WO2012007366A1

WO2012007366A1 - Method for applying coloured coating slip

Info

Publication number: WO2012007366A1
Application number: PCT/EP2011/061578
Authority: WO
Inventors: John Bergman; Uwe Fröhlich
Original assignee: Voith Patent Gmbh
Priority date: 2010-07-16
Filing date: 2011-07-08
Publication date: 2012-01-19
Also published as: DE102010031436A1

Abstract

The invention relates to a method for applying application medium, more particularly coloured coating slip, to the surface of a moving web of paper or card in order to make it suitable, for example, for inkjet printing or for flexographic printing, using cationically and anionically formulated application media. In accordance with the invention, provision is made for a basecoat (5b, 5c), consisting of an anionically formulated application medium (5), and a topcoat (6b, 6c), consisting of a cationically formulated application medium (6), to be applied in succession to the surface of the paper or card web (1) and/or to the same web side.

Description

Method of applying coating color

The invention relates to a method for applying application medium, in particular coating color on the surface of a running paper or board web to make them suitable for example for an ink jet printing or flexographic printing, wherein the application medium is set cationic or anionic.

Above all, papers for ink-jet printing or flexographic printing should have a high absorption capacity, so that the printing ink to be applied later is picked up and held by the paper surface. Therefore, the paper web is coated during its production process in the paper machine or in a subsequent refining process in a coating machine with anionic or cationic coating colors. In some cases, two consecutive process steps are carried out, namely the first step anionic and the second step cationic.

A disadvantage of an application of cationic media that they bring a good order result, but the cationic medium is very expensive. On the other hand, the anionic medium, which is less expensive, produces a less good coating quality. If the two components - anionic and cationic medium mixed, this leads to clumping and therefore insufficient job qualities.

Another disadvantage is that the mixed components can only dissipate mixed and therefore are not suitable for reprocessing.

It is therefore an object of the invention to provide an improved method for applying application medium to the surface of a running paper or board web, with which above all cationic application medium can be saved.

The object of the invention is achieved by a method according to the features of claim 1. Appropriate designs result from the Dependent claims.

According to the invention, it is provided that a base layer consisting of an anionically adjusted, i. negatively charged coating medium and a topcoat consisting of a cationic, i. positively charged set application medium is applied to the surface of the paper web. This is done spatially separated from each other on the same web page.

This means that both media are not mixed together, which no longer leads to clumping, which was previously not possible. This increases job quality, which in turn leads to better print results later. But above all, you have the ability to each medium individually z. B. in the strength content, in line amount, etc. adjust. The fact that both differently charged application media are applied separately, a separate collection of excess medium is made possible. This is the case both when starting and ending the coating process and / or during the coating process, when the application medium or the coating color is dispensed over the width of the web (overboard). For a separate return or refeeding in the coating process is possible.

With the aid of the method according to the invention, the very expensive cationic application medium can be saved.

The anionic base layer applied in an on-line papermaking machine or in an off-line coater provides the necessary optical properties such as opacity, whiteness and brightness, whereas the cationic overlay provides for rapid immobilization of the inks subsequently applied in the presses provides.

In order to improve the application quality or for a good anchoring of the applied cover layer with the underlying layer, it is expedient if an intermediate layer consisting of gelatin or polyvinyl alcohol is applied between the anionic base layer and the cationic cover layer. The method can be advantageously designed if the individual layers, ie both the anionic base layer and the cationic top layer, but also the intermediate layer are each applied with the aid of at least one curtain applicator. The respective application media are delivered to the paper or board web in separate single-layer or multilayer curtains, essentially following the principle of gravity. Since the job is done 1: 1, that is applied only in the amount that is to remain on the web surface, you save again expensive application medium. Preferably, the cationic cover layer and / or the intermediate layer or intermediate layers wet in wet, that is applied without the application of an intermediate drying on the already located on the paper surface base layer. The base layer anchors on the surface of the paper and the cationic top layer is particularly well anchored to the base layer or the intermediate layer as a result of wet-on-wet application. In addition, costs for the unneeded drying facilities are saved.

In an alternative method it can be provided that a cationic multilayer is applied to an anionic multilayer. Preferably, however, is intended in each case to a double layer.

Another possibility is to place a simple cationic topcoat over an anionic basecoat, to which an intermediate coat is applied, as well. It is also possible to use an anionic base bilayer (or double coat), but also a base single coat (or single layer) to apply a cationic double layer (or double layer).

Thus, at least two layers or layers always form the total application layer.

In the context of the invention is for the application of the individual layers or layers Both known curtain slot nozzles or slot Dies, as well as per se known one or more layers applying sliding layer nozzle blocks or slide thought this. These application units apply the coating colors very evenly and, as explained above, without excess on the paper or cardboard surface.

It has been found that the coating weight of the single or multiple anionic base layer should be higher than the coating weight of the single or multiple cationic layer. The following quantity ranges are suggested for this:

- The anionic base layer is in an amount or in a total line weight of 2 to 20 g / m ² , preferably 2 to 18g / m ² and

- The cationic topcoat is applied in an amount or in a total coat weight of 2 to 18g / m ² , preferably 1 to 10 g / m ² .

In this case, one will select the higher values for the anionic layer and the lower values for the cationic layer.

This can save a significant amount of expensive cationic application medium or coating color.

Further costs are saved by the fact that the solids content of the cationic top layer is lower than that of the anionic bottom layer, ie the base layer.

In the context of the invention is intended to a solids content of the cationic top layer of 25 to 70%, preferably 15-35% and a solids content of the anionic base layer of 30 to 70%, preferably 55 to 65%.

The method according to the invention achieves the following advantages:

- saving costs for expensive cationic chemicals;

- the anionic and cationic application media can be recovered separately;

- The elements loaded with application medium, such as nozzles, application chambers and supply lines, can be cleaned separately. The invention will be explained in more detail with reference to an embodiment. In a schematic representation:

FIG. 1 shows a first variant with which the method according to the invention is carried out,

FIG. 2 shows a second variant with which the method according to the invention is carried out,

FIG. 3 shows a third variant with which the method according to the invention is carried out,

In the figures, the same components are provided with the same reference numerals.

FIG. 1 shows a paper or board web 1 which runs in the direction L over two guide rollers 2 which are spaced apart from one another. Above the web 1 and spaced from her two curtain applicators 3 and 4 are arranged, which are designed as a so-called slot nozzles. These slot nozzles, i. referred to as "slot dies" in the jargon, are already known from DE-A1 102007 000782. The two commissioned works 3 and 4 have identically constructed components and are visible in the running direction of the web 1 as shown in Figure 1, arranged one after the other, but could - as not shown here - also be combined to form a structural unit. The applicator 3 is intended for dispensing anionic application medium 5 or coating color in the form of a single-layer curtain 5a. The curtain falls down on the track surface essentially due to gravity. The individual curtain 5a then generates on the surface of the paper or board web 1 a contour layer which forms a monolayer base layer 5b.

The commissioning unit 4 arranged at a certain distance is likewise intended here for dispensing cationic application medium 6 or coating color here in the form of a single-layered curtain 6a. The individual curtain 6a then generates on the surface of the paper or board web 1 also a single layer, which forms a single-layer cover layer 6b. All orders are made on the same web page and in only one pass of the web 1.

As with the high-speed paper or board web 1 unwanted air boundary layers are carried before each commissioned work 3 and 3 corresponding removal facilities air boundary layer control devices 7 are available. In addition, catchers 8, e.g. Drip trays or gutters, for the curtain when starting and stopping the curtain drawn with.

Overall, in this example, two layers of application medium, ie single-layer base layer 5b and single-layer cover layer 6b, form a total coating layer S. FIG. 2 shows that a double-layered anionic base layer 5c is applied to the surface of the paper or board web 1. Subsequently, as in FIG. 1, a single-layer cationic top layer 6c is applied. This figure also applies to the case where a single-layer base layer 5b and above an intermediate layer 9, consisting of a gelatin or polyvinyl alcohol is applied.

To form the base layer 5b or 5c and possibly the intermediate layer 9, a so-called sliding layer nozzle 10, which is referred to in the art as "slide die", is used as a curtain applicator. Such a commissioned work 10 is known for example from EP-A1 - 1 255 615. With this curtain coater, several application media or multiple layers of the application medium, ie, for example, one or more layers of anionic medium and the medium for the intermediate layer 9 can be dispensed. This so-called sliding layer nozzle contains several individual application medium chambers 10.1 to 10.n. From each application chamber branches up from a supply gap, which in turn merges upward into a slot-shaped outlet nozzle, which were not designated here for reasons of clarity with. From these outlet nozzles flows the anionic Auftragmediunn, for example, for a first layer of the base layer 5c on an outer sliding surface of the Gleitschichtdüse. The order mediunn for a second layer of the base layer 5c, or the layer of the medium for the intermediate layer 9, emerging from a further outlet nozzle arranged parallel next to it, lies over the first layer and arrives at the same as the multi-layered or double-layered curtain 5d Coating track surface.

Overall, in a selected example of FIG. 2, three layers, ie double-layer base layer 5c and single-layer cover layer 6b, form the overall layer S.

FIG. 3 shows a further variant of the method. In this case, two double layers, each with a removable from Figure 2 curtain applicator in the form of a respective Gleitschichtdüse 10 are successively applied. That is, the anionic base layer 5c is formed here by means of a double-layered curtain 5d consisting of the anionic coating medium 5. The following cationic cover layer 6c is formed here by means of a double-layered curtain 6d consisting of the cationic application medium 6.

Overall, four layers of application medium form the overall layer S. It should be noted that an intermediate layer 9 can likewise be applied between the base layer and the cover layer. This is very efficiently possible due to the use of the described sliding layer nozzles 10 with the plurality of application medium chambers.

It should also be added that all illustrated curtain applicator units 3, 4 and 10 work without contact. That is, the deposited application media are applied without web-contacting components. The individual layers are also applied wet-on-wet.

Incidentally, in all examples, the anionic base layer is applied in a coating weight of 18 g / m ² and the cationic topcoat in a coating weight of about 10 g / m ² . The solids content of the cationic outer layer is approx. % and the solids content of the anionic base layer about 55%.

LIST OF REFERENCE NUMBERS

1 paper or board web

2 guide roller

3 curtain applicator slot nozzle

4 curtain applicator slot nozzle

5 anionic application medium

5a single curtain

5b single layer base layer

5c double layer base layer

5d double-layered curtain

6 cationic application medium

6a single curtain

6b monolayer base layer

6c double layer base layer

6d double layer curtain

7 air boundary layer control device

8 curtain catcher

9 interlayer

10 applicator sliding layer nozzle

10.1 -I O.n application medium chamber

L running direction

S overall coating

Claims

claims

1 . Method for applying application medium, in particular coating color, to the surface of a moving paper or board web in order to render it suitable, for example, for ink-jet printing or flexographic printing, using cationically and anionically adjusted application medium,

characterized in that

a base layer (5b, 5c) consisting of an anionically adjusted application medium (5), and a cover layer (6b, 6c) consisting of a cationically adjusted application medium (6) successively on the surface of the paper or board web (1) or is applied to the same side of the web.

2. The method according to claim 1,

characterized in that

between the base layer (5b, 5c) and cover layer (6b, 6c) an intermediate layer (9) consisting of gelatin or polyvinyl alcohol is applied.

3. The method according to claim 1 or 2,

characterized in that

the base layer (5b, 5c), the cover layer (6b, 6c) and the intermediate layer (9) can be applied in multiple layers.

4. The method according to at least one of the preceding claims,

characterized in that

the individual layers (5b, 5c, 6b, 6c, 9) or layers are respectively applied by means of at least one curtain applicator (3, 4, 10), from which the respective application media in the form of single-layer and / or multi-layer curtains (5a , 5d, 6a, 6d), substantially in accordance with gravity, are delivered to the paper or board web (1).

5. The method according to at least one of the preceding claims, characterized in that

the intermediate layer (9) wet in wet, i. without the use of intermediate drying, onto the base layer (5b, 5c) already on the paper web surface and also the cationic cover layer (6b, 6c) wet on wet, i. without application of an intermediate drying, on which already on the web surface located base layer (5b, 5c) or intermediate layer (9) is applied.

6. The method according to claim 4 or 5,

characterized in that

on a base anionic double layer (5c) a single-layer, cationic top layer (6b) is applied. (Fig.2)

7. The method according to claim 4 or 5,

characterized in that

onto a monolayer anionic base layer (5b), to which an intermediate layer (9) is applied, a single-layer cationic cover layer (6b) is placed over it. (Fig.2)

8. The method according to claim 4 or 5,

characterized in that

on an anionic double layer (5c), a cationic double layer (6c) is applied. (Fig.3)

9. The method according to at least one of the preceding claims,

characterized in that

for the application of the individual layers (5b, 5c, 6a, 6b, 6c, 9) curtain applicators in the form of curtain slot dies or slot dies (3, 4) and / or per se known slide dies (10) can be used.

10. The method according to at least one of the preceding claims, characterized in that

the coating weight of the anionic base layer (5b, 5c) is higher than the coating weight of the cationic coating layer (6b, 6c).

1 1. Method according to claim 10,

characterized in that

the anionic base layer (5b, 5c) in an amount or in a coating weight of 2 to 20 g / m ² , preferably 2 to 18 g / m ² and the cationic top layer (6b, 6c) in an amount or in a coating weight from 2 to 18 g / m ² , preferably 1 to 10 g / m ^{2 is} applied.

12. The method according to at least one of the preceding claims,

characterized in that

the solids content of the cationic top layer (6b, 6c) is lower than that of the anionic bottom layer, ie the base layer (5b, 5c).

13. The method according to claim 12,

characterized in that

the solids content of the cationic top layer (6b, 6c) is about 25 to 70%, preferably 15 to 35%, and the solids content of the anionic base layer (5b, 5c) is about 30 to 70%, preferably 55 to 65%.