JP2801385B2 - White conductive fiber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a conductive conjugate fiber having excellent static elimination performance, and particularly to a dielectric conjugate fiber having excellent static elimination performance having excellent fiber physical properties and wearing durability.

More specifically, a fiber-forming polymer is used as a non-conductive layer component (A), and a thermoplastic polymer containing a conductive metal oxide is used as a conductive layer component (B). A composite fiber having excellent static elimination performance can be obtained only by adding 0.01% to 10% by weight (% by weight) of the conductive composite fiber to a normal non-conductive fiber, and after one year of actual wearing The present invention also relates to a conductive composite fiber whose static elimination performance does not decrease so much.

(Conventional technology) Conventionally, 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. 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 methods that are complicated and technically difficult in the production process, and are used in preparation steps for putting conductive fibers into practical use, for example, chemical treatment in the refining process for weaving and knitting, and in practice. There has been a problem that the conductivity is easily lowered due to the external action such as abrasion and repeated washing in the use of the material, 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 application in practice.

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

(Problems to be Solved by the Invention) For example, as disclosed in JP-B-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, it is not possible to obtain a practically useful conductive conjugate fiber with the above-mentioned known technology. 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-57-6762 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 produced. In such a case, there has been proposed a method in which a composite spun yarn is produced and stretched, and then the fiber is further subjected to a heat treatment so that the conductive layer is melted to be continuous and repaired. That is, 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-mentioned patent publication 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 still insufficient. doing.

Further, in the technique described in JP-B-62-29526, a thermoplastic resin suitable as a binder for a conductive metal oxide having a high degree of crystallinity is used, provided that the composite fiber is subjected to a heat treatment after drawing. However, the conductive conjugate fiber obtained using a polymer having a high degree of crystallinity has a problem that the wearing durability is 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 in which 0.1 wt% to 10 wt% of electrostatic fibers are woven 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 amount of charge in the electrostatic safety guideline issued by the Ministry of Labor, Labor Safety Laboratories is 7 μC / m ² , and it is necessary to 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 the crystalline thermoplastic resin is used as the thermoplastic polymer, the resistance of the filament immediately after the preparation of the conductive conjugate fiber is 9 ×.
It can be 10 ¹⁰ Ω / cm · f or less, and can meet the standard charge value of the fabric.However, due to poor durability, the antistatic performance of the fabric decreases, Have difficulty. 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.

(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, static elimination performance and actual wear durability, excellent static elimination performance, a white or colorless conductive composite fiber having actual wear durability was found, and the present invention was achieved. is there.

The gist of the present invention is a conductive composite comprising a fiber-forming thermoplastic polymer as a non-conductive component (A) and a mixture of conductive metal oxide particles and a thermoplastic resin as a conductive component (B). Fibers, the thermoplastic resin used for the conductive component is a thermoplastic elastomer, and the conductive metal oxide particles are conductive indium oxide particles having an average particle size of 0.01 to 2.0 μm, and The conductive composite fiber is characterized in that the mixed amount of the conductive metal oxide particles in the conductive layer component is 50 to 90% by weight. A conductive composite fiber satisfying such conditions has a filament resistance of 9 × 10 ¹⁰ Ω.
/ cm · f or less and 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 an effective method for re-adhering 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 have found that a conductive conjugate fiber having a conductive layer made of a mixture of conductive metal oxide particles and a thermoplastic elastomer has a low resistance value and a high durability in actual use. It was 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). Generally, thermoplastic elastomers are classified into the following two types.

1. Those composed of an amorphous molecular chain (called a soft segment) with easy molecular rotation and a resin molecular chain (called a hard segment) with high crystallinity. The soft segment portion is constrained by the hard segment portion.

2. The basic skeleton is constrained by the soft segment but is ionically crosslinked (dissociated by heat but recombines at low temperature)
Those who are restricted by. Examples of the thermoplastic elastomer having such a structure include a carboxylate polymer and a tertiary amine pendant NBR.

As the thermoplastic elastomer used in the present invention, any of the above thermoplastic elastomers can be used, but those having rubber elasticity,
It is good to use one having a tensile elongation at break (JIS K-6301) of 100% or more, preferably 200% or more.

In the present invention, it is particularly preferable to use a thermoplastic elastomer composed of a hard segment and a soft segment as the thermoplastic elastomer. When this is used as a binder for the conductive metal oxide particles, a conductive conjugate fiber having a low resistance value and a high durability in actual use can be obtained.

Examples of the thermoplastic elastomer used in the present invention include SBS (polystyrene-polybutadiene-polystyrene block copolymer) and its hydrogenated product, SIS
(Polystyrene-polyisoprene-polystyrene block copolymer) and its hydrogenated product, styrene-based polymer and conjugated diene-based polymer represented by SI (polystyrene-polyisoprene block copolymer) and its hydrogenated product, etc. Block copolymers comprising a hydrogenated product of a block copolymer or a styrene-based polymer and a conjugated diene-based polymer are listed as suitable elastomers, and particularly, from a hydrogenated product of a styrene-based polymer and a conjugated diene-based polymer. The block copolymer is particularly excellent in terms of static elimination performance and durability. In these block copolymers, it is particularly preferable that the proportion of the styrene-based polymer is 10 to 50% by weight. If it is less than 10% by weight, spinnability and heat resistance are poor. Certain conductivity decreases. It is not necessary that all of the double bonds of the conjugated diene polymer be hydrogenated, and hydrogenation may be performed to the extent that the majority of the double bonds of the conjugated diene polymer are hydrogenated.

Other thermoplastic elastomers that can be used in the present invention include polyurethane thermoplastic elastomers, polyester thermoplastic elastomers, polyamide thermoplastic elastomers, sulfonated ethylene propylene rubbers,
EPDM, tertiary amine pendant NBR and the like can be mentioned.

As the fiber-forming polymer forming the non-conductive layer (A) of the conductive composite fiber of the present invention, any polymer material that can be melt-spun is used. For example, polyethylene terephthalate, polyesters such as polybutylene terephthalate,
Various types of polyamides such as nylon 6 and nine 66, and polyolefins such as polyethylene and polypropylene are used. More preferably used thermoplastic polymer forming a non-conductive layer, polyethylene terephthalate,
A polyester-based polymer containing polybutylene terephthalate as a main component is exemplified. When this polymer is used, the processing durability and the actual wearing durability are remarkably improved.

When polyethylene terephthalate is used, the heat resistance (thermal decomposition resistance) required of the thermoplastic elastomer is 300 ° C. or higher. Examples of the thermoplastic elastomer suitably used under such conditions include a hydrogenated product of SIS, a hydrogenated product of SI, a hydrogenated product of SBS, a polyester-based thermoplastic elastomer, and a polyamide-based thermoplastic elastomer.

The conductive metal oxide particles used in the present invention,
Conductive indium oxide particles (ITO). Many of the metal oxides are semiconductors that are close to insulators. However, the conductivity can be improved by adding an appropriate second component. Examples of such a conductivity enhancer (so-called doping agent) include oxides of different metals or same and different metals. For example, tin oxide is added to indium oxide. The amount of addition is 2 to 25% by weight based on indium 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.

Conventionally, as a conductive metal oxide, those using titanium oxide particles whose main surface is zinc oxide or tin oxide and using antimony oxide as a doping agent have been widely used. The increased amount of doping agent is gray and is not suitable for white conductive fibers. In contrast, conductive indium oxide (ITO) particles, even those with significantly enhanced conductivity, are pale yellow and are very suitable for the present invention.

In the present invention, the conductive particles having an average particle diameter (median diameter: sedimentation method) of 2 μm to 0.01 μm are preferred in that the electric conductivity can be increased and the spinning processability is good.

In order to increase the electrical conductivity of the mixture, the ITO particles must be in contact with each other. For this purpose
It is important to increase the concentration of ITO and cause aggregation of the ITO 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 ITO particles can be extremely increased. According to the study results of the present inventors, when such a polymer material is used, ITO is used.
The mixing amount of the particles can be increased to about 80 to 90% by weight. However, in this case, the mixing amount of the ITO particles can be increased, but it is difficult to increase the electric conductivity of the mixture. For this reason, 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 a binder and the amount of ITO particles mixed is increased. On the other hand, when a thermoplastic elastomer 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 ITO particles and the thermoplastic elastomer is such that the role of the ITO particles in the conductive mixture is 50%.
The range is about 90% by weight. It is preferably from 60 to 85% by weight, particularly preferably from 70 to 80% by weight. In the case of a crystalline thermoplastic resin that has been conventionally proposed as a binder for ITO particles, when the mixing amount of the ITO particles exceeds 70 wt%, no further improvement in the conductivity is observed. The fluidity of the conductive component of the fiber is remarkably 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.

When producing a mixture of the thermoplastic elastomer and the ITO particles in the present invention, a surface treating agent for the ITO particles may be added. Further, a fluidity 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 spun fiber may be used, or a highly oriented undrawn conductive conjugate fiber which does not require a drawing step can be directly obtained by performing high-speed spinning.

The composite form of the conductive composite fiber in the present invention can take any form. Typical forms of the conductive composite fiber in the present invention are shown in FIGS. 1 is a single-core conductive conjugate fiber, FIG. 2 is a multi-core conductive conjugate fiber, FIG.
The figure shows a side-by-side type, FIG. 4 shows a multiple side-by-side type, and FIG. 5 shows a three-layer type. The most preferred form in the present invention is a core-sheath structure. Either a single-core type or a multi-core type may be used.

When the white conductive fiber of the present invention is used for 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. Generally, the conductive layer component is fragile because it contains a large amount of ITO particles, and is susceptible to damage by a hot chemical or the like during processing.
Especially for fabrics mainly composed of polyethylene terephthalate, high temperature dyeing and high temperature setting are inevitable.
In some cases, the conductive layer component of the conductive composite fiber was 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] A 9: 1 (molar ratio) mixed aqueous solution of 0.5 mol / indium nitrate and tin sulfate was supplied to a commercially available two-fluid nozzle (Akijet,
ITO particles were obtained by spraying a quartz reactor heated to 900 ° C. by a heating furnace at Ikeuchi Co., Ltd.).
The obtained ITO particles were pale yellow particles having an average particle size of 0.2 μm, and had a volume resistivity of 1.0 Ω · cm.

Hydrogenated SIS was used as a thermoplastic elastomer comprising a hard segment and a soft segment. It has a number average molecular weight of about 50,000, a melting point of 110 ° C., a styrene content of 30 wt%, rubber elasticity, and a breaking elongation of 580.
%.

75% by weight of the above ITO fine particles and 25% by weight of hydrogenated SIS at 210 ° C
The mixture was mixed using a small Brabender at a temperature of.
In order to uniformly mix the ITO fine particles and reduce the viscosity of the mixture, a trace amount of a titanate-based coupling agent (manufactured by Nippon Soda Co., Ltd.) was added during the mixing of the ITO particles and the hydrogenated SIS. The volume resistivity of the mixed chip of the ITO particles and the hydrogenated SIS thus obtained was 4 × 10 ³ Ω · cm. 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 in 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 a core portion and (A) forms a sheath portion. Spinning at 4 ° C from 4 holes and spinning speed
The film was wound in two at 4500 m / min to obtain a 25-denier / 2-filament highly oriented undrawn conductive composite fiber. The obtained fiber was a pale yellow color close to white, and the core resistance of the filament was 6 × 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 warp yarn, 80% warp 80 / in 50/1 / in 2/1 Twill fabric. Subsequently, dyeing and finishing were carried out under the conditions of ordinary polyester cotton blend fabric. The conductive yarn in the woven fabric was inconspicuous and good. The charge amount of the fabric was 3.5 μcoulomb / m ² . After wearing for 1 year as work clothes, the charge amount after repeated washing 100 times is 3.5μ
The woven fabric had a coulomb / m ² and an excellent static elimination performance. That is, it passed the standard value (hereinafter referred to as the standard value) of 7 μclone / m ² of the electrostatic safety guideline issued by the Ministry of Labor, Industrial Safety Research Institute, and was extremely excellent in durability.
The conductive fiber was recovered from the woven fabric and the core resistance was measured. However, it was 9 × 10 ⁸ Ω / cm · f, and the rate of decrease in resistance was satisfactory.

Examples 2 and 3 Various conductive mixtures were produced under the same conditions as in Example 1 by changing the mixing amount of the ITO particles. Using this, a composite fiber was produced, and the antistatic performance was evaluated. The results are shown in Examples 2 and 3 (Tables 1 and 2). In each case, a conductive conjugate fiber having a low resistance value of the fiber and good antistatic performance could be obtained. In addition, the woven fabric was good in that the conductive yarn was not noticeable. Further, the durability for actual wearing was also evaluated, and it was found that in all cases, good performance was obtained.

Comparative Examples 1 and 2 Conductive mixtures were prepared by setting the mixing ratio of ITO particles to 45 wt% and 92 wt%. The manufacturing conditions and performance of these devices are shown in Comparative Examples 1 and 2 (Tables 1 and 2). When the mixing ratio was 92% by weight, the packing life was extremely short and the composite fiber could not be spun. When the mixing ratio was 45% by weight, a conjugate fiber could be easily obtained, but the fiber did not have a static elimination performance due to its high resistance value.

Example 4 A conductive conjugate fiber was produced in the same manner as in Example 1 except that polybutylene terephthalate was used as a sheath component. This had good antistatic performance and excellent durability (Tables 1 and 2).

Example 5 A conductive conjugate fiber was produced in the same manner as in Example 1 except that nylon 6 was used as a sheath component. This had good antistatic performance and excellent durability.

Example 6 As a binder, a polyester / polyether type thermoplastic elastomer (Toyobo Pelprene P40H, the structure is shown below; elongation at break: 690%) was used. Mixing with ITO was performed at 240 ° C. Other conditions were the same as in Example 1 to produce a conductive conjugate fiber. The antistatic performance of the fiber was inferior to that of the case where hydrogenated SIS was used as a binder, but was good and the durability was excellent (Tables 1 and 2).

Example 7 Using a tertiary amine pendant NBR (the structure is shown below) and polybutylene terephthalate as a sheath component, an attempt was made to produce a conductive composite fiber. 2,2'-Dichloroparaxylene was used as a crosslinking agent for the tertiary amine pendant NBR (1.5 wt% was added to the tertiary amine pendant NBR). Mixing with ITO was performed at 210 ° C. Although the composite fiber was inferior to the case where hydrogenated SIS was used as a binder for static elimination performance, it had a resistance value of 10 ⁹ Ω / cm · f and excellent durability (Table 1, Table 1). 2).

Comparative Examples 3 and 4 Conductive composite fibers were produced in the same manner as in Example 1 except that nylon 6 (crystallinity: 45%) was used as a binder. The mixing ratio of ITO was 65 or 70 wt%, and the mixing temperature was 240 ° C. The antistatic performance immediately after the production of this composite fiber was excellent, but the antistatic performance had disappeared one year after actual wearing (Tables 1 and 2). When the mixing ratio of ITO was 70 wt%, filter clogging occurred and the pack life was extremely short.

Comparative Example 5 A conductive composite fiber was produced using high-density polyethylene (crystallinity: 70%), which is a crystalline thermoplastic resin, as a binder, and the mixing ratio of the conductive particles was 65 wt%. Immediately after the production of this fiber, the antistatic performance was good, but one year after actual wearing, the electrostatic performance had disappeared.

[Brief description of the drawings]

1 to 5 are representative cross-sectional views of a conjugate fiber applicable in the present invention. In the figure, the hatched portion is the conductive layer component (B).
Is shown.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-289118 (JP, A) JP-A-63-270811 (JP, A) JP-A-61-201014 (JP, A) JP-A-59-1984 9218 (JP, A) JP-A-49-50216 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) D01F 8/00-8/18 D01F 1/09 D01D 5/30

Claims (1)

(57) [Claims] 1. A non-conductive layer portion (A) comprising a fiber-forming thermoplastic polymer and a conductive layer component (B) comprising a mixture of conductive metal oxide particles and a thermoplastic polymer. In the conductive composite fiber, the thermoplastic polymer constituting the conductive layer component is a thermoplastic elastomer, and the conductive metal oxide particles are conductive indium oxide particles having an average particle size of 0.01 to 2.0 μm, and A conductive conjugate fiber, wherein a mixing amount of the conductive metal oxide particles in a conductive layer component is in a range of 50% by weight to 90% by weight.