WO2009049564A2

WO2009049564A2 - Collecting electrode of the device for production of nanofibres through electrostatic spinning of polymer matrices, and device comprising this collecting electrode

Info

Publication number: WO2009049564A2
Application number: PCT/CZ2008/000123
Authority: WO
Inventors: David Lukas; Jana Ruzickova; Eva Kostakova; Ondrej Novak; Pavel Pokorny; Jiri Briestensky; Libor Samek
Original assignee: Nanopeutics S.R.O.; Technická univerzita v Liberci; Elmarco S.R.O.
Priority date: 2007-10-18
Filing date: 2008-10-15
Publication date: 2009-04-23
Also published as: CZ2007727A3; WO2009049564A3; TW200938667A

Abstract

The invention relates to the collecting electrode (5) of the device for production of nanofibres through electrostatic spinning of polymer matrices, whose principle consists in that it comprises system of singular electric charges. The invention further relates to the device for production of nanofibres through electrostatic spinning of polymer matrices in electrostatic spinning field between the collecting electrode (5) and at least one spinning electrode (4), whose principle consists in that, it comprises the collecting electrode (5) comprising system of singular electric charges.

Description

Collecting electrode of the device for production of nanofibres through electrostatic spinning of polymer matrices, and device comprising this collecting electrode

Technical field

The invention relates to the collecting electrode of the device for production of nanofibres through electrostatic spinning of polymer matrices.

Further the invention relates to the device for production of nanofibres through electrostatic spinning of polymer matrices in electrostatic field induced by difference of potentials between the collecting electrode and at least one spinning electrode.

Background art

To date known devices for production of nanofibres through electrostatic spinning of solutions or melts of polymers utilise at present several various types of collecting electrodes, out of which each shows differently significant advantages as well as disadvantages. The most widespread type of collecting electrode is a plate collecting electrode formed of board of electrically conductive materia), because it is the simplest as to its structure and simultaneously it shows very advantageous properties from the point of view of co-induction of the electrostatic spinning field. Besides, the impact of the plate collecting electrode on this field can be theoretically easily deduced, modelled and foreseen. Disadvantage of the plate collecting electrode nevertheless is that after the high voltage is brought in vicinity of its sharp edges and peaks, and also in vicinity of the contact of electrode with the means for its mounting in the spinning chamber, the cluster electric charge - the corona is created, which destabilises electrostatic spinning field and reduces its intensity, by which it negatively influences the process of electrostatic spinning and reduces overall performance of the device for electrostatic spinning. To eliminate these disadvantages or at least to reduce them, e.g. the cylindric collecting electrode according to CZ PV 2006-477 was developed, which is formed of a conductive thin-walled body, whose advantage against the plate collecting electrode consists in that the body of electrode does not contain on its surface any sharp shapes or transits, and places, where three various dielectrical solid environments are touching (triple points), are hidden in inner space of electrode body, where the electrostatic spinning field shows practically zero intensity. Finally, on surface of the collecting electrode there are not created any coronas, and the collecting electrode is thanks to this more friendly towards the electrostatic spinning field. The disadvantage is complicated structure and maintenance of such collecting electrode and also its relatively small surface, which takes part in induction of the spinning electrostatic field, and in process of electrostatic spinning. Due to this it is usually necessary for an equivalent substitution of one plate collecting electrode to use several cylindric collecting electrodes arranged side by side and/or one after another, which increases total costs of acquisition and operation of the device for production of nanofibres.

Nevertheless even the cylindric structure of collecting electrode does not remove one of the most decisive disadvantages, which relate to all to date known collecting electrodes utilised at electrostatic spinning. This disadvantage is that the nanofibres before contact with the collecting electrode must be caught on a suitable carrying substrate, e.g. fabric, foil, etc., because at their direct contact with the collecting electrode the nanofibres would, thanks to its consistency and geometry, get stuck on the smooth surface of collecting electrode , and their removal by mechanical or chemical means would be not only relatively complicated, but it would require shut-down of the whole device, possibly of the whole production line. Moreover, in such cases it would not be possible to ensure forming of applicable, non-damaged and consistent layer of nanofibres. The result of present production of nanofibres through electrostatic spinning is always layer of nanofibres applied on carrying substrate - thus a composite layered product - whose applicability to a certain extent is bound to mechanical or chemical properties of the substrate, and mostly it does not permit full utilisation of all advantageous properties of the nanofibres themselves, among which also belongs e.g. low weight, high specific surface and relatively low pressure drop. In spite of the fact there are known devices for removal, namely cutting-off the layer of nanofibres from the substrate, their application is thanks to low efficiency and high mechanic damage of nanofibres practically zero.

From some patent documents, e.g. from US2005/0048274 is further known the device, which works on principle of electrostatic spinning of polymer solution or melt from the tip of capillary, where are the produced nanofibres deposited directly on surface of the given body, or e.g. in case of device according to CA 2386674 even on surface of human body. While the spinning electrode of such devices is formed of one or several capillaries, the collecting electrode of these devices represents the grounded object, on which are the nanofibres deposited. These devices and generally all to date known devices for spinning of solutions or melts of polymers from the tip of capillary or capillaries nevertheless show very low productivity, due to which they do not find any industrial applicability. Moreover such devices require nearly continuous supervision, because frequent caking of polymer solution in capillaries results in reduction of intensity of the electrostatic spinning process and gradually in its full stopping and shut-down of the entire device. Also, by these devices created layer of nanofibres is not applicable independently, as it is during its production deposited on any object, thus being applicable only in combination with this object.

From the above mentioned it is obvious, that to date there does not exist industrially applicable device, which would be able continuously or at least discontinuously produce an separate planar layer of nanofibres, or the linear nanofibrous formation, without being deposited on a carrying substrate or an object. This restriction arises especially from the structure of to date known and used collecting electrodes. Goal of the invention is to construct the collecting electrode enabling formation and depositing of self-supporting layer of nanofibres or of linear nanofibrous formation, whose utilisation is not restricted by properties of the substrate, and simultaneously the collecting electrode, which co-induces the most suitable spinning electrostatic field, and which is thanks to this applicable in combination with all to date known types of spinning electrodes.

Principle of the invention

The goal of the invention has been achieved by collecting electrode of the device for production of nanofibres through electrostatic spinning of polymer matrices, whose principle consists in that it comprises a system of singular electric charges, which contributes on induction of electrostatic spinning field and on the process of electrostatic spinning in a similar manner as the plate collecting electrode with surface distribution of electric charge.

It is known that electric charge brought to a thin and straight conductive body concentrates significantly on its ends, so that for creating of a system of singular point charges, the system of suitably shaped electrically conductive active elements positioned on electrically non-conducting substrate may be used. Peaks of these active elements may basically be of any shape without negative influencing the electrostatic spinning field. Their peaks then may be formed e.g. by a tip and/or blade and/or flat, without any decisive change in characteristics and behaviour of collecting electrode.

Arrangement of active elements on electrically non-conducting substrate depends to a certain degree on the requirements as to appearance and spatial arrangement of nanofibrous formation. E.g. for formation of linear nanofibrous formations, are the active elements positioned in one line, which is either abscissa, circle, perimeter of n-angle or arbitrary curve. On the contrary, for forming of planar nanofibrous structures, the active elements are with advantage arranged into a planar grid. The whole such a grid, or its part may be formed of active elements arranged on circle or on several circles, while the best contribution to formation of nanofibrous structure and its homogenity is exercised if these circles are concentric. A portion of active elements in planar grid may be, next to this, arranged on perimeter of arbitrary n-angle, or of several similar concentric n-angles. Favourable results are achieved also at arrangement of active elements on several circles and perimeters of n-angles concentric with them.

The requirement of the greatest homogeneity in distribution of nanofibres in planar nanofibrous formation, thus also its constant surface density is nevertheless best fulfilled by positioning of active elements into equidistant square grid.

At the simplest embodiments of collecting electrodes are all the active elements of the same length, however by utilisation of active elements of various lengths it is possible to influence and in a certain degree also to control the spatial structure of nanofibrous formation, as this relatively exactly copies the coating surface of ends of active elements.

For the spatial shaping of nanofibrous formation by means of length of active elements it is then advantageous, if the length of active elements is adjustable and if is possible to change it, e.g. upon actually detected parameters of nanofibrous formations.

In the structurally least demanding example of embodiment the base of collecting electrode is in the processing space mounted non-movably and is simultaneously of a planar form. If nevertheless the immovable base of collecting electrode and arrangement of active elements on it does not ensure enough sufficient homogeneity of nanofibrous formation and its surface density, or of other parameters, it is advantageous, if the base of collecting electrode is moveable. Motion of the base and of entire collecting electrode substantially contributes to homogenous distribution of deposited nanofibrous formation, thus to some of its most decisive properties.

For continuous production of nanofibrous formations without shut-downs of entire device for its removal from active elements, the embodiment of collecting electrode is designated when the base of the collecting electrode is formed of endless loop embraced around at least one stretching roller and at least one driving roller. By motion of such base the nanofibrous formation is carried out of the spinning space, where it is continuously removed and deposited.

The moveable as well as immovable base of collecting electrode may be formed basically by any geometric body without any special requirements as to its shape or geometry. Especially in case of moveable base nevertheless the most advantageous seems to be if this base is formed of geometric body being axially symmetric, which facilitates its mounting in the processing space and its possible, especially rotation motion. Such suitable body for example is cylinder, which is especially applicable at production of planar nanofibrous formations, or the annulus which is designated for production of linear nanofibrous formations.

These embodiments of collecting electrode may further be modified through arrangement of collecting electrode in the processing space. Here, the collecting electrode may be mounted in such a way that its longitudinal axis is vertical, but also in such a way that its longitudinal axis is horizontal. Active elements are usually positioned perpendicular to surface of the base, but nothing prevents that they are deflected from this position, so that their longitudinal axis forms a sharp angle with surface of the base. Such structural provision does not exert any substantial influence to the process of electrostatic spinning or depositing of nanofibres on active elements, or even their quality. In some cases nevertheless facilitates removal of nanofibrous formation from active elements.

The collecting electrode according to any structure, whose principle consists in that it contains a system of singular point charges, is applicable in the device for production of nanofibres through electrostatic spinning by means of the spinning electrostatic field induced between at least one spinning electrode and the collecting electrode, because its share in induction of this field is basically the same as an effect of an universal plate collecting electrode. Description of the drawing

Various variants of embodiment of collecting electrode of the device for production of nanofibres through electrostatic spinning of polymer matrices according to the invention are schematically represented on the enclosed drawing, where Fig. 1 represents cross section of the device for production of nanofibres through electrostatic spinning of polymer matrices with static collecting electrode and cylindric spinning electrode, Fig. 2 shapes of equipotential lines of electrostatic spinning field in vicinity of collecting electrode according to the invention, Fig. 3 shows cross section of the device for production of nanofibres through electrostatic spinning of polymer solutions with one of possible variants of moveable collecting electrode designated for continuous production of planar nanofibrous formations and of the cylindric spinning electrode, Fig. 4 cross section of the device for production of nanofibres through electrostatic spinning of polymer solutions with one of possible variants of static linear collecting electrode for production of linear nanofibrous formations and of the cylindric spinning electrode, Fig. 5 cross section of the device for production of nanofibres through electrostatic spinning of polymer solutions with one of possible variants of rotating collecting electrode for continuous production of linear nanofibrous formations with utilisation of spinning electrode formed of capillary, and Fig. 6 shows another variant of collecting electrode for continual production of linear nanofibrous formations.

Examples of embodiment

Collecting electrode of the device for production of nanofibres through electrostatic spinning of polymer matrices according to the invention and its various variants will be explained on particular, however only illustrating examples of embodiment, which are schematically represented in Fig. 1 and

Fig. 3 to Fig. 6. To increase clearness, on these drawings there is illustrated cross section through entire device for production of nanofibres through electrostatic spinning of polymer matrices comprising the collecting electrode according to the invention, whose spinning electrode is formed of an oblong cylindric body or capillary. Nevertheless these are not the only possible configurations for utilisation of the collecting electrode according to the invention, because this can be thanks to its electrical properties used in principle on any device for production of nanofibres through electrostatic spinning, regardless the shape, structure, number and arrangement of spinning electrodes. The collecting electrode according to the invention is applicable also as a substitution of the used types of electrodes at already existing devices, and its positioning towards the collecting electrode is in principle also arbitrary. Below are described only solutions ensuring the most advantageous interaction of the collecting electrode with the selected types of spinning electrodes. Polymer matrix is formed of any electrostatic spinnable form of polymer possibly with various additives or mixture of polymers, to which also various additives may be added, while usually is the electrostatic spinnable form the solution or melt. The device for production of nanofibres through electrostatic spinning of polymer matrices represented in Fig. 1 comprises the spinning chamber 1 defining the processing space, in which the process of production of nanofibres is running. In the lower section of the spinning chamber 1 there is arranged the spinning electrode 4, which is in the represented example of embodiment formed of the cylindric body rotatably mounted in reservoir 2 of polymer matrix, which is in the represented example of embodiment formed of an opened vessel. As a polymer matrix the solution 3 of polymer is used. Section of surface of the cylindric body of the spinning electrode 4 extends into the solution 3 of polymer. The spinning electrode 4 is in a known manner connected with one pole of not represented source of high voltage and simultaneously with the not represented drive for rotating motion along the longitudinal axis 41_,.

In upper part of the spinning chamber 1_, above the spinning electrode 4 there is arranged the collecting electrode 5 according to the invention. In the represented example of embodiment is the collecting electrode 5 formed of horizontally arranged planar rectangular base 5J. °f electrically non-conducting material, which is provided with a system of through openings 52 arranged into equidistant square grid. In openings 52 are mounted the active elements 53 of electrically conductive material, which extend to both sides of the base 51_^ and are mutually parallel. Above the base 51. all active elements 53 are electrically conductively connected by the connecting conductor 54, which is further connected with opposite pole of high voltage source than the spinning electrode 4 or grounded. In the space under the base 51. the active elements 53 are ended by tips 55, while coating surface of the tips 55, which is in case of embodiment according to Fig. 1 the plane 56 being parallel with the base 5_i, represents active surface in which majority of nanofibres is deposited, that form here the planar nanofibrous formation. Due to difference of potentials between the spinning electrode 4 and the active elements 53 of the collecting electrode 5, the electrostatic spinning field of high intensity is induced between the spinning electrode 4 and the active elements 53 of collecting electrode 5. The charge brought to active elements 52 concentrates thanks to their geometry on peaks of the tips 55, due to which is in the active surface 56 the equidistant grid of point singular charges formed, that contributes to induction of the spinning electrostatic field and to the process of electrostatic spinning of polymer matrices in principle very similarly like the plate collecting electrode.

Electrostatic field induced between the surface grid of equidistant distributed point charges and the opposite endless plate electrode is described by the potential φ, which is specified e.g. by linear combination of Fourier components. From this it is obvious, that amplitude of the potential φ decreases exponentially with increasing distance from the grid, while the most slowly decreasing component of the potential is the first harmonic, whose curve, in dependence on the increasing distance from the grid of point charges, is represented in Fig. 2. The points on x axis represent individual singular electric charges. Amplitude drop of the potential φ is of such character, that in the distance of b/2π the potential is nearly identical with potential generated by the charge with constant density of distribution. Potential of the collecting electrode 5 according to the invention is thus in this distance from it basically identical as the potential of plate collecting electrode known from the background art. In the distance smaller than b/2π from the collecting electrode 5 on the contrary, the potential of electrostatic field is thanks to singular charges strongly deformed, as it is apparent from the curve of equipotential lines illustrated in Fig. 2. Between the tips 55 of active elements 53 and in their vicinity is induced so called electrostatic cushion, characterised especially by deformed equipotential lines, and adequately to it by deformed lines of force of electrostatic field, which in dependence on polarity of electric charge on the tips 55 and electric charge on the spinning electrode 4 direct either to the peaks of tips 55 of active elements 53 or from them. Gradient of electrostatic field in vicinity of active surface in principle directs always to this surface. Electrostatic cushion acts thanks to this by a force to the charged nanofibres, which it catches, and is able to change the speed and direction of their motion.

The collecting electrode 5 according to the invention together with the spinning electrode 4 induces the spinning electrostatic field and it takes part in the process of electrostatic spinning in a similar manner like the plate collecting electrode, because at the same conditions and values in difference of electric potentials ensures inducing of electrostatic field of intensity sufficient for initiation and maintaining the process of electrostatic spinning. Similar relations and connections are valid also for system formed of the collecting electrode 5 according to the invention and spinning electrode 4 in principle of any shape and type, so that the collecting electrode 5 may be used in combination with spinning electrode 4 formed of cylindric body, capillary, or system of capillaries or by other known spinning electrode.

Into such induced electrostatic spinning field is by means of the rotating motion of the spinning electrode 4 carried the electrically charged solution 3 of polymer, which is here subject to action of electric forces. Thanks to action of the Coulomb forces, that overcome not only the surface tension of polymer solution, but also forces arising out of its viscosity, there occurs deformation and folding of layer of polymer solution 3 on surface of the spinning electrode 4 and creating of so called Taylor cones, out of which are the nanofibres subsequently formed. The formed nanofibres are electrically charged and their charge corresponds to polarity of the charge brought to the spinning electrode 4. Thanks to this the individual nanofibres are mutually repulsed, but simultaneously they all are attracted to the collecting electrode 5, in whose active surface they are deposited in layer, whose shape copies relatively exactly just the shape of this active surface. Direct contact between the nanofibres and active elements 53 simultaneously enables carrying-away of electric charge of nanofibres, and thanks to the fact that in principle it is a point contact only, it enables an easy subsequent removal of nanofibrous layer without its damage. Speed and intensity of carrying-away the charge from nanofibres may distinctly be influenced by content of residual solvent and also by character and composition of spinnable polymer matrix itself which in some cases contains, as per requirements to the resultant nanofibrous layer, various additives, e.g. salts, surface-active substances, low-molecular bactericidal substances, etc. However most decisively the electric conductivity of nanofibres is changed through content of electrically conductive solvent, while conductivity of the polymer nanofibre itself is practicably negligible and does not nearly enable transfer of electric charge between opposite ends of nanofibres. Due to this the partially dried nanofibre loses at first contact with active element 55 usually only a certain portion of carried electric charge. To this moment charged part of nanofibre is thanks to force relations in vicinity of active elements 53 and action of surrounding electrically charged nanofibres deflected to the most advantageously positioned active element 53, or to its tip 55, where the nanofibre loses the rest of its electric charge or at least its essential part. Such active element 53 is either active element 53 on which the first section of nanofibre is already positioned, and/or, if this is permitted by length of nanofibre, the neighbouring active element 53.

On tips 55 of active elements 53 and between them is by this method during relatively short time period formed the carrying layer of nanofibres, which represents for further arriving nanofibres the physical obstacle on which these nanofibres are caught and deposited. The carrying layer of nanofibres also in dependence on its electric conductivity enables entire or at least partial carrying-away of their electric charge. The result of application of the collecting electrode 5 according to the invention is thus the self-supporting planar layer of nanofibres deposited on the tips 55 of active elements 53, which has after its removal from the point of view of most applications other utility value than to date common outputs of similar devices, when the layer of nanofibres is always deposited on a carrier, e.g. fabric, foil, etc. This planar layer formed exclusively of nanofibres may be used e.g. for filtration, nevertheless by further mechanical modification securing its sufficient consistency especially in tension may be transformed e.g. to nanofibrous yarn. Disadvantage of the described solution of collecting electrode 5 is the necessary shut-down serving to remove the layer of nanofibres from the tips 54 of active elements 53. Removing the layer of nanofibres from the tips 55 is relatively simple, because the contact between this layer and collecting electrode 5 is not surface, but only a point one.

Modification of the collecting electrode 5 according to the invention, which ensures continuous removal of nanofibrous layer without shut-down of the device, is positioning of several above described collecting electrodes 5 on the replaceable device, which places these electrodes 5 alternately into the processing space. After applying the layer of nanofibres carries this device the given collecting electrode 5 outside the processing space where the layer of nanofibres is removed form it, and simultaneously, with advantage still before carrying out the collecting electrode 5, it inserts into the processing space in sequence following the collecting electrode 5 without a layer of nanofibres or with layer of nanofibres, whose parameters, e.g. thickness or the surface density does not reach the required values. Arrangement of the plate collecting electrode 5 in the processing space is nevertheless not limited only to the described horizontal embodiment. Collecting electrode 5 in further not represented examples of embodiment is arranged vertically, nevertheless in this embodiment are into the process of electrostatic spinning engaged the most actively only active elements 53, that are closest to the spinning electrode 4, and due to this the formed nanofibrous formation is strongly inhomogeneous. On the contrary, Fig. 3 schematically represents another possible variant of embodiment of collecting electrode 5 according to the invention, which enables continuous production of a layer of nanofibres and its continuous removal from active elements 52 without necessity to shut down the device, which results in higher efficiency and utility value of this device.

The base 5_i of collecting electrode 5 is in this case formed of flexible, electrically non-conducting material, and it is closed into endless loop embraced around the stretching roller 61 and driving roller 62. Like in the previous example of embodiment the base 5J. is on all its surface provided with evenly distributed through openings 52 arranged into a square equidistant grid, in which there are mounted the active elements 53 extending to both sides of the base 51.. The longitudinal axis 521 of equidistant square grid in projection into ground plan with the longitudinal axis 41. of collecting electrode 4 forms the right angle. On inner surface of the base 5J. the active elements 53 are conductively terminated on the conductor 54 in the represented example of embodiment formed by a flexible, electrically conductive, e.g. plastic graphite foil mounted on the inner surface of the base 51.. This foil thus conductively connects all the active elements 53, while it is further connected with opposite pole of the not represented high voltage source than the spinning electrode 4 or grounded. Opposite ends of active elements are provided with the tips 55.

The stretching roller §1 as well as the driving roller 62, are parallel with the longitudinal axis 4J. of the spinning electrode 4, and in the represented example of embodiment they are positioned outside the spinning chamber ±. The driving roller 62 is further coupled with the not represented drive for rotating motion, which may be the drive for rotating motion of the spinning electrode 4. Thanks to rotation of the driving roller 62 the base 52 of collecting electrode 5 and the active elements 52 are moving smoothly, and through their motion in the processing space is achieved higher homogeneity of layer of nanofibres. At the same time the layer of nanofibres continuously deposited on the tips 55 of active elements 53 is simultaneously carried out outside the spinning chamber i, where it is continuously removed and deposited without necessity to interrupt operation of the whole device. In the represented example of embodiment serves for removal of layer of nanofibres from active elements 53 e.g. the comb 7, whose teeth JJ. extend between the neighbouring rows of active elements 53, and thanks to motion of collecting electrode 5 they pull down from them the layer of nanofibres without its damage. To increase adhesion of layer of nanofibres to the comb 7 and to facilitate manipulation with it, the comb 7 is in the not represented example of embodiment added by openings and coupled with source of vacuum. The device for removal of layer of nanofibres from the collecting electrode 5 may in further examples of embodiment considerably differ, however due to the fact, that this device is not a subject of the invention, its individual variants will not be described, because it is always a device whose function and structure are obvious from the objective task, for which these devices are designated and whose utilisation or structure does not require exertion of any inventive step.

Principle of the collecting electrode 5 according to the previous examples of embodiment consists in that this electrode contains a surface grid of point singular charges, whose positioning, e.g. on the tips 55 of active elements 53 enables forming of the self-supporting planar layer of polymer nanofibres and its relatively undemanding continuous or discontinuous removal. Principle of the invention is not changed with change in polarity of charges brought to the collecting electrode 5 and/or the spinning electrode 4, possibly with grounding of some of them. Also the shape of active elements 53 possibly their active tips

55 may in various cases differ, because the tips 55 of active elements 53 may be replaced e.g. by active flats and/or active blades, etc. Arbitrary is also the cross section of active elements 53, however the most suitable seems to be the circle or other cross section without sharp transits between the neighbouring walls.

The active elements 53 need not to be in all applications arranged into equidistant square grid, but into a general grid, because by decreasing and/or increasing their distances the density of the self-supporting nanofibrous layer may be modelled relatively easily. Higher concentration of active elements 53, and thus smaller distance between them, increases density of deposited layer of nanofibres, while lower concentration of active elements 53 on the contrary decreases the density of nanofibrous layer. This effect may easily be utilised for production of structured layers of nanofibres, when on relatively small distances there may be reached great differences in surface density, permeability, porosity and further mechanical, but also some chemical properties of this layer.

With respect to the fact that the layer of nanofibres relatively exactly copies the shape of active surface, which is the coating surface of the tips 55 of the active elements 53, through a suitable spatial shaping of this active surface the space structure of the resultant layer of nanofibres may be affected. For example by application of active elements 53 of various lengths the corrugation of layer of nanofibres, or other spatial effects may be achieved, etc. Impact of a different length of the active elements 53 moreover very easily may be combined with impact of different distances between them, by which complex space patterns with various distribution of surface density may be achieved. Quantity of various variants may be created also in the structural embodiment itself of the collecting electrode 5 and through its positioning in the spinning chamber. For example the stretching roller 61_ and/or driving roller 62 may in further not represented examples of embodiment be positioned in the spinning chamber I₁, possibly any of them may be replaced by system of two or more stretching or driving rollers, nevertheless these changes do not exert any substantial impact to the principle and functioning of the collecting electrode 5 and they themselves do not require to exert any inventiveness, because they are obvious.

Any of the above mentioned variants of the collecting electrode 5 for carrying out the layer of nanofibres outside the spinning chamber I_^ or for increasing its effectiveness may be also completed with the not represented moving carrying-out stripes, which are moving in the space between the neighbouring rows and/or columns of the active elements 53.

Contrary to the shown examples of embodiment designated for production of planar nanofibrous layers or formations, the embodiment of the collecting electrode 5 represented in Fig. 4 is designated for production of linear nanofibrous formations. The collecting electrode 5 comprises in this case, similarly like in the previous example of embodiment, the base 5_i however the through openings 52 and active elements 53 are equidistantly arranged only in one row, which is parallel with longitudinal axis 41 of the spinning electrode 4. The nanofibres at usage of such collecting electrode form on the tips 55 of active elements 53 and in the space among them the linear formation, which may be from active elements 53 easily removed, and in principle without any further technological operations utilised, e.g. as a filtration component for fine filtration, or at sufficient consistency of this formation or after its additional increasing e.g. by twist, as a nanofibrous yarn, etc. Very similar result is reached at mutual alternate deflection of the active elements 53 of collecting electrode 5 from the straight position, when the longitudinal axes of neighbouring active elements 53 together form a sharp angle.

Also at the collecting electrode 5 designated for production of linear nanofibrous formations is through a change of distance between the active elements 53 and their length possible to modify properties of the resultant linear nanofibrous formation and its spatial arrangement.

In further not represented examples of embodiment there may be in combination utilised two or more parallel arranged collecting electrodes 5 according to Fig. 4, for production of planar nanofibrous layers, while the individual collecting electrodes 5 may be variously shifted one towards another. The different distance of the tips 55 of active elements 53 or their different length is, in the same way as in the previous examples of embodiment, usable for the targeted spatial modification of layer of nanofibres. Next to this, in other not represented examples of embodiment the collecting electrodes 5 are mutually arranged under various angles, e.g. so that their active elements 53 are positioned on perimeter of one or combination of several geometric shapes, e.g. squares, rectangles, etc. At these embodiments it is advantageous, if the individual collecting electrodes 5 are connected e.g. by means of the common base 51_ into larger units. In other not represented examples of embodiment the active elements are arranged on perimeter of geometric formations within only one collecting electrode 5. An independent group of collecting electrodes 5 are the collecting electrodes 5, whose active elements 53 are arranged on circle or on several concentric circles, or, e.g. for the purpose of spatial modification of the linear nanofibrous formation, on the displaced circles. Geometric shapes into which the active elements 53 of collecting electrodes 5 are arranged may be mutually variously combined, at the same time they may differ one from another not only by size of the active elements 53, but by their number, or by distance between the neighbouring active elements, or by the shape of the tips 55. Disadvantage of the static embodiments of collecting electrodes 5 is that removal of layer of nanofibres from the tips 55 of active elements 53 requires shut-down of the whole device, which reduces its performance and applicability of static collecting electrodes 5 according to the invention. In cases when the spatial arrangement of active elements 53 enables it, this disadvantage may be reduced or even removed by usage of a system of the not represented moveable carrying-out stripes, which at their motion carry-out a layer of nanofibres from the active space, possibly even outside the spinning chamber 1

Any of the above mentioned types of collecting electrode may also be repeatedly, or in combination with other types be positioned on a moving transporting conveyor, that ensures a smooth motion of collecting electrodes through the processing space and carrying-out of layers of nanofibres outside the spinning chamber JL

Of much higher applicability especially for continuous production of nanofibrous linear formations at simultaneous less structural and operational demand and complexity is the embodiment of the collecting electrode 5 represented in Fig. 5, where it is utilised in combination with the spinning electrode 4 formed of capillary. The base 51. of collecting electrode is formed of annulus of electrically non-conducting material, which is evenly along its whole perimeter provided with through openings 52. In each of the openings 52 there is mounted the active element 53 of electrically conductive material, which overlaps the inner surface 510 as well as the outer surface 5100 of the base 51. All active elements 53 in the inner space of the base 5J. are electrically conductively connected by the conductor 54, which is interconnected with opposite pole of high voltage than the collecting electrode 4 or grounded. Opposite ends of active elements 53 above the outer surface 5100 of the base 51. are ended by tips 55. The base 5_1 of the collecting electrode 5 is further by means of the shaft coupled with the not represented drive for rotating motion.

In the processing space the collecting electrode 5 is arranged above the spinning electrode 4 and its longitudinal axis 50 is perpendicular to the longitudinal axis 41. of the spinning electrode 4.

Upon rotation of the collecting electrode 5 around the longitudinal axis 50 its active elements 53 gradually move near and move away from the peak of the spinning electrode 4, through which their participation in the process of electrostatic spinning is changed, and also the quantity on them deposited nanofibres. The active space is in the given example of embodiment formed of a line running through the peaks of the tips 55 of active elements 53 being situated on a part of outer surface 5100 of the base 5I- adjacent to the spinning electrode 4. Impact of the active elements 53 outside the active space to co- inducing of electrostatic spinning field and process of electrostatic spinning is negligible.

Like as in the previous examples of embodiment, the tips 55 of active elements 53 in active space represent a line of singular point charges, on which the linear nanofibrous formation is deposited. Rotational motion of this line at the same time contributes to even distribution of nanofibres between all active elements 53 of the collecting electrode 5 and to homogeneous properties of the nanofibrous formation along its whole length. Relatively small number of active elements 53 and small dimensions of its tips 55 simultaneously enable an easy continuous removal of this nanofibrous formation. To this purpose serves the not represented removing device, which in certain cases of embodiment may be positioned inside the spinning chamber I-, preferably above the active space, at the same time it is preferably made of electrically non-conducting material. In other not represented examples of embodiment extend some active elements 53 of the collecting electrode 5 temporarily outside the spinning chamber 1, where the deposited nanofibrous material is being removed carefully from them. On the same principle and with very similar results works also the collecting electrode 5 represented in Fig. 6, whose base 51 is formed of endless belt embraced around the stretching roller 61 and the driving roller 62, along its whole length provided with one row of active elements 53. The endless stripe may be in the not represented embodiment substituted by an endless loop consisting of fixed segments.

The not represented combination of several moving collecting electrodes 5, whose base 5J. is formed by an annulus, cylinder or endless belt, in dependence on further conditions in the processing space enables the simultaneous continuous production and removing of several independent linear nanofibrous formations or production of a planar nanofibrous formation. These collecting electrodes 5 moreover may differ by a size and number of active elements 53. In other examples of embodiment on the contrary the collecting electrodes 5 comprise the same number of the same active elements 53, and their bases, with advantage, merge into a one. In other not represented examples of embodiment also the positioning of the collecting electrode 5 may differ towards further elements of the device for production of nanofibres, especially towards the spinning electrode 4, because the collecting electrode 5 may be in the spinning chamber 1 positioned vertically like as at the solution in Fig. 5, but also horizontally. At horizontal mounting of the collecting electrode 5, when its axis 50 is arranged vertically, it is advantageous if at least some active elements 53 are deflected towards the spinning electrode 4, due to which the tips 55 of these active elements 53 are ,,more attractive" for the approaching nanofibres, which deposit on them in preference. Such solution of the collecting electrode 5 is applicable especially at usage of several spinning electrodes 4, out of which each performs spinning of other polymer matrix. The resultant nanofibrous formation thanks to it comprises a mixture of polymer nanofibres of different mechanical or chemical properties, etc.

Very substantial impact to the appearance and structure of the resultant nanofibrous formation, next to spatial arrangement of active elements 53 of the collecting electrode 5, exerts especially the size of their free conducting surface. Decreasing of this size results in decreasing of electric forces acting to nanofibres, so that nanofibres are not attracted strictly to the tips 55 of active elements 53, but gradually between these tips 55 is formed relatively homogenous planar nanofibrous formation. For this effect e.g. controlled covering of a section of the length of the active elements 53 by means of insulator may be utilised. This process may be relatively easily automated and utilised continuously in dependence on evaluated actual parameters of the nanofibrous formation.

Very similar effect is also achieved upon motion of the collecting electrode 5 in the processing space, while this motion is with advantage performed in a plane of the collecting electrode 5, so that there is no change in distance of the tips 55 of active elements 53 towards the spinning electrode 4 and corresponding pulsation of electrostatic spinning field. Thanks to motion ofthe collecting electrode 5 the area to which the nanofibres are attracted is increased, and these are on this surface deposited in relatively homogenous planar formation.

The described examples of embodiment of collecting electrodes 5 are nevertheless not the only possibilities of their structural embodiment, these are only the illustrative examples of collecting electrodes 5 showing the most advantageous behaviour. In other not represented examples the base §Λ_ of collecting electrode 5 may be formed of any geometric body, which is provided with a system of active elements 53, while this collecting electrode 5 may further in the processing space perform basically any motion contributing to formation of self-supporting layer of nanofibres, to its spatial modification, or distribution of surface density. List of referential markings

1 spinning chamber

2 reservoir

3 solution

4 spinning electrode

41 axis of the spinning electrode

5 collecting electrode

50 longitudinal axis

51 base

510 inner surface

5100 outer surface

52 openings

521 axis of system of openings

53 active elements

54 conductor

55 tips of active elements

56 surface

61 stretching roller

62 driving roller

Claims

1. The collecting electrode of the device for production of nanofibres through electrostatic spinning of polymer matrices, characterised in that it comprises system of singular electric charges.

2. The collecting electrode according to the claim 1 , characterised in that the system of singular electric charges is formed of peaks of electrically conductive active elements (53) positioned on the base (51), while on the active elements (53) is brought voltage.

3. The collecting electrode according to the claim 1 , characterised in that the peaks of at least some active elements (53) are formed of tips (55).

4. The collecting electrode according to the claim 1 or 2, characterised in that the peaks of at least some active elements (53) are formed of blades.

5. The collecting electrode according to any of the claims 1 to 4, characterised in that the peaks of at least some active elements (53) are formed of flats.

6. The collecting electrode according to any of the previous claims, characterised in that the active elements (53) are on the base (51) arranged in one line.

7. The collecting electrode according to any of the previous claims, characterised in that the line is an abscissa.

8. The collecting electrode according to any of the previous claims, characterised in that the line is a circle.

9. The collecting electrode according to any of the previous claims, characterised in that the line is perimeter of an n-angle.

10. The collecting electrode according to any of the previous claims, characterised in that the line is a curve.

11. The collecting electrode according to any of the claims 1 to 5, characterised in that the active elements (53) on the base (51) are arranged into a grid.

12. The collecting electrode according to the claim 11 , characterised in that at least a part of the grid is formed by a circle.

13. The collecting electrode according to the claim 11 or 12, characterised in that at least a part of the grid is formed of circles.

14. The collecting electrode according to the claim 13, characterised in that at least a part of the grid is formed of concentric circles.

15. The collecting electrode according to any of the claims 11 to 14, characterised in that at least a part of the grid is formed of perimeters of n- angels.

16. The collecting electrode according to the claim 15, characterised in that at least a part of the grid is formed of perimeters of concentric n-angels.

17. The collecting electrode according to the claim 15, characterised in that at least a part of the grid is formed of concentric circles and n-angels being concentric with them.

18. The collecting electrode according to any of the claims 1 , 2 and 11 characterised in that the active elements (53) on the base are arranged into equidistant square grid.

19. The collecting electrode according to any of the previous claims, characterised in that the length of all active elements (53) is identical.

20. The collecting electrode according to any of the claims 1 to 18, characterised in that the length of active elements (53) is different.

21. The collecting electrode according to any of the previous claims, characterised in that the length of active elements (53) is adjustable.

22. The collecting electrode according to any of the previous claims, characterised in that the base (51) of collecting electrode (5) is immovable.

23. Collecting electrode according to any of the previous claims, characterised in that the base (51) of the collecting electrode (5) is planar.

24. The collecting electrode according to any of the claims 1 to 21 and

23, characterised in that the base (51) of the collecting electrode (5) is moveable.

25. The collecting electrode according to any of the claims 1 to 21 , 23 and 24, characterised in that the base (51) of the collecting electrode (5) is formed of endless loop embraced around at least one stretching roller (61) and at least one driving roller (62).

26. The collecting electrode according to the claim 25, characterised in that the base (51) of collecting electrode (5) is formed of a belt.

27. The collecting electrode according to any of the claims 1 to 22 and

24, characterised in that the base (51) of the collecting electrode (5) is formed of geometric body.

28. The collecting electrode according to the claim 27, characterised in that the base (51) of the collecting electrode (5) is formed of axially symmetric geometric body.

29. The collecting electrode according to the claim 28, characterised in that the base (51) of the collecting electrode (5) is formed of cylinder.

30. The collecting electrode according to the claim 27, characterised in that the base (51) of the collecting electrode (5) is formed of annulus.

31. The collecting electrode according to any of the claims 23 and 28 to 30, characterised in that its longitudinal axis (50) is arranged vertically.

32. The collecting electrode according to any of the claims 23 and 28 to 30, characterised in that its longitudinal axis (50) is arranged horizontally.

33. The collecting electrode according to any of the previous claims characterised in that at least some active elements (53) are perpendicular to the base (51).

34. The collecting electrode according to any of the previous claims, characterised in that at least some active elements (53) form with the base (51) an angle smaller than 90°.

35. The device for production of nanofibres through electrostatic spinning of polymer matrices in electrostatic field induced by difference of potentials between the collecting electrode and at least one spinning electrode, characterised in that it comprises the collecting electrode (5) according to any of the previous claims.