JPH0377302B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing electret fibers made of insulating polymeric materials. BACKGROUND ART Special dust removal filters have been developed in the electronics industry, medical field, etc. in order to create clean rooms that keep the concentration of dust in the air extremely low. This is made by electrically charging the fibers that make up the filter, for example,
-Electrified fiber made by splitting a film as described in Publication No. 47299 (Electrified fiber)
For example, there is a method for producing the same. However, even with this filter, charging could not be guaranteed for a long period of time, and there was still a problem with the life of the filter. The present invention was discovered as a result of intensive studies to eliminate the drawbacks associated with conventional electrified fibers. That is, the present invention is a method for producing electret fibers, which comprises melt-spinning an insulating polymeric material, drawing the resulting undrawn yarn, and subjecting it to charging treatment using a corona element. The insulating polymer material used in the present invention is not particularly limited, but polypropylene, polyethylene, etc. are preferred. This polymeric material is then melt spun and it is necessary to charge the undrawn yarn with a corona element while drawing it. By performing this operation, stable and high dust removal efficiency can be achieved over a long period of time. It is surmised that this is because the charge is trapped inside the material by applying charge injection using a corona element at the same time as stretching, thereby creating a highly polarized state. The method of the present invention will be explained below with reference to the drawings. FIG. 1 illustrates a means for producing an electret fiber according to the present invention. The undrawn yarn 1 passes through a guide 2 and is sent out at a constant speed by a feed roller 4. The thread coming out from feed roller 4 is 50
It slides on a hot plate 5 maintained at ~150°C, preferably 100~130°C, and is pulled by a draw roller 8 at a faster speed than the feed roller 4. At this time, by applying a high voltage of 5 to 20 KV on the hot plate 5 through the corona electrode 6,
The undrawn yarn 1 receives charge injection while being drawn.
The yarn sent out from the draw roller 8 passes through the guide 3, the air jet 9, and is blown onto the suction box 10 which is passed through the net. Thereafter, the nonwoven fabric thus produced is subjected to, for example, a needle punching process to form a nonwoven fabric dust removal filter. Incidentally, the above-mentioned corona charge application can be carried out using a conventional method and apparatus. In addition, there is no particular restriction on the stretching ratio in stretching the undrawn yarn;
1.5 to 10 times is preferable. Further, there is no restriction on the denier of the spun fibers. The electrified fibers produced in this manner maintain a semi-permanently charged state and can efficiently collect dust in the air by Coulomb force or induced force. The target dust is cigarette smoke particles, pollen, sand dust, etc. with a particle size of about 0.1 to 1 μm, and is particularly suitable for cleaning the air in living rooms and automobiles. By using this electretted fiber, a dust removal filter that can be stably produced over a long period of time and guarantee high dust removal efficiency can be advantageously produced. 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 Polypropylene was used as the insulating polymer material. This was melt-spun in a conventional manner to form an undrawn yarn of 18 denier, which was subjected to corona charge treatment while sliding on a hot plate at 115° C. while applying a draw ratio of 3 times. The applied voltage during charge processing is
It was 13KV. A filter was produced using the electretted fiber thus produced. The dust removal performance and ventilation performance of this filter were measured and shown in Table 1. For comparison, we prepared a filter that was made only by stretching without charge injection using a corona element.
Its performance was measured. The results are also listed in Table 1.

【table】

[Table] Example 2 An electret fiber was produced under the same conditions as in Example 1 except that the stretching ratio was increased to 3.5 times. The results are shown in Table 2.

[Table] Example 3 9 denier undrawn polypropylene yarn at 115℃
While sliding the film onto a hot plate, a corona charge treatment was performed while applying a stretching ratio of 3.5 times. The applied voltage is
It was heated at 14KV. The properties of the obtained electretted fibers were as shown in Table 3.

[Table] Comparative Example 4 A filter was prepared in which the corona charge treatment was not performed during the stretching operation in Example 2, and the filter was once prepared into a nonwoven fabric and then subjected to the charge treatment, and its performance was measured. The dust removal efficiency was a low 50.2%. It was hot.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing a means for producing an electret fiber according to the present invention.

Claims (1)

[Claims] 1. A method for producing electret fibers, which comprises subjecting an undrawn yarn obtained by melt-spinning an insulating polymeric substance to electrical charging using a corona element while drawing the undrawn yarn.