JPH0733637B2 - 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.

The second method is a case where powder of a conductive substance is dispersed in a thermoplastic resin to form a core layer, and a fiber-forming polymer is used 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 substance is not conductive carbon, it causes troubles such as appearing dark if the sheath layer is not completely covered, or 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 portion as described above, the discomfort caused by the static electricity of the cloth using the same (the clinging to the body of the worn clothes, the discharge sound during undressing, the 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, an object of the present invention is to provide a conductive fiber which is excellent in washing resistance and chemical resistance as well as imparting good conductive performance by lowering the electric resistance of the fiber surface without damaging the fiber. It is a thing.

(Means for Solving the Problems) As a result of repeated studies for solving the above problems, the present inventors have used a special copolyester as the polyester constituting the core and The inventors have found that by making the cross-sectional shape an irregular cross-sectional shape having a sharp protrusion, the conductive fiber excellent in washing resistance and chemical resistance can be obtained without damaging the fiber, and the present invention has been accomplished.

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 the core-sheath type composite fiber which is less than ¹¹ Ω / cm, and the ratio of the electric resistance value of the surface and the internal electric resistance value of the cross section is 10 ³ or less, the core component has a melting point of 80 to 180 ° C. A sheath made of a copolymerized polyester having a core and a conductive substance, wherein the core component has a modified cross-sectional shape having two or more sharp protrusions, and the sheath is formed by the sharp protrusions and the outer peripheral portion of the sheath component. All of the component minimum thicknesses Vi are 0.3 μm or more, and at least one of them is 5 μm or less, and the conductive fiber is 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, and it is important to use a special copolyester polymer having a melting point of 80 to 180 ° C as the matrix polymer. In this case, if the melting point is less than 80 ° C, the deformed cross-sectional shape of the core is likely to vary, and a uniform yarn cannot be obtained, and if it exceeds 180 ° C, it is difficult to disperse a predetermined amount of the conductive agent in the core component. Spinning itself becomes impossible.

Such copolyesters include, in particular, 5 to 50 mol% of isophthalic acid or dimethyl isophthalate and 95 to 50
Copolyester consisting of dicarboxylic acid component consisting of mol% terephthalic acid or dimethyl terephthalate and diol component consisting of hexamethylene glycol, or 40 to 80 mol% isophthalic acid or dimethyl isophthalate and 60 to 20 mol% It is preferable to use a copolyester comprising a dicarboxylic acid component consisting of terephthalic acid or dimethyl terephthalate and a diol component consisting of 2 to 10 mol% ethylene glycol and 98 to 90 mol% tetramethylene glycol.

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 excellent feeling and handleability in the processing step, and further 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 previously found that even if the sheath component was composed of a fiber-forming polymer, the electric resistance value of the fiber surface was 10 ¹⁰ 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 Kogyo Co., Ltd.) on both cross-sections of a fiber whose both ends are cut in the cross-sectional 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 0.5 KV is applied to the sample under the condition of temperature and humidity of 20 ° C × 30% RH.
g Apply the current using the doutite-attached surface to find the current flowing between the two sections, and calculate the electrical resistance value Ω / cm according to Ohm's law.

(B) Surface electrical resistance value A sample in which the above-mentioned Ag doutite was adhered 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 used as a sample, and the sample was electrically insulating. On a polyethylene terephthalate film, under the conditions of temperature and humidity of 20 ° C. × 30% RH, a DC voltage of 0.5 KV is applied between the Ag doutites to obtain the current flowing between the Ag doutites, and the distance between the Ag doutites. And the surface electrical resistance value Ω / cm is calculated according to Ohm's law.

The fiber of the present invention reduces the surface electric resistance value by performing an electric discharge treatment, reduces the ratio of the surface electric resistance value and the internal electric resistance value between cross sections, and imparts conductivity, As the treatment method, an 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, spark discharge, glow discharge, arc discharge, etc. Can be processed by the high-voltage discharge treatment method described above.

As the applied voltage, a voltage of more than 1 KV and up to 100 KV can be used, preferably 5 to 100 KV, particularly preferably 10 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 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 the state of a yarn, a cloth such as a knitted fabric, or a state of a non-woven fabric. 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 one pole and the other pole is separately provided and a high voltage is applied to both poles for electrical discharge treatment, the electrical insulating property of the fiber-forming polymer is lost and the same as an electrical semiconductor is obtained. Properties can be imparted.

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

That is, since the core component is made of a copolyester having a melting point of 80 to 180 ° C. that exhibits good adhesiveness with the polyester of the sheath component, the sheath component formed by the sharp protrusion of the core portion and the outer peripheral portion of the sheath component. Even if the value of the minimum thickness Vi is small, it can have sufficient washing resistance. This is not seen in the conventional core-sheath type conductive fiber. Furthermore, 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 tips 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) Hereinafter, examples will be described. The washing durability and chemical resistance were evaluated by the following methods.

The sample is made according to the textile 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 places, and the individual ratio of the broken portions was expressed in%. 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 woven fabric surface 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, dimethyl terephthalate 90 mol% as dicarboxylic acid component, dimethyl isophthalate 10 mol% and hexamethylene glycol 100 mol% as diol component (melting point: 138 ° C, intrinsic viscosity: 0.6
6) 75 parts by weight were charged into a kneader and kneaded at 220 ° C for 1 hour. The specific resistance of the obtained conductive resin was 3.1 × 10 ² Ω · cm.

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 3.0 × 10 ² Ω · cm. The properties after melt spinning, drawing, and corona discharge treatment as in Example 1 are shown in Table 1.

Comparative Example 2 Example 1 was repeated except that nylon 6 was used instead of the copolyester and kneaded at 250 ° C. for 1 hour.
I went the same way. 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.

Example 3 In Example 1, a dicarboxylic acid component consisting of 40 mol% of dimethyl terephthalate and 60 mol% of dimethyl isophthalate as a copolyester, and a diol component consisting of 5 mol% of ethylene glycol and 95 mol% of tetramethylene glycol. Example 1 was repeated except that the copolyester consisting of The results are shown in Table 1.

As is clear from the results shown in Table 1, when the core component is composed of a conductive substance and a copolyester and the value of Vi is within the range of the present invention (Examples 1 to 3), the core component is Is nylon 6 or polyethylene (Comparative Examples 1 and 2),
Alternatively, as compared with the case where the value of Vi is lower than the range of the present invention (Comparative Example 3), the washing resistance and the chemical resistance are excellent,
Furthermore, it can be seen that the surface electric resistance value is low and the antistatic property is excellent as compared with the case where the value of Vi is higher than the range of the present invention (Comparative Example 4).

Comparative Example 5 The conductive material, core polymer and sheath polymer used in Example 1 were melt-spun to form a concentric composite fiber, which was then stretched 3.1 times, 25 denier and 5 single yarns.
A multifilament of Corona discharge treatment was performed by the same method as in Example 1. The obtained yarn has a Vi (μm)
= 7.3, surface electric resistance value 5.0 × 10 ¹² Ω · cm, cross-section internal electric resistance value 4 × 10 ⁷ Ω · cm, strength 3.9 (g / de), and elongation 39%. As is clear from this result, when the cross-sectional shape of the core portion is not a modified cross-section having sharp protrusions (Comparative Example 5), the surface electric resistance value is higher than that in the case of the present invention (Example 1). High and practically not electro-discharge machined.

Examples 4 to 5 and Comparative Example 6 Spin spinning and drawing were performed in the same manner as in Example 1 except that the amount of dimethyl isophthalate was changed as shown in Table 2 to use core component polymers having different melting points, and discharge treatment was performed. I went.
Table 2 shows the electric resistance value, the strength and elongation, the washing resistance and the chemical resistance.

Comparative Example 7 In Example 3, 82 mol% of dimethyl terephthalate,
The procedure of Example 3 was repeated except that dimethyl isophthalate was 18 mol%, ethylene glycol was 3 mol%, and tetramethylene glycol was 97 mol%. The results are shown in Table 2.

As is clear from the results shown in Table 2, when the melting point of the core component copolymerized polyester is less than 80 ° C. (Comparative Example 6), the yarn cross section becomes non-uniform and the strength and elongation are low and 180 ° C. When it exceeds 10 (Comparative Example 7), the spinning itself was impossible because the viscosity of the core polymer was high.

On the other hand, when the melting point is within the range of the present invention (Example 3 to
In 4), 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 (3)

[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 the core-sheath type composite fiber of less than m, and the ratio of the electric resistance value of the surface and the internal electric resistance value between the cross sections is 10 ³ or less, the core component has a melting point of 80 to 180 ° C. A core component composed of a polymerized polyester and a conductive substance has a modified cross-sectional shape having two or more sharp protrusions, and the minimum thickness of the sheath component formed by the sharp protrusions and the outer peripheral portion of the sheath component. A conductive fiber characterized in that all of Vi is 0.3 μm or more and at least one of them is 5 μm or less, and is subjected to electric discharge machining. 2. The fiber-forming polyester is mainly polyethylene terephthalate, and the copolyester constituting the core component is 5 to 50 mol% of isophthalic acid or dimethyl isophthalate and 95 to 50 mol% of terephthalic acid or terephthalate. A copolyester comprising a dicarboxylic acid component composed of dimethyl acid and a diol component composed of hexamethylene glycol.
The conductive fiber according to the item. 3. A copolymerized polyester constituting a core component,
Dicarboxylic acid component consisting of 40-80 mol% isophthalic acid or dimethyl isophthalate and 60-20 mol% terephthalic acid or dimethyl terephthalate, 2-10 mol% ethylene glycol and 98-90 mol% tetramethylene The conductive fiber according to claim 1, which is a copolyester composed of a diol component composed of glycol.