SE427903B - Method and arrangement for covering both sides of a moving material web at two consecutive coating stations - Google Patents

Abstract

The invention concerns a method and an arrangement for covering both sides of a moving material web, for example, a paper web, with aqueous coating composition at two consecutive coating stations, wherein the first coating station - looking in the direction of travel of the web - contains a counter roll and a coating arrangement, so that the side of the web away from the counter roll is covered with the coating composition by means of said coating arrangement. After this, the web is taken to a nearby roll constituting the counter roll in the other coating station, where the other side of the web is covered. The envelope surface of the counter roll at the second coating station is held at such temperature that a condensate film is maintained between the envelope surface and the web lying against it. According to the invention, a water film is created entirely or partially by condensation by a separate controlled supply of warm moist atmosphere to at least one part of the zone of the envelope surface of the counter roll at the second coating station, which temporarily does not lie against the paper web. In this way, a uniform, thin and controllable water film can be formed between counter roll and paper web, which film by suitable control and/or regulating elements can be made to take up an optimal quantity regardless of possible variations in the moisture content and temperature of the paper web, coating mixture and surrounding air. <IMAGE>

Description

71311722-3 It is previously known to utilize the sheet coating technique coating both sides of a paper web, for example. In leaf- coating and other similar coating methods are used herein. in the case of a rotating roller as a counter or support roller in a sheet coating station. The paper web then passes beStIYkni fl9 SStati0 fl ên, wherein the outwardly facing side of the paper web is coated from the roll with a coating composition by means of a coating device and where the leveling of the coating composition takes place by means of a flexible blade. Because such devices require a counter roll the paper web thus coated on one side is thus dried in the other side of the web is coated in a second, similar coating station with counter-roller and blade to prevent deposits of coating mesh on the second counter roll. Because such facilities thus require two separate coating stations with intermediate drying, they are extremely space-consuming. they and also extremely complicated in their construction.

Recently, new interesting developments have been made to achieve a simultaneous coating of a paper both sides are paved with, for example, two leaves facing each other or with a blade acting against a counter roller. Such devices have the advantage that they are not very space consuming and in rule easy to operate and provides a simultaneous impregnation through the liquid phase of the coating agent. A disadvantage here, however, is that it is difficult to set different coating quantities on the base nans both sides, if desired.

It has also been proposed (Swedish patent 396,558) that coating both sides of your material web with water rich coating composition arranges two separate leaf coatings. ironing stations with a counter roll in each station on one in such a way that no intermediate drying is required.

According to the proposed method, it is possible to through strong cooling of the counter or support roller in the second coating station separating the batter layer from the support roll in a condensate film generated on the cold roll surface. The condensate film is generated due to the temperature difference between the cooled surface of the support shaft and the hot coating layer and the main 7811722-3 of the water present in the batter layer. When coating of the web with thick layers of batter, it is desirable to enlarge the temperature difference between the cooled support roll and the mare the batter layer by infrared radiation or otherwise arranged heating of the coating composition. The from the batter layers through the heating, the water evaporated densifies on the surface of the cooled support roll and also contributes to the generation of the condensate film. The cooled support roller is suitable of steel or metal and cooled by means of a coolant which fed to the roller through tubes.

However, the latter procedure is associated with disadvantages. It has proved important to lead desired effect must achieve a smooth and even well-fitted condensate film. Excessive condensate mark on the coated paper small amount of condensate tends to stain the coating, which gives markings considerable to achieve its amount quantity has shown the surface and one for provisions of on the paper surface.

This known method involves maintaining a temperate temperature. turn difference between the cooled mantle surface and the humidity in the paper web. As is well known, however, a paper path varies during, for example, the paper production with respect to its temperature and moisture content and the same applies to the the ironing agent. Such variations can occur relatively Quickly. Cooling of the jacket surface by means of suitable cooling devices, for example through a tube in the center of the counter roll through which the coolant passes, however, provides a sluggish temperature control system, partly due to the fact that the counter-rollers must for constructive reasons have large lots. In reality, this means variations in incoming moisture from the paper web and coating let knqgmst can be counteracted by a corresponding change of the temperature of the cooling roller, but will lead to an rollable change of the condensate film, which is not desirable. Admittedly, according to this prior art, a certain adjustable setting is achieved by means of a preheating of the paper web, for example, through an infrared dryer, but also this system tem is fraught with disadvantages. It is difficult to participate 7811722-3 preheater equipment compensate for changes in the input heating the amount in the paper web. It has been shown that for example changes in the air movements around the equipment give undesirable variations in the condensate layer both along and across telytan.

Another disadvantage of this prior art is that a large part of the condensation occurs between the web and the cooling roller. Then have already the coating layer has come to get at least pointwise contact with the mantle surface of the roller and in these places is easy sticking or deposits.

This prior art has additional disadvantages. As mentioned must in some cases resort to extra heating of paper the track on its way from the first to the second coating station with, for example, infrared radiation. One such arrangements are also space consuming, as the two stations must be placed at a certain distance usually exceeding 2 - 3 meters apart to enable efficient heating. In the case of high-speed machines, for example, one must be free paper web length of up to 6 - 7 meters is available for man shall receive sufficient time for the heating. This famous technology is also associated with other inconveniences. As you know there is always some swelling of the paper web when it is coated with a coating composition due to the fibrous material water uptake. This means that the paper web since it passed the first coating station at this known technology nik through said swelling gets longitudinal wrinkles depending on that the distance between the two stations amounts to perhaps 2 meters and more. In traditional coating devices with two separate coating stations and intermediate drying this is usually not a problem as the paper web is dry. and smoothed before passing the second coating the station. In the previously mentioned devices for simultaneous ironing both sides of the web does not cause wrinkling either no problem. According to the prior art treated without intermediate drying, however, difficulties arise after as one has to smooth out the wrinkles that occur through the paper moisture absorption during coating in the first station before 5 7811722-3 the track hits the roller in the other station to avoid bumps coating in this. In such a case, one must use one number of guide rollers, s.k. wide stretch rollers, which are specially designed shaped to smooth the paper web by stretching it sideways. This is a complication and especially when it comes to coating of relatively thin paper at higher web speeds difficulties arise in achieving good operational reliability, in particular as the paper web due to the coating in the first state tion is wet and fragile. Furthermore, provisions are easily made such intermediate rollers.

It has now surprisingly proved possible to eliminate the above-mentioned disadvantages and difficulties of the initial be ~ written way thereby, that a to its amount adapted thin water film in whole or in part in the form of condensate is produced by separately controlled supply of warm, humid atmosphere to at least a portion of the zone of the counter surface of the counter roll in it the second coating station, which is temporarily not adjacent to the paper web.

According to the proposed method, one is thus provided quantity and evenness controlled thin water film on the counter roller mantle surface in the second coating station before the mantle surface touched by the coated paper web by a separate controlled warm, humid atmosphere in suitable and adjustable amount is applied to at least a portion of that zone of the counter roll mantle surface in the second coating station as temporarily not abuts the paper web, at the same time as the temperature of the mantle surface in a similarly controllable manner is set to a suitable one temperature lower than that of the supplied, warm, humid atmosphere.

By the method proposed according to the invention, an even, thin and controllable water film is formed between the counter roller and paper web, which film by appropriate control and / or control means can be made to consume the optimum amount independently of possible variations in e.g. moisture content and temperature of paper web, coating batter and ambient air. Through that the proposed method also eliminates the need for between the counter rollers 7811722'3 5 horizontal heating devices and because of this be able the two counter-rollers are placed so close to each other that the risk for wrinkling is eliminated. For this reason it is not needed nor any leveling devices to eliminate wrinkles during the transport of the paper between the first and second coatings. station. Another benefit is gained by both the coating stations together form an extremely com- pact, clear and cheap unit. In a special embodiment according to the invention, the coating device can also be used 'as s.k. adhesive press for surface gluing or impregnation of paper bmnm.by causing the counter-rollers to be pressed against each other and possibly imparted the reverse direction of rotation. In an out embodiment according to the invention a water film is provided on the mantle surface, the temperature thereof being approximately equal high as the temperature of the incoming paper web. On so This way, cooling down of the web is avoided, which is a great advantage from an energy point of view. According to another embodiment man a water film with a temperature on the mantle surface, which is higher than the temperature of the paper web.

When using relatively warm mantle surfaces, do not set such high demands on good heat conduction at the mantle surface. Through this rubber-coated mantle surfaces can also be used, which is a great advantage part because you get a smoother coating.

The invention also comprises a device for carrying it out proposed method and this device is mainly characterized by bodies for the controlled separate supply of a warm, humid atmosphere to the part »of the counter surface of the counter roll in the second coating station, which does not abut the web. other features of the invention are apparent from those of the appended claims specified characteristics.

The invention will be described in more detail below reference to some embodiments shown in the accompanying drawings forms there v 72311722-3 Figs. 1-6 show schematic views of different embodiments.

Fig. 1 illustrates a first embodiment according to the invention where l denotes a paper web to be treated by coating with a coating composition, 2 denotes the counter roll in a first coating station, the coating of which device is denoted by 3 and comprises an application roller 4 and a leveling blade 5, all according to the prior art.

The paper web 1 thus coated on one side is brought to leave the counter roll 2 and then, after backing up, laid a short, free stretch with the coated side inwards partially enclose a counter roll 6, which is a counter roll in a second coating station, consisting of a coating device with an application roller 8 and a leveling sheet 9. The web 1 is then passed further in the direction of the arrows A over a guide roller 10 to the following the drying.

The counter roller 6, the jacket surface 12 of which is suitably constituted by a heating conductive material, such as steel or steel with an elastic rubber coating is provided with devices for supply or heat removal. In the embodiment according to Fig. 1 this is shown only in the form of a tubular bore 6a in the center of the roller body. Through this drilling can suitably a suitable medium in the form of, for example, a liquid is brought to supply or remove heat, all depending on the temperature desired maintain on the mantle surface. How this is done in detail is shown not in Fig. 1, as this can be done on many in and for known ways.

By means of a member II, a humid atmosphere is supplied by blowing on a limited suitable part of the circumferential surface 12 of the counter roll 6, i.e. the part which is not currently affected by the track l the inflated atmosphere is suitably composed of warm, humid air and with a temperature suitably exceeding the temperature at the mantle surface 12. By means of a suitable choice of temperature and water content in the blown air, a controlled coating of water film on at least a portion of the counter roll 7811722-3 s mantle surface that is not paper-affected. Through the formation of a thin water film prevents deposits on the counter roll 6 from that layer applied to one side of the web in the first coating the station. By means of the method according to the invention, one can include in and devices known per se carefully adjust the amount of water film, which is very important. An excessively strong water film can, as mentioned destroy the coating layer applied in the first station and a too thin or uneven water film leads to deposits reach the counter roller in the other coating station.

The moisture in the blown air can partly be water vapor and partly by very fine and evenly distributed water drops. If the air has a relatively high content of water vapor and small content or no content of water droplets, the water film is produced mainly by condensation. This may be the case in some cases preferred but means that in that case large amounts of water film is required at e.g. high-speed machines, large heating amounts are released during the condensation of the water vapor against the mantle surface, which can be a disadvantage. In other cases, it may be more appropriate that the water film is mainly produced by the moisture content of the conveyed air mainly consists of non-evaporated water, ie. very finely divided water droplets. In the latter In this case, small amounts of heat are released when the water film is formed, which in some cases can be an advantage. In some cases, it may on the other hand, it is appropriate that the moisture in the blown air it of water film consists of a mixture of water vapor and much fine water drops.

The device 11 in Fig. 1 for supplying a warm, humid atmosphere is shown only schematically and may consist of per se known components for the treatment of e.g. air as a device for heating of the air, supply of moisture, device for forced inflation, for example through nozzles or slits of the hot moist air against the mantle surface. To enable one after the other special conditions appropriate composition of the moisture in the air in the form of finely divided water droplets and water vapor, can in and Humidifiers known per se are used. A suitable one is e.g. a moisture chamber consisting of nozzles that atomize 9 7811722-3 the nozzles added water. The nozzles are suitably mounted in the ceiling on the humidity chamber while the air which is suitably heated to the temperature is brought to pass the humidity chamber in horizontal direction. At the bottom of the humidity chamber there is a collecting device for water. The device works in such a way that the hot air during its passage through the humidity chamber supplies heat energy, so that at least some of the droplets of water evaporate. Other water droplets remain in liquid form and the smallest ryokes with off the air flow and distributed in it. Larger drops of water fall either down to the bottom of the moisture chamber or can be removed in a special separator for water droplets that the humidified air the current passes after it has passed the humidity chamber.

By means of such a device, by suitable choice of heat supply, supply to the air, appropriate setting of moisture supply to the humidity chamber and the appropriate setting of the air speed the humid atmosphere so that it can be adapted in relation to mantle surface temperature, speed and other conditions such as prevails when coating.

With the device a certain amount of water can be brought in a controllable manner to coat the mantle surface in the form of a thin film. In that event if a small or moderate heat development is desired, it is set described device suitably so that the content of atomized water particles in liquid form are relatively high in relation to evaporated water. In the event that it is desired that the water film to be achieved by condensation, the device is so that all or most of the water supplied evaporated in the humidifier. In the former case, kept a relatively cold, moist film, while in the latter In this case, the film formed emits relatively large amounts of heat.

The device also includes suitable control means not shown, so that optimal data on temperature, humidity and air volume can set and regulated.

A simple way to obtain a constant and suitable condensate sation film is to control the setting of e.g. heat and moisture of the supplied air in relation to the temperature of the mantle surface. which is conveniently poured at a constant temperature. The latter said method is simple because a temperature gauge can easily 10 7811722-3 incorporated into the circulatory system of the medium supplying or remove heat to or from the roller.

It has also been found possible that according to the method avoid finding a cooling of the paper web due to the mantle surface does not need to be cooled but can be kept relatively warm.

This is a great advantage in terms of avoiding energy luster. For example, the mantle surface can be kept as warm as the paper the track and in some cases significantly warmer than the same but still obtain an even and well-adjusted condensate film. In the latter the case not only eliminates the heat loss but adds heat banana, which contributes to its drying. This is further an advantage because it facilitates the subsequent drying.

Fig. 2 illustrates another embodiment of the invention. Paper- the web has been denoted by l, a first coating device by 7 14, the counter roll to this with 13, the counter roll in the second coating station with 15, a bore for supplying liquid with l5a and a blade coating device for the second counter roll with l6. The blade coating device 16 in this case consists of and s.k. puddle type coater. Such a coater is known within coating technique and consists of a pond with a coating batter that is coated and smoothed using a downward-facing blade which presses against the paper web. A controlled hot, humid atmosphere inflated with a device designated 17. According to the In Fig. 2, the rollers are set very close to each other and in this way a very advantageous course is obtained without risks for creasing or abnormal stress on the paper web. This device can also be changed in a simple manner to used as a glue press. The paper web 18 (dashed) is then led for example over a guide roller 19 (dashed) between the rollers 13 and 15, which press against each other in the reverse direction of rotation (dashed arrows B). In this way, for example, surface gluing can be performed by means of the supply of e.g. starch solution per se known method, in which case glue solution is suitably added to the nip between the rollers. In this case, one or both stations 14 and 16 are disabled.

Fig. 3 shows another embodiment within the scope of the invention.

The paper web has been designated 1, the first coating device. the puddle type with 20, the counter roll to this with 13 and one 11 7811722-3 second coating device with 20a and a device for keeping the temperature constant on the mantle surface of the roll 15 has nats with l5a.

The second coating station 20a is also of the puddle type but the paper web is in this case bent off from the counter-roller 15 at an angle greater than the tangent through the point of contact of the blade on the the surface of said roll. Also in this case, the two counter-rollers are 13 and 15 were placed very close to each other so that any horizontal leveling roller against wrinkling is not needed.

Fig. 4 illustrates a further embodiment of the invention.

The paper web is denoted by l and it passes over the guide rollers 21 and 22 and is passed around the counter-roller 13 in a first coating station where a sheet coating device of in and for known type has been designated 41. The track is then transferred to the counter roll 15 in a second coating station where a second coating device is designated by 23. The paper web then leaves the counter roller 15 to pass between two hot air dryers 24 and 25.

These can consist of e.g. s.k. airfoil dryers, ie. boxes like provided with a suitable blowing device through which outflows hot dry air for contactless drying of the paper web. Organizer the application of hot, humid air according to the invention has been designated by 26 and a device for imparting the surface a controlled temperature has been denoted by l5a. In this In this case, the blowing device 26 is connected to the hot air the generator which generates hot air for the drawers 24 and 25 and which not shown in the figure. The hot air from the generator is dry and an auxiliary device for humidifying the incoming hot and dry air has been denoted by 27. This embodiment has it the advantage that a common hot air source can be used for both heating of the counter-roller 15 which for the subsequent contact free drying in the drying boxes 24 and 25.

According to the invention, a controlled and adjustable temperature temperature difference is maintained between the counter roll 15 and the jacket the surface and the added hot, humid atmosphere, which is directed against the part of the roller surface 15 of the roller which is temporarily not standing in contact with the track. To ensure good control, so that the required temperature difference is maintained should be appropriate .___ __...., ...__..._ ..-_ .., _ de ” 7811722- »3 i 12 the atmosphere is adjusted to its temperature, moisture content and quantity at appropriate values. This can be done, for example, by a continuous temperature measurement of the mantle surface 15 is performed.

This can be done in many ways, for example contactless through an infrastructure meter. Such has been designated by 28 in Fig. 4.

Conveniently, the temperature gauge that measures the surface temperature can the part of the mantle surface not enclosed by the web controls moisture content, temperature and / or air volume of the inflated air.

Fig. 5 shows a further embodiment of the invention. Pap- press lane designated l passes the coating plant. in the direction of arrow A. The track first passes a guide roller 21 and a counter-roller 13 belonging to a first, lower coating station comprising a blade coating device 14 of gare shown kind. Then turn the paper web from the counter roller 13 side coated with coating batter, it passes over one paper guide roll 29 to then with the coated side inward pass over the mantle surface of a roller 15 which constitutes the counter-roller of a second coating station with a blade coating device 23.

The paper web then leaves the counter roll 15 to pass between two hot air dryers_24 and 25 for contact-free drying. An an- arrangement for supply and removal of heat-carrying medium for maintaining the surface temperature of the mantle surface 15 has the nats with l5a.

A device for supplying moist, hot air to the jacket the surface of the counter roll 15 has been denoted by 30. In this case, a guide roller 29 is placed between the counter-rollers 13 and 15. As more mentioned, it is a great advantage if guide rollers between the two counter-rollers can be avoided and the risk of creasing on such types of paper, which are prone to moisture absorption swell and form folds, can be eliminated by placing the rollers are shown close to each other, as shown, for example, in Figs. 1, 2, 3 and 4.

The embodiment in Fig. 5 with intermediate guide rollers 29 is suitable for less fragile paper, such as high basis weight paper or carton. In such a case, a greater distance between the two counter-rollers 13 and 15 are accepted without risk of creasing. ning. In the device according to Fig. 5, by placing the rollers 'ïß11722-š 13 at a greater distance more space has been obtained between the coating devices 14 and 23, which in some cases may be a part.

Fig. 6 shows an embodiment of a supply device of hot, moist air against the counter roller in the second coating station according to the invention. In this case, the supply device remains of a central drawer 31, which extends across the paper banana. The box is connected by means of pipes to a device for supply of hot, humid air under overpressure. This connection damaged by the dashed circle 32. On the supply line the airflow, for example, can be regulated by means of dampers. One another way is to regulate the amount of air by means of speed control ring of a fan. The box 31 has two parallel walls 33 and 34, which forms a gap 35 directed towards the mantle surface 36. The box 3l is surrounded of two box-shaped spaces 37 and 38, each of which has a gap 39 and 40, respectively, which on both sides surround the gap opening 35.

Due to the prevailing overpressure, hot, humid air is forced into the arrows 41 direction towards the gap opening 35. The air hits that part of the jacket surface 36, which is located substantially in front of the gap opening. By the air in the gap according to the invention to its quantity, moisture content and temperature have adapted to the surface temperature of the mantle surface 36, one occurs immediately condensation on the same, releasing heat. The main part of the air flow is then caused to flow in through the 39 and 40, respectively, by imparting a certain negative pressure spaces 37 and 38. This negative pressure can most easily be achieved by placing the spaces by means of suitable devices connection with the suction side of the previously mentioned but not shown the fan for blowing air into the box 31.

The invention has been practically tested in various embodiments. the attached figures. Thus, for example, the mold according to Fig. 3 has been tested. The counter roller 15 has in an experimental series consisting of stainless steel with a chrome coating. Water has been added to the center tube 15a. As an example it can be mentioned that at on one occasion the water temperature was 20 ° od1den inflated atmosphere the vessel through the supply device 17 exhibited a temperature of 60 ° C and an estimated moisture content of 90% relative humidity 14 7811722-3 tighet. By a simple adjustment of the air volume by a damper a well-fitted thin water film could be obtained on the mantle surface 15. Despite varying speed, temperature and moisture content of the incoming paper web 1 and the brought the coating agent into the coating station 20 could be by a simple adjustment of said damper an optimal water film is maintained in a very simple and fast setting. bare way. In the example given, the roll diameter of the roll was l5 500 mm and the free web length of the paper web between them last point of contact on roller l3 and first contact with roller then l5 only 100 mm, which guaranteed a wrinkle-free and safe Track.

In another series of experiments, an experimental device according to Fig. 2, In this case the water was supplied with a temperature of turn of about 40 ° C. The incoming web and coating agent temperature was also about 40 ° C. In the blower 17 a humid atmosphere was maintained which had a temperature of about 75 ° C. Even in this case, a well av-e could in a very simple way suitable thin water film is maintained 'on the mantle surface. In this case, the rollers ll and 15 were so close to each other that almost contact was present, i.e. the paper web 1 was under transport. the door through the coating equipment at all times in contact with the support rollers 13 and 15, respectively, which is a great advantage, different when coating at high speeds of paper with a lot low basis weight (down to 19 g / m2).

In an experiment with equipment closest to that of Fig. 4 hot water was added to the roll so that the outer temperature of the roll surface : ur amounted to about 70 ° C. the rolling surface was rubbery, which gave a good coating result. The device provided by the device 26 the humidified atmosphere had a temperature of about 100-110 ° C, which gave a well-adjusted. water film on the mantle surface. In this case, it was obvious that the paper web during its passage around if the roller body 15 was supplied with a certain amount of heat from the jacket surface. The free path length of the paper between the rollers was varied and amounted to a maximum of 1 meter without risk of wrinkling. 7811722-3 15 The embodiments shown and described above constitute only a few exemplary embodiment of the applicability of the invention. Thus can by means of many completely different, per se known devices, warm atmosphere is applied to the mantle surface of the counter roller in the other the coating station and likewise know many different in and for known devices are used for temperature control at the counter roller. Thus, of course, do not need temperature control be done by supplying or removing heat through a central tube through the roller body.

Another way is to blow cold, dry atmosphere through a gap belonging to a suitable device, located before the hot air gap seen in the roller running lö mg, so that the roller surface cools immediately before passing through the shown inflators too hot, humid atmosphere. However, such a way can be normal only used for long-distance machines.

Claims (16)

-78117221-3, 16 P A T E N T K R A V A method of coating the two sides of a continuous web of material (1), for example a paper web, having an aqueous coating composition in two successive coating stations, the first coating station - seen in the running direction of the web - comprising a counter roll (2, 13) and a coating device (3, 14, 20) so that the web facing away from the counter-roller is coated with a coating composition by means of said coating device, after which the web without intermediate drying is caused to be transferred to a nearby roller constituting the counter roll (6, 15) in a second coating station, in which the previously coated side of the web is brought into abutment against the mantle surface (12) of the counter roll (6, 15) and in which the uncoated and from the second counter roll (6, 15) the outer surface of the web (12) is coated with the coating composition by means of a coating device, the outer surface (12) of the counter roll in the second coating station being kept at such a temperature. temperature that it causes moisture in the coating and in the surrounding atmosphere to condense on the mantle surface (12) of the second counter roll (6, 15) and thereby form a water film between the mantle surface (12) and the adjacent paper web (1). , characterized in that from a supply means (11, 17, 26, 30) a stream of warm, humid atmosphere of controllable composition is supplied to the part of the mating surface (12) of the counter roll (6, 15) in the second station which is temporarily out of contact with the running paper web (1), the composition of this hot, humid atmosphere being controlled so that an addition of moisture condensate is deposited on the jacket surface (12) of the second counter roll in order to maintain a substantially even thickness on the thin water film on the mantle surface (12). 2. A method according to claim 1, characterized in that the supplied moist, warm atmosphere is regulated with respect to its amount, its moisture content and its temperature to obtain a controllable heating of the mantle surface of the counter roll and a controlled formation of the water film thickness. 7811722-3 17 3. A method according to claim 1, characterized in that the temperature of the water film formed on the jacket surface (12) of the counter roll (6, 15) in the second coating station is set to a temperature which substantially corresponds to the temperature of the incoming the paper web. 4. A method according to claim 1, characterized in that the temperature of the water film formed on the mantle surface of the counter roll in the second coating station is set to a temperature which exceeds the temperature of the incoming paper web. 5. A method according to claims 1 - 4, characterized in that a hot moist air stream is blown against said part of the mantle surface of the second counter-roller. 6. A method according to claims 1 - 5, characterized in that the heat and moisture content of the supplied moist hot air stream is set in relation to the temperature of the web and / or the coating composition. 7. A method according to one or more of claims 1 - 6, characterized in that the moist hot air stream is generated in a hot air generator intended for connecting drying devices (24, 25), which for the purpose is arranged to cooperate with a humidifying device. 8. A seat according to claims 1-7, characterized in that the two successive counter-rollers are caused to assume such a position relative to each other that the free distance which the web of paper is transported between these counter-rollers becomes so short that the web can be advanced without contact with support and / or guide rollers. 9. A method according to claims 1 - 8, characterized in that the free web length of the paper web between the counter rollers does not exceed 1 meter. 10. A method according to claims 1 - 9, characterized in that the free web length of the paper web amounts to between 0 and 10 cm. 7811722-3 18 11; Device for coating the two sides of a continuous web of material (1), for example a paper web, with aqueous coating composition in two successive coating stations, the first coating station - seen in the running direction of the web - comprising a counter roll (2, 13) and a coating device (3, 14, 20), so that the web facing away from the counter roll is coated with the coating composition by means of said coating device, after which the web without intermediate drying is caused to be transferred to a nearby roll constituting the counter roll (6, 15) in a second coating station, in which the previously coated side of the web is brought into abutment against the circumferential surface (12) of the counter-roller (6, 15) and in which it is uncoated, and from the outer surface (12) of the second counter-roller (6, 15) the facing side of the web is coated with the coating composition by means of a coating device (7, 16, 20a, 23), the mantle surface (12) of the counter roll in the second coating station maintained at such a temperature that it causes the moisture in the coating composition and in the ambient atmosphere to condense on the jacket surface (12) of the second counter roll (6, 15) and thereby form a thin water film between the jacket surface (12) and the paper web (1) to give carrying out the method according to claim 1, characterized by supply means (11, 17, 26, 30) for supplying a stream of hot, humid atmosphere of controllable composition on the part of the mating surface (12) of the counter roll (6, 15) in the second station, which is temporarily not in contact with the running paper web (1) and means (27, 28, 31) for regulating the composition of the hot, humid atmosphere so that an addition of moisture condensate is deposited on the second counter roll mantle surface (12) in order to maintain a substantially uniform thickness of the thin water film on the mantle surface (12) thereby preventing the coating composition applied to one side of the paper web from being deposited on the mantle surface of the counter roll (6, 15) (12). Device according to claim 11, characterized in that said supply means (11, 17, 26, 30) comprise an outlet directed towards the circumferential surface of the counter-roller (6, 15) with outwardly extending outlet openings extending across the generator of the jacket surface and that the supply means the means is connected to a heat source and a humidifier (27). 7811722-3 19 Device according to Claims 11 to 12, characterized in that the heat source is the hot air generator for the connecting drying equipment (24, 25). Device according to claims 11 - 13, characterized in that the mantle surface (12) comprises a rubber coating. Device according to one or more of Claims 11 to 14, characterized in that the supply device comprises a central box (31) which, during the formation of a slit-shaped opening (35), extends transversely across the paper web (1) together with two box-shaped spaces (37, 38) which, during the formation of slit-shaped spaces (39, 40) on both sides, surround the opening (35). Device according to one or more of claims 11 - 15, characterized by means for alternative adjustment of the counter-rollers so that they abut each other and with the reverse direction of rotation form a so-called limpress. 17l Device according to one or more of claims 11 ~ 16, characterized in that the successive counter-rollers are arranged at such a distance from each other that the free web length between the rollers does not exceed 1 meter. 181 Device according to one or more of claims 11 - 17, characterized in that the free web length between the rollers does not exceed 10 cm.