JP2005279554A - Air filter unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air filter medium in which an excellent dust removing property is provided and the degradation of filter characteristics is suppressed. <P>SOLUTION: The air filter unit 1 of this invention is provided with the air filter medium 2 and a support frame 4 which supports it within the frame. One main surface of the air filter medium 2 is formed of a PTFE (polytetrafluoroethylene) porous film 2a and the air filter unit 1 is provided with a protective material 3 arranged on the side of the PTFE porous film 2a and provided with a plurality of through-holes 3a. The ratio of the total of the opening areas of the plurality of through-holes 3a to the area of the main surface of the protective material 3 is ≥60%. The protective material 3 and the air filter medium 2 are inseparably fixed to the support frame 4. The air filter unit 1 is used by turning the side of the protective material 3 to the upstream side of the flow of a gas. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an air filter unit, and more particularly to an air filter unit including an air filter medium including a polytetrafluoroethylene (hereinafter referred to as “PTFE”) porous membrane and a support frame that supports the air filter medium.

Air filter media used in cyclone vacuum cleaners, etc. are made by adding paper to a glass fiber to make paper (hereinafter referred to as `` glass fiber filter media '') or non-woven fabric produced by the melt blown method. Filter media (hereinafter referred to as “electret filter media”) are used (see, for example, Patent Document 1). These air filter media have the same collection performance as the semi-HEPA filter. In recent years, an air filter medium including a PTFE porous membrane has begun to be used as a high-performance air filter medium (see, for example, Patent Document 2). These air filter media are pleated, fixed to a support frame, and used as an air filter unit.
Japanese Patent Laid-Open No. 5-214 JP 2000-61280 A

  However, glass fiber filter media and electret filter media collect dust in the thickness direction of the air filter media, so when dust is removed for reuse, it simply enters the inside of the air filter media when vibration is applied. The dust cannot be removed. For this reason, the pressure loss is not sufficiently reduced, and the dust suction force by the vacuum cleaner or the like is reduced. On the other hand, the porous PTFE membrane is excellent in dust removability, but has a drawback that it is easily damaged because of its low strength, and the collection efficiency is likely to decrease due to damage or the like.

  As described above, the conventional air filter medium cannot achieve both excellent dust removal and maintenance of filter characteristics.

  The air filter unit of the present invention is an air filter unit including an air filter medium and a support frame that supports the air filter medium in a frame, and one main surface of the air filter medium is formed of a PTFE porous membrane. The air filter unit further includes a protective material disposed on the PTFE porous membrane side and having a plurality of through holes, and a total opening area of the plurality of through holes with respect to an area of the main surface of the protective material The protective material and the air filter medium are fixed to the support frame so as not to be separated.

  In the air filter unit of the present invention, one main surface of the air filter medium is formed of a PTFE porous membrane, and the air filter unit is provided with a protective material disposed on the PTFE porous membrane side and having a plurality of through holes. In addition, since the ratio of the total opening area of the plurality of through holes to the area of the main surface of the protective material is 60% or more, dust removal is possible when the protective material side is used toward the upstream side of the gas flow. And the deterioration of filter characteristics due to damage to the porous PTFE membrane is suppressed.

  Hereinafter, an example of the air filter unit of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view of the air filter unit according to the present embodiment, and FIG. 2 is a cross-sectional view taken along the line AA ′ of the air filter unit shown in FIG.

  As shown in FIGS. 1 and 2, the air filter unit 1 of the present embodiment includes an air filter medium 2, a support frame 4 that supports the filter medium 2 in a non-separable manner within the frame, and a protection having a plurality of through holes 3a. Material 3 is provided. One main surface of the air filter medium 2 is formed of a PTFE porous membrane 2a, and a protective material 3 is disposed on the PTFE porous membrane 2a side. The ratio of the total opening area of the plurality of through holes to the area of the main surface of the protective material 3 (hereinafter also referred to as “opening ratio”) is 60% or more. The main surface of the protective material 3 is a surface disposed on the upstream side of the gas flow when the protective material 3 side is used toward the upstream side of the gas flow. Since the air filter medium 2 is pleated, it has a sufficient filtration area. The protective material 3 is fixed to the end face of the support frame 4 so as not to be separated from the support frame 4, and is arranged so as not to contact the pleated air filter medium 2. There is no restriction | limiting in particular in the means to fix the protective material 3 to the support frame 4, For example, adhesion | attachment by an adhesive agent, melt | fusion, insert molding, etc. are employable. Further, the protective material 3 may be fixed to the support frame 4 by molding the support frame 4 with the same material as the support frame 4 by an injection molding method or the like.

  As shown in FIG. 3, in the air filter medium 2, a breathable support material 2b is laminated on the PTFE porous membrane 2a to increase the strength of the PTFE porous membrane 2a. The breathable support material 2b is preferably provided in at least one layer, and may be provided in two or more layers.

  As shown in FIG. 2, the air filter unit 1 is used with the protective material 3 side facing the upstream side of the gas flow. Dust hardly passes through the protective material 3 and passes through the protective material 3 and is captured by the PTFE porous membrane 2a. Since the PTFE porous membrane 2a is excellent in dust removability, the dust trapped in the PTFE porous membrane 2 is easily separated from the PTFE porous membrane 2a by vibration or the like. Dust away from the PTFE porous membrane can be removed out of the air filter unit 1 from the through hole 3 a of the protective material 3. In order to remove dust, the air filter medium 2 may be rubbed with a brush or the like. However, since the protective material 3 is disposed on the PTFE porous membrane 2, damage to the PTFE porous membrane 2 due to external force or the like may occur. It is suppressed. In this way, in the air filter unit 1, when the protective material side is used toward the upstream side of the gas flow, the dust filter is excellent and has sufficient strength.

  Furthermore, the air filter unit 1 of the present embodiment includes a PTFE porous membrane 2a having water repellency in the air filter medium 2, so that, for example, a decrease in strength due to cleaning is small as compared with a glass fiber filter medium. The degree of performance degradation due to washing is small compared to electret filter media. The air filter unit 1 can be reused even if it is cleaned by ultrasonic cleaning, for example.

  In addition, it is preferable that the upper limit of the aperture ratio of the protective material 3 is 95% or less. If the aperture ratio is too large, the function of protecting the PTFE porous membrane 2a is impaired, and the workability at the time of secondary processing such as pleating processing also decreases.

  The protective material 3 is not particularly limited as long as it is a porous body having a plurality of through-holes and an opening ratio of 60% or more and 95% or less. However, the protective material 3 is a mesh (net network) in which regularly-shaped through-holes 3a are regularly arranged. Also referred to).

  The pressure loss of the protective material 3 is preferably 2 Pa to 30 Pa. In addition, the said pressure loss is the value measured by adjusting the linear velocity of the air which permeate | transmits the protective material 3 to 5.3 cm / sec.

  Examples of the material for the protective material 3 include polyolefins (polyethylene (PE), polypropylene (PP), etc.), polyamides, polyesters (polyethylene terephthalate (PET), etc.), aromatic polyamides, metals, and composites thereof. Is used.

  There is no restriction | limiting in particular about the shape of the protection material 3, As shown in FIG. 2 or FIG. 4, a sheet form may be sufficient, and as shown in FIG. 5 and FIG. 6, the shape seen from the side is pleated. It may be a continuous W shape.

  The entire surface of the protective material 3 facing the PTFE porous membrane 2a may be in contact with the PTFE porous 2a, but is it disposed so as not to contact the PTFE porous membrane 2a as shown in FIG. , It is preferable that a portion is arranged so as not to contact the PTFE porous membrane 2a. Thus, when the protective material 3 is arranged so that at least a part of the protective material 3 does not contact the PTFE porous membrane 2a, for example, the entire surface of the protective material 3 facing the PTFE porous membrane 2a. Is better than the form in contact with the PTFE porous 2a, and is preferable.

  Moreover, in the example shown in FIG. 4, since a part of the protective material 3 and the top part 2c of the PTFE porous membrane 2a are in contact with each other, when vibration is applied to the air filter unit 1, the vibration of the protective material 3 The vibration of the air filter medium 2 is transmitted to the protective material 3 to the filter medium 2 and the dust removal performance is improved.

  As shown in FIG. 6, when the protective material 3 is arranged so as not to contact the PTFE porous membrane 2a, a spacer 5 may be arranged between the protective material 3 and the PTFE porous membrane 2a. When vibration is applied to the air filter unit 1, the vibration of the protective material 3 is transmitted to the air filter medium 2 through the spacer 5, and the vibration of the air filter medium 2 is transmitted to the protective material 3 through the spacer 5, thereby improving dust removal. To do. In the example shown in FIG. 6, a plurality of spacers 5 are provided on the support frame 4, and the plurality of spacers 5 are arranged at intervals between the protective material 3 and the PTFE porous membrane 2 a. Therefore, vibration is easily transmitted and is particularly preferable.

  The PTFE porous membrane 2a is not particularly limited with respect to the average pore diameter, structure, form, etc., but the average pore diameter is, for example, 0.01 μm to 5 μm, and the average fiber diameter is, for example, 0.01 μm to 0.3 μm. It is preferable.

  The pressure loss of the PTFE porous membrane 2a is preferably 20 Pa to 150 Pa, for example. The higher the collection efficiency, the better. For example, it is preferably 90% or more, more preferably 99% or more. The pressure loss is a value measured by adjusting the linear velocity of air passing through the PTFE porous membrane 2a to 5.3 cm / sec. The collection efficiency is a value measured by transmitting particles having a particle size of 0.3 μm to 0.5 μm at a linear velocity of 5.3 cm / sec.

  Next, an example of a method for producing the PTFE porous membrane 2a will be described. 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 the PTFE fine powder and can be removed by extraction or heating. For example, hydrocarbons such as naphtha and white oil can be used. The amount of liquid lubricant added is, for example, about 5 to 50 parts by weight per 100 parts by weight of PTFE fine powder. The preforming may be performed at a pressure that does not squeeze out the liquid lubricant.

  Next, the preformed body is extruded and rolled to form, for example, a sheet, and the sheet-like formed body thus obtained is stretched at least in a uniaxial direction to obtain a PTFE porous membrane 2a. The stretching may be performed after removing the liquid lubricant. The stretching conditions can be set as appropriate, but the temperature is usually 30 to 320 ° C. The area stretch ratio (the product of the stretch ratio in the longitudinal direction and the stretch ratio in the transverse direction) is preferably 50 to 900 times. If the PTFE porous membrane 2a is heated to a melting point of PTFE or higher and fired after stretching, the strength can be increased.

  The air-permeable support material 2b constituting the air filter medium 2 is not particularly limited in its structure, form, etc., but a material having higher air permeability than the PTFE porous membrane 2a, for example, felt, non-woven fabric, woven fabric, mesh ( Reticulated sheet) and other porous materials are used. However, a mesh or a non-woven fabric is preferable from the viewpoint of strength, collection property, flexibility, and workability.

  The pressure loss of the breathable support material 2b is usually preferably 2 Pa to 30 Pa, and the collection efficiency is not particularly limited. The pressure loss is a value measured by adjusting the linear velocity of air passing through the air-permeable support material 2b to 5.3 cm / sec, and the collection efficiency is such that the particle size is 0.3 μm to 0.5 μm. This is a value measured by transmitting the particles at a linear velocity of 5.3 cm / sec.

  The material of the breathable support material 2b is not particularly limited. For example, polyolefin (polyethylene (PE), polypropylene (PP), etc.), polyamide, polyester (polyethylene terephthalate (PET), etc.), aromatic polyamide, or these The composite material etc. are used.

  At least one of the PTFE porous membrane 2a or the air-permeable support material 2b may be colored in a desired color. There is no restriction | limiting in particular about the coloring method, For example, the method of kneading a pigment, the method of dyeing with dye, the method by printing, etc. are mentioned.

  When coloring by the method of kneading the pigment, in the breathable support material 2b, the pigment is generally kneaded with the raw material resin in a molten state. In the PTFE porous membrane 2a, a pigment and a liquid lubricant are added to the PTFE fine powder to form a paste-like admixture, and the admixture may be processed into a porous membrane. In the case of dyeing with a dye, at least one of the PTFE porous membrane 2a and the air-permeable support material 2b may be immersed in the dye before lamination, or may be immersed in the dye after being laminated. As a printing method, gravure printing or the like is common.

  The PTFE porous membrane 2a and the breathable support material 2b may be joined or simply overlapped. There is no restriction | limiting in particular about the joining method of the PTFE porous membrane 2a and the air permeable support material 2b, For example, methods, such as an adhesive laminate and a thermal lamination, are mentioned. In the case of heat laminating, for example, a part of the breathable support material 2b may be melted by heat and partially bonded to the PTFE porous membrane 2a. Moreover, you may adhere | attach via a melting agent like a hot melt.

  Although the thickness of the air filter medium 2 is not particularly limited, it is preferably 0.05 mm to 1 mm, for example, considering the shape stability after pleating.

  The pressure loss of the air filter medium is preferably 5 Pa to 300 Pa, more preferably 10 Pa to 150 Pa, for example. The higher the collection efficiency of the air filter medium, the better. However, for example, it is preferably 90% or more, more preferably 99% or more. The pressure loss is a value measured by adjusting the linear velocity of air passing through the air filter 1 to 5.3 cm / sec. The collection efficiency is a value measured by transmitting particles having a particle size of 0.3 μm to 0.5 μm at a linear velocity of 5.3 cm / sec.

  The pleating process of the air filter medium 2 and the protective material 3 is, for example, a rotary method in which a material is folded while rotating a pair of rotating drums having blades disposed on the outer periphery, and a predetermined interval is provided in the material transfer direction. It can be performed by a reciprocating method in which a material is alternately folded from both sides while moving a pair of arranged blades. The air filter medium that has been pleated may be strengthened by forming a bead with hot melt or the like.

  There is no restriction | limiting in particular as a material of the support frame 4, For example, wood, a metal, resin etc. are used. Examples of the resin that can be used include polyolefin resins, polyamide resins, polyurethane resins, polyester resins, polystyrene resins, and composite materials thereof. Further, rubber or elastomer may be used as long as the shape stability of the support frame is not impaired. As the elastomer, polyolefin, polyurethane, polyester, polystyrene, or the like is used. The support frame 4 may contain additives such as pigments, antibacterial agents, and carbon fibers in addition to the resin.

  The air filter medium 2 and the support frame 4 may be integrated using an adhesive such as hot melt. When the support frame is made of resin, as shown in FIGS. 2 and 4 to 6, the support frame 4 may be integrally formed around the air filter medium 2. Further, the protective material 3 may be integrally formed.

Although there is no limitation in particular about the pressure loss of the air filter unit 1, it is preferable that it is 1000 Pa or less when the air of 2 m < ³ > / min is permeate | transmitted from a viewpoint of energy efficiency. The pressure loss of 1000 Pa or less can be realized by appropriately selecting the pressure loss of the air filter medium and the filtration area.

  There is also no particular limitation on the collection efficiency of the air filter unit 1, and the higher the better, but it is preferably 90% or more, and more preferably 99% or more, for example. The collection efficiency is a value measured by transmitting particles having a particle size of 0.3 μm to 0.5 μm at a linear velocity of 5.3 cm / sec.

  Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples.

A PTFE porous membrane (thickness 15 μm, pressure loss 50 Pa, collection efficiency 99%) and a polyester non-woven fabric (pressure loss 6 Pa, basis weight 190 g / m ² ) are bonded with a polyolefin-based hot melt agent to prepare an air filter medium. (Thickness 0.42 mm, pressure loss 80 Pa, collection efficiency 99.3%) was obtained.

  The obtained air filter medium was pleated to a shape that fits within a predetermined area (116 mm × 116 mm). The number of folds was 18 and the height of the mountain was 20 mm. Subsequently, the periphery of the pleated air filter medium was surrounded by a strip-shaped polyester nonwoven fabric having a width of 20 mm. The strip-shaped polyester nonwoven fabric is a substitute for the support frame. Next, the polyester nonwoven fabric and the air filter medium were bonded by hot melt. Furthermore, a plastic net (wire diameter: 0.2 mm) having an aperture ratio of 69% was attached to the end face of the polyester nonwoven fabric by hot melt to obtain an air filter unit. In addition, the top part of the pleated air filter medium and the plastic net are in contact.

  An air filter unit was obtained in the same manner as in Example 1 except that the air filter medium pleated with a 30 mm wide striped polyester nonwoven fabric was enclosed instead of the 20 mm wide striped polyester nonwoven fabric. The distance between the top of the pleated air filter medium and the plastic net was 10 mm.

(Comparative Example 1)
An air filter unit was obtained in the same manner as in Example 1 except that a plastic net was not attached.

(Comparative Example 2)
An air filter unit was obtained in the same manner as in Example 2 except that a plastic net (wire diameter 0.2 mm) having an aperture ratio of 51% was used instead of the plastic net having an aperture ratio of 69%.

The pressure loss and the collection efficiency of the air filter units of Examples and Comparative Examples were measured, and the results are shown in Table 1. Table 2 shows the relative pressure loss when the initial stress loss is 100. As shown in FIG. 7, the pressure loss is as follows. (2) As shown in FIG. 7, the obtained air filter unit 1 is set in the funnel-shaped frame 6, and then the test powder 8 types ( Kanto Loam, JIS Z 8901) Immediately after sucking 1 g, (3) Immediately after dropping the air filter unit sucking the test powder three times from a height of 10 cm, (4) Toothbrush after dropping (5) Immediately after the surface of the upstream side was rubbed, (5) Immediately after sucking again 1g of 8 kinds of test powder, (6) Immediately after washing with water from the upstream side. The initial pressure loss is a value measured by passing air having a flow rate of 2 m ³ / min. In measuring the pressure loss in (2) to (6), the air flow rate was adjusted to 2 m ³ / min. The pressure loss was measured with a pressure gauge (manometer).

  The air filter unit was set in the frame 6 as follows. In the air filter unit of Example 1 or 2 and Comparative Example 2, the net was directed to the upstream side of the gas flow. In the air filter unit of Comparative Example 1, the PTFE porous membrane was directed upstream of the gas flow.

  The collection efficiency was determined from the change in weight before and after suction of the test powder.

  As shown in Table 1, in the air filter unit of Comparative Example 1, the value measured for the second time was much smaller than the value measured for the first time for the collection efficiency. Such a result was obtained because the PTFE porous membrane was completely exposed in the air filter unit of Comparative Example 1, and therefore, when the air filter unit was dropped or rubbed with a brush, the PTFE porous membrane was removed. Seems to have been damaged. In the air filter unit of Comparative Example 2, there is no deterioration in filter characteristics (collection efficiency), but because the opening ratio of the plastic net is small, the powder is easily held in the entangled part of the net, and the cleaning time is long. It took. In practical use, household waste contains a large amount of fiber dust, so it can be easily estimated that fiber dust is entangled with the entangled portion of the net and cleaning becomes difficult.

  On the other hand, in the air filter units of Examples 1 and 2, the value measured for the first time and the value measured for the second time for the collection efficiency are substantially equal. The difference from Comparative Example 1 regarding this point is that, in the air filter media of Examples 1 and 2, the protective film (mesh) is disposed on the PTFE porous film, so that damage to the PTFE porous film is suppressed. It seems to be because.

  Moreover, in the air filter unit of Example 1 or 2, since the PTFE porous membrane is covered with a protective film having an opening ratio of 60% or more, it can be seen when the air filter medium is viewed in plan from the protective membrane side. The PTFE porous membrane is 60% or more of the entire PTFE porous membrane. Therefore, most of the test powder is captured by the PTFE porous membrane 2 having excellent dust removal properties. When the air filter medium was visually confirmed after washing with water, most of the powder was washed away, the appearance of the air filter medium was close to the initial state, and no scratches were seen.

  As described above, when the air filter unit of the present invention is used with the protective material side facing the upstream side of the gas flow, the dust filter is excellent and the filter characteristics are deteriorated due to damage to the porous PTFE membrane. This is useful as an air filter unit.

The perspective view which shows an example of the air filter unit of this invention AA 'sectional view of the air filter unit shown in FIG. Sectional drawing of the air filter medium used for the air filter unit shown in FIG. Sectional drawing which shows an example of the air filter unit of this invention Sectional drawing which shows an example of the air filter unit of this invention Sectional drawing which shows an example of the air filter unit of this invention The figure explaining the measuring method of the pressure loss of the air filter unit of an Example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air filter unit 2 Air filter medium 2a PTFE porous membrane 2b Breathable support material 3 Protective material 3a Through-hole 4 Support frame 5 Spacer

Claims (7)

An air filter unit including an air filter medium and a support frame that supports the filter medium in the frame,
One main surface of the air filter medium is formed of a polytetrafluoroethylene porous membrane,
The air filter unit further includes a protective material disposed on the polytetrafluoroethylene porous membrane side and having a plurality of through holes,
The ratio of the total opening area of the plurality of through holes to the area of the main surface of the protective material is 60% or more,
The air filter unit, wherein the protective material and the air filter medium are fixed to the support frame so as not to be separated.   The air filter unit according to claim 1, wherein the air filter medium is pleated.   2. The air filter unit according to claim 1, wherein at least a part of the protective material is disposed so as not to contact the polytetrafluoroethylene porous membrane.   The air filter unit according to claim 3, wherein the protective material is disposed so as not to contact the polytetrafluoroethylene porous membrane. A plurality of spacers provided on the support frame;
5. The air filter unit according to claim 4, wherein the plurality of spacers are arranged with a space between the protective material and the polytetrafluoroethylene porous membrane.   The air filter unit according to claim 1, wherein the protective material is pleated.   The air filter unit according to claim 1, wherein the air filter medium further includes at least one air-permeable support member laminated on the polytetrafluoroethylene porous membrane.

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