JP2913698B2 - Conductive composite fiber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a conductive fiber, and particularly to a conductive conjugate fiber containing a low-melting metal as a conductive substance.

(Prior art) Synthetic fibers, such as polyester fibers and polyamide fibers, have low conductivity and are liable to generate static electricity due to friction. An obstacle has occurred. In order to solve such a problem, it is known to mix a conductive fiber with a fiber product. As the conductive fiber, a metal fiber, a metal-plated fiber, a carbon black and / or a fiber blended with a conductive substance, or the like is used. Has been proposed
No. 53-44579, JP-B-56-37322, JP-A-57-37357
No. 193520).

However, these conductive fibers have various problems in yarn physical properties, cross knitting with other fibers, cross weaving, hue, dyeing properties, and the like, and have not been satisfactory.

(Problems to be Solved by the Invention) Further, as a fiber having excellent conductivity and dyeing properties, a composite fiber having a core portion made of an alloy and a sheath portion made of a thermoplastic polymer (JP-A-51-11909) is known. However, in addition to having low viscosity, high surface tension,
Furthermore, it is very difficult to supply the molten alloy constantly, so it is difficult to keep the diameter of the core constant,
Thick parts appear irregularly. As a result, when the film is stretched, it often breaks from a narrow portion, and not only the diameter of the core alloy fluctuates, but also the length of the core alloy and the length of the hollow portion become non-uniform, thereby significantly impairing the appearance. It was difficult to obtain satisfactory conductivity and yarn properties, and it was not one that could be put on the market.

(Means for Solving the Problems) The inventors of the present invention have finally completed the present invention as a result of intensive studies to provide a conductive fiber without the above-mentioned disadvantages. That is, the present invention relates to a conjugate fiber in which the sheath portion is made of a thermoplastic polymer and the core portion is made of a low-melting-point metal. The conductive conjugate fiber is characterized in that the variation rate is 25% or less, and the total of discontinuous portions per 1 m in the length direction of the core is 5 cm or less.

The thermoplastic polymer constituting the sheath of the conductive composite fiber of the present invention may be any fiber-forming polymer that can be melt-spun,
Its melt viscosity is 3000 ~ 8000 poise / 300 ℃, especially 4000 ~ 70
00 poise / 300 ° C. is preferred. If the melt viscosity is out of the above range, the balance between the sheath and the core deteriorates, and the sheath is cracked,
The molten metal in the core portion is not preferred because it is difficult to enter the core continuously and uniformly. Specific examples of such polymers include polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyamides such as nylon 6 and nylon 66; polyolefins such as polyethylene and polypropylene; And heat-resistant thermoplastic polymers such as polyetheretherketone, polyethylene 2,6-naphthalate, and wholly aromatic polyester.

In addition, the thermoplastic polymer of the sheath may contain an optional additive such as a delustering agent, a coloring agent, an oxidation stabilizer and the like, if necessary. In particular, considering the whiteness and the dyeability of the conductive composite fiber, it is preferable to contain 1 to 2% of titanium dioxide.

Examples of the low melting point metal constituting the core of the conductive composite fiber of the present invention include metals having a melting point of about 50 ° C. or higher to about the melting point of the thermoplastic polymer, and specifically, indium (In) , Selenium (Se), tin (Sn), bismuth (Bi),
There are metals such as lead (Pb) and cadmium (Cd) and alloys of these metals such as binary, ternary and quaternary systems. Specific examples of alloys include Bi / Sn, Bi / In, Sn / Pb, Bi / Sn / I
n, Bi / Pb / Cd, Bi / Pb / Sn, Bi / Sn / In / Pb, Bi / Sn / Pb / Cd, B
i / Sn / In / Pb / Cd and the like.

In the conjugate fiber of the present invention, the area ratio occupied by the core in the cross section of the conjugate fiber, the rate of change and continuity in the longitudinal direction greatly affect the conductivity, yarn physical properties, hue and dyeability of the conjugate fiber. The area ratio of the part is 0.2 to 50%, but is preferably 0.5 to 30% in consideration of yarn physical properties, dyeing properties and the like. The variation rate in the length direction of the core area is required to be 25% or less because it affects the stretchability and yarn physical properties of the conjugate fiber.
It is preferable to make it 10% or less.

Although the continuity in the longitudinal direction of the core affects the conductive performance,
If the total of the discontinuous portions per 1 m is 5 cm or less, there is no problem in the conductive performance, but 1 cm or less is preferable. If the discontinuous portion per 1 m exceeds 5 cm according to the present invention, not only is the conductivity deteriorated, but the yarn also becomes ununiform in terms of physical properties.

When trying to make the conductive performance of a product using conductive yarn fall within the standards described in the Ministry of Labor's Industrial Safety Research Institute “Static Standard for Electrostatic Products” and JIS T-8118, the electrical resistivity (volume resistivity) of the conductive yarn is usually A value of about 10 ⁴ Ω · cm is required.

The conductive conjugate fiber obtained from the present invention not only has an electric resistivity satisfying the above criteria, but also has a yarn physical property that does not cause any problem even if it is knitted and woven with other fibers, and in terms of dyeability. There was no problem.

Next, a method for producing the conductive composite fiber of the present invention will be specifically described with reference to the drawings.

FIG. 1 and FIG. 2 are schematic sectional views of an embodiment of an apparatus for producing the conductive conjugate fiber of the present invention.

In FIG. 1, the metal melted in a melting tank 5 is transferred to a melting tank 6 by a gear pump 4, and the level of the melting tank 6 is controlled to be constant. Next, the melting tanks 5 and 6 are pressurized with the inert gas 10 at a constant pressure controlled by the control circuit 3, the power amplifier 2 and the electric control valve 1,
A certain amount of the molten metal 12 is supplied to the spinning nozzle 8 shown in FIG. 2, and the composite fiber 9 is obtained through the nozzle 8a together with the thermoplastic polymer 11 discharged from the nozzle 8b.

The conjugate fiber of the present invention can be a monofilament or a multifilament, and is not particularly limited. The spinning speed during spinning is preferably in the range of 600 to 2000 m / min in consideration of the final yarn quality.

The usual drawing method can be applied to stretch the conjugate fiber after spinning, but it is necessary to heat the core component to a temperature equal to or higher than the melting point by a heating roller or the like before stretching. It is not preferable because the wire breaks and the yarn quality becomes uneven.

(Example) Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to the examples. In addition, each characteristic in an Example was measured by the method shown below.

Melt viscosity Load 50.0KGF, Shimadzu flow tester (CFT-500), D
This is the melt viscosity at a constant temperature measured under the conditions of IE (radius: 1.000 mm, length: 10.00 mm).

Strength and elongation were measured by a tensile tester. Strength (g / d) is the breaking strength when stretched at a rate of 100% / min.

-Elongation (%) is the elongation at break when elongated at a rate of 100% / min.

Mixing ratio of core component (%) It is an area ratio to the total cross-sectional area of the conjugate fiber observed with an optical microscope.

Length of discontinuous portion of core component The side surface of the conjugate fiber is observed with an optical microscope, and is indicated by the total length (cm) per meter.

Conductivity The conductivity of the conjugate fiber is the volume resistivity (Ω · cm) when 10 V is applied, measured by the following method.

Dyeability Uses polyester fiber. 1 Conductive fiber on white twill.
This was sewn at a pitch of 10 mm and dyed with a disperse dye under the following conditions, and the degree of dyeability was visually determined.

Dispersion formulation: Dianix Blue AC-E 1% owf 130 ° C × 60 minutes Acidic formulation: Kayanol Mill Blue BW 1% owf 100 ° C × 60 minutes Example 1 IV = 0.95, titanium oxide having a melt viscosity of 5500 poise / 300 ° C. Is melted and pressurized (N ₂ ) by using an apparatus shown in FIG. 1 with a polyethylene terephthalate containing 2% as a sheath component and melting at 78.8 ° C. (bismuth / tin / indium system).
Gas, 0.40 kg / cm ² ) and supply it to the composite nozzle shown in Fig. 2. After spinning at a spinning temperature of 285 ° C and a spinning speed of 700 m / min, a preheating roller (85 ° C) and a heater (150 ° C) Equipped with a stretching machine
Stretched 2.5 times. The resulting composite fiber had a denier of 18d (monofilament), a strength of 3.1 g / d and an elongation of 38%. The area occupied by the core in the cross section of the conjugate fiber was about 7 to 8%, and the total number of discontinuous parts per meter in the length direction of the core was 1 cm or less.

Comparative Example 1 Composite spinning and stretching were performed under the same conditions as in Example 1 except that the pressure of the molten alloy was set to 0.1 kg / cm ² . The resulting composite fiber has a denier of 17d (monofilament) and a strength of 3.5 to 4.3 g / d.
And the elongation was 25-35%. The area ratio of the core in the cross section of the composite fiber was 0.05 to 0.1%, and the total number of discontinuous parts per meter in the length direction of the core was 10 cm.

Comparative Example 2 Composite spinning and drawing were performed under the same conditions as in Example 1 except that the pressure of the molten alloy was set to 2.5 kg / cm ² . The resulting composite fiber has a denier of 43d (monofilament) and a strength of 2.1 g / d,
The elongation was 35%. The area ratio of the core in the cross section of the conjugate fiber was 55 to 65%, and the total number of discontinuous parts per meter in the length direction of the core was 1 cm or less.

Example 2 Nylon 6 having an RV of 3.53 and a melt viscosity of 3700 poise / 300 ° C. was used as a sheath component and spun and stretched at a spinning temperature of 285 ° C. in the same manner as in Example 1. Denier of the obtained composite fiber was 17d (monofilament), strength was 2.8 g / d, and elongation was 50%. Further, the mixing ratio of the core was 4 to 5%, and the total of the discontinuous portions 1 m in the length direction of the core was 3 cm.

Example 3 An alloy (In / Sn) having a sheath component of polyethylene terephthalate having an IV of 0.98 and a melt viscosity of 7400 poise / 300 ° C. and a melting point of 117 ° C. was melt-pressed using the apparatus shown in FIG. Gas: 0.4 kg / cm ² ) After supplying to the composite nozzle shown in Fig. 2 and spinning at a spinning temperature of 300 ° C and a spinning speed of 700 m / min, a preheating roller (90 ° C) and a heater (150 ° C) were provided. The film was stretched 2.5 times with a stretching machine. The denier of the obtained composite fiber is 16d
(Monofilament) had a strength of 3.3 g / d and an elongation of 30%. The mixing ratio of the core is 3.5 to 5.5%, and the length of the core is 1m in the length direction.
The total discontinuity per hit was 4.5 cm.

Table 1 shows the properties (volume resistivity, hue, and dyeability) of the composite fibers obtained in Examples 1 to 3 and Comparative Examples 1 and 2.

FIG. 3 shows a cross-sectional state of the conjugate fiber obtained in Example 1.

(Effect of the Invention) The conductive conjugate fiber of the present invention is characterized in that the mixing ratio of the core made of a low melting point metal and the morphology in the longitudinal direction are sufficiently controlled. As a result, not only the conductive performance but also the yarn physical properties, hue, Has excellent properties in terms of dyeability, antistatic work clothes, uniforms, carpets, using the conductive composite fiber of the present invention,
It can be used as a car seat and electromagnetic wave shielding material.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of one embodiment of a supply apparatus of a molten metal used for producing a conductive composite fiber of the present invention.
FIG. 3 is a schematic cross-sectional view of the composite nozzle used in the apparatus shown in FIG. 1, and FIG. 3 is a photograph showing the “fiber shape”. It shows a state where the microscope is magnified 800 times. 1: Electric control valve, 2: Power amplifier 3: Control circuit, 4: Gear pump 5: Melting tank, 6: Melting tank 7: Pressure gauge, 8: Composite nozzle 9: Composite fiber, 10: Inert gas 11: Thermoplastic polymer, 12: molten metal

Claims (1)

(57) [Claims] In a composite fiber having a sheath made of a thermoplastic polymer and a core made of a bismuth / tin / indium alloy metal having a low melting point, the area occupied by the core in the cross section of the composite fiber is 0.2 to 50%. , The variation rate in the length direction of the core area is 25%
The conductive conjugate fiber according to claim 1, wherein a total of discontinuous portions per meter in the length direction of the core is 5 cm or less.