JPS6297918A - Electrically conductive fiber - Google Patents

Abstract

PURPOSE:The titled fibers which are conjugate fibers, constituted of a sheath component consisting of a fiber-forming polymer and a core part, consisting of a specific low-temperature flowable highly crystalline polymer and having an organic acid present in the inner surface layer of the sheath part in contact with the core part and having improved flex durability. CONSTITUTION:Fibers, consisting of (A) a sheath part consisting of a fiber- forming polymer, e.g. polyethylene terephthalate or nylon-6, and (B) a core part consisting of a low-temperature flowable highly crystalline polymer, e.g. polyethylene or polypropylene, containing dispersed electrically conductive metal oxide fine powder, e.g. stannic oxide or zinc oxide, and having an organic acid present in the inner surface layer of the sheath part thereof in contact with the core part. The above-mentioned organic acid is preferably a >=4C organic carboxylic acid and/or organic sulfonic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to conductive fibers, particularly white conductive core-sheath type composite fibers having excellent bending durability.

(b) Prior Art Thermoplastic polymers such as polyethylene, polyamide, and polyester are used in many applications as fibers, films, and other molded products, but they have the disadvantage of being easily charged due to poor electrostatic properties. For example, clothing made of polyethylene terephthalate fibers tends to cling to the body when worn due to its electrostatic properties, easily gets dirty by attracting dust floating in the air, and even when walking on carpets made of such fibers. There are many problems, such as the fact that when you touch a door handle, you can easily receive an electric discharge shock.

To address such problems, many proposals regarding conductive fibers have been made. The first method involves kneading conductive carbon particles into fibers, or composite fibers having a core made of conductive carbon powder dispersed in a thermoplastic polymer and a sheath made of a fiber-forming polymer. There is a way to do it.

However, such conductivity! ! Since the conductive carbon is black, navy blue is extremely colored and cannot be used in fields where aesthetics are required, so its uses are extremely limited.

As a second method, there is a method of providing a surface conductive material layer on an IIi rough surface. In more detail, this is a method in which chemically plated metal-plated fibers, metal powder, and conductive powder such as carbon black are applied onto the fiber surface. Although these conductive fibers certainly have good initial conductive performance, not only do the conductive agent layer on the surface peel off due to wear and washing during wearing, the conductivity decreases considerably, but their chemical resistance is also poor. It becomes a source of dust in dust-proof clothing, etc., and furthermore, it is unavoidable that it will be colored by conductive substances.

As a method for solving the above-mentioned drawbacks, a method has recently been proposed for producing conductive fibers using a colorless or light-colored conductive metal compound.

(C) Problems to be solved However, the conductive fibers manufactured based on these proposals lose their conductivity due to bending and abrasion several hundred times, and the expected effect of electroconductive properties after wearing them for a short time is lost. As a result, the above-mentioned clinging to clothing causes dust to accumulate.

(d) Means for Solving the Problem The present inventors have conducted extensive research in an effort to provide conductive fibers free of such defects. As a result, the core of conductive core-sheath type composite fibers contains Although a conductive metal oxide is present in the matrix of the coalescence, conductivity cannot be observed if this is merely uniformly dispersed. Spinning/drawing/
The heat received during heat treatment causes a highly crystallized orientation phenomenon in the low-temperature fluid polymer, which causes the conductive metal oxide to be blown out of the low-temperature fluid polymer system, resulting in phase separation. , gold fi! The conductive function is only achieved when the compounds aggregate and rearrange to form a chain structure. However, when the 17 fibers are bent and abraded in this manner, the electrical resistance value becomes high and the conductivity becomes poor. The inventors,
After various analyzes of this phenomenon, they found that it is caused by low interfacial adhesion between the highly crystallized low-temperature fluid polymer layer in the core and the polymer layer in the sheath. That is, it has been found that poor interfacial adhesion easily causes the core and sheath to separate during bending wear, leading to destruction of the chain structure of the metal oxides present in the core. As a result of intensive research on technology to improve the interfacial adhesion between the core and sheath, we have found that bending durability is improved by adding 11 to a mixed system of metal oxide and low-temperature fluid high-crystalline polymer. It was very successful. That is, by blending an organic acid in the core, when the low-temperature fluid polymer undergoes high crystal orientation, not only the conductive metal compound but also the organic acid is phase separated, and the core system is A bleed-out phenomenon occurs in which the released organic acid diffuses and permeates into the inner layer of the sheath. As a result, the interfacial adhesion between the core layer and the inner surface layer of the sheath has been dramatically improved, and the electrical resistance value of the conductive TA navy blue, which is flex-wear-fast, is maintained at 109Ω/Cm without swirling, and when it is tied, it is free from dust adhesion. We discovered that it is possible to obtain fabrics that do not have
This is what the present invention has been achieved.

That is, the present invention provides a composite fiber composed of a sheath made of a fiber-forming polymer and a core made of a low-temperature fluid highly crystalline polymer in which conductive metal oxide fine powder is dispersed,
The present invention relates to a conductive fiber in which an organic acid is present in the inner layer in contact with the core of the sheath. The conductive fibers of the present invention have UJ [2
This conductive composition or core is melt-spun into a composite fiber so that the fiber-forming polymer constitutes a sheath, and if necessary, it is produced by stretching and heat treatment. By blending an organic acid into the core component in this way, it is possible to absorb the heat received during processes such as spinning, stretching, and heat treatment, as described above, and to reduce the amount of heat that is received during processes such as spinning, stretching, and heat treatment.
Due to the heat received during the dyeing process, the acid migrates to the inner surface layer of the sheath in contact with the core, as shown in FIG. 1, and comes to exist there. The presence of organic acid in the inner layer of the sheath can be easily identified in an electron micrograph of the fiber cross section magnified approximately 2000 times.

The polymer constituting the sheath portion of the conductive fiber of the present invention may be a thermoplastic polymer having fiber-forming ability. For example, polyethylene terephthalate 1~.

Examples include nylon-6, nylon-6,6, and polypropylene.

The low-temperature flowable highly crystalline polymer is the I! that constitutes the sheath. Any thermoplastic polymer may be used as long as it has a flow temperature lower than that of the fiber-forming polymer and is highly crystalline, specifically polyethylene and polypropylene.

Polystyrene, polybutadiene, polyisoprene.

The main targets are Teton-6, Nylon-6,6, polyethylene terephthalate, polyethylene terephthalate, etc., but some of these may be replaced with copolymer components, and even those with low temperature fluidity and high crystallinity may be used. For example, materials other than those mentioned above may be used depending on the purpose, and two or more of them may be mixed as necessary.

As the conductive metal oxide in the present invention, stannic oxide and zinc oxide are particularly preferred. The stannic oxide mentioned here also includes stannic oxide containing a small amount of antimony compound and a conductive metal composite made by coating the surface of titanium oxide particles with stannic oxide containing a small amount of antimony compound. It will be done. Zinc oxide also includes conductive zinc oxide in which small amounts of aluminum oxide, lithium oxide, indium oxide, etc. are dissolved. These are usually treated as fine powders.

The organic acid to be blended in advance into the low-temperature-fluid, highly crystalline polymer of the core is preferably an organic carboxylic acid or an organic sulfonic acid having 14 or more carbon atoms, and particularly preferably an organic acid having up to 24 carbon atoms. The organic residues bonded to carboxyl groups and sulfonic acid groups are preferably alkyl groups, alkylene groups, aryl groups, alkylaryl groups, and aralkyl groups, and if these groups are non-carboxyl groups, It may have any substituent.

Specific examples of such organic carboxylic acids include n-proic acid, n-hebutanoic acid, benzoic acid, n-caprylic acid, phenylacetic acid, toluic acid, n-nonanoic acid, and stearic acid. In addition, as a specific example of shrine sulfonic acid, n
- Pentanesulfonic acid, penpinesulfonic acid, dodecylbenzenesulfonic acid, etc. These are organic carboxylic acids.

The organic sulfonic acids may be used singly or in appropriate combinations.

Note: In order to incorporate a mechanical acid into a low-temperature fluid polymer, consider the thermal properties of the organic carboxylic acid or organic sulfonic acid, which is 0V phosphoric acid.(1) Low-temperature fluid polymer and conductive metal oxidation (2) a method in which a conductive metal oxide is previously treated with an organic acid and then melt-mixed with a low-temperature fluid polymer, as appropriate.

For example, it is undesirable to melt conductive compositions by directly melt-mixing a low-boiling organic acid such as n-hebutanoic acid with a conductive metal oxide into a relatively high-melting low-temperature fluid polymer. . In such a case, it is preferable to treat the conductive metal oxide with n-hebutanoic acid in advance and then melt-mix it with the low-temperature fluid polymer.

On the other hand, even if the same n-hebutanoic acid is used as an organic acid, if the low-temperature fluid polymer used has a relatively low melting point such as polyethylene, a conductive metal oxide and n-hebutanoic acid may be used as an organic acid. There is no problem in directly melt-mixing it with polyethylene.

In the method of pre-treating a conductive metal oxide with an acid, the desired conductive metal oxide powder is inhaled and dispersed in a solution prepared by dissolving an organic acid in an organic solvent, and after stirring for several hours. An extremely simple method is used in which the solvent and the powder are separated by filtration.

When pre-treating a conductive metal oxide with an organic acid, it is possible to simply add and disperse the conductive metal oxide in an organic solvent solution of an organic acid and stir it at room temperature as described above, but it is also possible to treat the conductive metal oxide in a shorter time. For this purpose, it is effective to heat and stir. The organic solvent used here is not particularly limited as long as it dissolves the organic carboxylic acid and/or organic sulfonic acid compound that is the organic acid. Furthermore, when a large amount of organic acid is used in this treatment, the excess organic acid may be washed and removed after filtration. The amount of the professional acid used is preferably kept to a necessary and sufficient minimum amount, and is usually preferably in the range of 0.1 to 3 parts by weight per 100 parts by weight of the conductive metal oxide powder. When the amount of organic acid is 0.1 part by weight or less,
The interfacial adhesion between the core and sheath portions covered by the conductive layer is not sufficiently improved, and a sufficient effect of improving bending resistance cannot be obtained. Also, 3
If the amount exceeds the seedling area, it becomes difficult to filter the organic solvent from the dispersion after treatment, or it becomes necessary to wash away excess organic acid after filtration, which is not preferable. Furthermore, when an organic acid and a conductive metal oxide are directly melt-mixed with a low-temperature fluid polymer, it is not preferable to add an excessive amount of the organic acid because this will impair the physical properties of the low-temperature fluid polymer.

(f) Effects of the Invention The conductive fiber of the present invention has significantly improved bending abrasion resistance, and can be extremely effectively applied to any form such as yarn or fabric. Furthermore, no change in electrical resistance was observed in the white conductive fiber of the present invention even after post-treatments such as washing, cleaning, and steaming.

(g) Examples The present invention will be specifically explained below using Examples.

Measurement method (1) Flexural abrasion test method: 1FF13 conductive regions were sewn onto a 100% polyester plain weave fabric at 0.5 cm intervals, placed in a universal abrasion tester, and subjected to a tensile load of 220 (]).

Bending and abrasion were repeated 0 to 1,200 times without any presser load (20'Cx 50%RH).

(2) Electrical resistance value (Rs) measurement method Precisely measure 2 on an insulating polyethylene terephthalate film.
．． Ag dotite (conductive resin paint, manufactured by Fujikura Industries) was attached to the cross section of a conductive fiber whose ends were cut in the cross-sectional direction to 0 cm, and a DC voltage of 1 KV was applied under 20'Cx 30% R1-1. The electrical resistance value was measured (unit: Ω/
cm).

Example 1 The surface of titanium oxide fine particles was coated with conductive tin oxide containing a small amount of antimony trioxide, with an average particle size of 0.2
3.1 toluene was added to 1 kg of conductive powder with μ, non-resistance 10 Ω cm and 20 stearic acid, and the mixture was heated under reflux for 5 hours with vigorous stirring.The mixture was allowed to stand overnight, and then decane was added. Most of the toluene is removed by dision,
The powder was separated by filtration, thoroughly washed with toluene, and dried.

250 parts of the powder thus obtained, 20 parts of liquid paraffin
fR foot and melt index 75 (JISK676
0-1971) was charged into a kneader, heated to 175°C, and mixed for 5 hours.

The specific resistance of the electrically conductive composition obtained was 1 x 102Ω・
It was cm. A core-sheath type composite fiber (core-sheath ratio = 1/6) with this conductive composition as a core and polyethylene terephthalate as a sheath was made by melt spinning, and was stretched 4 times to 100%.
Conductive multifilament with denier and single thread count of 12 (
It was.

Table 1 shows the results of investigating the relationship between the number of times of bending abrasion and the electrical resistance value of this conductive composite fiber. Furthermore, a cross-sectional photograph enlarged to 2000 mm with a scanning electron microscope is shown in FIG. From the photograph, it can be seen that stearic acid, an organic acid, bleeds out from the inner layer of the sheath and forms a third layer.

It is considered that this third layer improves the interfacial adhesion between the sheath portion and the core portion, and improves the bending abrasion durability of the conductive material.

Comparative Example A conductive composite fiber having a polyethylene terephthalate sheath was obtained in the same manner as in Example 1, except that zinc stearate was used instead of the stearic acid used in Example 1.

This fiber was subjected to a bending test in the same manner as in Example 1 to examine the relationship between the number of bends and the electrical resistance value, and the results shown in Table 1 were obtained. In the scanning electron microscopy cross-sectional photograph, no third layer due to the bleed-out phenomenon as shown in Figure 1 was observed, indicating that the interfacial adhesion ↑4 between the core and sheath was poor, causing peeling, and as a result, the electrical resistance value decreased. The bending abrasion durability is poor, and the conductivity is far below the practical level.

Table 1 Example 2 250 parts by weight of conductive metal powder made of stannic oxide containing a small amount of antimony trioxide and melt flow index 1
．． 0 (AST) 101238-651) was charged into a kneader and melted at 200°C for 30 minutes, followed by 2 parts by weight of dodecylbenzenesulfonic acid, 50 parts by weight of liquid paraffin, and Irganox 101.
00.5 parts by weight was added and kneaded for further 4 hours.

The specific resistance of the conductive composition thus obtained is 6.0X102
It was Ωcm. By melt spinning, a core-sheath type composite fiber (core-sheath ratio = 115) with this conductive composition as a core and polyethylene terephthalate as a sheath was made, and it was drawn 4 times to make a 100-denier conductive multifilament with a monofilament number of 12. (q.

This conductive composite fiber was subjected to dry heat treatment at 160″C x 1 minute,
Table 2 shows the results of investigating the relationship between the number of bending wear and the electrical resistance value.

Table 2

[Brief explanation of drawings]

FIG. 1 is a 2000 times enlarged photograph of the cross section of the conductive fiber of the present invention taken with a scanning electron microscope.

Claims (1)

[Claims] 1. A composite fiber composed of a sheath made of a fiber-forming polymer and a core made of a low-temperature fluid highly crystalline polymer in which conductive metal oxide fine powder is dispersed. A conductive fiber having an organic acid present in the inner layer in contact with the core of the sheath. 2. The conductive fiber according to claim 1, wherein the organic acid is at least one organic acid selected from organic carboxylic acids and organic sulfonic acids having 4 or more carbon atoms.