CH625570A5 - One-piece electroconductive textile thread and use thereof - Google Patents

Description

The present invention relates to a one-piece electrically conductive textile thread with a resistance of not more than 109 ohm / cm and the use thereof.

The accumulation of static electricity when using textiles is a phenomenon that has for some time attracted the attention of the textile industry. The presence of static electricity is not only uncomfortable e.g. B. in connection with garments that adhere to the body or other clothing, or in connection with fine particles of dust that are attracted to the upholstery fabric, which consequently has to be cleaned frequently, or can lead to slight electric shocks if, for example touched a door handle after walking across a carpet. The presence of static electricity can e.g. B. also be dangerous

for example, it can lead to sparks that can ignite flammable mixtures, such as those made of ether and air, which mixture normally occurs in hospitals, in particular in operating theaters. All of these effects occur in atmospheres with low relative humidity.

Of the many measures which are used to remedy the build-up of static electricity, those which provide for the use of conductive fibers, for example metal fibers, fibers coated with electrically conductive materials and fibers, seem to have proven to be best in terms of effectiveness and durability which have conductive, block-copolymeric materials which are integrally mixed with the fibers in the form of long, thin particles and have a layer or a core which contains electrically conductive material. Furthermore, layered metallic fibers have proven to be expedient in connection with conventional, natural or synthetic fibers, which are processed into a woven, knitted, knotted or tufted or other material structure which easily releases the static charges generated when they are generated. Some of the best known of these methods and structures are e.g. See, for example, U.S. Patent Nos. 2,129,594, 2,714,569, 3,069,746.3,288,175, 3,329,557, 3,582,444.3,582,445.3,582,448.3,586,597.3,590,570,3 637 908, 3 639 502, 3 729 449, 3 803 453 and 3 823 035. Furthermore, information is contained in the article “Metal Fibers” in the Modern Textile Magazine from May 1966, on pages 72-75 and in the Belgian patent specifications No. 775 935 and 790 254, as well as in the French patent specification No. 2 116 106.

Aside from the effectiveness of these and similar processes, they have been unsatisfactory in certain aspects.

The production of metallic fibers with fine denier, in particular in the form of monotilaments, is a difficult and costly process because such fibers have a very different character than textile fibers, so that problems arise in connection with the mixture and with the processing and with the finished product .

On the other hand, metal-coated threads are not associated with any problems in terms of mixing and processing, because of the great similarity to normal textile fibers, and as a result, nothing can be objected to the handle of the resulting product. In contrast, the cost of such fibers is very high compared to the natural or artificial fibers with which they are mixed.

Textile fibers, the surfaces of which are coated by vapor deposition, electrical deposition or by applying adhesive mixtures contained in finely divided particles of electrically conductive material, are in some cases less expensive than metal fibers and / or metal-coated threads, depending on the type the electrically conductive materials used and the coating process used. However, such coatings often have inadequate cohesion and adhesion and often become too thick so that they cannot be used for various purposes, which is particularly true when the type of electrically conductive particles is such that a high concentration of these particles ensures sufficient conductivity is required. As a result, an economical solution is only possible if concessions are made regarding the durability of the conductivity of the fibers.

The extrusion of a mixture of powdery, synthetic polymer and finely divided, electrically conductive material directly into fibers, or as coatings on fiber sub-

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

3rd

625 570

strate with the same or different mixture is known. Unfortunately, these practically homogeneous mixtures require a high concentration of the electrically conductive material. They are usually not, if at all, fully extruded, and many fibers and fiber coatings made therefrom have particularly poor cohesion and adhesion and, as a result, have very poor durability.

Polymeric fiber structures which contain conductive polymeric materials, for example polyalkylene ethers or polyamide block copolymers, which are distributed in the polymer substrates in the form of long, thin particles or layers, the longitudinal axes of which are practically parallel to the direction of the molecular orientation of the fiber, are difficult to reproduce Shape available. This increases their costs and / or their possible uses are reduced.

Although they have been found to be very useful for most applications, such fiber structures with a layer or a one-piece core that contains electrically conductive materials are of relatively limited use or are not suitable because a very low resistance is required.

Although multi-component fibers are already known and are described, for example, in U.S. Patent No. 3,531,368, which describes a multi-component fiber in a plurality of fine fiber parts that run continuously through the axis of the fiber, and although so It has long been known to modify one of the components of multi-component fiber structures by introducing additives, for example antistatic agents, to which electrically conductive carbon black belongs (US Pat. Nos. 2,428,046 and 3,582,448) is the present Invention, as explained in more detail below, is not obvious to a person skilled in the art, since only the specific combination of elements, as explained here, leads to fibers with properties which overcome the disadvantages of the existing embodiment, as described above.

The aim of the invention is to provide an inexpensive, but durable, electrically conductive textile thread which has reproducible, conductive properties over a wide range of conductivities and practically retains the desired physical properties of the unmodified, polymeric substrate, with no problems when blending and processing them with normal, natural or artificial textile fibers.

This aim is achieved according to the invention by a product with the features in the characterizing part of claim 1.

A use of this textile thread is characterized according to the invention in that the textile thread is cut and spun into yarn together with electrically non-conductive staple fibers.

Embodiments of an electrically conductive textile thread according to the invention are explained in more detail below with reference to the drawing.

Show it:

1 and 2 oblique representations of embodiments of a one-piece, electrically conductive thread, and

3 shows a cross section of the thread according to FIG. 1.

The polymer from which a one-piece, electrically conductive textile thread is made can be a known, film-forming or fiber-forming polymer, and can be, for example, an acrylic, acetate, a modacrylic, cellulose, polystyrene, polyolefin, polyester or polyamide. Acrylonitrile polymers have at least about 85% by weight of acrylonitrile and up to about 15% by weight of other polymerizable mono-olefin monomers,

which are copolymerizable with acrylonitrile, and have proven to be particularly advantageous. The textile thread must have at least two layers of fiber-forming polymer aligned in the longitudinal direction, in which carbon black is embedded in a fine distribution and which are therefore electrically conductive. The particle size is advantageously about 20 to 40 m | x.

The number of electrically conductive layers and the proportion of electrically conductive soot in the individual layers was determined empirically. It is desirable that the electrical resistance of the textile thread be no more than about 109 ohms / cm and should be between 104 and 109 ohms / cm. Textile threads of this type are used in a large number of substances in order to prevent static charging, so that no significant electrical discharge occurs.

The thread according to the present invention therefore consists of:

of two components which differ in their physical properties and are based on the same thread-forming polymer, one of which contains carbon black in a finely divided form and is therefore electrically conductive, while the other component which is connected to the electrically conductive in side-by-side arrangement contains no such soot particles and consequently has no conductivity for electricity, furthermore the electrically conductive thread component is divided into 2 to 1000 partial polymer strands extending in the thread longitudinal direction, which appear on the thread surface in the form of longitudinal strips 12, which by their Shaped surface areas 13 are separated from partial polymer strands of the soot-free thread component which has no conductivity for electricity, with the proviso that the polymer partial strand belonging to the polymer of each electrically conductive thread component is fine The distribution of the amount of soot stored is of the order of 30-70% by weight, and the lower value for a textile thread which is either a) a total carbon concentration of 0.25% by weight with two polymer partial strands containing soot or b) a total carbon concentration of approximately 2 wt .-% for 1000 polymer strands, comes into consideration, and the upper value denotes an electrically conductive textile thread, which either c) a total carbon concentration of 0.5 wt .-% with two carbon black polymer strands or d) a total carbon concentration of about Has 17 wt .-% with 1000 polymer strands.

Furthermore, the one-piece, electrically conductive textile thread is particularly useful when four electrically conductive,

Layers of fiber-forming polymer extending in the longitudinal direction are present, each of which has 40 to 60% by weight of electrically conductive soot particles in a uniform fine distribution, the total carbon concentration in the textile thread being between 4 and 6% by weight.

As shown in FIG. 1, there are two electrically conductive thread components 12 that extend in the longitudinal direction, a larger number of electrically conductive thread components 12 having proven to be particularly advantageous. The embodiment shown in FIG. 2 has four electrically conductive thread components 12. The electrically conductive component 12 is connected in the longitudinal direction and in side-by-side arrangement to an electrically non-conductive thread component 13 made of a polymer containing no soot particles to form a one-piece textile thread 11. Since the thread components in these designs cannot be separated or removed individually,

10th

15

20th

25th

30th

35

40

45

50

55

60

65

625 570

4th

the described textile thread 11 clearly differs from a known, composite thread, which consists of individual layers which are connected to one another by adhesive and / or heat or pressure, and are subjected to separation and / or peeling. Furthermore, the electrically conductive thread component 12 of the textile thread described differs from the known embodiment, which has long, thin particles of distributed, conductive, block-like copolymers, which are very difficult to obtain in a reproducible form.

In contrast to the known structures, the electrically conductive component 12 of the textile thread has soot particles in a fine distribution, namely rough, spherical particles made of electrically conductive carbon black, which have an average diameter of approximately 20 to 40 nm. Furthermore, the desired electrical conductivity for many polymeric threads is easily and economically attainable and easy to reproduce.

The thickness of each electrically conductive component 12 is not critical. It varies with the diameter of the textile thread, with the number of components it contains and with the carbon concentration in each layer. It should be noted that the layers are well delineated and connected.

It is pointed out that the drawings are schematic representations and that the individual components shown as layers do not have to be defined correctly or not necessarily.

Each electrically non-conductive component of the textile thread 11 consists of the same polymer as the electrically conductive component 12. An example of a preferred method for producing the textile thread 11 will now be explained in more detail.

A number of special processes can be used to produce an electrically conductive textile thread, the most appropriate of which is a modification of a well-known process for spinning a solution. The improvements include:

1. The formation of a first stream from a solution from the polymer,

2. the formation of a second stream of the same solution, finely divided, electrically conductive carbon black, which does not dissolve or react with the solution, being distributed in the second stream in amounts of 30 to 70% by weight,

3. the formation of a third stream which corresponds to the first stream,

4. the formation of a fourth stream, which corresponds to the second stream, and

5. the merging of the first, the second, the third and the fourth stream into a composite stream without an appreciable mixing of the individual component streams taking place, after which the resulting composite stream is spun into one-piece threads. The polymer is a known, film or fiber-forming polymer. The solution is prepared by dissolving the polymer in a liquid in which the polymer is readily soluble, but which does not react with soot. The individual streams are first degassed and then introduced simultaneously and in parallel into a cylinder body, which ends in a nozzle. If a wet spinning process is chosen, the composite stream is spun or extruded through the die into a coagulation bath containing a liquid that is miscible with the polymer but does not dissolve the polymer itself and causes the polymer to precipitate. The textile thread produced in this way is normally washed in countercurrent with water to remove the spinning solution, then dried and finally wound up. If a dry spinning process is used, the solution contained in the composite stream must be volatile. The composite stream is spun or extruded through a nozzle in air or into an inert gas atmosphere, after which a textile thread is formed by evaporation of the solution from the composite stream. Dry spinning is usually done with a cylinder body in a vertical position. In order to control the temperature, the cylinder body is usually provided with a double jacket and designed in such a way that air, steam or inert gases are passed over the nozzle either with or against the flow, as required. Down spinning is used for low denier textile threads and upward spinning for high denier textile threads to remove the influence of gravity when spinning.

A particular feature and advantage of this method is the simultaneous introduction of the aforementioned first and second streams, to the inlet of a static mixer and then in the resulting multi-component stream through the nozzle into a coagulation bath or into the air or a inert gas atmosphere. The static mixers described in U.S. Patent Nos. 3,440,860 and 3,583,678 can be used with good results.

In a preferred embodiment, particularly good results have been obtained when the thread-forming polymer is a long chain of synthetic polymer consisting of at least 85% by weight acrylonitrile units and the rest of one or more other mono-olefin monomers copolymerizable therewith, such as Vinyl acetate, alkyl esters from acrylic or methacrylic acids, vinyl bromide and monomers with an affinity for acid dyes, especially those which contain tertiary or quaternary nitrogen in the molecule, such as vinyl pyridine or methyl vinyl pyridine, and monomers with an affinity for basic dyes, especially those containing a sulfonic or carboxylic acid group, such as alkyl sulfonic acid, itaconic acid. The electrically conductive material used in the preferred embodiment is an electrically conductive carbon black with a particle size of 20 to 40 m | i. The acrylonitrile polymer is dissolved in an inorganic solvent as described in U.S. Patent Nos. 2,558,730 and 2,916,348, or in an organic solvent as described in the Knudsen article in Textile Research Journal 33,13- 20 (1963). The first and second streams are introduced into the inlet of a static mixer as described in U.S. Patent No. 3,583,678 to form a composite stream of 8 to about 2000 sub-strands. This stream is then spun through a nozzle into a coagulation bath, in which the polymer is deposited, and the textile thread is produced by washing it in countercurrent with water and then stretching, crimping and drying.

The present invention can be better understood if reference is made to the following examples, in which all percentages are given in% by weight, if no information is given.

example 1

This example relates to details of a preferred method of making an electrically conductive textile thread in accordance with the present invention, and illustrates some basic properties of that thread.

An acrylonitrile homopolymer, the preparation of which is described in U.S. Patent No. 2,847,405, was dissolved in a 60% solution of zinc chloride to form a solution of about 11% of the acrylic polymer. A first s

io

15

20th

25th

30th

35

40

45

50

55

60

65

5

625 570

Electricity from this solution was put into a tube. A commercially available, electrically conductive carbon black, which had an average diameter size of 30 μm, was added to part of the solution used to form the first stream, in an amount sufficient to to produce a second solution with 6% acrylonitrile homopolymer and 6% carbon black, which is used as a second stream. Using two measuring pumps, the first and second streams were simultaneously introduced into the inlet of a static mixer in the following ratio: 90% of the first stream and 10% of the second stream. The static mixer depicted and described in U.S. Patent No. 3,583,678 comprises a single interfacial element with four continuous channels so that a total of eight thread components (4 electrically conductive and 4 electrically non-conductive) are produced will. The resulting composite stream was spun through a nozzle into a 42% zinc chloride coagulation bath in water, and the thread was countercurrently rinsed with water, stretched to about 9X the original length, and then air dried. 2 «The thread was finally wound onto a spool and used to produce an antistatic material. The

Textile thread has a denier of 15 and a total carbon concentration of 5%. Using a Keithley 610C electrometer, the electrical resistance of the textile thread was measured to be 107 ohms / cm. This textile thread, hereinafter referred to as thread A, is compared to a 15 denier acrylonitrile homopolymer thread, referred to as thread B, which has an electrical resistance of 1014 ohms / cm (Table I). Such a comparison shows that the desired properties of the polyacrylic thread are retained by the thread A, with a significant conductivity being achieved.

Example 2

A series of tests, which are otherwise identical to the method according to Example 1, were carried out, the number of electrically conductive thread components and the composition of the electrically conductive thread component in the textile thread according to Table I being varied. Threads C and E and others described below were prepared and their physical properties were determined. The results of these determinations are also shown in Table I.

thread

number of

Carbon in

Total coals

resistance

strain

toughness

electrical any electrical material in

Ohm / cm

%

g / den.

conductive conductive

Textile thread

Thread compo

Thread compo

nenten nenten

A (before

lying

Invention)

4th

50%

5%

107

13.8

3.9

B (for

Comparison)

0

0

0

101 *

10.0

4.0

C (before

lying

Invention)

64

60%

10%

10s

14.6

3.3

D (before

lying

Invention)

1000

50%

2%

109

15.1

4.2

E (before

lying

Invention)

1000

50%

5%

10 «

14.1

3.2

With more than about 1000 electrically conductive polymer partial strands, the resistance value of the textile thread exceeded 109 ohm / cm. With the exception of a conductive polymer strand, the thread fibrillated undesirably.

Example 3

This example illustrates the usability and durability of a one-piece, electrically conductive textile thread according to the present invention.

Trial A

Thread A from Example 1 above was cut into staple lengths of approximately 7.5 cm and mixed by normal methods with 16 denier nylon 6 staple fibers having a staple length of 15 cm to form a blend of 2% of thread A to build. This mixture was processed by normal methods using a 2.25 / 2 cotton yarn with 3.5 Z-bonds and 2.5 S-bonds per 2.54 cm. This yarn is called yarn A. With this yarn, a bouclé carpet of 100 gr / m2 was produced on a jute base fabric using a tufting machine, hereinafter referred to as carpet A.

45 Experiment B

Carpet A was tested for static electricity as explained below, the results of which are shown in Table II as the original static charge.

After this test, carpet A was subjected to accelerated wear for 60 hours, after which the static charge was determined again. The results of this test are also shown in Table II under final static electricity.

55 Table II also shows that carpet A was not only protected against static charge when new, i.e. He does not attribute a static charge of more than 3000 V, which is normally regarded as the average threshold for human sensitivity, but the

60 Carpet A was protected against static electricity after extensive wear. Furthermore, the electrically conductive threads A were examined with a microscope, with virtually no wear being found.

65 Static test

The material to be tested was first cut into 90 X 90 cm squares. These test pieces were conditioned for 7 days by placing them on racks in one

625 570

6

Test room was hung, which is covered with rubber flooring and has an area of at least 9.3 m2, the temperature being kept at 21.1 ° ± 1 ° C and the relative humidity at 20% ± 1%. All test pieces were exposed to a free flow of air without the different test pieces touching each other. Two shoes with neolith or PVC soles were conditioned under the same conditions.

The remaining static buildup of the floor covering was then dissipated by bringing the entire surface 2X into contact with a device consisting of 6 polonium 210 alloy tires attached to a handle at one end. A test piece was then placed on the floor and the remaining static electricity was discharged in the same way. The PVC soles of the shoes were then cleaned by cleaning their entire area with emery paper, followed by rubbing with a gauze to remove the dust particles.

The static charge was measured by walking on the carpet sample with the shoes with PVC soles at a rate of 2 steps per second for 30 seconds and using a grounded measuring device, taking care that no friction occurred between the PVC soles and the carpet sample. The average of the highest voltage measured from two tests is given in Table V below.

Table II

S Original static electricity in volts

Final static

Electricity in volts

Carpet sample of Neolith soles PVC soles

Neolith soles PVC soles

A (before

lying

io invention) 1400 1200

1500 1600

Pile fabrics, e.g. carpet A, the manufacture of which has been described above, when used in a relative humidity of at least 20%, will have no static charge above about 3000 volts. Under the same conditions, a conventional nylon 6 carpet can have up to 14,000 volts.

Due to the unique combination of the properties of the one-piece, electrically conductive thread according to the present invention, this thread can be used not only for carpets and other floor coverings, but also for bed covers and curtains, in particular in hospitals, and also for clothing, in particular uniforms and Underwear can be used. The thread is also suitable as a sewing thread 2s.

B

1 sheet of drawings

Claims (4)

625 570 1. One-piece, electrically conductive textile thread with a resistance of not more than 109 ohm / cm, characterized in that it consists of two components with different physical properties, which are based on the same thread-forming polymer, one of which contains carbon black in a fine distribution contains and is therefore electrically conductive, while the other component connected to the electrically conductive side-by-side arrangement contains no such soot particles and consequently has no conductivity for electricity, furthermore the electrically conductive thread component in 2 to 1000 extends in the longitudinal direction of the thread extending polymer partial strands is divided, which appear on the thread surface in the form of longitudinal strips (12), which of their own get by also longitudinal strip-shaped surface areas (13) of polymer partial strands of the soot-free, no conductivity for electricity thread component runs, with the proviso that the amount of carbon black embedded in the polymer of each polymer sub-strand belonging to the electrically conductive thread component in fine distribution has an order of magnitude of 30-70% by weight, the lower value for a textile thread which is either a) a Total carbon concentration of 0.25 wt .-% with two carbon black polymer strands or b) has a total carbon concentration of about 2 wt .-% for 1000 polymer strands, and the upper value indicates an electrically conductive textile thread that either c) one Total carbon concentration of 0.5% by weight for two soot-containing polymer partial strands or d) has a total carbon concentration of approximately 17% by weight for 1000 polymer partial strands. 2. Textile thread according to claim 1, characterized in that the polymer consists of at least 85% by weight of acrylonitrile and up to 15% by weight of other mono-olefinic monomers copolymerizable with the acrylonitrile. 2nd PATENT CLAIMS 3. Textile thread according to claim 2, characterized in that 4 electrically conductive, in the longitudinal direction oriented layers of thread-forming polymer are present, each containing 40-60 wt .-% electrically conductive soot particles in a uniform fine distribution, the total carbon concentration in the textile thread from 4 to Is 6% by weight. 4. Use of the textile thread according to claim 1, for producing a staple fiber yarn, characterized in that the textile thread is cut into staple fibers and the staple fibers thus obtained are spun together with electrically non-conductive staple fibers to the staple fiber yarn.