EP3604670A1 - Device for dewatering a wetlaid non-woven web - Google Patents

Abstract

Apparatus for dewatering a wet-laid nonwoven web from a fibrous suspension, comprising a plurality of dewatering strips arranged at a distance from one another, whereby adjacent dewatering strips together delimit a dewatering gap for removing liquid from the fibrous suspension, with at least three format slides, which are distributed relative to one another along the longitudinal direction of the respective dewatering gap are arranged or can be arranged and which partially hide the drainage gap in such a way that the liquid is prevented from being drained off via the hidden part of the drainage gap. The invention further relates to the use of the device and a machine comprising such a device.

Description

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

Different methods of nonwoven formation are known from the prior art. The nonwoven web is usually carried out by a wet laying process on a inclined screen 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 a hemmer, especially if nonwoven webs are made from long fibers (long fibers). Because the long fibers get caught on e.g. Edge hemmer designed as a knife. This leads to unclean edges. When they are transferred to the subsequent sections of the machine, such as to the binder section or dryer section, these cause tears. The latter lead to unwanted machine downtimes.

In addition, other resources, such as compressed air or spray water, are required for edge edgers, which had to be kept available and supplied to it. In the case of the known edge seamers or format plates, there was also hydraulic swirling of the fiber suspension around the edge seamers. This resulted in an unwanted basis weight deviation at the edges of the finished nonwoven.

The present invention relates to the generic objects mentioned at the outset.

The present invention has for its object to provide 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 set more easily and which provide clean edges of the nonwoven web (s). Furthermore, the invention relates to the use of such and a machine comprising such a device.

The task is solved 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 varied - even during the intended operation of the machine in which the nonwoven web is manufactured. For example, two or more (particularly narrow) nonwoven webs can be produced side by side on the dewatering device. By at the same time it is meant that several nonwoven webs can be produced on the same device, that is to say from the same pulp suspension emerging from the headbox. One could also say that the sliding format slides thus act as a divider for the fiber 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 less 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 nonwoven webs that can be produced at the same time can thus be achieved without having to use edge seamers.

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

Under a nonwoven web in the sense of the invention is a scrim made of a fiber suspension or knitted fabric of fibers of limited length, e.g. To understand continuous fibers (filaments) or from cut yarns. The nonwoven web initially has such a low strength that it itself is not load-bearing. For the purposes of the present invention, it is a wet-laid, ie a hydraulically (also: hydrodynamically) formed nonwoven. The nonwoven web can finally be solidified to form the nonwoven. Such a nonwoven is considered to be finally consolidated if it essentially 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 by a binder that is applied to the dewatered nonwoven web or by hydraulic consolidation, e.g. using water jets. For the purposes of the present invention, a (final) consolidation can also be a combination of (also multi-stage) water jet consolidation - that is to say a hydraulic consolidation process - and an additional impregnation by means of a binder - that is to say a chemical consolidation process. Following the consolidation of the nonwoven web e.g. by impregnating them with the binder that has been applied to them in a binder section, the nonwoven web can be dried. A subsequent mechanical consolidation, for example by means of a needle machine, can optionally further increase the strength of the nonwoven web.

Binding agents are agents that bond the fibers to one another so that, for example, there is a firm bond between the fibers. The term binders includes chemical binders which are applied, for example, in liquid form to the nonwoven web or mixed into the fiber suspension. They bond the fibers to each other by adhesion.

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

If, for example, the nonwoven web is hydraulically consolidated on the forming fabric - and preferably there finally - then the total length of the device for producing a nonwoven web can be considerably reduced in the running direction of the nonwoven web to be produced. However, it would be conceivable to develop the hydraulic consolidation in several stages. For example, pre-consolidation by water jet consolidation could 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 consolidated nonwoven web quickly and effectively, it can be mechanically, e.g. by means of a press, by means of a vacuum extraction or thermally by means of a dryer (e.g. with through-flow drying technology, then called through-flow dryer).

Nonwoven fabrics within the meaning of the invention do not include fiber structures produced by crossing or intertwining yarns, as is the case with weaving, knitting, knitting, lace manufacture, braiding and the manufacture of tufted products. Films and papers are also not among the nonwovens. Nonwovens according to the invention can preferably be produced from glass, metal, mineral, ceramic or carbon fibers. One then speaks of technical fleeces. 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, for example steel, stainless steel or titanium fibers can be considered. The materials mentioned often have an elastic modulus of at least 10 GPa. They are then comparatively hard, brittle and rigid and can not do well devour and tangle with each other. It is therefore particularly advantageous if, in addition to the fibers, binding fibers that are less rigid are used.

A former, such as an inclined screen former in the sense of the invention, is assigned a forming screen which at least in sections - e.g. along a first section - at an angle to the horizontal. At least one headbox is then arranged in this section of the route in such a way that it applies the fibrous stock suspension to the top of the forming fabric. The top means that the fiber 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 rotates and, on the other hand, faces the headbox outlet. 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 fiber 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 screen former. As a rule, the inclined screen former is arranged in such a way that the first route section rises in the direction of the deposited nonwoven web at an angle to a horizontal plane.

Forming sieve and / or support sieve are usually as endless, e.g. Closed loops running on rollers. They can be set up in such a way that the nonwoven web can be needled on the same water jet. This means that the corresponding forming screen and / or support screen is permeable to water so that the water jets can pass through it.

The decomposition temperature is 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 the temperature at which the material, for example the fiber, passes from the solid state into the melt.

In addition to the device for dewatering a wet-laid nonwoven web from a fiber suspension, the present invention also relates to the use thereof for producing a nonwoven fabric which has industrially produced long fibers and preferably inorganic fibers or fibers made 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 fundamentally suitable for all fiber lengths, ie not just long fibers.

Furthermore, the present invention relates to a machine for producing a wet-laid nonwoven web, comprising a former, such as an inclined screen former, a forming fabric assigned to the former for producing the nonwoven web by laying down the fibers of the fibrous suspension on the forming fabric with the device for dewatering according to the invention, which is preferably below the forming fabric 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 generality. In the drawings:

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 top view of an inventive drainage device according to a first embodiment;

Fig. 3

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

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

When the machine is operating as intended, the fibrous suspension passes through the outlet of the headbox 1.1 to the forming screen 2, which moves relatively past the headbox 1.1 or the dewatering device 1.2 via the rollers. The water flows through the forming screen 2 into the dewatering device 1.2. The fibers from the fiber suspension get caught on the forming wire 2 and are transported further with it. In this way, a corresponding nonwoven web F is continuously deposited or formed on the forming wire 2.

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

In the case shown, the nonwoven web V is guided past its formation on the forming fabric 2 for its hydraulic consolidation under the consolidation device 4. The latter is assigned a multiplicity of water jet nozzles 4.1, which here above the forming fabric 2 and an outlet 4.2 for water, which lies 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 steel nozzles 4.1 and the outlet 4.2 are arranged. According to this embodiment, the nonwoven web V is finally consolidated on the forming fabric 2.

The former thus forms the forming section of the machine. In the running direction of the nonwoven web V to be produced, a binder section of the machine directly adjoins the forming section in the present case. 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. The finally hydraulically consolidated nonwoven web V can be impregnated with a chemical binder by means of the application device 7. In the running direction of the nonwoven web V to be produced (in the view of 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).

A pre-consolidation device 6 can be connected upstream of the hydraulic consolidation device 4 in the running direction of the nonwoven web to be produced. In principle, it can be analogous to the hydraulic consolidation device 4 be set up, but be 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 necessarily have to, as in Fig. 1 shown, take place on the forming fabric 2. It can also take place on a further part of the machine which adjoins the former in the running direction of the nonwoven web V, for example on the support screen 3.

The Fig. 2 and 3 each show an embodiment of the invention in a partially cut, unscaled top view of the device for drainage 1.2, namely in the direction in which the liquid of the fiber 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, that is to say the direction in which the nonwoven web is made 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 plurality of drainage strips 1.3 arranged at a distance from one another. The latter are longer than they are wide. Their longitudinal extent runs in the representation of the Fig. 2 and 3 thus at right angles to the longitudinal or symmetry axis L.

Two directly adjacent drainage strips 1.3 together form a drainage gap 1.5 with one another. This serves to remove the liquid from the fiber suspension, which passes 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 local drainage through the device 1.2. 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 screen 2 ( Fig. 1 ) no fibers are deposited, ie no nonwoven web V is generated 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 it can be detachably connected to the device 1.2, e.g. can be connected to the drainage strips 1.3. This means that e.g. are captively detectable by positive and / or non-positive connection on the device 1.2, e.g. to which at least one of the two adjacent drainage strips 1.3 can be clamped. 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 spacing of the format slide 1.4 within the one drainage gap 1.5 can be adjusted as desired. This can e.g. by axial displacement - also independently of one another - this can be achieved along the drainage gap 1.5 assigned to them, namely at right angles to the longitudinal or symmetry axis L. As a result, the width of the nonwoven web V to be produced can be adjusted.

As in the Fig. 2 and 3 indicated, the respective format slides 1.4 of mutually 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 mutually adjacent drainage gaps 1.5 can be set equidistantly, so that rows of format slides 1.4 which run parallel to the longitudinal or symmetry axis L result via the device for drainage 1.2.

If an even number of format slides 1.4 is selected, which are assigned to the same drainage gap 1.5, for example four, then one half of the number, ie two - seen in the longitudinal direction 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, which in Fig. 2 and 3 corresponds to the longitudinal extent of the drainage strips 1.3, ie a right-angled to the longitudinal and symmetry axis L. One could also say that the opposing axial ends of the drainage strips 1.3 correspond to the drainage device 1.2 of the drive and the driver side of the machine according to the invention.

In the embodiment of the Fig. 3 is shown a possibility of individual adjustment of the spacing of the format slide 1.4 to each other. For this purpose, all slides of a corresponding drainage gap 1.5 have a slide mechanism, by means of which they are preferably mounted continuously, axially displaceably along the drainage gap 1.5. In this sliding mechanism, a push rod 1.7 is assigned to the outer format slide, which is in each case closer to the axial end of the drainage strip. 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. For example, the inner format slide can be moved by axially moving the sleeve and the outer format slide can be moved by axially moving 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, to adjust them axially. By means of the sliding mechanism according to the invention, the individual format slides 1.4 can be adjusted as desired, even continuously, and particularly preferably even during operation of the machine for producing the wet-laid nonwoven web. By using the format slide 1.4, edge edgers and the additional resources required for this, such as compressed air or spray water, can be dispensed with. Also, by using the device, several nonwoven webs can be placed side by side and simultaneously on the same Forming screen can be produced. The finished nonwoven also has a particularly uniform basis weight cross profile.

Claims (15)

Device for dewatering a wet-laid nonwoven web from a fibrous suspension, comprising a multiplicity of dewatering strips (1.3) arranged at a distance from one another, whereby adjacent dewatering strips (1.3) together delimit a dewatering gap (1.5) for removing liquid from the fibrous suspension, with at least three format slides (1.4 ), which are arranged along the longitudinal direction of the respective drainage gap (1.5) or can be arranged relative to each other and which partially hide the drainage gap (1.5) in such a way that the liquid is prevented from being drained away via the hidden part of the drainage gap (1.5). Device according to claim 1, characterized in that the format slides (1.4) at least partially extend into the drainage gap (1.5) of two directly adjacent drainage strips (1.3). Apparatus according to claim 1 or 2, characterized in that the format slides (1.4) along the one drainage gap (1.5) can be positioned relatively to one another and are preferably axially displaceable independently of one another in the longitudinal direction. Device according to one of claims 1 to 3, characterized in that the format slide (1.4) of a drainage gap (1.5) and the format slide (1.4) of another drainage gap (1.5) of the device independently of one another, within the same drainage gap (1.5) relative to each other and are preferably axially displaceable independently of one another in the longitudinal direction. Device according to one of claims 1 to 4, characterized in that the format slides (1.4), preferably assigned to the same drainage gap (1.5), can be detachably connected to the device in order to adjust the width of the nonwoven web to be produced as a function of the axial distance in the longitudinal direction of the drainage gap ( 1.5) seen to each other, adjust. 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 drainage gap (1.5), two format slides (1.4) each being the one - in the longitudinal direction, the axial end of the drainage gap (1.5) forming two adjacent drainage strips (1.3) - and the remaining two format slides (1.4) are assigned to the opposite axial end. Device according to one of claims 1 to 6, characterized in that the format slides (1.4) in the area of the axial ends on the device are mounted in an axially displaceable manner, preferably continuously, via a sliding mechanism. Apparatus according to claim 7, characterized in that the outer format slide (1.4) closer to the axial end of the drainage strip (1.3) - by means of a push rod (1.7) and the inner one which is further away from the opposite axial end of the drainage strip (1.3) Format slide (1.4) is axially displaceable relative to the device in the longitudinal direction of the drainage gap (1.5) by means of a sleeve (1.6) surrounding the push rod (1.7). Device according to one of claims 1 to 8, characterized in that a drive, such as a linear drive, is provided for adjusting the spacing of the format slides (1.4) as seen in the longitudinal direction from one another or relative to an axial end of the corresponding drainage strip (1.3). 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 adjacent drainage strips (1.3) which form the drainage gap (1.5). Device according to one of claims 1 to 10, characterized in that the format slide (1.4) of a drainage gap (1.5) together with the two adjacent drainage strips (1.3), which the Form a drainage gap (1.5) that is sealed against the passage of liquid into the uncovered part of the drainage gap (1.5). Device according to one of claims 1 to 11, characterized in that the device is free of an edge hemmer to trim the edge of the nonwoven web to be dewatered. Use of a device according to one of the preceding claims for the production of a nonwoven fabric 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. Use according to claim 13, characterized in that the fibers are long fibers with a length between 6 and 38 mm and preferably glass fibers of such length. Machine for producing a wet-laid nonwoven web (V), comprising a former, such as an inclined screen former (1), a forming fabric (2) assigned to the former for producing the nonwoven web (V) by laying down the fibers of the fibrous suspension on the forming former (2) and a device for dewatering, which is preferably arranged below the forming fabric (2), characterized in that the device is set up according to at least one of claims 1 to 12.

Images