JP2856486B2 - Honeycomb type electret filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used for collecting fine dust mixed in a gas and separating it from the gas for the purpose of air purification, dust collection, dust removal, etc. The electret filter to be used.

[Conventional technology]

In a gas filter that filters and separates fine powder contained in a gas such as the atmosphere, in a conventional technique, a filter material made of synthetic fiber, natural fiber, or glass fiber is bent into a flat shape or a pleated shape to form a filter material. A so-called medium-performance filter is used, which is housed in a container frame so that the outer peripheral portion can maintain airtightness.

[Problems to be solved by the invention]

The collection mechanism of these filters allows fine air containing fine dust to pass through the filter media in the vertical direction, thereby filtering fine dust using mechanical functions such as inertia, diffusion, gravity, and blocking. , To collect. However, the collection of particles is highly dependent on the gap between the fibers, that is, the mesh. Naturally, it is difficult to collect fine particles smaller than the mesh between the fibers.

Therefore, in order to collect fine particles, it is necessary to reduce the mesh between the fibers by reducing the fiber diameter, increasing the fiber filling amount, or increasing the fiber density by treatment with a hot roll or the like.

The filter thus produced naturally has a high airflow resistance, and when fine particles in the gas are collected, the resistance further increases, and the load on the suction fan increases. It has to be expensive. In addition, the life of the filter is short, and the management cost for replacing the filter is high.

A pleated method may be considered as a method of reducing the ventilation resistance. However, as long as a trapping mechanism that allows air to pass through the filter medium in the vertical direction is used, there is a limit and the effect is insufficient.

As described above, it was difficult to collect fine particles and to form a filter having extremely low airflow resistance.

[Means for solving the problem]

In order to solve this problem, the present invention intends to solve the problem by using an electret filter medium as a honeycomb structure.

That is, the honeycomb type electret filter of the present invention continuously folds the first sheet made of electretized nonwoven fabric or woven fabric, forms folds on the entire surface of the first sheet to create a large number of continuous voids, The electret sheet is overlapped on a flat second sheet made of electretized nonwoven fabric or woven fabric, and the tips of the folds are fused or adhered to the second sheet surface, and the obtained units are further stacked in multiple layers. A honeycomb structure, wherein two or more different honeycomb structures are formed by changing any one or all of the size, shape, and porosity of the folds formed by the first sheet, and forming them. The filter is characterized by being alternately or irregularly arranged in the air passage direction of the filter, combined, and connected by fusion or adhesion.

Further, the honeycomb type electret filter of the present invention continuously folds a first sheet made of electretized nonwoven fabric or woven fabric, forms folds on the entire surface of the first sheet to form a large number of continuous voids, The electret sheet is overlapped with a flat second sheet made of electretized nonwoven fabric or woven fabric, and the tip of the fold is placed in the second sheet.
A honeycomb structure formed by fusing or adhering to a sheet surface and further stacking the obtained units in multiple stages,
When two or more honeycomb structures having the same size, shape, and porosity of the folds formed by the sheet are formed, and the honeycomb structures are aligned in the air passage direction of the filter, the honeycomb pitch is shifted, and It is characterized by being connected by attachment or adhesion.

[Action]

The greatest feature of the present invention is that it has a honeycomb structure, and the first sheet and the second sheet constituting the honeycomb structure are non-woven fabrics or woven fabrics made into electrets.

Therefore, since the air passing through the filter not only passes through the continuous gap but also passes through each sheet itself, dust in the air constitutes not only the surface of each electretized sheet but also the sheet. Captured between the fibers, the dust collection efficiency increases.

More specifically, the conventional filter structure is flat or pleated, and allows dirty air to pass perpendicularly through the filter medium, and filters and collects fine dust by the mechanical function described above.

On the other hand, the present invention has a structure in which an electret filter medium made of a nonwoven fabric or a woven fabric has a honeycomb structure, and adsorbs and collects fine particles on the surface of a fiber by a horizontal method in which dirty air passes in parallel with the filter medium. .

As is well known, the electret collection principle is based on the mechanical collection function and the action of Coulomb force and induced force, that is, the particles are adsorbed and collected on the fibers of the filter medium by the particle suction force of static electricity, which is generally called static electricity. There are two functions. By using the function of adsorbing particles by static electricity, a high-performance filter can be obtained even in a horizontal blowing system having a honeycomb structure in which the airflow resistance can be reduced. The air passing at the same time passes between the constituent fibers of the sheet made of non-woven fabric or woven fabric, and at that time, dust is adsorbed and collected on the surface of the fiber by the particle suction force,
And it is trapped between the fibers by the mechanical trapping function.

The greatest advantage of the honeycomb structure in terms of filter performance is that the porosity through which air passes can be large, and the airflow resistance can be extremely reduced due to horizontal ventilation.

In addition, since the life of the electret is almost proportional to the fiber surface area of the filter medium, the life of the honeycomb structure is improved by obtaining a surface area several times larger than that of a conventional flat type or pleated type filter.

Further, different honeycomb structures are formed on the first sheet by changing the size, shape, and porosity of the folds, and are formed in the thickness direction of the filter (the air passing direction).
Even if the electret filters are laminated alternately or irregularly, and two or more layers are laminated by fusion or adhesion, or the same honeycomb structure, when they are combined in the thickness direction of the filter (air passing direction), An electret filter laminated in two or more layers by fusing or bonding with shifted pitches is more excellent as described below.

With a single-layer honeycomb filter made with the same honeycomb pattern, the air flow tends to be laminar, and the fine particles in the dirty air are mainly adsorbed on the surface of the fiber layer of the filter medium, making effective use of the entire filter medium collected. Hateful.

In contrast, an electret filter having a composite honeycomb structure in which filters having different patterns are stacked in the thickness direction (air passing direction) and a composite having the same honeycomb structure in which the pitches of the honeycombs are shifted are stacked in the thickness direction. In the case of a honeycomb filter, the air flow becomes turbulent due to the blocking effect (baffle plate effect), and the fine particles in the air penetrate deep into the fiber layer of the filter medium and are adsorbed and collected by the filter medium fibers, making effective use of the entire filter medium. it can.
Therefore, the collection efficiency is remarkably improved, and the life is also improved.

The filter medium used in the present invention is electretized by various known methods such as a heat electret method, an electro-electret method, a magne electret method, and a mechano-electret method.

In this electretization treatment, there are two types of application of static electricity in the fiber stage and in the form of a sheet. In the case of the application in the form of a sheet, a single electric charge is applied to the surface of the sheet, but it is applied at the center. , Which has little charge density and low trapping performance, and lacks long-term stability of charge.

On the other hand, the application of static electricity at the fiber stage has a high charge density because it is applied to each fiber one by one, and the charge is distributed over the entire fiber layer.
A long-life electret filter is obtained.

When a nonwoven fabric or a woven fabric of such electretized fibers is used as a flat or pleated filter, a more excellent collection performance is obtained, but a sufficiently small airflow resistance is obtained as described above. Absent.

The nonwoven fabric or woven fabric used in the present invention may be, as a thermoplastic resin, a polyolefin such as polyethylene, polypropylene, or poly-4-methyl-1pentene; or an ethylene-vinyl compound copolymer such as an ethylene-vinyl chloride copolymer. Styrene resins; polyvinyl chloride resins such as polyvinyl chloride and polyvinylidene chloride; polyacrylic esters; polyamides; polyester fibers such as polyethylene terephthalate alone or mixed to form fibers.

And the collection efficiency, pressure loss, by selecting and combining the fiber diameter and fiber density of the nonwoven fabric or woven fabric,
Various properties such as life can be controlled.

As the nonwoven fabric used in the present invention, those manufactured by a dry method such as a card method, a spun bond method, a split fiber method, and a melt blow method and a wet method can be used.

〔Example〕

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

The electretized filter medium used in the present example was manufactured for the purpose of laminating the honeycomb structure in the thickness direction.

FIG. 1 shows a specific example of a honeycomb structure. In FIG. 1, a first sheet 1 made of a nonwoven fabric is continuously folded, and saw-shaped folds 2 are formed on the entire surface of the first sheet 1 to form a large number of sheets. A continuous gap 3 is formed, and this creased electret sheet is superimposed on the flat second sheet 4 from the electretized nonwoven fabric, and the tip of the crease 2 is adhered to the surface of the second sheet 4. It is configured to further overlap.

The used non-woven fabric is made of polypropylene resin as raw material,
The wave obtained by the dry card method is bonded together with a net by an embossing machine. The role of the net is to facilitate honeycomb processing. The constituent fibers have a rectangular shape obtained by disintegrating a stretched film, and all the constituent fibers are charged by the electret method. The basic data of the obtained nonwoven fabric are as shown in Table 1 below.

Here, the collection efficiency was calculated as follows.

A schematic diagram of the device is shown in FIG. NaCl particles (particle size = 0.3μ) are supplied to the chamber 12 by clean air from an aerosol generator 11 manufactured by Nippon Chemical Industry Co., Ltd.
10 ⁶ pieces / CF), the blower 13 is operated, and the NaCl particle concentration upstream and downstream of the electret filter 14 at a constant speed (V = 50 cm / sec) (C _IN , C
_out ) with Rion's particle counter KC-01B (1
It measured by 5) and calculated by the following formula.

The pressure loss ΔP is V = 50 cm / sec in the above apparatus.
The pressure loss before and after the filter 14 was measured by an electronic differential pressure gauge 17 manufactured by Yamatake Honeywell.

In FIG. 7, reference numeral 16 denotes a clean air filter, reference numeral 18 denotes an air flow adjusting valve, and reference numeral 19 denotes an anemometer.

FIG. 2 shows a specific example of the actual use of the electret filter, which is a filter unit in which all the honeycomb structures 5 having the same honeycomb shape are inserted into a box frame 6 having front and rear open sides. .

FIG. 3 shows a single-layer honeycomb type electret filter structure having the same honeycomb shape and having a fold length of 4 mm.

FIG. 4 shows two layers of a honeycomb structure 7 (having a fold length of 7 mm) having a large honeycomb pattern and a honeycomb structure 8 having a small honeycomb pattern (having a fold length of 4 mm) in the rear, that is, in the air passing direction. 2 shows a composite honeycomb type electret filter structure (Example 2) bonded to the above.

FIG. 5 shows a composite honeycomb type electret filter structure in which two layers of the same honeycomb pattern structures 9 and 10 of Example 1 are combined and bonded with shifted pleat pitches (Example 3).

ΔP and E were measured by flowing air to be purified before and after the box frame 6 and passing through the continuous gap 3.

The filter according to the present invention is a flat type electret nonwoven fabric filter (Comparative Examples A and B) and a pleated type filter using a polyolefin nonwoven fabric and a glass fiber filter material obtained by a conventional dry method (Comparative Examples C and D in FIG. 6). ) Are as shown in Table 2. The reference example is a case where the glass fiber filter has the same structure as that of the first embodiment.

[Effects of the Invention] As described above, according to the honeycomb type electret filter of the present invention, a honeycomb type electret filter is formed by arranging and combining the honeycomb structures having different honeycomb patterns in the air passing direction and connecting and combining them. In addition, the flow of the air passing through the electret filter becomes turbulent, so that the dust collection efficiency and the life can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a specific example of a honeycomb structure, FIG. 2 is a perspective view showing an embodiment, FIG. 3 is a single-layer honeycomb type electret filter having the same honeycomb shape (Example 1),
FIG. 4 shows a composite honeycomb type electret filter having a structure having a different honeycomb pattern (Example 2), FIG. 5 shows a composite electret filter having the same honeycomb pattern shifted in pitch (Example 3), and FIG. 6 shows a pleated type. FIG. 7 is a schematic diagram of a filter performance evaluation device. DESCRIPTION OF SYMBOLS 1 ... 1st sheet, 2 ... fold 3 ... Continuous gap, 4 ... 2nd sheet

Claims (2)

(57) [Claims] 1. A first sheet made of an electretized nonwoven fabric or a woven fabric is continuously folded, and a plurality of continuous voids are formed by forming folds on the entire surface of the first sheet. A honeycomb structure comprising a flat second sheet made of a nonwoven fabric or a woven fabric, and a tip of a fold fused or adhered to the second sheet surface, and the obtained units are further stacked in multiple stages. hand,
The size, shape, and porosity of the folds formed in the first sheet are changed to form one or all of two or more different honeycomb structures, and they are alternately formed in the air passage direction of the filter or A honeycomb type electret filter characterized by being randomly arranged, combined, fused or bonded, and connected. 2. The electret-formed nonwoven fabric or woven fabric is continuously folded, and folds are formed on the entire surface of the first sheet to form a large number of continuous voids. A honeycomb structure comprising a flat second sheet made of a nonwoven fabric or a woven fabric, and a tip of a fold fused or adhered to the second sheet surface, and the obtained units are further stacked in multiple stages. hand,
When the two or more honeycomb structures having the same size, shape, and porosity of the folds formed by the first sheet are formed, and the honeycomb structures are arranged side by side in the air passage direction of the filter, the honeycomb pitch is shifted. And a honeycomb type electret filter connected by fusion or adhesion.