EP2160496B1 - Method for producing a mainly wood-free coated paper web - Google Patents

Abstract

The present invention provides a method and device for the efficient production of a substantially wood free coated web. In particular, a method for producing an at least substantially wood free coated web includes the application of a double coating on at least one side of the web, whereby the last coating application occurs by means of a contactless coating process.

Description

The invention relates to a method for producing a substantially wood-free coated paper web containing a fiber content of more than 55% pulp fibers, wherein applied to at least one web page a double line and thereby the last line application by means of a contactless application method in the form of a curtain applicator (32 ) is applied and wherein a precoat is applied by means of a film applicator (18,24) or a contactless application method.

• Gapformer
• Pressenpartie
• Vortrockenpartie Vorkalander mit Softnip, hartem Nip oder in Bahnlaufrichtung verlängertem Breitnip
• MSP-Presse (MSP = metered size press) zum Auftragen von Leim oder zur Vorbeschichtung
• Rakelstreichvorrichtung (blade coater)
• Rakelstreichvorrichtung (blade coater)
• Online- oder Offline-Mehrfachnipkalander für Glanzgrade

In the hitherto known methods for producing a wood-free or approximately wood-free double-coated paper web at higher speeds above 1400 m / min, the following stages are provided successively:

• Gapformer
• press section
• Pre-drying section Pre-calender with soft nip, hard nip or extended nip in the direction of web travel
• MSP press (MSP = metered size press) for applying glue or pre-coating
• Blade coater
• Blade coater
• Online or offline multiple nip calenders for gloss levels

The main disadvantage of the previously known concepts is that the overall efficiency (time and material) is considerably reduced by the doctor blade coating units. Thus, in a conventional off-line calendering process, the time lost in the area of the two blade coaters is about 4 to about 7%. Due to this substantial loss of time, the maximum speed potential of the paper machine can not be exhausted.

• NBKP (needle bleached kraft pulp, Langfaser)
• LBKP (leaf bleached kraft pulp, Kurzfaser)
• BCTMP SF (bleached chemithermomechanical pulp, short fibre)
• Füllstoff

Currently, the furnish for the woodfree or nearly woodfree dual level grades comprises:

• NBKP (needle bleached kraft pulp, long fiber)
• LBKP (leaf bleached kraft pulp, short fiber)
• BCTMP SF (bleached chemithermomechanical pulp, short fiber)
• filler

The fiber content of the substance input consists of at least 85% pulp fibers (NBKP (needle bleached kraft pulp, long fiber), LBKP (leaf bleached kraft pulp, short fiber)).

At one of the WO 2005/071158 A1 known method for producing a wood-free coated matte or semi-matt paper web, the paper web is painted after Vorkalandrierung at least one means for applying liquid or pasty application medium at least on one side and then dried by means of at least one drying device. In this case, the paper web is simply painted on a first side before its Vorkalandrierung by means of a film or a curtain applicator.

Furthermore, from the WO 02/103109 A1 a method for producing a LWC (light weight coated) printing paper, in which the paper is coated on both sides by means of film coating or contactless coating method simply.

The invention has for its object to provide an improved method of the type mentioned, with which the time efficiency potential of the papermaking process is significantly improved for a double line on at least one web page.

With regard to the method, this object is achieved by the features of claim 1. There is thus provided a method for producing an at least substantially wood-free coated paper web, in which the fiber content of the paper web consists of less than 75% pulp fibers and the paper web is produced with a filler content> 10% with a basis weight <90 g / m ² or a filler content> 12% with a basis weight ≥ 90 g / m ² .

An important aspect of the invention is the avoidance of direct application coating application systems which operate with stationary squeegee elements such as, for example, so-called blade coaters. The resulting load on the web due to the relative speed between doctor and web increases the number of breaks. Therefore, according to the invention, at least the last application device operates without contact.

Advantageous embodiments and further developments of the invention are specified in the subclaims.

According to a further embodiment of the invention, the fiber content of the substance input of less than 60% pulp fibers (NBKP (needle bleached kraft pulp, long fiber), LBKP (leaf bleached kraft pulp, short fiber)) exist. The remainder may consist of wood-containing fibers (e.g., groundwood, BCTMP-SF (bleached chemothermomechanical pulp, short fiber)). A paper web from this substance entry, which contains a proportion of pulp fibers of more than 55%, is hereinafter referred to as "essentially wood-free paper web". Compared to the prior art can be reduced by the inventive solution, the entry of expensive fibers, with the same or better quality of the line.

In this case, the fiber content in the paper web essentially corresponds to that of the substance input, whereby differences in the fiber content between the substance input and the paper web can arise due to the retention.

According to the invention, the precoat is applied by means of a film applicator or by means of a contactless application method.

In this case, it is particularly advantageous if the application is applied by means of a surface moving with the web, as is the case, for example, with a film applicator. This reduces the stress on the web compared to the blade application process.

If, after a predrying of the paper web, a color coat is applied as a precoat, the paper web is expediently passed through a Vorglättwerk before the application of the color precoat.

On the other hand, if a glue application is applied in particular after pre-drying the paper web as a precoat, the paper web is preferably passed through a calender after application of the glue application.

Particularly advantageous is a higher consistency of the applied glue on the stroke quality of the contactless applied last stroke. According to one embodiment of the invention, the consistency may be> 12%, preferably> 15% and in particular> 20%.

It is particularly advantageous if the paper web is guided in a closed train through the press section. It is therefore provided in this case in the press section a closed web guide, in which the web is supported in particular by means of a covering and / or provided in the press felt, transfer belt, etc.

Advantageously, the paper web is guided in the press section by only one shoe press with only one nip.

According to an alternative advantageous embodiment, however, the paper web in the press section can also be guided by a plurality of shoe presses arranged one behind the other, each with a wide nip.

Preferably, the paper web is also guided by at least one calender.

In this case, the paper web can be guided, for example, by at least one calender with a soft nip which is formed between two calender rolls, of which at least one is provided with a soft plastic cover, in particular in comparison to steel rolls or chill rolls.

Alternatively or additionally, the paper web can also be guided through at least one calender with a hard nip which is formed between two calender rolls, in particular steel rolls and / or chill rolls, each of which has a hard roll surface, in particular in comparison to a plastic cover.

Alternatively or additionally, the paper web can also be passed through at least one calender, in particular shoe calender or metal belt calender, with a long nip extended in the running running direction.

With the curtain coating process, time efficiency can be improved by about 3 to about 6% compared to conventional blade coating techniques. It is assumed that the web breaks occurring in the after-dryer sections occur with the same frequency as with the doctor blade coaters.

The additional advantage associated with the curtain coating method is that even at low application weights, a significantly higher application weight coverage can be achieved. This results in a significant improvement in the ability to shift ash from the coating layer to the filler, resulting in significant cost savings for the papermaker.

Paper quality can be optimized by adequately precalendering the paper prior to application using the curtain applicator or applicator units.

The optimum quality range for the total on-line concept is the range of about 60 to about 200 g / m ² , especially in the range of about 80 to about 150 g / m ² .

The final calendering of the paper can advantageously be done online or, if necessary, offline. The main advantage of the curtain coating method compared to a conventional blade coating method is that the efficiency of calendering is much higher, while reducing the risk of deposits on the calender rolls.

The paper web produced by the process according to the invention preferably has a filler content> 12% with a basis weight <90 g / m ² or a filler content> 14% with a basis weight ≥ 90 g / m ² . Preferably, the paper web has a top coat with a coating weight ≤ 10, in particular ≤ 9 and preferably ≤ 8 g / (m ² ˙ side) at a basis weight <90 g / m ² or with a coating weight ≤ 16, in particular ≤ 14 and preferably ≤ 12 g / (m ² ˙ page) at a basis weight> 90 g / m ² on.

Fig. 1

eine schematische Darstellung einer beispielhaften Ausfüh- rungsform einer Vorrichtung zur Herstellung einer zumindest im Wesentlichen holzfreien gestrichenen Papierbahn,

Fig. 2a und 2b

eine vereinfachte schematische Teildarstellung einer weite- ren beispielhaften Ausführungsform der Vorrichtung mit ei- nem Hochleistungstrockner,

Fig. 3

eine schematische Darstellung einer zwei Vorhang- Auftragseinrichtungen umfassenden Anordnung für die Auf- tragung von Streichfarbe auf beide Bahnseiten im kontaktlo- sen Verfahren und

Fig. 4

ein Diagramm, in dem das Abdeckverhalten einer Vorhang- Auftragseinrichtung dem Abdeckverhalten einer Rakel- streichvorrichtung gegenübergestellt ist.

The invention will be explained in more detail below with reference to exemplary embodiments with reference to the drawing; in this show:

Fig. 1

1 is a schematic representation of an exemplary embodiment of a device for producing an at least substantially wood-free coated paper web,

Fig. 2a and 2b

2 is a simplified schematic partial representation of a further exemplary embodiment of the device with a high-performance dryer,

Fig. 3

a schematic representation of an arrangement comprising two curtain applicators for the application of coating color on both sides of the web in the non-contact method and

Fig. 4

a diagram in which the covering behavior of a curtain application device is opposite to the covering behavior of a doctor blade coating device.

Fig. 1 1 shows a schematic representation of an exemplary embodiment of an apparatus 10 for producing an at least substantially wood-free coated paper web with a wire section 12, a press section 14 of a pre-dryer section 16, a device 18 for applying a glue application, an after-dryer section 20, a smoothing or pre-calendering unit 22, a device 24 for applying a paint application, a drying device 26 and a reel-up 28.

As based on the Fig. 1 For example, the means 18 for applying a glue application and the means 24 for applying an application of paint can each be, for example, a film applicator.

In the area "X" after the drying device 26 and before the reel-up 28, two contactless application devices 30, 32 for double-sided application, which are each designed as a curtain application device, are preferably provided as last application devices.

The optimum quality range for the overall online concept is the range between 60 to about 200 g / m ² , in particular in the range of about 80 and 150 g / m ² .

The final calendering of the paper web can advantageously take place online or, if necessary, also offline. The advantages of a curtain coating process compared to a conventional doctor blade coating process This is because the calendering efficiency is much higher, while the risk of deposits on the calender rolls is reduced.

The device thus comprises means for applying at least one double line to at least one side of the web, wherein a curtain application device is provided for applying the last coating application.

To apply the precoat, a film applicator or a contactless applicator is provided.

After a means for predrying the paper web, which may comprise, for example, the pre-drying section 16 and the after-dryer section 20, the device 24 may be provided for applying a color pre-coat, wherein Vorglättwerk 22 is preferably provided in front of this device 24.

The device 18 for applying a glue application is arranged between the pre-drying section 16 and the after-drying section 20. The calender 22 is provided following the pre-drying section 20.

The paper web is preferably guided in a closed train through the press section 14.

The paper web can be guided in the press section by only one shoe press with only one shoe press nip or by a plurality of successively arranged shoe presses, each with a shoe press nip.

The device 10 further preferably comprises at least one calender 34, which in the present case is, for example, between the means 24 for application the paint application or the drying device 26 and the reel 28 is arranged.

In this case, for example, at least one calender can be provided with a soft nip which is formed between two calender rolls, of which at least one is provided with a soft plastic cover, for example, in comparison to steel rolls.

Alternatively or additionally, at least one calender with a hard nip can be provided, which is formed between two calender rolls, in particular steel rolls, each having a hard surface.

Alternatively or additionally, at least one calender, in particular shoe calender or metal belt calender can be provided with a long nip extended in the running direction.

The wire section 12 preferably comprises a gap former.

As in particular on the basis of Fig. 2 can be seen, at least one high-performance dryer 36 may be provided after the press section 14. In this case, such a high-performance dryer 36, for example, at least one impingement dryer (see. Fig. 2 ) or, for example, comprise at least one drying cylinder whose surface temperature is> 120 ° C and preferably 130 ° C.

Preferably, the paper web after the high-performance dryer 36 has a dry content> 63%.

Like also on the basis of Fig. 2 can be seen, after the high-performance dryer 36, for example, a single-row pre-dryer section 16 may be provided. The show Fig. 2a and 2 B in a simplified schematic partial representation of such an exemplary embodiment of the device 10 with a high-performance dryer 36 and an adjoining single-row pre-dryer section 16th

The wire section 12 may in particular comprise a gap former again.

The press section 14 comprises a press 38 with a suction press roll 40 and a nip, through which the paper web 42 is passed together with a top felt 44 and a bottom felt 46. The press 44 is followed by a shoe press 48, through whose broad nip the paper web 42 is guided together with a top felt 50 and a bottom band 52, which may be, for example, a felt or a transfer belt.

Following the shoe press 48, the high-performance dryer 36 is provided, which here comprises, for example, a single-drum dryer. As already mentioned, alternatively or additionally, for example, at least one drying cylinder may be provided, whose surface temperature is> 120 ° C. and preferably> 130 ° C.

The high-performance dryer 36 is followed by the preferably single-row pre-drying section 16.

This pre-drying section 16 is followed again by a device 18 for applying a glue application, which again comprises a film applicator in the present case.

Again Fig. 2b can be removed, in the web running direction L after the means 18 for applying a glue application successively a drying device 54, a smoothing or Vorglättwerk 22, a film applicator 56, a drying device 58, a lower web curtain applicator 60, a web top curtain applicator 62, a non-contact diverter 64 such as an air turn, an impingement dryer 66, optionally a calender 68, a cylinder group 70 such as one Pull and / or cooling group and a reel 28 is provided.

In the web running direction L in front of the two curtain application devices 60, 62, an air boundary layer suction 72 or 74 can be provided for higher speeds in each case in order to ensure a good coating quality.

Fig. 3 1 schematically shows an exemplary embodiment of an arrangement comprising two curtain applicators 30, 32 for the application of coating color to both sides of the web in the contactless method. As based on Fig. 3 can be seen, a drying device 76 is provided following this arrangement.

• Former: Gapformer (Doppelsiebformer);
• Schuhpresse:
  • zugfrei, d.h. die Bahn ist ständig unterstützt, entsprechend keine Abrisse;
  • mit der Schuhpresse ergibt sich ein schonendes Pressen, was bezüglich des Volumens (bulk) gut ist, ausreichend Entwässerung bei höheren Geschwindigkeiten;
• Vortrocknung:
  • auf die Presse folgt vorzugsweise ein Hochleistungstrockner (z.B. Impingement-Trockner, Trockenzylinder mit hoher Oberflächentemperatur > 120°C und vorzugsweise > 130°C),
  • nach dem Hochleistungstrockner besitzt die Bahn einen Trockengehalt >63 %, woraus sich eine höhere Bahnfestigkeit beim ersten freien Zug ergibt,
  • danach folgt eine einreihige Trockenpartie;
• Streichverfahren: ohne Rakel ergeben sich weniger Abrisse, mit einer Vorhang-Auftragseinrichtung ergibt sich zudem eine bessere Abdeckung, wodurch das Strichgewicht reduziert werden kann, während der Füllstoff im Papier erhöht werden kann, was kostengünstiger und wirtschaftlicher ist.

In this case, the arrangement according to Fig. 3 for example in the area "X" of the device 10 according to FIG Fig. 1 be provided. In this case, a drying device 76 can be provided in each case again following the curtain application devices 30, 32. The solution according to the invention has advantages, especially at higher speeds, since the overall process has fewer breaks and thus better runability. In particular, the following measures contribute to this:

• Former: Gapformer (twin-wire former);
• Shoe press:
  • draft-free, ie the railway is constantly supported, accordingly no breaks;
  • with the shoe press results in a gentle pressing, which is good in terms of volume (bulk), sufficient drainage at higher speeds;
• Pre-drying:
  • the press is preferably followed by a high-performance dryer (eg impingement dryer, drying cylinder with a high surface temperature> 120 ° C. and preferably> 130 ° C.),
  • after the high-performance dryer, the web has a dry content> 63%, resulting in a higher web strength at the first free draw,
  • This is followed by a single-row dryer section;
• Coating procedure: less doctor blade results in fewer breaks, and a curtain applicator also provides better coverage, which can reduce the coating weight while increasing the filler in the paper, which is cheaper and more economical.

Fig. 4 shows a diagram in which the covering behavior of a curtain applicator is compared to the covering behavior of a blade coater. In this diagram, the coverage [%] of the coating weight [g / m ² ] for a blade coater and a curtain applicator is shown in this diagram. The cover can be determined, for example, as an area fraction of the coating order for which the thickness of the coating application exceeds a certain minimum thickness of, for example, 1 micron.

As a result of the better Abdeckverhaltens the coating weight to the curtain applicator in comparison to the knife coater at 95% coverage of 12 g / m ² per side at about 8 g / m ² per side are reduced. For this can as Mass balance 2 times 4 g / m ² more filler in the pulp are added, which significantly reduces the cost.

The inventive method is an at least substantially wood-free coated paper web having a filler content> 10% and preferably> 12% at a basis weight <90 g / m ² or with a filler content> 12%, preferably> 14% with a basis weight ≥ 90 g / m ² produced. The paper web preferably has a cover coat having a coating weight ≦ 10, in particular ≦ 9 and preferably ≦ 8 g / (m ² ˙ side) at a basis weight <90 g / m ² or with a coating weight ≦ 16, in particular ≦ 14 and preferably ≦ 12 g / (m ² ˙ page) at a basis weight> 90 g / m ² on.

The present invention thus relates to the production process of at least substantially woodfree coated papers, in particular to the sequences of inking methods, glue application methods and smoothing devices and to filler contents in paper and line weights.

LIST OF REFERENCE NUMBERS

10

contraption

12

Wire section

14

press section

16

pre-dryer

18

Device for applying a glue application

20

Afterdryers

22

Glättwerk, Vorglättwerk

24

Device for applying a paint application

26

drying device

28

retractor

30

contactless application device

32

contactless application device

34

calender

36

High Speed Dryer

38

Press

40

suction press

42

paper web

44

overfelt

46

bottom felt

48

shoe press

50

overfelt

52

lower band

54

drying device

56

Film applicator

58

drying device

60

Curtain applicator

62

Curtain applicator

64

non-contact deflection device, Airturn

66

Impingement drying device

68

calender

70

cylinder group

72

Luftgrenzschichtabsaugung

74

Luftgrenzschichtabsaugung

76

drying device

L

Web direction

X

Area

Claims (12)

1. Method for producing an essentially wood-free coated paper web (42) which contains a fibrous proportion of pulp fibres of more than 55% and less than 75%, a double coating being applied to at least one side of the web and the last application of coating being applied by means of a non-contact application method in the form of a curtain applicator (32), and a pre-coat being applied by means of a film applicator (18, 24) or a non-contact application method, and the paper web being produced with a filler content > 10% at a grammage < 90 g/m² or a filler content > 12% at a grammage ≥ 90 g/m².
2. Method according to Claim 1,
   characterized in that
   following pre-drying of the paper web, a coating colour is applied as pre-coat and, before the application of the colour pre-coat, the paper web (42) is led through a pre-calendering unit (22).
3. Method according to Claim 1,
   characterized in that
   in particular hollowing pre-drying of the paper web, size is applied as pre-coat and, after the application of the size, the paper web is led through a calendering unit (22).
4. Method according to one of the preceding claims,
   characterized in that
   the paper web (42) is led through the press section (14) in a closed draw.
5. Method according to one of the preceding claims,
   characterized in that
   in the press section (14), the paper web (42) is led through only one shoe press having only one nip.
6. Method according to one of Claims 1 to 4,
   characterized in that
   in the press section (14), the paper web (42) is led through a plurality of shoe presses arranged one after another, each having one nip.
7. Method according to one of the preceding claims,
   characterized in that
   the paper web (42) is led through at least one calender (34, 68).
8. Method according to Claim 7,
   characterized in that
   the paper web (42) is led through at least one calender having a soft nip which is formed between two calender rolls, at least one of which is provided with a soft plastic cover.
9. Method according to Claim 7 or 8,
   characterized in that
   the paper web (42) is led through at least one calender having a hard nip which is formed between two calender rolls, in particular steel rolls, each of which has a hard roll surface.
10. Method according to one of Claims 7 to 9,
    characterized in that
    the paper web (42) is led through at least one calender, in particular a shoe calender or metal band calender, having an extended nip lengthened in the web running direction.
11. Method according to one of the preceding claims,
    characterized in that
    the paper web is produced with a filler content > 12% at a grammage < 90 g/m² or with a filler content > 14% at a grammage ≥ 90 g/m², and/or in that the paper web has a top coat with a coat weight ≤ 10, in particular ≤ 9 and preferably ≤ 8 g/(m² · side) at a grammage < 90 g/m², or with a coat weight ≤ 16, in particular ≤ 14 and preferably ≤ 12 g/(m² · side) at a grammage > 90 g/m².
12. Method according to one of the preceding claims,
    characterized in that
    the fibrous proportion of the paper web is composed of less than 60% pulp fibres.

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