CA2275993A1

CA2275993A1 - Method and device for applying a medium on a running web of material

Info

Publication number: CA2275993A1
Application number: CA002275993A
Authority: CA
Inventors: Albrecht Meinecke; Volker Schmidt-Rohr; Ingolf Cedra
Original assignee: Individual
Current assignee: Voith Patent GmbH
Priority date: 1997-10-24
Filing date: 1998-10-22
Publication date: 1999-05-06
Also published as: ATE284467T1; EP0948678A1; BR9806717A; WO1999022067A1; US6383337B1; EP0948678B1; JP2001507090A

Abstract

The invention relates to a method and device for applying a liquid or pasty application medium on a running web of material, especially of paper or cardboard, in a twin wire area of a wet splitting device (33) of a paper machine. The inventive method is characterized in that an additional liquid or pasty application medium is applied on the web of material (38) by means of at least one applying device (14, 15, 16, 17, 25, 28, 31, 32, 36, 48, 52, 53) after a first press element (13) of the press section (34). The inventive device has the following features: an applying device (5, 10, 44, 46) is arranged in said twin wire area on at least one side of a wire (3, 4, 39, 40), said side being opposite the web of material; and at least one additional applying device (14, 15, 16, 17, 25, 28, 31, 32, 48, 52, 53) which directly faces the web of material is provided after a first press element (13) of a press section (34).

Description

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P179.63.503 Method and device for applying a medium on a running web of material The invention relates to a method for applying a liquid or pasty application medium on a running web of material, especially of paper ar cardboard, in accordance with the characterizing portion of claim 1 and a paper ma.ahine with a device suitable for implementing the method.
U. S. patent document 5,152, 872, for example, i;; known in the state of art.
In it, a one-sided application is made directly onto the fiber web by means of a roll application mechanism in a single-wire wet splitting device. In the application area, the wire loops around a roll supporting the web. The web lies cm the side of the wire facing away from the roll. The roll application mechanism contact,. the web in the looping area of the supporting roll. The roll application mechanism is a device comprising three rolls.
Moreover, in the gap between the actual applicator roU and the web of material that has already been wetted, during the detachment process of the applicator roll surface from the web surface, roughening or picking occurs on the web surface. In this state of art, application of a medium in a twin wire area of a wet splitting device is not possible.
U.S, patent document 4,793,899 discloses a similar applying device, as described above.
In it, however, the application is made not in the wet spIitfmg device but in the press section of a paper or cardboard machine. Moreover, the application medium is applied by means of a machine-wide stream from an application mechanism onto a combined application-and-press roll. Then this roll transfers the application medium to the web of material. This construction also causes picking o;n the web -of material and in any event does not peimit application in the twin wire area of a paper machine.

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P 17963 , S03 U. S. patent document 5,622,599 is also known i;itom the state of art. In it, by means of spray nozzles, a one-sided application from above directly onto the still-wet web takes place in the wire section of a paper machine. The spray application occurs in the area of the straight wire course, in which wire washboard marks can form in part transverse with respect to the wire direction_ In this manner, the spray application can occur irregularly on the surface of the web of material (viewed transversely with respect to the direction in which the wire moves). This constriction also does not include application in a twin wire area. Moreover, a downstream roll comacting the spray application mechanism and the wetted web of material also results in the disadvantage of the pinking described above.
An applying device is descnbed in the as yet unpublished German patent applications DE 197 47 091 and DE 297 23 289, in which the application medium is applied to the still-wet web of material in an area supported by a roll. In so doing, the web of material can lie both between taro wires and also on one wire onhy. If the surface of the web of material is covered by a wire, for example, the applying device feeds tl'ne application medium of the surface of the web of material through the wire. An additional application possibility is a way to apply the medium indirectly onto the web v~material. Here, by means of the application mechanism, the medium is $rst applied to the surface of the roll supporting the wire.
Through the rotation of the roll, the application medium is then fed through the supporting wire to the surface of the web of material. This application method is used, for example, if the surface of the web of material that faces away from the roll is not covered by a wire. The application media can be, for example, color coatings, starches, or also althet substances. The disclosure content of the application spec'ifled above is incorporated inl its entirety in this application.
ZS Extremely high paper surface strengths are required particularly for heat-set and cold-set offset printing. In the state of the art, the pigm~mt particles of the color coating are only moderately anchored with the surface of the web of material. During printing, picking then occurs on the surface of the web of material, since the fiber and pigment particles are often -2.

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~e P 17963.503 held more strongly by the printing ink than by the web of material. In this process, fluffing or delaminating (i.e., separation of layers) partially occurs. The consequence is rather significant unevenness in the printed image.
It is therefore the object of the invention to find a method and a device in which an improved anchoring of the application medium on the web of material is achieved, so that its printability is improved and the technical outlay is reduced tQ the extent possible with respect to previous solutions.
This task is achieved through the features of the independent claims.
The inventor has recognised that the application, for example) of a color coating with a suitable bonding agent (off for example, mineral filling materials such a kaolin, clays, talcum, zeolite, CaC03 or TiOv etc.) in the twin wire aria of the wet splitting device of a paper or cardboard machine experiences a good anchoring with the web of material. This can be explained by the fact that in the wet splitting device, the fibers lie relatively loosely at first in relation to their final condition after drying. Through the dewatering pressure - caused by dewatering strips or through traction of the wire on a curved rwire path -water is more intensively driven from the fiber suspension, I~ in this phase, the application medium is pressed under pressure through the wire into the fiber web via an applying device, the medium interlocks with the Sbers of the surface of the web of material. Since some water is still present inside the web of material, the medium does not penetrate to the center of the web of material, but remains primarily in the outer layers. The consequence is a steep distribution of the medium in the z direction of the sheet of paper (i.e., over the flat cross-section), whereby the printability is significantly improved.
An applicator is used as an applying device in the twin wire area. This is a distributing pipe that is transverse with respect to the direction in which the wire moves, having a slot-shaped ""m~ w ~ i~W I ~ lrJf l W 71CLL11DLW I U LnLf~l'IJ I L117 11v. 77u (- .
P17963.503 nozzles that also extends in that direction. The nnedium is pressed aut from the slot-shaped noale through pressure of 0.05 to 0.5 bar - preferably at 0.1 to 0.4 bar.
Since this applicator is positioned near or in the immediate vicinity of the elements supporting the surface of the wire (dewaxering strips or rolls, for example), wore washboard marks extending transversely with respect to the direction in which the wire moves is eliminated. A wire surface smoothed in this way makes a very close positioning of the applicator to the wire surface possible. Even a direct contact with the surface of the wire is possible. ?his even distance between the applicator and the surface of the wire that can be realized in this manner results in homogenous hydrodynamic conditions when viewed across the width of the machine. In this manna, a high degree of evenness of application its achieved transversely with respect to the direction in which the wire moves. The application weight (dry weight of the application medium) ranges from 1 to 10 g/m2 per side, depending on the instance of utilization.
The application described above can be suppartEd by a first addition of additives that have a surface bonding effect. These agents include, for example) starches, surface sizing agents, lattices, latex, and polyvinyl alcohols. These agents are applied jointly with the actual application medium or separately. Prc-dosing in the. fiber material upstream from the headbox is also possible.
It is a p:imary idea of the inventor to proceed wish a residual addition of the additives in an area ofthe paper machine in which the web of material already has a rather high dry content.
This leads to a higher retention of the additives in the web of material, since, owing to the higher dry convent, less water flow fi om the web of material occurs. This application location is located preferably downstream fi om the first press element of the press section. The initial anchoring of the application medium in the twin wire area of the wet splitting device in combination with a downstream further application with at least one additive results in an improved surface strength and thus to an improved evenness of the printed image.

Jull. v1 . yJ.m i yyi n n VI\v.W IW Ui n a W w 1.~ n Urn i r1a963,s03 Furthermore, a reduced load of the water circuit of the paper machine is achieved since the additive remains more intensively in the web of material.
This combination of the measured application can also avoid the need for an additional sizing press or a coating machine, The applicator mentioned above or also spray no2iles can be considered as applying devices for the additives.
A further idea of the inventor is the application of fine fiber material in the twin wire area of the wet splitting device. In this manner as well, ~a surface bonding of the web of material is achieved. The fine fiber material i s unintentionally washed out during dewatering - mainly from the surface of the web o~ material. Recirculating the fine fiber material causes it to be added back to the layer in the web of material from which it was lost. The fiber mat located between the wires thus functions as a filter. Tru s fine fiber material can, for example, be recovered through fractionation ofthe~wire water.
Additional embodiments of the invention are presented in the subclaims to the first method claim and to the first device claim, and in the folJiowing descriptions of the ~~ures.
It is understood that the features of the invention specified above and to be explained below are not applicable only in the respectively undicated combination, but also in other combination or individually, without exceeding the scope of the inventi on.
Additional features and advantages of the invention are presented in the following description of preferred embodiments, with reference to the drawings.
The invention is explained in further detail below, with reference to the drawings.

JUI'I.G1.1777 f ~ llrll 171CLLl'IDLUI I ex DLfCIYJILlII ny. JJ~ , . , P 17963.S03 Figure 1 shows a partial view of a paper or cardboard machine having examples of mounting locations of the applying devices;
Figure Z shows a section of a twin wire area of a wet splitting device;
Figure 2a shows a section of a twin wire area of a wet splitting device (further exemplary embodiment);
Figure 3 shows a section of a single-row drying group;
Figure 4 shows a section of a double-row drying group, In Figure 1, the fiber 4naterial suspension is produced between the wires 3 and 4 (machine foundation = 6) via the headhox 1. On the radius of a deflection device F
(such as a forming roll, far example), the wires nm on a slant toward each other and the fiber suspension is con~uently enclosed between the wires. A first: dewatering of the fiber suspension occurs here and a fiber mat 38 (web of material) forms. After the deflection device F
begins the twin wire area, the end point of which is located at the roll S, such as a wire suction roll, for example. In the twin wire area, additional dewatering elements 7, 8, and 9 may also be located. For example, the dewatering element 7 cam thus be a dewatering box with stationary dewatering strips. Then, generally flexible, pre;ssable dewatering strips 9 are positioned opposite the dewatering box 7. The dewatering element 8 can, for example, be a so-called wire suction box. The area of the twin wire area can also be curved. By means of applicators 5 and 10 positioned on the wires 3 and 4 (or possibly positioned at a slight distance from the wire surface), an application medium can be applied to the already partially dewatered web of material 38 through the wire into the fiber web of the web of material.
This application medium can contain color coatings, starches, ;surface-bonding media, or also fine fiber suspensions.
In over to ensure as accurate an application as possible from the applicators 5 and 10, they are preferably positioned in the vicinity of the elements S, 7, 8 and 9 that are in contact with and hence support the wire webs 3 and 4. By supporting the wires, a possible surface JUI'1. G1 . 1777 f ~ llrl'I VKLL17DLU1 1 ~ LLICI'IJ I L111 n W . W ~ , . r.
P17963.503 washboard mark ofthe wire transverse with respect to the direction in which the wire moves is prevented to the greatest possible extent.
The structure of the applicatora 5 and 10 is known from the state of the art.
They are comprised of a pressure space with the application medium having a slot-shaped opening in the output direction.
After the first application of an application mediurn in the wet splitting device 3 3, the web of material 38 is guided over the wire 4 of the press section 34. A continuous loop IZ transfers the web of material 38 to the press section 34., An additional transfer device (not shown) (such as a blowing device) guides the web of material 38 along a course through a first :press element I3 indicated either as a broken or dotted :line. The web of material 3 8 then has a dry content that allows for an additional application of a medium the bonds the surface of the web.
it is also particularly advantageous from this point forward that the applying devices 14, 16, and 17 of the press section 34 and also the subsequent applying devi ces in the drying section can be directed directly onto the surface of the web, since the web of material 38 already has suf~ciertt tensile strength under certain circumsi;ances and does not necessarily have to be supported continuously by felts and thus is also not covered by felts or, later, drying wires.
In addition to the applicators already mentionedl, the applying devices can, from thin point forward, also be spray nozzles arranged in a row transversely with respect to the direction in which the wire moves. An additional application location in the press section is the press gap of the press 15. Here, by means of an applying dlevice on the press roll surface, the second application medium can be applied. Through the rotation of the press rolls, the medium is then transferred onto the surface of the web of material.
Downstream from the press section 34, the web of material 38 is forwarded by means of a J UI'i. G1 . 1~'~'7 f ~ 1Ch'I'I uKttIYbLUI'I a: bLKI7J I Lll7 ~ w.. gym, P 17963 , 503 transfer device (also not shown) around the papler guiding roll 37 to the drying section 35.
In this process, the drying cylinders 18, 19, 20, the drying wire 27, and the drying web suction rolls 26 form a single'row, top-felted drying group. In the area where the web of material 3 8 lies open oa the drying cylinder 18 - i. e., where it is not covered by the drying wife 27 - is a suitable place for positioning an applying device 36, for the web of material is supported here by the drying cylinder 18. In a single-tow drying group, there is respectively only one opportunity to perform an application directly onto the side of the web of material 38 facing away from the drying cylinder. As a tule, this is possible at the beginning or at the end. Looping the drying wirE; suction roll 26 causes the web of material 38 to lie on the outside on the drying wire 27 and to be supported by the roll body. This position is also suitable for adding an additional applying device 25, in order to apply media for bonding the surface onto the surface t~f the web.
The drying cylin ders 21, 22, 23, 24 and tire drying wires 29, 3 0 h eve a daubl e-row drying group, shown partially, In this location, the applying devices 28, 31, and 32 can be positioned in such a way between an upper and ;a lower drying cylinder that both surfaces of the web of material can always be treated alternately with application media.
This allows for the applying devices to be positioned both at the beginning aid end areas of the drying gaup, in which the web of material is st~l lying on the drying cylinder and is therefore supported by the drying cylinder, and in the area where the web of material is located in transition between two drying cylinders, i.e. in the free drawing area.
In Figure Z, a twin wire area of a wet splitting device that differs from the ooe in Figure 1 is presented. The web of material 3 8 is located between the upper wire 3 9 and the lower wire 40. The arrow 41 indicates the direction of movement. The web of material is dewatered alternately between the dewatering elements 42 and 43, shown by way of example only. A first applicator 44 with its slot-shaped node 45 is located on the _g_ ~uW . L1 . W ~ n ~ 1Lf i i uI~LLW LW W .: LLfW 1J i L1W m. rr~ , , y' P1'7963. S03 circumference of a first roll (such as a forming null FW, for example). If a second application in the wet splitting device is desired, an additional applicator 46 can be positioned in an additional twin wire area supported by a second roU, here a wire suction roll SSW.
An additional embodiment of a twin wire area o:f a wet splitting device is shown in Figure 2a, ht Figure Za, the double wire, comprising the upper wire 39 and the lower wire 40, can be seen, carrying the emerging paper web between them. The paper web 3 8 is shown in dotted lines, in contrast to Figure 2, in which is iit not shown separately in the interest of malting the uppor and lower wires clearly visible. The two wires run from the right over the first wire suction roll SSW 1, on the undersidle of which an applying device 44 is positioned that applies a medium on the undetside of the paper web 38, Thereafter the double wire is forwarded to the second wire suction roll SSWZ, which is looped from the side of the lower wire, whereby simultaneously a second applying device 46 is positioned on the side of the upper wire 39, which applies a~ second medium to the surface of the web of material 38. Following the second wire suction roll SSWZ, the double wire is conveyed on a downstream deflection roll that lifts the upper wire 39 firom the web of material, after which the emerging paper web 38 is conveyed onward lying on the lower wire 40.
Figure 3 shows a partial enlargement of the singlle-row drying group from Figure 1. After looping around the paper guiding roll 37, the web of material 38 is moving toward the drying cylinder 18. The drying wire guiding roll ~49 is positioned high enough so that one side of the web lies freely on the cylinder surface:. In this way, sufficient room is provided so that an applying device 36 can be allocated to the surface of the web. rn order to remove any contamination on the part of the applying device 36 on the surface of the drying cylinder 18, a cleaning ductor 47 is allocated to it. The applying device ZS and any additional applying device 48 impinge upon the surface of the web of material 38 facing toward the cylinder surface. The lower drying wiire 30 and a drying wire guiding roll 50 _g_ JU17. L1 . 1 JJ~ 1 ~ 1Jr 1 I V~'vl.L, iLJVUI 1 U W 1\11J 1 ill 1 P 17963.S03 belonging to it of the downstream double-row drying group can be seen at the left edge of Figure 3 .
Figure 4 shows a partial enlargement of the double-row drying group from Figure 1. The web of material 38 comes from the single-row dlrying group and first loops around the drying cylinder 21, The drying wire guiding roll 51 is positioned high enough that the web of material 38 partially lies open on the cylinder surface of the drying cylinder. An applying device 28, which handles the application of the second medium, is allocated to the open area of the web of material 3 8 supported by the drying cylinder 22.
In the free stretches of the web of material 38 between the upper and the lower rows of cylinders, additional applying devices 31, 32, 52, and 53 are positioned. Tn the process, the applying devices 31 and 32 are allocated to different surflaces of the web of material.
Alternatively, the applying devices 52 and 53 can also be brought into use. In this example, in order to avoid additional tensile stresses in the web of material 38, the applying device 31 is arranged opposite an applying device 53.
The arrangements of the applying devices descrtibed above are applicable both for one-sided application and for two-sided application on the web of material.

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P17963.S03 Li st of Reference Numbers I hlaadbux Z wire guiding roll 3 wire S 4 wire pplying device (applicator) 6 paper machine foundation 7 dewatering element (dewatering box) d~watering element (wire suction box) 9 dmvatering element (dewatering strips) 10 applying device (applicator) 11 wire guiding roll 12 Gmtinuous loop 13 Ifrst press element 14 applying device (applicator) 1 S applying device (press) 16 applying device (applicator) 17 applying device (applicator) 1$ dying cylinder drying cylinder 19 dying cylinder drying cylinder 21 drying cylinder 22 drying cylinder 23 drying cylinder Baying cylinder 2~ applying device (applicator) 26 drying wire suction roll ~UI'I.G1.1777 ( ~ 1~-It'I~I bKLLIYDLUI'I ix .DLICIYJIL1I'I my. a.J.r P 1'7963 . S03 2? dying wire 28 pplying device (applicator) 29 dying wire 30 dy~8 ~

31 applying device (applicator) 32 applying device (applicator) 33 wet splitting device 34 pess section 35 dying section 36 applying device (applicator) 37 piiper guiding roll 3g web of material 39 upper wire 40 lower wire 1 S 41 running direction 42 de:watering element 43 de:watering element 44 applying device (applicator) 45 Blot-shaped nozzle 46 applying device (applicatot) 4? cllaaning doctor 48 aplplying device (appvcator) 49 drying wire guiding roll $0 drying wino guiding mll S I drying wire guiding roll applying device (applicator) 53 applying device (applicator) J UI 'I . C 1 . 1'77'7 f ~ 14t'I' I bKLLI YbLUI' I a: DLKI Y5 I L 117 ~ ", , ~
~,_, , , y P17953.So3 r dWection device (foaming roll) S wire suction roll FW fanning mll SSW wire suction roll

Claims

1. Method for applying a fluid or pasty application medium on a running web of material, especially of paper or cardboard, with the following steps:
1.1 a web of material 38 is formed in the twin wire area of a wet splitting device (33) of a paper machine, 1.2 in this twin wire area a fluid or pasty application medium is applied to the web of material 38 on at least one side by means of an applying device (5, 10), wherein 1.3 after a first press element (13) of the press section (34), an additional fluid or pasty application medium is applied to the web of material 38 by means of at least one applying device (14, 15, 16, 17, 25, 28, 31, 32, 35, 48, 52, 53).

2. Method as in claim 1, wherein the additional application occurs at the end of the press section (34).

3. Method as in one of claims 1-2, wherein the additional application occurs within the drying section (35).

4. Method as in one of claims 1-3, wherein the first application medium contains a pigment suspension.

5. Method as in one of claims 1-4, wherein the first application medium contains surface bonding additives.

6. Method as in one of claims 1-5, whereon the second application medium contains surface bonding additives.

7. Method as in claim 6, wherein the surface-bonding additives are latex or polyvinyl alcohols or starches.

8. Method as in one of claims 1-7, wherein the application zone is supported by wire-guiding elements (S, F, 7, 8, 9, FW, SSW) in the twin wire area.

9. Method as in one of claims 1-8, wherein the application zone is supported by at least one roll (F, S, FW, SSW).

10. Method as in one of claims 1-9, wherein the application zone is supported by at least one non-rotating element (7, 8, 9).

11. Method for application of a fluid or pasty application medium on a running web of material according to the characterizing portion of claim 1 or according to one of claims 1-10, wherein the application medium contains components from the wire water.

12. Method as in one of claims 1-11, wherein the application medium is a fine fiber material suspension.

13. Method as in at least one of claims 1-12, wherein the application medium is produced from the flows of wire water through fractionation.

14. Paper machine with a device for application of a fluid or pasty application medium on a running web of material, especially of paper or cardboard, characterized by the following features:
14.1. the wet splitting device (33) of a paper machine has a twin wire area, 14.2. in this twin wire area, an applying device (5, 10, 44, 46) is positioned at least on one side on the side of a wine (3, 4, 39, 40) facing away from the web of material, 14.3. after a first press element (13) of a press section (34), at least one additional applying device (14, 15, 16, 17, 25, 28, 31, 32, 48, 52, 53) is provided that is facing directly toward the web of material.

15. Paper machine with a device as in claim 14, wherein at least one additional applying device (5, 10) is provided in the twin wire area.

16. Paper machine with a device according to one of claims 14-15, wherein at least one additional applying device (14, 15, 16, 17) is positioned in the press section (34).

17. Paper machine with a device as in one of claims 14-16, wherein at least one additional applying device (25, 28, 31, 32, 36, 48, 52, 53) is positioned in the drying section (35).

18. Paper machine with a device as in one of claims 14-17, wherein the applying devices (5, 10) in the wet splitting device (33) are applicators.

19. Paper machine with a device as in one of claims 14-18, wherein the applying device (14, 16, 17, 25, 28, 31, 32, 36, 48, 52, 53) in the press section (34) and drying section (35) are applicators, spray nozzles, or press rolls (15).

20. Paper machine with a device as in one of claims 14-19, wherein the pressure in the applying device (5, 10, 14, 16, 17, 36, 25, 28, 31, 32, 44, 46, 48, 52, 53) lies between 0.05 and 0.5 bar, preferably between 0.1 and 0.4 bar.

21. Paper machine with a device as in one of claims 14-20, wherein the solid content of the web of material 38 at the end of the twin wiry area ranges from 5% to 50%, preferably from 8% to 17%.

22. Paper machine with a device as in one of claims 14-21, wherein the application weight of the first application medium ranges from 1 to 10 g/m2 dry weight per surface area of the web of material.

23. Paper machine with a device as in one of claims 14-22, wherein the first application medium is comprised of a color coating or mineral filling materials such a kaolin, clays, talcum, zeolite, CaCO3, or TiO2.

24. Paper machine with a device as in one of claims 14-23, wherein the second application medium is comprised of starches, surface sizing agents, latex, and polyvinyl alcohols or optical brightening agents.