JP2008279359A - Filter medium and filter unit using this filter medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter medium which does not allow impurities to be included into the treated air due to self-generation of dust etc. and can hardly generate a structural pressure loss even when the filter medium is exposed to high wind pressure, and a filter unit using this filter medium. <P>SOLUTION: This filter medium 1 includes a PTFE porous membrane 2 and a ventilative support material 3 laminated on the PTFE porous membrane 2. In addition, the filter medium 1 shows 1.0 to 8.0 mN cm rigidity/softness index and has one side exposed surface of the PTFE porous membrane 2. The filter unit includes the filter medium 1 and a support frame supporting the filter medium 1. In the filter unit, the filter medium 1 is supported by the support frame in such a direction in which the PTFE porous membrane 2 is positioned on the upstream side to the ventilative support material 3 with regard to gas circulation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a filter medium and a filter unit.

In recent years, high-performance cyclone vacuum cleaners having a large suction force have become widespread. In such a high-performance cyclone vacuum cleaner, a filter with improved dust collection efficiency is used. In general, as a filter with improved collection efficiency, a filter medium formed by adding a binder to glass fiber (hereinafter referred to as glass filter medium) or a filter medium formed by electrifying a melt blown nonwoven fabric (hereinafter referred to as electret). Called filter media). Moreover, what pleat-processed these filter media may be fixed to a support frame, and may be used as a filter unit. Such a filter unit is produced, for example, by fixing a pleated filter medium to a support frame with a sealing material, or by integrating it with a resin support frame by insert molding.
JP 2000-015021 A

  However, in the case of a glass filter medium, there is a problem that self-generated dust is generated during bending by processing, and pressure loss is high.

  On the other hand, in the case of electret filter media, when used in a high-performance cyclone vacuum cleaner with a large suction force, the processed pleats are deformed by wind pressure, and as a result, pressure loss (hereinafter referred to as structure) due to deformation (structural change). There was a problem of increasing pressure loss).

  Therefore, the present invention provides a filter medium that is less likely to cause structural pressure loss even when exposed to a large wind pressure without mixing impurities into the processing air due to self-dusting or the like, and that can realize low pressure loss. Furthermore, it aims at providing the filter unit using the same.

  The filter medium of the present invention is a filter medium comprising a polytetrafluoroethylene (hereinafter referred to as PTFE) porous membrane, and a breathable support material laminated on the PTFE porous membrane. The degree is 1.0 to 8.0 mN · cm, and one surface of the porous PTFE membrane is exposed. In the present specification, the bending resistance is a value obtained in accordance with JIS L 1096.

  The filter unit of the present invention includes the filter medium of the present invention and a support frame for fixing the filter medium. In the filter unit of the present invention, the filter medium is supported on the support frame in such a direction that the porous PTFE membrane is located upstream of the air-permeable support material in the flow of gas.

Since the filter medium of the present invention has a high bending resistance of 1.0 mN · cm or more, for example, the filter medium is not easily deformed even when exposed to a large wind pressure of about 2.0 m ³ / min. An increase in pressure loss can be suppressed and a low pressure loss can be maintained. Further, since it has such a high bending resistance, even when a PTFE porous membrane having a relatively low air permeability than the air-permeable support material is arranged on the dust collecting surface side, the deformation due to the wind pressure is sufficiently generated. Can be suppressed. Further, since the bending resistance of the filter medium of the present invention is 8.0 mN · cm or less, good workability can be obtained at the same time. Moreover, since the PTFE porous membrane used for the filter medium of the present invention does not generate dust, there is no possibility that impurities are mixed into the processing air. Furthermore, in the filter medium of the present invention, one surface of the PTFE porous membrane is exposed. Therefore, if the surface on which the PTFE porous membrane is exposed is the dust collection surface (the upstream surface in the gas flow), good dust separation can be realized.

  Since the filter unit of the present invention uses the filter medium of the present invention, it can similarly suppress an increase in structural pressure loss, and can also have good workability and dust separation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an embodiment of the filter medium of the present invention. The filter medium 1 shown in FIG. 1 is formed by laminating one layer of PTFE porous membrane 2 and one layer of air-permeable support material 3. Here, an example of a filter medium in which a PTFE porous membrane and a breathable support material are used one by one is shown, but the filter medium of the present invention is not limited to this, and at least one layer of PTFE porous membrane is used. And at least one breathable support material, and one surface of the PTF porous membrane may be exposed, that is, the PTFE porous membrane may be disposed on the outermost surface. Accordingly, a plurality of PTFE porous membranes and / or air-permeable support materials may be provided.

  The bending resistance of the filter medium 1 is 1.0 to 8.0 mN · cm. Since the filter medium 1 has such a range of bending resistance, it can be realized with good workability such as suppression of deformation and pleating when exposed to a large wind pressure. In order to obtain better processability, the bending resistance of the filter medium 1 is preferably set to 1.0 to 4.0 mN · cm. The thickness of the filter medium 1 is not particularly limited, but is preferably 0.05 to 1 mm. The pressure loss of the filter medium 1 is preferably 300 Pa or less, for example, 20 to 300 Pa, more preferably 20 to 150 Pa, when the linear velocity of the passing gas is 5.3 cm / sec. The collection efficiency of the filter medium 1 is 90% or more when the particle size of the collection target particles is 0.3 to 0.5 μm and the linear velocity of the passing gas is 5.3 cm / sec. Preferably, it is 99% or more, more preferably 99.97% or more.

  The PTFE porous membrane 2 is not particularly limited, but those having an average pore diameter of 0.01 to 5 μm and an average fiber diameter of 0.01 to 0.3 μm are preferable. The pressure loss of the PTFE porous membrane 2 is preferably 20 to 150 Pa when the linear velocity of the passing gas is 5.3 cm / sec.

  An example of a method for producing the PTFE porous membrane 2 will be described below.

  First, a paste-like mixture obtained by adding a liquid lubricant to PTFE fine powder is preformed. The liquid lubricant is not particularly limited as long as it can wet the surface of PTFE fine powder and can be removed by extraction or heating. For example, hydrocarbons such as liquid paraffin, naphtha and white oil can be used. The addition amount of the liquid lubricant is suitably about 5 to 50 parts by weight with respect to 100 parts by weight of PTFE fine powder. The preforming is performed at a pressure that does not squeeze out the liquid lubricant.

  Next, the preform is formed into a sheet by paste extrusion or rolling. The sheet-like molded body thus formed is stretched at least in a uniaxial direction to obtain a PTFE porous membrane. The sheet-shaped molded body is preferably stretched after removing the liquid lubricant. The draw ratio is not particularly defined, and may be appropriately set according to the pressure loss and the collection efficiency. Considering stretching unevenness and breakage during stretching, the area stretching ratio (integration of the stretching ratio in the uniaxial direction and the stretching ratio in the direction perpendicular to the uniaxial direction) is preferably 50 to 900 times.

  The breathable support material 3 is not particularly limited with respect to the material, structure and form. For example, a material having better air permeability than the PTFE porous membrane 2, such as a nonwoven fabric, a mesh (mesh net), and other porous materials can be used. Among these, non-woven fabrics are preferable in consideration of strength, collection property, flexibility, and workability. In addition, as a material used for the air-permeable support material 3, for example, polyolefin (polyethylene (PE), polypropylene (PP), etc.), polyamide, polyester (polyethylene terephthalate (PET), etc.), aromatic polyamide, and a composite material thereof. Etc.

  The pressure loss of the air-permeable support material 3 is preferably 100 Pa or less, more preferably 50 Pa or less when the linear velocity of the passing gas is 5.3 cm / sec.

  The PTFE porous membrane 2 and the breathable support material 3 may be colored. The method of coloring is not particularly limited, and examples thereof include a method of kneading a pigment, a method of dyeing with a dye, and a method of printing.

  For example, when a pigment is kneaded into a breathable support material formed using a plastic resin, a method of melting the plastic resin as a raw material and kneading the pigment into the molten plastic resin is generally used. Further, when the pigment is kneaded into the PTFE porous membrane, the paste and liquid lubricant may be added to the PTFE fine powder to produce a paste-like mixture.

  When the PTFE porous membrane 2 and the breathable support material 3 are dyed with a dye, each of the PTFE porous membrane and the breathable support material may be immersed in the dye, or the PTFE porous membrane and the breathable support material may be combined. The laminated filter media may be immersed in the dye. In the case of coloring by printing, gravure printing or the like is generally used.

  Moreover, when coloring the PTFE porous membrane 2 or the air-permeable support material 3, an antibacterial agent or a water repellent may be added. Further, a plurality of materials for expressing other functions such as conductivity may be kneaded into the PTFE porous membrane 2 and the air-permeable support material 3.

  The method for forming the filter medium 1 by laminating the PTFE porous membrane 2 and the air-permeable support material 3 is not particularly limited. They may be simply overlapped or may be adhered to each other using methods such as adhesive lamination or thermal lamination. For example, a part of the breathable support material 3 may be melted by heating, and the breathable support material 3 and the PTFE porous membrane 2 may be bonded and laminated together. Alternatively, a fusing agent such as hot melt powder may be interposed between the PTFE porous membrane 2 and the breathable support material 3 and bonded and laminated together by heating.

  Next, an embodiment of the filter unit of the present invention will be described with reference to FIG. FIG. 2 is a perspective view showing the filter unit 4 of the present embodiment. The filter unit 4 is formed using the filter medium 1 shown in FIG. 1, and the filter medium 1 pleated so that the cross-sectional shape is W-shaped is housed in the support frame 5, and the filter unit 4 A gap between the peripheral edge of the filter medium 1 and the support frame 5 is sealed. In the case where the support frame 5 is made of resin, the gap between the filter medium 1 and the support frame 5 can be sealed by insert molding using the resin of the support frame 5, and the two can be integrated. When insert molding is performed, no adhesive or sealing material is required, so that the number of materials can be reduced, and the peripheral edge of the filter medium 1 can be completely sealed. In addition, the method of accommodating the filter medium 1 in the support frame 5 is not limited to insert molding, and after attaching the filter medium 1 in the support frame 5, the gap may be sealed using an adhesive or a sealant. Is possible.

The pressure loss as the filter unit 4 is not particularly limited, but is preferably 1000 Pa or less in the initial state, for example, when the flow rate of the gas to be passed is 2 m ³ / min from the viewpoint of energy efficiency. A filter medium having an appropriate pressure loss may be selected according to the filter design, and the filter medium area may be determined. The collection efficiency of the filter unit 4 can also be adjusted by selecting a filter medium having an appropriate collection efficiency according to the filter design. The filter unit 4 has a collection efficiency of 90% or more (preferably 99% or more) when, for example, Kanto Loam (eight kinds), which is a test powder of JIS Z 8901, is sucked at a flow rate of 2.0 m ³ / min. Is preferably realized.

  In the filter unit 4, the filter medium 1 is arranged in such a direction that the PTFE porous membrane is located on the upstream side in the flow of gas. If the filter medium 1 is arranged in this way, the dust collection surface becomes the PTFE porous membrane 2, so that the dust separation is good.

[Example]
Next, the filter medium and the filter unit of the present invention will be specifically described using examples.

Example 1
25 parts by weight of hydrocarbon oil (trade name “Isopar M”, manufactured by Esso Petroleum Corporation) as a liquid lubricant is uniformly added to 100 parts by weight of PTFE fine powder (trade name “Polyflon F-104”, manufactured by Daikin Industries, Ltd.) The mixture thus mixed was subjected to compression pre-molding at a pressure of 1.96 MPa (20 kgf / cm ² ). Next, the preform was extruded into a rod shape, and the rod-shaped product was passed between a pair of metal rolling rolls to obtain a long sheet having a thickness of 0.2 mm and a width of 150 mm.

  Next, the long sheet was heated to 220 ° C. to remove the liquid lubricant, and then wound around the tubular core body in a roll shape. Next, this sheet was stretched 20 times in an unfired state and then transversely stretched 30 times, fixed in dimensions and fired to obtain a porous PTFE membrane.

  A PTFE porous membrane having an area stretch ratio of 600 times and a polyester nonwoven fabric prepared as described above and a polyester nonwoven fabric were adhered and laminated together using a polyolefin-based hot melt agent to prepare a filter medium. The polyester nonwoven fabric used in this example was “Valcompo TKC95” manufactured by Toyobo.

Such a filter medium had a bending resistance of 1.1 mN · cm, a basis weight of 95 g / m ² , and a thickness of 0.35 mm. Moreover, the pressure loss of this filter medium was 80 Pa, and the collection efficiency was 99.0%. The pressure loss and collection efficiency of the filter medium were measured by the following methods.

<Pressure loss of filter media>
The pressure loss when the flow rate of air passing through the filter medium was adjusted to 5.3 cm / sec (flow rate 31.8 m ³ / min) with a flow meter was measured with a pressure meter (manometer).

<Filtering filter collection efficiency>
The flow rate of air passing through the filter medium is adjusted to 5.3 cm / sec (flow rate 31.8 m ³ / min) with a flow meter, and dioctyl phthalate particles (DOP) (DOP) defined in JIS Z 8901 are upstream of the air flow ( The particle size was 0.3-0.5 μm). The upstream and downstream DOP particle concentrations with respect to the filter medium were measured to obtain the collection efficiency. The area of the filter medium used was 100 cm ² .

  Next, the produced filter medium was pleated so that 18 peaks could be stored in 116 mm × 116 mm with a width of 116 mm and a height of 20 mm. Further, the periphery of the pleated filter medium was surrounded by a 20 mm wide strip-shaped polyester nonwoven fabric and sealed with a hot melt agent to obtain a filter unit. The strip-shaped polyester nonwoven fabric is a substitute for the support frame.

  About the obtained filter unit, the pressure loss and the collection efficiency were measured, and the presence or absence of deformation of the filter medium and the powder wiping out property (dust separation property) were evaluated. Specific measurement methods and evaluation methods are as follows.

<Pressure loss of filter unit>
The pressure loss when the flow rate of air passing through the filter unit was adjusted to 2.0 m ³ / min was measured with a pressure gauge (manometer). Note that the pressure loss is the pressure loss before (initial) the powder is collected by the method described later, the pressure loss after the powder is collected (after the load) by the method described later, and the powder by the method described later. The pressure loss after each was removed (after the withdrawal) was measured.

<Filter unit collection efficiency>
In the measuring device 6 shown in FIG. 3, the filter unit 4 is arranged so that the PTFE porous membrane is upstream of the air flow of the test air 7, and for the test of JIS Z 8901 upstream of the filter unit 4. 0.7 g of Kanto Loam (8 types) as powder was supplied. 0.7 g of this Kanto loam (8 types) was sucked with a suction force of a flow rate of 2.0 m ³ / min using a vacuum cleaner. The change in weight of the Kanto loam before and after collection was measured to determine the collection efficiency of the filter unit.

<Presence / absence of deformation of filter medium and removal of powder>
In the measuring device 6 shown in FIG. 3, the filter unit 4 is disposed so that the PTFE porous membrane is on the upstream side of the air flow, and is a test powder of JIS Z 8901 on the upstream side of the filter unit 4. 0.7 g of Kanto Loam (8 types) was supplied. 0.7 g of this Kanto loam (8 types) was sucked with a suction force of a flow rate of 2.0 m ³ / min using a vacuum cleaner. After suction, the presence or absence of deformation of the pleats of the filter medium was confirmed visually. After confirming the presence or absence of deformation of the filter medium, the surface of the filter unit is dropped by dropping the filter unit three times from a height of 10 cm with the upstream surface of the filter unit on which the powder is collected facing down. I have paid off. The pressure loss before the powder was removed (after loading) and the pressure loss after the removal were measured by the above methods, and the powder loss was evaluated by comparing them.

  Table 1 shows the pressure loss, the collection efficiency, and the presence or absence of deformation of the filter medium of the filter unit of Example 1.

(Example 2)
The same PTFE porous membrane as that in Example 1 was used. The PTFE porous membrane and the polyester nonwoven fabric were bonded and laminated together using a polyolefin hot melt agent to produce a filter medium. The polyester nonwoven fabric used in this example was “Style 2040” manufactured by BBA. Such a filter medium had a bending resistance of 2.1 mN · cm, a basis weight of 140 g / m ² , and a thickness of 0.52 mm. Moreover, the pressure loss of the filter medium was 80 Pa, and the collection efficiency was 99.0%. The pressure loss and the collection efficiency of the filter medium were measured by the same method as in Example 1.

  A filter unit was produced in the same manner as in Example 1 using the filter medium produced as described above. About the obtained filter unit, the pressure loss etc. were measured using the method similar to Example 1. FIG. The results are shown in Table 1.

(Example 3)
The same PTFE porous membrane as that in Example 1 was used. The PTFE porous membrane and the polyester nonwoven fabric were bonded and laminated together using a polyolefin hot melt agent to produce a filter medium. The polyester nonwoven fabric used in this example was “Type 032/180” manufactured by Johns Manville. Such a filter medium had a bending resistance of 4.7 mN · cm, a basis weight of 180 g / m ² , and a thickness of 0.76 mm. Moreover, the pressure loss of the filter medium was 80 Pa, and the collection efficiency was 99.0%. The pressure loss and the collection efficiency of the filter medium were measured by the same method as in Example 1.

  A filter unit was produced in the same manner as in Example 1 using the filter medium produced as described above. About the obtained filter unit, the pressure loss etc. were measured using the method similar to Example 1. FIG. The results are shown in Table 1.

(Comparative Example 1)
A filter unit was produced in the same manner as in Example 1 using the same filter material as in Example 3. The obtained filter unit was measured for pressure loss and the like in the same manner as in Example 1 except that the porous PTFE membrane was configured to be on the downstream side. The results are shown in Table 1.

(Comparative Example 2)
The same PTFE porous membrane as that in Example 1 was used. The PTFE porous membrane and the polyester nonwoven fabric were bonded and laminated together using a polyolefin hot melt agent to produce a filter medium. The polyester nonwoven fabric used in this comparative example was “LDH 7813W” manufactured by Freudenberg. Such a filter medium had a bending resistance of 0.7 mN · cm, a basis weight of 130 g / m ² , and a thickness of 0.54 mm. Moreover, the pressure loss of the filter medium was 80 Pa, and the collection efficiency was 99.0%. The pressure loss and the collection efficiency of the filter medium were measured by the same method as in Example 1.

  A filter unit was produced in the same manner as in Example 1 using the filter medium produced as described above. About the obtained filter unit, the pressure loss etc. were measured using the method similar to Example 1. FIG. The results are shown in Table 1.

(Comparative Example 3)
The same PTFE porous membrane as that in Example 1 was used. The PTFE porous membrane and the polyester nonwoven fabric were bonded and laminated together using a polyolefin hot melt agent to produce a filter medium. In this comparative example, a polyester nonwoven fabric obtained by bonding “Valcompo TKC95” manufactured by Toyobo and “Type 032/180” manufactured by Johns Manville was used. Such a filter medium had a bending resistance of 8.3 mN · cm, a basis weight of 280 g / m ² , and a thickness of 1.00 mm. Moreover, the pressure loss of the filter medium was 80 Pa, and the collection efficiency was 99.0%. The pressure loss and the collection efficiency of the filter medium were measured by the same method as in Example 1.

  Using the filter medium prepared as described above, pleating was performed in the same manner as in Example 1. However, because the filter medium has high bending resistance, there are many variations in peak height and there are problems with workability. there were.

As shown in Table 1, with respect to the filter units of Examples 1 to 3 and Comparative Example 1, no deformation of the filter medium was confirmed when air was permeated at a flow rate of 2.0 m ³ / min. In contrast, the filter medium of Comparative Example 2 was confirmed to be deformed when air was permeated at a flow rate of 2.0 m ³ / min. This is because the bending resistance of the filter media of Examples 1 to 3 and Comparative Example 1 is 1.0 mN · cm or more, whereas the bending resistance of the filter media of Comparative Example 2 is more than 1.0 mN · cm. It is thought that this is because it is low. Further, due to such deformation of the filter medium, the filter unit of Comparative Example 2 has a higher pressure loss than Examples 1 to 3 and Comparative Example 1. In addition, since the PTFE porous membrane is arrange | positioned downstream in the filter unit of the comparative example 1, it turns out that the pressure loss after wiping off is high, and the wiping-off property of powder is bad. For this reason, the pressure loss after removing the powder is higher in Comparative Example 1 than in Comparative Example 2.

  Generally, since the air permeability of the PTFE porous membrane is lower than that of the air-permeable support material, when the flow rate of the air to be passed is large, the air permeability support material is the upstream side when the PTFE porous membrane is the upstream side. It is considered that deformation is likely to occur due to higher pressure. However, since the filter units of Examples 1 to 3 use a filter medium having high bending resistance, even if a PTFE porous membrane is disposed on the upstream side and a large amount of air is allowed to pass through, the filter medium is not deformed. Did not occur.

  In addition, since the filter medium of Comparative Example 3 had too high bending resistance, pleating could not be performed.

  From the above results, the filter unit made using a filter medium having a bending resistance of 1.0 to 8.0 mN · cm is not easily deformed even when the flow rate of permeating air is large. It was confirmed that structural pressure loss hardly occurs and low pressure loss can be realized. Furthermore, by making one surface of the PTFE porous membrane constituting the filter medium exposed, and making the surface where the PTFE porous membrane is exposed toward the upstream side, it is possible to achieve good scraping performance. It was also confirmed that it can be obtained.

  Since the filter medium and the filter unit of the present invention are not easily deformed even when the flow rate of the permeating air is large, an increase in structural pressure loss can be suppressed. Thereby, it is applicable also as a filter exposed to high wind pressure like the filter of a high-performance cyclone cleaner. Moreover, since it is excellent also in the dusting-off property of the collected dust, it can be used suitably also as a filter for household appliances used while removing the collected dust by washing off or washing.

It is sectional drawing which shows one Embodiment of the filter material of this invention. It is a perspective view which shows one Embodiment of the filter unit of this invention. It is a figure for demonstrating the measuring method of the pressure loss and collection efficiency of a filter unit.

Explanation of symbols

1 Filter media 2 PTFE porous membrane 3 Breathable support material 4 Filter unit 5 Support frame 6 Measuring device 7 Test air

Claims (5)

A filter medium comprising a polytetrafluoroethylene porous membrane, and a breathable support material laminated on the polytetrafluoroethylene porous membrane,
A filter medium having a bending resistance of 1.0 to 8.0 mN · cm, and one surface of the porous polytetrafluoroethylene membrane is exposed.   The collection efficiency is 99% or more when the particle size of the particles to be collected is in the range of 0.3 μm to 0.5 μm and the linear velocity of the passing gas is 5.3 cm / sec. Item 2. A filter medium according to Item 1.   The collection efficiency is 99.97% or more when the particle diameter of the collection target particles is in the range of 0.3 μm to 0.5 μm and the linear velocity of the passing gas is 5.3 cm / sec. The filter medium according to claim 2.   The filter medium according to claim 1, wherein the pressure loss when the linear velocity of the passing gas is 5.3 cm / sec is 300 Pa or less. The filter medium according to any one of claims 1 to 4, and a support frame for fixing the filter medium.
The filter unit is a filter unit that is supported on the support frame in a direction in which the polytetrafluoroethylene porous membrane is located upstream of the air-permeable support material in a gas flow.

Images