JPH0481847B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a manufacturing method for obtaining an excellent electrifying material by subjecting an insulating polymeric substance to corona charging treatment. In the case of film-like materials, electrified polymer substances are used for elements of various electrostatic acoustic transducers such as microphones, headphones, and speakers. A fibrous material made of an electrified polymer substance is used as a dust removal filter that uses its electrostatic force to remove dust floating in a gas. Such dust removal filters are widely used in air conditioning systems in the electronics industry, medical field, etc. to realize clean rooms that keep the concentration of dust in the air extremely low. Conventionally, this system uses a pre-filter mainly made of a polymer material with low ventilation resistance to target dust with large particle diameters, and a HEPA filter mainly made of glass fiber with a thin fiber diameter to target dust of submicron size or less. It is being used. Improving the dust removal performance of a prefilter is effective in improving the performance of the entire system, so filters with high dust removal performance by charging fibers are suitable materials for prefilters in air conditioning systems that aim for high cleanliness. can. Dust removal filters made of electrified fiber materials in the form of sheets, threads, or splits have lower ventilation resistance and can be operated with lower pressure loss than non-electrified dust removal filters with the same removal performance. Since it exhibits high dust removal performance against micron particles, it can be applied to devices aimed at removing tobacco smoke, such as the main filter of indoor air purifiers. It can also be used as a material for dust masks for work in industries that generate fume, dust, and mist, and as a material for masks for preventing pollen allergies. For example, it is shown in Japanese Patent Publication No. 47299/1987 that a dust removal filter made of such a fiber material can have a certain degree of dust removal performance by charging the fibers themselves that make up the filter. . In this method, a non-polar polymeric substance is once formed into a film, which is stretched and charged using a corona element, and then the charged film is made into a fibrillated yarn using a needle roll. Although this method is used to form a filter, no study has been made in this method from the perspective of improving the electrification properties of the nonpolar polymer material.
The method disclosed in Japanese Patent Application Laid-Open No. 54-133680 involves processing a nonwoven fabric made of polypropylene fibers and rayon fibers with resin, and then mechanically applying bending and shearing force, a so-called tanning process, to reduce the surface layer of the fibers. However, since no positive charging means such as a corona element is used, the resulting filter has the disadvantage that it cannot have a sufficiently high level of dust removal performance. The object of the present invention is to provide an electret suitable for filter material that is highly charged, has high dust removal performance with low pressure loss, and maintains stable dust removal performance by preserving the charge for a long period of time. The object of the present invention is to provide a method for producing a chemically modified material. As a result of detailed research into materials with high long-lasting electrification and electrification techniques, the present inventors discovered that an electrified material suitable for filters with high dust removal performance could be obtained. reached. The gist is to blend a fatty acid metal salt into an insulating polymer material and melt-spun it, and to perform corona charging treatment while drawing the obtained undrawn yarn and/or while maintaining the undrawn yarn in a tension state after drawing. This is a method for producing an electret material. First, the insulating polymer material used in the present invention has a large volume resistivity, preferably 10 ¹⁵ Ω・
Any spinnable material having a diameter of cm or more may be used, such as polypropylene, polyethylene, polyester, polyamide, polyvinyl chloride, polymethyl methacrylate, and the like. In addition, the fatty acid metal salt added to this is saturated fatty acid (CH ₃ (CH ₂ )
nCOOH, where n is preferably 4 or more), or metal salts of unsaturated fatty acids, such as salts of aluminum, magnesium, zinc, etc., such as lauric acid, palmitic acid, stearic acid, and oleic acid. In the present invention, the blending ratio of such fatty acid metal salts is 100 ppm or more, preferably 300 ppm or more based on metals.
It is within the range of 2000ppm or less. The electret fiber according to the present invention is produced as follows. That is, a fatty acid metal salt is blended into this insulating polymer material and melt-spun, and the resulting undrawn yarn is drawn while sliding on a hot plate, and/or after the undrawn yarn is once drawn. It is necessary to charge it with the corona element while sliding it over the metal plate while keeping it under tension again. The material subjected to such treatment is made into a nonwoven fabric using an air jet, or is wound up as a thread to form an electrified fiber material. Hereinafter, the method of the present invention will be explained in more detail with reference to the drawings. FIG. 1 illustrates the manufacturing process of an electrified material according to the present invention. The undrawn yarn 1 passes through a guide 2 and is fed out by a feed roller 3 at a constant speed. feed roller 3
The yarn coming out of the
, it is stretched at a faster speed than the feed roller 3 , and is kept under tension by the draw roller 7 while sliding on the grounded metal plate 6 . At this time, it is charged by the corona electrode 9 and the height is increased. An electrified material 8 which is electrically charged is obtained. The tension state suitable for charging between the draw rollers 5 and 7 changes depending on the stretching conditions between the rollers 3 and 5, but this is a sufficiently well-stretched condition, that is,
When set to 75-80% or more of the maximum stretching ratio,
The ratio of the peripheral speed of draw roller 7 and the peripheral speed of 5 (peripheral speed of draw roller 7) / (weekly speed of draw roller 5)
This can be ensured by setting it to 0.95 or more, preferably 1.0 to 1.3. In addition, in FIG. 1, the hot plate 4 is grounded,
A corona electrode 9' is provided on top of this, and while stretching,
By charging, a highly charged electrified material can be obtained without using the metal plate 6 or the draw roller 7. Moreover, although the undrawn yarn 1 is wound up into a cheese shape, it is also possible to directly introduce it into this drawing apparatus from the melt spinning process without winding it up into a cheese shape. Incidentally, the above-mentioned application of corona charge can be performed using a conventional method and apparatus. Further, the stretching ratio in stretching the undrawn yarn is not particularly limited, but is preferably 1.5 to 10 times. Furthermore, the fibers (denier) of the spun fibers can range from fine denier to thick denier and are not subject to any restrictions. The electrified material produced in this way is
A stable charged state is maintained over a long period of time, and a filter made using this can efficiently collect dust in the air using Coulomb force or induced force. This excellent effect in electrification is due to the synergistic effect of mechanoelectret, which is created by blending fatty acid metal salts into insulating polymers and subjecting them to friction stretching, and the so-called electroelectret effect, which is caused by charging by corona elements. This was achieved through the efforts of Examples of the present invention will be described below, but the present invention is not limited in any way by the description of these Examples. Example 1 Using polypropylene as an insulating polymer,
Magnesium stearate (C ₁₇ C ₃₅ COO) ₂ Mg was selected as the fatty acid metal salt to be blended, and these were blended at a ratio of 500 ppm based on magnesium.
The undrawn yarn was melt-spun to obtain an undrawn yarn, and the undrawn yarn was slidably stretched on a hot plate set at 115°C at a drawing speed of 42 m/min and a draw ratio of 3.0. The yarn was charged by applying −13 KV to the corona electrode to obtain an electret drawn yarn having a single fiber fineness of 6 deniers. Next, the obtained electretted drawn yarn was blown onto the net using an air jet to form a mat having a fabric weight of 200 g/m ² to form a dust removal filter. For comparison, (i) the above formulation without corona charging, (iii) polypropylene without magnesium stearate, spun and stretched under the same conditions as above, and (iii) corona charging. A dust removal filter was prepared for each case. The dust removal efficiency of this was measured and the results are shown in Table 1. The dust removal efficiency is 0.5 of atmospheric dust at a passing speed of 10 cm/sec.
It was determined using the light scattering counting method for ~1.0μ particles.

[Table] The dust removal performance of the dust removal filter made using the electret fiber obtained by the method of the present invention is as follows:
Almost no changes were observed even after 4 months had passed since the filter was manufactured. Example 2 Using polypropylene as the insulating polymer,
Aluminum palmitate (C ₁₅ H ₃₁ COO) ₃ Al was selected as the fatty acid metal salt to be blended, and these were blended at a ratio of 500 ppm based on aluminum.
In the same manner as in Example 1, pine with a basis weight of 200 g/m ² was made to prepare a dust removal filter.

[Table] Almost no change was observed in the dust removal performance of the dust removal filter according to the present invention even after 4 months had passed since the filter was manufactured.

[Brief explanation of the drawing]

FIG. 1 shows a manufacturing process for producing an electrified material according to the present invention. 1... Undrawn yarn, 2... Guide, 3... Feed roller, 4... Hot plate, 5... Draw roller
(1), 6...Metal plate, 7...Draw roller (2), 8
...drawn yarn, 9...corona electrode, 9'...corona electrode, 10...DC high voltage power supply.

Claims (1)

[Claims] 1 Melt-spinning a fatty acid metal salt blended into an insulating polymeric material, and subjecting the obtained undrawn yarn to corona charging treatment while drawing it and/or while maintaining the undrawn yarn in a tensioned state after drawing. Characteristic method for producing electrified materials.