JP2007301436A - Filter medium for air filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter medium for an air filter which has an extremely low pressure loss, is most suitable for the air filtration treatment and is capable of trapping fine powder with high efficiency. <P>SOLUTION: The air filter medium 10 is provided with a sheet-like nanofiber structure layer 12 with which the nanofiber is three-dimensionally entangled, an upstream side porous material layer 14 which integrally overlies the surface of the filtration upstream side of the nanofiber structure layer 12 and a downstream side porous material layer 16 which is integrally laminated on the surface of the filtration downstream side of the nanofiber structure layer 12. The face which is integrally laminated with the nanofiber structure layer 12 of the upstream side porous material layer 14 and the downstream side porous material layer 16 is flat and smooth with no fluffy projections. The downstream side porous material layer 16 has gas permeability of which the pressure loss is 100 pa or less at the air flow rate of 1 m/second. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an air filter medium, and more particularly to an air filter medium that is extremely low in pressure loss and optimal for gas filtration with a high air volume and that can collect fine dust with high efficiency.

As conventional air filters, pre-filters, medium performance filters, high performance (HEPA) filters, and ultra high performance filters (ULPA) filters are widely used in air conditioning facilities in factories, buildings, hospitals, etc., depending on the size and collection efficiency of collected dust. in use. A high-performance HEPA filter used in a clean room for factory air conditioning, for example, is a 610 mm long x 610 mm wide x 50 mm deep case in which a pleated filter medium is set, and the filter unit has a dust of 0.3 μm or more. Is used at a processing air volume of 10 m ³ / min, a pressure loss of 300 pa, a processing air speed of 0.5 m / s (an air speed in the filter medium of around 0.05 m / sec). The medium performance filter is set by pleating a filter material in a case of 594 mm long × 594 mm wide × 96 mm deep, with a collection efficiency of 65% or more of dust of 0.3 μm or more and a processing air flow of 50 m ³ / min / pressure loss. It is used at a rate of 170 pa · processed wind speed of 2.0 m / s (around 0.06 m / second in the filter medium). In the filter material for air filters used in these air filter units, the performance as a HEPA filter material of a nonwoven fabric composed of glass fibers and synthetic fibers (performance on a flat plate without pleating) is a surface wind speed of 5.3 cm / The initial dust collection efficiency of 0.3 to 0.5 μm per second is about 97%, and the medium performance filter material using non-woven fabric such as meltblown is the initial dust at a surface wind speed of 5.3 cm / sec. Efficiency is about 50%. An air filter using nanofibers can be expected to have high efficiency, but for example, as seen in Patent Document 1, it is used without sufficiently grasping that a nanofiber layer shows a unique state when placed in an air flow. ing.
JP 2005-527344 A

  In the conventionally used air filter, the design wind speed in the filter medium is 5 to 6 cm / second in the medium performance filter / HEPA filter and 5 cm / second or less in the ULPA filter. When used in an environment above the design wind speed in the filter medium, the pressure loss increases as the wind speed increases, and the collected dust or the like rescatters, reducing the dust collection efficiency of the filter. This is because when the air flow rate rises, Karman vortices and turbulent vortices generated downstream of the air filter gradually increase, and the force pulling the entire filter medium in the downstream direction acts to drop off the dust. Due to the natural vibration in the direction perpendicular to the air flow direction, the dust collected in the filter medium gradually moves and flows downstream of the air flow, thereby reducing the collection efficiency. In addition, in an air filter composed of nanofibers, if there are free fibers or tangle-like fibers in contact with the nanofibers, they will vibrate vigorously with the Karman vortex / turbulent vortex and disturb the nanofiber arrangement or damage. Occurrence is also born, which also leads to a decrease in collection efficiency. Since the conventionally used air filter material is mainly composed of short fibers, this phenomenon is likely to occur. The present invention has been made in view of the above problems, and provides an air filter medium that is extremely low in pressure loss and is optimal for gas filtration with a high air volume, and that can collect fine dust with high efficiency. For the purpose.

  The invention according to claim 1 is a sheet-like nanofiber structure layer in which nanofibers are entangled three-dimensionally, and an upstream porosity layered integrally on the surface of the nanofiber structure layer on the upstream side of filtration. And a downstream porous body layer integrally laminated on a filtration downstream side surface of the nanofiber structure layer, the upstream porous body layer and the downstream porous body layer nanofiber structure The surface on the side laminated with the layer is smooth with no protrusions, and the downstream porous body layer has air permeability such that the pressure loss at an air flow rate of 1 m / sec is 100 pa or less. A filter medium for an air filter, characterized in that no turbulent flow is generated on the downstream side of the filtration.

  In the invention according to claim 2, the nanofiber structure layer is composed of a plurality of layers having different fiber diameters for each layer, and the fiber diameter of the nanofibers of each layer constituting the nanofiber structure layer is determined on the downstream side of the filtration. The filter material for an air filter according to claim 1, which decreases as it goes to the layer.

  The invention according to claim 3 is a filter medium for an air filter obtained by combining the filter medium for general-purpose air filter and the filter medium for air filter according to claim 1 or claim 2, wherein the filter medium for air filter is claim 1 or claim 2. The filter medium for air filter described in the above is disposed in close contact with the downstream surface of the filter medium for general-purpose air filter, or is disposed at a distance within the range of the turbulence of the air stream on the downstream side of the filter medium for general-purpose air filter. This is a filter medium for an air filter.

  The invention according to claim 4 is the air filter medium according to claim 3, wherein either or both of the general-purpose air filter and the air filter medium are unitized.

  According to the air filter medium according to the present invention, it is possible to provide an air filter medium that is extremely low in pressure loss and optimal for gas filtration with a high air volume and that can collect fine dust with high efficiency. This makes it possible to improve the performance of the air treatment facility, reduce initial costs, and reduce running costs. Furthermore, excellent materials for industrial products and hygiene products can be provided.

  FIG. 1 is a cross-sectional view showing an embodiment of a filter medium for an air filter according to the present invention. The air filter medium 10 includes a nanofiber structure layer 12. The nanofiber structure layer 12 is composed of a sheet-like fiber structure in which nanofibers 12a are three-dimensionally entangled. The nanofiber structure layer 12 is manufactured by a fiber structure manufacturing method such as a known nanofiber web manufacturing method, but the electrospinning method is easy because the fiber diameter of the nanofibers 12a, the basis weight of the web, and the pore size can be easily controlled. It is preferable to be manufactured by. The fiber diameter of the nanofiber 12a and the basis weight of the nanofiber structure layer 12 are factors that determine the pore size of the nanofiber structure layer 12, and the smaller the fiber diameter and the larger the basis weight, the smaller the pore size formed. Although dust can be collected, it is preferable that the fiber diameter of the nanofibers 12a is 500 nm or less because the filtered gas becomes easier to escape as the fiber diameter becomes smaller than about 500 nm.

  The raw material of the nanofiber 12a is polyacrylonitrile, 6 nylon, 66 nylon, polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyethylene oxide, cellulose, polyether urethane, conductive polymer, polylactic acid. , Polymers such as polycaprolactan, fibroin, collagen and other proteins can be used. The method for producing the nanofiber structure layer 12 will be described in detail later.

  An upstream porous body layer 14 is integrally laminated on the surface of the nanofiber structure layer 12 on the upstream side of filtration. The upstream porous body layer 14 is a porous body that functions as a prefilter for the nanofiber structure layer 12. That is, in the filter medium 10 for an air filter according to the present invention, dust having a large particle size is collected by the upstream porous body layer 14, and dust having a size as a main target for collection is collected by the nanofiber structure layer 12. It is configured to collect. The upstream porous body layer 14 preferably functions as a prefilter for the nanofiber structure layer 12, and a porous body having a pore size larger than the pore size of the nanofiber structure layer 12 is preferably used.

  The upstream porous body layer 14 has a pore or a flow path through which a gas to be filtered such as a nonwoven fabric, a web, a woven fabric, paper, a net, a perforated film, or the like made of organic fibers or inorganic fibers can pass. Things are applicable. In addition, the surface laminated | stacked integrally with the nanofiber structure layer 12 of the upstream porous body layer 14 is made into a smooth surface without a fibrous mark. The reason is that some Karman vortices and turbulent vortices are generated downstream of the upstream porous body layer 14 in a state in which the gas to be filtered is filtered. In the state where Karman vortex or turbulent vortex is generated, if free fiber or fluffy fiber is present, the fiber or flake vibrates vigorously, disturbing the arrangement of nanofibers 12a in the nanofiber structure layer 12, This is because there is a possibility of damage, and as a result, the collection efficiency of the air filter medium 10 is reduced. This phenomenon is likely to occur when the upstream porous body layer 1 is formed of a porous body made of short fibers. In view of this problem, it is desirable to use a spunbonded nonwoven fabric that is made of continuous fibers and has no surface fluff and is smooth for the upstream porous body layer 14. However, the porous body applicable to the upstream porous body layer 14 is not limited to the spunbonded nonwoven fabric, but the surface in contact with the nanofiber structure layer 12 is baked, heat-rolled, or resin coated. By making the surface smooth and free from flaws, it is possible to use a general-purpose air filter medium such as the medium performance filter, HEPA filter, or ULPA filter made of the above-mentioned materials. The upstream porous body layer 14 may be used by appropriately selecting one having a desired dust holding capacity in consideration of the product life of the air filter medium 10.

  A downstream porous body layer 16 is integrally laminated on the surface of the nanofiber structure layer 12 on the downstream side of filtration. The downstream porous body layer 16 supports the nanofiber structure layer 12 from the downstream side of filtration, and prevents the nanofiber structure layer 12 from being damaged by wind pressure or the like applied from the gas to be filtered. As the downstream porous body layer 16, similarly to the upstream porous body layer 14, a gas to be filtered such as a nonwoven fabric, a web, a woven fabric, paper, a net, a perforated film made of organic fibers or inorganic fibers is allowed to pass through. However, the pressure loss must be low so as not to disturb the air flow smoothly flowing through the nanofiber structure layer 12. Further, if there is a fibrous mark on the upstream surface of the downstream porous body layer 16 in the filtration, the flow of the air flow in the nanofiber structure layer 12 is hindered as in the upstream porous body layer 14. In addition, the kerberous fibers vibrate vigorously, and the arrangement of the nanofibers 12a in the nanofiber structure layer 12 may be disturbed or damaged. As a result, the air filter medium 10 is collected. There is a possibility of causing a decrease in efficiency. Accordingly, the downstream porous body layer 16 is preferably a porous body having a pressure loss of 100 pa or less at an air flow rate of 1 m / s. Moreover, in order to cope with the problem caused by the chipping, it is desirable to use a spunbonded nonwoven fabric which is composed of continuous fibers and has no surface fluff and is smooth like the upstream porous body layer 14. However, the porous body applicable to the downstream porous body layer 16 is not limited to the spunbonded nonwoven fabric, but the surface in contact with the nanofiber structure layer 12 is baked, heat-rolled, or resin-coated. By making the surface smooth with no blemishes on the surface, it is possible to use a medium air filter material such as a medium performance filter, HEPA filter, or ULPA filter made of the above-mentioned materials. Furthermore, the downstream porous body layer 16 may be a composite in which a porous body and a strength retaining material such as a net material are combined as long as the above-described conditions are satisfied. .

  In the conventional filter, when the wind speed of the gas to be processed increases, the filter medium vibrates due to Karman vortices and turbulent flow generated downstream of the filter medium, and a re-scattering phenomenon occurs in which the collected and retained dust is scattered again. Although the collection efficiency is reduced, in the filter medium 10 for air filter according to the present invention, Karman vortices and turbulent vortices are less likely to be generated and the fluid to be filtered flows smoothly due to the above-described configuration. The collection efficiency does not decrease even under high airflow.

  FIG. 2 is an illustrative sectional view showing another embodiment according to the present invention. The air filter medium 20 of this embodiment differs from the embodiment shown in FIG. 1 in the structure of the nanofiber structure layer. The nanofiber structure layer 22 is formed from a plurality of layers configured in the order of the nanofiber structure layer 22a, the nanofiber structure layer 22b, and the nanofiber structure layer 22c from the upstream side of the filtration. The nanofiber structure layers 22a, 22b, and 22c are all formed of nanofibers having a fiber diameter of 500 nm or less, but the fiber diameter of the nanofibers 23 constituting the layer decreases as it goes to the downstream layer of filtration. It has become. Thereby, in this embodiment, in addition to the effect that the embodiment shown in FIG. 1 has, the sieving effect is generated in the nanofiber structure layer 22 so that the filtered dust can be collected more efficiently. In addition, the product life can be extended. In the present embodiment, the nanofiber structure layer 22 has a three-layer structure. However, the number of layers is not limited to this, and the number of layers may be increased or decreased to an appropriate number so that desired dust collection efficiency and product life can be obtained. May be.

  FIG. 3 is an illustrative view showing still another embodiment according to the present invention. The present embodiment is an air filter medium 30 configured by integrally arranging and combining the air filter mediums 10 and 20 and the general-purpose air filter medium 32 shown in FIG. 1 or 2. The general-purpose air filter medium 32 shown in the present invention refers to an air filter medium used for gas filtration such as conventional medium performance filters, HEPA filters, ULPA filters and the like.

  In the air filter medium 30 of the present embodiment, the general-purpose air filter medium 32 is integrally disposed on the surface of the air filter medium 10 or the air filter medium 20 on the upstream side of the filtration. In the present embodiment, the air filter medium 10 or the air filter medium 20 rectifies the Karman vortex and the turbulent flow vortex generated on the downstream side of the filtration by the general-purpose air filter medium 32 with the above-described configuration. Extinguish. Thereby, in the filter medium 30 for air filter of this embodiment, compared with the case where the general-purpose air filter medium 32 is used alone, the dust re-scattering caused by Karman vortex or the like is less likely to occur. The wind speed that can be processed by the filter medium 32 can be improved by about 10 times. The general-purpose air filter medium 32 is most preferably arranged in close contact with the upstream surface of the air filter medium 10, 20. However, if the air filter mediums 10 and 20 are arranged in a range where Karman vortices and turbulent flow affected by the general-purpose air filter medium 32 are produced, the influence of the Karman vortex and the like on the general-purpose air filter medium 32 is reduced. Therefore, the air filter media 10 and 20 need only be arranged within a range where Karman vortices, turbulence, and the like that affect the general-purpose air filter media 32 are generated. In this embodiment, the general-purpose air filter media 32 and the air filter media 10 and 20 are used in the form of a flat sheet, but the general-purpose air filter media 32 and the air filter media 10 and 20 are used. Both or either one may be unitized by pleating.

  Subsequently, the method for producing the air filter medium 10 according to the present invention will be described using the method for producing the air filter medium 10 as an example. In addition, the electrospinning apparatus used for manufacturing the filter medium 10 for this air filter omits description about an electrospinning apparatus and its each part from using the electrospinning apparatus which exists conventionally.

  First, in order to form the nanofiber structure layer 10 by the electrospinning method, the polymer exemplified in paragraph 0007, which is the material of the nanofiber structure layer 12, is prepared by using an optimum solvent (acetone, electrospinning of each polymer). (Chloroform, ethanol, methanol, toluene, xylol, cyclohexane, dimethylformamide, formic acid, acetic acid, etc.) to prepare a solution having a concentration of 2 to 20% by weight.

  Next, this solution is discharged from the needle nozzle electrode of the electrospinning apparatus, and nanofibers 12a are deposited on the collector electrode to form the nanofiber structure layer 12. The solution is discharged with an electric field strength of 1 KV to 5 KV / cm to form the nanofiber structure layer 12 on the collector electrode. However, the nanofiber structure layer 12 itself has a strength as an air filter medium. Since it is not provided, the downstream porous body layer 16 is disposed on the collector electrode, and the nanofiber structure layer 12 is deposited on the downstream porous body layer 16.

  At this time, if there are extreme irregularities such as fibrous kerks on the surface of the downstream porous body layer 16 on which the nanofiber structure layer 12 is deposited, the arrangement of the nanofibers 12a is disturbed and the nanofiber structure has a uniform pore size. Layer 12 is not formed. In particular, in the vicinity of a fibrous kerb with a length of 10 μm or more, as shown in FIG. 4, the nanofibers 12a flying from the needle-like nozzle electrode slide on the kerf and accumulate in a substantially U shape at the root of the kerb. End up. Further, when the nanofibers 12a do not slide on the cutout, as shown in FIG. 5, the nanofibers 12a are deposited in a tunnel shape while supporting the cutout, and it is easy to make a large pore that is a defect. Therefore, it is preferable that the downstream porous body layer 16 is a porous body having no fluff and a smooth surface. For the reason described in paragraph 0017, a spunbond nonwoven fabric composed of continuous fibers is used. It is preferable. Here, the downstream porous body layer 16 is disposed on the collector electrode to form the nanofiber structure 12, but this is not limiting, and the upstream porous body layer 14 is disposed on the collector electrode. The nanofiber structure layer 12 may be formed. Even in this case, for the reason described in this paragraph, the surface of the upstream porous body layer 14 is preferably smooth and free from fluff. Further, when a general-purpose air filter medium or the like is used for the upstream porous body layer 14, at least the surface of the upstream porous body layer 14 on which the nanofiber structure layer 12 is laminated is subjected to baked or heat treatment. It is preferable that the surface is smooth without rolls by roll processing or resin coating processing.

  Next, immediately after the nanofiber structure layer 12 is deposited and formed on the surface of the downstream porous body layer 16, the upstream porous body layer 14 is laminated and integrated with the nanofiber structure layer 12. In addition, in order to firmly integrate the upstream porous body layer 14 and the nanofiber structure layer 12, post-treatment such as ultrasonic fusion and hot roll may be performed in post-treatment. Further, when the nanofiber structure layer 12 is deposited and formed on the upstream porous body layer 14, the downstream porous body layer 16 may be laminated and integrated with the nanofiber structure layer 12. .

  The air filter medium 10 manufactured through the above-described steps does not form large pores that cause fiber disturbance or defects in the nanofiber structure layer 12, and hinders air flow in the nanofiber structure layer 12. It is a good state with no injuries that cause damage to the array of nanofibers 12a or damage.

  In the present embodiment, the case where the nanofiber structure layer 12 is configured as a single layer has been described. However, the nanofiber structure layer 12 is more than a plurality of layers in which the fiber diameter becomes smaller toward the downstream layer of filtration. In this case, the nanofiber structure layer 12 may be formed on the upstream porous body layer 14 or the downstream porous body layer 16 with different electrospinning conditions for each layer.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these. A desired filter material for an air filter may be produced by appropriately changing within the scope described in the claims.

Nylon 6 pellets (A1030BRL manufactured by Unitika Ltd., molecular weight 16000) were used as the material of the nanofiber structure layer 12. 15 g of this nylon 6 pellet was dissolved in 85 g of formic acid (concentration 98% manufactured by Kishida Chemical Co., Ltd.) at room temperature to prepare a nylon 6 solution having a concentration of 15 wt%. This nylon 6 solution is placed in a luer lock tip syringe and attached to an electrospinning apparatus (Esprayer ES-2000 manufactured by Fuence Co., Ltd.). The downstream porous body layer 16 placed on the collector electrode becomes 13 cm long × 12 cm wide. The nanofiber structure layer 12 was produced by electrospinning on a spunbond of a size of. The downstream porous body layer 16 has a nylon 6 spunbond (weight per unit area 20 g / m ² , thickness 0.11 mm, longitudinal tensile strength 7 kg / 5 cm width) with a pressure loss of 50 pa when the air flow is 1 m / s. )It was used. The electrospinning conditions at this time were MN-27G-13 (manufactured by Iwashita Engineering Co., Ltd.) having an inner diameter of 0.21 mm as a spray nozzle, a solution feed speed of 1 μl / min, and a nozzle collector electrode voltage of 20 kV. The distance between the nozzle collector electrodes was 10 cm. Three types of weights of 0.2 g / m ² , 0.19 g / m ² , and 0.15 g / m ² are formed on the nylon 6 spunbond under the above-mentioned conditions so that the average fiber diameter is 100 nm and the average pore size is 140 nm. Formed.

  Thereafter, the same spunbond as the spunbond used for the downstream porous body layer 16 is integrally laminated on the nanofiber structure layer 12 as the upstream porous body layer 14 so that three examples with different basis weights are formed. Produced.

(Air flow test 1)
A polyethylene screen for a screen door having a wire diameter of 0.1 mm on the downstream side of the air filter medium 10 having a basis weight of the nanofiber structure layer 12 of Example 1 of 0.2 g / m ² (pressure loss 5 pa at an air flow rate of 1 m / s). ), And this was cut into a length of 85 mm × width of 85 mm to produce Example 2, and an air flow state observation test was performed. Further, as Comparative Example 1, a medium-performance filter made of a melt-blown nonwoven fabric having an average fiber diameter of 20 μm and having an average fiber diameter of 20 μm (manufactured by Kanai Important Industry Co., Ltd., product number 90p, basis weight 120 g / m ² , thickness 0.4 mm) Similarly, an observation test of the air flow state was conducted.

  The apparatus shown in FIG. 6 was used to observe the air flow passing through the air filter medium. As the transparent wind tunnel 4, an acrylic plate (thickness 3 mm) is molded to form two hollow prisms with an outer dimension of 80 mm × width 80 mm × length 160 mm, and a filter medium 6 for air filter is set at the center and an aluminum seal tape is used. It was integrally bonded and fixed to two hollow acrylic prisms. The air outlet of the transparent wind tunnel was connected to the air suction device 3 by a connecting plastic duct 7. Prepare a mosquito-repellent incense stick at the air inlet of the transparent wind tunnel, and shine the light from the metal halide fiber lighting device (LS-M250 made by Sumita Optical Glass Co., Ltd.) on the flow of smoke (particle size 0.1-0.15 μm) The images were taken with a high-speed camera (Motionscope-M2 manufactured by Nippon Rover Co., Ltd.) and the images were taken into a personal computer.

  FIG. 7 is an image obtained by imaging the air flow at a wind speed of 1 m / sec in Example 2 with a high-speed camera, and FIG. 8 is an image obtained by imaging the air flow at a wind speed of 1 m / sec in Comparative Example 1 with a high-speed camera. is there. As is apparent from FIG. 8, in Comparative Example 1, smoke flows in a straight line up to the upstream side of the filter medium, but after passing through the filter medium, the smoke has a zigzag shape in which a vortex is wound. . Since the smoke concentration is high at the vortex and the smoke concentration is low at other portions, it can be confirmed that intense turbulence is generated on the downstream side of Comparative Example 1. On the other hand, in Example 2, as shown in the image of FIG. 7, the smoke flows straight up to the upstream side of the filter medium, diffuses in the filter medium 12, and then the smoke becomes wider. The smoke that goes is uniform with no shading. In Example 2, it was confirmed that there was no Karman vortex and turbulent vortex generation, and that the air exited smoothly.

Example 3
Example 4
(Filter media test 1 for combination air filter)
Next, the conventional medium performance filter and the HEPA filter are applied to the general-purpose air filter medium 32, and the filter medium 30 is combined with the air filter medium 10 of Example 2 to obtain an air filter medium 30 shown in paragraph 0014. About Example 3 and Example 4 which comprised, it tested about the air wind speed and dust collection efficiency. A synthetic rubber sheet (250 mm long x 250 mm wide x 1 mm thick) has an opening of 80 mm long x 80 mm wide, medium performance filter (90 mm long x 90 mm wide) upstream of air, and air filter medium 10 (90 mm long) downstream. × 90 mm in width, 0.19 g / m ² ), and attached, and the periphery was adhered and fixed with an aluminum seal tape to produce Example 2. Further, the HEPA filter having the above dimensions on the upstream side of the air and the filter medium 10 for air filter (length 90 mm × width 90 mm, basis weight 0.15 g / m ² ) are attached to the downstream side, and the same processing as above is performed. 3 was produced. Further, only a medium performance filter having the same dimensions as those of Examples 3 and 4 was fixed to the opening of the rubber sheet as Comparative Example 2, and only a HEPA filter having the same dimensions as those of Examples 3 and 4 was used as the rubber sheet. What was fixed to the opening of was prepared as Comparative Example 3. As the filter performance test apparatus, a filter medium test apparatus S030951 manufactured by Nippon Kanomax Co., Ltd. was used.

  As dust for performance measurement, dust contained in general indoor air was used. Dust collection by sucking room air with a test device and introducing a certain amount of upstream and downstream air into the particle counter with small diameter tubes, measuring the number of particles with a particle size of 0.3 to 0.5 μm Efficiency was calculated. In the test method, after the test filter sample is attached to the test device, the wind speed is gradually increased from 0.05 m / sec to 1 m / sec, the collection efficiency at each wind speed is calculated, and then the appropriate time interval is obtained. The same measurement work was carried out. The test results are shown in the table and graph.

なお、表１は、比較例２の各風速に対する濾過効率の値を示す表であり、図９は、表１の値をグラフ化した図である。また、表２は、比較例３の各風速に対する濾過効率の値を示す表であり、図１０は、表２の値をグラフ化した図である。表３は、実施例３の各風速に対する濾過効率の値を示す表であり、図１１は、表３の値をグラフ化した図である。また、表１は、実施例４の各風速に対する濾過効率の値を示す表であり、図１２は、表４の値をグラフ化した図である。

In addition, Table 1 is a table | surface which shows the value of the filtration efficiency with respect to each wind speed of the comparative example 2, FIG. 9 is the figure which graphed the value of Table 1. FIG. Table 2 is a table showing the value of the filtration efficiency for each wind speed of Comparative Example 3, and FIG. 10 is a graph of the values of Table 2. Table 3 is a table showing the value of the filtration efficiency for each wind speed in Example 3, and FIG. 11 is a graph of the values in Table 3. Moreover, Table 1 is a table | surface which shows the value of the filtration efficiency with respect to each wind speed of Example 4, FIG. 12 is the figure which graphed the value of Table 4. FIG.

  As is apparent from FIG. 9, in Comparative Example 2, the dust collection efficiency decreases as the wind speed increases from about 50% at a filter medium wind speed of 0.05 m / sec in which a medium performance filter is normally used. I will do it. As FIG. 10 shows, the same tendency is shown for Comparative Example 3. However, as shown in FIG. 11, in Example 3, the dust collection efficiency increases as the wind speed rises from the wind speed of 0.5 m / second, in which the medium performance filter is normally used, and the dust collection efficiency of about 95%. The maximum point is shown at 8 m / sec. Also, as shown in FIG. 12, in Example 4, the dust collection efficiency gradually increased to 100% at a wind speed of 1.1 m / sec.

Example 5
Polyacrylonitrile fiber (molecular weight: about 60,000, manufactured by Teijin Techno Products Co., Ltd.) was used as the material for the nanofiber structure layer 12. 10 g of this polyacrylonitrile fiber was dissolved at room temperature with 90 g of N, N-dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd., concentration: 99.5%) to prepare 100 g of a 10 wt% polyacrylonitrile solution. This polyacrylonitrile solution is placed in a luer lock tip syringe (capacity 1 ml, hard glass) and attached to an electrospinning apparatus (Esprayer ES-2000 manufactured by Fuence Co., Ltd.), and the downstream porous body layer 16 placed on the collector electrode is placed on the collector electrode. The nanofiber structure layer 12 was produced by electrospinning on a spunbond having a size of 13 cm in length and 12 cm in width. Note that the downstream porous layer 16, Nylon 6 manufactured by spunbond (basis weight 20 g / m ² pressure loss is 50pa when the air flow 1 m / s, thickness 0.11 mm, the longitudinal tensile strength 7 kg / 5 cm width )It was used. In addition, electrospinning conditions at this time were as follows: MN-21G-13 (manufactured by Iwashita Engineering Co., Ltd.) having an inner diameter of 0.52 mm as a spray nozzle, a solution feed speed of 6 μl / min, and a nozzle collector electrode voltage of 14 kV. The distance between the nozzle collector electrodes was 15 cm. Under the conditions described above, two types of basis weights of 0.36 g / m ² and 0.2 g / m ² were formed on the nylon 6 spunbond so as to have an average fiber diameter of 190 nm and an average pore size of 230 nm, respectively.

Example 6
(Air flow test 2)
In the same manner as in the air flow observation test 1, a screen door polyethylene having a wire diameter of 0.1 mm on the downstream side of the air filter medium 10 having a basis weight of the nanofiber structure layer 12 of Example 5 of 0.2 g / m ^2. The net was placed on top of each other, and this was cut into a length of 85 mm × width of 85 mm to produce Example 6, and an air flow state observation test was performed. FIG. 13 is an image obtained by capturing the air flow at a wind speed of 1 m / second in Example 6 with a high-speed camera. As is apparent from the image, the Karman vortex is arranged downstream of Example 6 as in Example 2. , No turbulent vortices are generated.

Example 7
Example 8
(Filter medium test 2 for combination air filter)
The same medium performance filter and HEPA filter are applied to the general-purpose air filter medium 32 in the same manner as in the filter medium test 1 for the combined air filter, and these filter medium and the air filter medium 10 of Example 6 are combined. About Example 7 and Example 8 which comprised the filter medium 30 for air filters shown to the paragraph 0014, it tested about the air wind speed and dust collection efficiency. The test results are shown in the table and graph.

表５は、実施例７の各風速に対する濾過効率の値を示す表であり、図１４は、表５をグラフ化した図である。また、表６は、実施例８の各風速に対する濾過効率の値を示す表であり、図１５は、表６をグラフ化した図である。図１４が示すように、実施例７においては風速０．３ｍ／秒近傍に於いて捕集効率８５％の極大点が存在し、中性能フィルタが通常使用される風速０．５ｍ／秒に於ける粉塵捕集効率５０％より向上した。また、実施例８においては、図１５が示すように、風速が上がるに従って捕集効率は向上した。グラフ上には図示していないが、後の実験によって風速１ｍ／秒近傍に於いて捕集効率１００％の極大点が存在する事が判明した。なお、グラフには記入できていないが、後の実験によって風速１ｍ／秒近傍に於いて捕集効率１００％の極大点が存在する事が判明した。

Table 5 is a table showing the value of the filtration efficiency for each wind speed of Example 7, and FIG. 14 is a graph of Table 5. Table 6 is a table showing the value of the filtration efficiency for each wind speed in Example 8, and FIG. 15 is a graph of Table 6. As shown in FIG. 14, in Example 7, there is a maximum point with a collection efficiency of 85% near the wind speed of 0.3 m / second, and at a wind speed of 0.5 m / second where the medium performance filter is normally used. The dust collection efficiency was improved from 50%. Moreover, in Example 8, as FIG. 15 showed, the collection efficiency improved as the wind speed increased. Although not shown on the graph, it has been found by experiments later that there is a maximum point with a collection efficiency of 100% in the vicinity of a wind speed of 1 m / sec. Although not shown in the graph, it was found by a later experiment that there was a maximum point with a collection efficiency of 100% near a wind speed of 1 m / sec.

  From the above results, when the processing wind speed increases, the dust collection efficiency decreases due to the re-scattering phenomenon. However, in the air filter filter medium according to the present invention, Karman vortices and turbulent vortices are unlikely to occur downstream. Since air flows smoothly, it is possible to obtain a high-performance filter material without re-scattering. In addition, the air filter medium in which the air filter medium according to the present invention is disposed downstream of any air filter medium that has existed conventionally can increase the treatment wind speed by 10 times or more, and at the same time dust collection efficiency. Will rise significantly.

It is a cross-sectional solution figure which shows one Embodiment of the filter medium for air filters concerning this invention. It is a cross-sectional schematic solution figure which shows another embodiment concerning this invention. It is an illustration figure which shows another embodiment concerning this invention. It is an illustration figure which shows the state which the nanofiber which flew from the needle-shaped nozzle electrode slipped on the mark, and was deposited in the substantially U shape at the root of the mark. FIG. 3 is an illustrative view showing a state in which nanofibers are deposited in a tunnel shape while supporting a knot. It is the image which image | photographed the test apparatus for observing an air flow. It is the image which imaged the air flow in the wind speed of 1 m / sec of Example 2 with the high-speed camera. It is the image which imaged the air flow in the wind speed of 1 m / sec of the comparative example 1 with the high speed camera. It is the figure which made the value of Table 1 into a graph. It is the figure which made the value of Table 2 into a graph. It is the figure which made the value of Table 3 into a graph. It is the figure which made the value of Table 4 into a graph. It is the image which imaged the air flow in the wind speed of 1 m / sec of Example 6 with the high-speed camera. FIG. 6 is a graph of Table 5. FIG. 7 is a graph of Table 6.

Explanation of symbols

10, 20, 30 Air filter media 12, 22 Nanofiber structure layer 14 Upstream porous material layer 16 Downstream porous material layer 32 General-purpose air filter media

Claims (4)

A sheet-like nanofiber structure layer in which nanofibers are entangled three-dimensionally;
An upstream porous body layer integrally laminated on the filtration upstream surface of the nanofiber structure layer;
A downstream porous body layer integrally laminated on the filtration downstream surface of the nanofiber structure layer,
The surfaces of the upstream porous body layer and the downstream porous body layer, which are laminated integrally with the nanofiber structure layer, are smooth and free from protrusions.
The downstream porous body layer has air permeability such that a pressure loss at an air flow rate of 1 m / sec is 100 pa or less,
A filter medium for an air filter, characterized in that no turbulent flow is generated on the downstream side of the filtration. The nanofiber structure layer is composed of a plurality of layers having different fiber diameters for each layer,
The filter medium for an air filter according to claim 1, wherein the fiber diameter of the nanofiber of each layer constituting the nanofiber structure layer decreases as it goes to the layer on the downstream side of the filtration. A filter medium for air filter comprising a combination of the filter medium for general-purpose air filter and the filter medium for air filter according to claim 1 or 2,
The air filter medium according to claim 1 or 2 is disposed in close contact with the filtration downstream surface of the general air filter medium, or the air flow downstream of the general air filter medium is filtered. Air filter media placed at a distance within the turbulence range. The air filter medium according to claim 3, wherein one or both of the general-purpose air filter and the air filter medium are unitized.

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