DE10352978A1 - A method for coating a continuous band of material by application of an aerosol spray has an additional alternating current electrode creating a corona discharge - Google Patents

Abstract

The band of material (2) is transported from a supply roll (1) to a take up roll (5) passing an AC electrode (8) extending the width of the band and a roller (3) to be charged by a DC electrode (9) and roller (4) before an aerosol spray (7). The corona discharge creates a chemical efect for a short period.

Description

The The invention relates to a plant for coating material webs, in which a material web to be coated at one across the width the material web extending electrode for electrical charging the web is passed in the form of a stretched band, being seen in the transport direction of the web behind this Electrode an aerosol spray is arranged, with an aerosol on the electrically charged Area of the material web sprayed becomes.

at a web can be z. B. to a plastic film, a Textile, paper or foam web as well as a felt or nonwoven web (non-woven) act.

Such a plant is in the DE 199 50 009 A1 described. Specifically, it is a device for moistening a material web. The moistening is carried out with the aid of an aerosol of finely distributed water droplets, which is sprayed on both sides on a band-shaped stretched and vertically extending portion of the web.

Around the effectiveness to increase this order, the web is previously charged electrostatically. This will be she over a grounded roller, opposite arranged as a corona charging electrode formed electrode is.

Similar Facilities are also used to make films with thin layers to provide. This can be, for example, a paint or a nanocoating act, with the example of the gas impermeability be increased by slides should. The one for it each needed Substances are sprayed onto the foil as aerosols.

However, it has been shown that the electrostatic charge, in particular a film by a device according to the DE 199 50 009 A1 is insufficient to achieve improved adhesion of the aerosol particles that are to form the coating.

The Invention is thus based on the problem of a coating system of material webs so to develop that for aerosols all types improved adhesion is achieved.

The Problem is inventively achieved in that in a plant for coating material webs according to the preamble of claim 1 in addition to the electrode which serves to electrify the foil, an AC electrode is provided on the web, which with an AC power source is connected.

As such, it is known to generate a corona discharge by means of AC electrodes, which acts on the film to be coated, thereby creating a rough microstructure and chemically activating the surface molecules of the film. Because of this pretreatment, there is good adhesion of the applied particles to the film. Such a device is for example in the DE 37 05 482 A1 described.

The special effect of the invention relates to the interaction the two electrodes, wherein by the AC electrode, a chemical surface activation done while it is by the other electrode, which is preferably a DC electrode acts as an electrical charge Foil comes. The charge attracts the particles, which then due to the Microstructure and surface activation one make firm connection with the film.

Of the special feature of the invention lies in the interaction of two coronary discharges, with a coronary discharge by a DC electrode and the other by an AC electrode is produced.

in the Principle does not matter, whether initially the discharge of the DC electrode or the AC electrode acts on the web. However, it has been shown that particularly good effects are achieved be, if at first the material web is chemically activated by an AC electrode is then electrically charged by the DC electrode becomes.

Obviously namely stick Also, the charge applied by the DC electrode charges better on the slide after it has been activated, forming so an intense electric field that leads to a particularly strong electrostatic attraction of the aerosol leads.

The Aerosol is over a wide flat nozzle that over the width of the web extends, applied to this. there the aerosol is taken up by the air stream entrained with the material web and thereby forms a kind of curtain in front of the film.

This is particularly uniform and provided with little vortex, when the system is arranged so that the web portion, on which the aerosol sprayer is aligned, runs approximately vertically. Because the air from the material then pulled down, resulting in a relatively uniform fall wind, which leads to a correspondingly uniform aerosol curtain.

to Realization of the vertical course of the material web is an upper one Deflection pulley provided. Preferably, the electrode is for electrical Charging the web, so the DC electrode, the pulley across from mounted in front of the web, as usual, the pulley grounded is.

It has proved to be advantageous, the electrode at the zenith to arrange the pulley, so that the air flow on the pulley can tear off.

It is natural conceivable to arrange both electrodes on the upper deflection roller. this leads to to a compact design. But to mutual interference too avoid, it has proven another pulley - in Transport direction of the web seen - in front of the upper pulley to arrange, opposite the other, preferably the AC electrode installed is.

The Surface activation, which is generated by the AC electrode can be exploited to be a part of the coating before charging the film apply. This concludes to the AC electrode a parallel to the web extending Canal on, in which an aerosol is introduced.

From It is also an advantage if between the AC electrode and the DC electrode disposed a discharge device on the web is: The AC electrode causes not only an activation the surface, but also an electric charge. However, this is uneven, with the unevenness not by the extra Charging can be compensated by the DC electrode, the for taken a uniform charge would effect. A discharge after the AC electrode erases the uneven charge, so that the renewed, caused by the DC electrode charging is even.

The Discharge can be passive or active, in the first case a discharge rod only grounded and in the second case with a Counter tension is applied. The discharge can be done with a discharge rod on the electrode side of the web or with two discharge bars on both Pages of the web take place.

In the following, the invention will be explained in more detail with reference to several embodiments, which show in particular the different variations of the arrangement of DC electrode, AC electrode and aerosol spray. To show the 1 - 3 different configurations.

First, on the 1 Based on which also the most important elements of the plant for coating material webs are shown, which are repeated in the representations of the other figures.

A plant for coating material webs consists of a supply roll 1 on the z. B. a film to be coated is wound. From this it is in the form of a band-shaped web 2 unwound, the material web 2 via a lower pulley 3 to an upper pulley 4 runs where it is deflected by about 180 ° and vertically in the direction of a take-up roll 5 runs on the now coated material web 2 is wound up.

For coating the material web is located in the vertical material web section 6 an aerosol sprayer 7 , Such devices are known and therefore need not be described in detail. In principle, it is a wide flat nozzle, through which the aerosol-atomized material on the width of the web 2 is blown.

To improve the adhesion, on the one hand, an AC electrode 8th and on the other hand, a DC electrode 9 intended. The AC electrode 8th is not shown in detail, connected to an AC power source, while the DC electrode 9 is connected to a DC voltage source. Both sources are high voltage sources, so that a coronary discharge is created, which on the passing material web 2 is directed so that the electrons in the discharge cloud bombard the web. The electrodes 8th . 9 are each opposite to the lower and the upper pulley 3 . 4 , which are each grounded.

Through the AC voltage electrode 8th becomes the passing material web 2 activated, so that it becomes chemically reactive. This activation will persist for some time, leaving the web 2 Before the aerosol is applied, first at the top pulley 4 through the DC electrode 9 can be electrostatically charged. The electrostatic charge causes the aerosol particles to strike the web 2 be pulled, creating a relatively uniform curtain from which the particles on the web 2 knock down and there due to their Re a strong bond.

This embodiment can be supplemented by that with the AC electrode 8th a subsequent channel is connected, in which a first aerosol is introduced, so that the material web 2 already partially coated before it is electrostatically charged.

The execution after 2 differs in that both electrodes 8th . 9 on the upper pulley 4 are arranged. The same applies to the execution after 3 However, the order of the electrodes 8th . 9 is reversed, so that first a charge and then an activation takes place.

In both cases, the AC electrode 8th As mentioned above, be provided with an aerosol introduction channel, so that the coating takes place in two stages.

In cases where initially the AC electrode 8th on the material web 2 acts, this can from a discharge device 10 (please refer 1 and 2 ), so that with the adjoining DC electrode 9 a homogeneous and uniform charge distribution is achieved.

1

supply roll

2

web

3

lower idler pulley

4

upper idler pulley

5

up roll

6

web section

7

Aerosol spray

8th

AC electrode

9

DC electrode

10

discharger

Claims (9)

Plant for coating material webs, in which a film to be coated in the form of a material web is guided past an electrode extending across the width of the material web for electrical charging of the film, an aerosol spraying device being arranged behind this electrode in the transport direction of the material web an aerosol is sprayed onto the electrically charged region of the material web, characterized in that, in addition to the electrode which serves to electrify the film, an AC electrode ( 8th ) on the material web ( 2 ) is provided, which is connected to an AC power source. Plant for coating material webs according to claim 1, characterized in that the electrode for electrically charging the film is a DC electrode ( 9 ), which is connected to a DC voltage source. Plant for coating material webs according to claim 2, characterized in that the direct current electrode ( 9 ) in the transport direction of the material web ( 2 ) seen behind the AC electrode ( 8th ) is arranged. Plant for coating material webs according to one of the preceding claims, characterized in that the plant is set up so that a material web section runs approximately vertically and that the aerosol spraying device ( 7 ) is aligned with this vertically extending material web section. Plant for coating material webs according to claim 4, characterized in that a deflecting roller lying in front of the vertical material web section for the material web ( 2 ) is provided that the pulley is grounded and that the electrodes ( 8th . 9 ) for the electrical charging of the material web ( 2 ) of the pulley opposite. Plant for coating material webs according to claim 5, characterized in that the direct current electrode ( 9 ) Opposite the zenith of the pulley. Plant for coating material webs according to one of the preceding claims, characterized in that viewed in the transport direction of the material web in front of the upper deflection roller ( 4 ) another, grounded pulley ( 3 ) is provided below the upper pulley ( 4 ) is arranged, and that the AC electrode of this pulley ( 3 ) is opposite. Plant for coating material webs according to one of the preceding claims, characterized in that the AC electrode ( 8th ) a parallel to the material web ( 2 ) extending channel connects, in which an aerosol can be introduced. Plant for coating material webs according to one of the preceding claims, characterized in that between the AC electrode ( 8th ) and the DC electrode ( 9 ) a discharge device ( 10 ) is arranged on the material web.