EP2113607B1 - Machine for producing a sheet of one-sided smooth sheet of paper - Google Patents

Abstract

The machine (10) has a pressing nip (32) formed between a felted pressing element (48) and a polishing and/or Yankee cylinder (44), where the pressing nip is assigned to a drying area (18). A paper web (12) is guided in a web running direction (L) by a pressing nip (50) assigned to the drying area after the pressing nip (32) is assigned to the drying area. The pressing nip (50) is formed between a smooth press surface (52) and the polishing and/or Yankee cylinder, where a rear side (42) of the paper web contacts with the smooth press surface in the pressing nip (50).

Description

The invention relates to a machine for producing a one-sided smooth paper web, with a forming area, a press area and a drying area, in which the rear side of the paper web opposite the side to be smoothed both in a press nip assigned to the press area and in a first press nip assigned to the drying area comes into contact with a press felt, wherein the first drying nip associated Pressnip between a felted pressing element and a smoothing and / or Yankee is formed wherein the paper web is guided after the first drying nip associated press nip by a second drying nip assigned to the press nip. Such a machine is in the not yet published German patent application 10 2007 027 270.9 described.

The production of one-sided smooth papers with a basis weight of usually 25 to 50 g / m ² is carried out today on so-called MG machines (MG = machine smoothing). The web is transferred with a comparatively low dry content by means of a pressure roller to the smoothing or Yankee.

To produce a high degree of smoothness, it has in particular already been proposed to press the paper web with its front or facing side to be smoothed over two press rolls against the smoothing or Yankee cylinder. In this case, the back of the paper web opposite the face to be smoothed has no contact with a smooth roll. Accordingly, the back of the paper web has a high roughness. Typical PPS values for papers produced by means of a conventional, classic Yankee machine are for example 3.0 μm for the front side, while the relevant values for the rear side are> 7 μm.

In many applications, however, a lower roughness is also desired on the back of the paper web, for which purpose the Yankee machine has been followed by a calender, which is now relatively complicated.

Furthermore, from the document US 3,198,695 A Such a machine is known, wherein the paper web is guided by two felted press nips on Yankee cylinder in order to achieve the best possible drainage.

In more modern concepts for the production of one-sided smooth papers a press concept with shoe press and transfer belt is used to improve the dry content and the smoothness of the front, as in the older German patent application 10 2007 027 270.9 described machine is the case. However, the problem of high roughness of the back of the paper web is still present here. To be able to reduce the roughness of the back, an additional Softnip calender with thermo roll on the back is required, which brings additional investment and operating costs, or at least an extension of the machine with it. Conventional, ie in particular hard pressure rollers with a solid roll shell, which may also be coated with rubber, can adapt to the deformed under operating conditions contour of the smoothing or Yankee cylinder jacket only limited. They have to be cambered for one operating point. Changes in vapor pressure and line force lead to uneven contact over the length of the cylinder and also to unsatisfactory smoothness and gloss cross sections. If you want to achieve a uniform contact pressure against the smoothing or Yankee, the operating window is severely limited with respect to the vapor pressure of the cylinder and the line force of the two pressure rollers on Yankee smoothing or Yankee, which impairs the flexibility of the entire machine.

The invention has for its object to provide an improved machine of the type mentioned, in which the aforementioned problems are eliminated. In particular, the highest possible uniformity of smoothness and gloss over the machine width should be given in the widest possible operating window with reduced roughness of the back side of the paper web.

According to the invention, this object is achieved in that the second press nip assigned to the drying area is formed between a smooth pressing surface and the smoothing or Yankee cylinder and in which the back side of the paper web comes into contact with the smooth pressing surface.

Since the second pressing nip assigned to the drying area is not felted and formed between the smoothing or Yankee cylinder and a smooth pressing surface, the roughness of the backside is reduced, comparable to an offset press. The front side improves the gloss and smoothness values.

According to a preferred practical embodiment of the machine according to the invention, the smooth pressing surface which comes into contact with the back side of the paper web is formed by a deflection iris roll provided in particular with an elastic jacket.

In this case, the deflection-adjusting roller advantageously comprises a non-rotatable yoke, around which the particular elastic roll shell rotates, and between the yoke and the roll shell arranged, distributed transversely to the web running direction in particular hydraulic Anpresseinheiten or support elements. Appropriately, in this case the Anpresseinheiten via a deflection of the adjusting roller associated control and / or Control device individually, in groups and / or jointly controlled.

It is particularly advantageous if the jacket of the deflection adjustment roller in the roll longitudinal direction is so elastic and / or the Anpresseinheiten via the control and / or regulating device are controlled so that the deflection adjustment at least substantially to the contour of the surface of the smoothing or Yankeezylinders in the longitudinal direction adapts. The elastic sheath adapts optimally to the contour of the smoothing or Yankee cylinder jacket over a wide range of line force. In this case, the circular-cylindrical shape of the deflection-adjusting roller, which is considered in cross-section, should at least essentially be maintained. Preferably, therefore, the modulus of elasticity in the longitudinal direction of the deflection adjustment roller is smaller than the elastic modulus in the circumferential direction of the deflection adjustment roller. This deflection adjustment roller may therefore in particular be a so-called "NipcoElast" roller (Voith). In principle, the different pressing units can be subjected to the same pressure or at least partially to different pressures.

The elastic roll shell of the deflection adjustment roll may in particular consist of plastic and / or fiber-plastic composite and has a modulus of elasticity in the longitudinal direction E _L of 7000 to 12000 N / m ² , preferably of 10000 N / m ² and in the circumferential direction has a modulus of elasticity of Eu of 25000 to 45000 N / m ² , preferably Eu = 35000 N / m ² .

The elastic roll shell preferably has a relation. This roll cover may consist of an elastomeric material, in particular rubber and or polyurethane. There are also composite covers possible, such as carbon fiber or glass fiber reinforced plastics (CFRP, GFRP). The hardness range of the roll cover is between 0 and 90 Pussey & Jones (P & J), preferably between 10 and 40 P & J, and more preferably in the soft range of 20 P & J. In the hard area preferably between 85 and 95 ShoreD.

The elastic roll shell then forms together with the cover the Elastmantel.

According to an alternative embodiment of the machine according to the invention, the smooth pressing surface coming into contact with the rear side of the paper web is formed by a cambered pressure roller provided with an elastic cover preferably made of rubber or polyurethane. In this embodiment, however, results in respect of the vapor pressure and the load, a relatively smaller operating window.

According to a further expedient embodiment, the smooth pressing surface coming into contact with the rear side of the paper web is formed by an un-felted shoe press roll which is provided with a smooth pressing jacket.

A preferred practical embodiment of the machine according to the invention is characterized in that the paper web to be produced is taken over by the forming area by means of a water-receiving first press felt and guided together with the first press felt and a smooth transfer belt receiving at least substantially no water through the press nip associated with the press area is, led away the first press felt immediately after the pressing nip assigned to the press nip of the paper web and the paper web together with the smooth transfer belt from the press area is then carried away associated press nip, then by means of a particular conditioned water receiving, not passed through the press section associated press nip out second press felt is taken over by the smooth transfer belt and is then guided together with the second press felt through the first press nip assigned to the drying area.

Due to the more efficient mechanical dewatering of the web before the start of the thermal drying in the drying area, a significant increase in production output is achieved. In addition, a closed and tear-free web guide results from the forming area or sieve to the smoothing or Yankee cylinder of the drying area.

According to a preferred practical embodiment, immediately after the press nip assigned to the press area, the first press felt is guided away from the paper web under an angle of> 0 °, preferably> 10 °, formed with the transfer belt and corresponding to the paper web.

It is also particularly advantageous if the press nip associated with the press area is formed by a shoe press.

The front side of the paper web to be smoothed is expediently formed by the lower side of the paper web in relation to the sheet formation.

Preferably, the first press felt is passed as a top felt and the smooth transfer belt as a lower belt through the press nip associated press nip.

The paper web is expediently taken over by the second press felt in the area of a pickup roller looped by the second press felt from the smooth transfer belt. Subsequently, the paper web can then be guided together with the second press felt through the first press nip assigned to the drying area.

According to a preferred embodiment of the machine according to the invention, together with the smoothing or Yankee cylinder, the first press nip forming the drying area is a suction roll, a pickup roll looped by the second press felt, a hard roll or a shoe press unit, in particular a shoe press roll educated.

In this case, in particular a well-conditioned second press felt can be used, which allows a further increase in dry content to dry contents to, for example, 50% or more. Correspondingly less water must be evaporated. With the same evaporation performance, the production increases, or with the same production, the specific drying costs decrease after, for example, less gas is required for the crowning or Yankee cylinder associated hood heating and / or optionally a smaller smoothing or Yankee cylinder can be used.

It is also of particular advantage that the paper web is transferred to the smoothing or Yankee cylinder with its side previously brought into contact with the smooth transfer belt.

Tests have shown that as the dry content of the paper web running up onto the smoothing or Yankee cylinder increases, so does the pressure with which the web is fed to the smoothing or Yankee cylinder is pressed to produce high smoothness and gloss values on the front of the paper web. It is achieved by the use of a non-felted pressure roller even at relatively low loads, that is, for example, at a line force in the range of about 30 to about 80 N / mm, a high specific contact pressure.

Due to the solution according to the invention, the roughness, for example, generated by the felt contact in the two preceding press nips on the back of the paper web is significantly reduced. By using the elastomer roller or "NipcoElast" roller, the load on the press nip can be varied within a wide range, depending on the respective requirements, without adversely affecting the smoothness, gloss or thickness cross section.

Unlike the production of tissue paper in the present case no creping takes place on the smoothing or Yankee cylinder. The papers have a much lower air permeability and a higher smoothness and / or gloss. The papers should therefore primarily have the highest possible smoothness or gloss. The specific volume (bulk) are secondary.

With the machine according to the invention can be produced particularly advantageously one-sided smooth papers with low back roughness. The basis weight range is from 30 to 120 g / m ² , preferably in the range from 35 to 70 g / m ² . The density of the paper after the Yankee cylinder is between 0.65 and 0.77 g / cm ³ , preferably 0.67 to 0.74 g / cm ³ . Compared to tissue paper, the papers have a higher air flow resistance, which - measured according to Gurley, in the range between 15 to 90 s / (100ml) and preferably between 25 to 60 s / (100ml). The porosity measured by Bendtsen is in the range from 100 to 700 ml / min, in particular between 150 and 500 ml / min. According to the invention, particularly good roughness values can be achieved, in particular for the rear side, although this has no direct contact with the Yankee cylinder. The roughness of the front side, which has contact with the Yankee cylinder, measured according to Bendtsen after the Yankee cylinder at 100 to 500 ml / min, preferably between 120 and 250 ml / min. Although the back has no contact with the Yankee cylinder, roughness values of less than 1500 ml / min, in particular from 300 to 900 ml / min according to Bendtsen can be achieved.

Fig. 1

eine schematische Teildarstellung einer beispielhaften Ausführungsform einer erfindungsgemäßen Maschine zur Herstellung einer einseitig glatten Papierbahn,

Fig. 2

eine schematische Längsschnittdarstellung eines End- bereichs einer beispielhaften Ausführungsform, sowie eine schematische Querschnittsdarstellung der elasti- schen Durchbiegungseinstellwalze der Maschine

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

Fig. 1

FIG. 2 a schematic partial representation of an exemplary embodiment of a machine according to the invention for producing a one-sidedly smooth paper web, FIG.

Fig. 2

a schematic longitudinal sectional view of an end portion of an exemplary embodiment, and a schematic cross-sectional view of the elastic deflection adjustment of the machine

Fig. 1 shows a schematic partial representation of an exemplary embodiment of a machine 10 for producing a one-sided smooth paper web 12 with a forming region 14, a press area 16 and a drying area 18th

In this case, the paper web 12 to be produced by means of a water-absorbing first press felt 20 in the region of a first pickup roller 22 looped by the press felt 20 of a screen 24 of the Formierbereichs 14 taken and guided together with the first press felt 20 and an at least substantially not water-absorbing smooth transfer belt 26 through a press section 16 associated press nip 28. The first press felt 20 is led away from the paper web 12 and the smooth transfer belt 26 immediately after the pressing nip 28 assigned to the press region 16.

Subsequently, the paper web 12 is taken over by the smooth transfer belt 26 by means of a preferably conditioned, and in particular non-structured, water-absorbing second press felt 30, which is not guided by the press nip 28 assigned to the press region 16. The paper web 12 is then guided together with the second press felt 30 through a first press nip 32 assigned to the drying area 18. Also in this first the drying region 18 associated nip 32 so again a pressing force is generated.

In this case, the first press felt 20 can be guided away from the paper web 12 immediately after the press nip 28 assigned to the press region 16 under an angle of> 0 °, preferably> 10 °, formed with the transfer belt 26 and corresponding to the paper web 12.

As based on the Fig. 1 can be seen, the pressing nip 28 associated with the press area 16 may be formed in particular by a shoe press. In the present case, the shoe press comprises, for example, an overhead shoe press unit, in particular a shoe press roll 36 and a lower counter roll 38.

The first press felt 20 can be guided, in particular, as an upper felt and the smooth transfer belt 26, in particular as a lower belt, through the press nip 28 assigned to the press region 16.

The paper web 12 is taken over by the second press felt 30 from the smooth transfer belt 26 in the region of a second pickup roll 40 looped by the second press felt 30.

In this case, in the present case, the first pressing nip 32 assigned to the drying region 18 is formed, for example, between a suction roll 48 separated from the second pickup roll 40 and a smoothing and / or Yankee cylinder 44. In the present embodiment, therefore, the suction roller 48 serves as a pressing element cooperating with the smoothing or Yankee cylinder 44. In principle, however, such an embodiment is conceivable, for example, in which the relevant pressing element is formed simultaneously by the second pickup roller 40.

The smoothing or Yankee cylinder 44 may be associated with a drying hood 46.

The rear side 42 of the paper web 12, which lies over the front side 34 to be smoothed, thus comes into contact both with a press felt 20 and 30 in the press nip 28 assigned to the press region 16 and in the first press nip 32 assigned to the drying region 18. In this case, the first pressing nip 32 assigned to the drying region 18 is formed between the felted pressing element 48 and the smoothing or Yankee cylinder 44, wherein the pressing element 48 in the present case is formed, for example, by a suction roll.

The paper web 12 is guided in the web running direction L after the first press nip 32 assigned to the drying region 18 by a second press nip 50 assigned to the drying region 18, which is formed between a smooth pressing surface 52 and the smoothing or Yankee cylinder 44 is and in which the back 42 of the paper web 12 comes into contact with the smooth pressing surface 52.

In this case, the smooth pressing surface 52 which comes into contact with the back side 42 of the paper web 12 is in the present case, for example, one with an elastic sheath 54 (cf. Fig. 2 formed deflection roll 56 formed. This may in particular be a so-called "NipcoElast" roll (Voith). In Fig. 2 an embodiment of such a "NipcoElast" roller is shown.

For example, based on the Fig. 2 can be seen, such a deflection set roller 56 comprises a non-rotatable yoke 58, around which the elastic roll shell 54 rotates, and arranged between the yoke 58 and the roll shell 54, transversely distributed to the web running direction L hydraulic Anpresseinheiten or support elements 60th Die Fig. 2 shows a schematic longitudinal sectional view of an end portion and a schematic cross-sectional view of the elastic deflection set roller 56. The elastic roll shell 54 has a roll cover 62 and thus forms the Elastmantel 64 of the deflection set roller 56th

The elastic roll shell 54 of the deflection adjustment roll consists of a fiber-plastic composite and has a modulus of elasticity in the longitudinal direction E _L of 10000 N / m ² and in the circumferential direction has a modulus of elasticity of E _U = 35000 N / m ² .

The roll cover 62 of the elastic roll shell 54 is made of an elastomeric material, in particular of rubber and / or polyurethane. There are also composite covers possible, such as carbon fiber or glass fiber reinforced plastics (CFRP, GFRP). The hardness range of the Roller coating. 62 is 20 P & J. In the hard area preferably between 85 and 95 ShoreD.

The pressing units 60 may be individually, groupwise and / or jointly controllable via a control and / or regulating device associated with the deflection adjustment roller 56. The various, for example, hydraulic pressing units 60 can therefore be acted upon, for example, by the same pressure or at least partially by a different pressure.

For example, such an embodiment is conceivable in which the jacket 54 of the deflection adjustment roller 56 is so elastic in the roll longitudinal direction and / or the contact units 60 can be controlled via the control and / or regulating device in such a way that the deflection adjustment roller 56 or its elastomer jacket 64 in particular is adapted over a large line force range at least substantially to the contour of the surface of the smoothing or Yankee cylinder 44 in the longitudinal direction. On the other hand, during operation, the roll shell 54 can maintain its at least substantially circular-cylindrical cross-sectional shape (compare FIG. 3). Preferably, therefore, the modulus of elasticity in the longitudinal direction of the deflection adjustment roller is smaller than the elastic modulus in the circumferential direction.

The elastic deflection roll or "NipcoElast" roll 56 with elast jacket results in a significant reduction of the back roughness with uniform, intensive contact pressure on the smoothing or Yankee cylinder for optimum smoothness and gloss.

• großer Walzendurchmesser, zum Beispiel D = 730 mm
• gleichmäßige Linienkraft im Arbeitsbereich von beispielsweise etwa 10 bis etwa 100 N/mm
  → Selbstanpassung des Mantels an die Gegenwalze (z. B. Glättzylinder)
  → keine Linienkraftfehler durch fehlerhafte Bombierungseinstellung oder sonstige Einflüsse möglich
• sehr einfache Steuerung (Druck/Linienkraft = proportional)
  → beispielsweise nur 1 Zonendruck
  → hydraulische Durchbiegungsanpassung entfällt im Fall eines einheitlichen Zonendrucks
• hohe Dämpfungseigenschaft durch geringe Mantelmasse
  → Bezugsschonung

The advantages of the elastic deflection roll or "NipcoElast" roll include:

• large roll diameter, for example D = 730 mm
• uniform line force in the working range of, for example, about 10 to about 100 N / mm
  → self-adaptation of the jacket to the mating roll (eg smoothing cylinder)
  → No line force errors due to incorrect crown adjustment or other influences possible
• very simple control (pressure / line force = proportional)
  → For example, only 1 zone pressure
  → Hydraulic deflection adjustment is not necessary in case of uniform zone pressure
• high damping properties due to low jacket mass
  → Covering protection

LIST OF REFERENCE NUMBERS

10

machine

12

paper web

14

forming region

16

Press area

18

drying area

20

first press felt

22

first pickup roller

24

scree

26

smooth transfer ribbon

28

press nip

30

second press felt

32

press nip

34

front

36

Shoe press unit, shoe press roll

38

backing roll

40

second pickup roller

42

back

44

Smoothing or Yankee cylinder

46

Trockenhaube

48

Pressing element, suction roll

50

press nip

52

smooth pressing surface

54

elastic coat,

56

Deflection adjustment roller, "NipcoElast" roller

58

yoke

60

Pressing unit, support element

62

Roll cover, cover of the elastic roll shell

64

Elastmantel (elastic roll cover with cover)

L

Web direction

Claims (18)

1. Machine (10) for producing a paper web (12) smooth on one side, having a forming area (14), a pressing area (16) and a drying area (18), in which the reverse (42) of the paper web (12), opposite the front side (34) that is to be smoothed, in each case comes into contact with a press felt (20, 30) both in a press nip (28) assigned to the pressing area (16) and also in a first press nip (32) assigned to the drying area (18), the first press nip (32) assigned to the drying area (18) being formed between a felted pressing element (48) and an M.G. and/or Yankee cylinder (44), the paper web (12) being led through a second press nip (50) assigned to the drying area (18) after the first press nip (32) assigned to the drying area (18) in the web running direction (L),
   characterized in that
   the second press nip (50) assigned to the drying area is formed between a smooth press surface (52) and the M.G. or Yankee cylinder (44) and, in this nip, the reverse (42) of the paper web (12) comes into contact with the smooth press surface (52).
2. Machine according to Claim 1,
   characterized in that
   the smooth press surface (52) coming into contact with the reverse (42) of the paper web (12) is formed by a controlled deflection roll (56), in particular provided with a resilient shell (54, 64).
3. Machine according to Claim 2,
   characterized in that
   the controlled deflection roll (56) has a yoke (58) which is fixed against rotation and around which the in particular resilient roll shell (54) revolves, and comprises pressing units (60), in particular hydraulic pressing units, arranged between the yoke (58) and the roll shell (54) and distributed transversely with respect to the web running direction.
4. Machine according to Claim 3,
   characterized in that
   the pressing units (60) can be activated individually, in groups and/or jointly via an open-loop and/or closed-loop control device assigned to the controlled deflection roll (56).
5. Machine according to one of the preceding claims,
   characterized in that
   the shell (54) of the controlled deflection roll (56) is so resilient in the roll longitudinal direction and/or the pressing units (60) can be activated via the open-loop and/or closed-loop control device in such a way that the controlled deflection roll is at least substantially matched to the contour of the surface of the M.G. or Yankee cylinder (44) in the longitudinal direction of the latter.
6. Machine according to Claim 1,
   characterized in that
   the smooth press surface (52) coming into contact with the reverse (42) of the paper web (12) is formed by a cambered pressure roll provided with a resilient cover, preferably made of natural rubber or polyurethane.
7. Machine according to Claim 1,
   characterized in that
   the smooth press surface (52) coming into contact with the reverse (42) of the paper web (12) is formed by a shoe roll with a smooth press shell.
8. Machine according to one of the preceding claims,
   characterized in that
   the paper web (12) to be produced is picked up from the forming area (14) by means of a first press felt (20) absorbing water and, together with the first press felt (20) and a smooth transfer belt (26) at least substantially not absorbing water, is led through the press nip (28) assigned to the pressing area (16), the first press felt (20) is led away from the paper web (12) immediately after the press nip (28) assigned to the pressing area (16), and the paper web (12), together with the smooth transfer belt (26), is led away from the press nip (28) assigned to the pressing area (16), is then picked up from the smooth transfer belt (26) by means of a second press felt (30) absorbing water, in particular conditioned water, which second press felt is not led through the press nip (28) assigned to the pressing area (16) and then, together with the second press felt (30), the paper web is led through the first press nip (32) assigned to the drying area (18).
9. Machine according to Claim 8,
   characterized in that,
   immediately after the press nip (28) assigned to the pressing area (16), the first press felt (20) is led away from the paper web (12) at an angle > 0°, preferably > 10°, formed with the transfer belt (26) and accordingly with the paper web (12).
10. Machine according to Claim 8 or 9,
    characterized in that
    the press nip (28) assigned to the pressing area (16) is formed by a shoe press (36, 38).
11. Machine according to one of the preceding claims,
    characterized in that,
    in relation to the sheet formation, the front side (34) of the paper web (12), which is to be smoothed, is formed by the underside of the paper web (12).
12. Machine according to one of the preceding claims,
    characterized in that
    the first press felt (20) is led through the press nip (28) assigned to the pressing area (16) as a top felt, and the smooth transfer belt (26) as a bottom belt.
13. Machine according to one of the preceding claims,
    characterized in that
    the paper web (12) is picked up from the smooth transfer belt (26) by the second press felt (30) in the area of a pick-up roll (40) around which the second press felt (39) wraps.
14. Machine according to one of the preceding claims,
    characterized in that
    the pressing element which, together with the M.G. or Yankee cylinder (44), forms the first press nip (32) assigned to the drying area (18), is formed by a suction roll (48).
15. Machine according to one of the preceding claims,
    characterized in that
    the pressing element (48) which, together with the M.G. or Yankee cylinder (44), forms the first press nip (32) assigned to the drying area (18), is formed by the pick-up roll around which the second press felt (30) wraps.
16. Machine according to one of the preceding claims,
    characterized in that
    the pressing element which, together with the M.G. or Yankee cylinder (44), forms the first press nip (32) assigned to the drying area (18), is formed by a hard roll.
17. Machine according to one of Claims 1 to 15,
    characterized in that
    the pressing element (48) which, together with the M.G. or Yankee cylinder (44), forms the first press nip (32) assigned to the drying area (18), is formed by a shoe press unit, in particular a shoe press roll.
18. Machine according to one of the preceding claims,
    characterized in that
    the paper web (12) is transferred to the M.G. or Yankee cylinder (44) with its side previously coming into contact with the smooth transfer belt (26).

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