JPH05186953A - Nonwoven fabric and its production - Google Patents

Abstract

PURPOSE:To obtain uniform nonwoven fabric capable of being produced at a high speed without causing the discharge of sparks by specifying the weight irregularity of a continuous filament web. CONSTITUTION:The standard deviation delta (weight irregularity) of the brightnesses of nonwoven fabric 9 obtained by sucking a continuous filament group 2 with an air sucker 7 at a high speed and catching the sucked filament group on a continuously moved catching net 8 is controlled to <=2.8. The surface of an earthing electrode 3 disposed in the state faced to a knife-like application electrode 5 is moved with a driving device 4. The knife-like application electrode is connected to a high voltage generator 6 to generate an uniform electric discharge between the knife-like application electrode and the earthing electrode, thereby uniformly opening the filament group and decreasing the weight irregularity of the nonwoven fabric.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-woven fabric comprising continuous filaments and having a small unevenness in weight and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, when a filament group is towed at a high speed by an air sucker or the like and stretched and then deposited on a collecting surface to produce a nonwoven fabric, the filament group is used to produce a nonwoven fabric with less unevenness of eyes. Various methods for opening and uniformly dispersing have been proposed. For example, a method has been proposed in which a continuous filament group spun from a spinneret is towed and stretched by an air sucker to collide with a collision plate to be charged, and then two or more filament groups are deposited while separately traveling. (JP-A-59-216963). Further, a method has also been proposed in which a filament group is passed through a drawing roll group, a corona discharge device such as a roll target and a needle-shaped electrode, and a slit type air sucker in this order to open the fiber and then form a nonwoven fabric (JP-A-58-41960). In addition, in guiding and charging a plurality of filaments together with an air flow in a corona discharge electric field composed of a needle electrode and a planar target electrode, the filament is caused to run along the tip surface side of the needle electrode. There is also provided a method for electrically charging (Japanese Patent Laid-Open No. 58-174671).

[0003]

However, in the method disclosed in Japanese Patent Laid-Open No. 59-216963, the degree of freedom in the width direction of the filament is obtained by the following separation traveling even though the collision plate is charged and charged. It is considered that the non-woven fabric obtained is still large in weight per unit area, because it increases the number of particles and improves the opening and separation.

Next, the method disclosed in JP-A-58-41960 uses a corona discharge device in which a needle electrode and a roll or flat plate target are combined on an air sucker.
Therefore, as time elapses, dust in the air, impurities in the polymer, and the like are attached to cause spark discharge, which reduces the fiber-spreading effect and increases eye spots. Also, trying to prevent spark discharge,
When the voltage applied to the needle electrode is lowered, the fiber-spreading effect is lowered, and further, when the yarn is broken, the yarn is caught at the tip of the needle.

Further, in the method disclosed in Japanese Patent Laid-Open No. 58-174671, when a plurality of filaments are guided and charged together with an air flow in a corona discharge electric field composed of a needle electrode and a planar target electrode, the needle is charged. The filament bundle is opened at about 1000 m / min in order to cause the filament to run along the end surface of the electrode.
In the field of so-called spunbond production, which is produced at about 0 m / min, the opening was not sufficient and the eye spot was large.

[0006] The present invention provides a non-woven fabric having a small non-uniform weight which is not obtained by the conventional method, and a non-woven fabric having a small non-uniform mottle by stably opening the filament group at a high speed of 5000 m / min without causing spark discharge. It is intended to provide a manufacturing method.

[0007]

The present invention takes the following means in order to solve the above problems. That is,
The present invention is a non-woven fabric made of continuous filament,
A non-woven fabric characterized by a non-uniformity of density of 2.8 or less displayed by a brightness standard deviation δ, when a filament group is pulled by an air sucker at high speed and collected on a moving collection net to produce a non-woven fabric. In addition, a knife-shaped application electrode and an earth electrode are provided above the air sucker so as to face each other, and the surface of the earth electrode is made movable, and the filament group is provided between the application electrode and the earth electrode. It is a method for producing a nonwoven fabric which is characterized in that it is pulled by the air sucker after it has been passed, and a method for producing a nonwoven fabric in which the surface of the ground electrode moves in one direction. The present invention will be described in detail below.

The nonuniformity of the nonwoven fabric of the present invention is 2.8 or less when expressed by the brightness standard deviation δ. When δ exceeds 2.8, it is not preferable because it is not suitable for the field where a high quality product is required because of a large areal weight. The brightness standard deviation δ is expressed by calculating the brightness unevenness of a target object with a television camera and calculating the brightness unevenness from the video frame memory via the interface.

Next, the method for producing the nonwoven fabric of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of an apparatus used in the manufacturing method. In FIG. 1, a thermoplastic resin such as polypropylene, polyethylene, polyamide, polyester is melt-spun from a spinning nozzle 1 to be a filament group 2.
When manufacturing a nonwoven fabric by collecting on a collection net 8 which is continuously drawn by being pulled by a high-speed air sucker 7, the ground electrode 3 and the knife-shaped application electrode 5 whose surfaces move are mutually separated. It is provided facing each other. The ground electrode 3 is, as shown in FIG.
The surface 13 of the ground electrode 3 that gradually moves from 2 in the direction of the arrow and contacts the filament group 2 is controlled so as to maintain a clean surface.

If the ground electrode 3 is not provided in this way, dust in the air or scraps of filaments are deposited, or polymer impurities are deposited on the surface 13 of the ground electrode 3 to increase the insulation resistance. Specifically, the insulation resistance of the surface 13 becomes about 10 ⁸ Ω · cm, spark discharge occurs, the filament group does not open uniformly, and the uniformity of the basis weight of the nonwoven fabric decreases. Therefore, if the ground electrode 3 is moved and the surface 13 is held on a clean surface, the filament group is subjected to a uniform discharge to improve the fiber opening property, reduce the non-uniformity of the non-woven fabric, and The quality will be improved. It is preferable to use a thin metal plate or a metal foil as the material of the ground electrode 3.

The knife-shaped application electrode 5 is applied by a high voltage generator 6 to generate a uniform discharge as shown in FIG. 2. However, when a needle electrode is used as in the prior art, one filament in the filament group is different. There is a problem that the needle is caught by the needle when it is cut for some reason. On the other hand, the linear electrode has a problem that the linear electrode itself is cut when the same trouble occurs. By using the knife-shaped application electrode 5 as in the present invention, continuous operation becomes possible without such a problem. In addition, 10 is a suction box, 11 is a uniform discharge electric field, and 12 is a package.

[0012]

【Example】

Example 1 252 from a rectangular spinning nozzle with 252 spinning holes
Polyethylene terephthalate was spun at a discharge rate of g / min. and pulled by a high-speed air sucker at a speed of 5000 m / min.
/ M ² of non-woven fabric was produced. In this step, as shown in FIG. 2, the distance between the tip of the knife-shaped application electrode (high voltage of 22 KV) and the surface 13 of the ground electrode 3 was set to 16 mm,
As the ground electrode 3, a stainless steel having a width of 300 mm and a thickness of 30 μm that moves at a speed of 2 cm / hour was adopted. Continuous operation was carried out for 4 days (96 hours) by using such a device, and the situation and the non-uniformity of the obtained nonwoven fabric (web) were measured and shown in Table 1. Spark discharge did not occur for 96 hours, and a spot density δ of 2.8 (passing point) or less was obtained from beginning to end.

Comparative Example 1 A ground electrode made of stainless steel having a thickness of 5 mm and a height of 70
The same experiment as in Example 1 was conducted by using a fixed type of mm. In this experiment, as shown in Table 1, spark discharge was generated in 8 hours, and after that, only a web having an unsatisfactory density of δ of 3.5 was obtained. Comparative Example 2 The same experiment as in Example 1 was performed using a linear electrode of tungsten wire 0.08φ as the applying electrode. 0.5
There was a situation where the wire was cut in the case / day space.
The results are shown in Table 1.

Example 2 Example 1 using copper 40 μm metal foil as a ground electrode
The same experiment was performed. Spark discharge did not occur for 4 days, and a clean web was obtained as an acceptable product. The results are shown in Table 1. Example 3 The same experiment as in Example 1 was conducted using an iron electrode having a metal foil of 30 μm as the ground electrode. As a result, continuous operation for 4 days was possible without the occurrence of spark discharge. Moreover, the mottle of the web was 2.7, which was within the criteria of the passing score. The results are shown in Table 1.

[0015]

[Table 1]

The speckled spots described in this specification are speckle measuring instruments manufactured by Hamamatsu Photonics (Specification No. S61-
00003-01). Measurement condition Sample size 30 cm × 40 cm Measurement size 290 mm × 390 mm Number of data 113100 (1 data = 1 mm ² ) processing 8 bits (brightness value 0 to 255) Luminance standard deviation δ 3 samples were collected and each mottled spot was measured. The average value was used to determine δ in this specification.

[0017]

EFFECT OF THE INVENTION The nonwoven fabric of the present invention is a uniform web having a small unevenness of weight and the production method of the present invention is 5000 m 2 / mi.
Even under a high speed of n., continuous operation is possible without any spark discharge for a long period of 4 days or more, and a remarkable effect of obtaining a product with a small eye spot is obtained.

[Brief description of drawings]

FIG. 1 is a perspective view of a manufacturing apparatus used in the present invention.

FIG. 2 is a side view of the vicinity of the electrode of FIG.

[Explanation of symbols]

 1 Spinning Nozzle 2 Filament Group 3 Earth Electrode 5 Knife Applying Electrode 7 Air Soccer 8 Collection Net

Claims (3)

[Claims] 1. A non-woven fabric comprising a continuous filament, wherein the non-woven fabric having a brightness standard deviation δ of 2.8 or less. 2. When manufacturing a nonwoven fabric by pulling a filament group at high speed with an air sucker and collecting it on a moving collecting net, a knife-shaped application electrode and an earth electrode are opposed to each other above the air sucker. Further, the non-woven fabric is characterized in that the surface of the ground electrode is made movable, and the space between the applying electrode and the ground electrode is passed through the filament group and then pulled to the air sucker. Law. 3. The method for producing a nonwoven fabric according to claim 2, wherein the surface of the ground electrode moves in one direction.