A method for modifying filter material

Abstract

The present invention provides a method for modifying a filter material, comprising the following steps: S1, mixing methyltriethoxysilane and deionized water to achieve thorough hydrolysis, then dropwise adding ammonia water and continuing stirring to obtain a sol; S2, soaking the filter material in the sol, and drawing the soaked filter material in anhydrous ethanol for 1 to 30 times; S3, aging and drying the drawn filter material in anhydrous ethanol to form a film-like protective layer on the filter material. The modified filter material exhibits excellent hydrophobicity, acid resistance, and high temperature resistance.

Description

Technical Field

[0001] The present application relates to a method for modifying a filter material, and belongs to the technical field of filter material preparation. Background Art

[0002] Particulate matter emissions are a major air pollutant in industries such as electricity, steel, and cement, seriously impacting human health. Currently, electrostatic precipitators and bag filters are the primary methods used to treat these emissions. Traditional electrostatic precipitators are no longer able to meet the industry's requirements for pollutant emissions. Bag filters offer advantages such as high filtration efficiency, stable operation, and ease of use, and thus have broad application prospects. The core component of a bag filter is the filter bag, made of filter material. The performance of this filter material directly impacts dust removal effectiveness. However, bag filters are subject to long-term operation in humid, acidic, and high-temperature environments. Conventional filter materials often exhibit suboptimal moisture, acid, and high-temperature resistance, leading to damage and significantly reducing their efficiency and service life. Therefore, improving the moisture, acid, and high-temperature resistance of filter materials and enhancing their overall filtration performance has become a research priority.

[0003] Existing technologies primarily improve filter material performance by modifying it. Existing filter material modification methods primarily involve forming a silica protective layer on the surface of the filter material. However, existing silica protective layers are typically composed of particulate matter, making it difficult to form a dense protective layer. Consequently, the filter material is incompletely coated, and exposed areas are not effectively protected. This results in suboptimal overall moisture resistance, acid resistance, and high temperature resistance. Summary of the Invention

[0004] The present invention provides a method for modifying a filter material, which can effectively solve the above problems.

[0005] The present invention is achieved in that:

[0006] A method for modifying a filter material comprises the following steps:

[0007] S1, mixing methyltriethoxysilane and deionized water and stirring to fully hydrolyze them, then adding ammonia water dropwise and continuing to stir to obtain a sol;

[0008] S2, soaking the filter material in the sol, and pulling the soaked filter material in anhydrous ethanol for 1 to 30 times;

[0009] S3, placing the pulled filter material in anhydrous ethanol for aging and drying to form a film-like protective layer on the filter material.

[0010] As a further improvement, the filter material is selected from one or more of organic fibers and glass fibers.

[0011] As a further improvement, in step S1, the volume ratio of methyltriethoxysilane, deionized water and ammonia water is (1-3):1:(0.012-0.036); and the concentration of ammonia water is 25-28 wt%.

[0012] As a further improvement, in step S1, the hydrolysis temperature is 20-30°C and the time is 1-10 hours.

[0013] As a further improvement, in step S2, the filter material needs to be ultrasonically washed with anhydrous ethanol and then dried before being immersed in the sol.

[0014] As a further improvement, in step S2, the soaking time is 1 to 120 seconds.

[0015] As a further improvement, in step S2, during the pulling process, the angle between the normal line of the dust-facing surface of the filter material and the horizontal plane is 0 to 90 degrees; and after each pulling, the filter material must stay in the air for 20 to 80 seconds.

[0016] As a further improvement, in step S3, the aging time is 6 to 64 hours and the temperature is 20 to 30°C.

[0017] As a further improvement, in step S3, the drying time is 12 to 36 hours and the temperature is 40 to 80°C.

[0018] A filter material modified by the above method.

[0019] The beneficial effects of the present invention are:

[0020] The embodiment of the present invention uses methyltriethoxysilane as a single precursor and ammonia water as a catalyst. After soaking and pulling, and ensuring a small sol loading amount, and then undergoing aging and drying steps, a continuous and complete film-like protective layer can be coated on the surface of the filter material. The hydrophobic layer improves the acid and high temperature resistance of the filter material, making it suitable for humid, acidic and high temperature application environments.

[0021] In the modification method of the filter material of the present invention, no toxic modifier is used, and the precursor methyltriethoxysilane used will not decompose into toxic by-products, which is green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 The surface micromorphology of the filter material before and after modification provided in Example 1 of the present invention, wherein (a) is the unmodified filter material and (b) is the modified filter material.

[0024] Figure 2 is the water contact angle of the modified filter material provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention for which protection is sought, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] An embodiment of the present invention provides a method for modifying a filter material, comprising the following steps:

[0027] S1, mixing methyltriethoxysilane and deionized water and stirring to fully hydrolyze them, then adding ammonia water dropwise and continuing to stir to obtain a sol;

[0028] S2, soaking the filter material in the sol, and pulling the soaked filter material in anhydrous ethanol for 1 to 30 times to ensure a small sol loading amount and a small weight gain rate of the filter material, so as to form a film-like protective layer;

[0029] S3, placing the pulled filter material in anhydrous ethanol for aging and drying to form a film-like protective layer on the filter material.

[0030] In the prior art, the protective layer formed by the material of the particulate matter is often not dense, and the exposed part thereof cannot be effectively protected. The improvement method is usually to increase the thickness of the protective layer to improve the protection effect.

[0031] The present invention utilizes methyltriethoxysilane as a single precursor and ammonia as a catalyst. Through soaking, pulling, aging, and drying, the sol loading and weight gain rate are controlled appropriately. This allows the surface of the filter material to be coated with a continuous, complete, film-like protective layer, rather than a granular protective layer, with no exposed portions, resulting in excellent hydrophobicity. This improves the filter material's acid and high-temperature resistance, making it suitable for use in humid, acidic, and high-temperature environments. Excessive or low sol loading and weight gain rates can result in the formation of a granular protective layer, resulting in incomplete coating.

[0032] As a further improvement, the filter material is selected from one or more of organic fiber and glass fiber. This filter material is easily hydrolyzed and has poor heat or acid resistance. After being modified by the method of the embodiment of the present invention, its hydrophobicity, acid resistance and high temperature resistance can be improved.

[0033] As a further improvement, in step S1, the volume ratio of methyltriethoxysilane, deionized water, and ammonia is (1-3):1:(0.012-0.036); the ammonia concentration is 25-28 wt%. This concentration ratio affects the sol loading and the final weight gain rate, especially the concentration ratio of methyltriethoxysilane to deionized water. This appropriate concentration ratio can form a dense, film-like protective layer rather than a granular protective layer, forming a complete coating.

[0034] As a further improvement, in step S1, the hydrolysis temperature is 20-30°C and the time is 1-10 hours. Under these conditions, the hydrolysis is more complete, which is conducive to the formation of a dense film-like protective layer.

[0035] As a further improvement, in step S2, before soaking the filter material in the sol, the filter material is ultrasonically washed with anhydrous ethanol and then dried. This pretreatment removes surface stains, prevents stains from forming cores and a granular protective layer, and facilitates the formation of a complete membrane-like protective layer. Preferably, the anhydrous ethanol concentration is ≥99.7%, the number of washes is 3-5, each 5-10 minutes, the drying temperature is 40-80°C, and the drying time is 2-5 hours.

[0036] As a further improvement, in step S2, the soaking time is 1 to 120 seconds. This soaking time is intended to control the sol loading and the weight gain rate of the filter material, keeping the overall weight gain rate within the range of 5 to 20%. The embodiments of the present invention use a relatively small amount of sol, resulting in a dense xerogel. This forms a film-like protective layer on the surface of the filter material, rather than a granular gel powder. If the weight gain rate is greater than or less than 20%, it will be difficult to form a film-like protective layer, resulting in a granular gel powder that is less protective.

[0037] As a further improvement, in step S2, the pulling is to soak the filter material in anhydrous ethanol and then quickly lift it out of the anhydrous ethanol to ensure a smaller sol loading amount and a weight gain rate of the filter material; during the pulling process, the angle between the normal of the dust-facing surface of the filter material and the horizontal plane is 0 to 90°, and the dust-facing surface of the filter material is inclined at a certain angle to the horizontal plane to ensure that excess sol loaded during the pulling process can flow down and reduce the sol loading amount; after each pulling, it must stay in the air for 20 to 80 seconds to ensure that the sol has enough time to flow down.

[0038] As a further improvement, in step S3, the aging time is 6 to 64 hours and the aging temperature is 20 to 30° C. This aging time can further control the sol loading and reduce the weight gain rate; at this aging temperature, a more complete film-like protective layer can be formed with a smaller sol loading.

[0039] As a further improvement, in step S3, the drying time is 12 to 36 hours and the temperature is 40 to 80° C. Such drying time and temperature can form a more complete film-like protective layer under the premise of a smaller sol loading amount.

[0040] A filter material modified by the above method has good hydrophobicity, acid resistance and high temperature resistance, and is suitable for use in humid, acidic and high temperature environments.

[0041] Example 1

[0042] Step 1: Pretreatment of aramid / glass fiber composite needle felt

[0043] The aramid / glass fiber composite needled felt was ultrasonically washed with anhydrous ethanol for 10 min, washed three times, and dried in an oven at 60 °C for 2 h.

[0044] Step 2: Prepare a methyltriethoxysilane sol using a volume ratio of methyltriethoxysilane: deionized water: ammonia water of 1.4:1:0.024, respectively, to obtain solutions ① and ② in two steps. The methyltriethoxysilane concentration is ≥98% and the ammonia concentration is 28 wt%.

[0045] (1) Solution ①: At room temperature, methyltriethoxysilane and deionized water were mixed in a volume ratio of 1.4:1 and hydrolyzed under magnetic stirring for 5 h;

[0046] (2) Solution ②: Add the above volume ratio of ammonia water to solution ① and continue stirring for 10 minutes at a stirring temperature of 25°C;

[0047] Step 3: Filter material modification

[0048] (1) Soak the aramid / glass fiber composite needle-punched felt in solution ② for 10 seconds, then take it out and let it stand in the air until no solution drips (40 seconds);

[0049] (2) When the aramid / glass fiber composite needle-punched felt is pulled in anhydrous ethanol, the normal line of the dust-facing surface is perpendicular to the horizontal plane. The felt is immersed and pulled 13 times, each time immersed in anhydrous ethanol for 10 seconds. After each immersion, it is horizontally lifted to the air for 40 seconds. After the pulling is completed, it is placed in anhydrous ethanol and sealed for aging for 24 hours. After unsealing, it is dried at 60°C for 24 hours to obtain a modified filter material.

[0050] After testing, the weight gain rate of the prepared modified filter material was 17%.

[0051] Example 2

[0052] Step 1: Pretreatment of aramid / glass fiber composite needle felt

[0053] Same as Example 1

[0054] Step 2: Same as Example 1

[0055] Step 3: Filter material modification

[0056] (1) Soak the aramid / glass fiber composite needle-punched felt in solution ② for 15 seconds, then take it out and let it stand in the air until no solution drips (1 minute);

[0057] (2) When the aramid / glass fiber composite needle-punched felt is pulled in anhydrous ethanol, the normal line of the dust-facing surface is parallel to the horizontal plane. It is immersed and pulled 7 times, each time immersed in anhydrous ethanol for 15 seconds. After each immersion, it is vertically lifted into the air for 1 minute. After the pulling is completed, it is placed in anhydrous ethanol and sealed for aging for 24 hours. After unsealing, it is dried at 60°C for 24 hours to obtain a modified filter material.

[0058] According to the test, the weight gain rate of the prepared modified filter material is 18%.

[0059] Comparative Example 1

[0060] Step 1: Pretreatment of aramid / glass fiber composite needle felt

[0061] Same as Example 1

[0062] Step 2: Same as Example 1

[0063] Step 3: Filter material modification

[0064] (1) Soak the aramid / glass fiber composite needle-punched felt in solution ② for 10 seconds, then take it out and let it stand in the air until no solution drips (40 seconds);

[0065] (2) The aramid / glass fiber composite needle-punched felt was placed in anhydrous ethanol and sealed for aging for 24 hours. After unsealing, it was dried at 60°C for 24 hours to obtain a modified filter material.

[0066] The difference from Example 1 is that the pulling in anhydrous ethanol is not performed, and the other operations are the same as in Example 1.

[0067] According to the test, the weight gain rate of the prepared modified filter material is 42%.

[0068] Comparative Example 2

[0069] Step 1: Pretreatment of aramid / glass fiber composite needle felt

[0070] Same as Example 1

[0071] Step 2: Same as Example 1

[0072] Step 3: Filter material modification

[0073] (1) Soak the aramid / glass fiber composite needle-punched felt in solution ② for 10 seconds, then take it out and let it stand in the air until no solution drips (40 seconds);

[0074] (2) When the aramid / glass fiber composite needle-punched felt is pulled in anhydrous ethanol, the normal line of the dust-facing surface is perpendicular to the horizontal plane. The felt is immersed and pulled 13 times, each time immersed in anhydrous ethanol for 10 seconds. After each immersion, it is horizontally lifted to the air for 40 seconds. After the pulling is completed, it is placed in anhydrous ethanol and sealed for aging for 74 hours. After unsealing, it is dried at 60°C for 24 hours to obtain a modified filter material.

[0075] The difference from Example 1 is that the aging time is changed to 74 hours, and the other operations are the same as Example 1.

[0076] After testing, the weight gain rate of the prepared modified filter material was 51%.

[0077] Comparative Example 3

[0078] Step 1: Pretreatment of aramid / glass fiber composite needle felt

[0079] Same as Example 1

[0080] Step 2:

[0081] Prepare a methyltriethoxysilane sol in a volume ratio of 4:1:0.036 for methyltriethoxysilane: deionized water: aqueous ammonia, respectively, in two steps to obtain solution ① and solution ②. The methyltriethoxysilane concentration is ≥98% and the aqueous ammonia concentration is 28 wt%.

[0082] (1) Solution ①: At room temperature, methyltriethoxysilane and deionized water were mixed in a volume ratio of 1.4:1 and hydrolyzed under magnetic stirring for 5 h;

[0083] (2) Solution ②: Add the above volume ratio of ammonia water to solution ① and continue stirring for 10 minutes at a stirring temperature of 25°C;

[0084] Step 3: Same as Example 1.

[0085] The difference from Example 1 is that the volume ratio of methyltriethoxysilane:deionized water:ammonia water is 4:1:0.036, and other operations are the same as Example 1.

[0086] After testing, the weight gain rate of the prepared modified filter material was 24%.

[0087] The surface micromorphology of the filter material before and after modification of Example 1 was observed using a field emission scanning electron microscope. Figure 1 shown. Figure 1 (a) is an unmodified filter material with a smooth and flat fiber surface. The fibers are randomly interwoven with each other, and there are tiny gaps between the fibers. Figure 1 (b) is a modified filter material. The fiber surface is covered with a continuous and complete protective film, and the pores between the fibers are still retained.

[0088] The water contact angle of the modified filter material of Example 1 was 101.1° as measured by a video optical contact angle meter. Figure 2 As shown, the protective film of the material exhibits good hydrophobicity.

[0089] A tensile testing machine was used to test the warp and weft breaking strength of the unmodified and modified filter materials from Examples 1-2 and Comparative Examples 1-3 before and after temperature treatment and acid treatment. The temperature treatment consisted of subjecting the filter materials to a 225°C temperature treatment for 24 hours, and the acid treatment consisted of immersing the filter materials in a 30% by mass sulfuric acid solution at 95°C for 24 hours. The filter materials were tested three times in both the warp and weft directions. The dynamic filtration performance of the filter materials was evaluated using a VDI filter material simulation test apparatus according to the test methods specified in GB / T6719-2009, "Technical Requirements for Bag Dust Collectors." The test results are shown in Table 1.

[0090] Table 1

[0091]

[0092] As shown in Table 1, the modified filter materials of Examples 1-2 can improve the filtration efficiency, acid resistance, and high temperature resistance (225°C) compared to the unmodified materials while maintaining the quality factor basically unchanged. Comparative Example 1 does not perform the pulling operation, the aging time of Comparative Example 2 is too long, and the volume ratio of methyltriethoxysilane: deionized water: ammonia water in Comparative Example 3 exceeds the appropriate range. The acid resistance and high temperature resistance (225°C) of the modified materials of Comparative Examples 1-3 are worse than those of Examples 1-2. Analysis shows that factors such as the pulling operation, aging time, and the volume ratio of methyltriethoxysilane: deionized water: ammonia water all affect the sol loading and the final weight gain rate. Excessive or insufficient sol loading and final weight gain rate are not conducive to the formation of a dense protective film, resulting in reduced acid resistance and high temperature resistance.

[0093] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for modifying a filter material, characterized in that: The following steps are involved: S1, mixing methyltriethoxysilane and deionized water and stirring to fully hydrolyze them, then adding ammonia water dropwise and continuing to stir to obtain a sol; S2, soaking the filter material in the sol, and pulling the soaked filter material in anhydrous ethanol for 1 to 30 times; S3, placing the pulled filter material in anhydrous ethanol for aging and drying to form a film-like protective layer on the filter material; In step S1, the volume ratio of methyltriethoxysilane, deionized water, and ammonia water is (1-3):1:(0.012-0.036); the concentration of ammonia water is 25-28 wt%; In step S1, the hydrolysis temperature is 20-30°C and the time is 1-10 hours; In step S2, the soaking time is 1 to 120 seconds; In step S2, during the pulling process, the angle between the normal line of the dust-facing surface of the filter material and the horizontal plane is 0 to 90 degrees; after each pulling, the filter material is left in the air for 20 to 80 seconds; In step S3, the aging time is 6 to 64 hours and the temperature is 20 to 30° C.; In step S3, the drying time is 12 to 36 hours and the temperature is 40 to 80°C.

2. The method for modifying the filter material according to claim 1, wherein: The filter material is selected from one or both of organic fiber and glass fiber.

3. The method for modifying the filter material according to claim 1, wherein: In step S2, before the filter material is immersed in the sol, the filter material needs to be ultrasonically washed with anhydrous ethanol and then dried.

4. A filter material modified by the method according to any one of claims 1 to 3.

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