EP3219849A1

EP3219849A1 - Device for treating fiber webs

Info

Publication number: EP3219849A1
Application number: EP16160408.7A
Authority: EP
Inventors: Jani Hakola; Reijo PIETIKÄINEN; Tapio Pitkäniemi; Aaron Mannio; Vesa Ahvenniemi
Original assignee: Valmet Technologies Oy
Current assignee: Valmet Technologies Oy
Priority date: 2016-03-15
Filing date: 2016-03-15
Publication date: 2017-09-20
Also published as: DE202017100655U1

Abstract

The invention relates to a device for treating fiber webs (W) by applying treatment substance on at least one surface of the fiber web (W), which device (10) comprises a first roll (11) and a second roll (12) or the first roll (11) and a counter element, in between of which first and second roll (11, 12) or between the first roll (11) and the counter element a treatment nip (N) is formed, means (21, 22) for applying treatment substance (TS) by spraying and a treatment chamber (14, 15), in which the treatment substance (TS) is applied, and which treatment chamber (14, 15) comprises an inlet opening and an outlet opening, which device (10) applies the treatment substance via at least one the rolls (11, 12) or via the counter element onto at least one surface of the fiber web. The device (10) further comprises means (27) for creating underpressure inside the treatment chamber (14, 15) and the outlet opening of the treatment chamber (14, 15) is provided with means (26) for creating a sealing air flow directed substantially into the treatment chamber (14, 15).

Description

The invention relates to a device for treating fiber webs. Especially the invention relates to a device for treating fiber webs by applying treatment substance on at least one surface of the fiber web, which device applies the treatment substance via a roll onto at least one surface of the web. In particular the invention relates to a device according to the preamble of claim 1.
As known from the prior art in fiber web producing processes typically comprise an assembly formed by a number of apparatuses arranged consecutively in the process line. A typical production and treatment line comprises a head box, a wire section and a press section as well as a subsequent drying section and a reel-up. The production and treatment line can further comprise other devices and sections for finishing the fiber web, for example, a sizer, a calender, a coating section. In this description and the following claims by fiber webs are meant for example paper and board webs.
In production of fiber webs, for example of paper or board webs, sizing is used to alter the properties of a fiber web by adding sizing substances, for example glue chemicals. In surface sizing the sizing substance is added onto the surface of the fiber web directly or via a roll at the dry end of the fiber web machine. The sizing of paper and board web typically utilize a separate sizer. In connection with the sizer different kinds of sizing technology are employed in prior art arrangements, for example pond sizing technology or film-transfer technology or spray sizing technology.
Coated fiber web grades and coating are becoming more and more popular and thus the coating process and equipment have increasing demands imposed thereon. In coating, especially in pigment coating, the surface of a fiber web is formed with a layer of coating color (coating substance) at a coating station followed by drying. The process of coating can be divided in supplying the coating color onto the web surface, which is called the application of the coating color, as well as in the adjustment of final amount of coating color. The coating of paper and board web typically utilize a coating device - a coater. In connection with the coater different kinds of coating technology are employed in prior art arrangements, for example curtain coating, blade coating, spray coating or film transfer coating technology.
In sizing and film transfer sizing/coating rolls are used to press the treatment substance into the web in nip formed between these rolls and through which nip the fiber web is guided.
The present invention relates to spray technology and to spray sizing application via a roll onto the surface of the fiber web. By using spray technology good and fast adjustability of treatment substance amount is achieved. In general, spray application method has fast and accurate control of applied treatment substance amounts and further, the method is contactless and the recirculation of the applied substance is minimal. Therefore the treatment substance contamination due to the impurities from the web is avoided, which makes this method very suitable for treating dirty recycled fiber based products, like fluting or liner boards. Spray sizing with one or two sided application onto the surfaces of the web is known from prior art. Typically application beams of a spray sizer are positioned above the rolls in top position near the converging nip. The downside of this solution is that application beam movement is needed, for example during tail threading or cleaning the application beams. Further, eventual accumulation of impurities at beam surfaces may lead to dropping of impurities directly onto the roll or onto the web, thus creating a risk of web breaks.
In patent application publication EP 2811069 is disclosed a device for applying treatment substance on at least one surface of the fiber web, which treatment device for applying treatment substance on the at least one surface of the fiber web may apply the treatment substance directly onto the at least one surface of the web or the treatment substance may be applied onto the at least one surface of the web via a roll onto surface of which the treatment device is provided to apply the treatment substance, which device comprises a treatment zone, such as a spraying zone, in which the treatment substance is applied. In the example of figure 8 of this publication the treatment devices for applying treatment substance on the both surfaces of the passing fiber web are located inside a hood. The treatment devices apply the treatment substance by spraying means onto the surfaces of rotating rolls and in the nip formed between the rolls the treatment substance is applied onto the both surfaces of the fiber web. The treatment device comprises a treatment zone, such as a spraying zone, in which the treatment substance is applied by spraying means. The treatment zone is located inside the hood and means for providing gas flows are located at the inlet and the outlet opening of the treatment zone i.e. nozzles providing gas flows are located at the inlet and at the outlet edge of the hood.
In patent publication EP 2811069 disclosed arrangement the treatment zone containing hood is equipped with nozzles at its inlet and outlet edges for blowing gas flows in order to prevent the roll boundary air layer disturbing the spraying. However, the gas flow at inlet opening and the gas flow at outlet opening are directed towards the roll and the web and not preventing the mist leaking out of the hood but merely directing the mist flow towards the roll surface.
An object of the present invention is to create a device for treating fiber webs in which the problems and disadvantages of the devices known from the prior art are eliminated or at least minimized.
An object of the present invention is to create a new type of device for treating fiber webs in connection with a production and treatment line of a fiber web.
An object of the present invention is to provide a device for treating fiber web in which spray technology is used for applying treatment substance, in which device the treatment substance is applied onto the surface of the fiber web via a roll and in which disadvantages especially to mist formation of the treatment substance and/or to accumulation of the treatment substance onto walls of the device and/or to dropping the formed debris and/or to dripping of the treatment substance onto the fiber web and/or onto the surface of the roll as well as problems relating to cleanliness of the device are eliminated or at least minimized.
An object of the present invention is also to provide a device for treating fiber web in which spray technology is used for applying treatment substance, in which device the treatment substance is applied onto the surface of the fiber web via a roll in which the applied treatment substance can be applied to the web with better evenness and in general with better film quality than in the from prior art known spraying methods.
An object of the present invention is also to provide a device for treating fiber web in which spray technology is used for applying treatment substance, in which device the treatment substance is applied onto the surface of the fiber web via a roll in which disadvantages relating to maintenance are eliminated or at least reduced.
Further an object of the present invention is also to create a device for treating fiber web in which spray technology is used for applying treatment substance with a simple and economical construction design.
In order to achieve the above objects and those which will come apparent later the device is characterized by the features of claim 1. Advantageous embodiments and features are disclosed in the dependent claims.
According to the invention the device for treating fiber webs by applying treatment substance on at least one surface of the fiber web comprises a first roll and a second roll or the first roll and a counter element, in between of which first and second roll or between the first roll and the counter element a treatment nip is formed, means for applying treatment substance by spraying and a treatment chamber, in which the treatment substance is applied, and which treatment chamber comprises an inlet opening and an outlet opening, which device applies the treatment substance via at least one the rolls or via the counter element onto at least one surface of the fiber web, wherein the device further comprises means for creating underpressure inside the treatment chamber and that the outlet opening of the treatment chamber is provided with means for creating a sealing air flow directed substantially into the treatment chamber.
According to an advantageous feature of the invention the means for creating the sealing air flow comprise at least one nozzle and the sealing air flow is directed towards the outlet opening from outside the treatment chamber.
According to an advantageous feature of the invention the sealing air flow provides an air brush effect and smoothens and/or doctors onto the roll and/or onto the counter element applied treatment substance layer.
According to an advantageous feature of the invention the device further comprises means for removing excessive treatment substance from the treatment chamber and wall structure of the treatment chamber, which is formed as a downward towards the means for removing excessive treatment substance, which means for removing excessive treatment substance comprise a discharge opening, declining wall structure and comprising a discharge opening, which is located at the lowermost end of the treatment chamber and the wall structure comprises no horizontal walls.
According to an advantageous feature of the invention at least partially inner surfaces of the wall structure of the treatment chamber are hydrophilic or wettable.
According to an advantageous feature of the invention the means for applying the treatment substance are spray applicators comprising spray nozzles creating by treatment substance sprays the treatment substance layer onto the surface of the roll or onto the surface of the counter element in the treatment chamber.
According to an advantageous feature of the invention each spray applicator comprises one or more rows of spray nozzles extending in the longitudinal direction of the roll.
According to an advantageous feature of the invention the treatment substance sprays are overlapping.
According to an advantageous feature of the invention the nozzles of the spray applicator are releasably attached outside to a wall structure of the treatment chamber.
According to an advantageous feature of the invention the nozzles of the spray applicator are attached to a turnable nozzle holder outside to a wall structure of the treatment chamber.
According to an advantageous feature of the invention the treatment chamber is positioned at least partially below an imaginary horizontal line passing through the middle point of the roll, advantageously tip of at least one nozzle of the device is on or below the imaginary horizontal line passing through the middle point of the roll.
According to an advantageous feature of the invention the underpressure is at least 100 Pa.
According to an advantageous feature of the invention the inlet opening of the treatment chamber comprises a mechanical sealing lip, which is adjustable such that distance between the mechanical sealing lip and the roll surface is at most 8 mm.
According to an advantageous feature of the invention the treatment chamber extends in longitudinal direction of the roll over the axial length of the roll and over the width of the fiber web, onto which the treatment substance is to be applied.
According to an advantageous feature of the invention the device comprises means for providing moisturizing liquid for the treatment chamber.
By the invention and its advantageous features several advantages are achieved. In the present invention the spray technology is utilized and the treatment substance is applied onto the fiber web via the rolls. As the spray application is noncontact process, application method does not set requirements on roll covers, and for example, either hard or soft elastic covers can be used. In addition, the present invention provides improved quality potential in surface treatment process, for example by using multiple overlapping spray nozzles, selecting optimal wettable roll covers, using the sealing air blow for flattening the sprayed film layer on the roll and providing sufficient time for the sprayed film to settle down on the roll before pressing the film to the fiber web in the nip. In the present invention, the inventive position of the treatment chamber for the spray applicator provides an advantageous arrangement for applying treatment substance via roll onto the fiber web, in which the treatment substance does not drip onto the fiber web, in which constructional design can be made simple and provides for easy maintenance. In particular, the position of the treatment chamber can be chosen conveniently without needing to construct complicated application beam movement systems. In the device according to the invention the advantageous arrangement of the air sealing blow and at least partial underpressure in combination with the inventive position and design of the treatment chamber improves mist collection and cleanliness of the device, prevents dropping and dripping the treatment substance onto web or roll surface and provides easy and efficient recovery of the treatment substance. The application beam design and general layout of the sizer can be simplified considerably due more convenient installation positions and less need for beam moving equipment. The process reliability, robustness and cleanliness are improved when application beam is placed next to the roll in lower position, instead of placing the application beam next to the web above the rolls. In particular, when positioning the application beams under the rolls, and the application direction is from below to up towards the roll, the dropping and the dripping of the treatment substance onto the surfaces of the roll and the web can be avoided totally.
In the following the invention is described in more detail with reference to the accompanying drawing in which

figures 1 - 2 shows schematically one example of a device according to the invention,
figure 3 shows schematically one further example of a device according to the invention,
figure 4 shows schematically one further example of a device according to the invention,
figure 5 shows schematically the example of figure 4 in nozzle removal and/or change position,
figures 6 and 7A-7B show schematically examples of the invention in connection with different fiber web runs,
figure 8 shows schematically an example of the invention, in which the counter element is a belt and
figure 9 shows yet an example of the invention with connection of one type of a fiber web run.

In the following description and in the accompanying drawing by same reference signs similar or corresponding parts and part-components are denoted unless otherwise mentioned. It should especially be noted that in some of the examples the details and the structure of the device might have been shown in the figures and explained in the following with reference to a treatment chamber in connection of one of treatment chambers in connection with one of the rolls only. By this is not meant that the treatment chamber in connection with the other roll could not comprise the corresponding details and structures, the treatment chambers in connection with one or both of the rolls may be as explained.
In the example of figures 1-9 is shown a device 10 for treating a fiber web W such as a paper or cardboard, which comprises two rolls 11, 12, such as sizing rolls or coating rolls, in between of which rolls 11, 12 a treatment nip N such as a sizing nip or a coating nip is formed, figures 1-7B and 9. The treatment nip N can also be formed in between a roll and a counter element, figure 8, for example a belt loop or a metal belt, instead of a roll. The treatment nip N is advantageously a pressing nip and in the nip N treatment substance TS is transferred from the surfaces of the rolls 11, 12 onto the fiber web. The rolls 11, 12 can be provided with an elastic coating. The fiber web W runs through the treatment nip N in direction SW. The rolls 11, 12 are rotatable and have in rotation direction S11, S12. The device 10 also comprises means 21, 22 for applying treatment substance. The means 21, 22 are spray applicators 21, 22 which apply treatment substance TS onto the surface of the corresponding roll 11, 12. The spray applicator 21 applies the treatment substance TS onto the roll 11 and the spray applicator 22 onto the roll 12.
Typically the spray applicator 21, 22 comprises spray nozzles, which are for example pressure atomizing or air atomizing nozzles, spaced apart and located in a row extending in the axial direction of the roll 11, 12. Each nozzle creates of spray, which is a spray fan, and in the figure 1 the treatment substance sprays are indicated by reference signs 21 S, 22S. In the example of the figure 1 there is one row of nozzles in the spray applicator 21 for the roll 11 and two rows of nozzles in the spray applicator 22 for the roll 12. In the examples of other figures there is one row of nozzles in each application chamber. The number of rows for each applicator may vary depending on the demands of the application of the treatment substance TS, advantageously more than one row of nozzles is used for providing multilayer application of the treatment substance TS onto the roll 11, 12. The treatment substance sprays 21 S, 22S are advantageously overlapping such that the treatment substance layer formed onto the roll is formed from at least two overlapping sprays. The nozzles of the spray applicator 21, 22 are releasably attached outside to a wall structure of the treatment chamber 14, 15 and thus the nozzles can be released for maintenance or replacement without moving the chamber even during the running of the device 10, especially when more than one nozzle row is used. The nozzles of the spray applicator 21, 22 may be attached to a nozzle holder 25 as shown in the examples of figures 3 - 5. The nozzles are advantageously pressure atomizing or air atomizing nozzles.
The spray applicators 21, 22 are provided at the treatment chamber 14, 15, which is formed by wall structure forming a turned hood like structure covering the area in which the treatment substance is applied by the spray nozzles of the spray applicators 21, 22 and the treatment chamber 14, 15 is positioned at a small distance from the surface of the roll 11, 12, advantageously at a distance of 10 - 50 mm from the surface of the roll 11, 12. The treatment chamber 14, 15 also has a discharge opening 16, 17 to treatment substance recovery outlet line by which the possibly dropping and/ or dripping treatment substance is collected. The treatment chamber 14, 15 can also be provided with means 26 for providing a sealing air blow at the outlet gap, or the outlet opening of the treatment chamber 14, 15 and means 27 for creating underpressure and for mist evacuation. The treatment chamber 14, 15 is advantageously at least partially under underpressure, preferably the underpressure is at least 100 Pa. The inlet gap or the inlet opening of the treatment chamber 14, 15 advantageously comprises a mechanical sealing lip 18, 19.
The device 10 may also comprise means 38 for providing moisturizing liquid as shown in the example of figures 1 and 3-5. The moisturizing liquid is for keeping the outer surfaces of treatment chamber 14, 15 clean. The moisturizing liquid may also be guided inside the treatment chamber 14, 15, where the moisturizing liquid helps in keeping the inner surfaces of the treatment chamber 14, 15 clean. By temperature of the moisturizing liquid also the temperature of the treatment chamber 14, 15 can be controlled, which is important in connection with certain treatment substances in view of their applicability and also in view of keeping the treatment chamber clean. The means 38 for providing moisturizing liquid is typically a liquid nozzle creating a moisturizing liquid spray.
In the example of figure 1 - 9 the treatment chamber 14, 15 is located at a position beneath the corresponding roll 11, 12 and thus dropping and/or dripping of the treatment substance onto the fiber web W and onto the surfaces of the rolls 11, 12 is prevented and maintenance is easy as the chambers are at an easily reachable position and for example no elevated walkways, service platforms or corresponding elevated structures are needed. The position of the treatment chamber 14, 15 is below horizontal level of middle point of the corresponding roll 11, 12.
The treatment chamber 14, 15 also may comprise means to turn or to tip the chamber position for example for maintenance, like cleaning or nozzle change, figure 5. The position of the chamber 14, 15 is also advantageous as they do not easily collect impurities from the surroundings. The position of the treatment chamber 14, 15 also enables a simple design and construction of the application chamber and wall structures thereof as space and mounting possibilities are easily available.
The wall structure of the treatment chamber 14, 15 is formed as a downward towards the discharge opening 16, 17 declining wall structure and thus the discharge opening is located at the lowermost end of the treatment chamber 14, 15. The wall structure of the treatment chamber 14, 15 advantageously comprises no horizontal walls onto which the treatment substance could accumulate. Advantageously at least partially inner surfaces of the wall structure of the treatment chamber 14, 15 are hydrophilic and wettable such that liquid drops spread on the surface and therefore the surfaces prevent any accumulation of substance on the inner surfaces of the treatment chamber 14, 15. The wall structure is advantageously made of stainless steel with brushed, sandblasted or cold-rolled steel with type 2B finish.
As can be seen from figure 2 the treatment chamber 14, 15 advantageously extends in longitudinal direction of the corresponding roll 11, 12 over the axial length of the roll 11, 12 and over the width of the fiber web W onto which the treatment substance TS is to be applied. The treatment substance TS is scraped from the edge areas i.e. from the areas of the roll 11, 12 surface not becoming into contact with the fiber web W by doctors 31, 32. The ends of the treatment chamber 14, 15 in longitudinal direction are advantageously sealed by a narrow suction zone 23, 24 or mechanical sealing.
The means 27 for creating underpressure reduces air pressure inside the treatment chamber 14, 15 and creates suction effect through the inlet gap between the roll 11, 12 and the treatment chamber 14, 15 at the sealing lip 18, 19 side. The suction effect creates a suction air flow into the treatment chamber 14, 15 and the suction air flow and boundary layer air flow created by the rotating roll 11, 12 flowing near the roll surface together eliminate mist and air escaping from the treatment chamber 14, 15 through the inlet gap. The means 26 for creating sealing air blow create powerful external air stream towards outlet gap of the treatment chamber 14, 15 and increase air pressure near the outlet gap. The means 27 for creating underpressure reduce air pressure inside the treatment chamber 114, 15 and create suction effect through the outlet gap. Together the means 27 for creating underpressure and the means 26 for creating sealing air blow create pressure difference over the outlet gap and create air flow flowing through the outlet gap from outside to inside of the treatment chamber.
In the device the mist collection is thus advantageously arranged as an air-collecting underpressure system, which is created as a selected combination of suction by the means 27 for creating underpressure, by air flows of the means 26 for creating sealing air blow. The sealing air blow provided by the means 26 for creating sealing air blow is advantageously directed into the treatment chamber 14, 15. The means 26 for creating the sealing air blow can be constructed as an integrated structure with the treatment chamber 14, 15 or as a separate device, such as an air knife or other another type of slot nozzle known as such to one skilled in the art.
The sealing air blow created by means 26 creates also an air brush effect, in which air flow friction against the surface creates forces in the sprayed treatment substance layer. These forces create flow in the substance layer and the flow flattens the unevenness of applied treatment substance layers. The flows can even repair incomplete wetting of the surface by making separate droplet joining together for example when spray coverage is not complete.
The gap between the surface of the roll 11, 12 and the edge of the wall structure of the treatment chamber 14, 15 at the outlet opening of the treatment chamber is small, advantageously 10 - 50 mm. At edge areas of longitudinal direction of the roll 11, 12 the edge doctor 31, 32, known as such to one skilled in the art, can be used. By the edge doctor 31, 32 also the treatment substance TS application width is adjustable.
The mist and drips of the treatment substance is collected in the treatment chamber 14, 15 and guided by the declining wall structure to the outlet opening 16, 17 and via recovery lines to the treatment substance recovery device and advantageously therefrom via return line (now shown) back to a supply system (not shown) of the spray applicator 21, 22. The treatment substance collected is clean from impurities, f. ex. of fibers, as due to the position of the treatment chamber the possible fibers detaching from the fiber web will not drift to the treatment chamber.
The device 10 is very advantageous enabling stable and clean starting and ending phases of the application of the treatment substance as the uncontrolled droppings and/or drippings are guided by the wall structure of the treatment 14, 15 chamber to the discharge opening 16, 17. The sealing air blow can be used as an air blade doctor to remove possible treatment substance from the surface of the roll 11, 12.
In the example of figures 1 and 3 the means 26 for creating sealing air flow are attached integrated to the wall structure of the treatment chamber 14, 15 in connection with the roll 11. In the examples of figures 4 - 5 the means 26 for creating the sealing air flow is constructed separated from the treatment chamber 14. In the example of figure 5 is shown the nozzle holder 25 in a position turned for maintenance, for example for nozzle removal and/or change. In the example of figures 6 - 7B and 9 is shown some examples of fiber web runs in connection with the invention: in figure 6 the fiber web run is horizontal in the figure direction SW from right to left, in figures 7A - 7B the fiber web run direction SW is vertical, in figure 7A downwards and in figure 7B direction SW is upwards in the figure, and in the example of figure 9 the fiber web run is guided directly from the surface of one roll 11 to the surface of the other roll 12. In the example of figure 9 two treatment substance layers are applied on one surface of the fiber web W the first layer directly onto the fiber web W and the second layer via the roll 12 and on the other surface of the fiber web W one layer of the treatment substance is applied via the roll 11. The example of figure 9 may also be formed as a wet stack calender in connection with a multinip calender or a one or two nip calender with soft or hard nips, in which water and/or chemicals is applied onto the fiber web by in the treatment chamber 14, 15. In the example of figure 8 one element forming the treatment nip is formed as a belt 35 that is arranged to form a rotating continuous loop guided by rolls 36 and it may also comprise a counter roll 37 for the nip roll 11 inside the belt loop 35. It should be noted that in the examples of figures 6 - 9 the treatment chambers 14, 15 are shown simplified and advantageously at least one treatment chamber 14, 15 shown in each example comprises features of the invention.
Above only some advantageous examples of the invention has been described to which examples the invention is not to be narrowly limited and many modifications and alterations are possible within the invention.
Reference signs used in the drawings:

10 device for treating fiber webs
11, 12 roll
14, 15 treatment chamber
16, 17 discharge opening
18, 19 sealing lip
21, 22 applicator
23, 24 suction zone, mechanical sealing
25 nozzle holder
26 means for providing a sealing air blow
27 means for creating underpressure and for mist evacuation
31, 32 edge doctor
35 belt
36 roll
37 counter roll
38 moisturizing liquid nozzle
21 S, 22S nozzle spray
S11, S12 rotation direction
N nip
W fiber web
SW running direction

Claims

Device for treating fiber webs (W) by applying treatment substance on at least one surface of the fiber web (W), which device (10) comprises a first roll (11) and a second roll (12) or the first roll (11) and a counter element, in between of which first and second roll (11, 12) or between the first roll (11) and the counter element a treatment nip (N) is formed, means (21, 22) for applying treatment substance (TS) by spraying and a treatment chamber (14, 15), in which the treatment substance (TS) is applied, and which treatment chamber (14, 15) comprises an inlet opening and an outlet opening, which device (10) applies the treatment substance via at least one the rolls (11, 12) or via the counter element onto at least one surface of the fiber web, characterized in that the device (10) further comprises means (27) for creating underpressure inside the treatment chamber (14, 15) and that the outlet opening of the treatment chamber (14, 15) is provided with means (26) for creating a sealing air flow directed substantially into the treatment chamber (14, 15).
Device according to claim 1, characterized in that the means (26) for creating the sealing air flow comprise at least one nozzle and the sealing air flow is directed towards the outlet opening from outside the treatment chamber (14, 15).
Device according to claim 1 or 2, characterized in that the sealing air flow provides an air brush effect and smoothens and/or doctors onto the roll and/or onto the counter element applied treatment substance layer.
Device according to any of claims 1-3, characterized in that the device (10) further comprises means (16, 17) for removing excessive treatment substance from the treatment chamber (14, 15) and wall structure of the treatment chamber (14, 15), which is formed as a downward towards the means for removing excessive treatment substance, which means for removing excessive treatment substance comprise a discharge opening (16, 17), declining wall structure and comprising a discharge opening, which is located at the lowermost end of the treatment chamber (14, 15) and that the wall structure comprises no horizontal walls.
Device according to claim 4, characterized in that at least partially inner surfaces of the wall structure of the treatment chamber (14, 15) are hydrophilic or wettable.
Device according to any of claims 1 - 5, characterized in that the means (21, 22) for applying the treatment substance are spray applicators (21, 22) comprising spray nozzles creating by treatment substance sprays (21 S, 22S) the treatment substance layer onto the surface of the roll (11, 12) or onto the surface of the counter element in the treatment chamber (14, 15).
Device according to claim 6, characterized in that each spray applicator (21, 22) comprises one or more rows of spray nozzles extending in the longitudinal direction of the roll (11,12).
Device according to claim 6 or 7, characterized in that the treatment substance sprays (21 S, 22S) are overlapping.
Device according to any of claims 6 - 8, characterized in that the nozzles of the spray applicator (21, 22) are releasably attached outside to a wall structure of the treatment chamber (14, 15).
Device according to any of claims 6 - 9, characterized in that the nozzles of the spray applicator (21, 22) are attached to a turnable nozzle holder (25) outside to a wall structure of the treatment chamber (14, 15).
Device according to any of claims 1 - 10, characterized in that the treatment chamber (14, 15) is positioned at least partially below an imaginary horizontal line passing through the middle point of the roll (11, 12), advantageously tip of at least one nozzle of the device is on or below the imaginary horizontal line passing through the middle point of the roll.
Device according to any of claims 1 - 11, characterized in that the underpressure is at least 100 Pa.
Device according to any of claims 1 - 12, characterized in that the inlet opening of the treatment chamber (14, 15) comprises a mechanical sealing lip (18, 19), which is adjustable such that distance between the mechanical sealing lip and the roll surface is 8 mm or less.
Device according to any of claims 1 - 13, characterized in that the treatment chamber (14, 15) extends in longitudinal direction of the roll (11, 12) over the axial length of the roll (11, 12) and over the width of the fiber web (W) onto which the treatment substance (TS) is to be applied.
Device according to any of claims 1 - 14, characterized in that the device (10) comprises means (38) for providing moisturizing liquid for the treatment chamber (14, 15).