JPH08318114A - Electret filter - Google Patents

Abstract

PURPOSE: To further increase the efficiency to collect the dust suspending in the atmosphere by laminating porous fluororesin films one on another and converting the laminate to an electret. CONSTITUTION: A specified number of porous fluororesin films are laminated one on another, and the film is converted to an electret. A porous fluororesin film consisting of a polytetrafluoroethylene is appropriately used from the standpoint of its resistance to heat and chemicals. Although the thickness, etc., of the film are appropriately set, the thickness is ordinarily controlled to 5-5O0μm, the diameter of the micropore to 0.1-20μm and the porosity to 70-95%. The films can be partially bonded or fused to one another in the shape of point, streak, reticulation, etc. The film laminate is converted to a thermal electret, mechanoelectret, etc., by the respective conversion processes. Alternately, the films converted to an electret can be laminated. Consequently, an electret filter capable of collecting dust with high efficiency and decreased in pressure drop is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an electret filter used for cleaning semiconductor, electronic equipment, chemicals, biochemical substances and the like, and for cleaning the internal atmosphere of electronic equipment.

[0002]

2. Description of the Related Art An electret filter removes dust floating in an atmosphere by utilizing Coulomb force and induction force. As such an electret filter,
For example, it is known that one fluororesin porous film is electretized.

[0003]

By the way, in recent years, it has been increasingly demanded to further enhance the cleaning of the atmosphere for manufacturing the above products and the atmosphere inside the equipment. However, according to the conventional electret filter, the dust collection rate is about 99.985% (the particle size of dust is about 0.1
(When 0.15 μm) is the limit, and such a request cannot be met. Therefore, an object of the present invention is to provide an electretized filter having a higher dust collection rate.

[0004]

Means for Solving the Problems The electret filter according to the present invention is characterized in that a predetermined number of porous fluororesin films are superposed, and these porous fluororesin films are electretized. is there.

The porous film used in the present invention is polytetrafluoroethylene (hereinafter referred to as "PTFE"), tetrafluoroethylene-perfluoroalkylvinylether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene. It is made of fluororesin such as fluoroethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, etc. From the viewpoint of heat resistance and chemical resistance, PTFE is preferable.

The thickness and the like of this porous fluororesin film can be appropriately set, but normally, a thickness of about 5 to 500 μm, a fine pore diameter of about 0.1 to 20 μm, and a porosity of about 70 to 95% are used. To be

In the present invention, a predetermined number of the above porous fluororesin films are superposed. The fluororesin films may be partially adhered or fused in a dot shape, a stripe shape, a mesh shape, or the like.

In the electret filter according to the present invention, a predetermined number of porous fluororesin films are superposed on each other, and the superposed body is then electretized by a thermal electret, an electro electret, a mechano electret, a radio electret, a magnet electret or the like. To apply electret,
Alternatively, it can be obtained by a method of stacking a predetermined number of electretized porous fluororesin films.

The electret filter according to the present invention is formed by stacking a predetermined number of porous fluororesin films in this way, and there was a concern that pressure loss during use would increase, but it is also shown in Examples. As described above, it was confirmed that the inconvenience of increase in pressure loss does not occur.

[0010]

The present invention will be described in more detail with reference to the following examples.

Example: Thickness 17 μm, average fine pore diameter 3 μm, porosity 90%
5 sheets of PTFE porous film are piled up. next,
The superposed porous films were subjected to corona discharge treatment for 10 seconds under a condition of 10 kv / cm to obtain an electret filter.

Dioctyl phthalate particles (particle size 0.1 to 0.15 μm) were added to this electret filter in an amount of 1 × 10.
Wind velocity of ¹⁰ pieces / m ³ (temperature 25 ℃)
When the air collection rate and pressure loss were measured by blowing air at a rate of cm / sec, the collection rate was 99.998% and the pressure loss was 55 m.
It was mAq.

Comparative Example Thickness 85 μm, average fine pore diameter 2 μm, porosity 90%
One of the PTFE porous films of No. 1 is electretized by corona discharge treatment under the same conditions as in the examples. When this electret filter was tested in the same manner as in the example, the collection rate was 99.985% and the pressure loss was 57 mmAq.

[0014]

The present invention is configured as described above,
There are advantages that the collection rate is high and the pressure loss is small.

Claims (1)

[Claims] 1. An electret filter, characterized in that a predetermined number of porous fluororesin films are laminated, and these porous fluororesin films are electretized.