DEVICE FOR SMOOTHING AND FOR APPLYING A TREATMENT SUBSTANCE

Abstract

Device for smoothing a paper or board web (9) with at least one nip (6) formed between two rolls (3, 4), wherein at least one of the rolls (3) for controlling a thickness transverse profile of the paper or board web (9) in the web transverse direction is a deflection-adjustable and zone-controlled roll (3) for setting a line load distribution over the roll width which can be selected in the at least one nip (6), wherein the at least one nip (6) is provided for smoothing the thickness transverse profile of the paper or board web (9) by means of an adjustable line load profile and simultaneously introducing a treatment medium (2) into the paper or board web (9), for which purpose at least one coater (1) having a delivery nozzle (8) for applying application medium (2), in particular starch, is arranged in such a way that the application of the treatment medium (2) to at least one of the two rolls (3, 4) of the nip (6) is provided and is designed for indirect application of the treatment medium (2) to at least one side of the running paper or board web (9) and the at least one coater (1) has at least one delivery nozzle (8) with a device (13) for cross-profile adjustment of a volume flow of the treatment medium (2) which can be adjusted zone by zone over the web width.

Claims

1. Device for smoothing a paper or board web, having at least one nip which is formed between two rolls, at least one of the rolls being a deflection-adjustable and zone-controlled roll for controlling a thickness transverse profile of the paper or board web in the web transverse direction in order to set a line load distribution over the roll width which can be selected in the at least one nip, wherein the at least one nip is provided for surfacing the thickness transverse profile of the paper or board web by means of an adjustable line load profile and simultaneously bringing a treatment substance into the paper or board web, for which purpose at least one coater having a delivery nozzle for applying a treatment substance, in particular starch, is arranged in such a way that the application of the treatment substance to at least one of the two rolls of the nip is provided and is designed for indirect applying of the treatment substance to at least one side of the running paper or board web and the at least one coater has at least one delivery nozzle with a device for cross-profile adjustment of a volume flow of the treatment substance which can be adjusted zone by zone over the web width.

2. Device for smoothing according to claim 1, wherein the at least one deflection-adjustable and zone-controlled roll, by means of which the line load distribution in the at least one nip is controlled, is adjustable for calibrating the paper or board web in the transverse web direction.

3. Device for smoothing according to claim 1, wherein the coater is a curtain application unit or a free jet application unit.

4. Device for smoothing according to claim 1, wherein the at least one deflection-adjustable and zone-controlled roll is a hydrostatically supported roll with zone-by-zone control of elements along the width of the roll, each zone being designed to be controlled in groups or by individual elements.

5. Device for smoothing according to claim 1, wherein sensor means are provided which scan and/or detect the paper or board web on one or both sides in the transverse direction of the web for adjusting the amount of pressure to be applied, depending on the surface quality and/or the thickness of the paper or board web in the transverse direction.

6. Device for smoothing according to claim 1, wherein the cross-profile setting of the volume flow of the treatment substance, which can be set zone by zone over the web width, is controlled as a function of an area-related mass distribution of the paper or board web in the transverse direction of the web.

7. Device for smoothing according to claim 1, wherein the consistency of a pulp suspension in the outlet of the headbox, which defines the basis weight produced, is selected as input variable for the amount of treatment substance supplied zone by zone in each case.

8. Device for smoothing according to claim 1, wherein consistency sensors are provided with which a consistency transverse and longitudinal profile of a fibrous stock suspension in the outlet of the headbox can be measured in the resolution of an actuator division, which profile is selected as input variable of a control loop for the amount of treatment substance supplied zone by zone in each case.

9. Device for smoothing according to claim 1, wherein the at least one nip is designed for line loads in a range from 20 to 200 kN/m.

10. Device for smoothing according to claim 1, wherein the at least one nip is designed as a hard nip or soft nip.

11. Device for smoothing according to claim 1, wherein the delivery nozzle comprises a plurality of slot nozzles each having an outlet slot with an accuracy in the range±2.5 μm to ±10 μm in slot length at a slot width of 100 to 2000 μm.

12. Device for smoothing according to claim 1, wherein the space arrangement of the at least one coater relative to the nip is adjustable for an arrangement for indirect applying of the treatment substance and control of a dwell time of the treatment substance on the one of the two rolls (3, 4) which is simultaneously an applicator roll.

13. Device for smoothing according to claim 1, wherein the coater is designed to control the solids content of the treatment substance in at least one layer from 6% to 55%.

14. Device for smoothing according to claim 1, wherein the coater is designed to form a multilayer curtain.

15. Device for smoothing according to claim 1, wherein zone widths of the profile adjustment at a slot nozzle of the delivery nozzle and/or the hydrostatically supported elements for profile correction are 50 to 300 mm, in particular 150 to 280 mm.

16. Device for smoothing according to claim 1, wherein at least one roller of the at least one nip is designed as a heatable applicator roller and is designed for a temperature of the roller surface of 60° C. to 160° C.

17. Device for smoothing according to claim 1, wherein the rolls of the at least one nip have coatings with less than 30 P&J.

18. Device for smoothing according to claim 1, wherein an angle α for an impact point of the treatment substance on an application roller of the press nip is between −90° and +45°.

19. Device for smoothing according to claim 1, wherein the adjustable line load distribution and the adjustable quantitative application of treatment substance can be matched to one another by means of a control system in such a way that a compacted paper or compacted board with a leveled surface having selectable strength properties (CMT, SCT, RCT) in the transverse direction of the web can be produced.

20. Device for smoothing according to claim 1, wherein a volume flow profile at the coater is adjustable by offline measurement of paper/board web samples.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0038] FIG. 1B schematically shows a device according to the invention for smoothing with at least one coater in cross-section according to a second embodiment, preferably with a free-jet coater,

[0039] FIG. 1C schematically shows the curtain coater in comparison to the free jet coater,

[0040] FIG. 1D schematically shows a device according to the invention for smoothing with at least one curtain coater in cross-section and an associated section A-A in the CD direction according to a third embodiment,

[0041] FIG. 2 schematically shows a device according to the invention for smoothing with at least one curtain coater in cross-section and an associated section B-B in the CD direction according to a fourth embodiment,

[0042] FIG. 3 schematically shows a device according to the invention for smoothing with at least one curtain coater in cross-section and an associated section C-C in the CD direction according to a fifth embodiment,

[0043] FIG. 4 to FIG. 10 show sections in the CD direction according to further embodiments,

[0044] FIG. 11 schematically shows a setting of the parameters print profile and coating profile according to the invention, starting from a basis weight profile and a strength/thickness profile as the result variable in the CD direction,

[0045] FIG. 12 schematically shows a section of a prior art paper or board machine,

[0046] FIG. 13 schematically shows a section of a paper or board web according to the invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

[0047] As shown in FIG. 1A to FIG. 1D, the invention relates to a device for smoothing with at least one nip 6 formed between two rolls 3, 4. At least one of the two rolls 3, 4, here the roll 3, is designed as a deflection-compensation (deflection-adjustable) and zone-controlled roll 3 for controlling a thickness transverse profile of a running material web 9, in particular a paper or board web, in the web transverse direction.

[0048] For this purpose, the roll 3 has a roll shell 7 rotating about an axis of rotation, on the inner circumference of which supporting elements 5 exert a force. The support elements 5 form individual hydrostatic pressure elements. A plurality of support elements 5 are distributed over the roll width and are divided into zones (pressure zone (1) to pressure zone (n)) so that pressure profiling is possible over the machine width. By means of the roll 3, also referred to as profiling roll with MHV elements, it is consequently possible to set a local line load distribution selectable in the at least one nip 6 over the roll width/machine width.

[0049] The at least one nip 6 is thus provided to smooth the thickness transverse profile of the material web 9 by means of an adjustable line load profile when the material web 9 passes through the nip 6. On the other hand, and simultaneously with the exertion of a pressing pressure in the nip 6, a treatment substance or treatment/application medium 2 is placed into the material web 9. For this purpose, at least one coater 1 comprising a dispensing nozzle 8 is provided for applying application medium 2, in particular starch.

[0050] The at least one applying device 1 is arranged to provide for the application of the treatment medium 2 to at least one of the two rolls 3, 4 of the nip 6. The mass flow of treatment medium 2 is applied to the surface of at least one of the two rollers 3, 4 rotating in opposite directions, for example roller 3 (FIG. 1D). Due to the rotation of the rolls 3, 4, the 14 treatment medium 2 applied to the surface of the roll(s) 3, (4) is conveyed towards the material web 9 and penetrates the material web 9 in the press nip 6. This so-called indirect application of the treatment medium 2 to at least one side of the running material web 9 is thus provided.

[0051] As shown in FIG. 1A, the treatment medium 2 can also be applied to both sides of the material web 9, in which case two coater 1 first apply it to the rollers 3, 4. In this respect, the rollers 3, 4 have the function of applicator rollers. The treatment medium 2 may in particular be starch, coating colors, plastic compounds such as PVA or a mixture of these media. The treatment medium 2 is then transferred to both sides of the material web 9, in particular a paper or board web, in the nip 6 between the rolls 3, 4. One roll, in this case roll 4, is preferably a hard roll, particularly preferably a roll which is also heated and which can be equipped with a ceramic cover. The other roll 3 is the bend-adjustable and zone-controlled profiling roll, which can be equipped, for example, with a hard ceramic cover or with a soft cover made of polymer with a hardness of less than 30 P&J, in particular 15-30 P&J.

[0052] As shown in FIG. 1A and FIG. 1D, the coater 1 can be a curtain coating unit. As FIG. 1B shows, a free-jet coater can be used as an alternative to a curtain coater for applying the treatment medium 2, in particular starch, to one or both sides of the rotating applicator roll 3, 4.

[0053] As FIG. 1C illustrates, in a curtain coater, a free-falling curtain of the treatment medium 2 forms in the outlet slot of the (delivery) nozzle 8, which is continuously accelerated by the effect of gravity. The height of fall of the curtain of treatment medium 2 between the outlet slot of the (delivery) nozzle 8 and the point of impact on the applicator roll 3, 4 is usually 50-200 mm. A velocity V2 of the curtain at the point of impact is therefore considerably higher than an exit velocity V1 of the treatment medium 2 at the outlet slot of the (delivery) nozzle 8.

[0054] As FIG. 1C further illustrates, in the free jet coater, a free jet of the treatment medium 2 is generated in the outlet slot of the (delivery) nozzle 8. A jet velocity V4 at the impact point and the exit velocity V3 of the treatment medium 2 are approximately the same in this case. The exit velocity V3 of the treatment medium 2 from a free jet application unit is significantly higher than the exit velocity V1 from the (discharge) nozzle 8 of a curtain application unit. The two different applicators 1 have independent operating windows with regard to machine speeds and coating weights.

[0055] FIG. 1A thus shows a device for smoothing comprising coater 1, for example curtain coating units, with which the coating medium is applied on both sides with two slot nozzles 8 to the rolls 3, 4, which to this extent operate as coating rolls. The slot nozzle 8 is positioned with respect to the respective roller 3, 4 in such a way that the angle α for the point/location of the coating on the roller 3, 4 is, for example, between −45° and +45°. FIG. 1b shows a device for smoothing with coating units 1, for example free-jet coating units, with which the coating medium is applied on both sides with two slot nozzles 8 to the rolls 3, 4, which in this respect operate as coating rolls. The slot nozzle 8 is positioned relative to the roll 3, 4 in such a way that the angle α can lie in the range −90° and +45°.

[0056] In a known manner, the device according to the invention for smoothing and applying a treatment medium 2 may preferably comprise preparation pans/blades 23, collecting tanks/guide plates 26, scrapers 27 and spray water or steam nozzles 28 for cleaning the (application) rollers 3, 4.

[0057] As FIG. 1D shows, according to the invention the at least one applying device 1 has at least one (delivery) nozzle 8, to which a device 13 is assigned for cross-profile adjustment of a mass flow 2 of the application medium 2, which is adjustable zone by zone over the web width. As shown in section A-A according to FIG. 1D, the device 13 generates partial flows 22 of the mass flow 2, which are preferably continuously adjustable from zero to a maximum value specified by the applicator. The individual partial streams 22 can provide different constant mass flows. The number of partial streams 22 is selectable.

[0058] As FIG. 1D shows in section A-A, the applicator 1 is formed, for example, by a curtain applicator whose delivery nozzle 8 is divided into several sections 19. Starting from a cross-flow distributor 10, for example, a starch suspension is distributed across the width via throttle valves 12 and diffusers 11. Via the throttle valves 12, the mass flow 2 in the individual sections can be defined by partial flows 22. An actuator 16 for the respective throttle valve 12 is used here for automation, for example. In principle, however, an adjustment can also be made manually.

[0059] The break-down of the mass flow of treatment medium 2 into partial flows 22 in relation to a number of sections 19 is carried out in coordination with the pressure profiling in the nip 6 by the profiling roll 3. The pressure zones (1) to (n) formed can be selected to be equal to, smaller than or larger than the zones of the sections 19 of application medium 2 in the CD direction. The respective amount of treatment medium 2 in a partial stream 22 can be adjusted as well as the respective line load in the pressure zones (1) to (n) of the profiling roll 3. Together with a hydrostatic pressure element 5 of the profiling roll 3 defining one of the pressure zones (1) to (n), an associated section 19 can form a continuous zone.

[0060] If a starch is to be applied on both sides, the nip 6 can be formed by two rolls 3, 4, both of which can be designed as heated rolls. In all other respects, the roll 4 is preferably designed like the roll 3 described above.

[0061] The line loads in the press nip is preferably between 20 kN/m and 200 kN/m, preferably between 80 kN/m and 120 kN/m. The technique according to the invention can be used for starch application (sizing) and for pigmentation (pigmenting).

[0062] The starch is preferably applied with a solids content between 6% and 35%, particularly preferably between 15% and 35%, and a viscosity between 20 mPa s and 200 mPa s. The application weight is preferably in the range between 0.5 g/m.sup.2 and 6 g/m.sup.2 per side. A film of the thickness in the range of 10 ml/m.sup.2 to 40 ml/m.sup.2 can be applied to the smoothing roller with the additional function of an applicator roller.

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

[0064] FIG. 2 shows a fourth possible embodiment of the invention, among others, in section B-B. The supplied amount of treatment medium 2, in particular starch, can be controlled here by supplying dilution water. The starch suspension passes from the cross-flow distributor 10 via a feed line 24 to the diffuser 11. Dilution water is introduced into the feed line 14. The dilution water can be metered by means of a throttle valve 15. In all other respects, the explanations to FIG. 1D apply.

[0065] In FIG. 3, the locally desired application quantity of treatment medium 2, in particular of the starch suspension, can be achieved by zonal adjustment of an outlet slot 17 of the nozzle 8. For this purpose, the nozzle 8 can be equipped with a flexible lip 18 in the region of the nozzle slot 17. This can be positioned, for example, with the aid of actuators 16. In section C-C, the partial flows 22 are shown as a common, continuous mass flow field 25 in the CD direction. The enveloping profile line 21 stands as a border for the height of the mass flow in CD direction.

[0066] FIGS. 4 to 10 show further possible arrangements and embodiments in section to illustrate the interaction according to the invention of the break-down of the (application) nozzle 8 into sections, the set amount of application medium 2 in the sections and the division into pressure zones by means of the profiling roller 3, in each case in the CD direction, i.e., machine cross direction.

[0067] FIG. 4 shows the direct assignment of a nozzle outlet zone to a pressure zone of the profiling roll according to the multichannel principle of FIG. 1. Here, the outlet width is the same as the effective area of the pressure zone. In addition, it is also possible to arrange the outlet zones and pressure zones in an overlapping or offset manner. This may be necessary, for example, to avoid striping. FIG. 5 shows an overlapping arrangement with the same zone and run-out width.

[0068] The outlet widths of the (application) nozzle 8 do not necessarily have to have the same width as the effective zones of the pressure elements 5. FIG. 6 shows, for example, an arrangement in which the outlet widths are half as large as the effective width of the pressure elements 5. There are different zone and outlet widths with direct assignment.

[0069] Even with smaller outlet widths, it can make sense to arrange the pressure zones (1) to (n) and the outlet positions in an overlapping arrangement, as shown in FIG. 7. FIG. 7 shows different zone and outlet widths with overlapping arrangement.

[0070] Of course, it is also conceivable to reduce the outlet widths even further if necessary. The lip adjustment as a form of execution is suitable here. The adjustment makes it possible to very finely adjust the distribution of the application medium over the machine width. Further possible variations are shown in FIG. 8 to FIG. 10. FIG. 8 shows a medium distribution via a nip adjustment with nip width equal to print zone width. FIG. 9 shows a nip adjustment with a smaller nip width than print zone width with overlap. FIG. 10 shows a slot adjustment with different and variable pitch width as pressure zone width.

[0071] The following applies equally to all of the above examples of embodiments:

[0072] One or more scanners (not shown) can be assigned to the system, which record quality characteristics such as paper thickness, coating weight or paper moisture in CD direction and process them for control purposes and make them available for cross-profile control.

[0073] The zone width of the profile setting on the slot die 8 is, for example, 50 to 300 mm, preferably 150 to 280 mm.

[0074] The zone width of the hydrostatic elements 5 for profile correction is, for example, 50 to 300 mm, preferably 150 to 280 mm.

[0075] On at least one of the slot nozzles 8, the device for zone-wise slot width adjustment or a device for zone-wise adjustable mass flow control is provided.

[0076] The hardness of the covers of the smoothing rolls 3, 4 is 0 to 30 P&J, preferably 0 to 5 P&J. The diameters of the smoothing rolls 3, 4 are preferably in the range 1000 to 1800 mm, particularly preferably 1200 to 1600 mm. The discharge slot 17 of the discharge nozzle 8 is preferably 100-500 μm.

[0077] The pressure in each zone of the treatment nip 6 and the quantitative starch application are matched to achieve a desired cross profile of paper thickness and strength properties (CMT, SCT, RCT).

[0078] The zone of the applying system and the associated, downstream press zone of the profiling roll are linked with each other in terms of control technology, so that automatic balancing of the press pressure and starch application quantity is possible. The overall system can be integrated into the process control system of the paper machine. Scanner data from the machine can be used to control the zones individually so that the desired paper strengths (CMT, SCT, RCT) can be set in machine width. The macro surface roughness of the paper after treatment nip 6 is <800 ml/min at Bendtsen, preferably <500 ml/min.

[0079] The coating weight of the starch is in the range 0.5-6 g/m.sup.2 per side. The line loads in the 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 rolls 3, 4 is 60° to 160° C. The paper or board web speed is preferably between 250 m/min and 2000 m/min, more preferably between 600 m/min and 1800 m/min. The dry content of the material web 9 is preferably more than 90% and is preferably between 92% and 98%. The starch can be applied with a solids content between 6% and 35%, preferably between 15% and 35%, and a viscosity between 20 mPa s and 200 mPa s. The temperatures of the starch are preferably between 50° C. and 110° C., particularly preferably between 70° C. and 100° C.

[0080] For further designing of the device for smoothing according to the invention, the following is provided:

[0081] The at least one deflection-adjustable and zone-controlled roll 3, which is used to influence the line pressure distribution in the at least one nip 6, can be adjusted in the transverse direction of the web for calibrating the material web 9.

[0082] The at least one deflection-adjustable and zone-controlled roll 3, which is used to influence the line load distribution in the at least one nip 6, can be adjusted to control a thickness of the material web 9 in the transverse direction of the web.

[0083] The at least one deflection-adjustable and zone-controlled roll 3 is a hydrostatically supported roll with zone-wise control of elements 5 along the width of the roll, wherein each (pressure) zone can be designed to be controlled in groups or by individual elements.

[0084] As FIG. 11 shows, sensor devices, in particular scanners 30, can be provided which scan and/or detect the material web 9 in the transverse direction of the web on one or both sides for setting the level of pressure to be applied, i.e. pressure profile 33, depending on the surface quality and/or thickness of the material web 9 in the transverse direction before it enters the nip 6.

[0085] Alternatively or additionally, a volume flow profile can be set at the applicator by offline measurement of paper/board web samples.

[0086] The cross-profile setting of the volumetric flow/mass flow of the application medium 2, which can be set zone by zone over the web width, can be controlled as a function of an area-related mass distribution of the material web 9 in the transverse direction of the web.

[0087] As FIG. 11 further shows, the consistency of a pulp suspension in the outlet of the headbox 31, which defines the manufactured basis weight and its profile 32, can be selected as the input variable for the respective zonally supplied quantity of application medium 2 through the application nozzle 8 and its zones and throttle valves 12 (FIG. 1) or actuators for lip adjustment (FIG. 3). The respective adjustable mass flows/volume flows are shown in the sectional views of FIG. 1 to FIG. 11 as discrete arrows of the medium 2 or as a continuous flow profile curve of the application medium 2.

[0088] Consistency sensors can be provided with which a consistency transverse and longitudinal profile of a pulp suspension can be measured in the resolution of an actuator division at the outlet of the headbox, which can be selected as an input variable of a control loop 35 for the quantity of application medium 2 fed in each zone. The adjustable line pressure distribution 33 and the adjustable quantity of application medium 2 can be coordinated with each other by means of a control 36 in such a way that a compacted paper with a levelled surface with selectable strength properties (CMT, SCT, RCT) 34 can be produced in the cross-web direction.

[0089] FIG. 11 in particular shows the technical connection that areas of the paper or board web with higher basis weight of the paper or board web are treated with higher line load and less application medium while calibrating and penetrating application medium, in particular starch, according to the invention than areas of the paper or board web with lower basis weight where more treatment medium and lower line load are applied to obtain a uniform strength/thickness profile.

[0090] Finally, the dispensing nozzle 8 of the curtain coater, which dispenses the medium 2 under the action of gravity, may have a plurality of slit nozzles 18, each with a discharge slit 8 having an accuracy in the range±2.5 μm to ±10 μm in slit length with a slit width of 100 to 2000 μm.

[0091] The coater 1 may be designed to control the solids content of the application medium 2 in at least one layer from 6% to 55%.

[0092] The curtain coater 1 can be designed to form a multilayer curtain.

[0093] The specific volume flow from the nozzle 8 of the curtain applicator 1 can be in the range of 4 l/(min x m) to 30 i/(min x m). A film of the application medium 2, in particular starch, in the range from 5 ml/m.sup.2 to 100 ml/m.sup.2 is preferably applied to the respective smoothing roll 3, 4.

[0094] Furthermore, guide rollers (not shown) can also be provided, which can define a treatment path of the running material web 9 between curtain coater 1 and press nip 6.

[0095] A certain roll outer circumference length corresponding to the dwell time can be set between an impact of the curtain 2 and its entry into the press nip 6, thus increasing or decreasing the dwell time as indicated by the angle α. If the smoothing roll 3, 4 is heated, the dwell time can be used to influence a temperature increase of the application medium 2 before it enters the press nip 6. The treatment medium 2 can then be thermally pretreated in this way in the press nip 6 between the smoothing rolls 3, 4 and pressed into the material web 9 on one or both sides.

[0096] The invention now being fully described, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the appended claims.