Polyimide / mineral cotton composite fabric and preparation method thereof

Abstract

The invention provides a polyimide / mineral cotton composite fabric and a preparation method thereof, and belongs to the field of filter materials. The polyimide / mineral cotton composite fabric provided by the invention comprises fibers and polyimide resin bonded between the fibers, the fibers comprise polyimide fibers and mineral cotton fibers; the mass ratio of the polyimide fibers to the mineral cotton fibers is (3-7): (3-7); the mass ratio of the fibers to the polyimide resin is 1.23: (0.12-0.6). The filtering efficiency of the polyimide / mineral cotton composite fabric is 90% or above, the heat treatment time is 60 min at the temperature of 220 + / -5 DEG C, the mass change rate is within 6%, and the polyimide / mineral cotton composite fabric has good filtering efficiency and heat stability.

Description

Technical Field

[0001] The present invention relates to the field of filter materials, and particularly to a polyimide / slag wool composite fabric and a preparation method thereof. Background Art

[0002] With the rapid development of the Chinese industry, during the operation of industries such as thermal power plants and iron and steel smelting, a large amount of high-temperature dust-containing flue gas will inevitably be generated. The content of suspended particulate matter in these flue gases is relatively high, which is one of the main factors affecting air quality and human health, and has seriously threatened ecological stability and the human living environment.

[0003] In order to reduce the emission of waste gas pollutants, an economical and efficient method is to use high-temperature resistant filter materials to treat waste gas pollutants. Among them, the bag filter technology is particularly common and effective in the field of high-temperature air filtration due to its significant advantages. The core part of the bag filter is the filter bag, which is usually made of fiber filter materials with significant filtration effects and simple structures. To meet the requirements of specific high-temperature environments, high-temperature resistant filter bags need to be made of special filter materials that can withstand temperatures exceeding 200°C.

[0004] Currently, high-temperature resistant filter materials are mainly divided into two categories: organic and inorganic. Among them, organic materials such as PPS, PTFE, and PI fibers are widely used in medium and high-temperature environments due to their excellent flexibility and processing performance. However, their oxidation resistance and high-temperature limit are relatively low, and decomposition will occur at high temperatures, resulting in a reduction in service life; inorganic materials such as glass fiber and basalt fiber have higher temperature resistance and can work at higher temperatures for a long time, and are suitable for extreme high-temperature environments. However, the filter materials prepared from inorganic fibers usually have relatively low filtration efficiency because the surface of the fibers is relatively smooth and the adsorption force between particles and fibers is weak. Summary of the Invention

[0005] The purpose of the present invention is to provide a polyimide / slag wool composite fabric and a preparation method thereof. The polyimide / slag wool composite fabric provided by the present invention has good filtration efficiency and thermal stability.

[0006] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a polyimide / slag wool composite fabric, which includes fibers and polyimide resin bonded between the fibers; the fibers include polyimide fibers and slag wool fibers;

[0008] The mass ratio of the polyimide fibers to the slag wool fibers is (3 - 7):(3 - 7);

[0009] The mass ratio of the fibers to the polyimide resin is 1.23:(0.12 - 0.6).

[0010] The present invention also provides a method for preparing the polyimide / slag wool composite fabric described in the above technical solution, comprising the following steps:

[0011] (1) Mix polyimide fibers, slag wool fibers, an aqueous solution of a water-soluble dispersant and water, and then carry out papermaking to obtain a polyimide / slag wool composite fabric precursor;

[0012] (2) Immerse the polyimide / slag wool composite fabric precursor obtained in step (1) in a polyimide resin solution and then cure it to obtain a polyimide / slag wool composite fabric; the solid content of the polyimide resin solution is 1-3%.

[0013] Preferably, the polyimide fibers and slag wool fibers in step (1) are subjected to surface pretreatment before use.

[0014] Preferably, the surface pretreatment is: mixing the polyimide fibers and slag wool fibers with a surfactant solution and then standing and drying them in sequence.

[0015] Preferably, the surfactant in the surfactant solution includes sodium dodecylbenzenesulfonate, lignin sulfonate or a nonionic surfactant.

[0016] Preferably, the concentration of the surfactant is (1-1.5)×10 -3 mol / L.

[0017] Preferably, the polyethylene oxide in step (1) is used in the form of an aqueous solution; the mass concentration of the water-soluble dispersant solution is 0.01-0.07%.

[0018] Preferably, the volume ratio of the water-soluble dispersant solution to water in step (1) is (0.8-1.2):1.

[0019] Preferably, the impregnation time in step (2) is 25-35 min.

[0020] Preferably, the curing temperature in step (2) is 100-120°C, and the curing time is 1.5-2 h.

[0021] The present invention provides a polyimide / slag wool composite fabric, which includes fibers and polyimide resin bonded between the fibers; the fibers include polyimide fibers and slag wool fibers; the mass ratio of the polyimide fibers to the slag wool fibers is (3-7):(3-7); the mass ratio of the fibers to the polyimide resin is 1.23:(0.12-0.6). The present invention utilizes the high filtration efficiency of polyimide fibers and the high heat resistance performance of slag wool fibers. By combining the two and controlling the mass ratio of polyimide fibers and slag wool fibers, the composite fabric has good filtration efficiency and thermal stability; using polyimide resin as a binder and limiting its content can bond polyimide fibers and slag wool fibers, enabling the composite fabric to have a certain strength, while improving the service life of the composite fabric and ensuring that the composite fabric has good thermal stability. The results of the examples show that the polyimide / slag wool composite fabric provided by the present invention has a filtration efficiency of more than 90%, and after heat treatment at 220±5°C for 60 minutes, the mass change rate is within -6%, having good filtration efficiency and thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the SEM diagram of the polyimide / slag wool composite fabric obtained in Example 1 of the present invention;

[0023] Figure 2 It is the SEM diagram of the polyimide / slag wool composite fabric obtained in Example 3 of the present invention;

[0024] Figure 3 It is the SEM diagram of the polyimide / slag wool composite fabric obtained in Example 5 of the present invention;

[0025] Figure 4 It is the SEM diagram of the slag wool fiber fabric obtained in Comparative Example 1 of the present invention;

[0026] Figure 5 It is the SEM diagram of the polyimide fiber fabric obtained in Comparative Example 2 of the present invention;

[0027] Figure 6 It is the SEM diagram of the polyimide / slag wool composite fabric obtained in Example 6 of the present invention;

[0028] Figure 7 It is the SEM diagram of the polyimide / slag wool composite fabric obtained in Comparative Example 4 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention provides a polyimide / slag wool composite fabric, which includes fibers and polyimide resin bonded between the fibers.

[0030] In the present invention, the fibers include polyimide fibers and slag wool fibers; the mass ratio of the polyimide fibers to the slag wool fibers is (3 to 7):(3 to 7), preferably (4 to 7):(3 to 6), more preferably (5 to 7):(3 to 5), and further preferably (6 to 7):(3 to 4). By limiting the mass ratio of the polyimide fibers to the slag wool fibers within the above range, the composite fabric can have good high-temperature resistance and good filtration efficiency at the same time.

[0031] In the present invention, the mass ratio of the fibers to the polyimide resin is 1.23:(0.12 to 0.6), preferably 1.23:(0.4 to 0.55), and more preferably 1.23:(0.5 to 0.55). By using polyimide resin as a binder and limiting its content, the polyimide fibers and the slag wool fibers can be bonded, enabling the composite fabric to have a certain strength, while improving the service life of the composite fabric and ensuring that the composite fabric has good thermal stability.

[0032] The present invention utilizes the high filtration efficiency of polyimide fibers and the high high-temperature resistance of slag wool fibers. By combining the two and controlling the mass ratio of the polyimide fibers to the slag wool fibers, the composite fabric has good filtration efficiency and thermal stability; by using polyimide resin as a binder and limiting its content, the polyimide fibers and the slag wool fibers can be bonded, enabling the composite fabric to have a certain strength, while improving the service life of the composite fabric and ensuring that the composite fabric has good thermal stability.

[0033] The present invention also provides a method for preparing the polyimide / slag wool composite fabric according to the above technical solution, comprising the following steps:

[0034] (1) Mix the polyimide fibers, slag wool fibers, water-soluble dispersant solution and water, and then carry out papermaking to obtain a polyimide / slag wool composite fabric precursor;

[0035] (2) Immerse the polyimide / slag wool composite fabric precursor obtained in step (1) in a polyimide resin solution and then cure it to obtain a polyimide / slag wool composite fabric.

[0036] The present invention mixes the polyimide fibers, slag wool fibers, water-soluble dispersant solution and water, and then carries out papermaking to obtain a polyimide / slag wool composite fabric precursor.

[0037] As an embodiment of the present invention, the mass ratio of the polyimide fiber to the slag wool fiber can be (3-7):(3-7), can also be (4-7):(3-6), can also be (5-7):(3-5), and can also be (6-7):(3-4). Limiting the mass ratio of the polyimide fiber to the slag wool fiber within the above range in the present invention can enable the composite fabric to have good high-temperature resistance and good filtration efficiency at the same time.

[0038] In a specific embodiment of the present invention, the polyimide fiber used is from Hubei Jiateng Textile Co., Ltd.; the length of the polyimide fiber is 5.9 mm; the diameter of the polyimide fiber is 12-16 μm. Limiting the length and diameter of the polyimide fiber within the above range in the present invention can better make the polyimide fiber and the slag wool fiber mix evenly.

[0039] In a specific embodiment of the present invention, the slag wool fiber used is from Jiaocheng Yiwang Ferroalloy Co., Ltd.; the length of the slag wool fiber is 2-4 mm; the diameter of the slag wool fiber is 4-6 μm. Limiting the length and diameter of the slag wool fiber within the above range in the present invention can better make the polyimide fiber and the slag wool fiber mix evenly.

[0040] As an embodiment of the present invention, the polyimide fiber and the slag wool fiber can be subjected to surface pretreatment before use; the surface pretreatment can be: mixing the polyimide fiber and the slag wool fiber with a surfactant solution and then carrying out static settlement and drying in sequence.

[0041] As an embodiment of the present invention, the surfactant in the surfactant solution can include sodium dodecylbenzenesulfonate, lignin sulfonate or a non-ionic surfactant; the concentration of the surfactant solution can be (1-1.5)×10 -3 mol / L, and can also be 1.2×10 -3 mol / L. Limiting the type of the surfactant and the concentration of the surfactant solution within the above range in the present invention can improve the surface activity of the fiber and play a role in dispersing the fiber.

[0042] As an embodiment of the present invention, the ratio of the total mass of the polyimide fiber and the slag wool fiber to the volume of the surfactant solution can be (1-1.5) g:(300-400) mL. In the embodiment of the present invention, the ratio of the total mass of the polyimide fiber and the slag wool fiber to the volume of the surfactant solution is 1.23 g:350 mL.

[0043] The present invention has no special limitation on the operation of mixing the polyimide fiber and the slag wool fiber with the surfactant, and it is only necessary to fully mix the polyimide fiber and the slag wool fiber with the surfactant.

[0044] As an embodiment of the present invention, the temperature for standing can be 55-65°C, and can also be 60°C; the time for standing can be 30-50 min, can also be 35-45 min, and can also be 40 min. By standing, the present invention can enable the polyimide fiber and the slag wool fiber to sufficiently modify the fiber surface under the action of the surfactant, making the fiber dispersion better.

[0045] As an embodiment of the present invention, cleaning can also be performed after standing; the cleaning solution used for cleaning can be deionized water. The present invention has no special limitation on the cleaning operation, and it is only necessary to clean the surfactant remaining on the fiber.

[0046] As an embodiment of the present invention, the drying can be carried out in a forced air drying oven; the drying temperature can be 110-120°C; the drying time can be 0.5-1 h. Limiting the drying temperature and time within the above ranges in the present invention can ensure sufficient drying of the fiber.

[0047] As an embodiment of the present invention, the water-soluble dispersant in the water-soluble dispersant solution can be polyethylene oxide or polysorbate 80; the solvent of the water-soluble dispersant solution can be water; the mass concentration of the water-soluble dispersant solution can be 0.01-0.07%, can also be 0.02-0.06%, can also be 0.03-0.05%, and can also be 0.04-0.05%. Limiting the mass concentration of the water-soluble dispersant solution within the above ranges in the present invention can further improve the fiber dispersion.

[0048] As an embodiment of the present invention, the volume ratio of the water-soluble dispersant solution to water can be (0.8-1.2):1, and can also be 1:1. Limiting the volume ratio of the water-soluble dispersant solution to water within the above ranges in the present invention can better disperse the fiber.

[0049] The present invention has no special limitation on the mixing ratio of the polyimide fiber and the slag wool fiber (total fiber) to the water-soluble dispersant solution and water (total liquid), and it is only necessary to completely immerse all the fibers. In the examples of the present invention, the ratio of the total mass of the polyimide fiber and the slag wool fiber to the total volume of the water-soluble dispersant solution and water is 1.23 g:1000 mL.

[0050] As an embodiment of the present invention, the mixing of the polyimide fiber, slag wool fiber, water-soluble dispersant solution and water can be carried out under stirring; the rotation speed of the stirring can be 500 r / min; the stirring time can be 2 to 3 h. The present invention limits the rotation speed and time of stirring within the above ranges to further disperse the fibers.

[0051] As an embodiment of the present invention, after the polyimide fiber and slag wool fiber are pretreated and mixed with the water-soluble dispersant solution and water, a polyimide / slag wool fiber suspension is obtained.

[0052] As an embodiment of the present invention, the papermaking can be to manually make the suspension into a fabric using a 90-mesh sieve in the polyimide / slag wool fiber suspension. The specific operation of the manual papermaking can be: using a papermaking frame with a sieve mesh of 90 meshes, and carrying out papermaking in the polyimide / slag wool fiber suspension to make there be a uniform layer of fabric in the papermaking frame. As an embodiment of the present invention, the size of the fabric can be 10 cm × 10 cm.

[0053] As an embodiment of the present invention, after the papermaking, drying can also be carried out to obtain a polyimide / slag wool composite fabric precursor.

[0054] As an embodiment of the present invention, the drying can be carried out in a forced-air drying oven; the drying temperature can be 90 °C; the drying time can be 1 to 2 h. The present invention can fully remove the moisture in the fabric obtained by papermaking through drying.

[0055] After obtaining the polyimide / slag wool composite fabric precursor, the present invention impregnates the polyimide / slag wool composite fabric precursor in a polyimide resin solution and then cures it to obtain a polyimide / slag wool composite fabric.

[0056] As an embodiment of the present invention, the solid content of the polyimide resin solution can be 1 to 3%, or 1.5 to 2.5%, or also 2%. The present invention limits the solid content of the polyimide resin solution within the above ranges to better bond the fibers.

[0057] As an embodiment of the present invention, the solvent in the polyimide resin solution can be N,N-dimethylacetamide.

[0058] As an embodiment of the present invention, the temperature of the impregnation can be room temperature; the impregnation time can be 25 to 35 min, or also 30 min. The present invention limits the temperature and time of the impregnation within the above ranges to enable the polyimide / slag wool composite fabric precursor to fully contact with the polyimide resin solution.

[0059] The present invention does not particularly limit the amount of the polyimide resin solution, and it is only necessary to completely immerse the polyimide / slag wool composite fabric precursor. In a specific embodiment of the present invention, the mass ratio of the polyimide / slag wool composite fabric precursor to the volume of the polyimide resin solution is 1.23 g:500 mL.

[0060] As an implementation manner of the present invention, the curing can be carried out in a blast drying oven; the curing temperature can be 100-120 °C, or 105-115 °C, or 110 °C; the curing time can be 1.5-2 h. Through curing, the polyimide / slag wool composite fabric of the present invention can have a certain strength.

[0061] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0062] Example 1

[0063] A polyimide / slag wool composite fabric is composed of fibers and polyimide resin bonded between the fibers; the fibers are polyimide fibers and slag wool fibers; the mass ratio of the polyimide fibers to the slag wool fibers is 7:3;

[0064] The mass ratio of the fibers to the polyimide resin is 1.23:0.4.

[0065] The preparation method of the polyimide / slag wool composite fabric:

[0066] (1) Polyimide fibers with a length of 5.9 mm and a diameter of 12-16 μm and slag wool fibers with a length of 2-4 mm and a diameter of 4-6 μm are mixed in a mass ratio of 7:3 (the total mass of the polyimide fibers and the slag wool fibers is 1.23 g) with 1.2×10 -3A sodium dodecylbenzenesulfonate solution (350 mL) with a concentration of mol / L was mixed and left to stand for 30 min in a constant temperature water bath at 60 °C. After being washed with deionized water and dried in a forced-air drying oven at 115 °C for 1 h for pretreatment, it was then stirred with 500 mL of a polyethylene oxide solution with a mass concentration of 0.05% (using water as the solvent) and 500 mL of water at 500 r / min for 2.5 h to obtain a polyimide / slag wool fiber suspension. A forming frame with a mesh size of 90 meshes was used to form a fabric in the polyimide / slag wool fiber suspension, such that there was a uniform layer of fabric in the forming frame, obtaining a fabric with a size of 10 cm × 10 cm. Then, it was dried in a forced-air drying oven at 90 °C for 2 h to obtain a polyimide / slag wool composite fabric precursor; the volume ratio of the polyethylene oxide solution to water was 1:1;

[0067] (2) The polyimide / slag wool composite fabric precursor (1.23 g) obtained in step (1) was impregnated in 500 mL of a polyimide resin solution with a solid content of 3% (using N,N-dimethylacetamide as the solvent) at room temperature for 30 min, and then cured in a forced-air drying oven at 100 °C for 1.5 h to obtain a polyimide / slag wool composite fabric.

[0068] Example 2

[0069] The difference between Example 2 and Example 1 is only that the mass ratio of polyimide fibers to slag wool fibers in the polyimide / slag wool composite fabric is 6:4, and the mass ratio of polyimide fibers to slag wool fibers in the preparation method is 6:4. Otherwise, it is the same as Example 1, obtaining a polyimide / slag wool composite fabric.

[0070] Example 3

[0071] The difference between Example 3 and Example 1 is only that the mass ratio of polyimide fibers to slag wool fibers in the polyimide / slag wool composite fabric is 5:5, and the mass ratio of polyimide fibers to slag wool fibers in the preparation method is 5:5. Otherwise, it is the same as Example 1, obtaining a polyimide / slag wool composite fabric.

[0072] Example 4

[0073] The difference between Example 4 and Example 1 is only that the mass ratio of polyimide fibers to slag wool fibers in the polyimide / slag wool composite fabric is 4:6, and the mass ratio of polyimide fibers to slag wool fibers in the preparation method is 4:6. Otherwise, it is the same as Example 1, obtaining a polyimide / slag wool composite fabric.

[0074] Example 5

[0075] Example 5 is only different from Example 1 in that the mass ratio of polyimide fibers to slag wool fibers in the polyimide / slag wool composite fabric is 3:7, and the mass ratio of polyimide fibers to slag wool fibers in the preparation method is 3:7. Other conditions are the same as those in Example 1, and a polyimide / slag wool composite fabric is obtained.

[0076] Example 6

[0077] Example 6 is only different from Example 1 in that the mass ratio of fibers to polyimide resin in the polyimide / slag wool composite fabric is 1.23:0.15, and the solid content of the polyimide resin solution in the preparation method is 1%. Other conditions are the same as those in Example 1, and a polyimide / slag wool composite fabric is obtained.

[0078] Example 7

[0079] Example 7 is only different from Example 1 in that the mass ratio of fibers to polyimide resin in the polyimide / slag wool composite fabric is 1.23:0.3, and the solid content of the polyimide resin solution in the preparation method is 2%. Other conditions are the same as those in Example 1, and a polyimide / slag wool composite fabric is obtained.

[0080] Example 8

[0081] Example 8 is only different from Example 3 in that the mass concentration of the polyethylene oxide solution (with water as the solvent) in the preparation method is 0.01%. Other conditions are the same as those in Example 3, and a polyimide / slag wool composite fabric is obtained.

[0082] Example 9

[0083] Example 9 is only different from Example 3 in that the mass concentration of the polyethylene oxide solution (with water as the solvent) in the preparation method is 0.03%. Other conditions are the same as those in Example 3, and a polyimide / slag wool composite fabric is obtained.

[0084] Example 10

[0085] Example 10 is only different from Example 3 in that the mass concentration of the polyethylene oxide solution (with water as the solvent) in the preparation method is 0.07%. Other conditions are the same as those in Example 3, and a polyimide / slag wool composite fabric is obtained.

[0086] Example 11

[0087] Example 11 is only different from Example 3 in that the mass concentration of the polyethylene oxide solution (with water as the solvent) in the preparation method is 0.09%. Other conditions are the same as those in Example 3, and a polyimide / slag wool composite fabric is obtained.

[0088] Comparative Example 1

[0089] The difference between Comparative Example 1 and Example 1 is only that it does not contain polyimide fibers, and polyimide fibers are not added in the preparation method. Other conditions are the same as those in Example 1, and a slag wool fiber fabric is obtained.

[0090] Comparative Example 2

[0091] The difference between Comparative Example 2 and Example 1 is only that it does not contain slag wool fibers, and slag wool fibers are not added in the preparation method. Other conditions are the same as those in Example 1, and a polyimide fiber fabric is obtained.

[0092] Comparative Example 3

[0093] The difference between Comparative Example 3 and Example 1 is only that the mass ratio of fibers to polyimide resin in the polyimide / slag wool composite fabric is 1.23:0.65, and the solid content of the polyimide resin solution in the preparation method is 4%. Other conditions are the same as those in Example 1, and a polyimide / slag wool composite fabric is obtained.

[0094] Comparative Example 4

[0095] The difference between Comparative Example 4 and Example 1 is only that the mass ratio of fibers to polyimide resin in the polyimide / slag wool composite fabric is 1.23:0.75, and the solid content of the polyimide resin solution in the preparation method is 5%. Other conditions are the same as those in Example 1, and a polyimide / slag wool composite fabric is obtained.

[0096] The fabrics obtained in Example 1, Example 3, Example 5, Example 6, Comparative Example 1, Comparative Example 2, and Comparative Example 4 were observed by scanning electron microscopy. The SEM images of the polyimide / slag wool composite fabric in Example 1 are as Figure 1 shown. The SEM images of the polyimide / slag wool composite fabric in Example 3 are as Figure 2 shown. The SEM images of the polyimide / slag wool composite fabric in Example 5 are as Figure 3 shown. The SEM images of the slag wool fiber fabric in Comparative Example 1 are as Figure 4 shown. The SEM images of the polyimide fiber fabric in Comparative Example 2 are as Figure 5 shown. The SEM images of the polyimide / slag wool composite fabric in Example 6 are as Figure 6 shown. The SEM images of the polyimide / slag wool composite fabric in Comparative Example 4 are as Figure 7 shown. It can be seen from Figures 1 - 5 that the polyimide fibers are thicker, while the slag wool fibers are thinner. As the proportion of polyimide fibers increases, the network structure formed by the fibers becomes looser, the coating effect of the resin is more uniform, and the coverage of pores decreases, only existing in the pores formed between the slag wool fibers or between the slag wool and polyimide fibers. From Figure 6 and Figure 7It can be seen that when the solid content of the polyimide resin solution is 1%, a small amount of resin almost exists at the nodes where the fibers overlap, playing a role in bonding the fibers together. As the solid content of the resin increases, the resin is more likely to exist in flakes at the places where pores are formed, covering the pores. After being covered, the tensile breaking strength of the fabric increases, and when the pores of the fabric are small, the filtration resistance of the fabric increases and the filtration efficiency decreases.

[0097] An automatic filter media detector was used to test the filtration performance of the fabrics obtained in Examples 1-5 and Comparative Examples 1-2, and the filtration efficiency and filtration resistance data obtained are shown in Table 1.

[0098] Table 1 Filtration performance data of the fabrics obtained in Examples 1-5 and Comparative Examples 1-2

[0099] Example Filtration efficiency / % Filtration resistance / Pa Comparative Example 2 93.1 11.63 Example 1 93.0 21.93 Example 2 91.3 17.63 Example 3 91.0 20.34 Example 4 90.4 20.12 Example 5 90.36 27.52 Comparative Example 1 89 31.23

[0100] As can be seen from Table 1, among the pure polyimide fiber fabrics in Comparative Example 1, the filtration efficiency is the highest and the filtration resistance is the lowest, which are 93.1% and 11.63 Pa respectively. When the proportion of slag wool fibers in the composite fabric continuously increases, the filtration efficiency of the fabric continuously decreases, and at the same time, the filtration resistance mainly shows an increasing trend. The filtration efficiency of the pure slag wool fiber fabric in Comparative Example 1 is too low.

[0101] An automatic filter media detector was used to test the filtration performance of the polyimide / slag wool composite fabrics obtained in Example 1, Examples 6-7 and Comparative Examples 3-4, and the filtration efficiency and filtration resistance data obtained are shown in Table 2.

[0102] Table 2 Filtration performance data of the polyimide / slag wool composite fabrics obtained in Example 1, Examples 6-7 and Comparative Examples 3-4

[0103] Example Filtration efficiency / % Filtration resistance / Pa Example 6 95.22 20.40 Example 7 95.44 19.71 Example 1 94.48 20.20 Comparative Example 3 95.45 18.24 Comparative Example 4 95.44 20.00

[0104] As can be seen from Table 2, the influence of the solid content of the polyimide resin on the filtration performance of the filter material is not obvious, and there is basically no obvious fluctuation. This may be because when the mass ratio of polyimide fibers to slag wool fibers is 7:3, a small fluctuation in the resin content will not affect the number and size of pores.

[0105] An automatic filter media detector was used to test the filtration performance of the polyimide / slag wool composite fabrics obtained in Example 3 and Examples 8-11, and the filtration efficiency and filtration resistance data obtained are shown in Table 3.

[0106] Table 3 Filtration performance data of the polyimide / slag wool composite fabrics obtained in Example 3 and Examples 8-11

[0107] Example Filtration efficiency / % Filtration resistance / Pa Example 8 91.88 24.22 Example 9 92.72 24.52 Example 3 93.05 24.42 Example 10 95.43 20.10 Example 11 95.25 18.44

[0108] As can be seen from Table 3, when the mass fraction of the polyethylene oxide solution continuously increases, the filtration efficiency of the composite fabric becomes greater, while the filtration resistance continuously decreases. The mass fraction of the polyethylene oxide solution affects the uniformity of fiber distribution, thereby affecting the filtration performance of the filter medium; the higher the mass fraction of the polyethylene oxide solution, the dispersibility of the fibers will first increase and then decrease. When the mass fraction of the polyethylene oxide solution is 0.07%, the fiber dispersibility is the best. At this time, the uniform dispersion of the fibers can make the pore size and distribution formed between the fibers relatively uniform, thereby enabling the filter medium to have better filtration efficiency.

[0109] The thermal stability tests were carried out on the fabrics obtained in Examples 1 to 5 and Comparative Examples 1 to 2: Before the test, the samples were placed in a constant temperature blast drying oven to be completely dried to obtain the initial weight, and then placed in a muffle furnace and heated at a temperature of 220 ± 5 °C for 60 min. After the heating was completed, the weight of the samples was measured again, and the mass change rate of the samples was calculated. The thermal stability test data of the fabrics obtained in Examples 1 to 5 and Comparative Examples 1 to 2 are shown in Table 4.

[0110] Table 4 Thermal stability test data of the fabrics obtained in Examples 1 to 5 and Comparative Examples 1 to 2

[0111]

[0112] As can be seen from Table 4, after heat treatment, the warp and weft dimensions of the fabric did not change, and the sample morphology was stable. The mass loss of the polyimide fiber fabric in Comparative Example 2 reached 6.97% after high-temperature treatment, indicating that there was a certain decomposition at high temperature; the greater the proportion of slag wool fibers, the smaller the mass loss of the composite fabric, because the slag wool fibers have more excellent high-temperature resistance. Therefore, after adding slag wool fibers to the traditional polyimide-based fabric, the thermal stability of the composite fabric can be improved; the mass loss of the slag wool fiber fabric in Comparative Example 1 was only 0.29% after heat treatment, indicating that it did not decompose itself at high temperature and could be used well under high-temperature conditions.

[0113] The thermal stability tests were carried out on the polyimide / slag wool composite fabrics obtained in Example 1, Examples 6 to 7 and Comparative Examples 3 to 4: Before the test, the samples were placed in a constant temperature blast drying oven to be completely dried to obtain the initial weight, and then placed in a muffle furnace and heated at a temperature of 220 ± 5 °C for 60 min. After the heating was completed, the weight of the samples was measured again, and the mass change rate of the samples was calculated. The thermal stability test data of the polyimide / slag wool composite fabrics obtained in Example 1, Examples 6 to 7 and Comparative Examples 3 to 4 are shown in Table 5.

[0114] Table 5 Thermal stability test data of the polyimide / slag wool composite fabric obtained in Example 1, Examples 6-7 and Comparative Examples 3-4

[0115]

[0116]

[0117] As can be seen from Table 5, the greater the solid content of the polyimide resin solution, the greater the mass change rate of the composite fabric. It can be seen that the polyimide resin has a relatively large impact on the stability of the composite fabric at high temperatures. Relatively speaking, the polyimide resin has poor stability at high temperatures and is prone to decomposition, thus affecting the service life of the composite fabric. When the solid content of the polyimide resin solution exceeds 3%, the mass change rate of the composite fabric exceeds -6%, and the thermal stability of the composite fabric is poor.

[0118] The filtration efficiency of the polyimide / slag wool composite fabric prepared by the preparation method provided by the present invention is above 90%. After heat treatment at 220±5°C for 60 minutes, the mass change rate is within -6%, and it has good filtration efficiency and thermal stability.

[0119] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A polyimide / slag wool composite fabric, comprising fibers and polyimide resin bonded between the fibers; the fibers include polyimide fibers and slag wool fibers; The mass ratio of the polyimide fibers to the slag wool fibers is (3-7):(3-7); The mass ratio of the fibers to the polyimide resin is 1.23:(0.12-0.6).

2. A method for preparing the polyimide / slag wool composite fabric according to claim 1, comprising the following steps: (1) Mix polyimide fibers, slag wool fibers, an aqueous dispersant solution and water, and then perform papermaking to obtain a polyimide / slag wool composite fabric precursor; (2) Immerse the polyimide / slag wool composite fabric precursor obtained in step (1) in a polyimide resin solution and then cure it to obtain a polyimide / slag wool composite fabric; the solid content of the polyimide resin solution is 1-3%.

3. The preparation method according to claim 2, wherein The polyimide fibers and slag wool fibers in step (1) are subjected to surface pretreatment before use.

4. The preparation method according to claim 3, characterized in that, The surface pretreatment is: mixing the polyimide fibers and slag wool fibers with a surfactant solution and then standing and drying in sequence.

5. The preparation method according to claim 4, wherein The surfactant in the surfactant solution includes sodium dodecylbenzenesulfonate, lignosulfonate or a nonionic surfactant.

6. The preparation method according to claim 4 or 5, characterized in that, The concentration of the surfactant solution is (1 - 1.5)×10 -3 mol / L.

7. The preparation method according to claim 2, wherein The mass concentration of the aqueous dispersant solution in step (1) is 0.01-0.07%.

8. The preparation method according to claim 7, wherein The volume ratio of the aqueous dispersant solution to water in step (1) is (0.8-1.2):

1.

9. The preparation method according to claim 2, characterized in that, The impregnation time in step (2) is 25-35 min.

10. The preparation method according to claim 2, wherein, The curing temperature in step (2) is 100-120 °C, and the curing time is 1.5-2 h.

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