EP2146003A2 - Curtain application device - Google Patents

Abstract

The curtain coating tool comprises a curtain coating head (3) arranged above a fiber material web (2). The single or multi-layered curtain that reduces the gravity following on the fiber material web. On a web edge, an edge scarper is arranged by which the coating medium subjected by curtain (7) on the surface of the fiber material web in the adjusted coating width is removable at the edge area of the coating width. A desired coating width is attainable without undesirable peripheral thickening. A suction unit is equipped for the coating medium removed by the edge scraper (10). The curtain coating tool comprises a curtain coating head (3) arranged above a fiber material web (2). The single or multi-layered curtain that reduces the gravity following on the fiber material web. On a web edge, an edge scarper is arranged by which the coating medium subjected by curtain (7) on the surface of the fiber material web in the adjusted coating width is removable at the edge area of the coating width. A desired coating width is attainable without undesirable peripheral thickening. A suction unit is equipped for the coating medium removed by the edge scraper (10), which is movable in the width direction of the fiber material web. The edge scraper is arranged in the downstream direction of the curtain coating head and/or an impact (13) of the curtain before drying. The edge scraper and/or the suction unit comprise a suction nozzle that is directed in its effect against the motion direction of the fiber material web. The suction nozzle has a slot height of 0.2-3.0 mm and a slot width of 19-50 mm. The suction nozzle comprises an offset between its slit opening and/or scraper edge and its lower slit opening and scraper edge, where the offset lies 1-10 mm. The lower scraper edge is formed in an angle of 5-45[deg] . The suction nozzle comprises a recess that lies on the side turned away the lower scraper edge and has a height of 2-8 mm, and a scraper chamber in which a suction channel flows. The suction channel is formable in any cross-section form. The curtain coating heads are assigned an edge guide through which the multi-layered curtain is guidable over a part stretch of its fall path between a cutting edge and the surface of the fiber material web at its lateral edges. The edge guides are adjustable in width direction of the curtain for adjusting a coating width. The edge scraper is assigned a web support element present over the fiber material web, where the web support element forms a spring air cushion between it and the lower side of the fiber material web. The air cushion has a thickness of 1-3 mm. Independent claims are included for: (1) edge scraper for curtain coating tool; and (2) method for coating a moving paper, cardboard or other fibrous material web with fluid to pasty coating medium in the form of single or multi-layered curtain.

Description

The invention relates to a curtain applicator for coating a running paper, cardboard or other fibrous web with at least one liquid to pasty application medium in the form of a single or multi-layer curtain, which falls substantially to gravity following the fibrous web, with a above the Fiber web arranged curtain-order head.
The invention also relates to a method of coating and also an edge scraper.

A generic device and a method are for example from the DE -A1 102 32 949 known. It has been proposed that the application medium curtain can be guided or guided for a curtain application method and a corresponding curtain application unit by means of edge guides and corresponding emitted beams of an operating medium.
Edge guides are also in the WO 03/049870 and the WO 03/049871 disclosed.

The latter document discloses an applicator head with which a plurality of application media or a plurality of layers of an application medium can be delivered. This embodiment of a curtain commissioned work is among other things from the EP-A1- 1 255 615 known and is referred to in professional circles as "Slide Die", ie Gleitschichtdüse. This so-called sliding layer nozzle contains at least two application medium chambers from which the medium in each case reaches a sliding surface of the sliding layer nozzle via a feed gap, which in turn merges in each case into a slot-shaped outlet nozzle. The application medium emerging from the discharge nozzles arranged in parallel one behind the other overlaps one another. At a trailing edge or as a detachment line to be designated edge of the nozzle, this multilayer separates and falls down as a multilayer curtain either initially on an intermediate guide plate or directly on the substrate to be coated or the surface of the moving fibrous web.

When painting - both single-layer and multi-layer application - with the Curtain Coater (Curtain Coater), the coating width can be equal to or less than the width of the fibrous web.

The edge of the curtain or film has a tendency, due to surface tension, to contract and form a thickening of the line at the edge of the layer.

In so-called "overboard driving style", i. If the curtain width is greater than the fibrous web width, it may therefore come to contamination of the fibrous web edges.

Often, therefore, an "inboard mode" where the curtain width is less than the fibrous web width is preferred by the process operators or users of the apparatus.

The latter inboard variant requires flat edges without edge thickening of the line edge.

• Beschädigung der Walzen von nachfolgenden Kalandern,
• ungleichmäßige Ränder und dadurch ungleichmäßige Pressung an der aufgewickelten Faserstoffbahnrolle
• starke Verschmutzung von nachfolgenden Leitwalzen, weil sich die Randverdickung nicht wegtrocknen lässt

Generally, the thickness of the curtain coated coating layers is between 5 and 50 microns. The edge thickening can reach a height of up to 100 microns or higher. This local unevenness leads to various problems, such as:

• Damaging the rolls of subsequent calenders,
• uneven edges and thus uneven pressure on the wound fibrous web roll
• Heavy contamination of subsequent guide rollers, because the edge thickening can not be dried

It is therefore an object of the invention to provide a device and a method, where the disadvantages of the prior art do not occur.

The object of the invention is achieved with a curtain applicator with the features of claim 1. According to the invention, an edge scraper is additionally arranged on at least one web side with which the application medium applied by means of a curtain to the surface of the fibrous web in the set coating width can be removed from the edge region of the coating width. This achieves a final application width without unwanted edge thickening, which, on the one hand, can dry poorly and contaminate the web guide elements, etc., and on the other hand affect the quality of the coating layer.
The marginal application medium is therefore removed immediately after application. It can be scrapped purely mechanically from the edge. The removed or shaved medium can then flow outward.

It is particularly advantageous if a suction device is also provided for the application medium scraped off by means of the edge scraper. Thus, the removed or shaved medium can be quickly and cleanly discharged to the outside and possibly recycled and introduced into the coating process.

It is useful if the edge scraper in the width direction of the curtain or the fibrous web is movable. This allows you to set exact, final job widths as well as a line-free edge.

The edge scraper can also be deflected suspended or designed to be liftable. He does not bother in a Splicedurchgang the web or when retracting the web.

The edge scraper is downstream of the curtain applicator head and its edge guides or a line of impact of the curtain on the fibrous web downstream. The edge scraper should preferably before the first subsequent deflection, in any case, but before the first drying be arranged.
During edge removal or doctoring, the edge scraper (ie, these elements are typically present on both sides of the machine) remains in this downstream position. The removal or Abschabeprocess then takes place due to the movement of the fibrous web in the running direction.

Advantageously, a distance of the edge scraper to the impact line of the curtain between 5 and 500 mm. However, the distance should not be greater than 2000mm, because until then the application medium has not yet solidified and therefore it can scrape off quite well and can also be vacuumed.

An expedient embodiment of the edge scraper is that it has at least one suction nozzle connected to a vacuum generating device as the suction device. This suction nozzle is preferably designed as a slot die and aligned against the direction of movement of the fibrous web.

The suction nozzle has a slot height between 0.2 and 3.0 mm and a width between 10 and 50 mm. The slot width corresponds approximately to the desired width of the uncoated edge.

The slot die should, according to another useful embodiment, have an offset between its upper and lower slot opening or scraper edges. The offset should be between 1 and 10mm, with the larger the web speed, the larger value should be selected. It is also proposed to form the lower scraper edge at an acute angle β between 5 and 45 °.

It is also advantageous if a shoulder of the suction nozzle is present on the side facing away from the lower scraper edge side. This paragraph prevents the backflow of the particular liquid, scraped medium. As the height of the paragraph preferably 2 to 8 mm are proposed.

According to the invention, the suction nozzle has a scraper chamber. In this opens a suction channel, wherein the suction channel can be connected from above, from the side or from the back to the scraper chamber. However, lateral connection is considered preferable. Incidentally, the suction channel can have any cross-sectional shape, for example a round or polygonal shape. In this respect, a shape which is approximately adapted to the cross-sectional shape of the slot nozzle is considered to be preferred because it allows a higher speed of the suction to be achieved.

It is also very advantageous if the suction channel projects with its suction opening into the scraper chamber. However, preference is given to such an orientation of the suction opening, which is opposite to the direction of movement of the fibrous web.

The edge scraper can act on both a supported, as well as an unsupported area of the fibrous web on this. With regard to the scraper effect but a support of the fibrous web at the level of the edge scraper is more advantageous. The support can be done with a roller or a flat guide surface (support beams, endless belt, etc.), so that the edge scraper above these support or web guide elements can act.

A very advantageous embodiment is achieved by the web support member is formed so that a resilient air cushion is formed between the web support member and the underside of the fibrous web, wherein the air cushion can substantially reach a thickness between 1 and 3mm. The applicant's company describes and distributes such web support elements as so-called TopTurns. Thus, the fibrous web can be guided without contact and also the edge scraper are resiliently pressed against against the surface of the fibrous web. This design avoids the risk of tearing the web in the edge region.

The object of the invention is also achieved with an edge scraper, which is characterized by the features of claim 13. This Inventive edge scraper can be easily retrofitted in existing curtain coaters.

The object of the invention is also achieved by a method according to claim 14.

According to the invention, it is provided that with the aid of at least one pressed against the surface of the fibrous web edge scraper, which is applied by curtain to the surface of the fibrous web in the set coating width applied application medium at the edge region of the coating width, whereby a final application width is achieved without unwanted edge thickening.

The edge scraper is pressed against the freshly coated fibrous web. By changing the angle of inclination of the scraper, the effectiveness of the edge removal can be changed.

During the Beschaberung or the edge scraper keeps the once set distance - for example, the commissioned work - at.

Preferably, a mechanical Beschaberung the edge is provided. The application medium scraped off in this way can then be sucked off with a device connected to a vacuum generating device and removed to the outside.

Further embodiments of the method will become apparent from the dependent claims that will not be discussed further at this point, because this was done already in the explanation of the operation of the curtain applicator invention.

With the present invention edge thickening of the line edge and their adverse effects are avoided. It can be clean uncoated Reach web margins and even job widths.

• Figur 1 : ein Vorhang-Auftragswerk gemäß dem Stand der Technik in schematischer, perspektivischer Darstellung
• Figur 2 : eine erste Ausführungsform eines erfindungsgemäßen Vorhang-Auftragwerkes mit einem mechanisch wirkenden Randschaber in schematischer perspektivischer Darstellung
• Figur 3 : eine zweite Ausführungsform eines erfindungsgemäßen Vorhang-Auftragwerkes mit einem mechanisch wirkenden Randschaber und einer Absaugeinrichtung in schematischer perspektivischer Darstellung
• Figur 4 : eine vergrößerte Darstellung der Absaugeinrichtung aus Figur 3 im Schnitt
• Figur 5 : eine Darstellung des erfindungsgemäßen Vorhang-Auftragswerkes mit Randschaber und Absaugung einschließlich Mediums- Rücklaufführung
• Figur 6 und 7 : weitere Ausführungsformen eines erfindungsgemäßen Vorhang-Auftragwerkes im Schnitt
• Figur 8 : eine Draufsicht auf einen Teil eines Randbereiches einer doppelt beschichteten Faserstoffbahn

The invention will be explained in more detail with reference to an embodiment. In a schematic representation:

• FIG. 1 : A curtain applicator according to the prior art in a schematic, perspective view
• FIG. 2 A first embodiment of an inventive curtain applicator unit with a mechanically acting scraper edge in a schematic perspective representation
• FIG. 3 A second embodiment of a curtain applicator according to the invention with a mechanically acting edge scraper and a suction device in a schematic perspective view
• FIG. 4 : an enlarged view of the suction from FIG. 3 on average
• FIG. 5 : An illustration of the curtain applicator invention with edge scraper and suction including medium return guide
• FIGS. 6 and 7 : Further embodiments of a curtain applicator invention in section
• FIG. 8 : A plan view of a part of an edge region of a double-coated fibrous web

It should be noted that in the examples according to FIG. 2 and 3 and also in the illustration of the prior art according to FIG. 1 only a single-layer order is shown. But it could also be issued a multi-layer curtain or a multi-layer coating are generated, as in the FIGS. 4 to 6 is specified.

In the individual figures, the same components or designations are provided with the same reference numerals.

In the FIG. 1 is a curtain applicator 1 for coating a running paper, cardboard or other fibrous web 2 with a liquid to pasty application medium M according to the prior art shown. It includes, in addition to some other not shown here units, such as gutters, air boundary layer control devices, measuring devices, feeders, etc. above the fibrous web 2 and spaced therefrom arranged curtain application head 3. This application head 3 is designed as a sliding layer and running machine. For a multi-layer application, that is to say for each application medium M or M1 to Mn, the application head 3 has its own application medium chamber with supply gap, all of which on the surface of the curtain application head 3 each transition into a slot-shaped exit nozzle 4 to 4n for one each Application medium layer to be dispensed. The outlet nozzles 4, 4n are arranged parallel to each other and in the direction of movement L of the fibrous web 2 in succession. The curtain application head 3 has on its surface also a downwardly inclined and curved located sliding surface 5. The sliding surface 5 merges into a separation or tear-off edge 6, which points in the direction of the fibrous web 2 to be coated. From this Ablösekante 6, which is indeed machine-wide, as the entire applicator head 3, the previously formed on the sliding surface 5 coating medium layer (or more superposed coating medium layers in multi-layer application) dissolves and forms or form a single or multi-layered Curtain 7 off. The curtain 7 drops from the detaching edge 6 (here covered by the falling curtain 7) substantially following gravity, down onto the fibrous web 2 and deposits on its surface 2a as a coating layer AS.

How out FIG. 1 can be seen, the curtain applicator has 1 edge guides 8. This edge guides are constructed strip-like and serve to guide the single or multilayer curtain 7 at least over a part of its fall path between the trailing edge 6 and the surface of the fibrous web 2 at its lateral edges 7a and 7b. The edge guides 8 are adjustable in the width direction of the curtain 7 for setting a coating width BB or ensure the receipt of a line-free edge.

In this case, unwanted edge thickening 9 of the application layer AS often occur, which can contaminate subsequent rolls, web guide elements and also the web edge in the case of overboard driving.

In FIG. 2 a first embodiment of a curtain applicator 1a according to the invention is shown, which in order to avoid the unwanted edge thickening 9 (see FIG. 1 ) has an edge scraper 10 on at least one web edge 2.1.

This edge scraper 10, which is drawn on the left side of the image, is additionally capable of mechanically scrapping the application medium on the edge region R applied by means of a curtain 7 to the upper side 2a of the fibrous web 2 in the set coating width BB. This achieves a desired application width AB in the so-called in-board mode without undesirable edge thickening.
On the right side of the picture, the so-called overboard driving style is shown for comparison. The excess, scrapped medium MÜ flows in the inboard driving, so when using the edge scraper 10 to the outside via a flow 11 from.

The edge scraper 10 is movable in the width direction of the fibrous web 2, as the horizontal arrow shows. During the Beschaberung the Randschaber 10 but still. The Beschaberung is then exclusively due to the edge scraper over in the direction L moved fibrous web. 2

The remaining drawn and numbered components correspond to those from FIG. 1 and therefore should not be described here again.

In FIG. 3 a second embodiment of a curtain applicator 1b according to the invention is shown. This commissioned work additionally has a suction device 12 for the excess application medium MÜ scraped off by means of the edge scraper 10. The suction is indicated by the vertical arrow.

The remaining drawn and numbered components correspond to those from the FIG. 1 and therefore should not be described here again.

In both Figures 2 and 3 Incidentally, it can also be seen that the edge scraper 10 is arranged downstream of the curtain applicator head 3 and the edge guides 8 or an impingement line 13 of the curtain 7 on the fibrous web 2 in the downstream direction (running direction L).

FIG. 4 shows an enlarged view of the edge scraper 10 with suction device 12 in section.

The edge scraper 10 has at least one suction nozzle 14, which is directed against the direction of movement L of the fibrous web 2. The suction nozzle 14 has a slot height A between 0.2 and 3.0 mm and a width E between 10 and 50 mm. The slot width results from the desired width of the uncoated edge. In addition, the suction nozzle 14 has between its upper scraper edge 15 and its lower Schlitzöffnungs- or scraper edge 16 an offset D, which is between 1 and 10mm. The greater the web speed, the larger the offset D should be.
The lower scraper edge 16 contacts the upper side or surface 2 a of the fibrous web 2 and, so to speak, scrapes the application layer AS (which in each case is the upper layer in the case of a multi-coated layer) cleanly. The scraper edge 16 is formed at an acute angle at an angle β between 5 and 45 °. The suction nozzle 14 also has a rear shoulder B, which lies on the side facing away from the lower scraper edge 16 side and about 2 to 8mm high. This design is intended to prevent backflow of the scraped-off medium.

The suction nozzle 14 also has a scraper chamber 17 into which a suction channel 18 of the suction device 12 opens. The suction channel 18 may be formed in any cross-sectional shape. Its suction opening 19 is arranged at a distance C from the bottom of the edge scraper 10 or the scraper chamber 17, the distance C being approximately 4 to 20 mm.
The effective direction of the suction opening 19 is preferably opposite to the direction of movement of the fibrous web 2.

FIG. 5 shows an overall view of the curtain applicator 1 b according to the invention with edge scraper 10 and the suction device 12 including medium return lines 20. After appropriate preparation in special facilities 21, such as filters, degasifier, the extracted excess medium MÜ again the curtain application head. 3 be supplied via supply lines 22 again.
In this figure it is also clear that the edge scraper 10 is arranged in the selected example at a distance F to the impact line 13 of the curtain 7. This distance the scraper 10 maintains during the Beschaberung.

FIGS. 6 and 7 show that the edge scraper 10 is associated with a located below the fibrous web 2 web support member 23. The support can be done with a roller or a flat guide surface (support beams, endless belt, etc.), so that the edge scraper 10 can act above this support or web guide element 23. According to FIG. 6 the web support member 23 is resilient.

According to FIG. 7 is the web support member 23 is formed so that forms a resilient air cushion 24 between this element 23a and the bottom 2b of the fibrous web 2, wherein the air cushion 24 can substantially reach a thickness between 1 and 3mm. The applicant's company describes and distributes such web support elements as so-called TopTurns. Thus, the fibrous web can be guided without contact and also pressed the edge scraper 10 resiliently against the surface of the fibrous web 2 become. This design avoids the risk of tearing off the web 2 in the edge region.

FIG. 8 Finally, shows a schematic plan view of a portion of an edge region R of a double and simultaneously coated fibrous web 2. It was used here not shown with curtain applicator 3. The precoat or underscore 30 was in the experiment at 800m / min with a stroke weight of 7.5 g / m ² and the top coat 40 applied at 8 g / m ² . Due to the use of the edge scraper 10 according to the invention, including the extraction of scraped off in the edge region excess medium a very clean uncoated edge 50 has been achieved and edge thickening especially the top coat 30 avoided.

LIST OF REFERENCE NUMBERS

1, 1a, 1b

Curtain applicator

2

Fibrous web

2a

surface

2 B

bottom

3

gun

4, 4n

exhaust nozzle

5

sliding surface

6

tear-off edge

7

single-layer or multi-layer curtain

7a, 7b

lateral curtain edge

8th

edge guide

9

selvage

10

edge scraper

11

procedure

12

suction

13

Impact line of the curtain

14

suction nozzle

15

upper scraper edge

16

lower scraper edge

17

scraper chamber

18

suction

19

suction

20

Return line

21

conditioning device

22

feed

23

Web supporting element

24

bubble

30

primer

40

topcoat

50

smooth edge

A

slot height

FROM

desired order width

AS

application layer

B

paragraph

BB

coating width

C

distance

D

offset

e

slot width

L

Movement or running direction

M

application medium

MT

excess, shabby medium

R

web edge

Claims (17)

Curtain coater (1, 1a, 1b) for coating a running paper, board or other fibrous web (2) with at least one liquid to pasty application medium (M) in the form of a single- or multi-layer curtain (7) substantially following gravity falling onto the fibrous web (2), with a curtain application head (3) arranged above the fibrous web (2),
characterized in that
on at least one web edge (R) an edge scraper (10) is arranged, with which by means of curtain (7) on the surface of the fibrous web (2) in the set coating width (BB) applied application medium (M) at the edge region of the coating width (BB) is removable, whereby a desired application width (AB) without unwanted edge thickening (9) can be achieved. Curtain coater according to claim 1,
characterized in that
a suction device (12) for the means of edge scraper (10) remote application medium (MT) is provided. Curtain coater according to claim 1 or 2,
characterized in that
the edge scraper (10) in the width direction of the fibrous web (2) is movable. Curtain coater according to at least one of the preceding claims,
characterized in that
the edge scraper (10) is liftable and / or deflectable. Curtain coater according to one of the preceding claims,
characterized in that
the edge scraper (10) in the downstream direction of the curtain application head (3) or a line of impact (13) of the curtain (7) arranged downstream, but is arranged before a subsequent drying. Curtain coater according to at least one of the preceding claims, characterized in that
the edge scraper (10) or the suction device (12) has at least one suction nozzle (14) which is directed in its action against the direction of movement (L) of the fibrous web (2). Curtain coater according to claim 6,
characterized in that
the suction nozzle (14) has a slot height (A) between 0.2 and 3.0 mm and a slot width (E) between 19 and 50 mm. Curtain coater according to claim 6 or 7,
characterized in that
the suction nozzle (14) between its upper Schlitzöffnungs- or scraper edge (15) and its lower Schlitzöffnungs- or scraper edge (16) has an offset (D) which is between 1 and 10mm, wherein the lower scraper edge (16) at an acute angle in an angle β between 5 and 45 ° is formed. Curtain coater according to claim 8,
characterized in that
the suction nozzle (14) has a shoulder (B) which lies on the side facing away from the lower scraper edge (16) and is approximately 2 to 8 mm high. Curtain coater according to at least one of claims 6 to 9,
characterized in that
the suction nozzle (14) has a scraper chamber (17), into which a suction channel (18) opens, wherein the suction channel (18) can be formed in any desired cross-sectional shape. Curtain coater according to at least one of the preceding claims,
characterized in that
the curtain applicator head (3) are associated with edge guides (8) through which the monolayer or curtain (7) at least over a partial stretch of its fall between a trailing edge (6) and the surface of the fibrous web (2) at its lateral edges ( 7a, 7b) is feasible and the edge guides (8) in the width direction of the curtain (7) for adjusting a coating width (BB) are adjustable. Curtain coater according to at least one of the preceding claims,
characterized in that
the edge scraper (10) is associated with a below the fibrous web (2) located web support member (23) which preferably between it and the bottom (2b) of the fibrous web (2) forms a resilient air cushion (24), wherein the air cushion (23) in Substantially has a thickness in the range between 1 and 3mm. Edge scraper (10) for a curtain applicator (1, 1 a, 1 b),
marked by
at least one of the features according to the characteristics of claims 2 to 12 for producing a bar-free edge (50) and a desired application width (AB) without unwanted edge thickening (9) on the surface (2a) of a moving paper, board or other fibrous web ( 2) during their coating within a manufacturing or finishing process of the fibrous web (2). Process for coating a running paper, board or other fibrous web (2) during its coating within a manufacturing or finishing process of the fibrous web (2) with at least one liquid to pasty application medium (M), which in the form of a single or multi-layered Curtain (7) substantially following the gravity, with a curtain applicator head (3) is applied to the fibrous web (2) from above,
characterized in that
with the aid of at least one edge scraper (10) pressed against the surface of the fibrous web (2), the application medium (M) applied by curtain (7) to the surface of the fibrous web (2) in the set coating width (BB) at the edge region of the coating width (BB) is scraped, whereby a desired application width (AB) without unwanted edge thickening (9) is achieved. Method according to claim 14,
characterized in that
the application medium (MT) scraped off and then sucked off. Method according to claim 14,
characterized in that
the single-layer or multi-layer curtain (7) is guided at least over a partial section of its fall path between a tear-off edge (6) and the surface of the fibrous web (2) by means of edge guides (8) at its lateral edges (7a, 7b) and an adjustment of a coating width (BB) by adjusting the edge guides (8) in the width direction of the curtain (7) is made. Method according to at least one of claims 14 to 16,
characterized in that
the fibrous web (2) is guided over at least one web support element (23), wherein the edge scraper (10) is pressed against the web support element (22, 22a) during the edge layer removal or doctoring.

Images