WO2021037612A1

WO2021037612A1 - Method for forming a shaped appearance on the surface of paper, and coating machine for coating surfaces of paper

Info

Publication number: WO2021037612A1
Application number: PCT/EP2020/073115
Authority: WO
Inventors: Ronny Schreiter; Andy Diedrich; Billy Kurth; Silvio Müller
Original assignee: Schönfelder Papierfabrik GmbH
Priority date: 2019-08-23
Filing date: 2020-08-18
Publication date: 2021-03-04
Also published as: EP4018038A1; DE102019122745A1

Abstract

The invention relates to a method for forming a shape on the surface of paper, wherein a paper web (12), in order to coat the surface with a surface application (36, 38), is coated, dried, and finally rolled on a roll for further use. In order to achieve a shaped appearance of the paper particularly efficiently, according to the invention, while the paper web (12) is being coated, the coating substance is to be applied inhomogeneously as a surface application according to the desired shape of the paper. The invention further relates to a coating machine (22) for carrying out the above method.

Description

METHOD FOR DEVELOPING A PROFILE OPTICS ON THE SURFACE OF PAPER AND COATING MACHINE FOR COATING SURFACES OF PAPER

According to the preamble of claim 1, the invention relates to a method for forming a profile optics of the surface of paper, a paper web for coating the surface being coated with a surface application, dried and finally rolled up on a roll for further use. The subject of the method is also a device for carrying out the method.

The production of paper has been known for a long time and is now mostly done on continuously operating machines. Roughly simplified, the paper machine has a wet section, a wire section and a press section, which is followed by a dryer section. To achieve better surface finishes, which can be advantageous for printing or generally for the optical appearance, a surface application, which can also be referred to as a surface coating, is usually applied to the paper web by means of a coating device, and then Another dryer section follows before the paper web is rolled up. A device for applying a surface application can in the sense of the present application both a painting process to achieve a smooth

and closed surface as well as an application of starch or surface sizing, which also aims to change the surface quality.

As a rule, the coating device is integrated into the paper machine and arranged there between two drying sections for the paper web running through. But it is also possible to provide a coating device independently of a paper machine in so-called offline mode. The paper web is then unwound from a supplied roll of raw paper and passed through the coating device and subsequent drying before it is wound up again.

The surface application in the coating device is carried out by uniform application of a coating substance with a defined layer thickness, whereby e.g. squeegees can be used.

There is occasionally the customer request to provide a paper with a profiled look. This can be implemented in terms of color and / or by appropriately profiling the paper structure.

Known solutions intervene in the wet end of papermaking, with the intervention being able to take place either in the wire section or in the press section. The results are also known as watermarks. In the case of continuously operating machines, these measures are technically and financially complex and may also require a lot of space in the system. The downtimes for retrofitting also result in high costs if you want to switch between the types of paper during operation. Interventions in the wet section can also impair the strength of the paper web, as they partially weaken the structure.

Another known solution for forming a structure provides to mechanically emboss the quasi-finished paper web. Here, too, there are very high investment costs and, if necessary, changeover times when changing between the types of paper.

Finally, there is of course the possibility of subsequently printing the paper web in a suitable manner, with relief-like printing also being possible. Regardless of the type of printing, there are also considerable additional costs here due to the printing device, in particular because an additional work step must be carried out. In the case of a printing device, there are also high costs due to the additional consumption of printing ink.

The object of the invention is to develop a method of the type mentioned at the outset in such a way that, without a great deal of additional effort, a profile appearance of the paper produced can be achieved. The present invention also provides a device for performing the method according to the invention.

The main features of the invention are set out in the characterizing part of claim 1. From designs of the method are the subject of claims 2 to 7. An apparatus for performing the method is specified in claim 8, the preferred Ausführungsfor men in claims 9 to 13 are set out.

According to the invention, a method of the type mentioned at the beginning is designed in such a way that the application of the surface coating is carried out inhomogeneously in accordance with the desired profile appearance of the paper during the spreading of the paper web.

It has been shown that this technically easy to implement measure achieves a visually clearly perceptible profiling, which is achieved by slight color deviations in the final state and / or by a relief-like structure of the surface. The exact nature of the optics and / or structure of the paper surface can be influenced by the recipe of the coat, its coloring and the differences in thickness of the surface application, although these possible measures mentioned above are not to be understood as conclusive.

The advantage is that existing coating devices can be converted with simple means, so that the method according to the invention can be used with minimal effort in existing paper machines or coating machines for subsequent surface application that are used independently of a paper machine can be converted.

It is also advantageous that the basic structure of the paper is not weakened, so that its mechanical properties are fully preserved.

Since the surface application is generally not set to zero even at the points where its thickness is reduced, the overall surface quality improved by the painting remains and the paper can be printed in a previously known manner, if this is desired .

In a preferred embodiment of the method, it is provided that the line is applied in the form of a line. This type of application leads to a rib-like appearance of the paper surface, which creates a particularly harmonious appearance and is often requested and, moreover, can also be implemented particularly easily in a process with a continuously running paper web.

Of course, in a further embodiment of the method it can be provided that the surface coating is applied to both sides of the paper web, the application being carried out inhomogeneously on at least one side in order to achieve the desired profiling. The profiling can of course be carried out on both sides of the paper web.

A practical embodiment of the method provides that the paper web is guided between two rollers and the coating is applied over the entire surface of at least one roller, where the thickness of the coating on at least this roller is partially reduced or completely removed by means of a scraper.

The application of the coating substance to a roller and subsequent transfer to the paper web is known per se, but the roller is also very suitable for interaction with a scraper in order to enable the inhomogeneous order without changing the order on the roller.

A particularly expedient development of the method for forming a linear profiling provides that the scraper is designed like a comb and is pressed with its prongs in the direction of the surface of the respective roller.

A particularly preferred embodiment of the method provides that the position of the scraper is changed axially with respect to the roller continuously or at certain time intervals. This avoids that the roller could wear out prematurely at the contact pressure points of the scraper due to the formation of scoring.

As already mentioned, the coating of the paper web can preferably be integrated into the manufacturing process of the paper, the paper first being dewatered, pressed and dried to form a paper web before the inhomogeneous coating of the surface of at least one side of the paper web is carried out.

The present invention also relates to a coating machine for coating surfaces of a paper web, at least one roller on which the paper web is guided and at least one application device for applying coating substance to a Roller is provided, in which according to the invention in the direction of rotation between the device and the application of the roller to the paper web, a scraper is provided, which rests over part of the roller length on the surface thereof.

Such a coating machine can either already be integrated into a paper machine for paper production or be used independently of such a machine, with the retrofitting of an existing coating machine by means of a scraper on at least one applicator roll according to the invention being possible, please include in a particularly simple manner.

The advantage of using a scraper to partially remove a previously applied full-surface application is that a residual surface application is retained even at the points where the application is removed, so that the printability and the surface appearance of the paper are not impaired. but only changed in the desired way.

In a preferred embodiment of the coating machine, the scraper is designed like a comb with tines which define the contact points on the roller. It should be noted that, as a rule, a residual film of the surface application can remain between the scraper and the roller surface, that is, the material of the scraper is not in direct contact with the roller surface.

In this way, a linear surface application can be implemented in a particularly simple manner on the paper web running past.

In order to enable the previously discussed axial displacement of the scraper in relation to the roller surface, it is also preferably provided that the scraper is connected to an adjusting device with which the axial relative position of the scraper to the roller surface can be changed continuously or at time intervals.

Yet another embodiment of the invention can provide a pressure device which presses the scraper against the roller surface with a defined contact force. This can be provided as an alternative to a likewise possible, fixed, very small distance between the plant locations and the roll surface

To apply a surface application on both sides, a particularly preferred embodiment of the invention provides that two rollers with application devices and scrapers are provided, the paper web being guided between the rollers. Finally, in a preferred embodiment of the invention it is provided that the application device has a doctor blade for setting a homogeneous layer thickness of the application of coating substance. It has been shown that the scrapers according to the invention, in particular in their comb-like design, interact particularly well with such an application device.

Further features, details and advantages of the invention emerge from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings. Show it:

1 shows a schematic representation of the process steps in a paper machine in the production of paper;

2 shows a schematic representation of a system for the surface treatment of a paper web independently of a paper machine;

3 shows a system according to the invention for a surface application according to the invention inde pendent of a paper machine;

4 is a schematic side view of a coating machine for surface application.

In Fig. 1, the schematic sequence in a paper machine 10 for paper production is vorgese hen, which preferably operates continuously, in that the paper is guided as a paper web 12 (see FIG. 4) between the individual process steps.

The basic process steps of paper production are not the subject of the inven tion and are therefore only briefly explained. In the wet section, the processed raw material suspension is evenly distributed and applied at the correct speed to the wire of a wire section 14 to form an endless, wet fiber fleece and drained. The fleece is transported further into a press section 16, where further water is driven out of the fiber web under pressure. The belt then passes through a first drying section 18 in which the paper web 12 is thermally dried to a final moisture content.

To improve the surface quality of the paper web 12, a device 20 is provided for bringing on a surface application, which can be designed as a coating machine 22 or a film press, depending on the technological objective. In the following, reference is made to the application of a line.

After the surface application, the paper web runs through a second drying section 24, since the paper web has to be dried again after the surface application. 1 also shows a station 26 for surface treatment, as is known from the prior art, in order to post-process the paper web by mechanical measures and to give it a profile, which is indicated by the arrow C. This measure can be implemented by an embossing tool that continuously acts on the paper web passing by. It is also possible, in addition or as an alternative, to arrange a printing device for printing the paper web 12 in front of the final reeling station 28.

Further or alternative measures for producing a profiled appearance of the produced paper web 12 can also be taken in the wet end of the paper machine, which is illustrated by the thin arrows A and B.

In Fig. 2 a plant 100 is illustrated which provides a surface treatment outside of a paper machine by means of a suitable station 126, for example by embossing, as has already been described above. For this purpose, a paper web is rolled down from a supply roll 102, processed and rewound onto a supply roll 104.

As a novelty, a modified device 20 for applying a surface application is provided which, instead of an even application of a coating substance, causes a partial difference in the thickness of the application layer.

In FIG. 4, such a device 20 is shown in an embodiment as a coating machine 22. The coating machine has two rollers 32, 34 between which the paper web 12 is guided. The coating machine 30 shown in FIG. 4 is designed to provide the paper web with a surface application on both sides. The surface application material 36, 38 is stored in containers 40, 42 which are arranged below the rollers 32, 34, and is applied to the roller surface 48, 50 with a suitable application device 44, 46. A roller squeegee 52, 54 on each roller 32, 34 spreads the applied material to a desired, homogeneous layer thickness so that the roller surfaces in the wake of the roller squeegee 52, 54 is covered with a homogeneous, full-surface application of coating substance. Excess material is returned to the storage container 40, 42.

At a certain distance from the roller doctor blades 52, 54, scrapers designed as comb scrapers 56, 58 are arranged on the rollers, the prongs 60, 62 of which are in contact with the roller surface, with a film forming between the prongs 60, 62 and the roller surface Surface material can remain. The individual prongs 60, 62 can not be seen in Fig. 4, they distribute themselves evenly over the length of the scraper 56, 58 over the entire width of the paper web 12 and the roller length. By means of the comb scrapers 56, 58, the surface application in the area of the prongs 60, 62 is removed in a line-like manner or distributed over the gaps. This creates a rib-like structure running in the circumferential direction of the rollers 32, 34 in the wake of the comb scrapers 56, 58.

In the contact areas of the rollers 32, 34 with the paper web 12, the rib-like orders - here consisting of coating color - are transferred to the paper web. The paper web is therefore continuously provided with a rib-shaped surface application on both sides. After the paper web coated in this way has dried, the result is a rib-like, structured appearance of the paper web, which nevertheless remains printable and its surface quality does not suffer.

The comb scrapers 56, 58 are adjustable in the axial direction of the rollers 32, 34, whereby the adjustment can be made automatically by a suitable drive continuously or at certain intervals. The adjustment is useful in order to avoid that the prongs 60, 62 always run on the same places on the roller circumference, which in the long run could lead to scoring, even if a thin film of surface application still remains between the prongs and the roller surface .

The appearance can be influenced by the choice of application material, which can also be colored if necessary in order to enhance the visual effect.

The coating machine 22 shown in FIG. 4 can be integrated into the paper machine shown in FIG. 1 as a device 20 for surface application (see arrow D). The station 26 shown in Fig. 1 for embossing the surface can be omitted, since the coating machine 22 according to FIG. 4 is able to give the paper the rib-like appearance by the measures described.

However, the coating machine 22 shown in FIG. 4 can also be used in a system 200 separately from a paper machine to provide a previously produced paper web with the desired grooved appearance. For this purpose, the paper web is again unwound from a supply roll 102, then passes through the coating machine 22 and, after passing through a drying station 224, is rewound onto a supply roll 104.

The invention is not restricted to one of the embodiments described above, but can be modified in many ways. So it is through appropriately modified application devices and / or scrapers or with the help of other means for selective reduction of the Layer thickness of the surface order possible to produce other structures of the surface order on the paper web 12 that differ from a purely line-like structure.

All of the claims, the description and the drawing features and advantages, including structural details, spatial arrangements and process steps, can be essential to the invention both individually and in a wide variety of combinations.

Reference numbers list paper machine paper web wire section press section first drying section device for applying a surface application coating machine second drying section station for surface treatment roll-up station, 34 rollers, 38 surface application material, 42 storage container, 46 application device, 50 roller surface, 54 roller doctor blade, 58 comb scraper, 62 prongs 0 system for surface treatment a paper web 2 supply roll 4 supply roll 0 system for a surface application on a paper web 4 drying station

Claims

1. A method for forming a profile optics on the surface of paper, wherein a paper web (12) for coating the surface with a surface application (36, 38) is painted, dried and finally rolled up on a roll for further use, characterized in, that during the coating of the paper web (12), the application of the surface application (36, 38) is carried out inhomogeneously in accordance with the desired profile appearance of the paper.

2. The method according to claim 1, characterized in that the surface application (36, 38) is applied linearly.

3. The method according to claim 1 or 2, characterized in that the surface application (36, 38) is applied to both sides of the paper web (12), wherein the Aufträ gene is carried out inhomogeneously on at least one side.

4. The method according to any one of the preceding claims, characterized in that the paper web (12) is guided between two rollers (32, 34) and the coating substance is applied over the entire surface of at least one roller, the thickness of the coating substance being applied to at least one roller (32 , 34) is partially reduced or removed by means of a scraper (56, 58).

5. The method according to claim 4, characterized in that the scraper (56, 58) has a comb-like design and is pressed with its prongs (60, 62) in the direction of the surface (48, 50) of the respective roller (32, 34).

6. The method according to claim 4 or 5, characterized in that the position of the scraper (56, 58) axially with respect to the roller (32, 34) is changed continuously or at certain time intervals

7. The method according to any one of the preceding claims, characterized in that the coating of the paper web (12) is involved in the manufacturing process of the paper, wherein the paper is first screened, pressed and dried to form a paper web (12), before the inhomogeneous painting of the surface of at least one side of the paper web (12) is carried out.

8. Coating machine (22) for coating surfaces of a paper web (12), wherein at least one roller (32, 34) on which the paper web (12) is guided, and at least an application device (44, 46) for applying coating color or a glue substance to a roller (32, 34) is provided, characterized in that in the direction of rotation between the application device (44, 46) and the system of the roller (32, 34 ) a scraper (56, 58) is provided on the paper web (12), which rests against it over part of the width of the roll.

9. Coating machine according to claim 8, characterized in that the scraper (56, 58) is designed like a comb with prongs (60, 62) which define the contact points on the roller (32, 34).

10. Coating machine according to claim 8 or 9, characterized in that the scraper (56, 58) is connected to an adjusting device with which the axial relative position of the scraper (56, 58) to the roll surface can be changed continuously or at time intervals.

11. Coating machine according to one of claims 8 to 10, characterized in that a pressure device is provided which presses the scraper (56, 58) with a defined contact force on the roller surface (48, 50).

12. Coating machine according to one of claims 8 to 11, characterized in that two rollers (32, 34) with application devices (44, 46) and scrapers (56, 58) are provided, the paper web (12) between the rollers ( 32, 34).

13. Coating machine according to one of claims 8 to 12, characterized in that the application device (44, 46) has a doctor blade (52, 54) for setting a homogeneous layer thickness of the surface application (36, 38).