comprising component A and component B, wherein the volume ratio of component A to component B is 1:1; Component A, by mass parts, comprises: 60 to 90 parts of bio-based terminal amine polyether, 5 to 15 parts of amine chain extender, and 1 to 5 parts of functional additives. Component B is a phosphorus-doped isocyanate prepolymer, which is prepared by a prepolymerization reaction from the following raw materials in parts by weight: 100-120 parts hexamethylene diisocyanate, 15-25 parts 4,4'-(pentane-2,2-diyl)diphenol, and 8-15 parts acetylated phenylphosphine.

[0008] Furthermore, the bio-based terminal amine polyether is a polyether amine prepared based on vegetable oil, with a number-average molecular weight of 1000-2000, an amine value of 180mgKOH / g-220mgKOH / g, and a bio-based content of ≥70%.

[0009] Furthermore, the amine chain extender is a compound of 4,4'-diaminodicyclohexylmethane and m-phenylenediamine, with a mass ratio of 2:1.

[0010] Furthermore, the functional additives include antioxidant 1076, ultraviolet absorber UV-327, and defoamer BYK-066N, with a mass ratio of 2:1:1.

[0011] Furthermore, polyurea material is sprayed onto the pipe for repair. The performance of the repaired pipe is as follows: it can be applied to a damp substrate with a relative humidity of ≥90% and maintains an adhesion strength of ≥1.0MPa; it can be stably molded in an environment of 5~40℃; the flame retardant rating reaches UL94 V-0; the tensile strength is ≥25MPa and the elongation at break is ≥300%; after immersion in corrosive media for 12 months, its mechanical properties are retained at ≥90%, which can extend the service life of the repaired pipe to more than 30 years.

[0012] A method for preparing a sprayable polyurea material suitable for in-situ spray repair of underground pipelines includes the following steps: Step S1: Preparation of component A: After mixing the bio-based terminal amine polyether with the amine chain extender evenly, add the functional additives and stir until a uniform and transparent material is formed. Step S2, Preparation of Component B: Component B is a phosphorus-doped isocyanate prepolymer, prepared by a two-step prepolymerization method, including: Step S21, First prepolymerization reaction: Hexamethylene diisocyanate and 4,4'-(pentane-2,2-diyl)diphenol are stirred and mixed in a reactor at 35℃~45℃ until completely dissolved to form a transparent and homogeneous material. Then the temperature is raised to 85℃~90℃ to carry out a prepolymerization reaction. When the -NCO content is measured to reach 35%~40%, the reaction is stopped to obtain the first prepolymer. Step S22, Second Prepolymerization Reaction: The first prepolymer is cooled to 25℃~30℃. Under the condition that the system temperature is controlled not to exceed 40℃, acetic acid phenylphosphine is added dropwise at a rate of 80g / min~150g / min. After the addition is completed, the temperature is raised to 85℃~90℃ and the reaction continues for 2 hours~2.5 hours. When the -NCO content is measured to reach 30%~34%, the reaction is stopped to obtain the phosphorus-doped isocyanate prepolymer, which is component B. Step S3, Mixing and Spraying: Mix component A obtained in step S1 and component B obtained in step S2 at a volume ratio of 1:1 using a spraying device, and spray the mixture onto the surface of the substrate.

[0013] Further, in step S21, the 4,4'-(pentane-2,2-diyl)diphenol is pretreated before the first prepolymerization reaction. The pretreatment includes drying it in a vacuum drying oven and grinding it to a particle size of less than 120 mesh.

[0014] Furthermore, the chemical reaction formula of the first prepolymer is as follows: Furthermore, the chemical reaction formula of the phosphorus-doped isocyanate prepolymer is as follows: The beneficial effects of this invention are: 1. The covalent bonding of phosphorus (P) in this invention endows the material with highly efficient and stable flame-retardant properties. Component B undergoes a two-step prepolymerization reaction, in which phosphorus from acetic acid phenyl hypophosphite is covalently embedded into the isocyanate prepolymer molecular chain, forming a stable, inherently flame-retardant structure. From a molecular mechanism perspective, phosphorus forms phosphorus-containing heterocycles or phosphorus-oxygen bonds within the molecular chain. These structures preferentially decompose at high temperatures, releasing flame-retardant intermediates such as phosphoric acid and polyphosphoric acid. These intermediates catalyze the dehydration and carbonization of the material surface, forming a dense, glassy carbonized layer. This layer physically isolates oxygen from the material's interior, blocking the combustion chain reaction; it also inhibits the release of combustible gases, achieving a dual flame-retardant effect of "physical isolation + chemical inhibition." Compared to traditional additive flame retardants, this covalent bonding method avoids the flame-retardant performance degradation caused by flame retardant precipitation and migration, ensuring the material consistently meets the UL94V-0 flame-retardant standard. In the enclosed space of underground pipelines, even when exposed to flammable substances such as methane, the material can effectively suppress the spread of fire and prevent flame dripping, ensuring the fire safety of the enclosed space at the molecular level, and without releasing pollutants, meeting the needs of green and environmentally friendly remediation.

[0015] 2. The rigid benzene ring group of this invention enhances the mechanical properties of the material and the ring stiffness of the pipeline. During the preparation of component B, 4,4'-(pentane-2,2-diyl)diphenol is introduced. The benzene ring in its molecule is covalently embedded in the prepolymer backbone, significantly optimizing the mechanical properties of the material and the ring stiffness of the pipeline. From a molecular structure mechanism perspective, the benzene ring has a planar conjugated structure with high cohesive energy and significant steric hindrance, which enhances the rigidity and regularity of the molecular chain, greatly improving the tensile strength, compressive strength, and other rigidity indicators of the material. Simultaneously, the benzene ring and the flexible segments (such as polyether chains) in the polyurea molecular chain form an alternating rigid-flexible molecular structure. The flexible segments can absorb external force energy through chain segment movement, preventing the material from becoming brittle due to excessive rigidity, achieving a synergistic balance between rigidity and toughness. This molecular structure characteristic gives the lining formed by the material spraying excellent resistance to deformation. When the pipeline is subjected to external loads, the benzene ring in the lining molecular chain can resist circumferential tensile and compressive deformation, while the flexible segments buffer the load impact, thereby significantly improving the ring stiffness of the pipeline. Test data shows that the load-bearing capacity of the pipeline is increased by more than 40% after the material is sprayed. It can effectively share the soil pressure and traffic load borne by the pipeline, delay the deformation of the pipeline structure, and achieve structural reinforcement of concrete pipelines. It solves the pain points of insufficient stiffness and limited structural reinforcement effect of traditional polyurea materials.

[0016] 3. The hydrophobicity of the bio-based terminal amine polyether of this invention eliminates the adverse effects of moisture on the reaction. Component A is a bio-based terminal amine polyether (number average molecular weight 1000-2000, amine value 180mgKOH / g-220mgKOH / g) prepared from vegetable oils. Its molecular structure contains hydrophobic groups such as long-chain alkyl groups, giving the material excellent hydrophobicity. From the perspective of the mechanism of action, the hydrophobic groups of the bio-based terminal amine polyether form a dense hydrophobic barrier on the material surface, which can effectively resist the intrusion of moisture from the damp substrate and avoid side reactions between moisture and the isocyanate (-NCO) groups in component B. Traditional polyurea materials suffer from insufficient hydrophobicity of amino polyethers, making them susceptible to foaming reactions of the -NCO groups caused by moisture. This generates carbon dioxide gas, resulting in a porous structure within the material and a significant decrease in mechanical and adhesive properties. In contrast, the bio-based terminal amino polyether in this invention physically blocks the contact between moisture and the -NCO groups. Simultaneously, it synergizes with the hydrophobic structure in component B prepolymer, further enhancing the overall system's water resistance. Even in a damp environment with relative humidity ≥90%, the material cures without bubbles or pinholes, maintaining a high adhesive strength of over 1.0 MPa. This completely eliminates moisture interference with the reaction process, ensuring stable performance and repair effectiveness in the humid environment of underground pipelines. Detailed Implementation

[0017] The present invention will be further described below with reference to specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0018] A sprayable polyurea material suitable for in-situ spraying repair of underground pipelines includes component A and component B, wherein the volume ratio of component A to component B is 1:1, wherein: Component A, by mass parts, includes: 60 to 90 parts of bio-based terminal amine polyether, 5 to 15 parts of amine chain extender, and 1 to 5 parts of functional additives; Component B is a phosphorus-doped isocyanate prepolymer.

[0019] In component A: the bio-based terminal amine polyether is selected from polyether amines prepared based on vegetable oils, with a number average molecular weight of 1000-2000, an amine value of 180mgKOH / g-220mgKOH / g, and a bio-based content of ≥70%; The chain extender is a compound system of 4,4'-diaminodicyclohexylmethane (PACM) and m-phenylenediamine (MXDA) in a mass ratio of 2:1; The additives include antioxidant 1076, ultraviolet absorber UV-327 and defoamer BYK-066N, with a mass ratio of 2:1:1. Component B is a phosphorus-doped isocyanate prepolymer.

[0020] The phosphorus-doped isocyanate prepolymer is prepared by a two-step prepolymerization reaction of hexamethylene diisocyanate (HDI), 4,4'-(pentane-2,2-diyl)diphenol, and acetophenyl hypophosphite. The mass parts of each component are as follows: hexamethylene diisocyanate (HDI) 100-120 parts, 4,4'-(pentane-2,2-diyl)diphenol 15-25 parts, and acetophenyl hypophosphite 8-15 parts; wherein the purity of HDI is ≥99.5%.

[0021] A method for preparing sprayed polyurea materials includes the following steps: Step S1: Preparation of component A: After mixing the bio-based terminal amine polyether with the amine chain extender evenly, add the functional additives and stir until a uniform and transparent material is formed. Step S2: Preparation of component B: Component B is a phosphorus-doped isocyanate prepolymer, which is prepared by a two-step prepolymerization method; Step S3, Mixing and Spraying: Mix component A obtained in step S1 and component B obtained in step S2 at a volume ratio of 1:1 using a spraying device, and spray the mixture onto the surface of the substrate.

[0022] Step S2 specifically involves: Step S21: Raw material pretreatment: Dry 4,4'-(pentane-2,2-diyl)diphenol in a vacuum drying oven at 110℃ for 5 hours, grind it until the particle size is less than 120 mesh, and seal it for later use; Step S22: Synthesis of the first prepolymer: In a reactor equipped with a stirring device, a temperature control system, a nitrogen protection device, and a circulating cooling system, HDI and pretreated 4,4'-(pentane-2,2-diyl)diphenol are added sequentially. The mixture is stirred and mixed at 35℃~45℃ for 10 hours until completely dissolved, forming a transparent and homogeneous material. Then, the temperature is gradually increased to 85℃~90℃, and the prepolymer is continuously stirred for 3 hours. When the -NCO content reaches 35%~40%, the reaction is stopped to obtain the first prepolymer 1. Step S23: Preparation of phosphorus-doped prepolymer. The temperature of the reactor is reduced to 25℃~30℃ using a circulating cooling system. A quantitative amount of acetic acid phenylphosphine is slowly added dropwise. During the dropwise addition, the system temperature is controlled to not exceed 40℃ using the cooling system. The dropwise acceleration rate is 80g / min~150g / min. After the dropwise addition is completed, the temperature is raised to 85℃~90℃ and the reaction continues for 2 hours~2.5 hours. When the mass content of -NCO reaches 30%~34%, the reaction is stopped using a chemical titration method (di-n-butylamine method). The reactor is then filled with nitrogen and sealed in packaging to obtain the phosphorus-doped isocyanate prepolymer.

[0023] Example 1: The raw materials and specific mass ratios used in this example are shown in Table 1. Table 1: Raw material ratios for Example 1

[0024] 1. The preparation method is as follows: Step S1: According to the proportions in Table 1, add the bio-based terminal amino polyether, PACM, and MXDA sequentially to a clean and dry reactor, and stir at 25°C and 300 r / min for 30 minutes until completely mixed. Then add antioxidant 1076, ultraviolet absorber UV-327, and defoamer BYK-066N, and continue stirring for 60 minutes to form a homogeneous and transparent material. Seal and package under nitrogen protection for later use.

[0025] Step S2: Prepare component B according to the mass ratio in Table 1, specifically as follows: Step S21: Raw material pretreatment. Place 4,4'-(pentane-2,2-diyl)diphenol in a vacuum drying oven at 110℃ and dry for 5 hours. Grind until the particle size is less than 120 mesh and seal for later use.

[0026] Step S22: Synthesis of the first prepolymer. In a reactor equipped with a stirring, temperature control, nitrogen protection, and circulating cooling system, HDI and pretreated 4,4'-(pentane-2,2-diyl)diphenol were added. The mixture was stirred and mixed at 38°C for 10 hours until completely dissolved, forming a transparent and homogeneous system. The temperature was then gradually increased to 88°C, and the reaction was continued with stirring for 3 hours. When the -NCO content of the system reached 35.5%–37.1%, the reaction was stopped, yielding the first prepolymer.

[0027] Step S23: Preparation of phosphorus-doped prepolymer. The temperature of the material in the reactor was lowered to 28°C using a circulating cooling system. While controlling the system temperature to not exceed 40°C, acetic acid phenylphosphine was slowly added dropwise at a rate of 100 g / min. After the addition was complete, the temperature was raised to 88°C and the reaction continued for 2.2 hours. When the -NCO content reached 30.5%–32.2%, the reaction was stopped, and the product was sealed and packaged under a nitrogen atmosphere to obtain component B.

[0028] Step S3: Material mixing and molding. Using high-pressure spraying equipment, components A and B are injected into the mixing chamber at a volume ratio of 1:1. After being fully mixed at 25°C, the mixture is sprayed onto the mold simulating the inner wall of a concrete pipe.

[0029] 2. Performance testing and results: The performance of the sprayed polyurea material prepared by the above method was tested, and the results are shown in Table 2. The results confirm that its comprehensive performance is excellent and fully meets the stringent requirements for in-situ repair of underground pipelines.

[0030] Table 2: Performance test results of the material obtained in Example 1 when sprayed onto a mold simulating the inner wall of a concrete pipe.

[0031] Example 2: This example provides another sprayable polyurea material suitable for in-situ spraying repair of underground pipelines and its preparation method, to verify the implementation effect of the present invention under another set of proportions within the required range.

[0032] Raw material ratio: The raw materials and their specific mass ratios used in this embodiment are shown in Table 3. Table 3: Raw material ratio of Example 2

[0033] In this embodiment, the number average molecular weight of the bio-based terminal amine polyether is 1200, the amine value is about 190 mg KOH / g, and the bio-based content is ≥72%; the HDI can be a commercially available high-purity product (with a purity ≥99.5%).

[0034] 1. Preparation method Step S1: Preparation of Component A. According to the proportions in Table 3, bio-based terminal amine polyether, PACM, and MXDA were added sequentially to a clean and dry reactor and stirred at 28°C and 350 r / min for 40 minutes until completely mixed. Then, antioxidant 1076, ultraviolet absorber UV-327, and defoamer BYK-066N were added, and stirring was continued for 60 minutes to form a homogeneous and transparent material. The material was then sealed and packaged under nitrogen protection to obtain Component A.

[0035] Step S2: Preparation of component B, prepared according to the mass ratio in Table 1, as detailed below. Step S21: Raw material pretreatment: Place 4,4'-(pentane-2,2-diyl)diphenol in a vacuum drying oven at 110℃ and dry for 5 hours. Grind until the particle size is less than 120 mesh and seal for later use.

[0036] Step S22: Synthesis of the first prepolymer: In a reactor equipped with a stirring, temperature control, nitrogen protection, and circulating cooling system, 1HDI and pretreated 4,4'-(pentane-2,2-diyl)diphenol were added. The mixture was stirred and mixed at 42°C for 10 hours until completely dissolved, forming a transparent and homogeneous system. The temperature was then gradually increased to 89°C, and the reaction was continued with stirring for 3 hours. When the -NCO content of the system reached 39.1%–39.9%, the reaction was stopped, yielding the first prepolymer.

[0037] Step S23: Preparation of phosphorus-doped prepolymer. The temperature of the material in the reactor was lowered to 29°C using a circulating cooling system. Under the condition that the system temperature was controlled to not exceed 40°C, 8 kg of acetylated phenylphosphine was slowly added dropwise at a rate of 120 g / min. After the addition was complete, the temperature was raised to 89°C and the reaction continued for 2.3 hours. The reaction was stopped when the -NCO content reached 32.5%–33.9%, and the product was sealed and packaged under a nitrogen atmosphere to obtain component B.

[0038] Step S3: Material mixing and molding. Using high-pressure spraying equipment, the above-prepared component A and component B are injected into the mixing chamber at a volume ratio of 1:1. After being fully mixed at 15°C, the mixture is sprayed onto a mold simulating the inner wall of a concrete pipe (with a relative humidity of 95% on the substrate). After molding, performance testing is performed.

[0039] 2. Performance Testing and Results: The performance of the sprayed polyurea material prepared by the above method was tested, and the results are shown in Table 4. The results indicate that, under another set of proportions within the required range, the material of this invention still exhibits excellent overall performance. Table 4: Performance test results of the material obtained in Example 2 sprayed onto a mold simulating the inner wall of a concrete pipe.

[0040] Example 3: This example provides a third type of sprayable polyurea material suitable for in-situ spraying repair of underground pipelines and its preparation method, to verify the implementation effect of the present invention near the required upper limit ratio.

[0041] Raw material ratio: The raw materials and their specific mass ratios used in this embodiment are shown in Table 5. Table 5: Raw material ratio of Example 3

[0042] 1. The preparation method is as follows: Step S1: Preparation of Component A. According to the proportions in Table 5, bio-based terminal amine polyether, PACM, and MXDA were added sequentially to a clean and dry reactor and stirred at 25°C and 300 r / min for 30 minutes until completely mixed. Then, antioxidant 1076, ultraviolet absorber UV-327, and defoamer BYK-066N were added, and stirring was continued for 60 minutes to form a homogeneous and transparent material. The material was then sealed and packaged under nitrogen protection to obtain Component A.

[0043] Step S2: Preparation of component B, prepared according to the mass ratio in Table 5, specifically as follows: Step S21: Raw material pretreatment. Place 4,4'-(pentane-2,2-diyl)diphenol in a vacuum drying oven at 110℃ and dry for 5 hours. Grind until the particle size is less than 120 mesh and seal for later use.

[0044] Step S22: Synthesis of the first prepolymer. In a reactor equipped with a stirring, temperature control, nitrogen protection, and circulating cooling system, HDI and pretreated 4,4'-(pentane-2,2-diyl)diphenol were added. The mixture was stirred and mixed at 38°C for 10 hours until completely dissolved, forming a transparent and homogeneous system. The temperature was then gradually increased to 88°C, and the reaction was continued with stirring for 3 hours. When the -NCO content of the system reached 35.1%–35.8%, the reaction was stopped, yielding the first prepolymer.

[0045] Step S23: Preparation of phosphorus-doped prepolymer. The temperature of the material in the reactor was lowered to 28°C using a circulating cooling system. Under the condition that the system temperature was controlled to not exceed 40°C, 15 kg of acetylated phenylphosphine was slowly added dropwise at a rate of 100 g / min. After the addition was complete, the temperature was raised to 88°C and the reaction continued for 2.2 hours. When the -NCO content reached 30.1%–30.8%, the reaction was stopped, and the product was sealed and packaged under a nitrogen atmosphere to obtain component B.

[0046] Step S3: Material mixing and molding. Using high-pressure spraying equipment, the above-prepared component A and component B are injected into the mixing chamber at a volume ratio of 1:1. After being fully mixed at 25°C, they are sprayed onto the mold simulating the inner wall of a concrete pipe. After molding, performance testing is performed.

[0047] 2. Performance Testing and Results: The performance of the sprayed polyurea material prepared by the above method was tested, and the results are shown in Table 6. The results indicate that, even at proportions close to the upper limit of the claims, the material of this invention still exhibits excellent overall performance. Table 6: Performance test results of the material obtained in Example 3 sprayed onto a mold simulating the inner wall of a concrete pipe.

[0048] Example 4: Engineering Application Verification. This example verifies the feasibility and long-term service performance of the sprayed polyurea material of the present invention in in-situ spraying repair by actually applying the material of the present invention to pipeline repair.

[0049] The sprayed polyurea material of the present invention has the same formulation as in Example 1, and the construction process is as follows: 1) Pipe pretreatment: Use high-pressure water jet equipment to thoroughly remove dirt, debris, and loose attachments from the inner wall of the pipe. For any obvious local cracks, temporarily seal them with fast-setting epoxy resin. After treatment, ensure the substrate is firm, clean, and damp but without standing water.

[0050] 2) Equipment Commissioning: High-pressure spraying equipment was preheated to operating temperature. The volume ratio of components A and B was set to 1:1, and the spraying pressure was 15 MPa. Construction personnel used a pipeline inspection robot for positioning and continuously sprayed from one end of the pipeline to the other, controlling the spraying speed to 5 m / min to ensure a continuous and uniform lining layer. After spraying, ventilation was maintained inside the pipeline, and curing was carried out at 25℃ for 1 hour before use. Multiple tests were conducted on the repair effect after project completion and during the follow-up period. The results are shown in Table 7.

[0051] Table 7: Test Results of Pipeline Repair Effectiveness in Engineering Applications

[0052] Through multiple embodiments, it can be concluded that the sprayed polyurea material and its construction method provided by this invention can be efficiently and reliably applied to in-situ trenchless repair of underground pipelines. The material not only meets all performance requirements but also demonstrates excellent performance in key aspects such as adhesion to damp substrates, rapid curing, and long-term durability, fully achieving the technical problem intended to be solved by this invention, and possessing outstanding practicality and significant technological advancement.

[0053] The foregoing has provided a detailed description of the sprayable polyurea material and its preparation method suitable for in-situ spraying repair of underground pipelines, as provided by this invention. Specific examples have been used to illustrate the structure and working principle of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of this invention.

Claims

1. A sprayable polyurea material suitable for in-situ spraying repair of underground pipelines, characterized in that: It includes component A and component B, with a volume ratio of 1:1 between component A and component B; Component A, by mass parts, comprises: 60 to 90 parts of bio-based terminal amine polyether, 5 to 15 parts of amine chain extender, and 1 to 5 parts of functional additives. Component B is a phosphorus-doped isocyanate prepolymer, which is prepared by a prepolymerization reaction from the following raw materials in parts by weight: 100-120 parts hexamethylene diisocyanate, 15-25 parts 4,4'-(pentane-2,2-diyl)diphenol, and 8-15 parts acetylated phenylphosphine.

2. The sprayable polyurea material suitable for in-situ spraying repair of underground pipelines according to claim 1, characterized in that: The bio-based terminal amine polyether is a polyether amine prepared based on vegetable oil, with a number average molecular weight of 1000-2000, an amine value of 180mgKOH / g-220mgKOH / g, and a bio-based content of ≥70%.

3. The sprayable polyurea material suitable for in-situ spraying repair of underground pipelines according to claim 1, characterized in that: The amine chain extender is a compound of 4,4'-diaminodicyclohexylmethane and m-phenylenediamine, with a mass ratio of 2:

1.

4. The sprayable polyurea material suitable for in-situ spraying repair of underground pipelines according to claim 1, characterized in that: The functional additives include antioxidant 1076, ultraviolet absorber UV-327, and defoamer BYK-066N, with a mass ratio of 2:1:

1.

5. The sprayable polyurea material suitable for in-situ spraying repair of underground pipelines according to claim 1, characterized in that: Polyurea material is sprayed onto pipes for repair. The material's properties are as follows: it can be applied to damp substrates with relative humidity ≥90% and maintains an adhesion strength of ≥1.0MPa; it can be stably molded in environments ranging from 5℃ to 40℃; its flame retardant rating reaches UL94 V-0; its tensile strength is ≥25MPa and its elongation at break is ≥300%; after immersion in corrosive media for 12 months, its mechanical properties are retained at ≥90%, which can extend the service life of the repaired pipes to more than 30 years.

6. A method for preparing a sprayable polyurea material suitable for in-situ spraying repair of underground pipelines as described in any one of claims 1 to 5, characterized in that: Includes the following steps, Step S1: Preparation of component A: After mixing the bio-based terminal amine polyether with the amine chain extender evenly, add the functional additives and stir until a uniform and transparent material is formed. Step S2, Preparation of Component B: Component B is a phosphorus-doped isocyanate prepolymer, prepared by a two-step prepolymerization method, including: Step S21, First Prepolymerization Reaction: Hexamethylene diisocyanate and 4,4'-(pentane-2,2-diyl)diphenol are stirred and mixed in a reactor at 35℃~45℃ until completely dissolved to form a transparent and homogeneous material. Then, the temperature is raised to 85℃~90℃ to carry out a prepolymerization reaction. When the mass content of -NCO reaches 35%~40%, the reaction is stopped to obtain the first prepolymer. Step S22, Second Prepolymerization Reaction: The first prepolymer is cooled to 25℃~30℃. Under the condition that the system temperature is controlled not to exceed 40℃, acetic acid phenylphosphine is added dropwise at a rate of 80g / min~150g / min. After the addition is completed, the temperature is raised to 85℃~90℃ and the reaction continues for 2 hours~2.5 hours. When the -NCO content is measured to reach 30%~34%, the reaction is stopped to obtain the phosphorus-doped isocyanate prepolymer, which is component B. Step S3, Mixing and Spraying: Mix component A obtained in step S1 and component B obtained in step S2 at a volume ratio of 1:1 using a spraying device, and spray the mixture onto the surface of the substrate.

7. The method for preparing a sprayed polyurea material suitable for in-situ spraying repair of underground pipelines according to claim 6, characterized in that: In step S21, the 4,4'-(pentane-2,2-diyl)diphenol is pretreated before the first prepolymerization reaction. The pretreatment includes drying it in a vacuum drying oven and grinding it to a particle size of less than 120 mesh.

8. The method for preparing a sprayed polyurea material suitable for in-situ spraying repair of underground pipelines according to claim 6, characterized in that: The chemical reaction formula of the first prepolymer is as follows: 。 9. The method for preparing a sprayed polyurea material suitable for in-situ spraying repair of underground pipelines according to claim 6, characterized in that: The chemical reaction formula for the phosphorus-doped isocyanate prepolymer is as follows: 。

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