JPH0137487B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a conductive fiber and a method for manufacturing the same. (Prior Art) Thermoplastic resins such as polyethylene, polyamide, and polyester are used in many applications as textile products, but they have the disadvantage of being easily charged due to poor antistatic properties. For example, clothing made of polyethylene terephthalate fibers can become electrostatically charged and cling to the body when worn, and can also attract dust floating in the air, making it easy to get dirty, or if you walk on a carpet and touch a door handle. This causes many problems such as discharge shock when the battery is heated. A number of methods have been proposed for conductive fibers to address such issues. The first method is to coat the fiber surface with a conductive substance. More specifically, it is a method of coating chemically plated metal-plated fibers, metal powder, or conductive powder such as carbon black on the fiber surface. These conductive fibers certainly have good initial conductive performance, but not only do they have poor abrasion durability when worn, or the conductive agent layer on the surface peels off when washed, but their conductivity also decreases significantly. However, it also has poor chemical resistance and becomes a source of dust when used in dustproof clothing. A second method involves dispersing conductive material powder in a thermoplastic resin and forming a sheath-core composite fiber using a fiber-forming polymer as a core layer. For example, conductive fibers containing conductive carbon cannot be used in fields where the core layer is visible because the conductive carbon is black, or where the sheath layer is thin, and where the coloring is extremely high and aesthetics are required. , the core layer is completely within the sheath layer, and
Another problem is that if the sheath layer is not thick enough, its uses are extremely limited. Even if the conductive material is a conductive metal compound such as stannic oxide or zinc oxide and forms a sheath/core composite fiber, the sheath layer will completely cover the sheath layer, although not as much as the conductive carbon described above. If they are not covered, they may appear dark or fall off during use, causing problems such as reduced functionality. However, such a complete covering structure with a sheath layer has the following problems. In other words, the conductivity between the core parts of the fiber cross section is good and there is no problem, but the sheath layer is made of a polymer with good fiber forming properties, so it is an electrical insulator and the surface The problem is that the electrical resistance value is high and the conductivity is poor. Therefore, even with a sheath-core composite fiber containing a conductive substance in the core, it is possible to experience discomfort due to the static electricity of the fabric (i.e., when wearing clothing clings to the body, when taking off clothes, etc.). There were problems with discharge noise, dust adhesion in the air, etc. Furthermore, in order to solve the problem of such core-sheath type composite fibers, it has been proposed to make the core component eccentric and reduce the thickness of the sheath component to 3 μm or less, as described in JP-A-60-110920. There is. However, such composite fibers are very difficult to spin and have problems such as the electrical resistance value cannot be lowered as expected. (Object of the Invention) The object of the present invention is to solve the above problems and provide a novel conductive fiber, which is a complete sheath-core composite fiber,
Even if the conductive substance contained in the core layer is not exposed on the surface at all due to its anti-coloring effect, the fiber can have a low electrical resistance on the surface. (Structure of the Invention) The present invention comprises a core component containing a conductive substance and a sheath component surrounding the core component and made of a fiber-forming polymer that does not contain metal or metal compound. In the core-sheath type composite fiber, the core component is completely covered with the sheath component, the electrical resistance value of the fiber surface is on the order of 10 ¹⁰ Ω/cm or less, and the electrical resistance value of the fiber surface ( Ω/cm) and internal electrical resistance value between cross sections (Ω/cm)
A conductive fiber having a ratio of 10 ³ or less, and a method for producing the same. The core component of the fiber of the present invention contains a conductive substance, and as the conductive substance, known substances such as conductive carbon black and conductive metal compounds can be used. Examples of the types of carbon black include acetylene black, oil furnace black, thermal black, channel black, and buttress black. On the other hand, the conductive metal compound is mainly a conductive metal oxide, and particularly preferred are stannic oxide and zinc oxide, which have excellent whiteness. The stannic oxide mentioned here also includes stannic oxide containing a small amount of antimony compound, and conductive metal composites obtained by coating the surface of titanium oxide particles with stannic oxide containing a small amount of antimony compound. It will be done. Zinc oxide also includes conductive zinc oxide in which small amounts of aluminum oxide, lithium oxide, indium oxide, etc. are dissolved. These are usually treated as fine powders. In addition, the conductive metal compound is used in combination with a low-temperature fluidity substance and a lipophilic agent, and examples of the low-temperature fluidity substance include polyethylene, polypropylene, polystyrene, polybutadiene, polyisoprene, nylon-6, and nylon-6. , 6, polyethylene terephthalate, polybutylene terephthalate, etc. are preferably exemplified. In addition, some of these may be replaced with copolymerized components, and resins other than those mentioned above may be used depending on the purpose as long as they are low-temperature fluid materials, and if necessary, two types of resins may be used. A mixture of the above may also be used. Furthermore, as a lipophilic agent for such a conductive metal compound, an organic carboxylic acid having 6 or more carbon atoms and an organic sulfonic acid having 5 or more carbon atoms are preferable, and the organic residue bonded to the carboxyl group or sulfonic acid group is an alkyl group. It is preferable to have a group, an alkylene group, an aryl group, an alkylaryl group, or an aralkyl group, and as long as these groups are other than a carboxyl group or a sulfonic acid group, they may have any substituent. can not use. Specific examples of the organic carboxylic acid include n-caproic acid, benzoic acid, n-caprylic acid, phenylacetic acid, triylic acid, n-nonanoic acid, n-caprylic acid, stearic acid, and the like. Further, specific examples of the organic sulfonic acid include n-pentanesulfonic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, and the like. These organic carboxylic acids and organic sulfonic acids used as lipophilic agents may be used alone or in appropriate combinations. Next, a sheath component surrounding the core component is comprised of a fiber-forming polymer. The fiber-forming polymers include, for example, polyester, nylon-6,
Examples include nylon-6,6 and polypropylene. Among the above-mentioned polyesters, polyethylene terephthalate is best exemplified because it has a good texture and is easy to handle during processing. Composite fibers whose sheath components are composed of such fiber-forming polymers still have high surface electrical resistance and poor conductivity, even if the core component containing a conductive substance has conductivity. It is easily charged. The fibers of the present invention are obtained by subjecting them to a discharge treatment as described below, and as a result, the electrical resistance value of the fiber surface is on the order of 10 ¹⁰ Ω/cm or less, and the internal electrical resistance value between the fiber cross sections (Ω It is important that the ratio between the surface electrical resistance (Ω/cm) and the surface electrical resistance value (Ω/cm) is 10 ³ or less. Normally, the surface resistance value of fibers made of fiber-forming polymers is very high, for example, on the order of 10 ¹³ Ω ^/ cm.
Even if it is as low as on the order of Ω/cm, the ratio of the surface electrical resistance to the cross-sectional internal electrical resistance is as large as about 10 ⁶ , and the fiber surface exhibits almost no conductive effect. Even though the fiber of the present invention is composed of a fiber-forming polymer, the electrical resistance value of its surface is low, on the order of 10 ¹⁰ Ω/cm or less, as described above. Here, the electrical resistance value (Ω/cm) is measured as follows. (b) Cross-sectional internal electrical resistance value Ag doutite (conductive resin paint containing silver particles, manufactured by Fujikura Industries) is applied to both cross sections of a fiber whose ends are cut in the cross-sectional direction so that the length in the fiber axis direction is 2.0 cm. The sample to which the
Under the conditions of ℃ x 30% RH, apply a DC voltage of 1 KV using the Ag tie-attached surface to determine the current flowing between both cross sections, and calculate the electrical resistance value Ω/cm using Ohm's law. (b) Surface electrical resistance value The above-mentioned surface was applied to the surface near both ends (fiber sides) of the fiber glue cut to a length of about 2.0 cm in the fiber axis direction.
As a sample with Ag doutite attached,
The sample was placed on an electrically insulating polyethylene terephthalate film under conditions of temperature and humidity of 20°C x 30% RH, and a DC voltage of 1 KV was applied between the Ag doutite to determine the current flowing between the Ag doutite, and Measuring the distance between Ag doutites,
Calculate the surface electrical resistance value Ω/cm using Ohm's law. Next, the discharge treatment will be described. That is, the discharge treatment method used in the present invention includes an energization method in which the core-sheath type composite fiber obtained as described above is brought into contact with a high voltage electrode and a high voltage is applied, a corona discharge with different discharge shapes, and a spark discharge. , glow discharge, arc discharge, and other high-voltage discharge treatment methods. As the applied voltage, a high voltage exceeding 1KV and a range up to 100KV can be used, preferably 5 to 100KV, particularly preferably 10 to 50KV.
Preferred examples include those within the range of . The polarity of the voltage may be positive, negative (direct current), or alternating current. The distance between the electrodes can be in the range of 0 to 10 cm, and can be determined depending on the discharge form and processing speed. Alternatively, the core component containing a conductive substance is used as one pole, and the other pole is provided separately.
The best example is to apply a high voltage to the two electrodes and perform the discharge treatment under the high voltage electrodes, but the method is not limited to this method. Through this discharge treatment, the surface electrical resistance value can be increased.
10 ¹⁰ Ω/cm or less, and
The ratio of the surface electrical resistance value to the cross-sectional internal voltage resistance value is
10 ³ or less, preferably this ratio is 10 ² or less, especially when used in harsh conditions
It can be as follows. The value of this ratio can be adjusted by adjusting the time of the discharge treatment and the high voltage KV. (Function of the invention) The fiber of the present invention has a surface electrical resistance value and an internal electrical resistance value between cross sections (current is passed through the core component containing a conductive substance, so this internal electrical resistance value is approximately equal to the electrical resistance value of the core component). Equally less than 10 ⁸ Ω/cm order,
(preferably 10 ⁷ Ω/cm or less), the ratio is 10 ³ or less, and the surface electrical resistance value is on the order of 10 ¹⁰ Ω/cm or less. This is because the electrical resistance value of the fiber-forming polymer can be lowered by high voltage discharge treatment. Fiber-forming polymers usually exhibit an electrical resistance value on the order of 10 ¹³ Ω/cm, which causes problems due to electrostatic charging. Even if the electrical resistance of the core component containing the conductive substance is as low as 10 ⁷ Ω/cm, if the electrical resistance of the surrounding fiber-forming polymer is as high as described above, sufficient control is required. No electric effect can be obtained. For this reason, in conventional core-sheath type composite fibers of this kind, a part of the core component containing a conductive substance is exposed on a part of the fiber surface, or the position of the core component in the fiber cross section is made eccentric. Some ingenuity was needed. In the present invention, the surface electrical resistance value of the fiber-forming polymer as a sheath component is on the order of 10 ¹⁰ Ω/cm or less,
Furthermore, if necessary, 10 ⁹ order or less, 10 ⁸ Ω/
It is possible to obtain a low electrical resistance value on the order of cm or less, or even on the same order as the electrical resistance value of the core component, and eliminate problems caused by static electricity. Such a low electrical resistance value can be obtained by subjecting a core-sheath type composite fiber, which is composed of a core component containing a conductive substance and a sheath component made of a fiber-forming polymer surrounding it, to electrical discharge treatment at a high voltage, as described above. However, in particular, when the core component is used as one pole and the other pole is provided separately and a high voltage is applied to these two poles and discharge treatment is performed, the electrical insulation properties of the fiber-forming polymer are lost. , it is possible to impart properties similar to those of electrical semiconductors. In addition, the present invention exhibits antistatic properties even though the conductive core component (which causes various troubles) is completely covered with the sheath component, so it does not cause discoloration or falling off during use. You can avoid problems. In particular, it is not necessary to set the distance between the core component and the fiber surface to 3 μm or less, and spinning is easy, and even such a complete core-sheath type composite fiber can sufficiently exhibit an antistatic effect. This has never been seen before and is an epoch-making action and effect of the present invention. Example 1 Titanium oxide fine particles whose surface was coated with conductive tin oxide had an average particle diameter of 0.25μ and a specific resistance of 9Ω.
cm conductive powder 240 parts by weight, melt index
Add 75 parts by weight of polyethylene to 75 in a kneader,
After kneading at 180° C. for 30 minutes, 18 parts by weight of liquid paraffin and 4 parts by weight of stearic acid as a lipophilic agent were added and kneaded for a further 5 hours. The specific resistance of the obtained conductive resin was 3.0×10 ² Ω·cm. By melt-spinning, a core-sheath type composite fiber (core-sheath ratio = 1/6) with this conductive resin as a core component and polyethylene terephthalate as a sheath component was made, and it was drawn 4 times to make a 110 denier multi-filament fiber with a single yarn count of 12. Got filament. This core-sheath type composite fiber is applied at minus 50KV, 2m/
The core component of the core-sheath type composite fiber was used as one pole and subjected to corona discharge treatment. As shown in Table 1,
The corona discharge treatment improves the surface conductivity and brings it to the level of cross-sectional internal electrical resistance.

[Table] (Effects of the invention) Since the present invention is a complete core-sheath type composite fiber, the core component does not appear on the surface at all, so there is no darkening.
It is possible to obtain a thread that has no troubles such as shedding and can be handled in the same way as ordinary fibers, yet has a low surface electrical resistance value similar to that when the core component is exposed on the surface, and has an outstanding antistatic effect.

Claims (1)

[Scope of Claims] 1. A core component containing a conductive substance, and a fiber-forming polymer surrounding the core component, which is made of a metal, or
In a core-sheath type composite fiber composed of a sheath component that does not contain a metal compound, the core component is completely covered with the sheath component, and the electric resistance value between the fiber surfaces is reduced to 10 by electrical discharge machining. It is on the order of ¹⁰ Ω/cm or less, and the ratio of the electrical resistance value of the surface (Ω/cm) to the internal electrical resistance value (Ω/cm) between the cross sections perpendicular to the fiber axis is 10 ³ or less. A conductive fiber characterized by: 2. The fiber according to claim 1, wherein the core component of the composite fiber is covered with a sheath component having a thickness of at least 3 μm or more as measured from the surface of the sheath component. 3. The fiber according to claim 1 or 2, wherein the fiber-forming polymer is primarily polyethylene terephthalate. 4. A core component containing a conductive substance and a fiber-forming polymer surrounding the core component, which is a metal, or
Using a core-sheath type composite fiber in which the core component is completely covered with the sheath component and the sheath component does not contain a metal compound, high voltage is applied between the core component and one electrode. The electric resistance value between the fiber surfaces is reduced to ¹⁰ Ω/cm by discharging between the electrodes.
or less, and the ratio of the electrical resistance value (Ω/cm) of the surface to the internal electrical resistance value (Ω/cm) between the cross sections orthogonal to the fiber axis is 10 ³ or less. Method for producing conductive fibers.