DE3935057A1 - Electrically conducting 2-component fibre - has shell of thermoplastic polymer and uniform core of low-melting metal, with variable shell-core cross-sectional area ratio - Google Patents

Abstract

(1) Electrically conducting 2-component fibre (I) has a shell of thermoplastic polymer (II) and a core of low-melting metal (III); the core makes up 0.2-50% of the fibre cross-sectional area, the cross-sectional area of the core does not vary by more than 25% along the fibre, and the total length of the discontinuities in the core is not above 5 cm/metr of core. (2) Device (a) for prodn. of (I) has a closed fusion tank below a 2-component spinning nozzle and connected to it by a feeder line for molten (III); a line for supplying inert gas at a predetermined pressure is connected to the upper space in the tank, and a controlling device is provided to maintain a constant level of liq. in the tank. Or device (b) has a 2-component nozzle with a feed line for molten (III) which is filled with metal, glass, inorganic substances and/or ceramic, and a gear pump. (3) Processes for prodn. of (I) comprise (a) passing molten (III) from the tank to the nozzle under inert gas pressure which is controlled so that variations do not exceed 0.1 bar and the molten metal is kept at a constant level in the tank, or (b) feeding molten (III) to the nozzle by means of a gear pump. USE/ADVANTAGE - The invention enables the prodn. of textile-quality, 2-component fibre with a reasonably uniform, conductive core (e.g. as an antistatic measure); the fibre has excellent conductivity and can be dyed.

Description

The invention relates to electrically conductive fibers, in particular special electrically conductive two-component fibers that a low-melting metal as an electrically conductive sub have punch, and an apparatus and a method to create these fibers.

Synthetic fibers load because of their low electrical conductivity easily due to electrical friction on. Therefore, when using textile material, it happens that consists of such synthetic fibers, to different unwanted side effects, such as attracting dust or electrical discharges. A solution to these problems is known to be the storage of electrically conductive Fibers in textile goods. For example, Metal fibers, metalli sized fibers, fibers mixed with carbon and / or an electrically conductive substance, etc. as electrical conductive fibers (JP-B-44 579/1978, JP-B-37 322/1981 and JP-A-1 93 520/1982).

The use of these electrically conductive fibers is ever but with some difficulties. They still exist  Problems in the yarn properties, in the shade and in the Dyeability in the manufacture of ge with other fibers mixes knitted and mixed woven textiles.

It is known that two-component fibers with an alloy as the core and a thermoplastic polymer as the shell have excellent electrical conductivity and dyeability (JP-A-11 909/1976). However, with the known devices ( Fig. 5) for producing two-component fibers, it is very difficult to supply the molten alloy at a constant rate because it has a high viscosity and a high surface tension. The result is difficulty in creating a defined core diameter, and there are irregular thickening and thinning. Therefore, when the alloy is drawn, the alloyed core breaks at the dilutions, so that the diameter and length of the core alloy and the cavity of the fiber also vary or become non-uniform. Therefore, not only is the appearance impaired, but it is also problematic to achieve a satisfactory electrical conductivity and satisfactory yarn properties, so that textile material containing two-component fibers has not yet been brought onto the market.

With thin two-component fibers (diameter 50 µm or white niger) as they are used in clothing, it is very difficult, the molten metal continuously and to be delivered in a defined quantity. For these purposes both two-component fibers with satisfactory Qua lity as well as an apparatus and a method for its Generation not yet developed.

The invention has for its object a device and to provide a method which it ge equip a molten metal stable, continuous and in a predetermined amount to a two-component spinneret  lead, with two-component fibers of the core type with uniform core can be generated.

This task is ge with the features of the claims solves.

For the formation of the shells of the electrically conductive Zweikom Component fibers can be any fiber-forming polymer that is used for Melt spinning is suitable to be used. A preferred However, the polymer is one with a melt viscosity of 300 to 800 Pas at 300 ° C, 400 to 800 are particularly suitable 700 Pas at 300 ° C. With a melt viscosity of less 300 Pas at 300 ° C is the balance between the core and the The cover is lost and the cover is torn off. About If the melt viscosity increases 800 Pas at 300 ° C, the continuous and uniform flow of the molten me talls in the shell, and the discontinuity of the Kernes is increasing. Excellent electrical conductivity speed can therefore only be achieved with selected polymers the.

Examples of such polymers are polyesters (e.g. polyethylene lenterephthalate, polybutylene terephthalate), polyamides (e.g. Nylon-6, Nylon-66), polyolefins (e.g. polyethylene, Polypro pylene) and copolymers consisting essentially of these Po lymeren are composed. In addition, e.g. warmer resistant thermoplastic polymers, such as polyphenyl sulfide, Polyether ketones, polyethylene-2,6-naphthalate, fully aromatic Polyester are used.

If necessary, can also be used in the thermoplastic Polymer that forms the layer, additives such as matting, coloring and antioxidant agents are incorporated. Butt lyester and nylon with 1 to 2% titanium dioxide are preferred thermoplastic polymers, if white and easily dyeable, conductive two-component fibers are required.  

Under a low melting metal, which is the core of the is an electrically conductive two-component fiber Metal with a melting point between 50 ° C and the enamel to understand the point of the thermoplastic polymer. Such Metals are e.g. indium (In), selenium (Se), tin (Sn), bismuth (Bi), lead (Pb) or cadmium (Cd) as well as binary, ternary and quaternary alloys from these metals. Examples sol Alloys are Bi / Sn, Bi / In, Sn / Pb, Bi / Sn / In, Bi / Pb / Cd, Bi / Pb / Sn, Bi / Sn / In / Pb, Bi / Sn / Pb / Cd and Bi / Sn / In / Pb / Cd.

In the two-component fibers according to the invention that has Ratio of the cross-sectional area of the core to that of the Fiber, the percentage variation in cross-sectional area of the Core in the longitudinal direction, and the continuity of the core in same direction a great influence on the electrical Conductivity, yarn properties, color and Dyeability of the two-component fibers. Therefore, the ge named ratio varies from 0.2 to 50%. Particularly good The ratio is in the range of 0.5 to 30%, if the yarn properties and dyeability are taken into account will. Deviations from this ratio of 25% or we Niger are admitted, but an Ab is particularly cheap softening of less than 10%.

The continuity of the core in the longitudinal direction affects the electrical conductivity, but there are no problems with the electrical conductivity with discontinuous parts of 5 cm or less per m core length. However, discontinuities less than 1 cm in length are more favorable. If the core has discrepancies greater than 5 cm per meter, there is not only a reduction in the electrical conductivity, but also inhomogeneities in the yarn quality. The electrical conductivity of electrically conductive yarns is standardized ("Recommended Standards of Construction of Appliances used for Protection against Electrostatic Hazards", Industrial Safety Research Institute of Minstry of Labor, Japan, and JIS T-8118). According to this, a specific electrical resistance (volume resistance) of approximately 10 ⁴ Ω × cm is required for electrically conductive yarns.

The electrically conductive two-components according to the invention ten fibers have a specific electrical resistance, which corresponds to the mentioned standard, and the yarn quality ten are so good that they can be shared with others without any problems Yarn in mixed, knitted or woven textile goods can be applied. There are also no problems with the dyeability.

The device and method for generating the inventions inventive electrically conductive two-component fibers sol len now explained in more detail with reference to the drawings the. Show it:

Fig. 1 shows a schematic representation of the apparatus for Erzeu gene of the bicomponent fibers,

Fig. 2 an enlarged cross-section of the bicomponent spinning nozzle of Fig. 1,

Fig. 3 shows a schematic representation of another embodiment of the device according to the invention for producing a two-component fiber;

Fig. 4 is an enlarged cross section of the supply line for ge molten metal of Fig. 2;

Fig. 5 cross section of a conventional spinning device;

Fig. 6 representation of the measurement of volume resistance.

The numbers in the drawings have the following meaning:

1 pressure control valve
2 power amplifiers
3 control circuit
4 gear pump
5 subtank
6 melting tank
7 pressure measuring instrument
8 two-component spinneret
9 two-component fibers
10 inert gas supply line
11 Thermoplastic polymer
12 Molten metal
13 pressure control device
14 a , 14 b electrical connections
15 overflow pipe
16 Feed pipe for molten metal
17 Pipe for molten metal
18 Molten metal feed pipe
19 pressure sensor
20 melting tank
21 gear pump
22 filters
23 Molten metal
24 spinneret for two-component fibers
25 Thermoplastic polymer
26 two-component fiber
27 filling

Fig. 1 shows schematically a device according to the invention. In addition to the two-component spinneret 8 according to FIG. 2, other embodiments of the two-component spinneret are also conceivable. The two-component spinneret 8 is connected via a feed line 18 for molten metal to a fusion tank 6 . The level of the molten metal 12 in the fusion tank 6 is set so that it is below the tip of the two-component spinneret 8 . This ensures that the molten metal does not flow spontaneously under the influence of gravity to the nozzle 8 . The apparatus of FIG. 1 is constructed so that a constant Zufüh tion of molten metal easily by controlling the pressure of an inert gas is achieved. A Steuereinrich device C is provided to keep the level of the liquid in the melting tank 6 constant. The control device C be consists of a subtank 5 , an overflow line 15 , for connecting the subtank 5 to the melting tank 6 and a feed line 16 for molten metal. A gear pump 4 is located in line 16 . The upper opening of the overflow line 15 is at the required Ni level in the melting tank 6 , so that the molten metal 12 flows above the level into the overflow and down the line 15 into the subtank 5 . When the molten metal is supplied from the melting tank 6 to the two-component spinneret 8 , the level in the tank gradually drops. The To drove of molten metal to the melting tank 6 from the sub tank 5 via line 16 is slightly stronger than the drain to the nozzle 8th Excess molten metal 12 is discharged via the overflow 15 , the level of the molten metal 12 in the fusion tank 6 being kept constant. The space 6 a above the molten metal in the melting tank 6 is connected to an inert gas supply line 10 , and a device 13 for controlling the pressure is arranged at an arbitrary position in the vicinity of the supply line 10 . The device 13 has a control valve 1 , which is arranged on the line 10 , a control circuit 3 for regulating the degree of opening of the valve 1 , a power amplifier 2 and a pressure sensor 19 . The other end of line 10 is connected to a pressure generation source, not shown here, such as fans or pressure pumps, etc.

The control device C described is not limited to the example of FIG. 1, but can also be formed differently if only flow or level sensors are used. The inert gas pressure control device 13 can have a compensation tank or a conventional pressure control device.

An inert gas at a predetermined pressure, controlled by the pressure control device 13 , exerts a pressure on the melting tank 6 via the supply line 10 and presses it through an amount of molten metal 12 to the two-component spinneret 8 . The spinneret 8 is also a ge melted thermoplastic polymer 11 by an extruder ( E in Fig. 5), which is connected in the nozzle 8 with the Me tall so that a shell core structure is formed. The structure of the nozzle 8 is shown in cross section in FIG. 2. Inside the nozzle, molten metal 12 is fed to an inner nozzle 8 a via a line 17 for molten metal, and the molten thermoplastic polymer 11 is fed to an outer nozzle 8 c via a chamber 8 b . The spinning process takes place for both at the same time through the nozzles, so that two-component fibers 9 of the shell-core type are obtained which have the metal as the core and the thermoplastic polymer as the shell.

Nitrogen, argon or helium, for example, can be used as inert gases for supplying a certain amount of molten metal to the two-component spinneret 8 . The pressure of the gas depends on the intrinsic viscosity of the thermoplastic polymer, the dimension of the two-component spinneret, the position of the tank for molten metal, etc. The pressure should be in the range of 0.05 to 10 bar, more favorably in the range of 0.1 to 5 bar. At pressures less than 0.05 bar, the force for pushing the molten metal down from the melting tank 6 is too low to ensure a continuous and stable supply to the two-component spinneret 8 . At a pressure greater than 10 bar, the amount of molten metal supplied becomes too large and the balance between the amount of metal and that of the thermoplastic polymer is disturbed. As a result, the polymer layer tears or breaks.

The essential features of the method according to the invention for producing the electrically conductive two-component fibers consist of supplying a low-melting metal in the molten state to the two-component spinneret 8 under pressure, the pressure fluctuations of the inert gas should be less than 0.1 bar, and the liquid level in the melting tank 6 constant held in front of the nozzle. With pressure fluctuations less than 0.1 bar, the deviation from the core-core cross-section ratio is low, so that good physical properties of the yarns produced and a good color tone of the fibers are achieved. Pressure variations less than or equal to 0.05 bar are even more favorable for the yarn properties and the uniformity of the knitted or woven goods. With pressure fluctuations greater than 0.1 bar, the core-core cross-section ratio fluctuates so much that the physical properties of the yarns and the color of the fibers are adversely affected.

Fig. 3 shows a schematic representation of another embodiment of the device according to the invention for generating two-component fibers. In Fig. 3, a molten metal from a melting tank 20 by means of a gear pump to the two-component nozzle 24 is passed through a filter 22 . A molten thermoplastic polymer 25 from an extruder (not shown) is also fed to the nozzle 24 . Inside the nozzle 24 , the metal and polymer are brought together to form a two-component fiber. The two-component spinneret 24 has the same structure as shown in FIG. 2. Fig. 4 shows a ver enlarged cross section of the line 17 for molten metal from Fig. 2. According to Fig. 4 is a package 27 , which may consist of metals, glasses, inorganic substances and ceramics, in the line 17 for molten zenes metal. The metals can be used as thin rods, sintered filters or sintered metal particles. The glasses can be in the form of ordinary glass beads or porous glass beads and the inorganic substances in the form of zeolite, sand or the like. Ceramics can be used in the form of sintered products of aluminum oxide, zirconium oxide, magnesium oxide, silicon carbide, silicon nitride and the like.

If the diameter of the packing particles is less than 0.1 mm, there is a risk that the nozzle opening will be blocked. If the packing particles have a diameter greater than 3.0 mm, their filling into line 17 is made more difficult. Favorable diameters are therefore between 0.1 and 3.0 mm. In view of a stable supply of molten metal, a pack length of 5 to 20 mm in line 17 is preferred. In order to achieve particularly good yarn properties, a spinning rate in the range from 600 to 200 m / minute is preferred.

Fig. 5 shows a schematic representation of a conventional device for producing two-component fibers. A melting tank 6 is arranged above the head of an extruder E for thermoplastic polymers, and the tank and the head are connected to one another as a cross head. The space above the liquid metal in the fusion tank 6 is with egg ner inlet line 6 a for pressurized gas verbun through which the gas is passed into the tank 6 to press the molten metal 12 in the axial direction from the two-component spinneret 8 . A thermoplastic poly mer 11 is also brought out in the molten state so that it envelops the molten metal, so that the metal and the polymer form a two-component fiber 9 of the shell-core type when exiting the nozzle. In a method using this type of device, it is very difficult to deliver the molten metal uniformly and in a defined amount to the two-component spinneret 8 . It is therefore also difficult to produce bicomponent fibers with a core of uniform cross-section and without tearing in the longitudinal direction.

The invention will now be illustrated by the following examples len are explained. The properties of the fibers were determined with the following measurement methods:

• (1) melt viscosity: flow tester CFT-500 (Shimadzu Corp.), at 300 ° C, load 490.5 N, nozzle diameter 1.00 mm, Nozzle length 10.0 mm.
• (2) toughness and elongation: tensile tester; the toughness will determined at break if the sample is at a rate of Stretched 100% / minute; the elongation (in%) is at Breakage determined when the sample at a rate of 100% is stretched per minute.
• (3) Shell-core ratio (in%): microscopic determination the ratio of the cross-sectional areas of the core and the two-component fiber.
• (4) Length of the discontinuity of the core: total length of the dis continuous parts in cm / meter, determined by microscopic observation along the two-component fa ser.
• (5) Electrical conductivity: see Fig. 6, coating the two-component fiber 9 with silver paste at two points, which are a predetermined distance apart to create two electrical connections 14 a and 14 b , applying a voltage of 10 volts between them conclusions, determine the volume resistance according to the equation: l : distance between the connections,
  Δ V : potential difference,
  I : current,
  S : total cross-sectional area of the fiber
  Measurement conditions: l = 5 cm; Room temperature = 20 ° C; relative humidity = 65%.
• (6) Dyeability: Electrically conductive fibers were made in with a white body of textured polyester yarn a portion of one fiber sewn per 10 mm, the Body was made with the dispersed dye Dianix Blue AC-E (2% of the woven fabric) for 60 minutes dyed at 130 ° C, and the degree of dyeability was macroscopically assessed.

example 1

Polyethylene terephthalate with 2% titanium oxide, an intrinsic viscosity [ η ] of 0.85 and a melt viscosity of 400 Pa · s [300 ° C] was used as the shell, and a Bi / Sn / In alloy with a melting point of 78.8 ° C was the core. In the device of FIG. 1, the alloy was melted, passed under pressure (N ₂ gas, 0.4 bar) to the two-component tensile nozzle according to FIG. 2 and together with the polyethylene terephthalate, which is fed to the nozzle in the molten state, at one Spinning temperature of 285 ° C and a spinning rate of 700 m / minute connected to a two-component fiber. The two-component fibers were then drawn up to 2 1/2 times the original length in a drawing machine with a preheating roller (85 ° C.) and a heater (150 ° C.). The resulting two-component fibers had a mass of 2 tex (monofilament), a toughness of 3.1 g / den (g / den = 8.82 · 10 ^-2 N / tex) and an elongation of 38%. The ratio of the cross-sectional area of the core to the cross-sectional area of the bicomponent fiber ranged from about 6.8 to about 7.2%. The total length of the discontinuous parts of the core in the longitudinal direction was less than 1 cm / m core expansion.

Comparative Example 1

With a conventional apparatus of FIG. 5 in an embodiment with a pressurized gas inlet 6 a Zweikom ponentenfasern were prepared and drawn in the same manner as in Example 1. The resulting two-component fibers of the sheath-core type had quality many inhomogeneities in the yarn. The fibers had a mass of 1.22 to 2 tex, a toughness of 2.4 to 4.8 g / den and an elongation of 31 to 52%.

Comparative Example 2

The two-component fibers were produced in the same manner as in Example 1 in one embodiment, the conventional device having a fusion tank 6 , which was connected to the two-component spinneret 8 via a gear pump 4 , and the molten metal was supplied by means of the gear pump. The supply of the molten metal was discontinuous, and the spun fibers broke immediately under the nozzle when the fibers were rolled up.

Comparative Example 3

Was not provided with a device according to Fig. 1, but the pressure control means 13, Zweikompo were prepared nentenfasern and drawn in the same manner was kept constant as in Example 1 such that the liquid level in the fusion tank 6, but the pressure deviation of the inert gas 0 , Exceeded 1 bar. The resulting two-component sheath core type fibers had many inhomogeneities in the yarn quality. The fibers had a mass of 1.44 to 2 tex, a toughness of 2.5 to 4.2 g / den and an elongation of 32 to 48%.

Example 2

Polyethylene terephthalate with an intrinsic viscosity ( η ) of 0.95 and a melt viscosity of 620 Pa · s / 300 ° C was used as a shell and a Bi / Sn alloy with a melting point of 138 ° C was used as the core. In a device according to Fig. 1, the alloy was melted, under pressure (N ₂ gas, 0.43 bar) to the two-component spinneret 8 and together with the polyethylene terephthalate, which was fed to the nozzle in the molten state, at a spinning temperature of 300 ° C and a spinning rate of 700 m / minute spun into two-component fibers. The two-component fibers were then drawn to 1.5 times the original length in a drawing machine with a preheating roller (145 ° C) and a heater (150 ° C). The resulting sheath core type two-component fibers had a mass of 1.77 tex (monofilament), a toughness of 2.6 g / den and an elongation of 25%.

Table I shows the characteristic features (envelope Core ratio of the core, volume resistance and color), that of Examples 1 and 2 and the Comparative Examples 1 and 3 produced two-component fibers.  

Table I

Example 3

Bicomponent fibers were made and drawn in the same manner as in Example 1, except that an apparatus as shown in Figs. 3 and 4 was used. In this device, particles with a diameter of 0.3 to 0.5 mm were used as a packing.

Comparative Example 4

Bicomponent fibers were made and drawn in same way as in Example 3 with the difference that the two-component spinneret is not filled with a package was.  

Example 4

Polyethylene terephthalate with an intrinsic viscosity ( η ) of 0.95 was used as the shell and a Bi / Sn alloy with a melting point of 138 ° C. as the core. In the apparatus of FIGS. 3 and 4 (pack: sintered alumina having a diameter of 0.3 to 0.4 mm), the alloy coins tion melted, the Zweikomponentenspinndüse supplied together with the polyethylene terephthalate, which is supplied to the nozzle in a molten state was spun at a spinning temperature of 300 ° C and a spinning rate of 1000 m / minute to a two-component fiber. The resulting two-component fibers were drawn to twice the original length in a drawing machine with a preheating roller (145 ° C) and a heater (150 ° C).

Tables II and III show the physical properties characteristics and characteristic features of the two-component ten fibers of Examples 3 and 4 and the Comparative Example 4th

Table II

Table III

The electrically conductive two-components according to the invention ten fibers are characterized by the fact that they Core ratio of a core from a low-melting Metal and have a longitudinal extension of the core, the are adequately controlled. Therefore, the two components Excellent properties not only in electrical engineering conductivity, but also in the yarn properties, in color and dyeability. The elec Trically conductive two-component fibers can be manufactured by Her provision of antistatic work clothes, uniforms, tep and vehicle covers as well as shielding materials of electromagnetic waves, etc.

Claims (8)

1. Electrically conductive two-component fiber ( 9 ; 26 ) with a thermoplastic polymer ( 11 ; 25 ) as the sheath and a low-melting metal ( 12 ; 23 ) as the core, as characterized by

• a) that the cross-sectional area of the core occupies 0.2 to 50% of the fiber cross-sectional area,
• b) that the percentage variation in the cross-sectional area of the core in the longitudinal direction is at most 25% and
• c) that the total length of the discontinuous parts of the core in the longitudinal direction is 5 cm or less per meter of the core.

2. Electrically conductive two-component fiber ( 9 ; 26 ) according to claim 1, wherein the melt viscosity at 300 ° C of the thermoplastic polymer ( 11 ; 25 ) is 300 to 800 Pa · s be. 3. Electrically conductive two-component fiber ( 9 ; 26 ) according to claim 1 or 2, wherein the thermoplastic polymer ( 11 ; 25 ) is a polyalkylene terephthalate. 4. Electrically conductive two-component fiber ( 9 ; 26 ) according to any one of claims 1 to 3, wherein the core is a low-melting alloy. 5. Device for producing an electrically conductive two-component fiber ( 9 ; 26 ) with a thermoplastic polymer ( 11 ; 25 ) as a sheath and a low-melting metal ( 12 ; 23 ) as a core, characterized in that

• a) that a closed fusion tank ( 6 ; 20 ) is provided below a two-component spinneret ( 8 ; 24 ),
• b) that the tank and the nozzle are connected to one another by a line ( 16 , 18 ) for supplying molten metal,
• c) that the upper space of the tank ( 6 ) is connected to a line ( 10 ) for supplying inert gas at a predetermined pressure to the tank, and
• d) that a control device ( C ) is provided to keep the level of the liquid in the tank constant.

6. Device for producing an electrically conductive two-component fiber ( 9 ; 26 ) with a thermoplastic polymer ( 11 ; 25 ) as a sheath and a low-melting metal ( 12 ; 25 ) as a core, characterized in that a two-component spinneret ( 8 ; 24 ) is provided , which comprises: a feed line ( 17 ) for molten metal, which is charged with at least one substance from a group consisting of metals, glasses, inorganic substances and ceramics, and a gear pump ( 21 ). 7. A method for producing an electrically conductive two-component fiber ( 9 ; 26 ) with a thermoplastic polymer ( 11 ; 25 ) as a sheath and a low-melting metal ( 12 ; 23 ) as a core, characterized in that a low-melting metal in the molten state of a fusion tank ( 6 ; 20 ) to a two-component spinning nozzle ( 8 ; 24 ) and is pushed through the pressure of an inert gas, which is controlled so that only a pressure deviation of 0.1 bar or less is admitted, the level of the molten metal in the tank is kept substantially constant. 8. A method for producing an electrically conductive two-component fiber ( 9 ; 26 ) with a thermoplastic polymer ( 11 ; 25 ) as a sheath and a low-melting metal ( 12 ; 23 ) as a core, characterized in that the low-melting metal in the molten state with means of a gear pump in a two-component spinneret ( 8 ; 24 ) via a feed line ( 17 ) which is filled with at least one substance from a group consisting of metal glasses, inorganic substances and ceramics.