EP2392195B1 - Apparatus for modifying the surfaces of web, plate and sheet products using a device for generating plasma - Google Patents

Description

The invention relates to a device for modifying the surfaces of sheet, plate and sheet goods with a device for generating a plasma by means of a corona or barrier discharge at atmospheric pressure, wherein the plasma generating device is provided with an electrode and a counter electrode, wherein at least one of the electrodes consists of a hollow body of conductive material comprising a lower wall of conductive material, an upper wall and two side walls, the walls including at least one chamber having a gas inlet for introducing a gaseous medium into the chamber, wherein the bottom wall facing the commodity has at least one row of adjacent outlet openings for the medium and wherein the outlet openings are arranged such that the gas exits the outlet openings via the inwardly directed wall surface of the bottom wall transverse to the row of the outlet can flow openings, and having a transport device, to pass out the product in a direction transverse to the row of outlet openings direction of movement of the group consisting of a hollow body electrode.

Such a device is both in the WO 2007/017271 as well as in the US 2006/0222779 A1 described. The electrode and the counter electrode are arranged opposite to both sides of the web, sheet and sheet goods.

From the US Pat. No. 6,489,585 B1 It is known to perform the edges of square in cross-section electrodes rounded.

In principle, it is known that in corona or barrier discharges, plasmas also occur at atmospheric pressure. The gases introduced into the discharge zone determine the properties of the resulting plasmas. In general, the discharge is simply carried out in air and z. B. used for chemical modification of surfaces in a dry process. When treating web, sheet or sheet goods in a continuous process in air atmosphere, no special lock technology is required even at high web speeds.

However, if an off-gas composition is to be used, it must be adjusted by appropriate measures in the discharge area. In continuous processes, this requires a corresponding lock technology and a feed for the desired media into the discharge area.

For the supply of gases in the discharge area various concepts are possible. In the DE 195 38 176 A1 a device is described in which electrodes are flowed around in a housing of air, wherein the gas flow is directed in the direction of the treated surfaces.

In the WO 02/06503 A3 describes a device in which gases are passed over a porous ceramic between the electrodes of a barrier discharge.

EP 0 914 876 B1 reports a process in which a gas mixture passes through a distributor between roller electrodes is introduced, wherein the rollers are covered by the web.

Disadvantage of these methods is the indirect supply of the gases in the discharge space, which requires a very high gas consumption, especially in continuous operation, in order to achieve the desired gas composition in the discharge area. Even with the use of somewhat thicker porous materials such as textiles, sufficient gas mixing in the material is achieved with the described methods, so that a very irregular plasma is formed. The same applies to higher web speeds, in which an air cushion over the material is formed, so that even with very complex lock systems air fractions are introduced into the discharge area.

In the already mentioned above WO 2007/017271 It is therefore proposed to guide the gas through the electrode into the discharge area.

The invention is based on the object to set the desired media concentration in the discharge region with the simplest and most effective delivery, with additional cooling of the electrode is unnecessary.

To solve the problem, it is provided that the edges extending transversely to the direction of movement between the side walls and the lower wall are curved and that the average radius of curvature of the edges is greater than 8 mm, preferably greater than 10 mm and that the counter electrode in the chamber Electrode is arranged.

This requires a turbulence-free flow even at a high web speed, so that the media concentration in the gap between electrode and product remains very uniform and the entry of foreign medium is minimized.

If the counterelectrode is not positioned outside, but installed in the hollow body electrode opposite the outlet openings, the counterelectrode is thus in a chamber of the electrode, the plasma is generated in the hollow body of the electrode when the high voltage is applied and due to the overpressure in the electrode through the openings of the electrode discharged.

Preferably, the counter electrode is arranged above the outlet openings, wherein the distance of the counter electrode to the bottom wall in the region of the outlet openings is less than 1 mm. It has been shown that optimal effects can thus be achieved.

Preferably, the curvature is formed by a quarter arc, since such a curved edge on the one hand is easy to manufacture and on the other hand so that a fluidically optimal effect can be achieved.

Another advantage arises when an overpressure is built up in the chamber, so that the gaseous medium flows out of the outlet openings under pressure.

Preferably, the electrode is designed to be flat, wherein the front and back of the electrode are designed as circular sections.

The electrode is easy to produce when formed from a profile with a closed cross-section is, with the end faces are closed by caps.

The gap between the electrode and the ware is uniformly filled over its entire width with a plasma, if a plurality of rows of outlet openings are provided, which are arranged one behind the other viewed in the direction of movement of the goods. The openings are designed so that even at low flow rates, a uniform media outlet over the entire electrode width is possible.

To enable high exit velocities, the electrode is also designed for higher internal pressures (up to 6 bar). The geometry of the electrode is preferably rod-shaped with rounded or oval edges, or flat with rounded oval edges. The counterelectrode can be of any type and geometry and must be positioned opposite the outlet openings.

Preferably, the electrode is made of aluminum or E-delstahl.

The electrode may be provided with a non-conductive coating to provide the benefits of barrier discharge, even when the counter electrode is bare. This non-conductive coating can z. B. simply be an oxide layer, as occurs in the anodizing of aluminum, or a ceramic layer.

When the electrode is operated in a dielectric barrier discharge (eg with a ceramic coated roller as counter electrode) with air supply, a much more homogeneous discharge image can be produced, which can be visually observed by the disappearance of discharge filaments when the air supply is switched on becomes. When treating porous materials such as textiles, the flow of media from the electrode results in uniform treatment of the material, even in deeper areas of the tissue.

In order to be able to introduce various media into the discharge zone, it is provided that the hollow body is subdivided into a plurality of chambers extending transversely to the goods, which form a chamber system, each chamber having a connection for introducing a gaseous medium and having at least one row of adjacent outlet openings is provided for the medium, wherein all outlet openings are arranged on one side of the hollow body.

In addition to media such as pure gases, the electrode can of course also be operated with gas mixtures or with carrier gases. The carrier gases may be mixed with volatile components or suspended liquid or solid particles which are carried out of the electrode, so that the electrode can also be used for particularly effective plasma coatings.

By dividing the hollow body with a chamber system gases or carrier gases can escape with volatile or floating components at different locations of the gas electrode. So z. B. pure 1-nertgaskomponenten be directed via a chamber in the discharge region of the electrode, while a carrier gas discharges volatile components via a second chamber at the end of the discharge region, whereby z. B. fragmentation reactions of the volatile components in the plasma can be avoided or reduced.

Another embodiment of the device that does not fall under the scope of the invention provides that the counter electrode is constructed symmetrically to the electrode and is arranged opposite it, so that the outlet openings of the counter electrode and the electrode are located on opposite sides of the counter electrode and the electrode and the material is passed between the electrode and the counter electrode.

Fig. 1

ein erstes Beispiel, bei der die Elektrode ein Einkammersystem ist und die Gegenelektrode unterhalb der Elektrode angeordnet ist, wobei durch den Spalt zwischen Elektrode und Gegenelektrode die zu behandelnde Ware verläuft,

Fig. 2

ein zweites Beispiel, bei der die Elektrode ein Zweikammersystem hat,

Fig. 3

ein drittes Biespiel, bei der die Elektrode und die Gegenelektrode symmetrisch zueinander aufgebaut und gegenüberliegend angeordnet sind, und

Fig. 4

eine Ausführungsform, bei der die Gegenelektrode in der Kammer der Elektrode angeordnet ist.

The invention will be explained in more detail below with reference to four exemplary embodiments. In addition, each show in cross section:

Fig. 1

a first example in which the electrode is a single-chamber system and the counter electrode is arranged below the electrode, wherein the product to be treated passes through the gap between electrode and counter electrode,

Fig. 2

a second example in which the electrode has a bicameral system,

Fig. 3

a third Biespiel, in which the electrode and the counter electrode are constructed symmetrically to each other and arranged opposite, and

Fig. 4

an embodiment in which the counter electrode is arranged in the chamber of the electrode.

The FIG. 1 shows an electrode 1, which is designed as a hollow profile bar, which extends perpendicular to the plane of the drawing. The cross-section of the profile is rectangular, the surface of the long sides being parallel to a web 2 to be treated. Instead of a web can also be treated a sheet or sheet goods. The individual plates or sheets run successively past the electrode and thus also form a train in their sequence. In the electrode 1- thus a closed chamber 3 is formed, which extends over the width of the web 2 and is closed at the ends of the profile with caps, not shown here.

The edges between the short and long sides of the profile and in particular the web-facing edges 4, 5 are curved.

At the top of the electrode 1 facing away from the web there is a gas inlet 6.

On the underside facing the web are located in the wall of the electrode 1, three rows of gas outlets 7 in the form of nozzle-shaped outlet openings. The rows are parallel to each other and transverse to the web. 2

Because of the pressure drop in the gas outlets 7, an overpressure of up to 6 bar is applied to the chamber 3, which causes the medium flowing in through the gas inlet 6 to be uniformly distributed in the chamber 3.

A flat and compact counter electrode 8 is arranged below the electrode 1. As a result of the gap 9 formed between the electrode 1 and the counterelectrode 8, the web 2 runs in the direction of the arrow 10.

According to the Fig. 2 the electrode 1 has two chambers 3, 3 'and thus forms a two-chamber system. The chambers 3, 3 'run parallel to each other and across the web 2. Each chamber 3, 3' has its own gas inlet 6, 6 'and at least one row of gas outlets 7, 7'.

According to the Fig. 3 the counter electrode 8 is constructed symmetrically to the electrode 1 and thus also has a chamber 5a with a gas inlet 6a and gas outlets 7a. The counter electrode 8 is disposed opposite to the electrode 1. The gas outlets 7, 7a of counter electrode 8 and electrode 1 are located on opposite sides to the gap 9, through which the web 2 is passed.

According to the Fig. 4 is a flat and compact counter electrode 8 in the chamber 3 of the electrode 1 is arranged.

LIST OF REFERENCE NUMBERS

1

electrode

2

train

3

chamber

4

edge

5

edge

6, 6a

gas inlet

7, 7a

gas outlet

8th

counter electrode

9

gap

10

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Claims (9)

1. An apparatus for modifying the surfaces of web, plate and sheet products using a device for generating a plasma with the aid of a corona or barrier discharge at atmospheric pressure, wherein the plasma generation device is provided with an electrode (1) and a counter-electrode (8), wherein at least one of the electrodes comprises a hollow body made of conductive material, which comprises a lower wall made of a conductive material, an upper wall and two side walls, wherein the walls enclose at least one chamber (3), which comprises a gas inlet (6) for introducing a gaseous medium into the chamber (3), wherein the lower wall facing the products (2) comprises at least one row of exit openings (7) lying beside one another for the medium and wherein the exit openings (7) are disposed in such a way that the gas can flow to the exit openings (7) via the inwardly facing wall surface of the lower wall transverse to the row of exit openings, and with a transporting device for conveying the products in a direction of motion lying transverse to the row of exit openings past the electrode (1) comprising a hollow body, characterised in that the edges (4, 5) between the side walls and the lower wall running transverse to the direction of motion are constituted curved and that the average radius of curvature of the edges is greater than 8 mm, preferably greater than 10 mm, and that the counter-electrode (8) is disposed in the chamber (3) of the electrode (1).
2. The device according to claim 1, characterised in that the counter-electrode (8) is disposed above the exit openings and the distance of the counter-electrode (8) from the lower wall in the region of the exit openings is less than 1 mm.
3. The device according to any one of the preceding claims, characterised in that the curvature is formed by a quarter arc.
4. The device according to any one of the preceding claims, characterised in that an excess pressure is built up in the chamber.
5. The device according to any one of the preceding claims, characterised in that the electrode (1) is constituted flat, wherein the front and rear side of the electrode are constituted as a segment of a circle.
6. The device according to any one of the preceding claims, characterised in that the electrode (1) is formed from a profile with a closed cross-section, wherein the sides are closed by caps.
7. The device according to any one of the preceding claims, characterised in that a plurality of rows of exit openings (7) are provided which are disposed one behind the other viewed in the direction of motion of the products.
8. The device according to any one of the preceding claims, characterised in that the electrode (1) is provided with a non-conductive coating.
9. The device according to any one of the preceding claims, characterised in that the hollow body is split up into a plurality of chambers (3, 3') running transverse to the direction of motion of the products, said chambers forming a chamber system, wherein each chamber (3, 3') is provided with a gas inlet (6, 6') for introducing a gaseous medium and with at least one row of exit openings (7, 7') lying beside one another for the medium, wherein all the exit openings (7, 7') are disposed on a side of the hollow body.

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