An adhesive composition for high-temperature sealing

Abstract

This invention discloses an adhesive composition for high-temperature sealing, relating to the field of sealing technology. A hybrid bonding component is used to establish a continuous bonding network; a high softening temperature skeleton particle component is used to establish a continuous high softening temperature skeleton phase; an encapsulating low softening temperature backfill particle component is used to provide a temperature-triggered backfill material source at crack-prone locations; a toughening and crack-inhibiting component is used to delay crack propagation; a rheology modifier component is used to maintain the forming stability during the filling stage; and an interface modifier component is used to improve the adhesion stability of the joint inner wall. Therefore, the adhesive composition not only forms a stable sealing layer after initial curing but also locally backfills newly formed cracks during subsequent high-temperature cycling, thereby improving the high-temperature sealing life and operational stability.

Description

Technical Field

[0001] This invention relates to the field of sealing technology, specifically to an adhesive composition for high-temperature sealing. Background Technology

[0002] Adhesive compositions used for high-temperature sealing typically serve to simultaneously fill gaps, bond and fix components, and prevent leakage of high-temperature media in industrial furnaces, flue gas ducts, heat treatment equipment, refractory component joints, and high-temperature flange connections.

[0003] In the existing technology, conventional organic sealants are easy to apply and have good adhesion, but their temperature resistance is limited and they are difficult to use in higher temperature operating environments. Although inorganic sealants and high-temperature resistant hybrid sealants can meet higher temperature requirements, they still have problems such as cracking, embrittlement, delamination or decreased density under high temperature cycling, thick layer filling and repeated thermal stress.

[0004] To mitigate the aforementioned problems, existing technologies have proposed various improvement pathways. For example, high-temperature stability can be improved through vitrification and ceramization transitions; thermal expansion matching can be enhanced by adjusting the composition of the glass powder; and density, water resistance, impact resistance, and thermal shock resistance can be improved by adding components such as mullite, magnesium aluminum spinel, and inorganic fibers. The common goal of these solutions is to obtain a sealing layer that is as resistant to cracking as possible during the initial delamination stage. In other words, the main focus of existing technologies remains minimizing or delaying the occurrence of cracks.

[0005] Patent application CN107880786A discloses an inorganic sealant and its preparation and application methods. The document clearly points out that when the difference in the coefficient of thermal expansion between the inorganic sealant and the substrate is large, large internal stress will be generated during high-temperature operation, which may lead to cracking of the sealant and the generation of cracks.

[0006] Chinese invention patent CN114085644B discloses a high-temperature resistant sealant, its preparation method, and its application. It also points out that existing high-temperature adhesives are prone to cracking when used in thick layers, affecting sealing and moisture-proofing effects. This demonstrates that current technologies for addressing cracking issues remain focused on inhibiting crack formation or mitigating crack severity.

[0007] However, in actual service, the joints are usually subjected to multiple cycles of heating and cooling over a long period of time. After the initial curing of the adhesive composition used for high-temperature sealing, microcracks will gradually form in the local stress concentration areas due to factors such as differences in thermal expansion and contraction of the substrate, structural corner constraints, vibration loads, and media erosion. Microcracks are often small in size in the early stages of formation and are not easily detected by conventional detection methods. However, once microcracks connect with adjacent pores or interface defects, they will become channels for high-temperature media leakage. Although existing technologies can reduce the probability of crack formation through early formulation design, they cannot maintain the local flow and repair capabilities facing the microcrack location after the microcracks have formed. Therefore, existing technologies essentially solve the problem of crack reduction, rather than the problem of backfilling after cracking. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides an adhesive composition for high-temperature sealing, solving the problems mentioned in the background art.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An adhesive composition for high-temperature sealing, comprising, by weight: 10 to 18 parts of a hybrid binder component, said hybrid binder component comprising a polymethylsilsesquioxane precursor, ethyl silicate, and aluminum dihydrogen phosphate; 32 to 45 parts of high softening temperature skeleton particle component, wherein the high softening temperature skeleton particle component includes at least two of mullite powder, alumina powder and cordierite powder, and the melting initiation temperature of the particles in the high softening temperature skeleton particle component is higher than 900°C. Eight to sixteen parts of a coated low softening temperature backfill particle component, wherein the coated low softening temperature backfill particle component includes a low softening temperature glass core and an inorganic coating layer disposed on the outside of the low softening temperature glass core. The low softening temperature glass core includes at least one of phosphate glass, borosilicate glass and boron zinc silicon glass, and the softening temperature of the low softening temperature glass core is 400°C to 620°C. The inorganic coating layer includes at least one of silicon dioxide and alumina. Two to eight parts of a toughening and crack-resistant component, wherein the toughening and crack-resistant component includes at least one of zirconium oxide powder, hexagonal boron nitride sheets and chopped alumina fibers; 0.3 to 2 parts of rheology modifier, wherein the rheology modifier includes at least one of fumed silica and organobentonite; 0.1 to 1 part of an interface modifier, wherein the interface modifier comprises at least one of an aminosilane coupling agent and an epoxysilane coupling agent.

[0010] Preferably, the adhesive composition is initially cured at 100°C to 250°C to form a cured body. In the cured body, the hybrid adhesive component is cured to form a continuous adhesive network. The continuous adhesive network and the high softening temperature skeleton particle component together form a continuous high softening temperature skeleton phase.

[0011] Preferably, the coated low softening temperature backfill particle component is dispersed within the continuous high softening temperature skeleton phase and embedded in the particle boundary regions between adjacent high softening temperature skeleton particle components. It is also distributed in the pore junction regions surrounded by the high softening temperature skeleton particle components and at the interface regions between the continuous bonding network and the high softening temperature skeleton particle components.

[0012] Preferably, the median particle size D50 of the coated low softening temperature backfill particle component is 2 μm to 12 μm, the median particle size D50 of the high softening temperature skeleton particle component is 8 μm to 35 μm, and the softening temperature of the low softening temperature glass core material is more than 280°C lower than the particle melting initiation temperature in the high softening temperature skeleton particle component.

[0013] Preferably, when the solidified body is at a temperature higher than the softening temperature of the low softening temperature glass core material but lower than the melting initiation temperature of the particles in the high softening temperature skeleton particle component, the low softening temperature glass core material in the encapsulated low softening temperature backfill particle component undergoes local softening and flow, the particles in the high softening temperature skeleton particle component remain solid, and the continuous high softening temperature skeleton phase formed by the continuous bonding network and the high softening temperature skeleton particle component maintains an overall support state.

[0014] Preferably, the low softening temperature glass core material in the solidified body flows along the particle boundary, pore intersection and junction after local softening and flow.

[0015] Preferably, when cracks form at particle boundaries, pore junctions, or interfaces in the solidified body, the low softening temperature glass core material flowing along the particle boundaries, pore junctions, and interfaces enters the cracks.

[0016] Preferably, when the temperature of the cured body decreases below the softening temperature of the low softening temperature glass core, the low softening temperature glass core that has entered the crack is cured and retained within the crack.

[0017] This invention provides an adhesive composition for high-temperature sealing, which has the following beneficial effects: (1) The hybrid binder component is used to establish a continuous binder network, the high softening temperature skeleton particle component is used to establish a continuous high softening temperature skeleton phase, the encapsulated low softening temperature backfill particle component is used to provide a source of backfill material that can be triggered by temperature at crack-prone locations, the toughening and crack-inhibiting component is used to delay crack propagation, the rheology modifier component is used to maintain the forming stability during the filling stage, and the interface modifier component is used to improve the adhesion stability of the inner wall of the joint; thus, the adhesive composition can not only form a stable sealing layer after initial curing, but also locally backfill newly generated cracks during subsequent high-temperature cycling, thereby improving the high-temperature sealing life and operational stability.

[0018] (2) The median particle size D50 range of the coated low softening temperature backfill particle component is used to determine the spatial conditions for the coated low softening temperature backfill particle component to enter the crack-prone area. The median particle size D50 range of the high softening temperature skeleton particle component is used to determine the gap structure and support structure of the continuous high softening temperature skeleton phase. The temperature difference range between the low softening temperature glass core material and the high softening temperature skeleton particle component is used to determine the temperature conditions under which the low softening temperature glass core material softens first while the high softening temperature skeleton particle component remains solid. When the three are combined, the positional conditions of the coated low softening temperature backfill particle component can be correlated with the subsequent local softening flow conditions, thereby establishing a clear spatial and temperature basis for the subsequent crack thermal triggering backfill process.

[0019] (3) When cracks form at particle boundaries, pore junctions, or junctions, the low softening temperature glass core material can directly enter the crack from the adjacent location without needing to migrate over a long distance. At the same time, the location of crack formation corresponds to the flow path of the low softening temperature glass core material. Cracks formed at particle boundaries correspond to the flow path at particle boundaries, cracks formed at pore junctions correspond to the flow path at pore junctions, and cracks formed at junctions correspond to the flow path at junctions. Therefore, the low softening temperature glass core material can enter the crack in the early stage of crack formation. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the preparation process of an adhesive composition for high-temperature sealing according to the present invention. Figure 2 This is a flowchart illustrating the preparation and initial curing process of an adhesive composition for high-temperature sealing according to the present invention. Figure 3 This is a schematic diagram of the internal structure distribution of the solidified body. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] Example 1 This invention provides an adhesive composition for high-temperature sealing; please refer to [link / reference]. Figure 1 , Figure 2 and Figure 3 By weight, it includes: 10 to 18 parts of a hybrid binder component, said hybrid binder component comprising a polymethylsilsesquioxane precursor, ethyl silicate, and aluminum dihydrogen phosphate; 32 to 45 parts of high softening temperature skeleton particle component, wherein the high softening temperature skeleton particle component includes at least two of mullite powder, alumina powder and cordierite powder, and the melting initiation temperature of the particles in the high softening temperature skeleton particle component is higher than 900°C. Eight to sixteen parts of a coated low softening temperature backfill particle component, wherein the coated low softening temperature backfill particle component includes a low softening temperature glass core and an inorganic coating layer disposed on the outside of the low softening temperature glass core. The low softening temperature glass core includes at least one of phosphate glass, borosilicate glass and boron zinc silicon glass, and the softening temperature of the low softening temperature glass core is 400°C to 620°C. The inorganic coating layer includes at least one of silicon dioxide and alumina. Two to eight parts of a toughening and crack-resistant component, wherein the toughening and crack-resistant component includes at least one of zirconium oxide powder, hexagonal boron nitride sheets and chopped alumina fibers; 0.3 to 2 parts of rheology modifier, wherein the rheology modifier includes at least one of fumed silica and organobentonite; 0.1 to 1 part of an interface modifier, wherein the interface modifier comprises at least one of an aminosilane coupling agent and an epoxysilane coupling agent.

[0023] The application scenario is illustrated using the connection seam of an industrial furnace exhaust flange. The seam width of the industrial furnace exhaust flange connection seam is set to 2mm, the seam depth is set to 4mm, the flange base material is selected as heat-resistant stainless steel, and during the implementation process, the flange structure is not changed, the fastening method is not changed, and no additional gaskets are added. The connection seam is sealed only by filling in an adhesive composition for high-temperature sealing. The weight parts are used to indicate the relative mass relationship between the components, and the total weight parts of the components are not a limiting condition. By weight, it includes: 15 parts of hybrid binder component, 40 parts of high softening temperature skeleton particle component, 12 parts of coated low softening temperature backfill particle component, 4 parts of toughening and crack-inhibiting component, 1 part of rheology modifier component and 0.5 parts of interface modifier component. Of the 15 parts of the hybrid binder component, 6 parts are polymethylsilsesquioxane precursor, 5 parts are ethyl silicate, and 4 parts are aluminum dihydrogen phosphate. Of the 40 parts of high softening temperature skeleton particle components, 18 parts were mullite powder, 14 parts were alumina powder, and 8 parts were cordierite powder. The median particle size D50 of the high softening temperature skeleton particle components was controlled between 12 μm and 22 μm, and the particle melting initiation temperature of mullite powder, alumina powder, and cordierite powder were all higher than 900℃. In the 12-part coated low softening temperature backfill particle composition, the low softening temperature glass core material is borosilicate glass powder with a softening temperature of 520℃ and a median particle size D50 controlled between 4μm and 7μm. The inorganic coating layer is a silica-alumina composite coating layer. Of the four toughening and crack-resistant components, two are zirconium oxide powder, one is hexagonal boron nitride sheet, and one is chopped alumina fiber. In one part of the rheology modifier, there are 0.6 parts of fumed silica and 0.4 parts of organobentonite; Of the 0.5 parts of the interface conditioning component, 0.3 parts are aminosilane coupling agent and 0.2 parts are epoxysilane coupling agent; Coated low-softening-temperature backfill particle components can be prepared as follows: First, borosilicate glass powder is added to a mixed dispersion medium formed by ethanol and deionized water and stirred for 20 to 30 minutes to form a uniform suspension. Then, silica sol and alumina sol are added to the suspension in sequence to deposit the silicon and aluminum sources on the outer surface of the borosilicate glass powder. Subsequently, the mixture is filtered and dried at 80 to 120°C. After drying, it is heat-treated at 300 to 450°C for 0.5 to 1 hour to obtain a coated low softening temperature backfill particle component with an outer silica-alumina composite coating. After preparation in the above manner, the inorganic coating layer is located on the outside of the low softening temperature glass core material, which can keep the low softening temperature glass core material in a dispersed state during the storage, mixing, and initial curing stages, reducing premature adhesion or premature softening and flow of the low softening temperature glass core material.

[0024] In this embodiment, to ensure that the inorganic coating layer simultaneously provides isolation and confinement as well as subsequent release, the amounts of silica sol and alumina sol added are controlled to be 1% to 5% of the total solid content of the silica sol and alumina sol by the mass of the borosilicate glass powder. The volume ratio of ethanol to deionized water in the mixed dispersion medium formed by ethanol and deionized water is controlled to be 1:1 to 3:1. After the borosilicate glass powder is added to the mixed dispersion medium, it is stirred for 20 to 30 minutes, and then the silica sol and alumina sol are slowly added while stirring. This ensures that the silicon and aluminum sources preferentially deposit on the outer surface of the borosilicate glass powder rather than gelling separately in the dispersion medium. After filtration and drying at 80°C to 120°C, heat treatment is performed. The heat treatment temperature is controlled to be at least 30°C below the softening temperature of the borosilicate glass powder and within the range of 300°C to 450°C. In this embodiment, the softening temperature of the borosilicate glass powder is 520°C, therefore the heat treatment... The temperature can be controlled at 350℃ to 450℃ and maintained for 0.5h to 1h. When the low softening temperature glass core is replaced with phosphate glass or boron zinc silicon glass with a softening temperature of 400℃ to 450℃, the heat treatment temperature is controlled at 300℃ to 370℃, and no sintering densification treatment higher than the softening temperature of the low softening temperature glass core is performed. The resulting inorganic coating layer is an inorganic confined coating layer attached to the outside of the low softening temperature glass core. The inorganic confined coating layer is not a completely sealed shell layer, but has at least one release structure among micropores, locally discontinuous coating areas, and locally weak areas. When detected by scanning electron microscopy and energy dispersive spectroscopy, there is a silicon-aluminum enriched region on the outer edge of the low softening temperature glass core. When detected by laser particle size analysis, the median particle size D50 of the coated low softening temperature backfill particle component is still controlled within the range of 2μm to 12μm.

[0025] Mullite powder, alumina powder, cordierite powder, zirconium oxide powder, hexagonal boron nitride flakes, chopped alumina fibers, fumed silica, and organobentonite are added to a dual planetary mixer and dry-mixed for 10 to 20 minutes to achieve a uniform particle distribution of the high softening temperature skeleton particle component, toughening and crack-resistant component, and rheology modifier component. Then, a hybrid binder component consisting of polymethylsilsesquioxane precursor, ethyl silicate, and aluminum dihydrogen phosphate is added and wet-mixed for 20 to 30 minutes to allow the hybrid binder component to enter the interparticle gaps formed between the high softening temperature skeleton particle components. Subsequently, a coated low softening temperature backfill particle component and an interface modifier component are added, and mixing continues at low speed for 8 to 15 minutes to disperse the coated low softening temperature backfill particle component into the internal interstitial region surrounded by the high softening temperature skeleton particle components. After mixing, vacuum degassing is performed for 5 to 15 minutes to obtain an adhesive composition slurry for high-temperature sealing. After adopting the above feeding sequence, the hybrid binder first forms a continuous wetting channel between the high softening temperature skeleton particles, and then the coated low softening temperature backfill particles enter the continuous wetting channel. This is beneficial for the coated low softening temperature backfill particles to be dispersed at the particle boundary, pore intersection, and the interface between the continuous binder network and the high softening temperature skeleton particles.

[0026] A slurry of an adhesive composition for high-temperature sealing is filled into the joint of an industrial furnace exhaust flange and the surface is smoothed. After standing at room temperature for 20 minutes, it is first heated at 150°C for 1.5 hours, and then heated at 220°C for 1 hour to complete the initial curing. The initial curing temperature is in the range of 100°C to 250°C, and the highest initial curing temperature is lower than the softening temperature of the low softening temperature glass core material.

[0027] Under the aforementioned initial curing conditions, the low softening temperature glass core will not soften or flow during the initial curing stage. The hybrid binder undergoes condensation and curing reactions under heating conditions, forming a continuous bond network between the high softening temperature skeleton particles. After the initial curing is completed, a cured body is formed. In the cured body, the hybrid binder solidifies to form a continuous bond network, which together with the high softening temperature skeleton particles forms a continuous high softening temperature skeleton phase. The encapsulated low softening temperature backfill particles are dispersed within the continuous high softening temperature skeleton phase and embedded at the particle boundary between adjacent high softening temperature skeleton particles. They are also distributed at the pore junctions formed by the high softening temperature skeleton particles and at the interface between the continuous bond network and the high softening temperature skeleton particles.

[0028] During the initial curing stage, the inorganic coating layer functions to isolate adjacent low-softening-temperature glass core materials and restrict interparticle adhesion, rather than permanently sealing the low-softening-temperature glass core materials through complete sealing. In specific implementation, the maximum initial curing temperature is controlled to be at least 100°C lower than the softening temperature of the low-softening-temperature glass core material. In this embodiment, the maximum initial curing temperature is 220°C, which is lower than the softening temperature of borosilicate glass powder (520°C). This allows the low-softening-temperature glass core material to remain in a solid or high-viscosity state during the initial curing stage. Even if there are micropores, locally discontinuous coating areas, or locally weak areas in the inorganic coating layer, the low-softening-temperature glass core material does not have the ability to migrate outward through the aforementioned release structure. When the cross-section of the cured body is observed after the initial curing is completed, the coated low-softening-temperature backfill particle components are still retained in a dispersed particle state at the particle boundary, pore intersection, and junction.

[0029] After the industrial furnace enters the heating operation stage, when the temperature of the solidified body rises above 520°C but is still below the melting initiation temperature of the particles in the high softening temperature skeleton particle component, the low softening temperature glass core material in the coated low softening temperature backfill particle component begins to undergo local softening flow. At this time, the particles in the high softening temperature skeleton particle component remain solid, and the continuous high softening temperature skeleton phase formed by the continuous bonding network and the high softening temperature skeleton particle component maintains the overall support structure.

[0030] As the industrial furnace repeatedly undergoes heating and cooling processes, cracks form at particle boundaries, pore junctions, or the interface between the continuous bonded network and the high softening temperature skeleton particle components under thermal stress. The low softening temperature glass core material, which has already undergone local softening and flow, enters the crack along the particle boundaries, pore junctions, and interface. Subsequently, when the cured body is cooled to below 520°C by the industrial furnace, the low softening temperature glass core material that entered the crack is re-cured and retained in the crack, thus completing the refilling of the crack.

[0031] The composition was prepared near the boundary median of Example 1: 15 parts of hybrid binder, 40 parts of high softening temperature skeleton particles, 12 parts of coated low softening temperature backfill particles, 4 parts of toughening and crack-resistant components, 1 part of rheology modifier, and 0.5 parts of interface modifier. In the hybrid binder component, polymethylsilsesquioxane precursor, ethyl silicate and aluminum dihydrogen phosphate are set in a ratio of 6:5:4; the high softening temperature skeleton particle component is composed of 18 parts mullite powder, 14 parts alumina powder and 8 parts cordierite powder; the coated low softening temperature backfill particle component is composed of borosilicate glass powder with a softening temperature of 520℃, and a silica-alumina composite coating layer is formed on the outside. During mixing, the high softening temperature skeleton particle component, toughening and crack-inhibiting component, and rheology modifier component are first dry-mixed for 15 minutes. Then, the hybrid binder component is added and wet-mixed for 25 minutes. Finally, the coating-type low softening temperature backfill particle component and interface modifier component are added and mixed at low speed for 10 minutes. Vacuum degassing is then performed to obtain the slurry. After the slurry is filled into the flange connection seam, it is allowed to stand at room temperature for 20 minutes, and then a two-stage primary curing process is performed: 150℃ for 1.5 hours and 220℃ for 1 hour. After the cured body is formed, the sample is placed under a 520℃ thermal cycling condition. The single thermal cycle is set to "heat to 520℃ and hold for 30 minutes - naturally cool to 80℃". To establish a comparative relationship, four sets of comparative examples were set up for comparison with Example 1: Comparative Example 1: Removal of the inorganic coating layer; Comparative Example 2 increased the softening temperature of the low softening temperature glass core material to 780℃, which significantly reduced the temperature difference; Comparative Example 3 increased the median particle size D50 of the coated low softening temperature backfill particle component to 14 μm to 18 μm, making the particle size close to that of the high softening temperature skeleton particle component. Comparative Example 4 uses a conventional high-temperature resistant sealant system that does not contain encapsulated low-softening-temperature backfill particles. The test records the bond strength after initial curing, the hot leakage rate after 100 cycles at 520℃, the proportion of crack backfill area, the number of cycles before microcrack penetration, the interface peeling length, the mass loss rate, and the residual crack width after cooling. The results of the four sets of comparative experiments are summarized in Table 1. Table 1: Comparison Results of Example 1 and Comparative Examples 1-4

[0032] As can be seen from Table 1, the advantage of Example 1 is not the improvement of a single parameter, but the simultaneous improvement of multiple indicators. First, the bonding strength after initial curing reaches 5.8 MPa, which is significantly higher than that of Comparative Example 1 and Comparative Example 4. This indicates that the combination of hybrid bonding component and interface conditioning component can not only form a continuous bonding network, but also stably anchor the continuous bonding network to the inner wall of the joint. Secondly, after 100 thermal cycles at 520℃, the hot leakage rate was only 0.6 mL / min, far lower than that of Comparative Example 1 (2.7 mL / min), Comparative Example 2 (3.4 mL / min), Comparative Example 3 (2.9 mL / min), and Comparative Example 4 (6.1 mL / min). This indicates that Example 1 of the invention does not only improve the initial seal, but also maintains a high sealing capacity after thermal cycling. Combined with the data of 86% crack backfill area and 9 μm residual crack width after cooling, it further illustrates that the low softening temperature glass core material did indeed complete the process of local softening, entering the crack, and remaining in the crack after cooling in the service temperature range. After removing the inorganic coating layer in Comparative Example 1, the proportion of crack backfill area decreased to 34%, and the hot leakage rate increased, indicating that the inorganic coating layer is a necessary condition for "delayed release, dispersion into crack-prone locations, and subsequent re-release". In Comparative Example 2, after the softening temperature of the low softening temperature glass core was increased, the proportion of crack backfill area further decreased to 28%, and the number of cycles before microcrack penetration decreased to 82. This indicates that after the temperature difference was reduced, the low softening temperature glass core could not enter the local softening window in time when the continuous high softening temperature skeleton phase still maintained support, thus weakening the crack thermal triggering backfill effect. In Comparative Example 3, after increasing the particle size of the coated low softening temperature backfill particle component, the crack backfill area accounted for only 41%, indicating that the particle size relationship is not an arbitrary parameter. When the particle size is close, the coated low softening temperature backfill particle component is not easy to enter the particle boundary, pore intersection and junction, resulting in a longer subsequent backfill path and a decrease in crack repair efficiency. Comparative Example 4 represents the conventional high-temperature resistant sealant route. Although it has a certain initial sealing ability, the area of ​​crack backfilling is only 9%, and the number of cycles before microcracks penetrate is only 54. This shows that the conventional high-temperature sealing route mainly solves the problems of "initial sealing" and "temperature resistance without failure", but cannot solve the problem of "continuing to fill cracks after they form".

[0033] In this embodiment, after adopting the above composition and implementation method, the hybrid binder component is used to establish a continuous binder network, the high softening temperature skeleton particle component is used to establish a continuous high softening temperature skeleton phase, the encapsulated low softening temperature backfill particle component is used to provide a temperature-triggered backfill material source at crack-prone locations, the toughening and crack-inhibiting component is used to delay crack propagation, the rheology modifier component is used to maintain the forming stability during the filling stage, and the interface modifier component is used to improve the adhesion stability of the inner wall of the joint. Thus, the adhesive composition can not only form a stable sealing layer after initial curing, but also locally backfill newly generated cracks during subsequent high-temperature cycling, thereby improving the high-temperature sealing life and operational stability.

[0034] Example 2 Please see Figure 2 and Figure 3 Specifically, the adhesive composition is initially cured at 100°C to 250°C to form a cured body. In the cured body, the hybrid adhesive components are cured to form a continuous adhesive network. The continuous adhesive network and the high softening temperature skeleton particles together form a continuous high softening temperature skeleton phase.

[0035] The specific implementation process is as follows.

[0036] The adhesive composition slurry for high-temperature sealing prepared in Example 1 was used as the initial curing material, and the adhesive composition slurry for high-temperature sealing was filled into the connection seam of the industrial furnace exhaust flange. The connection seam of the industrial furnace exhaust flange had a seam width of 2 mm and a seam depth of 4 mm.

[0037] After filling the industrial furnace exhaust flange connection seam with an adhesive composition slurry for high-temperature sealing, the exposed surface of the adhesive composition slurry for high-temperature sealing is scraped smooth, so that the adhesive composition slurry for high-temperature sealing covers the entire cross-section of the industrial furnace exhaust flange connection seam, and the adhesive composition slurry for high-temperature sealing is continuously adhered to the inner wall surface of the industrial furnace exhaust flange connection seam.

[0038] After the leveling process is completed, the mixture is left to stand at room temperature for 20 minutes to allow macroscopic entrained air bubbles inside the adhesive composition slurry for high-temperature sealing to escape outward, and to allow the hybrid bonding components to enter the interparticle gaps on the surface of the high softening temperature skeleton particle components and the micro-uneven areas on the inner wall surface of the industrial furnace exhaust flange connection seam.

[0039] After standing at room temperature, the adhesive composition slurry used for high-temperature sealing, which is filled into the connection seam of the industrial furnace exhaust flange, is initially cured. The initial curing is carried out by a staged heating method. First, it is kept at 150℃ for 1.5 hours, and then the temperature is raised to 220℃ and kept for 1 hour. The temperature range of the entire initial curing process is controlled within 100℃ to 250℃.

[0040] During the initial curing process, the highest temperature of 220℃ is lower than the softening temperature of the low softening temperature glass core material of 520℃. Therefore, the low softening temperature glass core material in the coated low softening temperature backfill particle component does not soften and flow during the initial curing stage, and the coated low softening temperature backfill particle component maintains a particle dispersion state during the initial curing stage.

[0041] During the 150℃ curing stage, the polymethylsilsesquioxane precursor undergoes a polycondensation reaction, and the ethyl silicate undergoes hydrolysis and polycondensation reactions. Aluminum dihydrogen phosphate forms a bond with the surface of the high softening temperature skeleton particle components and the inner wall surface of the industrial furnace exhaust flange connection seam. As the above reactions continue, the hybrid bonding component changes from a fluid state to a bonded state and coats the outer surface of mullite powder, alumina powder and cordierite powder, while filling the particle gaps formed between adjacent high softening temperature skeleton particle components.

[0042] After curing at 150°C, the hybrid binder forms an initial bonding layer between adjacent high softening temperature skeleton particle components. The initial bonding layer is continuously distributed along the particle contact position, the particle adjacent position, and the particle gap, thereby connecting multiple high softening temperature skeleton particle components into an initial particle bonding structure.

[0043] During the 220℃ curing stage, the polycondensation degree of polymethylsilsesquioxane precursor and ethyl silicate continues to increase, aluminum dihydrogen phosphate forms a further cured inorganic bond structure, and the hybrid binder components dispersed among the high softening temperature skeleton particles continue to cure and interconnect, eventually forming a continuous bond network.

[0044] The continuous bonding network is not a locally isolated distribution structure, but extends continuously along the particle contact positions, particle adjacent positions and particle gaps between the high softening temperature skeleton particle components, and connects multiple high softening temperature skeleton particle components into an integral particle support structure that runs through the width and depth directions of the industrial furnace exhaust flange connection seam.

[0045] After curing at 220°C, an adhesive composition for high-temperature sealing transforms from a slurry state into a cured body. The hybrid bonding components inside the cured body solidify to form a continuous bonding network, which together with the high softening temperature skeleton particles form a continuous high softening temperature skeleton phase.

[0046] In the continuous high softening temperature skeleton phase, the high softening temperature skeleton particle component is continuously distributed as high temperature support particles, and the continuous bonding network is continuously distributed as particle connecting phase. After the two work together, they form a continuous support path inside the cured body that extends from one side of the industrial furnace exhaust flange connection seam to the other side and from the surface of the industrial furnace exhaust flange connection seam to the inside of the industrial furnace exhaust flange connection seam.

[0047] The reason for using 100℃ to 250℃ as the initial curing temperature range is that temperatures above 100℃ allow the polymethylsilsesquioxane precursor and ethyl silicate to complete significant polycondensation within 1.5 to 2.5 hours, and enable aluminum dihydrogen phosphate to form a stable bonded structure. Temperatures below 250℃ are lower than the softening temperature of the low-softening-temperature glass core material, thus enabling the initial curing stage to establish a continuous bonding network and a continuous high-softening-temperature framework phase, rather than the premature softening and flow of the low-softening-temperature glass core material.

[0048] In this embodiment, the significance of adopting the above-mentioned initial curing method is that after the hybrid binder component is cured in the range of 100°C to 250°C, it can stably form a continuous binder network. The continuous binder network can connect the high softening temperature skeleton particle components into a continuous high softening temperature skeleton phase. The continuous high softening temperature skeleton phase can maintain the overall support structure under subsequent high temperature cycling conditions. The low softening temperature glass core material is retained inside the encapsulated low softening temperature backfill particle components and is postponed to the subsequent actual working temperature stage before local softening and flow occur. Therefore, after implementing the above method, the implementer can first obtain a structurally stable cured body, and then trigger the low softening temperature glass core material to enter the crack and complete the refilling during the subsequent high temperature cycling process.

[0049] Example 3 Specifically, the encapsulated low softening temperature backfill particle components are dispersed within the continuous high softening temperature skeleton phase and embedded in the particle boundary regions between adjacent high softening temperature skeleton particle components. They are also distributed in the pore junction regions surrounded by the high softening temperature skeleton particle components and at the interface regions between the continuous bonding network and the high softening temperature skeleton particle components.

[0050] The specific implementation process is as follows.

[0051] Continuing with the adhesive composition formulation for high-temperature sealing in Example 1, and using the initial curing method in Example 2 to form a cured body, Example 3 focuses on illustrating the process by which the coated low softening temperature backfill particle component enters the interior of the continuous high softening temperature skeleton phase and disperses into the particle boundary, pore intersection and interface regions during the mixing and initial curing stages.

[0052] The median particle size D50 of the high softening temperature skeleton particle component is controlled within the range of 12μm to 22μm, and the median particle size D50 of the low softening temperature glass core material in the coated low softening temperature backfill particle component is controlled within the range of 4μm to 7μm. According to this particle size relationship, the particle size of the coated low softening temperature backfill particle component is smaller than that of the high softening temperature skeleton particle component. Therefore, the coated low softening temperature backfill particle component can enter the gap area formed between adjacent high softening temperature skeleton particle components during the mixing process, and will not mainly stay in the outer surface area formed by the accumulation of high softening temperature skeleton particle components.

[0053] In the mixing stage, the high softening temperature skeleton particle component, toughening and crack-inhibiting component and rheology modifier component are first added to the mixing container for premixing, so that the high softening temperature skeleton particle component forms a uniform particle packing structure in the mixing container, and an interconnected particle gap network is formed inside the particle packing structure.

[0054] After premixing, the hybrid binder is added to the particle packing structure, so that the hybrid binder first enters the interparticle gaps formed between the high softening temperature skeleton particles, and forms a continuous wetting channel along the particle contact position, the particle adjacent position and the interparticle gaps.

[0055] After the continuous wetting channel is formed, the coated low softening temperature backfill particle component is added to the mixing system and stirred continuously. Under shearing action, the coated low softening temperature backfill particle component enters the interparticle network formed between the high softening temperature skeleton particle components along with the hybrid binder component.

[0056] The mixing process is carried out by first mixing at medium speed and then mixing at low speed. The medium speed mixing stage is used to allow the hybrid binder components to spread fully and enter the interparticle gaps, while the low speed mixing stage is used to allow the coated low softening temperature backfill particle components to enter the continuous moist channel without significantly damaging the inorganic coating layer.

[0057] After low-speed mixing, the coated low-softening-temperature backfill particle components will not concentrate in large quantities on the surface of the slurry, but will migrate along the continuous wetting channel into the interior of the particle packing structure and enter the local gap area formed between the high-softening-temperature skeleton particle components.

[0058] During subsequent vacuum degassing, large air bubbles inside the slurry escape from the gaps between the particles. The spaces previously occupied by these large air bubbles become empty spaces. Under the action of the pressure difference, the coated low softening temperature backfill particle components continue to redisperse into the particle packing structure, thereby increasing the distribution ratio of the coated low softening temperature backfill particle components near the particle boundaries and pore junctions.

[0059] In this embodiment, the particle boundary specifically refers to the location where two adjacent high softening temperature skeleton particles approach each other and form the minimum particle spacing.

[0060] In this embodiment, the pore junction specifically refers to the pore connection location formed by three or more high softening temperature skeleton particles that are interconnected with each other.

[0061] In this embodiment, the interface refers specifically to the location where the continuous bonding network comes into contact with the high softening temperature skeleton particle component and forms an interface connection.

[0062] The specific process of the coated low softening temperature backfill particle component entering the particle boundary is as follows: after the hybrid binder component enters the particle gap formed between adjacent high softening temperature skeleton particle components, a thin layer connection area is formed at the particle boundary. After the coated low softening temperature backfill particle component enters the thin layer connection area along with the hybrid binder component, it is restricted between two adjacent high softening temperature skeleton particle components, thus forming an embedded state.

[0063] In this embodiment, the embedded state is specifically manifested as follows: at least a portion of the particles of the encapsulated low softening temperature backfill particle component are located between two adjacent high softening temperature skeleton particle components, and the outer surface of the particles is simultaneously adjacent to the two high softening temperature skeleton particle components on both sides.

[0064] The specific process by which the coated low softening temperature backfill particle component enters the pore junction is as follows: the pore connection position surrounded by three or more high softening temperature skeleton particle components has a larger local accommodation space than the particle boundary position. During the flow process, the coated low softening temperature backfill particle component enters the above-mentioned local accommodation space and stays at the position. After vacuum degassing, the voids in some pore connection positions are occupied by the coated low softening temperature backfill particle component, thereby distributing the coated low softening temperature backfill particle component in the pore junction.

[0065] The specific process of the coated low softening temperature backfill particle component entering the interface is as follows: before the initial curing, the hybrid binder component is in a flowable state. During the flow of the hybrid binder component, the coated low softening temperature backfill particle component enters the position where the hybrid binder component and the high softening temperature skeleton particle component are in contact. After the initial curing is completed, the coated low softening temperature backfill particle component that was originally located at the contact position remains at the interface between the continuous binder network and the high softening temperature skeleton particle component.

[0066] With the above distribution method, the encapsulated low softening temperature backfill particle component not only exists between the high softening temperature skeleton particle components, but also exists at the position where the continuous bonding network and the high softening temperature skeleton particle components come into contact, so that the local softening flow path of the subsequent low softening temperature glass core material simultaneously covers the internal crack path and the interface crack path.

[0067] After the initial curing is completed, when the cross-section of the cured body is observed, it can be seen that the high softening temperature skeleton particle component forms the main particle stacking structure, the continuous bonding network is distributed between the high softening temperature skeleton particle components to form a continuous connecting layer, and the encapsulated low softening temperature backfill particle component exists in the continuous high softening temperature skeleton phase in a dispersed particle state.

[0068] The cross-section can be confirmed by scanning electron microscopy and energy dispersive spectroscopy. The coated low softening temperature backfill particle components are not concentrated in a single location, but are distributed at particle boundaries, pore junctions and interfaces, thereby shortening the distance between the coated low softening temperature backfill particle components and the subsequent crack formation location.

[0069] In this embodiment, the significance of adopting the above settings is as follows: First, the particle size of the coated low softening temperature backfill particle component is smaller than that of the high softening temperature skeleton particle component. Therefore, the coated low softening temperature backfill particle component can enter the internal gap network formed by the high softening temperature skeleton particle component, instead of being distributed only on the surface of the slurry. Second, the order of adding the hybrid binder first and then the coated low softening temperature backfill particle component can utilize the continuous wetting channel formed by the hybrid binder to carry the coated low softening temperature backfill particle component into the interior of the continuous high softening temperature skeleton phase. Third, vacuum degassing can reduce the occupation of large-sized air bubbles inside the particle packing structure, thereby allowing the coated low-softening-temperature backfill particle components to continue to enter the particle boundary and pore junction areas. Fourth, after the coated low softening temperature backfill particle components are distributed at particle boundaries, pore junctions, and interfaces, the local softening flow path of the low softening temperature glass core material during subsequent high-temperature cycling coincides with the crack initiation path, thereby allowing the low softening temperature glass core material to enter the crack in the early stage of crack formation.

[0070] Ultimately, the directional dispersion of the coated low softening temperature backfill particle components within the continuous high softening temperature skeleton phase can be achieved during the initial curing stage. This ensures that the coated low softening temperature backfill particle components neither prematurely aggregate nor primarily remain on the surface of the cured body, but rather preferentially enter the particle boundary, pore intersection, and interface regions.

[0071] Example 4 Specifically, the median particle size D50 of the coated low softening temperature backfill particle component is 2μm to 12μm, and the median particle size D50 of the high softening temperature skeleton particle component is 8μm to 35μm. Furthermore, the softening temperature of the low softening temperature glass core material is more than 280℃ lower than the particle melting initiation temperature in the high softening temperature skeleton particle component.

[0072] The specific implementation process is as follows.

[0073] Based on Example 3, the adhesive composition formulation for high-temperature sealing in Example 1 is continued to be used, and the initial curing method in Example 2 is continued to be used to form the cured body. Example 4 focuses on how to specifically control the particle size range of the coated low softening temperature backfill particle component, the particle size range of the high softening temperature skeleton particle component, and the temperature difference range between the low softening temperature glass core material and the high softening temperature skeleton particle component, and explains how the above parameter relationships correspond to the subsequent local softening flow and crack backfilling process.

[0074] The median particle size D50 of the coated low softening temperature backfill particle component is achieved by controlling the crushing and grading particle size of the low softening temperature glass core material. The median particle size D50 of the high softening temperature skeleton particle component is achieved by sieving mullite powder, alumina powder and cordierite powder separately and then mixing them in proportion.

[0075] Low softening temperature glass cores can be coarsely crushed by mechanical crushing first, and then the particle size distribution can be controlled by air classification or graded sieving, so that the median particle size D50 of the low softening temperature glass cores before coating treatment is within the range of 2μm to 12μm.

[0076] After the inorganic coating layer of the low softening temperature glass core material is deposited, the particle size of the coated low softening temperature backfill particles is re-inspected. During the re-inspection, a laser particle size analyzer is used to confirm that the median particle size D50 of the coated low softening temperature backfill particles is still within the range of 2μm to 12μm.

[0077] Mullite powder, alumina powder, and cordierite powder are sieved and gradation controlled before being mixed to ensure that the overall median particle size D50 of the mixed high softening temperature skeleton particle component is within the range of 8μm to 35μm. The median particle size D50 of the high softening temperature skeleton particle component is also detected by a laser particle size analyzer.

[0078] The softening temperature of the low softening temperature glass core material is controlled by selecting different types of glass powder. The glass powder material is selected from phosphate glass, borosilicate glass and boron zinc silicon glass, and the selection condition is that the softening temperature is in the range of 400℃ to 620℃.

[0079] The melting initiation temperature of the particles in the high softening temperature skeleton particle component is determined by the material itself. The particle material is selected from mullite powder, alumina powder and cordierite powder, and the selection condition is that the particle melting initiation temperature is higher than 900℃.

[0080] The softening temperature of the low softening temperature glass core material is determined by a thermomechanical analyzer or a high-temperature microscope. The melting initiation temperature of the particles in the high softening temperature skeleton particle component is determined by a high-temperature microscope or a differential scanning calorimeter. After the measurement is completed, the temperature difference between the two is calculated, and a temperature difference greater than 280℃ is used as the qualification criterion.

[0081] Under the formulation conditions of Example 1, the low softening temperature glass core material is selected from borosilicate glass powder, which has a softening temperature of 520°C. The high softening temperature skeleton particle components are selected from mullite powder, alumina powder, and cordierite powder, and the particle melting initiation temperature of the mullite powder, alumina powder, and cordierite powder is higher than 900°C.

[0082] After adopting the above material combination, the softening temperature of the low softening temperature glass core is at least 380°C lower than the particle melting initiation temperature of the high softening temperature skeleton particle component, thus satisfying the temperature difference condition of more than 280°C lower.

[0083] Under the formulation conditions of Example 1, the median particle size D50 of the coated low softening temperature backfill particle component was controlled between 4 μm and 7 μm, and the median particle size D50 of the high softening temperature skeleton particle component was controlled between 12 μm and 22 μm.

[0084] With the above particle size combination, the particle size of the coated low softening temperature backfill particle component is smaller than that of the high softening temperature skeleton particle component. Therefore, the coated low softening temperature backfill particle component can enter the particle boundary between adjacent high softening temperature skeleton particle components, the pore intersection area surrounded by high softening temperature skeleton particle components, and the interface between the continuous bonding network and the high softening temperature skeleton particle component.

[0085] When the median particle size D50 of the coated low softening temperature backfill particle component is controlled within the range of 2μm to 12μm, the coated low softening temperature backfill particle component can enter the gap region formed between the high softening temperature skeleton particle components. At the same time, the coated low softening temperature backfill particle component will not be distributed in a completely dispersed state in the continuous bonding network during the mixing stage.

[0086] When the median particle size D50 of the coated low softening temperature backfill particle component is higher than 12μm, the coated low softening temperature backfill particle component is more likely to remain in the large pore area formed by the accumulation of high softening temperature skeleton particle components or the surface area of ​​the slurry, and the proportion entering the particle boundary and interface area is reduced.

[0087] When the median particle size D50 of the coated low softening temperature backfill particle component is less than 2μm, the coated low softening temperature backfill particle component is more easily dispersed with the hybrid binder component to the entire area covered by the continuous binder network. After the low softening temperature glass core material softens, the source of backfill material in the local area is no longer concentrated.

[0088] The internal gaps formed between adjacent high softening temperature skeleton particle components when the median particle size D50 of the high softening temperature skeleton particle component is controlled within the range of 8 μm to 35 μm.

[0089] When the median particle size D50 of the high softening temperature skeleton particle component is controlled within the range of 8μm to 35μm, the internal gaps formed between adjacent high softening temperature skeleton particle components can accommodate the entry of the encapsulated low softening temperature backfill particle components, and can also maintain the particle support structure of the continuous high softening temperature skeleton phase after the initial curing.

[0090] When the median particle size D50 of the high softening temperature skeleton particle component is less than 8 μm, the interparticle gaps formed between adjacent high softening temperature skeleton particle components decrease, and the number of coated low softening temperature backfill particle components entering the particle boundary and pore intersection areas decreases.

[0091] When the median particle size D50 of the high softening temperature skeleton particle component is higher than 35 μm, the number of large pores formed between the high softening temperature skeleton particle components increases. After the coated low softening temperature backfill particle component enters the solidified body, it is easier to stay in the local large pores instead of forming a continuous distribution path along the particle boundary.

[0092] When the softening temperature of the low softening temperature glass core is more than 280°C lower than the melting initiation temperature of the particles in the high softening temperature skeleton particle component, after the industrial furnace is heated to above the softening temperature of the low softening temperature glass core, the low softening temperature glass core first undergoes local softening and flow, while the high softening temperature skeleton particle component remains solid.

[0093] Under the above temperature conditions, the continuous high softening temperature skeleton phase formed by the continuous bonding network and the high softening temperature skeleton particle components maintains the overall support structure. Therefore, the flow range of the low softening temperature glass core material is limited to the particle boundary, pore intersection and junction areas, and does not cause the overall flow of the cured body.

[0094] When the temperature difference between the softening temperature of the low softening temperature glass core and the melting initiation temperature of the particles in the high softening temperature skeleton particle component is less than 280℃, when the low softening temperature glass core begins to soften, the high softening temperature skeleton particle component is already close to the particle state change temperature range. The supporting stability of the continuous high softening temperature skeleton phase decreases, and the conditions for the low softening temperature glass core to undergo restricted flow along the particle boundary, pore intersection, and interface are weakened.

[0095] After adopting the above particle size and temperature difference relationships, in the initial curing stage, the coated low softening temperature backfill particle component remains in a dispersed particle state inside the continuous high softening temperature skeleton phase. In the high-temperature operation stage, the low softening temperature glass core material first undergoes local softening flow, while the high softening temperature skeleton particle component remains solid. In the crack formation stage, the low softening temperature glass core material enters the crack along its original distribution path. In the crack backfilling stage, the flow range of the low softening temperature glass core material is restricted to a local area and does not transform into the overall flow of the solidified body.

[0096] In this embodiment, the significance of the above-mentioned setup is that the median particle size D50 range of the coated low softening temperature backfill particle component is used to determine the spatial conditions for the coated low softening temperature backfill particle component to enter the crack-prone area; the median particle size D50 range of the high softening temperature skeleton particle component is used to determine the interstitial structure and support structure of the continuous high softening temperature skeleton phase; and the temperature difference range between the low softening temperature glass core material and the high softening temperature skeleton particle component is used to determine the temperature conditions under which the low softening temperature glass core material softens first while the high softening temperature skeleton particle component remains solid. When these three factors work together, the positional conditions of the coated low softening temperature backfill particle component can be correlated with the subsequent local softening flow conditions, thereby establishing a clear spatial and temperature basis for the subsequent crack thermal triggering backfill process.

[0097] Example 5 Specifically, when the temperature of the solidified body is higher than the softening temperature of the low softening temperature glass core material but lower than the melting initiation temperature of the particles in the high softening temperature skeleton particle component, the low softening temperature glass core material in the encapsulated low softening temperature backfill particle component undergoes local softening and flow, while the particles in the high softening temperature skeleton particle component remain solid, and the continuous high softening temperature skeleton phase formed by the continuous bonding network and the high softening temperature skeleton particle component maintains an overall support state.

[0098] The specific implementation process is as follows.

[0099] Based on the solidified body formed in Example 4, the solidified body was subjected to a heating operation treatment to simulate the heating stage experienced by the exhaust flange connection seam of an industrial furnace under actual working conditions.

[0100] The temperature rise process is carried out using a programmed temperature rise method. First, the cured body is raised from room temperature to 450°C and held for 20 minutes. Then, the cured body is raised from 450°C to 520°C and held for 30 minutes. Finally, the cured body is raised from 520°C to 580°C and held for 30 minutes.

[0101] During the above heating process, 520℃ corresponds to the lower limit trigger point of the softening temperature of the low softening temperature glass core material, and 580℃ is higher than the softening temperature of the low softening temperature glass core material but lower than the melting initiation temperature of the particles in the high softening temperature skeleton particle component. Therefore, the temperature range of 520℃ to 580℃ is used to trigger the local softening flow of the low softening temperature glass core material, but will not trigger the particles in the high softening temperature skeleton particle component to undergo a melting state change.

[0102] When the cured body temperature is below 520℃, the low softening temperature glass core material in the coated low softening temperature backfill particle component remains in a solid particle state, and the continuous high softening temperature skeleton phase formed by the continuous bonding network and the high softening temperature skeleton particle component maintains the original structure after curing and does not undergo dynamic changes.

[0103] When the temperature of the solidified body rises above 520°C, the low softening temperature glass core material in the coated low softening temperature backfill particle component begins to change from a solid particle state to a softened state. The outer layer of the low softening temperature glass core material first experiences a decrease in viscosity, and then the low softening temperature glass core material undergoes local softening flow near the location of the coated low softening temperature backfill particle component.

[0104] During the aforementioned localized softening flow process, the inorganic coating layer does not need to melt or soften entirely. Specifically, the solidified body reaches the softening temperature of the low-softening glass core material or is 20°C to 80°C higher and maintained for 10 to 60 minutes. In this embodiment, the softening temperature of the borosilicate glass powder is 520°C. The solidified body can trigger localized softening flow of the low-softening glass core material within the temperature range of 520°C to 580°C, while the inorganic coating layer still acts as a confined structure at the high softening temperature. The structure remains on the outside of the coated low softening temperature backfill particle component. Under the action of thermal expansion difference, local pressure difference and its own viscosity reduction, the low softening temperature glass core material is released outward through the micropores in the inorganic coating layer, local discontinuous coating areas, local weak areas or local micro-cracks formed by thermal cycle stress. The released low softening temperature glass core material first enters the particle boundary, pore intersection or interface where the coated low softening temperature backfill particle component was originally located, and the inorganic coating layer does not disintegrate as a whole, and the solidified body does not flow as a whole.

[0105] In this embodiment, localized softening flow specifically refers to short-distance flow occurring near particle boundaries, pore junctions, and interfaces of the low-softening-temperature glass core material. The flow range is limited to the original distribution area of ​​the coated low-softening-temperature backfill particle components and does not extend to continuous flow throughout the entire solidified body.

[0106] Within the temperature range of 520℃ to 580℃, the mullite powder, alumina powder, and cordierite powder particles in the high softening temperature skeleton particle component all remain in a solid particle state, with unchanged particle shape, unchanged particle support position, and unchanged main support pathways formed between particles.

[0107] Within the temperature range of 520℃ to 580℃, although the continuous bonding network is in a high-temperature environment, the connection between the continuous bonding network and the high softening temperature skeleton particle components still exists. Therefore, the continuous high softening temperature skeleton phase formed by the continuous bonding network and the high softening temperature skeleton particle components continues to maintain the overall support structure from the surface of the industrial furnace exhaust flange connection seam to the interior of the industrial furnace exhaust flange connection seam.

[0108] In this embodiment, the overall support structure is characterized by the continuous particle support path between the high softening temperature skeleton particle components, the continuous bonding network maintaining the connection layer between adjacent high softening temperature skeleton particle components, and the curing body not collapsing, sinking, or flowing within the temperature range of 520°C to 580°C.

[0109] Under the above temperature conditions, the low softening temperature glass core will not detach from the continuous high softening temperature framework phase and form a large-scale disordered flow after softening. Instead, it will maintain a restricted flow state within the particle-confined space formed by the high softening temperature framework particle components.

[0110] In this embodiment, the restricted flow state is specifically manifested as the low softening temperature glass core material shifting along its original distribution path near the particle boundary, pore intersection, and junction, with the shift distance being less than the scale range of the large pore region in the particle packing structure.

[0111] After heating using the above method, the low softening temperature glass core material first undergoes local softening and flow, while the particles in the high softening temperature skeleton particle component remain solid. The continuous high softening temperature skeleton phase continues to maintain an overall support state. Therefore, when the solidified body forms cracks later, it already has the material state basis required for crack thermal triggering backfilling.

[0112] When the temperature of the solidified body is further increased but still below the melting initiation temperature of the particles in the high softening temperature skeleton particle component, the local softening flow state continues to be maintained. The low softening temperature glass core material forms a local flowable material region near the particle boundary, pore intersection and junction, while the high softening temperature skeleton particle component continues to form a non-flowable support region.

[0113] In this embodiment, the significance of the above-mentioned setup is that the softening temperature of the low softening temperature glass core is lower than the melting initiation temperature of the particles in the high softening temperature skeleton particle component. Therefore, when the actual operating temperature reaches the softening range of the low softening temperature glass core, a local flowable material zone can be formed first, without simultaneously destroying the overall support structure of the continuous high softening temperature skeleton phase. At the same time, after the continuous high softening temperature skeleton phase maintains its overall support state, the flow of the low softening temperature glass core is restricted within the particle confinement space. Therefore, the subsequent movement direction of the low softening temperature glass core is more likely to remain near the particle boundary, pore intersection, and junction, thereby providing a direct flow prerequisite for subsequent entry into the crack.

[0114] Example 6 Specifically, after local softening and flow, the low softening temperature glass core material in the cured body flows along the particle boundary, pore junction, and interface. When cracks form in the cured body at the particle boundary, pore junction, or interface, the low softening temperature glass core material flowing along the particle boundary, pore junction, and interface enters the crack.

[0115] The specific implementation process is as follows.

[0116] Based on Example 5, the solidified body that has been heated to above 520°C but below the melting initiation temperature of the particles in the high softening temperature skeleton particle component is used as the implementation object. The solidified body is kept at 580°C for 30 minutes so that the low softening temperature glass core material in the coated low softening temperature backfill particle component is continuously in a local softening flow state.

[0117] During the 580℃ holding phase, the flow starting point of the low softening temperature glass core material is located at the original distribution position of the coated low softening temperature backfill particle components. The low softening temperature glass core material moves from the particle boundary to the adjacent particle boundary and extends to the pore junction and interface within the connecting layer covered by the continuous bonding network.

[0118] In this embodiment, the flow starting point of the low softening temperature glass core material is specifically the local glass phase starting point formed after the low softening temperature glass core material is released outward through the release structure of the inorganic coating layer, rather than the starting point formed after the entire coated low softening temperature backfill particle component melts. In specific implementation, the coated low softening temperature backfill particle component is pre-embedded or distributed at the particle boundary, pore junction, and interface. After the low softening temperature glass core material is released outward, it directly enters the local connected space formed in the above-mentioned locations. When the thermal cycle causes crack openings to form at the particle boundary, pore junction, or interface, a connecting path is formed between the crack opening, adjacent pores, and particle boundary. The softened low softening temperature glass core material enters the crack interior under the guidance of capillary traction, local pressure difference, and crack opening. Subsequently, when the temperature drops below the softening temperature of the low softening temperature glass core material, it is re-solidified and retained inside the crack.

[0119] In this embodiment, the flow along the particle boundary is specifically manifested as the low softening temperature glass core material moving within the minimum particle spacing region formed between two adjacent high softening temperature skeleton particle components. The direction of the position movement is consistent with the direction of the narrow slit formed between the two adjacent high softening temperature skeleton particle components.

[0120] In this embodiment, the flow along the pore junction is specifically manifested as follows: the low softening temperature glass core moves from a narrow slit path corresponding to a particle boundary to a pore connection position surrounded by three or more high softening temperature skeleton particles, and forms a local aggregation in the pore connection position, and then continues to move from the pore connection position to another narrow slit path corresponding to a particle boundary.

[0121] In this embodiment, the flow along the interface is specifically manifested as the low softening temperature glass core material moving at the point where the continuous bonding network contacts the high softening temperature skeleton particle component. The movement path is consistent with the direction of the interface bonding layer covering the surface of the high softening temperature skeleton particle component by the continuous bonding network.

[0122] After the 580℃ holding stage, the cured body is subjected to thermal cycling treatment. The thermal cycling treatment is carried out 20 times in a manner of heating to 580℃ and holding for 30 minutes, cooling to 200℃ and holding for 20 minutes, and then heating to 580℃ and holding for 30 minutes, in order to simulate the thermal stress changes of the exhaust flange connection seam of an industrial furnace during repeated heating and cooling.

[0123] During the thermal cycling process, local stress concentration occurs at the particle boundary due to the thermal expansion difference between adjacent high softening temperature skeleton particle components and the change in particle spacing. At the pore intersection, local stress superposition occurs due to the convergence of multiple particle gap paths. At the junction, local interface stress concentration occurs due to the interface deformation difference between the continuous bonding network and the high softening temperature skeleton particle components. Therefore, the particle boundary, pore intersection, and junction become the preferred locations for crack formation.

[0124] When cracks form at the particle boundary, the low softening temperature glass core material that has already flowed along the particle boundary directly enters the crack formed at the particle boundary and continues to fill the crack space along the crack length direction.

[0125] When a crack forms at the pore junction, the low softening temperature glass core material that has been stationary at the pore junction and continues to flow enters the crack that is connected to the pore junction from the pore junction and continues to fill the crack space in the direction of extension to both sides of the crack.

[0126] When a crack forms at the interface, the low softening temperature glass core material that has already flowed along the interface enters the crack formed at the interface from the interface connection between the continuous bonding network and the high softening temperature skeleton particle components, and continues to fill the crack space along the interface crack path.

[0127] In this embodiment, the entry into the crack is specifically manifested as the low softening temperature glass core material crossing the crack opening edge from the originally distributed particle boundary, pore intersection or junction, and entering the internal void surrounded by the crack walls on both sides, and forming a continuous filling segment in the internal void.

[0128] After 20 thermal cycles, when the cross-section of the solidified body was observed, it could be seen that some of the low softening temperature glass core material had entered the crack from the particle boundary, pore intersection and junction. There were filling areas inside the crack that were connected to the original distribution path of the surrounding low softening temperature backfill particles.

[0129] In this embodiment, the significance of the above-mentioned treatment method is that after the low softening temperature glass core material is in a locally softened flow state above 520°C, it does not flow randomly in all directions of the solidified body, but flows along the existing paths formed at the particle boundary, pore confluence, and interface. Therefore, when cracks form at the particle boundary, pore confluence, or interface, the low softening temperature glass core material can directly enter the crack from the adjacent position without needing to migrate over a long distance. At the same time, the crack formation position corresponds to the flow path of the low softening temperature glass core material. Cracks formed at the particle boundary correspond to the flow path at the particle boundary, cracks formed at the pore confluence correspond to the flow path at the pore confluence, and cracks formed at the interface correspond to the flow path at the interface. Therefore, the low softening temperature glass core material can enter the crack in the early stage of crack formation.

[0130] Example 7 Specifically, when the temperature of the cured body drops below the softening temperature of the low softening temperature glass core, the low softening temperature glass core that has entered the crack solidifies and remains within the crack.

[0131] The specific implementation process is as follows.

[0132] Based on Example 6, the solidified body that has completed the process of the low softening temperature glass core material entering the crack is used as the implementation object. The 580°C holding stage is ended while the low softening temperature glass core material is still in a softened and flowing state, and then the solidified body is subjected to controlled cooling treatment.

[0133] The controlled cooling process is carried out in stages. First, the cured body is cooled from 580°C to 480°C and held for 20 minutes. Then, the cured body is cooled from 480°C to 350°C and held for 20 minutes. Finally, the cured body is cooled from 350°C to 200°C and held for 30 minutes.

[0134] During the process of decreasing from 580℃ to 480℃, the flowability of the low softening temperature glass core material begins to decline. The low softening temperature glass core material that had already entered the crack continues to remain in the crack space and remains in a filling state along the crack length and crack depth directions.

[0135] During the process of decreasing from 480℃ to 350℃, the low softening temperature glass core gradually crosses the lower limit of the softening temperature and changes from a softened state to a bonded and reinforced state. The low softening temperature glass core that was originally located inside the crack no longer flows out of the crack, but remains in its original position inside the crack.

[0136] During the process of decreasing from 350℃ to 200℃, the low softening temperature glass core material entering the crack continues to transform from a bonded and reinforced state to a solidified state. The low softening temperature glass core material forms a fixed connection with the crack walls on both sides of the crack at the contact point, and a solidified filler corresponding to the shape of the crack is formed inside the crack.

[0137] In this embodiment, the solidification and retention within the crack is specifically manifested in that the low softening temperature glass core material entering the crack loses its ability to continue flowing after the temperature drops below 520°C, and maintains its original filling position between the crack walls on both sides of the crack, without flowing back from the inside of the crack to the particle boundary, pore confluence, or interface.

[0138] After controlled cooling is completed, when the cross-section of the solidified body is observed, it can be seen that there is a solidified low softening temperature glass core material filling area inside the crack. The low softening temperature glass core material filling area is connected to the original flow path in the particle boundary, pore intersection or junction, and is in contact with the crack walls on both sides of the crack.

[0139] After controlled cooling, when the solidified body is heated to 520°C again and held for 20 minutes, the low softening temperature glass core material that has been solidified inside the crack remains inside the crack and does not detach from the crack as a whole, nor does it leave the crack space empty.

[0140] In this embodiment, the significance of the aforementioned cooling treatment method lies in the fact that, after the low softening temperature glass core material enters the crack, by lowering the temperature below its softening temperature, the low softening temperature glass core material changes from a locally softened and flowing state to a solidified state. This transforms the crack-filling process, which was originally only in a flowing state, into a crack-sealing process that is stably maintained inside the crack. Simultaneously, after the low softening temperature glass core material completes solidification inside the crack, the crack space is occupied by the solidified material, and new internal connections are formed between the crack walls on both sides of the crack. Therefore, the space for further crack propagation is reduced, and the crack penetration path is blocked. Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is defined by the appended technical solutions and their equivalents.

Claims

1. An adhesive composition for high-temperature sealing, characterized in that, By weight, it includes: 10 to 18 parts of a hybrid binder component, said hybrid binder component comprising a polymethylsilsesquioxane precursor, ethyl silicate, and aluminum dihydrogen phosphate; 32 to 45 parts of high softening temperature skeleton particle component, wherein the high softening temperature skeleton particle component includes at least two of mullite powder, alumina powder and cordierite powder, and the melting initiation temperature of the particles in the high softening temperature skeleton particle component is higher than 900°C. Eight to sixteen parts of a coated low softening temperature backfill particle component, wherein the coated low softening temperature backfill particle component includes a low softening temperature glass core and an inorganic coating layer disposed on the outside of the low softening temperature glass core. The low softening temperature glass core includes at least one of phosphate glass, borosilicate glass and boron zinc silicon glass, and the softening temperature of the low softening temperature glass core is 400°C to 620°C. The inorganic coating layer includes at least one of silicon dioxide and alumina. Two to eight parts of a toughening and crack-resistant component, wherein the toughening and crack-resistant component includes at least one of zirconium oxide powder, hexagonal boron nitride sheets and chopped alumina fibers; 0.3 to 2 parts of rheology modifier, wherein the rheology modifier includes at least one of fumed silica and organobentonite; 0.1 to 1 part of an interface modifier, wherein the interface modifier comprises at least one of an aminosilane coupling agent and an epoxysilane coupling agent.

2. The adhesive composition for high-temperature sealing according to claim 1, characterized in that, The adhesive composition is initially cured at 100°C to 250°C to form a cured body. In the cured body, the hybrid adhesive component is cured to form a continuous adhesive network. The continuous adhesive network and the high softening temperature skeleton particle component together form a continuous high softening temperature skeleton phase.

3. The adhesive composition for high-temperature sealing according to claim 2, characterized in that, The coated low softening temperature backfill particle component is dispersed within the continuous high softening temperature skeleton phase and embedded in the particle boundary between adjacent high softening temperature skeleton particle components. It is also distributed in the pore junctions formed by the high softening temperature skeleton particle components and at the interface between the continuous bonding network and the high softening temperature skeleton particle components.

4. The adhesive composition for high-temperature sealing according to claim 3, characterized in that, The median particle size D50 of the coated low softening temperature backfill particle component is 2μm to 12μm, and the median particle size D50 of the high softening temperature skeleton particle component is 8μm to 35μm. Furthermore, the softening temperature of the low softening temperature glass core material is more than 280°C lower than the particle melting initiation temperature in the high softening temperature skeleton particle component.

5. The adhesive composition for high-temperature sealing according to claim 4, characterized in that, When the solidified body is at a temperature higher than the softening temperature of the low softening temperature glass core material but lower than the melting initiation temperature of the particles in the high softening temperature skeleton particle component, the low softening temperature glass core material in the encapsulated low softening temperature backfill particle component undergoes local softening and flow, the particles in the high softening temperature skeleton particle component remain solid, and the continuous high softening temperature skeleton phase formed by the continuous bonding network and the high softening temperature skeleton particle component maintains an overall support state.

6. The adhesive composition for high-temperature sealing according to claim 5, characterized in that, After local softening and flow, the low-softening-temperature glass core material in the solidified body flows along the particle boundary, pore intersection, and interface.

7. The adhesive composition for high-temperature sealing according to claim 6, characterized in that, When cracks form at particle boundaries, pore junctions, or interfaces in the solidified body, the low softening temperature glass core material flowing along the particle boundaries, pore junctions, and interfaces enters the cracks.

8. The adhesive composition for high-temperature sealing according to claim 7, characterized in that, When the temperature of the solidified body decreases below the softening temperature of the low softening temperature glass core, the low softening temperature glass core that has entered the crack solidifies and remains within the crack.

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