JPH0372749B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to conductive composite fibers. (Prior Art) Disturbances caused by static electricity have been a problem for a long time, but recently the problem of static electricity has been drawing particular attention. The reason for this is that research on static electricity has progressed, and it has become clear that many disasters such as fires and explosions whose causes were unknown until now are caused by static electricity. This is due to an increase in problems that are believed to be caused by static electricity in the field of computers. The background to these problems is that the number of things around us that are prone to static electricity, such as synthetic fibers and plastics, has increased, and with the spread of air-conditioning equipment, there has been an increase in environments and work in low humidity environments where static electricity is likely to occur. This is thought to be due to the fact that the spread of office automation equipment has made it more susceptible to electrostatic interference. Specifically, for example, clothing made of polyethylene terephthalate fibers becomes charged with electricity when worn, so it clings to the body or becomes tangled, making it impossible to walk, and it also attracts dust floating in the air. If it gets dirty or if you wear dust-free clothes, clogging may occur. Many other problems have arisen, such as discharge shock when walking on a carpet and touching a door handle, and the risk of ignition or explosion when flammable gases and liquids are nearby. 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, metal-plated fibers are chemically plated on the fiber surface.
This is a method of applying conductive powder such as metal powder or carbon black. Although these conductive fibers do have good initial conductivity, they not only have poor abrasion durability when worn, or the conductive agent layer on the surface peels off when washed, but their conductivity also decreases significantly. It also has poor chemical resistance and becomes a source of dust when used in dustproof clothing. The second method involves a composite fiber in which a conductive material powder is dispersed in a thermoplastic resin as a core layer and a fiber-forming copolymer is used as a sheath layer. For example, in composite conductive fibers containing conductive carbon, the carbon is black, so when the sheath layer becomes thin, the black coloration becomes significant and cannot be applied to fields where aesthetics are required. As a countermeasure to this, it is possible to greatly increase the amount of titanium oxide in the sheath polymer, and by reflecting the light incident and refracted into the sheath polymer on the titanium oxide surface, it is possible to improve the hue to a gray level. It is. In order to fully exhibit the carbon black coloring effect of titanium oxide, a distance from the surface of the sheath layer to the core layer is required, and it is important that the core portion be located approximately at the center of the cross section. On the other hand, even when the conductive substance is a white conductive metal compound such as tin oxide and forms a composite fiber with a sheath core, if it is not completely covered with a sheath layer, Oxidation-reduction chemicals decompose the conductive agent in the core, causing problems such as decreased conductivity or falling off during wear, resulting in decreased functionality. However, such a completely covered structure with a sheath layer has the following electrical problems. In other words, the conductivity between the cross sections of the fibers is good, but since the sheath layer is made of a polymer with good fiber forming properties, it is an electrical insulator, and the electrical resistance value of the surface is high, resulting in poor conductivity. The problem is that it has become so. Therefore, even with sheath-core composite fibers containing conductive substances in their cores, static electricity accumulates in fabrics woven into them, resulting in corona discharge caused by the original conductive fibers. If the static electricity removal function does not work, there will be problems such as clothes clinging to the body, crackling discharge noises when taking off clothes, dust adhesion, etc., and these static electricity may cause explosions and fires. have. 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 to reduce the thickness of the sheath component to 3 μm or less, as described in JP-A-60-110920. However, spinning was extremely difficult and the electrical resistance could not be lowered as expected.
Moreover, there are problems such as large variations in conductivity. (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,
The conductive substance contained in the core layer has a coloring prevention effect,
Because of its chemical resistance and abrasion resistance, it can be made into a conductive fiber with low electrical resistance on the surface even when it is not fully exposed on the surface. (Structure of the Invention) The present invention provides a composite fiber having a core-sheath structure formed by a core component containing a conductive substance and a sheath component consisting of an organic polymer compound, in which the core component is completely covered with the sheath component. and, on the surface of the composite fiber, discharge marks caused by high-voltage electrical discharge machining are scattered along the fiber axis direction, and at least one discharge mark is present per 10 microns in length in the fiber axis direction. The conductive composite fiber is characterized by having a distribution of The core component constituting the composite fiber of the present invention contains a conductive substance, and the conductive substance may be a known conductive substance such as conductive carbon black, metal, conductive metal compound, conductive non-metal compound, etc. Things can be used. Examples of types of carbon black include oil furnace black, acetylene black, thermal black, buttchain black, and channel black. Examples of metals include copper, iron, aluminum, nickel, and tin. On the other hand, conductive metal compounds contain metal oxides as their main target, and add traces to small amounts of metal oxides with different valences or ionic radii to achieve the desired high conductivity. is exemplified. Specific examples include combinations as shown in Table 1.

[Table] Examples of conductive metal non-oxides include titanium carbide (TiC), tantalum carbide (TaC), and niobium carbide (NbO). Furthermore, as conductive metal chambers, there are titanium chambers (TiC), tantalum chambers (TaN), zirconium chambers (ZrN), haunium chambers (HfN), vanadium chambers (VN, V ₃ N), There are also conductive metal halides (e.g. copper iodide), conductive metal sulfides (e.g. copper sulfide), conductive borides (e.g. manganese boride, boride), etc. beryllium), etc. A composite system or a mixture of the above-mentioned conductive agents can also be used as the conductive material of the core component. Specific examples include titanium black in which crystals of titanium oxide (TiO) and titanium nitride (TiN) coexist. These are usually treated as fine powders, but
The crystal form is not limited to circular, plate-like, scale-like, etc., and it can also be used as a conductive metal composite obtained by coating the surface of titanium oxide particles with such a conductive compound. Further, the conductive substance is used in combination with a low-temperature fluid material, and examples of the low-temperature fluid material include polyethylene, polypropylene, polystyrene, polybutadiene, polyisoprene, nylon-6, nylon-6,6, and polyethylene terephthalate. , polybutylene terephthalate and the like are preferred examples. 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, a lipophilic agent for such a conductive substance is used if necessary, but organic carboxylic acids having 6 or more carbon atoms and organic sulfonic acids having 5 or more carbon atoms are preferable.
The organic residue bonded to the carboxyl group or sulfonic acid group preferably has an alkyl group, an alkylene group, an aryl group, an alkylaryl group, or an aralkyl group. If so, it may have any substituent. 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, and stearic acid. 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, the sheath component surrounding the core component is composed of a fiber-forming polymer that is an organic polymer compound. Examples of the fiber-forming polymer include polyester, nylon-6, nylon-6,6, polypropylene, and the like. Among the above-mentioned polyesters, polyethylene terephthalate is best exemplified because it has a good texture, is easy to handle during processing, and has chemical resistance. Composite fibers whose sheath components are composed of such fiber-forming polymers have high surface electrical resistance and poor conductivity even if the core component containing a conductive substance has excellent conductivity. , it is still easily charged. In the composite fiber of the present invention, the core component is completely covered with the sheath component, but discharge marks caused by high-voltage electrical discharge machining are scattered along the fiber axis direction on the surface of the sheath component. be. FIG. 1 is a micrograph showing the state of discharge marks scattered on the surface of a composite fiber according to an embodiment of the present invention. FIG. 2 is a side view showing the position of the discharge mark 1 based on FIG. 1. The discharge traces are scattered in spots along the fiber axis direction, but they do not need to be present everywhere along the circumference of the surface, and the distribution of the discharge marks may be biased to one side. . Further, it is preferable that the discharge traces are scattered without interruption along the fiber axis direction. In addition, the scattered discharge traces 1 as shown in Figs. 1 and 2 have a diameter of 2 microns or less, are almost black in color, and are completely or partially carbonized by the electrical discharge machining process. It is thought that it is formed by Further, the number of discharge marks must be one or more per 10 microns of length in the fiber axis direction.
More preferably, the number of discharge marks is 5 or more per 10 microns, but if the number is less than 1 per 10 microns, there is a risk that a sufficient antistatic effect may not be obtained. In order to scatter such discharge traces on the fiber surface, electrical discharge machining treatment is performed at a high voltage. Next, the electrical discharge machining process will be described. That is, the electric discharge machining method for obtaining the fiber of 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, and a method in which a high voltage is applied to the core-sheath composite fiber obtained as described above, Examples include high voltage discharge treatment methods such as corona discharge, firework discharge, glow discharge, and arc discharge. As the applied voltage, a high voltage exceeding 1 KV and up to 100 KV can be used, preferably 5 to 100 KV, particularly preferably 5 to 50 KV. 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. Further, the best example is to use a core component containing a conductive substance as one pole, provide the other pole separately, apply a high voltage to both poles, and perform discharge treatment under this high voltage electrode. , but is not limited to this method. When such a composite fiber is subjected to electric discharge machining treatment, three stages are observed depending on the electric discharge intensity level.
At the initial stage of discharge, charge is injected into the surface of the sheath component, which is an insulator, and the surface becomes permanently charged, forming so-called microelectrets, but the electrical resistance value of the fiber surface is on the order of 10 ¹¹ Ω/cm or more. and
In addition, since the ratio of the internal electrical resistance value to the surface electrical resistance value between fiber cross sections was 10 ⁴ or more, it was found that the desired conductive fiber could not be obtained. However, if the discharge intensity is made extremely high more than necessary, it may lead to abnormal discharge accompanied by red flame, or oxidation may be promoted on the surface of the metal electrode, resulting in non-uniform discharge, and the discharge energy may be transferred to the fiber surface. It is converted into heat at the top, causing the fibers to melt and cut. Furthermore, although some cases of partial melting have been observed, the physical properties of the fibers are particularly markedly reduced in strength and elongation, and in these cases as well, the desired conductive fibers cannot be obtained. In order to scatter discharge traces on the fiber surface as in the present invention, the arc accompanying electric discharge machining treatment is blue,
In addition, in a state where the discharge occurs discontinuously, the electret stages or discharge traces cannot be scattered along the fiber axis direction. As the discharge intensity is increased, abnormal discharge will occur, so adjust the discharge intensity to a stage just before this abnormal discharge occurs, and adjust the distance between the electrodes so that blue arcs occur continuously. This is done by adjusting the voltage, processing atmosphere, etc. In order to obtain the composite fiber of the present invention, it is necessary to perform the process under conditions where the blue arc is generated continuously, but the distance between one electrode and the surface of the treated yarn is made as small as possible, and the discharge is carried out at that distance. It is preferable to use the lowest possible voltage. When reducing the distance between the electrode and the surface of the treated yarn, it is also necessary to pay attention to the running of the yarn so that vibrations and the like do not occur in the yarn in order to keep the distance as constant as possible. (Action of the invention) The fiber of the present invention has a core-sheath structure as described above, and the sheath component made of an organic polymer compound is subjected to high-voltage electric discharge machining treatment, so that the electric discharge traces are formed along the fiber axis direction. Since it is made to be scattered, it has excellent antistatic properties. Fibers made of fiber-forming polymers are typically
It exhibits an electrical resistance value on the order of 10Ω/cm, which causes problems due to electrostatic charging. Even if the electrical resistance value of the core component containing a conductive substance is
Even if the electrical resistance is as low as 10 ⁷ Ω/cm, if the electrical resistance of the surrounding fiber-forming polymer is as high as described above, a sufficient antistatic effect cannot be obtained. For this reason, in conventional core-sheath type composite fibers of this type,
It has been necessary to take measures such as exposing a part of the core component containing a conductive substance on a part of the fiber surface or making the position of the core component extremely eccentric in the cross section of the fiber. The fibers of the present invention have 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, 10 ⁸ Ω/ cm order or less,
(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. Here, the electrical resistance value (Ω/cm) is measured as follows. (a) Cross-sectional internal electrical resistance value Ag doutite (conductive resin paint containing silver particles, manufactured by Fujikura Industries) is applied to the cross section of a fiber whose both ends are cut in the cross-sectional direction so that the length in the fiber axis direction is 2.0 cm. Place the sample on an electrically insulating polyethylene terephthalate film at a room temperature of 20°C.
Under the conditions of ℃ x 30%RH, apply a DC voltage of 1KV using the Ag dotite attachment surface, measure 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. Furthermore, the discharge marks on the fiber surface depend on the discharge intensity. During high-voltage electrical discharge machining, the discharge intensity is affected by the voltage, distance between electrodes, electrode shape, and fiber surface condition, but in the present invention, the discharge marks are 2 microns or less in diameter and the number of them is The presence of at least one fiber per 10 microns of length in the fiber axis direction provides excellent conductivity and prevents extreme strength deterioration. That is, when the discharge intensity is weak, the electrical resistance value of the fiber surface does not decrease and good conductivity cannot be obtained. On the other hand, if the discharge intensity is too strong, the surface electrical resistance value decreases and at the same time the strength deteriorates significantly, making it impossible to withstand various processing during weaving and weaving. The decrease in strength to the extent that it cannot withstand machining is caused by excessive electrical discharge machining, and the discharge marks do not become spot-like as in the present invention, but become molten, and the size of the discharge marks becomes 2 microns in diameter. According to the present invention, when the discharge marks fall within the range of the present invention, good antistatic properties and the level of strength reduction can be prevented from being significantly reduced. Example 1 25 parts by weight of conductive oil furnace black and 75 parts by weight of polyethylene (melt index 12.0) were kneaded in a kneader at a temperature of 160°C for 2 hours to obtain conductive resin chips with a specific resistance of 5 x 10 Ωcm. . By melt spinning, a core-sheath type composite fiber (core-sheath ratio = 1/6) with this conductive resin as a core component and polyethylene tereftate as a sheath component was made, and it was drawn 4 times to make a 30 denier fiber with a single yarn count of 3. Obtained multifilament. A high voltage of +50 KV is applied between the core component of the core-sheath composite fiber as one electrode and the other electrode,
Electric discharge machining treatment was performed at a speed of 5 m/min. The distance between the surface of the core-sheath composite fiber and the other electrode (the tip of the needle electrode) was set at 20 mm, and the test was conducted while confirming that blue arcs were continuously generated. As shown in FIG. 1, black dots with a diameter of 2 microns or less were observed as discharge marks on the surface of the core-sheath composite fiber obtained by electrical discharge machining. In addition, as shown in Table 2, the electric discharge machining process
The surface conductivity has been improved to a level close to the cross-sectional internal electrical resistance. Furthermore, when this electric discharge processed yarn was made into a circular knitted fabric, the frictional charging voltage was measured, and it was found to be at an extremely good level of 350V. Comparative Example 1 In the core-sheath type composite fiber used in Example 1, the electric resistance value and strength and elongation properties of the yarn before electrical discharge machining treatment were
Shown in the table. Example 2 Titanium oxide fine particles whose surface was coated with conductive tin oxide had an average particle diameter of 0.24μ and a specific resistance of 9.5Ω.
cm conductive powder 235 parts by weight, melt index
76.8, put 75 parts by weight of polyethylene into a kneader, knead at 180℃ for 40 minutes, and then liquid paraffin 18
5 parts by weight of stearic acid as a lipophilic agent were added and kneaded for further 6 hours. The specific resistance of the obtained conductive resin was 4×10 ² Ω·cm. By melt spinning, a core-sheath type composite fiber (core-sheath ratio = 1/5) with this conductive resin as a core component and polyethylene terephthalate as a sheath component was made, and 3.5
A multifilament of 75 denier and 36 single filaments was obtained by double stretching. A high voltage of -45 KV was applied between the core component of this core-sheath type composite fiber as one electrode and the other electrode, and electric discharge machining was performed at a speed of 150 m/min.
The distance between the surface of the core-sheath type composite fiber and the other electrode (the tip of the needle electrode) was set at 10 mm, and the test was conducted while confirming that blue arcs were continuously generated. The conductivity and strength reduction are also shown in Table 2. Comparative Example 2 The electrical resistance value and strength and elongation characteristics of the core-sheath composite fiber used in Example 2 before the electrical discharge machining treatment are shown in Table 2. Comparative Example 3 When subjecting the core-sheath type composite fiber used in Example 1 to electrical discharge machining, the distance between the needle electrode tip and the fiber surface was set to 2.
mm, the discharge intensity was increased, and the other conditions were the same as in Example 1. The strength of the obtained yarn was significantly deteriorated and it was impossible to weave it.

[Table] However, <Number of discharge marks> Count the number of discharge marks with a diameter of 2 microns or less in the total surface area in a length of 10 microns in the fiber direction. <Measurement of antistatic properties> Cut the fabric into 4 cm length x 8 cm width, and use cotton broadcloth (30/-) as the wear cloth to cut 2.5 cm x 14 cm.
Samples were taken vertically, and the drum was rotated at a number of 700 rpm using a rotating drum type abrasion charge measuring device (Kyoto University Kaken type rotary static tester) in an atmosphere with a temperature and humidity of 20°C x 10% RH. , Read the friction voltage value after 1 minute of charging equilibrium time with contact pressure load of 60g. The unit of wear resistance is volt (V), and the smaller the value, the
Good antistatic properties. (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.

[Brief explanation of drawings]

FIG. 1 is a micrograph showing the state of discharge marks scattered on the surface of a composite fiber according to an embodiment of the present invention;
FIG. 2 is a side view showing the position of discharge marks in the photograph of FIG. 1. 1...Discharge trace.

Claims (1)

[Claims] 1 In a composite fiber with a core-sheath structure formed by a core component containing a conductive substance and a sheath component consisting of an organic polymer compound, the core component is completely covered with the sheath component, and the surface of the composite fiber is In addition, it is confirmed that discharge marks with a diameter of 2 microns or less due to high voltage electrical discharge machining are scattered along the fiber axis direction, and are distributed such that there is at least one per 10 microns of length in the fiber axis direction. Characteristic conductive composite fiber.