JPS6399314A - Electrically conductive conjugate fiber - Google Patents

Abstract

PURPOSE:To obtain the titled fibers having excellent chemical resistance and electric conductivity performance without dusting by friction, bending, etc., by using a polymer containing an electrically conductive substance as a core, forming recessed parts in a sheath part and providing a part of the minimum thickness of the sheath part in each recessed part present in a specific state. CONSTITUTION:Electrically conductive conjugate fibers having an electrically conductive core part (indicated by oblique lines) of a thermoplastic polymer containing an electrically conductive substance and a sheath part of a fiber- forming polymer. A recessed part satisfying the relation b/a>=0.5 (a is the shortest length between the mutually opposite two points of the topmost part of the recessed part; b is the shortest length between the deepest point of the recessed part and a point on a straight line connecting the above-mentioned two points) is formed on the surface of each sheath part. A part of the minimum thickness of the sheath part is present in the recessed part and the thickness thereof is 0.5-5mum.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a conductive composite am, and more particularly to a conductive mM having excellent wear resistance, chemical resistance, and surface conductivity.

(Prior Art) Fibers made of synthetic polymers such as nylon, polyester, and acrylic tend to generate static electricity due to their hydrophobicity, and many proposals have been made to prevent this static electricity. In particular, a composite fiber whose core/sheath is composed of a thermoplastic polymer in which conductive particles such as carbon black or metal powder are dispersed and a shadow-forming polymer is developed.
Since the proposal was made in Publication No. 450, various proposals have been made.

However, a composite mg in which a conductive component containing a conductive substance is completely covered with a non-conductive component has the disadvantage that dielectric breakdown of the sheath is required to generate corona discharge, resulting in poor conductivity.

In addition, composite fibers with a conductive component as a sheath and composite fibers with conductive and non-conductive components joined side-by-side! Composite fibers with a miscellaneous or conductive component exposed on the yarn surface have excellent conductivity, but because a large amount of conductive substances are present in the conductive component, they have low abrasion resistance (prone to wear during use). It has the disadvantage of being dusty.

In order to solve this drawback, JP-A-55-1337 discloses a three-layer composite fiber in which the conductive component is present in the intermediate between the core and sheath, JP-A-56-37313 and JP-A-56-3.
7314@publication describes a fiber with a multi-lobal cross section and localized conductive components around the concave portion, JP-A-57-29
No. 611 discloses a multicore type core-sheath composite fiber, JP-A-61-
No. 132626 discloses a composite m-fiber in which a part of the sheath surrounding a core containing a conductive component is made of a polymer soluble in a solvent, and then the part is washed off with a solvent to form a recess. is proposed.

However, the composite aIN proposed by these methods has insufficient abrasion resistance if the conductive component is too close to the yarn surface, and if the conductive component is localized in the recesses, it is similar to an exposed type, so it is difficult to resist bending or other forces. When this happens, the problem arises that dust is easily generated.

By the way, such conductive fibers are used for various purposes, but in particular, they are used in large quantities for dust-free clothing worn in clean rooms such as those in the electronics industry, and the above-mentioned dust generation must be avoided. This is a problem that cannot be solved.

Furthermore, with the development of electronics in recent years, dust-free clothing for clean rooms is required to have even more advanced a-bars, and at the same time, chemicals such as hydrogen fluoride and nitric acid have come to be used in clean rooms, making them chemically resistant. has also come to be required.

(Objective of the Invention) The object of the present invention is to provide a conductive composite fiber that does not generate dust due to friction or bending, has excellent chemical resistance and conductive performance, and is particularly suitable for use in dust-free clothing. It is about providing.

(Structure) As a result of studies to achieve the above object, the present inventors formed a recess in the sheath part of a core/sheath conductive composite fiber having a core made of a polymer containing a conductive substance, and formed a recess inside the recess. The inventors have discovered that wear resistance and chemical resistance are significantly improved when the sheath portion has the minimum thickness region, and has arrived at the present invention.

That is, in the cross section of the composite 111i, which is composed of a conductive core made of a thermoplastic polymer containing a conductive substance and a sheath made of an mN-forming polymer surrounding the conductive core, At least one concave portion having a shape that satisfies the following formula is formed on the surface of the sheath portion, and the minimum thickness portion of the sheath portion exists within the concave portion, and the thickness of the portion is 0.5 to 5 μm.
This is a conductive composite IIN characterized by the following.

Recess shape b/a) 0.5 a; Shortest length between two opposing points at the top of the recess; Shortest length between the deepest point of the recess and a point on the straight line connecting the two points. As the conductive substance blended into the thermoplastic polymer constituting the core, conductive carbon black, particles having a metal film on the surface of the metal particles 1, and conductive metal compounds can be used.

Examples of conductive carbon black include oil furnace type "Ketjen Black EC" (Japan Easy Co., Ltd.), "Conductex 975" and "Fundactex SC" (Columbia), and acetylene type "Denka Black". (Denki Kagakusha), etc.

The blending ratio of conductive carbon black to the thermoplastic polymer constituting the core is preferably 20 to 50% by weight, particularly preferably 25 to 40% by weight. 20
If it is less than 50% by weight, the conductive performance tends to deteriorate, and if it exceeds 50% by weight, uniform dispersion in the polymer tends to become difficult.

In addition, metal particles include silver, nickel, and copper.

Particles made of iron, aluminum, or an alloy thereof can be used, and as particles having a metal film on the surface, tin oxide mixed and fired with antilene oxide as the second component or aluminum oxide as the second component can be used. Zinc oxide, titanium oxide, magnesium oxide, silicon oxide, aluminum oxide, etc., which have a film of a conductive oxide such as tin oxide or zinc oxide, can be used. Further, examples of the conductive metal compound include copper sulfide, copper iodide, zinc sulfide, and cadmium sulfide.

The blending ratio of these metal particles, metal coating particles, and conductive metal compounds varies depending on the type of particles, particle size, conductivity, and the properties and crystallinity of the matrix polymer constituting the core, but it is ~80% by weight is preferable, and if it is less than 40% by weight, the conductivity tends to decrease,
When the amount is more than 80% by weight, uniform dispersion in the polymer tends to be difficult.

As the thermoplastic polymer constituting the core part, polymers such as polyamide, polyester, polyolefin, polyether, etc. can be arbitrarily selected, but considering ensuring conductivity at the spinning stage and adhesion with the sheath component, Nylon 6, polyethylene.

Polyethylene terephthalate and the like are preferred. The mg-forming polymer used as the sheath component may be any polymer with excellent chemical resistance, but polyesters, polyolefins and/or copolymers thereof are preferred.

Also, polyalkylene glycols and block polyether esters containing a surfactant such as an organic sulfonic acid or its metal salt, a modified phosphoric acid or its metal salt, etc. in the polymer constituting the core/sheath portion.

An organic antistatic component such as block polyether amide may be dispersed in the polymer by up to 51%.

Furthermore, known matting agents, heat resistant agents, antioxidants, light stabilizers,
H refueling agent, fluorescent agent, etc. may be added.

In the present invention, a composite fiber is comprised of a conductive core made of a thermoplastic polymer containing the aforementioned conductive substance and a sheath made of a fiber-forming polymer surrounding the core, It is important that, in its cross section, at least one recess is formed in the sheath, and that the region of minimum thickness of the sheath is located within said recess.

Composite of the present invention! IH will be explained using drawings.

1 and 2 are cross-sectional views of the composite tJAH of the present invention,
3 and 4 are cross-sectional views of a spinning discharge hole from which the composite fiber of the present invention can be obtained, and FIG. 5 is a cross-sectional view of a conventional composite fiber, respectively.

In FIG. 1, the shaded area (1) is a core containing a conductive substance, (2 is a sheath that surrounds the core (1), (3) is a recess formed in the sheath (a), ( C) shows the minimum thickness portion of the sheath portion.

As shown in FIG. 1, the composite fiber of the present invention has at least one recess (3) formed in the sheath (2), and a minimum thickness C1 of the sheath within this recess (3). There are several parts that exist.

On the other hand, if the cross-sectional shape is a composite fiber with a uniform sheath thickness as shown in FIG. The thickness must exceed 0 μm, and the conductive performance of the composite m-fiber is poor.

In addition, as shown in Figure 5 (f), composite fibers whose cores are eccentric and partially exposed can exhibit good electrical conductivity, but the core components are easily peeled off or dissolved by friction or chemicals. , it tends to generate dust and has poor chemical resistance.

In this regard, in the present invention, by adopting the shape shown in FIG. 1, the core portion containing a large amount of conductive material can be protected from friction and chemicals.

Furthermore, in the present invention, it is important that the shape of the recess (3) satisfies the following formula and that the minimum thickness C) of the sheath is 0.5 to 5 μm.

Recess shape b/a 〉0.5 Here, a is the shortest length between two opposing points on the top of the recess, and b is the shortest length between a point on the straight line connecting the two points and the deepest point of the recess. It is.

When b/a is less than 0.5, the core is FJ! Since the protective effect against external forces such as rubbing is small, the core component may be peeled off, which can cause breakouts. The concave portion of the present invention is preferably a concave portion in which b/a is 0.7 or more, particularly 1 or more, and the upper limit thereof is not particularly limited, but it is preferably 1.5 from the viewpoint of yarn spinning.

In addition, when the minimum thickness C) of the sheath existing in the recess (3) is thinner than 0.5 μm, the core component is likely to be peeled off because the ability to protect the core is small, and when it is thicker than 5μ Conductive performance is poor. The minimum thickness C) of such a sheath is 4μ.
It is preferably less than m, particularly less than 2.5μ skin.

In the present invention, the number of recesses formed in the sheath (2) may be one, but as shown in FIGS. 2(a) to 2(b), a plurality of recesses may be formed.

In addition, the higher the area ratio of the core in the cross section of the composite fiber, the better the conductive performance, but it is preferably 3 to 30% due to the strength of the fiber, and the position of the core is approximately in the cross section. Preferably, it is centrally located.

The conjugate fiber of the present invention described above can be manufactured by using a normal conjugate spinning apparatus and a spinning discharge hole having the shape shown in FIGS. 3 and 4.

That is, in FIGS. 3 and 4, by discharging the polymer forming the core from the central part (the part surrounded by the broken line) and discharging the polymer forming the sheath from the other parts, Composite fibers having the cross-sectional shapes shown in FIGS. 2(0) and 2(a) can be obtained. 'It is preferable to perform electrical discharge machining on the conductive composite m-fiber obtained in this manner to selectively cause dielectric breakdown at the minimum thickness portion of the sheath portion located within the recess. Such electrical discharge machining dramatically improves the yarn surface conductivity while protecting the core.

The electrical discharge machining conditions should be appropriately selected depending on various factors such as the polymer component constituting the sheath and the sheath thickness.
The needle electrode is placed at a gap of 0 to 1 m and a negative voltage of 10 to 20 KV is applied. At this time,
The conductive conjugate fiber may be twisted with a normal yarn and run, or an aqueous liquid may be applied to the conductive conjugate fiber in order to stably and efficiently cause dielectric breakdown to a solid line.

The composite tlJl of the present invention can be used in a desired form such as a filament or a staple, and can also be used in combination with other chargeable tli fibers.

(Function) Conductive composite of the present invention! i11 miscellaneous products are resistant to friction and chemicals because the minimum thickness of the sheath has a certain range of thickness within a specific shaped recess formed in the sheath made of a polymer with excellent chemical resistance. However, as a result of being able to protect the core, which contains a conductive substance that has poor durability, it prevents dust generation due to peeling of the core against external forces such as friction and bending, and at the same time has excellent chemical resistance. It can also have conductive performance.

(Effects of the invention) The conductive composite fiber of the present invention has excellent anti-sprout properties, chemical resistance,
Because it has wear resistance and conductivity, it can be preferably used for dustproof clothing for clean rooms.

(Example) Hereinafter, the present invention will be specifically explained with reference to Examples. Unless otherwise specified, parts and percentages indicate parts and weight ratios.

Examples 1 and 2 Conductive polymer chips (volume resistivity value 1 .3X 102Ω・crR)
and polyethylene terephthalate chips with an intrinsic viscosity of 0.64 measured at 25°C in orthochlorophenol containing 2.5% by weight of titanium oxide were combined at a spinning temperature of 290°C using a composite spinning device with a discharge hole shape shown in Figure 3. Ratio (discharge weight ratio) core/sheath = 115.

Number of filaments = 3. When the yarn was wound at a spinning speed of 700 m/min, a raw yarn having a cross-sectional shape approximately as shown in FIG. 2 (0) was obtained.

This yarn is preheated at a temperature of 110°C, heat set at a temperature of 180°C,
The yarn was drawn at a draw ratio of 3.86 times to obtain a drawn yarn of 30 denier and 3 filaments. The resulting composite TL miscellaneous cross-sectional shape 9 was evaluated for strength, elongation, electrical resistance before and after bending abrasion, and electrical resistance retention rate that was good against chemical treatment and bending abrasion, and the results are shown in Table 1.

Example 3 Two antimony oxide fine particles were added to titanium oxide with an average particle size of 0.24 μm and a tin oxide film of 12% by weight formed thereon.
A conductive polymer chip (volume resistivity value: 3
．． OX 103Ω・cm) is 11.

Using this chip as a core, a composite fiber having a polyethylene terephthalate sheath was spun and drawn in the same manner as in Example 1 to obtain 1q.
Ta. The properties of the obtained composite fiber are shown in Table-1.

Example 4 The same polymer as in Example 1 was used except that the spinning discharge hole had the shape shown in FIG. 4, and spinning and drawing was carried out under the same conditions. A thread was obtained. The properties of the obtained composite fiber are shown in Table-1.

Comparative Examples 1 to 3 Using the same polymer as used in Example 1, undrawn yarn with the cross-sectional shape shown in FIG. Stretched under certain conditions.

The properties of the obtained composite LLN are shown in Table 1.

The yarns obtained in Comparative Examples 1 and 3 were the yarns of the present invention (Examples 1 to 3).
Compared to 4), the electric resistance value of the yarn surface is higher, and the system obtained in Comparative Example 2 has a large deterioration of the electric resistance value of the surface and cross section after bending, and the cross-sectional electric resistance value retention rate after chemical treatment is also poor. .

Example 5 The 30 denier 3 filament composite conductive tam obtained in Example 1 was combined with a 75 denier 36 filament yarn, dipped in ion-exchanged water with a roll, and then
I ran it in minutes. At this time, the needle electrodes were placed facing each other at an interval of 0.5 am, a voltage of 5 KV was applied, and then the film was wound up. The surface electrical resistance of the obtained yarn was improved to 5×10 7 Ω/α, a value close to the cross-sectional electrical resistance.

[Brief explanation of the drawing]

The composite IIH of the present invention will be explained using the drawings. 1 and 2 are cross-sectional views of the composite fiber of the present invention;
4 and 4 are cross-sectional views of a spinning discharge hole from which the composite fiber of the present invention can be obtained, and FIG. 5 is a cross-sectional view of a conventional composite fiber. In the figure, 1 indicates a core portion, 2 indicates a sheath portion, and 3 indicates a recessed portion. Figure 1 Figure 2 (A) Figure 3 Figure 4

Claims (6)

[Claims] (1) In a cross section of a composite fiber composed of a conductive core made of a thermoplastic polymer containing a conductive substance and a sheath made of a fiber-forming polymer surrounding it, the sheath surface at least one recessed portion having a shape that satisfies the following formula is formed in the recessed portion, a portion of the sheath portion having the minimum thickness exists within the recessed portion, and the thickness of the portion is 0.5 to 5 μm. conductive composite fiber. Recess shape b/a≧0.5 a; Shortest length b between two opposing points at the top of the recess; Shortest length between the deepest point of the recess and a point on the straight line connecting the two points (2) The conductive composite fiber according to claim (1), wherein the conductive substance is conductive carbon black, metal particles, conductive metal compounds, or particles having a metal film on the surface. (3) The conductive composite fiber according to claim (2), wherein the blending ratio of conductive carbon black is 20 to 50% by weight based on the polymer constituting the core. (4) The compounding ratio of metal particles, particles having a metal coating on the surface, or conductive metal compound is 40 to 80% by weight with respect to the polymer constituting the core portion, according to claim (2). Conductive composite fiber. (5) The conductive composite fiber according to claim (1), wherein the polymer constituting the sheath portion is at least one polymer selected from polyester, polyolefin, and copolymers thereof. (6) The conductive composite fiber according to claim (1), wherein the sheath portion has dielectric breakdown at the minimum thickness portion.