EP1210481B1 - Method and device for single- or double-sided application - Google Patents

Abstract

A method for the application of liquid through viscid medium onto the surface of a pre-dried material web including the steps of applying a viscid medium to at least one side of the material web, routing the material web through a press nip and supporting the material web substantially without free draw.

Description

The invention relates to a method according to the preamble of claim 1 and to an apparatus for carrying out the method according to the preamble of claim 10.

Generic methods and devices are used in the context of so-called coating systems to provide a running material web, which consists for example of corrugated base paper, on one or both sides with one or more layers of the application medium, for example, starch or lmprägnierflüssigkeit to provide.

In so-called direct application, the liquid or pasty medium is applied by an applicator directly to the surface of the moving web, which is supported during the order on a rotating counter surface, such as a counter-roller or a circulating belt. In the indirect application of the medium, however, the liquid or pasty medium is first applied to a support surface, e.g. the surface of a roller serving as an applicator roll or applied to the surface of one side of a flexible belt to be transferred from there to the web.

In most cases, this indirect application is carried out by means of a so-called film press. These are two rollers which form a nip with one another, which transfer the medium successively or simultaneously to both sides of the material web-or else only to one side of the web.

On the US 5,683,509 is referenced here. In this solution, a flexible endless belt with an applicator roll forms a press-nip through which the web passes. Inside the endless belt, a press shoe is arranged, which leads to an extension of the nip and applied with the same unit Application medium pressed into the web. This is intended to improve the order result, in particular by avoiding film splitting.

Furthermore, be on the DE 198 23 739 A1 referred to, according to which a material web is still coated in or immediately anschleißend to the wet end of a paper machine. The preamble of claims 1 and 9 is based on this document. There, the web passes over the sieve 105/102, although some liquid may drip off, but this can not represent proper drying in terms of a dry assembly on which the web could be dried to a solids content of 85% to 95%. If an excessively large amount of the application material was applied to the web, which was slightly dehumidified only on the wire 102, and pressed in on the nip, as may be required in the processing of qualitatively moderate web material, this would lead to a substantial softening of the web because of the considerable residual moisture. and thus there is a significant risk of cracking, especially if the train is not supported largely draft-free after the nip.

Film or size presses have been in use for years, but have some significant disadvantages that do not always provide sufficient job quality in today's modern, slurrender machines and depending on the nature of the fibrous web and this application medium.

Increasingly, the raw material quality of paper or cardboard is decreasing. This applies in particular to the production of corrugated raw paper, which is produced to a high degree from waste paper. Moreover, there is increasingly a demand for decreasing amount of f lächen b ezogender M ass (also called grammage, but hereinafter referred to FbM). This low raw material quality and lower FbM cause the web strength after film press application is very low, so it comes in the train's free train after the order again and again of the web. This means huge production losses and high costs.

Film presses (also known as Speedsizer, Speedcoater, Optisizer, metering sizepress) often cause nip plaques and displacements in the nip. These effects, in turn, have a particularly negative effect on corrugated board production.

The web break is in practice, especially in the production of corrugated base paper, counteracted by increasingly modified starches come with low viscosity and high solids content as a coating medium used. The low viscosity should on the one hand a good penetration, the high solids content on the other hand should cause a low rewetting and thus allow only a small decrease in strength after the film press. However, modified starches are more expensive compared to native starches.

But even these measures do not always lead to satisfactory results.

The invention is therefore based on the object to develop a method and apparatus for the production of corrugated base paper, with which a deep penetration of the starch-containing coating medium in the web and regardless of the basis weight (FbM), while improving the utilization of the starch properties possible is and beyond web breaks after application largely avoided.

The object is achieved by a method according to claim 1 and with a device according to claim 9.

The inventors have recognized that the previously used, in viscosity and solids content modified starches only an insignificant increase in the strength of the coated or impregnated material web, in comparison to native starches effect.

Characterized in that the pre-dried corrugated base paper web is fed to a press nip only after coating and then passes through this first and also the wet, coated or impregnated, or glued web only is dried after that and beyond after the nip a substantial portion (which can ideally be done to the first drying cylinder of the subsequent drying section) without free train, the starch yield of the coating medium is significantly higher. Even at low FbM, a complete penetration up to the "middle of the blade" can be achieved, which increases the strength of the Railway is increased.

Another advantage is that it is now possible to use native starches despite the strong rewet. Reversals in corrugated base paper production are reliably avoided. In addition, these measures according to the invention lead to far fewer web breaks after the application process.

A particularly advantageous solution of the invention is to make the support of the wet web by means of at least one flexible band. The support surface on one or both sides of the web can be extended as desired.

Further expedient embodiments of the invention will become apparent from the dependent claims.

The invention will be described below with reference to an embodiment in more detail.

Figur 1:

ein erstes Beispiel der erfindungsgemäßen Lösung in einer schematisch dargestellten Seitenansicht der erfindungsgemäßen Vorrichtung.

Figur 2:

ein zweites Beispiel der erfindungsgemäßen Lösung

Show it:

FIG. 1:

a first example of the solution according to the invention in a schematically illustrated side view of the device according to the invention.

FIG. 2:

a second example of the solution according to the invention

In that, in FIG. 1 Example selected is a pre-dried corrugated base paper web B, which already runs with a dry content of about 85 to 95% from a last drying cylinder 2 of the pre-dryer 3 of a machine for producing the corrugated base paper on a first Auftagswalze 4. This application roller 4 is associated with an application device 5, with which the web B is coated on its upper side B _O. Applicators are all known devices, such as a short dwell time applicator (SDTA) or LDTA (for long dwell time), free-jet nozzle applicators or a curtain coating die into consideration. With this one- or two-sided application, a pre-penetration of the medium to be applied is achieved.

In order to support the web B, a transfer belt, which is a flexible endless belt 6 made of a plastic or rubber, is guided around a further roller 16, a support or counter roller 7 and a plurality of guide rollers or deflection rollers 8. A tension roller 21, which is mounted on the paper machine base PM _B , acts on the outside of the belt 6 and thereby biases it.

In the example provided, a two-sided order should be made. Therefore, a further application device 5a of the support roller 7 is assigned. The application medium is then transferred from the endless belt 6 on the bottom B _{U of} the web B, as soon as the belt 6 comes into contact with the web B. The order with the devices 5 and 5a can be done simultaneously or sequentially, with a time delay. If only a one-sided order on the upper or lower web page done, one of the unused application facilities can be swung. Like from the FIG. 1 can be seen here form the rollers 4 and 7 no press-nip with each other. This is so intentional, so that no delays of the web occur and it does not come to demolition.

In the in FIG. 1 shown embodiment is therefore a long pre-penetration distance P _S , which should be far more than 100 mm long, available and thus given a good penetration due to the extended exposure time by capillary action. This long distance is particularly advantageous for achieving the desired penetration.

The FIG. 2 which have substantially the same reference numerals for the same parts as FIG. 1 has, a further variant of the embodiment is shown. Instead of the presence of the roller 4, in this case only the applicator 5 is arranged, with a direct application to the web top B _O occurs.

Conceivable, but not shown, is also the placement of another endless belt instead of the roller 4, with which a support of the web B and in turn on the same unit an indirect application to the material web can be made.

After passing through the penetration distance P _S , the web B passes through a press zone 9 together with the belt 6 which can be used as the application and support belt.

The press zone can be realized in various ways.

In order to set the goal, which consists in a long residence time and the avoidance of displacements, as well as variable line pressures over the entire width of the web B, here offers the use of a known shoe press. In the press zone 9, the pre-penetrated starch can, so to speak, "nachpenetrieren" and thereby firmly anchored in the web B.

Another possibility for realizing the press zone can be the use of another flexible endless belt 10, which runs over guide rollers 11, 12, 13. The belt 10 should run with its inner surface over a sliding surface of a press shoe 14, wherein the sliding surface with a roller 15, which may for example also be a suction roll, forms a press nip N. This press shoe 14 is shown in simplified form and may extend over a wide area of the band 10. But the press zone can also consist of the two, a press nip N forming rollers 15 and 16, wherein the roller 16 in the FIG. 1 and 2 is shown in phantom and embodies a so-called, known from the press section Flexonipwalze. This version is from the DE 198 20 516 A1 already known, in which, however, no statements to support the web after pressing the order can be removed.

The roller 15 is at the same time one of those rollers, around which the endless belt 6 runs and which forms the opposite surface to the roller 16 and / or the belt acting as press, support, and optionally as an application belt 10. The endless belt 10 and the endless belt 6 each provide a support surface between them for the track B which has been penetrated through the nip N. The support surface S _F extends essentially as far as the first drying cylinder 18 of the following drying section, for example the after-dryer section 19 of the paper machine.

The endless belt 10 can, as in the FIG. 2 shown in dashed lines, its support surface S _F , for example, by adjusting the guide roller 13, and / or the belt 6 also extend its support surface by adjusting the upper guide roller 8 to a desired level. For extended support surface can as well in FIG. 2 see a blower or suction box 20 or other transfer aid to ensure the transfer of the web or a transfer strip to the drying cylinder 18.

In the FIG. 1 In addition, in dotted line the possibility of supporting the web B in the direction of the job site is located. For this purpose, the belt 10 (or else a separate belt 10a) can be deflected about the roller 4 or about an adequately arranged guide roller. In this case, the band can also be supported by the roller 11.

Conceivable, but not shown separately in the figures, is also the placement of another endless belt 10a instead of the roller 4, with which the said support of the web B and also the indirect application at the same position as in the roller 4 with the same aggregate on the web can be made.

The belts 6 and 10 are equipped with a drive. In the example, the rollers 4, 7, 15 are driven to. In Band 6, this Antieb Nip N, in order to ensure thereby a sufficient train of the web. In addition, clamping devices (eg, tension roller 21) and tension regulator for the belts, as well as the adjustment, as shown with a double arrow on the guide rollers present.

In order to be able to transfer the web B into the dryer section 19, a suction roll 22 with or without a foil 23 is provided after the press zone 9 or after the endless belt 10. By this arrangement, it is possible to transfer the train rope.

For completeness, it should be mentioned that for the safe transfer of the web B before the emergence of the belt 6 on the applicator roll 4 also one or more spray tubes (not shown in the drawing) are mounted, the targeted liquid on the belt or the web Apply B to ensure adhesion of the transfer strip or the entire web.

In order to avoid lifting the web on the press roller 16, additional support bands, so-called fibron bands or other known transfer aids can be used.

The Indian FIG. 1 and 2 The section of a paper machine shown corresponds essentially to a "closed transfer" in the dryer section.

In addition, it is conceivable to assign a further application device 5c to the endless belt 10, with which a double application to the upper web side Bo is possible. This can be done with and without intermediate drying. It is also possible to provide further support belts 10a... 10n or 6a... 6n on one or both sides of the web, to which respective application devices 5a... The advantage of such arrangements is that only a subset of starch is applied per application unit. This reduces the rewet of the web immediately after each application. The web does not lose strength, increasing runability.

Overall, it was found in experiments that the strength gain of the paper and board web is not as previously only about 20N /% strength, but 40N /% strength. This can reduce the amount of starch at the same quality by 30% or with the same amount of starch, the quality can be increased accordingly. This is particularly important in the currently declining qualities of the raw materials used to produce corrugated base paper.

In addition, native starches can now be used.

It should be emphasized that after the press nip only very few press nipbedingte outlines of the web are recorded, especially as this production losses (which are about 15 to 20 minutes per failure) can be saved.

Claims (18)

1. Method for the one-sided or two-sided application of liquid to pasty medium, preferably starch, onto the surface of a base stock material web (B), the application medium being applied directly to the surface of the material web (B) in direct application, and, in indirect application, being applied first to the surface of a transfer element (6, 10), for example an application strip (6, 10), from which the application medium is then transferred onto the surface of the material web (B), and the pre-dried material web (B) first being provided with the one-sided or two-sided application, only thereafter running through at least one press nip (N) and finally, after the press nip (N), running further on, supported, characterized in that the material web (B) is a corrugated cardboard base stock material web (B) which, after leaving a last drying cylinder (2) of a pre-drying subassembly (3) and before the medium is applied, has a dry content of between 85% and 95% and, after the press nip (N), runs further on, supported, essentially without a free pull.
2. Method according to Claim 1, characterized in that the material web (B) is supported by at least one flexible endless belt (6) essentially until it reaches a first drying cylinder (18) of a following drying group (19).
3. Method according to Claim 1 and/or 2,
   characterized in that the application of the medium onto one side (underside B_u) of the material web (B) takes place by means of the application of the medium onto the outer face of the flexible endless belt (6).
4. Method according to one or more of Claims 1 to 3,
   characterized in that the application of the medium onto the other side (top side B_o) of the material web (B) takes place onto the surface of an applicator roller (4) and/or onto the outside of a further flexible endless belt (10).
5. Method according to one or more of Claims 1 to 4,
   characterized in that the material web (B) is supported by the same belt (6, 10) onto which the application of the medium has been carried out.
6. Method according to one or more of Claims 1 to 5,
   characterized in that the application of the medium takes place in part-steps on a plurality of belts (10, 10a ... 10n) and in this case the material web (B) is supported by at least one of these belts.
7. Method according to one or more of Claims 1 to 6,
   characterized in that the material web (B) is guided through a penetration zone (P_s) of > 100 mm before the press nip (N) is reached.
8. Method according to one or more of Claims 1 to 7,
   characterized in that the material web (B) has a mass per unit area of at most 90 g/m².
9. Apparatus for carrying out the method according to Claim 1 and, if desired, one or more of Claims 2 to 8, with

   - at least one applicator device (5, 5a) for applying the liquid or pasty medium onto at least one side of the material web (B);

   - at least one flexible endless belt (6) which with its outside supports the material web (B) and with its inside runs over deflecting rollers (8), and

   - a press shoe (14) which with the endless belt forms a press nip (N),

   a supporting roller (7) and a supporting roller (15) arranged at a distance from the latter likewise carrying the endless belt (6), the supporting roller (15) forming, with the press shoe (14) arranged on the outside of the endless belt (6) and spaced apart from the location of the first application by means of the applicator device (5, 5a), the press nip (N) which the material web (B) runs through only after application by the at least one applicator device (5, 5a), and the endless belt (6) being designed in such a way that it supports the material web (B),
   characterized by a pre-drying subassembly (3), from the last drying cylinder (2) of which the material web (B) pre-dried therein to a dry content of between about 85% and about 95% is transferred to the applicator device (5, 5a),
   the endless belt (6) being designed in such a way that it supports the material web (B) essentially without a free pull.
10. Apparatus according to Claim 9, characterized in that the applicator device (5) for applying onto one side (underside B_u) of the material web (B) is assigned to the outer face of the endless belt (6), the roller (7) of the applicator device (5) being assigned as a counterface.
11. Apparatus according to Claim 9 and/or 10, characterized in that the applicator device (5a) for applying the medium onto the other side (top side B_o) of the material web (B) is assigned to the surface of an applicator roller (4) and/or to the outer face of a further endless belt (10), the endless belt (10) running around deflecting rollers (11, 12, 13) and being capable of being designed as a press belt.
12. Apparatus according to one or more of Claims 9 to 11, characterized in that that belt (6, 10) which discharges the medium applied to the said belt (6, 10) onto the material web (B) also supports the material web as far as the first drying cylinder (18) of the drying section (19).
13. Apparatus according to one or more of Claims 9 to 12, characterized in that a plurality of flexible endless belts (10, 10a... 10n) for application in part-steps onto the top side (B_o) of the material web (B) are provided, and in this case at least one of these belts supports the material web (B) as far as the first drying cylinder (18).
14. Apparatus according to one or more of Claims 9 to 13, characterized in that a penetration zone (P_s) of > 100 mm is provided between the location of the application of the medium onto at least one side of the material web and the point at which the press nip (N) is reached.
15. Apparatus according to one or more of Claims 9 to 14, characterized in that, after the press nip (N), a suction roller (22) and/or a suction or blow box (23) are/is present, whereby the material web (B) can be transferred to the first drying cylinder (18) of the drying section (19).
16. Apparatus according to one or more of Claims 9 to 15, characterized in that both the endless belt (6) and the second endless belt (10) are provided with a drive.
17. Apparatus according to one or more of Claims 11 to 16, characterized in that the deflecting roller (13) is designed adjustably, with the result that the supporting area (S_F) of the endless belt (10) for supporting the material web (B) can be lengthened, and/or the endless belt (10) can be deflected via the roller (4) and/or via the roller (11).
18. Apparatus according to one or more of Claims 9 to 17, characterized by its use in the drying section of a machine for the production of corrugated cardboard base stock.

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