EP2591862B1 - Curtain coater - Google Patents

Description

The invention relates to a curtain applicator for dispensing liquid or pasty application medium according to the preamble of claim 1.

Out DE 10 2009 048 820 A1 the features of the preamble of claim 1 are known.

Out DE 10 2009 036 853 B3 a generic curtain applicator is known, which ensures a homogenization of the pressure and / or quantity distribution of the application medium in the transverse direction of the commissioned work. For this purpose, a first and a second distribution chamber are arranged one behind the other in the flow direction and between them extends a flow gap which is subdivided into sectional streams.

When coating a paper or board web with a curtain coater, the coating should be applied as evenly as possible over the entire web width. The application thickness must be as constant as possible over the entire web surface. The basic prerequisite for this is a uniform distribution of the coating mass over the outlet width with regard to the volume flow and the speed. This task is particularly difficult to meet for large working widths of for example 8 to 10 m and low application weights of, for example, 2 to 10 g / m ² . Varying operating conditions, such as large ranges of variation in coating viscosity and application quantities, present an additional challenge in achieving an even distribution of the job.

Out DE 197 55 625 A1 a curtain applicator is known in which the nozzle body consists of two wall-shaped parts which have a desired working width corresponding length. In a longitudinal side of one of the parts, a longitudinal groove is incorporated, which forms a distribution chamber after the joining of the two parts. To the distribution chamber an over the working width extending discharge channel is connected, from which the coating color emerges. In order to be able to apply uniformly over the working width on paper or board webs with a large width even small amounts of coating under fluctuating conditions, eg fluctuating viscosity or changing application quantities, the flow conditions in the distribution chamber are influenced by the supplied volume flows. For this purpose, at least two supply channels are connected to the distribution chamber, each having a device for adjusting the supplied volume flow of coating color. Preferably Schlauchklemm- or diaphragm valves are used for the flow adjustment. The volume flows of each feed channel are therefore set separately. For a further homogenization, a second distributor chamber is arranged between the distributor chamber and the outlet channel. Between the then first distribution chamber and the second distribution chamber is an additional flow channel. The disadvantage is the requirement of additional actuators for the cross profile adjustment. A further disadvantage is that the individual partial flows from the individual sections can not be combined to form a uniform film flow in the outlet gap. In the exit slit and in the curtain then arise stripes that lead to coating defects and cause production disruptions.

The object of the invention is therefore to provide a curtain applicator, which ensures a high uniformity of the distribution of a coating medium over a discharge width.

This object is solved by the features of claim 1.

As a result, a curtain applicator is created, which connects the section streams (partial streams) to a uniform film flow in the curtain and avoids streaking. A homogenization of the pressure and / or quantity distribution of the application medium in the transverse direction of the commissioned work can thus be combined with a uniform film flow. The flowpath patterns are labyrinthine flowpath patterns.

Further embodiments of the invention are described in the following description and the dependent claims.

• Fig. 1 zeigt schematisch eine Querschnittsansicht des Düsenkörpers eines Vorhang-Auftragswerks,
• Fig. 2 zeigt schematisch eine perspektivische Ansicht einer zweiten Verteilerkammer gemäß einem ersten Ausführungsbeispiel,
• Fig. 3 zeigt schematisch eine perspektivische Ansicht einer zweiten Verteilerkammer gemäß einem zweiten Ausführungsbeispiel,
• Fig. 4 zeigt schematisch eine Querschnittsansicht einer Kaskadendüse für eine mehrschichtige Bahnbeschichtung.

The invention will be explained in more detail with reference to the embodiments illustrated in the accompanying drawings.

• Fig. 1 shows schematically a cross-sectional view of the nozzle body of a curtain applicator,
• Fig. 2 schematically shows a perspective view of a second distribution chamber according to a first embodiment,
• Fig. 3 schematically shows a perspective view of a second distribution chamber according to a second embodiment,
• Fig. 4 schematically shows a cross-sectional view of a cascade nozzle for a multilayer web coating.

The invention relates to a curtain applicator for dispensing liquid or pasty application medium in the form of a substantially gravitational moving curtain to a moving paper or board web.

As Fig. 1 shows the curtain applicator comprises a nozzle body having a first, along a feed width extending manifold chamber 1. This distribution chamber 1 is supplied via at least one supply line (not shown), the application medium. The flow direction S of the application medium to be supplied can start from one end of the distribution chamber 1. The nozzle body further comprises a second distribution chamber 3, which emits the application medium via a discharge gap 4 as a curtain. Between the first 1 and second distribution chamber 3, an additional flow channel 2 is provided, which decomposes the application medium into section streams 2.1, 2.2, 2.3. The flow direction S is here perpendicular to the transverse direction of the curtain applicator.

The second distribution chamber 3 has in the flow direction S a flow path with a plurality of changes in direction, which runs through throttling points 3.1 and expansion chambers 3.2. As Fig. 1 shows, preferably connects to the flow channel 2, a first throttle point 3.1. This first throttle point 3.1 is formed for example by a flow loop, which reduces the flow path. At the throttle point 3.1 is thus a local Strömungswegverengung. This reduction of the flow path is carried out eccentrically to a fluid line of the flow channel 2. The first throttle point 3.1 is followed in the flow direction S, preferably a first expansion chamber 3.2, in which the cross section of the flow path with respect to the throttle point 3.1 is greater. Preferably, the flow cross-section is substantially equal to or greater than the flow area of the flow channel 2. To the first expansion chamber 3.2 is preferably followed by a second throttle point 3.1, which in turn is arranged eccentrically, but laterally offset to the fluid line of the flow channel 2. At the second throttle point 3.1 is preferably followed by a second expansion chamber 3.2, to which a third throttle 3.1, offset to the second throttle point 3.1, followed. Before the outlet gap 4 is preferably still another expansion chamber 3.2 provided, the dimensions of which can be greater compared to the upstream expansion chambers 3.2. Due to the eccentric arrangement of the throttle points 3.1, the flow path has a plurality of changes in direction, which provide for a connection of the flow edges of the section streams 2.1, 2.2, 2.3, wherein the expansion chambers 3.2 provide for sufficient intermediate reassurance of the flow. The result is the formation of a uniform film flow in the distribution chamber 3, starting from the section streams 2.1, 2.2, 2.3. The arrangement of the throttle points 3.1 can determine a flow path pattern.

In the flow direction, a throttle 3.1 and an expansion chamber 3.2 are preferably arranged alternately. The throttle points 3.1 and the expansion chambers 3.2 are also preferably each formed machine width. The change of direction in the flow path can for example be regular.

The second distribution chamber 3 is formed labyrinthine.

The throttling points 3.1 can form a sequence of flow loops, wherein an expansion chamber 3.2 is arranged between each two flow loops.

At least three throttles 3.1 and two expansion chambers 3.2 are preferably arranged in the flow direction S successively.

As Fig. 2 shows, the flow channel 2 is divided into a plurality of individual guide channels for the section streams 2.1, 2.2, 2.3. Like the embodiment of Fig. 3 shows, the guide channels for the section streams 2.1, 2.2, 2.3 on the outlet side in each case into a diffuser 5.1, 5.2, 5.3 for a downstream merge the section streams 2.1, 2.2, 2.3 pass.

The section streams 2.1, 2.2, 2.3 preferably extend perpendicular to the transverse direction of the commissioned work from the first distribution chamber 1. Furthermore the section streams 2.1, 2.2, 2.3 preferably arranged in a row.

Between the outlet ends of the section streams 2.1, 2.2, 2.3 and the second distribution chamber 3, a remaining partial height of a flow channel 6 may be formed in the form of a machine-wide flow gap to merge the individual section streams 2.1, 2.2, 2.3 again before the entry into the second Distribution chamber 3 takes place.

The flow-contacting parts of the curtain applicator are mechanically and chemically stressed. It is therefore advantageous to produce these from stainless steels, for example from the following materials such as molybdenum-free Cr-Ni steels, molybdenum-containing Cr-Ni steels or ferritic-austenitic duplex steels.

Alternatively, the nozzle body may consist of a thermoplastic material. In order to meet high demands on dimensional stability, chemical resistance, moisture resistance (moisture absorption below 1.5%), dimensional stability (low swelling below 0.1%), the high performance plastics (amorphous and partially crystalline) such as PEI, PEEK, PPSU, PTFE, PVDF, POM according to DIN EN ISO 1043-1 as material for the production of the nozzle body, in particular of the main body 2.4.

The nozzle body described according to the invention can be used for a curtain coating by the slide-die method or a slot die method.

Fig. 4 shows a curtain applicator for multilayer application of liquid or pasty medium to a moving paper or board web. The nozzle body forms separate media streams 10, 11 for the layers to be applied, which are combined to form a curtain 12 at the exit of the outlet gaps 4 of a cascade nozzle body. For this purpose, a plurality of the nozzle bodies described above are arranged side by side, here for example two. Via a feed lip 13 with a trailing edge 14 flows from the outlet columns. 4 exiting curtain 12 on the moving web 15, which moves under the coating device in the transport direction T.

Notwithstanding the embodiments of the Fig. 1 to Fig. 3 is in the embodiment according to Fig. 4 the flow direction S upwards. According to Fig. 1 to Fig. 3 the flow direction S is directed downwards. Otherwise, the above statements apply accordingly.

Claims (10)

1. Curtain coater for discharging liquid or pasty application medium in the form of a curtain moving substantially under the force of gravity onto a moving paper or board web, comprising a nozzle body which has a first distributor chamber (1) extending along a discharge width, to which the application medium is supplied via at least one supply line, and in the flow direction (S), a flow channel (2) which breaks up the application medium into sectional flows (2.1, 2.2, 2.3), and has a second distributor chamber (3), which discharges the application medium as a curtain via an outlet slot (4), characterized in that the second distributor chamber (3) shows a labyrinthine form and, in the flow direction (S), has a flow path with a plurality of direction changes, which runs through throttling points (3.1) and expansion chambers (3.2).
2. Curtain coater according to claim 1, characterized in that the direction change is regular.
3. Curtain coater according to claims 1 or 2, characterized in that the throttling points (3.1) and the expansion chambers (3.2) are each formed to be as wide as the machine.
4. Curtain coater according to one of claims 1 to 3, characterized in that a throttling point (3.1) and an expansion chamber (3.2) are arranged alternately in the flow direction.
5. Curtain coater according to one of claims 1 to 4, characterized in that the arrangement of the throttling points (3.1) determines a flow path pattern.
6. Curtain coater according to one of claims 1 to 5, characterized in that the throttling points (3.1) form a sequence of flow loops, in each case an expansion chamber (3.2) being arranged between two flow loops.
7. Curtain coater according to one of claims 1 to 6, characterized in that at least three throttling points (3.1) and two expansion chambers (3.2) are arranged one after another in the flow direction (S).
8. Curtain coater according to one of claims 1 to 7, characterized in that the flow channel (2) is broken down into a multiplicity of individual guide channels which each merge on the outlet side into a diffuser (5.1, 5.2, 5.3) for the sectional flows (2.1, 2.2, 2.3) to be led together on the outlet side.
9. Curtain coater according to one of claims 1 to 8, characterized in that the sectional flows (2.1, 2.2, 2.3) extend from the first distributor chamber (1) at right angles to the transverse direction of the coater.
10. Curtain coater according to one of claims 1 to 9, characterized in that the sectional flows (2.1, 2.2, 2.3) are arranged in a row.

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