EP2096209A1 - Coating station - Google Patents

Abstract

A vacuum deaerator (12) has a pipeline (22) for supplying the deaerated coating agent (2a) to deaeration unit (34). A coating agent processing station (13) comprising a mixer (13.1) and storage container (13.2) are connected to upstream of vacuum deaerator. The vacuum deaerator is segmented into upper region (16) for performing deaeration of coating agent, and lower region (20) forming an additional work space (21) for storing the deaerated coating agent.

Description

The invention relates to a coating station for coating a running paper, cardboard or other fibrous web with at least one liquid to pasty application medium, comprising a above the fibrous web and spaced therefrom arranged applicator head of a curtain applicator, the at least one application medium in the form of a curtain emits to the fibrous web, the applicator a vacuum deaerator for degassing or venting of at least one application medium is connected upstream, wherein a discharge line for degassed application medium, a vacuum generating device and a discharge line for separated air or gas is present and the vacuum deaerator Mixer and / or reservoir containing processing station is connected upstream.

All coating stations need such a treatment station. High gas or air contents in the coating media, ie in the coating colors usually lead in connection with high coating machine speeds to the dreaded "skip coating", ie to holes and scratches in the applied coating, which of course adversely affects the quality of the coating layer.
High gas contents result primarily from the coating color formulation, the coating color preparation and the circulation, the already mentioned machine speed and the used or intended application system and from other influencing variables.

In conventional coating methods, such as the blade or film coating, coating color (in general terms, the application medium) is applied in multiple excess and then metered with a doctoring element.
The modern curtain coating eliminates the dosage because there is no excess. That is, when curtain coating only the amounts are applied, which should ultimately remain on the substrate. Consequently, the amounts of ink that must be supplied to the curtain applicator are very low. However, the curtain coating requires a nearly complete venting of the coating color because of the Commissioned and delivered curtain is very sensitive. Gas or air contents also cause problems in the system before the actual coating.
The applicant's company has therefore submitted proposals such that the largest possible surface area of the medium to be degassed or vented is created, which can improve the venting effect. In addition, the venting is carried out under the influence of a vacuum. Reference is made to DE-A1-10 2005 060 848, in which the degassing or venting is described in a vacuum deaerator. To improve the venting effect, a vent in a cyclone breather is provided in front of the vacuum breather. The deaerated application medium is preferably provided for a curtain coating process.
In the DE-A1 103 52 807 is also described a solution for curtain coating, in which two successively arranged vacuum deaerator are provided.
From the DE-A1 10 2005 060 853 . is a vacuum deaerator with built-in cascades and out of the DE-A1 10 2007 000 705 , .... 706, ... 708. are built-in turntable with baffle arrangements known.

When painting the curtain, it is also necessary to keep the system clean. Especially with a job media change a meticulous, time-consuming cleaning is required. In the stated known solutions, the cleaning and the device overhead and also medium losses in grade change is very high.

It is therefore an object of the invention to provide a compact coating station for venting or degassing, in which the disadvantages of the prior art do not occur.

The object of the invention is achieved with the features of the device claim 1.

According to the invention it is provided that the known per se vacuum deaerator additional work space (without internals) contains.
The otherwise necessary additional locally close to the commissioned work container - to achieve a short line path - is completely omitted according to the invention, which is why the required working volume is integrated into the here slightly enlarged vent container.

The creation of this additional working space is achieved by dividing the total volume of the deaerator into two sections.
The upper area serves for ventilation. In this upper area so the medium to be vented is surrounded by the gas phase.
The lower area, so the additional working space is provided for storing the vented medium and is filled by a level control in operation to the desired level completely with the application medium. The following commissioned work can work with this deaerated discharge medium present here. This room contains nearly 100% application medium. as a memory. The required application medium is removed via a discharge pump as required. In this case, such a regulation takes place according to which the medium to be deaerated is introduced into the upper area and is vented there. This deaerated medium then refills the lower area.
The advantage of this solution is that the storage made here takes place under venting pressure, whereby a consistently good quality of the venting of the application medium, ie the coating color, can be achieved.

A very useful embodiment of the coating station is obtained by, for example, known cascade-like installations with eg turntables, return plates, etc., which perform a multiple or stepwise degassing or venting are arranged in the upper region of the venting container. The application medium is existent only as a thin film or color droplets. The volume of this upper area is filled only by about 5% liquid application medium plus solids and about 95% gas phase (air and / or water vapor) in this embodiment.

• insgesamt weniger Platzbedarf
• weniger Rohrleitungs- und Behälteraufwand
• verkürzte Reinigungszeiten
• geringe Farbverluste bzw. weniger streichfarbenhaltige Abwässer
• geringe Kosten
• bessere Entlüftungswirkung, da das Auftragsmedium auch im Standby-Betrieb unter Vakuum steht.

As advantages arise in the inventive solution with integrated in the vent working space:

• overall less space
• less piping and container effort
• shorter cleaning times
• low color losses or less coating-containing wastewater
• low cost
• better venting effect, since the application medium is also in standby mode under vacuum.

The coating station according to the invention can expediently be further developed by opening at least one supply line from the at least one application medium processing station, as well as at least one return line from the curtain application unit, directly into the at least one vacuum deaerator.

If this is referred to as a "direct" cycle, this means that filters, measuring points, such as gas content gauges, valves, pumps, pulsation dampers, other pipe bends, etc., can nevertheless be integrated into this cycle.
The existing in the prior art additional work container (which is located there near the commissioned work and the previously also included the return of the breather) is said as completely omitted.

A particular advantage is the only short return between the commissioned work and the deaerator. Under reflux, the medium content, which is kept away from the edge of the web, and is returned via a bypass line and such medium, which is released in coating pauses further from the commissioned work, collected and returned, to understand.

The short return allows thus that the recirculated application medium can be degassed or vented very quickly before it comes back to a thorough mixing.

• weniger Auftragsmedium (z.B. Streichfarbe) im System,
• schnelle Auftragsmediums- Wechselzeiten bei Sortenwechsel möglich,
• weniger Mediumsverluste treten auf,
• schnellerer Start des Auftragsvorganges ist möglich,
• geringer Reinigung- und Vorrichtungs- (Maschinen-) Aufwand.

Further advantages are:

• less application medium (eg coating color) in the system,
• fast application medium change times possible when changing grades,
• less medium losses occur
• faster start of the order process is possible
• low cleaning and device (machine) effort.

In order to avoid the entry of air is in the return line, i. before the recirculated medium fed back to the vacuum vent, an idle protection or accumulation control provided. This comprises a collection element, e.g. a collection container of low volume, which is followed by a control valve.

Incidentally, in the case of a plurality of application media or coating colors to be applied, for example for producing double layers by means of a multi-layer curtain application unit, the coating station may comprise a plurality of mixers and possibly a plurality of associated storage containers.

Since each mixer and the said reservoir can be located outside the coating station, even outside the building accommodating the coating station, in the case of separate working containers no longer present according to the invention, a shortened circulation from the mixer or storage container to the ventilator is particularly significant.

There may be at least one deaerator per medium to be applied. It is also possible to use several deaerators for only a single application medium. The latter option makes sense for very wide machines.

Another very advantageous embodiment variant of the coating station according to the invention results from the fact that their individual units, such as vacuum deaerator, filters and measuring devices are mounted on a common frame. This makes it possible to create a very compact workstation. This leaves Add to existing paper manufacturing machines and expand them again. Overall, the maintenance, cleaning and machinery costs are much lower than before. In addition, the accessibility to the individual units is improved and also created a location near the commissioned work.
If you have more than one job media, you can have more than one frame.

With regard to the residence time and the venting effect, it is advantageous if the working space (lower area) of the vacuum deaerator has a working volume of about 100 to 2,000 l, preferably 200 to 1,500 l of medium.

It is also advantageous if a filter is installed in the discharge line for the vented application medium and / or in the return line between the vacuum venting container and the commissioned work.
For example, commercially available, relatively inexpensive and effective cartridge filters or rotary filters are available.

In order to be able to achieve an even further venting, it is often advantageous if at least one membrane degassing device is installed in the return line between the vacuum venting container and the applicator unit. This can be installed before and / or behind an existing filter.

Also useful is the installation of flow and air content measuring instruments after the vacuum-deaeration tank. Appropriate are those that work on a sonar basis. For example, such devices are available on the market under the name "Sonartrac".

It should be mentioned that the curtain applicator is both a single-layer, as well as a multi-layer curtain application to a paper carton or other fibrous web is possible. Accordingly, according to the number of applied to the fibrous web application media or coating color layers, a corresponding number of vacuum vents and mixers and / or Reservoirs be provided per to be vented coating color. But this also means that a single vent tank, a single mixer and reservoir can also serve several supply chambers of the commissioned work.

The advantage of the coating station according to the invention is that it is on the one hand very compact and still requires little space, less cleaning and device overhead, and on the other hand that when changing grades coating color losses are lower than before.

• Figur 1 : eine erste Variante einer kompakten Streichstation
• Figur 2 : eine zweite Variante einer kompakten Streichstation

The invention will be explained in more detail by means of exemplary embodiments.
In a schematic representation:

• FIG. 1 : a first variant of a compact coating station
• FIG. 2 : a second variant of a compact coating station

FIG. 1 shows a compact coating station 1 for coating a running in the direction L paper, cardboard or other fibrous web 2 with a liquid to pasty application medium. 3
The coating station 1 comprises a curtain applicator 4 with a curtain application head 5 arranged above the fibrous web 2 and spaced from it. The application head 5, which delivers the application medium (ie a coating color) 3 in the form of a curtain 6 to the fibrous web 2, is Machine-width executed.
The application head 5 has, for each application medium 3 to be applied for a multi-layer application, its own application chamber 7a to 7n, which in each case merges into a supply gap 8a-8n with a corresponding exit nozzle 9a-9n. The discharge nozzle (s) opens (s) on the surface 10 of the example in the form of a nozzle block (slide, ie, Gleitschichtdüse trained application head 5, wherein in multi-layer order the media discharged from the outlet nozzles 9a - 9n superimposed on the surface 10 and a create multi-layered curtain. The draining curtain 6 then generates an application medium layer 11 corresponding to the desired number of application layers on the fibrous web 2.

The applicator 4 or the applicator head 5 is preceded by a vacuum vent 12, which in turn is preceded by a coating medium processing station 13. This application medium processing station 13 comprises at least one mixer 13.1 and at least one storage container 13.2. The mixer 13.1 contains a strong stirrer and usually also has several feeds. The storage tank is used only for storage of the respective application medium and contains only a simple agitator for circulation. Mixer and reservoir can be far apart from the commissioned work spatially. Accordingly long then the connecting pipes are to be executed.

With this prepared in the station 13 medium 3 of the vent tank 12 is filled via a feed line 14 and a pump 15 directly.

The preparation of the application medium can be carried out continuously, which is preferably done without reservoir 13.2. The application medium is fed directly from the mixer 13.1 from the breather 12.

The preparation of the application medium can also be discontinuous, which is referred to as "batchwise". For this purpose, but works with the reservoir 13.2, from which then the application medium is fed directly to the breather 12.
From the FIG. 1 can be removed that the vacuum vent 12 is provided in its upper portion 16 with cascade-like fittings 17 for multiple degassing or venting of the application medium 3. These cascaded internals 17 are formed as a turntable 17a and are driven via a common motor 18 via a vertical shaft 19. In this case, a speed of about 1500 min ^{-1 is} reached. As a result of the rapid rotation, the application medium 3 to be deaerated is thrown from each turntable 17a or each cascade outwards to the container wall 12a, bounces there and then passes from there via oblique guides 17b down to the next turntable, whereby the application medium 3 is further vented in the same mode. This takes place until the partially degassed application medium has reached a lower region 20 of the venting container 12.

This area 20 serves as an additional working space 21. It has a working volume of on average about 1000 l of medium (per ventilator), which is directly available for the commissioned work. The vacuum deaerator 12 is therefore located very close to the commissioned work 5 and also takes on its return. These very short cycles from the mixer / reservoir to the breather and the commissioned work to the breather are very beneficial.

The almost completely deaerated application medium 3a is fed via a discharge line 22 to the applicator 5 or the curtain application head so to speak bubble-free by means of a discharge pump 23.

Between the vacuum vent 12 and the applicator head 5 there is still a filter 24 in the example shown, i. a commercial cartridge filter installed, so that impurities in the commissioned work are almost impossible, creating a high-quality and uniformly closed trained application layer 11 is achieved on the fibrous web 2.

It should be mentioned that in the example shown in the discharge line 22 immediately after the vacuum vent 12 and before the filter 24, an air content measuring device 25 is installed.
In addition, at the top of the breather 12, a vacuum generating device 27 and a discharge line 28 for separated air or gas and a Leerlaufabsicherung 29 in an outgoing from the commissioned work 4 and opening into the head of the vacuum vent 12 return line 26 is present. The idle protection 29 includes a back-up control with a collecting element 29.1 (eg small container) and a downstream control valve 29.2 or entry pump.

The vacuum deaerator 12 and other structural units, such as filter 24 and measuring point 26, etc., are otherwise mounted on a common frame 30, so that there is a close-spaced, easy vorzumontierende compact workstation. Of advantage here are the short cycles of the medium and also the associated pipe work.
For example, three media to be applied, three frames 30 could be present.

In FIG. 1 is also shown that at least one Membranentgasungsvorrichtung 34 is installed in the discharge line 22 for the deaerated application medium 3a between the vacuum vent tank 12 and the curtain coater 4.

Said Membranentgasungsvorrichtung 34 may be installed before and / or after the filter 24. In the FIG. 1 Therefore, the presence of a second Membranentgasungsvorrichtung 34 is shown in dashed lines. This additional degassing works, as the name implies, with a membrane module consisting of a single membrane or a plurality of membranes for the separation of gas, in particular dissolved gas from the coating medium. The membrane is preferably made of hydrophobic material.

Add is that shown in the FIG. 1 an example with a single-layer order of the application medium 3 (see supply via line 22 to the middle application chamber 8 and bypass line 26 from this application chamber back into the breather 12) is shown. This order could also be multi-layered, for example, two-, three- or n-layered, which is why in these cases, the number of application medium chambers with feed columns and outlet nozzles and the number of breather 12, mixer 13.1 and reservoir 13.2 could be increased accordingly.
For example, only a single vacuum venting container 12 for the application medium 3 is shown.

In FIG. 2 a further variant of the coating station 1 is shown. It essentially corresponds to that of FIG. 1 , which is why the figures are also essentially those of FIG. 1 corresponds and a corresponding explanation is not repeated here. Only in the return line 26, starting from the commissioned work 4 to the breather 12, a further filter 31 incorporated, the same time as a collection container serves. This filter 31 may be any known filter, such as a rotary filter or a cartridge filter. But other designs are also possible.

Before the breather 12, a control valve 32 is installed in the said line 26, which serves a controlled dosing of the application medium. It regulates the level in the filter 31 or the level in a pipeline.
The filter 24, however, only acts as a so-called police filter and is of smaller design.
In FIG. 2 In addition, a dashed line further supply line 33 is shown, which branches off from the feed line 14 in the breather 12 (solid line) and leads into the filter 31. This feed can alternatively be used to additionally guide fresh application medium or fresh coating color from the application medium preparation station 13 into the filter 31. After filtering, the vacuum deaerator 12 is supplied with this filtered application medium via the said line 26 and the control valve 32, as stated, instead of the direct feed line by means of a continuous feed line 14.

Not shown, but optionally applicable is the integration of a heat exchanger module and temperature-controlled piping at least one point in the system.

Experiments were carried out with the coating station according to the invention, wherein as a coating medium, for example, a microcapsules contained Strechfarbe having a solids content of 32% and a viscosity of 240 mPas was vented. Before deaeration, the gas content in the coating color was 2-25% and after deaeration less than 0.2%.

LIST OF REFERENCE NUMBERS

1

coating station

2

Fibrous web

3

application medium

4

Curtain applicator

5

Curtain applicator head

6

curtain

7a-7n

application chamber

8a-8n

feed gap

9a-9n

exhaust nozzle

10

surface

11

Application medium layer

12

Vacuum Deaerator

12a

Container inner wall

13

Application medium preparation station

13.1

mixer

13.2

reservoir

14

supply line

15

pump

16

upper area

17

cascade-like installations

17a

turntable

17b

oblique guides

18

engine

19

vertical wave

20

lower area

21

additional work space

22

withdrawal line

23

discharge pump

24

filter

25

measuring device

26

bypass line

27

Vacuum generator

28

Discharge line for separated air or gas

29

Idle Protection

29.1

collecting element

29.2

control valve

30

frame

31

filter

32

control valve

33

supply

34

Membranentgasungsvorrichtung

L

direction

Claims (15)

Coating station (1) for coating a running paper, board or other fibrous web (2) with at least one liquid to pasty application medium (3), comprising a above the fibrous web (2) and spaced from her applicator head (5) of a curtain Applicator (4), which delivers the at least one application medium (3) in the form of a curtain (6) to the fibrous web (2), the applicator (4) a vacuum vent (12) for degassing or venting of at least one application medium (3), wherein the vacuum vent (12) has a vent line (22) for degassed application medium (2a), a vacuum generator (27) and a discharge line (28) for separated air or gas and the vacuum vent ( 12) a mixing medium (13.1) and / or reservoir (13.2) containing application medium processing station (13) is connected upstream,
characterized in that
the vacuum deaerator (12) includes an additional working space (21) such that the vacuum deaerator (12) is divided into two portions of its total volume, the upper portion (16) serving to deaerate the application medium (3) and the lower area (20) forms the additional working space (21) for storing the vented application medium (3a). Coating station (1) according to claim 1,
characterized in that
the upper region (16) of the vacuum ventilator (12) is provided with cascade-like internals (17) for degassing or venting. Coating station (1) according to claim
characterized in that
the discharge line (22) for degassed application medium (3a) branches off from the lower region (20) of the vacuum deaerator (12) and the vacuum generating device (27) via a discharge line (28) for separated from the at least one feed line (14) from the at From the curtain applicator (4), each directly into the upper area (16) of the vacuum vent (12) open. Coating station (1) according to at least one of the preceding claims,
characterized in that
the additional working space (21) has a working volume for the application medium of approximately 100 to 2000 l, preferably 200 to 1000 l. Coating station (1) according to at least one of the preceding claims,
characterized in that
in the discharge line (22) for the deaerated application medium (3a) between the vacuum vent tank (12) and the curtain coater (4) a filter (24) is installed. Coating station (1) according to claim 5,
characterized in that
in the discharge line (22) for the deaerated application medium (3a) between the vacuum vent tank (12) and the curtain coater (4) at least one Membranentgasungsvorrichtung (34) is installed. Coating station (1) according to claim 6,
characterized in that
at least one membrane degassing device (34) is installed before and / or after the filter (24). Coating station (1) according to at least one of the preceding claims,
characterized in that
in the discharge line (22) between the vacuum vent (12) and the commissioned work (4) a measuring device (25), in particular for gas or
Air content measurement is installed. Coating station (1) according to at least one of the preceding claims,
characterized in that
in at least one of the return lines (26) starting from the commissioned work (4) and opening into the vacuum vent (12) a filter (31) is installed. Coating station (1) according to claim 7 and / or 9,
characterized in that
as a filter (24, 31) a commercial cartridge filter or rotary filter is provided. Coating station (1) according to claim 9 or 10,
characterized in that
in the filter (31) a supply line (33) for fresh application medium from the mixer (13.1) and / or reservoir (13.2) containing treatment station (13) opens, and that in the filter (31) filtered application medium via the line (26) and by means of valve (32) in the vacuum vent (12) can be introduced. Coating station (1) according to at least one of the preceding claims,
characterized in that
fresh application medium from the mixer (13.1) and / or reservoir (13.2) containing treatment station (13) only via the line (14) in the vacuum vent (12) can be introduced. Coating station (1) according to at least one of the preceding claims,
characterized in that
in the return (bypass) line (26) an open circuit protection (29), comprising a collecting element (29.1) and a control valve (29.2) is installed. Coating station (1) according to at least one of the preceding claims,
characterized in that
at least one vacuum deaerator (12) is provided per application medium (3) to be deaerated Coating station (1) according to at least one of the preceding claims,
characterized in that
the vacuum deaerator (12) and filter (24) and measuring means (25) are mounted on a common frame (30).

Images