JPH10131035A - Method for producing conductive fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably produce a conductive core-sheath type composite fiber containing a conductive substance in a core component, the conductive property of which is uniform in a length direction of the fiber. Provide a way. SOLUTION: A core-sheath type composite fiber containing a conductive material in a core component is subjected to a discharge treatment between high voltage electrodes after moisture is previously attached to the fiber surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core-sheath type conjugate fiber containing a conductive material in a core component, and a method for producing a conductive fiber having a conductive property uniform in a fiber length direction. .

[0002]

2. Description of the Related Art Thermoplastic resins such as polyethylene, polyamide and polyester are used in many applications as fiber products. However, they have a drawback that they are poor in antistatic properties and are easily charged, so that many conductive resins are used. Research has been done.

As a first method, there is a method of coating the surface of a fiber with a conductive substance. The conductive fiber thus obtained has good initial conductive performance, but has good wear resistance when worn. Furthermore, since they have insufficient washing resistance and chemical resistance, they are sources of dust when used in dustproof clothing and the like.

The second method is a method in which a powder of a conductive substance is dispersed in a thermoplastic resin to form a core component, and a fiber-forming polymer is used as a sheath component to form a core-sheath composite fiber. For example, conductive fibers containing conductive carbon black are colored black because the conductive carbon black is black, such as when the sheath component is thin, and cannot be used in fields where aesthetics are required. In addition, there is a problem that the use of the core component is extremely limited if the core component is completely contained in the sheath component and the thickness of the core component is not sufficient. Also, from a viewpoint other than aesthetics, if the core component is not covered with the sheath component, the conductive substance may fall off during use, causing trouble such as a decrease in function.

[0005] On the other hand, the coating structure using the sheath component also has the following problems. In other words, the conductivity between the cores at both ends of the fiber is good and there is no problem. However, since the sheath component is formed of a polymer having a good fiber-forming property, the sheath component is electrically an insulator, and The point is that the electric resistance value is high and the conductivity is poor. Therefore, even with such a core-sheath type composite fiber containing a conductive substance in the core, discomfort due to the static electricity of the cloth using the fiber (the wrapping of the worn clothes on the body, the discharge sound when undressing, the air (Dust adhesion inside).

In order to solve the problem of the core-sheath type composite fiber, Japanese Patent Application Laid-Open No. S60-110920 proposes that the core component is decentered and the thickness of the sheath component is 3 μm or less. However, such a conjugate fiber has problems that the electric resistance value cannot be lowered as expected, and that the core-sheath interface peels off and dust is easily generated.

To solve these problems, Japanese Patent Publication No.
Japanese Patent No. 37487 proposes a method of subjecting a sheath-core conjugate fiber containing a conductive substance to a core component to discharge treatment at a high voltage. According to this method, the electric resistance value of the fiber surface can be reduced. It is possible to obtain conductive fibers having excellent conductivity. However, according to the study of the present inventor, in some cases, the dielectric breakdown of the fiber-forming polymer as the sheath component is not uniformly performed in the length direction during the discharge treatment, and the obtained conductive fiber in the length direction may not be discharged. It has been found that there is a problem that the conductive performance becomes uneven, the quality of a product using the conductive fiber becomes unstable, and troubles such as thread breakage frequently occur during electric discharge machining.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a core component containing a conductive substance and a core-sheath that completely covers the core component. It is an object of the present invention to provide a method for producing a conductive fiber in which a conductive property in a yarn length direction of the conductive fiber becomes uniform when a discharge treatment is performed between the high-voltage electrodes.

[0009]

The present invention achieves the above object and has the following construction. That is, the present invention discharges a core-sheath type composite fiber composed of a core component containing a conductive substance and a sheath component made of a fiber-forming polymer that completely covers the core component between high-voltage electrodes. This is a method for producing a conductive fiber having stable conductive properties, which comprises performing a discharge treatment by attaching moisture to the surface of the core-sheath composite fiber beforehand.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The conductive fiber of the present invention is a core composed of a core component containing a conductive substance and a sheath component made of a fiber-forming polymer that completely covers the core component. It is a sheath type composite fiber. Here, as the conductive substance contained in the core component, known substances such as conductive carbon black and conductive metal compounds can be used. Examples of the type of carbon black include acetylene black, oil furnace black, thermal black, channel black, and Ketjen black. On the other hand, as the conductive metal compound, a conductive metal oxide is mainly used, and stannic oxide and zinc oxide which are particularly excellent in whiteness are preferable. The stannic oxide mentioned here includes stannic oxide containing a small amount of an antimony compound, and a conductive metal complex obtained by coating the surface of titanium oxide particles with stannic oxide containing a small amount of an antimony compound. It is. Zinc oxide also includes conductive zinc oxide containing a small amount of aluminum oxide, lithium oxide, indium oxide, and the like. They are,
Usually, it can be used as dispersed in a matrix polymer as fine powder.

The sheath component which completely surrounds the core component is not particularly limited as long as it is a fiber-forming polymer, and any one can be used, for example, polyester, nylon-6, nylon-6,6, polypropylene and the like. Can be Among them, polyester, particularly polyethylene terephthalate, is preferred because of its good texture, excellent handling in the processing step, and good chemical resistance.

It is desirable that the core-sheath type composite fiber made of such a substance has an irregular cross-sectional shape in which the cross-sectional shape of the core component in the fiber cross section is 2 or more, preferably 2 to 8 sharp projections. The cross-sectional shape having a sharp protrusion as referred to herein means a cross-sectional shape having a convex shape or a protruding convex portion, and the main ones are those shown in FIGS. further,
It is more preferable that at least one of the minimum thicknesses Vi of the sharp protrusion and the outer periphery of the sheath component illustrated in FIG. When all of Vis are larger than 5 μm, the applied voltage for the discharge treatment becomes high, the discharge treatment becomes insufficient, and the obtained conductive performance tends to decrease.

The composite fiber having a sheath component made of such a fiber-forming polymer has a relatively high surface electric resistance even if the core component containing a conductive substance has conductivity, so that the conductive property is high. Is insufficient and as a result, is still easily charged.

The conductive fiber of the present invention is characterized in that it has been subjected to a discharge treatment by a method described later, and as a result, the electric resistance of the fiber surface is in the order of 10 ¹⁰ Ω / cm or less; And the internal electric resistance value between the fiber cross sections (Ω /
cm) and the surface electrical resistance (Ω / cm) is 1
0 ³ or less, and furthermore, has the property that its conductive performance is uniform and stable in the length direction of the fiber.

The ordinary conductive core-sheath type composite fiber has a very high surface electric resistance value, for example, on the order of 10 ¹³ Ω / cm, because the sheath made of the fiber-forming polymer has a large electric resistance. Internal electrical resistance between end faces is 10 ⁷
Even if it is as low as Ω / cm, the ratio of the electric resistance of the surface to the internal electric resistance between the end faces is extremely large at about 10 ^6, and there is a problem that the effect of the conductive performance is hardly exhibited on the surface of the fiber. .

On the other hand, even if the conductive fiber of the present invention is composed of a fiber-forming polymer, its surface resistance is as low as 10 ¹⁰ Ω / cm or less, and the discharge treatment is carried out by the method described later. , The conductive performance is uniform in the length direction of the fiber.

Here, the electric resistance value (Ω / cm) is measured as follows. (A) Internal electric resistance value between fiber end faces Ag doutite (a silver particle-containing conductive resin paint, Fujikura Co., Ltd.) The sample having the above-mentioned method was applied on an electrically insulating polyethylene terephthalate film at a temperature of 20 ° C. and a relative humidity of 30% at 1 kV.
Is applied using the Ag-doutite-attached surface to determine the value of the current flowing between the two sections, and the electrical resistance (Ω / cm) is calculated according to Ohm's law.

(B) Surface electric resistance value A sample prepared by attaching the above-mentioned Ag doutite to the surface (fiber side surface) near both ends of a fiber cut to a length of about 2.0 cm in the fiber axis direction. Was applied on the electrically insulating polyethylene terephthalate film under the conditions of a temperature of 20 ° C. and a relative humidity of 30% to apply a DC voltage of 1 kV between the Ag doughites to obtain a current value flowing between the Ag doughites. The distance between them is measured, and the surface electric resistance Ω / cm is calculated according to Ohm's law.

As the discharge treatment method in the present invention, the core-in-sheath composite fiber obtained as described above is brought into contact with a high-voltage electrode to apply a high voltage, a corona discharge having a different discharge shape, and a spark. The treatment can be performed by any of high-voltage discharge treatment methods such as discharge, glow discharge, and arc discharge. The applied voltage is a high voltage exceeding 1 kV, and is suitably in a range up to 100 kV, preferably 2 to 5 kV.
The range is 0 kV. The polarity of the electrode may be positive or negative (DC) or AC. The distance between the electrodes is suitably 10 cm or less, and can be arbitrarily determined according to the discharge mode, the processing speed, and the target conductive performance. Further, a core component containing a conductive substance is used as one pole, and the other pole is separately provided, and a high voltage is applied to both poles,
The method of performing discharge treatment under the high-voltage electrode is exemplified as an optimal method, but is not limited to this method, and may be a method of performing discharge treatment by applying a high voltage to two separately provided poles. good.

Further, such a discharge treatment can be performed in a state of a yarn or a state of a fabric such as a woven or knitted fabric or a nonwoven fabric. Further, in the case of a yarn state, it may be applied to a drawn yarn or an undrawn yarn. By such discharge treatment,
Not only can the surface electric resistance value be in the order of 10 ¹⁰ Ω / cm or less, but the ratio of the surface electric resistance value to the electric resistance between the cross sections is 10 ³ or less, preferably 10 ² or less, and it is used under particularly severe conditions. In this case, the number can be set to 10 or less.

In the method for producing a conductive fiber according to the present invention, when performing the above-described electric discharge treatment, moisture is previously attached to the surface of the core-sheath composite fiber before electric discharge machining, and preferably, the entire surface is coated. It is important to attach moisture to the water. As a result, the electric resistance on the fiber surface has no unevenness and the stability of the discharge treatment is improved,
For the first time, it is possible to obtain a conductive fiber whose conductivity is stable in the length direction of the fiber. On the other hand, when water does not adhere to the fiber surface before the electric discharge machining, the stability of the electric discharge treatment is reduced, so that the uniformity of the electric discharge treatment is reduced and the length of the conductive fiber obtained in the length direction is reduced. Is unfavorable because the conductive performance, especially the uniformity of the surface electric resistance is lowered.

The method for adhering moisture to the fiber (original yarn) before the electric discharge machining is not particularly limited, but an oiling method (oiling roller, MO nozzle, etc.) usually used in the melt spinning step is adopted. Alternatively, the raw yarn may be immersed directly in a water bath. The amount of adhered moisture is not particularly limited as long as the fiber surface is covered with moisture.

Furthermore, if a small amount of a surfactant is contained in the water to be adhered, the friction between the raw yarn and the electric discharge machining electrode and the friction between the single yarns of the raw yarn can be reduced, so that the electric discharge machining with the single yarn can be performed. This is preferable because an increase in the area of contact with the electrode increases the EDM efficiency. In addition, the fiber surface can be coated with a smaller amount of attached moisture. The type and concentration of the surfactant may be appropriately set as needed.

[0024]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. In addition, the variation in the length direction of the surface electric resistance value of the conductive fiber was represented by the difference between the maximum value and the minimum value by measuring the surface electric resistance value at 10 points every 1 m.

Example 1 An ordinary composite spinning apparatus comprising a conductive resin composition composed of 30 parts by weight of conductive carbon black and 70 parts by weight of polyester as conductive materials and a sheath component of polyethylene terephthalate as a conductive material. Is melt-spun to obtain a core-sheath composite fiber having a cross-sectional shape as shown in FIG.
A multifilament having denier and 5 single yarns was obtained. After immersing this core-sheath type composite fiber in a water bath, 300 m / mi
The discharge treatment was performed at a speed of n. Table 1 shows the average value of the electric resistance value and the variation in the length direction of the obtained conductive fibers.

[Examples 2 to 3] Conductive fibers were obtained in the same manner as in Example 1 except that the moisture and Vi adhering to the raw yarn before the discharge treatment were changed as shown in Table 1.
The results are summarized in Table 1.

Example 4 240 parts by weight of conductive powder having titanium oxide particles coated with conductive stannic oxide and 75 parts by weight of polyethylene were charged into a kneader.
After kneading at 80 ° C. for 30 minutes, 18 parts by weight of liquid paraffin and 4 parts by weight of stearic acid as an oleophilic agent were added, and the mixture was further kneaded for 5 hours. A core-sheath composite fiber (core / sheath weight ratio = 1/6) having the obtained conductive resin composition as a core component and polyethylene terephthalate as a sheath component is spun and stretched four times to 30 denier. A multifilament with three single yarns was obtained. After immersing this core-sheath type composite fiber in a water bath, discharge treatment was performed at a speed of 300 m / min. Table 1 shows the average value of the electric resistance value and the variation in the length direction of the obtained conductive fibers.

[Comparative Example 1] The sheath-core composite fiber obtained in the same manner as in Example 1 was mixed with water for 300 minutes without adhering water.
The discharge treatment was performed at a speed of m / min. The results are summarized in Table 1.

[0029]

[Table 1]

[0030]

As described above, according to the method for producing a conductive fiber of the present invention, the electric resistance value of the fiber surface and the internal electric resistance value between the cross sections are low, and the conductive performance is reduced in the longitudinal direction. The conductive fibers can be stably obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a cross-sectional shape of a conductive core-sheath composite fiber of the present invention.

[Explanation of symbols]

Vi Minimum thickness of the sheath component formed by the sharp projection and the outer periphery of the sheath component

Claims (2)

[Claims] 1. A discharge treatment is performed between a high-voltage electrode and a core-in-sheath composite fiber comprising a core component containing a conductive substance and a sheath component made of a fiber-forming polymer that completely covers the core component. A method of producing a conductive fiber having a stable conductive property, wherein moisture is previously adhered to the surface of the core-sheath type conjugate fiber before discharging. 2. The core-sheath type conjugate fiber has an irregular cross-sectional shape in which the core component has two or more sharp projections, and a sheath component formed by the sharp projections and the outer periphery of the sheath component. Thickness V
2. The method according to claim 1, wherein at least one of i is 5 μm or less.