EP1936031B1 - Machine for producing a sheet of fibrous material - Google Patents

Abstract

The machine (20) has a former (24) in which a structured belt (26) is provided. The structured belt has a forming belt on which the fibrous web (22) is formed on the structured belt and de-watered between the structured belt and forming belt. The forming belt has a printed forming fabric (28) and a dimensional structured paper fabric with zonally different permeability. A drying device (30) is provided for further de-watering of the web. The web is guided together with the structured belt through the drying device. Hot air flows through the structured belt and the web in the drying device.

Description

The invention relates to a machine for producing a fibrous web, in particular paper, board or tissue web, with a former in which the fibrous web is formed on a structured band and dewatered between this and a forming belt, as well as with a drying device for further dewatering of the fibrous web through which the fibrous web is guided together with the structured band and in which the permeable structured band and the fibrous web are flowed through by hot air. Such a machine is for example in the WO 2005/075737 A1 described.

The document US 2006/0085998 describes a process for making a tissue or sanitary membrane. The web is formed in the forming part of the tissue machine between a structured sieve and an outer forming fabric in the region of a forming roll. Subsequently, the tissue web, lying on the structured wire, is passed through a drying device and then transferred to a Yankee drying cylinder for further treatment _.

From the WO 00/75423 A1 A so-called printed forming fabric is already known.

Such a printed forming belt can be used for example in conventional tissue machines. When used in such conventional tissue machines, however, the use of a printed forming belt brings no advantage because the sheet is 100% pressed and the volume is too small to produce a micro- and macro-embossed sheet in the machine , It is a corresponding processing plant for embossing the sheet required.

A printed forming belt can also be used in a TAD (Through Air Drying) machine where the volume and sheet capacity are 50 to 100% higher than conventional machines.

Again Fig. 1 can be removed, in such a TAD machine, the sheet between two mesh belts 10, 12 is formed. It shows Fig. 1 in schematic Partial representation of the Formierbereich such a TAD machine. In Fig. 2 is shown in a schematic representation of the TAD machine including the TAD cylinder 14. As in particular on the basis of Fig. 2 can be seen, in such a TAD machine, the fibrous web is dewatered by means of vacuum following the forming area, wherein such dewatering takes place to a dry content of between 22 and 26%. Only after such a high consistency has been achieved is the fibrous web then transferred from the one forming fabric or belt 10, which is a smooth belt, to an embossing or structured belt 16, where it is wet-embossed by means of a vacuum box or wet embossing box, which sucks the fibers into the wells of the structured band 16.

By now aspirating an already formed fibrous web at a consistency of more than 20%, the fibers are stretched into the wells, thereby reducing the sheet thickness and leaving only a small portion of the fibers protected within the structure of the web, which are the fibers which are not pressed to achieve a certain quality (see Fig. 1 and 2 ). Thus, such a TAD machine requires a negative pull between the forming zone and the TAD zone. Typically, TAD machines in the TAD section are driven at 20% less speed to brush the fibers into the troughs of the belt. This will destroy all macro imprinting (drawings) of the printed forming belt due to the difference in speed between the forming zone and the TAD zone. For such TAD machines, macro- and micro-embossing must be done with the textured tape in the TAD zone rather than in the forming zone.

With such a micro- and macro-embossing in the machine, it would be possible to avoid making such an embossing in the processing plant and thus compacting the sheet and a loss of quality.

With a TAD machine, the quality is generated in the TAD zone. The negative pull (-0.8 V) in such a machine, which serves to produce the quality, destroys the embossing effect. In the Fig. 2 In addition, the areas 18 can be seen in which the fibrous web has no contact with the Yankee cylinder after being transferred from the structured band 16 to the Yankee cylinder 14.

The invention has for its object to provide a machine of the type mentioned, which is comparable in terms of quality, volume and water absorbency of the fibrous web produced with a TAD machine.

This object is achieved in that the Formierband is formed by a printed Formierband or a DSP band with zonal different permeability, wherein the printed Formierband or DSP band formed by a Formierband whose passing with the pulp suspension in contact with the surface Lines, dots and / or the like is coated. As a printed Formierband can be used in particular such a printed Formierband, as in the WO 00/75423 A1 is described.

The invention thus provides a machine for producing a fibrous web, in particular paper, board or tissue web, which comprises a former in which the fibrous web is formed on a structured belt and between this and a printed forming belt or DSP belt with zonal different permeability is dewatered, as well as a drying device for further dewatering of the fibrous web comprises, through which the fibrous web is then guided together with the structured band and in which the permeable structured band and the fibrous web are flowed through by hot air.

Since the generated fibrous web is already wet-structured in the machine, it is no longer necessary to continue to emboss the web as it passes through an expensive processing facility to transfer the micro and macro structures into the fiber material web press. It is thus avoided in particular that the structure must be pressed into the already dry fibrous web in a processing plant, which would bring a compaction of the web with it, whereby the quality, the volume and the capacity would be reduced.

In this case, the coating material may for example consist of plastic, rubber and / or the like.

If the coating material consists of plastic, it is expediently composed of polyethylene, polyamide, polyurethane and / or the like.

As already mentioned, the printed forming belt can be designed in particular as shown in the WO 00/75423 A1 is described.

Advantageously, the printed forming tape or DSP tape is provided for macro embossing and the structured tape for micro embossing of the fibrous web.

It is particularly advantageous if the fibrous web is formed at a consistency in a range of about 0.15 to about 0.35% on the structured tape.

In a preferred practical embodiment of the machine according to the invention, the fibrous web is further dehydrated in the drying device between the structured belt and a dewatering belt, wherein the hot air successively passing through the permeable structured band, fibrous web and dewatering band.

The drying device advantageously comprises an evacuated device, such as in particular a suction roller, over which the structured belt, the fibrous web and optionally the dewatering belt are guided.

Preferably, the structured band, the fibrous web and optionally the dewatering belt are pressed by a permeable press belt against the evacuated device. In this case, preferably the permeable press belt and then the fibrous web flow through the hot air.

The drying device expediently comprises a hot air hood.

Advantageously, this hot air hood is at least substantially opposite to a suction zone of the evacuated device.

It is particularly advantageous if over the evacuated device an extended in the running direction press nip for the fibrous web is formed.

In a preferred practical embodiment of the machine according to the invention, the fibrous web is guided, together with the structured strip following the drying device, through a press nip formed between a drying cylinder, in particular a Yankee cylinder, and a pressing element.

In particular, means may be provided to crepe the dry fibrous web in the area of the drying cylinder.

The machine is preferably used for the production of tissue paper.

According to the invention, the fibrous web is thus dehydrated between a structured or embossing belt and a printed forming belt or DSP belt. Further dewatering of the fibrous web is expediently carried out between the structured band and a dewatering band. The fibrous web is dewatered through the dewatering belt opposite the structured belt. The dewatering is carried out by an air flow, in particular hot air flow, and a mechanical pressure field, which is preferably generated by a permeable pressing belt. The air flow runs from the permeable press belt to the drainage belt. The sandwiched bands form a stretching in the web running direction press nip on a vacuumed device such as in particular a suction roll. The maximum peak pressure can be 40 times less than in a conventional press, in addition to this extended press nip is traversed by air. The fibrous web is supported and / or protected by the structured web and advantageously continued to a Yankee drying device. The fibrous web is further dried by this, for example, a Yankee cylinder and a hood drying device and creped dry.

With such a machine according to the invention, a structured fibrous web is produced, which is comparable to a TAD product. The same high quality is achieved without the need for a complex and expensive TAD machine. The cost can be reduced to about 40%, with less equipment and less labor. The machine can be kept simpler in construction, while the operation and maintenance are simplified. Total expenditure including energy, clothing, chemicals, etc. is reduced to about 35%.

Of particular advantage is that in the machine according to the invention the fibrous web is formed on a structured band, with a very low consistency, for example, between 0.15% to 0.35%, and the same structured belt carries the fibers within its structure protected from the head box to the point of transfer to the Yankee drying unit. In the Yankee drying unit, only the fibers in the raised area (knuckle area) of the structured strip are pressed. The protected fibers within the structure of the patterned tape remain unpressed to achieve the appropriate quality. The troughs of the structured tape are filled with the largest possible amount of fibers, since this represents the mass of unpressed fibers, which entails the high quality of the final product. With the printed forming belt or DSP band, therefore, a forming belt is selected, with which it is ensured that the wells of the structured belt remain filled with the largest possible amount of fibers.

Since the fibrous web produced is already structured, it is no longer necessary to further emboss the fibrous web as it passes through an expensive processing plant in order to introduce the micro- and macro-structures in the web. It is thus avoided that compressing the structure in the dry fibrous web in a processing plant, the fibrous web and accordingly the quality, volume and capacity are reduced.

It has been found that with the machine according to the invention, the micro-embossing can be carried out within the machine without densification of the fibers on the structured or embossing band and the macro-embossing by using the special printed Formierbandes, as for example in the WO 00/75423 A1 is described. In principle, as already mentioned, a DSP band with different permeability can also be used. Instead of a conventional embossing according to the invention thus takes place a fiber shift in the forming zone. This results, inter alia, the advantage that the intimacy between the bands on the evacuated device, in particular suction roll, not lost goes. The evacuated device or suction roll therefore entails a maximum drainage and a maximum dry content increase.

In addition, the printed forming belt or DSP belt can be replaced much faster than the structured belt, if the machine with a different macro-embossing (drawing) to be driven.

Consequently, with the machine according to the invention, a high paper quality can be achieved while avoiding additional expensive and expensive processing machines for the micro- and macro-embossing.

Fig. 1

eine schematische Teildarstellung des Formierbereichs einer herkömmlichen TAD-Maschine,

Fig. 2

eine schematische Darstellung einer herkömmlichen TAD-Maschine einschließlich des TAD-Zylinders,

Fig. 3

eine schematische Darstellung einer beispielhaften Ausführungsform einer erfindungsgemäßen Maschine,

Fig. 4

eine schematische vereinfachte Teildarstellung einer Formierzone, in der ein strukturiertes Band und ein bedrucktes Formierband oder ein DSP-Band mit zonal unterschiedlicher Permeabilität zur Entwässerung der Faserstoffbahn zusammengeführt sind,

Fig. 5

eine vergrößerte Darstellung des Bereichs A der Fig. 4 mit dem strukturierten Band bzw. DSP-Band gegenüberliegendem bedrucktem Band,

Fig. 6

eine vergrößerte Darstellung des Bereichs B in Fig. 3 mit der Oberfläche des Yankee-Zylinders gegenüberliegenden strukturiertem Band und

Fig. 7

ein Ausschnitt der fertigen, mittels einer erfindungsgemäßen Maschine erzeugten Faserstoffbahn, in der durch das bedruckte Formierband bzw. DSP-Band hervorgerufene Muster zu erkennen sind.

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

Fig. 1

a partial schematic representation of the Formierbereichs a conventional TAD machine,

Fig. 2

a schematic representation of a conventional TAD machine including the TAD cylinder,

Fig. 3

a schematic representation of an exemplary embodiment of a machine according to the invention,

Fig. 4

a simplified schematic partial representation of a forming zone in which a structured band and a printed forming belt or a DSP band are combined with zonal different permeability for dewatering the fibrous web,

Fig. 5

an enlarged view of the area A of Fig. 4 with the structured band or DSP band opposite printed tape,

Fig. 6

an enlarged view of the area B in Fig. 3 with the surface of the Yankee cylinder opposite structured band and

Fig. 7

a section of the finished, produced by means of a machine according to the invention fibrous web, in the pattern caused by the printed forming belt or DSP tape pattern can be seen.

Fig. 3 shows a schematic representation of an exemplary embodiment of an inventive machine 20 for producing a fibrous web 22, which may be in particular a paper, board or tissue web, act. The machine 20 preferably serves to produce a tissue web.

The machine 20 comprises a former 24 in which the fibrous web 22 is formed on and dewatered between a patterned belt 26 and a forming belt formed by a printed forming belt 28 or a DSP belt of zonal different permeability.

The machine 20 further comprises a drying device 30 for further dewatering of the fibrous web 22, through which the fibrous web 22 is guided together with the structured band 26 and in which the permeable structured band 26 and the fibrous web 22 are flowed through by hot air.

The printed forming belt 28 or DSP belt can be formed, in particular, by a forming belt, the belt of which comes into contact with the pulp suspension Surface is coated with local lines, dots and / or the like. The coating material may in particular consist of plastic, rubber and / or the like. For example, the coating material can consist of polyethylene, polyamides, polyurethane and / or the like.

As a printed forming belt 26, for example, such a printed forming belt can be used, as in the WO 00/75423 A1 is described.

The machine 20 comprises a headbox 32 and a forming element, in particular a forming roller 34, over which the structured band 26 and the printed forming band 28 or DSP band are guided.

The structured band 26 or DSP band and the printed forming band 28 converge to form a material inlet gap 36, wherein they are guided over the forming roller 34 with the structured band 26 as inner band and the printed banding band 28 or DSP band as outer band , By means of the headbox 32 pulp suspension is introduced into the stock inlet gap 36.

When viewed in the web running direction L downstream of the forming roller 34, at least one evacuated embossing device 38 can be provided, which is arranged on the side of the permeable structured belt 26 facing away from the fibrous web 22 and through which the fibrous web 22 is sucked into the structure of the structured belt 22.

As based on the Fig. 3 it can be seen, the fibrous web 22 is fed to the forming device 34 along with the structured band 26 of the drying device 30, in which the fibrous web 22 between the structured band 26 and a dewatering belt 40 (for example, a felt), further dehydrated. In this drying device 30, the permeable structured band 26, the fibrous web 22 and the dewatering belt 40 successively flows through drying air, in particular hot air.

For this purpose, the drying device 30 comprises an evacuated device, in particular a suction roller 42, over which the structured belt 26, the fibrous web 22 and the dewatering belt 40 are guided.

In this case, the structured band 26, the fibrous web 22 and the dewatering belt 40 can be pressed against the suction roll 42 by a permeable pressing belt 44. In the present case, the permeable press belt 44, the structured belt 26 and the fibrous web 22 are thus successively flowed through by the drying air, in particular hot air.

In the present case, the drying device 30 comprises a hot air hood 46, which may face at least substantially a suction zone of the suction roll 42.

Over the suction roller 42 thus formed in the web running direction L extended press nip for the fibrous web, which is at least partially flowed through by hot air simultaneously.

The fibrous web 22, together with the structured band 26 following the drying apparatus 30, is guided through a press nip 52 formed between a drying cylinder 48, in particular a Yankee cylinder, and a pressing element 50, here for example a press roll. In addition, means may be provided to crepe the dry fibrous web 22 in the region of the drying cylinder or Yankee cylinder.

As based on the Fig. 3 As can be seen, the fibrous web 22 is supported by the structured band 26 from the former 24 to the drying cylinder or Yankee cylinder 48.

The printed forming belt 28 or DSP belt is provided for macro embossing and the structured belt 26 for micro embossing of the fibrous web 22.

In particular, the fibrous web 22 may be formed on the structured band 26 at a consistency in a range of about 0.15 to about 0.35%.

Fig. 4 shows a schematic simplified representation of a forming zone in which a structured band 26 and a printed forming belt 28 or a DSP band with zonal different permeability for the dewatering of the fibrous web 22 are merged.

Fig. 5 shows an enlarged view of the area A of Fig. 4 with the structured band 26 opposite printed Formierband 28 and DSP band. It can be seen that the quality of the paper is produced here in the forming zone.

Fig. 6 shows an enlarged view of the area B of Fig. 3 with the surface 54 of the Yankee cylinder 48 opposite structured band 26. As with this Fig. 6 can be seen, the embossing effect in the fibrous web 22 is maintained, which is guided on one and the same structured band 26 from the headbox 32 to the Yankee cylinder 48.

Fig. 7 shows a section of the finished, produced by the machine 30 according to the invention fibrous web 22, in which by the printed forming belt 28th or DSP band caused pattern 56, ie the respective macro imprints are visible.

LIST OF REFERENCE NUMBERS

10

screen belt

12

screen belt

14

TAD cylinder

16

textured band, embossing band

18

Area

20

machine

22

Fibrous web

24

molder

26

structured band

28

printed band, DSP band

30

drying device

32

headbox

34

Forming element, forming roller

36

Stock inlet gap

38

suctioned embossing device

40

dewatering belt

42

vacuumed device, suction roller

44

permeable press belt

46

Hot air hood

48

Drying cylinder, Yankee cylinder

50

Pressing element, press roller

52

press nip

54

surface

56

template

Claims (15)

1. Machine (20) for producing a fibrous web (22), in particular a paper, cardboard or tissue web, having a former (24), in which the fibrous web (22) is formed on a structured belt (26) and is dewatered between the latter and a forming belt (28), and having a drying apparatus (30) for further dewatering of the fibrous web (22), through which drying apparatus (30) the fibrous web (22) is guided together with the structured belt (26) and in which drying apparatus (30) hot air flows through the permeable structured belt (26) and the fibrous web (22), characterized in that the forming belt is formed by a printed forming belt (28) or a DSP belt with zonally variable permeability, the printed forming belt (28) or DSP belt being formed by a forming belt, the surface of which, which comes into contact with the fibrous stock suspension, is coated with local lines and points.
2. Machine according to Claim 1, characterized in that the coating material is composed of plastic or rubber.
3. Machine according to Claim 2, characterized in that the coating material is composed of polyethylene, polyamide or polyurethane.
4. Machine according to one of the preceding claims, characterized in that the printed forming belt (28) or DSP belt is provided for macro-embossing and the structured belt (26) is provided for micro-embossing of the fibrous web (22).
5. Machine according to one of the preceding claims, characterized in that the fibrous web (22) is formed on the structured belt (26) at a consistency in the range from approximately 0.15 to approximately 0.35%.
6. Machine according to one of the preceding claims, characterized in that the fibrous web (22) is dewatered further in the drying apparatus (30) between the structured belt (26) and a dewatering belt (40), the hot air flowing successively through the permeable structured belt (26), the fibrous web (22) and the dewatering belt (40).
7. Machine according to one of the preceding claims, characterized in that the drying apparatus (30) comprises an evacuated device (42) such as, in particular, a suction roll, over which the structured belt (26), the fibrous web (22) and optionally the dewatering belt (40) are guided.
8. Machine according to Claim 7, characterized in that the structured belt (26), the fibrous web (22) and optionally the dewatering belt (40) are pressed against the evacuated device (42) by a permeable press belt (44).
9. Machine according to Claim 8, characterized in that the hot air flows through first of all the permeable press belt (44) and subsequently the fibrous web (40).
10. Machine according to one of preceding claims 7 to 9, characterized in that the drying apparatus (30) comprises a hot-air hood (46).
11. Machine according to Claim 10, characterized in that the hot-air hood (46) lies at least substantially opposite a suction zone of the evacuated device (42).
12. Machine according to one of preceding claims 7 to 11, characterized in that a pressure nip which is lengthened in the web running direction (L) is formed for the fibrous web (22) over the evacuated device (42).
13. Machine according to one of the preceding claims, characterized in that, after the drying apparatus (30), the fibrous web (22) is guided together with the structured belt (26) through a pressure nip (52) which is formed between a drying cylinder (48), in particular a yankee cylinder, and a pressing element (50).
14. Machine according to Claim 13, characterized in that means are provided for creping the dry fibrous web in the region of the drying cylinder.
15. Machine according to one of the preceding claims, characterized in that the fibrous web (22) is carried by the structured belt (26) from the former (24) to the drying cylinder or yankee cylinder (48).

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