CURTAIN COATER FOR APPLYING A TREATMENT SUBSTANCE ON AT LEAST ON APPLICATOR ROLL

Abstract

A device for applying a treatment substance to a running paper web or board web (11) by means of at least one curtain applicator (2.1, 2.2) comprising a curtain coating die for applying the treatment substance to an applicator roll (6, 7) which, together with a second roll (6, 7), creates a treatment nip (15) in which the treatment substance is transported from the applicator roll (6, 7) to the respective side of the paper web or board web (11), and the curtain coating die has a slot adjustment (3.1, 3.2) for adjusting an exit slot (14.1, 14.2). To provide a device for applying treatment substances which improves the paper/board quality differently prepared treatment substances can be supplied to the at least one curtain coating die, and the curtain applicator (2.1, 2.2) combines the two operating modes of a film operation mode and a sump operation mode by providing an electrically and/or mechanically actuable adjusting device for the slot adjustment (3.1, 3.2) applied to the exit slot (14.1, 14.2) of the curtain coating die, which controls a die lip and sets the exit slot (14.1, 14.2) alternatively to 100 m to 500 m for a film operation mode or to 500 m to 2.0 mm for a sump operation mode, so that the at least one curtain applicator (2.1, 2.2) is designed to be performed with two different operating modes.

Claims

1. A device for applying a treatment substance to a running paper web or board web by means of at least one curtain applicator comprising a curtain coating die for applying the treatment substance to an applicator roll which, together with a second roll, creates a treatment nip in which the treatment substance is transported from the applicator roll to the respective side of the paper web or board web, and the curtain coating die has a slot adjustment for adjusting an exit slot, wherein differently prepared treatment substances can be supplied to the at least one curtain coating die, and the curtain applicator combines the two operating modes of a film operation mode and a sump operation mode by providing an electrically and/or mechanically actuable adjusting device for the slot adjustment applied to the exit slot of the curtain coating die, which controls a die lip and sets the exit slot alternatively to 100 m to 500 m for a film operation mode or to 500 m to 2.0 mm for a sump operation mode, so that the at least one curtain applicator is designed to be performed with two different operating modes.

2. Device according to claim 1, wherein for the slot adjustment of the exit slot of the curtain coating die an adjusting device is provided which can be actuated electrically and/or mechanically.

3. Device according to claim 1, wherein the position of the at least one curtain coating die relative to the applicator roll is variable.

4. Device according to claim 3, wherein the position of the at least one curtain coating die relative to the applicator roll can be changed in such a way that a curtain height remains essentially the same in the different operating modes.

5. Device according to claim 1, wherein at least one of the two rolls creating the treatment nip is designed as a deflection compensation roll.

6. Device according to claim 1, wherein the diameter of the at least one applicator roll is 1000 to 1800 mm, preferably 1200 to 1600 mm.

7. Device according to claim 1, wherein the hardness of a cover of a hard applicator roll is selected in the range of 0 to 5 P&J preferably 0 to 1 P&J.

8. Device according to claim 1, wherein one of the rolls is designed as a defection compensation roll with 5 to 30 P&J, preferably 0 to 10 P&J.

9. Device according to claim 1, wherein an overflow funnel is provided in an edge region of the at least one curtain coating die in each case per edge, which overflow funnel is formed laterally of the nip.

10. Device according to claim 1, wherein the line force in the treatment nip is between 20 kN/m and 200 kN/m, preferably between 80 kN/m and 120 kN/m.

11. Device according to claim 1, wherein the speed of the web is between 250 m/min and 2000 m/min, preferably between 600 m/min and 1800 m/min.

12. Device according to claim 1, wherein the dry content of the paper or board web is selected at more than 90%, in particular between 92% and 98%.

13. Device according to claim 1, wherein the starch is provided as a treatment substance with a specific volumetric flow of between 15 l/(min*m) and 150 l/(min*m) during the sump operation mode and between 5 l/(min*m) and 50 l/(min*m) during the film operation mode.

14. Device according to claim 1, wherein the starch is provided as treatment substance with a solids content of between 5% and 12% during the sump operation mode and between 10% and 25% during the film operation mode.

15. Device according to claim 1, wherein the viscosity of starch as the treatment substance is selected between 20 mPas and 200 mPas.

16. Device according to claim 1, wherein the temperatures of starch as application medium are selected between 50 C. and 110 C., preferably between 70 C. and 100 C.

17. Device according to claim 1, wherein in the film operation mode the angle for the zone of impingement of the curtain on the at least one applicator roller is selected between 0 and 45, preferably between 0 and 15, and in sump operation mode between 30 and 90, preferably between 45 and 60, with respect to the vertical.

18. Device according to claim 17, wherein the position of the curtain coating die and its lip is determined via a control device for a change of the operating mode during a production run.

Description

[0022] The invention is explained in more detail below with reference to the embodiments shown in the accompanying figures.

[0023] FIG. 1 schematically shows a cross-section of a device according to the invention for applying a treatment substance in a film mode,

[0024] FIG. 2 schematically shows a cross-section of a device according to the invention for applying a treatment substance in a sump mode,

[0025] FIG. 3 schematically shows a cross-section of a curtain coater die according to the invention with a slot adjustment via an eccentric shaft,

[0026] FIG. 4 schematically shows a cross-section of a curtain coater die according to the invention with a slot adjustment via a linear actuator.

[0027] The invention relates to a device for applying a treatment substance, in particular starch, a sizing agent, a glue or a gluing suspension, to a moving or running paper or paperboard web 11, in particular testliner or corrugating medium. The device comprises at least one curtain applicator 2.1, 2.2 with a curtain coating die or slit for applying the treatment substance in the form of a curtain 4.1, 4.2 to at least one applicator roll 6, 7. The curtain 4.1, 4.2 is preferably a liquid sheet that falls freely over a considerable height onto the at least one applicator roll 6, 7 that forces the coating liquid through a nip 15 on to the web 11. The one applicator roll 6 sets up the treatment nip or roll nip 15 with a second roll 7, which is also designed as an applicator roll in the case of applying treatment substance on both sides of the web 11. In the nip 15 the treatment substance, or any other kind of coating liquid used, is transferred from the applicator roll(s) 6, 7 to the respective side of the paper or paperboard web 11. The curtain coating slot of the respective curtain applicator 2.1, 2.2 also has a slot adjustment 3.1, 3.2 for adjusting the slot exit 14.1, 14.2 of the curtain coating die that defines a curtain applicator nozzle.

[0028] The at least one curtain coating die can be fed with differently prepared treatment substances. Furthermore, the slot adjustment 3.1, 3.2 of the exit slot 14.1, 14.2 to about 100 m to 500 m for the film operation mode and to about 500 m to 2.0 mm for the sump operation mode allows the at least one curtain applicator 2.1, 2.2 to be operated in different modes.

[0029] For the technical implementation of the invention, the use of a curtain applicator 2.1, 2.2 combined with applicator rolls 5, 6 is preferably provided, whereby at least one applicator roll 7 can be designed as a deflection compensation roll. These rolls are known, for example, under the name S-roll, MHV-roll or NIPCO-roll.

[0030] The rolls 6, 7 for forming the roll nip 15 can be provided with hard covers, for example ceramic, chrome, but can also be provided with hard covers made of polymer. The hardness of the roll surfaces is less than 30 Pusey & Jones, preferably less than 15 P&J. The applicator rolls 6, 7 can be temperature controlled.

[0031] FIG. 1 shows an embodiment of the device according to the invention in the film operation mode. The film operation mode is an applying system, which pre-doses an exact coating liquid film, which is transferred to the web 11 in the nip 15 without any or at least nearly any significant sump. The film operation mode of the curtain applicator 2.1, 2.2 allows to apply a very high solid content of starch. Reference sign 12 indicates a possible outlet for excess treatment media.

[0032] The running direction of a web is from top to bottom and is marked with an arrow. This is, for example, the coating of a test liner (TL). The solids content of the starch is relatively high and amounts to 15%. The volume flow for the coating is accordingly relatively low. A cleaning blade 9.1, 9.2 is applied to the coating roll 6, 7 and is in the operating position. The cleaning blade 9.1, 9.2 is used to clean the applicator roll 6, 7 permanently during production. Water spray or steam nozzles 10.1, 10.2 can be provided for cleaning the applicator rolls 6, 7. Fibers and starch particles adhering to the roll surface are removed from the roll 6, 7 by the cleaning blade. A drip tray 8.1, 8.2 prevents the water from dripping onto the running paper web 11.

[0033] The curtain coating die of the curtain applicator 2.1, 2.2 can be moved hydraulically or electrically by motor. A pivoting movement of the entire unit can be provided for this purpose. In the event of an interruption in production due to a malfunction or a web break, the die and the entire unit of the curtain applicator 2.1, 2.2 can be moved to a hold position. In the hold position, the starch preferably flows into a catch pan 5.1, 5.2 and is preferably returned from there to the working depot for reuse.

[0034] In the operating mode, the curtain coating die of the curtain applicator 2.1, 2.2 is positioned in such a way that, for example, the curtain 4.1, 4.2 has an impingement zone onto the applicator roll 6, 7 aligned to the roll axis. In this case, the angle is between zero and 45. This position of the curtain coating die is preferably selected so that the distance from the air boundary layer suction to the curtain is minimal. This prevents disturbing influences of the boundary layer air flow along the running roll surface on the curtain. In this position, it is possible to create a stable curtain without heel formation and without unwanted backflow on the running roll 6, 7. Below a positioning of a approx. 45, the thin curtain is disturbed by the boundary layer air flow and uniform contact with the roll surface is no longer possible.

[0035] The applicator rollers 6, 7 are preferably arranged at an angle of 0 to 15 to each other. The treatment medium can be applied first to the applicator rolls 6, 7 on both sides with a curtain 4.1, 4.2. To build up a curtain 4.1, 4.2 a die with an exit slot 14.1, 14.2 of 100-500 m is used.

[0036] The treatment substance can be starch, a sizing agent, a glue, a glue suspension or a mixture of these media. The treatment substance is then transported to the paper or paperboard web 11 in the nip 15 between the applicator rolls 6, 7.

[0037] The respective curtain 4.1, 4.2 can have a curtain height in the range of 50 to 300 mm between the point of impact on the applicator roll 6, 7 and the die exit. Thus the liquid sheet of the curtain 4.1, 4.2 falls freely over a considerable height before it impinges onto the applicator roll 6, 7 to apply a thin liquid layer while the applicator rolls 6, 7 rotate to transfer from there the coating liquid to the running web 11 in the nip 15.

[0038] As FIG. 2 shows, in the operating mode of a sump press, the treatment substance, in particular the starch or the size liquor, can first be applied to the applicator rolls 6, 7 via the die or fed directly into a sump 13. By means of a linear guide 1.1, 1.2, for example, the curtain coating die can be positioned.

[0039] Since the starch concentration is significantly lower in a sump operation mode, i.e. the treatment substance is prepared differently from the film operation mode described above, the volume flows are correspondingly higher here. In addition, the sump operation mode requires an additionally higher volume flow to ensure a certain sump height. For example, the volume flow in the sump operation mode can be higher by a factor of 2 to 3 than in the operating mode of a curtain sizer (film operation mode). With a high volume flow rate in combination with a small exit slot of the die, the exit velocities of the starch from the die slot 14.1, 14.2 would be very high. The high exit velocities could splash and cause turbulence when the starch hits the applicator roll 6, 7 or the sump 13. This could disrupt the coating process.

[0040] In order to reduce the exit velocities from the die, the exit slot 14.1, 14.2 is adapted to the volume flow according to the invention. The exit slot 14.1, 14.2 of the die for the sump operation mode is selected larger than for curtain coating operation in a film operation mode. According to the invention, an exit slot 14.1, 14.2 of 0.5 to 2.0 mm has proven to be optimal for the sump operation mode. In order to correct or adjust the exit slot 14.1, 14.2, a slot adjustment 3.1, 3.2 is provided, preferably on a nozzle lip of the die of the curtain applicator 2.1, 2.2.

[0041] The die of the curtain applicator 2.1, 2.2 is positioned during the sump operation mode so that the angle for the point of impact or impinge of the curtain 4.1, 4.2 on the applicator roll 6, 7 or the sump 13 is in the range between 30 and 90, preferably between 45 and 60.

[0042] A cleaning of the applicator roll 6, 7 is preferably not necessary in the sump operating mode, since the roll 6, 7 is cleaned by the flow of starch in the sump 13. The cleaning blade 9.1, 9.2 is swung off.

[0043] In most cases, corrugating medium (CM) and testliner (TL) are produced on the same paper machine. In this case, the changeover of grades often takes place without shutting down the paper machine. During a trouble-free change of the operating mode from film operation mode to sump operation mode, the curtain coating die of the curtain applicator 2.1, 2.2 and the entire unit can move in the direction of nip 15.

[0044] Let's assume that production on the paper machine is changed from testliner (TL) to corrugating medium (CM) while production is running. The course of procedure would then be as follows:

[0045] When switching to the operating mode of a sump press, the starch continues to be applied to the applicator roll 6, 7 via the curtain coating die. The sump operation mode requires an additional higher volume flow to set a certain sump height. According to the invention, the exit slot 4.1, 4.2 of the curtain coating die is increased for the sump operation mode in order to adapt the outlet speed to a higher volume flow. The exit slot 4.1, 4.2 of the coating die is therefore adjusted from, for example, 350 m to approx. 1 mm, in order to switch the applicator unit to the sump operation mode. The adjustment of the exit slot 4.1, 4.2 can be realized manually, automatically (motorized or hydraulically).

[0046] When using profiling rolls, it is also possible according to the invention to operate the system in regular calender mode. For this purpose, the hard covered roll 6 would have to be equipped in such a way that higher surface temperatures can be set (thermoroll)

[0047] FIG. 3 and FIG. 4, for example, show different embodiments of the slot adjustment 3.1, 3.2 on the exit slot of the coating die. FIG. 3 shows a slot adjustment 3.1, 3.2 via an adjustment device that engages the coating die lip. The adjusting device can be, for example, an eccentric shaft, a plunger or a wedge. The adjustment device can be electrically and/or mechanically actuated. Likewise, the coating die slot could be adjusted, for example, with the aid of linear actuators 3.3. The position of the at least one curtain coating die relative to the applicator roll can be changed in such a way that a curtain height remains essentially the same in the different operating modes.

[0048] The line force in the nip 15 can be between 20 kN/m and 200 kN/m, preferably between 80 kN/m and 120 kN/m. The paper or paperboard web speed can be between 250 m/min and 2000 m/min, preferably between 600 m/min and 1800 m/min. The dry content of the paper or paperboard web 11 may be selected at more than 90%, in particular between 92% and 98%. Starch as treatment substance can be provided with a specific volume flow of between 15 l/(min*m) and 150 l/(min*m) for the sump operation mode and between 5 l/(min*m) and 50 l/(min*m) for film operation mode. Starch as an treatment medium can be provided with a solids content between 5% and 10% for the sump operation mode and between 10% and 25% for film operation mode. The viscosity of starch as treatment substance can be selected between 20 mPas and 200 mPas. The temperatures of starch as treatment substance may be selected between 50 C. and 110 C., preferably between 70 C. and 100 C.

[0049] 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. In particular, the slot die mode described can be build up in a slide die mode as well.