JPH0461109B2 - - 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 filter life. The present invention was discovered as a result of intensive studies to eliminate the drawbacks associated with conventional electrified fibers. That is, in the present invention, an insulating polymer substance is melt-spun, the resulting undrawn yarn is stretched 1.5 times to 10 times, and the drawn yarn is further stretched 1.0 times to 5 times at a temperature of 5°C to 50°C. This is a method for producing electret fibers, the gist of which is to carry out charging treatment using a corona element while stretching the fibers at a specific speed. The insulating polymeric substance used in the present invention is not particularly limited, but preferably includes those having high electrical insulation resistance such as polypropylene and polyethylene. In the present invention, it is necessary to melt-spun this polymeric material, stretch the undrawn yarn, and then charge the drawn yarn using a corona element under tension. By carrying out such an operation, an electretted fiber that is stable for a long period of time can be obtained. This is because the charge is efficiently trapped inside the material by injecting charge with a corona element under tension after stretching, thereby forming 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 plate 5 maintained at ~150°C, preferably 100-130°C, and is pulled by a draw roller 6 at a faster speed than the feed roller 4. The drawn yarn is further drawn on the plate 7 by the draw roller 8, and at the same time, charge is injected from the corona electrode 9 by corona charging treatment. At this time, the plate 7 is maintained at a temperature of 5 to 50 DEG C., preferably 20 to 30 DEG C., and a high voltage of 5 to 20 KV is applied by a corona electrode. Incidentally, a conventional method and apparatus can be employed to apply the above-mentioned corona charge. In the present invention, the plate 7 serves as a ground electrode (earth).
Further, the stretching ratio in the unstretched state is not particularly limited, but it is preferably 1.5 to 10 times on the plate 5 and 1.0 to 5 times on the plate 7. Further, it is desirable that a tension of 0.38/denier or more is always applied to the thread on the plate 7. Further, there is no restriction on the denier of the spun fibers. The electret fiber 3 produced in this way is
It maintains a semi-permanently charged state and can efficiently collect dust in the air using Coulomb force and 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 used to purify the air in living rooms and cars, filters for dust masks, materials for removing dust from furniture, etc. It is particularly suitable for 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. In addition, the dust removal efficiency in the example is based on a passing speed of 10
It was determined using the light scattering counting method for 0.5-1.0 micron particles of atmospheric dust in cm/sec. Example 1 Polypropylene was used as the insulating polymer material. This was melt-spun in a conventional manner to form an 18 denier undrawn yarn, which was then placed on a plate at 115°C.
While sliding the top, apply a 3x stretching ratio, and then
The film was slid on a plate 7 at 30° C. and subjected to corona charging treatment while applying a stretching ratio of 1.05 times. The applied voltage during the charging treatment was 13 KV. A filter was produced using the electretted fiber thus produced. The dust removal performance and ventilation performance of this filter were measured and are 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] Example 2 Example 1 and the stretching ratio was 3.5 times on plate 5,
Electreted fibers were produced under the same conditions except that the size was multiplied by 1.02 on Plate 7. The results are shown in Table 2.

[Table] Example 3 9 denier undrawn polypropylene yarn at 115℃
While sliding it on plate 5 of
Corona charging treatment was performed while applying a stretching ratio of 1.04 times. The applied voltage was 13.5KV. The properties of the obtained electretted fibers were as shown in Table 3.

[Table] Example 4 4.5 denier undrawn polypropylene yarn at 120℃
While sliding it on plate 5 of
Corona charge treatment was performed while applying a stretching ratio of 1.08 times. The applied voltage was 14KV. The properties of the obtained electretted fibers were as shown in Table 4.

[Table] Comparative Example 5 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 53.5%. It was hot.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing a means for producing an electret fiber according to the present invention. DESCRIPTION OF SYMBOLS 1... Undrawn yarn, 3... Electreted fiber, 4... Feed roller, 5... Plate, 6
...Draw roller, 7...Plate, 8...Draw roller, 9...Corona electrode.

Claims (1)

[Claims] 1. Melt-spun an insulating polymer substance, stretch the resulting undrawn yarn by 1.5 times to 10 times, and hold the drawn yarn at 5°C.
A method for producing an electretted fiber, comprising further stretching at a temperature of ~50°C at a stretching ratio of 1.0 to 5 times, and subjecting the fiber to charging treatment using a corona element.