EP3574144B1 - Curtain coater and process for application of an application medium - Google Patents

Description

The invention relates to a curtain application device according to the preamble of claim 1 and a method for coating a running material web, in particular a fibrous web according to the preamble of claim 10.

When producing fibrous webs such as paper or cardboard webs, a coating, a so-called coating, is often applied to one or both sides of the material web to improve the surface properties. Coating using a curtain application system has become established for this purpose in recent years. A thin curtain of a liquid or pasty medium is deposited from a nozzle onto the material web under the influence of gravity.

In order to ensure that the coating medium is applied as evenly as possible, disruption of the thin curtain must be avoided as far as possible.

Such a curtain is particularly susceptible to air currents. The curtain is particularly sensitive in applications where a large curtain height is required or desired, or where the flow rate of coating color is low.

Air currents occur in many places around a paper machine.

For example, the material web itself carries drag air, which can disrupt the curtain. Various devices for removing such air boundary layers are known from the state of the art. Examples of this are the EN 10 2008 040 419 as well as the EN 10 2008 040 405 cited.

However, a large number of air currents occur that are not induced by the moving material web. The causes of such currents can be moving parts of the machine, but also the hall ventilation or the movements of the operating personnel. In order to keep such air currents away from the curtain, the curtain application units were enclosed in the past, for example in the EP1 538 263 However, such an enclosure has some disadvantages. Firstly, the enclosure must be relatively large so that the operating personnel can access the coating unit for inspection and maintenance. Such a large enclosure not only requires a correspondingly large amount of space in the machine hall, but also entails significant costs. Another disadvantage is that the operating personnel must enter the enclosure for maintenance and inspection. There is a risk that the movements of the operating personnel will generate air currents within the enclosure, which can disrupt the curtain.

The object of the present invention is therefore to propose a curtain application device in which the curtain remains largely unaffected by air currents even with a greater curtain height or a smaller application quantity of application medium.

A further object of the invention is to enable maintenance and control of the curtain application unit so that the curtain is not influenced at all or only to a very small extent by the movements of the operating personnel.

The object is completely achieved by a curtain application device according to the characterizing part of claim 1, as well as a method for coating a running material web according to the characterizing part of claim 10.

A curtain application unit is provided for applying a liquid or pasty application medium to at least one surface of a running material web, in particular a fibrous web.

The curtain applicator comprises an application nozzle, in particular a slot nozzle, which is suitable for applying a single or multi-layer curtain to the surface of the material web under the influence of gravity and possibly other forces. The curtain applicator also comprises a stripping device which is suitable for keeping the air carried along with the material web away from the curtain. According to the invention, at least one further blocking device which is suitable for keeping air movements of the ambient air away from the curtain.

The additional locking device according to the invention ensures that the curtain remains largely unaffected by air currents even with a greater curtain height.

As will be explained later, there are a wide range of options for the design and arrangement of the additional locking device, so that the curtain application unit can be adapted to the conditions of the installation situation, the path of the material web, etc., so that maintenance and inspection of the curtain application unit is easy without the curtain being significantly influenced by the movements of the operating personnel.

In particular, the invention makes it possible to dispense with the otherwise usual complete enclosure of the curtain coating unit together with part of the running material web. This significantly simplifies the design and installation of the curtain coating unit in a coating system and also significantly reduces the costs involved.

In general, all nozzles commonly used in curtain application can be used as application nozzles. The most common types are probably the so-called "slot dies", where the application medium emerges from a slot that is usually the width of the machine and can fall freely onto the material web. So-called "slide dies" are also often used. With this type of application nozzle, the application medium first runs a certain distance over an inclined surface before it falls freely onto the material web.

The application nozzles within the scope of this invention can also be suitable for applying single or multi-layer curtains.

However, the invention is not limited to these types of nozzles.

Advantageous embodiments of the invention are described in the subclaims.

For example, it can be provided that the distance between the opening of the application nozzle and the material web is at least 100 mm, preferably at least 200 mm, particularly preferably at least 300 mm. With such an embodiment, the drop height of the curtain during curtain application is comparatively very large. The curtain is also very susceptible to disturbances, in particular to air movements in the ambient air. The advantageous effect of the invention is particularly great with such an embodiment.

Furthermore, it can advantageously be provided that the at least one further blocking device is arranged in front of the application nozzle in the running direction of the material web.

In a particularly advantageous embodiment, the distance between the additional barrier device and the application nozzle can be less than 150 cm, in particular less than 100 cm, particularly preferably between 80 cm and 50 cm. This can, for example, reduce the risk of air movements being generated in the space between the additional barrier device and the curtain application device, which could have a disruptive effect on the curtain.

In particular, such a close arrangement can prevent operating personnel from being able to stay between the additional locking device and the curtain application unit during operation.

In a preferred embodiment, it can be provided, for example, that the at least one further blocking device comprises a plate which is attached to or in the immediate vicinity of the application nozzle and extends essentially parallel to the curtain. Such a plate can be attached before or after the curtain, viewed in the direction of travel of the material web. In a further, particularly preferred embodiment, a further plate can also be provided which is attached to or in the immediate vicinity of the application nozzle. In this case, one plate will often be provided before and the other plate after the curtain. In particular, it can be provided that one or both of these plates are provided at a distance from the curtain of less than 100 mm, preferably less than 50 mm.

In this embodiment of the invention, an extremely compact design of the curtain application unit is possible.

It is provided that the further blocking device has means for generating an air shield, comprising one or more air nozzles.

In particular, it can also be provided that the flow direction of the air of the air shield has a component that points away from the application nozzle and/or has a component that points away from the material web.

The blocking effect of the additional blocking device is achieved in these designs by generating a targeted air flow, which is directed in such a way that it does not disturb the curtain. It is often not possible to place such a blocking device as close to the curtain as the plate version in order to avoid disruption of the curtain by the air shield itself. The air flow of the air shield should be so strong that the air movements of the ambient air, which are generated, for example, by the movement of the operating personnel, do not penetrate through the air shield.

In order to achieve the greatest possible blocking effect, the air shield will often extend at least over the width of the material web or the width of the curtain, or even slightly beyond.

Since the required air volumes and speeds can vary greatly depending on the installation and operating conditions, particularly advantageous designs can include means for controlling or regulating the air volume and/or air speed. This gives the operator the opportunity to optimally adjust the air shield.

Another great advantage of this air shield is that the operating personnel can simply switch off the air shield for repair or maintenance work, or can simply reach through the air shield. This eliminates the need for the potentially time-consuming dismantling of a permanently installed rigid device.

For example, to take samples of application medium from the curtain, a suitable collecting vessel or sample carrier can be guided through the air shield to the curtain. This does not require the application process to be interrupted or the air shield to be switched off.

In a further advantageous embodiment, it can be provided that the at least one further blocking device comprises at least two air nozzles for producing an air shield, one of the air nozzles being provided before and another air nozzle after the curtain (viewed in the running direction of the material web). The flow direction of the air of the at least two air shields has a component that is directed towards the material web.

In this case, the two air nozzles are advantageously mounted close to the curtain. In particular, one or both of these air shields can be provided at a distance from the curtain of less than 100 mm, preferably less than 50 mm. For this purpose, the nozzles can be attached directly to the application nozzle, for example.

In this embodiment of the invention, an extremely compact design of the curtain application unit is possible.

It is particularly advantageous if the two air shields or air nozzles are provided at the same distance from the curtain. In particular, identical nozzles can be used.

It is also advantageous if the two air shields are symmetrical, i.e. in particular their direction and/or their air speed and/or the air volume are the same. This can prevent, for example, the air shield itself from disturbing the curtain even if the air nozzles are close to the curtain.

Advantageous air velocities for such a design can be between 5 m/s and 50 m/s, in particular between 10 m/s and 15 m/s.

With regard to the method, the object is achieved by a method for applying a liquid or pasty application medium to at least one Surface of a running material web by means of a curtain application device, whereby a single or multi-layer curtain is dispensed from an application nozzle under the influence of gravity and possibly the influence of other forces onto the surface of the material web, characterized in that drag air carried by the running material web is kept away from the curtain by means of a stripping device and, in addition, air currents of the ambient air are kept away from the curtain by means of a further blocking device.

Advantageous embodiments of the method are specified in the subclaims.

All of the locking devices described above are suitable for the additional locking device provided in the method. In particular, the locking devices according to one aspect of the invention are suitable as the application device.

An advantageous embodiment of the method is characterized in that the application medium is applied through the application nozzle at a flow rate of less than 10 l/min*m, in particular less than 6 l/min*m, particularly preferably between 2 l/min*m and 5 l/min*m. This produces a comparatively thin curtain, which can be particularly easily influenced by air movements in the ambient air. The additional blocking device provided according to the invention is particularly advantageous here. In particular when the drop height of the curtain is more than 100 mm, more than 200 mm, or even 300 mm and more.

In a further advantageous embodiment of the method, it can be provided that the material web is moved at a speed of between 100 m/min and 800 m/min, in particular between 200 m/min and 600 m/min. In order to be able to apply small quantities per unit area at these speeds, the composition and/or thickness of the curtain must be adjusted accordingly, which in turn makes the curtain more susceptible to ambient air.

For the significance of the flow rate, please refer to Table 1 below. As an example, the necessary flow rates are given here for a coating color as an application medium with a typical solids content of 63%, depending on the production speed and the desired coating weight. <b>Table 1 Flow rates in l/min/m</b> Line weight 8g/ ^m2 10g/ ^m2 12g/ ^m2 14g/ ^m2 Production speed 200m/min 1.7 2.1 2.5 3.0 300m/min 2.5 3.2 3.8 4.4 400m/min 3.4 4.2 5.1 5.9 500m/min 4.2 5.3 6.3 7.4 600m/min 5.1 6.3 7.6 8.9

Table 1 clearly shows that it is very important for a wide range of applications to be able to stably implement an application of low flow rates. Among other things, the invention is very advantageous for the designs shown in Table 1, particularly but not exclusively in combination with a curtain height of 100 mm or more.

The coating weights shown here between 8 g/m ² and 14 g/m ² are quite common. However, coating weights of up to 20 g/m ² or more can also be achieved using the method or device according to the invention.

The application medium can, for example, be a coating paint for coating paper or other fibrous webs.

The application medium usually contains a certain amount of solids. In the case of coating colors, for example, this may be CaCOs, kaolin and/or TiO ₂ , but other solids are also used.

In a particularly advantageous embodiment, the solids content of the application medium is between 55% and 72%.

Advantageously, the Brookfield viscosity (measured at 100 rpm) of the application medium can be between 100 mPas and 800 mPas, in particular between 300 mPas and 600 mPas.

Depending on the application, the air used for the air shield may also be treated. The treatment may include, for example, filtering and/or dehumidifying and/or heating.

Furthermore, in the case of an air shield, the speed of the air of the air shield can be between 15 m/s and 60 m/s.

• Figur 1 zeigt ein Vorhang-Auftragswerk gemäß einem nicht beanspruchten Aspekt der Erfindung
• Figuren 2 und 2b zeigen jeweils ein Vorhang-Auftragswerk gemäß einem Aspekt der Erfindung.
• Figur 3 zeigt ein Vorhang-Auftragswerk gemäß einem weiteren Aspekt der Erfindung.

In the following, the invention is explained in more detail using schematic figures that are not to scale.

• Figure 1 shows a curtain applicator according to a non-claimed aspect of the invention
• Figures 2 and 2 B each show a curtain applicator according to an aspect of the invention.
• Figure 3 shows a curtain applicator according to another aspect of the invention.

This in Figure 1 The curtain application unit shown comprises an application nozzle 1, from which a curtain 2 is applied to a material web 4, for example a paper or cardboard web, under the influence of gravity. The material web 4 is redirected by means of a deflection roller 3 so that its course below the curtain 2 is largely horizontal. The point of impact of the curtain is here, viewed in the direction of travel of the material web 4, slightly behind the deflection roller 3. The drag air carried along with the material web 4 is here removed by a stripping device 5 kept away from the curtain 2. Suitable stripping devices 5 are, for example, so-called air knives (air-cut) known in industry. The stripping device 5 often extends to just before the point of impact of the curtain.

In Figure 1 the at least one further locking device 9, 9a, 9b according to the invention is implemented in the form of two plates 9a and 9b. The two plates 9a, 9b are attached directly to the application nozzle. While it is also possible in principle to attach the plates in other ways, attachment directly to the application nozzle 1 offers the advantage that the distance between the plates 9a, 9b and the curtain 2 is extremely small. Distances of less than 100 mm and even less than 50 mm can be achieved here. This leads to a very compact design. In addition, the area around the application nozzle, for example the deflection roller 3 or the stripping device 5, is freely accessible for maintenance work and the like during operation, without the curtain 2 being disturbed by the resulting movement of the ambient air.

In Figure 2 a curtain application device according to a further aspect of the invention is shown. Here, the at least one further blocking device 9, 9a, 9b is implemented by an air shield 9. The air for producing the air shield 9 exits from an air nozzle 6 or a row of nozzles 6. The flow direction of the air, and thus the orientation of the air shield 9, can be vertically upwards, or can also be slightly inclined against this direction. This inclination is advantageously directed away from the application nozzle 1, and thus also away from the curtain 2, in order to avoid the curtain 2 being influenced by the air shield 9. The air shield 9 can advantageously extend at least over the entire width of the curtain 2 in the cross-machine direction.

At the Figure 2 In the embodiment shown, the air nozzle 6 or nozzle row 6 is attached directly to the scraper device 5. This can be advantageous, but depending on the situation, other fastening options may also be possible and useful.

Advantageously, the distance between the air shield and the application nozzle can be less than 150 cm, in particular less than 100 cm, particularly preferably less than 50 cm. At distances of 80 cm and less, it is possible, for example, for the machine operator to reach through the air shield 9 and carry out work on the nozzle or curtain, such as taking samples.

As in Figure 2 As shown, a further deflection device such as a deflection roller 3a will usually be provided after the curtain 2. The distance between this deflection device 3a and the curtain 3 can vary in different installations.

This in Figure 2b The commissioned work shown differs from that shown in Figure 2 in that it comprises a second blocking device 9 which is provided after the curtain 2 or the application nozzle 1. This second blocking device 9 is also implemented by an air shield 9. The air for producing the air shield 9 exits from an air nozzle 6 or a row of nozzles 6. The flow direction of the air, and thus the orientation of the air shield 9, can be vertically upwards, as with the first blocking device, or can be slightly inclined against this direction. This inclination is advantageously directed away from the application nozzle 1, and thus also away from the curtain 2, in order to avoid the curtain 2 being influenced by the air shield 9. The air shield 9 can advantageously extend at least over the entire width of the curtain 2 in the cross-machine direction.

The same applies to the distance of this second locking device 9 from the curtain as for the first locking device. Here too, distances between 80 cm and 50 cm are very advantageous. However, depending on the respective structural situation, such as the arrangement of the rollers 3a or the guidance of the material web 4, larger or smaller distances can also be selected.

In Figure 3 an embodiment is shown in which the at least one further blocking device comprises at least two air nozzles for producing an air shield. One of the air nozzles is provided in front of the curtain and another air nozzle is provided after the curtain (viewed in the direction of travel of the material web). The flow direction of the air of the two air shields has a component that points towards the material web.

The two air nozzles are advantageously mounted close to the curtain. The distance to the curtain can be less than 100 mm, preferably less than 50 mm In the execution of Figure 3 The nozzles are attached directly to the application nozzle. This allows an extremely compact design of the curtain application unit. Furthermore, the two air shields or the air nozzles are provided at the same distance from the curtain. Identical nozzles can be used for this.

In addition, the two air shields are symmetrical, which means that their direction and/or air speed and/or air volume are the same. This prevents the air shield itself from interfering with the air nozzles even if they are close to the curtain.

Advantageous air velocities for such a design can be between 5 m/s and 50 m/s, in particular between 10 m/s and 15 m/s.

Even if the figures show an example of a curtain applicator which applies a single-layer curtain, the invention is not limited to this. The known application nozzles 1 for two or more layered curtains 2 can also be used in a curtain applicator according to the invention. Even if the application nozzle 1 is shown in the figures as an example in the schematic form of a so-called 'slot die', the embodiments shown can also be implemented with other types of nozzles, for example so-called 'slot dies'.

Claims (14)

1. Curtain applicator for applying a liquid or pasty application medium to at least one surface of a running material web (4), in particular a fibrous web (4), wherein the curtain applicator comprises an applicator nozzle (1), in particular a slotted nozzle (1), which under the effect of gravity and optionally the effect of further forces is suitable for dispensing a single-tier or multi-tier curtain (2) onto the surface of the material web (4) and furthermore comprises a wiping device (5) which is suitable for keeping entrained air carried by the material web (4) away from the curtain (2), characterized in that at least one further blocking device (9, 9a, 9b) which is suitable for keeping air movements of the ambient air away from the curtain (2) is provided, wherein the at least one further the further blocking device (9, 9a, 9b) comprise means, in particular one or a plurality of air nozzles (6), for generating an air shield (9).
2. Curtain applicator according to Claim 1, characterized in that the spacing of the opening of the applicator nozzle (1) from the material web (4) is at least 100 mm, preferably at least 200 mm, particularly preferably at least 300 mm.
3. Curtain applicator according to one of the preceding claims, characterized in that the at least one further blocking device (9, 9a, 9b) in the running direction of the material web (4) is disposed ahead of the applicator nozzle (1).
4. Curtain applicator according to one of the preceding claims, characterized in that the spacing of the further blocking device (9, 9a, 9b) from the applicator nozzle (1) is less than 150 cm, in particular less than 100 cm, particular preferably between 80 cm and 50 cm.
5. Curtain applicator according to one of the preceding claims, characterized in that the at least one further blocking device (9, 9a, 9b) comprises a plate (9a, 9b) which is fastened to, or in the immediate proximity of, the applicator nozzle (1) and extends so as to be substantially parallel to the curtain (2).
6. Curtain applicator according to Claim 5, characterized in that the further blocking device (9, 9a, 9b) comprises a further plate (9b) which is fastened to, or in the immediate proximity of, the applicator nozzle (1), wherein the one plate (9a) in the running direction of the material web (4) is attached ahead of the curtain (2), and the further plate (9b) in the running direction of the material web (4) is attached behind the curtain (2).
7. Curtain applicator according to one of Claims 4 or 5, characterized in that the spacing of the one plate (9a) and/or of the further plate (9b) from the curtain (2) is less than 100 mm, preferably less than 50 mm.
8. Curtain applicator according to one of the preceding claims, characterized in that the flow direction of the air of the air shield (9) has a component which points away from the applicator nozzle (1) and/or has a component which points away from the material web (4).
9. Curtain applicator according to one of the preceding claims, characterized in that the at least one further blocking device (9, 9a, 9b) comprises at least two air nozzles (6) for generating in each case one air shield (9), wherein one of the air nozzles (6) is provided ahead of the curtain (2) and one further air nozzle (6) is provided behind the curtain (2), and wherein the flow direction of the air of the at least two air shields (9) has in each case a component which points toward the material web.
10. Method for applying a liquid or pasty application medium to at least one surface of a running material web (4) by means of a curtain applicator, wherein under the effect of gravity and optionally under the effect of further forces a single-tier or multi-tier curtain (2) is dispensed from an applicator nozzle (1) onto the surface of the material web (4), characterized in that entrained air carried by the running material web (4) is kept away from the curtain by means of a wiping device (5), and additionally air flows of the ambient air are kept away from the curtain (2) by means of a further blocking device (9, 9a, 9b), wherein the at least one further the further blocking device (9, 9a, 9b) comprise means, in particular one or a plurality of air nozzles (6), for generating an air shield (9).
11. Method according to Claim 10, characterized in that the application medium is applied by the applicator nozzle (1) at a flow rate of less than 10 l/min*m, in particular of less than 6 l/min*m, particularly preferably between 2 l/min*m and 5 l/min*m.
12. Method according to one of Claims 10 or 11, characterized in that the material web (4) is moved at a speed between 100 m/min and 800 m/min, in particular between 200 m/min and 600 m/min.
13. Method according to one of Claims 10 to 12, characterized in that the application medium has a solids content between 55% and 72%.
14. Method according to one of Claims 10 to 13, characterized in that the Brookfield viscosity of the application medium at 100 rpm is between 100 mPas and 800 mPas, in particular between 300 mPas and 600 mPas.

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