JP2593937B2 - White conductive composite fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of Industrial Application The present invention relates to a conductive conjugate fiber having excellent static elimination performance, particularly a conductive conjugate fiber having excellent static elimination performance with excellent fiber physical properties and wearing durability. .

More specifically, a white or colorless composite having excellent static elimination performance using a polyester-based polymer as a non-conductive layer component (A) and a specific thermoplastic elastomer containing a conductive metal oxide as a conductive layer component (B). By adding the conductive conjugate fiber to ordinary non-conductive fiber in an amount of only 0.01 wt% to 10 wt% (wt%), a composition such as cloth having excellent static elimination performance can be obtained. The present invention relates to a conductive composite fiber whose static elimination performance does not decrease even after years.

(2) Conventional technology Various proposals have been made for conductive fibers as fibers having excellent static elimination performance. For example, those in which metal is applied to the surface of a non-conductive fiber to impart conductivity. Also, there is a method in which a conductive carbon black is dispersed in a resin and then coated on the fiber surface to form a conductive coating layer. However, these are obtained by a method which is technically difficult due to a complicated manufacturing process, and are used in preparation steps for putting conductive fibers into practical use, such as chemical treatment in a refining process for weaving and knitting. There is a problem that the conductivity is easily reduced due to external action such as abrasion and repeated washing in actual use, and the practical use is lost. As other conductive fibers, metal fibers such as steel fibers are known as having excellent static elimination performance.However, metal fibers are hardly compatible with general organic materials and have poor spinnability, and in the weaving and dyeing finishing processes In addition, it is easy to cause disconnection and dropout due to washing when worn, and it also causes electric shock and sparking problems due to electrical conductivity and troubles in melting fabric. For the purpose of solving these problems even a little,
There has been proposed a conductive composite fiber in which a conductive layer component composed of a polymer mixed with a conductive carbon black and a protective component composed of a fiber-forming polymer are joined.

However, a major drawback of the conductive conjugate fiber using carbon black is that the fiber is colored black, which limits the use of the fiber.

As a method for solving this drawback, conductive composite fibers using white or colorless conductive metal oxide particles have recently been provided.

(3) Problems to be Solved by the Invention For example, as disclosed in Japanese Patent Publication No. 58-39175, titanium oxide particles having a coating of stannic oxide in a synthetic polymer are mixed with 3w.
Antistatic synthetic polymer compositions in which t% to 20% by weight are dispersed have been proposed. However, in this case, it is difficult to obtain a conductive conjugate fiber having the desired static elimination performance for the following two reasons.

a. Many of the metal oxides are semiconductors close to insulators, and it is necessary to add an appropriate doping agent to the metal oxide in order to obtain conductive fibers having static elimination performance.

b. With the low particle mixing ratio described, it is difficult to obtain the desired conductive conjugate fiber.

Due to the above two problems, practically useful conductive composite fibers cannot be obtained in the present invention. According to the study results of the present inventors, the amount of the conductive metal oxide needs to be at least 55% by weight or more, preferably 60% by weight or more.

In JP-A-57-6767 and JP-B-62-29526, a conductive composite fiber of a mixture (conductive layer) of a conductive metal oxide and a thermoplastic resin and a fiber-forming thermoplastic polymer is prepared. In such a case, there has been proposed a method in which a composite raw yarn is prepared and drawn, and then the fiber is subjected to a heat treatment to repair the conductive layer. When a thermoplastic resin is used as a binder for the conductive metal oxide, the conductive layer is cut by the stretching process. In this state, since the conductivity is lost, it cannot serve as the antistatic fiber. Such a heat treatment is necessary when a thermoplastic resin, particularly a thermoplastic resin having high crystallinity, is used as a binder for the conductive metal oxide. The antistatic fiber obtained in the above patent has a drawback that production efficiency is poor due to the presence of a heat treatment step after stretching, and the obtained antistatic fiber also has a major drawback that durability is insufficient. I have.

That is, Japanese Patent Publication No. 62-29526 discloses a thermoplastic resin having a high crystallinity as a thermoplastic resin suitable as a binder for a conductive metal oxide on condition that the composite fiber is subjected to a heat treatment after drawing. The crystallinity of the thermoplastic resin is preferably 40% or more, and specifically, polyethylene, polyethylene oxide, and nylon 6 are used. A method of using a thermoplastic resin having a high degree of crystallinity as a binder for the conductive metal oxide and performing a heat treatment after stretching the composite fiber is one method for obtaining a conductive composite fiber. The obtained conductive conjugate fiber had a problem that the wearing durability was insufficient.

As is well known, the antistatic performance refers to non-contact static elimination of the charge of a charged object. As a result of extensive studies by the present inventors, the filament resistance (hereinafter, also referred to as core resistance) is 1 × 10 ¹¹ Ω. /cm.f or less, a non-equilibrium electrolysis is formed,
The charge is eliminated by corona discharge, but the core resistance is 1 × 10 ¹¹ Ω / c
In the case of m · f or more, static elimination does not occur due to corona discharge, and no effective antistatic property is exhibited. Under these circumstances, antistatic fibers (fibers having static elimination performance) are always 9 × 10 ¹⁰ Ω / cm, regardless of the resistance of the filament, regardless of the usage conditions of the fiber.
-It must be less than or equal to f.

The durability of the antistatic fiber means that, for example, in the case of antistatic clothing, a woven fabric containing 0.1 to 10 wt% of antistatic fiber is actually worn for about one year, and at that time, it is determined whether or not the antistatic performance is present. I do. The standard value of the charge amount in the electrostatic safety guideline issued by the Ministry of Labor's Work Stability Research Institute is 7 μcoulomb / m ² , and it is necessary that the value be less than this value. The conventional white or colorless conductive conjugate fiber cannot satisfy the above-mentioned durability. For example, the present inventors have found that when the thermoplastic polymer is polyethylene, the actual wearing durability is insufficient, and the use thereof in dangerous work such as work clothes is inappropriate. When using a crystalline thermoplastic resin as the thermoplastic polymer,
The resistance of the filament immediately after the preparation of the conductive composite fiber is 9 × 10
It can be set to a value of ¹⁰ Ω / cm · f or less, and can satisfy the charge standard value of the fabric. However, the antistatic performance of the fabric is deteriorated due to poor durability, and it is difficult to actually use the fabric. is there. The reason why the durability is not good when the crystalline thermoplastic resin is used is that the conductive structure of the antistatic fiber is easily broken because the crystalline thermoplastic resin is brittle.

(4) Means for Solving the Problems The present inventors have conducted detailed studies in order to provide a conductive conjugate fiber free of such defects. In particular, as a result of intensive studies on the fiber structure, the static elimination performance and the actual wearing durability, a white or colorless conductive conjugate fiber having excellent static elimination performance and actual wearing durability was found and arrived at the present invention. .

The gist of the present invention is a conductive conjugate fiber comprising a polyester polymer as a non-conductive component (A) and a mixture of conductive metal oxide particles and a thermoplastic elastomer as a conductive component (B). A white or colorless conductive composite fiber, wherein the thermoplastic elastomer used for the conductive component is a polyester-based or polyamide-based elastomer or a tertiary amine pendant NBR. The conductive conjugate fiber produced under such conditions had a filament resistance of 9 × 10 ¹⁰ Ω / cm · f or less, and was excellent in actual wear durability.

The most important issue in obtaining a white or colorless antistatic fiber is that the conductive layer is often cut in the process of drawing the conjugate fiber.How to solve this and the durability in actual wearing The two points are how to give the gender. A method of using a crystalline thermoplastic resin as a binder and applying heat treatment after drawing the fiber is a useful method for reconnecting the conductive layer cut in the drawing step. According to the results of the study by the present inventors, the obtained conductive conjugate fiber had insufficient durability in actual wearing. The cause of the lack of durability is that when a thermoplastic resin is used as a binder, particularly when a crystalline thermoplastic resin is used, the conductive layer broken by heat treatment can be repaired, but the conductive layer itself is inherently brittle This is because the conductive layer breaks again in repeated expansion and contraction in actual wearing, and thus cannot exhibit durability.

The present inventors have conducted intensive studies and found that a conductive composite fiber having a conductive layer made of a mixture of conductive metal oxide particles and a specific thermoplastic elastomer has a low resistance value and a high durability in actual use. The invention has been completed. Moreover, the conductive composite fiber obtained in the present invention is useful in that the step of performing heat treatment after drawing the fiber is not required, and the step can be simplified.

The thermoplastic elastomer is a polymer material which is a rubber elastic body at normal temperature but plasticized and moldable at a high temperature (a temperature range higher than the melting point).

The thermoplastic elastomer used in the present invention has rubber elasticity and has a tensile elongation at break (JIS K-6301) of 100% or more, preferably 200% or more. .

Examples of the thermoplastic elastomer used in the present invention include polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, and tertiary amine pendants.
NBR can be mentioned. Such an elastomer is suitable for achieving the object of the present invention.

Examples of the polyester polymer forming the non-conductive layer of the conductive conjugate fiber of the present invention include polyethylene terephthalate and polyester polymers containing polybutylene terephthalate as a main component. Thus, the durability for actual wearing is improved.

When polyethylene terephthalate is used, the heat resistance (thermal decomposition resistance) required of the thermoplastic elastomer is 300 ° C. or higher. The above-mentioned thermoplastic elastomer satisfies this condition.

Examples of the conductive metal oxide particles used in the present invention include tin oxide, zinc oxide, silver oxide, copper oxide, cadmium oxide, and lead oxide. Many of the metal oxides are semiconductors that are close to insulators. But a suitable second
The conductivity can be improved by adding the components. Examples of such a conductivity enhancer (so-called doping agent) include oxides of different metals or same and different metals. For example, antimony oxide is added to tin oxide. Copper is added to copper oxide, aluminum oxide is added to zinc oxide, and tin or antimony is added to tin oxide and antimony oxide.
The addition amount of the doping agent is determined by the electric conductivity of the conductive metal oxide particles and the degree of coloring of the particles. That is, when the addition amount of the doping agent is increased to improve the electrical conductivity of the particles, the electrical conductivity increases but the degree of coloring of the conductive particles increases.

In order to solve this problem, a method has been proposed to increase the electrical conductivity of the conductive metal oxide while keeping the white state, and as one of the methods, the surface of the white metal oxide particles is exposed to the conductivity of the metal oxide. Covering with a film is performed. That is, titanium oxide particles whose surface is mainly composed of zinc oxide or tin oxide, and that uses antimony oxide as a doping agent are commercially available from various companies (for example, Mitsubishi Metal W-1, Titanium Kogyo ECT-52, etc.), In the present invention, it is also preferable to use these.

It is also useful to make the particle size of the conductive particles smaller than the wavelength of light in order to prevent coloring of the particles. Specifically, transparency can be imparted to the particles by setting the particle size to 0.1 μm or less, preferably 0.05 μm or less. In the present invention, such transparent conductive metal oxide particles may be used.

As the conductive particles preferably used in the present invention, particles having an average particle diameter of 1 μm to 0.01 μm are preferably used because the electric conductivity can be increased.

In order to increase the electrical conductivity of the mixture, the conductive metal oxide particles must be in contact with each other. For this purpose, it is important to increase the concentration of the conductive metal oxide in the mixture and to cause aggregation of the conductive metal oxide particles.

Generally, when a flexible or fluid polymer material such as a silicone elastomer or a liquid elastomer is used as a binder, the mixing amount of the conductive metal oxide particles can be extremely increased. According to the study results of the present inventors, when such a polymer material is used, the mixing amount of the conductive metal oxide particles can be increased to about 80 to 90 wt%. However, in this case, the amount of the conductive metal oxide particles mixed can be increased, but it is difficult to increase the electric conductivity of the mixture. For these reasons, it has not been possible to obtain a conductive composite fiber having a low resistance value even if a polymer material having high fluidity is simply used as the binder and the amount of the conductive metal oxide particles mixed is increased. When the binder of the present invention is used, a high mixing ratio and moderate aggregation occur, and the above-mentioned disadvantages can be avoided.

In the present invention, the mixing ratio of the conductive metal oxide particles to the thermoplastic elastomer is such that the ratio of the conductive metal oxide particles is 60 to 85% by weight of the mixture. Preferably it is 70-80 wt%. In the case of crystalline thermoplastic resin which has been conventionally proposed as a binder for conductive metal oxide particles, further improvement in conductivity is recognized when the mixing amount of metal oxide particles exceeds 70 wt%. However, the fluidity of the conductive component of the conductive conjugate fiber is significantly reduced, and the spinnability is extremely deteriorated. In particular, the life of a pack such as filter clogging is significantly shortened, and the process stability is lost. However, such a disadvantage could be overcome when a thermoplastic elastomer was used.

In the present invention, when preparing a mixture of the thermoplastic elastomer and the conductive metal oxide particles, a surface treating agent for the conductive metal oxide particles may be added. Further, a conductivity improver, a dispersant and the like may be mixed.

For the conductive conjugate fiber of the present invention, a normal conjugate fiber production method can be used as it is. That is, a drawn yarn obtained by drawing the original yarn of the conjugate fiber may be used, or a highly oriented undrawn conductive conjugate fiber in which the drawing step is omitted can be directly obtained by performing high-speed spinning.

As described above, the composite form of the conductive conjugate fiber in the present invention is a core-sheath type in which the non-conductive layer component forms the sheath and the conductive layer component forms the core. The number of cores is not limited to one and may be multi-core,
The shape of the core is also arbitrary. Further, it includes an eccentric core-sheath type, a composite form in which a conductive layer component constitutes an intermediate layer having a three-layer structure, and the like, in other words, a state in which the conductive layer component is completely covered by the non-conductive layer component. Further, the conductive layer component is compounded in a continuous state in the fiber axis direction, and by such a compound form, improvement in conductivity and durability in actual wearing of the conductivity are exhibited.

When the white conductive fiber of the present invention is used for an antistatic cloth, it is usually mixed with 0.1 wt% to 10 wt% of the cloth and used as in the case of the normal conductive fiber. Naturally, these fabrics are completed through a dyeing and finishing process. The conductive layer component is fragile because it contains a large amount of conductive metal oxide particles, and is susceptible to damage by a hot chemical or the like during processing. In particular, in the case of a cloth mainly composed of polyethylene terephthalate, high-temperature dyeing and high-temperature setting cannot be avoided, and the conductive layer component of the conductive composite fiber may be significantly affected by these steps. In order to avoid the effects of high-temperature dyeing and high-temperature setting, the use of a composite conductive fiber having a core-sheath structure is the one which is least affected by the process.

 Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 Titanium oxide fine particles (average particle size: 0.2 μm, W-1 manufactured by Mitsubishi Metals Co., Ltd.) coated on the surface with 15 wt% (wt%) stannic oxide (containing 2 wt% antimony oxide) were used as a conductive metal. Used as oxide particles. It had a volume resistivity of 10 Ω · cm and was almost white.

As the thermoplastic elastomer, a polyester / polyether type thermoplastic elastomer (Perprene P40H manufactured by Toyobo Co., Ltd., the structural formula is shown below. The elongation at break is 690%) was used.

70% by weight of the conductive white titanium oxide fine particles and 30% by weight of a polyester / polyether type thermoplastic elastomer
The mixture was mixed using a small lavender at a temperature of 240 ° C. In order to uniformly mix the titanium oxide fine particles and reduce the viscosity of the mixture, a small amount of titanate-based coupling agent (manufactured by Nippon Soda Co., Ltd.) is being mixed with the titanium oxide particles and a polyester / polyether type thermoplastic elastomer. Was added. Using this conductive chip, a white conductive composite fiber was produced.

This conductive chip (B) and a normal polyethylene terephthalate (A) chip (Tm ₂ = 256 ° C., [η] = 0.63 after spinning) are melted by separate extruders,
Using a composite spinning device, the composite ratio of the core-sheath composite yarn {(A) and (B) is 80:20:｝ by weight so that (B) forms the core and (A) forms the sheath. Spinning from 4 discharge holes at 300 ° C,
The film was wound in two at a spinning speed of 4500 m / min to obtain a 25-denier / 2-filament highly oriented undrawn conductive composite fiber. The spinning processability was good. The obtained fiber was white, and the core resistance of the filament was 5 × 10 ⁸ Ω / cm · f.

The obtained fiber is polyethylene terephthalate / cotton = 65
Covering with blended yarn of / 35, polyethylene terephthalate / cotton = 65/35, cotton yarn 20s / ₂ , drive into 80 warp yarn at a ratio of 1 yarn to 80 warp 80 / in 50 / in 2 / One twill fabric was used. Subsequently, dyeing and finishing were carried out under the conditions of ordinary polyester cotton blend fabric. The charge on the fabric is 4.3
It was μ coulomb / m ² . The garment was actually worn as work clothes for one year, and after being repeatedly washed 100 times, the charge amount was 4.7 μCoulomb / m ² , and it was a woven cloth having excellent static elimination performance. In other words, it passed the standard value (hereinafter referred to as the standard value) of 7 μCoulomb / m ² of the Electrostatic Safety Guidelines issued by the Ministry of Labor, Industrial Safety Research Institute, and had extremely excellent durability. When the conductive fabric was recovered from the fabric and the core resistance was measured, it was 3 × 10 ⁹ Ω / cm · f, and the rate of decrease in the resistance was satisfactory.

Example 2 Using tertiary amino pendant NBR (structure is shown below), polybutylene terephthalate (Tm ₂
= 226 ° C, [η] = 0.82 after spinning was used, and an attempt was made to produce a conductive composite fiber in the same manner as in Example 1. 2,2'-Dichloroparaxylene was used as a crosslinking agent for tertiary amino pendant NBR (1.5 wt% based on tertiary amino pendant NBR).
Was added. ) The mixing ratio with W-1 is 75 wt%.
Performed at 210 ° C. The spinning speed is 3700m / min. The spinning processability was good. The core resistance of this composite fiber is 3 × 10 ⁹ Ω /
cm · f. Using this fiber, a dyed fabric was produced in the same manner as in Example 1. The charge amount of the woven fabric was 4.7 μC / m ² . Further, the charge amount after being worn as work clothes for one year was 5.8 μC / m ² , which satisfied the standard value. The conductive fiber was recovered from the work clothes, and the core resistance was measured. The result was 8 × 10 ⁹ Ω / cm · f, indicating that both the antistatic performance and the durability were good.

Comparative Examples 1 and 2 Conductive composite fibers were prepared in the same manner as in Example 1 except that nylon 6 (crystallinity: 45%) was used as a binder. The mixing ratio of W-1 was 65 or 70 wt%, and the mixing temperature was 240 ° C. Although the antistatic performance immediately after the preparation of this composite fiber was excellent, the antistatic performance had disappeared one year after actual wearing (Tables 1 and 2). When the mixing ratio with W-1 was 70 wt%, filter clogging occurred and the packing life was extremely short.

Comparative Example 3 Conductive composite fibers were prepared by using high-density polyethylene (crystallinity: 70%), which is a crystalline thermoplastic resin, as a binder and mixing the conductive particles at 65 wt%. Immediately after the fiber was made, the antistatic performance was good, but after one year of actual wearing, the antistatic performance had disappeared.

Example 3 Polyether amide-type thermoplastic elastomer as a binder (MS Jiapan Co., Ltd. Grilamide ELY)
-60, melting point 160 ° C). 240 ° C with W-1
I went in. Other conditions were the same as in Example 1 to produce a conductive conjugate fiber. The antistatic performance of this fiber was good and the durability was also excellent (Tables 1 and 2).

[Brief description of the drawings]

1 and 2 are cross-sectional views of the core-in-sheath type conjugate fiber specified in the present invention. The hatched portion in the figure indicates the conductive layer component (B).

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazuhiko Tanaka 1621 Sazu, Kurashiki-shi, Okayama Prefecture Inside Kuraray Co., Ltd. JP-A-59-223309 (JP, A) JP-A-59-223313 (JP, A) JP-B-62-28410 (JP, B2) JP-B-61-16622 (JP, B2)

Claims (1)

(57) [Claims] A non-conductive layer component (A) composed of a polyester-based polymer as a sheath, and a conductive layer component (B) composed of a mixture of conductive metal oxide particles and a thermoplastic elastomer having a core portion of white or white. In the colorless conductive composite fiber, the thermoplastic elastomer is a polyester elastomer,
Polyamide elastomer or tertiary amine pendant
One kind selected from NBR, the amount of the conductive metal oxide particles in the conductive layer component (B) is in the range of 60 to 85% by weight, and the conductive layer component (B) is continuous in the fiber axis direction. A white conductive conjugate fiber, which is conjugated in a mixed state.