EP1409775A1

EP1409775A1 - Device for the production of fibers in an electrostatic spinning method

Info

Publication number: EP1409775A1
Application number: EP02754394A
Authority: EP
Inventors: Wolfgang Czado
Original assignee: Helsa Werke Helmut Sandler GmbH and Co KG
Current assignee: Mann+hummel Innenraumfilter & Co KG GmbH
Priority date: 2001-07-25
Filing date: 2002-07-19
Publication date: 2004-04-21
Anticipated expiration: 2022-07-19
Also published as: WO2003016601A1; DE10136256B4; DE50201852D1; DE10136256A1; EP1409775B1

Abstract

Disclosed is a device for the production of fibers (6) in an electrostatic spinning method, comprising a storage vessel for a polymer solution or a polymer melt, a conveyor device (1) arranged in the storage vessel (1), at least one sputter electrode (3; 3a; 3b) or at least one sputter metal sheet and a counter electrode (5), the at least one sputter electrode or the at least one sputter metal sheet being disposed on the conveyor device (1) in such a way that the polymer solution or polymer melt conveyed out of the storage vessel by the conveyor device (1) is drained onto the at least one sputter electrode (3; 3a; 3b) or the at least one sputter metal sheet. Also disclosed is a method for electrostatic spinning of polymers using the inventive device.

Description

Device for producing fibers in an electrostatic

spinning process

The present invention relates to a device for producing fibers in an electrostatic spinning process and to a process carried out using this device.

Such devices are basically known from the prior art. In these devices, a polymer in the form of a polymer melt or in the form of a solution is introduced into an electric field and spun into fibers by the action of the electric field. An electrode usually forms a receiving device for the spun fibers, while the counter electrode is designed as a spraying electrode or spray nozzle.

Frequently, the nano and microfibers produced using such a device are not isolated, but are immediately deposited as a fleece. In this connection, the production of filter materials should be mentioned, for example. The production of a fleece by an electrostatic spinning process is e.g. known from US 4,144,553. Other devices and electrostatic spinning processes are the subject of DE 20 32 072, EP 1 059 106, US 3,994,258, US 4,323,525 and US 4,287,139.

The methods and devices known from the prior art for the electrostatic spinning of molten or solution-containing polymers are, however, in need of improvement with regard to the supply of solution or melt in the device. In particular, it is disadvantageous in the prior art that the supply of the polymer solution or melt often does not take place uniformly over the entire width of the device, which leads to an uneven work result, ie generally to an unevenly sealed and / or thick fleece. Furthermore, a supply of the polymer in a constant concentration or at a constant supply rate is often unavoidable due to the system.

It is therefore an object of the present invention to provide a further device for producing fibers in an electrostatic spinning process which avoids at least some of the disadvantages known from the prior art. A method for electrostatically spinning polymers using this device is also the subject of the invention.

The present object is achieved by a device having the features of appended claim 1 and a method having the features of appended claim 20. Advantageous embodiments of the invention are the subject of claims 2 to 19 and 21.

A particular advantage of the device according to the invention is that a uniform delivery rate of polymer is ensured over the entire working width of the device without there being any fluctuations in the polymer feed or polymer concentration.

In a special embodiment of the present invention, the at least one spray electrode or the at least one spray plate has a serrated or corrugated spray edge. It is particularly preferred here if every second tooth or shaft is bent upwards or downwards out of the plane of the spraying electrode or the spraying plate. Such a design of the spray electrode or the spray plate is particularly advantageous compared to a smooth spray edge, since the field effect is increased by the peak effect and thus e.g. a lower high voltage or potential difference between the electrodes is required.

In a preferred development of this embodiment, there are several

Spray electrodes or several spray plates arranged side by side, in particular triangular, trapezoidal, square or rounded Are shape. It is preferred here if the spray electrodes or spray plates are arranged next to one another at a distance in the range from 2 to 10 cm. On the one hand, the peak effect is most pronounced and, on the other hand, the nano and / or microfibers produced by the electrostatic spinning process can be deposited into a particularly regular nonwoven with spray electrodes or spray plates. The same applies, of course, in the aforementioned embodiment with a jagged or corrugated design of the spray electrode or the spray plate. The tips of the spikes or the apexes of the waves are spaced from each other in the range of 2 to 10 cm.

In a further embodiment of the present invention, the conveyor device is formed by a conveyor roller or a conveyor belt. The conveyor roller or the conveyor belt runs through the polymer solution or melt, with a thin film adhering to the conveyor roller or the conveyor belt. In this embodiment of the present invention, the at least one spray electrode or the at least one spray plate rests at one point on the conveyor roller or the conveyor belt, as a result of which the film of the polymer solution or melt on the conveyor roller or the conveyor belt is scraped off the spray electrode or the spray plate becomes. The polymer solution or the polymer melt runs to the spray edge on the spray electrode or the spray plate, where it sprays evenly due to the high voltage present. In an expedient development, this embodiment of the present invention has a conveyor device which is segmented corresponding to the spray electrodes or the spray plates. This ensures that the polymer solution or the polymer melt exclusively in the area of

Spray electrodes or spray plates is promoted. As a result, the surface of the polymer solution or the polymer melt exposed to the environment is kept as small as possible, so that, for example, unnecessary solvent losses are avoided. In the case of a polymer melt, the heat loss is kept low, which advantageously contributes to energy savings when operating the device according to the invention. In another, special embodiment, the device according to the invention is closed or encapsulated with a lid such that only the at least one spraying electrode or the at least one spraying plate protrudes from the device. This advantageously further reduces the evaporation of solvents or cooling of the melt.

In an alternative embodiment of the present invention, the conveying device is formed by one or more lines or line systems for conveying the polymer solution or the polymer melt from the at least one storage vessel to the at least one spray electrode or the at least one spray plate. Here are the one or more lines or

Line systems for conveying the polymer solution or polymer melt from the at least one storage vessel are preferably attached to the deepest point of the storage vessel and the polymer solution or polymer melt is conveyed through these lines or line system solely by gravity, the polymer solution or the polymer melt at the end of the lines or

Line systems emerges from these and reaches the at least one spray electrode or the at least one spray plate. This design of the device according to the invention is particularly simple in terms of construction, but at the same time keeps possible solvent and / or heat losses within limits.

In a further development of this embodiment of the invention, the conveying device further comprises a conveying pump for conveying the polymer solution or the polymer melt through the lines or line systems located on the storage vessel.

In a preferred development of this embodiment of the present invention, the one or more lines or line systems have outlet openings for the polymer solution or polymer melt in the form of nozzles, in particular in the form of regulatable or adjustable nozzles. The one or more lines or line systems are optional, including any existing nozzles are provided with a heating device, which in particular facilitates the processing of a polymer melt and the susceptibility to failure of the Device reduced. It is particularly preferred if the nozzle or nozzles have an additional solvent supply or supply line and / or an additional compressed air supply line. This enables a solvent supply to the nozzles for cleaning purposes. Alternatively or additionally, one or more brushes can be arranged on the nozzle or on the nozzles, which brushes can optionally be rotated.

The above measures serve to solve the problem of blockages or incrustations of the parts that come into contact with the solution when working with solutions. To prevent this, the measures described above make it possible to clean each individual nozzle at appropriate time intervals and thus free it from polymer residues. For this purpose, a solvent can be introduced into the nozzle by means of a corresponding supply or feed line or it can be dripped onto the nozzle tip from the outside. It is also possible to e.g. to be cleaned by means of rotating brushes or by means of a blast of compressed air, with solvent optionally being added to the compressed air.

Since the spray electrodes or spray plates are particularly subject to the problem of incrustations, in a further particularly preferred embodiment of the present invention, several spray electrodes or spray plates are arranged on a holding or transport device, the holding or transport device being designed in particular as a circulating belt or as a transport wheel, and the transport device, including the spray electrodes or spray plates at least partially immersed in a cleaning bath for the latter. During operation of the device, the transport device is then actuated at certain time intervals, ie new spray electrodes or spray plates are used for electrostatic spinning, while spray electrodes and spray plates which have already been used and are encrusted are immersed in a cleaning bath. The incrustations on the spray electrodes or spray plates can also be completely dried instead of a solvent bath and then removed by a brush or a scraper. As an alternative to this, it is possible to use spray electrodes or spray plates which can be used only once, a plurality of spray electrodes or spray plates being arranged in a feed device for the same and designed to be detachable by feed. In the operation of this embodiment, a spray electrode or a spray plate is used until there is no longer sufficient efficiency due to incrustations formed. The feed device is then actuated either in a predetermined time interval or controlled by an operator and the used spray electrode or the used spray element is released from the device according to the invention and a new spray electrode or a new spray plate is brought into an operating position for electrostatic spinning of a polymer. The particular advantage of this embodiment is that additional handling of solvents and a corresponding cleaning of the spray electrodes or spray plates can be omitted, as a result of which a higher level of operational safety is achieved, because the effort to completely clean the spray plates or

Spray electrodes is comparatively large if the quality of the product, i.e. the fibers or nonwovens produced should be ensured.

In the device according to the invention, the counter electrode is preferably formed by a rigid sheet, an electrically conductive, circumferential band or a fleece. It is particularly preferred if the counter electrode is formed by an electrically conductive, circumferential band made of wire mesh or metal foil, this band moving in particular with a carrier material on which the fibers produced by the electrostatic spinning are placed. This avoids the application of tensile forces on the carrier material. It is most preferred if the counter electrode is formed from electrospun fibers of opposite polarity. This carrier material is then simultaneously coated on the top and bottom by two spray devices with fibers of opposite polarity. This creates a much more effective filter material, since a higher charge density can be achieved and both the positive and negative charges are firmly fixed in the fibers. In particular, it is also possible to arrange a plurality of spraying devices, each having at least one spraying electrode or a spraying plate, for sequential coating of a carrier material in a single pass. This makes it possible, in particular, to spin different polymers in one operation or else

Polymer solutions of various concentrations, e.g. Form fibers of different diameters.

According to the invention, the prescribed device for electrostatic spinning of polymers is used, the spinning taking place in an electrostatic field with a potential difference between the at least one spraying electrode or the at least one spraying plate and the counter electrode in the range from 5 kV to 1000 kV. Preferably in a field from 10 kV to 100 kV and most preferably in a field from 10 to 50 kV. In a preferred embodiment, different spray electrodes or. Spray plates spun different polymer solutions or polymer melts simultaneously and / or different potential differences are applied to different spray electrodes or spray plates during spinning.

With the device according to the invention it is possible to spin water-soluble polymers, e.g. Polyvinyl alcohol, polyvinyl pyrrolidine, polyethylene oxide and its copolymers, cellulose and its derivatives, starch and mixtures of these polymers. Polymers which are soluble in organic solvents can also be spun in the device according to the invention. Polystyrene, polycarbonate, polyvinyl chloride, polyacrylate, polymethacrylate, polyvinyl acetate, polyvinyl acetal, polyvinyl ether, polyurethane, polyamide, polysulfone, polyether sulfone, polyacrylonitrile, cellulose derivatives and mixtures of these polymers are particularly worth mentioning here. Polymers spinnable from the melt are e.g. Thermoplastics such as polyolefins, polyester, polyoxymethylene, polychlorotrifluoroethylene,

Polyphenylene sulfide, polyaryl ether ketone, polyvinylidene fluoride and mixtures of these polymers. To increase the charge in the fibers, the Polymer solution or the polymer melt substances are added which are able to take up or stabilize a charge. In particular, these are metal, without carbon or graphite powder, dyes (especially those with amino groups that can resonate with delocalized electron systems; metallocenes, amino and phosphines. Powders of other, electrically conductive materials such as electrically conductive polymers and ceramics are also suitable ,

Likewise, further additives to the polymer solutions or to the ambient air of the device are possible, which have an advantageous effect on the product or the spinning process.

The present invention is explained in more detail below with reference to the attached figures and using examples. Show it:

Figure 1 is a schematic representation of a first embodiment of the device according to the invention;

Figure 2 is a schematic plan view of a conveyor roller with adjacent spray electrodes or spray plates;

Figure 3 is a schematic representation of an embodiment in which the

Spray electrodes or spray plates are arranged on a transport device;

FIG. 4 shows a second embodiment of the present invention, in which the spray electrodes or spray plates are arranged on a transport wheel and pass through a cleaning bath; and

Figure 5 shows an embodiment in which the spray electrodes or

Spray plates can be detached from the device and disposed of after one use. FIG. 1 shows a first embodiment of the device according to the invention for the electrostatic spinning of polymers. In particular, a conveyor device 1 formed by a conveyor roller is arranged in a storage container for the polymer solution or the polymer melt 2, the conveyor roller 1 conveying polymer solution or polymer melt from the storage vessel and transferring it to the adjacent spraying electrode 3, generally also referred to as a spraying plate. A high-voltage generator 4 generates the potential difference required between the spray electrode 3 and the counter electrode 5, so that the polymer contained in the storage vessel 2 is spun into fibers 6 in the electrostatic field.

FIG. 2 shows a schematic top view of a conveyor roller 1 with spray electrodes 3 attached. In the illustrated embodiment, a plurality of spray electrodes 3 are arranged next to one another at a distance.

FIG. 3 shows an embodiment of the present invention, in which the spray electrodes 3a are arranged on a conveyor belt 7. In electrostatic spinning, i.e. during operation of the device, polymer solution or polymer melt runs from line 9 onto spray electrode 3a, which has a corresponding potential difference with respect to the counter electrode, so that fibers 6 are detached from spray electrode 3a.

The embodiment shown in Figure 4 is comparable to that previously described. Here only one transport wheel 10 is shown instead of the conveyor belt 7.

FIG. 5 finally shows a schematic illustration of an embodiment in which the spray electrodes 3b are contained in a feed device (not shown) along the line 9 for the supply of the polymer solution or polymer melt. The spray electrodes are moved in the direction of the arrow in the feed device until the first spray electrode 3 b reaches the operating position. Then polymer solution or polymer melt is conveyed through line 9 to the spray electrode 3 b located in the operating position. Since this is for Counter electrode has a corresponding potential difference

Detached polymer fibers. After an appropriate degree of incrustation has been determined by an operator, this person can actuate the feed device and ensure that the used spray electrode is released from the device, whereupon it falls into a collecting container 11 and a new spray electrode 3 b takes the place of the old one ,

example 1

A 5% polystyrene solution in dichloromethane is mixed with 0.5 rhodamine G6 and spun at 50 revolutions of the conveyor roller (diameter 7 cm) per minute. The spray plates are directly opposite each other at a distance of 20 cm, the carrier fleece (micro-spunbond polypropylene fleece with 60 g / m ² ) is in the middle at a speed of 0.5 m / min. passed. A high voltage of + or - 15 kV is applied to the spray plates. The carrier fleece coated in this way has a deposition rate of 50% of the 0.3-0.5 μm fraction of NaCl. Measured at a flow rate of 50 l / min. and a flow area of 100 cm ² . The air resistance of the carrier fleece was increased under these conditions by the coating from 8 to 16 Pa.

Example 2

A 10% polystyrene solution in ethyl methyl ketone mixed with 0.5 g / l crystal violet and spun at 50 revolutions of the conveyor roller (diameter 7 cm) per minute. The spray plates are directly opposite each other at a distance of 20 cm, the carrier fleece (micro-spunbond polypropylene fleece with 60 g / m ² ) is in the middle at a speed of 0.5 m / min. passed. A high voltage of + or - 15 kV is applied to the spray plates. The carrier fleece coated in this way has a deposition rate of 65% of the 0.3-0.5 μm fraction of NaCl. Measured at a flow rate of 50 l / min. and a flow area of 100 cm ² . The air resistance of the carrier fleece was increased under these conditions by the coating from 8 to 16 Pa. Example 3

A 5% polystyrene solution in dichloromethane is spun with 5 g / l chlorine and at 60 revolutions of the conveyor roller (diameter 7 cm) per minute. The spray plates are directly opposite each other at a distance of 20 cm, the carrier fleece (micro-spunbond polypropylene fleece with 60 g / m ² ) is in the middle at a speed of 0.5 m / min. passed. A high voltage of + or - 15 kV is applied to the spray plates. The carrier fleece coated in this way had a deposition rate of 60% of the 0.3-0.5 μm fraction of NaCl. Measured at a flow rate of 50 l / min. and a flow area of 100 cm ² . The air resistance of the carrier fleece was increased under these conditions by the coating from 8 to 15 Pa.

Claims

claims

1. Device for producing fibers (6) in an electrostatic

Spinning process with a storage vessel (2) for a polymer solution or a polymer melt, a conveyor device (1) arranged in the storage vessel, at least one spraying electrode (3; 3a; 3b) or at least one

Spray plate and a counter electrode (5), the at least one spray electrode (3; 3a; 3b) or the at least one spray plate being arranged on the conveying device (1) in such a way that the conveyed by the conveying device (1) from the storage vessel (2) Polymer solution or polymer melt runs on the at least one spray electrode (3; 3a; 3b) or on the at least one spray plate.

2. Device according to claim 1, characterized in that the at least one spray electrode (3; 3a; 3b) or the at least one spray plate has a serrated or corrugated spray edge, in particular every second prong up or down from the plane of the spray electrode ( 3; 3a; 3b) or the spray plate is bent out.

3. Device according to claim 1, characterized in that a plurality of spray electrodes (3; 3a; 3b) or a plurality of spray plates are arranged side by side and in particular are triangular, trapezoidal, square or rounded in shape.

4. The device according to claim 3, characterized in that the spray electrodes (3; 3a; 3b) or spray plates are arranged side by side at a distance in the range of 2 to 10 cm.

5. Device according to one of the preceding claims, characterized in that the conveyor (1) is formed by a conveyor roller or a conveyor belt.

6. The device according to claim 5, characterized in that the conveyor (1) corresponding to the spray electrodes (3; 3a; 3b) or the spray plates is segmented.

7. Device according to one of the preceding claims, characterized in that the storage vessel is closed with a lid so that only the at least one spray electrode (3; 3a; 3b) or the at least one spray plate protrudes from the device.

8. Device according to one of claims 1 to 4, characterized in that the conveying device (1) of one or more lines or line systems for conveying the polymer solution or polymer melt from the at least one storage vessel to the at least one

Spray electrode (3; 3a; 3b) or the at least one spray plate is formed.

9. The device according to claim 8, characterized in that the conveyor (1) further comprises a feed pump.

10. The device according to claim 8 or 9, characterized in that the one or more lines or line systems have outlet openings for the polymer solution or polymer melt in the form of nozzles, in particular in the form of adjustable or adjustable nozzles.

11. The device according to one of claims 8 to 10, characterized in that the one or more lines or line systems are provided with a heating device.

12. The device according to one of claims 8 to 11, characterized in that the nozzle or nozzles have an additional solvent supply or supply.

13. The device according to one of claims 8 to 12, characterized in that the nozzle or nozzles have an additional compressed air supply line.

14. Device according to one of claims 8 to 13, characterized in that the conveyor for cleaning the nozzle or nozzles has one or more brushes.

15. Device according to one of the preceding claims, characterized in that a plurality of spray electrodes (3; 3a; 3b) or spray plates are arranged on a holding or transport device (7; 10), the holding or transport device (7; 10) as a circumferential belt or a transport wheel is formed and the transport device (7; 10), including the

Spray electrodes (3; 3a; 3b) or spray plates, at least partially in one Cleaning bath (8) for the spray electrodes (3; 3a; 3b) or spray plates immersed.

16. The device according to one of claims 1 to 14, characterized in that a plurality of spray electrodes (3; 3a; 3b) or spray plates are arranged in a feed device for the same and are detachably formed by feed.

17. Device according to one of the preceding claims, characterized in that the counter electrode (5) is formed by a rigid sheet, an electrically conductive, circumferential band or a nonwoven.

18. Device according to one of the preceding claims, characterized in that at least two spray electrodes (3; 3a; 3b) or spray plates are arranged opposite one another in a fleece arranged or running between them as a counter electrode (5).

19. Device according to one of the preceding claims, characterized in that at least two spraying devices, each having at least one spraying electrode (3; 3a; 3b) or a spraying plate, are arranged one behind the other for the sequential coating of a carrier material.

20. A method for electrostatically spinning polymers using a device according to one of claims 1 to 19, characterized in that the spinning in an electrostatic field at a potential difference between the at least one spray electrode or the at least one spray plate and the counter electrode in the range of 5 kV to 1000 kV takes place, preferably in a field of 10 kV to 100 kV and most preferably in a field of 10 to 50 kV.

21. The method according to claim 20, characterized in that different spray electrodes or spray plates different

Polymer solutions or polymer melts are spun simultaneously and / or different potential differences are present on different spray electrodes or spray plates during spinning.