EP0643168B1 - Apparatus for coating a paper web - Google Patents

Description

The invention relates to a device for coating a paper web. On the preamble of claim 1 is referred to.

(1) DE-U-8 414 413

(2) US-A-2 729 192

(3) US-A-2 946 307

(4) US-A-3 084 663

(5) US-A-5 112 653

(6) EP-A-0 507 218

The prior art is known from the following publications:

(1) DE-U-8 414 413

(2) US-A-2 729 192

(3) US-A-2 946 307

(4) US-A-3,084,663

(5) US-A-5 112 653

(6) EP-A-0 507 218

The invention is based on document (6), in particular on its figure 1. Two application rollers are provided, which form a gap with one another form, through which a paper web runs. Both application rollers are ever a nozzle applicator assigned, each a coating color film on the Applying the outer surface of the roller in question. The nozzle applicator points a nozzle with two nozzle lips, one of which is at its free end carries a roller squeegee. This is a dosed application of coating color on the Shell surface of the roller in question is possible. It is about this accordingly, an indirect order process, since the line first applied the outer surface of the roller and from there to the paper web is transmitted.

It is also possible to order works other than those described there use. In addition, both sides of the paper web need not be deleted to become. So it is e.g. conceivable to only coat one side and the others not at all, or to paint in installments, whereby several of the roller pairs mentioned with the assigned applicators be provided, the paper web after receiving a stroke is dried in each case.

The type of coating device described has worked well in practice proven. However, there is a problem here that has not been solved yet solved satisfactorily. This is the so-called Orange peel effect. This is that the line on the paper web after leaving the nip is not flat, but one Surface that is reminiscent of the appearance of an orange peel. It there are always attempts to reduce the orange peel effect eliminate, e.g. through a downstream smoothing or grating element. This Measures are usually able to reduce the undesirable effect however not to be eliminated completely. These measures are also included connected with mechanical effort, e.g. with distributors.

The invention has for its object a coating device according to to design the preamble of claim 1 such that the Orange peel effect without any significant additional effort in even better Way is reduced or completely eliminated.

This object is achieved by the characterizing features of claim 1 solved.

Since then, they have been involved in trying to solve the problem deals with numerous different operating parameters. So it is known that the effect is influenced by the type of coating color itself, for example by their viscosity. The web speed also plays a role; this but you don't have it under control because of different paper qualities allow different path speeds. The paper quality too itself plays a role, especially its composition and its Surface. In addition, all parameters influence each other, so that it has so far been impossible to find measures that in all cases Remedy.

The inventor recognized that three parameters are crucial, that have not been considered so far: one parameter is the trigger angle, i.e. the angle at which the paper web after the application of the Dash leaves the nip and the other parameter is the Web tension that prevails in the paper web after the nip. Both must be precisely adjustable. The second parameter makes it special Difficulties because the coated paper web, which is still damp, cannot pass through a pair of draw rollers, i.e. a pair of driven rollers that clamp the web between them and the web thus transferring a certain traction.

After recognizing the meaning of the trigger angle, the inventor has therefore looked for suitable measures to a positive tension to put on the web. This measure consists of the characteristic Features of claim 1. According to the invention it is at least one Air-air bar immediately downstream of the nip, the Removal of the immediately downstream air bar from Roll gap of the two rolls 0.3 to 1 times the roll diameter is. Preferably, a distance on the order of 0.5 to 0.8 times the roll diameter is aimed for. It has been shown that so that ideal conditions can be established.

The further discovery of the inventor is that immediately the air beams must connect a dryer section, the very specific Features. Above all, these characteristics include exactly measured parameters with regard to the air outlet speed from the Air-supporting beams and in the air-floating dryers, furthermore a certain one Arrangement of the infrared dryer in relation to the air levitation dryer and finally a certain length fraction of the two types of dryer, in Seen the running direction of the web.

It has not been possible since then, formed directly on the nip the two application rollers of the coating station, with an infrared drying section to start. The separation point of the paper web from one roller has namely without the very special arrangement of the control organs - the Air bar - had no clearly defined separation point. Rather is the separation point - seen in the direction of travel of the railway - pendulum back and forth. The specific arrangement of the air-jet beams according to the invention was thus an important prerequisite for the immediate connection of a Infrared path following the nip. Adding the Infrared is particularly cheap because the infrared rays go deep into the Penetrate paper web, have a high energy density and that in the Heat up water contained in the paper web, so that in the downstream Suspended drying line the evaporation relatively easy can be made.

Further refinements of the inventive concept relate to the arrangement of the first infrared dryer that followed the nip Drying facilities. In some embodiments of the invention this first infrared dryer immediately behind the (at least) one Air beam arranged. In some cases, however, it is desirable to use the Infrared dryer at approximately the same distance from the nip to be arranged like the air beam. In this case - according to one another important idea of the invention - a special infrared dryer provided the one between himself and the coated paper web Can generate air cushion.

The invention is explained in more detail with reference to the drawing.

Figure 1 shows a coating system with two coating stations and with in between located drying facilities.

Figures 2 to 5 show coating stations, the guide organs in different embodiment and different arrangement are connected downstream.

General possibilities according to the invention for the series connection of Infrared dry lines and suspended dry lines are shown in FIGS. 2, 8, 9, 11 and 12.

1 shows a first coating station 1, which has two rollers. A coating unit 1.1 is assigned to one of these two rollers. Of the Coating station is followed by a pulling device, comprising two Lifting air beams 2 and 3. This is followed by an infrared drying section 4, a short one Dryer section 5 with three drying cylinders 5.1, 5.2 and 5.3, one Suction guide roller 5.4 and a number of guide rollers. A second Coating station 6 again has two rollers. One roller is one Assigned work 6.1. An infrared drying section then follows again 7 and an end dryer group 8.

The system shown in Figure 2 comprises a two-row Cylinder dryer section 1, of which one can still see the end, also a Smoothing unit 3, a first coating station 5, one of these downstream Dryer 6, a dryer section 7 with drying cylinders, a second Coating station 8, another dryer 9, a dryer section 9.1 with Drying cylinders and a take-up station 10.

However, the two coating stations 5 and 8 each have two Nozzle coater 5.1, 5.2 or 8.1 and 8.2. This means that the Paper web can be coated on both sides in each coating station. The Dryers 6 and 9 are levitation dryers that carry the web freely and up bring such a dry content (at least 70% dry) that the line in the subsequent cylinder dry groups 7 and 9.1 is touchable.

Figures 3-6 each show schematically application stations, downstream control organs and these downstream Drying facilities.

The application station according to Figure 3 comprises two rollers 10, 20. One of these two application rollers, namely roller 10, is one Nozzle applicator 10.1 assigned. The other roller 20 is free of one such commissioned work. The paper web 11 is in the direction of the arrow by a Roll nip passed out of the outer surfaces of the two Rollers 10 and 20 is formed. A guide element in follows the roller gap Shape of an air bar 12. The air bar is only schematic shown. It consists of a hollow profile beam that is on its Paper web 11 facing side has a plurality of holes 12.1. The holes 1 extend over the entire length of the Air bar 12, and thus over the entire width of the paper web 11th

An infrared drying section 13 connects to the air-air beam 12, followed by a floating dry section 14. This also points Support air bars 14.1, 14.2, 14.3, which are only indicated in outline.

As can be seen, the paper web 11 is guided as follows: the paper web 11 after the apex of the two rollers, first wraps around the Roller 10 by a certain wrap angle x. Wraps around her then the air beam 12, again a slight one Experiences redirection. Further redirections take place within the Floating dry section as it passes through the Lifting air beam 14.1,14.2,14.3.

The floating drying section 14 is a further infrared drying section 15 downstream.

It is important that the first drying after the air bar 12 a Infrared drying is. One could say that the Infrared drying section 13 directly to the order station with the Rolls 10, 20 follows, apart from the air bar 12. Still is important that the entire drying facility more than just two Includes dry sections, but at least three dry sections, and that the infrared dry lines on the one hand and the floating dry lines alternate on the other.

In Figure 4 you can again see a coating device with two Applicator rollers 10 and 20. In contrast to the embodiment according to FIG. 2 is both applicator rollers a nozzle applicator 10.1 or 10.2 assigned. The paper web 11 thus receives a line on both sides. The nozzle 10.1 can also be omitted, so that only a single side of the Paper web 11 receives a line.

Two air gaps 22 and 23 follow the application gap. These are open opposite sides arranged. There follow one Infrared section 24, a floating drying section 25 and another Infrared section 26. In this case, the three drying sections mentioned are - seen in the running direction of the paper web 11 - the same length.

The paper web 11 leaves the nip, it being only very slight wraps around the roller 10. The wrap angle x is thus so small that you don't recognize him in the illustration. The wrap is also the Air struts 22 and 23 only a very slight, so that you can also does not recognize.

In the embodiment according to FIG. 5, only one of the two is again Application rollers, namely the roller 10, assigned an application unit 10.1. It a bank of three supporting air beams 30, 31, 32 closes the roll gap followed by an infrared path 34, a floating drying path 35, a further infrared path 36 and another Floating drying line 37. It can be seen that the two Floating dry lines - seen in the direction of travel of paper web 11 - each have the same length, but with the floating drying section 37 is longer than the floating dry section 35. The reason is that the Paper web and in particular their water through the infrared drying section each must be heated and only then in the floating drying section arrives, and that it always because of the increasing dryness requires more effort, i.e. longer hovering dry routes to avoid this Drive out residual water from the paper web.

In the embodiment shown in FIG. 6, the paper web 11 again deleted on both sides. The nip follows first an air beam 40 located on one side of the web, followed by a bank arranged on the other side of the paper web 11 Trag air beams 41 and 42. An infrared path 43 and one close Floating drying section 44.

The arrangement according to the invention - see in particular the very small Distance E in Figure 6 - ensures a clearly defined separation point of the Lane 11 of roller 10. The separation point does not oscillate back and forth. Becomes Coating paint is applied to only one side, and is used for this Roller 10 used as an application roller with a relatively small Wrapping x (see Figure 3), roller 10 can have a softer surface have a back-up roller 20. This is quite unusual because normally the path follows the harder roller, so that the harder roller wraps around becomes.

Figure 7 shows an inventive device of special construction. The two rollers 10, 20 are arranged such that the paper web 11 at an angle of about 20 ° to the vertical through the nip runs through. The air girders 50 follow. This is followed by the Drying device, the elements of which are not specified in detail, but are easily recognizable. First comes - again immediately on the Roll nip or following the air bar 50 - one Infrared dry line, then a floating dry line, then one Deflection device, which is also equipped with air beams, then another three air girders, which ensure that the paper web 11 after the Deflection device takes a flawless stable run, then again an infrared dry line, a floating dry line and finally another infrared dry line. The paper web thus takes off a V-shaped course. The two legs of this V can under different angles, each at an angle of between 10 and 60 ° against the horizontal.

The arrangement of the drying sections according to FIG Peculiarity in that there are two types of drying sections - namely an infrared path on the one hand and a floating dry path on the other - are arranged opposite each other on both sides of the track. this leads to at the same time that in turn the one type of drying section with the others take turns. In the present case, however, this only applies to the first Leg of the V. In the second leg - and also in the area of the Redirection - dry sections of the same type are each other arranged opposite each other. Note that it can be different could. So it would be quite possible to equip the first leg to design the V exactly like that of the second leg, or that Swap the placement of the two legs.

In the arrangement according to FIG. 9 lie in each of the two legs similar dry sections opposite each other.

In the embodiment according to FIG. 10, the paper web 11 runs in the essentially straight through the entire facility, starting with the two rollers 10, 20 to the last drying section, which in turn is an IR drying section is.

The arrangement according to FIG. 11 again has a straight line Paper web guide on. There are different drying sections towards each other.

Figure 12 shows a system similar to that of Figure 9. The special here, however, is that air elements in the elements of the drying section are integrated. As you can see, the individual infrared dryer elements designed so that they between themselves and the coated paper web Can generate air cushion.

Figure 13 shows an embodiment in which the web from bottom to runs through the nip at the top. The train doesn't need to do that necessarily run vertically; it can also work against the vertical be inclined. Again, there is one-sided or two-sided Application of coating color possible.

FIGS. 14a to 14d show embodiments of air bar beams.

The wing of the air bar according to Figure 14a has a single line from holes from which the air flows out. The holes are arranged along a straight line.

In the embodiment according to FIG. 14b, the bores are opposite one another transferred. One could say that two lines of Air bores are arranged transversely to the direction of web travel, namely again along a straight line.

In the embodiment according to FIG. 14c, one can see two supporting air beams 50, 60, which carry the paper web 11 between them. The web running direction is through an arrow A indicated. The two air beams 50, 60 have slots on. These can extend across the entire width of the web (i.e. across the the entire length of the individual bar); however, per bar also several such slots can be arranged one behind the other. How one see, the slot is located upstream in each bar on the incoming paper web 11 related. An air curtain emerges from the slots off - see arrows B.

In the embodiment according to FIG. 14d, an air bar 60 can be seen. This in turn has air slots in its two edge areas, the over the entire width of the paper web and thus over the entire Extend the length of the air beam. Arrows B are again here shown, each of which is intended to illustrate an "air curtain". Within Trag air beam 60 is a box-like hollow body 60.1, which is also extends across the width of the paper web. This box is with one Provide row of holes 60.2. Through these holes, the air that was brought out of the slots, sucked in again and then laterally - not shown here - discharged from box 60.1. This Arrangement is used to create a stable air cushion. To one Creating uniform air curtain pressure is hollow Support air beam 60 provided a perforated plate.

Claims (8)

1. Device for coating a paper web

   1.1. with two rollers (10, 20), which are disposed parallel to one another, and which together form a roller slot for passing through the paper web (10);

   1.2 with at least one applicator nozzle (1.1, 5.1, 5.2, 8.1, 8.2, 10.1, 10.2) for applying a coating pigment layer to the peripheral surfaces of at least one of the rollers (10, 11) in order to transfer the coating pigment layer in the roller slot from the peripheral surface to one side of the paper web (11);

   1.3. with guide members following the roller slot, and which guide the paper web;

   1.4 the guide members are air support beams (2, 3, 12, 14.1, 14.2, 14.3, 22, 23, 30, 31, 32, 40, 41, 42, 50, 60), which provide a cushion of supporting air between the paper web (11) and the surface of the air support beam facing the paper web;

   1.5 the air support beams (2, 3, 12, 14.1, 14.2, 14.3, 22, 23, 30, 31, 32, 40, 41, 42, 50, 60) are so arranged that the paper web (11) is deflected at least once after the roller slot; characterised by the following features:

   1.6 at least one air support beam (2, 3, 12, 14.1, 14.2, 14.3, 22, 23, 30, 31, 32, 40, 41, 42, 50, 60) directly follows the roller slot;

   1.7 the immediately subsequent air support beam (2, 3, 12, 14.1, 14.2, 14.3, 22, 23, 30, 31, 32, 40, 41, 50, 60) is disposed at a distance from the roller slot of the two rollers (10, 20) which comes to 0.3 to 1 times the roller diameter, preferably 0.5 to 0.8 times.
2. Device according to claim 1 characterised by the following features:

   2.1 immediately following the guide members is a drying section which dries both sides of the paper web;

   2.2 the drying section has a plurality of infrared drying lengths (13, 15, 24, 26, 34, 36, 43) and suspended drying lengths (13, 15, 24, 26, 34, 36, 43);

   2.3 the infrared drying lengths (13, 15, 24, 26, 34, 36, 43) and the suspended drying lengths (14, 25, 35, 37, 43, 44) are arranged alternately, seen in the direction of transport of the web.
3. Device according to claim 1 or 2, characterised in that the air outlet speed of the suspended drying lengths (14, 25, 35, 37, 43, 44) comes to between 20 and 80 m/s.
4. Device according to one of claims 1 to 3, characterised in that each infra-red drying length (14, 25, 35, 37, 43, 44), measured in the direction of transport, has a length of 300 - 700 mm, and in that each suspended drying length (14, 25, 35, 37, 43, 44), seen in the direction of transport of the web, has a length of 50 - 400 mm.
5. Device according to one of claims 1 to 4, characterised in that at least two air support beams (14.1, 14.2, 14.3, 22, 23, 40, 41, 50) are provided, and in that the paper web is deflected through a corresponding arrangement of the air support beams at least twice in a respectively different direction of deflection (S-shaped deflection).
6. Device according to one of claims 1 to 5, characterised by such an arrangement of the first air support beam (12.1) following the roller slot, that the paper web passes round one of the two rollers after the roller slot.
7. Device according to one of claims 1 to 6, characterised in that the looping angle is between 0 and 5°.
8. Device according to one of claims 1 to 7, characterised in that a plurality of air support beams (41, 42) is combined to form a bank of air support beams.

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