EP4339359A1 - Installation for producing a fibrous web - Google Patents

Abstract

The invention relates to a system (1) for producing a fibrous web (2), in particular a long-fiber paper or wet nonwoven web, comprising a binder screen section (7) having a binder screen (8) for applying an aqueous binder to the fibrous web (2) and a drying screen (11) having a drying section (10) for drying and solidifying the fibrous web (2), the binder screen section (7) and the drying section (11) being arranged at a distance from one another so that the fibrous web (1) is separated from the binder screen (8). is guided to the drying screen (11) in a free pull, with at least one air suction device (27) being arranged on the edge of the system (1) in the area of the distance between the binder screen section (7) and the drying section (11).

Description

The invention relates to a system for producing a fibrous web, in particular a long-fiber paper or wet nonwoven web, comprising a binder screen section having a binder screen for applying an aqueous binder to the fibrous web and a drying section having a drying screen for drying and solidifying the fibrous web, the binder screen section and the drying section are arranged at a distance from one another, so that the fibrous web is guided from the binder wire to the dryer wire in a free pull.

Such a system is already published WO 2009/144195 A1 known from the applicant's company.

In the system described there, a fiber suspension unit, for example a glass fiber slurry, is added to a typical white water by adding a glass fiber having a fiber length in the range from 6 to 40 mm, preferably from 8 to 30 mm, in particular from 10 to 25 mm a pulper for dispersing the glass fiber in the white water to form the glass fiber slurry with a fiber concentration of about 0.2 to 1.0 percent by weight and allocated to a white water stream. This glass fiber slurry is then applied and dewatered in a web former with at least one at least single-layer, preferably multi-layer headbox onto an inclined wire which runs at least in some sections at an angle to the horizontal. By dewatering the fiberglass slurry, a fiberglass wet web is formed. The glass fiber wet fleece formed is then transferred to a binder screen of a binder screen section that runs at least partially horizontally or approximately horizontally. In this binder wire section, at least one aqueous binder, such as an aqueous urea-formaldehyde (UF) resin-based binder, is applied to the wet glass fiber wet fleece by means of at least one binder headbox. The excess binding agent is then sucked off. The aqueous binder solution is preferably applied to the wet fiberglass wet web using a curtain coater or a swap and squeeze applicator, although other application methods are also possible such as Suitable for spraying. The wet and still unglued glass fiber wet fleece is then transferred to a drying section with a drying screen for drying and curing (polymerization) of the binder that glues the glass fibers together in the glass fiber fleece. The drying section can, for example, have a heated continuous oven or a drum or belt dryer, whereby the glass fiber fleece is usually exposed to a temperature of 100 to 250 ° C, but not for longer than 1 to 2 minutes. Ultimately, the glass fiber fleece, which has a mass per unit area of 40 to 200 g/m2 and a binder content of 10 to 30%, is wound onto winding cores in a winder to form winding rolls in order to then be fed to subsequent processing or processing stations.

Already in print WO 2009/144195 A1 The following problem is pointed out that occurs when transferring the still wet and still unglued glass fiber fleece from the binder wire to the drying wire if, for example, a transfer roller is used instead of an open draw: The roller surface very quickly becomes contaminated with glass fibers as soon as it is exposed to the comes into contact with very wet fiberglass wet fleece that is sticky due to the binder application. This contamination causes a high level of production loss and the resulting poor runnability, as the system has to be shut down completely and the roller contaminated with glass fibers has to be cleaned. Although constructions are occasionally used for the purpose of "online" roller cleaning, the cleaning results that can be achieved with this are more than unsatisfactory, both in terms of cleaning qualities and cleaning times. The costs for such designs are usually not negligible, due, among other things, to the need to keep spare parts for a reserve roller.

In the WO 2009/144195 A1 It is proposed to dispense with the roller or the like and to transfer the fibrous web from the binder wire to the drying wire in a free pull, the web being supported in this area by an air flow from a blowing device for contactless levitation of the fibrous web. The blowing device extends over the entire width of the nonwoven web, blowing air onto it from above.

Although this concept has proven itself, in practice, when transferring the fibrous web from the binder wire to the drying wire in free pull, the problem always arises that folds form in the fibrous web during transfer, which sometimes leads to the web tearing off. The problem occurs more often the higher the speed at which the web is guided through the system and/or the lower the weight per unit area of the web.

The invention is based on the object of avoiding or at least reducing the aforementioned problems. In particular, the transfer of the wet and still unglued fibrous web from the binder wire section to the drying section in the open draw should be made more process-reliable, so that it does not negatively influence the runnability of the system and even at high machine speeds and/or low specific web weights without the formation of wrinkles and/or tears the railway works.

This task is solved by the features of the independent claims. The dependent claims relate to advantageous developments of the invention. In particular, the object is achieved according to the invention in a system of the type mentioned at the outset in that at least one air suction device is arranged on the edge of the system in the area of the distance between the binder screen section and the drying section.

The inventors have recognized that the wrinkling of the fibrous web is primarily caused by the air currents, which - especially at high operating speeds and / or low surface weights of the web - are generated by the binder wire and the opposing dryer wire in the transfer area between the binder wire and the drying section. These air currents create turbulence, particularly in the edge area of the system. This stretches the fibrous web, which leads to the formation of wrinkles or even tears in the web in the system. This is described in more detail below Figure 2 illustrated schematically.

A first approach to positively influencing the air flow was to work with baffles. In the areas where air flows influence the path of the web, flow guides in the form of baffles are used.

These direct the air flow so that the web running is not affected. However, this approach had the disadvantage that the air flows could be variable. Depending on the season, the temperature in the hall or whether the gates or doors in the hall are open or closed, the thermals and thus the flow in the area under consideration change. This means that the position of the baffles has to be changed again and again to ensure trouble-free operation.

This problem could only be solved through the use of at least one air suction device according to the invention. The at least one air suction device makes it possible to generate a stable flow in the transfer area between the binder wire and drying section, which is not influenced by the previously mentioned disruptive factors.

It has surprisingly been shown that it is completely sufficient to arrange the at least one air suction device only on the edge. This was not expected in advance. If it had proven necessary for stable air flow in the transfer area to provide an air extraction device that extends essentially over the entire width of the system in the transfer area below the fibrous web, this would inevitably have led to a very high maintenance and cleaning effort for the air extraction device , because in the transfer area, sticky fibers repeatedly fall down from the still wet and unglued fibrous web due to the binding agent. This approach with at least one air suction device would therefore also have been impractical.

Preferably, the at least one air suction device, viewed in the height direction, is arranged essentially below the fibrous web guided in free tension, but does not extend from the edge of the system to below the fibrous web guided in free tension. By "considered in the height direction substantially below" is meant that the at least one air suction device is arranged in the vertical direction, ie in the direction of gravity, predominantly, preferably completely, below the fibrous web when this is moved from the binder wire section during normal operation of the system the drying section is guided. At the same time, however, when viewed in the horizontal direction, the at least one edge-side air suction device should not extend from the edge to below the fibrous web that is transferred in a free pull, in order to avoid the aforementioned problem of high cleaning and maintenance costs.

The term “air suction device” preferably means a suction box. Such a suction box usually has an opening area through which the air is sucked out. The air suction device can be connected to a negative pressure source, such as a vacuum pump, via pipes or the like.

The invention has proven to be particularly efficient when an air extraction device is arranged on both the drive side and the driver side of the system. In this case, it is advantageous if the drive-side and driver-side air suction devices are designed in such a way that the negative pressure emanating from them can be adjusted independently of one another. In other words, the same negative pressure does not always have to be applied to both air extraction devices or the same amount of air must be extracted per unit of time. The setting can be done via a regulation or a controller. However, it is usually sufficient to adjust the negative pressure just once.

In order to generally avoid or at least reduce the contamination and maintenance problems described above, it is advantageous if the installation space below the fibrous web guided in free tension is at least in the area between a last roller of the binder wire section, over which the binder wire is guided when this Releases fibrous web, and a first roller of the drying section, over which the drying fabric is guided when it receives the fibrous web, is kept free. Air can then be extracted particularly efficiently from this free installation space by the at least one, preferably two, air suction device(s).

With regard to an efficient design of the binder section, it is proposed that the binder screen runs horizontally or approximately horizontally at least in sections and/or the binder screen section has at least one binder headbox.

In addition, it is advantageous if the system further comprises a forming section for dewatering an aqueous suspension, which is located upstream of the binder wire section in the process direction of the fibrous web through the system, the forming section preferably comprising an inclined wire former which has an inclined wire running at least in sections at an angle to the horizontal and has at least one at least single-layer, preferably multi-layer, headbox.

The system can also include a fiber suspension unit for producing the aqueous suspension for the forming section.

At the end, the system can also further comprise a rewinder for continuously winding the fibrous web onto winding cores to form winding rolls, the rewinder being downstream of the drying section in the process direction of the fibrous web through the system.

It is not mandatory, but possible, for at least one, preferably adjustable, blowing device to be provided between the binder screen section and the drying section for contactless floating end guidance of the fibrous web by means of air or another flowable medium, which has a plurality of independently controllable/adjustable blowing zones transversely to the running direction of the fibrous web having. The operation of such a blowing device, which blows onto the fibrous web from above in the transfer area in order to promote contactless floating of the fibrous web, is detailed in the publication mentioned at the beginning WO 2009/144195 A1 described, the content of which is hereby explicitly referred to in this regard and with regard to further advantageous embodiments of the blowing device.

A further aspect of the present invention relates to the use of a previously described system according to the invention for producing a fibrous web, in particular a long-fiber paper or wet fleece web, wherein during normal operation of the system, air is sucked out of the area between the binder wire section and the drying section by means of the at least one edge-side air suction device becomes.

The present invention has proven to be particularly efficient when the fibrous web is wet-laid glass fleece web. The transfer of the not yet dry and therefore sticky glass fiber fleece from the binder wire to the drying section is particularly susceptible to the contamination problem described above.

Furthermore, the advantages of the present invention are particularly effective when the fibrous web is produced at a speed of at least 170 m/min and/or when the fibrous web has a basis weight of less than 30 g/m ² , since here there is a risk of Wrinkling of the fibrous web is particularly large in the transfer area between the binder wire and the drying section.

Further features and advantages of the invention result from the following description of a preferred exemplary embodiment with reference to the drawing.

Fig. 1

ein schematisches Layout einer Anlage zur Herstellung einer Faserstoffbahn gemäß dem Stand der Technik;

Fig. 2

eine schematische Seitenansicht des Überführbereichs zwischen Bindersieb- und Trockenpartie gemäß dem Stand der Technik;

Fig. 3

eine schematische Seitenansicht des Überführbereichs zwischen Bindersieb- und Trockenpartie gemäß der vorliegenden Erfindung; und

Fig. 4

eine schematische dreidimensionale Ansicht des Überführbereichs zwischen Bindersieb- und Trockenpartie gemäß der vorliegenden Erfindung.

Show it

Fig. 1

a schematic layout of a plant for producing a fibrous web according to the prior art;

Fig. 2

a schematic side view of the transfer area between the binder wire and drying section according to the prior art;

Fig. 3

a schematic side view of the transfer area between the binder wire and dryer section according to the present invention; and

Fig. 4

a schematic three-dimensional view of the transfer area between the binder wire and drying section according to the present invention.

The Figure 1 shows a schematic layout of a system 1 for producing a fibrous web 2, in particular a long-fiber paper or wet fleece web.

This system 1 for producing the fibrous web 2 comprises a fibrous suspension unit 3, a forming section 4, which has an inclined wire 5 running at least in some sections at an angle α to the horizontal H and at least one at least single-layer, preferably multi-layer headbox 6, a Binder wire section 7, which has an at least partially horizontal or approximately horizontal binder wire 8 and at least one binder headbox 9, a drying section 10 having a dryer wire 11 and a winder 12 for continuously winding the fibrous web 2 onto winding cores 13 to form winding rolls 14.

In the fiber suspension unit 3, all components required to produce an aqueous suspension, such as water, chopped fibers, binders and the like, are placed in a first container ("pulper") 15 provided with an agitator 16 and then into a second container, also with an agitator 18 provided container ("pulper") 17 given; The transport of the aqueous suspension is carried out by the pumps 19, 20. The aqueous suspension can be, for example, a glass fiber slurry containing glass fibers with a fiber length in the range from 6 to 40 mm, preferably from 8 to 30 mm, in particular from 10 to 25 mm, and so-called white water and has a fiber concentration of about 0.2 to 1.0 percent by weight.

The fibrous suspension unit 3 is followed by the next process stage, namely the dewatering of the aqueous suspension and the formation of the fibrous web 2 with the aid of the inclined wire 5 arranged in the forming section 4. For this purpose, the aqueous suspension is applied to the by means of an at least single-layer, preferably multi-layer, headbox 6 Inclined sieve 5 applied. The water filtered from the aqueous suspension below the inclined sieve 5 is recycled according to the arrow 21 and, for example, added to the aqueous suspension leaving the second container ("pulper") 17 of the fiber suspension unit 3.

In the following process stage, at least one aqueous binder, such as an aqueous urea-formaldehyde (UF) resin-based binder, is applied by means of a binder headbox 9 to the still wet fibrous web 2 lying on the binder wire 8 of the binder wire section 7. In this binder screen section 7, the excess binder is then sucked off in a known manner. The aqueous binder can also be applied in a manner not shown using a curtain coater or an exchange and squeeze applicator the still wet fibrous web 2 can be applied, but other application methods, such as spraying, are also suitable.

The next process stage is used to dry and solidify the still wet fibrous web 2 by curing (polymerizing) the binder that glues the glass fibers together in the glass fiber fleece. For this purpose, it is passed through the drying section 10, which has the dryer screen 11 and which has two heated and shown continuous ovens 22 or a drum or belt dryer, not shown. The fibrous web 2 is generally exposed to a temperature of 100 ° C to 250 ° C, but not for longer than 1 to 2 minutes.

In a final process stage, the fibrous web, which has a basis weight range of 40 to 200 g/m ² and a binder content of 10 to 30%, is wound up in the rewinder 12 onto winding cores 14 to form winding rolls 13 in order to then be able to be fed to subsequent processing or processing stations .

Between the binder screen section 7 and the drying section 10, an adjustable blowing device (not shown) can also be provided for contactless floating guidance of the fibrous web 2 by means of air or another fluid medium, which has a plurality of independently controllable/adjustable blowing zones transversely to the running direction of the fibrous web 2.

Fig. 2 shows a schematic side view of the transfer area 24 between the binder wire section 7 and the drying section 10, as well as the problem of the formation of folds F in the prior art. The fibrous web 2 is transported on the binder wire 8 to a last roller 25 of the binder wire section 7, then guided in a free pull to a first roller 26 of the subsequent drying section 10, where it is picked up by the drying wire 11 and transported further. The arrows with the filled tips illustrate the flows of air which is carried along by the binder wire 8 of the fibrous web 2 and the drying wire 11 on their surfaces. These air currents cause turbulence in the space between the two rollers 25 and 26, which have a negative effect on the fibrous web 2, which is guided in free tension. Particularly shortly before the fibrous web 2 is placed on the drying fabric 11, it tends to form wrinkles F to train. This formation of wrinkles is critical for the further processing of the fibrous web 2 and can even lead to the fibrous web 2 being torn off.

Fig. 3 shows essentially the same schematic side view of the transfer area 24 as Fig. 2 , but with the solution according to the invention, which prevents the fibrous web 2 from forming wrinkles. An essential component of this solution is an air suction device 27, which is arranged in the transfer area 24 in the height direction below, but on the edge of, the fibrous web 2, which is guided in free tension. In other words, the air suction device 27 is not located directly under the fibrous web 2, but is in the cross-machine direction (direction orthogonal to the image plane of the Fig. 2 ) arranged laterally offset from this. The air suction device 27 has an opening surface 28 (cf. Fig. 4 ), which is directed towards the free space between the two rollers 25 and 26 in order to suck air out of this space and then specifically remove it (cf. downward arrow from air suction device 27). In this way, turbulence in the transfer area 24 between the two rollers 25 and 26 can be largely avoided, so that the fibrous web 2 runs no risk of forming folds F. At the same time, the air suction device 27 is largely protected from contamination by its arrangement at the edge of the still unglued fibrous web 2.

The system 2 according to the invention preferably comprises such an air suction device 24 on both its driver and its drive side, as in Fig. 4 shown schematically. In the three-dimensional representation of the Fig. 4 For the sake of clarity, only the first roller 26 of the drying section 10, a part of the drying fabric 11, which moves in the direction of the arrow, and the two edge air suction devices 27 are shown. The above-mentioned opening surface 28 can be seen in one of these two air suction devices 27. The two air suction devices 27 are designed here as suction boxes.

Reference symbol list

1

Attachment

2

fibrous web

3

Fiber suspension unit

4

Forming section

5

inclined screen

6

Headbox

7

Binder screen section

8th

Binder screen

9

Binder headbox

10

drying section

11

Dryer screen

12

Rewinder

13

winding core

14

wrap roll

15

first container (“pulper”)

16

Agitator

17

second container (“pulper”)

18

Agitator

19, 20

pump

21

Return circuit

22

Continuous oven

24

Transfer area

25

last roller of the binder wire section

26

first roller of the drying section

27

Air extraction device

28

Opening area

α

angle

F

wrinkle

H

horizontal

Claims (15)

Plant (1) for producing a fibrous web (2), in particular a long-fiber paper or wet nonwoven web, comprising a binder screen section (7) having a binder screen (8) for applying an aqueous binder to the fibrous web (2) and one having a drying screen (11). Drying section (10) for drying and solidifying the fibrous web (2), the binder wire section (7) and the drying section (11) being arranged at a distance from one another so that the fibrous web (1) moves from the binder wire (8) to the drying wire ( 11) is carried out in a free turn,
characterized in that at least one air suction device (27) is arranged on the edge of the system (1) in the area of the distance between the binder screen section (7) and the drying section (11). Plant (1) according to claim 1,
characterized in that the at least one air suction device (27), viewed in the height direction, is arranged essentially below the fibrous web (2) guided in free tension, but does not extend from the edge of the system (1) to below the fibrous web (2) guided in free tension ) extends. System (1) according to claim 1 or 2,
characterized in that the at least one air suction device (27) is a suction box. Plant (1) according to one of the preceding claims,
characterized in that an air suction device (27) is arranged on both the drive side and the driver side of the system. Plant (1) according to claim 4,
characterized in that the drive-side and driver-side air suction devices (27) are designed such that the negative pressure emanating from them can be adjusted independently of one another. Plant (1) according to one of the preceding claims,
characterized in that the installation space below the fibrous web (2) guided in free tension is at least in the area between a last roller (25) of the binder screen section (7), over which the binder screen (8) is guided when it releases the fibrous web (2). , and a first roller (26) of the drying section (10), over which the drying fabric (11) is guided when it receives the fibrous web (2), is kept clear. Plant (1) according to one of the preceding claims,
characterized in that the binder screen (8) runs horizontally or approximately horizontally at least in parts and/or the binder screen section (7) has at least one binder headbox (9). Plant (1) according to one of the preceding claims,
characterized in that the system (1) further comprises a forming section (4) for dewatering an aqueous suspension, which is located upstream of the binder wire section (7) in the process direction of the fibrous web (2) through the system (1), the forming section (4) preferably comprises an inclined wire former which has an inclined wire (5) running at least in some areas at an angle (α) to the horizontal (H) and at least one at least single-layer, preferably multi-layer, headbox (6). Plant (1) according to claim 8,
characterized in that the system (1) further comprises a fiber suspension unit (3) for producing the aqueous suspension for the forming section (4). Plant (1) according to one of the preceding claims,
characterized in that the system (1) further comprises a rewinder (12) for continuously winding the fibrous web (2) onto winding cores (13) to form winding rolls (14), the rewinder (12) of the drying section (10) being in the process direction of the fibrous web (2) is downstream through the system (1). Plant (1) according to one of the preceding claims,
characterized in that between the binder screen section (7) and the drying section (11) there is at least one, preferably adjustable, blowing device for contactless floating guidance of the fibrous web (2) by means of air or another flowable medium, which is transverse to the running direction of the fibrous web (2 ) has several independently controllable/adjustable blowing zones. Use of a system (1) according to one of the preceding claims for producing a fibrous web (2), in particular a long-fiber paper or wet fleece web, wherein during normal operation of the system (1) air is extracted from the area between the at least one edge-side air suction device (27). Binder screen section (7) and the drying section (11) are vacuumed. Use according to claim 12,
characterized in that the fibrous web (2) is a wet-laid glass fleece web. Use according to claim 12 or 13,
characterized in that the fibrous web (2) is produced at a speed of at least 170 m/min. Use according to one of claims 12 to 14,
characterized in that the fibrous web (2) has a basis weight of less than 30 g/m ² .

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