JPH0733606B2 - Conductive fiber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a conductive fiber, and more specifically to a conductive fiber having a core-sheath structure containing a conductive substance as a core component.

(Prior Art) Although thermoplastic resins such as polyethylene, polyamide, and polyester are used in many applications as textile products, they have a drawback that they are liable to be charged due to their poor antistatic property. Therefore, much research has been conducted on conductive fibers.

The first method is to coat the fiber surface with a conductive substance. These conductive fibers have good initial conductive performance, but have poor wear resistance when worn, poor wash resistance and chemical resistance, and are a source of dust when used for dustproof clothing, etc. Has become.

A second method is to disperse a powder of a conductive substance in a thermoplastic resin to form a core layer and a fiber-forming polymer as a sheath layer to form a sheath-core composite fiber. In this case, for example, the conductive fiber containing conductive carbon has a black conductive carbon. Therefore, when the sheath layer is thin, it is colored in black and used in a field requiring aesthetics. However, if the core layer is completely inside the sheath layer and the thickness of the sheath layer is not sufficient, its use is extremely limited. Even when the conductive material is not conductive carbon, it causes troubles such as appearing black if it is not completely covered with the sheath layer and falling off during use to deteriorate the function.

On the other hand, even the completely covered structure with the sheath layer has the following problems. In other words, the conductivity between the cores of the fiber cross section is good and there is no problem, but since the sheath layer is made of a polymer with a good fiber forming property, it is an electrical insulator and the surface The problem is that the resistance is high and the conductivity is poor.

Therefore, even in the case of the core-sheath type composite fiber containing a conductive substance in the core part as described above, the discomfort caused by the static electricity of the cloth using the same (glazing of the wearing clothes on the body, discharge sound when undressing, air, There was a problem of dust adhesion inside).
Furthermore, in order to solve the problem of such a core-sheath type composite fiber,
As described in JP-A-60-110920, it is also proposed that the core component is eccentric and the thickness of the sheath component is 3 μm or less, but such a composite fiber also has an electric resistance value. However, there is a problem that the core-sheath interface peels off and dust is easily generated. In order to solve these problems, the applicant of the present invention, as described in JP-A-62-53416, to discharge core-sheath type composite fibers containing a conductive substance in the core component at high voltage. Proposed.

(Problems to be Solved by the Invention) According to the method proposed in JP-A-62-53416,
Although fibers having excellent conductivity are obtained, there are problems such as damage to the fibers during electrical discharge machining and poor wash resistance. Therefore, the present invention provides an electrically conductive fiber that is excellent in washing resistance and chemical resistance, as well as imparting good electrical conductivity by lowering the electrical resistance of the fiber surface without damaging the fiber.

(Means for Solving the Problems) As a result of repeated studies to solve the above problems, the present inventors have used a special copolyester for the polyester constituting the core, and have a cross section of the core. The present inventors have found that by making the shape a modified cross-sectional shape having sharp protrusions, conductive fibers excellent in washing resistance and chemical resistance can be obtained without damaging the fibers, and arrived at the present invention.

That is, the present invention is composed of a core component containing a conductive substance and a sheath component made of a fiber-forming polyester that completely covers the core component, and the electric resistance value of the fiber surface is 10
^In a core-sheath type composite fiber which is less than ¹¹ Ω / cm, and the ratio of the electric resistance value of the surface to the internal electric resistance value of the cross section is 10 ³ or less, the core component does not show a clear melting point. , 150 ℃
The cross-sectional shape of the core component is a modified cross-sectional shape having two or more sharp protrusions, which is composed of a copolymerized polyester having the following softening point and a conductive substance, and is composed of the sharp protrusions and the outer peripheral portion of the sheath component. The minimum thickness of the formed sheath component Vi is 0.3 μm
Above, and at least one of them is 5 μm or less, and is a conductive fiber characterized by being electric discharge machined.

The core component of the fiber of the present invention contains a conductive substance, and as the conductive substance, conductive carbon black,
Known compounds such as conductive metal compounds can be used.

Examples of the carbon black include acetylene black, oil furnace black, thermal black, channel black, and Ketjen black.
On the other hand, examples of the conductive metal compound include copper iodide, copper sulfide, and the like, and examples of the conductive metal oxide include stannic oxide and zinc oxide which are particularly excellent in whiteness. The stannic oxide mentioned here also includes stannic oxide containing a small amount of antimony compound, and a conductive metal composite obtained by coating the surface of titanium oxide particles with stannic oxide containing a small amount of antimony compound. Be done. Zinc oxide also includes conductive zinc oxide in which a small amount of aluminum oxide, lithium oxide, indium oxide or the like is dissolved. These are usually used as fine powders dispersed in a matrix polymer, but it is important to use a special copolymerized polyester polymer having no softening point and a softening point of 150 ° C. or less for the matrix polymer. is there. When it exceeds 150 ° C, the viscosity of the system containing the conductive substance is too high, and the composite spinning itself is difficult.

As such a copolyester, in particular, isophthalic acid or dimethyl isophthalate is 45 to 80 mol% and terephthalic acid or dimethyl terephthalate is 55 to 20 mol% as the dicarboxylic acid component, and ethylene glycol is 80 to 90 as the diol component. It is preferable to use a copolyester composed of mol% and diethylene glycol of 20 to 10 mol%. This copolyester has good dispersibility even in a state in which a large amount of a conductive substance is dispersed, and since the adhesiveness with the polyester component of the sheath is particularly good, the sharp protrusion of the core and the outer periphery of the sheath are Even if the minimum thickness of the sheath component formed by is reduced, the washing durability is good, and even if the discharge treatment is performed at a lower voltage, sufficient conductive performance can be imparted, so damage to the fiber Never give.

The sheath component, which completely surrounds the core component, is composed of fiber-forming polyester. In particular, polyethylene terephthalate is preferable because it has a good feel, is excellent in handling in the processing step, and has good chemical resistance.

It is important that the conductive fiber made of such a substance has a modified cross-sectional shape in which the shape of the core component in the fiber cross section has two or more sharp protrusions. The number of sharp protrusions is preferably 2-8. The cross-sectional shape having a sharp projection referred to here means a cross-sectional shape having a convex shape or a projection-shaped convex part, and mainly includes
There are those shown in FIGS. 1 (a) to 1 (d). Furthermore, the first
The minimum thickness Vi between the sharp protrusion and the outer circumference of the sheath component shown in Fig. (B) is 0.3 μm or more, and at least one is 5 μm.
It must be: If there is a portion where Vi is smaller than 0.3 μm, the washing resistance is deteriorated, and if all of Vi is larger than 5 μm, there is a problem that the conductive performance is deteriorated.

Further, the electroconductive conjugate fiber of the present invention may be a hollow fiber as shown in Fig. 1 (e).

The conductive fiber of the present invention is obtained by performing a discharge treatment as described below, but the electric resistance value of the fiber surface is less than 10 ¹¹ Ω / cm, and the electric resistance value of the surface (Ω / cm) And the internal electrical resistance (Ω / cm) between the sections is 10 ³ or less. Usually, the surface resistance value of a fiber made of a fiber-forming polymer is
For example, it is very high such as 10 ¹³ Ω / cm order,
Even if the cross-section internal resistance value is as low as 10 ⁷ Ω / cm,
The ratio of the electric resistance value of the surface to the internal electric resistance value of the cross section is 10 ⁶
However, the surface of the fiber hardly exhibits the effect of conductivity.

The present inventors have previously found that even if the sheath component is composed of a fiber-forming polymer, the electric resistance value of the fiber surface is 10 ¹⁶ Ω / cm.
We proposed conductive fibers that are below the order of magnitude (Japanese Patent Laid-Open No. 62-5
3416 publication).

Here, the electric resistance value (Ω / cm) is measured as follows.

(A) Internal electrical resistance between cross-sections Ag doutite (silver particle-containing conductive resin paint, made by Fujikura Industries) on both cross-sections of the fiber cut at both ends in the transverse direction so that the length in the axial direction of the fiber is 2.0 cm. The sample with the attached is placed on an electrically insulating polyethylene terephthalate film, and a DC voltage of 1 KV is applied to the Ag under the conditions of temperature and humidity of 20 ° C × 30% RH.
The current flowing between the two cross sections is calculated by applying it using the doutite attachment surface, and the electrical resistance value Ω / cm is calculated according to Ohm's law.

(B) Surface electric resistance value A sample in which the above-mentioned Ag doutite was adhered to the surface (fiber side surface) near both ends of the fiber paste cut to a length of about 2.0 cm in the fiber axis direction was used as the sample On a polyethylene terephthalate film, under the conditions of temperature and humidity of 20 ° C. × 30% RH, a DC voltage of 1 KV is applied between the Ag doutites to obtain a current flowing between the Ag doutites, and the distance between the Ag doutites is determined. Measure and calculate the surface electrical resistance value Ω / cm according to Ohm's law. The fiber of the present invention reduces the surface electric resistance value by performing an electric discharge treatment, and reduces the ratio of the surface electric resistance value and the internal electric resistance value between the cross sections,
Although it imparts conductivity, the discharge treatment method is as follows.
Energization method of applying a high voltage by contacting the core-sheath type composite fiber obtained as described above with a high voltage electrode, corona discharge with different discharge shapes, firework discharge, glow discharge, high voltage discharge treatment such as arc discharge Can be processed by law.

The applied voltage is 100KV, which is a high voltage exceeding 1KV.
Can be used, preferably 5 to 100KV,
Particularly preferably, those in the range of 10 to 50 KV are suitably exemplified. Whether the polarity of the voltage is positive or negative (DC),
Or it may be an exchange. The distance between the electrodes can be in the range of 0 to 10 cm, and can be determined by the relationship between the discharge form and the processing speed. Further, it is best exemplified that the core component containing a conductive substance is used as one pole, the other pole is separately provided, a high voltage is applied to the both poles, and the discharge treatment is performed under the high voltage electrode. However, the method is not limited to this method, and a method of applying a high voltage to two electrodes provided separately and performing a discharge process may be used.

Further, such an electric discharge treatment can be performed in a yarn state, a cloth such as a knitted fabric, or a woven cloth state. Further, in the case of yarn, it may be applied to drawn yarn or undrawn yarn.

By this discharge treatment, the surface electric resistance value is 10 ¹⁰ Ω / cm.
It can be less than or equal to the order, and the ratio of the surface electric resistance value to the cross-section internal voltage resistance value can be 10 ³ or less, preferably, this ratio is 10 ² or less, particularly when used under severe conditions. Can be 10 or less.

(Function) The fiber of the present invention has a ratio of the surface electric resistance value to the internal electric resistance value between the cross sections of 10 ³ or less, a surface electric resistance value of less than 10 ¹¹ Ω / cm, and washing durability and chemical resistance. It has excellent properties.

Regarding the electric resistance value, the electric resistance value of the fiber-forming polymer can be lowered by the discharge treatment with a high voltage, and thus the above-mentioned value can be obtained. In particular, when the core component is used as one pole and the other pole is separately provided and a high voltage is applied to both poles for electric discharge treatment, the electrical insulating property of the fiber-forming polymer is lost, and the same property as an electric semiconductor is obtained. Can be given.

Further, as the core component, a special copolyester having excellent adhesiveness with the sheath component is used, and since the cross-sectional shape of the core part is a modified cross-sectional shape and the core part is completely covered by the sheath part, Excellent in washing durability and chemical resistance.

That is, since the core component is made of a copolyester having a softening point showing good adhesion to the polyester of the sheath component and having no clear melting point at 150 ° C. or less, the sharp protrusion of the core portion and the outer peripheral portion of the sheath component Even when the minimum thickness Vi of the formed sheath component is small, sufficient wash resistance can be obtained. This is not seen in the conventional core-sheath type conductive fiber. Further, since the cross-sectional shape of the core component is a modified cross-sectional shape having sharp protrusions, electric discharge treatment is performed at the tip of the sharp protrusions during electric discharge machining, and sufficient conductivity can be imparted even by treatment at low voltage. Therefore, damage to the sheath due to electric discharge machining can be minimized, and problems such as reduction in strength and elongation and yarn breakage during electric discharge machining can be prevented. Further, since the core component containing the conductive substance is completely covered with the sheath component and exhibits antistatic property, the color peculiar to the conductive substance does not appear on the fiber surface, and the core component falls off during use. The function does not deteriorate.

(Examples) Examples will be described below. The washing durability and chemical resistance were evaluated by the following methods.

The sample is made according to the fiber standard of T-89393, and the conductive thread is 1 cm.
Woven into stripes at intervals. For the durability of washing, the appearance of the surface of the woven fabric after repeated washing in a clean room was arbitrarily inspected at 20 locations, and the number of broken points was expressed as a percentage. The chemical resistance is as follows: After the fabric sample is immersed in the chemical at room temperature for 24 hours, washed with water and dried, and then repeatedly rubbed with a Scott tester 50 times.
The appearance of the surface of the woven fabric was arbitrarily inspected at 20 places, and ◯ was evaluated for no peeling, Δ for partial peeling, and x for most peeled.

Example 1 A conductive powder having an average particle size of 0.25 μ and a specific resistance of 9 Ωcm, obtained by coating the surface of titanium oxide fine particles with conductive stannic oxide 24.
Copolymerized polyester consisting of 0 parts by weight, 60 mol% of dimethyl terephthalate as a dicarboxylic acid component and 40 mol% of dimethyl isophthalate, and 88 mol% of ethylene glycol and 12 mol% of diethylene glycol as a diol component ( A kneader was charged with 75 parts by weight of a softening point: 90 ° C., intrinsic viscosity: 0.50) and kneaded at 250 ° C. for 30 minutes. The specific resistance of the obtained conductive resin was 3.0 × 10 ² Ωcm.

This conductive resin is used as a core component, and polyethylene terephthalate is used as a sheath component, and melt-spun using a composite spinning device to obtain a core-sheath type composite fiber having a cross-sectional shape as shown in FIG. It was drawn to obtain a multifilament having 25 denier and 5 single yarns.

The core-sheath type composite fiber was subjected to corona discharge treatment at -5 KV and 50 m / min. Table 1 shows the electric resistance value, the strength and elongation, the washing resistance and the chemical resistance.

Comparative Example 1 240 parts by weight of the conductive powder used in Example 1 and 75 parts by weight of polyethylene having a melt index of 75 were charged into a kneader and kneaded at 180 ° C. for 30 minutes. The specific resistance of the obtained conductive resin was 3.5 × 10 ² Ωcm. As in Example 1, the properties after melt spinning, drawing and corona discharge treatment were
Shown in the table.

Comparative Example 2 The procedure of Example 1 was repeated except that nylon 6 was used instead of the copolyester. The properties of the fibers obtained are shown in Table 1.

Example 2 The procedure of Example 1 was repeated, except that 30 parts by weight of conductive carbon black and 70 parts by weight of the copolyester used in Example 1 were kneaded as the conductive substance. The properties of the fibers obtained are shown in Table 1.

Comparative Examples 3 to 4 Spinning, drawing, and corona discharge treatment were performed in the same manner as in Example 1 except that the amounts of the core / sheath components were changed so that Vi had the values shown in Table 1. . The results are shown in Table 1.

In Table 1, L ₀ , L ₁₀₀ , and L ₂₀₀ indicate that the number of washings was ₀ , ₁₀₀ , and ₂₀₀ , respectively.

As is clear from the results in Table 1, when the core component is composed of the conductive substance and the copolyester and the value of Vi is within the range of the present invention (Examples 1 and 2), the core is When the component is nylon 6 or polyethylene (Comparative Examples 1 and 2), the value of Vi is outside the range of the present invention (Comparative Example 3).
It can be seen that the washing resistance and the chemical resistance are superior to those of (4) to (4).

Example 3 and Comparative Example 5 In Example 1, except that the amount of dimethyl isophthalate was changed as shown in Table 2 to use core component polymers having different softening points, spinning drawing was performed in the same manner, and discharge treatment was performed. went. Table 2 shows the electric resistance value, the strength and elongation, the washing resistance and the chemical resistance.

As is clear from the results shown in Table 2, when the softening point of the copolyester as the core component exceeds 150 ° C (Comparative Example 5), only poor yarns in the core-sheath section are obtained, and L ₀ is about half the number. Is a defect. On the other hand, when the softening point is within the range of the present invention (Example 3), the electric resistance value is low, and the strength and elongation, washing resistance and chemical resistance are good.

(Effect of the Invention) According to the present invention, there is provided a conductive fiber which is a core-sheath type composite fiber having a low electric resistance value on the fiber surface and excellent antistatic property, and having excellent washing resistance and chemical resistance. can do.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a cross-sectional shape of a conductive core-sheath type composite fiber of the present invention. Vi ... Minimum thickness of the sheath component formed by the sharp protrusion and the outer periphery of the sheath component.

Claims (2)

[Claims] 1. A core component containing a conductive substance and a sheath component made of fiber-forming polyester that completely covers the core component, and has an electric resistance value of 10 ¹¹ Ω / c on the fiber surface.
In a core-sheath type composite fiber having a ratio of the electric resistance value of the surface and the internal electric resistance value of the cross section of 10 ³ or less and less than m, the core component does not show a clear melting point, and is 150 ° C. The cross-sectional shape of the core component is a modified cross-sectional shape having two or more sharp protrusions, which is composed of a copolymerized polyester having the following softening point and a conductive substance, and is composed of the sharp protrusions and the outer peripheral portion of the sheath component. A conductive fiber having a minimum sheath component thickness Vi formed of 0.3 μm or more, and at least one of which is 5 μm or less, and which has been electric discharge machined. 2. The fiber-forming polyester is mainly polyethylene terephthalate, and the copolyester constituting the core component is 45-80 mol% of isophthalic acid or dimethyl isophthalate and 55-20 mol% of terephthalic acid or terephthalate. Dicarboxylic acid component consisting of dimethyl acid, 80-90 mol% ethylene glycol and 20-10 mol%
The electrically conductive fiber according to claim 1, which is a copolyester comprising a diol component comprising diethylene glycol.