Solventless fiber reinforced sealant for repairing stainless steel tank and its application method

Abstract

The application discloses a solvent-free fiber-reinforced sealant for plugging of a stainless steel tank body and an application method thereof. The sealant is a two-component high-temperature-resistant reactive solvent-free system, which is prepared from 49-58% of A component and 42-51% of B component in the total mass of the sealant. The A component contains the following raw materials in mass percentage: 80-85% of high-temperature-resistant epoxy resin and 15-20% of modified carbon fiber. The B component contains the following raw materials in mass percentage: 70-80% of aromatic amine and phenolic amine compounded curing agent, 3-7% of 2-methyl imidazole and 18-25% of butyl glycidyl ether. The solvent-free fiber-reinforced sealant has a bonding strength of greater than or equal to 15 MPa, an operation time of 30-45 min, and a sealant coating which is free of leakage, has an intact sealant layer, excellent hardness and corrosion resistance under the working conditions of high temperature above 250 DEG C, strong corrosion and salt spray.

Description

Technical Field

[0001] This invention belongs to the field of sealant material technology, specifically relating to a solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks and its application method. It is suitable for emergency sealing and long-term repair of stainless steel tanks such as desulfurization towers and high-temperature chemical storage tanks under high-temperature and strong corrosion conditions, and is especially suitable for harsh service environments such as high temperatures of 250°C and above, strong acids and alkalis, and salt spray. Background Technology

[0002] Stainless steel tanks are widely used in industrial applications such as desulfurization and high-temperature chemical reactions. However, leaks are prone to occur at welds and pitting areas, requiring the use of sealants for repair. Under high-temperature conditions of 250℃ and above, existing sealants have significant technical shortcomings: solvent-based sealants leave residual pores after curing, resulting in insufficient density and susceptibility to cracking and leakage at high temperatures; single-component silicone sealants have low bond strength (shear strength ≤2MPa) and are not resistant to strong acid and alkali corrosion; ordinary two-component sealants often use a single curing agent, making it difficult to balance curing efficiency and high-temperature stability, leading to problems such as thermal aging and bond strength attenuation during use, thus failing to meet long-term service requirements.

[0003] While technologies such as laser cladding and coating protection can improve the corrosion resistance of substrates, they are not suitable for emergency leak sealing of tanks in service. Existing solvent-free sealants also generally suffer from poor adaptability to wide temperature ranges, unreasonable working time, and insufficient interfacial bonding strength. Therefore, the development of a two-component sealant that is high-temperature resistant, solvent-free, has high bonding strength, and is easy to apply has become an urgent need in the field of leak sealing and repair of stainless steel tanks under high-temperature conditions.

[0004] For example, patent document CN105647453A discloses an anti-corrosion and antibacterial epoxy sealant, comprising component A and component B, with a weight ratio of A:B = 4:1. Component A comprises 100 parts of bisphenol A type epoxy resin, 5 parts of epoxy silane coupling agent KH-560, 10 parts of dry-process fumed silica, 5 parts of 2,3-epoxypropyltrimethylammonium chloride, and 5 parts of epoxy morpholine quaternary ammonium salt. Component B comprises 50 parts of amino-terminated polypyrrolidone prepolymer, 5 parts of phenolic amine, and 5 parts of amino silane coupling agent KH-550. However, this sealant is not intended for leak sealing and repair of stainless steel tanks. Summary of the Invention

[0005] This invention aims to provide a solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks and its application method, in order to solve the technical problems of existing sealants being prone to aging, leakage, and insufficient bonding strength under high-temperature conditions, and to achieve a solvent-free, environmentally friendly, wide-temperature-range stable, and convenient sealing and repair effect.

[0006] To achieve the above objectives, the present invention adopts the following specific technical solution: The solvent-free fiber-reinforced sealant for sealing stainless steel tanks of the present invention is a two-component, high-temperature resistant, reactive, solvent-free system, composed of component A (49%–58% by weight of the total sealant) and component B (42%–51% by weight of the total sealant). Component A (matrix adhesive) comprises the following raw materials by mass fraction: 80%–85% high-temperature resistant epoxy resin and 15%–20% modified carbon fiber; The B component (cured functional system) contains the following raw materials by mass fraction: 70%–80% aromatic amine and phenolic amine compound curing agent, 3%–7% 2-methylimidazole (curing accelerator), and 18%–25% butyl glycidyl ether, to achieve curing control and performance optimization. The high-temperature resistant epoxy resin is composed of E-54 epoxy resin (CAS No. 61788-97-4) and bisphenol A / F type liquid epoxy resin (such as Dow DER 351 or Hunan Sailway New Materials YLF-1700F) with an epoxy equivalent of 165-183 g / eq, mixed at a mass ratio of 1:(0.5-1.2). The modified carbon fiber is a short-cut carbon fiber modified with silane coupling agent KH-550, with a modulus of 200-300 GPa, a diameter of 4-10 μm, and a length of 4-6 mm. The modification method of the modified carbon fiber is as follows: the short-cut carbon fiber is impregnated in silane coupling agent KH-550 at 80-100℃ for 2-3 hours and then vacuum dried to obtain the modified carbon fiber. The modified carbon fiber has a 15%-20% higher hydroxyl content on its surface, which can enhance the interfacial bonding force with epoxy resin. The aromatic amine and phenolic amine compound curing agent is a compound of aromatic amine DDM (4,4-diaminodiphenylmethane) and phenolic amine curing agent T-31 at a mass ratio of 1:(0.8~1.2). The active hydrogen equivalent is 85~95g / eq, which can achieve complete curing at room temperature of 25℃ for 24h, balancing curing speed and curing quality. The epoxy value of the butyl glycidyl ether is 0.5 to 0.6 eq / 100g (determined according to GB / T 1677-2008).

[0007] Preferably, the mass ratio of the 2-methylimidazole to the aromatic amine and phenolic amine compound curing agent is controlled at 1:(12-18); the synergistic effect of 2-methylimidazole and butyl glycidyl ether can adjust the viscosity of the sealant to 5000-8000 mPa·s (measured at 25°C according to GB / T 2794-2022 "Determination of Viscosity of Adhesives"), and can stabilize the workable time of the adhesive at 25°C to 30-45 min, which is suitable for the on-site construction rhythm.

[0008] Preferably, component A further includes 0-2% by mass of an organosilane dispersant (e.g., Momentive SILQUEST A-1230 nonionic silane dispersant) to improve the dispersion uniformity of chopped carbon fibers in epoxy resin, prevent fiber agglomeration, and not affect the core performance of the sealant.

[0009] The application method of the solvent-free fiber-reinforced sealant for sealing stainless steel tanks described in this invention uses alkali-free glass fiber cloth with a thickness of 0.1 to 0.3 mm as a composite reinforcing carrier.

[0010] More specifically, the application method of the solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks according to the present invention includes the following steps: (1) Rubber compound preparation: Add component B to component A, stir for 5 to 10 minutes until the system is homogeneous, let stand for at least 1 minute to release the air, and obtain the mixed rubber solution; (2) Leakage sealing construction: The mixed adhesive is compacted and filled into the leaking part of the stainless steel tank. Then, 1 to 3 layers of alkali-free glass fiber cloth are laid on the surface of the leaking part in sequence. The surface of each layer of alkali-free glass fiber cloth should be coated with the mixed adhesive and ensure that it is fully soaked. (3) Curing and maintenance: Curing naturally at room temperature for at least 24 hours until the adhesive layer is dense and free of bubbles. After curing, the stainless steel tank can be directly put into use under working conditions of -40 to 250℃.

[0011] Preferably, before construction, the leaking part of the stainless steel tank and the surrounding 50mm area should be degreased, cleaned, and roughened by grinding; the grinding pattern should be intersecting at 45° to 60°, and the roughness should be controlled at Ra3.2 to 6.3μm; after secondary cleaning, subsequent construction should be carried out only after there are no volatile residues on the surface to prevent secondary oxidation or contamination of the substrate from affecting the bonding effect.

[0012] Preferably, in step (1), 0-2% of an organosilane dispersant is first added to component A, and the mixture is stirred at a speed of 300-500 r / min to form a homogeneous mixture, and then component B is added.

[0013] Preferably, in step (2), the alkali-free glass fiber cloth is soaked in acetone for 10-15 minutes and then laid on the leaking part; this method can make the alkali-free glass fiber cloth and the sealant layer form an integrated structure, and the tensile strength of the leaking part is increased by more than 30% and the resistance to media erosion is increased by more than 25%.

[0014] Preferably, in step (2), for pitting corrosion leakage, the diameter of the fiber cloth should extend at least 20 mm beyond the edge of the pit, and then a 1-2 mm thick mixed adhesive should be applied to its surface; for weld or crack leakage, a groove 5-8 mm wide and 3-5 mm deep is first opened at the leakage location, the mixed adhesive is compacted and filled into the groove, and then 2-3 layers of alkali-free fiberglass cloth are laid in sequence. More preferably, the overlap width of each layer of alkali-free fiberglass cloth is ≥20 mm, and the total adhesive layer thickness is controlled at 3-5 mm.

[0015] Compared with the prior art, the present invention has the following technical advantages: Firstly, it innovatively solves the problem of high-temperature service: This invention adopts a solvent-free system design, which is non-porous and highly dense after curing, effectively avoiding the problem of high-temperature cracking and leakage of solvent-based sealants, and combining environmental protection and reliability; through the synergistic effect of DDM and T-31 compound curing agent and modified carbon fiber, it breaks through the high-temperature service limit of existing solvent-free sealants, and can stably serve in a wide temperature range of -40℃ to 250℃, which is significantly better than the high-temperature performance of ThreeBond-1530C (long-term service at 150℃) and existing silicone sealants, filling the technical gap of solvent-free leak-stopping sealants for high-temperature conditions of 250℃ and above.

[0016] Secondly, the invention innovatively enhances bonding strength and corrosion resistance: By using modified carbon fiber and alkali-free glass fiber cloth for composite reinforcement, combined with a silane coupling agent pretreatment process, the bonding strength of the sealant is ≥15MPa, which is significantly higher than that of existing solvent-free sealants (maximum 12.6MPa) and single-component silicone sealants (≤2MPa). At the same time, it has excellent resistance to strong acids, alkalis and salt spray corrosion. After 1000h salt spray test, there was no red rust or cracking, making it suitable for the highly corrosive working conditions of stainless steel tanks.

[0017] Third, innovative optimization of construction adaptability: The operable time after mixing components A and B is precisely controlled to be 30-45 minutes, which is suitable for the pace of emergency leak plugging construction on site and solves the technical problem of unreasonable operable time of existing products; at the same time, the construction process is simple, no complicated equipment is required, and it can be put into use after 24 hours of natural curing at room temperature. This is different from the technical shortcomings of existing products that require high temperature curing and complicated construction, thus improving the feasibility of on-site application.

[0018] Fourth, feasibility assurance: The raw materials of this invention are all commonly used industrial materials, which are easy to purchase and have controllable costs; the preparation and application of the adhesive are simple, requiring no additional special equipment, and can quickly achieve large-scale production and on-site application, without technical barriers or implementation difficulties. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1 The solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks is a two-component, high-temperature resistant, reactive, solvent-free system, composed of 53.5% component A and 46.5% component B by mass fraction. Component A (matrix adhesive) contains the following raw materials by mass fraction: 84.1% high-temperature resistant epoxy resin (a mixture of E-54 and Dow DER351 bisphenol A / F type epoxy resin in a 1:1 mass ratio) and 15.9% modified carbon fiber; The short-cut carbon fiber uses HTA40 F13 12K carbon fiber filaments from Toho Japan. These filaments are immersed in an ethanol solution of silane coupling agent KH-550 (CAS No. 919-30-2) (KH-550 mass concentration is 2wt%) at 90℃ for 2.5h. After being removed and vacuum dried, the modified carbon fiber is obtained. Component B (curing functional system) contains the following raw materials by mass fraction: 75.5% of a curing agent compound made by blending DDM and T-31 in a 1:1 mass ratio, 4.5% of 2-methylimidazole (CAS No. 693-98-1) and 20% of butyl glycidyl ether (CAS No. 2426-08-6). The curing rate is controlled and the overall performance of the adhesive layer is optimized through the synergistic effect of the above components.

[0021] The application method of this solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks includes the following steps: (1) Substrate pretreatment: Use an angle grinder to grind the leaking part of the stainless steel tank and the surrounding 50mm range to thoroughly remove oxide scale and oil stains. Open a groove with a width of 5mm and a depth of 3mm. After cleaning the impurities in the groove, grind it to roughen it. The grinding lines are intersecting at 45° and the roughness is controlled at Ra4.5μm. Wipe it cleaned twice with acetone. After the solvent has completely evaporated, it is ready for use to ensure that the substrate is free from secondary pollution.

[0022] (2) Adhesive preparation: Before premixing, add Momentive SILQUEST A-1230 nonionic silane dispersant, accounting for 0.5% of the total mass of component A, and stir at a gradient speed of 300-500 r / min. For the first 2 minutes, stir at a low speed of 300 r / min to disperse the agglomerates, and for the next 2 minutes, stir at a high speed of 500 r / min to homogenize. Add component B and continue stirring for 6 minutes until the system is homogeneous. Let stand for 1.5 minutes to remove air, and the mixed adhesive solution is obtained. The workable time of the mixed adhesive solution at 25℃ is 38 minutes. (3) Leakage sealing construction: Soak the alkali-free fiberglass cloth in acetone for 12 minutes and set aside; compact the mixed adhesive into the groove, lay one layer of alkali-free fiberglass cloth, apply a layer of mixed adhesive with a thickness of about 2 mm evenly on the surface of the fiber cloth, lay another layer of alkali-free fiberglass cloth, and apply a layer of mixed adhesive with a thickness of about 2 mm evenly on the surface of the fiber cloth (a total of 2 layers of fiber cloth); the overlap width of each layer of fiber cloth is 25 mm, and ensure that the fiber cloth is completely soaked without gaps. The total adhesive layer thickness is controlled to be 4 mm, and the surface is leveled and compacted.

[0023] (4) Curing and maintenance: Curing naturally at room temperature for 24 hours, the adhesive layer is dense and free of bubbles; after curing, the stainless steel tank can be put into the dilute sulfuric acid medium at 300℃ and pH=2~3 for continued use.

[0024] Example 2 The solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks is a two-component, high-temperature resistant, reactive, solvent-free system, composed of 56.7% component A and 43.3% component B by mass fraction. Component A (matrix adhesive) contains the following raw materials by mass fraction: 84.7% high-temperature resistant epoxy resin (a mixture of E-54 and YLF-1700F bisphenol A / F type epoxy resin from Hunan Servi New Material Technology Co., Ltd. at a mass ratio of 1:0.8) and 15.3% modified carbon fiber; The short-cut carbon fiber uses HTA40 F13 12K carbon fiber filaments from Toho Japan. These filaments are immersed in an ethanol solution of silane coupling agent KH-550 (CAS No. 919-30-2) (KH-550 mass concentration is 2wt%) at 85℃ for 2.5h. After being removed and vacuum dried, the modified carbon fiber is obtained. Component B (curing functional system) contains the following raw materials by mass fraction: 74% curing agent compound made by blending DDM and T-31 in a 1:1 mass ratio, 5.3% 2-methylimidazole (CAS No. 693-98-1) and 20.7% butyl glycidyl ether (CAS No. 2426-08-6). The curing rate is controlled and the overall performance of the adhesive layer is optimized through the synergistic effect of the above components.

[0025] The application method of this solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks includes the following steps: (1) Substrate pretreatment: Use an angle grinder to grind the leaking part of the stainless steel tank and the surrounding 50mm range to thoroughly remove oxide scale and oil stains. The grinding lines are intersecting at 45°, and the roughness is controlled at Ra5.2μm. Wipe clean with acetone twice, and wait for the solvent to completely evaporate before use to ensure that the substrate is free from secondary pollution.

[0026] (2) Adhesive preparation: Before premixing, add Momentive SILQUEST A-1230 nonionic silane dispersant, accounting for 0.3% of the total mass of component A, and stir at a gradient speed of 300-500 r / min. For the first 2 minutes, stir at a low speed of 300 r / min to disperse the agglomerates, and for the next 3 minutes, stir at a high speed of 500 r / min to homogenize. Add component B and continue stirring for 8 minutes until the system is homogeneous. Let stand for 2 minutes to remove air, and the mixed adhesive solution is obtained. The workable time of the mixed adhesive solution at 25℃ is 32 minutes. (3) Leakage sealing construction: Soak the alkali-free glass fiber cloth in acetone for 15 minutes and set aside; fully fill the pitted pores with the mixed adhesive, then lay a circular fiber cloth with a diameter 30 mm beyond the edge of the pit, apply a 1.5 mm thick mixed adhesive to the surface of the fiber cloth, ensure that the fiber cloth is completely soaked without gaps, and level and compact the surface.

[0027] (4) Curing and maintenance: Natural curing at room temperature for 24 hours, the adhesive layer is dense and free of bubbles; after curing, the stainless steel tank can be put into alkaline medium at 250℃ and pH=10~12 and in a 24-hour cycle of alternating wet and dry conditions (soaking for 12 hours + drying for 12 hours) for continued use.

[0028] Example 3 The solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks is a two-component, high-temperature resistant, reactive, solvent-free system, composed of 52.5% component A and 47.5% component B by mass fraction. Component A (matrix adhesive) contains the following raw materials by mass fraction: 82% high-temperature resistant epoxy resin (a mixture of E-54 and Dow DER351 bisphenol A / F type epoxy resin at a mass ratio of 1:0.6) and 18% modified carbon fiber; The short-cut carbon fiber uses HTA40 F13 12K carbon fiber filaments from Toho, Japan. The filaments are immersed in an ethanol solution of silane coupling agent KH-550 (CAS No. 919-30-2) (KH-550 mass concentration is 1.0wt%) at 100℃ for 3 hours. After being removed and vacuum dried, the modified carbon fiber is obtained. Component B (curing functional system) contains the following raw materials by mass fraction: 71.4% curing agent compound made by blending DDM and T-31 in a mass ratio of 1:0.9, 4.8% 2-methylimidazole (CAS No. 693-98-1), and 23.8% butyl glycidyl ether (CAS No. 2426-08-6). The curing rate is controlled and the overall performance of the adhesive layer is optimized through the synergistic effect of the above components.

[0029] The application method of this solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks includes the following steps: (1) Substrate pretreatment: Use an angle grinder to grind the cracks and leaks in the stainless steel desulfurization tower to completely remove the oxide scale and oil stains. Open a groove with a width of 8mm and a depth of 5mm. After cleaning the impurities in the groove, grind it to roughen it. The grinding lines are intersecting at 60°. The roughness is controlled at Ra6.0μm. Wipe it cleaned twice with acetone. After the solvent has completely evaporated, it is ready for use to ensure that the substrate is free from secondary pollution.

[0030] (2) Adhesive preparation: Before premixing, add 1.5% Momentive SILQUEST A-1230 nonionic silane dispersant to component A and stir at a gradient speed of 300-500 r / min. For the first 1 minute, stir at a low speed of 300 r / min to disperse the agglomerates, and for the next 3 minutes, stir at a high speed of 500 r / min to homogenize. Add component B and continue stirring for 7 minutes until the system is homogeneous. Let stand for 1 minute to remove air, and the mixed adhesive solution is obtained. The workable time of the mixed adhesive solution at 25℃ is 42 minutes. (3) Leakage sealing construction: Soak the alkali-free fiberglass cloth in acetone for 15 minutes and set aside; compact the mixed adhesive into the groove, lay one layer of alkali-free fiberglass cloth, apply a layer of mixed adhesive with a thickness of about 1.5 mm evenly on the surface of the fiberglass cloth, lay another layer of alkali-free fiberglass cloth, apply a layer of mixed adhesive with a thickness of about 1.5 mm evenly on the surface of the fiberglass cloth, lay another layer of alkali-free fiberglass cloth, and apply a layer of mixed adhesive with a thickness of about 2 mm evenly on the surface of the fiberglass cloth (a total of 3 layers of fiberglass cloth); the overlap width of each layer of fiberglass cloth is 22 mm, and ensure that the fiberglass cloth is completely soaked without gaps. The total adhesive layer thickness is controlled to be 5 mm, and the surface is leveled and compacted.

[0031] (4) Curing and maintenance: Curing naturally at room temperature for 24 hours, the adhesive layer is dense and free of bubbles; after curing, the stainless steel tank can be put into use in a 320℃, neutral salt spray environment.

[0032] Example 4 The solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks is a two-component, high-temperature resistant, reactive, solvent-free system, composed of 56.7% component A and 43.3% component B by mass fraction. Component A (matrix adhesive) contains the following raw materials by mass fraction: 85% high-temperature resistant epoxy resin (a mixture of E-54 and YLF-1700F bisphenol A / F type epoxy resin from Hunan Servi New Material Technology Co., Ltd. at a mass ratio of 1:1.2) and 15% modified carbon fiber; The short-cut carbon fiber uses HTA40 F13 12K carbon fiber filaments from Toho Japan. These filaments are immersed in an ethanol solution of silane coupling agent KH-550 (CAS No. 919-30-2) (KH-550 mass concentration is 1.5wt%) at 90℃ for 2.5h. After being removed and vacuum dried, the modified carbon fiber is obtained. Component B (curing functional system) contains the following raw materials by mass fraction: 76% curing agent compound made of DDM and T-31 in a 1:1 mass ratio, 5.3% 2-methylimidazole (CAS No. 693-98-1) and 18.7% butyl glycidyl ether (CAS No. 2426-08-6). The curing rate is controlled and the overall performance of the adhesive layer is optimized through the synergistic effect of the above components.

[0033] The preparation and application method of the solvent-free fiber-reinforced sealant for sealing stainless steel tanks in Example 4 is basically the same as in Example 2, except that the proportions of high-temperature resistant epoxy resin (mixed with YLF-1700F bisphenol A / F type epoxy resin from Hunan Servi New Material Technology Co., Ltd. at a mass ratio of 1:1.2) and modified carbon fiber in component A (matrix adhesive) are adjusted to 50% and 7.7% respectively. Component A accounts for 57.7% of the total mass of the sealant, and component B accounts for 42.3% of the total mass of the sealant. The operable time at 25°C is 30 min, and the viscosity of the adhesive is 7800 mPa·s (measured according to GB / T 2794-2022), making it suitable for rapid emergency sealing scenarios.

[0034] Comparative Example 1 Compared to Example 2, Comparative Example 1 only adjusted component A to 56.7% high-temperature resistant epoxy resin, excluding chopped carbon fibers; the composition and proportion of component B remained unchanged (43.3%). All other raw materials and application methods were the same as in Example 2.

[0035] Comparative Example 2 Compared with Example 2, Comparative Example 2 only replaced the DDM and T-31 compound curing agent in component B with a common fatty amine curing agent (ethylenediamine), while the other raw materials and application methods were the same as in Example 2.

[0036] Comparative Example 3 Compared with Example 2, Component B of Comparative Example 3 contains the following raw materials by mass fraction: 74% of a curing agent compound made of DDM and T-31 in a mass ratio of 1:1, 5.3% of 2-methylimidazole, and 20.7% of ethyl acetate; the remaining raw materials, proportions, and application methods are the same as in Example 2.

[0037] Test Experiment Example 1. The sealants prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to performance testing. The bonding strength was determined according to GB / T14074-2017 "Test Methods for Adhesives and Resins for Wood Industry" (this standard is currently valid and can be applied to the bonding performance test of this sealant). The viscosity was determined according to GB / T 2794-2022 "Determination of Viscosity of Adhesives" (25℃). The workable time was determined by observing the curing state of the adhesive when left to stand at room temperature. The test results are shown in Table 1.

[0038] 2. All samples were applied to 100mm×100mm×10mm stainless steel test blocks (simulating tank defects) and run for 500 hours under alkaline medium at 250℃ and pH=10~12 with a 24-hour cycle of alternating dry and wet conditions to test the sealing performance and adhesive layer condition. The results are shown in Table 1.

[0039] 3. Neutral salt spray resistance test: According to ISO9227:2017 standard, a 3.5% NaCl aqueous solution was used to conduct a 1000-hour salt spray test at (35±2)℃ to evaluate the integrity of the adhesive layer. The test results are shown in Table 2.

[0040] Table 1. Performance and working condition test results of sealants in Examples 1-4 and Comparative Examples 1-3 Table 2. Salt spray resistance test results of Examples 1-4 and Comparative Examples 1-3 Analysis of the test results in Tables 1 and 2 shows that the sealant prepared in Examples 1 to 4 of this invention has a bonding strength ≥15MPa, an operable time of 30 to 45 minutes, and the sealant coating remains leak-free and intact under high temperature (above 250℃), strong corrosion, and salt spray conditions. It exhibits excellent hardness and corrosion resistance, is fully adaptable to the on-site construction schedule, effectively prevents the intrusion of corrosive media, and significantly extends the service life of stainless steel tanks. It is especially suitable for leak sealing and repair operations in harsh conditions such as high-temperature chemical processing and desulfurization.

[0041] Comparative Example 1, due to the lack of short-cut carbon fiber reinforcement, had a bonding strength of only 8.2 MPa, which is far lower than the core index of ≥15 MPa of this invention. The adhesive layer was prone to microcracks and had poor resistance to deformation, eventually resulting in slight leakage.

[0042] Comparative Example 2 used ethylenediamine to replace the compound curing agent, which significantly reduced the high-temperature stability and shortened the working time to 20 minutes, exceeding the on-site construction adaptability range of 30-45 minutes. The adhesive layer suffered severe thermal aging, yellowing, and brittleness, and obvious leakage occurred.

[0043] In Comparative Example 3, due to the addition of ethyl acetate solvent, residual bubbles remained after the adhesive layer cured. At high temperature, the bubbles burst, causing local cracking, which was also accompanied by slight leakage.

Claims

1. A solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks, characterized in that, It is a two-component, high-temperature resistant, reactive, solvent-free system, composed of component A (49%–58% by weight of the total sealant) and component B (42%–51% by weight of the total sealant). Component A comprises the following raw materials by mass fraction: 80%–85% high-temperature resistant epoxy resin and 15%–20% modified carbon fiber; Component B comprises the following raw materials by mass fraction: 70%–80% aromatic amine and phenolic amine compound curing agent, 3%–7% 2-methylimidazole, and 18%–25% butyl glycidyl ether; The high-temperature resistant epoxy resin is a mixture of E-54 epoxy resin and bisphenol A / F type liquid epoxy resin with an epoxy equivalent of 165-183 g / eq at a mass ratio of 1:(0.5-1.2); the modified carbon fiber is a short-cut carbon fiber modified with silane coupling agent KH-550.

2. The solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks according to claim 1, characterized in that, The modified carbon fiber has a modulus of 200–300 GPa, a diameter of 4–10 μm, and a length of 4–6 mm.

3. The solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks according to claim 1, characterized in that, The modification method of the modified carbon fiber is as follows: short-cut carbon fibers are impregnated in silane coupling agent KH-550 at 80-100℃ and kept at the temperature for 2-3 hours, and then vacuum dried to obtain the modified carbon fiber.

4. The solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks according to claim 1, characterized in that, The aromatic amine and phenolic amine compound curing agent is prepared by compounding aromatic amine DDM and phenolic amine curing agent T-31 at a mass ratio of 1:(0.8~1.2), and the active hydrogen equivalent is 85~95g / eq; the mass ratio of 2-methylimidazole to the aromatic amine and phenolic amine compound curing agent is controlled at 1:(12~18).

5. The solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks according to claim 1, characterized in that, Component A also includes 0-2% of an organosilane dispersant by mass of the total component A.

6. The application method of the solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks according to any one of claims 1 to 5, characterized in that, It is paired with alkali-free glass fiber cloth with a thickness of 0.1 to 0.3 mm as a composite reinforcing carrier.

7. The application method of the solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks according to claim 6, characterized in that, Includes the following steps: (1) Rubber compound preparation: Add component B to component A, stir for 5 to 10 minutes until the system is homogeneous, let stand for at least 1 minute to release the air, and obtain the mixed rubber solution; (2) Leak sealing construction: The mixed adhesive is compacted and filled into the leaking part of the stainless steel tank, and then 1 to 3 layers of alkali-free glass fiber cloth are laid on the surface of the leaking part in sequence; (3) Curing and maintenance: Curing naturally at room temperature for at least 24 hours until the adhesive layer is dense and free of bubbles. After curing, the stainless steel tank can be directly put into use under working conditions of -40 to 250℃.

8. The application method of the solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks according to claim 7, characterized in that, Before construction, the leaking part of the stainless steel tank and the surrounding 50mm area should be degreased, cleaned, and roughened by grinding; the grinding pattern should be intersecting at 45° to 60°, and the roughness should be controlled between Ra3.2 and 6.3μm; after secondary cleaning, the subsequent construction should be carried out only after there are no volatile residues on the surface.

9. The application method of the solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks according to claim 7, characterized in that, In step (1), 0-2% of organosilane dispersant is first added to component A, and the mixture is stirred at 300-500 r / min to form a homogeneous mixture, and then component B is added.

10. The application method of the solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks according to claim 7, characterized in that, In step (2), the alkali-free glass fiber cloth is soaked in acetone for 10-15 minutes and then laid on the leaking area.

11. The application method of the solvent-free fiber-reinforced sealant for sealing leaks in stainless steel tanks according to claim 7, characterized in that, In step (2), for pitting corrosion leakage, the diameter of the fiber cloth should extend at least 20 mm beyond the edge of the pit, and then a 1-2 mm thick mixed adhesive should be applied to its surface; for weld or crack leakage, first open a groove 5-8 mm wide and 3-5 mm deep at the leakage location, compact the mixed adhesive into the groove, and then lay 2-3 layers of alkali-free glass fiber cloth in sequence.

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