JPH0363406B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to an air filtration filter that collects dust and the like by electrostatic action. (Prior art) Conventionally, this type of filter has been made by impregnating or coating a nonwoven fabric made of wool or a blend of wool and synthetic fibers with a phenol-based resin, and then applying mechanical processes such as tanning, folding, beating, and crushing. It is known that static electricity is generated through subsequent processing, and the material is naturally cooled to become an electret. When air containing dust, etc. is passed through a filter configured in this way, the dust is attracted by its electrostatic action,
Collect. Note that some of the synthetic fibers used have polygonal or star-shaped cross-sections to increase the surface area and increase the amount of charge. These conventionally used fibers usually have a RH40
% or less, it can have a considerable amount of charge. However, when dust or the like comes into contact with this, electric discharge occurs instantaneously, and as a result, the amount of charge decreases rapidly. That is, the life as a filter was short and the dust collection capacity was relatively small. (Object of the Invention) The present invention has been made in order to eliminate the drawbacks of the above-mentioned conventional examples, and provides an electrostatic air filtration filter that has little deterioration over time and has a large dust collection capacity. (Structure of the Invention) In order to achieve the above object, synthetic fibers having a hollow structure are mixed into the fibers constituting the nonwoven fabric. That is, the main component is wool fiber with a fiber diameter of about 17 to 20 μm, and it is also made of polyester, polyamide, vinylon, nylon, polypropylene (PP), styrene, polyethylene (PE), etc., which have high insulation resistance.
Fibers with a hollow structure and low hygroscopicity are blended and processed into a nonwoven fabric. Static electricity is generated by impregnating or coating this with a phenol-based resin or the like, and then subjecting it to secondary mechanical processing such as tanning, bending, beating, and crushing. With hollow fibers, most of the static electricity generated is effectively retained within the hollow structure.
The state is close to permanent electrification.
Further, when a mechanical impact is applied from the outside to the fibers having the hollow structure, distortion is easily caused, and therefore charging polarization can be effectively caused. For these reasons, compared to a filter with a conventional configuration, the amount of charge can be increased by about 10 times, and the change over time is extremely small. (Example) Examples will be described in detail below. 60% wool Polyester (Tetoron) hollow fibers, triangular cross section, 2D (denier) 40% Wool 60% Polyester (Tetoron) hollow fibers, cross section star shape, 4D, 40% Wool 60% as above and as above and polyester hollow fibers at a ratio of 40% and processed into a felt-like nonwoven fabric, which was subjected to resin processing and mechanical secondary processing by known methods to produce a filter. Separately, for comparison, we prepared a conventional product made of 100% wool nonwoven fabric that was treated in the same way. For the present invention product and conventional product, JIS
A test was conducted in accordance with -T-8151, and the results shown in the table below were obtained.

[Table] As is clear from the table, the product of the present invention has an amount of charge per gram weight that is approximately one order of magnitude larger than that of the conventional product, and is also very superior in terms of collection efficiency. Next, the functions and effects of the present invention will be explained.
FIG. 1 shows a charging model for hollow fibers, in which numeral 1 represents a fiber having a hollow portion 2, and numeral 3 represents a resin such as a phenolic resin attached to the surface of the fiber 1. Generally, when a resin is attached to fibers and subjected to mechanical secondary processing such as crushing, a portion of the resin is peeled off, the resin becomes negatively charged, and the fibers become positively charged. This charged static electricity is usually gradually discharged by moisture in the air, free electrons, etc., and the amount of charge decreases over time. On the other hand, in the case of the hollow fibers used in the present invention, the negative electricity on the surface of the fiber 1 is transferred to the resin 3 due to strong compression, deformation, impact, friction, etc. caused by mechanical secondary processing, and the fiber surface Since the resin 3 is peeled off and dispersed from the hollow fiber 1, a strong electrical imbalance occurs between the inner space surface of the hollow fiber 1 and the fiber surface, and a considerable amount of static electricity is generated at this moment. In this way, since the internal space surface of the hollow fiber 1 is also polarized, it becomes less susceptible to the effects of collisions of external free electrons, etc., and static electricity can be maintained for a long period of time. FIG. 2 shows the change over time in the amount of charge (Q/g) per gram of the filter when stored in a sealed state. The initial charge amount is approximately 10 times greater than that of conventional products (100% wool), and the decrease in charge amount over time is also extremely small. FIG. 3 shows the relationship between the collection efficiency and ventilation resistance with respect to the amount of accumulated dust. It can be seen that the product of the present invention has a smaller increase in ventilation resistance than the conventional product, and is therefore a filter that is less likely to become clogged. In addition, there is very little decrease in collection efficiency. Further, FIG. 4 shows the change over time in the collection efficiency when stored in a sealed state. Conventional product
In contrast, the product of the present invention maintains a performance of 99.95% or more even after more than one year. Conventional electrostatic collection type filters had the problem of extremely low collection efficiency at high linear speeds, but as is clear from the table, the product of the present invention
It shows extremely high collection efficiency even at linear speeds of about sec. Although not shown in the examples, good results were obtained by using synthetic fibers with irregular cross sections instead of wool and blending them with hollow synthetic fibers. (Effects of the Invention) As explained above, according to the present invention, by including synthetic fibers with a hollow structure in the fibers constituting the nonwoven fabric, it is possible to greatly increase the amount of electrostatic charge, and the amount of charge is extremely high, and it is extremely resistant to deterioration over time. A small air filtration filter can be provided. Further, the filter having this configuration can be sufficiently applied to high linear velocity filtration. Furthermore, since the amount of electrostatic charge is large, it is possible to obtain dust collection efficiency equal to or higher than that of conventional products even though the fiber density is low and with a basis weight of about half that of conventional products. Capture capacity can be significantly increased.

[Brief explanation of drawings]

Figure 1 is a diagram showing a charging model for hollow fibers, Figure 2 is a diagram showing changes in the amount of charge over time, and Figure 3 is a diagram showing a charging model for hollow fibers.
The figure shows the relationship between the collection efficiency and ventilation resistance with respect to the amount of accumulated dust, and FIG. 4 is a diagram showing the change in the collection efficiency over time. 1...Hollow fiber, 2...Hollow part, 3...Resin.

Claims (1)

[Scope of Claims] 1. An electrostatic air filtration filter made by applying resin processing and mechanical secondary processing to an electret nonwoven fabric, characterized in that the fibers constituting the nonwoven fabric include synthetic fibers with a hollow structure. Electrostatic air filtration filter. 2. The electrostatic air filtration filter according to claim 1, wherein the fibers constituting the nonwoven fabric are made of hollow synthetic fibers and wool. 3. The electrostatic air filtration filter according to claim 1, wherein the fibers constituting the nonwoven fabric are composed of synthetic fibers having a hollow structure and synthetic fibers having an irregular cross section.