EP1626122B1 - Method and device for producing a fibre strip provided with a three-dimensional surface structure - Google Patents

Abstract

In a process to manufacture a tissue web with a three-dimensional embossed surface, the wet web (less than 35% dry matter content) is pressed by suction to the surface of a pre-embossing belt. The pre-dried web is then transferred to and pressed onto a second embossing belt where the three-dimensional structure is fixed. Also claimed is a commensurate tissue or hygiene material (12) drying and embossing assembly (10) with first (I) and second (II) de-watering and embossing zones. The web is embossed by an embossing sieve belt (14) moving around first (30) and second (24) embossing drums. The second embossing drum (22) squeezes the web (12) and embossing belt (14) against a drying cylinder (20).

Description

The invention relates to a method and an apparatus for producing a provided with a three-dimensional surface structure fibrous web, in particular tissue or sanitary membrane.

The embossing of a three-dimensional structure in the surface of a paper web, in particular a tissue web, in particular of hand-tissue, is known (see, for example WO 99/47749 . WO 01/18307 ). Furthermore, it is known that a very good paper quality can be achieved by a so-called through-air drying (TAD = Through Air Drying). The disadvantage, however, is that the use of TAD dryers is very expensive and correspondingly expensive.

The aim of the invention is to provide an improved method and an improved device of the type mentioned, with which, in particular, even without the use of a larger TAD-drying device in an economical and correspondingly cost-effective manner, a high quality of the final product can be achieved. In this case, in particular with regard to the water retention capacity, the water absorption rate, the volume (bulk), etc., a corresponding quality can be achieved.

The WO 93/00475 and the WO 00/19014 describe a process for the production of tissue paper in which the tissue web is pressed onto an embossing sieve and then dried by means of air flow in the direction of the embossing sieve in a TAD process.

The US 6,103,062 describes a process for the production of tissue paper in which the tissue paper is pressed onto a stamping belt in front of the Yankee drying cylinder by means of a shoe press. According to this publication, the tissue web is further dehydrated in the shoe press, with a press felt with capillary action being arranged on both sides of the tissue web.

The WO 99/47749 shows a process for the production of tissue paper, in which the tissue web is guided on an embossing belt together with a felt through a press nip formed between a roller and a Yankee cylinder.

The US 4,102,737 teaches a machine for the production of tissue paper, in which the tissue web is dried on a stamping tape by means of a TAD process.

According to the invention, this object is achieved by a method for producing a fibrous web provided with a three-dimensional surface structure, in particular tissue or hygiene web, in which the fibrous web is pressed at a dry content <35% by means of a first pressure field on an embossing belt, e.g. sucked, and thereby pre-embossed and then for further dewatering and drying by means of another pressure field is pressed once more on an embossing belt to fix the three-dimensional surface structure and strength and at least one fine-pored fabric with capillary effect is used to drain the web a covering with a foamed layer, wherein the fabric with foamed layer is guided together with an embossing belt and fibrous web lying therebetween around a suction roller and the clothing is in contact with a suction roller.

Due to this configuration, in the relevant fibrous web, i. in particular the paper, tissue or hygiene web in question, produces a sustainable three-dimensional surface structure which, even after the drying process in the desired manner in the web, i. in the paper, for example. Furthermore, the capillary action is used for dewatering to obtain the desired dry content. The use of a complex and correspondingly expensive TAD method is no longer necessary. Even without such a TAD drying device, it is now possible in particular to produce a sustainable surface structure, for example a tissue or hygiene web, after the forming area or forming zone.

As an embossing or structured band ("imprinting fabric", "structured fabric"), preferably an embossing screen or an embossing membrane is used.

In general, the fibrous web is pre-stamped after the forming area.

According to a preferred embodiment, at least the first pressure field is generated by means of a arranged on the side facing away from the fibrous web side of the embossing belt Saugelements to suck the fibrous web in the surface structure of the embossing belt. In this case, in particular a so-called wet vacuum can be used as a suction element.

It is also advantageous if the fibrous web in the further pressure field is gentle, i. preferably over a lengthened in the web running direction distance, is pressed.

The further pressure field is preferably generated by means of a press nip. In order to accomplish the most gentle pressing of the web, this Preßnip can be generated for example between a 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. As a drying cylinder, in particular a so-called Yankee cylinder can be used. As a counteracting element cooperating with the drying cylinder, it is possible in particular to use a shoe press unit which comprises a flexible band guided in the region of the press nip via a press shoe. In this case, a shoe press roll provided with a flexible roll shell is preferably used as the shoe press unit.

Advantageously, a provided within the loop of the embossing belt, preferably soft band, in particular felt, is guided by the Preßnip generating the further pressure field. The soft felt may, for example, be a felt with a foamed layer, which, as will be explained in more detail below, contributes to drainage of the fibrous web due to its capillary action (capillary fabric).

A preferred practical embodiment of the method according to the invention is characterized in that the pre-embossed fibrous web is dried on the drying cylinder or Yankee cylinder, the fibrous web is creped and / or the fibrous web is subsequently wound up.

According to a preferred embodiment of the method according to the invention, the dry content at which the fibrous web is pre-embossed, and / or the dry content at which the three-dimensional surface structure is fixed, in each case <35%, in particular <30% and preferably <25%. This will u.a. the water retention capacity and the volume increased sustainably, which means that even with the use of the final product, such as a respective tissue or tissue web, the desired embossment is still present. In particular, the advantage of a higher water retention capacity for towel tissue (towel paper) also comes into play when using the end product in question.

According to a preferred practical embodiment of the method according to the invention, an evacuated device is used between the suction pad producing the first pressure field and the press pad generating the further pressure field and the fibrous web is guided together with an embossing belt both via the evacuated device and through the press nip. It is advantageous if the evacuated device has a curved surface and the fibrous web and the embossing belt are guided over this curved surface. As a suctioned device, for example, a suction roll can be used.

The felt is conveniently passed between the embossing belt and the flexible belt of the shoe press unit through the press nip.

In certain cases, it is advantageous if the particular soft felt is also passed over the evacuated device. Here, since the suction of the evacuated device is reduced accordingly, this is preferably associated with a standing under pressure hood to support the negative pressure effect of the evacuated device.

Further advantages result from the relatively long common leadership of felt and embossing belt, as over a longer distance, the capillary action of the felt is used for dewatering the fibrous web.

The felt can be conditioned, for example, by means of a suction device, in particular by means of a suction box, before it is brought together with the embossing belt carrying the fibrous web. By appropriate conditioning, in particular, the dry content of the felt can be increased and the felt can be cleaned.

In particular, the embossing band can be placed in front of the evacuated device, i. For example, the suction roller, are guided over the suction element or the Naßsauger to suck the fibrous web in the three-dimensional surface structure of the embossing belt and thus impart this structure to the band. At the same time the relevant suction element brings a corresponding increase in dry content with it.

According to another advantageous embodiment of the method according to the invention, the felt is brought together only after the evacuated device with the embossing belt carrying the fibrous web. The evacuated device is therefore not wrapped in this case of the felt, whereby the suction effect of this device is increased and increased according to the dry content. The wet molding effect is maintained by the gentler dewatering by the so-called TissueFlex, which operates at a lower pressure and longer residence time compared to a shoe press roll.

It is also advantageous if the length of the press nip of the drying cylinder and the shoe press unit considered in the web running direction greater than a value of about 80 mm selected and the shoe press is designed so that over the Preßniplänge results in a pressure profile with a maximum pressure, which is less than or equal to a value of about 2.5 MPa. This ensures a gentle pressing, with which it is avoided that the structure produced in the fibrous web, such as tissue or sanitary membrane, is flattened out again.

As already mentioned, it is possible, for example, to insert a suction roll between the suction element producing the first pressure field and the press nip, which is preferably associated with a pressure hood.

According to a preferred practical embodiment of the method according to the invention, at least one dewatering screen with zonal different screen permeability is used in the forming area. The relevant drainage sieve can be provided in particular as an outer sieve. A corresponding embodiment of the method is particularly advantageous in the production of towel tissue. The screen produces a fine structure which increases the rate of water absorption and, in conjunction with the embossing of the present invention, brings with it increased water retention.

In certain cases, it is advantageous if a former with two circulating dewatering belts is used, which converge to form a Stoffeinlaufspaltes and are passed over a forming element such as in particular a forming roller, and as not coming into contact with the forming element in contact Outside belt and / or as inner band a drainage sieve with zonal different Siebdurchlässigkeit is used. In this case, for example, an embossing belt and preferably as an outer belt, a dewatering screen with zonal different Siebdurchlässigkeit be used as an inner band. It is also possible, for example, that the fibrous web is preferably taken over by an embossing belt from the inner band.

In wet embossing in a tissue machine provided with an embossing belt, it is particularly important to achieve the desired dry content. The web can be wet embossed by means of the embossing belt, for example by means of a suction box in front of the press. In order to avoid that the three-dimensional surface structure, which was pre-stamped by the wet embossing in the wet suction box, is again destroyed by a brief high pressure in the press nip, as is the case with a conventional suction press roll, according to advantageous practical embodiment of the method according to the invention by the Preßnip an embossing belt, eg embossing screen or embossing membrane, led, which is structured so that results for this embossing belt compared to the area ratio of recessed zones or holes smaller area ratio of raised or closed zones and Accordingly, in the Preßnip a smaller area fraction of the fibrous web is pressed. The smaller areal proportion of raised or closed zones provides the high density web areas for strength, while the larger areal fraction of recessed zones or holes remaining at least substantially unpressed will provide the desired water absorbency and volume as previously limited a complex and expensive Durchströmungs- or TAD drying were achieved.

In this case, an embossing belt can advantageously be used in which the areal proportion of raised or closed zones is ≦ 40% and is preferably in a range from about 25 to about 30%.

Conveniently, an embossing belt is used in which the raised zones and recessed zones are offset by cranks, i. result from crossing points of weft and warp threads, a screen mesh. As already mentioned, for example, an embossing membrane can also be used, with which the raised and recessed zones result through the holes. In this case, it is advantageous that 100% of the surface is pressed around the holes and results in a higher strength.

The embossing belt in question can be guided together with the fibrous web, for example, again over a drying cylinder, in particular Yankee cylinder. As a counter-element cooperating with the drying cylinder, a shoe press unit can in particular be used again. The length of the press nip considered in the web running direction as well as the pressure profile resulting over the press nip length can in particular be selected again as stated above.

It has been shown that with the inventive method, a 50% higher water absorption capacity (g H20 / g fibers) and a 100% higher volume (cm ³ / g) at the same tensile strength when using an embossing belt instead of a conventional felt in Preßnip can be achieved before creping.

Creping the web can improve the water absorbency by 50%, and taking this into account, TAD towel quality water absorption can be achieved.

The WO 93/00475 and the WO 00/19014 describe a process for the production of tissue paper in which the tissue web is pressed onto an embossing sieve and then dried by means of air flow in the direction of the embossing sieve in a TAD process.

The US 6,103,062 describes a process for the production of tissue paper in which the tissue paper is pressed onto a stamping belt in front of the Yankee drying cylinder by means of a shoe press. According to this publication, the tissue web is further dehydrated in the shoe press, with a press felt with capillary action being arranged on both sides of the tissue web.

The WO 99/47749 shows a process for the production of tissue paper, in which the tissue web is guided on an embossing belt together with a felt through a press nip formed between a roller and a Yankee cylinder.

The US 4,102,737 teaches a machine for the production of tissue paper, in which the tissue web is dried on a stamping tape by means of a TAD process.

For example, the foamed layer fabric may comprise a suction roll having a diameter of e.g. about 2 to 3 m or more suction rolls of smaller diameter, preferably two suction rolls with a diameter of, for example, in each case about 2 m, loop. The residence time of the web in the area of the suction roll or the suction rolls should expediently be greater than about 0.15 s and less than about 0.40 s.

The respective suction roll can be placed on its underside, e.g. be applied with vacuum, or it can be used a Saugsalze with associated Siphonabzug. In particular, with a smaller diameter, the water can be thrown off, for example by centrifugal force in a gutter.

A drainage taking advantage of the capillary action is already in the US 5,701,682 described. However, the capillary element in question is part of the suction roll here.

Despite the utilization of the capillary action for dehydration, the suctioned device can, in particular, again be associated with a hood under overpressure in order to support the negative pressure effect of the evacuated device.

According to a further preferred embodiment of the method according to the invention, the fibrous web for expelling water by gas pressure together with an embossing belt at least once, preferably twice, passed through a pressure chamber bounded by at least four parallel rollers and into which a compressed gas is introduced. The fibrous web is preferably guided together with the embossing belt and a membrane through the pressure chamber. The basic principle of such a displacement press, at the water in the fibrous web is displaced by air, for example, in the DE 19946972 described.

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

The invention is particularly applicable to Crescent Formers, Duo Formers, C-Wrap Formers, S-Wrap Formers and to the manufacture of multi-layer and multi-ply tissue.

Fig. 1

eine schematische Teildarstellung einer Vorrichtung zur Herstellung einer mit einer dreidimensionalen Oberflächenstruktur versehenen Faserstoffbahn,

Fig. 2

eine schematische Teildarstellung einer abgewandelten Ausführungsform der Vorrichtung, bei der der Filz nicht über die besaugte Einrichtung geführt ist,

Fig. 3

eine schematische Teildarstellung einer Ausführungsform einer Vorrichtung zur Herstellung einer mit einer dreidimensionalen Oberflächenstruktur versehenen Faserstoffbahn, bei der zusätzlich eine Entwässerungsvorrichtung vorgesehen ist, in der zur Entwässerung die Kapillarwirkung eines Filzes mit geschäumter Schicht ausgenutzt wird,

Fig. 4

eine schematische Teildarstellung einer weiteren Ausführungsform einer Vorrichtung zur Herstellung einer mit einer dreidimensionalen Oberflächenstruktur versehenen Faserstoffbahn, bei der zusätzlich eine Entwässerungsvorrichtung vorgesehen ist, in der zur Entwässerung die Kapillarwirkung eines Filzes mit geschäumter Schicht ausgenutzt wird,

Fig. 5

eine schematische Teildarstellung einer Ausführungsform einer Vorrichtung zur Herstellung einer mit einer dreidimensionalen Oberflächenstruktur versehenen Faserstoffbahn, bei der zusätzlich eine Verdrängungspresse vorgesehen ist,

Fig. 6

eine schematische Teildarstellung eines Prägebandes mit einem im Vergleich zum Flächenanteil an zurückgesetzten Zonen kleineren Flächenanteil an erhabenen Zonen und

Fig. 7

einen schematischen Schnitt durch einen Preßnip, durch den das in der Fig. 6 dargestellte Prägeband zusammen mit der Faserstoffbahn und einem vorzugsweise weichen Filz hindurchgeführt ist.

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

Fig. 1

FIG. 2 a schematic partial representation of a device for producing a fibrous web provided with a three-dimensional surface structure; FIG.

Fig. 2

a schematic partial view of a modified embodiment of the device in which the felt is not passed over the evacuated device,

Fig. 3

1 is a schematic partial representation of an embodiment of an apparatus for producing a fibrous web provided with a three-dimensional surface structure, in which a dewatering device is additionally provided, in which the capillary action of a foamed-layer felt is utilized for dewatering;

Fig. 4

a schematic partial view of another embodiment of an apparatus for producing a provided with a three-dimensional surface structure fibrous web, in which a drainage device is additionally provided in which the capillary action of a felt with foamed layer is used for dewatering,

Fig. 5

FIG. 2 a schematic partial representation of an embodiment of an apparatus for producing a fibrous web provided with a three-dimensional surface structure, in which a displacement press is additionally provided, FIG.

Fig. 6

a schematic partial view of an embossing belt with a smaller compared to the area ratio of recessed zones area ratio of raised zones and

Fig. 7

a schematic section through a Preßnip, through which in the Fig. 6 shown embossing belt is passed together with the fibrous web and a preferably soft felt.

Fig. 1 shows a schematic partial representation of an apparatus 10 for producing a provided with a three-dimensional surface structure fibrous web 12 (see also Fig. 7 ), which may in particular be a paper web and preferably a tissue or hygiene web.

The fibrous web 12 is pressed at a dry content <35% by means of a first pressure pad I on a stamping or structural band 14, e.g. sucked, and thereby pre-embossed and then pressed for further drainage and drying by means of another pressure pad II a further time on the embossing belt 14 to fix the three-dimensional surface structure and strength. In this case can be provided as embossing belt 14, in particular an embossing screen.

In the present embodiment, the same embossing belt 14 is provided for embossing and fixing the surface structure.

The first pressure field I is produced by means of a suction element 16 arranged on the side of the embossing belt 14 facing away from the fibrous web 12, whereby the fibrous web 12 is sucked into the surface structure of the embossing belt 14. The suction element 16 may be provided in particular as a suction box or wet vacuum.

In the further pressure field II, the fibrous web 12 is preferably gently, ie in particular over a lengthened in the direction of web travel L distance pressed. In this case, the further pressure field II can be generated in particular by means of a Preßnips 18, between a drying cylinder 20 and a counter-element 22 is formed. The guided through the press nip 18 fibrous web 12 is in this case in contact with the surface 20 'of the drying cylinder 20. With its other side it lies against the embossing belt 14.

As a drying cylinder 20 may be provided in particular a Yankee cylinder.

As a cooperating with the drying cylinder 20 counter element is preferably a Schuhpreßeinheit 22 is provided which comprises a guided in the region of the press nips 18 via a press shoe 24 flexible belt 26. In the present embodiment is provided as Schuhpreßeinheit 22 provided with a flexible roll shell 26 shoe press roll.

This results in a lengthened in the web running direction L Preßnip 18, whereby a relatively gentle pressure of the fibrous web 12 is achieved.

Within the loop of the embossing belt 14, a preferably soft band 28 (capillary fabric), in particular a soft felt or a soft foam felt, may be guided through the press nip 18. This soft band 28 thus runs between the embossing belt 14 and the flexible belt 26 of the shoe press unit 22.

The fibrous web 12 may be placed on the drying cylinder 20, i. For example, on a Yankee cylinder, dried. In addition, the fibrous web 12 can be creped. Finally, the web 12 can be wound up by appropriate means.

The dry content at which the fibrous web 12 is pre-stamped and / or the dry content at which the three-dimensional surface structure is fixed is as already mentioned, <35%, and may in particular be <30% and preferably <25%.

Between the suction element 16 and the press nip 18, a suctioned device 30 is provided, which may in particular be a suction roll. The fibrous web 12 is guided together with the embossing belt 14 both via the evacuated device 30 and through the press nip 18. The felt 28 is guided between the embossing belt 14 and the flexible belt 26 of the shoe press unit 22 through the press nip 18.

In the present embodiment, the felt 28 is guided not only by the Preßnip 18, but also on the evacuated device 30. Since the Saugwi kung of the device 30 is reduced by the resistance of the felt 28, the evacuated means 30 may be associated with an over-standing hood to support the vacuum effect of the evacuated device 30.

For conditioning the felt 28, a suction device 32, in particular a suction box or the like, may be provided. As based on the Fig. 1 can be seen, this felt conditioning device serving suction device 32 is disposed in front of the evacuated device 30, in the region of the felt 28 is merged with the embossing belt 14 carrying the fibrous web 12. In this case, the suction device 32 is preferably arranged in front of (shown in solid lines) a lower deflection roller 72. In principle, however, an arrangement behind this lower guide roller 72 is possible (dashed line 32 ').

Due to the relatively long joint leadership of felt 28 and embossing belt 14 water is removed by the capillary action of the felt 28 of the fibrous web 12 over a longer distance. Previously, the felt 28 is over the suction device 32 conditioned, which increases its dry content and the felt is cleaned.

In front of the evacuated device 30, the embossing belt 14 is guided over the suction element 16, which causes a pre-embossing of the fibrous web 12 in addition to a dry content increase. This is sucked into the three-dimensional surface structure of the embossing belt or sieve 14, whereby the structure of the web is impressed.

The in the Fig. 2 illustrated embodiment differs from that according to Fig. 1 essentially only in that the felt 28 is brought together after the suctioned egg n-direction 30 with the fibrous web 12 carrying embossing belt 14. The evacuated device 30 is thus not wrapped in this case by the felt 28, whereby their suction effect is increased and the dry content is increased accordingly. The wet embossing effect is maintained by the relatively gentle dewatering of the TissueFlex, where the pressure is lower than that of a conventional shoe press.

Moreover, this embodiment, at least substantially as the according to Fig. 1 be designed. Thus, here too, the suction device 32 is preferably arranged again before (representation in solid lines) of the lower deflection roller 72, wherein in principle, however, an arrangement behind this lower deflection roller 72 is again possible (dashed representation 32 ').

Fig. 3 shows a schematic partial representation of an embodiment in which a drainage device 34 is additionally provided, in which the capillary action of a felt 36 with foamed layer is used for dewatering. In this case, the foam coating may in particular be selected so that pores in a range of about 3 to about 6 microns.

In the present case, the foamed layer felt 36 together with an embossing belt 14 and intermediate fibrous web 12 is guided around a larger suction roll 38, the felt 36 preferably being in contact with the suction roll 38. For example, the suction roll 38 wrapped around the felt 36 may have a diameter of about 2 to about 3 meters. The suction roller 38 may be acted upon by vacuum on its underside. In principle, the suction roll 38 can also be assigned a siphon outlet. The funds in question are in the Figure 3 denoted by "40".

In the forming region, at least one drainage sieve with zonal different sieve permeability can be provided.

In the present case, a former with two circumferential dewatering belts 14, 42 is provided, the inner belt 14 also serving as an embossing belt. The two dewatering belts 14, 42 converge to form a material inlet gap 44 and are guided over a shaping element 46 such as in particular a forming roller.

In the present case, the embossing belt 14 is formed by the element 46 coming into contact with the inner band of the former. The outer band 42, which does not come into contact with the forming element 46, can be provided in particular as a dewatering screen with zonal different screen permeability.

By means of a headbox 48, the pulp suspension is introduced into the stock inlet gap 44. Behind the forming element 46, a pickup or separating element 50 is provided, through which the web is held on the embossing belt 14 during the separation from the dewatering belt 42. Preferably in front of the egg n-direction 34 with capillary action is again a suction element 16 (solid Representation) provided by the fibrous web 12 is pressed onto the embossing belt 14. However, this suction element can also be arranged between the device 34 with capillary action and the evacuated device or suction roller 30 (dashed representation 16 ').

Together with the fibrous web 12 and the embossing belt 14, a soft belt or felt 28 is again guided through the press nip 18 formed between a drying cylinder 20 and a shoe press unit 22. In the present case, the soft band is according to the embodiment according to Fig. 1 again guided around the evacuated device 30. For example, this soft band 28 may again be a capillary felt. For example, the felt 28 can be conditioned again via a suction device or a so-called UHLE box. The drying cylinder 20 may in particular be a Yankee cylinder again. In this case, this drying cylinder 20 may be associated with a drying hood 52.

In the present embodiment, the dry content of the fibrous web before the capillary drainage device 34 is about 10 to about 25%, in the area downstream of this device 34 e.g. about 30 to about 40%.

The in the Fig. 4 illustrated embodiment differs from that according to Fig. 3 initially by the fact that the fibrous web 12 is taken over by the embossing belt 14 of an inner band 54 of the former. In the present case, for example, this inner band 54 or the outer band 42 of the former can again be provided as a dewatering screen with zonal different Siebdurchlässigkeit. The two circulating dewatering belts 42, 54 converge again to form a material inlet gap 44, wherein they are guided again over a forming element 46 such as in particular a forming roller. By means of a headbox 48 of the material inlet gap 44 is again with pulp suspension fed. Unlike the embodiment according to the Fig. 3 However, the pulp suspension is supplied in the present case from below.

Within the loop of the embossing belt 14, a pickup or separating element is again provided, through which the fibrous web 12 is held on the embossing belt during the separation from the inner band 54 of the former.

The provided within the loop of the embossing belt 14 suction member 16 is arranged in front of the dewatering device 34 with capillary action, in principle, however, an arrangement according to this device 34 is possible.

In the present case, the felt 28 is missing.

The dry content of the fibrous web in the present embodiment is about 10 to about 25% in the region of the pickup element 50, about 15 to about 30% in the region upstream of the dewatering device 34 and about 35 to about 45% downstream of the device 34.

Moreover, this embodiment may have at least substantially the same structure as that according to Fig. 3 , Corresponding elements are assigned the same reference numerals.

Fig. 5 shows a schematic partial view of an embodiment of the device 10, in which a displacement press 56 is provided. The fibrous web 12 is guided to expel water by means of gas pressure with the embossing belt 14 at least once through a pressure chamber 58 which is bounded by at least four parallel rollers 60 - 66 and in which a compressed gas can be introduced. The fibrous web 12 is preferably guided together with the embossing belt 14 and a membrane 68 through the pressure chamber 58.

In the present case, the membrane 68 forms the inner band of the former, which again comprises a forming member 46, in particular a forming roller, in the region of which provided as a membrane inner band 48 and the outer band 42 converge to form a Stoffeinlaufspaltes 44 which feeds by means of a headbox 48 with pulp suspension becomes.

Following the air press 56, the fibrous web 12 together with the embossing belt 14 again via an evacuated device 30, in particular a suction roll, and passed through the formed between a drying cylinder 20, in particular Yankee cylinder, and a shoe press 22 Preßnip 18. In the illustrated embodiment, the drying cylinder or Yankee cylinder 20 is again associated with a drying hood 52.

In the present case, the first pressure field I, by which the fibrous web 12 is pressed at a dry content of <50% on the embossing belt 14 and pre-embossed, for example, be generated by the air press 56.

For example, based on the 6 and 7 can be seen, the respective guided by the press nip 18 embossing belt 14, for example embossing screen (see, in particular, the left part of Fig. 6 ) or Prägemembran (see in particular the left part of Fig. 6 ), be structured so that there is a smaller area ratio of raised or closed areas 68 compared to the area portion of recessed zones or holes 74 for this embossing belt 14 and accordingly a smaller surface portion of the fibrous web 12 is pressed in the press nip 18.

In this case, the area fraction of raised or closed zones 68 can be in particular ≦ 40% and preferably in a range of about 25 to about 30%.

The raised zones 68 and the recessed zones may result, for example, by offsets, ie by intersections of weft and warp threads, of a mesh fabric. In the case of the right part of the Fig. 6 reproduced Preßmembran results in a corresponding structuring through the holes 74th

Fig. 6 shows a schematic partial view of a corresponding embossing belt 14, for example, embossing felt or embossing membrane, with a smaller compared to the area ratio of recessed zones or holes 74 surface portion of raised or closed areas 68th

The thickness d of the right part of the Fig. 6 For example, the embossing membrane shown may be about 1 to about 3 mm. In particular, the open area may be greater than 50%, and more preferably greater than 60%, and preferably within a range of from about 70% to about 75%. The membrane expediently i-wise of a resistant to the pulp chemistry material. It can for example consist of polyester.

Fig. 7 shows a schematic section through a Preßnip 18, through which in the Fig. 6 shown embossing belt 14 is passed together with the fibrous web 12 and a preferably soft belt or felt 28. In this case, this soft band 28 is in contact with the flexible band 26 of the shoe press unit, which is guided in the region of the press nips 18 via a press shoe 24, via which the desired contact pressure can be applied.

The fibrous web 12 is applied to the drying cylinder 20, preferably a Yankee cylinder.

In the Fig. 7 Moreover, the pressing zones 70 resulting from the raised zones 68 can be seen.

The fibrous web 12 is already marked before the nip. As based on the Fig. 7 can be seen, is already on the embossing belt before the nip.

LIST OF REFERENCE NUMBERS

10

contraption

12

Fibrous web

14

embossing tape

16

suction

18

press nip

20

Drying cylinder, Yankee cylinder

20 '

surface

22

Counter element, shoe press unit

24

press shoe

26

flexible band, flexible roll jacket

28

soft band, soft felt

30

vacuumed device, suction roller

32

Suction device, suction roller

34

Drainage device with capillary action

36

Felt with foamed layer

38

big suction roll

40

Vacuum, siphon outlet

42

dewatering belt

44

Stock inlet gap

46

Forming element, forming roller

48

headbox

50

Pickup or separating element

52

Trockenhaube

54

inner drainage sieve

56

air press

58

pressure chamber

60

roller

62

roller

64

roller

66

roller

68

raised zones

70

nips

72

deflecting

74

holes

d

thickness

L

Web direction

I

first pressure field

II

another pressure field

Claims (39)

1. Method for producing a fibrous web (12) provided with a three-dimensional surface structure, in particular a tissue or hygiene web, in which the fibrous web (12) at a dryness of < 35% is pressed onto an embossing belt (14) by means of a first pressure area (I) and is pre-embossed as a result and subsequently, for the purpose of further dewatering and drying, is pressed onto an embossing belt (14) a further time by means of a further pressure area (II) in order to fix the three-dimensional surface structure and strength, characterized in that in order to dewater the web, at least one fine-pored fabric (36) having a capillary effect is used, which is a fabric (36) with a foamed layer, the fabric (36) with foamed layer, together with an embossing belt (14) and a fibrous web (12) lying between them, being guided around at least one suction roll (38) and the fabric (36) being in contact with the suction roll (38).
2. Method according to Claim 1, characterized in that the embossing belt used is an embossing fabric (14).
3. Method according to Claim 1, characterized in that the embossing belt used is an embossing membrane.
4. Method according to one of the preceding claims, characterized in that the fibrous web (12) is pre-embossed after the forming region.
5. Method according to one of the preceding claims, characterized in that the fibrous web (12) is formed on the embossing belt (14) used for the embossing.
6. Method according to one of the preceding claims, characterized in that the fibrous web (12) is transferred to the embossing belt (14) used for the pre-embossing.
7. Method according to one of the preceding claims, characterized in that the same embossing belt (14) is used for pre-embossing and for fixing the surface structure.
8. Method according to one of the preceding claims, characterized in that at least the first pressure area (I) is produced by means of a suction element (16, 16') arranged on the side of the embossing belt (14) facing away from the fibrous web (12), in order to suck the fibrous web (12) into the surface structure of the embossing belt (14).
9. Method according to Claim 8, characterized in that the suction element used is a wet suction means.
10. Method according to one of the preceding claims, characterized in that the fibrous web (12) is pressed gently in the further pressure area (II), that is to say over a section which is extended in the web running direction (L).
11. Method according to one of the preceding claims, characterized in that the further pressure area (II) is produced by means of a press nip (18).
12. Method according to Claim 11, characterized in that the press nip (18) forming the further pressure area (II) is produced between a drying cylinder (20) and an opposing element (22), the fibrous web (12) guided through the press nip (18) being in contact with the surface of the drying cylinder (20) and resting with its other side on the embossing belt (14).
13. Method according to Claim 12, characterized in that the drying cylinder used is a Yankee cylinder (20).
14. Method according to Claim 12 or 13, characterized in that the opposing element interacting with the drying cylinder (20) is a shoe press unit (22) which comprises a flexible belt (26) guided over a press shoe (24) in the region of the press nip (18).
15. Method according to Claim 14, characterized in that the shoe press unit used is a shoe press roll provided with a flexible roll cover.
16. Method according to one of the preceding claims, characterized in that a belt (28), preferably a soft belt, provided within the loop of the embossing belt (14), in particular a felt (28), is guided through the press nip (18) producing the further pressure area (II).
17. Method according to one of the preceding claims, characterized in that the pre-embossed fibrous web (12) is dried on the drying cylinder (20), in that the fibrous web (12) is creped and/or in that the fibrous web (12) is subsequently wound up.
18. Method according to one of the preceding claims, characterized in that the dryness at which the fibrous web (12) is pre-embossed and/or the dryness at which the three-dimensional surface structure is fixed are in each case chosen to be < 35%, in particular < 30% and preferably < 25%.
19. Method according to one of the preceding claims, characterized in that, between the suction element (16, 16') producing the first pressure area (I) and the press nip (18) producing the further pressure area (II), an evacuated device (30) is used, and in that the fibrous web (12), together with an embossing belt (14), is guided both over the evacuated device (30) and through the press nip (18).
20. Method according to Claim 19, characterized in that the evacuated device (30) has a curved surface, and the fibrous web (12) and the embossing belt (14) are guided over this curved surface.
21. Method according to Claim 20, characterized in that the evacuated device (30) used is a suction roll (30).
22. Method according to one of Claims 16 to 21, characterized in that the felt (28) is guided through the press nip (18) between the embossing belt (14) and the flexible belt (26) of the shoe press unit (22).
23. Method according to one of Claims 16 to 22, characterized in that the felt (28) is also guided over the evacuated device (30).
24. Method according to one of the preceding claims, characterized in that the evacuated device (30) is assigned a hood under a positive pressure in order to assist the negative pressure action of the evacuated device (30).
25. Method according to one of the preceding claims, characterized in that the felt (28) is conditioned by means of a suction device (32), in particular by means of a suction box, before it is led together with the embossing belt (14) carrying the fibrous web (12).
26. Method according to one of Claims 16 to 25, characterized in that the felt (28) is led together with the embossing belt (14) carrying the fibrous web (12) only after the evacuated device (30).
27. Method according to one of Claims 14 to 26, characterized in that the length, viewed in the web running direction (L), of the press nip (18) of the shoe press comprising the drying cylinder (20) and the shoe press unit (22) is chosen to be greater than a value of about 80 mm, and the shoe press is designed in such a way that the result over the press nip length is a pressure profile with a maximum pressing pressure which is less than or equal to a value of about 2.5 mPa.
28. Method according to one of the preceding claims, characterized in that, in the forming region, at least one dewatering fabric (42, 54) with a zonally different fabric permeability is used.
29. Method according to Claim 28, characterized in that a former having two circulating dewatering belts (14, 42, 54) is used, which run together, forming a stock inlet gap (44), and are guided over a forming element, such as in particular a forming roll (46), and in that a dewatering fabric with a zonally different fabric permeability is used as the outer belt (42) not coming into contact with the forming element (46) and/or as the inner belt (14).
30. Method according to Claim 29, characterized in that the inner belt used is an embossing belt (14) and, preferably, the outer belt (42) used is a dewatering fabric with a zonally different fabric permeability.
31. Method according to Claim 30, characterized in that the fibrous web (12) is preferably picked up from the inner belt (54) by an embossing belt (14).
32. Method according to one of the preceding claims, characterized in that an embossing belt (14), for example an embossing fabric or embossing membrane, is guided through the press nip (18), which embossing belt (14) is structured in such a way that the result for this embossing belt (14) is a smaller proportion of the area of elevated or closed zones as compared with the proportion of the area of recessed zones or holes and, accordingly, a smaller proportion of the area of the fibrous web (12) is pressed in the press nip (18).
33. Method according to Claim 32, characterized in that an embossing belt (14) is used in which the proportion of the area of elevated or closed zones is ≤40% and preferably lies in a range from about 25% to about 30%.
34. Method according to Claim 32 or 33, characterized in that an embossing belt (14) is used in which the elevated zones and the recessed zones result from shoulders, i.e. from crossing points of weft and warp fibres of a fabric weave.
35. Method according to one of the preceding claims, characterized in that the fine-pored fabric with foamed layer (36) is a felt with a foamed layer.
36. Method according to Claim 35, characterized in that the foam coating is chosen such that the result is pores in a range from about 3 to about 6 µm.
37. Method according to one of the preceding claims, characterized in that the fabric with foamed layer (36) wraps around a suction roll (38) with a diameter from about 2 to about 3 m or a plurality of suction rolls with a smaller diameter, preferably two suction rolls with a diameter of, for example, about 2 m in each case.
38. Method according to one of the preceding claims, characterized in that the suction roll (38) has vacuum applied to its underside.
39. Method according to one of the preceding claims, characterized in that a suction roll with associated siphon extraction is used or the water is thrown off into a trough by centrifugal force.

Images