JPH11200149A - White conductive fiber - Google Patents

Abstract

(57) [Summary] (with correction) [PROBLEMS] To provide a conductive fiber which is free from dullness such as gray and has excellent whiteness. SOLUTION: In a core-sheath composite fiber in which conductive fine particles are present in a core portion and the conductivity of the core portion is 1.0 × 10 ⁻⁴ S / cm or more, the layer thickness of the sheath portion is 0.7 μm or more, 75 whiteness
The white conductive fiber described above. The conductive fine particles have a specific resistance of 10
^{It is} a white conductive fine particle of ² Ω · cm or less, and its content in the core is 60 to 90 wt%. The sheath portion is made of an acrylonitrile-based polymer containing 5% by weight or less of a white pigment. White pigments include metal oxides such as titanium oxide, zinc oxide and tin oxide, metal sulfides such as zinc sulfide and barium sulfate, ITO (isodium tin oxide), and ATO.
It consists of fine particles of a white electron conductive ceramic such as (antimony tin oxide).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive fiber excellent in whiteness, which can be widely used for apparel such as inners and sweaters which require a high whiteness.

[0002]

2. Description of the Related Art Conductive fibers are widely used in industrial and household applications for the purpose of eliminating static electricity, avoiding electrostatic explosions, preventing electronic components from malfunctioning, preventing clothes from clinging, and remarkable during low humidity periods in winter. It is an indispensable material for avoiding the generation of sparks caused by frictional electrification of various clothes, mats, carpets and the like.

Conventionally, conductive fibers have been produced by a method in which a conductive material is compounded on the fiber surface by post-processing, a method in which a conductive material is used for the fiber itself, a method in which the conductive material is kneaded into the fiber, and the like. Have been used. For example, as post-processing technology, carbon black or metal (compound)
A method of embedding conductive fine particles such as copper compound in a fiber surface, a method of depositing a conductive metal compound such as copper sulfide and copper iodide in a fiber or a surface layer by chemical treatment after impregnating with a metal compound such as a copper compound, There is known a method of immobilizing an ion-conductive substance such as an ether compound or a polyetherester compound on a fiber surface layer by a method such as a chemical crosslinking method.

As a method of using a conductive material for the fiber itself, there are known a method using a metal fiber, a method using a carbon fiber, a method using an ionic conductive polymer, a method using a π-electron conjugated conductive polymer, and the like. Have been. Examples of the method of kneading the conductive material into the fiber include a method in which conductive fine particles such as carbon black or a metal (compound) are compounded by a method such as blend spinning or composite spinning, a polyether compound, a polyether ester compound, an ionic compound. There is known a method of compounding an ion-conductive substance such as a compound or a polymer obtained by blocking or graft-polymerizing these compounds with a fiber-forming polymer by a method such as blend spinning or composite spinning.

However, in a method using an electron conductive material such as carbon black, a metal (compound), or a π-electron conjugated polymer compound, these materials may be used alone, or they may be combined with ordinary fibers. The resulting conductive fiber has the excellent feature that it can impart antistatic properties to a processed fiber product only by blending it in a small amount (generally, about 1%) with ordinary fiber, In general, these electron conductive materials are colored, and thus have a drawback that the applications for which they are used are limited.

On the other hand, in a method using an ion-conductive substance such as a polyether compound, a polyether ester compound, or a polymer obtained by blocking or graft-polymerizing these compounds to a fiber-forming polymer, these substances are generally colorless. Fibers, which are composites of these materials, have the unique feature that they can be used for a wide range of applications, but because the mechanism of electrical conduction depends on the movement of ions, they are highly moisture-dependent and have a high blending ratio with ordinary fibers. (Generally 40 to 100%), and there are drawbacks such as a decrease in dyeing properties, a decrease in dyeing fastness, and a deterioration in the original properties of a processed fiber product such as a hardened texture.

Under the circumstances described above, a white electron conductive material is formed into a continuous phase in order to obtain a white conductive fiber having no humidity dependency without impairing the original properties of the processed fiber product. Thus, there has been a demand for a technique for forming a composite into ordinary fibers by a minimum amount.

As a method for responding to such a demand, a method of kneading white electron conductive fine particles into a fiber has been proposed. In particular, the effectiveness of the method of kneading the core with a core-sheath composite spinning has been emphasized. I have. Examples of the white electron conductive fine particles include fine particles of transparent conductive ceramics typified by ITO (indium tin oxide) and ATO (antimony tin oxide), or fine particles obtained by coating these materials on carrier fine particles. Generally known.
Fibers in which these white conductive fine particles are kneaded into the core by a core-sheath composite spinning can impart good antistatic properties, and almost impair the original properties of a processed fiber product such as dyeability and texture. Because it is not available, it has begun to be used in the city. However, since these white conductive fine particles are not completely white, the resulting conductive fibers are usually grayish white.

Heretofore, the use of the core-sheath composite conductive fiber has been developed mainly for use in building bedding / interior, in which the fineness of the constituent fibers is generally large. On the other hand, for apparel applications such as inners and sweaters where the fineness of the yarn composition is generally small and whiteness is strictly required, since the fineness is small, it is necessary to increase the core area with respect to the sheath to maintain conductivity. This is necessary, and therefore, the obtained conductive fibers are often grayish white. As a result, the conductive fiber obtained by the conventional core-sheath spinning has not yet been sufficiently satisfied with respect to the whiteness level for clothing, and the field of application is currently limited.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and provides a white conductive fiber having good conductivity and excellent whiteness.

[0011]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have arrived at the present invention. The gist of the present invention is that a core-sheath conjugate fiber in which conductive fine particles are present in the core and the conductivity of the core is 1.0 × 10 ⁻⁴ S / cm or more, the layer thickness of the sheath is 0.7 μm that's all,
A white conductive fiber having a whiteness of 75 or more.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The whiteness in the present invention is JIS L 1015
7.13 (3) Hunter type color difference meter (Macbeth MS-2020PLUS color management system (Instrumental Color Systems Limited, Instrumental C)
L, a, and b were measured by using the following (Europe Systems Limited) and calculated by the following equation. Whiteness = 100 − [(100−L) ² + a ² + b ² ] ^1/2

In the white conductive fiber of the present invention, conductive fine particles are present in the core and the conductivity of the core is 1.0 × 10 ⁻⁴ S / s.
cm or more, it is necessary that the layer thickness of the sheath portion is 0.7 μm or more, more preferably 0.8 μm or more. When the thickness of the sheath is less than 0.7 μm, the hue of the fiber tends to be dull and the whiteness tends to be poor because the thickness of the sheath is thin. 0.7 layer thickness of sheath
The mechanism by which the whiteness is poor at less than μm is unknown at present, but the present inventors speculate that a reduction in the scattering effect of visible light on the sheath is related. That is, the factors defining the whiteness in the core-sheath composite fiber include the degree of coloring of the core portion, transparency due to the material of the sheath portion, the sheath thickness, and the like. In the case of a visible light wavelength (about 350 to about 700 nm),
Since visible light passes through the sheath and reaches the core, it is presumed that the fiber surface has reduced whiteness.

Further, the white conductive fiber of the present invention must have a whiteness of 75 or more. If the whiteness is less than 75, gray dullness or the like appears, which is not preferable in terms of product appearance.

The white conductive fiber of the present invention has a specific resistance of 10
White conductive fine particles of ² Ω · cm or less
Preferably, it is contained in an amount of up to 90% by weight. When the specific resistance of the conductive fine particles contained in the core component exceeds 10 ² Ω · cm, the conductivity becomes weak. It is more preferable to use white conductive fine particles in order to obtain the conductive fiber having excellent whiteness of the present invention. Examples of such white conductive fine particles include tin oxide, zinc oxide and tin oxide or titanium oxide whose surface is coated with zinc oxide, and antimony oxide with respect to tin oxide as an additive for improving conductivity. However, a combination of zinc oxide and a metal oxide such as aluminum, potassium, isodium, germanium, and tin can be used.

The proportion of such white conductive fine particles in the core is preferably in the range of 60 to 90 wt%, more preferably 70 to 80 wt%. The reason is that, by kneading the conductive fine particles into the core at a high ratio, the ratio of the core to the fiber having a small fineness is reduced and the thickness of the sheath is increased. As a result, the performance of the conductivity is maintained and It is estimated that the effect of improving whiteness is exhibited. When the ratio of the conductive fine particles to the core is less than 60 wt%, there is a concern that the ratio of occurrence of unevenness between fibers in the development of conductivity may increase sharply. If it exceeds 90 wt%, the rate of occurrence of unevenness in the development of conductivity tends to increase, for example, because spinnability may suddenly deteriorate. Therefore, 70-80 wt% is required for more stable development of conductivity and improvement of whiteness.
Is preferably within the range.

The white conductive fiber of the present invention is desirably made of an acrylonitrile polymer having a sheath containing 5 wt% or less, preferably 3 wt% or less of a white pigment. If the amount of the white pigment exceeds 5% by weight, in each step from spinning to spinning, abrasion of various guides and fluffing of fibers are liable to occur.

Examples of white pigments include metal oxides such as titanium oxide, zinc oxide and tin oxide, metal sulfides such as zinc sulfide and barium sulfate, ITO (isodium tin oxide), and ATO (antimony tin oxide). And the like are preferable. Alternatively, fine particles having a carrier coated with the substance may be used. Further, as the constitution of the white pigment, any of the above substances may be used alone or in combination.

On the other hand, in the conductive core-sheath composite fiber, the cross-sectional area ratio between the core and the sheath is as follows: core / sheath = 5/95 to 15/8
5 is desirable. If the core ratio is less than 5%, it may be difficult to form a continuous phase of the core conductive fine particles during spinning or stretching, and there is a concern that the conductivity may be insufficient. If the core ratio exceeds 15%, the whiteness tends to be poor.

In general, the mechanism of the antistatic property of the conductive fiber blend is such that the lines of electric force are collected on the conductive fibers from the charged object charged by friction, and an unequal strong electric field is formed in the vicinity thereof. For this reason, an ion pair of air is generated in the vicinity, so-called corona discharge occurs, and ions of the opposite polarity to the charged object move to the charged object, and ions of the same polarity diffuse to the air or move to the grounded body . As a result, the static electricity of the charged object is neutralized. As a result, the conductive fibers are said to be self-discharged and discharged by the electric field formed by the charged body itself (static electricity handbook, 1st edition, p. 81).
6 The Electrostatics Society of Japan, published by Ohmsha). When considering the above mechanism from both conductivity and whiteness, an eccentric core-sheath composite form in which the core is eccentrically located near the fiber surface is preferable in order to obtain more sufficient discharge characteristics with a small core ratio, but an eccentric type However, the present invention is not limited to this.

The fineness of the white conductive fiber of the present invention is preferably not less than 0.3 denier, more preferably 0.6 denier.
Denier or more. If the fineness is less than 0.3 denier, the spinnability may be poor, and the continuous phase of the conductive substance in the core may be unstable, which may cause variations in the expression of conductivity. There is. Further, considering the texture of the spun yarn after the cotton blending in the subsequent step, the denier is preferably 30 denier or less, and the fineness for clothing use is preferably 10 denier or less, but the upper limit of the fineness is not particularly limited.

The polymer constituting the conductive fiber of the present invention is not particularly limited, and a heat-fusible polymer represented by polyester, nylon, polyethylene, polypropylene and the like,
Solvent-soluble polymers such as polyacrylonitrile, rayon, and polyurethane can be used.However, by using acrylonitrile-based polymers, the texture, appearance, color development, etc. are excellent, and the most antistatic requirements in the clothing field It can be used for sweater applications with high weight.

The acrylonitrile-based polymer is not particularly limited as long as it is a polymer constituting a normal acrylic fiber.
% Is desirable. If the acrylonitrile content in the polymer is less than 50% by weight, the original yarn loses its original properties as an acrylic fiber and becomes incompatible with the object of the present invention.

As the acrylonitrile copolymerization component,
There is no particular limitation as long as it is a copolymer monomer constituting a general acrylic fiber, and examples thereof include the following monomers. That is, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate,
Acrylic esters represented by 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, etc., methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methacryl Methacrylic esters represented by t-butyl acid, n-hexyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, diethylaminoethyl methacrylate, acrylic acid, methacrylic acid , Maleic acid, itaconic acid, acrylamide, N-
It is an unsaturated monomer such as methylol acrylamide, diacetone acrylamide, styrene, vinyl toluene, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl bromide, vinylidene bromide, vinyl fluoride, and vinylidene fluoride. Further, p-sulfophenyl methallyl ether, methallyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, 2-acrylamide-
2-Methylpropanesulfonic acid and alkali metal salts thereof may be copolymerized.

Although the molecular weight of the acrylonitrile-based polymer is not particularly limited, it is desirably from 100,000 to 1,000,000. If the molecular weight is less than 100,000, the spinnability tends to decrease and the yarn quality of the original yarn tends to deteriorate. Molecular weight 1
If it exceeds 100,000, the concentration of the polymer giving the optimum viscosity of the spinning dope becomes low, and the productivity tends to decrease.

The solvent for the acrylonitrile polymer is not particularly limited as long as it dissolves the acrylonitrile polymer. Examples of such a solvent include nitric acid (aqueous solution), an aqueous zinc chloride solution, an aqueous rhodanate salt, dimethylformamide, and the like. Examples include dimethylacetamide, dimethylsulfoxide, ethylene carbonate, propylene carbonate, γ-butyrolactone, and acetone.

The spinning method used to obtain the white conductive fiber of the present invention is not particularly limited, and examples thereof include general spinning methods such as melt spinning and solution spinning. 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. The two spinning dope solutions forming the core and the sheath, respectively, are shaped into a fiber form using an ordinary core-sheath composite spinneret to form undrawn yarn. The undrawn yarn is stretched 2 to 7 times in hot water at 70 ° C. or more and desolvated, and then shrinks by 5% or more by drying and relaxing heat treatment. If the temperature of hot water at the time of drawing is lower than 70 ° C., a sufficient draw ratio cannot be obtained, so that sufficient fiber quality cannot be imparted to the fiber. If the draw ratio is less than 2 times, similarly, sufficient yarn quality cannot be obtained, and if it exceeds 6 times, thread breakage frequently occurs and the core is cut, which is not preferable because the conductive performance is lowered. The above-mentioned drying and relaxation heat treatment can be performed alone or in combination with relaxation methods such as drying and annealing using a hot roll or a net process, a thermal relaxation plate, and steam relaxation, which are conventionally used in the production of acrylic fibers. The shrinkage ratio in the relaxation heat treatment is set to 5% or more, preferably 10% or more in order to secure good dyeability or necessary yarn quality at the time of spinning and weaving.

[0028]

The present invention will be described more specifically with reference to the following examples. In the examples, the layer thickness of the sheath portion was measured from a micrograph of a cross section of ten fibers and determined as an average value. The conductivity of the fiber was measured by the following method.
That is, a single fiber is taken out from the fiber bundle, separated exactly 1 cm, and bonded to a metal terminal with a silver paste (Doitite manufactured by Fujikura Kasei Co., Ltd.). 20 ° C, relative humidity 40
At RH%, a DC voltage of 1000 V is applied between the terminals, and the resistance value R (Ω) between the terminals is measured using a super insulation meter (SM-8).
210, manufactured by Toa Denpa Co., Ltd.).

The conductivity σ (S / cm) is obtained by the following equation. σ = 1 / {1.11 × 10 ⁻⁶ × R × (d / ρ)} where d is the fineness (denier) of the fiber core in the single fiber, and ρ is the specific gravity of the fiber core. (Example 1) An acrylonitrile polymer having an average molecular weight of 160,000, comprising 93.5 wt% of acrylonitrile, 6.0 wt% of methyl acrylate, and 0.5 wt% of sodium methallylsulfonate, and having a powder resistance of 2 to 5 Ωcm. Granular conductive titanium oxide (ET-500W manufactured by Ishihara Sangyo Co., Ltd.)
Was added to dimethylformamide and mixed to obtain a core spinning solution having a core component having an acrylonitrile polymer concentration of 30% by weight and a conductive titanium oxide concentration of 75% by weight. On the other hand, an acrylonitrile-based polymer and titanium oxide as a white pigment were added to dimethylformamide, mixed and slurried.
By heating and dissolving at 0 ° C., a sheath spinning solution of a sheath component having an acrylonitrile-based polymer concentration of 30 wt% and a titanium oxide concentration of 0.5 wt% as a white pigment was obtained. After individually heating the spinning stock solutions of the core component and the sheath component to 130 ° C, the unstretched yarn is obtained by discharging into an inert gas at 230 ° C using a concentric core-sheath spinneret having 400 holes and a hole diameter of 0.2 mm. Was. Then, after drawing the undrawn yarn in hot water at 100 ° C,
After washing in hot water at 95 ° C., drying and relaxation heat treatment were performed to obtain white conductive fibers having a single fiber fineness of 3 denier. The results are shown in Table 1.

Example 2 White conductive fibers were obtained under the same conditions as in Example 1 except that the concentration of the conductive titanium oxide in the spinning solution of the core component was 65 wt%. The results are shown in Table 1.

(Example 3) White conductive fibers were obtained under the same conditions as in Example 1 except that the concentration of titanium oxide, which is a white pigment of the spinning solution for the sheath component, was 2 wt%. Table 1 shows the results.
It was shown to.

Example 4 White conductive fibers were obtained under the same conditions as in Example 1 except that the concentration of titanium oxide as a white pigment of the spinning stock solution of the sheath component was changed to 6% by weight. Table 1 shows the results.
It was shown to.

Example 5 White conductive fibers were obtained under exactly the same conditions as in Example 1 except that the spinneret was changed to an eccentric type. The results are shown in Table 1.

Comparative Example 1 A conductive fiber was obtained under the same conditions as in Example 1 except that the spinneret was changed to an eccentric type having a greater eccentricity than in Example 5. The results are shown in Table 1.

[0035]

[Table 1]

[0036]

According to the present invention, it is possible to provide a white conductive fiber which has no dullness such as gray and is excellent in whiteness which has never existed before.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masakazu Hoshino 20-1 Miyukicho, Otake City, Hiroshima Prefecture Inside Mitsubishi Rayon Co., Ltd. Otake Works

Claims (4)

[Claims] 1. A core-sheath conjugate fiber in which conductive fine particles are present in a core portion and the conductivity of the core portion is 1.0 × 10 ⁻⁴ S / cm or more, wherein the layer thickness of the sheath portion is 0.7 μm or more. , Whiteness is 75
A white conductive fiber as described above. 2. The white conductive fiber according to claim 1, wherein the conductive fine particles are white conductive fine particles having a specific resistance of 10 ² Ω · cm or less, and the content in the core is 60 to 90 wt%. 3. The white conductive fiber according to claim 1, wherein the sheath is made of an acrylonitrile-based polymer containing 5% by weight or less of a white pigment. 4. A white pigment is a metal oxide such as titanium oxide, zinc oxide or tin oxide, a metal sulfide such as zinc sulfide or barium sulfate, or ITO (isodium tin oxide);
The white conductive fiber according to claim 3, comprising fine particles of a white electron conductive ceramic such as TO (antimony tin oxide).