WO2016021053A1

WO2016021053A1 - Dust collection filter and dust collection device using same

Info

Publication number: WO2016021053A1
Application number: PCT/JP2014/071049
Authority: WO
Inventors: 水野　善之
Original assignee: ユーエスウラサキ株式会社
Priority date: 2014-08-08
Filing date: 2014-08-08
Publication date: 2016-02-11

Abstract

A dust collection filter for collecting fumes is constituted of a fiber having an oil repelling coating layer formed on the surface thereof. The dust collection filter has oil repellency of grade 6 or greater according to AATCCT Test Method 118, and transmittance of 70% or greater according to JIS B 9927 (particle size of 0.3 µm for test particles).

Description

Dust collection filter and dust collector using the same

The present invention relates to a dust collecting filter and a dust collecting device using the dust collecting filter.

For example, during metal processing (welding, fusing, etc.) using a laser processing machine or the like, so-called fume (metal fume) is generated in which metal vapor is aggregated into fine particles. Conventionally, a dust collector provided with a dust collection filter for collecting fume is known (refer to patent documents 1). In such a dust collecting device, the dust attached to the dust collecting filter is removed by blowing pressurized air on the dust collecting filter or applying a mechanical force (for example, vibration) to the dust collecting filter. .

JP 2009-106945 A

However, the conventional dust collector filter has the following problems. The fume adhering to the dust collection filter contains a little oil component. For this reason, the fumes adhering to the dust collection filter cannot be easily separated from the dust collection filter by pressure air, vibration, or the like, and the fume removal work has become very complicated.

Therefore, it is desirable to provide a dust collection filter and a dust collection apparatus using the dust collection filter that can easily dispose of adhering fume.

One aspect of the present invention is a dust collection filter for collecting fume, and the dust collection filter is made of a fiber having an oil-repellent coating layer formed on a surface thereof, and is formed of AATCC Test Method 118 (AATCC). : American Association of Textile Chemists and Colorists, American Textile Chemical Technology and Dyeing Technology Association) has oil repellency of 6th grade or higher, and JIS B 9927 (JIS: Japan Industrial Standards, rate for Japanese Industrial Standards) The dust collection filter is characterized in that the particle diameter is 0.3% or more.

The dust collection filter is composed of fibers having an oil-repellent coating layer formed on the surface. The dust collection filter has characteristics (oil repellency, transmittance) according to the specific test method satisfying the specific conditions. Therefore, after the fume containing oil is collected by the dust collection filter, the adhered fume can be easily separated from the dust collection filter. Thereby, the operation | work which wipes off a fume from a dust collection filter becomes easy.

Another aspect of the present invention is a dust collecting apparatus including the dust collecting filter.
The dust collecting device includes the dust collecting filter. Therefore, after the fume containing oil is collected by the dust collection filter, the adhered fume can be easily separated from the dust collection filter. Thereby, the operation | work which wipes off a fume from a dust collection filter becomes easy.

In this way, it is possible to provide a dust collection filter that facilitates the removal of attached fume and a dust collector using the same.
In the dust filter, the dust filter preferably has a zeta potential of −10 mV or more. In this case, the adhesion force of the fumes adhering to the fiber surface of the dust collection filter is reduced, and the fumes can be more easily separated from the dust collection filter. Thereby, the efficiency of the operation | work which removes a fume from a dust collection filter can be raised.

It is explanatory drawing which shows the structure of the dust collector in Embodiment 1. FIG. It is explanatory drawing which shows the structure of the dust collection filter in Embodiment 1. FIG. It is a schematic diagram which shows the fume collected by the conventional dust collection filter. It is a schematic diagram which shows the fume collected by the dust collection filter of Embodiment 1. It is a SEM photograph of the dust collection filter of sample 1 in an experimental example. It is a SEM photograph of the dust collection filter of sample 2 in an experimental example. It is a SEM photograph of the dust collection filter of sample 3 in an experimental example. It is a SEM photograph of the dust collection filter of sample 5 in an experimental example. It is a SEM photograph of the dust collection filter of sample 6 in an experimental example. It is a SEM photograph of the dust collection filter of sample 7 in an experimental example. It is a figure which shows the analysis result of the fume by X-ray CT of the dust collection filter of the sample 1 in an experiment example. It is a figure which shows the analysis result of the fume by X-ray CT of the dust collection filter of the sample 7 in an experiment example.

1 ... Dust collector 22 ... Dust collector filter

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
As shown in FIGS. 1 and 2, the dust collector 1 includes a dust collection filter 22 for collecting fumes. The dust collection filter 22 is composed of fibers having an oil-repellent coating layer formed on the surface. The dust collection filter 22 has an oil repellency according to AATCC Test Method 118 (hereinafter simply referred to as “oil repellency” as appropriate) of grade 6 or higher and a transmittance according to JIS B 9927 (hereinafter simply referred to as “transmittance” as appropriate). (The particle diameter of the test particles is 0.3 μm) is 70% or more. Hereinafter, the dust collector 1 and the dust collection filter 22 will be described in detail.

As shown in FIG. 1, the dust collector 1 collects fine particles (hereinafter referred to as fume) in which metal vapor generated during metal processing (welding, fusing) using a laser processing machine is aggregated. Device. The dust collector 1 includes a housing 10 and the like. The housing 10 is partitioned into a dust collection chamber 11, an intake chamber 13, an intermediate chamber 12 that connects the dust collection chamber 11 and the intake chamber 13, and the like.

In the dust collection chamber 11, a cylindrical duct 111 is disposed. The duct 111 connects the dust collection chamber 11 and the outside of the housing 10. A collection unit 2 is disposed in the dust collection chamber 11. The collection unit 2 collects fumes in the air (atmosphere) in the dust collection chamber 11 and removes the fumes in the air. The direction of the arrow in the figure indicates the flow of air containing fume.

An intake fan 131 is disposed in the intake chamber 13. The intake fan 131 guides air containing fume from the outside of the housing 10 into the dust collection chamber 11 through the duct 111. The intermediate chamber 12 is formed between the dust collection chamber 11 and the intake chamber 13.

As shown in FIG. 2, the collection unit 2 includes a cylindrical core member 21, a dust collection filter 22 folded in a bellows shape, and the like. The collection part 2 is comprised by the substantially cylindrical shape. A plurality of through holes 211 are formed in the metal core material 21. The dust collection filter 22 is disposed so as to cover the outside of the core material 21. Details of the dust collection filter 22 will be described later.

The one end side in the axial direction of the dust collection filter 22 (core material 21) is closed by a closing body 23. For this reason, the air which passed the dust collection filter 22 distribute | circulates the inside of the dust collection filter 22 (core material 21) toward the other end side from the axial direction one end side.

As shown in FIG. 1, air containing fume is guided into the dust collection chamber 11 through a duct 111 by an intake fan 131. The air guided into the dust collection chamber 11 flows from the outside of the collection unit 2 toward the core member 21. When the air passes through the dust collection filter 22, fumes are collected by the dust collection filter 22.

The fume collected by the dust collection filter 22 is accumulated on the outer peripheral surface side of the dust collection filter 22. On the other hand, the air filtered by the dust collection filter 22 circulates in the core member 21 and is then discharged out of the housing 10 through the intermediate chamber 12 and the intake chamber 13.

Next, the dust collection filter 22 will be described.
The dust collection filter 22 is made of a long fiber nonwoven fabric. The dust collection filter 22 of the present embodiment is composed of a spunbond nonwoven fabric (manufactured by Toray Industries Inc., polyester long fiber nonwoven fabric, G2260-1S).

A coating layer having oil repellency is formed on the surface of the fibers of the dust collection filter 22. The dust collection filter 22 of this embodiment is a spunbonded nonwoven fabric that has been processed with a fluorine-based water and oil repellent (manufactured by Nikka Chemical, NK Guard S-09). That is, a coating layer made of a fluorine-based water and oil repellent is formed on the surface of the fibers of the dust collection filter 22. The coating layer of this embodiment has water repellency and oil repellency.

The dust collection filter 22 has an oil repellency of 6 or higher according to the oil repellency test of AATCC Test Method 118. A detailed test method will be described later.
The dust collection filter 22 has a transmittance (test particle size of 0.3 μm) according to “Clean air filter performance test method” of JIS B 9927 of 70% or more. A detailed test method will be described later.

The dust filter 22 has a zeta potential (Z-potential) of −10 mV or more on the surface thereof. The zeta potential can be measured using, for example, a zeta potential measuring device.

Next, a method for producing the dust collection filter 22 will be described.
First, a spunbond nonwoven fabric (manufactured by Toray Industries, Inc., polyester long fiber nonwoven fabric: G2260-1S) is prepared. The spunbonded nonwoven fabric has a size of 506 mm × 2800 mm. The spunbonded nonwoven fabric has a pleated shape, a height of 35 mm, and a number of peaks of 40. The spunbonded nonwoven fabric has a basis weight of 260 g / m ² and a thickness of 0.62 mm.

Next, the spunbonded nonwoven fabric is impregnated with a fluorine-based water and oil repellent (manufactured by Nikka Chemical Co., Ltd., NK Guard S-09). Specifically, a processing liquid (pure water: fluorine water / oil repellent = 100: 8) is prepared by diluting a fluorine water / oil repellent to 8% by pad treatment. The nonwoven fabric is immersed in the processing liquid (immersion time: 20 minutes).

Next, the spunbonded nonwoven fabric is squeezed three times with a mangle (pressure: 34.2 kg / cm ² , speed: 5 m / min). Thereafter, the spunbonded nonwoven fabric is dried at 130 ° C. for 1 minute and heat treated at 170 ° C. for 1 minute. Thereby, the dust collection filter 22 (refer FIG. 2) is produced.

Next, the effect of this embodiment is demonstrated.
The dust collection filter 22 of the present embodiment is composed of fibers having an oil-repellent coating layer formed on the surface. The dust collection filter 22 has an oil repellency according to AATCC Test Method 118 of 6 or higher and a transmittance according to JIS B 9927 (particle diameter of test particles 0.3 μm) is 70% or higher.

Therefore, after the fume containing oil is collected by the dust collection filter 22, the attached fume can be easily separated from the dust collection filter 22. Thereby, the operation | work which removes a fume from the dust collection filter 22 becomes easy. Moreover, the same effect is acquired also in the dust collector 1 provided with the dust filter 22.

The reason why the above-mentioned action and effect can be obtained is estimated as follows. FIG. 3 is a schematic diagram showing the fume 8 collected by the conventional dust collection filter 922. FIG. 4 is a schematic diagram showing the fume 8 collected by the dust collection filter 22 of the present embodiment. 3 and 4 indicate the flow of air containing fume.

As shown in FIG. 3, in the conventional dust collection filter 922, in the initial stage, fumes having a relatively large particle diameter in which fumes having a relatively small particle diameter pass through the gaps of the fibers 221 and the particles are aggregated (81 82) is collected in the gaps of the fibers 221. At this time, the fume 8 (81, 82) is collected to the position where it enters the inside from the surface 220 of the dust collection filter 922. Thereafter, the fume 8 (83) blocked by the fume 8 (81, 82) collected in the gap between the fibers 221 is deposited on the surface 220 of the dust collection filter 922.

Thus, in the conventional dust collection filter 922, the fume 8 enters the inside from the surface 220 of the dust collection filter 922 and is collected. Therefore, the dust collection filter 922 is clogged by the fume 8, and the fume 8 cannot be easily separated from the dust collection filter 22. This makes it difficult to remove the fume 8 from the dust collection filter 22.

On the other hand, as shown in FIG. 4, in the dust collection filter 22 of the present embodiment, in the initial stage, fumes having a relatively small particle diameter pass through the gaps of the fibers 221 and the particles are more aggregated. In addition, the fumes 8 (81, 82) having a relatively large particle diameter are collected in the gaps between the fibers 221. Here, in the dust collection filter 22 of the present embodiment, an oil-repellent coating layer is formed on the surface of the fiber 221, the oil-repellent function is high (oil repellency is 6th or higher), and the transmittance is also high (transmittance). 70% or more). Therefore, the fume 8 (81, 82) that has entered the dust collection filter 22 is less likely to adhere to the surface of the fiber 221 and easily passes through the gap between the fibers 221. As a result, the fume 8 (81, 82) is collected near the surface 220 of the dust collection filter 922. Thereafter, the fume 8 (83) blocked by the fume 8 (81, 82) collected in the gap between the fibers 221 is deposited on the surface 220 of the dust collection filter 922.

Thus, in the dust collection filter 22 of the present embodiment, the fume 8 is collected at a position close to the surface 220 of the dust collection filter 22. In addition, an oil-repellent coating layer is formed on the surface of the fiber 221 of the dust collection filter 22. Therefore, the fume 8 attached to the dust collection filter 22 can be easily separated from the dust collection filter 22. Thereby, the operation | work which wipes off the fume 8 from the dust collection filter 22 becomes easy.

Further, as described above, the dust collection filter 22 of the present embodiment has a high transmittance of 70% or more. However, the process in which the fume 8 is deposited and collected on the surface 220 of the dust collection filter 22 is a conventional process. Since it is the same as dust collection filter 922 (refer to Drawing 3 and Drawing 4), the collection function of fume 8 does not fall especially. That is, the dust collection filter 22 according to the present embodiment has a function of collecting the fume 8 and can easily remove the fume 8.

In this embodiment, the dust collection filter 22 has a zeta potential of −10 mV or more. Therefore, the adhesion force of the fume adhering to the fiber surface of the dust collection filter 22 is reduced, and the fume can be more easily separated from the dust collection filter 22. Thereby, the efficiency of the operation | work which removes a fume from the dust collection filter 22 can be raised.

As described above, according to this embodiment, it is possible to provide the dust collection filter 22 and the dust collector 1 using the dust collection filter 22 that can easily remove the attached fume after collecting the fumes.

(Experimental example)
This experimental example is an example in which the characteristics of the dust collection filter of the present invention were evaluated.
In this experimental example, a plurality of different types of dust collection filters (Sample 1 to Sample 7) were prepared or produced. Specifically, a dust collection filter (sample 6, sample 7) as an example of the present invention and a dust collection filter (sample 1 to sample 5) as comparative examples were prepared or produced. And various evaluation was performed about each sample. Below, the kind and evaluation method of each sample are demonstrated.

<Type of each sample>
Sample 1 is a spunbond nonwoven fabric (manufactured by Toray Industries, Inc., polyester long fiber nonwoven fabric: G2260-1S).

Sample 2 is a water-repellent spunbond nonwoven fabric (manufactured by Toray Industries, Inc., polyester long fiber nonwoven fabric: G2260-TR).
Sample 3 is a spunbond nonwoven fabric (polyester long fiber nonwoven fabric: G2260-TF manufactured by Toray Industries, Inc.) laminated with a PTFE (polytetrafluoroethylene) membrane.

Sample 4 is a CVD treatment of cyclic silane 1,3,5,7-tetramethylcyclotetrasiloxane (D ₄ ^H ) on the spunbond nonwoven fabric of sample 1 (polyester long fiber nonwoven fabric: G2260-1S manufactured by Toray Industries, Inc.) And water repellent finish.

Sample 5 is obtained by subjecting the spunbond nonwoven fabric of Sample 1 (manufactured by Toray Industries, Inc., polyester long fiber nonwoven fabric: G2260-1S) to oil-repellent processing. Specifically, cyclic silane 1,3,5,7-tetramethylcyclotetrasiloxane (D ₄ ^H ) is subjected to CVD treatment on the spunbonded nonwoven fabric to make the surface water repellent. Next, the surface is hydrophilized by vacuum plasma. Thereafter, heptadecafluoro-1,1,2,2-trimethoxysilane (FAS17) is subjected to CVD treatment to make the surface oil repellent. Hydrophilization may use methods such as ozone microbubbles and ultraviolet irradiation instead of vacuum plasma.

Sample 6 is a water- and oil-repellent finish using a fluorine-based water- and oil-repellent agent (manufactured by Nikka Chemical Co., Ltd., NK Guard S-09) for a spunbonded nonwoven fabric (manufactured by Toray, polyester long-fiber nonwoven fabric, G2200-1S). Is given. The spunbonded nonwoven fabric has a basis weight of 200 g / m ² and a thickness of 0.54 mm. In addition, the size and shape of the spunbonded nonwoven fabric are the same as those in the first embodiment. The water / oil repellent treatment was performed in the same manner as in the first embodiment.

Sample 7 is the same as the dust collection filter of Embodiment 1 described above, and is a fluorine-based water and oil repellent (Nikka Chemical Co., Ltd.) for a spunbonded nonwoven fabric (manufactured by Toray Industries, polyester long fiber nonwoven fabric, G2260-1S). Manufactured by NK Guard S-09).

<Oil repellency>
The oil repellency was evaluated according to AATCC Test Method 118 (1997). Specifically, nine hydrocarbon solvents having different surface tensions shown below were dropped on a sample (dust collection filter), and it was visually determined whether or not each solvent permeates (wetability). And among each solvent, it was a solvent which does not osmose | permeate a sample (dust collection filter), and the largest number was made into the evaluation result of oil repellency. That is, the larger the number, the higher the oil repellency. The evaluation criteria for oil repellency are as follows.

0: None (Failes Kaydol)
1: Kaydol
2:65:35 Kaydol: hexadecane (volume ratio)
3: n-hexadecane
4: n-tetradecane
5: n-dodecane
6: n-decane
7: n-octane
8: n-heptane
<Transmissivity>
The transmittance was determined according to JIS B 9927 (1999). Specifically, a particle collection rate measuring device equipped with a dust collection filter for each sample was prepared. Next, air containing test particles was passed through the dust collection filter, and the number of test particles that passed through the upstream side and the downstream side of the dust collection filter was measured. As test particles, DOP (dioctyl phthalate, Class 4 Class 4 Petroleum) was used. The particle size of the test particles was 0.3 μm. And the transmittance | permeability P (%) was computed using the following formula | equation (1).

P = (C ₂ / C ₁ ) × 100 (1)
P: Transmittance (%)
C ₁ : Measurement value of particles for test on the upstream side of the dust collection filter (pieces / L)
C ₂ : Measurement value of test particles on the downstream side of the dust collection filter (pieces / L)
<Zeta potential>
Using a zeta potential measuring device (manufactured by Otsuka Electronics Co., Ltd., zeta potential / particle size measuring system: ELSZ), the zeta potential on the surface of the dust collecting filter of each sample was measured.

<Ventilation resistance>
A dust collection filter of each sample (excluding sample 4) was attached to a dust collector having the same configuration as that of Embodiment 1, and dust collection was performed for one week. Next, mechanical dusting was performed on the dust collecting filter to which the fumes adhered. Next, air was passed through the dust collection filter after the dust was removed, and the pressure difference ΔP (Pa) between the upstream side and the downstream side of the dust collection filter was measured. And ventilation resistance R (Pa * s / m) was computed using the following formula | equation (2).

R = ΔP / (Q / A) (2)
R: Ventilation resistance (Pa · s / m)
ΔP: Pressure difference (Pa)
Q: Air flow rate (m ³ / s)
A: Sample area (area of air passage surface) (m ² )
<SEM observation>
A dust collection filter of each sample (excluding sample 4) was attached to a dust collector having the same configuration as that of Embodiment 1, and dust collection was performed for one week. Next, mechanical dusting was performed on the dust collecting filter to which the fumes adhered. Then, the surface of the dust collection filter after the removal was observed with a scanning electron microscope (SEM, manufactured by JEOL Ltd., electronic probe microanalyzer: JXA-8600).

<X-ray CT analysis>
A dust collection filter for each sample (only sample 1 and sample 7) was attached to a dust collector having the same configuration as that of the first embodiment, and dust collection was performed for one week. Next, the dust collecting filter to which the fumes adhered was analyzed by X-ray CT (manufactured by Shimadzu Corporation, microfocus X-ray CT apparatus: SMX-160LT).

Table 1 shows the result of the characteristic evaluation of each sample.

As shown in the table, Sample 1, Sample 3 and Sample 4 which are comparative examples had an oil repellency of less than grade 6 and a transmittance of less than 70%. In particular, since the PTFE membrane with a very fine mesh was laminated on the surface of the dust collecting filter, the transmittance of Sample 3 was very low compared to other samples. Samples 2 and 5, which are comparative examples, had an oil repellency of grade 6 or higher, but had a transmittance of less than 70%. Samples 1 to 5 had a zeta potential of less than −10 mV.

On the other hand, Sample 6 and Sample 7, which are examples of the present invention, had oil repellency of grade 6 or higher and transmittance of 70% or higher. Samples 6 and 7 had a zeta potential of −10 mV or higher.

In addition, as shown in the table, Sample 6 and Sample 7 which are examples of the present invention have lower values of ventilation resistance than Samples 1 to 3 and Sample 5 which are comparative examples. In addition, when compared with the ventilation resistance before dust collection (sample 1 and sample 7 are 1.33 kPa · s / m, sample 6 is 0.91 kPa · s / m), In Sample 7, an increase in the ventilation resistance is suppressed as compared with Sample 1 which is a comparative example. In this experimental example, the airflow resistance of the sample 4 is not obtained, but the results are the same as those of the other comparative examples (samples 1 to 3 and sample 5).

For this reason, it is considered that Sample 1, Sample 2, and Sample 5 are clogged by fume because fume enters inside from the surface of the dust collection filter and is collected. Sample 3 is considered to be clogged with fume in the PTFE membrane laminated on the surface of the dust collection filter. On the other hand, in Sample 6 and Sample 7, since the fumes are collected at a position close to the surface of the dust collection filter, the attached fumes can be easily removed from the dust collection filter, and clogging by the fumes is suppressed. Conceivable.

Next, SEM photographs of each sample are shown in FIGS.
5 to 10 are SEM photographs of Sample 1, Sample 2, Sample 3, Sample 5, Sample 6, and Sample 7, respectively. Only the SEM photograph of sample 5 (FIG. 7) has a magnification of 100 times, and the SEM photographs of other samples have a magnification of 40 times.

As shown in FIGS. 5, 6, and 8, the sample 1, sample 2, and sample 5, which are comparative examples, have fumes remaining in the gaps between the fibers of the dust collection filter after being removed, and clogging due to the fumes has occurred. It was happening. Further, as shown in FIG. 7, in the sample 3 as a comparative example, the fumes remained adhered to the PTFE membrane laminated on the surface of the dust collecting filter, and the fume was clogged in the PTFE membrane.

On the other hand, as shown in FIGS. 9 and 10, the sample 6 and the sample 7 according to the embodiment of the present invention have almost no fumes remaining in the gaps between the fibers of the dust collection filter after being removed, and are clogged by the fumes. Was suppressed.

Next, X-ray CT analysis results of Sample 1 and Sample 7 are shown in FIGS. Air containing fume flows from the upper side to the lower side in the figure.
As shown in FIG. 11, it can be seen that the sample 1 as a comparative example has fume F entering the inside (from the bottom of the surface S1 in the figure) of the dust collection filter S1 and being collected. The result is the same as the schematic diagram shown in FIG.

On the other hand, as shown in FIG. 12, the sample 7 which is an embodiment of the present invention has an extremely large amount of fumes F collected inside the dust collection surface S7 from the inside (the lower side of the surface S7 in the figure). Very few. The result is the same as the schematic diagram shown in FIG. Therefore, the attached fume F can be easily removed from the dust collection filter.

From the above results, it was found that the dust collecting filter of the present invention has an oil repellency of 6 grade or higher and a transmittance of 70% or higher, so that the attached fume can be easily removed. Further, it was found that the zeta potential is preferably −10 mV or more in the dust collection filter of the present invention.

(Other embodiments)
The present invention is not limited to the above-described embodiments and experimental examples, and it goes without saying that the present invention can be implemented in various modes without departing from the present invention.

(1) Although the spunbonded nonwoven fabric is used as the material (filter material) constituting the dust collection filter in the above-described embodiment and the like, other known filter materials may be used.
(2) In the above-described embodiment, the shape of the dust collection filter is a pleated shape, but other shapes (for example, a bug shape) may be used.

(3) In the above-described embodiment and the like, an impregnation method for impregnating an oil repellent was used as an oil repellent method for the dust collection filter. However, other known processing methods (for example, spray processing method, CVD, etc.) A processing method or the like) may be used.

Claims

A dust collection filter for collecting fume,
The dust collection filter is composed of fibers having an oil-repellent coating layer formed on the surface, oil-repellency according to AATCC Test Method 118 is grade 6 or higher, and transmittance according to JIS B 9927 (particle size of test particles). A dust collecting filter having a diameter of 0.3 μm) of 70% or more.
The dust collection filter according to claim 1, wherein the dust collection filter has a zeta potential of -10 mV or more.
A dust collection filter for collecting fume, which is composed of a fiber having an oil-repellent coating layer formed on its surface, has an oil repellency according to AATCC Test Method 118 of 6 or higher, and is according to JIS B 9927 A dust collecting device comprising a dust collecting filter having a transmittance (particle diameter of test particles 0.3 μm) of 70% or more.
The dust collection device according to claim 3, wherein the dust collection filter has a zeta potential of -10 mV or more.