JP2010017711A - Apparatus for coating and drying face and back of web, especially web made of paper or pasteboard - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus that enables coating and drying of both sides of a web, especially a web made of paper or pasteboard in a space- and energy-saving way. <P>SOLUTION: The apparatus includes a first coating unit 14 for applying a liquid or paste-like coating medium to the first side 12a of the web 12, especially the web made of paper or pasteboard moving in the traveling direction L. The coating/drying apparatus further includes a second coating unit 16 for applying a liquid or paste-like coating medium to the second side 12b of the web 12 which is the other side of the first side 12a, and a drying unit 18. The second coating unit 16 works without contacting the web. The drying unit 18 is located downstream from both coating units 14 and 16 in the traveling direction L of the web 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coating / drying device, which has a first application device for applying a liquid or paste-like application medium on a first surface of a material web that moves in the direction of travel, in particular paper or cardboard. And it has the 2nd coating device which apply | coats a liquid or a paste-form application medium to the 2nd surface of the material web on the opposite side to a 1st surface, and has a drying apparatus.

  This type of coating / drying apparatus is well known in the prior art. In these devices, a layer of coating medium is usually applied to one side of the material web and then dried in a drying device. Only then is the coating medium layer applied to the other side of the material web and dried as well. The disadvantage of such a coating / drying device is that, firstly, it must be equipped with two drying devices, which is not only expensive for the purchase and maintenance of these drying devices, but also more Requires space. Second, the energy efficiency of single-sided drying, that is, the drying effect per unit of energy applied, leaves many points to be demanded.

  In contrast, an object of the present invention is to provide a coating / drying device of the type mentioned at the outset, which makes it possible to coat and dry both sides of a material web in a space-saving and energy-saving manner.

  According to the invention, this object is achieved by a general-purpose type coating / drying device, in which the second coating device is a non-contact operating coating device, and the drying device in the device is in the direction of travel of the material web. Located downstream of the two applicators. According to the present invention, therefore, intermediate drying is not performed, in other words, there is no drying device provided between the position of the first coating device and the position of the second coating device. This saves firstly all the space otherwise required for the second drying device and secondly saves the costs required to purchase and maintain the second drying device. Furthermore, the heat provided by the drying device can be absorbed not only by one wet application medium layer but also by two wet application medium layers. Heat absorption results in higher efficiency and improves the energy efficiency of the coating / drying device according to the invention when compared to the coating / drying device according to the prior art.

  According to another aspect of the present invention, for a general-purpose type coating / drying device, the two applicators are arranged at substantially the same position in the direction of travel of the material web, and the drying devices are arranged in the direction of travel of the material web. It is proposed to arrange downstream. At least one, and preferably both, of the applicator can be advantageously designed as an applicator operating in a non-contact manner. However, this excludes the case where at least one coating device becomes a coating device for transporting the coating medium indirectly using the transport surface of a transport element, preferably a transport roller, which transports the coating medium in the form of a coating medium layer. Not what you want.

  With the arrangement according to the invention of the coating / drying device according to the second aspect, it is likewise possible to dispense with intermediate drying when both sides of the material web are coated, the arrangement of the two applicators being the running of the material web In the case of approximately the same position in the direction, this omission of intermediate drying is also perfectly compatible with contact application, where appropriate applying extra to the material web.

  The described non-contact application device applies the application medium to the material web with substantially no excess (“one-to-one application”). Therefore, there is no need to scrape off excess coating media and no physical contact with the material web occurs. As a result, the non-contact applicator applies only a low stress to the material web, in particular only due to the softening of the material web by the liquid contained in the application medium. As the non-contact coating device used, for example, a spray coating device or a curtain coating device is also possible.

  In principle, the first applicator can also be an applicator for coating in contact with the material web, for example a blade applicator, a doctor blade for flattening and / or metering the application layer of the application medium The material web travels through a roll gap formed between two rollers, such as a coating device or a film coating device, and in this roll gap, a coating medium applied to one surface of the roller. A coating device such as a coating device that comes into contact with the film is conceivable. However, according to the present invention, the first coating device is also preferably a coating device that operates in a non-contact manner, such as a curtain coating device. The low stress of the material web associated with this is important for the present invention, in particular according to the present invention the material web is subjected to intermediate consolidation by performing moisture recovery in an intermediate dryer between the two applicators. It is because it does not experience.

  Depending on the total space available for the coating / drying device arrangement and other boundary conditions, at least one curtain applicator can apply the application medium to the material web from above by gravity. However, in addition or as an alternative, it is also possible to assign a deflection device to at least one curtain coating device, which deflects the coating medium curtain from the curtain coating device from the path of gravity. The deflection of the application medium curtain can be based, for example, on electrostatic and / or electromagnetic interactions that occur between the application medium in the application medium curtain and the deflection device. This type of deflecting device that operates electrostatically and / or electromagnetically is well known in the prior art and will not be described in further detail here.

  According to the above, it is also possible to deflect the coating medium curtains from both curtain coating devices from their respective paths due to gravity using a deflection device. According to an exemplary web path, the material web can travel substantially vertically from bottom to top, the two applicators are each located on either side of the material web, and the two applicator media curtains start the deflection device By doing so, it is deflected from the path of gravity that does not wet the material web as it is, to the operating path that wets the material web.

  Particularly when deflecting both coating medium curtains, it is advantageous if the two coating devices are arranged at approximately the same position in the direction of travel of the material web.

  Furthermore, it is proposed that the two applicators be arranged on a section of the material web that runs in a substantially vertical direction, preferably from bottom to top. Reference to “running in a substantially vertical direction” herein includes, as a whole, a larger angular tolerance for a precisely vertical path, up to ± 45 degrees if appropriate. However, a smaller angular difference, for example ± 20 degrees, would be more appropriate for a precisely vertical path.

  However, in principle, the second applicator can also be arranged downstream from the first applicator in the direction of travel of the material web. For example, the two applicators can also be arranged in a section of the traveling part of the material web that travels substantially horizontally to allow application from above the application medium. This is particularly advantageous when curtain applicators are used. Since this “from the top” application is still easily possible even with tolerances up to 45 degrees from the exact horizontal path of the material web, the expression “substantially horizontal travel” is interpreted fairly widely.

  The arrangement of the applicator device, one on top of the other, takes advantage of the available height and thereby saves the overall length, so that, for example, the material web between sections running almost horizontally is It is deflected approximately 180 degrees using at least one web deflection unit. It will be appreciated that the expression “deflected approximately 180 degrees” is also broadly interpreted according to the above and can include deflections of approximately 140-210 degrees.

  In order to be able to prevent any influence by the web deflection unit that provides a curved web path on the surface properties of the coating medium layer that has just been applied and is therefore still wet, the first coating device and the second coating device. The web deflection unit between the two is arranged on the second uncoated side of the material web. However, when a device known as an “air turn” is used, in other words, the material web is guided in a non-contact manner over the compressed air cushion released from these “air turns”, so that the first application device and the second application device The web deflection unit to and from the device can in principle also be arranged on the first coated surface of the material web.

  Finally, it is also possible to arrange a web turning device between the first application device and the second application device. The axis or shaft of the deflection unit of this web turning device extends parallel to the web section of the material web traveling towards the respective deflection unit and at a predetermined angle with respect to the transverse direction of the traveling web section. ing. With this connection, an “air turn” can also be used as a web deflection unit. These can be configured, for example, as perforated pipes, and the perforations are used to release compressed gas that forms a compressed gas cushion.

  However, regardless of the arrangement of the two applicators, it is advantageous to accommodate the two applicators in a common housing, in particular in order to prevent contamination of the entire coating apparatus by application medium droplets or the like.

  In a further development of the invention, it is further proposed that the curved section of the web running portion of the material web between the first application device and the drying device has a radius of curvature of at least 300 mm. Only when this minimum radius of curvature is observed, in the area of the curved section of the web running part, the centrifugal force acting on the still wet coating layer is weak enough to prevent the coating medium droplets from splashing by the centrifugal force. State is secured. This is especially true at web speeds in excess of 1000 m / min.

  The coating / drying device according to the invention comprises at least one non-contact device for stabilizing the moving material web and / or for avoiding or reducing the waviness of the moving material web, in particular the lateral waviness. Can be advantageously provided. For example, at least one Coanda effect nozzle device can be advantageously provided. It is also advantageous to use at least one nozzle device that produces a counter swell, especially a longitudinal swell, that counteracts the swell to be avoided or reduced, in particular the lateral swell.

  Furthermore, the coating / drying device according to the invention can advantageously comprise at least one device for breaking, preferably removing or mitigating the air boundary layer dragged along the moving material web. This device should ideally be located near or close to the upstream of each application device so that the application of the application medium is not hindered by the air boundary layer, so that a coating that meets the high quality requirements can be achieved. Achieved.

  The present invention will be described in more detail in the following description, with reference to the accompanying drawings, for several exemplary embodiments.

FIG. 2 is a schematic diagram of arrangement and web travel in an embodiment of a coating / drying apparatus according to the present invention. FIG. 2 is a schematic diagram of arrangement and web travel in an embodiment of a coating / drying apparatus according to the present invention. It is a figure of another example in it. FIG. 2 is a schematic diagram of arrangement and web travel in an embodiment of a coating / drying apparatus according to the present invention. It is a figure of another example in it. FIG. 2 is a schematic diagram of arrangement and web travel in an embodiment of a coating / drying apparatus according to the present invention. FIG. 4 is a diagram of another example of a coating apparatus according to the present invention connected downstream of the drying section of a papermaking machine. FIG. 3 is a similar view of an example in a papermaking machine coating / drying apparatus. FIG. 4 is another schematic diagram of placement and web travel in an embodiment of a coating / drying apparatus according to the present invention. FIG. 4 is another schematic diagram of placement and web travel in an embodiment of a coating / drying apparatus according to the present invention. FIG. 4 is another schematic diagram of placement and web travel in an embodiment of a coating / drying apparatus according to the present invention. FIG. 2 is a similar schematic diagram of placement and web travel in an embodiment of a coating / drying apparatus according to the present invention with contact application of a coating medium to a moving material web. FIG. 2 is a similar schematic diagram of placement and web travel in an embodiment of a coating / drying apparatus according to the present invention with contact application of a coating medium to a moving material web.

  In FIG. 1, a coating / drying apparatus according to the present invention is indicated generally at 10. This device includes a first coating device 14 for applying a first layer of a coating medium on a first surface 12a of a material web 12 that moves in a running direction L, and a coating medium on a surface 12b of the material web 12 opposite to the surface 12a. A second coating device 16 for coating the second layer, and a drying device 18 disposed downstream of the two coating devices 14 and 16 in the running direction L of the material web 12. According to the invention, there is no separate drying device for the web running between the two applicators 14 and 16. That is, the material web 12 is not intermediately dried between the coating device 14 and the coating device 16.

  As shown in FIG. 1, both applicators 14 and 16 in the present exemplary embodiment are configured as curtain applicators, in other words, the applicator medium as a self-contained applicator curtain within the apparatus, from the nozzle of the applicator. It is a coating device that exits and moves through free space towards the material web 12 under the influence of external forces, in particular gravity. This non-contact application of the application medium to the material web 12 ensures that the material web 12 is only slightly stressed. In particular, there is no risk of damage that occurs as a result of physical interaction between the material web and the elements of the applicator device, such as a doctor blade. However, in principle, the applicators 14 and 16 can also be configured as spray applicators.

  It is further noted that the two applicators 14, 16 are arranged in sections 12 ′ and 12 ″ that extend substantially horizontally in the path of the material web 12 and apply the application medium to the material web 12 from substantially above. Should. In order to allow this arrangement, according to FIG. 1, a deflection roller 20 is provided to deflect the material web 12 between the two applicators 14 and 16. These deflecting rollers 20 of the exemplary embodiment according to FIG. 1 are both arranged on the uncoated surface 12b of the material web 12, so that the layer applied to the surface 12a of the material web 12 by the application device 14 is not impaired. I'm sorry. In addition, since the two deflecting rollers 20 have a relatively large diameter, the layer applied to the material web 12 by the applicator 14 is only subjected to a weak centrifugal force while deflecting the material web 12.

  Finally, a deflecting device 22 that operates without contact is also arranged between the coating device 16 and the drying device 10. This deflection device 22 can be formed, for example, by a device known as an “air turn” and guides the material web 12 in a non-contact manner over a compressed air cushion.

  Another embodiment of the coating / drying device according to the invention, which corresponds approximately to the embodiment according to FIG. 1, is shown in FIG. Accordingly, in FIG. 2, similar parts are indicated by the same reference numerals as in FIG. Furthermore, the embodiment according to FIG. 2 differs from the embodiment according to FIG. 1 only in that the description of FIG. 1 is otherwise indicated here in the following text.

  The coating / drying device 110 according to FIG. 2 is different from the coating / drying device 10 according to FIG. 1 only in terms of the structure of the deflection roller 120 that deflects the material web 112 between the first curtain coating device 114 and the second curtain coating device 116. Is different. Specifically, the deflection roller 120 according to FIG. 2 is placed on the surface 112a of the initially coated material web 112. They are thus configured as non-contact deflection devices, for example devices known as “air turns”, as described using the example of the deflection device 22 with reference to the embodiment according to FIG. Also in the embodiment according to FIG. 2, a deflecting device 122 operating in a non-contact manner is provided between the applicator device 116 for coating the second surface 112 b of the material web 112 and the drying device 118.

  Another embodiment of the coating / drying apparatus according to the present invention, which corresponds approximately to FIG. 1, is shown in FIG. Therefore, in FIG. 3, the similar parts are indicated by the same reference numerals as in FIG. Furthermore, the embodiment according to FIG. 3 differs from the embodiment according to FIG. 1 only in that the description of FIG.

  In the coating / drying device 210 according to FIG. 3, the two curtain applicators 214 and 216 are arranged on either side of a material web 212 that moves substantially from bottom to top. Using the deflecting device 224 shown schematically, the two coating media curtains 214a and 216b from the two coating devices 214 and 216 are removed from the purely gravitational path shown in dashed lines in FIG. The surface 212a and 212b are deflected in a course of moistening. The deflecting device 224 can operate based on, for example, electrostatic interaction with the application medium.

  Another embodiment of the coating / drying apparatus according to the present invention, which corresponds approximately to FIG. 1, is shown in FIG. Therefore, in FIG. 4, similar parts are indicated by the same reference numerals as in FIG. Furthermore, the embodiment according to FIG. 4 differs from the embodiment according to FIG. 1 only in that the description of FIG.

  The coating / drying device 310 according to FIG. 4 differs from the embodiment according to FIGS. 1 and 2 only in the way in which the material web 312 is deflected between the first curtain coating device 314 and the second curtain coating device 316. Specifically, according to FIG. 3, a web turning device 326 is used for this purpose. The axis or shaft 328a of the deflection unit 328 of the web turning device 326 extends parallel to the web section of the material web 12 traveling to each deflection unit 328, and has a predetermined length in the longitudinal direction Q in which the web section travels. It extends at an angle.

  These shafts or shafts are configured as pipes, have a large number of openings, and cooperate with a compressed air supply source to form an air cushion for conveying the web.

  FIG. 5 shows a coating apparatus 410 according to the invention connected downstream of the drying section 440 of the papermaking machine. The moving material web 412 is guided from above into the coating device (coating machine) by the deflection of the web performed using the guide rollers 442. The further path of the web guidance device under the first curtain applicator 414 and the second curtain applicator 416 is generally consistent with the exemplary embodiment of FIG. The use is formed by two deflection rollers 420. However, upstream of each applicator, elements such as suction boxes 444 or 446 are preferably provided to remove or at least reduce the air boundary layer dragged by the moving material web.

  As indicated by the double arrows, the two applicators 414 and 416 are preferably vertically adjustable. The material web travels between each applicator 414 or 416 and the groove 448 or 450, which collects excess coating media.

  After passing under the second application device, the material web 412 is directed to a drying device (not shown) that operates in a contactless manner over the air turn 422. For example, a hot air dryer can also be provided. In place of or in addition to the air turn 422, a guidance device may be further provided by the air nozzle 452. An exemplary path of the material web through the air nozzle is indicated by a dashed line (412 ′). In a moving material web, air nozzles can be arranged so that a light wave is produced in which the wave bottom and wave apex alternate in the direction of travel or longitudinal direction of the material web. And cancels unwanted lateral undulations in the web of material with alternating wave bottoms in the transverse direction.

  For the deflection roller 420, first consider a roller having a relatively large diameter, for example, greater than 600 mm, to avoid detachment of the application medium (coating dye).

  As can be clearly seen from the figure, according to the present invention, there is no intermediate drying of the material web between the application by the first application device 414 and the application by the second application device 416. An important aspect of the web guidance apparatus diagram implemented in accordance with FIG. 5 is that each coated web surface does not contact any web guide roller or the like until sufficient drying is complete. .

  In the arrangement according to FIG. 6, the coating / drying device is likewise connected downstream of the drying section 540 of the papermaking machine. The material web 512 is guided from below into the coating apparatus, and then the web is deflected using a plurality of guide rollers in the direction opposite to the machine running direction. The first applicator 514 preferably has an element, such as a suction box 544, for removing or avoiding an upstream air boundary layer. Since the material web 512 is deflected using two air turns 520 in a manner similar to the arrangement according to FIG. 2, the material web is again deflected in the direction of travel of the machine. The second applicator 516 applies the material web piece that again moves in the machine travel direction. Preferably, an element 546 that removes / avoids the air boundary layer is further connected upstream of the second application device 516.

  The two air turns 520 act with guide air on the surface of the material web coated by the first applicator 514. In order to ensure a stable material web guidance device, it is possible to assign one or more support rollers to the other uncoated side of the material web. The material web travels through an air nozzle 552 used for stabilization, just like the first applicator 514, after passing under a second applicator 516, preferably designed as a curtain applicator. . Thereafter, another air turn 522 is deflected into the non-contact drying device 518, downstream of which another drying device 560 can be connected that operates in contact with the normal drying sector.

  According to FIGS. 5 and 6, the material web fed to each coating / drying device is first coated on the lower surface and then on the upper surface. The reverse is of course also possible, i.e. the top surface is coated first and then the bottom surface is coated. Both solutions according to FIGS. 5 and 6 are very compact, just like the solution of the exemplary embodiment described above, and are therefore also suitable as a reconstruction means in existing illustrations. Compared to conventional solutions (eg blade coating or film coating instead of the preferred curtain coating for construction), it is possible to envisage a sufficiently low investment cost, this low cost being especially intermediate This is achieved by eliminating drying and by the compactness associated with this.

  The coating / drying device 610 according to FIG. 7 generally corresponds to the arrangement according to FIG. As used so far in the exemplary embodiment described above, similar or identical components are indicated by the same symbolic designation, each plus 100. A deflection roller that provides a deflection opposite to the machine travel direction and an element 644 connected upstream for removal of the air boundary layer in the first curtain coating device 614 for the underside of the material web (instead of a suction box, for example One type of doctor blade is also suitable), a deflection roller 620 that again deflects the machine in the direction of travel, and a second curtain coating device 616 ideally for removing the air boundary layer as well Reference may be made to those with upstream connected elements 646 and further guidance devices that direct the web of material 612 into the non-contact drying device 618 by air turns 622. In the X region indicated by the dashed circle, a Coanda effect device or a stabilizing nozzle device, for example a device corresponding to the device 452 or 552, can be provided as appropriate.

  Another suitable arrangement is shown in FIG. In either case, suction boxes 744 and 746, or another element for air boundary layer removal or mitigation, is preferably connected upstream of curtain applicators 714 and 716. The air turn device 720 and the air turn 722 designed with split sections provide non-contact web deflection towards the second curtain applicator 716 and the dryer not shown, respectively.

  An arrangement very similar to that of FIG. 6 is shown schematically in FIG. The type and function of the components shown are indicated as such by a symbolic representation that matches the symbolic representation used in FIG. The air turn 722 deflects the material web 712 diagonally upward rather than downward as in FIG.

  FIG. 10 shows indirect application on both sides by application rollers 860 and 862, in which coating films are filled in the rollers using curtain coating devices 814 and 816, respectively. The material web travels through the roll gap belonging to the application rollers 460 and 462. Thus, the two applicators, 814, 860 on one side and 816, 862 on the other side, are arranged at approximately the same position for the material web in the direction of travel of the material web. Roller surfaces that are coated using curtain applicator heads 814 and 816 are preferably assigned elements 844 and 846, respectively, which are elements that remove or at least reduce the air boundary layer, for example, known as air cut. . Corresponding elements can also be assigned to the faces of the material web that run into the roll gap.

  Although very similar to the arrangement of FIG. 10, an arrangement in which the material web 912 is coated on only one side is shown in FIG. The coating roller 960 is therefore assigned to only one support and guide roller 962, which deflects the material web 912 and forms a coating roll gap with the roller 960. The material web moving away from the roller 962 can be fed by a non-contact guidance device to another coating device, such as a curtain coating device, which coats the other side of the material web.

  Referring once again to the components or elements 452, 552 and region X, and further to elements 444, 446, 544, 546, 644, 646, 744, 746, 844, 846, 944, a valuable coating outcome is obtained. It should be noted that, in practice, it is very important to avoid undulations and to achieve a high degree of stability of the web guidance device, and to avoid or at least reduce the air boundary layer that impedes application. For the stabilization of the web and the avoidance of disturbing undulations, the previously described Coanda effect air nozzle device is advantageous and suitable, which forcibly controls the web guidance device by the generation of a vacuum, The coating nozzle device having a plurality of nozzles as described above is arranged alternately in the running direction on different surfaces of the web, and gives a undulation in the running direction to the material web in a predetermined manner. This swell counteracts the harmful lateral swell.

Claims (14)

Two coating devices for coating the coating medium on one side of the material web moving in the running direction (L) and the other side opposite to the one side;
At least one deflection unit arranged between the two applicators in the travel direction (L) of the material web and deflecting the material web;
A coating / drying device comprising said two coating devices and a drying device arranged downstream of said deflection unit in said travel direction (L) of said material web,
The shaft of the deflection unit extends parallel to the web section of the material web traveling toward the respective deflection unit and at a predetermined angle with respect to the transverse direction (Q) of the traveling web section. Coating / drying equipment.   The coating / drying apparatus of claim 1, wherein at least one of the two applicators operates without contact with the material web.   The coating / drying device according to claim 2, wherein the coating device that operates without contact with the material web among the two coating devices is a spray coating device or a curtain coating device.   The coating / drying apparatus of claim 1, wherein at least one of the two applicators is a curtain applicator.   5. The coating / drying apparatus according to claim 4, further comprising a deflecting device assigned to at least one of the curtain coating devices and deflecting a coating medium curtain from the curtain coating device from a path due to gravity.   The coating / drying apparatus according to claim 1, wherein at least one of the two applicators applies an application medium to the material web from above by gravity.   The coating / drying device according to claim 1, wherein the two applicators are arranged on a section of the course of the material web that runs substantially horizontally.   The coating / drying device according to any one of claims 1 to 7, wherein the deflection unit is arranged on an uncoated surface of the material web.   The coating / drying apparatus according to claim 1, further comprising a housing that accommodates the two application apparatuses.   The curved section of the web running of the material web between the coating device and the drying device arranged upstream in the running direction of the material web of the two coating devices has a radius of curvature of at least 300 mm. The coating / drying apparatus according to claim 1, comprising:   11. The apparatus according to claim 1, further comprising at least one non-contact device for stabilizing the moving material web and / or avoiding or mitigating waviness, in particular lateral waviness, of the moving material web. The coating / drying apparatus according to any one of the above.   12. The coating / drying device of claim 11, further comprising at least one Coanda effect nozzle device directed to the material web.   13. The coating / drying apparatus of claim 12, wherein the at least one nozzle device avoids or reduces lateral undulations by producing at least one of opposing undulations and longitudinal undulations.   14. A coating / drying device according to any one of the preceding claims, further comprising at least one device for breaking, removing or mitigating an air boundary layer dragged along the moving material web.

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