KR100487017B1 - Method for drying a surface-treated paper web or equivalent in an after-dryer of a paper machine and after-dryer carrying out the method in a paper machine - Google Patents

Abstract

The invention concerns a method for drying a surface-treated paper web or equivalent in an after-dryer of a paper machine, in which method the paper web (W) is first finished in a finishing section, in which finishing section the paper web (W) is surface-sized or coated by means of a finishing device (10), after which the paper web (W) is dried. In the after-dryer the paper web (W) is dried in a dryer group/groups making use of a normal single-wire draw, and, in connection with or after the drying, the paper web (W) is treated by means of a device/devices (192, 191, 201, 202) in order to compensate for a tendency of curling of the paper web (W). Further, the invention concerns an after-dryer for a paper machine for applying the method to the drying of a surface-treated paper web or equivalent, which after-dryer is placed after the finishing device (10), by means of which finishing device (10) the paper web (W) is surface-sized or coated. The after-dryer comprises at least one dryer group that applies a normal single-wire draw so as to dry the paper web (W) and a device/devices (191, 192, 201, 202) for compensating for a tendency of curling of the paper web (W).

Description

TECHNICAL FOR DRYING A SURFACE-TREATED PAPER WEB OR EQUIVALENT IN AN AFTER-DRYER OF How to Dry Surface Treated Paper Webs or Equivalents thereof in a Paper Machine A PAPER MACHINE AND AFTER-DRYER CARRYING OUT THE METHOD IN A PAPER MACHINE}

The present invention relates to a method of drying a surface treated paper web or equivalent in an after-dryer of a raising machine, in which the paper web is first trimmed in the finishing section, in which the paper web is applied to the finishing device. After surface dimensioning or coating, the paper web is dried.

The present invention also relates to an after-dryer for a paper machine, which applies the method according to the present invention to the drying operation of a surface-treated paper web or equivalent, which is disposed behind the finishing apparatus, and is arranged by the finishing apparatus. Paper webs are surface dimensioned or coated.

As is known, in multi-cylinder dryers of papermaking machines, double-wire draw and / or single-wire draw are used. In a double-wire draw, the group of drying cylinders comprises two wires, which press the web wire from the top and the other wire from the bottom to the heated cylinder surface. Between the rows of drying cylinders, which are generally horizontal rows, the webs have unsupported free draws that are sensitive to fluttering, which will cause web breakage, especially when the webs are relatively moist and consequently have low strength. Can be. Because of this, the use of the single wire draw has increased in recent years, in which each group of drying cylinders comprises only one drying wire, on which the web has a drying cylinder against the cylinder surface on which the drying wire is heated. The web runs on the entire group to squeeze the phase onto, while the web is on the side of the outer curve on the reversing cylinder or roll between the drying cylinders. Thus, in a single wire draw, the drying cylinder is disposed outside the wire loop and the reversible cylinder or roll in the loop.

In a standard group with a single wire draw, the heated drying cylinders are placed in the top row and the reversible cylinders are placed in the bottom row, which rows are generally horizontal and parallel to each other. On the other hand, in the opposite group with a single wire draw, the reversible cylinders are arranged in the top row and the drying cylinders in the bottom row. In the following, when the terms “standard (dryer) group” and “opposite (dryer) group” are used, it is meant exactly the group having a single wire draw in a multi-cylinder dryer of the above-mentioned classification.

If paper is dried by a standard group with a single wire draw from the side of the bottom surface and this asymmetrical drying extends over the total length of the front dryer section, drying occurs preferentially such that the lower side surface of the paper web is dried, If drying proceeds, the drying effect also extends to the side of the upper surface of the paper web. Under this condition, the dried paper is generally curled and becomes concave when viewed from above.

As is known, the tendency to curl paper is already affected in connection with web formation, especially at the sheet forming stage by the choice of the speed difference between the slice jet and the wire and by other rotational parameters. As is known, in the case of copy paper, etc., by the inequality of drying in the after-dryer, the appropriate initial curl shape is adjusted relative to the sheet so that the curling of the paper after single-sided or double-sided copying can be optimized. In the case of radiant papermaking, the reactivity of curling, such as the extent to which curling occurs per unit of change in moisture, is more strongly influenced by the multilayered structure of the paper formed in association with web formation in the wet end.

In high speed paper machines, in particular fine paper machines, the most recent technology related to the present invention has been based on a dryer section in which a single wire draw is present over most of the length of the machine, and in fact in terms of controlling the curling tendency of paper, The opposite group has also been used so that drying can be sufficiently symmetric in the z direction.

In conventional after-dryers in papermaking machines in which the web is dried after coating or surface dimensioning, swelling of the web resulting from moisture caused by the coating in the web has been a problem, which swelling in the web It causes "wrinkling" and equivalent problems that degrade running. In the double wire draw commonly used in after-dryers, the webs flutter between the top and bottom rows, and tend to cause web breakage at any connection, and, on the drying cylinder in the bottom row, the web is corrugated. If caught, the bottom row of dry wire has been easily damaged as a result of wrinkling, which often leads to the problem of replacing the underlying tissue.

In addition, as is known, problems are also caused by a drop in web strength by coating, and long free draw of the web at any connection has caused considerable problems.

From the prior art, a solution is known for an after-dryer to be coated with paper, in particular fine paper or its equivalent, in which one group uses a standard single wire draw followed by the upper cylinder and the lower cylinder and the latter and Behind the former is a group of dryers using double wire draw. In this application, there is a problem in that the ratio of the upper and lower cylinders is wrong even if the curling is efficiently controlled in view of the curling tendency of the paper. As is known, it was necessary to keep the temperature of the first cylinder low due to the adhesion of the web and the size / paste of the cylinder in the after-dryer.

1 is a schematic illustration of an exemplary embodiment of an after-dryer composed of a group of dryers using a standard single wire draw.

FIG. 2 is a device in which a web after pass is passed directly onto an upper cylinder in a group with a single wire draw on a reversible blow-box or reversible roll or equivalent thereof, in which case a closed draw is obtained over its entire length Schematic drawing of the.

The group of classifications mentioned above for the finishing of the paper to be coated, in particular fine paper , is described first of all in the Applicant's Finland Patent Application No. 950434 . Accordingly, it is an object of the present invention to further develop the solutions set forth in this application so that the curling tendency of papermaking can be more efficiently adjusted in the after-dryer.

An additional object of the present invention is to provide such a solution in an after-dryer suitable for use in a dryer section where it is not possible or desirable to control the curling of the paper web in the front dryer.

It is also an object of the present invention to form a device free of long free draw while the web is still wet after coating.

An additional object of the present invention is to provide such an after-dryer in a papermaking machine in which the runability can be improved to a particularly high level.

Furthermore, an additional object of the present invention is to provide such an after-dryer in a paper machine where so-called ropeless threading can be suitably applied within the total length of the after-dryer in the machine direction, which simplifies and shortens manufacturing. Contribute in part.

In view of the achievements of the above-mentioned and later objects, the process according to the present invention mainly comprises a paper web in the after-dryer which is dried in the dryer group (s) using a standard single wire draw, after drying or The paper web in association is characterized by being processed by the device (s) to compensate for the curling tendency of the paper web.

In addition, after-dryers using the method of the present invention mainly include at least one group of dryers using a standard single wire draw to dry paper webs and a device (s) that compensates for the curling tendency of the paper webs. It is characterized by including a dryer.

In the apparatus according to the invention in which the after-dryer is formed as a single wire draw or consists of a group having a single wire draw, the web is supported over the total length of the dryer section, in which case the running is very good. Possible curling of the web is compensated by steam boxes and / or by soft calendering or the like. The web can also be passed directly to the upper cylinder after coating, in which case the draw is closed directly from the start of the after-dryer over the entire length of the after-dryer.

In the following, the invention is described in more detail with reference to the accompanying drawings, but the invention is not strictly limited to the description of the above examples.

In FIG. 1, the coating device is indicated by reference numeral 10, and the coating device 10 is a coating device distributed by the applicant under the SYM-SIZER ™ name, and the device is provided with two opposite coating rolls 11, 12. And a size feed device exists in association with each of the rolls so that the paper web W is coated from both sides in the coating nip between the rolls 11, 12. The traveling direction of the paper web W is indicated by the reference arrow S. FIG. Following the sheathing device 10, the web W is passed through a drying cylinder 171 into a group of dryers using a standard single wire draw, in which a drying wire loop 176 guided by a guide roll 177. Reversible rolls / cylinders fitted within are denoted by reference numeral 175 and the drying cylinder is denoted by reference numeral 174. The paper web W to be dried in the drying group travels from the drying cylinder 174 disposed in the upper row RY onto the reversible roll 175 disposed in the lower row RA, thereby the web on the drying cylinder 174. W is disposed with respect to the heated surface of drying cylinder 174, and web W is on the side of the outer curve on wire 176 on reversible roll 175 disposed in bottom row RA. Following the group of dryers, the paper web W is passed on the guide roll 195 to a soft calender 191 comprising two calender nips N1, N2. In association with the soft calender, two steam boxes 192 are also arranged, the curling of the paper web W being compensated by soft calendering and by the steam box. On the guide roll 197 the paper web is passed through the nip device 198 to an additional processing device. Between the calendar nips N1, N2 the web is guided onto the guide roll 196.

In FIG. 1, after the coating apparatus 10, a predrying unit 15 is installed, which is not in contact with the web W and can be an infrared dryer or an airborne web dryer or a combination thereof. At the end of the after-dryer, a blower unit 201 is installed, by means of which attempts to promote evaporation through the wire, for example to equalize the distribution of moisture in the thickness direction of the paper spaced apart from the after-dryer. Attempt is made. Furthermore, in this device, it may be a known vapor box 202 of the kind described in Finland Patent Application No. 906216 or known moisture device 202 or the like, by means of which device 202 the moisture in the Z direction of the web. The distribution of is uniform or the curling of the web is reduced. Of course, all these additional devices are not necessarily used in the same structure.

In connection with the curling of paper webs, we have conducted tests with a newspaper printing machine, in which the dryer section is provided exclusively with a single wire draw, followed by a steam box followed by a 2-nip soft calender. Progressed. In this reference test run, it was noted that the web was curled in the direction of the top surface and the edge of the sample 100 mm in diameter was raised to 3 cm in the direction of the top surface. If the running condition did not change in other respects and the bottom surface of the web was steamed prior to the latter soft calender nip, curling was significantly reduced to a value of 1.2 cm. In the second test, the dryer section ran normally, in which case the curling was measured at 1.5 ... 2 cm, and when the lower surface of the web was steamed in the manner mentioned above, the web was no longer curled.

With regard to the main features, the exemplary embodiment shown in FIG. 2 is similar to the exemplary embodiment shown in FIG. 1, but in the embodiment of FIG. 2, the reversible blower device 14 is fitted followed by a coating device, the By means the web is rotated such that it passes directly onto the drying cylinder 174 in the top row. There are then two groups of dryers using a standard single draw, with a closed draw between the groups. Parts in the first group of dryers using a standard single wire draw are indicated by the reference symbols corresponding to FIG. 1, the drying cylinders in the second group of dryers by reference number 182 and the reversible roll / cylinder by reference number 181. Is indicated by). The drying wire 186 in the second group of dryers is guided and guided by the guide roll 187. Following the dryer group and following the guide roll 184, the dried paper web W is passed into the soft calender 191 as shown in FIG. 1, in which a steam box 192 is also installed. Preferably, in this case it is possible to control the curling of the web W by the increasing box 193 and by adjusting the calendering nips N1, N2 of the soft calender 191 in a suitable manner.

In the device according to the invention, it is particularly advantageous to use, as reversible rolls / cylinders, a suction cylinder which is distributed by the applicant under the trademark " VAC-ROLL " ™ and without an internal suction box: in the description of the structure of the roll. See, Applicant's Finland Patent Nos. 83,680 (corresponding US Pat . Nos . 5,022,163 and 5,172,491) .

While the invention has been described above with reference to some preferred exemplary embodiments, the invention is in no way deemed to be strictly limited to the description of the embodiment.

Claims (23)

A method of drying a surface treated paper web or equivalent thereof in an after-dryer of a paper machine, wherein the paper web W is preferentially trimmed in the finishing section, wherein the paper web W is the finishing device 10. Surface size or coated on both sides, and then in the method in which the paper web W is dried, in the after-dryer the paper web W uses only a standard single wire drawer group (s) After or in conjunction with, the paper web W is treated by the device (s) 192, 191, 201, 202 to compensate for the curling tendency of the paper web W. Way to dry. 2. The papermaking web (W) in the after-dryer is dried in the dryer group (s) using a standard single wire draw, and after drying the paper web (W) tends to curl the paper web (W). Guided through at least one vapor box (192) or through at least one soft-calender nip (N1; N2) to compensate for this. 3. The papermaking web according to claim 1 or 2, wherein in the after-dryer the paper web is dried in the dryer group (s) using a standard single wire draw and after drying the paper web is guided through at least one blower unit 201 and By means of which evaporation through the wire is promoted as the moisture distribution in the thickness direction in the web W disappears from the after-dryer is uniform. 3. The papermaking web of claim 1 or 2 wherein the papermaking web in the after-dryer is dried in the dryer group (s) using a standard single wire draw, after which the papermaking web (W) exhibits moisture distribution in the Z direction in the web. Characterized in that it is guided past a steam box or moisture device (202) to homogenize or reduce curling of the web (W). 3. The papermaking web according to claim 1 or 2, wherein the paper web in the after-dryer is dried at the very front of the after-dryer by means of a contactless predryer section 15 prior to the dryer group (s) using a single wire draw. How to. 3. The paper web (W) finishing device (10), followed by paper web (W), is guided to a group of dryers (s) using a single wire draw on a drying cylinder (171). Following the group, the paper web W is passed through a steam box 192 where the curling of the paper web W is compensated, and the soft calendar in which the paper web W is calendared in two consecutive calendaring nips N1, N2. Guided to 191, wherein curling of the paper web (W) between the nips is compensated by a vapor box (192). Method according to claim 1 or 2, characterized in that the paper web (W) in the process is dried in one group of dryers using a single wire draw (FIG. 1). Method according to claim 1 or 2, characterized in that the paper web (W) in the process is dried in two groups of dryers using a single wire draw (FIG. 2). Method according to claim 1 or 2, characterized in that the finishing device (10) followed by the paper web (W) is passed through a reversible blow device (14) to a group of dryers using a single wire draw. The method according to claim 1 or 2, characterized in that the finishing web (10) is followed by a paper web (W) passing through a drying cylinder (171) arranged in the bottom row (RA) to a group of dryers using a single wire draw. How to. 3. The method according to claim 1 or 2, wherein in the method, following the finishing apparatus 10, the paper web W is placed in the top row RY in the group of dryers using a standard single wire draw as a closed draw. 1 passing through onto a drying cylinder. Method according to claim 1 or 2, characterized in that the paper web (W) in the method is passed from one group of dryers to the other as a closed draw. An after-dryer for a paper machine, which applies the method according to claim 1 or 2 to the drying of a surface-treated paper web or its equivalent, which is disposed behind the finishing apparatus 10, 10) In the after-dryer, wherein the paper web W is surface sized or coated on both sides, the after-dryer uses only a standard single wire drawer to dry the paper web W. ) And device (s) (191, 192, 201, 202) for compensating for the curling tendency of the paper web (W). 14. The after-dryer according to claim 13, characterized in that a soft calender (191) or steam box (192) is installed to compensate for the curling tendency of the paper web, followed by dryer group (s) using a single wire draw. 15. The method of claim 13 or 14, wherein at the end of the after-dryer, the blower unit 201 promotes evaporation occurring through the wire and removes moisture distribution in the thickness direction in the paper web (W) that is lost in the after-dryer. After-dryer, characterized in that installed to equalize. 15. The steam box or moisture device 202 of claim 13 or 14 is installed in the after-dryer to equalize the distribution of moisture in the Z direction in the paper web W or to reduce curling of the paper web W. After-dryer, characterized in that. 15. The method according to claim 13 or 14, characterized in that, prior to the dryer group (s) using a single wire draw, a predryer 15 is installed at the beginning of the after-dryer for contactless predrying of the paper web. After-dryer. The after-dryer according to claim 13 or 14, characterized in that the after-dryer comprises one group of dryers using a single wire draw and is arranged behind the finishing device (10). The after-dryer according to claim 13 or 14, characterized in that the after-dryer comprises two groups of dryers using a single wire draw and is arranged behind the finishing device (10). 15. The after-dryer according to claim 13 or 14, wherein two vapor boxes (192) are installed behind the dryer group (s). 21. The after-dryer according to claim 20, wherein the steam box (192) is installed in front of the calendering nips (N1, N2) of the soft calender (191). The after-dryer according to claim 13 or 14, characterized in that the finishing device (10) is followed by a reversible blowing device (14) in front of the group of dryers using a single wire draw. 15. The after-dryer according to claim 13 or 14, characterized in that the paper web (W) has a closed draw between groups of dryers in the after-dryer.