A composite sewing thread resistant to ultra-high temperatures

Abstract

This application relates to the field of high-temperature filtration materials technology, specifically disclosing a composite sewing thread resistant to ultra-high temperatures. It includes a composite sewing thread and a high-temperature resistant filter felt; wherein the composite sewing thread is woven from 31024 stainless steel wire and other high-temperature resistant alloy materials, achieving a temperature resistance of over 700°C; the high-temperature resistant filter felt is made of high-temperature resistant carbon felt material, and its temperature resistance matches that of the composite sewing thread. The composite sewing thread of this application can be used to sew high-temperature resistant carbon felt filter felts to manufacture filter bag assemblies for use in ultra-high temperature flue gas filtration environments. It has the advantages of maintaining high strength at temperatures above 700°C, synergistic matching with the thermophysical properties of the filter felt material, and effectively avoiding localized failures caused by differences in material temperature resistance. Therefore, the filter bag assembly possesses excellent high-temperature resistance, corrosion resistance, and overall structural stability during long-term operation.

Description

Technical Field

[0001] This application relates to the field of high-temperature filtration materials technology, and more specifically, it relates to a composite sewing thread resistant to ultra-high temperatures. Background Technology

[0002] High-temperature filter materials are used in the chemical and metallurgical fields to efficiently separate gas-solid two-phase flows under extreme conditions. Their applications include high-temperature reaction gas purification and catalyst recovery in chemical production, as well as flue gas dust removal and valuable metal enrichment in metallurgical processes. Compared with traditional room temperature or water washing processes, these materials, with their excellent thermal shock resistance, corrosion resistance, and high filtration accuracy, can achieve hot separation in high-temperature environments. This avoids energy loss and dew point corrosion caused by gas cooling, and can efficiently recover high-value-added fine-particle products in a dry state, thereby improving energy utilization efficiency, simplifying process flow, and providing technical support for meeting environmental emission standards.

[0003] High-temperature filter materials are made by stitching high-temperature resistant filter felt together with ordinary metal wire or single-material sewing thread. However, under ultra-high temperature conditions, the sewing thread and filter felt have different thermophysical properties such as thermal expansion coefficient and thermal conductivity. In addition, the sewing thread itself suffers severe strength decay at high temperatures. As a result, the filter bag assembly will experience local stress concentration and structural failure due to material thermal stress mismatch during long-term operation, which in turn affects the overall reliability and service life of the filtration system. Summary of the Invention

[0004] To address the problem of localized stress concentration and structural failure in filter bag assemblies due to material thermal stress mismatch caused by sewing high-temperature filter felt with ordinary metal wire or single-material sewing thread, this application provides an ultra-high temperature resistant composite sewing thread.

[0005] This application provides a composite sewing thread resistant to ultra-high temperatures, using the following technical solution:

[0006] A composite sewing thread resistant to ultra-high temperature includes a composite sewing thread and a high-temperature resistant filter felt; wherein, the composite sewing thread is woven from 31024 stainless steel wire and other high-temperature resistant alloy materials, the high-temperature resistant filter felt is made of high-temperature resistant carbon felt material, and the temperature resistance of the composite sewing thread reaches above 700°C.

[0007] It also includes the use of composite sewing thread, including the following steps:

[0008] S1. Select high-temperature resistant carbon felt material as the main body of the filter bag;

[0009] S2. Use composite stitching thread to sew the edges and seams of the filter bag;

[0010] S3. When installing the filter bag, ensure that the seams are not stretched excessively.

[0011] S4. Regularly check the integrity of the seams of the filter bags.

[0012] By adopting the above technical solution, the use of 31024 stainless steel wire with a temperature resistance of over 700°C as the base material for the sewing thread provides inherent high-temperature and corrosion resistance. Combined with other high-temperature alloy materials, this enhances its mechanical properties under ultra-high temperatures. Simultaneously, the high-temperature filter felt is made of high-temperature carbon felt, whose temperature resistance matches that of the composite sewing thread, ensuring the synergy of the thermophysical properties of the filter bag body and the sewing thread under high-temperature conditions. This avoids localized failures caused by mismatched material temperature resistance. Therefore, the entire filter bag assembly achieves overall high-temperature resistance, corrosion resistance, and structural stability in high-temperature flue gas filtration environments.

[0013] Preferably, before weaving, the composite sewing thread is subjected to surface pretreatment of the 31024 stainless steel wire and other high-temperature resistant alloy materials, and the surface pretreatment includes pickling, passivation and drying treatments performed in sequence.

[0014] By adopting the above technical solution, the pickling treatment of 31024 stainless steel wire and other alloy wires before weaving removes oxide scale, oil, and other impurities from the surface of the metal wire, resulting in a clean metal surface. Subsequent passivation treatment forms a dense and chemically stable passivation film on the clean metal surface, enhancing the material's corrosion resistance in subsequent high-temperature and corrosive environments. Finally, drying removes residual moisture from the previous treatments, providing dry, uniformly active raw materials for subsequent weaving processes. Therefore, this method improves the surface quality of the composite sewing thread raw materials, enhances their corrosion resistance, and ensures the stability of subsequent composite weaving processes and product lifespan.

[0015] Preferably, the pickling uses a nitric acid solution with a mass fraction of 10% to 20%, the treatment temperature is 40 to 60°C, and the treatment time is 10 to 30 minutes; the passivation treatment uses a citric acid solution with a mass fraction of 5% to 15%, the treatment temperature is room temperature, and the treatment time is 5 to 15 minutes; the drying treatment is carried out at 80 to 100°C, and the drying time is 20 to 40 minutes.

[0016] By adopting the above technical solution, the pickling process uses nitric acid solution within a preset concentration, temperature, and time range, which can remove surface impurities while avoiding corrosion damage to the 31024 stainless steel wire and other high-temperature alloy substrates. The use of citric acid solution for room-temperature passivation is an environmentally friendly and efficient passivation method that can promote the formation of a dense passivation film within a specified time. Subsequent drying at a set temperature for a period of time can fully evaporate moisture without causing unnecessary thermal stress or changes in the microstructure of the material, ensuring that the metal wire enters the next process in optimal surface condition. Therefore, a standardized and controllable set of surface pretreatment process parameters is obtained, laying the foundation for manufacturing composite sewing threads with consistent performance.

[0017] Preferably, the composite sewing thread is made by a multi-strand braiding process, with 3 to 9 strands, a twist of 30 to 80 twists / m, a diameter of 0.3 to 1.5 mm, and a breaking strength ≥200N.

[0018] By adopting the above technical solution, the pre-treated 31024 stainless steel wire is combined with other high-temperature resistant alloy wires using a multi-strand braiding process. With the number of braided strands set within an appropriate range, the cross-sectional area is provided to withstand loads while ensuring the thread's flexibility and sewingability. The braiding twist is controlled within a specific range, allowing the strands to tightly bind together, forming a structurally stable composite that enhances the overall strength and wear resistance of the thread. The final product diameter is within a specific range, and its breaking strength is ensured to be no less than the specified value. These parameters collectively define the mechanical properties of the thread, enabling it to withstand the stress generated by the high-temperature filter bag during filtration and cleaning. Therefore, a high-temperature resistant composite sewing thread with flexibility, high strength, high structural stability, and applicability is obtained.

[0019] Preferably, the other high-temperature resistant alloy material is selected from one or more of nickel-based alloys, cobalt-based alloys, or iron-chromium-aluminum alloys, and the temperature resistance of the other high-temperature resistant alloy material is not lower than 700°C, and the mass ratio of the other high-temperature resistant alloy material to 31024 stainless steel wire is 1:0.5 to 2.

[0020] By adopting the above technical solution, since the selected nickel-based alloys, cobalt-based alloys, or iron-chromium-aluminum alloys all have a temperature resistance of not less than 700°C, they can still maintain mechanical strength, oxidation resistance, and creep resistance at ultra-high temperatures, complementing or enhancing the high-temperature performance of 31024 stainless steel wire. By controlling the mass ratio of these high-temperature resistant alloy materials to 31024 stainless steel wire within a preset range, the final performance ratio of the composite sewing thread can be adjusted, allowing the material composition of the composite sewing thread to be adapted to different specific high-temperature working conditions. Therefore, the effect of expanding the selection range of composite sewing thread materials, achieving performance designability, and ensuring that its comprehensive performance at high temperatures surpasses that of single-material sewing threads is achieved.

[0021] Preferably, the high-temperature resistant filter felt is pretreated before sewing. The pretreatment includes heat setting at 120-180°C for 30-60 minutes, and the heat shrinkage rate of the high-temperature resistant filter felt is controlled to be ≤1.5% in the length direction and ≤1.0% in the width direction.

[0022] By adopting the above technical solution, the filter felt made of high-temperature resistant carbon felt material undergoes heat setting pretreatment before sewing, and is maintained at a set temperature for a period of time. This process can promote stress relaxation and structural adjustment of the internal fiber structure of the carbon felt under heat, releasing some of the shrinkage stress that may occur during subsequent high-temperature use. By controlling the dimensional change rate after heat setting within the allowable range, the dimensional stability of the filter felt as the main material of the filter bag can be improved, preventing the sewn filter bag from deforming, experiencing stress concentration in the seams, or experiencing a decrease in filtration performance due to substrate shrinkage under high-temperature conditions. Therefore, the dimensional stability and shape retention of the high-temperature resistant filter felt are improved, providing a guarantee for subsequent precision sewing and the dimensional reliability of the filter bag under long-term high temperatures.

[0023] Preferably, the high-temperature resistant filter felt is a multi-layer composite structure, comprising an upper carbon felt, a middle high-temperature resistant fiber mesh, and a lower carbon felt arranged sequentially. The mesh size of the middle high-temperature resistant fiber mesh is 1-5 mm. The multi-layer composite structure is composited by a needle punching process with a needle punching density of 50-100 needles / cm², and the overall thickness after composite is 2-8 mm.

[0024] By adopting the above technical solution, the high-temperature resistant filter felt is designed as a multi-layer composite structure consisting of an upper carbon felt layer, a middle high-temperature resistant fiber mesh layer, and a lower carbon felt layer. The carbon felt layer provides high-temperature resistance and filtration function, while the middle high-temperature resistant fiber mesh layer serves as a reinforcing skeleton, with its specific range of mesh pore sizes supporting the upper and lower carbon felt layers. The three-layer structure is composited at a preset density through a needle-punching process, with the needle-punched hooks carrying the fibers interlacing to firmly entangle each layer into a whole. The resulting composite felt, with an overall thickness within a specific range, combines filtration accuracy, overall mechanical strength, anti-delamination ability, and air permeability. Therefore, a high-temperature resistant filter felt with reinforced structure and balanced performance is obtained, overcoming the shortcomings of insufficient strength and easy damage that can occur with a single carbon felt.

[0025] Preferably, during the sewing process, a double-lock stitch is used, the stitch length is 3-8mm, the sewing tension is controlled at 2-8N, the sewing temperature is controlled between room temperature and 150°C, and the joints of the sewing thread are fixed by hot melt adhesive bonding or metal sleeve pressing, wherein the temperature resistance of the hot melt adhesive is not less than 700°C.

[0026] By adopting the above technical solutions, the use of double-lock stitches in the sewing process provides a strong and anti-unraveling structure suitable for applications subject to dynamic stress. Controlling the stitch spacing within a specific range ensures dense stitching to bear the load and guarantee sealing, while preventing damage to the filter felt substrate from excessively small stitches. Controlling the sewing tension within a preset range ensures the stitches are taut and adhere to the material, preventing excessive tension from damaging the filter felt or impairing the stitch performance. Controlling the sewing temperature between room temperature and a certain temperature helps adapt to filter felt materials in different pretreatment states. Using high-temperature resistant hot melt adhesive or metal sleeves to fix the sewing thread joints ensures that the joints will not loosen under high temperatures, maintaining the overall continuity of the sewing thread. Therefore, the improved sewing process parameters and specifications effectively utilize the properties of the composite sewing thread and filter felt material, forming sewing joints.

[0027] Preferably, the surface of the composite sewing thread is coated with a high-temperature resistant coating, which is an organosilicon resin coating or a ceramic-based composite coating, with a coating thickness of 10-50 μm. The coating method is immersion or spraying, and the coating is cured at 150-250°C for 20-40 minutes.

[0028] By adopting the above technical solution, a high-temperature resistant coating is applied to the surface of the braided composite sewing thread. This coating can be made of silicone resin or a ceramic-based composite material, both of which are heat-resistant and chemically inert. By controlling the coating thickness within a certain range, surface protection can be provided to the thread without increasing its diameter or stiffness. Uniform coverage of the coating can be achieved through dipping or spraying. After coating, curing at a set temperature for a certain time allows the coating material to cross-link or sinter, forming a firmly adhered protective film. This coating can isolate the metal wire from corrosive media, reduce high-temperature oxidation, and improve the wear resistance of the sewing thread. Therefore, the surface protection performance of the composite sewing thread is enhanced, extending its service life in high-temperature corrosive environments.

[0029] Preferably, after the high-temperature resistant filter felt is sewn into a filter bag, the seam area is subjected to a secondary reinforcement treatment. The secondary reinforcement treatment involves applying a high-temperature resistant sealant to the seam area. The high-temperature resistant sealant has a temperature resistance of not less than 700°C, the coating width is 5-15 mm on each side of the seam, the coating thickness is 0.2-0.8 mm, and after coating, it is pre-dried at 80-120°C for 10-20 min, and then fully cured at 200-300°C for 30-60 min.

[0030] By adopting the above technical solution, a secondary reinforcement treatment is performed on the seam area after the filter bag is sewn. Specifically, a high-temperature resistant sealant with a temperature resistance of not less than 700°C is applied. This sealant is applied within a certain width and thickness on both sides of the seam, covering and penetrating the needle holes and gaps in the stitches. After application, it is pre-dried at a set temperature for a period of time to remove solvents or low-boiling-point components from the sealant, forming an initial tack state. Subsequently, it is fully cured at a higher temperature for a period of time, allowing the sealant to be fully vulcanized or polymerized, forming a strong, dense, and elastic sealing layer. This secondary reinforcement layer can seal micropores caused by sewing needle punctures, enhance the sealing performance of the filter bag, prevent flue gas short circuits, and provide additional protection and mechanical anchoring for the seam itself, dispersing the local stress on the seam. Therefore, the overall sealing reliability, structural strength, and service durability of the filter bag sewn area are improved.

[0031] In summary, this application has the following beneficial effects:

[0032] 1. This application uses a stitching thread made of high-temperature resistant 31024 stainless steel wire and other high-temperature resistant alloy materials, which is used in conjunction with a filter felt made of high-temperature resistant carbon felt material. The composite stitching thread can maintain high strength at high temperatures and works synergistically with the thermophysical properties of the filter felt material, thereby avoiding local failure caused by the mismatch of material temperature resistance. This achieves the effect of making the filter bag assembly have high-temperature resistance, corrosion resistance and overall structural stability in ultra-high temperature flue gas filtration environment.

[0033] 2. In this application, the preferred design of the high-temperature resistant filter felt is a multi-layer composite structure consisting of an upper layer of carbon felt, a middle layer of high-temperature resistant fiber mesh, and a lower layer of carbon felt. The composite structure is achieved through a needle-punching process. The middle layer of high-temperature resistant fiber mesh serves as a reinforcing skeleton to enhance mechanical strength. The needle-punching process binds the layers together, thereby obtaining a high-temperature resistant filter felt with reinforced structure and balanced performance. This filter felt maintains high filtration accuracy and air permeability while overcoming the shortcomings of insufficient strength and easy breakage of a single material, and also helps the filter bag achieve easy dust removal performance.

[0034] 3. The method of this application improves the corrosion resistance of composite sewing thread by performing surface pretreatment, while controlling the number of strands and twist of multi-strand weaving to improve its mechanical properties. During the sewing process, the stitch length and tension are controlled and double-thread lockstitch is used to ensure a firm sewing. After sewing, the sewing area is coated with high-temperature resistant sealant for secondary reinforcement, thereby improving the reliability of each link from raw materials to the final sewn product. Therefore, the service life of filter bags in harsh high-temperature and corrosive environments is extended. Attached Figure Description

[0035] Figure 1 A flowchart illustrating the use of a high-temperature resistant composite sewing thread proposed in this application. Detailed Implementation

[0036] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0037] Technical concept:

[0038] High-temperature filter materials are made by stitching high-temperature resistant filter felt together with ordinary metal wire or single-material sewing thread. However, under ultra-high temperature conditions, the sewing thread and filter felt have different thermophysical properties such as thermal expansion coefficient and thermal conductivity. In addition, the sewing thread itself suffers severe strength decay at high temperatures. As a result, the filter bag assembly will experience local stress concentration and structural failure due to material thermal stress mismatch during long-term operation, which in turn affects the overall reliability and service life of the filtration system.

[0039] This application discloses a composite sewing thread resistant to ultra-high temperatures. It includes a composite sewing thread and a high-temperature resistant filter felt; wherein the composite sewing thread is woven from 31024 stainless steel wire and other high-temperature resistant alloy materials, and its temperature resistance reaches over 700°C; the high-temperature resistant filter felt is made of high-temperature resistant carbon felt material, and its temperature resistance matches that of the composite sewing thread.

[0040] This application uses a stitching thread made of high-temperature resistant 31024 stainless steel wire and other high-temperature resistant alloy materials, which is used in conjunction with a filter felt made of high-temperature resistant carbon felt material. The composite stitching thread can maintain high strength at high temperatures and works synergistically with the thermophysical properties of the filter felt material, thereby avoiding local failure caused by the mismatch of material temperature resistance. This achieves the effect of enabling the filter bag assembly to have high-temperature resistance, corrosion resistance and overall structural stability in ultra-high temperature flue gas filtration environment.

[0041] Example 1: This example provides a composite sewing thread resistant to ultra-high temperature, including a composite sewing thread and a high-temperature resistant filter felt; wherein, the composite sewing thread is woven from 31024 stainless steel wire and other high-temperature resistant alloy materials, and its temperature resistance reaches above 700°C; the high-temperature resistant filter felt is made of high-temperature resistant carbon felt material, and its temperature resistance matches that of the composite sewing thread.

[0042] Before weaving, the 31024 stainless steel wire and other high-temperature alloy materials were subjected to surface pretreatment, which included pickling, passivation and drying in sequence.

[0043] Pickling was performed using a 10% nitric acid solution at 40°C for 10 minutes; passivation was performed using a 5% citric acid solution at room temperature for 5 minutes; and drying was carried out at 80°C for 20 minutes.

[0044] The composite sewing thread is made through a multi-strand braiding process, with 3 strands and a twist of 30 twists / m. The diameter of the braided composite sewing thread is 0.3mm, and its breaking strength is 200N.

[0045] Among them, the other high-temperature resistant alloy materials are nickel-based alloys with a temperature resistance of 700°C and a mass ratio of 1:0.5 with 31024 stainless steel wire.

[0046] The high-temperature resistant filter felt was pre-treated before sewing. The pre-treatment included heat setting at 120°C for 30 minutes. After treatment, the heat shrinkage rate of the high-temperature resistant filter felt was 1.5% in the length direction and 1.0% in the width direction.

[0047] The high-temperature resistant filter felt is a multi-layer composite structure, consisting of an upper carbon felt, a middle high-temperature resistant fiber mesh, and a lower carbon felt arranged sequentially. The mesh size of the middle high-temperature resistant fiber mesh is 1mm. The multi-layer composite structure is composited by needle punching, with a needle punching density of 50 needles / cm². The overall thickness after composite is 2mm.

[0048] During the sewing process, a double-lock stitch is used, the stitch length is 3mm, the sewing tension is controlled at 2N, the sewing temperature is at room temperature, and the joints of the sewing thread are fixed by hot melt adhesive, which has a temperature resistance of 700°C.

[0049] The composite sewing thread is coated with a high-temperature resistant coating, which is an organosilicon resin coating with a thickness of 10μm. The coating method is immersion, and the coating is cured at 150℃ for 20min after coating.

[0050] Among them, after the high-temperature resistant filter felt is sewn into a filter bag, the seam area is subjected to secondary reinforcement treatment. The secondary reinforcement treatment is to apply high-temperature resistant sealant to the seam area. The high-temperature resistant sealant has a temperature resistance of 700°C, the coating width is 5mm on each side of the seam, the coating thickness is 0.2mm, and after coating, it is pre-dried at 80°C for 10min, and then fully cured at 200°C for 30min.

[0051] Example 2: This example provides a composite sewing thread resistant to ultra-high temperature, including a composite sewing thread and a high-temperature resistant filter felt; wherein, the composite sewing thread is woven from 31024 stainless steel wire and other high-temperature resistant alloy materials, and its temperature resistance reaches above 700°C; the high-temperature resistant filter felt is made of high-temperature resistant carbon felt material, and its temperature resistance matches that of the composite sewing thread.

[0052] Before weaving, the 31024 stainless steel wire and other high-temperature alloy materials were subjected to surface pretreatment, which included pickling, passivation and drying in sequence.

[0053] Pickling was performed using a 15% nitric acid solution at 50°C for 20 minutes; passivation was performed using a 10% citric acid solution at room temperature for 10 minutes; and drying was carried out at 90°C for 30 minutes.

[0054] The composite sewing thread is made through a multi-strand braiding process, with 6 strands and a twist of 55 twists / m. The diameter of the braided composite sewing thread is 0.9mm, and its breaking strength is 350N.

[0055] Among them, the other high-temperature resistant alloy materials are cobalt-based alloys with a temperature resistance of 750°C and a mass ratio of 1:1.25 with 31024 stainless steel wire.

[0056] The high-temperature resistant filter felt was pre-treated before sewing. The pre-treatment included heat setting at 150°C for 45 minutes. After treatment, the heat shrinkage rate of the high-temperature resistant filter felt was 1.0% in the length direction and 0.5% in the width direction.

[0057] The high-temperature resistant filter felt is a multi-layer composite structure, consisting of an upper carbon felt, a middle high-temperature resistant fiber mesh, and a lower carbon felt arranged sequentially. The mesh size of the middle high-temperature resistant fiber mesh is 3mm. The multi-layer composite structure is composited by needle punching, with a needle punching density of 75 needles / cm². The overall thickness after composite is 5mm.

[0058] During the sewing process, a double-lock stitch is used, the stitch length is 5mm, the sewing tension is controlled at 5N, the sewing temperature is 100°C, and the thread joints are fixed by metal sleeve crimping.

[0059] The composite sewing thread is coated with a high-temperature resistant coating, which is a ceramic-based composite coating with a thickness of 30μm. The coating is applied by spraying and then cured at 200℃ for 30 minutes.

[0060] Among them, after the high-temperature resistant filter felt is sewn into a filter bag, the seam area is subjected to secondary reinforcement treatment. The secondary reinforcement treatment is to apply high-temperature resistant sealant to the seam area. The high-temperature resistant sealant has a temperature resistance of 750°C, the coating width is 10mm on each side of the seam, the coating thickness is 0.5mm, and after coating, it is pre-dried at 100°C for 15min, and then fully cured at 250°C for 45min.

[0061] Example 3: This example provides a composite sewing thread resistant to ultra-high temperature, including a composite sewing thread and a high-temperature resistant filter felt; wherein, the composite sewing thread is woven from 31024 stainless steel wire and other high-temperature resistant alloy materials, and its temperature resistance reaches above 700°C; the high-temperature resistant filter felt is made of high-temperature resistant carbon felt material, and its temperature resistance matches that of the composite sewing thread.

[0062] Before weaving, the 31024 stainless steel wire and other high-temperature alloy materials were subjected to surface pretreatment, which included pickling, passivation and drying in sequence.

[0063] Pickling was performed using a 20% nitric acid solution at 60°C for 30 minutes; passivation was performed using a 15% citric acid solution at room temperature for 15 minutes; and drying was carried out at 100°C for 40 minutes.

[0064] The composite sewing thread is made through a multi-strand braiding process, with 9 strands and a twist of 80 twists / m. The diameter of the braided composite sewing thread is 1.5mm, and its breaking strength is 500N.

[0065] Among them, the other high-temperature resistant alloy materials are iron-chromium-aluminum alloys, which have a temperature resistance of 800°C and a mass ratio of 1:2 with 31024 stainless steel wire.

[0066] The high-temperature resistant filter felt was pre-treated before sewing. The pre-treatment included heat setting at 180°C for 60 minutes. After treatment, the heat shrinkage rate of the high-temperature resistant filter felt was 0.5% in the length direction and 0.2% in the width direction.

[0067] The high-temperature resistant filter felt is a multi-layer composite structure, consisting of an upper carbon felt, a middle high-temperature resistant fiber mesh, and a lower carbon felt arranged sequentially. The mesh size of the middle high-temperature resistant fiber mesh is 5mm. The multi-layer composite structure is composited by a needle punching process with a needle punching density of 100 needles / cm². The overall thickness after composite is 8mm.

[0068] During the sewing process, a double-lock stitch is used, with a stitch length of 8mm, a sewing tension of 8N, and a sewing temperature of 150°C. The joints of the sewing thread are fixed by hot melt adhesive, which has a temperature resistance of 800°C.

[0069] The composite sewing thread is coated with a high-temperature resistant coating, which is an organosilicon resin coating with a thickness of 50μm. The coating method is immersion, and the coating is cured at 250℃ for 40 minutes after coating.

[0070] Among them, after the high-temperature resistant filter felt is sewn into a filter bag, the seam area is subjected to secondary reinforcement treatment. The secondary reinforcement treatment is to apply high-temperature resistant sealant to the seam area. The high-temperature resistant sealant has a temperature resistance of 800°C, the coating width is 15mm on each side of the seam, the coating thickness is 0.8mm, and after coating, it is pre-dried at 120°C for 20min, and then fully cured at 300°C for 60min.

[0071] Comparative Example 1: This comparative example refers to the content of Example 1, except that the other high-temperature resistant alloy materials in the composite sewing thread are replaced with ordinary 304 stainless steel wire, which has a temperature resistance of about 600°C. The mass ratio of the 304 stainless steel wire to the 31024 stainless steel wire is still 1:0.5. The rest of the contents are the same as in Example 1.

[0072] Comparative Example 2: This comparative example refers to the content of Example 1, except that the mass fraction of nitric acid solution used in the pickling step of the surface pretreatment is 3%, and other pickling parameters such as treatment temperature and time, as well as subsequent passivation and drying treatment parameters are the same as those in Example 1. The rest of the content is the same as that in Example 1.

[0073] Comparative Example 3: This comparative example refers to the content of Example 1, except that the number of braided strands in the braiding process parameters of the composite sewing thread is changed to 1 strand, and the other braiding parameters such as braiding twist and diameter are adjusted according to the single-strand process, but the same mechanical properties as in Example 1 are no longer pursued. The rest of the content is the same as in Example 1.

[0074] Comparative Example 4: This comparative example refers to the content of Example 1, except that the heat setting temperature of the high-temperature resistant filter felt before sewing is changed to 80°C, and the processing time is still 30 minutes. The rest of the content is the same as Example 1.

[0075] Comparative Example 5: This comparative example refers to the content of Example 1, except that the stitch length during the sewing process is changed to 10mm, while the sewing tension, stitch length and other sewing parameters are the same as in Example 1, and the rest of the content is the same as in Example 1.

[0076] Comparative Example 6: This comparative example refers to the content of Example 1, except that the high-temperature resistant coating on the surface of the composite sewing thread is replaced with an ordinary epoxy resin coating. The coating thickness is still 10μm, and the coating and curing methods are the same as in Example 1. The rest of the content is the same as in Example 1.

[0077] Performance testing

[0078] Sample preparation: The samples used for performance testing are prepared according to the methods described in the examples and comparative examples to produce complete filter bag samples that meet the design requirements; at least three parallel samples must be prepared for each test item to ensure the reliability of the test results.

[0079] High-temperature heat aging resistance test: The prepared complete filter bag sample was placed in a muffle furnace at a set temperature of 700℃ and continuously heat-treated for 168 hours, and then cooled to room temperature in a desiccator; the composite sewing thread was cut from the treated filter bag to test its breaking strength retention rate, and samples were cut from the filter felt to test its air permeability change rate after heat treatment, and the cracking or peeling failure phenomena between the sewing area and the filter felt matrix were observed; Test standard reference: GB / T3923.1 Textiles - Tensile properties of fabrics - Part 1; GB / T5453 Textiles - Determination of air permeability of fabrics.

[0080] Table 1: Comparison of high-temperature thermal aging resistance test results (700°C, 168 hours)

[0081] Example 1 85 +8 No cracks or peeling Example 2 90 +5 No cracks or peeling Example 3 92 +3 No cracks or peeling Comparative Example 1 50 +25 The sutures showed slight signs of aging and localized peeling. Comparative Example 2 80 +10 No cracks, but the stitches have darkened in color. Comparative Example 3 60 +12 There is slight wear on the stitching at the bend. Comparative Example 4 82 +20 The felt is slightly wrinkled near the seams, but has not peeled off. Comparative Example 5 83 +15 There was a slight amount of dust at the pinhole, but no cracks. Comparative Example 6 55 +30 The coating was completely burned away, and the bonding strength between the stitching and the felt decreased.

[0082] Corrosion resistance testing: During testing, the composite sewn thread sample and the filter felt sample coated with a high-temperature resistant coating were completely immersed in a corrosive solution simulating acidic flue gas and continuously soaked at 80°C for 96 hours. After soaking, the samples were removed, rinsed with deionized water, and dried. Subsequently, the surface morphology of the composite sewn thread was observed, and its tensile strength after corrosion was tested to calculate the strength loss rate. At the same time, the filter felt sample was tested for changes in filtration efficiency after corrosion treatment. Test standard reference: GB / T10125 Artificial Atmosphere Corrosion Test Salt Spray Test; for filter media, ISO11057 Air Quality Filter Media Test Method can be referred to.

[0083] Table 2: Comparison of Corrosion Resistance Test Results

[0084] Sample number Strength loss rate of composite sewing thread (%) Changes in filter felt filtration efficiency (percentage points) Surface morphology observation of composite sewing thread Example 1 5 -0.5 The surface coating is intact, with slight loss of gloss. Example 2 3 -0.2 The surface coating is intact and unchanged. Example 3 2 -0.1 The surface coating is intact and unchanged. Comparative Example 1 20 -3.0 The surface has obvious pitting corrosion. Comparative Example 2 15 -2.0 The surface has localized rust spots and the coating is incomplete. Comparative Example 3 8 -0.8 The corrosion of the single-strand wire is relatively uniform, with slight thinning. Comparative Example 4 6 -1.5 The surface appears normal, but there are localized corrosion marks on the anchor body. Comparative Example 5 6 -2.5 The surface appears normal, but the large needle spacing allows for greater penetration of corrosive media. Comparative Example 6 40 -8.0 The epoxy resin coating completely dissolved and peeled off, and the steel wire was severely corroded.

[0085] Structural stability and fatigue resistance testing: The filter bag sample is installed on a pulse cleaning test bench, and periodic pulsed compressed gas is applied inside to simulate the cleaning action, so that the sewing thread and the sewing area are subjected to alternating stress, and the test is carried out continuously for 100,000 cycles. After the test, the filter bag needs to be disassembled and the sewing thread needs to be systematically checked for breakage or wear, whether the multi-layer structure of the filter felt has delamination, and the remaining breaking strength of the sewing thread at key nodes and the dimensional changes of the filter felt are measured to comprehensively evaluate its fatigue resistance and structural stability. Test standard reference: For the industry-standard test method for filter bag cleaning life, refer to JB / T10341 Cartridge Dust Collector.

[0086] Table 3: Results of Structural Stability and Fatigue Resistance Tests

[0087] Sample number Remaining breaking strength of the sewing thread (N) Filter felt thickness change rate (%) Structural inspection results Example 1 180 -3 No cracks, no wear, no delamination Example 2 320 -2 No cracks, no wear, no delamination Example 3 460 -1 No breakage, slight wear, no delamination Comparative Example 1 90 -8 The thread broke at the sewing corner. Comparative Example 2 165 -4 There were no breaks, but the surface of the stitches had worn burrs. Comparative Example 3 100 -10 Single strand of wire breaks under alternating stress Comparative Example 4 160 -12 The felt has a loose structure with slight delamination between multiple layers. Comparative Example 5 175 -4 The needle hole was stretched and deformed, but the stitches were intact. Comparative Example 6 110 -5 The coating is worn and peeling off, and the stitching is worn.

[0088] Filtration accuracy and dust removal performance testing: A specific concentration of polydisperse dust was introduced into the filter bag sample using a standard dust generator, and the dust concentration in the filtered gas was measured to calculate the initial filtration efficiency. Subsequently, the dust-laden filter bag was subjected to simulated pulse cleaning, and the resistance recovery after cleaning was tested. By repeating several complete filtration and cleaning cycles, the long-term stability of the filter bag's filtration performance and the effectiveness of its cleaning were systematically evaluated. Test standards referenced: ISO16890 Air Filters; GB / T6719 Technical Requirements for Bag Filters.

[0089] Table 4: Test Results of Filtration Accuracy and Dust Removal Performance

[0090] Sample number Initial filtration efficiency (%) Resistance recovery rate after dust removal (%) Long-term stability (efficiency retention rate after 5 cycles, %) Example 1 99.95 95 99.92 Example 2 99.98 97 99.96 Example 3 99.99 98 99.98 Comparative Example 1 99.0 85 98.5 Comparative Example 2 99.90 92 99.85 Comparative Example 3 99.80 90 99.75 Comparative Example 4 99.85 88 99.70 Comparative Example 5 94.0 92 93.5 Comparative Example 6 99.50 80 99.0

[0091] Test on air tightness and reinforcement effect of sewn area: The sewn area of ​​the filter bag sample is sealed in a special fixture to form a pressure interface. A stable test pressure difference is applied to one side, and then a precision instrument is used to measure the gas leakage rate through the sewn area, including needle holes and stitch gaps. This test can quantitatively reflect the actual effect of sewing process quality and secondary reinforcement treatment with high-temperature resistant sealant on ensuring the overall air tightness of the filter bag. Test standard reference: The principle of scanning leak detection method for high efficiency air filters in EN1822 can be used as a reference to conduct customized air tightness tests for the sewn area.

[0092] Table 5: Test Results of Air Tightness and Reinforcement Effect of Sewn Area

[0093] Sample number Gas leakage rate @Test pressure difference) evaluate Example 1 0.5 Excellent, the sealant effectively blocked the blockage. Example 2 0.3 Excellent, the sealant effectively blocked the blockage. Example 3 0.2 Excellent, the sealant effectively blocked the blockage. Comparative Example 1 8.0 Poor quality; micro-gaps have appeared in the suture area due to heat aging. Comparative Example 2 1.0 good Comparative Example 3 3.0 Generally, single-strand wire structures are prone to leakage. Comparative Example 4 2.5 Generally, uneven shrinkage of the felt affects air tightness. Comparative Example 5 15.0 Poor quality; excessively large needle spacing leads to direct leakage. Comparative Example 6 5.0 Poor quality; coating failure weakens the sealing effect.

[0094] Example Conclusion:

[0095] As can be seen from Examples 1-3 and Comparative Example 1, and Tables 1, 2, 3, and 5, the temperature resistance rating of other high-temperature alloy materials selected in the composite sewing thread is the core factor determining the long-term structural integrity of the product in ultra-high temperature environments. Using alloy materials with higher temperature resistance ratings can synergistically enhance the bonding strength and mechanical properties of the sewing thread and filter felt after thermal aging, thereby ensuring that the filter bag does not crack or peel under severe thermal stress and obtains better corrosion resistance, fatigue resistance, and airtightness.

[0096] As can be seen from Examples 1-3 and Comparative Example 2, and Table 2, sufficient surface pretreatment of metal materials, especially ensuring sufficient strength of the pickling step, is an important prerequisite for improving the corrosion resistance of materials and ensuring the adhesion of subsequent coatings. Sufficient pretreatment can effectively remove impurities from the material surface and form a stable passivation layer, providing a good substrate for high-temperature resistant coatings, thereby synergistically enhancing the overall corrosion resistance of the sewing thread and enabling it to maintain stable performance in simulated harsh flue gas environments.

[0097] As can be seen from Examples 1-3 and Comparative Example 3, and Tables 1, 3, and 5, the composite sewing thread made using multi-strand braiding technology has significantly better structural stability than the single-strand structure. The redundant structure and synergistic load-bearing capacity brought about by multi-strand braiding greatly enhance the mechanical strength of the sewing thread in terms of tensile strength and resistance to alternating stress, effectively avoiding the risk of breakage under dynamic loads such as long-term pulse cleaning, and helping to reduce gas leakage caused by the thin sewing thread structure.

[0098] As can be seen from Examples 1-3 and Comparative Example 4, and Tables 1, 3, and 4, sufficient heat setting pretreatment of the high-temperature resistant filter felt before sewing is crucial to ensuring the structural stability and filtration accuracy of the filter bag. Sufficient heat setting can effectively pre-shrink the material and release internal stress, thereby ensuring the dimensional stability of the filter felt during subsequent high-temperature use and avoiding wrinkling, fluffing, or delamination of the seam area due to excessive shrinkage, thus ensuring the long-term stability of filtration efficiency and dust removal performance.

[0099] As can be seen from Examples 1-3 and Comparative Example 5, and Tables 4 and 5, the stitch distance parameter during the sewing process is a key process factor affecting the filtration accuracy and airtightness of the filter bag. A reasonable stitch distance can minimize the gap between needle holes while ensuring sewing efficiency and structural strength, effectively preventing dust penetration and gas leakage. An excessive stitch distance will directly disrupt the continuity of the filter medium and seriously damage the core filtration function of the filter bag.

[0100] As can be seen from Examples 1-3 and Comparative Example 6, and Tables 1, 2, 3, and 5, coating the surface of the composite sewing thread with a special high-temperature resistant coating that matches the ambient temperature of the operating environment has a comprehensive effect on improving product performance. This coating not only directly protects the metal thread from high-temperature oxidation and chemical corrosion, but also fills gaps and smooths the surface, thereby synergistically enhancing the mechanical durability of the sewing thread, its bonding strength with the filter felt, and the overall sealing of the sewing area. It is an indispensable protective layer for dealing with complex and harsh working conditions.

[0101] This specific embodiment is merely an explanation of this application and is not intended to limit it. Those skilled in the art can make modifications to this embodiment without contributing any inventive step after reading this specification, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A superhigh temperature resistant composite sewing thread, characterized by, It includes a composite sewing thread and a high-temperature resistant filter felt; wherein, the composite sewing thread is woven from 31024 stainless steel wire and other high-temperature resistant alloy materials, the high-temperature resistant filter felt is made of high-temperature resistant carbon felt material, and the temperature resistance of the composite sewing thread reaches above 700°C. It also includes the use of composite sewing thread, including the following steps: S1. Select high-temperature resistant carbon felt material as the main body of the filter bag; S2. Use composite stitching thread to sew the edges and seams of the filter bag; S3. When installing the filter bag, ensure that the seams are not stretched excessively. S4. Regularly check the integrity of the seams of the filter bags.

2. The super-high temperature resistant composite sewing thread according to claim 1, characterized in that, Before weaving, the composite sewing thread undergoes surface pretreatment of 31024 stainless steel wire and other high-temperature resistant alloy materials, including pickling, passivation and drying processes performed sequentially.

3. The super-high temperature resistant composite sewing thread according to claim 2, characterized in that, The pickling process uses a nitric acid solution with a mass fraction of 10%–20%, a treatment temperature of 40–60°C, and a treatment time of 10–30 min; the passivation process uses a citric acid solution with a mass fraction of 5%–15%, a treatment temperature of room temperature, and a treatment time of 5–15 min; the drying process is carried out at 80–100°C for a drying time of 20–40 min.

4. The super-high temperature resistant composite sewing thread according to claim 1, wherein, The composite sewing thread is made by a multi-strand braiding process, with 3 to 9 strands, a twist of 30 to 80 twists / m, a diameter of 0.3 to 1.5 mm, and a breaking strength ≥200N.

5. The super-high temperature resistant composite sewing thread according to claim 1, wherein, The other high-temperature resistant alloy material is selected from one or more of nickel-based alloys, cobalt-based alloys, or iron-chromium-aluminum alloys. The temperature resistance of the other high-temperature resistant alloy material is not lower than 700°C, and the mass ratio of the other high-temperature resistant alloy material to 31024 stainless steel wire is 1:0.5 to 2.

6. The super-high temperature resistant composite sewing thread according to claim 1, wherein, The high-temperature resistant filter felt is pre-treated before sewing. The pre-treatment includes heat setting at 120-180°C for 30-60 minutes, and the heat shrinkage rate of the high-temperature resistant filter felt is controlled to be ≤1.5% in the length direction and ≤1.0% in the width direction.

7. The super-high temperature resistant composite sewing thread according to claim 1, wherein, The high-temperature resistant filter felt is a multi-layer composite structure, including an upper carbon felt, a middle high-temperature resistant fiber mesh, and a lower carbon felt arranged in sequence. The mesh size of the middle high-temperature resistant fiber mesh is 1-5 mm. The multi-layer composite structure is composited by needle punching process with a needle punching density of 50-100 needles / cm². The overall thickness after composite is 2-8 mm.

8. The super-high temperature resistant composite sewing thread according to claim 1, wherein, During the sewing process, a double-lock stitch is used, with a stitch length of 3-8mm, sewing tension controlled at 2-8N, and sewing temperature controlled between room temperature and 150℃. The joints of the sewing thread are fixed by hot melt adhesive bonding or metal sleeve crimping, and the temperature resistance of the hot melt adhesive is not less than 700°C.

9. The super-high temperature resistant composite sewing thread according to claim 1, wherein, The surface of the composite sewing thread is coated with a high-temperature resistant coating, which is an organosilicon resin coating or a ceramic-based composite coating. The coating thickness is 10-50 μm, and the coating method is immersion or spraying. After coating, it is cured at 150-250℃ for 20-40 min.

10. The super-high temperature resistant composite sewing thread according to claim 1, wherein, After the high-temperature resistant filter felt is sewn into a filter bag, the seam area is subjected to a secondary reinforcement treatment. The secondary reinforcement treatment involves applying a high-temperature resistant sealant to the seam area. The high-temperature resistant sealant has a temperature resistance of not less than 700°C. The coating width is 5-15 mm on each side of the seam, and the coating thickness is 0.2-0.8 mm. After coating, it is pre-dried at 80-120°C for 10-20 minutes, and then fully cured at 200-300°C for 30-60 minutes.

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