DE102019103703A1 - Apparatus and method for coating - Google Patents

Abstract

Application device and method for applying a liquid or pasty medium to a moving fibrous web, in particular a paper or cardboard web, the application device having a first roller and a second roller which form a treatment nip and the fibrous web is passed through this treatment nip, a first Side of the fibrous web is in contact with the first roller, furthermore at least one first film applicator for applying the medium to the first roller, characterized in that at least one first spray applicator is provided for applying the medium to the first side of the fibrous web, as well as a control device which is set up to change the order quantity of the first spray applicator.

Description

The invention relates to a device for applying a liquid or pasty medium to a moving material web according to the preamble of claim 1 and a method for operating an application device according to the preamble of claim 6.

When producing paper or cardboard in a paper machine, it is necessary at certain points to apply a liquid or pasty application medium, such as starch, to the paper or cardboard web running through the paper machine. For this so-called. Surface sizing of the paper or cardboard web various techniques are known, such. B. size pressing or film pressing.

Since size presses can only be used up to a certain production speed, film presses are particularly popular in modern systems.

With film presses, as it is in the German utility model DE 298 02 811 U1 is shown, the paper or cardboard web to be treated also runs through a nip formed by two rollers, but the surface thickness is applied by applying the starch as a film layer to one of the two rollers in front of the nip. The starch on the surfaces of the roller is then pressed into the paper or cardboard web in the roller gap.

From the utility model DE 298 02 811 U1 it is also known that a film application can be combined with a size press in an application device.

What is unsatisfactory about this prior art, however, is that the applied amount of starch can only be adapted to a very small extent via the contact pressure of the metering doctor blade. If, for example, a significantly larger or smaller amount of starch is to be applied in the course of a brand change, a different doctor rod must be used. The exchange of a doctor rod is usually only possible when the paper machine is at a standstill, which leads to an undesirable loss of production. Likewise, it is often desirable if the quality of the input raw material changes, e.g. Recovered paper, to keep the strength of the paper constant or to increase it by increasing the application of starch, or to reduce the application of starch if the strength of the web allows this. With the devices described in the prior art, this is also only possible to a very limited extent during operation.

It is therefore an object of the present invention to propose an application device and a method which enable a quick type change without production downtime in paper manufacture.
It is a further object of the invention to provide a way of regulating the strength by changing the starch application during operation.
Another object of the invention is to reduce the outlay on keeping a large number of different doctor rods in stock.

The object is completely achieved by a device according to claim 1 and a method according to claim 6. Further advantageous features are mentioned in the dependent claims.

An application device is provided for applying a liquid or pasty medium to a running fibrous web, in particular a paper or cardboard web, the application device having a first roller and a second roller which form a treatment nip and the fibrous web is passed through this treatment nip, with a first side of the fibrous web is in contact with the first roller, furthermore at least one first film applicator for applying the medium to the first roller.

According to the invention, at least one first spray applicator is also provided for applying the medium to the first side of the fibrous web, as well as a control device which is set up to change the amount applied by the first spray applicator.

The fibrous web has a first and a second side, the first side being in contact with the first roller and the second side being in contact with the second roller.

In the context of this application, the term control device is also intended to include a control device. The control device can not only be used to control the spray application units. In particular, it can also be provided that the control device controls one or more of the film applicator units.

With such an application device, a defined amount of an application medium, for example a starch solution, a pigment-containing coating color or the like, can be applied to an application roller and thus indirectly to the fibrous web by means of the film applicator. This film application is also suitable for relatively large application quantities and high web speeds e.g. stable possible over 1400 m / min or over 1600 m / min.

The additionally provided spray applicator now makes it possible to quickly increase or decrease the application quantity during operation. Spray applicators often include a large number of applicator nozzles from which the medium is sprayed onto the web. A change in the amount applied can be done very easily, for example by opening or closing a few nozzles. be switched on, or by changing the pressure with which the medium reaches the nozzles. Appropriate valves can be activated by the control device.

If in the context of this application it is mentioned that a medium is applied to the fibrous web by means of spray application, then - unless explicitly stated otherwise - both the direct application, i.e. direct spraying on the moving fibrous web, and the indirect one should be meant Assignment. In this indirect application, the medium is first applied to a roller, e.g. sprayed the first or second roller, and then transferred from this roller to the fibrous web. In particular, with embodiments according to some aspects of the invention, it can happen that a film of application medium is first applied to a roller by means of a film application, and then application medium is applied to this applied film by means of spray application, before both layers of application medium are then applied in the treatment nip the fibrous web are transferred.

It is advantageous in a device that the spray applicators can be operated in a range that is optimal for them. The majority of the application quantity can be done via film application, while only the variable quantity e.g. need to be balanced due to different variety or strength requirements. Such a compensation is not possible with a pure film applicator by varying the squeegee pressure. This division into a type of basic order and a regular order can be made with knowledge of the range of types produced on the system. Both the doctor rod used and the spray nozzles used can be adapted to this.

The operator of such an application device is of course still free to use a different doctor rod in the film applicator. However, this will no longer be necessary every time the variety is changed. Complex storage of a large number of different doctor rods can be dispensed with, since a separate type of doctor rod does not have to be kept for each order quantity.

In preferred embodiments, it can also be provided that a second film applicator for applying the medium to the second roller and / or a second spray applicator for applying the medium to the second side of the fibrous web are provided, and the control device is set up to measure the amount of the first and to change the second spray applicator. With such an embodiment, the application medium can be applied to both sides of the fibrous web at the same time. With this embodiment of the invention, the same amount of medium can be applied to both sides of the fibrous web. However, different amounts of medium can also be applied to the two sides. This can in particular also be set via the control device - which can also be designed as a regulating device, in that, for example, the first and second spray applicators apply different amounts of medium to the respective side of the fibrous web.

In further advantageous embodiments it can be provided that the first spray applicator and / or the second spray applicator are arranged in the direction of travel of the fibrous web in front of, in particular, directly in front of the treatment nip. This is advantageous because the sprayed application medium, e.g. Starch, after being applied in the treatment gap, is further pressed into the fibrous web. This is usually advantageous for achieving internal strength in the web. In the case of indirect spray application, i.e. spraying onto the first / second roller, this effect is achieved by first applying the film to the roller and then applying further medium to this film by means of spray application. In the treatment nip, the sprayed-on medium first comes into contact with the fibrous web.

In other embodiments, however, it can also be advantageous if the first spray applicator and / or the second spray applicator are arranged in the running direction of the fibrous web, in particular immediately after the treatment nip. In this case, the sprayed application medium is not pressed in. It can thus be achieved that this tends to remain on the surface of the fibrous web and achieve its effect there.

The terms "immediately before" and "immediately after" the treatment nip are intended to mean that no further devices for processing the web are arranged between the spray application and the treatment nip. Such spray units are often arranged at a distance of less than 2 m, in particular less than 1 m, from the treatment nip.
In alternative embodiments, however, it can also be provided that between the spray application and a -preferably non-contact drying device is arranged on the treatment nip.

Furthermore, it can be advantageous that at least one strength sensor is provided for determining a strength value of the fibrous web. This can be any desired strength value of the fibrous web, for example tensile strength, splitting strength or bursting strength. Since the direct measurement of these strength values is often a destructive measurement that can only be carried out online with difficulty or not at all, such a strength sensor can in particular be a virtual sensor - also known as a soft sensor - that provides the desired strength value on the basis of available measured values and a model. Such soft sensors are known from the prior art, for example EP 1 785 526 .

Furthermore, means for determining the amount of the applied medium can advantageously be provided. This can be done either by a suitable sensor, e.g. determines the weight applied to the web. Alternatively or additionally, the flow rates of application medium can also be measured and, if necessary, quantity balances can be calculated. The latter is particularly advantageous for spray application, since here essentially the entire sprayed-on medium lands on the fibrous web. In contrast, with film application, part of the medium runs back with the roller after the treatment nip. Since the amount applied by film application is largely constant in the devices described here - and this value can be determined once in the laboratory if necessary - and the changes are made via the spray application, the measurement of the sprayed amount of application medium - together with the knowledge of the Web speed etc. - can be concluded very well on the total amount of medium applied.

With regard to the method, the object is achieved by a method for applying a liquid or pasty medium to a moving fibrous web, in particular a paper or cardboard web, by means of an application device according to one aspect of the invention. It is provided that, to change the amount of application medium, only the application amount of the first and / or second spray applicator is changed, while the application amount of the first and / or second film applicator remains constant or largely constant.

Here too, advantageous embodiments are described in the subclaims. The indication that the order quantity of the film applicator unit remains largely constant is intended to mean that this quantity can change by a maximum of + -10%, in particular by a maximum of + -5%, by the mean order quantity of the film applicator unit.

In particularly preferred embodiments, a starch solution can be used as the application medium. Starch solutions, such as those used in the manufacture of fibrous webs, can contain other components in addition to the starch, for example to improve the processability of the medium

It can be advantageous if the same application medium is applied in all film and spray applicators.
Alternatively, however, it can also be provided that different application media are applied, in particular that the application medium of the first film application and the first spray application differ in at least one parameter, in particular in solids content, viscosity or temperature.
In particular, different types of starch solution can be applied. An advantageous embodiment can be, for example, to first apply an application medium with a low viscosity, which penetrates deeper into the fibrous web and therefore acts on the internal strength of the web. Then a higher-viscosity application medium can be selected, which tends to stay on the surface of the web and develop its effect there, for example surface strength or pick resistance in writing paper.

It will often be advantageous if the average application amount of the first film applicator is greater than the average application amount of the first spray applicator. (The same applies to the second commissioned works)
For example, it can be provided that the "base load" of the film applicator is approximately twice as great as the mean application of the spray applicator. However, it must be taken into account that in such a case the application quantity of the spray application can have a greater range of fluctuation than that of the film applicator. For example, the spray application can fluctuate between 0% and 100% of the mean film application quantity, while the film application quantity can only fluctuate between 80% and 120% or only between 90% and 110% around the mean value. These values are only to be understood as guidelines. Processes according to aspects of this invention can also have other quantitative ratios in individual cases.

In a further advantageous embodiment of the method it can be provided that the control device is provided with a strength value of the paper web, and the The amount of medium applied is changed so that the strength value remains within a specified range. Such a strength value can be made available, for example, by a sensor, in particular a virtual sensor. An online strength control is thus possible.

In further advantageous embodiments, it can alternatively or additionally be provided that a type parameter of the paper web is made available to the control device, and the application quantity of medium is set to a predetermined type guide value. For example, if there is a brand change, the order quantity can be automatically and extremely quickly adjusted to the new type. In this case, it is particularly advantageous to initially set a type-specific mean value which, if necessary, can then be continuously adapted to the current production conditions as a function of a strength parameter made available.

The first and / or second roller can be designed, for example, as a soft roller, with a surface hardness of preferably 10-70 P&J. Such roller surfaces are often constructed from a rubber or polyurethane material.
The first and / or second roller can also be designed as a hard roller, with a surface hardness of preferably 80-100 ShoreD, in particular 85-95 ShoreD. Such roller surfaces are often constructed from a rubber, polyurethane material or composite material.
In an application device according to one aspect of the invention, two hard rollers, two soft rollers or one hard and one soft roller can be used as the first and second roller.
Usual diameters for such rolls are between 1.0m and 2.2m, in particular between 1.8m and 2m.
In advantageous embodiments, the first roller can be designed to be zone-controlled. This enables different line forces to be set across the width

Furthermore, a computer program product with machine-readable instructions for executing a method according to one aspect of the invention, in particular also for operating the control device.

• 1 zeigt schematisch eine Auftragsvorrichtung gemäß einem Aspekt der Erfindung
• 2 zeigt schematisch eine Auftragsvorrichtung gemäß einem weiteren Aspekt der Erfindung

The invention is explained in more detail below with the aid of schematic figures.

• 1 shows schematically an application device according to an aspect of the invention
• 2 shows schematically an application device according to a further aspect of the invention

In the 1 The application device shown comprises a first roller 1 and a second roller 2 that are arranged so that they have a treatment nip 6th train through which the fibrous web 5 , for example a paper or cardboard web 5 to be led.

There is also a first film applicator on the two rollers 11 and a second film applicator 12 intended. These commissioned works 11 , 12 , apply a film of application medium, for example starch, to the respective roller. This medium is then used in the treatment nip 6th onto the fibrous web 5 transferred and pressed in to a certain extent. Furthermore, in 1 two spray applicators 21st , 22nd intended. These are both in the web running direction immediately before the treatment nip 6th arranged. The first spray applicator 21st carries the application medium directly onto the first side of the material web 5 while the second spray applicator applies the medium directly to the second side of the web 5 applies. Between the spray applicators 21st , 22nd and the treatment nip 6th no further elements are arranged. The distance between the spray application and the treatment nip 6th is usually less than 2m.
The control device 100 is provided here to the order quantity of the first spray applicator 21st and the second spray applicator 22nd to change. With a device of this type it is possible to change the amount of application medium, for example a starch solution, during operation, without structural changes to a film applicator 11 , 12 to have to make. Will the control device 100 also a strength value of the paper web 5 made available, it is also possible to regulate the strength of the fibrous web. Such a strength value can be determined, for example, by a virtual sensor.
In 1 are two more spray applicators 21 ' , 22 ' shown. These are arranged so that the spray application onto the web 5 after the treatment nip 6th he follows. These spray applicators 21 ' , 22 ' can in addition to the spray applicators 21st and 22nd be provided or an alternative positioning of these orders 21st , 22nd represent. The order quantity of these additional spray applicators 21 ' , 22 ' can also be changed by means of the control device.
The first roller 1 and / or second roller 2 can, for example, be designed as a soft roller, with a surface hardness of preferably 10-70 P&J. Such roller surfaces are often constructed from a rubber or polyurethane material.

The first roller 1 and / or second roller 2 can also be designed as a hard roller, with a surface hardness of preferably 80-100 ShoreD, in particular 85-95 ShoreD. Such Roll surfaces are often constructed from a rubber, polyurethane material or composite material.
In an application device according to one aspect of the invention, the first roller 1 and second roller 2 two hard rollers, two soft rollers or one hard and one soft roller can be used.

2 Figure 3 shows an embodiment according to a further aspect of the invention. She is different from 1 in that the two spray applicators 21st , 22nd the application medium is now not directly on the fibrous web 5 apply, but indirectly. The application medium is applied to the first roller 1 and the second roller 2 sprayed. Again, by means of the control device 100 the order quantity can be controlled. Also in a device of the in 2 The type shown can also have additional spray applicators 21 ' , 22 ' be provided, which are arranged in particular after the treatment nip6.

List of reference symbols

1

first roller

2

second roller

5

Fibrous web

6th

Treatment nip

11

first commissioned film

12

second commissioned film

21st

first spray applicator

22nd

second spray applicator

21 '

first spray applicator

22 '

second spray applicator

100

Control device

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 29802811 U1 [0004, 0005]
• EP 1785526 [0022]

Claims (13)

Application device for applying a liquid or pasty medium to a running fibrous web (5), in particular a paper (5) or cardboard web (5), the application device having a first roller (1) and a second roller (2) which have a treatment nip (6) and the fibrous web (5) is passed through this treatment nip (6), a first side of the fibrous web (5) being in contact with the first roller (1), and at least one first film applicator (11) for applying the Medium on the first roller (1) characterized in that at least one first spray applicator (21) is provided for applying the medium to the first side of the fibrous web (5), as well as a control device (100) which is set up to measure the amount of the first spray applicator (21) to change. Application device according to Claim 1 characterized in that a second film applicator (12) for applying the medium to the second roller (2) and / or a second spray applicator (21) for applying the medium to the second side of the fibrous web (5) are provided, and the control device (100) is set up to change the application quantity of the first (21) and the second spray applicator (22). Applicator according to one of the preceding claims, characterized in that the first spray applicator (21) and / or the second spray applicator (22) are arranged in the direction of travel of the fibrous web (5) in front of in particular immediately in front of the treatment nip (6). Application device according to one of the preceding claims, characterized in that at least one strength sensor is provided for determining a strength value of the fibrous web (5). Application device according to one of the preceding claims, characterized in that means are provided for determining the amount of the applied medium. Method for applying a liquid or pasty medium to a moving fibrous web (5), in particular a paper or cardboard web by means of an application device according to one of the preceding claims, characterized in that to change the amount of application medium only the application amount of the first (21) and / or the second spray applicator (22) is changed, while the application quantity of the first (11) and / or second film applicator (12) remains constant or largely constant. Procedure according to Claim 6 , characterized in that the medium is a starch solution. Method according to one of the Claims 6 or 7th , characterized in that the same medium is applied in all order units (11, 12, 21, 22, 21 ', 22'). Method according to one of the Claims 6 to 8th , characterized in that the application medium of the first film application and the first spray application differ in at least one parameter, in particular in solids content, viscosity or temperature. Method according to one of the Claims 6 to 9 , characterized in that the application amount of the first film applicator (11) is greater than the average application amount of the first spray applicator (21) Method according to one of the Claims 6 to 10 , characterized in that the control device (100) is provided with a strength value of the fibrous web (5), and the amount of medium applied is changed so that the strength value remains in a predetermined range. Method according to one of the Claims 6 to 11 , characterized in that a type parameter of the fibrous web (5) is made available to the control device (100), and the application quantity of medium is set to a predetermined type guide value. Computer program product with machine-readable instructions for carrying out the method according to one of the Claims 6 to 12 .

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