DE102007026617A1 - Method for applying a double layer - Google Patents

Abstract

Double coating application involves applying pre-coating (3) and deck line (5) with film spreading units (2,4), where an applying medium (M1) is used for pre-coating, which contains platelet like pigments.

Description

The Invention relates to a method for applying a double layer, consisting of primer and top coat, with a liquid until pasty Application medium, in particular aqueous Pigment suspension on at least one side of a running paper, Cardboard or other fibrous web in their production and / or Finishing.

at the manufacture or processing of paper marked with a double line, So priming and top coat were to be treated, at least the Cover coat previously applied with blade coaters (blade coaters). These coaters work with a squeegee element (blade), with which in surplus Applied application medium brought to the desired coating weight and thereby evened or is leveled. These coaters are particularly suitable for higher machine and web speeds have runnability. In addition, is for Each paper page to provide its own order aggregate.

It was therefore also attempted to apply the cover coat with so-called film applicators, wherein two applicator rollers together form a nip (press nip) through which the fibrous web to be coated passes and where at least one of the applicator rolls transfers the application medium applied to it in the nip to the fibrous web. Although in this type of job, the running efficiency is better than blade blending, but the applied bar weights in g / m ² are greatly limited in their magnitude or amount, because when deducting the coated fibrous web from the nip a so-called, undesirable Misting occurs. This is characterized by spraying application medium into the environment, to machine parts, but also to the produced and / or to be refined fibrous web, which ultimately suffers the job quality. The higher the line weights and the higher the speed of the fibrous web, the more intense the misting occurs. For double-coated webs, this negative effect is particularly pronounced.

Misting but also occurs in a single stroke.

The Occurrence of misting depends also strong on the absorption capacity the fibrous web from. In the case of the top coat, this absorption capacity is due to the preprint significantly reduced, so it is here in particular Dimensions too Misting can come.

Of the The invention is therefore based on the object of specifying a method which avoids the disadvantages of the prior art.

According to the invention Task according to the mark of claim 1 solved by that for the applied to the fibrous web bilayer, so primer and top coat, each a known film applicator for Application of the coating medium used in an indirect manner is, where for the pre-coat such a coating medium is to be used, the platelet-shaped pigments contains. This is the case, for example, with kaolin. Is appropriate it if the job medium for the precursor is an aspect ratio (ie length to thickness ratio of a Platelet) of> 5, preferably> 15.

It is the merit of the inventor to have recognized that the primer strongly favors the occurrence of misting in the top coat. Will now be a special application medium, ie the platelet-shaped pigments containing order medium, for used the precursor leaves Misting in the coverline in a surprise Reduce or even eliminate completely.

By Adding according to the invention of kaolin (also talcum is possible) to the usual Based on calcium carbonate primer, the structure of the precursor can be so that the precursor becomes more open and its absorption capacity increases. This allows the subsequent and laying on the primer Drain the top coat better. So it is possible for the first time to use high line weights or order quantities without it to the undesirable Misting is coming.

Misting is known to occur at high machine speeds, when in the nip, the coating color transferred to the fibrous web, d. H. the job medium is not enough can be immobilized.

This is especially the case when the order quantity is high. In addition to the properties of the coating itself, plays here the absorption capacity of the raw fiber or raw paper or just as in the case of a Pre- and top coat, the absorbency of the pre-coat a crucial Role.

Of the The inventor has also found that when double-film painting the prepainted web has only a low absorption capacity. The cause is the relatively dense, compact and impermeable precoat, in the form of mostly ground, not too fine calcium carbonate with natural, wide grain size distribution used as a pigment, in particular for the achievement of opacity and whiteness is viewed. Therefore, especially when applying the top coat, even with low order volume the dreaded Misting on.

With the method according to the invention, it is now possible to apply both the precoat, as well as the top coat without misting, each with a film applicator, with high order quantities or line weights are possible, such that for the top coat more than 6 g / m ² , in particular 8 g / m ² , preferably more than 10 g / m ^{2 are} applied.

In order to the runnability in the manufacturing or finishing machine improves and also the degree of coverage of the fibrous web with the application medium, which affects the later Printability has a positive effect.

Furthermore can the inventive method at a high web speed during manufacture and / or Finishing the fibrous web to be performed. This railway or Machine speed can now exceed 1000 m / min, in particular more than 1200 m / min and preferably more than 1300 m / min, whereby the economic efficiency of the procedure or the railway production is particularly high.

It should be mentioned be that following the double coating according to the invention and subsequent Drying made a calendering of the fibrous web and / or other coating operations can be. That depends on in which state or in which quality the raw paper web is present. The goal is a complete one and even coverage often up to over 10 m wide track.

Further advantageous design options the method according to the invention result from further claims.

following the invention will be explained in more detail using an exemplary embodiment.

It shows the 1 in a rough schematic representation of the principle of the method according to the invention.

In 1 is shown to be a fibrous web 1 , which is already pre-dried with a double layer D is provided.

This is a first Filmauftragswerk 2 to achieve a first coating layer or a primer 3 and a second film commission 4 which is the commissioned work 2 in the path L of the fibrous web 1 is subordinate and the achievement of a second coating layer or a top coat 5 serves, exists.

The first film order 2 consists of two applicator rolls forming a nip N1 with each other 2.1 and 2.2 each one a task aggregate 2.3 and 2.4 assigned. With the application aggregates 2.3 and 2.4 First, the application medium M1 is applied to the surface of the two applicator rollers and then in Nip N1 at the same time both sides of the web 1a and 1b (with simultaneous double-sided coating) transferred. That on the web page 1a and train side 1b Applied application medium M1 is shown in dashed lines. The second film order 4 is identical to the first film order work 2 , which is very advantageous in terms of web guide, spare parts inventory, space requirements, maintenance, installation, etc. Accordingly, the application rollers with 4.1 and 4.2 and the associated application aggregates 4.3 and 4.4 , which denotes Nip with N2 and the application medium with M2.

The top coat 5 is marked with a dotted line. This example is only one-sided on the web page 1a applied, which is why the application aggregate 4.4 from the applicator roll 4.1 was swung.

For the primer 3 , in the example, simultaneously on both sides of the web 1a and 1b is applied (on web page 1b this forms at the same time the finished line), the following pigment composition is chosen in the example:
90 parts of Hydrocarb 60 (calcium carbonate) and 10 parts of Capim NP (kaolin), the kaolin having an aspect ratio (width / thickness ratio) of 20.

The The rest of the coating M1 form latex and thickener.

1

Fibrous web

1a

web side

1b

web side

2

first Film applicator

2.1

applicator roll

2.2

applicator roll

2.3

application unit

2.4

application unit

3

primer

4

second Film applicator

4.1

applicator roll

4.2

applicator roll

4.3

application unit

4.4

application unit

5

topcoat

D

bilayer

L

path

M1

application medium

M2

application medium

N1

nip

N2

nip

Claims (6)

Method for applying a double layer, consisting of primer and top coat, with a liquid to pasty application medium, in particular aqueous pigment suspension on at least one side of a running paper, cardboard or other fibrous web in their production and / or finishing, characterized in that the double layer , ie primer ( 3 ) and top coat ( 5 ) each with a film applicator ( 2 . 4 ) are applied, wherein for the primer ( 3 ) a coating medium (M1) is used which contains platelet-shaped pigments. Method according to claim 1, characterized in that that as the application medium (M1) such is used, which an aspect ratio (length to thickness ratio a slide) from bigger than 5, preferably greater than 15 has. Method according to claim 1 or 2, characterized in that for the top coat ( 5 ) equal to or more than 6 g / m ² , in particular> 8 g / m ² , preferably> 10 g / m ² application medium (M2) are applied. Method according to one of claims 1 to 3, characterized in that the fibrous web ( 1 ) is moved during application of the double layer (D) at a speed of more than 1000 m / min, in particular more than 1200 m / min, preferably more than 1300 m / min by a machine for producing and / or refining the fibrous web. Method according to one of claims 1 to 4, characterized in that the primer ( 3 ) and the top coat ( 5 ) simultaneously on both sides of the web ( 1a . 1b ) are applied. Method according to one of claims 1 to 4, characterized in that the primer ( 3 ) simultaneously on both sides of the web ( 1a . 1b ) and the top coat ( 5 ) is applied only on one of the two web pages.