FI121931B - A method for treating surface-glued paper, especially fine paper, in a paper machine finishing section and a paper machine finishing section - Google Patents

Description

The present invention relates to a method according to the preamble of claim 1 and to a paper machine post-treatment part and to a paper machine post-treatment part.

The invention further relates to a papermaking finishing part according to the preamble of claim 9 for treating surface-glued paper, in particular fine paper.

As is known in the prior art, multi-cylinder dryers of a papermaking machine use a two-wire feeder and / or a single wire feeder. In a two-wire feeder, the drying cylinder groups have two wires that press one of the webs above and one below against the heated cylinder surfaces. Between the rows of drying cylinders, generally horizontal rows, the web has free and unsupported strokes that are prone to flutter, which can cause web breaks, especially when the web is still relatively damp and consequently weak. As a result, there has recently been an increasing use of said single-wire thread, with each dryer cylinder group having only one dryer wire in support of which the web passes through the entire group so that the dryer wire presses the web against the heated cylindrical surfaces of the drying cylinders remains on the outside of the curve. Thus, in a single-wire delivery, the drying cylinders ° are outside the wire loop and the turning cylinders or rollers inside it.

o 25 O) o In the previously known so-called. in normal single-wire export groups, the heated drying cylinders are in the top row and the turning cylinders are in the bottom rows, which rows are generally horizontal and parallel to each other. As used herein, the terms "normal (drying) group" and "reversed (drying) group" are used to refer specifically to the single wire export groups of multicylinder dryers of the type mentioned above.

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It is also known in the art to dry the paper web by non-contact drying. One non-contact drying method is fluidized-bed drying, for which prior art reference is made to U.S. Patent Nos. 98944 and 107623. Kos-5 non-contact drying is also blow-drying, and related prior art reference may be made to FI patent application 20002429 and F1 patent 106269.

When the paper is dried with normal single-wire filament groups on its underside side, and if such asymmetric drying is extended over the entire length of the front dryer section, drying occurs first by drying the underside of the paper web and as drying progresses to the upper surface of the paper web. The paper thus dried generally has a tendency to curl due to asymmetric drying.

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It is already known to influence the tendency of the paper to curl in connection with the stripping process, especially in the sheet forming step, by selecting the difference between the speed of the lip jet and the wire, and other running parameters. However, in paper machines, particularly fine paper machines, which have a single wire thread for most of the drying section length 20, other arrangements need to be made in practice to control the paper curl tendency in order to achieve a sufficiently symmetrical drying in the z direction.

Thus, it is known in the art that paper is warped if wetted

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o 25 on one side and dry on one or two sides or dry paper on one side. It is also known that the curvature g of the paper can be controlled by a one-sided air dryer, e.g. Paper drying on one side

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o dries and curls to the dried side, and the curl can also be adjusted by o 30 contacting the other side of the paper with a humidifier and drying it to straighten the paper.

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For the purpose described above, e.g. Applicant FI patent 98387 discloses various paper finishing groups, in particular fine paper.

In the prior art, reference is also made to FI Patent Publication No. 101981 which discloses a method for drying surface-treated paper, especially fine paper, wherein the paper web is first dried in a successive downwardly open . In the method, hot damp air is supplied to the drying groups by the post-drying section to control evaporation or hot dry air to promote evaporation from the desired side of the web to control curling, whereby the curling tendency of the front drying section to substantially curl or compensate.

Reference may also be made, in the prior art, to U.S. Patent No. 105935, which discloses a method for drying paper, comprising the steps of: a) directing a paper web to be dried from a press section to a front drying section wherein the paper web is dried from its underside b) from the front drying section, the paper web is guided to the post-treatment section, where the paper web is coated / glued with a coating / surface sizing apparatus, dried in a post-drying section where the paper web is dried;

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o 25 are at least one of the drying groups employing standard single-wire threading, o then the paper web is calendered in the calender and led to a winding station, g where the paper web is rolled into a machine roll. In the method, the curvature of the paper web is controlled through at least one steam box in the area of at least the aftertreatment section, the effect of which is enhanced by cooling the web before said steam box and the method of controlling the paper web

Further, reference may be made to FI-A-101488 where prior art discloses a method for drying a surface-treated paper web or the like in a post-drying section of a papermaking machine, wherein the paper web is first cured, cured, or cured. In the post-drying section, the paper web is dried only in the drying group (s) employing the standard 10-wire single thread, and that the paper web, during or after drying, is treated with a device (s) to compensate for the paper web warping tendency.

Reference may also be made, in the prior art, to FI Patent 106270, which discloses a method for drying a surface treated paper web or the like in a post-drying section of a papermaking machine, wherein the paper web is first cured in a post-treatment section In the aftertreatment section, the paper web is dried in at least one drying group suitable for single-wire threading, and the paper web is simultaneously dried by means of a blowing device fitted to at least one cylinder or roll of said drying group.

c3 It is, therefore, an object of the invention to further develop the above solutions i 00 0 25 so that the post-drying section provides more efficient control of the ...

o tendency to cross.

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^ One problem with prior art solutions is that the front

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o in a tiny portion of the single-wire, downward-opening drying groups with drying ...

The strong curl tendency of 30 paper and the stresses it causes are not completely relaxed by the wetting caused by the surface sizing, especially when switching to the use of ever higher dry matter surface sizing. It is an object of the invention to provide a solution which, even in such a situation, can eliminate or at least minimize the tendency of the paper web to warp.

It is an object of the invention to provide a novel solution for a method for the post-treatment of paper, particularly surface-bonded fine paper, in which the problems associated with paper warping are eliminated or at least minimized.

In order to achieve the above and later objects, the method according to the invention is essentially what is set forth in the characterizing part of claim 1.

The dry top of the paper machine according to the invention, in turn, is essentially characterized by what is stated in the characterizing part of claim 9.

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The invention relates to a papermaking machine in which the front dryer section uses downwardly open drying groups using a single-wire feeder, whereby the paper web has a tendency to curl, or at the end of the front dryer section there are dual-wire feeders, although the need for curl adjustment is reduced. After the pre-drying section, the paper web is surface glued, after which the paper web in the post-drying section post-drying section is dried mainly by non-contact drying; fluidized bed drying and / or air drying and / or blow drying and / or infrared drying. At least 60%, preferably at least 75%, up to 90-100% of the power required to evaporate the amount of water between the moisture content and the final moisture of the surface sizing co cp 25 of the web is also referred to below as the contact drying. .

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In a preferred embodiment of the invention, at least part of the non-contact dry drying is accomplished by fluidized drying in which the fluidized dryers located on different sides of the web are adjustable to provide any unrelaxed stresses during surface sizing and subsequent curvature bending. The proportion of fluidized bed drying after post-drying is at least 60%, preferably at least 70%, up to 90-100%. In the context of the invention, non-contact drying can also be used with non-contact drier non-contact drying without adjusting the curvature and can be dried with an infrared dryer, for example, 10% of post-drying. In the context of the invention, it is also possible to use the heating cylinders as holding group cylinders, whereby they can be used for adjusting the curvature below the web or only for increasing the drying power. In this case, the holding group cylinders can evaporate about 10-20% of the post-drying water dried.

In another preferred embodiment of the invention, at least part of the post-drying is also carried out on the basis of blow-drying, preferably using blow-off units with curvature control. In this case, the proportion of drying achieved by the blow-off is at least 50% of the post-drying, preferably 70% or even 90%. The curvature can then be accounted for by dimensioning the blow-drying portion on different sides of the web, for example, to different lengths, i.e., on the prewer underneath, more over-drying with the after-drying portion, whereby the blowing speeds and temperatures are still adjustable.

According to a further preferred embodiment of the invention, various combinations of fluidized bed and blow-drying may be used to construct a suitable non-contact, post-c3 junction-controlling post-drying section.

! The method and paper machine of the invention provide for controlled curvature of the single-wire export front drying section.

σ> <o o According to the invention, the after-drying section thus uses a surface sizing technique of o 30 and non-contact drying, at least a part of which is fluid-dried or blow-dried, for curve adjustment. Thus, the tendency of the web to warp 7 is eliminated. The invention uses a fluidized or impingement, which are located on either side of the web and having on both sides of the dryers that is, the opposite sides of the drying ratio can be controlled individually, wherein the web is obtained by eliminating the manner required by the käyristymätaipumuksen dehydrated. Preferably, dryers can also be used which also have the ability to profile cross-directional drying power, thereby also affecting the curvature profile, for example, by adjusting blowing speeds and / or blowing temperature in the cross-direction.

leijujen used in the preferred embodiment of the invention in connection with the nozzle arrangement 10 is preferably asymmetrical relative to the upper and lower side of the web, whereby it is possible to make a one-side, wherein the drying efficiency is not lost, it is ristymäsäädön, but because the heat transfer takes into account the presumed peruskäyristymän nozzle arrangement still leaves the full curl control power use. Alternatively, the invention can operate with a lower curvature control power, for example, with one adjustable fluidized bed unit.

The after-drying section according to the invention does not necessarily use cylinder drying, but any cylinder / roll groups have to be placed on the after-drying section as web holding groups also to provide and improve the runnability of the web. 20 However, the cylinders of this holding group may be used to increase the drying power, even though they are on the wrong side of the web in terms of curvature. However, the web lower surface of the drying cylinder can also act curl-i-Sä counterpart of adjustment.

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In a preferred embodiment of the invention, the drying in the after-drying section is mainly provided with fluidized dryers, wherein the drying provided by the fluidized dryers g is at least 60%, preferably 70%, located on either side of the web. the hollow eno 30 dry cavities located on either side of the web have separate control of drying power, preferably control of blowing speed and / or temperature.

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According to another preferred embodiment of the invention, the surface-glued paper is dried by air dryers located on both sides of the web, in which the temperatures and blowing speeds of the different sides are preferably controlled separately. In this preferred embodiment of the invention, the curvature is controlled by a double-sided drain 11a, the various sides of which are adjustable independently of each other, thereby avoiding the use of wetting water and the significant drying costs it causes.

According to a preferred embodiment of the invention, a steam box is used in the after-drying section to assist in the curvature adjustment, which steam box can be used, for example, if the paper is naturally straight, no steam box is used. If the paper web is curled upwards, as is usually the case after a single-wire front drying section, a steam box is used, and if the paper web tends to curl the edges down, for example, the cylinders of the post-drying section hold group are used. The steam box is preferably located in a position just before the reel, whereby the web is colder than the dryer section and is not much needed since the drying has been mainly non-contact drying.

According to a preferred embodiment of the invention, non-contact drying uses over-blow drying, for which prior art reference may be made to Applicant FI Patent Application 20002429, which discloses solutions for uncoated paper and Applicant FI patent 106269, wherein cv front / after drying is disclosed. whose applications i 00 cp 25 can be utilized in connection with the invention.

According to a further feature of the invention, a control option is a T-blow blast drying system in which, for example, a pivoting cylinder or a grooved guide roll

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or a suction roller or suction cylinder preferably under the applicant's trademark VAC ROLL

An overflow drying unit is provided in connection with a suction cylinder of the type 30 marketed. The blow-drying units 9 used in connection with the invention may also be so-called vertical blow-drying units, the details of which are described in more detail, for example, in the aforementioned Applicant's FI Patent Application 20002429.

5 If necessary, the paper may also be corrected for any curl as described above using an adhesive press or otherwise lightly coated paper. Normally, however, there is no need to adjust the curvature in the coating, but when switching to higher dry solids thin coatings, possibly even with a slight fish-sharpening (which also has an anti-curling effect), a need may arise. In this way, the coated paper can also control the water movements in the paper to reduce the smoothness of the paper due to the fiber roughening of the paper and to reduce dusting caused by migration.

In the following, the invention will be described in more detail with reference to the figures in the accompanying drawing 15, however, the details of which are not intended to be narrowly limited.

Figure 1 schematically illustrates an embodiment of the invention.

Figure 2 schematically illustrates another embodiment of the invention.

Figure 3 schematically illustrates another embodiment of the invention.

Fig. 4 is a diagram illustrating another embodiment of the invention; Fig. 5 is a diagram illustrating an embodiment of the invention.

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1-5 the same reference numerals are used for similar parts unless otherwise indicated

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g otherwise stated, o 30 cm 10

Figure 1 schematically illustrates an embodiment of the invention in which the paper web W is guided from the front drying section (not shown) to the surface sizing station 20, wherein the paper web W is surface glued on both sides in the nip between rolls 22,23 where the aqueous surface sizing agent wets on both sides. In this way, the asymmetrically dried curved web in the front-5 drying section is treated in a state where its internal stresses are relaxed or at least reduced. The surface sizing rolls 22,23 are supplied with a surface sizing agent from the feeder 21,24. Thereafter, the web W is subjected to non-contact drying and the web W is first dried by fluidized bed apparatuses 31,32 located on both sides of the web. The web is then guided over the cylinder or roller 33 and its upper surface is dried by blow-drying with a flow of air to be dried from the blow-off felt 34. Subsequently, fluidized bed units 35,36 are provided for further drying of the web on both sides, whereupon the web is guided to a holding group of two cylinders / rolls 41,42 with 15 wires 46 which support the passage of the web as it passes through cylinder 42. A steam box 45 is provided. if necessary, to further adjust the purpose of the curvature. Frame structures and foundations are identified by reference number 10.

In the exemplary embodiment shown in Figure 2, the first part of the application is similar to Figure 20. After the holding group 40, the web is passed through a cylinder 43 for further contactless drying, which first has fluidized bed units 51.52 drying on both sides of the web. This is followed by a cylinder or roll 53 over which the web is guided and at the same time dried over the upper surface side by blow-drying cm by means of blow-drying air blown at 00 ° 25. Thereafter, the web is further guided between the fluidized bed units 55,56, where <y> o web is dried on both sides thereof, followed by a second holding group g 60 consisting of cylinders / rolls 61.62 and a web 62 supporting web 66 and holding group a steam box 65 connected to the connection, whereby, if necessary, the tendency of the web to be warped can be further adjusted, oo 30

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In the embodiments shown in Figures 1 and 2, the fluidized drying units 31,32,35,36,55,56 are adjustable so that the drying power of the web on different sides thereof can be adjusted, whereby any curvature of the web remaining after surface sizing can be corrected. If desired, the fluidized drying units can be provided with a profiling feature, whereby the drying power they provide, for example through the blowing speed and / or temperature, is adjustable in the cross-sectional direction, whereby the curvature profile of the web can also be adjusted.

The blowing lip 34 may also be designed to be profiled in cross-sectional power if necessary. The roll or cylinder 33.53 arranged in connection with the blow-off hood may be of a drying cylinder type, a paper guide roll or a suction roll, for example a suction roll of the type marketed by the applicant under the trademark VAC ROLL without an internal suction box.

Figure 3 schematically shows a paper machine employing an embodiment of the invention. From the headbox H of the papermaking machine, the pulp is fed to the web forming section F where the web W is formed and dewatered therefrom. The press section P further dehydrates the web in the press nipples, after which the web W is led to the front drying section D. The front drying section D comprises a plurality of downwardly open single to 20 wire thread drying groups G1, G2 ... G6. After the pre-drying section D, the web W passes through the measuring unit M to the surface sizing unit 20, after which the web W is dried on both sides of the fluidized dryers 31,32 on each side of the web, individually adjustable for adjusting the curvature tendency. Through roll / cylinder 33, web 25 is led to the next fluidized-drying step, whereby the web is further dried on both sides by a fluidized-bed 35.36 g on each side of the web, which are individually adjustable so that the curvature tendency can be controlled by the drying power. If desired, the fluid-drying units 31,32,35,36 may also be adjustable in the transverse direction of the web W, whereby it is also possible to influence the curvature profile. This is followed by a holding group 40 consisting of cylinders / rolls acting as a holding group comprising a cylinder / roll 41,42,43,44 and 12 wire 46 and a steam box 45 disposed adjacent to the lower row cylinder / roll 43. The web is then calendered in the calender C, after which the web W is guided to the reel to roll the web of web R into a machine reel.

Figure 4 schematically illustrates an embodiment of the invention employing so-called vertical blow blowers 72,73,74, the details of which may be referred to, for example, in Applicant FI Patent Application 20002429. Each vertical blowing unit 72,73,74 comprises blow blowers 91.92, disposed substantially horizontally with respect to the machine direction, substantially perpendicular to the machine direction, and in which the web W passes supported by the wires 95 over the web W in the overhead blowing units 72,74 and below the overhead blowing unit 73 in the overhead blowing unit 73. The wire feed is supported by guide and guide rollers 94 and pivoting cylinders or rollers 93. In the embodiment of Figure 4, the surface suction unit 20 is followed by a fluid or infrared dryer 70 on both sides of the web W, followed by a blow drying unit 72 . From the fluidized bed or infrared dryer 70, the web W is led through a rotating suction roll 71 to a first blow-drying unit 79 followed by a single-wire thread holding group 79 having a wire 20 denoted by 79 and having a single blow-drying unit 73. 77 and 78. The latter overhead blowing unit 74 is followed by a holding group designated by the reference numeral 83 and having cylinders / rolls by the reference numerals cu 81.82. From the pivoting suction roll 71, the web W is led to the first blow-dry

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cp 25 to a drying unit 72, wherein the web is dried from the upper surface and its curvature is controlled by a blow-dry blow to provide 91.92. Subsequently, the web W is led to a so-called lower blow-drying unit 73 which dries one side of the web W, which may also be of co-curved structure, followed by a single-wire holding group of 30 mm and reference numerals 75.77. 79 and reversing suction rolls with reference numerals 76.78. A further so-called vertical blow-drying unit 74, which corresponds, for example, to a first overhead blow-drying unit 72, can also be disposed, which may also be of curved design and adjustable in blow speed and power. This is followed by a group consisting of a cylinder 82 5 and a wire 83 and a swivel suction roll 82. Figure 4 utilizes suction boxes 99 at web transfer points to control and secure web transfer. The hold groups include the cylinders in the top row except for the blower units and the rotary suction rolls in the bottom row.

In the schematic embodiment shown in Fig. 5, both fluid-dried and blow-drying are used to control the curvature of the web W. From the surface sizing unit 20, the web W is led to a fluidized bed which is provided by fluidized bed units 31,32 located on either side of the web W, which are preferably adjustable in power and preferably also adjustable in the transverse direction of the web W to control the curvature profile. Fluid drying is followed by a so-called vertical blow-drying unit 72 in which the web W is dried on its upper surface. The hoods of the overhead blowing unit are denoted by reference numerals 91.92, and in overblowing drying, the web W runs supported by the wire 95. The web W is then guided to the next blow-drying unit 73, where the web W is dried on one side and, for example, has the structure described above. Naturally, the dimensions of the hoods and the height of the units are dimensioned as needed. The blowing units may be controlled by the blowing speed and power. Thereafter, the web W is subjected to fluidized bed drying, which is carried out on cv fluidized dryers 35,36 which are located on both sides of the web W. This ice cp 25 is followed by a holding group, the wire of which is denoted by reference numeral 87 and the upper row of cylinders by reference numeral 84.86 and the lower pivoting suction roll by reference numeral 85.

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In the above figures, the fluidized dryers and the blow-drying units are, if necessary, adjustable in their blowing speeds and wattages to effect the curvature adjustment, and can also be capable of profiling the curvature adjustment in the transverse direction of the web.

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In the figure, particular attention must be paid to the fact that the dimensions of the overflow hoods and the unit heights are indicative and dimensioned as required.

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The invention is further described with reference only to some preferred embodiments thereof, the details of which, however, are not to be construed as being narrowly limited.

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Claims (16)

A method of treating surface-glued paper, especially fine paper in a finishing unit of a paper machine, in which method a paper web (W) is first dried in a drying portion (D) of the paper machine in several successively open, drying groups (Gi ... Ge) applying single-wire drawing, after which the paper web (W) is post-treated in a finishing unit, in which the finishing web (W) is surface-glued in a surface-bonding unit (20) and the surface-glued paper-web (W) is dried mainly by contact-free drying, at least partially in fan dryers (31,32,34,36; 51,52,55,56; 70) or by blow drying (72,73,74), characterized in that in the process the effect of fan / the blow drying is regulated on either side of the web (W) in such a way that the curl propensity that occurs in the web (W) in the pre-drying portion (D) can be controlled. 15 2. A process according to claim 1, characterized in that at least 60% of the drying in the post-drying portion is achieved by contact drying. 3. A method according to claim 1 or 2, characterized in that at least 60 20. of the drying in the post-drying portion is achieved by fan / blow drying. 4. A method according to any of the preceding claims, characterized in that, as non-contact drying, fan drying is mainly used, the drying obtained with fan dryers (31,33,35,36; 51,52,55,56; 70) constitutes at least 70% of the drying in the post-drying portion. X cc Q_ Method according to any of the preceding claims, characterized in that the blow-drying (34; 54; 72,73,74) is used as contactless drying in the process. CM 19 Process according to any of the preceding claims, characterized in that air drying is used as contact-free drying in the process. 7. A method according to any of the preceding claims, characterized in that in the regulation of the curry in the method, an angled mud (45) is used in a position in the post-drying section, with which the curl tendency of the web is further controlled. 8. A method according to any of the preceding claims, characterized in that profiling contactless drying is used in the method for checking the curl profile in the transverse direction of the web. 9. Finishing unit in a paper machine for the treatment of surface-glued paper, especially paper in the finishing unit for paper, wherein the paper machine 15 before the finishing unit comprises a drying section (D) having several successively open, drying groups (Gi ... Ge) applying single-wire coating, the finishing unit comprising surface sizing devices (20) and drying devices, which are mainly based on contact-free drying, of which devices are at least part of which are fan / blow dryers (31,32,35,36; 51,52 , 55.56; 70; 72.73.74), characterized in that the fan / blow dryers (31,32,35,36; 51,52,55,56; 70; 72,73,74) have adjustable effect on in such a way that the curvature of the web can be controlled by the drying action to which the two sides of the web (W) are exposed. δ (M o 25 10. Finishing unit in a paper machine according to claim 9, characterized in that at least 60% of the drying in the post-drying section is touching and drying. δ 11. Finishing unit in a paper machine according to claim 9 or 10, characterized in that at least 60% of the drying in the post-drying section is fan / blow drying. 20 12. Finishing unit in a paper machine according to any one of claims 9-11, characterized in that the non-contact drying is mainly blow drying, that the blow drying portion of the drying is at least 70%. 13. Finishing unit in a paper machine according to any one of claims 9-12, characterized in that the drying devices comprise dryers (31,32,35,36; 51,52,55,56; 70; 72,73,74) based on fan - and blow drying. 14. Finishing unit in a paper machine according to any of claims 9-13, 10, characterized in that the drying devices comprise air dryers. 15. Finishing unit in a paper machine according to any one of claims 9-14, characterized in that an angel bed (45) is provided in a position in the post-drying section where the web is substantially cooled. 15 16. Finishing unit in a paper machine according to any of claims 9-15, characterized in that the drying devices are profiling wipers for checking the curl profile in the transverse direction of the web. δ CM CO O 05 O X X CL δ co o co o o CM