EP1314817B1 - Method and machine for manufacturing a fibrous web - Google Patents

Abstract

The assembly to produce a web (12), especially of tissue or toilet paper, carries the web through at least two press nips (I,II) with a blanket (14). The press nips are formed between a smooth roller (16) and counter rollers (18,20). The web is given a wet creped effect at the smooth roller, and is then pressed against an embossing belt (22). The web is detached from the smooth roller by a scraper (34), to move in a free path to the embossing belt of ≤ 50 mm and preferably ≤ 30 mm. After the wet embossing action, the web is pressed against a drying cylinder (24).

Description

The invention relates to a method and an apparatus for producing a fibrous web, in particular tissue or hygiene web. A method and a device of this type is known for example from DE 195 48 747 C2. Although the known from this DE 195 48 747 C2 compact press provides the required drainage performance. A process for drying tissue is given accordingly. However, if the fibrous web is now driven 100% through such a press, the paper quality properties, in particular volume and water-shrinking capacity, are completely lost.

Prior art US4,356,059 discloses a machine for making a tissue web in which a tissue web is fed together with a felt by two press nips formed between a smooth roll and a respective backing roll and unsupported by the smooth roll over a free draw on a stamping tape arrives.

US Pat. No. 4,849,054 discloses a machine for producing tissue paper in which a tissue web is passed through a press nip formed between a smooth roll and a counter roll and then passes onto an embossing belt.

WO 00/14330 describes a tissue machine in which the tissue ride passes through a shoe press nip along with a smooth belt and then from the smooth belt without free draw, i. supported, transferred to an embossing belt. According to this publication, the tissue web is transferred from the embossing belt to dry it on a Yankee drying cylinder and then creped by this in a dry state.

US8,051,105 further discloses a tissue machine having a shoe press unit and a subsequent Yankee pad cylinder on which it is dried.

The aim of the invention is to provide an improved method and an improved device of the type mentioned, with which a higher quality of the final product can be achieved. In this respect, a better quality should be achieved, in particular with regard to the volume (bulk) and the water holding capacity.

According to the invention, this object is achieved by a method for producing a fibrous web, in particular tissue or sanitary web, in which the fibrous web is guided together with a felt by at least one press nip formed between a smooth roll and a respective counter element, wherein the counter element of a press nip formed by a shoe press unit is, and in which the fibrous web is finally wet embossed on a stamping tape and after the wet embossing on a drying cylinder, in particular Yankee drying cylinder is guided, the fibrous web is released from the smooth roll by wet creping and unsupported by a free train from the smooth roll to Embossing belt arrives.

The free draw between the smooth roller and the embossing belt should be less than 50 mm, preferably less than 30 mm, in the interests of stable guidance.

Due to this configuration, an improved volume and an improved retention capacity are achieved for the relevant fibrous web, ie in particular the paper, tissue or hygiene web in question. The method is particularly applicable to tissue papers and in particular towel tissue. With the wet embossing, the volume and the Water retention capacity rebuilt. It is particularly advantageous that it can be ensured with the embossing band following that only a small portion of the fibrous web is pressed again, while a larger proportion of the fibrous web is no longer pressed.

Following the wet embossing, the fibrous web can be pressed against a drying cylinder. For this purpose, the fibrous web is expediently guided together with the embossing belt by a press nip formed between the drying cylinder and a counter element, wherein the guided through the press nip fibrous web is in contact with the surface of the drying cylinder and rests with its other side on the embossing belt.

According to a preferred embodiment, the embossing belt takes over the falling down under the action of gravity from the smooth roller fibrous web.

The fibrous web is preferably sucked into the surface structure of the embossing belt by means of a suction element arranged on the side of the embossing belt remote from the fibrous web. In this case, the suction element is advantageously arranged in the region in which the embossing belt takes over the fibrous web.

As a drying cylinder, in particular a so-called Yankee cylinder can be used.

According to a preferred practical embodiment of the method according to the invention, the fibrous web is guided at a dry content in the range of about 25% to about 45% on the smooth roll and wet creped.

Advantageously, an embossing belt is used which is structured in such a way that, for this embossing belt, there are zones which are set back in comparison to the area ratio or holes smaller area fraction results in raised or closed zones and correspondingly a smaller area fraction of the fibrous web is pressed. In this case, an embossing belt is preferably used in which the area fraction of raised or closed zones is ≤40% and preferably in a range of about 20% to about 30%.

The fibrous web is conveniently passed over the drying cylinder at a dry content in the range of about 35% to about 50%.

According to an expedient practical embodiment, the fibrous web is preferably dry-creped at a dry content of about 95% and then wound up.

As a suction element, in particular a stamping box or the like can be used.

In particular, a scraper for wet creping and detachment of the fibrous web from the smooth roll and for cleaning this roll can be used in conjunction with the smooth roll.

According to an advantageous practical embodiment of the method according to the invention, a press with two press nips is formed using the smooth roller by this smooth roller is assigned as a further counter element a Sauganpresswalze or suction roll. The shoe press unit comprises a flexible band guided in the area of the press nip via a press shoe. It can be used as shoe press unit in particular provided with a flexible roll shell shoe press roll. It should be the Press nip the shoe press unit in the interest of a good but gentle drainage in the web running direction be longer than 80, preferably longer than 120 mm. In order not to reduce the volume too much, the maximum pressing pressure in the press nip of the shoe press unit should be less than 2.5 MPa, preferably less than 1.6 MPa.

According to an advantageous expedient embodiment, the felt is guided through the two press nips together with the fibrous web in each case.

According to a further advantageous embodiment of the method according to the invention, a press is formed with only one press nip using the smooth roller and the shoe press unit. The fibrous web is guided together with the felt through this press nip. In this case, the fibrous web is preferably sucked against the felt by means of a suction element disposed on the side of the felt facing away from the fibrous web and in the web running direction in front of the press nip. As a suction element, in particular a suction box or the like can be used.

In particular, an embossing screen or an embossing membrane or a TAD screen (TAD = Through Air Drying) can be used as embossing or structural strip.

The felt is preferably a forming felt.

The object specified above is also achieved by a device for producing a fiber web. In particular, tissue or hygiene web, in which the fibrous web is guided together with a felt by at least one press nip formed between a smooth roll and a respective counter element, wherein the counter element of a press nips is formed by a shoe press unit, and in which the fibrous web then on a stamping tape and is wet embossed on this, and in which the fibrous web after the wet embossing on a drying cylinder, in particular Yankee drying cylinder is guided, and wherein the smooth roller is associated with a scraper for wet creeping and detachment of the fibrous web and the fibrous web supported by the smooth roller over a free train passes to the embossing belt.

Preferred embodiments of the device according to the invention are specified in the subclaims.

The invention can be applied to any formers and in particular to Crescsnt-Formem. Duo-Formers, C-Wrap Formers, S.Wraph-Formem.

Figur 1

eine schematische Teildarstellung einer Vorrichtung zur Herstellung einer Faserstoffbahn, wobei der glatten Walze zur Bildung einer Presse mit zwei Pressnips eine Sauganpresswalze oder Saugwalze und eine Schuhpresseinheit zugeordnet sind und zusammen mit der Faserstoffbahn jeweils auch der Filz durch die beiden Pressnips geführt ist,

Figur 2

eine schematische Teildarstellung einer weiteren Ausführungsform der Vorrichtung, wobei der glatten Walze zur Bildung nur eines Pressnips eine Schuhpresseinheit zugeordnet ist, und

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

FIG. 1

a schematic partial view of an apparatus for producing a fibrous web, wherein the smooth roller for forming a press with two press nips a Sauganpresswalze or suction roll and a shoe press unit are assigned and together with the fibrous web in each case the felt is guided by the two press nips,

FIG. 2

a schematic partial view of a further embodiment of the device, wherein the smooth roller is assigned to form only a press nip a shoe press unit, and

FIG. 1 shows, in a schematic partial representation, a device 10 for producing a fibrous web 12, which may in particular be a tissue or hygiene web.

In this case, the fibrous web 12 is guided together with a felt 14 by at least one formed between a smooth roller 16 and a respective counter element 18, 20 Pressnip I, II, wet creped on the smooth roller 16 and the smooth roller 16 in free train on an embossing belt 22 pressed. The free train has a length of approx. 30 mm.

Subsequent to the wet creping and wet embossing, the fibrous web 12 is pressed against a drying cylinder 24, which may in particular be a so-called Yankee cylinder. The fibrous web 12 is guided together with the embossing belt 22 by a press nip 28 formed between the drying cylinder 24 and a counter element 26. The through the press nip 28 guided fibrous web 12 is in this case in contact with the surface of the drying cylinder 24. With its other side it lies against the embossing belt 22.

The wet creping of the fibrous web 12 takes place at a dry content in the range of 25 to 45%.

Embossing belt 22 takes over the fibrous web 12 which slopes downwards under the action of gravity from smooth roller 16. In the region of this transfer point, a suction element 30 is arranged on the side of embossing belt 22 facing away from fibrous web 12, through which fibrous web 12 enters the surface structure the embossing belt 22 is sucked and pressed with it.

The embossing belt 22 can in particular be structured so that this results in an embossing belt 22 in comparison to the area ratio of recessed zones or holes smaller area fraction of raised or closed zones and correspondingly a smaller area fraction of the fibrous web 12 is pressed.

The surface portion of the embossing belt 22 at raised or closed zones may be in particular ≦ 40% and is preferably in a range from about 20% to about 30%.

The fibrous web 12 can be guided over the drying cylinder 24, in particular at a dry content in the range from about 35% to about 50%. As can be seen with reference to FIG. 1, a drying hood 32 can be assigned to this drying cylinder 24.

The fibrous web 12 may then preferably be dry-creped at a solids content of about 95% and subsequently wound up.

In particular, an embossing box can be provided as the suction element 30.

As can be seen from Figure 1, the smooth roller 16 is a scraper 34 for wet creeping and thus also associated with detachment of the fibrous web 12 and for cleaning the roller 16.

In the present embodiment, the smooth roller 16 for forming a compact press with two press nips I, II as counter-elements, a Sauganpresswalze or suction roller 18 and a shoe press unit 20 are assigned. The shoe press unit 20 comprises a guided in the press nips II via a press shoe 36 flexible tape. It can be provided as a shoe press unit 20 in particular provided with a flexible roll shell shoe press roll.

In the present case, together with the fibrous web 12, the felt 14 is guided through the two press nips I, II. As can be seen from FIG. 1, the felt 14 in the area between the two press nips I, II is separated from the fibrous web 12 which continues on the smooth roller 16.

In the present case, a former with two circumferential dewatering belts 14, 38 is provided, wherein the inner belt is formed by the felt 14 in the form of a forming felt. The two dewatering belts 14, 38 merge to form a stock inlet gap 40 and are conveyed by a forming member 42, such as e.g. a forming roll out. By means of a headbox 44, the pulp suspension is introduced into the stock inlet gap 40.

The roller 16 has a smooth or closed surface (flat and release surface). For example, an embossing screen or an embossing membrane or a TAD screen can be used as embossing belt 42.

As indicated in FIG. 1, the dry content of the fibrous web 12 immediately after the first press nip I may, for example, be in a range from approximately 20% to approximately 35%. As indicated in the figure 1 and also already mentioned, is the fibrous web 12 is preferably passed over the drying cylinder 24 at a dry content in the range of about 35% to about 50%.

In principle, any types of shapers are conceivable. For example, the invention can be applied to crescent formers, duo-formers, C-wrap formers, S-wrap formers and so on.

FIG. 2 shows a schematic representation of a further embodiment of the device 10. In this case, the smooth roller 16 is associated with a shoe press unit 20, which again may in particular be a shoe press roll, to form a press with only one press nip I as counter element. The fibrous web 12 is guided together with the felt 14 through this press nip I.

On the side facing away from the fibrous web 12 of the felt 14 and in the web running direction L before the press nip I is a suction element 46, z. As a suction box or the like, provided by the fibrous web 12 is sucked against the felt 14.

Moreover, this embodiment may at least substantially again have the same structure as that of Figure 1, wherein corresponding parts corresponding reference numerals are assigned.

The press nip of the shoe press unit 20 has a length of about 100 mm, the maximum pressing pressure being less than 2 MPa.

LIST OF REFERENCE NUMBERS

10

contraption

12

Fibrous web

14

felt

16

smooth roller

18

Counter element, Sauganpresswalze or suction roll

20

Counter element, shoe press unit

22

embossing tape

24

drying cylinders

26

counter-element

28

press nip

30

suction

32

Trockenhaube

34

scraper

36

press shoe

38

dewatering belt

40

Stock inlet gap

42

forming element

44

headbox

46

suction

L

Web direction

I

press nip

II

press nip

Claims (47)

1. Method of producing a fibrous web (12), in particular tissue or hygienic product web, in which the fibrous web (12), together with a felt (14), is guided through at least one press nip (I, II) formed between a smooth roll (16) and a respective opposing element (18, 20), the opposing element of a press nip (I, II) being formed by a shoe press unit (20), and in which the fibrous web (12) is then wet embossed on an embossing belt (22) and, after the wet embossing, is led over a drying cylinder (24), in particular a Yankee drying cylinder, characterized in that the fibrous web (12) is separated from the smooth roll (16) by means of wet creping and passes unsupported over a free draw from the smooth roll (16) to the embossing belt.
2. Method according to Claim 1, characterized in that the fibrous web (12) is pressed onto the embossing belt (22) after the free draw.
3. Method according to Claim 1 or 2, characterized in that the fibrous web (12) is wet creped and separated from the smooth roll (16) with the aid of a doctor.
4. Method according to one of the preceding claims, characterized in that the free draw between smooth roll (16) and embossing belt (22) is less than 50, preferably less than 30 mm.
5. Method according to one of the preceding claims, characterized in that the felt (14) is constructed as a forming felt.
6. Method according to one of the preceding claims, characterized in that after the wet embossing, the fibrous web (12) is pressed against the drying cylinder (24).
7. Method according to Claim 6, characterized in that the fibrous web (12) is guided together with the embossing belt (22) through a press nip (28) formed between the drying cylinder (24) and an opposing element (26), the fibrous web (12) guided through the press nip (28) being in contact with the surface of the drying cylinder and resting with the other side on the embossing belt (22).
8. Method according to one of the preceding claims, characterized in that the embossing belt (22) accepts the fibrous web (12) falling downwards from the smooth roll (16) under the action of the force of gravity.
9. Method according to one of the preceding claims, characterized in that the fibrous web (12) is sucked into the surface structure of the embossing belt (22) by means of a suction element (30) arranged on the side of the embossing belt (22) facing away from the fibrous web.
10. Method according to Claim 9, characterized in that the suction element (30) is arranged in the area in which the embossing belt (22) accepts the fibrous web (12).
11. Method according to one of the preceding claims, characterized in that a Yankee cylinder is used as the drying cylinder (24).
12. Method according to one of the preceding claims, characterized in that the fibrous web (12) is guided and wet creped on the smooth roll (16) at a dryness content in the range from about 25% to about 45%.
13. Method according to one of the preceding claims, characterized in that use is made of an embossing belt (22) which is structured such that the result for this embossing belt (22) is a smaller surface proportion of elevated or closed zones as compared with the surface proportion of set-back zones or holes, and accordingly a smaller surface proportion of the fibrous web (12) is pressed.
14. Method according to Claim 13, characterized in that use is made of an embossing belt (22) in which the surface proportion of elevated or closed zones is ≤40% and preferably lies in a range from about 20% to about 30%.
15. Method according to one of the preceding claims, characterized in that the fibrous web (12) is guided over the drying cylinder (24) at a dryness content in the range from about 35% to about 50%.
16. Method according to one of the preceding claims, characterized in that the fibrous web (12) is preferably dry creped at a dryness content of about 95% and is then reeled.
17. Method according to one of Claims 9 to 16, characterized in that the suction element (30) used is an embossing box.
18. Method according to one of the preceding claims, characterized in that, by using the smooth roll (16), a press having two press nips (I, II) is formed, by this smooth roll (16) being assigned a suction press roll or suction roll (18) as further opposing element.
19. Method according to Claim 18, characterized in that the felt (14) is in each case also guided through the two press nips (I, II) together with the fibrous web (12).
20. Method according to one of Claims 1 to 17, characterized in that, by using the smooth roll (16) and the shoe press unit (20), a press having only one press nip (I) is formed.
21. Method according to one of Claims 18 to 20, characterized in that the press nip of the shoe press unit (20) is longer than 80, preferably longer than 120 mm in the web running direction (L).
22. Method according to one of Claims 18 to 21, characterized in that the maximum pressure in the press nip of the shoe press unit is less than 2.5 MPa, preferably less than 1.6 MPa.
23. Method according to one of Claims 20 to 22, characterized in that the fibrous web (12) is sucked against the felt (14) by means of a suction element (46) arranged on the side of the felt (14) facing away from the fibrous web (12) and arranged upstream of the press nip (I) in the web running direction (L).
24. Method according to Claim 23, characterized in that the suction element (46) used is a suction box arranged upstream of the press nip (I) in the web running direction (L).
25. Apparatus (10) for producing a fibrous web (12), in particular tissue or hygienic product web, in which the fibrous web (12) is guided together with a felt (14) through at least one press nip (I, II) formed between a smooth roll (16) and a respective opposing element (18, 20), the opposing element of a press nip (I, II) being formed by a shoe press unit (20), and in which the fibrous web (12) then reaches an embossing belt (22) and is wet embossed on the latter, and in which, after the wet embossing, the fibrous web (12) is led over a drying cylinder (24), in particular a Yankee drying cylinder, characterized in that the smooth roll (16) is assigned a doctor (34) for wet creping and separating the fibrous web (12), and in that the fibrous web (12) passes unsupported over a free draw from the smooth roll (16) to the embossing belt.
26. Apparatus according to Claim 25, characterized in that the fibrous web (12) is pressed onto the embossing belt (22).
27. Apparatus according to Claim 25 or 26, characterized in that the felt (14) is constructed as a forming felt.
28. Apparatus according to one of Claims 25 to 27, characterized in that the free draw between the smooth roll (16) and the embossing belt (22) is less than 50, preferably less than 30 mm.
29. Apparatus according to one of Claims 25 to 28, characterized in that, after the wet embossing, the fibrous web (12) is pressed against the drying cylinder (24).
30. Apparatus according to Claim 29, characterized in that the fibrous web (12) is guided together with the embossing belt (22) through a press nip (28) formed between the drying cylinder (24) and an opposing element (26), the fibrous web (12) guided through the press nip (28) being in contact with the surface of the drying cylinder and resting with its other side on the embossing belt (22).
31. Apparatus according to one of Claims 25 to 30, characterized in that the embossing belt (22) accepts the fibrous web (12) falling downwards from the smooth roll (16) under the action of the force of gravity.
32. Apparatus according to one of Claims 25 to 31, characterized in that on the side of the embossing belt (22) facing away from the fibrous web (12) there is arranged a suction element (30), in order to suck the fibrous web (12) into the surface structure of the embossing belt (22).
33. Apparatus according to Claim 32, characterized in that the suction element (30) is arranged in the area in which the embossing belt (22) accepts the fibrous web (12).
34. Apparatus according to one of Claims 25 to 33, characterized in that the drying cylinder 24 provided is a Yankee cylinder.
35. Apparatus according to one of Claims 25 to 34, characterized in that the fibrous web (12) is guided and wet creped on the smooth roll (16) at a dryness content in the range from about 25% to about 45%.
36. Apparatus according to one of Claims 25 to 35, characterized in that the embossing belt (22) is structured such that for this embossing belt (22), the result is a smaller surface proportion of elevated or closed zones as compared with the surface proportion of set-back zones or holes, and accordingly a smaller surface proportion of the fibrous web (12) is pressed.
37. Apparatus according to Claim 36, characterized in that the surface proportion of the embossing belt (22) of elevated or closed zones is ≤40% and preferably lies in a range from about 20% to about 30%.
38. Apparatus according to one of Claims 25 to 37, characterized in that the fibrous web (12) is guided over the drying cylinder (24) at a dryness content in the range from about 35% to about 50%.
39. Apparatus according to one of Claims 25 to 38, characterized in that the fibrous web (12) is preferably dry-creped at a dryness content of about 95% and then reeled.
40. Apparatus according to one of Claims 32 to 39, characterized in that the suction element (30) provided is an embossing box.
41. Apparatus according to one of Claims 25 to 40, characterized in that the smooth roll (16) is assigned a suction press roll or suction roll (18) as further opposing element in order to form a press having two press nips (I, II).
42. Apparatus according to Claim 41, characterized in that the felt (14) is in each case also guided through the two press nips (I, II) together with the fibrous web (12).
43. Apparatus according to one of Claims 25 to 40, characterized in that a press having only one press nip is formed.
44. Apparatus according to one of Claims 41 to 43, characterized in that the press nip of the shoe press unit (20) is longer than 80, preferably longer than 120 mm in the web running direction (L).
45. Apparatus according to one of Claims 41 to 44, characterized in that the maximum pressure in the press nip of the shoe press unit is less than 2.5 MPa, preferably less than 1.6 MPa.
46. Apparatus according to one of Claims 43 to 45, characterized in that on the side of the felt (14) facing away from the fibrous web (12) and upstream of the press nip (I) in the web running direction (L) there is provided a suction element (46), in order to suck the fibrous web (12) against the felt (14).
47. Apparatus according to Claim 46, characterized in that the suction element (46) provided is a suction box arranged upstream of the press nip (I) in the web running direction (L).

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