JP2009144265A - Conductive monofilament and industrial woven fabric - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive monofilament that can maintain extremely stable conductive performance even when receiving scratch and abrasion by a long-term use and an industrial woven fabric using the conductive monofilament as a constituent material. <P>SOLUTION: The monofilament 1 having a core-sheath structure is a monofilament comprising a non-conductive layer 2 of core part and a conductive layer 3 of sheath part covering the non-conductive layer and has an auxiliary conductive layer 4 in which parts of the conductive layer of sheath part are convexly projected toward the inside of the non-conductive layer of core part in a cross section perpendicular to the length direction of the monofilament. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  INDUSTRIAL APPLICABILITY The present invention relates to a conductive core-sheath structure monofilament and an industrial fabric using the conductive monofilament that can maintain extremely stable conductive performance even when subjected to abrasion or wear due to use, compared to conventional conductive monofilaments It is about.

  Synthetic resin monofilaments are used in many types of paper, such as papermaking wires, paper press felts and paper dryer canvas, which are installed in paper machines, belt fabrics such as conveyor belts and dewatering belts, and various filter fabrics. It has been used as a constituent material for industrial fabrics.

  However, since the synthetic resin monofilament has extremely low electrical conductivity, problems such as various problems have been pointed out due to static electricity being easily charged.

  For example, when monofilament made of polyethylene terephthalate is used for industrial fabrics such as paper dryer canvas mounted on paper machines, conveyor belts, drying and conveyor belts used in the manufacture of nonwoven fabrics, this occurs during use. Static electricity accumulates in the fabric, causing the risk of dust adhering to the product and the risk of ignition and explosion due to discharge sparks, causing problems in operation.

  As a means for solving these problems, conductive monofilaments containing an antistatic agent or having an outer layer of fibers covered with a conductive metal have been used as a constituent material for industrial fabrics. In order to increase the performance of paper machines, the speed of paper machines has been increasing, so not only higher antistatic performance but also long-term performance such as antistatic performance has been required. Various proposals have been made.

For example, as a shape of the conductive fiber, a fiber composite in which a conductive composite fiber composed of a conductive thermoplastic component and a fiber-forming component is mixed, and the conductive composite fiber is made of a thermoplastic polymer containing carbon black. A fiber composite having a specific resistance of 10 ⁶ Ω · cm or less, wherein the conductive thermoplastic component covers 50% or more of the fiber surface, and has a continuous structure in the fiber major axis direction. A body (see, for example, Patent Document 1) has been proposed. However, although the conductive fiber obtained by the present technology has excellent conductive performance, the conductive performance cannot be maintained for a long time because the sheath portion containing the conductive component is easily worn and peeled by rubbing with guides during weaving. There was a problem.

  Moreover, in the single fiber cross section of the conductive fiber formed by joining the sheath part made of a thermoplastic resin containing 15 to 50% of conductive carbon black and the core part made of a fiber-forming polyester-based thermoplastic resin, the sheath part The joint surface curve of the core portion is convex toward the sheath portion, the ratio of the minimum curve radius r of the joint surface curve to the single yarn fiber radius R, r / R is 0.6 or less, A conductive conjugate fiber (see, for example, Patent Document 2) characterized in that the circumference occupying the sheath portion is 2 to 40% of the total circumference has been proposed. According to the present technology, the conductive polymer layer is abraded. In addition, the conductive fiber has excellent durability against repeated use and can maintain the performance over a long period of the antistatic property. However, this technology is a multifilament technology, and when applied to monofilaments, not only does it not provide sufficient electrical conductivity, but it has poor durability against scratching and wear, and has a sufficient effect. There was a problem that it was not possible.

Furthermore, a conductive polymer layer made of thermoplastic polyamide containing 15-50% of conductive carbon black and a protective polymer layer made of fiber-forming polyamide are combined, and the conductive polymer layer is exposed on the fiber surface, and the surface exposure When the portion is 3 or more per filament and the exposure distance in the fiber cross-section circumferential direction is L ₁ (μm), and the fiber cross-section circumference of one filament is L ₂ (μm), formula 1 ≦ _{L 1} ≦ L 2/10 and the electric resistance value at 100V applied R (Ω / cm · f) and the time to satisfy both of the formula logR = from 6.3 to 11.9, and the protective polymer layer fibers A conductive conjugate fiber (see, for example, Patent Document 3) that occupies 60% or more of the cross-sectional circumference and is formed with 50% to 97% by weight of the total weight of the fiber has been proposed. . However, this technology is effective for multifilaments with a small fiber diameter, but with monofilaments with a large fiber diameter, the protective polymer layer that does not contain a conductive component becomes thick, so that the electrical resistance value of the surface is increased and the conductive performance is increased. There was a problem of not reaching the practical range.
Republished 2002-0775030 JP 2006-274502 A JP 2001-49532 A

  In view of the circumstances as described above, the present invention has been achieved as a result of investigations to solve the problems in the prior art.

  Therefore, the object of the present invention is to maintain extremely stable conductive performance over a long period of time without significant deterioration in conductive performance even when the conductive sheath conductive layer is scratched or worn by use. An object of the present invention is to provide a conductive monofilament having a core-sheath structure that can be used, and an industrial fabric using the same.

  In order to achieve the above object, according to the present invention, a monofilament having a core / sheath composite structure, comprising a core non-conductive layer and a sheath conductive layer covering the core, is orthogonal to the length direction of the monofilament. In a cross section, a conductive monofilament having an auxiliary conductive portion in which a part of the sheath conductive layer protrudes in a convex shape toward the inside of the core nonconductive layer is provided.

In the conductive monofilament of the present invention,
Having at least two auxiliary conductive portions in which a part of the sheath conductive layer protrudes in a convex shape toward the inside of the core non-conductive layer,
The core area ratio comprising the sheath conductive layer including the auxiliary conductive part and the non-conductive component is in the range of 1:95 to 50:50;
When the monofilament is connected to both ends of the electrode and applied, the resistivity value (Ω) of the measured monofilament ÷ the volume resistivity represented by the distance between the electrodes (cm) when the resistance value is measured is 1 × 10 ⁸ Ω / cm or less Being
In the forced wear test conducted in accordance with the JIS-1095-9.10.2B method, the volume resistivity values of the conductive monofilament before and after the forced wear test are A (Ω / cm) and B (Ω / cm), respectively. The conductivity retention indicated by B ÷ Ax100 is 50% or more,
Is mentioned as a more preferable condition.

The industrial fabric of the present invention is characterized in that the conductive monofilament is used in at least a part of the weft and / or warp. When the conductive monofilament of the present invention is used as an actual industrial fabric, the conductive fabric is electrically conductive. Even when the conductive monofilament is rubbed or worn, it exhibits excellent effects such as being able to maintain extremely stable conductive performance over a long period of time.

  According to the present invention, it is possible to obtain a conductive monofilament suitable as a constituent material of an industrial fabric that maintains excellent conductive performance even in long-term use and does not cause various problems due to generation of static electricity.

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

  FIG. 1 is a cross-sectional view perpendicular to the fiber axis direction showing an example of the conductive monofilament of the present invention, and FIG. 2 is a cross-sectional view showing another example.

  In FIGS. 1 and 2, 1 is an overall cross-sectional view of the conductive monofilament of the present invention, 2 is a core non-conductive layer, 3 is a sheath conductive layer, and 4 is an auxiliary conductive portion.

  As shown in FIG. 1, the conductive monofilament 1 of the present invention includes a core non-conductive layer 2 and a sheath conductive layer 3 covering the core non-conductive layer 2, and the core non-conductive in a cross section perpendicular to the length direction of the monofilament. It has a core-sheath composite structure having an auxiliary conductive portion 4 in which a part of the sheath conductive layer 3 protrudes in a convex shape toward the inside of the layer 2.

  Here, when the sheath conductive layer 3 is scraped off due to wear or abrasion of the conductive monofilament of the present invention, the auxiliary conductive portion 4 is exposed to the monofilament surface layer. At this time, however, the sheath conductive layer 3 is scraped off by abrasion or wear, and the core non-conductive layer 2 is exposed. However, since the auxiliary conductive portion 4 remains, a decrease in conductive performance is suppressed.

  That is, the conventional conductive monofilament has a problem that when the sheath conductive layer is worn, the sheath conductive layer is peeled off or cracked, resulting in a decrease in the conductive performance. Even when the sheath conductive layer 3 is worn, the auxiliary conductive portion 4 remains, so that the effect of maintaining excellent conductive performance over a long period can be exhibited.

  In addition, when the conductive monofilament of the present invention has at least two auxiliary conductive portions protruding in a convex shape toward the inside of the core non-conductive layer, a more preferable effect can be expected. Here, a preferable condition is that the auxiliary conductive portion is continuously present in the length direction of the monofilament.

  Further, the number of auxiliary conductive portions is not particularly limited as long as it is 2 or more, but preferably 3 to 16, more preferably 4 to 8 auxiliary conductive portions, particularly desired effects. Can be expected.

  That is, for example, when the number of auxiliary conductive parts is as small as 1 to 3, it is preferable to keep the physical strength of the conductive monofilament high, but conversely, it is high when the sheath conductive layer is worn or peeled off due to abrasion or the like. In order to maintain the conductive performance over a long period of time, it is important to have many auxiliary conductive portions in order to effectively maintain the desired conductive performance. For this reason, in the conductive monofilament of the present invention, the required conductive performance is effectively obtained in consideration of the conductive performance and physical strength characteristics required for industrial products using the conductive monofilament. In order to maintain it, it is possible to provide as many auxiliary conductive parts as necessary within a desired range.

  The shape of the auxiliary conductive portion 4 in the conductive monofilament of the present invention is not particularly limited as long as a part of the sheath conductive layer 3 protrudes inwardly toward the inner side of the core non-conductive layer 2. By forming it like the substantially triangular shape of FIG. 1 or the substantially semicircular shape of FIG. 2, the desired effect can be expected.

  In the conductive monofilament of the present invention, the area ratio represented by the sheath conductive layer including the auxiliary conductive portion: core non-conductive layer is preferably 5:95 to 50:50, more preferably 10:90. When it is in the range of ˜35: 65, and further 15:85 to 30:70, particularly excellent effects are exhibited. That is, in the conductive monofilament of the present invention, when the area of the sheath conductive layer including the auxiliary conductive part is large, the conductive monofilament contains a larger amount of the conductive component, so that a favorable effect is exhibited in improving the conductive performance. Is done. On the other hand, when the area of the core non-conductive layer containing no conductive component is large, an effect of maintaining a high physical strength can be obtained. Therefore, in order to maintain a good balance between the conductive performance and the physical strength, it is desirable that the area ratio indicated by the sheath conductive layer: core nonconductive layer is as described above.

  In addition, although the diameter represented by the length of the line segment which passes through the gravity center of the electroconductive monofilament cross section of this invention can be suitably selected according to a use, it is preferable to set it as the range of 0.05 mm to 2.5 mm. Further, the required strength varies depending on the purpose of use, but if it is approximately 2.0 cN / dtex or more, a more preferable effect can be expected.

The conductive performance of the conductive monofilament of the present invention varies depending on the conductive component used in the sheath conductive layer including the auxiliary conductive portion, its concentration, the core-sheath ratio, and the number of auxiliary conductive portions. (Ω) ÷ Volume specific resistance value represented by the distance (cm) between the electrodes when the resistance value is measured is preferably 1 × 10 ⁸ Ω / cm or less, more preferably 1 × 10 ⁵ Ω / cm or less.

That is, if the electrical resistance value of the conductive monofilament is 1 × 10 ⁸ Ω / cm or less, it has a function as an antistatic material, and if the electrical resistance value is 1 × 10 ⁵ Ω / cm or less, it is extremely excellent as an antistatic material. Performance can be demonstrated.

  Further, in the forced wear test conducted according to the JIS-1095-9.10.2B method, the volume resistivity values of the conductive monofilament before and after the forced wear test are A (Ω / cm) and B (Ω / cm), respectively. In this case, the conductivity retention indicated by B ÷ Ax100 is preferably 50% or more. That is, the conductive monofilament of the present invention has a conductivity retention rate because the auxiliary conductive portion can be exposed to the monofilament surface and maintain sufficient conductivity when the forced wear test is performed forcibly. If it is 50% or more, it can be expected to have a conductive performance required as an antistatic material and to maintain a long-term conductive performance.

  The shape of the conductive monofilament of the present invention is not particularly limited, and even if the cross-sectional shape perpendicular to the fiber axis direction is an ellipse, a square, a rectangle, a hexagon, a polygon, etc., the same stable conductive performance Is obtained.

  Here, the material constituting the conductive monofilament of the present invention is not particularly limited, and examples of the polymer resin constituting the core non-conductive layer include polyolefins such as polyethylene and polypropylene, polyvinyl chloride, and polyvinylidene chloride. Polyamide resins such as 6 nylon, 66 nylon, 610 nylon, 612 nylon, 6/66 copolymer or copolymers thereof, polyethylene terephthalate (hereinafter referred to as PET), polybutylene terephthalate (hereinafter referred to as PBT), polyethylene naphthalate (Hereinafter referred to as PEN), polyesters such as polycyclohexanedimethylene terephthalate or polymers thereof, polyvinylidene fluoride, ethylene tetrafluoroethylene copolymer, tetrafluoroethylene / hexafluoropropylene Fluorine resins such as vinylidene fluoride copolymer, polycarbonates, polyphenylene sulfide (hereinafter referred to as PPS), polysulfone, amorphous polyarylate, polyetherimide, polyethersulfone, polyetheretherketone, polyamideimide, Examples include polyimide, polyallyl ether nitrile, and liquid crystal polyester.

  Furthermore, the above PET and PBT are a part of the dicarboxylic acid component terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, dimer acid and sulfone. It may be replaced with an acid metal salt-substituted isophthalic acid or the like, and ethylene glycol or a part of 1,4-butanediol as a glycol component may be replaced with diethylene glycol, neopentyl glycol, 1,4-cyclohexanediol, 1 , 4-cyclohexanedimethanol and polyalkylene glycol may be substituted. Moreover, these may be used as a single component or may be used as a blend of a plurality of components.

  On the other hand, as the conductive polymer resin composition for forming the sheath conductive layer, a conductive carbon black blended at a high concentration is used. For the polymer resin as the main component, the core non-conductive layer is used. Resins similar to those exemplified as the polymer resin for forming can be used.

  Moreover, when forming a sheath part conductive layer and an auxiliary | assistant conductive part, what contains 6-40 weight% of conductive carbon black can be used for the polymer resin composition to be used, and this polymer resin composition is used. When used, since the conductive carbon black contains a high concentration, excellent conductivity can be exhibited even if the volume occupied by the sheath conductive layer and the auxiliary conductive portion is small. A filament with excellent diameter spots is obtained.

  However, when the content of the conductive carbon black is less than that, sufficient conductivity cannot be obtained, and conversely, when the content is more than that, the fluidity of the polymer resin composition is remarkably lowered. Cracks are likely to occur.

  The conductive carbon black contained in the sheath conductive layer is not particularly limited as long as it has high conductivity, and among them, a furnace carbon having a DBP oil supply amount (9 g method) of 340 ml / 100 g or more. The use of black is desirable. As such furnace-based carbon black, “Ketjen Black” (trademark) EC and “Ketjen Black” (trademark) EC600JD manufactured by Ketjen Black International are known. As carbon black, acetylene black having a DBP oil supply of 340 ml / 100 g or less is also known. However, since this has lower conductivity than the above-mentioned “Ketjen Black” (trademark) EC, etc., acetylene black is used. In order to obtain a more satisfactory conductivity, for example, an addition amount of about three times that of “Ketjen Black” (trademark) EC is required, and the fluidity of the conductive layer polymer tends to decrease.

  In addition, the conductive monofilament of the present invention may contain various additives in a polymer resin or a polymer resin composition without limitation for the purpose of adding further characteristics as long as the target characteristics are not excluded. For example, an ionomer resin or a silicone resin can be added to the sheath conductive layer in an amount of 0.1 to 0.5% by weight for the purpose of improving wear resistance.

  The production method of the conductive monofilament of the present invention does not require any special method. For example, a known core such as a production method of melt extrusion using an extruder type composite melt spinning machine and a desired composite spinneret. It can be produced by a sheath composite spinning method.

  The conductive monofilament of the present invention thus obtained has sufficient physical strength as an industrial material, has sufficient conductive performance required as an antistatic material, and the sheath conductive layer is worn. Even in such a case, since it has an extremely stable conductive performance continuously, it exhibits an extremely excellent effect as an antistatic material in various industrial fabrics, and can be suitably used as warps and / or wefts of these industrial fabrics. Is.

  Hereinafter, although embodiment of the electroconductive monofilament of this invention is described in detail, this invention is not limited to a following example, unless the summary is exceeded.

  In addition, the area ratio of the sheath part conductive layer and the core part non-conductive layer, the volume specific resistance value, and the forced wear test described above and below are evaluated by the following methods.

[Area ratio between the sheath conductive layer and the core non-conductive layer]
A cross-sectional observation sample cut in a direction perpendicular to the fiber axis direction of the conductive monofilament is observed with a digital microscope VHX-100F manufactured by KEYENCE, and the sheath conductivity of the conductive monofilament is measured using the area measurement tool of this digital microscope. The area of the layer (including the auxiliary conductive layer) and the area of the core non-conductive layer were measured, and the area ratio was determined as a percentage.

[Volume resistivity]
Both ends of a monofilament sample 5 cm were gripped with a crimp (electrode), applied to measure the resistance value of the yarn, and the resistance value was determined by the following formula. The distance between the electrodes of the monofilament sample gripped by the crimp was 4 cm, the environmental conditions at the time of measurement were 20 ° C. and the humidity 65%, and the resistance value was a super insulation meter SM- manufactured by Toa Denpa Kogyo Co., Ltd. Measurements were made using type 10.
Volume resistivity (Ω / cm) = Measured resistance (Ω) ÷ Distance between electrodes (cm)

[Forced wear test]
In accordance with the JIS L-1095-9.10.2B method, conductive monofilaments brought into contact with a fixed φ1.0 mm friction element (hard steel wire (SWP-A)) A load of 0.22 cN / dtex is applied to one end of a conductive monofilament through two free rollers (100 mm distance between rollers) provided at an angle of 55 degrees and over another free roller. Then, the conductive monofilament was brought into contact with the friction element 300 times and was worn under the conditions of a speed of 120 reciprocations / minute and a reciprocation stroke length of 25 mm.

[Conductivity retention]
The volume resistivity value of the conductive monofilament before the forced wear test was A, and the volume resistivity value of the conductive monofilament after the forced wear test was B, and the conductivity retention was determined by the following formula.
Conductivity retention (%) = B ÷ Ax100

  The raw materials used in the production of the conductive monofilament in the examples of the present invention were as follows unless otherwise specified.

1. Polyester pellets Dry PET pellets (hereinafter abbreviated as PET pellets) produced by known melt polycondensation and solid phase polycondensation and having an intrinsic viscosity of 0.94 and a terminal carboxyl group concentration of 15 equivalents / 10 ⁶ g.

2. Carbon black-containing PET master batch pellets PET pellets containing 11% by weight of Ketjen Black EC (Ketjen Black International Co., Ltd.), which is carbon black, on a PET chip having an intrinsic viscosity of 0.67.

[Example 1]
A PET master batch pellet containing PET pellets in the core non-conductive layer and carbon black in the sheath conductive layer and auxiliary conductive layer so that each of the pellets has a uniaxial extension so as to have the composite area ratio shown in Table 1. Continuously fed to the ruder.

  Each pellet was melt-kneaded at about 290 ° C. in each extruder, and then merged immediately before the nozzle discharge hole through each filter layer in the composite spinning pack via a gear pump, and was spun from the spinneret for circular cross-sectional yarn. . Thereafter, the spun monofilament was cooled and solidified in a 70 ° C. hot water bath, subsequently stretched to a total of 5.5 times, further heat-set, and 0.5 mm in diameter, core non-conductive layer: sheath conductive layer = 67:33, and a conductive monofilament having a circular cross-sectional shape with six auxiliary conductive portions was obtained. Table 1 shows the evaluation results of the volume resistivity value, the volume resistivity value after forced wear, and the conductivity retention rate of the obtained conductive monofilament.

[Examples 2 to 6]
A conductive monofilament was obtained by the same production method as in Example 1 except that the area ratio between the core non-conductive layer and the sheath conductive layer and the number of auxiliary conductive portions were changed. Table 1 shows the evaluation results of the volume specific resistance value, the volume specific resistance value after forced wear, and the conductivity retention rate of each conductive monofilament obtained.

[Comparative Examples 1-2]
A conductive monofilament was obtained by the same production method as in Example 1 except that a conductive monofilament having a core-sheath composite structure having no auxiliary conductive layer was used. Table 1 shows the evaluation results of the volume specific resistance value, the volume specific resistance value after forced wear, and the conductivity retention rate of each conductive monofilament obtained.

  As is clear from the results in Table 1, it can be seen that the conductive monofilament of the present invention maintains extremely stable conductive performance because the auxiliary conductive portion remains even when the sheath conductive layer is worn.

  On the other hand, conductive monofilaments having no auxiliary conductive portion (Comparative Example 1 and Comparative Example 2) have a lower conductivity retention after the forced wear test than the conductive monofilaments of the present invention, and have poor conductivity performance. It was enough.

  The conductive monofilament of the present invention continues to maintain excellent conductive performance even in long-term use as compared to conventional conductive monofilaments. Therefore, when this conductive monofilament is used as a constituent material for industrial fabrics, it will last for a long period of time. An industrial fabric that maintains the antistatic effect can be obtained.

It is sectional drawing which appears when an example of the electroconductive monofilament of this invention is cut | disconnected perpendicularly | vertically to the fiber axis direction. It is sectional drawing which appears when another example of the electroconductive monofilament of the present invention is cut perpendicularly in the fiber axis direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive monofilament 2 Core part non-conductive layer 3 Sheath part conductive layer 4 Auxiliary conductive part

Claims (6)

A monofilament having a core-sheath composite structure, the monofilament comprising a core non-conductive layer and a sheath conductive layer covering the core, in the cross section perpendicular to the length direction of the monofilament, the inner side of the core non-conductive layer A conductive monofilament having an auxiliary conductive portion in which a part of the sheath conductive layer protrudes in a convex shape toward the surface. 2. The conductive monofilament according to claim 1, comprising at least two auxiliary conductive portions in which a part of the sheath conductive layer protrudes in a convex shape toward the inside of the core non-conductive layer. The conductive monofilament according to claim 1 or 2, wherein an area ratio of the sheath conductive layer including the auxiliary conductive portion and the core nonconductive layer is in the range of 5:95 to 50:50. An electrode is connected to both ends of the monofilament, and the volume specific resistance value expressed by the resistance value (Ω) of the monofilament to be measured / the distance (cm) between the electrodes when the resistance value is measured is 1 × 10 ⁸ Ω / cm The conductive monofilament according to any one of claims 1 to 3, wherein: When the volume resistivity of the conductive monofilament before and after the forced wear test is A (Ω / cm) and B (Ω / cm) in the forced wear test according to JIS-1095-9.10.2B method, respectively. The conductive monofilament according to any one of claims 1 to 4, wherein the conductivity retention represented by B ÷ Ax100 is 50% or more. An industrial fabric comprising the conductive monofilament according to any one of claims 1 to 5 as at least a part of warp and / or weft.

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