EP3604670B1 - Device for dewatering a wetlaid non-woven web - Google Patents

Description

The invention relates to a device for producing a wet-laid nonwoven fabric. The invention also relates to the use of such a device and a machine comprising such a device.

Different methods of web formation are known from the prior art. Usually the nonwoven web is carried out by a wet laying process on an inclined wire former with a very low consistency of the fiber suspension, in particular with a solids content of 0.01 to 0.1% by weight based on 100% by weight of the nonwoven obtained.

The production of such wet-laid nonwoven webs on machines known from the prior art is unsatisfactory in that, on the one hand, the width of the nonwoven web cannot be set as small as desired. On the other hand, the edges are difficult to cut with an edge hemmer, especially if nonwoven webs are made from long fibers (long fibers). Because the long fibers get caught on the edge trimmer, e.g. designed as a knife. This leads to unclean edges. When they are transferred to the following sections of the machine, such as the binder section or dryer section, these cause breaks. The latter lead to unwanted machine downtimes.

In addition, additional resources such as compressed air or spray water are required for edge trimmers, which had to be kept available and supplied to it. In the case of the known edge trimmers or format plates, hydraulic turbulence in the pulp suspension also resulted around the edge trimmer. This led to an undesired deviation in weight per unit area at the edges of the finished nonwoven.

The present invention relates to the aforementioned generic objects.

The present invention is based on the object of specifying a device for dewatering a wet-laid nonwoven web from a fiber suspension, by means of which the aforementioned problems can be eliminated in the simplest and most reliable way possible. In particular, a device is to be specified on which the width of the nonwoven web (s) to be produced can be adjusted more easily and which provides clean edges of the nonwoven web (s). The invention also relates to the use of such a device and a machine comprising such a device.

The object is achieved according to the independent claims. Particularly preferred and advantageous embodiments of the invention are given in the subclaims.

The inventor has recognized that by providing at least three format slides in the same drainage gap, the width of the nonwoven web to be produced can be set variably - even during normal operation of the machine in which the nonwoven web is produced. For example, two or more (particularly narrow) nonwoven webs can be produced next to one another on the drainage device at the same time. Simultaneously it is meant that several nonwoven webs can be produced on the same device, that is to say from the same fiber suspension emerging from the headbox. One could also say that the sliding format slide thus act as a divider for the pulp suspension emerging from the headbox. In other words, with the arrangement of at least two format slides per axial end of the drainage bar, any format width that is equal to or smaller than the format width of the former can be set. With the solution according to the invention, a clean separation of the edges of the one or more simultaneously produced nonwoven webs can be achieved without having to use edge trimmers.

A fiber suspension in the context of the invention is a mixture of a liquid - such as water - and fibers.

In the context of the invention, a nonwoven web is to be understood as meaning a laid or tangled fabric of fibers of limited length, e.g. continuous fibers (filaments) or cut yarns, made from a fiber suspension. The nonwoven web initially has such a low strength that it is itself not stable. In the context of the present invention, it is a wet-laid, ie a hydraulically (also: hydrodynamically) formed nonwoven fabric. The nonwoven web can then be produced in a bonded manner to form the nonwoven. Such a nonwoven is considered to be finally consolidated if it has such a high strength as a result of the consolidation that it is suitable for the intended use, e.g. for its further processing into corresponding products such as hygiene articles. For this purpose, the nonwoven web can be consolidated in the forming section after it has been produced. This can be done using a binding agent that is applied to the dewatered nonwoven web or through hydraulic consolidation, e.g. by means of water jets. In the context of the present invention, a (final) consolidation can also be a combination of a (also multi-stage) hydroentanglement - i.e. a hydraulic consolidation process - and an additional impregnation by means of a binder - i.e. a chemical consolidation process. Following the consolidation of the nonwoven web, e.g. by impregnating it by means of the binding agent that has been applied to this in a binder section, the nonwoven web can be dried. Optionally, a subsequent mechanical consolidation, for example by means of a needle loom, can further increase the strength of the nonwoven web.

Binding agents are agents that stick the fibers together so that, for example, a solid bond between the fibers results. The term “binders” includes chemical binders which, for example, are added to the nonwoven web in liquid form or are mixed with the fiber suspension. They bond the fibers with one another by means of adhesion.

The term hydroentanglement or water jet needling is a hydraulic consolidation process for producing a solid bond between the fibers of a fleece. This entangles the fibers and thus the compression and solidification of the fleece by swirling, by z. B. focused high pressure water jets act on the nonwoven web.

If, for example, the hydraulic solidification of the nonwoven web takes place on the forming wire - and preferably finally there - then the total length of the device for producing a nonwoven web in the running direction of the nonwoven web to be produced can be reduced considerably. However, it would be conceivable to design the hydraulic consolidation in several stages. For example, pre-consolidation by hydroentanglement could first take place on the forming fabric and the final consolidation could take place in a further process step outside the forming fabric.

In order to dry the bonded nonwoven web quickly and effectively, it can be dewatered mechanically, e.g. by means of a press, by means of vacuum suction or thermally by means of a dryer (e.g. with through-flow drying technology, then called through-flow dryer).

Nonwovens for the purposes of the invention do not include fiber structures produced by crossing or intertwining yarns, as happens in weaving, warp knitting, lace production, braiding and the production of tufted products. Foils and papers are also not considered nonwovens. Nonwovens according to the invention can preferably be made from glass, metal, mineral, ceramic or carbon fibers. One then also speaks of technical nonwovens. Such fibers can be glass fibers but also plastic fibers such as aramid fibers, but also mineral fibers such as basalt fibers. In the case of metallic fibers, steel, stainless steel or titanium fibers, for example, come into consideration. The materials mentioned often have a modulus of elasticity of at least 10 GPa. They are then comparatively hard, brittle and rigid and can feel bad devour and tangle with each other. It is therefore particularly advantageous if, in addition to the fibers, binding fibers are used which are less rigid.

A former, such as inclined wire former, within the meaning of the invention, is assigned a forming wire which runs at least in sections - e.g. along a first section - at an angle to the horizontal. In this route section, at least one headbox is then arranged in such a way that it applies the pulp suspension to the top of the forming fabric. Top side means that the pulp suspension is applied to the top of the forming fabric. This is the side that on the one hand faces away from the rollers on which it is rotating and on the other hand faces the outlet of the headbox. On the underside, that is to say in the area of the underside of the forming fabric, at least one dewatering element can be arranged for dewatering the pulp suspension just applied. The mentioned drainage element can be the device according to the invention. The headbox can in turn be assigned to the inclined wire former. As a rule, the inclined wire former is arranged in such a way that the first section increases in the direction of the deposited nonwoven web at an angle to a horizontal plane.

Forming wire and / or carrying wire are usually designed as endless, self-contained loops, e.g. rotating on rollers. They can be set up in such a way that the nonwoven web can be water-jet needled onto the same. This means that the corresponding forming wire and / or carrying wire is permeable to water so that the water jets can pass through it.

The decomposition temperature is understood to be the temperature at which the material of the fibers decomposes chemically or thermally. The decomposition temperature is characteristic, for example, of materials that do not melt, such as thermosets. The melting temperature is understood to mean that temperature at which the material, for example the fiber, changes from the solid state to the melt.

In addition to the device for dewatering a wet-laid nonwoven web from a fibrous suspension, the present invention also relates to its use for the production of a nonwoven which has industrially produced long fibers and preferably inorganic fibers or fibers from synthetically produced polymers and preferably whose fibers have a decomposition or melting temperature of at least 300 ° C. Glass fibers are an example of such fibers. Long fibers are fibers with a length of 6 to 38 mm. The invention is basically suitable for all fiber lengths, that is not just long fibers.

The present invention also relates to a machine for producing a wet-laid nonwoven web, comprising a former, such as inclined wire former, a forming wire assigned to the former for producing the nonwoven web by depositing the fibers of the fibrous suspension on the forming wire with the device according to the invention for dewatering, which is preferably below the forming wire is arranged.

The present invention also relates to the product produced directly by means of the method according to the invention, that is to say the nonwoven fabric itself.

Fig. 1

eine stark schematisierte Darstellung einer erfindungsgemäßen Vorrichtung in einer Seitenansicht gemäß einer möglichen Ausführungsform;

Fig. 2

eine stark schematisierte, teilgeschnittene Draufsicht auf eine erfindungsgemäße Vorrichtung zur Entwässerung gemäß einer ersten Ausführungsform;

Fig. 3

eine stark schematisierte, teilgeschnittene Draufsicht auf eine erfindungsgemäße Vorrichtung zur Entwässerung gemäß einer weiteren Ausführungsform.

The invention is explained in more detail below with reference to the drawings without restricting the generality. In the drawings shows:

Fig. 1

a highly schematic representation of a device according to the invention in a side view according to a possible embodiment;

Fig. 2

a highly schematic, partially sectioned plan view of a device according to the invention for drainage according to a first embodiment;

Fig. 3

a highly schematic, partially sectioned plan view of a device according to the invention for drainage according to a further embodiment.

In the Fig. 1 a part of a machine according to the invention for producing a wet-laid nonwoven web is shown schematically in a side view and therefore not to scale. The device comprises a former, in the present case designed as an inclined screen former 1. This is assigned an endless forming wire 2, here rotating on rollers. The latter rotates relative to the stationary inclined wire former 1. Above the forming wire 2, a headbox 1.1 is arranged. The latter is assigned to the inclined screen former 1. A pulp suspension can be fed to the headbox 1.1, which can be applied via an outlet of the headbox 1.1 to the forming fabric 2, more precisely to its upper side. The pulp suspension usually has a pulp suspension, such as a water-fiber mixture. The forming screen 2 is designed so that it lets the water through. Below the forming wire 2, on the side facing the headbox 1.1, the device 1.2 according to the invention, also referred to as a drainage box, is arranged for discharging the liquid (here the water) of the pulp suspension. The device for dewatering 1.2 is assigned to the inclined wire former 1 of the machine.

When the machine is operating as intended, the pulp suspension passes via the outlet of the headbox 1.1 onto the forming wire 2, which moves over the rollers relative to the headbox 1.1 or the device for dewatering 1.2. The water flows through the forming wire 2 into the device for dewatering 1.2. The fibers from the pulp suspension remain hanging on the forming wire 2 and are transported on with it. In this way, a corresponding nonwoven web F is continuously deposited or formed on the forming wire 2.

The forming wire 2 is - viewed in its running direction or in the running direction of the nonwoven fabric web V - inclined upwards in a first section, relative to the horizontal. The inclined wire former 1 is in this first section arranged, ie the nonwoven web V is formed on this section. The first route section is limited by the upper rollers that follow one another in the running direction of the carrier screen 3. For this purpose, at least two such upper rollers are provided. In the illustration shown, the forming wire 2, which in the present case is rotating in a clockwise direction, rises from the bottom left to the top right in said first route section.

In the case shown, the nonwoven web V is guided past its formation on the forming wire 2 for its hydraulic consolidation under the consolidation device 4. The latter is assigned a large number of water jet nozzles 4.1, which are assigned here above the forming fabric 2 and an outlet 4.2 for water, which is below the forming fabric 2. As shown, the forming wire 2 runs horizontally or at least in sections essentially parallel to the horizontal plane in the area in which the water jet nozzles 4.1 and the outlet 4.2 are arranged. According to this embodiment, the nonwoven web V is finally consolidated on the forming wire 2.

The former thus forms the forming section of the machine. In the running direction of the nonwoven web V to be produced, in the present case, a binder section of the machine immediately follows the forming section. This comprises an application device 7 which is arranged above a support screen 3 running horizontally or at least in sections essentially parallel to the horizontal plane. By means of the application device 7, the finally hydraulically consolidated nonwoven web V can also be impregnated with a chemical binder. In the running direction of the nonwoven web V to be produced (in the view of FIG Fig. 1 from left to right), a thermal drying device, for example, can directly adjoin the binder section in order to dry the nonwoven web V provided with a binder (not shown).

The hydraulic consolidation device 4 can be preceded by a pre-consolidation device 6 in the running direction of the nonwoven web to be produced. In principle, this can be done analogously to the hydraulic consolidation device 4 be set up, but operated at a lower pressure than the solidification device 4, which is, for example, only 5 to 25 bar. The respective consolidation device 4, however, can be operated at a pressure of 15 to 400 bar. The consolidation by means of the consolidation device 4 does not have to be mandatory, as in FIG Fig. 1 shown, take place on the forming fabric 2. It can also take place on a further part of the machine that adjoins the former in the running direction of the nonwoven web V, for example on the carrier screen 3.

The Fig. 2 and 3 each show an embodiment of the invention in a partially sectioned, not to scale plan view of the device for dewatering 1.2, namely in the direction in which the liquid of the pulp suspension from the headbox 1.1 ( Fig. 1 ) flows. The longitudinal or symmetry axis L shown corresponds at the same time to the running direction of the machine, i.e. the direction in which the nonwoven web is from Fig.1 is transported inside the machine.

According to these two embodiments, the device for drainage 1.2, that is to say the drainage box, comprises a multiplicity of drainage strips 1.3 arranged at a distance from one another. The latter are longer than wide. Their longitudinal extension runs in the illustration of Fig. 2 and 3 i.e. at right angles to the longitudinal or symmetry axis L.

In each case two directly adjacent drainage strips 1.3 together form a drainage gap 1.5 with one another. This is used to remove the liquid from the pulp suspension that has passed through the forming wire 2 ( Fig. 1 ) passes through the device 1.2. For this purpose, the drainage gaps 1.5 can be connected to a discharge line (not shown) in order to discharge the liquid.

As in the Fig. 2 and 3 shown, exactly four format slides 1.4 are assigned to each drainage gap 1.5 shown. These should cover the drainage gap 1.5 locally. They can be arranged so that they extend into the drainage gap 1.5. The purpose of the format slide 1.4 is to prevent drainage through the device 1.2 locally. In these four, of the Format slides 1.4 "shaded" areas of the respective drainage gap 1.5 are placed on top of the forming fabric 2 ( Fig. 1 ) no fibers are deposited, ie no nonwoven web V is produced locally. For this purpose, the longitudinal extension of the format slide 1.4 is only a fraction of the longitudinal extension of the respective drainage gap 1.5.

The format slide 1.4 can be designed so that they can be detachably connected to the device 1.2, e.g. with the drainage strips 1.3. This means that they can be locked securely, e.g. by form and / or force fit on the device 1. 2, e.g. can be clamped to at least one of the two adjacent drainage strips 1.3. However, this connection can also be released. A variable adjustment of the format slide 1.4 within the one drainage gap 1.5 relative to one another can thus be achieved. In other words, the distances between the format slide 1.4 within the one drainage gap 1.5 can be adjusted as desired. This can be achieved, for example, by axially displacing them - also independently of one another - along the drainage gap 1.5 assigned to them, at right angles to the longitudinal or axis of symmetry L. This allows the width of the nonwoven web V to be produced to be adjusted.

As in the Fig. 2 and 3 indicated, the respective format slide 1.4 of adjacent drainage gaps 1.5 can be set in the same position to one another. In other words, the distances between corresponding format slides 1.4 of adjacent drainage gaps 1.5 can be set equidistantly, so that rows of format slides 1.4 result via the device for dewatering 1.2, which run parallel to the longitudinal or axis of symmetry L.

If an even number of format slides 1.4 is selected which are assigned to the same drainage gap 1.5, e.g. four, then half of the number, i.e. two - seen in the longitudinal direction, is an axial end of the two adjacent drainage strips 1.3 forming the drainage gap 1.5 - and the remaining half of the format slide 1.4 assigned to the opposite axial end of the device for drainage 1.2. The axial ends are related to a longitudinal axis that is shown in Fig. 2 and 3 the longitudinal extension of the drainage strips 1.3, that is, a right-angled to the longitudinal and symmetry axis L corresponds. One could also say that the opposite axial ends of the drainage strips 1.3 of the device for drainage 1.2 correspond to the drive and the operator side of the machine according to the invention.

In the embodiment of Fig. 3 a possibility of the individual adjustment of the distances between the format slide 1.4 is shown. For this purpose, all the slides of a corresponding drainage gap 1.5 have a sliding mechanism, by means of which they are preferably mounted continuously, axially displaceably along the drainage gap 1.5. In this sliding mechanism, the outer format slide, which is closer to the axial end of the drainage bar, is assigned a push rod 1.7. The inner format slide, which is further away from the axial end of the drainage strip, is guided axially displaceably relative to the device in the longitudinal direction of the drainage gap by means of a sleeve 1.6 surrounding the push rod 1.7. The inner format slide can be displaced by axially displacing the sleeve and the outer format slide by axially displacing the push rod.

The respective push rod 1.7 and sleeve 1.6, which are assigned to each individual axially displaceable drainage element, can be driven by hand or via a drive 1.8, such as a linear drive, for their axial adjustment. By means of the sliding mechanism according to the invention, the individual format slides 1.4 can be adjusted as desired, also steplessly, and particularly preferably even during operation of the machine for producing the wet-laid nonwoven web. By using the format slide 1.4, you can dispense with edge trimmers and the additional resources required for this, such as compressed air or spray water. By using the device, several nonwoven webs can be placed next to one another and simultaneously on the same Forming screen are produced. The finished nonwoven also has a particularly uniform basis weight cross profile.

Claims (15)

1. Device for dewatering a wet-laid non-woven web from a fibrous suspension, comprising a multiplicity of dewatering strips (1.3) which are disposed so as to be mutually spaced apart, wherein mutually neighboring dewatering strips (1.3) conjointly delimit a dewatering gap (1.5) for discharging liquid from the fibrous suspension, having at least three format slides (1.4) which along the longitudinal direction of the respective dewatering gap (1.5) are disposed or disposable so as to be distributed relative to one another and which partially obscure the dewatering gap (1.5) in such a manner that any discharging of the liquid by way of the obscured part of the dewatering gap (1.5) is prevented.
2. Device according to Claim 1, characterized in that the format slides (1.4) at least partially reach into the dewatering gap (1.5) of two directly neighboring dewatering strips (1.3).
3. Device according to Claim 1 or 2, characterized in that the format slides (1.4) along the one dewatering gap (1.5) are positionable in a mutually relative manner and, preferably in a mutually independent manner, are axially displaceable in the longitudinal direction.
4. Device according to one of Claims 1 to 3, characterized in that the format slides (1.4) of a dewatering gap (1.5) and the format slides (1.4) of another dewatering gap (1.5) of the device within the same dewatering gap (1.5) are positionable in a mutually independent and mutually relative manner and, preferably in a mutually independent manner, are axially displaceable in the longitudinal direction.
5. Device according to one of Claims 1 to 4, characterized in that the format slides (1.4) that are preferably assigned to the same dewatering gap (1.5) are capable of being releasably connected to the device so as to set the width of the non-woven web to be produced as a function of the axial mutual spacing, when viewed in the longitudinal direction of the dewatering gap (1.5) .
6. Device according to one of Claims 1 to 5, characterized in that at least four, preferably exactly four, format slides (1.4) are assigned to the one dewatering gap (1.5), wherein two format slides (1.4), when viewed in the longitudinal direction, are in each case assigned to the one axial end of the two neighboring dewatering strips (1.3) that form the dewatering gap (1.5), and the remaining two format slides (1.4) are assigned to the opposite axial end.
7. Device according to one of Claims 1 to 6, characterized in that the format slides (1.4) in the region of the axial ends are mounted on the device so as to be axially displaceable, preferably in a stepless manner, by way of a slide mechanism.
8. Device according to Claim 7, characterized, wherein the outer format slide (1.4) which in each case is more proximal to the axial end of the dewatering strip (1.3), by means of a push rod (1.7), and the inner format slide (1.4) which is more distal from the opposite axial end of the dewatering strip (1.3), by means of a sleeve (1.6) that surrounds the push rod (1.7), are embodied so as to be axially displaceable, relative to the device, in the longitudinal direction of the dewatering gap (1.5).
9. Device according to one of Claims 1 to 8, characterized in that, when viewed in the longitudinal direction, a drive such as a linear drive is provided for setting the spacing of the format slides (1.4) mutually or relative to an axial end of the respective dewatering strip (1.3).
10. Device according to one of Claims 1 to 9, characterized in that the format slide (1.4) is supported on the at least one of the two neighboring dewatering strips (1.3) which configure the dewatering gap (1.5).
11. Device according to one of Claims 1 to 10, characterized in that the format slides (1.4) of a dewatering gap (1.5), conjointly with the two neighboring dewatering strips (1.3) which configure the dewatering gap (1.5), are sealed in relation to the passage of liquid into the non-covered part of the dewatering gap (1.5).
12. Device according to one of Claims 1 to 11, characterized in that the device is free of an edge trimmer for cutting the edge of the non-woven web to be dewatered.
13. Use of a device according to one of the preceding claims, for producing a non-woven fabric which comprises industrially-made long fibers and preferably inorganic fibers or fibers from synthetically-made polymers, the fibers of said non-woven fabric preferably having a decomposition or melting temperature of at least 300°C.
14. Use according to Claim 13, characterized in that the fibers are long fibers having a length between 6 and 38 mm, and preferably glass fibers of such length.
15. Machine for producing a wet-laid non-woven web (V), comprising a former such as an inclined screen former (1); a forming screen (2) assigned to the former, for producing the non-woven web (V) by depositing the fibers of the fibrous suspension onto the forming screen (2); and a device for dewatering which is preferably disposed below the forming screen (2), characterized in that the device is specified according to at least one of Claims 1 to 12.

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