EP1120492B1 - Machine and method for manufacturing a tissue web - Google Patents

Abstract

The present invention is directed to a machine and process for producing a tissue web. The machine includes a forming area including at least one rotating continuous dewatering wire with zonally varied wire permeability, and at least one shoe press. The process includes dewatering the tissue web with at least the at least one continuous dewatering wire with zonally varied wire permeability, and pressing the tissue web in the at least one shoe press.

Description

The invention relates to a machine for producing a tissue web according to the preamble of claim 1. It relates Furthermore, a method according to the preamble of claim 14.

Heretofore, attempts have been made to adjust the quality parameters of a tissue web, such as a tissue web. the Water absorption capacity, the water retention capacity and the Water absorption rate, by the design of the surface structure of the web to influence. In the prior art (see, for example, US 5,746,887, US 5,492,598, SE 427053) It is proposed to use so-called embossing screens or felts. These characterize the already formed tissue web their own surface structure. In this process the tissue web is subjected to pressure and thereby to a desired high volume (bulk) counteracted. At the same time, this process requires a high level of apparatus Effort because the embossing screens are used only for this purpose. Often These methods still use special, expensive drying methods to increase the specific volume combined.

WO 96/35018 discloses a machine for the production of tissue paper, wherein the Machine in forming area a drainage screen with zonal different Having permeability.

DE 42 24 730 C1 discloses the use of shoe presses in tissue machines for Increasing the dry content of the tissue web after passing through the press section.

The aim of the invention is to provide a machine and a method of the type mentioned with which the construction and the structure, i. the arrangement of the fibers of a tissue web especially at high Machinery speeds can be designed so that the water absorption capacity, the water retention capacity, the water absorption rate and the specific volume (bulk) on as possible be increased or improved economic way.

This object is according to the invention with respect to the tissue machine solved by the features of the characterizing part of claim 1.

Due to this design is achieved that the drainage process in the foliation forming zone areas of high drainage rate and areas of low drainage speed arise. This results in a tissue web with zonal different fiber proportions generated, whereby the water absorption of the web is increased and this also faster. This not only affects the tissue web the leaf surface, but over the entire leaf volume, thereby the quality parameters improve significantly. The use of a DSP screen in combination with a shoe press brings in particular the Advantage with it, that with the achieved by the shoe press gentle pressing dewatering the beneficial structure in the tissue web for improving the water absorption capacity, water retention capacity and the water absorption rate is maintained and at the same time achieving a voluminous web of high specific volume (bulk) becomes.

Sieves zonal different permeability are for example from the SE 427053 known. Thereafter, the screens in question may e.g. from a Tissue consist in which provided in one or more levels Longitudinal and transverse threads according to a predeterminable pattern interwoven, that systematically distributed areas more suitable Showing size in which the number of intersections equal Zero or significantly smaller than in the weave structure of the remaining fabric.

A preferred practical embodiment of the machine according to the invention comprises a former with two continuous endless drainage belts, which converge to form a Stoffseinlaufspaltes and then via a forming element such as in particular a Forming roller are performed, as not with the forming element in Contact kicking outside band and / or as interior band a drainage sieve is provided with zonal different Siebdurchlässigkeit.

In an alternative embodiment of the machine according to the invention is the following of the forming element by one of the two dewatering belts entrained tissue web along with this Dewatering tape passed through the shoe press.

As a counter element to Schuhpreßeinheit the shoe press expediently includes a drying cylinder, preferably a Yankee cylinder.

For example, the shoe press unit may be configured as shown in FIG EP 99 125 789 is described. Thereafter, the Schuhpreßeinheit For example, have a press nip, considered in the web running direction Length is less than or equal to a value of about 60 mm and whose over the press nip length resulting pressure profile a maximum Compressing pressure which is greater than or equal to a value of about 3.3 MPa is ("ShortShoe"). With such a shoe press unit can under extensive compliance with the quality features required for the produced web the highest possible dry content and / or specific Volume can be achieved.

According to an alternative, also described in EP 99 125 789 Embodiment, the shoe press unit may have a press nip, its length considered in the tape running direction is greater than a value of about 80 mm and preferably less than 200 mm, in particular at most 150 mm, and whose pressure profile resulting over the press nip length has a maximum pressing pressure which is less than or equal to one Value of about 2 MPa is ("LongShoe"). This makes the track special gently dehydrated and in combination with a DSP sieve a special reached high bulk. This gives the web a higher water absorption capacity. Another positive effect is that the water is recorded faster.

For the rest, the shoe press unit can for example be designed in this way be, as described in EP 99 125 789.

In certain cases, it may also be beneficial if a Drying zone is provided, in which the tissue web at least partially can be acted upon by pressurized displacement gas (TAD, Through Air Drying).

According to an expedient embodiment, as a former, for example a twin-wire former may be provided. It can be used as an outer band and / or as inner band a drainage screen with zonal different Sieve permeability, i. a so-called DSP screen, be provided. Is only one of the two bands formed by such a DSP sieve, so the other band may be a conventional tissue dewatering screen be.

In a useful alternative embodiment is as a former Crescentformer provided, the outer band through a drainage sieve with zonal different Siebdurchlässigkeit and its inner band formed by a felt belt.

The largest extent of the area of the sections of the dewatering screen with zonal different Siebdurchlässigkeit is expediently Az <5 mm, preferably Az <3 mm.

It is also advantageous if the drainage sieve zonal different Sieve permeability is not needled with felt-like fibers, but from a weft and warp formed fabric, i. only from Weft and warp threads exists.

The zones of different sieve permeability of a respective dewatering belt are advantageously by the use of Web threads of different diameter and / or different Web pattern generated.

Advantageously, the dewatering screen with zonal different Sieve permeability in a range in which the dry content of the Tissue web smaller than about 20% and especially less than about 12% is, and preferably in the initial foliation range at a dry content less than about 6% used.

Because of the different permeability fibers in the volume The sieve can penetrate and settle there is the drainage sieve zonal different Siebdurchlässigkeit preferably a conditioning device such as in particular a sieve cleaning device assigned. Thereby, e.g. Spray pipes with over the machine width be provided distributed nozzles. It can, however, for example also a "Duocleaner" from Voith Sulzer with rotating high-pressure nozzles and integrated extraction or a "Jet Cleaner" from Voith Sulzer be used.

The inventive method is solved accordingly by the features of the characterizing part of claim 14.

Advantageous embodiments of the method according to the invention are specified in the dependent claims.

As sieves zonal different permeability come for example Sieves of the type in question, as described in PCT / GB99 / 02684 (WO-A-00 12817) are described. Thereafter, the sieves in question, in particular from a tissue exist in the one or more levels envisaged in one first direction extending threads extending in a second direction Threads are interwoven to form a grid, a multitude of systematically distributed areas of specifiable configuration separates and determines accordingly, taking the systematic distributed areas each have at least three in one and at least three in the other direction extending threads comprises. At the threads can these are in particular wefts and warp threads.

Figur 1

eine schematische Darstellung eines Doppelsiebformers einer Maschine zur Herstellung einer Tissuebahn, bei dem als Außenband und/oder als Innenband ein Entwässerungssieb mit zonal unterschiedlicher Siebdurchlässigkeit vorgesehen und dieses sogenannte DSP-Sieb in Kombination mit einer freistehenden Schuhpresse eingesetzt ist,

Figur 2

eine schematische Darstellung eines Crescent-Formers, bei dem als Außenband ein Entwässerungssieb mit zonal unterschiedlicher Siebdurchlässigkeit und als Innenband ein Filzband vorgesehen ist, und bei dem die im Anschluß an die Formierwalze durch das Filzband mitgenommene Tissuebahn zusammen mit diesem Filzband durch eine Schuhpresse geführt ist, welche nicht als vom Formierbereich getrennte Einheit ausgebildet ist,

Figur 3

eine schematische Darstellung eines Formers, der sich aus einer Kombination der beiden in den Figuren 1 und 2 gezeigten Former ergibt, und

Figur 4

ein Webmusterdiagramm eines sich wiederholenden Abschnitts eines durch ein Gewebe gebildeten Entwässerungssiebes mit zonal unterschiedlicher Siebdurchlässigkeit.

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

FIG. 1

a schematic representation of a Doppelsiebformers a machine for producing a tissue web, in which a drainage sieve zonal with different Siebdurchlässigkeit provided as outer band and / or as inner band and this so-called DSP screen is used in combination with a freestanding shoe press,

FIG. 2

a schematic representation of a crescent former, in which a dewatering sieve with zonal different Siebdurchlässigkeit and as inner band a felt is provided as the outer band, and in which the entrained following the forming roller through the felt belt tissue web is guided together with this felt belt through a shoe press, which is not formed as a unit separate from the forming area,

FIG. 3

a schematic representation of a former, which results from a combination of the two shaper shown in Figures 1 and 2, and

FIG. 4

a weave pattern diagram of a repeating portion of a dewatering screen formed by a tissue with zonal different Siebdurchlässigkeit.

The former 10 shown in FIGS. 1 and 2 are each part of a machine for the production of a tissue web 12. In the forming area, preferably in the initial drainage area, in each case at least one Drainage screen with zonal different screen permeability, i. a DSP sieve provided. This DSP sieve is in combination with each provided a shoe press.

The two formers 10 each comprise two continuous endless drainage belts 14, 16, which converge to form a Stoffeinlaufspaltes 18 and then over here through a forming roll 20 formed forming element are guided.

In the stock inlet gap 18 by means of a headbox 22, the pulp suspension brought in.

1 shows a schematic representation of a twin-wire former 10, in which both as with the forming roller 20 in contact passing inner band 14 as well as outer band a sieve is provided in each case.

At least one of the two drainage sieves 14, 16 is as a sieve with Zonal different Siebdurchlässigkeit, i. as DSP screen, provided. In this case, a respective DSP sieve a conditioning in particular, be associated with a sieve cleaning device 50 (cf. Figure 2).

In the present case, the stock suspension 22 supplied pulp suspension from diagonally down into the between the two drainage bands 14, 16 formed Stoffeinlaufspalt 18 injected. The outer band 16 is coming from below via a guide roller 24 past the Headbox 22 led to Formierwalze 20 and from there via another Guide roller 26 returned again.

The two drainage belts 14, 16 are still in the field of Forming roller 20 separated again. The inner band 14 is fed back via a guide roller 28. In strip running direction L Before the deflection roller 28, the tissue web is in the region of a deflection roller 30 taken over by a waterproof tape 32 of the inner band 14 and the press nip of a shoe press 34 fed to a bottom shoe press unit 36 and an overhead mating roll 38 includes. Through the press nip of the shoe press 34 is in addition to the Tissuebahn with leading upper watertight band 32 an underfelt 40 passed before and after the shoe press 34 each is guided over a guide roller 42 and 44, respectively. The underfelt 40 becomes immediate after the nip of the shoe press 34 again from the waterproof Volume 32 separated to avoid rewet. The waterproof tape 32 is connected to the shoe press 34 together supplied with the tissue web of a transfer roller 46, in whose Area the tissue web to a tissue cylinder or Yankee cylinder 48 is handed over.

In the present case, the shoe press 34 is thus as a separate unit in Tape running direction L behind the forming element 20 and the two Drainage bands 14, 16 comprehensive unit provided.

Figure 2 shows a schematic representation of a Crescentformer 10, at the outer band which does not come into contact with the forming roller 20 16 a drainage sieve with zonal different sieve permeability, i.e. a so-called DSP screen, is provided. The inner band 14 is formed here by a felt band. The DSP screen 16 may include a conditioning device 50 as assigned in particular a screen cleaning device be.

The forming tissue web 12 is connected to the forming roller 20 together with the inner band 14 the press nip 52 of a shoe press 57, which is a Schuhpreßeinheit, here a shoe press roller 56, and as a counter element a drying cylinder, preferably a Yankee cylinder 54, included.

The following taken by the forming roller 20 through the inner band 14 Tissuebahn 12 is thus in the present case together with this formed by a felt inner band 14 through the shoe press 57 led. This embodiment thus does not fall within the scope of the claims.

In the strip running direction L in front of the press nip 52, this is the tissue web 12 leading inner band 14 via an evacuated device, here a suction roller 58, guided.

The Yankee cylinder 54 may be associated with a dryer hood 60. The shoe press 34 or 57 may for example be designed as this is described in EP 99 125 789. After that, such Shoe press 34 and 57, for example, have a press nip whose Length considered in strip running direction L is less than or equal to a value is about 60 mm and its resulting over the press nip length Pressure profile has a maximum pressure, the greater or equal a value of about 3.3 MPa ("ShortShoe").

According to an alternative also described in EP 99 125 789 Embodiment, the shoe press 34 and 57, for example, also have a press nip whose length considered in the tape running direction L. greater than a value of about 80 mm, and preferably less than 200 mm, in particular at most 150 mm, and which is above the Press nip length resulting pressure profile has a maximum pressing pressure, which is less than or equal to a value of about 2 MPa ("LongShoe").

The respective tissue machine may comprise a drying zone in which the tissue web 12 at least partially by pressurized displacement gas can be acted upon (TAD, Through Air Drying).

The respective drainage sieves with zonal different Siebdurchlässigkeit For example, from a by shot and Warp threads formed tissue. The zones can be different Siebdurchlässigkeit for example by the use of Web threads of different diameter and / or different Web pattern generated.

As sieves zonal different permeability come for example Sieves of the type in question, as described in PCT / GB99 / 02684 (WO-A-00 12817) are described. Thereafter, the sieves in question, in particular from a tissue exist in the one or more levels envisaged in one first direction extending threads extending in a second direction Threads are interwoven to form a grid, a multitude of systematically distributed areas of specifiable configuration separated and determined accordingly, the systematic distributed areas each at least three in one and at least includes three extending in the other direction threads. At the threads these may in particular be weft threads and warp threads.

FIG. 3 shows a former which consists of a combination of the two in FIG the shaper shown in Figures 1 and 2 results. There are corresponding ones Parts provided with the same reference numerals.

Also in the present case, the delivered from the headbox 22 pulp suspension from diagonally down into the between the two drainage bands 14, 16 formed Stoffeinlaufspalt 18 injected. The outer band 16 is coming from below over a guide roller 24 over led at the headbox 22 to Formierwalze 20 and from there via a further deflection roller 26 returned again.

The two drainage belts 14, 16 are still in the field of Forming roller 20 separated again. The inner band 14 is fed back via a guide roller 28. In strip running direction L Before the deflection roller 28, the tissue web is in the region of a deflection roller 30 taken over by a band 32 of the inner band 14 and the Pressing nip 52 of a shoe press 57 supplied, which is a Schuhpreßeinheit, here a shoe press roll 56, and as a counter element a drying cylinder, preferably a Yankee cylinder 54.

In the strip running direction L in front of the press nip 52, this is the tissue web 12 leading volume 32 again on an evacuated device, here a suction roll 58, guided.

FIG. 4 purely by way of example shows a weaving pattern diagram of a repetitive one Section of a possible embodiment of a through such fabric formed drainage sieve with zonal different Wire permeability. The repeating weave pattern diagram in the present embodiment comprises ten warp threads and ten Wefts. In the area of the hatched squares is the respective Weft below the respective warp thread. In contrast, lies in the area the bright squares of each weft above the respective Warp. Depending on the circumstances, one or the other the other side of the weave pattern diagram are outside.

The hatched areas form a grid 62, through which finally a Variety of systematically distributed areas 64 specifiable configuration separated and determined accordingly.

LIST OF REFERENCE NUMBERS

10

molder

12

tissue web

14

Drainage tape, inner band

16

Drainage tape, outer band

18

Stock inlet gap

20

forming roll

22

headbox

24

deflecting

26

deflecting

28

deflecting

30

deflecting

32

waterproof band

34

shoe press

36

shoe press

38

backing roll

40

bottom felt

42

deflecting

44

deflecting

46

Transfer roll

48

Tissue cylinder, Yankee cylinder

50

conditioning device

52

nip

Claims (22)

1. Machine for manufacturing a tissue web (12), comprising at least one circulating endless dewatering fabric (14, 16) and a forming element (20), in particular a forming region comprising a forming roll, the dewatering fabric (14, 16) being led over the forming element, at least one dewatering fabric (14, 16) having a fabric permeability that is different zone by zone, characterized in that at least one shoe press (34, 57) is provided, which is arranged after the forming region in the belt running direction (L) as a unit separate from the forming region.
2. Machine according to Claim 1, characterized in that it comprises a former (10) having two circulating endless dewatering belts (14, 16) which run together, forming a stock inlet gap (18), and are then led over the forming element (20), such as in particular a forming roll, and in that a dewatering fabric (14) with a fabric permeability that is different zone by zone is provided as an outer belt (16) which does not come into contact with the forming element and/or as an inner belt.
3. Machine according to Claim 2, characterized in that the tissue web (12) carried along by one of the two dewatering belts (14, 16) after the forming element (20) is led through the shoe press (57) together with this dewatering belt (14).
4. Machine according to one of the preceding claims, characterized in that the shoe press (57) comprises a shoe press unit (56) and, as an opposing element, a drying cylinder, preferably a Yankee cylinder (54).
5. Machine according to one of the preceding claims, characterized in that the shoe press (34, 57) has a press nip of which the length, viewed in the band running direction (L), is less than or equal to a value of about 60 mm, and in which the pressure profile resulting over the press nip length has a maximum pressing pressure which is greater than or equal to a value of about 3.3 MPa.
6. Machine according to one of Claims 1 to 5, characterized in that the shoe press (34, 57) has a press nip of which the length, viewed in the band running direction (L), is greater than a value of about 80 mm and preferably less than 200 mm, in particular at most 150 mm, and in which the pressure profile resulting over the press nip length has a maximum pressing pressure which is less than or equal to a value of about 2 MPa.
7. Machine according to one of the preceding claims, characterized in that it comprises a drying zone in which the tissue web (12) can be acted on, at least to some extent, by a displacement gas that is under pressure.
8. Machine according to one of the preceding claims, characterized in that at least one dewatering fabric (14, 16) is provided with a fabric permeability that is different zone by zone in the initial dewatering region.
9. Machine according to one of the preceding claims, characterized in that the former (10) provided is a twin-wire former.
10. Machine according to one of Claims 1 to 9, characterized in that the former (10) provided is a crescent former, of which the outer belt (16) is formed by a dewatering fabric with a fabric permeability that is different zone by zone and of which the inner belt (14) is formed by a felt.
11. Machine according to one of the preceding claims, characterized in that at least one dewatering fabric (14, 16) having a fabric permeability that is different zone by zone is provided and consists of a fabric formed by weft and warp threads.
12. Machine according to Claim 11, characterized in that the zones of different fabric permeability of the dewatering fabric (14, 16) are produced by using weaving threads of different diameter and/or different web pattern.
13. Machine according to one of the preceding claims, characterized in that the dewatering fabric (14, 16) having a fabric permeability that is different zone by zone is assigned a conditioning device (50) such as in particular a fabric cleaning device.
14. Method for manufacturing a tissue web (12) by means of a tissue machine comprising at least one circulating endless dewatering fabric (14, 16) and a forming element (20), in particular a forming region comprising a forming roll, the dewatering fabric being led over the forming element (20), and at least one dewatering fabric (14, 16) having a fabric permeability that is different zone by zone, characterized in that at least one shoe press (34, 57) is used, which is arranged after the forming region in the belt running direction (L) as a unit separate from the forming region.
15. Method according to Claim 14, characterized in that use is made of a former (10) having two circulating endless dewatering belts (14, 16) which run together, forming a stock inlet gap (18), and are then led over a forming element (20), such as in particular a forming roll, and in that a dewatering fabric with a fabric permeability that is different zone by zone is used as an outer belt (16) which does not come into contact with the forming element and/or as an inner belt (14).
16. Method according to Claim 15, characterized in that the tissue web (12) carried along by one of the two dewatering belts (14, 16) after the forming element (20) is led through the shoe press (57) together with this dewatering belt (14).
17. Method according to one of the preceding Claims 14 to 16, characterized in that the dewatering is carried out at a machine speed which is higher than about 1300 m/min, in particular higher than about 1500 m/min and preferably higher than about 1800 m/min.
18. Method according to one of the preceding Claims 14 to 17, characterized in that at least one dewatering fabric (14, 16) having a fabric permeability that is different zone by zone is used in the initial dewatering region.
19. Method according to one of the preceding Claims 14 to 18, characterized in that the former (10) used is a twin-wire former.
20. Method according to one of Claims 14 to 19, characterized in that the former (10) used is a crescent former, of which the outer belt (16) is formed by a dewatering fabric with a fabric permeability that is different zone by zone and of which the inner belt (14) is formed by a felt.
21. Method according to one of the preceding Claims 14 to 20, characterized in that at least one dewatering fabric (14, 16) having a fabric permeability that is different zone by zone is used and consists of a fabric formed by weft and warp threads.
22. Method according to one of the preceding Claims 14 to 21, characterized in that the zones of different fabric permeability of the at least one dewatering fabric (14, 16) used are produced by using weaving threads of different diameter and/or different web pattern.

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