JPH09324320A - Conductive fiber and manufacturing method thereof - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] In an environment in which static electricity of a relatively high voltage is generated due to friction or the like, excellent antistatic property can be imparted by exhibiting conductivity, and a relatively low voltage inside an electronic device or the like. (EN) Provided are a conductive fiber and a method for producing the same which have a low conductivity and do not cause a problem such as a short circuit in a circuit. SOLUTION: The conductivity is 1 at an applied voltage of 5 V / cm.
A conductive fiber having a conductivity of not more than × 10 ^-6 S / cm and a conductivity at 1000 V / cm of 10 ^-5 S / cm or more, and a method for producing the same.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive fiber which can be used for clothing / interior applications and material applications, and a method for producing the same.

[0002]

2. Description of the Related Art Conductive fibers are widely used for industrial and household purposes for removing static electricity, to prevent electrostatic explosion, to prevent malfunction of electronic parts, to prevent clogging of clothes,
It is an indispensable material for avoiding sparks caused by frictional electrification of clothes, mats, carpets, etc. which are remarkable in the low humidity season of winter.

Conventionally, conductive fibers are formed by a method in which a conductive material is composited on the surface of the fiber by post-processing, a method in which the conductive material is used as the fiber substrate itself, or a method in which the conductive material is kneaded into the fiber.
(For example, JP-A-57-39213 and 57-10.
6716) and has been used in various fields. For example, as a post-processing technique, a method of embedding conductive fine particles such as carbon black or a metal (compound) on the surface of a fiber substrate, or a method of impregnating a metal compound such as a copper compound and then chemically treating them to form copper sulfide, copper iodide, etc. A method of depositing a conductive metal compound inside the fiber or on the surface layer is known. As a method of using a conductive material for the fiber substrate itself, a method of using metal fibers, a method of using carbon fibers, and the like are known. As a method of kneading a conductive material into the interior of a fiber, a method of compounding conductive fine particles such as carbon black or a metal (compound) by blend spinning or composite spinning is known.

In the method of using an electronically conductive substance such as carbon black or metal (compound), whether the substance is used alone or a method of forming a composite into an ordinary fiber, the obtained conductive material is used. The characteristic fiber has an excellent feature that the fiber processed product can be imparted with antistatic property only by blending a small amount (generally around 1%) with ordinary fiber.

In the past, in the development and industrialization of conductive fibers, the kind of conductive material, the amount added, and the structure in which the conductive layer was exposed on the fiber surface for exhibiting excellent antistatic performance when mixed were used. Although various studies have been conducted on the required critical conductivity, improvement of conductivity, or blended amount of fibers and antistatic performance of monofilaments that are essentially involved in the expression of electrical conductivity, regarding the harmful effects of electrical properties in conductive fibers, , Was barely touched.

For example, conductive fibers generally containing an electron conductive material exhibit high conductivity. If such a highly conductive fiber mixes inside the electronic device and is present on the board or the wiring, the circuit may be short-circuited and may cause an erroneous operation.
In particular, personal computers, word processors, and other devices that are composed of electronic circuits have become widespread around the world, and at the same time, clothing that is a composite of conductive fibers is also in circulation. It is estimated that there is a great potential need for conductive fibers that have electrical characteristics that correspond to the environment in which the equipment is used.

[0007]

DISCLOSURE OF THE INVENTION The object of the present invention is to consider the actual conditions as described above, and by controlling the electrical properties of the conductive fiber, it is possible to avoid static electricity of a relatively high voltage due to friction or the like. To provide a conductive fiber that can impart excellent antistatic property by expressing conductivity and does not cause a problem such as a short circuit of a circuit due to a low conductivity under a relatively low voltage such as inside an electronic device. It is in. That is,
An object of the present invention is to provide a conductive fiber that exhibits a desired conductivity according to an applied voltage and a method for manufacturing the conductive fiber.

[0008]

Means for Solving the Problems The inventors of the present invention have made extensive studies in order to achieve the above-mentioned object, and as a result, arrived at the present invention.
That is, according to the present invention, the conductivity at an applied voltage of 5 V / cm is 1 × 10 ⁻⁶ S / cm or less, and 1000 V / cm.
Conductivity fiber having a conductivity of 10 ⁻⁵ S / cm or more is defined as the first gist, and the applied voltage dependence of the conductivity measured by changing the volume content of the conductive fine particles in the conductive layer of the conductive fiber. The above-mentioned conductivity for determining the conductivity at a low applied voltage and the conductive fine particle volume content in the conductive layer, which cannot be measured, is superimposed on the curve on the graph showing A second gist is a method for producing fibers.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. In the present invention, the applied voltage (V / cm) and the electrical conductivity (S / cm) of the fiber are obtained by the following methods. A single fiber is taken out of the fiber bundle, cut into exactly 1.5 cm, and a silver paste (Fujikura Kasei Co., Ltd. Dotite) is used for the metal terminal in which the distance between the terminals is accurately set to 1 cm. Glue to cover with paste. 50V, 100V, 250V, 500 between these terminals at 20 ℃ and relative humidity 40RH%
DC voltage of V and 1000V is applied and resistance value between terminals is R
(Ω) is a super insulation meter (SM-821 manufactured by Toa Denpa Co., Ltd.)
0), σ = 1 / (1.11 × 10 ⁻⁶ × R × (d / ρ)) (where d is the fineness and ρ is the specific gravity of the fiber) and the conductivity σ ( S / cm) is calculated.

As a result of earnest analysis of the electrical characteristics of the conductive fine particles in the conductive fibers, the inventors have found that the conductivity of the conductive fibers using the specific conductive fine particles as a conductive material is positive with respect to the applied voltage. It was found that there is a correlation (Fig. 1).

Then, when the reference volume content of the conductive fine particles is determined and the curve of the content lower than that is horizontally moved to the low applied voltage side and the curve of the high content is horizontally moved to the high applied voltage side, respectively The composite curve (Fig. 2) was obtained by the combination, and the applied voltage and the volume content of the conductive fine particles in the conductive fiber (however, when the composite fiber was used, the volume content of the conductive fine particles in the conductive layer, hereinafter referred to as "conductivity"). It was found that a conversion rule is established between the content ratio of "particulate fine particle volume content"). It should be noted that the amount of horizontal movement to superimpose the curves of the conductive fine particle volume contents, that is, the transfer coefficient is a function of only the conductive fine particle volume contents (FIG. 3).

By using the conversion rule between the applied voltage and the conductive fine particle volume content, it is possible to know the conductivity of the conductive fiber at that time if the conductive fine particle volume content and the applied voltage are known. Becomes That is, it is possible to obtain the required conductivity at an arbitrary applied voltage by controlling the content rate of the conductive fine particles in the conductive layer. In particular,
When trying to develop anti-static performance by mixing conductive fiber with normal raw cotton, the conductivity becomes high at high applied voltage such as static electricity generated by friction, and the conductive fiber is not generated in electronic equipment that operates at low voltage. When mixed, the electrical properties of the conductive fiber can be designed so that the conductivity will not cause short circuit.

The conductive fiber of the present invention is a conductive fiber that utilizes the fact that the conductivity changes depending on the applied voltage described above, and due to this constitution, in an environment where static electricity of a relatively high voltage is generated due to friction or the like, By exhibiting conductivity, it is possible to provide excellent antistatic properties, and it is possible to obtain a conductive fiber that does not cause problems such as short circuit of the circuit due to low conductivity under relatively low voltage such as inside electronic equipment. is there. When the applied voltage is 1000 V / cm, the conductivity of the fiber is 10 ^-5 S /
If it is less than 10 cm, it tends to be difficult for the spun yarn after blending to exhibit antistatic performance.

The conductive fiber of the present invention is designed so that the applied voltage-
If the conversion rule is established between the conductive fine particle volume content and
This is particularly advantageous because the conductivity can be designed at an arbitrary applied voltage and volume content of the conductive fine particles.

In the conductive fiber, the mechanism by which the conversion rule is established between the applied voltage and the volume content of the conductive fine particles is not clear at present, but the high electric field conduction phenomenon in which electric conduction is carried out through the polymer thin film. Can be interpreted as

In general, for metals, according to Ohm's law, the conductivity is not dependent on the voltage, that is, the electric field strength. However, it is said that the voltage-current characteristic of the polymer is such that a region in which the current rapidly increases appears following the region according to Ohm's law, and finally dielectric breakdown occurs. Space charge limited conduction, pool-Frenkel conduction, hopping conduction, electron avalanche conduction, and the like have been proposed as a mechanism in which electric conduction depends on an electric field in a rapid current increase region (“Electrostatic Handbook”, first edition, pages 119 to 119). 127 pages, edited by The Institute of Static Electricity, published by Ohmsha).

In the conductive fiber obtained by kneading the conductive fine particles, it is presumed that the conductive fine particles are in a state of being covered with the polymer thin film, and the electric conduction is performed through the polymer thin film. It is presumed that this reflects the electrical properties of the polymer.

The inventors of the present invention determine the establishment of the conversion rule between the applied voltage and the volume fraction of the conductive fine particles in the conductive fiber because the polymer thin film existing at the contact interface between the conductive fine particles is It is estimated to be the material and thickness. That is, when the conductive fine particles are in direct contact, they have the same electrical characteristics as metal, and when the specific resistance value and thickness of the material of the polymer thin film present at the contact interface between the conductive fine particles become large, the insulator becomes Get closer to. In order to show that the electrical characteristics of the polymer thin film at the contact interface of the conductive fine particles deviate from Ohm's law and increase non-linearly, that is, to show the dependence of the conductivity on the applied voltage, the electric field strength applied to both ends of the polymer thin film is It is necessary to set the current in the rapid increase region, and this can be realized by controlling the thickness of the polymer thin film. The polymer thin film may be made of any material that does not conduct electrons.

Factors related to the thickness of the polymer thin film include the following two. One is the content rate of the conductive fine particles in the conductive layer. The theoretical interparticle distance (thickness of the polymer thin film) of the conductive particles that does not consider the aggregation of the conductive particles is uniquely determined by the volume ratio of the conductive fine particles in the conductive layer. However, in the actual conductive fine particles, the specific surface area changes depending on the particle diameter, and the cohesiveness of the conductive fine particles changes, so that the distance between particles (the thickness of the polymer thin film) changes. Therefore, it is necessary to consider the particle diameter of the conductive fine particles as another factor.

In the conductive fiber, preferable values are preferable because the conversion rule is established between the applied voltage and the volume content of the conductive fine particles, the conductivity is 10 ⁻³ S / cm or more, and the average particle diameter is 0.0.
The volume content of the conductive particles of 1 to 5 μm in the conductive layer is 1
It is 5 to 70% by volume. More preferred is
The conductive fine particles are contained in the conductive layer in an amount of 20 to 60% by volume.

When the electroconductivity of the electroconductive fine particles is less than 10 ^-3 S / cm, it becomes difficult to develop the electroconductivity of the electroconductive fiber of the present invention. Such conductive fine particles are generally iron,
Metals typified by copper, aluminum, lead, tin, gold, silver and nickel, and their oxides, sulfides, carbonyl salts, ITO (indium tin oxide), A
Conductive metal oxides such as TO (antimony tin oxide) and zinc oxide, and barium sulfate, titanium oxide,
Examples thereof include potassium titanate, ceramic-based conductive fine particles coated with aluminum carrier fine particles, and the like.
More specifically, ITO (indium tin oxide),
Examples thereof include granular conductive ceramics in which titanium oxide carrier fine particles are coated with a conductive metal oxide such as ATO (antimony / tin oxide) and zinc oxide.

Further, when the volume content of the conductive fine particles in the conductive layer is less than 15% by volume, the rate of occurrence of unevenness between fibers due to the development of the conductivity increases sharply. If the volume fraction of fine particles exceeds 70% by volume, the distance between the contact between the conductive fine particles becomes short and the distance between the particles (thickness of the polymer thin film) becomes too thin, and the dependency of the conductivity on the applied voltage tends not to be recognized. In addition, due to the sudden deterioration of the spinnability and the like, the rate of occurrence of unevenness among fibers in the expression of conductivity is similarly increased.

When the average particle size of the conductive fine particles in the conductive layer in the fiber is less than 0.01 μm, the specific surface area of the conductive fine particles becomes large, and the cohesiveness of the conductive fine particles becomes large, so that the particles become large. The thickness of the polymer thin film at the contact interface becomes too thin, and the dependency of the conductivity on the applied voltage tends to decrease. On the other hand, when it exceeds 5 μm, the spinning nozzle pressure rises, and it becomes difficult to form a composite into fibers.

The substrate of the conductive fiber is not particularly limited,
Generally, heat-meltable polymers represented by polyester, nylon, polyethylene, polypropylene and the like, solvent-soluble polymers represented by polyacrylonitrile, rayon, polyurethane and the like can be used, and they are spun by melt spinning or solution spinning. It

More preferable conditions for the conversion rule to be established between the applied voltage and the conductive fine particle volume content are the average particle diameter of the conductive fine particles and the conductive fine particle volume content of the conductive fine particles in the conductive layer. Is within the above range and the conductive fine particles can be concentrated in the conductive layer, and in particular, the conductive fiber is obtained by kneading the conductive fine particles into the core portion of the core-sheath composite fiber.

The conductive fine particles may be contained in the core,
It is preferable from the viewpoint of process passability in processing steps such as spinning step and spinning step. When the conductive fine particles are contained in the sheath portion, the above-mentioned process passability is significantly deteriorated, and at the same time, when used for clothing and the like, there are drawbacks such as poor wearing feeling.

The core / sheath composite fiber core / sheath volume ratio is not particularly limited, but is preferably 5/95 to 60/40, and more preferably 10 /.
90 to 50/50 is desirable. When it exceeds 60/40,
There is a tendency that the core-sheath structure collapses and the target fiber cannot be obtained.

The substrate polymer forming the fiber is not particularly limited as long as it is a polymer that does not conduct electrons, but generally,
A heat-meltable polymer represented by polyester, nylon, polyethylene, polypropylene, etc., an acrylonitrile polymer, a solvent-soluble polymer represented by rayon, polyurethane, etc. can be used. Further, depending on the case, other polymers, compounds, additives and the like may be used for the purpose of improving spinnability and conductivity.

By using an acrylonitrile polymer as the substrate polymer, the texture, the appearance, the color development, etc. are excellent,
It is preferable because it can be applied to a sweater which has the highest demand for antistatic property in the clothing field. Further, it is more preferable that the substrate polymer of the fiber is an acrylonitrile-based polymer and the fineness is in the range of 1 to 30 d. If the fineness is less than 1 d, the spinnability tends to be poor, and if it exceeds 30 d, the texture of the spun yarn after blended cotton tends to deteriorate.

The acrylonitrile-based polymer is not particularly limited as long as it is a polymer which constitutes an ordinary acrylic fiber, but 50% by weight of acrylonitrile is used as a monomer component.
It is desirable to contain the above. If the volume content of acrylonitrile in the polymer is less than 50% by weight, the raw yarn loses its original properties as an acrylic fiber, which is not suitable for the purpose of the present invention.

The copolymerization component of the acrylonitrile-based polymer is not particularly limited as long as it is a copolymerization monomer that constitutes an ordinary acrylic fiber, and examples thereof include the following monomers.

That is, acrylates represented by methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, etc. Methyl methacrylate, ethyl methacrylate, isopropyl methacrylate,
N-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-hexyl, cyclohexyl methacrylate, lauryl methacrylate, methacrylic acid 2
-Hydroxyethyl, methacrylic acid esters represented by hydroxypropyl methacrylate, diethylaminoethyl methacrylate, etc., acrylic acid, methacrylic acid, maleic acid, itaconic acid, acrylamide, N-methylol acrylamide, diacetone acrylamide,
Styrene, vinyl toluene, vinyl acetate, vinyl chloride,
Unsaturated monomers such as vinylidene chloride, vinyl bromide, vinylidene bromide, vinyl fluoride, and vinylidene fluoride. Further, for the purpose of improving dyeability, p-sulfophenylmethallyl ether, methallylsulfonic acid, allylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2
-Methylpropanesulfonic acid, and alkali metal salts thereof may be copolymerized.

The molecular weight of the acrylonitrile polymer is not particularly limited, but a molecular weight of 100,000 or more and 1,000,000 or less is desirable. If the molecular weight is less than 100,000, the spinnability tends to decrease, and at the same time, the yarn quality of the raw yarn tends to deteriorate. Molecular weight 10
If it exceeds 0,000, the concentration of the polymer giving the optimum viscosity of the spinning dope will be low, and the productivity will tend to be low.

The solvent for the acrylonitrile-based polymer is not particularly limited as long as it is a solvent that dissolves the acrylonitrile-based polymer.
Examples thereof include nitric acid (aqueous solution), zinc chloride aqueous solution, rhodan salt aqueous solution, dimethylformamide, dimethylacetamide, dimethylsulfoxide, ethylene carbonate, γ-butyrolactone and acetone.

The spinning method used to obtain the fiber of the present invention is not particularly limited, and general spinning methods such as melt spinning and solution spinning are mentioned. More specifically, examples of the acrylonitrile-based polymer spinning method include a wet spinning method, a dry-wet spinning method, and a dry spinning method.

[0036]

EXAMPLES The present invention will be described more specifically with reference to the following examples. (Examples 1 to 5) Acrylonitrile 93.1 wt%, acrylic polymer consisting of vinyl acetate 6.9 wt% (molecular weight 150,000) and conductive fine particles (Mitsubishi Materials Corporation granular conductive titanium oxide WP (average) Although the mixing ratio with a particle size of 0.2 μm and an electrical conductivity of 0.4 S / cm) is changed, the solid content in the spinning dope is dissolved in dimethylformamide so as to be 50% by weight in any case, and an acrylic polymer is obtained. Spinning stock solutions (A1 to A5) having different mixing ratios of conductive fine particles were obtained.

An acrylonitrile polymer (molecular weight: 150,000) consisting of 93.1 wt% acrylonitrile and 6.9 wt% vinyl acetate was dissolved in dimethylformamide to a concentration of 25 wt% to obtain a spinning dope (B).

The spinning dope A1 and the spinning dope A were separately heated to 130 ° C., and then the spinning dope A1 was fed from the core side and the spinning dope B from the sheath side by using a core-sheath spinneret having a number of holes of 400 and a hole diameter of 0.2 mmφ. The core / sheath volume ratio is 25/75 in an inert gas at ℃
It was discharged so that The obtained undrawn yarn is continuously
Stretched 3.75 times in hot water at 100 ° C, then 95 ° C
Washed in hot water. The obtained fiber bundle was dried and relaxed at a relative humidity of 40% and a temperature of 150 ° C. in a non-tensed state, and then 2
Shrink 0%. This operation was performed using the spinning stock solutions A2 to A5 instead of the spinning stock solution A1 to obtain a total of five types of fibers. The fineness of the obtained fibers was 3 denier in each case.

The conductivity of each fiber is set to 50, 10 by applying voltage.
The values were changed to 0, 250, 500 and 1000 V / cm, and shown in Table 1. Further, since the electric conductivity at an applied voltage of 5 V / cm and the electric conductivity of 1 × 10 ⁻⁷ S / cm or less cannot be measured, the electric conductivity was read from FIGS.

[0040]

[Table 1]

FIG. 1 shows a graph plotting the electric conductivity of the conductive fibers having a volume content of each conductive fine particle at an applied voltage of 50 to 1000V. The electrical conductivity of the fibers obtained in the examples showed a positive correlation with the applied voltage.

FIG. 2 shows a composite curve when the volume concentration of the reference conductive fine particles is 43% by volume, and the curve of lower concentration is horizontally moved to the left. From this, it was found that a conversion rule was found between the applied voltage and the conductive fine particle volume content.

Further, the amount (logV) moved to superimpose the curves of the volume ratio of the conductive fine particles was used as the transfer coefficient, and the relationship between the transfer coefficient and the volume ratio of the conductive fine particles is shown in FIG. From this, it was found that there is no contradiction in the conversion rule and that the transfer coefficient is a function of concentration only.

(Comparative Example) Carbon black (# 40 manufactured by Mitsubishi Chemical Corporation (average particle size 2.7
The same acrylonitrile-based polymer as that used in the example was used except that a 10 × ^{2 -2} μm, conductivity 0.4 S / cm) was used. The spinning solution was prepared so that the volume content of the conductive particles was adjusted to obtain fibers having a fineness of 3 denier. The conductivity of the obtained fiber is also shown in Table 1.

[0045]

EFFECTS OF THE INVENTION The conductive fiber of the present invention exhibits excellent antistatic properties by exhibiting conductivity in an environment in which static electricity of relatively high voltage is generated due to friction etc. by controlling its electrical properties. It is a conductive fiber that is provided and does not cause a problem such as a short circuit in a circuit due to a low conductivity under a relatively low voltage such as inside an electronic device. In addition, the method for producing the conductive fiber of the present invention can determine the conductivity at a low applied voltage and the volume content of the conductive fine particles that cannot be measured, and is convenient for obtaining the conductive fiber of the present invention. is there.

[Brief description of drawings]

FIG. 1 is a graph showing the applied voltage dependence of the electrical conductivity of the conductive fibers obtained in the examples.

FIG. 2 is a graph showing a composite curve when the conductive fine particle content rate in FIG. 1 is 43% by volume and a curve having a lower concentration than that is horizontally moved to the left.

FIG. 3 is a graph showing the relationship between the volume of conductive fine particles and the amount (logV; transfer coefficient) moved to superimpose the curves of the volume percentage of conductive fine particles in FIG.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuhiro Matsunaka 20-1 Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Co., Ltd. Otake Office

Claims (2)

[Claims] 1. A conductivity of 1 at an applied voltage of 5 V / cm.
A conductive fiber having a conductivity of × 10 ^-6 S / cm or less and a conductivity at 1000 V / cm of 10 ^-5 S / cm or more. 2. The curve is horizontally moved onto the curve on the graph showing the applied voltage dependence of the conductivity measured by changing the volume content of the conductive fine particles in the conductive layer of the conductive fiber. The method for producing a conductive fiber according to claim 1, wherein the synthesized curves are overlapped to determine the conductivity at a low applied voltage that cannot be measured and the content rate of the conductive fine particles in the conductive layer.