EP1964970A2 - Method for producing a coated length of paper, cardboard or other fibre sheet - Google Patents

Abstract

Production method involves forming a web from a fibrous material mixture with a headbox (2) and a wire section (3). one of the web sides (7a,7b) is provided with doubly medium and in indirect way with another medium. The web side is provided with a film line or a pre-coating (11a) in a film coating unit (10), and with another film line or cover line (13a) in another film coating unit (12). A ratio of the coat weight of the former line (11b) is stopped to the later line (13b), and 40-55 g/m 2>coat weight is obtained. A surface-related mass of the web is obtained between 90-150 g/m 2>. An independent claim is also included for a machine for producing a coated paper, cardboard or other fibrous material webs.

Description

• Bahnbildung aus einem Faserstoffgemisch mit einem Stoffauflauf und einer Siebpartie, Entwässerung in einer Pressenpartie, Vortrocknung, um die gebildete Faserstoffbahn zumindest bis auf einen Restfeuchtegehalt zu trocknen, mehrfache Beschichtung wenigstens einer Bahnseite, Nachtrocknung und Aufrollung der Bahn.

The invention relates to a method for producing a coated paper, board or other fibrous web in a web-making machine, comprising the following steps:

• Web formation from a pulp mixture with a headbox and a wire section, dewatering in a press section, predrying to dry the formed fibrous web at least to a residual moisture content, multiple coating at least one side of the web, post-drying and reeling of the web.

Such a method is known in practice.

As a precoat in each case one film coat is applied with a film applicator in one of the known methods on both sides of the web. This is done with known glue or film presses or sold by the company of the applicant Speedsizern or Speedcoatern. So far, a so-called Bladecoater, ie a blade coater was used for the top coat.
The disadvantage is that due to the existing blade are often on or tears of the web and thus poor runnability (web running properties) are recorded.

If a wood-free paper is to be painted, which is to be used for high-quality magazines, it is necessary to meet special requirements in terms of gloss. These would be feasible with said Bladecoater, but only at the expense of poor runnability.

At present, the coating is also only at the expense of complicated and long web tracks.

The object of the invention is therefore to provide an improved process for the production of coated papers, in particular wood-free papers, which does not have the disadvantages mentioned.

The object of the invention is achieved by a method according to the characterizing part of claim 1.

According to the invention, at least one side of the web is provided twice and indirectly with a coating medium, one web side being provided with a first film coat as precoat in a first film coating unit and a second film coat as top coat in a second film coating unit, wherein a ratio of the line weight of the first line to the second line (ie precoating the cover line on a web page) in the order of about 1.3 to 1.0 and a total stroke weight between 30 and 55g / m ² set, and a basis weight (FbM) of Trajectory between 70 and 150 g / m ^{2 is} achieved.

This is possible for the first time on a relatively short railway. The process is characterized by optimum runnability. The track shows a high quality.

• Offset glänzend: 75°- Glanz; gemäß Tappi- Norm: >72 %. Die verbliebene Rauhigkeit betrug nach PPS- S10: ca. 1,5 µm. Im Vergleich dazu betrug die Rauhigkeit bei Film/Blade- gestrichenen Papieren gemäß dem Stand der Technik ca. 1µm);
• Offset satin: 72°- Glanz; gemäß Tappi- Norm: ca.40 %. Die verbliebene Rauhigkeit betrug nach PPS- S10: ca. 3 µm. Im Vergleich dazu betrug die Rauhigkeit bei Film/Blade- gestrichenen Papieren gemäß dem Stand der Technik ca. 2 µm.

As a quality feature were achieved:

• Offset glossy: 75 ° - gloss; according to Tappi norm:> 72%. The residual roughness according to PPS-S10 was approx. 1.5 μm. In comparison, the roughness in film / bladed coated papers according to the prior art was about 1 μm);
• Offset satin: 72 ° - gloss; according to Tappi standard: approx. 40%. The residual roughness according to PPS-S10 was about 3 μm. In comparison, the roughness in film / bladed coated papers according to the prior art was about 2 μm.

In certain cases, it may be sufficient and shorten the process or reduce its cost if the other side of the web is simply coated, that is, provided with a single stroke.

This can be done in different ways. Thus, this other web side can either be directly fed with a knife coater, i. A blade applicator or Bladecoater or indirectly with a film coating unit (film / size press, Speedcoater / Speedsizer) are coated.

An alternative, however, which is preferred because better quality is achieved, is that the other side of the web is also double-coated by applying both the first and second lines, ie, a topcoat and topcoat, indirectly with film coating units, respectively become.

An alternative to the double coating of the other or second side of the sheet may be that the first line, ie the precoat, is applied in a direct manner with a knife coater and the second line, ie the top line, in an indirect manner with a film coating unit.

Another variant of the double coating of the other side of the web can consist of the reverse order of the types of coating. Accordingly, the first stroke, i. the precoat indirectly with a film coater and the second bar, i. the top coat, applied with a doctor blade (ie a blade applicator or Bladecoater) directly to the relevant web page.

By indirect order is meant that the application medium is applied by means of a coating unit to an applicator roll from which the liquid to pasty medium is then transferred to a web side of the web to be coated. Such an applicator roll forms with a second such applicator roll a nip, which passes through the web to be coated. At the same time, both web pages receive the order medium in this nip. If, for example, only one side of the web is to be coated, the applicator assigned to the other web side is left unused and, as a rule, swung away.

In the case of this indirect application, so-called misting occurs at high web speeds or machine speeds, ie color misting after the nip, which should be prevented as far as possible.
Therefore, it is provided within the scope of the invention that in each case such applicator rolls are used which have a large diameter. The ideal diameters have proven to be more than 1300 mm in size.

Because of the high applied coating weight, the web expands strongly. Therefore, a short residence time in the nip is beneficial for runnability.
In this context, harder applicator rollers are advantageous. As a roll cover material therefore rubber is proposed with a hardness of at least 50 P & J (after Pussey and Jones).

According to the invention, it is also provided that the web is dried between the precoat and the top coat. For a contactless drying, consisting of air and infrared dryers is sufficient. One of the dryers can additionally be designed as a deflection device (Airturn).

With regard to quality and runnability in the manufacturing, i. Web-making machine, it is advantageous if the web is pre-smoothed before the first stroke

In addition, it is expedient if at least the first line, ie the precoat is porous and is applied to the at least one web page a coating color, in which up to 50 parts of kaolin are mixed with an aspect ratio> 5, preferably> 10. The kaolin used is in platelet form and is approximately hexagonal in shape. The aspect ratio is the ratio between the length of the platelets and the thickness. This means that the primer is given a certain porosity by the admixing of the platelet-shaped kaolin, so that the top coat can be applied by means of a film coating method without misting, ie without color fogging

An alternative to the coating color may be that in the case of coating colors containing calcium carbonate, 10 to 30 parts of talc having an aspect ratio> 5, preferably> 10, are admixed.

Another possibility may be that, at least for the first line, ie for the precoat, on the at least one web page a coating color is used which contains pigments with steep or narrow particle size distribution. Due to separated coarse and fine fractions gives a tighter, ie steeper distribution.
Such pigments are known, for example, under the trade name Covercarb 60 or Covercarb 75.

It is also possible that, at least for the precoat on at least one web page, a coating color is used which contains kaolin with an aspect ratio> 5, preferably> 10 as the main component, in particular between 50 and 70 parts.

To achieve the high coating weight initially described, it is advantageous if the solids content of the coating color is more than 63%, preferably more than 65%.
However, the maximum amount of solids that can be processed depends essentially on the pigment composition and other coating color components.

The coated web can finally be smoothed. This can be done with different types of calenders. It is possible that either each side of the web is treated individually and successively with a one-nip calender or both sides of the web are smoothed with a multi-pin calender.

Decisive for the selection of the calender type concerned is the required quality of the paper, ie whether a very glossy or rather matt glossy paper is needed.

It should be added that the speed of the web-making machine is longer than 800 m / min, in particular more than 1200m / min, preferably more than 1600 m / min.

Advantages of the method according to the invention are the low investment costs, short possible machine lengths, reduction of web tearing and tearing tendency as well as good coverage and print quality.

Since a double film coating on at least one web side is preferred instead of the previous final bladder coating, the number of wear parts is reduced and therefore the machine efficiency is increased. There are no Rakelelements- or Blade- or change blade to make.

The object of the invention is also achieved with a device according to claim 20.

Accordingly, it is provided that for the double coating of at least one side of a web indirectly provided a first film coating unit for a primer and a second film coating unit for a cover coat, wherein the second film coating unit of the first film coating unit is arranged in the path of the web and wherein the ratio of the applied coating weights the two film coating units is about 1.3 to 1.0 and a total coating weight between 30 and 55 g / m ² and a basis weight (FbM) of the web between 70 and 150 g / m ^{2 is} achievable.

Further expedient refinement possibilities of the device according to the invention can be found in further subclaims, the content of which should not be dealt with further here, because their function and significance result from the method described above.

In the context of the invention, a paper according to claim 31 is finally proposed, which is produced with the features described in the method claims 1 to 19.

Based on embodiments, the invention will be explained in more detail.

• Figur 1 : in schematischer Darstellung eine Gesamtmaschine zur Herstellung einer beschichteten Faserstoffbahn in der das erfindungsgemäße Verfahren stattfindet,
• Figuren 2 und 3 : verschiedene Varianten der gegenüber der in Fig.1 gezeigten Variante veränderten Verfahrensführung,
• Figuren 4a bis 4d : verschiedene Varianten des Aufbringens der einzelnen Auftragsschichten mit entsprechenden Auftragseinheiten,

Show it:

• FIG. 1 in a schematic representation of an overall machine for producing a coated fibrous web in which the method according to the invention takes place,
• FIGS. 2 and 3 : different variants of the opposite in Fig.1 variant shown modified procedure,
• FIGS. 4a to 4d : different variants of the application of the individual order layers with corresponding order units,

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

In the FIG. 1 is within a web-making machine 1, the known process steps or machine configurations only roughly schematically represented as a box and mean:

Web formation from a pulp mixture, with a headbox 2 and a wire section 3, dewatering in a press section 4, drying in a drying section 6 consisting of drying cylinders 5 in order to dry the formed web 7 at least to a residual moisture content.

Roughly it is shown that the web 7 is then pre-smoothed with a Vorglätteinrichtung 8, which may be a Hartnip- or a Softnipkalander.

Subsequently, the web passes over a paper guide roller 9 to a first film coating unit 10, consisting of two together forming a Nip N applicator rollers 10.1 for a first indirectly applied film or primer 11a and 11b on both web pages 7a and 7b. Everyone is coating Application roller 10.1 assigned a coating unit 10.2, which applies the application medium on the surface of the applicator rolls. The application medium is then dispensed simultaneously in the nip N to the web side 7a and 7b.

For double coating of at least one of the web sides 7a or 7b in an indirect manner, a second film coating unit 12, which has the same structure as the first one, is provided for a top coat 13a and / or 13b. This second film coating unit 12, consisting of applicator rollers 12.1, each associated with a coating unit 12.2, the first film coating unit 10 in the path (see arrow) of the web 7 downstream.

The ratio of the coating weights applied with both film coating units 10 and 12, or rather the ratio between the precoat 11a and top coat 13a or 11 bundle 13b, is about 1.3 to 1.0. Overall, a line weight between 30 and 55 g / m ² and a basis weight (FbM) of the total web 7 between 70 and 150 g / m ^{2 is} achieved.

For the coating of the web page 7b, ie for the pre-coat 11b, a doctor blade applicator or a device called a blade applicator or a blade coater would also be possible. This possibility is not in the FIG. 1 shown.

Likewise, for the double coating of the web page 7b for the pre-coat 11b, as shown, the first film coating unit 10 and for the top coat 13b said Bladecoater could be used. This possibility is for the sake of simplicity and because the components are known in principle, not in the FIG. 1 shown.

The described applicator rollers 10.1 and 12.1 all have the same diameter. The diameter should be more than 1300 mm. It is advantageous if a relatively hard rubber coating of at least 50 P & J is used (even for smaller diameters than 1300 mm). This will be the dreaded misting avoided and the web and components of the web-making machine 1 kept clean.

Between the pre-coat 11a and the top coat 13a, or between primer 11b and top coat 13b, a contactless web guide unit 14 is provided. It consists on the web page 7a of a so-called Airturn 14.1, which on the basis of its blown air the freshly painted web 7 continues on an air cushion or a thin layer of air and also deflects. The web guide unit 14 also consists of downstream, above the web page 7a and below the web page 7b arranged infrared and / or air dryers 14.2, with which a predrying is performed.

From the FIG. 1 can still be seen that the second film coating unit 12, a second contactless acting after-drying unit 15, again consisting of one of the web page 7a associated Airturn - here with 15.1- and both web pages 7a and 7b associated infrared and / or air dryers 15.2.
It is followed by an existing drying cylinders after drying section 16, which is shown for reasons of simplification only in the form of a narrow box. Subsequently, the web is wound up with a reel 17.

To achieve particularly high quality parameters of the web, a Nachglätteinrichtung 18 is still provided. For this, either one-nip calender or a multi-pin calender or even a combined design into consideration.

In FIG. 1 This smoothing or Satinage 18 is offline, so is carried out spatially separated from the papermaking. Therefore, this device is in the FIG. 1 stand alone in the upper right position.

FIG. 2 shows in principle the same procedure and the machine parts, as in FIG. 1 , however, here the smoother or calendering takes place online. Therefore, the main machine parts or devices are shown in this figure and only for orientation and provided with reference numerals.

FIG. 3 also shows the same procedure and the machine parts as in FIG. 1 However, the steps 2 to 8, so the paper making, starting from the headbox to Vorglättung offline. Thereafter, the web is rolled up with a reel 19, to be subsequently unwound again with a dispenser 20. Separated from the previous method, the now unrolled web 7 is as in FIG. 1 described twice coated with the film coating units 10 and 12. The final smoothing (or satinage) 18 takes place in the example chosen, as in FIG. 1 offline, but could also (not drawn) online, as in the FIG. 2 shown variant.

With the method according to the invention, a total of a maximum of four lines or application layers are applied to the web running in the direction L.
How that is done is in the FIGS. 4a to 4d shown.

FIG. 4a shows a first variant in which both sides of the web 7a and 7b are coated at the same time. With a first film coating unit 10 and a second film coating unit 12, each consisting of two applicator rollers 10.1 and 12.1 forming a nip, the web is coated twice simultaneously. For this purpose, each applicator roll 10.1 or 12.1 of a film coating unit 10 or 12 is associated with a coating unit 10.2 or 12.2, whereby on the top of the web 7a a precoat 11a and a top coat 13a is formed. At the same time, a precoat 11b and a top coat 13b are applied to the underside 7b of the web 7, thus achieving a total of four application layers or lines.

FIG. 4b shows that the one web side 7a, this is the top of the web as at FIG. 4a coated twice and indirectly with an applicator roller 10.1 and 12.1. Although the second variant of the coating shown here indicates that the other side of the sheet 7b, which represents the underside, is likewise double-coated, only the first line or the pre-coat 11b is applied here in an indirect manner to the film coating unit 10. The second stroke or the top coat 13b is here with a doctor blade (Blade applicator or Bladecoater) 21 applied in a direct manner.

Figure 4c shows in a third variant, carried out in reverse order coating the web page 7b. Thus, this web page 7b is also double-coated by first applying a pre-coat 11b in a direct manner with a knife coater 21. This is followed by the second line, or the top coat 13b in an indirect manner with a film coating unit 12.

FIG. 4d shows that the web page 7b is only coated easily, that is provided with only a single stroke. Therefore, this line is given as 11b = 13b.
In this case, two alternatives are possible, namely the coating is carried out in a direct manner with the doctor blade coating device 21 or indirectly with the film coating unit 10 or 12. Since these mentioned, various alternatives are possible in the FIG. 4d the possible order facilities are shown in brackets.

LIST OF REFERENCE NUMBERS

1

Railway manufacturing machine

2

headbox

3

Wire section

4

press section

5

drying cylinders

6

drying section

7

train

8th

Vorglätteinrichtung

9

paper roll

10

first film coating unit

10.1

applicator roll

10.2

application unit

11 a

Pre-stroke or first stroke on one side of the web

11 b

Primary stroke or first stroke on the other side of the web

12

second film coating unit

12.1

applicator roll

12.2

application unit

13a

Top coat or second line on one side of the sheet

13b

Top coat or second line on the other side of the sheet

14

contactless web guide unit

14.1

Airturn

14.2

Air and / or infrared dryer

15

contactless web drying unit

15.1

Airturn

15.2

Air and / or infrared dryer

16

Afterdryers

17

retractor

18

Nachglätteinrichtung

19

retractor

20

dispensers

21

Blade coater

L

direction

N

nip

Claims (31)

Method for producing a coated paper, board or other fibrous web (7) in a web-making machine (1), comprising the following steps: Web formation from a fiber mixture with a headbox (2) and a wire section (3), - dewatering in a press section (4), Predrying (5, 6) to dry the formed web (7) at least to a residual moisture content, multiple coating of at least one web side (7a, 7b), - Post-drying (14, 16) and Curling (17) of the web (7), characterized in that
at least one of the web sides (7a, 7b) is provided with an application medium in duplicate and in an indirect manner, with one web side (7a, 7b) having a first film coat (11a) in a first film coating unit (10) and with a second film coat Film coat or top coat (13a) is provided in a second film coating unit (12), wherein a ratio of the coating weight of the first bar (11a, 11b) to the second bar (13a, 13b) of 1.3 to 1.0 and a total stroke weight between 40 and 55 g / m ^{2 is} set, and a basis weight (FbM) of the web (7) between 90 and 150 g / m ^{2 is} achieved. Method according to claim 1,
characterized in that
the other side of the web (7b) is simply coated, ie provided with a single line. Method according to claim 2,
characterized in that
the other web side (7b) is directly coated with a doctor blade (21) or indirectly with a film coating unit (10). Method according to claim 1,
characterized in that
the other side of the sheet (7b) is also double-coated by applying both the first coat (11b) and the second coat (13b) indirectly with a film coating unit (10; 12), respectively. Method according to claim 1,
characterized in that
the other side of the sheet (7b) is also double-coated, in which the first bar or line (11b) is directly coated with a doctor blade applicator (21) and the second bar or top coat (13b) is applied indirectly with a film coating unit (11b). 12) are applied. Method according to claim 1,
characterized in that
the other side of the sheet (7b) is also double-coated by exposing the first line (11b) indirectly to a film coating unit (10) and the second line (13b) directly to a blade coater (21st ) are applied. Method according to at least one of claims 1 to 6,
characterized in that
the precursors (11a, 11b) and / or cover streaks (13a, 13b) to be applied indirectly on both web sides (7a, 7b) in each case simultaneously with applicator rollers (10.1, 12.1), to each of which a coating unit (10.2, 12.2) is assigned, be applied. Method according to at least one of claims 1 to 7,
characterized in that
in the indirectly applied lines for primer (11a, 11b) and top coat (13a, 13b) each application rollers (10.1, 12.1) are used, which have a diameter of more than 1300 mm. Method according to claim 7 or 8,
characterized in that
For the application rollers (10.1; 12.1), hard coverings, in particular of rubber with at least 50 P & J are used. Method according to at least one of claims 1 to 9,
characterized in that
between two lines, ie between the precoat (11a, 11b) and top coat (13a, 13b), the web (7) is dried. Method according to at least one of claims 1 to 10,
characterized in that
the web (7) is pre-smoothed before the first line or the pre-coat (11a, 11b) in a pre-smoothening device (8). Method according to at least one of claims 1 to 11,
characterized in that
at least for the first line or the precoat (11a, 11b) on the at least one web page (7a; 7b) a coating color is used, in which up to 50 parts of kaolin with an aspect ratio> 5, preferably> 10 are mixed. Method according to at least one of the preceding claims,
characterized in that
for coating colors containing calcium carbonate, 10 to 30 parts of talc with an Aspect Ratio> 5, preferably> 10 are admixed. Method according to at least one of the preceding claims,
characterized in that
at least for the first line or the pre-coat (11a; 11b) on the at least one web side (7a; 7b) a coating color is used which contains pigments with a steep particle size distribution. Method according to at least one of the preceding claims,
characterized in that
at least for the first line or the pre-coat (11a, 11b) on the at least one web page (7a, 7b) a coating color is used, the main component, in particular between 50 and 70 parts of kaolin with an aspect ratio> 5, preferably> 10 be mixed. Method according to at least one of the preceding claims,
characterized in that
the solids content of the coating color is more than 63%, preferably more than 65%. Method according to at least one of the preceding claims,
characterized in that
the coated web (7) is finally smoothed in a post-smoothing device (18), such that either each web side (7a; 7b) is treated individually and successively with one-nip calenders or the web sides with a multi-nip calender. Method according to at least one of the preceding claims,
characterized in that
it is used in particular for coating a wood-free web (7). Method according to at least one of the preceding claims,
characterized in that
the speed of the web-making machine (1) is> 800 m / min, in particular> 1200 m / min, preferably> 1600 m / min. Machine (1) for producing a coated paper, board or other fibrous web (7), comprising a headbox (2) and a wire section (3), a press section (4), a predrying (5, 6), means for multiple Coating at least one web side (7a), after-drying (15, 16) and reeling (17) of the web (1),
characterized in that
for the double coating of at least one web side (7a) is indirectly provided a first film coating unit (10) for a precoat (11a) and a second film coating unit (12) for a top coat (13a), the second film coating unit (12) of the first Film coating unit (10) in the path of the web (7) is arranged downstream and wherein the two film coating units (10, 12) are adapted to apply a ratio of the applied coating weights of about 1.3 to 1.0 and a total weight of between 40 and 55g / m ² and a basis weight (FbM) of the web (7) between 90 and 150 g / m ² can be achieved. Machine according to claim 20,
characterized in that
for simple coating of the other side of the web (7b) directly a doctor blade coating device (21) or for indirect coating a film coating unit (10) is provided. Machine according to claim 20,
characterized in that
for double coating the other web side (7b), a first film coating unit (10) for a pre-coat (11b) and a second film coating unit (12) for a top coat (13b) in an indirect manner is provided, wherein the second film coating unit (12) of the first film coating unit (10) in the path of the web (7) is arranged downstream. Machine according to claim 20,
characterized in that
for the double coating of the other web side (7b) for the precoat (11b) a doctor blade coating device (21) and for the top coat (13b) a film coating unit (12) is provided. Machine according to claim 20,
characterized in that
for double coating of the other side of the web (7b) for the precoat (11b) a film coating unit (10) and for the top coat (13b) a doctor blade coating device (21) is provided. Machine according to at least one of claims 20 to 24,
characterized in that
the film coating units (10, 12) for the precursors (11a, 11b) and cover slips (13a, 13b) to be applied in an indirect manner on both sides of the web (7a, 7b) each have two application rollers (10.1; 12.1), to each of which an application unit (10.2, 12.2) is assigned. Machine according to at least one of the preceding claims,
characterized in that
Application rollers (10.1, 12.1) are provided, which have a diameter of more than 1300 mm. Machine according to claim 25 or 26,
characterized in that
the application rollers (10.1; 12.1) have hard coverings, in particular consisting of rubber with a roller hardness of at least 50 P & J. Machine according to at least one of the preceding claims,
characterized in that
between the pre-coat (11a, 11b) and the top coat (13a, 13b) is provided a non-contact web guide unit (14). Machine according to at least one of the preceding claims,
characterized in that
a smoothing device (8) for pre-smoothing the web (7) is provided in front of the coating devices (10; 12). Machine according to at least one of the preceding claims,
characterized in that
the after the top coat (13) following night drying device (15) is followed by a Nachglätteinrichtung (18), such that for this either one-nip calender or a multi-pin calender is or are provided. Wood-free paper,
characterized in that
it has been produced by a process according to claims 1 to 19, coated on both sides and double-coated at least on one side of the web (7a or / and 7b).

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