Ultrafine fiber foamed coating needle-punched composite filter material and preparation method thereof

Abstract

The invention relates to an ultrafine fiber foaming coating needle-punched composite filter material and a preparation method thereof. The composite filter material comprises an ultrafine glass fiber reinforced PTFE microporous membrane layer and an aramid fiber needle-punched felt layer with PTFE coated on the fiber surface, which are sequentially arranged from top to bottom. The preparation method comprises: firstly forming an ultrafine glass fiber layer on the surface of the aramid fiber needle-punched felt with an average pore size of not less than 20 μm, then spraying a PTFE emulsion with a solid content of not more than 30% on the surface of the ultrafine glass fiber layer, and then drying it immediately to obtain the ultrafine fiber foaming coating needle-punched composite filter material; wherein the spraying amount of the PTFE emulsion on the surface of the ultrafine glass fiber layer is 90-120 g / m 2 The spraying pressure is 500-800 Pa. The product of the invention performs filtration based on the surface filtration mechanism, has good filtration effect, low filtration resistance, and has good bonding force between the ultrafine glass fiber and the aramid fiber needle felt. The method of the invention is simple and easy to operate.

Description

Technical Field

[0001] The invention belongs to the technical field of filter materials and relates to an ultrafine fiber foaming coating needle-punched composite filter material and a preparation method thereof. Background Art

[0002] Bag filters are widely valued as a filtering device to reduce pollution. They have the advantages of effectively capturing dust particles, good dust removal stability, high filtration efficiency, and a wide applicable temperature range. The quality of the filter material in the bag filter will directly affect the resistance and filtration performance of the dust removal system, and ultimately affect the use and life of the bag filter. At present, the focus of research and development of new filter materials is mainly on improving efficiency, reducing resistance, and reducing energy consumption.

[0003] Needle-punched nonwoven materials are commonly used industrial smoke filter materials with advantages such as good permeability and dimensional stability. However, while needle-punched reinforcement gives the fiber web dimensional stability, the needles produce needle-punched holes inside and on the surface of the fiber web, with an average pore size greater than 20μm, which cannot meet the current ultra-low emission requirements.

[0004] In order to improve the filtration efficiency of needle-punched filter bags, Reference 1 (Current Status and Research Progress of Ultra-clean Filter Materials for Carbon Capture, Textile Guide, 2022, (3): 41-46.) adopts a polytetrafluoroethylene (PTFE) coating post-treatment method. The coated filter material has a high filtration efficiency for fine particles, which has become the first choice for ultra-low emissions under the increasingly stringent emission standards. However, PTFE coated filter materials have disadvantages such as small film thickness, low mechanical strength and poor wear resistance. At the same time, the coating fastness of some coated filter materials is low, resulting in good effect in the initial use, but the film falls off and breaks after a period of use.

[0005] Polytetrafluoroethylene (PTFE) emulsion impregnation is a common finishing process technology for needle-punched filter media, which can improve the water and oil repellency and temperature resistance of the filter media, avoid the problem of bag sticking during use, and greatly reduce the operating resistance of the filtering equipment. Therefore, it is widely used in the industrial field. Patent CN102634979A relates to the preparation of polyphenylene sulfide fiber filter media resistant to instantaneous high-temperature oxidation, in which polytetrafluoroethylene and epoxy phenolic are used as finishing liquids to impregnate the polyphenylene sulfide fiber filter material, which can improve the temperature resistance and corrosion resistance of the fiber filter material.

[0006] Document 2 (Study on the Effect of Impregnation Finishing on the Performance of PAN Pre-oxidized Fiber / Aramid Composite Filter Material, New Chemical Materials, 2019, 47(1): 116-119.) found that when the amount of PTFE emulsion impregnation is large enough, the pore size of the filter material decreases and has a higher filtration efficiency. The average pore size of the PAN pre-oxidized fiber / aramid composite filter material can be reduced from 121μm to 95μm by impregnating it with PTFE emulsion. The filtration efficiency of the impregnated composite filter material for 0.3μm particles is increased from 33.11% to 65.87%. However, the impregnated filter material is still based on the deep filtration mechanism, and the filtration resistance will increase as the filtration process proceeds. Summary of the invention

[0007] The purpose of the present invention is to solve the problems of poor bonding force, short service life and large filtration resistance of composite filter materials in the prior art, and to provide an ultrafine fiber foaming coating needle-punched composite filter material and a preparation method thereof.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A superfine fiber foaming coating needle-punched composite filter material comprises a superfine glass fiber reinforced PTFE microporous membrane layer and an aramid fiber needle-punched felt layer with PTFE coated on the fiber surface which are arranged in sequence from top to bottom.

[0010] The ultrafine fiber foam coating needle-punched composite filter material of the present invention is composed of a PTFE microporous membrane layer reinforced by ultrafine glass fiber and an aramid fiber needle-punched felt layer with PTFE coated on the fiber surface. Therefore, the composite strength of the two adjacent layers in the ultrafine fiber foam coating needle-punched composite filter material of the present invention is high because PTFE can connect the ultrafine glass fiber and the aramid fiber. At the same time, the filtration mechanism of the ultrafine fiber foam coating needle-punched composite filter material of the present invention is a "surface filtration mechanism" rather than a "deep filtration mechanism", thereby avoiding the filtration resistance from increasing as the filtration process proceeds.

[0011] Figure 4 (a) is a deep filtration mechanism diagram. Traditional filter materials are mainly woven fabrics, non-woven fabrics and their composite filter materials. Under the deep filtration mechanism, as the filtration proceeds, particulate dust forms a "filter cake" on the surface of the filter material and enters the interior of the filter material in large quantities, making dust cleaning difficult and the filtration resistance increasing; Figure 4 (b) is a surface filtration mechanism diagram. A microporous filtration layer is formed on the surface of the traditional fiber filter material. Its pore size is smaller than that of the lower filter material. During filtration, most dust particles are first intercepted by the surface layer to form a "filter cake" structure. Few particles are adsorbed inside the filter material, so it is called surface filtration. The advantages are easy dust cleaning, small filtration resistance, and small pressure drop.

[0012] As the preferred technical solution:

[0013] The above-mentioned ultrafine fiber foam coating needle-punched composite filter material has a mass loss of 73.2-89.7 mg after being rubbed 1000 times with a circular ultrafine fiber foam coating needle-punched composite filter material having a diameter of 38 mm; the ultrafine fiber foam coating needle-punched composite filter material has a filtration efficiency of >99.94% after being sprayed 30 times at a constant pressure of 1000 Pa, and an emission concentration of 2.5-4.5 mg / m 3 .

[0014] In the ultrafine fiber foamed coating needle-punched composite filter material as described above, the average pore size of the ultrafine glass fiber reinforced PTFE microporous membrane layer is 4.16-8.03 μm.

[0015] The present invention also provides a method for preparing a superfine fiber foam coating needle-punched composite filter material, firstly forming a superfine glass fiber layer on the surface of an aramid fiber needle-punched felt having an average pore size of not less than 20 μm, then spraying a PTFE emulsion having a solid content of not more than 30% onto the surface of the superfine glass fiber layer, and then drying it immediately (250° C., 10 min) to obtain a superfine fiber foam coating needle-punched composite filter material; wherein the spraying amount of the PTFE emulsion on the surface of the superfine glass fiber layer is 90 to 120 g / m 2 , the spraying pressure is 500~800Pa.

[0016] PTFE emulsion with a solid content not exceeding 30% is a liquid with very low viscosity. When it is sprayed at a certain amount and pressure onto an aramid fiber needle felt having an ultra-fine glass fiber layer on the surface, it will penetrate through the ultra-fine glass fiber layer and penetrate into the interior of the aramid fiber needle felt. The average pore size of the ultrafine glass fiber layer is small, and the fiber spacing is close. After PTFE penetrates into the ultrafine glass fiber layer, the PTFE emulsion solidifies to form a microporous membrane structure reinforced (reinforced) by ultrafine glass fibers. At the same time, PTFE adheres the ultrafine glass fiber layer to the surface of the aramid needle-punched layer, thereby improving the adhesion strength of the glass fiber surface layer of the composite material and giving the needle-punched felt a water- and oil-repellent effect. The average pore size of the aramid fiber needle-punched felt is large, and the fiber spacing is far. After PTFE penetrates into the aramid fiber needle-punched felt, the PTFE emulsion solidifies and cannot form a microporous membrane structure, but is coated on the surface of the aramid fiber to form an aramid fiber needle-punched felt with PTFE coated on the fiber surface. At the same time, the PTFE emulsion is sprayed onto the surface of the ultrafine glass fiber layer and immediately dried, and the amount of PTFE emulsion that penetrates into the aramid fiber needle-punched felt is small, which also leads to the inability to form a microporous membrane structure.

[0017] As the preferred technical solution:

[0018] The method for preparing the ultrafine fiber foamed coating needle-punched composite filter material as described above, wherein the gram weight of the aramid fiber needle-punched felt is 350 to 650 g / m 2The average pore size is not less than 20μm; the average fineness of the aramid fiber is 2.5~3D, and the average length is 50~55mm.

[0019] In the method for preparing the ultrafine fiber foamed coating needle-punched composite filter material as described above, the average fineness of the ultrafine glass fiber is 6 to 8 μm, and the average length is 2 to 4 mm.

[0020] The method for preparing the ultrafine fiber foamed coating needle-punched composite filter material as described above comprises the following steps:

[0021] (1) preparing ultrafine glass fiber foaming solution;

[0022] A dispersion containing ultrafine glass fibers and a surfactant (such as betaine, which reduces surface tension and makes it easy to generate foam during the stirring process of introducing air, which disperses the ultrafine glass fibers and makes the fibers randomly arranged) is passed through a multi-line lantern-shaped stirring paddle (the structure of the multi-line lantern-shaped stirring paddle is as shown in FIG. Figure 6 As shown) and stirred to obtain an ultrafine glass fiber foam solution with a foaming multiple of 4 to 5 times, a foam outer diameter of 50 to 100 μm and an ultrafine glass fiber mass content of 0.4% to 1%;

[0023] The present invention uses surfactant foaming technology for the dispersion and web formation of ultrafine fibers for the first time, and adjusts the dispersion degree and disorderly arrangement of ultrafine glass fibers by controlling the foaming multiple to 4 to 5 times and the outer diameter of the foam to 50 to 100 μm, thereby controlling the uniformity of the ultrafine glass fiber layer.

[0024] (2) applying the ultrafine glass fiber foaming solution to the surface of the aramid fiber needle felt, and vacuum filtering to form an ultrafine glass fiber layer;

[0025] If the ultra-fine glass fiber dispersion is not coated on the surface of the needle felt, it will result in: 1) the ultra-fine glass fiber layer is oriented in two dimensions instead of three dimensions, because the role of the foam is to make the fibers arranged randomly and dispersed more evenly. When the fibers are directly dispersed in water, the fibers are unevenly dispersed, easily agglomerated and flocculated, and the disorder is low, thus forming a two-dimensional orientation instead of a three-dimensional orientation; 2) the dosage is high, because the fiber content of the evenly dispersed ultra-fine glass fiber dispersion is low, and compared with the foaming solution, more dispersion is required to form an ultra-fine glass fiber layer of the same thickness on the surface of the aramid fiber needle felt;

[0026] (3) Spraying a PTFE emulsion with a solid content of 10% to 30% onto the surface of the ultrafine glass fiber layer, and drying it immediately (250° C., 10 min) to obtain an ultrafine fiber foaming coating needle-punched composite filter material.

[0027] In the method for preparing a superfine fiber foamed coating needle-punched composite filter material as described above, in step (1), the mass content of the surfactant in the dispersion is 2% to 3%, and the dispersion medium is water; the stirring speed is 1500 to 2000 rpm, and the time is 10 to 15 minutes.

[0028] In the method for preparing a superfine fiber foamed coating needle-punched composite filter material as described above, in step (2), the coating amount of the superfine glass fiber foaming solution on the surface of the aramid fiber needle-punched felt is 2000-2500 g / m 2 The suction pressure of vacuum filtration is 20~25KPa.

[0029] In the method for preparing a superfine fiber foamed coated needle-punched composite filter material as described above, in step (3), the preparation process of a PTFE emulsion with a solid content of 10% to 30% is as follows: a PTFE emulsion with a solid content of 60% is mixed with deionized water, and then stirred at 1500 to 2000 rpm for 10 to 15 minutes to obtain a PTFE emulsion with a solid content of 10% to 30%.

[0030] Beneficial Effects

[0031] (1) In the ultrafine fiber foamed coating needle-punched composite filter material of the present invention, an ultrafine glass fiber microporous filter layer is adhered to the surface of the aramid fiber needle-punched felt layer, and high-efficiency filtration is achieved through the surface filtration mechanism. At the same time, ultra-low filtration resistance can be maintained for a long time, and the filtration performance is excellent;

[0032] (2) Compared with conventional PTFE emulsion impregnation, PTFE emulsion not only gives the filter material water and oil repellency and improves its temperature resistance, but also adheres the ultrafine glass fiber layer to the surface of the needle-punched felt, greatly improving the adhesion strength of the glass fiber surface layer of the composite material. Compared with PTFE microporous membrane, the ultrafine glass fiber layer has an adjustable thickness, high adhesion strength with the surface of the needle-punched felt, good wear resistance, and will not fall off or break during long-term use;

[0033] (3) The glass fiber mass content of the traditional wet-laid web-forming process is only 0.01% to 0.1%. Compared with the traditional non-woven wet-laid web-forming process technology, the glass fiber mass content of the ultrafine fiber foamed coated needle-punched composite filter material of the present invention is 0.4% to 1%. The glass fiber content in the aqueous solution is higher, the water consumption is less, and it is then dried and formed once after being impregnated with PTFE emulsion, which saves energy and reduces carbon emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a PTFE microporous membrane layer reinforced with ultra-fine glass fiber;

[0035] Figure 2This is a cross-sectional electron microscope image of the ultrafine fiber foam coating needle-punched composite filter material;

[0036] Figure 3 This is a schematic diagram of the preparation process of the ultrafine fiber foaming solution;

[0037] Figure 4 Figure 1 is a filtration mechanism diagram; (a) is a deep filtration mechanism diagram; (b) is a surface filtration mechanism diagram;

[0038] Figure 5 Dynamic filtration performance test of ultra-fine fiber foam coating needle-punched composite filter material at 1000Pa constant pressure spraying for 30 cycles;

[0039] Figure 6 It is a schematic diagram of the structure of a multi-line lantern-shaped stirring paddle. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0041] The performance testing method of the composite filter material in each embodiment and comparative example is as follows:

[0042] Test method for mass loss: refer to GB / T 21196.3-2007 "Textiles - Determination of the abrasion resistance of fabrics by the Martindale method - Part 3: Determination of mass loss";

[0043] Test method for filtration efficiency: refer to Appendix B of GB / T 6719-2009 Technical Requirements for Bag Dust Collectors, Dynamic Filtration Performance Test of Filter Materials, and ISO 11057-2011;

[0044] Test method for emission concentration: Refer to Appendix B of GB / T 6719-2009 Technical Requirements for Bag Dust Collectors for dynamic filtration performance test of filter media; cut the ultrafine fiber foam coating needle-punched composite filter material into a circle with a diameter of 155 mm, and the filtration area of ​​the filter media is 0.0154 m 2 Then fix it on the fixture of the VDI equipment and start the test. Under the pressure of 1000Pa, the dust is continuously generated with a dust concentration of 5g / m 3 , constant pressure soot blowing for 30 cycles, pulse soot cleaning starts when the pressure before and after the filter material reaches 100Pa, and the soot blowing process is repeated 30 times; the test uses alumina dust with the following particle size distribution.

[0045] Particle size / μm ＜4 ＜25 ＜100 percentage / % 50 90 99

[0046] Example 1

[0047] A method for preparing a superfine fiber foamed coating needle-punched composite filter material, the specific steps are as follows:

[0048] (1) Prepare raw materials:

[0049] Aramid fiber needle felt: weight 640g / m 2 , the average pore size is 20 μm, the average fineness of the aramid fiber is 2.5D, and the average length of the aramid fiber is 50 mm;

[0050] Ultrafine glass fiber: average fineness is 6μm, average length is 2mm;

[0051] PTFE emulsion with a solid content of 20% is prepared by mixing PTFE emulsion with a solid content of 60% with deionized water and stirring at 1500 rpm for 15 minutes;

[0052] (2) Preparation of ultra-fine glass fiber foaming solution:

[0053] like Figure 3 As shown, the dispersion consisting of the ultrafine glass fiber of step (1), betaine and water is stirred at a rotation speed of 1500 rpm for 10 minutes by a multi-line lantern-shaped stirring paddle to obtain an ultrafine glass fiber foam solution with a foaming multiple of 4.7 times and an average outer diameter of the foam of 94 μm, wherein the mass content of the ultrafine glass fiber in the dispersion is 0.4%, and the mass content of the betaine is 2%;

[0054] (3) Applying ultra-fine glass fiber foaming solution:

[0055] The ultrafine glass fiber foaming solution prepared in step (2) is applied to the surface of the aramid fiber needle felt in step (1), and the excess solvent is removed by vacuum filtration to form an ultrafine glass fiber layer; wherein the coating amount of the ultrafine glass fiber foaming solution on the surface of the aramid fiber needle felt is 2350g / m 2 , the suction pressure of vacuum filtration is 20KPa;

[0056] (4) Spraying PTFE emulsion:

[0057] The PTFE emulsion of step (1) is sprayed onto the surface of the ultrafine glass fiber layer prepared in step (3), and dried immediately to obtain an ultrafine fiber foaming coating needle-punched composite filter material, wherein the spraying amount of the PTFE emulsion on the surface of the ultrafine glass fiber layer is 120 g / m 2 , the spraying pressure is 500Pa, the drying temperature is 250℃, and the time is 10min.

[0058] like Figures 1-2As shown in the figure, the final ultrafine fiber foam coating needle-punched composite filter material is composed of an upper ultrafine glass fiber reinforced PTFE microporous membrane layer and a lower fiber surface coated with PTFE aramid fiber needle-punched felt layer, wherein the ultrafine glass fiber reinforced PTFE microporous membrane layer has an average pore size of 4.16 μm, and the mass loss of the circular ultrafine fiber foam coating needle-punched composite filter material with a diameter of 38 mm after rubbing 1000 times is 73.2 mg; Figure 5 As shown in the figure, a constant pressure is applied to the sample (a circular ultrafine fiber foaming coated needle-punched composite filter material cut into a diameter of 155 mm) to start blowing dust. The initial pressure difference of the sample is 71 Pa. As the dust gradually accumulates on the surface of the sample, the pressure difference gradually increases. When the pressure difference increases to 1000 Pa, reverse blowing is performed to blow off the dust accumulated on the surface of the sample, and then the dust is blown forward. This forward and reverse blowing is repeated for 30 cycles. Due to the accumulation of dust, the time required for the pressure difference to increase to 1000 Pa is getting shorter and shorter, from 549 s in the first cycle to 172 s. The average cleaning cycle is 252.7 s, and the time for 30 cycles is 7580 s. After the ultrafine fiber foaming coated needle-punched composite filter material is sprayed 30 times at a constant pressure of 1000 Pa, the filtration efficiency is 99.95%, and the emission concentration is 2.7 mg / m 3 .

[0059] Example 2

[0060] A method for preparing a superfine fiber foamed coating needle-punched composite filter material, the specific steps are as follows:

[0061] (1) Prepare raw materials:

[0062] Aramid fiber needle felt: weight 640g / m 2 , the average pore size is 20 μm, the average fineness of the aramid fiber is 2.5D, and the average length of the aramid fiber is 50 mm;

[0063] Ultrafine glass fiber: average fineness is 6μm, average length is 2mm;

[0064] PTFE emulsion with a solid content of 20% is prepared by mixing PTFE emulsion with a solid content of 60% with deionized water and stirring at 1600 rpm for 15 minutes;

[0065] (2) Preparation of ultra-fine glass fiber foaming solution:

[0066] The dispersion consisting of the ultrafine glass fiber of step (1), sodium dodecyl sulfate and water is stirred at a rotation speed of 1500 rpm for 10 minutes by a multi-line lantern-shaped stirring paddle to obtain an ultrafine glass fiber foam solution with a foaming multiple of 4.6 times and an average outer diameter of the foam of 99 μm, wherein the mass content of the ultrafine glass fiber in the dispersion is 0.4%, and the mass content of the sodium dodecyl sulfate is 3%;

[0067] (3) Applying ultra-fine glass fiber foaming solution:

[0068] The ultrafine glass fiber foaming solution prepared in step (2) is applied to the surface of the aramid fiber needle felt in step (1), and the excess solvent is removed by vacuum filtration to form an ultrafine glass fiber layer; wherein the coating amount of the ultrafine glass fiber foaming solution on the surface of the aramid fiber needle felt is 2300 g / m 2 , the suction pressure of vacuum filtration is 20KPa;

[0069] (4) Spraying PTFE emulsion:

[0070] The PTFE emulsion of step (1) is sprayed onto the surface of the ultrafine glass fiber layer prepared in step (3), and dried immediately to obtain an ultrafine fiber foaming coating needle-punched composite filter material, wherein the spraying amount of the PTFE emulsion on the surface of the ultrafine glass fiber layer is 110 g / m 2 , the spraying pressure is 500Pa, the drying temperature is 250℃, and the time is 10min.

[0071] The final ultrafine fiber foam coating needle-punched composite filter material is composed of an ultrafine glass fiber reinforced PTFE microporous membrane layer on the top and an aramid fiber needle-punched felt layer with PTFE coated on the fiber surface on the bottom. The average pore size of the ultrafine glass fiber reinforced PTFE microporous membrane layer is 7.98 μm. The mass loss of a circular ultrafine fiber foam coating needle-punched composite filter material with a diameter of 38 mm after rubbing 1000 times is 75.4 mg; the filtration efficiency of the ultrafine fiber foam coating needle-punched composite filter material after spraying 30 times at a constant pressure of 1000 Pa is 99.95%, and the emission concentration is 4.5 mg / m 3 .

[0072] Example 3

[0073] A method for preparing a superfine fiber foamed coating needle-punched composite filter material, the specific steps are as follows:

[0074] (1) Prepare raw materials:

[0075] Aramid fiber needle felt: weight 450g / m 2 , the average pore size is 40μm, the average fineness of the aramid fiber is 2.7D, and the average length of the aramid fiber is 50mm;

[0076] Ultrafine glass fiber: average fineness is 7μm, average length is 3mm;

[0077] 10% solid content PTFE emulsion: prepared by mixing 60% solid content PTFE emulsion with deionized water and stirring at 1700 rpm for 12 minutes;

[0078] (2) Preparation of ultra-fine glass fiber foaming solution:

[0079] The dispersion consisting of the ultrafine glass fiber of step (1), potassium laurate and water is stirred by a multi-line lantern-shaped stirring paddle at a rotation speed of 1800 rpm for 13 minutes to obtain an ultrafine glass fiber foam solution with a foaming multiple of 4.5 times and an average outer diameter of the foam of 82 μm, wherein the mass content of the ultrafine glass fiber in the dispersion is 0.6%, and the mass content of potassium laurate is 2%;

[0080] (3) Applying ultra-fine glass fiber foaming solution:

[0081] The ultrafine glass fiber foaming solution prepared in step (2) is applied to the surface of the aramid fiber needle felt in step (1), and the excess solvent is removed by vacuum filtration to form an ultrafine glass fiber layer; wherein the coating amount of the ultrafine glass fiber foaming solution on the surface of the aramid fiber needle felt is 2250g / m 2 , the suction pressure of vacuum filtration is 22KPa;

[0082] (4) Spraying PTFE emulsion:

[0083] The PTFE emulsion of step (1) is sprayed onto the surface of the ultrafine glass fiber layer prepared in step (3), and dried immediately to obtain an ultrafine fiber foaming coating needle-punched composite filter material, wherein the spraying amount of the PTFE emulsion on the surface of the ultrafine glass fiber layer is 110 g / m 2 , the spraying pressure is 600Pa, the drying temperature is 250℃, and the time is 10min.

[0084] The final ultrafine fiber foam coating needle-punched composite filter material is composed of an ultrafine glass fiber reinforced PTFE microporous membrane layer on the top and an aramid fiber needle-punched felt layer with PTFE coated on the fiber surface on the bottom. The average pore size of the ultrafine glass fiber reinforced PTFE microporous membrane layer is 6.54 μm. The mass loss of a circular ultrafine fiber foam coating needle-punched composite filter material with a diameter of 38 mm after rubbing 1000 times is 80.1 mg. After the ultrafine fiber foam coating needle-punched composite filter material is sprayed 30 times at a constant pressure of 1000 Pa, the filtration efficiency is 99.95%, and the emission concentration is 3.9 mg / m 3 .

[0085] Example 4

[0086] A method for preparing a superfine fiber foamed coating needle-punched composite filter material, the specific steps are as follows:

[0087] (1) Prepare raw materials:

[0088] Aramid fiber needle felt: weight 450g / m 2 , the average pore size is 40μm, the average fineness of the aramid fiber is 2.7D, and the average length of the aramid fiber is 50mm;

[0089] Ultrafine glass fiber: average fineness is 7μm, average length is 3mm;

[0090] PTFE emulsion with a solid content of 10% is prepared by mixing PTFE emulsion with a solid content of 60% with deionized water and stirring at 1800 rpm for 12 minutes;

[0091] (2) Preparation of ultra-fine glass fiber foaming solution:

[0092] The dispersion consisting of the ultrafine glass fiber of step (1), hexadecyltrimethylammonium bromide and water was stirred for 13 minutes by a multi-line lantern-shaped stirring paddle at a rotation speed of 1800 rpm to obtain an ultrafine glass fiber foam solution with a foaming multiple of 4.6 times and an average outer diameter of the foam of 78 μm, wherein the mass content of the ultrafine glass fiber in the dispersion is 0.6%, and the mass content of hexadecyltrimethylammonium bromide is 3%;

[0093] (3) Applying ultra-fine glass fiber foaming solution:

[0094] The ultrafine glass fiber foaming solution prepared in step (2) is applied to the surface of the aramid fiber needle felt in step (1), and the excess solvent is removed by vacuum filtration to form an ultrafine glass fiber layer; wherein the coating amount of the ultrafine glass fiber foaming solution on the surface of the aramid fiber needle felt is 2300 g / m 2 , the suction pressure of vacuum filtration is 22KPa;

[0095] (4) Spraying PTFE emulsion:

[0096] The PTFE emulsion of step (1) is sprayed onto the surface of the ultrafine glass fiber layer prepared in step (3), and dried immediately to obtain an ultrafine fiber foaming coating needle-punched composite filter material, wherein the spraying amount of the PTFE emulsion on the surface of the ultrafine glass fiber layer is 100 g / m 2 , the spraying pressure is 600Pa, the drying temperature is 250℃, and the time is 10min.

[0097] The final ultrafine fiber foam coating needle-punched composite filter material is composed of an ultrafine glass fiber reinforced PTFE microporous membrane layer on the top and an aramid fiber needle-punched felt layer with PTFE coated on the fiber surface on the bottom. The average pore size of the ultrafine glass fiber reinforced PTFE microporous membrane layer is 6.24 μm. The mass loss of a circular ultrafine fiber foam coating needle-punched composite filter material with a diameter of 38 mm after rubbing 1000 times is 80.9 mg. After the ultrafine fiber foam coating needle-punched composite filter material is sprayed 30 times at a constant pressure of 1000 Pa, the filtration efficiency is 99.95%, and the emission concentration is 2.7 mg / m 3 .

[0098] Example 5

[0099] A method for preparing a superfine fiber foamed coating needle-punched composite filter material, the specific steps are as follows:

[0100] (1) Prepare raw materials:

[0101] Aramid fiber needle felt: weight 350g / m 2 , the average pore size is 60 μm, the average fineness of the aramid fiber is 3D, and the average length of the aramid fiber is 55 mm;

[0102] Ultrafine glass fiber: average fineness is 8μm, average length is 4mm;

[0103] PTFE emulsion with a solid content of 30% is prepared by mixing PTFE emulsion with a solid content of 60% with deionized water and stirring at a high speed of 1900 rpm for 10 minutes;

[0104] (2) Preparation of ultra-fine glass fiber foaming solution:

[0105] The dispersion consisting of the ultrafine glass fiber, alkyl polyglycoside and water in step (1) is stirred at a speed of 2000 rpm for 15 minutes by a multi-line lantern-shaped stirring paddle to obtain an ultrafine glass fiber foam solution with a foaming multiple of 4.7 times and an average outer diameter of the foam of 55 μm, wherein the mass content of the ultrafine glass fiber in the dispersion is 0.8%, and the mass content of the alkyl polyglycoside is 2%;

[0106] (3) Applying ultra-fine glass fiber foaming solution:

[0107] The ultrafine glass fiber foaming solution prepared in step (2) is applied to the surface of the aramid fiber needle felt in step (1), and the excess solvent is removed by vacuum filtration to form an ultrafine glass fiber layer; wherein the coating amount of the ultrafine glass fiber foaming solution on the surface of the aramid fiber needle felt is 2000 g / m 2 , the suction pressure of vacuum filtration is 25KPa;

[0108] (4) Spraying PTFE emulsion:

[0109] The PTFE emulsion of step (1) is sprayed onto the surface of the ultrafine glass fiber layer prepared in step (3), and dried immediately to obtain an ultrafine fiber foaming coating needle-punched composite filter material, wherein the spraying amount of the PTFE emulsion on the surface of the ultrafine glass fiber layer is 90 g / m 2 , the spraying pressure is 700Pa, the drying temperature is 250℃, and the time is 10min.

[0110] The final ultrafine fiber foam coating needle-punched composite filter material is composed of an ultrafine glass fiber reinforced PTFE microporous membrane layer on the top and an aramid fiber needle-punched felt layer with PTFE coated on the fiber surface on the bottom. The average pore size of the ultrafine glass fiber reinforced PTFE microporous membrane layer is 7.85 μm. The mass loss of a circular ultrafine fiber foam coating needle-punched composite filter material with a diameter of 38 mm after rubbing 1000 times is 85.6 mg. After the ultrafine fiber foam coating needle-punched composite filter material is sprayed 30 times at a constant pressure of 1000 Pa, the filtration efficiency is 99.95%, and the emission concentration is 4.5 mg / m 3 .

[0111] Example 6

[0112] A method for preparing a superfine fiber foamed coating needle-punched composite filter material, the specific steps are as follows:

[0113] (1) Prepare raw materials:

[0114] Aramid fiber needle felt: weight 350g / m 2 , the average pore size is 60 μm, the average fineness of the aramid fiber is 3D, and the average length of the aramid fiber is 55 mm;

[0115] Ultrafine glass fiber: average fineness is 8μm, average length is 4mm;

[0116] PTFE emulsion with a solid content of 30% is prepared by mixing PTFE emulsion with a solid content of 60% with deionized water and stirring at a high speed of 2000 rpm for 10 minutes;

[0117] (2) Preparation of ultra-fine glass fiber foaming solution:

[0118] Stirring the dispersion consisting of the ultrafine glass fiber of step (1), Tween 80 and water with a multi-line lantern-shaped stirring paddle at a rotation speed of 2000 rpm for 10 minutes to obtain an ultrafine glass fiber foam solution with a foaming multiple of 5 times and an average outer diameter of the foam of 68 μm, wherein the mass content of the ultrafine glass fiber in the dispersion is 1%, and the mass content of Tween 80 is 3%;

[0119] (3) Applying ultra-fine glass fiber foaming solution:

[0120] The ultrafine glass fiber foaming solution prepared in step (2) is applied to the surface of the aramid fiber needle felt in step (1), and the excess solvent is removed by vacuum filtration to form an ultrafine glass fiber layer; wherein the coating amount of the ultrafine glass fiber foaming solution on the surface of the aramid fiber needle felt is 2500g / m 2 , the suction pressure of vacuum filtration is 25KPa;

[0121] (4) Spraying PTFE emulsion:

[0122] The PTFE emulsion of step (1) is sprayed onto the surface of the ultrafine glass fiber layer prepared in step (3), and dried immediately to obtain an ultrafine fiber foaming coating needle-punched composite filter material, wherein the spraying amount of the PTFE emulsion on the surface of the ultrafine glass fiber layer is 90 g / m 2 , the spraying pressure is 800Pa, the drying temperature is 250℃, and the time is 10min.

[0123] The final ultrafine fiber foam coating needle-punched composite filter material is composed of an ultrafine glass fiber reinforced PTFE microporous membrane layer on the top and an aramid fiber needle-punched felt layer with PTFE coated on the fiber surface on the bottom. The average pore size of the ultrafine glass fiber reinforced PTFE microporous membrane layer is 4.01 μm. The mass loss of a circular ultrafine fiber foam coating needle-punched composite filter material with a diameter of 38 mm after rubbing 1000 times is 89.7 mg; the filtration efficiency of the ultrafine fiber foam coating needle-punched composite filter material is 99.99% after being sprayed 30 times at a constant pressure of 1000 Pa, and the emission concentration is 2.5 mg / m 3 .

Claims

1. A method for preparing a superfine fiber foamed coating needle-punched composite filter material, characterized in that: The following steps are involved: (1) Preparing ultrafine glass fiber foaming solution; The dispersion containing ultrafine glass fibers and surfactants is stirred by a multi-line lantern-shaped stirring paddle to obtain an ultrafine glass fiber foam solution having a foaming multiple of 4 to 5 times, a foam outer diameter of 50 to 100 μm, and an ultrafine glass fiber mass content of 0.4% to 1%; (2) applying the ultrafine glass fiber foaming solution onto the surface of the aramid fiber needle felt having an average pore size of not less than 20 μm, and performing vacuum filtration to form an ultrafine glass fiber layer; (3) Spraying a PTFE emulsion with a solid content of 10% to 30% onto the surface of the ultrafine glass fiber layer and drying it immediately to obtain an ultrafine fiber foaming coating needle-punched composite filter material; wherein the spraying amount of the PTFE emulsion on the surface of the ultrafine glass fiber layer is 90 to 120 g / m 2 , the spraying pressure is 500~800Pa.

2. The method for preparing a superfine fiber foamed coating needle-punched composite filter material according to claim 1, characterized in that: The gram weight of aramid fiber needle felt is 350~650g / m 2 The average pore size is not less than 20μm; the average fineness of aramid fiber is 2.5~3D, and the average length is 50~55mm.

3. The method for preparing a superfine fiber foamed coating needle-punched composite filter material according to claim 1, characterized in that: The average fineness of ultrafine glass fiber is 6~8μm and the average length is 2~4mm.

4. The method for preparing a superfine fiber foamed coating needle-punched composite filter material according to claim 1, characterized in that: In step (1), the mass content of the surfactant in the dispersion is 2% to 3%, and the dispersion medium is water; the stirring speed is 1500 to 2000 rpm, and the time is 10 to 15 minutes.

5. The method for preparing a superfine fiber foamed coating needle-punched composite filter material according to claim 1, characterized in that: In step (2), the coating amount of the ultrafine glass fiber foaming solution on the surface of the aramid fiber needle felt is 2000~2500g / m 2 The suction pressure of vacuum filtration is 20~25KPa.

6. The method for preparing a superfine fiber foamed coating needle-punched composite filter material according to claim 1, characterized in that: In step (3), the preparation process of the PTFE emulsion with a solid content of 10% to 30% is as follows: after mixing the PTFE emulsion with a solid content of 60% with deionized water, the mixture is stirred at a high speed of 1500 to 2000 rpm for 10 to 15 minutes to obtain a PTFE emulsion with a solid content of 10% to 30%.

Images