JP2006175313A - Filter medium for air filter and air filter unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter medium for an air filter from which dust is removed easily, the collection efficiency of which is hardly deteriorated even when the filter medium is washed with water and the pressure loss of which is made low and to provide an air filter unit using the filter medium for the air filter. <P>SOLUTION: This filter medium 3 for the air filter comprises at least one layer of a porous membrane 1 of polytetrafluoroethylene and at least one layer of an air-permeable supporting material 2. At least one of two layers arranged as the outermost layers is the porous membrane of polytetrafluoroethylene. This filter medium 3 for the air filter has such a characteristic even when not used or even when washed with water and then dried that when the talc regulated in the fourth class of JIS test powder is brought into contact with one of the outermost layers, where the porous membrane of polytetrafluoroethylene is arranged, in the ratio of 25 g per m<SP>2</SP>area of the porous membrane of polytetrafluoroethylene and at 18.8 cm/second flow velocity, the regulated talc does not blow/leak out of the other of the outermost layers. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an air filter medium, and further relates to an air filter unit using the air filter medium.

Conventionally, an electret nonwoven fabric made of polypropylene or a filter material made of glass fiber has been used as an air filter medium used for air purification (see Patent Document 1).

JP 5-214

However, with these conventional air filter media, dust separation is poor and cleaning of the filter is not easy, it is difficult to repeatedly use after washing with water, or the pressure loss is high, which impedes energy saving of air purification. There is a problem of doing.

SUMMARY OF THE INVENTION An object of the present invention is to provide an air filter medium that has good dust separation, is less likely to reduce its collection efficiency even when washed with water, and has low pressure loss. Another object of the present invention is to provide an air filter unit using the air filter medium.

The air filter medium of the present invention includes at least one polytetrafluoroethylene porous membrane and at least one air-permeable support material, and at least one of the two layers disposed in the outermost layer is the polytetrafluoroethylene porous material. The JIS test powder 4 from the outermost layer side on which the polytetrafluoroethylene porous membrane is disposed, whether it is an unused membrane or in a state of being washed and then dried. When talc specified by the seed is brought into contact with the outermost polytetrafluoroethylene porous membrane at a rate of 25 g / m ² and at a flow rate of 18.8 cm / sec, the other outermost polytetrafluoroethylene porous membrane is contacted. There is no talc jet leakage on the outer layer side.

According to the present invention, even in an unused state, even after being washed with water and dried,
From the outermost layer side on which the polytetrafluoroethylene (PTFE) porous membrane is arranged, talc specified in four types of JIS test powder is added to the outermost polytetrafluoroethylene porous membrane at 25 g / When contacted at a rate of m ² and at a flow rate of 18.8 cm / sec, an air filter medium is provided in which there is no talc jet leakage on the other outermost layer side. Also,
PTFE has a high releasability, and this PTFE porous membrane is arranged on the intake side to collect dust, so that dust can be easily removed from the air filter media. Can increase the sex. Moreover, pressure loss can be reduced. This excellent cleaning resistance, dust separation, and low pressure loss property are useful as an air filter medium for an air filter unit of, for example, a home appliance or an automobile.

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

The air filter medium 3 shown in the cross-sectional view of FIG. 1 is polytetrafluoroethylene (PTFE).
It has a porous membrane 1 and a breathable support material 2. This PTFE porous membrane 1 and a breathable support material 2
Are laminated so that each one main surface is in contact therewith. The other main surface of the PTFE porous membrane 1 is exposed on the surface of the air filter medium 3.

The PTFE porous membrane 1 preferably has an average pore diameter of 0.01 to 5 μm. Also,
The area stretch ratio is preferably in the range of 300 to 750 times.

This PTFE porous membrane 1 can be obtained by a known production method. For example, the PTFE sheet may be produced by uniaxial stretching or biaxial stretching. PTFE sheet is generally PTF
It is produced by pre-molding a paste-like mixture obtained by adding a liquid lubricant to E fine powder, extruding the preform, and forming it into a sheet by rolling. The liquid lubricant is
There is no particular limitation as long as the surface of the PTFE fine powder can be wetted and removed by extraction or heating, and hydrocarbons such as liquid paraffin, naphtha, and white oil may be used. The amount of liquid lubricant added is 5 with respect to 100 parts by mass of PTFE fine powder.
-50 mass parts is suitable. The preforming may be performed at a pressure that does not squeeze out the liquid lubricant. The liquid lubricant may be removed from the stretched PTFE sheet in advance, but may be removed after stretching.

The breathable support material 2 is not particularly limited in its material and structure as long as it can act as a reinforcing material for the air filter medium. As the material, for example, polyolefins such as polyethylene and polypropylene, polyesters such as polyamide and polyethylene terephthalate, and aromatic polyamides can be used alone or in combination. The structure may be, for example, a felt, a nonwoven fabric, a woven fabric, a mesh (mesh-like sheet), or the like, but preferably has a structure excellent in air permeability as compared with the PTFE porous membrane 1. In addition, it is preferable to use a nonwoven fabric or a mesh from the viewpoints of strength, catchability, flexibility, ease of handling, and the like.

The breathable support material 2 is colored, antibacterial, antifungal, deodorant, water repellent, oil repellent,
Treatment such as hydrophilization may be performed. Further, the surface may be corona-treated in order to improve the adhesion with the PTFE porous membrane.

The PTFE porous membrane 1 and the air-permeable support material 2 may be simply overlapped or may be combined by a method such as thermal lamination or adhesive lamination. Specifically, for example, a hot melt agent (powder or web) having a melting point lower than that of the raw material of the breathable support material and PTFE is interposed between the PTFE porous membrane and the breathable support material, The method of bonding each by heating is mentioned. If the melting point of the breathable support material is lower than the melting point of PTFE, a part of the support material may be melted and combined. A method of combining the PTFE porous membrane and the breathable support material using an adhesive may be used. In this case, the adhesive is 2
Liquid-mixing type or heat self-crosslinking type adhesives are suitable. An epoxy resin may be used as the two-component mixed type, and a vinyl acetate-ethylene copolymer or an ethylene-vinyl chloride copolymer may be used as the self-crosslinking type by heat.

The thickness of the air filter medium 3 is not particularly limited, but preferably has a thickness that allows the shape of the air filter medium 3 to be maintained after pleating. For example, it can be in the range of 0.05 mm to 2 mm. Further, the pressure loss of the air filter medium 3 is preferably 20 to 150 Pa, and more preferably 20 to 70 Pa. The pressure loss is defined based on a value obtained by measuring air through a flow rate of 5.3 cm / second. In addition, when the particles having a volume average particle size of 0.3 to 0.5 μm are contacted at a flow rate of 5.3 cm / second, the collection efficiency of the particles is preferably 80% or more, and 90% or more. More preferably. In the measurement of the pressure loss and the collection efficiency of the air filter medium 3, P
It is preferable to bring air and particles into contact from the other main surface side of the TFE porous membrane 1.

The air filter medium 3 thus obtained is subjected to a continuous W-shaped fold process (hereinafter referred to as “pleating process”) as shown in FIG. 2, and the PTFE porous membrane 1 and the air-permeable support material. A bead is formed with a hot melt agent or the like so as not to come into contact with each other on the surface facing 2, and further, the air filter unit 5 is framed with a resin or metal outer frame 4 or the like.

The pleating process is, for example, a rotary method in which a pair of rotating drums having blades arranged on the outer periphery is rotated while the filter medium is folded, while a pair of blades arranged at a predetermined interval in the transfer direction of the filter medium is moved. This is done by a reciprocating method in which the filter medium is folded alternately from both sides.

The air filter medium of the present invention is not limited to the structure shown in FIG.
As long as it includes a porous membrane and at least one air-permeable support material and at least one of the two layers arranged as the outermost layer is a PTFE porous membrane, a wide variety of structures can be adopted. For example,
A plurality of porous PTFE membranes and a breathable support material may be included, and for example, the PTFE porous membrane may be disposed on the outermost layers on both sides.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. Measurement of pressure loss and collection efficiency was performed by the following methods.

[Pressure loss]
As shown in FIG. 3, a sample (for example, the air filter medium of the above embodiment) was set in a circular holder 6 having an effective area of 100 cm ² . In addition, this holder 6 was arrange | positioned so that a PTFE porous membrane might be exposed to the upstream of the test device 7. FIG. A pressure difference was applied between the upstream side and the downstream side of the holder 6, and the pressure loss was measured with a pressure gauge (manometer) when the air permeation speed was adjusted to 5.3 cm / second with a flow meter. The measurement was performed at 10 locations per sample, and the average of each measurement value was taken as the pressure loss of the sample.

[Collection efficiency]
Using the same tester 7 as the measurement of the pressure loss, talc specified in four kinds of JIS test powder is supplied on the upstream side, at a rate of 25 g / m ² with respect to the PTFE porous membrane, and 18 .8cm
It adjusted so that it might contact at the flow rate of / second. The upstream talc concentration and the downstream talc concentration permeating the sample were measured with a particle counter, and the collection efficiency was determined based on the following equation (1).
Collection efficiency (%) = (1−downstream particle concentration / upstream particle concentration) × 100 (1)

Example 1
PTFE fine powder (Aflon CD123 manufactured by Asahi Glass Fluoropolymers) 100
20 parts by mass of a liquid lubricant (dodecane) was uniformly mixed with respect to part by mass, and this mixture was preformed, and then formed into a round bar shape by paste extrusion. Further, this round bar-shaped molded body was passed between a pair of metal rolling rolls to obtain a sheet-shaped molded body having a thickness of 0.2 mm. Subsequently, the liquid lubricant was removed from the sheet-like molded body by an extraction method using normal decane.

The sheet-like molded body was stretched biaxially to obtain a PTFE porous membrane (average pore diameter 1.1 μm) having an area stretch ratio of 600 times. This PTFE porous membrane and polyester nonwoven fabric (weight per unit area 13)
0g / m ² ) are superposed on each other via a polyolefin-based hot melt agent, and then heated at a temperature higher than the melting point of the hot melt agent, whereby a two-layer air filter medium according to Example 1 is used. (Thickness: 0.3 mm) was obtained.

(Example 2)
Example 2 is the same air filter medium as Example 1 except that a PTFE porous membrane (average pore diameter 1.3 μm) having an area stretch ratio of 650 times was used.

(Example 3)
Example 3 is an air filter medium similar to Example 1 except that a PTFE porous membrane (average pore diameter: 1.0 μm) having an area stretch ratio of 540 times was used.

(Comparative Example 1)
This Comparative Example 1 was carried out in the same manner except that an electret polypropylene non-woven cloth (20 g / m ² ) was used instead of the PTFE porous membrane, and the thickness of the air filter medium was 0.42 mm. This is the same air filter medium as in Example 1. The electretization refers to a dielectric state in which each filter fiber is given a charge and is permanently polarized.

For the air filter media according to Examples 1 to 3 and Comparative Example 1, pressure loss and collection efficiency were measured. The pressure loss of Example 1 was 80 Pa, 40 Pa in Example 2, 130 Pa in Example 3, and 30 Pa in Comparative Example 1, both showing excellent values of 150 Pa or less. In addition, the collection efficiency of Example 1 is 99.4%, 98.3% in Example 2, 99.97% in Example 3, and 99.1% in Comparative Example 1, both high values. As shown, no talc particle jet leakage downstream was observed.

However, when each filter medium whose talc collection efficiency was measured was washed with running water, in Examples 1 to 3, most of the dust could be removed from the surface PTFE porous membrane by washing with water, that is, dust was removed. In Comparative Example 1, a considerable amount of dust remained in the PTFE porous membrane although it could be almost washed away.

Furthermore, each air filter medium was washed with water under the same conditions, then sufficiently air-dried, and a collection test was performed again using a tester. In Examples 1 to 3, talc particles were not observed to leak to the downstream side, but in Comparative Example 1, talc powder was significantly leaked to the extent that it was difficult to use as a filter.

The air filter media according to Examples 1 to 3 were pleated so that 18 ridges with a height of 20 mm were formed in a 120 mm × 120 mm range, and then the outer edge was surrounded with a 20 mm wide polyester nonwoven fabric. Even when an air filter unit having an outer frame welded thereto was produced, it was confirmed that the above-described excellent cleaning resistance and dust separation performance were exhibited.

The present invention can be applied to an air filter medium that has good dust separation and does not easily lower its collection efficiency even when washed with water, and has a low pressure loss, and an air filter unit that uses this air filter medium.

It is sectional drawing which shows an example of the air filter medium of this invention. It is a perspective view which shows an example of the air filter unit of this invention. It is a figure which shows the test device used for the talc powder jet-leak test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 PTFE porous membrane 2 Breathable support material 3 Air filter medium 4 Outer frame 5 Air filter unit 6 Holder 7 Tester

Claims (4)

Comprising at least one polytetrafluoroethylene porous membrane and at least one breathable support;
At least one of the two layers arranged in the outermost layer is the polytetrafluoroethylene porous membrane,
Whether in an unused state or in a state after being washed with water and dried, the outermost layer side on which the polytetrafluoroethylene porous membrane is disposed is defined as four types of powder for JIS testing. When talc is brought into contact with the outermost polytetrafluoroethylene porous membrane at a rate of 25 g / m ² and at a flow rate of 18.8 cm / sec, the talc is placed on the other outermost layer side. An air filter medium characterized by no air leakage. The air filter medium according to claim 1, wherein a pressure loss is 20 to 150 Pa when air is permeated at a flow rate of 5.3 cm / sec. The air filter medium according to claim 1, wherein a pressure loss is 20 to 70 Pa when air is permeated at a flow rate of 5.3 cm / sec. An air filter unit using the air filter medium according to any one of claims 1 to 3.

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