CN119816632A

CN119816632A - Method for producing linear nanofibrous structures from polymer solutions or polymer melts in an alternating current (AC) electric field and apparatus for carrying out the method

Info

Publication number: CN119816632A
Application number: CN202380063107.8A
Authority: CN
Inventors: J·贝兰; J·瓦特拉; J·斯克里瓦内克; O·巴特卡; M·比莱克; O·弗里德里希; D·卢卡斯; E·库泽洛娃科斯塔科娃; V·詹科娃; V·海德维卡科娃; M·利斯年科; K·斯特纳多娃
Original assignee: Technicka Univerzita v Liberci
Current assignee: Technicka Univerzita v Liberci
Priority date: 2022-09-02
Filing date: 2023-08-24
Publication date: 2025-04-11
Also published as: WO2024046515A2; WO2024046515A3; JP2025530575A; EP4581199A2; CZ2022370A3

Abstract

The present invention relates to a method for producing a linear nanofiber structure from a polymer solution or a polymer melt in an AC electric field, wherein nanofibers (5) are formed from a polymer solution (21) or a polymer melt in a spinning area (110, 120, 130) formed on spinning electrodes (1, 11, 12, 13) and are transported away from the spinning area in the direction of the gradient of the generated electric field by the action of an electric wind. The polymer solution (21) or polymer melt is conveyed to the spinning area (110, 120, 130) by moving spinning electrodes (1, 11, 12, 13) and subjected to an electric field of supercritical strength (E) to form nanofibers (5), which move away from the spinning area (110, 120, 130) and are deposited on the collecting area (40, 410, 420) of the moving electrically neutral collector (4, 41, 42), on which they form a fluffy band (51) of nanofibers, which moves to the drawing area (401, 4101, 4201) by the movement of the electrically neutral collector (4, 41, 42), in which the surface of the electrically neutral collector (4, 41, 42) is drawn out by the pulling force of a winding device (7) or a take-off device, and then wound. The twisting of the fluffy band of nanofibers (51) into a nanofiber yarn (54) after it has been drawn from the electrically neutral collector (4, 41, 42) can be performed before and after winding. Furthermore, the invention relates to a device for carrying out the method.

Description

Method for producing linear nanofibrous structures from a polymer solution or polymer melt in an Alternating Current (AC) electric field and device for carrying out the method

Technical Field

The invention relates to a method for producing linear nanofibrous structures from a polymer solution or melt in an AC electric field, wherein a spinning zone with supercritical AC electric field strength is formed on a spinning electrode. In the spinning zone, nanofibers are formed which are transported away from the spinning electrode by the action of the electric wind in the direction of the maximum value of the gradient of the generated electric field.

The invention also relates to an apparatus for producing linear nanofibrous structures from a polymer solution or melt in an AC electric field, wherein a spinning zone having a supercritical value of the AC electric field strength is generated on a spinning electrode which is mounted in a spinning chamber and connected to a high alternating voltage source and which is coupled to means for applying the polymer solution or melt to the surface of the spinning electrode.

Background

In the preparation of nanofiber yarns, oriented nanofibers are the basis for the construction of nanofiber yarns. Currently, in the field of DC electrospinning, a number of methods have been developed to obtain longitudinally oriented fiber bundles, which can be attributed to two main aspects, namely obtaining highly ordered nanofibers by improving the collecting device or by influencing the electric field by means of auxiliary electrodes.

CN111118677 discloses the production of nanofiber yarns by DC electrospinning. The apparatus comprises a cylindrical collector consisting of a chamber and a throat rotatable about its axis, wherein the diameter of the upper opening of the throat is smaller than the diameter of the lower opening of the chamber. Inside the lower opening of the cavity a DC electrostatic spinning electrode is mounted, which spinning electrode is connected to a high voltage DC source into which the solution to be electrospun is fed. In the upper part of the collector chamber, the pressurized air inlet opens into the interior space of the collector and above it a counter electrode is arranged, which may be grounded or connected to a voltage source of opposite polarity to the spinning electrode that rotates.

The nanofibers formed on the spinning electrode are transported to the counter electrode by the action of the electrostatic field and by the action of the air flow they are transported upwards into the throat of the rotating cylindrical collector and, due to its rotation and the supplied air flow, a vortex is generated which twists the nanofibers into a yarn which is then drawn out and wound onto a bobbin.

Due to the rotation of the spinning electrode and the subsequent swirling action, the nanofibers are twisted immediately after their formation, so that there is no parallelization of the nanofibers before twisting, twisting occurs unevenly, and thus their strength and appearance are variable.

CN111286792 describes a horizontal arrangement of a DC electrospinning apparatus comprising a rotating spray spinning electrode and a collecting electrode formed by a hollow cylinder arranged coaxially with respect to the spray spinning electrode, wherein a DC electric field is formed between the spinning electrode and the collecting electrode. At least two air jets directed toward the axis of the collecting electrode are arranged around the rotating jet spinning electrode. The nanofibers formed by the rotating jet spinning electrode are transported due to the electric wind to the hollow cylinder forming the collecting electrode, wherein due to the rotation of the jet spinning electrode and the air flow from the jet, the nanofibers are twisted into a yarn which is drawn out after passing through the cavity of the collecting electrode and wound on a bobbin.

In this solution, too, the aim is to twist the nanofibers as soon as possible after their formation, without achieving their parallelization.

In both cases, the disadvantages of DC electrostatic production of nanofiber yarns include low yarn cohesion, irregular twist of the nanofibers, and poor orientation.

At present, a method for continuously producing nanofibre yarns is also known, for example from CN110644080, wherein nanofibres are formed from a polymer solution in a jet head, from which they are drawn by the action of a high-speed air flow generated in a venturi tube, and through a funnel-shaped collecting tube into a venturi collecting system, where they are straightened and oriented into oriented nanofibre bundles by sucking the nanofibre bundles by means of venturi effect. The oriented nanofiber bundles are then twisted and gathered into nanofiber yarn by the action of a twisting device, which yarn is wound on a bobbin in the next step. The twisting device comprises an air nozzle for supplying an air flow in tangential direction towards the yarn to be twisted.

From the point of view of subsequent processing and use of the nanofiber yarn, it is not enough to obtain only oriented fibers in order to meet the current demands for its preparation, but it is also necessary to be able to continuously obtain oriented fibers or fiber bundles and to be able to uniformly apply a certain degree of twist thereto to ensure the length and the degree of orientation thereof. In order to optimize the strength of the nanofiber yarn, it is advantageous if the nanofibers in the nanofiber bundles have been oriented longitudinally due to the method of their formation, i.e. they are oriented in line with the axis of the bundles. Existing DC electrospinning techniques for continuous production of nanofiber yarns have low yields and poor quality of the produced nanofiber yarns. Thus, core yarns are currently produced by DC electrospinning.

For example, CZ PV 2007-179 discloses a linear fibrous structure comprising polymeric nanofibers that form a coating on the surface of a core formed by a supporting linear fibrous structure, at least some of the nanofibers being trapped between the fibers of the surface portion of the core. Nanofibers are produced by DC electrospinning (i.e., using a high voltage DC source), wherein a supporting linear structure is guided through a spinning space between a spinning electrode and a collecting electrode, and outside the spinning space, the nanofibers are false twisted. Thus, the supporting linear structure in the spinning space rotates about its axis and individual nanofibers transported through the spinning space to the collection electrode are deposited on its surface. Not all nanofibers are captured on the support linear structure, but some of the nanofibers fly through and are captured only on the collection electrode. This problem is not eliminated even by embodiments in which the collecting electrode is formed of a conductive supporting linear structure. Also in this embodiment, most of the nanofibers fly through the linear support structure and are trapped on the walls of the spinning space.

Although the nanofibers are trapped between the fibers of the surface portion of the core, during their unwinding, the nanofiber coating is pulled away from the core due to forces between the surfaces of adjacent fibers in the package (these forces being greater than the cohesion force between the coating of nanofibers and the core).

The above-mentioned problems are partially solved by CZ PV 2009-797, wherein the nanofibers are secured to the core with at least one cover wire. For most possible applications, the wrapping by the cover wire ensures that the nanofibers are sufficiently strong and durable fixed to the core, and at the same time, the cover wire allows to make full use of the specific properties of the nanofibers, as it does not hinder access to the nanofibers.

The actual fiber structure is produced by passing the supporting linear structure several times through the spinning space, wherein the supporting linear structure outside the spinning space is returned through a part of the circumference of at least one cylinder, which is obliquely approaching onto the cylinder, so that after the return the supporting linear structure faces the spinning electrode with its opposite sides. In this embodiment, there is no false twist and, therefore, the supporting linear structure does not rotate about its axis when passing through the spinning space and, therefore, the nanofibers are deposited on the side of the supporting linear structure facing the spinning electrode during each pass. Since the supporting linear structure passes through the spinning space multiple times, a larger amount of nanofibers are deposited on the structure than in previous solutions, however some of the nanofibers fly through until reaching the collecting electrode. The nanofibers are deposited as individual nanofibers in a layer in a disordered manner on the surface of the supporting linear structure and their cohesion to the core surface is low. The fixation of the nanofibers to the surface of the supporting linear structure is achieved by subsequent wrapping with at least one cover wire.

EP 2931951B 1 discloses a method for producing polymer nanofibers, wherein the polymer nanofibers are formed by applying an electric field to a polymer solution or melt placed on the surface of a spinning electrode, wherein the electric field for spinning is alternately formed between the spinning electrode to which an AC voltage is applied and air and/or gas ions generated and/or supplied in the vicinity of the spinning electrode without collecting electrodes, whereby, depending on the phase of the AC voltage on the spinning electrode, polymer nanofibers with opposite charges and/or with segments with opposite charges are formed, which after formation aggregate to a linear structure in the form of a cable or ribbon due to the effect of electrostatic forces, which cable or ribbon is free to move away from the spinning electrode in the direction of the gradient of the electric field in space.

Spinning by AC high voltage method is another way to produce nanofibers instead of electrospinning. However, the yield has not reached the level of pure nanofiber yarn produced by this method. Thus, EP3303666 proposes a method for producing a core yarn with a coating of polymer nanofibers that surrounds a supporting linear structure forming the core during its passage through the spinning chamber. In this method, a spinning electrode connected to an inlet of a polymer solution and supplied with an AC high voltage is arranged below a supporting linear structure on the face of which nanofibers are formed in a spinning space immediately adjacent to and above the face of the spinning electrode, wherein the supporting linear structure rotates around its own axis in the spinning space. Nanofibers are formed around the circumference of the face of the spinning electrode and in the spinning space. They are formed as hollow electrically neutral nanofibres hairiness, wherein the nanofibres are arranged in an irregular grid structure in which the nanofibres in the short sections change their direction, wherein the hollow electrically neutral nanofibres hairiness is transported by the electric wind towards the supporting linear structure and becomes flat strips, which strips are brought to the circumference of the supporting linear structure, wherein the strips produced by the hollow electrically neutral nanofibres hairiness are wrapped in a spiral shape around the supporting linear structure rotating and/or forming a balloon (ballooning) on which a coating of nanofibres is produced, wherein the nanofibres are arranged in an irregular grid structure in which the individual nanofibres in the short sections change their direction.

Nanofiber hairiness represents an ideal material for the coating of core yarns, because due to its electrical neutrality and irregular lattice structure in which individual nanofibers in the short sections change their direction, the nanofiber hairiness is able to form a solid coating surrounding the yarn core, whereby the coating is inert to its surroundings when wound on a bobbin and during subsequent unwinding during processing. However, if pure nanofiber yarns are to be produced from nanofiber hairiness, there will be a problem that the number of nanofibers is insufficient and the lattice structure of the hairiness, which structure does not allow parallelization of the nanofibers.

Currently, there is no satisfactory method to produce nanofiber yarns with potential for industrial application. Current methods of making nanofiber yarns are hampered by low productivity, low reliability, and limited material selection. Their production was only achieved on a laboratory scale as part of the research effort.

See, e.g., zhou B. Et al ,Developments in Electrospinning of Nanofibrous yarns,Journal of Physics:Conference Series 1790(2021)012081doi:10.1088/1742-6596/1790/1/012081).

It is an object of the present invention to provide a method for producing nanofiber yarns by AC electrospinning of a polymer solution or melt, wherein the nanofibers will be produced in sufficient quantity, partially parallelized prior to twisting, and after twisting will be sufficiently strong to allow winding on bobbins and subsequent processing into textile structures using or by known textile techniques.

Furthermore, it is an object of the invention to provide an apparatus for performing the method.

Disclosure of Invention

The object of the invention is achieved by a method for producing a linear nanofibrous structure in an alternating electric field by spinning a polymer solution or melt, wherein the principle of the invention consists in that at least one spinning zone is produced on a spinning electrode having a supercritical AC electric field strength and a finite length, from which spinning zone the emerging nanofibres are transported away from the spinning zone towards a moving charge neutral collector by the action of electric wind in the direction of the maximum of the electric field gradient, on the circumferential surface of the charge neutral collector situated opposite the spinning zone and forming the collecting zone of the moving charge neutral collector, the nanofibres are deposited in the form of a bulk ribbon of nanofibres which is moved with the movement of the charge neutral collector into a pull-out zone, in which the bulk ribbon of nanofibres is pulled from the surface of the charge neutral collector with a ribbon tension and is subsequently wound onto a bobbin of a winding device, the nanofibres being at least partially parallelized by a tension.

In a preferred embodiment, the fluffed strips of nanofibers are rounded during transfer to the pull-out area on the surface of the electroneutral collector, tapering them so that they can be wound directly, or more easily formed into twisted triangular areas during tapering, without risk of damaging the edges of the fluffed strips of nanofibers when twist is applied.

The pulling force of the bulk ribbon for pulling out the nanofibers is generated by a winding device or a pulling device arranged between the pulling area and the winding device. This separates the process tension from the winding force so that an appropriate tension can be selected for winding for the construction of the bobbin.

Prior to winding or drawing, the fluffed tape of nanofibers is acted upon by a twisting device that tapers the fluffed tape of nanofibers into a twisted triangle and then applies a twist thereto, thereby forming a nanofiber yarn.

A significant feature of the method is that a twist is applied to the bulk ribbon of nanofibers between two nip points (i.e. between the pull-out area of the charge neutral collector and the point of winding or pulling-out of the nanofiber yarn on the bobbin), wherein the residual amount of twist applied to the bulk ribbon of nanofibers by the twisting device remains in the nanofiber yarn that is wound after leaving the twisting device.

An important feature of the method according to the invention is also that the spinning field of the spinning electrode is formed on the circumference of the disk-type spinning electrode, or at the bending point of the belt-type spinning electrode, where the spinning field is arranged transversely to the direction of movement of the spinning belt, or on the linear flexible structure of the linear spinning electrode.

In order to perform the method, an apparatus for producing a nanofiber yarn by AC electrospinning of a polymer solution or melt is provided, the principle of which is that an electrically neutral collector coupled to a drive is arranged above the spinning electrode in the path of the nanofibers, wherein the area of the electrically neutral collector facing the spinning electrode forms a collecting area of the nanofibers for continuous deposition of the nanofibers in the form of a bulk ribbon of nanofibers, wherein a pull-out area of the bulk ribbon of nanofibers is formed on the surface of the electrically neutral collector in the direction of movement of the collector downstream of the collecting area, downstream of which a winding apparatus is arranged in the pull-out direction of the bulk ribbon of nanofibers. The winding device is used to generate a pulling force to pull the bulk ribbon of nanofibers from the surface of the electrically neutral collector.

The pulling force may also be generated by a take-off device located between the pull-out area and the winding device. In this way, it is possible to separate the process tension (i.e. the tension associated with balloon formation and pull-out strength of the yarn) from the winding tension (i.e. the winding tension). An appropriate winding tension can then be selected for the construction of the bobbin.

In a preferred embodiment, upstream of the winding device or the drawing device, a twisting device is arranged in the direction of the pull-out of the bulk ribbon of nanofibers, so that the nanofiber yarn is fed into the winding device.

The spinning electrode may be formed from a disk spinning electrode, a ribbon spinning electrode, or a linear spinning electrode, or from another type of spinning electrode.

The charge neutral collector may consist of a charge neutral roller collector or a charge neutral belt collector.

If the charge neutral collector is formed by a charge neutral drum collector, in a preferred embodiment a collecting area for the nanofibers is formed on the charge neutral drum collector against the spinning electrode and a pulling area of the drum collector is formed in the area of the surface of the drum collector facing away from the spinning electrode for pulling out the bulking strips of nanofibers.

In this embodiment it is advantageous if a rounding device is assigned to the fluffy strip of nanofibres between the collecting zone and the pulling-out zone of the electrically neutral drum collector. The rounding means reduces the width/thickness of the bulk ribbon of nanofibers and thus simplifies its twisting and/or winding.

If the electrically neutral collector is formed from a belt collector, the collector is an endless conveyor belt that encircles two upper cylinders and two lower cylinders, at least one of which is a drive cylinder. The lower branch of the endless conveyor forms a collecting area for the nanofibers deposited on the collecting area as fluffy strips of nanofibers.

In a preferred embodiment, the bulk ribbon of nanofibers is fed through the movement of the endless conveyor into an upper branch of the endless conveyor, which upper branch forms a pull-out area for pulling out the bulk ribbon of nanofibers from the electrically neutral belt collector at the end of the endless conveyor in the direction of movement. This embodiment allows to distribute a rounding device to the fluffed bands of nanofibres on the upper branch of the endless conveyor, which tapers the fluffed bands of nanofibres and improves their properties for pulling out and subsequent twisting.

In another preferred embodiment, a pull-out zone is formed at the end of its lower branch in the direction of movement of the endless conveyor for pulling out the fluffy strip of nanofibres from an electrically neutral belt collector connected to a collecting zone formed by the lower branch of the endless conveyor, on which collecting zone the nanofibres are deposited in the form of a fluffy strip.

Drawings

In the drawings the device according to the invention is schematically represented, wherein fig. 1 shows a side view of the device with a rotating disc spinning electrode and an electrically neutral drum collector, fig. 2 shows the device of fig. 1 in a front view, fig. 3 shows the device of fig. 1 in a top view, fig. 4 shows the distribution of the electric field strength over the circumference of the disc electrode, fig. 5 shows a side view of the device with a rotating disc spinning electrode and an electrically neutral belt collector, fig. 6 shows the device of fig. 5 in a front view, fig. 7 shows the device of fig. 5 in a top view, fig. 8a shows the device with a belt spinning electrode and an electrically neutral belt collector in a side view, fig. 8b shows the device of fig. 8a in a front view, fig. 8c shows the device with a belt spinning electrode and an electrically neutral belt collector in a side view, fig. 9a shows the device of fig. 9a in a front view, fig. 9a shows the device of a belt spinning electrode and a neutral belt collector in a front view, fig. 9c shows the device of a front view of a belt spinning electrode and a neutral belt collector in a front view, fig. 9a front view of a belt collector in a front view of a belt collector.

Detailed Description

An apparatus for producing nanofibres through AC electrostatic spinning of polymer solution or polymer melt comprises a spinning electrode 1, in the embodiment of fig. 1 to 7 the spinning electrode 1 consists of a rotating disc spinning electrode 11, the rotating disc spinning electrode 11 being mounted with its lower part of the circumference in a reservoir 2 of polymer solution 21 or melt and being coupled to a known not illustrated drive. Since spinning of the polymer melt is performed in the same manner as spinning of the polymer solution 21, only spinning of the polymer solution will be described hereinafter. The polymer solution typically consists of PVB, PCL, PVA solutions or other spinnable polymer solutions. The spinning electrode 1 and the reservoir 2 of polymer solution are mounted in a spinning chamber 3.

The spinning electrode 1 is connected to a high voltage AC source, not shown, having an effective voltage of 32kV and a frequency of 50Hz, for example. Connected to the AC voltage source can also be a polymer solution to be spun, through which the spinning electrode 1 and the AC voltage source are interconnected. According to the first exemplary embodiment, the spinning electrode 1 is formed by a rotating disc type spinning electrode 11 having a horizontal rotation axis. The rotating disk spinning electrode 11 is mounted with its lower part of the circumference in the polymer solution 21 in the reservoir 2. The rotary disk spinning electrode 11 is coupled to a known, not-shown rotary drive such that it carries the polymer solution 21 to a circumferential portion of its surface during rotation thereof. The amount of polymer solution 21 is typically regulated by known, not shown wiping devices. In the spin chamber 3, there is a spinning space 31 near and above the upper part of the circumference of the disk spinning electrode 11. Above the spinning electrode 1 in the spinning chamber 3, an electrically neutral collector 4 coupled to a known drive, not shown, is rotatably mounted. The upper part of the disc spinning electrode 11 forms a spinning zone 110 in which the nanofibres 5 are formed, the nanofibres 5 being transported to the surface of the charge neutral collector 4 covered with a suitable coating, for example through the spinning space 31 by means of a flat textile made of a material allowing easy drawing out of nanofibres from the surface of the charge neutral collector 4.

In the embodiment of fig. 1 to 3, the collector 4 is formed by an electrically neutral roller collector 41. The axis of the electroneutral cylinder collector 41 is parallel to the axis of the disk spinning electrode 11. The surface of the electrically neutral drum collector 41 forms a collection area 410 of nanofibers opposite the area of the disk spinning electrode 11, and the nanofibers 5 are deposited on the collection area 410 in the form of a fluffy band 51 of nanofibers. The area of the surface of the electrically neutral drum collector 41 facing away from the disk spinning electrode 11 forms the pull-out area 4101 of the fluffy strip 51 of nanofibers.

Outside the spinning space 31, in the tangential direction of the circumference of the electrically neutral drum collector 41 and in the flow direction of the drawn-out nanofibres 5, a twisting device 6 is arranged, which twisting device 6 consists for example of a rotation guiding eyelet outside the axis of rotation of the twisting device 6 or of another known twisting device. The winding device 7 with the bobbin 71 is arranged downstream of the twisting device 6 in the flow direction of the drawn-out nanofibres 5 and in the drawing-out direction of the yarn 54. In an exemplary embodiment, not shown, an extraction device for generating a pulling force for extracting the fluffy tape 51 of nanofibers from the surface of the electrically neutral collector is arranged between the pulling zone 4101 and the winding device 7.

The effective value of the voltage (e.g., 32 kV), the waveform of the voltage function (e.g., sinusoidal, sawtooth, step), and the frequency (e.g., 50 Hz) are not limiting, and other suitable values may be used over a very wide range.

During rotation, the disk spinning electrode 11 carries the polymer solution 21 out of the reservoir 2 over its circumference and portions of its face near its circumference. During spinning in an AC electric field, the aim is to produce the largest possible amount of nanofibres 5 per unit time, which nanofibres 5 are formed in the whole spinning area 110 of the disc spinning electrode 11 and transported in the direction of the gradient of the generated electric field by means of electric wind (optionally also by means of an auxiliary air flow) from the disc spinning electrode 11 to the electrically neutral drum collector 41, which is neither grounded nor connected to the source of voltage. The formation of nanofibres 5 starts at a critical value of the electric field strength E, which varies according to the type of polymer solution 21 to be spun, the value of the voltage, the waveform, the frequency of the AC voltage, the quality of the gas in the spinning chamber 3 and other parameters. At values of the electric field strength E below the critical value, the nanofibers 5 do not form or cease to form.

The critical value of the electric field strength E for AC electrospinning purposes means the minimum value of the electric field strength E that will provide a sufficient amount of nanofibers for further processing for a given shape of the spinning electrode, type of polymer solution, and value and waveform of the frequency.

Thus, during conventional spinning in a specifically designed AC electric field using the spinning electrode 1, an electric field strength E higher than the critical strength (i.e. supercritical electric field strength) is used for the selected frequency of the electric field and its waveform, which creates an electric field of high strength E on the spinning electrode 1 in order to prevent the risk of interruption of the spinning process, to ensure sufficient evaporation of solvent from the emerging taylor cone of the polymer solution, and to provide a sufficiently strong electric wind to transport the formed nanofibers 5 to the electrically neutral collector 4.

The distribution of the electric field strength E of the conventional spinning of the above-mentioned polymer solution 21 on the disk spinning electrode 11 is shown in FIG. 4 for a disk diameter of 300mm, a disk thickness of 1mm, a polymer solution layer thickness of 0.2mm and a voltage amplitude of 50 kV. The PVB polymer solution has an electric field strength E with a supercritical value equal to or greater than 3000MV/m. As is apparent from the figure, the supercritical value of the electric field strength E is obtained in a wide area around the circumferential portion of the disk spinning electrode 11. Thus, spinning of the polymer solution 21 takes place over the entire width of the circumferential surface of the disk spinning electrode 11 and over a part of the face in the vicinity of its circumference, and the formed nanofibers 5 are carried away from the disk spinning electrode 11 in the direction of the gradient of the generated electric field, through the spinning space 31 to the surface of the electrically neutral drum collector 41, to its collecting area 410, and, if necessary, to assist the effect of the electric wind by flowing air in the desired direction. Given the size of the region of supercritical electric field strength E, it is apparent that a sufficient amount of nanofibers 5 will be produced for their further processing.

The nanofibres 5 are deposited as narrow fluffy strips 51 of nanofibres on the circumferential collecting area 410 of the electrically neutral drum collector 41 and by rotating the drum collector 41 the fluffy strips 51 of nanofibres are transported to the upper part of the electrically neutral drum collector 4, i.e. to the pull-out area 4101, where the fluffy strips 51 of nanofibres are pulled out. The fluffy strips 51 of nanofibers produced by AC electrospinning consist of three-dimensional layers of nanofibers 5 deposited on the surface of the electrically neutral drum collector 41 due to the action of electric wind and attractive forces between oppositely polarized portions of the nanofibers 5 and partially parallelized during deposition, wherein the fluffy strips 51 of nanofibers represent a linear nanofiber structure. The fluffy strip 51 of nanofibers can be pulled in a three-dimensional shape from the surface of the pull-out area 4101 of the electrically neutral drum collector 41 and by subsequently drawing it out and twisting it, a twisting triangle 52 and nanofiber yarn 54 can be formed from it in a similar manner as when processing fiber strands with permanent twist on the yarn.

If nanofibers were produced by DC electrospinning on a similar device, the drum collector would serve as a collecting electrode connected to a DC voltage of opposite polarity to the spinning electrode, and the nanofibers would be deposited thereon in a flat, very thin ribbon that would appear as a solid flat structure after being pulled from the drum and then subjected to twisting and would twist into a helix formed by the ribbon.

The peripheral speed of the electrically neutral drum collector 41 is adjusted such that the fluffy strip 51 of nanofibres produced on the drum collector 41 has sufficient mechanical resistance when it is pulled out from the surface of the electrically neutral drum collector 41 in the pull-out area 4101 and is used for the subsequent application of twist or for the direct winding on the bobbin 71 of the winding device 7.

The fluffy strip 51 of nanofibres is pulled out of the rotating electrically neutral drum collector 41 and led to the twisting device 6, wherein after pulling it tapers into a twisting triangle 52, from which twisting triangle 52 the fluffy strip 51 of nanofibres tapers and is twisted simultaneously into a nanofibrous yarn 54 under the action of the twisting device 6 and the moment transferred from the twisting device 6 by the partly twisted nanofibres 5. Since the nanofibers 5 of the fluffy strips 51 of nanofibers are deposited with a certain degree of adhesion on the surface of the electrically neutral drum collector 41, when the nanofibers 5 are released from the surface of the electrically neutral drum collector 41 in the pull-out area 4101, a pulling force is generated in the nanofibers 5, which pulling force is necessary to parallelize the nanofibers 5 before twisting, so that the formation of twist and thus of nanofiber yarns 54 occurs after the nanofibers are partially parallelized. Furthermore, the pulling out of the fluffed strips 51 of nanofibres from the surface of the electrically neutral drum collector 41 occurs due to the drafting between the two clamping points, i.e. between the surface of the drum collector 41 and the winding point on the bobbin 71, the nanofibres 5 are elongated and partly parallelized in their flow direction, which facilitates the nanofibres 5 to arrange into a spiral when they are subsequently twisted and thus ensures a sufficient strength of the produced nanofibre yarn 54.

During twisting, the nanofibers are no longer parallelized, but are twisted into spirals. If the drawing is performed at a speed greater than the speed of the collector, at the moment of drawing the nanofibers will straighten and stretch/elongate, but then immediately begin to twist into a helix in the twisting triangle.

After drawing the nanofibers 5 out of the drawing area 4101 of the electrically neutral drum collector 41, the bulk ribbons 51 of drawn nanofibers are formed into twisted triangle 52 by the twisting device 6 and from the twisted triangle 52 into nanofiber yarns 54, wherein the nanofiber yarns 54 form a balloon before entering the twisting device 6. The twist propagates from the twisting device 6 against the process direction of the flow of the nanofibers 5 towards the electrically neutral drum collector 41, thereby helping to pull the fluffy strips 51 of nanofibers from the pull-out area 4101 of the drum collector 41.

The twisting device 6 applies a twist to the nanofiber yarn 54 between the two gripping points, i.e. between the pull-out area and the point of winding or pulling-out, so that in case of yarn from conventional fibers false twisting will occur, in case of yarn from conventional fibers the false twisting will be eliminated after passing through the twisting device. This is not applicable to the twisting of the nanofiber yarn 54, because due to the high surface area of the nanofibers 5, the binding force between the individual nanofibers 5 and the low twist multiplier, a relatively high twist is retained as a residual amount of twist on the nanofiber yarn 54 downstream of the twisting device 6. According to experiments performed on nanofibers made of different types of polymers, it is 10% to 60% of twist, so it is a permanent twist. In a particular test, the residual twist was about 1,400 twists per meter of yarn length at a twisting device speed of about 10,000 rpm. Subsequently, in the winding device 7, the nanofiber yarn 54 is wound onto the bobbin 71 in a known manner.

In order to increase the strength and uniformity of the produced nanofiber yarn 54, it is advantageous to round the fluffed strips 51 of nanofibers on the surface of the drum collector 41 before pulling the fluffed strips 51 of nanofibers from the electrically neutral drum collector 41, thereby achieving a narrowing of the fluffed strips 51 of nanofibers, a more uniform effect of the forces holding the nanofibers 5 on the surface of the electrically neutral drum collector 41 and easier pulling of the nanofibers 5 in the pulling area 4101 of the electrically neutral drum collector 41 in the whole cross section of the fluffed strips 51 of nanofibers, and a smooth transition of them to the twisting triangle 52. At the same time, rounding reduces the bottom of the twisting triangle 52, thereby reducing the pulling force in the circumferential portion of the fluffy strip 51 of nanofibers and thus reducing the risk of breakage of the fluffy strip 51 of nanofibers during pulling out from the pull-out area 4101 of the electrically neutral drum collector 41. The linear structure formed by the rounding of the fluffy strips 51 of nanofibres can also be used for winding directly onto the bobbins 71 of the winding device 7 without twisting on the twisting device 6.

Further increases in the strength of the produced nanofiber yarn 54 may be achieved, for example, by twisting the nanofiber yarn 54 with a permanent twist on a suitable device (not shown).

The amount of nanofibers 5 formed, the peripheral speed of the electrically neutral drum collector 41 and the exit speed of the fluffy tape 51 of nanofibers determine the line quality of the nanofiber yarn 54, which is critical to the resulting strength of the nanofiber yarn 54.

A further alternative variant of the embodiment of the apparatus according to the invention is shown in fig. 5 to 7, in which the electroneutral collector 4 is formed by a belt collector 42 arranged in the spinning chamber 3 above the rotating disc spinning electrode 11. The belt collector 42 comprises an endless conveyor 421 surrounding two upper cylinders 422 and two lower cylinders 423, wherein at least one cylinder 422, 423 is a drive cylinder. The rotational axis of all cylinders 422, 423 of the belt collector 42 is parallel to the rotational axis of the disk spinning electrode 11. In the embodiment according to fig. 5 to 7, the endless conveyor 421 moves counter-clockwise, wherein its lower branches 4211 between the lower cylinders 423 are arranged against the spinning zone 110 of the rotating disc spinning electrode 11, and the nanofibres 5 formed in the spinning zone 110 of the rotating disc spinning electrode 11 are deposited as fluffy strips 51 of nanofibres on the lower branches of the endless conveyor 421. The lower branch 4211 of the endless conveyor 421 thus forms the collecting region 420 of the electrically neutral belt collector 42. Due to the direction of movement of the endless conveyor 421, in this embodiment the fluffy strips 51 of nanofibres are fed to the upper branches 4212 of the endless conveyor 421, the ends of which upper branches 4212 form the pull-out areas 4201 of the electrically neutral belt collector 42, from which areas the fluffy strips 51 of nanofibres are pulled out and guided to the twisting device 6, by means of which twisting is applied to the fluffy strips. After pulling out, the fluffy tape 51 of nanofibers tapers into a twisted triangle 52 due to the effect of the twist and is then formed into nanofiber yarn 54 as described in the previous variant of the apparatus with electrically neutral drum collector 41. This arrangement allows a greater number of nanofibers 5 to be deposited on the electrically neutral belt collector 42, forming a fluffy belt 51 of nanofibers having a greater thickness and weight. Furthermore, this arrangement provides sufficient space on the upper branch 4212 of the endless conveyor 421 for rounding the fluffed strips 51 of nanofibres by means of known, not illustrated rounding means. If the endless conveyor 421 moves in the opposite direction, the pull-out area 4201 will again be formed at the end of the upper branch 4212 of the endless conveyor 421, but according to the drawing, it will be on the right-hand side.

In an alternative embodiment of this arrangement, not shown, it is possible to change the position of the pull-out region 4201 of the fluffy strip 51 of nanofibers by changing the direction of rotation of the drive cylinders of the cylinders 422, 423 around which the endless conveyor 421 is wrapped, and to place the pull-out region 4201 of the fluffy strip 51 of nanofibers at the end of the lower branch 4211 in the direction of movement of the endless conveyor 421. Thus, the deposition of the nanofibers 5, the formation of the bulk ribbon 51 of nanofibers and their pulling out occurs on the lower branch 4211 of the endless conveyor 421 of the electrically neutral belt collector 42, the upper branch 4212 being empty.

In the arrangement of the apparatus according to fig. 5 to 7, the rotating disc spinning electrode 11 may be replaced by a spinning electrode having a direct spinning zone, which spinning electrode may consist of a belt spinning electrode 12 or a linear spinning electrode 13 formed of a linear flexible structure, the linear spinning electrode 13 being described below.

In fig. 8a to 8d, an apparatus with a belt spinning electrode 12 is shown. The apparatus comprises a reservoir 2 of polymer solution 21, into which reservoir 2a rewind shaft 8 coupled to a drive 81 extends with a part of its circumference. Above the rewinding shaft 8, the scraper 121 is fixedly mounted in the spinning chamber 3 on the machine frame, for example by means of a strut 82. The rewind shaft 8 is wrapped with the flights 121 by spinning bands 122, the spinning bands 122, 122 extending from the polymer solution 21 and bending over the flights 121 above the rewind shaft 8. The spinning band 122 carries the polymer solution 21 out of the reservoir 2 and the bending of the spinning band 122 forms a spinning zone 120 of the belt spinning electrode 12, which spinning zone 120 is connected to an AC voltage source. Above the spinning zone 120 of the belt spinning electrode 12, at least along its entire width, there is arranged a lower branch 4211 of the endless conveyor belt 421 of the electrically neutral belt collector 42, as shown in fig. 8 b.

The electrically neutral belt collector 42 is constructed in the same way as in the embodiment according to fig. 5 to 7. The belt collector 42 comprises an endless conveyor 421 surrounding two upper cylinders 422 and two lower cylinders 423, wherein at least one cylinder 422, 423 is a drive cylinder. The rotation axes of all cylinders 422, 423 of the belt collector 42 are perpendicular to the rotation axis of the rewind shaft 8. In the embodiment of fig. 8a, 8b, the endless conveyor 421 moves counter-clockwise, wherein the lower branches 4211 of the endless conveyor between the lower cylinders 423 are arranged against the spinning zone 120 of the belt spinning electrode 12, and the nanofibres 5 formed in the spinning zone 120 of the belt spinning electrode 12 are deposited as fluffy strips 51 of nanofibres on the lower branches of the endless conveyor 421. The lower branch 4211 of the endless conveyor 421 represents the collection area 420 of the electrically neutral belt collector 42. In this embodiment, the fluffed strips of nanofibres 51 are fed to the upper branch 4212 of the endless conveyor 421 with respect to the direction of movement of the endless conveyor 421, the end of this upper branch 4212 forming a pull-out area 4201 of the electrically neutral belt collector 42, from which pull-out area the fluffed strips of nanofibres 51 are pulled out and guided in the direction of the arrow to the twisting device 6, by means of which twisting device the fluffing strips 51 are applied with twist. After pulling out, the fluffy tape 51 of nanofibers tapers into a twisted triangle 52 due to the twist effect and subsequently forms nanofiber yarn 54 therefrom, as described in the previous variant of the apparatus with electrically neutral drum collector 41. As already described above, the direction of movement of the endless conveyor belt can be reversed, and the arrangement mentioned above is only a sideways reversal.

An alternative embodiment of such an arrangement of the apparatus for producing nanofiber yarns is shown in fig. 8c and 8 d. In this embodiment the direction of rotation of the drive cylinders of the cylinders 422, 423 around which the endless conveyor 421 is wrapped is reversed, so that the endless conveyor moves clockwise as shown in fig. 8 d. Other parts of the device and its function remain the same as in the embodiment of fig. 8a and 8 b. Thus, the deposition of the nanofibers 5, the formation of the bulk ribbon 51 of nanofibers and their pulling out occurs on the lower branch 4211 of the endless conveyor 421 of the electrically neutral belt collector 42, the upper branch 4212 being empty. The pull-out region 4201 of the electrically neutral belt collector 42 is thus at the end of the lower branch 4211 of the endless conveyor 421, in which pull-out region 4201 the fluffy strips 51 of nanofibres are pulled out of the endless conveyor 421. As described above, the fluffy tape 51 of nanofibers is fed in the direction of the arrow from the pull-out area 4201 to a twisting device where it is twisted into nanofiber yarns 54. As already described above, the direction of movement of the endless conveyor belt can be reversed, and the arrangement mentioned above is only a sideways reversal.

In the embodiment with a linear spinning electrode 13, the linear spinning electrode 13 consists of an annular linear flexible structure, which in the embodiment shown in fig. 9a to 9d is mounted on two rotatably mounted pulleys 131, which pulleys 131 are coupled to a not shown drive. At least one of the pulleys 131 extends with a part of its circumference to the reservoir 2 of the polymer solution 21. In the embodiment shown, each pulley 131 has a reservoir 2 of its polymer solution 21.

The linear flexible structure composed of the linear spinning electrode 13 may be formed of, for example, a thin wire, a tape, a band, or a structure having a more dispersed surface composed of a plurality of portions interlaced with each other (such as a cable, a rope, a multicore formation, etc.). Similar to the previous embodiment, a spinning field 130 of limited length is formed on the linear spinning electrode 13 between pulleys 131. The spinning field 130 is connected to an AC voltage source by one of known methods.

Above the spinning zone 130 of the linear spinning electrode 13 is arranged an electrically neutral belt collector 42, the lower branch 4211 of which is arranged at least over the entire length of the spinning zone 130 of the linear spinning electrode 13, as shown in fig. 9b and 9 d. The electrically neutral belt collector 42 is constructed similarly to the previous embodiment and comprises an endless conveyor 421, which endless conveyor 421 surrounds two upper cylinders 422 and two lower cylinders 423, wherein at least one cylinder 422, 423 is a drive cylinder. The rotational axes of all cylinders 422, 423 of belt collector 42 are parallel to the axis of pulley 131. In the embodiment according to fig. 9a, 9b, the endless conveyor 421 moves counter-clockwise, wherein its lower branches 4211 between the lower cylinders 423 are arranged against the spinning zone 130 of the linear spinning electrode and the nanofibers 5 formed in the spinning zone 130 of the linear spinning electrode 13 are deposited as fluffy strips 51 of nanofibers on the lower branches of the endless conveyor 421. The lower branch 4211 of the endless conveyor 421 thus represents the collection area 420 of the electrically neutral belt collector 42. In this embodiment, the fluffy strip 51 of nanofibers is fed to the upper branch 4212 of the endless conveyor 421 with respect to the direction of movement of the endless conveyor 421, the end of this upper branch 4212 forming a pull-out area 4201 of the electrically neutral belt collector 42, from which pull-out area the fluffy strip 51 of nanofibers is pulled out and guided in the direction of the arrow into the twisting device 6 and by twisting it, a nanofiber yarn is formed. As described above, the moving direction of the endless conveyor belt may be reversed, and the arrangement mentioned above is only a lateral reversal.

An alternative embodiment of this arrangement of the apparatus for producing nanofiber yarns is shown in fig. 9c and 9 d. In this embodiment, the direction of movement of the endless conveyor 421 is changed and thus it moves clockwise as shown in fig. 9 d. The other parts of the device and its function remain the same as in the embodiment according to fig. 9a and 9 b. Thus, the deposition of the nanofibers 5, the formation of the bulk ribbon 51 of nanofibers, and their pulling out are on the lower branch 4211 of the endless conveyor 421 of the electrically neutral belt collector 42, the upper branch 4212 being empty. The pull-out region 4201 of the charge neutral belt collector 42 is thus at the end of the lower branch 4211 of the endless conveyor 421. The fluffy strip 51 of nanofibers is fed from the pull-out zone 4201 in the direction of the arrow to a twisting device and by twisting it a nanofiber yarn is formed. As described above, the moving direction of the endless conveyor belt may be reversed, and the arrangement mentioned above is only a lateral reversal.

In embodiments having a linear spinning electrode 13, the annular linear flexible structure may be replaced with a linear flexible structure of limited length wound on a pulley 131. In this embodiment, two pulleys 131 extend to the polymer solution 21 at a lower portion of the circumference thereof. The pulley 131 is coupled to a known, not shown, reciprocating drive and rotates alternately in two directions with the linear flexible structure held in tension therebetween.

INDUSTRIAL APPLICABILITY

Yarns and threads made of fibers are the most common structural elements in the textile industry for the production of various types of textiles, such as fabrics and knits. The use of 100% nanofiber yarns in conventional textile production means a great potential for producing so-called nano textiles which exhibit excellent optical, electrical, mechanical and biological properties due to the effects associated with their extremely large specific surface area and low flexibility (flexural modulus).

The nanofiber yarn will find application as a structural unit for surgical threads, tissue carriers for repairing nerves, tendons, bones and blood vessels. They may be structural elements for collecting and storing energy, actuators for mechatronic devices, sensors and filters.

List of reference numerals

1. Spinning electrode

11. Rotary disk type spinning electrode

Spinning zone of 110 rotary disk spinning electrode

12-Belt spinning electrode

Spinning area of 120 band spinning electrode

121. Scraper blade

122. Spinning band

13. Linear spinning electrode

130 Spinning field of linear spinning electrode

131. Pulley wheel

2. Reservoir for polymer solution

21. Polymer solution

3. Spinning room

31. Spinning space

4. Neutral collector

40 Collecting area of electrically neutral collector

Drawing out area of 401 electrically neutral collector

41. Roller collector

410. Collecting area of roller collector

4101 Draw-out area of a roller collector

42. Belt collector

420. Collecting area of belt collector

4201 Pull-out region of belt collector

421. Endless conveyor belt

4211 Lower branch of endless conveyor belt

4212 Upper branch of endless conveyor belt

422. Upper cylinder

423. Lower cylinder

5. Nanofiber

51. Fluffy band of nanofiber

52. Twisting triangle

54. Nanofiber yarn

6. Twisting device

7. Winding device

71. Bobbin tube

8. Rewinding shaft

81. Driver(s)

82. Support post

E electric field strength

Claims

1. A method for producing linear nanofibrous structures from polymer solutions or melts in an AC electric field, wherein a spinning zone (110, 120, 130) with supercritical AC electric field strength E is formed on a spinning electrode (1,11,12,13), wherein nanofibres (5) are formed in the spinning zone (110, 120, 130), which nanofibres (5) are transported away from the spinning electrode by the action of electric wind in the direction of the maximum value of the gradient of the generated electric field, characterized in that at least one spinning zone (110, 120, 130) with supercritical AC electric field strength (E) and limited length is formed on a linear spinning electrode, wherein from the spinning zone (110, 120, 130) presented nanofibres (5) are transported by electric wind in the direction of the maximum value of the electric field gradient away from the spinning zone towards a neutral electrically charged collector (4, 41, 42), which is deposited on a circumferential surface of the collecting zone (40,410,420) located opposite the spinning zone and forming the moving neutral electrically charged collector (4, 41, 42) in the form of the spinning zone, and which nanofibres (5) are subsequently deposited in the form of fluffed fluff (4, 51) by a continuous ribbon (51) which is drawn off the collecting zone (4, 51) in the form of fluff (51), wherein the nanofibers (5) are at least partially parallelized due to the tensile force.

2. The method according to claim 1, characterized in that the fluffy strips (51) of nanofibers are rounded during transfer to the pull-out areas (401,4101,4201) on the surface of the electrically neutral collectors (4, 41, 42) so as to narrow into bands of nanofibers.

3. The method according to claim 1 or 2, characterized in that during the pulling out of the fluffy tape (51) of nanofibers, a pulling force is generated by a winding device (7).

4. The method according to claim 1 or 2, characterized in that during the pulling out of the fluffy tape (51) of nanofibers, a pulling force is generated by a pulling-out device arranged between the pulling-out area and the winding device.

5. The method according to any of the preceding claims 1 to 4, characterized in that upstream of the winding device (7) or the drawing device, the fluffy tape (51) of nanofibers is acted upon by a twisting device (6), which twisting device (6) tapers the fluffy tape (51) of nanofibers into a twisting triangle (52) and subsequently applies a twist thereto, thereby forming a nanofiber yarn (54).

6. The method according to claim 5, characterized in that after leaving the twisting device (6), a residual amount of twist applied to the fluffy tape (51) of nanofibers by the twisting device (6) is preserved, thereby forming nanofiber yarns (54).

7. An apparatus for producing linear nanofibrous structures from polymer solution or melt in AC electric field using the method according to any of the previous claims 1 to 6, wherein a spinning zone (110, 120, 130) with supercritical value of the AC electric field strength (E) is generated on a spinning electrode (1,11,12,13), which spinning electrode (1,11,12,13) is mounted in a spinning chamber and connected to a high voltage AC source and connected to a device for applying the polymer solution or melt to the surface of the spinning electrode, characterized in that above the spinning electrode (1,11,12,13) an electrically neutral collector (4, 41, 42) coupled to a driver is arranged in the path of the nanofibres (5), wherein the surface of the electrically neutral collector (4, 41, 42) forms a collecting zone (40,410,420) of nanofibres against the zone of the spinning electrode (1,11,12,13), a continuous deposition of nanofibres in form of a fluffed tape (51), wherein the fluffed tape (51) of nanofibres is pulled out of the nanofibres is arranged in the direction of the collecting zone (497) in the direction of the pulling-out zone (4, 41, 42) of the drawing device in the direction of the pulling-out zone (4, 498) of the drawing-out zone (4, 41, 42) of the nanofibres is arranged in the path of the collecting zone (5), for generating said fluffy strips (51) for pulling out nanofibers from said surface of said electrically neutral collectors (4, 41, 42).

8. The apparatus according to claim 7, characterized in that an extraction apparatus for generating a pulling force of the fluffy tape (51) for extracting nanofibres from the surface of the electrically neutral collector (4, 41, 42) is arranged between the pulling area (401,4101,4201) and the winding apparatus (7).

9. The apparatus according to claim 7 or 8, characterized in that upstream of the winding apparatus (7) or the drawing apparatus, a twisting apparatus (6) is arranged in the direction of the bulk ribbon (51) from which the nanofibers are drawn.

10. The apparatus according to any one of claims 7 to 9, characterized in that the spinning electrode is formed by a rotating disc type spinning electrode (11).

11. The apparatus according to any one of claims 7 to 9, characterized in that the spinning electrode is formed by a belt spinning electrode (12).

12. The apparatus according to any one of claims 7 to 9, characterized in that the spinning electrode is formed by a linear spinning electrode (13).

13. The apparatus according to any one of claims 7 to 12, characterized in that the charge neutral collector is formed by a charge neutral roller collector (41).

14. The apparatus according to claim 13, characterized in that on the electrically neutral drum collector (41), a collecting area (410) of nanofibers (5) of the electrically neutral drum collector (41) is formed in an area facing the spinning electrode (1,11,12,13), and in an area of the surface of the drum collector (41) facing away from the spinning electrode (1,11,12,13), a drawing-out area (4101) of the drum collector is formed for drawing out the fluffy strips (51) of nanofibers.

15. The apparatus according to claim 14, characterized in that between the collecting zone (410) and the pull-out zone (4101) of the electrically neutral drum collector (41), the fluffy strips (51) of nanofibres are allocated a rounding device.

16. The apparatus according to any one of claims 7 to 12, characterized in that the charge neutral collector is formed by a charge neutral belt collector (42).

17. The apparatus of claim 16, wherein the electrically neutral belt collector (42) comprises an endless conveyor belt (421), the endless conveyor belt (421) encircling two upper cylinders (422) and two lower cylinders (423), at least one of the two upper cylinders (422) and the two lower cylinders (423) being a drive cylinder, wherein the lower branches (4211) of the endless conveyor belt (421) form the collection area (420) of nanofibers (5) for depositing nanofibers in the bulk bands (51) of nanofibers.

18. The apparatus of claim 17, characterized in that the endless conveyor (421) has an upper branch, the end of which in the direction of movement of the endless conveyor (421) forms a pull-out area (4201) for pulling out the fluffy strips (51) of nanofibres from the electrically neutral belt collector (42).

19. The apparatus according to claim 18, characterized in that on the upper branch (4212) of the endless conveyor (421) the fluffy strips (51) of nanofibres are distributed with rounding means.

20. The apparatus according to claim 17, characterized in that at the end of the lower branch (4211) of the endless conveyor (421) in the direction of movement of the endless conveyor (421), the pull-out area (4201) of the fluffy belt (51) for pulling out nanofibers from the electrically neutral belt collector (42) is created, which electrically neutral belt collector (42) is connected to the collection area (420) formed by the lower branch (4211) of the endless conveyor (421) for depositing the nanofibers (5) in the form of fluffy belt (51).