Equipment for smoothing and applying coating media

Abstract

The invention relates to an apparatus for smoothing a paper or board web, wherein, in order to adjust the transverse thickness profile of the paper or board web in the transverse direction of the web, at least one of the rollers is a roller with adjustable deflection and controlled in an area, for setting a selected linear load distribution in at least one roll gap across the roll width, the at least one roll gap being designed to smooth the transverse thickness profile of the paper or board web by means of an adjustable linear load profile and simultaneously introduce a coating medium into the paper or board web, for which purpose at least one coater with a discharge nozzle for applying the coating medium is arranged so that the coating medium is applied to at least one of the two rollers in the roll gap and is designed to apply the coating medium indirectly to at least one side of the running paper or board web, and the at least one coater has at least one discharge nozzle with a device for transversely profiling a volume flow of the coating medium that can be adjusted region by region across the web width.

Description

Technical Field

[0001] The invention relates to a device for smoothing having at least one nip formed between two rollers, wherein, according to the invention, at least one of the rollers is a roller with adjustable deflection and controlled area for adjusting the thickness profile of a paper or board web. Background Art

[0002] WO 2004 / 001132 A2 discloses a machine capable of producing and processing in so-called online or offline operation, including applying a coating medium to at least one side of a material web. For many applications, a material quality with high smoothness and, if necessary, gloss is required. To achieve this quality, the machine includes a material web smoothing device along the material web path, at least upstream of the coating device. Smoothing the material web upstream before applying the coating medium is particularly suitable and effective, as non-contact coating methods, particularly coating methods, largely preserve the contours of the material web surface. This means that rough contours of the material web are not compensated for by the coating medium, or are only relatively slightly compensated for, and are therefore smoothed. The smoother the material web is before applying the coating medium, the higher the productivity achieved. In this regard, it has been found that smoothing the material web first and then applying the contour stroke is more effective than smoothing the rough contours after coating. For application of the coating medium, the so-called curtain coating method is preferably used.

[0003] From publications EP 3 617 403 A1 and AT 519598 A2, WO 2020020626 A1, non-contact methods for coating starch, such as curtain sizers and spray sizers, are known. With this method, the coating amount is metered by adjusting the number of coating nozzles themselves. No scraper device is required.

[0004] EP 0 374 292 A1 discloses a device for leveling and calibrating paper, which compacts and levels the paper. Fluctuations in the paper thickness are compensated and the paper is calibrated. This results in a compacted paper with a leveled surface. To achieve this, uneven density, reduced thickness, rigidity, and opacity must be accepted. To calibrate the paper, i.e., to ensure that the paper has the same thickness at all locations, the pressure exerted by the deadweight of the rollers of the leveler is usually too low. The leveler is therefore additionally loaded with pressure. In order not to limit the flexibility of the device to a few grammage-pressure pairs, one of the rollers is preferably designed as a zone-controlled deflection-compensating roller, which replaces the rigid crown (German: Bombierung).

[0005] Papermakers are currently faced with the challenge of using waste paper fibers in the production of paper, packaging paper, and board, as well as in specialty papers. In the EU, linerboard (German: Testliner) is primarily made from waste paper and fillers. The high proportion of secondary fibers reduces the strength properties of packaging paper. Starch can be used to compensate for this loss of strength in paper production. Starch is typically added directly to the fiber suspension or sprayed onto the wet web on the wire section. Furthermore, starch can be applied to the paper web immediately after the predrying station using contact or non-contact coating methods.

[0006] Linerboard and folding board can be coated multiple times. After coloring in a film press, an intermediate and top coat are typically applied to the paper web using a blade coater. The subsequent coating process using the blade coater requires a smooth surface (macrosurface roughness Bendtsen <500 ml / min, microsurface roughness PPS <3 μm) and a very uniform paper thickness (2 sigma deviation <1%-1.5%). The paper thickness must exhibit only slight variations across the paper web width. Therefore, pre-smoothing is typically performed before coating using a smoothing mill or a hard nip calender, specifically for pre-smoothing before coating and for calibrating the paper thickness. For single-sided smoothing of linerboard and folding board, only a single nip is used. The smoothing mill preferably consists of two rollers, preferably heated steel or chilled cast iron, and an unheated profile roller. Transverse thickness profile control is usually achieved using zone-controlled elements.

[0007] Contact coating methods are known as glue presses and film presses, as described in DE 3417487 A1 and DE 4131131 A1. A starch or glue suspension is applied to a coating roller using a metering applicator and metered using a doctor blade. The paper or board web is coated on both sides in the nip between the coating rollers. The starch temperature is typically between 50°C and 80°C. The coating weight per side is 0.5 to 6 g / m². 2 In the case of film presses, the typical solids content of starch lies between 8% and 15%. In individual cases, coatings consisting of starch and pigment granules with a solids content of up to 40% can also be applied to paper or board webs using this type of construction. The line force between the application rollers is typically between 40 and 70 kN / m. The film press can be equipped with all roller types common in the industry, as described in DE 10 2018 100924 A1. It can be advantageous for at least one of the rollers to be a shoe roller or a deflection-controlled roller, so that the pressure acting in the roll gap can be adjusted to set the conditions in the process roll gap and optimize the transfer of starch to the web, depending on the characteristics of the product being produced, such as the paper thickness, grammage, or the quality of the fiber material used.

[0008] EP 2 603 636 B1 discloses smoothing a paper web using a calender. Here, the coating medium is sprayed directly onto the paper web while it rests on the calender rolls. However, these methods have the disadvantage that coating errors (overlapping errors, blockages, etc.), which occur when using spray nozzles, for example, can manifest directly on the paper.

[0009] The main disadvantage of the known arrangement is the high energy consumption of the arrangement. Here, compromises must be made in the mechanical structure and the production process, which compromises are usually made at the expense of paper quality. Summary of the Invention

[0010] The technical problem to be solved by the present invention is therefore to create a smoothing machine with which a uniform paper thickness and a uniform transverse profile of strength properties (CMT (flat rolling resistance), SCT (compressive strength), RCT (burst resistance)) can be achieved after surface coating with a coating medium, in particular a starch product, using cost-effective technology.

[0011] This technical problem is solved by a device for smoothing a paper or board web, the device having at least one roll nip formed between two rollers, wherein, in order to adjust the transverse thickness profile of the paper or board web in the transverse direction of the web, at least one of the two rollers is a roller with adjustable deflection and controlled area for setting a linear load distribution that can be selected across the roll width in the at least one roll nip. According to the invention, it is provided that the at least one roll nip is designed to smooth the transverse thickness profile of the paper or board web by means of an adjustable linear load profile and simultaneously introduce a coating medium into the paper or board web. For this purpose, at least one coating machine having a discharge nozzle for applying the coating medium, in particular starch, is arranged such that the coating medium is applied to at least one of the two rollers in the roll nip and is designed to apply the coating medium indirectly to at least one side of the running paper or board web. The at least one coating machine has at least one discharge nozzle with a device for transversely profiling a volume flow of the coating medium that can be adjusted region by region across the web width.

[0012] This creates a flattening system that combines the pre-flattening / forming and coating processes in a single unit. The medium is applied indirectly and contactlessly to at least one roller in at least one roll nip. According to the present invention, the transition of the coating medium "inside" the web is optimized, whereas the prior art attempts to optimize the transition "onto" the web.

[0013] According to the present invention, measures for ensuring the strength properties of a paper or board web, in particular the SCT value, also involve applying a coating agent, in particular a starch solution, to the surface of the paper / board. However, this is not performed via a glue press or a film press, but rather via the smoothing device according to the present invention. The smoothing device according to the present invention combines the technical measures of smoothing the web and penetrating the coating agent, in particular starch, into the web in a single unit.

[0014] By means of pressure in at least one roll nip of the smoothing device, the smoothing of the web and the penetration of the coating medium into the web are technically carried out together, with the resulting joint benefits. Surprisingly, it has been discovered that these two treatment measures, which influence paper strength, can be combined in a mutually advantageous manner, specifically by applying a combined pressing pressure / hydraulic pressure to the paper or board web as it passes through the at least one roll nip.

[0015] The main disadvantage of the prior art, namely the need for two separate units, is eliminated. The construction space does not present any space problems for possible modifications. Figure 12 By way of example and diagrammatically, the structure of a paper or board machine before the dryer section (VTP) and after the dryer section (NTP) according to the prior art is shown, wherein a calender and a film press are arranged as units one behind the other. Figure 13 By way of example and diagrammatically, a device for smoothing according to the invention is shown at a comparable position in a paper or board machine, said device having a coating machine 1 as a component unit.

[0016] Therefore, if a papermaker needs or wants to retrofit an existing system with an additional coating unit and calender, the solution according to the invention offers a high degree of flexibility. No additional space is required. According to the prior art, installing additional calenders and coaters would require extending the paper machine, making installation in the existing plant often no longer possible. This necessitates compromises in both mechanical design and manufacturing processes, often at the expense of paper quality.

[0017] According to the prior art, machines for producing flexible packaging are considered an example of this disadvantage. Due to the increased use of waste paper fibers for cost reasons, the paper web needs to be smoothed before coating. Previously, the machine configuration had no space for this, which is why operators of prior art machines face significant challenges.

[0018] Significantly, the inventors discovered that uniform strength properties can be achieved across the entire width of a paper web because the local pressing pressure required for forming the web and the locally introduced amount of coating medium, particularly starch, can be coordinated with one another. The required pressing pressure is predetermined by the local paper thickness. The amount of coating medium supplied, particularly starch, is influenced by this predetermined pressing pressure.

[0019] The penetration of the coating agent (particularly starch) and the resulting increase in paper strength are directly dependent on the local pressing pressure. Consequently, significantly improved paper strength properties (CMT, SCT, RCT) are achieved at locations where a greater paper thickness previously existed. The improved paper strength properties are caused by the higher starch content (due to the increased pressing pressure) and the higher paper density. This results in undesirable strength variations in the CD direction, which are overcome according to the present invention by at least one coating machine having at least one delivery nozzle with a device for transversely profiling the volume flow rate, which can be adjusted regionally across the web width.

[0020] What is crucial is that the starch application amount and the pressing pressure are coordinated in the regions so that the paper strength properties are as identical as possible in all regions. This means that regions with higher pressing pressure must be supplied with less starch than regions with lower pressing pressure.

[0021] According to the invention, the implementation of this discovery not only leads to significantly more uniform paper properties and thus to improved quality, but also to a saving of starch and thus to a cost saving for the customer. The invention is therefore highly economical.

[0022] According to the present invention, a technically and economically efficient technique for improving the strength properties of paper or board by increasing starch penetration is proposed. According to the invention, this objective is achieved by using a non-contact coating process, preferably a coating method using a slit nozzle, which allows the application of very high starch solids contents (up to 35%).

[0023] The transverse profile can also be influenced in a targeted manner, for example by using starch coating and pressing pressure in an additive manner (higher pressure combined with a higher starch content) to achieve better strength properties in selected areas of the paper web (e.g., in the edge regions). Of course, it is also possible to locally degrade the strength properties if this would benefit the further process of papermaking. This is illustrated by adjusting the coating amount with dilution water. In some cases, it may make sense to add more water to the edge regions to counteract drying out of the paper edges, even if this reduces the starch content and, therefore, degrades the strength properties.

[0024] The smoothing device according to the invention can thus be used to profile the linear forces in at least one roll gap, for example using a scanner, so that the desired transverse thickness profile is achieved. The volume flow of the coating medium, in particular starch, can be adjusted with a local, regionally controlled volume flow at the nozzle in order to adjust the amount of medium / starch applied to the strength properties of the web.

[0025] Furthermore, the functional dependence of the paper strength on the parameters (properties of the raw material and the grammage of the fiber material used) can be taken into account as an influencing variable on the distribution of the coating medium and the amount of the volume flow. Since the concentration of the fiber material suspension at the headbox outlet defines the resulting grammage, the concentration measurement values ​​can be measured in each area of ​​the headbox with the aid of sensors. The measured transverse and longitudinal profiles of the concentration can be used as regulating variables in a control loop for determining the local volume flow in the CD direction. The headbox plays a key role in ensuring paper quality. Important paper properties are significantly influenced by the headbox. Within the scope of automatic process control, the headbox is gaining increasing influence as a corrective mechanism for targeted deviations that require downstream process steps (such as leveling and coating). The device for leveling according to the invention utilizes this corrective mechanism, the headbox.

[0026] To implement the invention, a non-contact coating machine with a slit nozzle can be used in combination with rollers used as coating rollers in a smoothing device, wherein at least one coating roller is designed as a zone-controlled profile roller. These rollers are known, for example, as "MHV rollers" or "NIPCO rollers." The zone widths typically range from 50 to 300 mm. These zones can be individually controlled, enabling precise profile correction.

[0027] The coating system used here is also divided into a plurality of zones. Such coating systems are known in particular from DE 10 2009 036 853 B3 and DE 10 2009 048 820 A1. These zones allow different amounts of coating medium / starch to be applied across the machine width. This can be achieved, for example, by mixing water into each zone or by supplying each zone with a different amount of starch suspension. Another simple method for applying different amounts of starch across the machine width can be to set different gap widths at the nozzle outlet using gap adjustment.

[0028] Due to the high moisture content of the fiber web in the calender nip, the process can preferably be carried out at relatively moderate temperatures (such as those prevailing in starch penetration). While common moisture contents in conventional calendering are in the moderate moisture range of 4% to 8%, in the technology according to the invention the moisture content depends on the application area and is, for example, in the range between 20% and 60%.

[0029] For forming to be possible, the increased moisture content means that in a conventional calender with an 8% moisture content, the fiber temperature must be around 80°C in order to deform the fiber. At 4% humidity, the fiber temperature must already be around 135°C. Since the temperature must be applied to a depth of approximately 15 to 20 μm during the short nip passage to achieve sufficient deformation, the actual temperature of the roll surface must be approximately 20 to 30°C above the glass transition temperature.

[0030] In this respect, the technology according to the invention can be significantly distinguished from conventional calendering. A crucial difference is that an already heated coating medium can be introduced into the fiber web, which in turn increases the fiber temperature even in deeper layers. Consequently, there is no need to heat the rollers significantly above the glass transition temperature of the cellulose fibers.

[0031] Since the moisture content of the fiber web can lie in the range of 20% to 60%, the usual temperatures for applying the starch (between 70° C. and 100° C.) are completely sufficient for forming the fiber web.

[0032] In order to achieve a high penetration of the starch into the paper web despite, for example, a high solids content, according to the invention, the starch can be extruded into the paper at high pressure and temperature, for example.

[0033] One or both rollers of the smoothing device can be tempered. The rollers can also be provided with a hard coating (ceramic, chrome, etc.), but can also be provided with a hard covering made of polymer.

[0034] One or both rollers may also be designed as soft rollers. The hardness of the surface is preferably less than 30 Pusey & Jones hardness.

[0035] Further advantages and embodiments of the invention can be found in the following description and the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawings.

[0037] Figure 1a A device for smoothing according to the invention with at least one coater, preferably a curtain coater, is shown schematically in cross section according to a first embodiment.

[0038] Figure 1b A device for smoothing according to the invention with at least one coater, preferably a free jet coater, is shown schematically in cross section according to a second embodiment.

[0039] Figure 1c Schematic diagram showing a comparison between a curtain coater and a free jet coater,

[0040] Figure 1d A device for smoothing according to the invention with at least one curtain coater according to a third embodiment is schematically shown in cross section and in the associated section AA in the CD direction,

[0041] Figure 2 A device for smoothing according to the invention with at least one curtain coater according to a fourth embodiment is schematically shown in cross section and in the associated section BB in the CD direction,

[0042] Figure 3 A device for smoothing according to the invention with at least one curtain coater according to a fifth embodiment is schematically shown in cross section and in the associated section CC in the CD direction,

[0043] Figures 4 to 10 shows a cross section in the CD direction according to other embodiments,

[0044] Figure 11 Schematically showing the parameter settings of the pressure profile and the coating profile based on the grammage profile and the strength / thickness profile according to the present invention as the result variables in the CD direction,

[0045] Figure 12 Schematically shows a section of a paper or board machine according to the prior art,

[0046] Figure 13 A partial section of a paper or board machine according to the invention is shown schematically. DETAILED DESCRIPTION

[0047] like Figures 1a to 1d As shown, the present invention relates to a device for smoothing having at least one roller gap 6, which is formed between two rollers 3, 4. At least one of the two rollers 3, 4, here the roller 3, is designed as a roller 3 with adjustable deflection and controlled area in order to adjust the transverse thickness profile of a moving material web 9, in particular a paper or cardboard web, in the transverse direction of the web.

[0048] For this purpose, the roller 3 has a roller shell 7 that rotates about an axis of rotation, on the inner circumference of which support elements 5 exert a force. The support elements 5 form individual hydrostatic pressure elements. A plurality of support elements 5 are arranged distributed over the roller width and divided into a plurality of zones (pressure zone (1) to pressure zone (n)), thereby enabling a pressure cross-section to be varied across the machine width. With the roller 3, also referred to as a forming roller with MHV elements, a local linear load distribution can be set across the roller width / machine width, which can be selected in at least one roller gap 6.

[0049] Therefore, at least one roll gap 6 is configured to smooth the thickness transverse profile of the material web 9 by means of an adjustable linear load distribution as the material web 9 passes through the roll gap 6. On the other hand, and simultaneously with the application of the pressing pressure in the roll gap 6, the coating medium 2 is introduced into the material web 9. For this purpose, at least one coating machine 1 is provided with an outlet nozzle 8 for applying the coating medium 2, in particular starch.

[0050] At least one coating machine 1 is arranged so that the coating medium 2 is applied to at least one of the two rollers 3, 4 in the roller gap 6. The mass flow of the coating medium 2 is applied to at least one of the two counter-rotating rollers 3, 4, for example roller 3 ( Figure 1d ) on the surface of the rollers 3, 4. Due to the rotation of the rollers 3, 4, the coating medium 2 applied to the surface of one roller 3 (or rollers 3, 4) is transported toward the material web 9 and penetrates into the material web 9 in the press nip 6. This provides for so-called indirect application of the coating medium 2 to at least one side of the running material web 9.

[0051] like Figure 1a As shown, the coating medium 2 can also be applied to both sides of the material web 9. To this end, the two applicators 1 first apply the coating medium to rollers 3 and 4. In this respect, rollers 3 and 4 function as coating rollers. The coating medium 2 can, in particular, be starch, a paint, a plastic compound such as PVA, or a mixture of these media. The coating medium 2 is then transferred to the material web 9, in particular a paper or cardboard web, on both sides in the nip 6 between the rollers 3 and 4. The roller, in this case roller 4, is preferably a hard roller, particularly preferably a heated roller that can be equipped with a ceramic coating. The other roller 3 is a profile roller with adjustable deflection and controlled area. It can be equipped with, for example, a hard ceramic coating or a soft polymer coating with a hardness of less than 30 P&J, in particular 15-30 P&J.

[0052] like Figure 1a and Figure 1d As shown, the coating machine 1 can be a curtain coating machine. Figure 1b As shown, as an alternative to a curtain coater, a free jet coater can be used to apply the coating medium 2 , in particular starch, to one or both sides of the rotating coating rollers 3 , 4 .

[0053] like Figure 1c As shown, in a curtain coater, a freely falling curtain of coating medium 2 forms in the outlet gap of the discharge nozzle 8, which is continuously accelerated by gravity. The drop height of the coating medium 2 curtain between the outlet gap of the discharge nozzle 8 and the impact point on the coating rollers 3, 4 is typically 50-200 mm. Therefore, the velocity V2 of the curtain at the impact point is significantly higher than the exit velocity V1 of the coating medium 2 in the outlet gap of the discharge nozzle 8.

[0054] like Figure 1c As further shown, in a free jet coater, a free jet of coating medium 2 is generated in the outlet gap of the (discharge) nozzle 8. In this case, the jet velocity V4 at the impact point and the outlet velocity V3 of the coating medium 2 are approximately the same. The outlet velocity V3 of the coating medium 2 from the free jet coater is significantly higher than the outlet velocity V1 of the (discharge) nozzle 8 from the curtain coater. The two different coaters 1 have independent operating ranges with respect to machine speed and coating weight.

[0055] therefore, Figure 1a The present invention shows an apparatus for smoothing with a coating machine 1, for example a curtain coater, with which a coating medium is applied on both sides to rollers 3, 4 using two slit nozzles 8, which thus function as coating rollers. The slit nozzles 8 are positioned relative to the respective rollers 3, 4 such that the angle α of the coating to a point / position on the rollers 3, 4 is, for example, between -45° and +45°. Figure 1b The present invention shows a smoothing device having a coating machine 1, for example a free jet coating machine, with which a coating medium is applied on both sides to rollers 3, 4 using two slit nozzles 8, which thus operate as coating rollers. The slit nozzles 8 are positioned relative to the rollers 3, 4 such that the angle α can lie within a range between -90° and +45°.

[0056] The device according to the invention for smoothing and applying the coating medium 2 can preferably have a preparation disk / scraper 23 , a collecting disk / guide plate 26 , a doctor blade 27 and water or steam nozzles 28 for cleaning the (coating) rollers 3 , 4 in a known manner.

[0057] like Figure 1d As shown, according to the invention, at least one coating machine 1 has at least one (discharge) nozzle 8, which is assigned a device 13 for transversely profiling the mass flow 2 of the coating medium 2, which can be adjusted region by region across the web width. Figure 1d As shown in the section AA of FIG, a branch flow 22 of the mass flow 2 is generated by the device 13, which branch flow can preferably be infinitely adjusted from zero to a maximum value predetermined by the coating machine. The individual branch flows 22 can provide different constant mass flows. The number of branch flows 22 can be selected.

[0058] For this reason, Figure 1d As shown in section AA, the coating machine 1 is formed, for example, by a curtain coater whose delivery nozzle 8 is divided into a plurality of sections 19. For example, starting from a transverse flow distributor 10, the starch suspension is distributed across its width via a throttle valve 12 and a diffuser 11. The mass flow 2 in the individual sections can be defined by the throttle valves 12, which are defined by the branch flows 22. For example, actuators 16 for the respective throttle valves 12 are used for automation. However, manual adjustment is also possible.

[0059] The mass flow of the coating medium 2 is divided into a plurality of sub-flows 22 in accordance with the change in the pressure cross section through the forming roller 3 in the roller gap 6, depending on the number of sections 19. The pressure zones (1) to (n) formed can be selected to be equal to, smaller than, or larger than the area of ​​the sections 19 of the coating medium 2 in the CD direction. The corresponding amount of coating medium 2 in the sub-flows 22 and the corresponding linear load in the pressure zones (1) to (n) of the forming roller 3 can be set. Together with the hydrostatic pressure element 5 of the forming roller 3 defining one of the pressure zones (1) to (n), the associated section 19 can form a continuous zone.

[0060] If two-sided coating of the starch agent is to be provided, the press nip 6 can be formed by two rollers 3, 4, both of which can be designed as heated rollers. In addition, the roller 4 is preferably designed as the same roller 3 as described above.

[0061] The linear force in the press nip is preferably between 20 kN / m and 200 kN / m, preferably between 80 kN / m and 120 kN / m. The technology according to the invention can be used for starch coating (sizing) and for pigmenting (pigmenting).

[0062] The starch is preferably applied with a solids content of between 6% and 35%, particularly preferably between 15% and 35%, and a viscosity of between 20 mPa·s and 200 mPa·s. The coating weight is preferably 0.5 g / m² per side. 2 Up to 6g / m 2 The range is between 10ml / m 2 Up to 40ml / m 2 The starch film in the range is coated onto a smoothing roller which has the additional function of a coating roller.

[0063] In the case of pigmentation, the solids content may be between 15% and 40%, and the viscosity may be between 50 mPa·s and 400 mPa·s. The coating weight is preferably 2 g / m² per side. 2 Up to 5g / m 2 within the range between.

[0064] Figure 2 In particular, section BB shows a possible fourth embodiment of the invention. Here, the amount of coating medium 2 supplied, in particular the amount of starch, can be adjusted by supplying dilution water. The starch suspension is passed from the transverse flow distributor 10 via the supply device 24 to the diffuser 11. The dilution water is introduced into the supply device 14. The dilution water can be metered by means of a throttle valve 15. For the rest, the same applies. Figure 1d implementation method in .

[0065] exist Figure 3The locally desired application amount of coating medium 2, in particular starch suspension, can be achieved by adjusting the outlet gap 17 of the nozzle 8 region by region. To this end, the nozzle 8 can be equipped with a flexible lip 18 in the region of the nozzle gap 17. This flexible lip can be positioned, for example, by means of an actuator 16. In section CC, the subflows 22 are shown as a common, continuous mass flow field 25 in the CD direction. The envelope contour 21 delimits the height of the mass flow in the CD direction.

[0066] Figures 4 to 10 Other possible arrangements and embodiments are shown in cross-section to illustrate the coordination according to the invention, more precisely in the CD direction, i.e. the cross direction of the machine: the (coating) nozzle 8 is divided into a plurality of parts, the amount of coating medium 2 in these parts is set and the forming roller 3 is used to divide the parts into a plurality of pressure zones.

[0067] Figure 4 The distributor principle of Figure 1 shows a direct assignment of the nozzle outlet area to the pressure zone of the forming roller. The outlet width is identical to the effective area of ​​the pressure zone. Furthermore, the outflow and pressure zones can be arranged overlapping or staggered. This can be necessary, for example, to prevent streaking. Figure 5 An overlapping arrangement with identical zone widths and outlet widths is shown.

[0068] The outlet width of the (coating) nozzle 8 does not necessarily have to have the same width as the effective area of ​​the pressing element 5. For example, Figure 6 An arrangement is shown in which the outlet width is half the effective width of the pressing element 5. Direct assignments with different area widths and outlet widths exist.

[0069] Even in the case of small outlet width, e.g. Figure 7 As shown, it is also expedient to arrange the pressure zones (1) to (n) and the outlet points so as to overlap. Figure 7 Different zone widths and outlet widths are shown with an overlapping arrangement.

[0070] Of course, it is also conceivable to further reduce the outlet width if necessary. Here, the lip adjustment is provided as an embodiment. By adjusting, the distribution of the coating medium over the machine width can be set very finely. Figures 8 to 10 Other possible variations are shown. Figure 8 The medium distribution adjusted by the gap is shown, wherein the graduation width is equal to the pressure zone width. Figure 9 The gap adjustment with overlap is shown, wherein the graduation width is smaller than the pressure zone width. Figure 10 A gap adjustment is shown, wherein the graduation width is different from the pressure zone width and is variable.

[0071] The following also applies to all the above embodiments:

[0072] The system may be equipped with one or more scanners (not shown) which record and correct for adjustment purposes quality characteristics such as paper thickness, coating weight or paper moisture in the CD direction and provide these quality characteristics for cross-direction profile adjustment.

[0073] The contour arrangement at the slit nozzle 8 has a region width of, for example, 50 to 300 mm, preferably 150 to 280 mm.

[0074] The width of the area of ​​the static pressure element 5 for contour correction is, for example, 50 to 300 mm, preferably 150 to 280 mm.

[0075] Devices for adjusting the gap width region by region or for influencing the mass flow region by region are provided on at least one of the slot nozzles 8 .

[0076] The hardness of the coating of the smoothing rollers 3 and 4 is 0 to 30 P&J, preferably 0 to 5 P&J. The diameter of the smoothing rollers 3 and 4 is preferably in the range of 1000 to 1800 mm, particularly preferably in the range of 1200 to 1600 mm. The outlet gap 17 of the discharge nozzle 8 is preferably 100-500 μm.

[0077] The pressure and the starch application amount in each region of the process nip 6 are coordinated with one another in such a way that the desired transverse profile of the paper thickness and strength properties (CMT, SCT, RCT) is achieved.

[0078] The zones of the coating system and the associated, subsequent pressing zones of the forming rollers are interconnected in terms of control technology, allowing for automated coordination of the pressing pressure and the amount of starch applied. The entire system can be integrated into the process control system of the paper machine. The machine's scanner data can be used to control the zones individually in this way, allowing the desired paper strength (CMT, SCT, RCT) to be set across the machine width. After the treatment nip 6, the paper has a macroscopic surface roughness of Bendtsen roughness <800 ml / min, preferably <500 ml / min.

[0079] The coating weight of starch is between 0.5-6 g / m per side. 2The linear force in the press nip is between 20 kN / m and 200 kN / m, preferably between 80 kN / m and 120 kN / m. The surface temperature of at least one of the smoothing rollers 3 and 4 is 60°C to 160°C. The paper or board web speed is preferably between 250 m / min and 2000 m / min, particularly preferably between 600 m / min and 1800 m / min. The dry content of the material web 9 is preferably greater than 90%, preferably between 92% and 98%. The starch can be applied at a solids content of between 6% and 35%, preferably between 15% and 35%, and a viscosity of between 20 mPa·s and 200 mPa·s. The starch temperature is preferably between 50°C and 110°C, particularly preferably between 70°C and 100°C.

[0080] In order to further design the equipment for leveling of the present invention, the following contents are set:

[0081] At least one deflection-adjustable, area-controlled roller 3 for influencing the linear pressure distribution in at least one roll nip 6 can be adjusted for aligning the material web 9 in the cross-web direction.

[0082] At least one deflection-adjustable, area-controlled roller 3 for influencing the linear pressure distribution in at least one nip 6 can be adjusted to control the thickness of the material web 9 in the cross-web direction.

[0083] The at least one deflection-adjustable, zone-controlled roller 3 is a hydrostatically supported roller with zone-by-zone control elements 5 along the roller width, wherein each (pressure) zone is designed as a group-controlled or individually element-controlled zone.

[0084] like Figure 11 As shown, a sensor device, in particular a scanner 30, can be provided which scans and / or detects the material web 9 on one or both sides in the cross-web direction in order to set the pressure level to be applied, i.e., the pressure profile 33, depending on the surface quality and / or thickness of the material web 9 in the cross-web direction before entering the nip 6. Alternatively or additionally, the volume flow profile at the coating machine can be set by offline measurement of paper / board web samples.

[0085] The transverse profile setting of the volume flow / mass flow of the coating medium 2 , which can be set region by region across the web width, can be controlled as a function of the area-dependent mass distribution of the material web 9 in the transverse web direction.

[0086] like Figure 11As further shown, the concentration of the fibrous stock suspension at the outlet of the headbox 31, which defines the resulting grammage and its profile 32, can be selected as an input variable for the amount of coating medium 2, which is supplied via the coating nozzle 8 and its area and the throttle valve 12 ( FIG. 1 ) or the actuator for lip adjustment ( Figure 3 ) are supplied region by region. Figure 11 In the sectional illustration of , the respectively adjustable mass flow / volume flow is shown as discrete arrows of the medium 2 or as a continuous flow profile curve of the coating medium 2 .

[0087] A consistency sensor can be provided, with which the transverse and longitudinal consistency profile of the fiber suspension at the headbox outlet can be measured with a resolution corresponding to the control mechanism graduation, and this transverse and longitudinal consistency profile can be selected as input variables for the control circuit 35 for the amount of coating medium 2 supplied in each region. The adjustable linear pressure profile 33 and the adjustable application amount of the coating medium 2 can be coordinated with one another by means of a controller 36 in such a way that a compacted paper with a smoothed surface having selectable strength properties (CMT, SCT, RCT) 34 in the cross-web direction can be produced.

[0088] Figure 11 In particular, the following technical connection is drawn: according to the invention, during simultaneous calibration and penetration of the coating medium, in particular starch, areas of the paper or board web with a higher grammage are treated with a higher linear load and less coating medium than areas of the paper or board web with a lower grammage, in which more coating medium and a lower linear load are applied, in order to obtain a uniform strength / thickness profile.

[0089] The outlet nozzle 8 of a curtain coater conveying the medium 2 under gravity can ultimately have a plurality of slot nozzles 18 , each having an outlet gap 8 with an accuracy in the gap length range of ±2.5 μm to ±10 μm for a gap width of 100 to 2000 μm.

[0090] The curtain coater 1 may be designed to control the solids content of the coating medium 2 in at least one layer to be between 6% and 55%.

[0091] The curtain coater 1 is designed for forming a multi-layer curtain.

[0092] The specific volume flow rate from the nozzle 8 of the curtain coater 1 can be in the range of 4 l / (min×m) to 30 l / (min×m). Preferably, 5 ml / m 2 Up to 100ml / m 2 A film of a coating medium 2 , in particular starch, is applied to the respective smoothing rollers 3 , 4 within the scope of the present invention.

[0093] Furthermore, guide rollers (not shown) can be provided, which can define a treatment path section of the running material web 9 between the curtain coater 1 and the press nip 6 .

[0094] A certain roller outer circumference length corresponding to the dwell time can be provided between the impact of the curtain 2 and its entry into the press nip, and thus the dwell time can be increased or decreased, as indicated by the angle α. If the smoothing rollers 3, 4 are heated, the temperature increase of the coating medium 2 before entering the press nip 6 can be influenced by the dwell time. The coating medium 2 can then be thermally pretreated in the press nip 6 between the smoothing rollers 3, 4 and pressed into the material web 9 on one or both sides.

Claims

1. A device for smoothing a paper or board web (9), said device comprising at least one nip (6) formed between two rollers (3, 4), wherein: In order to adjust the thickness transverse profile of the paper or cardboard web (9) in the transverse direction of the web, at least one of the two rollers (3) is a roller (3) with adjustable deflection and controlled area for setting a linear load distribution that can be selected in the at least one roller gap (6) across the roller width, characterized in that the at least one roller gap (6) is configured to smooth the thickness transverse profile of the paper or cardboard web (9) by means of an adjustable linear load profile and simultaneously introduce a coating medium (2) into the paper or cardboard web (9), for which purpose at least one coating machine (1) having an output nozzle (8) for applying the coating medium (2) is arranged so that the coating of the coating medium (2) is provided on at least one of the two rollers (3, 4) of the roller gap (6) and is The invention relates to a coating machine (1) for indirectly applying the coating medium (2) to at least one side of a running paper or board web (9), wherein the at least one coating machine (1) has at least one discharge nozzle (8), wherein the at least one discharge nozzle has a device (13) for transversely profiling a volume flow of the coating medium (2) that can be set region by region across the web width, wherein the roller (3) whose deflection can be set and whose area is controlled is a hydrostatically supported roller having a support element (5) that can be controlled region by region along the roller width, the hydrostatically supported roller having a plurality of pressure zones distributed over the roller width, and the discharge nozzle (8) is divided in width into a plurality of parts each having an outflow zone, wherein the outflow zone and the pressure zone are arranged in an overlapping or offset manner.

2. The apparatus for leveling according to claim 1, characterized in that The at least one deflection-adjustable and area-controlled roller (3) for influencing the linear pressure distribution in the at least one nip (6) can be adjusted for aligning the paper or board web (9) in the cross-web direction.

3. The apparatus for leveling according to claim 1 or 2, characterized in that: The coating machine (1) is a curtain coating machine or a free jet coating machine.

4. The apparatus for leveling according to claim 1 or 2, characterized in that: Each zone is designed in a group control or single element control mode.

5. The apparatus for leveling according to claim 1 or 2, characterized in that: A sensor device (30) is provided which scans and / or detects the paper or cardboard web (9) on one or both sides in the cross-web direction in order to set the pressure level to be applied depending on the surface quality and / or thickness of the paper or cardboard web (9) in the cross-web direction.

6. The apparatus for leveling according to claim 1 or 2, characterized in that: The transverse profile setting of the volume flow of the coating medium (2) which can be set region by region across the web width is controlled as a function of the area-dependent mass distribution of the paper or board web (9) in the transverse web direction.

7. The apparatus for leveling according to claim 1 or 2, characterized in that: The concentration of the fibrous stock suspension at the outlet of the headbox ( 31 ), which defines the resulting grammage, is selected as an input variable for the amount of coating medium ( 2 ) supplied in each region.

8. The apparatus for leveling according to claim 1 or 2, characterized in that: A concentration sensor is provided, by means of which the transverse and longitudinal concentration profiles of the fiber suspension at the outlet of the headbox (31) can be measured with a resolution of the adjustment mechanism graduation, the transverse and longitudinal concentration profiles being selected as input variables for a control circuit (35) for the amount of coating medium (2) supplied respectively region by region.

9. The apparatus for leveling according to claim 1 or 2, characterized in that: The at least one roll gap (6) is designed for a linear load in the range of 20 to 200 kN / m.

10. The apparatus for leveling according to claim 1 or 2, characterized in that: The at least one roll nip (6) is designed as a hard roll nip or a soft roll nip.

11. The apparatus for leveling according to claim 1 or 2, characterized in that: The output nozzle (8) has a plurality of slit nozzles, each of which has an outlet gap (17). When the gap width is 100 to 2000 μm, the accuracy of the outlet gap in the gap length ranges from ±2.5 μm to ±10 μm.

12. The apparatus for leveling according to claim 1 or 2, characterized in that The spatial position of the at least one coating machine (1) relative to the roller gap (6) is adjustable for arranging the indirect coating of the coating medium (2) and controlling the residence time of the coating medium (2) on one of the two rollers (3, 4) being the coating roller.

13. The apparatus for leveling according to claim 1 or 2, characterized in that: The coating machine (1) is designed to control the solid content of the coating medium (2) in at least one layer to be between 6% and 55%.

14. The apparatus for leveling according to claim 1 or 2, characterized in that The coating machine (1) is designed for forming a multi-layer curtain.

15. The apparatus for leveling according to claim 1 or 2, characterized in that: The area width of the profile setting at the slit nozzle of the outlet nozzle (8) and / or the area width of the support element (5) for the hydrostatic support for profile correction is 50 to 300 mm.

16. The apparatus for leveling according to claim 1 or 2, characterized in that At least one roller (3, 4) of the at least one roller nip (6) is designed as a heatable coating roller and is designed for a roller surface temperature of 60°C to 160°C.

17. The apparatus for leveling according to claim 1 or 2, characterized in that The rollers (3, 4) of the at least one nip (6) have a coating of less than 30 P&J.

18. The apparatus for leveling according to claim 1 or 2, characterized in that The angle α of the impact point of the coating medium (2) on the rollers (3, 4) of the roller gap lies between -90° and +45°.

19. The apparatus for leveling according to claim 1 or 2, characterized in that: The adjustable linear pressure distribution and the adjustable application amount of the coating medium (2) can be coordinated with one another by means of a controller (36) so that compacted paper and compacted board with a smoothed surface having selectable strength properties CMT, SCT, RCT in the cross-web direction can be produced.

20. The apparatus for leveling according to claim 1 or 2, characterized in that The volume flow profile at the coating machine (1) can be set by off-line measurement of paper / board web samples.

21. The apparatus for leveling according to claim 1, wherein The coating medium (2) is starch.

22. The apparatus for leveling according to claim 1 or 2, characterized in that The area width of the profile setting at the slit nozzle of the outlet nozzle (8) and / or the area width of the support element (5) for the hydrostatic support for profile correction is 150 to 280 mm.

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