DE20102638U1 - Partially bond-strengthened nonwoven, in particular as an outer material for clothing - Google Patents

Description

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Adhesive fiber consolidation

Gunter Schmidt 14.02.2001

Emmendingen

Partially adhesive-bonded nonwoven fabric, especially as outer material for clothing

The invention is based on a nonwoven fabric consisting exclusively of unspun fibers according to the preamble of claim 1, as known for example from DE 195 46 43 0 Cl.

Nonwovens can be used in different places for outerwear purposes, e.g. as stiffening materials, as heat-insulating quilted inserts or as shoulder pads. In this case, however, nonwovens are particularly intended to be used as visible carrier material for outerwear, i.e. as the outer fabric of clothing that is subject to tension.

DE 44 14 253 A1 shows a voluminous nonwoven fabric for insulation purposes, with clothing also mentioned as an application. However, due to the nonwoven fabric structure mentioned there, it can be assumed that it is not a carrier material in the visible area of outer clothing, but rather, for example, quilted inserts for heat insulation. The nonwoven fabric described in the publication mentioned is made of a pile arranged in close succession to form pile folds, whereby the web thus produced is mechanically strengthened with a high proportion of standing fibers on the top and bottom by meshing the fibers. This technology can be used to produce a voluminous nonwoven fabric in an efficient and cost-effective manner. It is stated that the nonwoven fabric intended for insulation purposes should also have a high dimensional and volume stability. Experience

However, tests with nonwovens of this type suggest that the dimensional and volume stability achieved by the nonwoven is only sufficient for use as a heat or sound insulation medium, but not as a visible carrier material subject to tensile stress in all directions in the area of clothing.

Another proposal, also in the field of knitted nonwoven technology (cf. DE 198 43 078 A1), for producing a voluminous knitted nonwoven with a high proportion of standing fibers involves first laying a uniform fiber pile with preferably longitudinally oriented fibers in a zigzag pattern to form a stronger nonwoven of any width, in which the fibers of the nonwoven thus formed are oriented transversely to its longitudinal direction. The further processing of this nonwoven takes place transversely to the working direction of the nonwoven former of the primary pile and transversely to the orientation of the fibers. By mechanically strengthening the nonwoven thus formed by meshing at least one flat side, the strength in the longitudinal direction is increased because many fibers are aligned in the working direction during meshing. The low longitudinal strength of the zigzag-shaped template can be increased by stitch reinforcement, thus reducing the unevenness of longitudinal and transverse strength, although this can only be achieved to a very limited extent. Otherwise, the absolute level of longitudinal and transverse strength is only low and, above all, the permanent stretch is high, especially if the fleece thickness is not particularly high, which can certainly happen when used for visible carrier materials for outerwear. Such fleeces therefore have a strong tendency to bulge and warp.

Nonwovens used as visible carrier material for outerwear should be sufficiently dimensionally stable so that the garments do not bulge and/or distort when worn and thus lose their shape. This means that the nonwovens should be

They must have a certain minimum strength in both the longitudinal and transverse directions. In order to achieve this, the nonwovens used in the visible area of outerwear are often designed as needle punched nonwovens, in which the fibers are needled onto a prefabricated carrier web. The carrier web - a woven or knitted fabric made of spun threads - provides the required longitudinal and transverse strength, whereas the needled fibers provide the volume and fluffiness of the nonwoven. Needle punched nonwovens produced or constructed in this way are well suited for outerwear purposes and are therefore also widely used by the population at least for clothing in the sports and leisure sector. The well-known needle punched nonwovens do not consist exclusively of unspun fibers. Rather, the woven or knitted carrier web made of spun threads is an intermediate product produced in several processing stages - fiber production, spinning, weaving/knitting - and is therefore relatively expensive. Due to their complex production, these needle punched nonwovens are therefore not particularly cheap.

Needle-punched nonwovens are also known which consist exclusively of unspun fibers, i.e. in which no woven or knitted carrier web is integrated. Needle-punched nonwovens of this type are based on a thinner nonwoven fabric, which may be bonded with adhesive fibers, onto which additional fibers are needled and matted with it and with each other. These needle-punched nonwovens, even if they should have strength and/or elongation values at a level sufficient for tensile-loaded outer materials of clothing, are impermissibly stiff and not supple, as one would expect for clothing materials. If, on the other hand, needle-punched nonwovens consisting exclusively of unspun fibers are manufactured in such a way that they are sufficiently flexible and supple, they do not have sufficient strength and/or elongation values.

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The aforementioned DE 195 46 430 Cl shows a voluminous, longitudinally stable surface structure which can be incorporated into outerwear materials as a quilted insert for heat insulation. In order to achieve a certain thickness stability of the voluminous nonwoven fabric used, its fibers are to be partially designed as thermally activated adhesive fibers which bond some of the fiber contact points. In order to achieve a certain longitudinal stability, - only - one side of the voluminous nonwoven fabric is at least partially meshed in thickness, with the mesh wales in the longitudinal direction of the nonwoven fabric and in the direction of the fiber orientation.
The disadvantage of this nonwoven fabric is its insufficient strength in the transverse direction, which makes it unsuitable as a carrier material in the visible area of outerwear. If the nonwoven fabric is mechanically strengthened to a higher degree and/or the starting fibres are
higher levels of adhesive fibres are added, so that a higher
Degree of adhesive fiber consolidation and thus higher strength
and elongation values can be achieved, then
the fleece would be unacceptably stiff. It would then be
Basically not suitable as a supple outer material for clothing.

The object of the invention is to improve the generic nonwoven fabric so that it can be produced more cost-effectively than a needle-punched nonwoven fabric with an integrated carrier web, but at the same time at least approximately
whose strength values and low values of permanent elongation in the longitudinal and transverse directions and, in particular, is as flexible and supple as a needle-punched nonwoven fabric.
It is important that a good elastic stretch of the nonwoven fabric is achieved.

This task is carried out using the generic
Nonwoven fabric is solved according to the invention by the characterizing features of claim 1.

·

The inventive adhesive fiber consolidation of the mechanically consolidated nonwoven material, which is limited to a portion of the thickness of the nonwoven material, i.e. partial thickness, means that the nonwoven material remains flexible and pliable, but at the same time achieves a sufficiently high level of strength and a low level of permanent elongation, i.e. a high level of elastic elongation. The inventive combination of mechanical consolidation and partial adhesive fiber consolidation of the nonwoven material in the thickness direction results in an elastic, spatially stable fiber structure that can only be torn apart with considerable resistance. This in turn results in the high longitudinal and transverse strength and buckling resistance of the inventive nonwoven material, while at the same time being flexible.

In principle, the invention can be used with all types of nonwovens. In a practical embodiment of the invention, however, a preferably multi-layered template nonwoven is used, which contains at least one fiber layer made of a zigzag-shaped pile in which the fibers are predominantly oriented transversely. In conjunction with mechanical consolidation of the nonwoven by meshing, this achieves a better balance between the longitudinal and transverse strength of the nonwoven.

Further expedient embodiments of the invention can be found in the subclaims; furthermore, the invention is explained below with reference to various embodiments shown in the drawings, in which:

Fig. 1 shows a single-layer template fleece formed by zigzag laying of a pile for producing a nonwoven fabric according to the invention with essentially transversely oriented fibers,

Fig. 2 and 3 a two-layer (Figure 2) or three-layer (Figure 3) template fleece for producing a nonwoven fabric, which consists of at least one fleece layer with longitudinal

oriented fibres and another fleece layer with transversely oriented fibres,

Fig. 4 Cross sections through a one-sidedly bonded nonwoven fabric in different stages of completion,

Fig. 5 a cross-section through a nonwoven fabric bonded on both sides with a high standing fibre content,

Fig. 6 a cross-section through a relatively thin nonwoven fabric reinforced on both sides by meshes, in which the meshes of the opposite sides overlap each other in the middle of the nonwoven fabric,

Fig. 7 a greatly enlarged cross-section through a nonwoven fabric reinforced on one side by meshes and only partially reinforced with adhesive fibres in the thickness direction and

Fig. 8 shows a cross-section through a production device for the thickness-partial thermal bonding of a nonwoven fabric.

The subject matter of the invention, which will be discussed using various embodiments, is a nonwoven fabric consisting exclusively of unspun fibers, which is mechanically consolidated in any way, preferably by meshing the fibers close to the surface, at least on one flat side and which is also partially consolidated with adhesive fibers by embedded, thermally activated adhesive fibers at mutual contact points of the fibers of the nonwoven fabric in the thickness direction.

The nonwoven fabric according to the invention is intended to be more cost-effective than a needle-punched nonwoven fabric with an integrated carrier web, but on the other hand, despite the absence of an integrated carrier web, it should at least approximate its strength.

values as well as low values of permanent elongation and high elastic elongation in the longitudinal and transverse directions and, above all, be at least as flexible and supple as a needle-punched nonwoven with an integrated carrier web. The actual aim for an optimized design of the nonwoven according to the invention itself and its production is to significantly surpass a needle-punched nonwoven with regard to the properties mentioned.

For this purpose, a new nonwoven structure and a modified method of manufacturing it are used. The nonwoven according to the invention uses a preferably multi-layered template nonwoven of basically any nature, but preferably with transversely oriented fibers, which is mechanically strengthened in some way, preferably mesh strengthened, with the nonwoven also being partially strengthened with adhesive fibers in the thickness. The sensible combination of mechanical and adhesive fiber strengthening of the nonwoven creates a spatially stable fiber structure that can only be torn apart with considerable resistance, with high longitudinal and transverse strength and high dent resistance of the nonwoven, but which is also highly elastic, flexible and supple. Due to this combination of mechanical properties, the nonwoven according to the invention can be used without any problem for outerwear, in particular as a visible carrier material for items of clothing.

In the simplest case, the manufacture of the nonwoven fabric according to the invention starts from a zigzag-shaped pile 2 shown in perspective in Figure 1, in which the fibers 3, which are mainly aligned longitudinally in the pile, are aligned essentially transversely to the longitudinal direction of the template nonwoven 1 and to the later attached wales of the fiber mesh due to the zigzag arrangement.

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According to a more complex variant of the invention, the nonwoven fabric in the initial state consists of at least two nonwoven layers, namely at least one nonwoven layer with essentially longitudinally oriented fibers and a further nonwoven layer consisting of a zigzag-shaped pile with essentially transversely oriented fibers, as shown in perspective in Figure 2 for a two-layer template nonwoven and in Figure 3 for a three-layer template nonwoven. In the two-layer template nonwoven 4 according to Figure 2, the upper nonwoven layer 1' with transversely oriented fibers 3 consists of the zigzag-shaped pile, whereas the lower, "straight" nonwoven layer 5 contains predominantly longitudinally oriented fibers 3 ¹ . The three-layer template fleece 6 shown in Figure 3 has a "straight" fleece layer 5 ¹ or 5" on the bottom and top sides with predominantly longitudinally oriented fibers 3', whereas the "zig-zag-shaped" fleece layer 1" arranged between them contains predominantly transversely oriented fibers 3'.

In order to be able to partially strengthen the nonwoven fabric with adhesive fibers in a later step of production, a certain proportion of adhesive fibers must be added to the nonwoven fibers before the nonwoven is formed. Adhesive fibers of this type are known in various forms. They are usually fibers with a similar titer to that of the natural or artificial main fiber of the nonwoven, but the adhesive fibers consist of a thermoplastic polymer whose melting point is significantly below the temperature level at which the natural or artificial main fibers of the nonwoven could be damaged, at least if exposed for a short time. Alternatively, so-called bicomponent binding fibers are used as adhesive fibers. These consist of two different thermoplastic polymers, one of which has a significantly lower melting point than the other. Thermally activatable hot melt adhesive fibers or bicomponent binding fibers are expediently contained in the nonwoven fabric in a proportion of 2 to 20% by weight, with the optimal content of adhesive fibers depending very strongly on the respective application or intended use of the material to be produced.

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If the nonwoven fabric is to have a very soft drape, similar to clothing fabric, a lower content of adhesive fibers will be added and/or the adhesive fiber consolidation in the thickness direction will be limited to a small part of the nonwoven thickness. If, on the other hand, the nonwoven fabric is to have a certain inherent stiffness, more adhesive fibers will be added.

The single or multi-layered template fleeces 1, 4 or 6 shown in Figures 1 to 3 must therefore be formed from a fiber mixture enriched with adhesive fibers. The template fleeces 1, 4 or 6 formed in this way are then first mechanically strengthened by forming stitches, for which various, known methods are available, which will be briefly discussed below in general, i.e. without reference to an embodiment.

In connection with the stitch consolidation of nonwovens, particular reference is made to the book publication "Nonwovens Raw Materials, Production, Application, Properties, Testing", published by W. Albrecht, H. Fuchs, W. Kittelmann, Wiley-VCH, Weinheim, 2000, ISBN 3-527-29535-6. This textbook discusses the known processes for stitch consolidation of nonwovens in subsection 6.2 "Stitch formation processes" (pages 302-325). At this point, a stitch consolidation process is briefly discussed in general terms, i.e. without reference to an example.

In the case of one-sided consolidation by means of stitch formation, the mechanical consolidation of the fleece can be carried out, for example, on a nonwoven machine with the protected trade name Kunit® from Karl Mayer Malimo Textilmaschinenfabrik GmbH in Chemnitz. Such a well-known nonwoven machine is used to process a pre-prepared fleece into a voluminous nonwoven and has a device for creating standing pile folds in the material to be processed.

A template fleece and a further device for pulling loops out of the fibres and for folding them into stitches. The voluminous fleece fabric formed with a Kunit machine consists on its upper side of fibre pile folds that are perpendicular to the fleece surface and on its underside exclusively of fibre stitches that lie in the fleece surface.

If the nonwoven fabric is to be mechanically strengthened by meshes on both opposite flat sides, this can be done, for example, using a so-called Multiknit® machine - also a product of the above-mentioned company Malimo. As a rule, a Kunit machine is used for this, which is extended in tandem with another Multiknit® device. The voluminous nonwoven fabric formed with such a combination machine consists exclusively of fiber meshes in the nonwoven fabric surface on the top side and predominantly of fiber meshes on the bottom side. The layer in between contains fibers that are predominantly oriented perpendicular to the outside of the nonwoven fabric.

There is also the option of forming and consolidating the nonwoven fabric using the so-called Malivlies® process from the company Malimo mentioned above. For example, by laying a pile in a zigzag pattern, a template fleece is first formed in which the fibers of the pile are predominantly oriented transversely to the direction of further processing. This template fleece is consolidated using a device for pulling loops out of the fibers and for beating them into stitches, whereby fibers are grabbed from a relatively large depth of the secondary fleece and pulled into loops.

Only after the nonwoven fabric has been mechanically bonded by meshing is it partially bonded to the adhesive fibres, which is achieved by targeted heating of the nonwoven fabric close to the surface, for example by radiant heating of the nonwoven fabric, by contact heating

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and/or forced convective heating using hot air. Due to the heating of the adhesive fibers mixed into the nonwoven fabric, these are thermally activated, i.e. melted, so that clumps of melted adhesive accumulate at the points where the fibers contact and cross. After the adhesive has solidified, a stable fiber structure remains, which can only be deformed elastically, but in principle not permanently. This and the fibers aligned lengthwise and crosswise in the nonwoven fabric web give the nonwoven fabric its high, isotropic longitudinal and crosswise strength and a low permanent longitudinal and crosswise elongation.

After the present invention has been explained in general terms, but with reference to the layer structure shown in Figures 1 to 3 and the fiber layer in the template fleeces, the embodiments shown in the other figures will now be discussed below.

In the nonwoven fabric 12, which is solidified on one side and is shown in cross-section in Figure 4 at different stages of completion, the two-layer template fleece 4 according to Figure is further processed with the two fleece layers 1' and 5. The template fleece 4 is folded into pile folds 7, thus producing a thick fleece with the thickness D and a high standing fiber content of at least about 15% by weight of the total fibers used, with the standing fibers extending essentially transversely between the two opposite flat sides of the fleece. The nonwoven fabric is mechanically solidified on only one flat side, shown at the top in Figure 4, by a mesh 8 of the fibers close to the surface. The wales 9 of the mesh 8 lie in the longitudinal direction of the web. The standing fibers contained in the nonwoven fabric in the form of pile folds extend essentially across the meshed flat side and protrude from there in the manner of a velour. The adhesive fiber consolidation of the nonwoven fabric, e.g. by adding,

014 * ♦-*··* .·■·,

thermally activated adhesive fibers is limited to a partial area 10 (thickness t) of the nonwoven fabric with the total thickness D, close to the surface. In fact, only the side of the nonwoven fabric that is already stitch-bonded is also partially bonded with adhesive fibers (relative to the total thickness D). Partial bonding of the thickness will be discussed in more detail below in connection with Figures 7 and 8. The pile folds 7 or pile fibers that extend in the direction of the opposite side of the nonwoven fabric are neither mechanically stitch-bonded nor bonded with adhesive fibers, but rather protrude softly and loosely from the doubly bonded side of the nonwoven fabric. These loose pile fibers are mechanically treated, e.g. sheared and brushed flat like a loden, so that the pile fibers all extend in a certain direction on one side, like the hairs of a brushed fur. In this way, a hard-wearing, loden-like nonwoven fabric can be produced cost-effectively, which can be processed into coats, traditional suits, traditional costumes, etc.

In the embodiment shown in cross-section in Figure 5, the single-layer, zigzag-shaped template fleece 1 according to Figure 1 is further processed into a nonwoven fabric 16. The template fleece 1, which has predominantly transversely oriented fibers, is formed into a more voluminous fleece by laying pile folds 13, which thereby has a high proportion of standing fibers. The nonwoven fabric is mechanically bonded on both sides close to the surface by both upper (14) and lower side intermeshing 15, with the mesh wales 9' lying parallel to the nonwoven web, i.e. transverse to the orientation of the majority of the nonwoven fibers. In addition, the nonwoven fabric mechanically bonded on both sides is partially bonded with adhesive fibers on one of the two outer sides, which will be discussed in more detail below in connection with Figures 7 and 8.

The nonwoven fabric according to Figure 5 is, despite its pre-

luminosity, flexible and supple. The nonwoven fabric according to Figure 5 has the surface texture of a knitted fabric on both sides, but has the strength and stretch properties of a stretchable material. Due to these optical and physical properties, the nonwoven fabric can be used as a visible material for outerwear that can withstand tension and stretch. Due to the bulkiness of the voluminous nonwoven fabric according to Figure 5, it is preferably intended for winter items.

In principle, it is also conceivable to bond the nonwoven fabric, which is bonded on both sides , close to the surface by gluing. In the case of embedded adhesive fibers, this can be done, for example, in a forced convective manner by blowing hot air onto both sides and then cooling them, preferably also by forced convective means, using cold air. Contact heating or radiation heating on both sides can also lead to bonding of the adhesive fibers close to the surface. In particular, it is also possible to carry out the one-sided, partial thickness bonding of the adhesive fibers described in connection with Figures 7 and 8, initially on one side of the nonwoven fabric and then locally offset on the opposite side of the nonwoven fabric in the same processing step.

The embodiment of a further nonwoven fabric 20 shown in cross section in Figure 6 is also based on a single-layer template fleece 1 according to Figure 1 with fibers predominantly aligned transversely to the longitudinal direction of the web, the template fleece being folded into pile folds 17. This relatively thin nonwoven fabric is also mechanically strengthened on both sides by stitch reinforcements 18 and 19. The thickness S of the nonwoven fabric on the one hand and the height h of the stitches on the other hand are coordinated in such a way that the common size of the stitches on one and the other side, measured in the thickness direction, is larger than the thickness S of the nonwoven fabric. Relatively large stitches with a height h are thus folded in the respective stitch layer, this height being larger than half the fleece thickness S. It is

It is by no means necessary that the height of the mesh on one flat side matches that of the opposite side. Due to the great height of the mesh layers in the nonwoven fabric, the meshes on the opposite sides overlap each other in the middle of the nonwoven fabric (overlap zone u). This overlapping of the opposite meshes 18 and 19 means that a particularly large number of fibres are drawn from the mesh on one flat side and fibres from the mesh on the other flat side in a common plane lying approximately in the middle of the nonwoven fabric, whereby the fibres in this central plane are particularly closely interwoven (also known as entangled in regional colloquial language), which results in a higher degree of integration of these in a common plane lying approximately in the middle of the nonwoven fabric. At the same time, these centrally located fibres are preferably drawn or aligned parallel to the flat sides. This and the additional adhesive fibre consolidation of the nonwoven fabric give the nonwoven fabric a high level of elasticity and stretch resistance, while at the same time being very flexible. The thin and flexible nonwoven fabric, which has a knitted texture on both sides, is ideal for making lightweight garments.

The nonwoven fabric according to Figure 6, which is particularly intensively "tangled" in the middle, is advantageously not bonded to the outer layers close to the surface, but in the "tangled" middle layer, partially in the thickness. In this context, the possibility of dielectric or capacitive heating of the nonwoven fabric in a high-frequency field should also be mentioned. The nonwoven fabric, which is to be partially heated in the thickness, is placed as a dielectric between two plate electrodes, between which a high-frequency alternating electric field is maintained. The strongest heating of the introduced nonwoven fabric is achieved in the middle. By using suitable process parameters, e.g. energy density of the electric field, frequency level and possible cooling of the nonwoven fabric on the outside, it can be achieved that only in a thickness in the

The activation temperature of the adhesive fibers integrated in the fleece is exceeded in the middle area of the fleece, but not in the less heated outer layers. Such dielectric heating can also achieve partial thickness consolidation of the adhesive fibers in the middle of the fleece. The device required for this will be discussed in more detail at the end of the description.

Based on the representations in Figures 7 and 8, the possibility of how a nonwoven fabric can be only partially bonded with adhesive fibers in the thickness direction will be discussed in more detail below. Figure 7 shows a nonwoven fabric 21 bonded on one side by meshes in a greatly enlarged cross section, with the area 22 of adhesive fiber bonding being limited to the area of mesh bonding (stitch wales 23) at the bottom in Figures 7 and 8, which in the thickness direction only accounts for a fraction t of the total thickness D of the nonwoven fabric. Only in this area is heat introduced into the cross section of the nonwoven fabric, thereby activating the adhesive fibers, whereas the adhesive fibers integrated in the nonwoven fabric above this area 22 are not activated due to less heating or even cooling. The adhesive fibers activated within the region 22 form melt beads 24, which collect at the contact points of the fibers or preferentially migrate there due to capillary action and, in the solidified state, solidify in the form of wedges corresponding to the crossed fibers, thereby firmly binding the fibers together.

The device shown in cross-section in Figure 8 serves for the partial thickness thermal consolidation of a nonwoven fabric, e.g. that according to Figure I ₁ , which is conveyed through the device by an air-permeable transport screen 25 at a defined, adjustable speed v.

At the point where the nonwoven fabric is treated for partial thickness bonding of the adhesive fibers, the transport screen is supported by a warm air box 26 with a permeable cover plate 27. In order to give the warm air the opportunity to come into heat-exchanging contact with the fibers of the nonwoven fabric for a longer period of time and to create an opportunity to influence the depth of penetration of the warm air into the nonwoven fabric, the warm air box is divided by partition walls 28 into an alternating sequence of blowing chambers (33) and suction chambers 32 that are short in the conveying direction. In accordance with this division, the cover plate is also provided with outlet slots 29 on the blowing chambers and with suction slots 30 on the suction chambers, each of which could also be designed as a sequence of holes extending across the working width of the device. In order to avoid a transverse inflow or outflow of air in the illustrated embodiment, the outlet slots 29 and the suction slots 30 are arranged inclined to the plane of the cover plate in the direction of a more tangential inflow or outflow of air into the transport screen and the nonwoven fabric.

The blowing chambers 33 are connected to the pressure line of a blower 36 via a branching blowing line 35. In a similar way, the suction chambers 32 are also connected to the suction nozzle of this blower via a branched suction line 34. A controllable heat exchanger 37 for heating the conveyed air is also installed in the blowing line 35, whereby the heating energy from a temperature sensor 38 installed downstream of the heat exchanger in the blowing line can be controlled via a control line 39 extending from it and the conveyed air can be heated to predeterminable temperature values within narrow limits. An adjustable suction flow throttle 41 is also installed in the suction line in front of the blower 36 and a blowing flow throttle 40, which is also adjustable, is installed in the pressure nozzle of the blower.

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By adjusting and coordinating the blowing (40) and suction quantity throttles 41, not only the absolute delivery quantity can be adjusted for a given drive speed of the blower, but also whether the conveyed warm air is pressed more or less strongly into the transport screen and the nonwoven fabric at the outlet slots 29 of the blowing chambers or whether it is sucked out more or less strongly at the suction slots 30. If the air blowing in predominates over the suction, which can be determined by means of the manometers 31, 31' on the blowing and suction lines 35 and 34, respectively, the heated air penetrates deeper into the nonwoven fabric and the area 22 of adhesive fiber consolidation is relatively large. However, if the heated air is sucked out of the nonwoven fabric faster than it was fed into it, the zone of warm air supply is limited to an area close to the screen; the area 22 of the adhesive fiber consolidation is then relatively thin.

In order to be able to efficiently produce the air box with a narrow division into an alternating series of narrow chambers, it is advisable to form the series of partition walls from a meandering or zigzag-shaped bent metal strip which is welded "standing" between the base and cover plate of the air box. The function of the suction and blow lines 34 and 35 can also be easily integrated into the air box by leaving elongated free spaces on both sides of the meandering or zigzag-shaped bent metal strip within the side outer walls of the air box, which are provided with a line connection leading outwards. The various walls of the air box do not need to be welded together over the entire contacting length; instead, repeated tacking of the walls at intervals of 20 to 100 times the wall thickness is sufficient. To seal the joints of the walls, it may be sufficient to fill them with a hardenable, temperature-resistant synthetic resin or to hot-dip galvanize them.

4··

In the embodiment shown in Figure 8, a flat cooling plate 42 is also provided in the device in the same position as the warm air box 26, which rests loosely directly on the top of the nonwoven fabric 21. The cooling plate is freely movable in the vertical direction and is only held or guided in the horizontal direction to prevent it from drifting sideways or running along with the nonwoven fabric. In addition, the cooling plate in the embodiment shown is designed as a hollow body through which tempered cooling water can flow, so that it can be kept at a constant, low temperature.

The cooling plate has two functions. Firstly, its weight is intended to prevent the fleece from lifting off the transport screen in the area of the warm air box due to the warm air supply and to ensure that the pressure of the fleece on the transport screen remains constant even if the thickness of the fleece fluctuates. If the weight of the cooling plate is too great for this purpose - the fleece must not be compressed too much during heating - the cooling plate may need to be relieved, for example by counterweights guided by cables or adjustable tension springs. Secondly, the cooling plate is intended to prevent the upper zones of the fleece cross-section from heating up due to its constant low temperature and constant contact with the top of the fleece.

It can be advantageous if the cooling plate is longer in the transport direction than the warm air box and extends beyond the latter on the inlet side and/or outlet side. This can be used to achieve pre-cooling and/or post-cooling of the nonwoven fabric on its upper side if required. If the cooling plate is cooled with a supercooled sole as a cooling medium, temperatures can be set significantly below room temperature on the upper side of the nonwoven fabric. This may be the case with particularly thin nonwoven fabrics and/or

can be advantageous in areas of very low percentage of adhesive fiber consolidation. In other cases, it may be sufficient to keep the fleece top side at approximately room temperature or slightly above. In such a case, the cooling plate does not necessarily have to be designed as a liquid-coolable hollow body, but can be designed as a solid plate, possibly with cooling fins on the top, which is kept at room temperature on the top side by a cooling fan using room air.

The possibility of double-sided, thickness-partial adhesive fiber reinforcement has already been briefly mentioned in connection with the double-sided mesh-reinforced nonwoven fabric according to Figure 5. In such a case, only the mesh-reinforced areas of the nonwoven fabric close to the surface are additionally reinforced with adhesive fibers, whereas the central area with the standing fiber portion is neither mechanically nor adhesively reinforced, and is therefore soft and fluffy, which gives the nonwoven fabric good flexibility despite its strength. For the purpose of double-sided, thickness-partial adhesive fiber reinforcement, the device shown in Figure 8, for example, is provided in the same treatment plant at a different location, but inverted. A running screen 2 5 would be arranged above the nonwoven fabric and above it another warm air box 2 6 with all the technical peripherals, with which only the top side of the nonwoven fabric can be heated to predeterminable temperatures within an adjustable thickness range. The underside of the nonwoven fabric would have to be cooled, which could be done, for example, by a cooling plate 42 that is directly in contact with the underside. If the cooling plate is to be in direct contact with the nonwoven fabric, the running screen 25 would have to be guided along a different path than the nonwoven fabric. Instead, it would also be conceivable to leave the underside running screen on the nonwoven fabric during the adhesive hardening process on the top side and to cool the underside of the nonwoven fabric through the running screen. In principle, this can also be done by contact cooling using a cooling plate.

In this case, however, it would be more advantageous to use forced convective cooling of the lower and middle areas of the fleece thickness by means of a cooling device constructed similarly to the warm air box 2 6 and operated with forced-cooled circulating air.

For the sake of completeness, another possibility for partial thickness bonding of adhesive fibers should be mentioned, i.e. for targeted heating of only a portion of the fleece cross-section. It is, for example, entirely conceivable to bring the fleece to the activation temperature of the adhesive fibers on one side by contact heating and to prevent the heat from penetrating too deeply on the opposite flat side of the fleece by forced convection by supplying cold air. This type of procedure is particularly advisable if - for whatever reason - you want to prevent the structure of a transport screen from remaining visible on the surface of the side of the fleece to be heated. With contact heating, you would use an air-impermeable, smooth-surfaced Teflon tape as the transport belt, which moves the fleece over a heating plate under a predeterminable contact pressure.

Another design alternative for the "contact heating" approach is to guide the nonwoven fabric, which is to be partially bonded with adhesive fibers, with the side to be bonded over a heatable roller or drum, which is wrapped around the nonwoven fabric by at least 180°. The exposed back of the nonwoven fabric, which is to be partially bonded, can be cooled by forced convection through an intensive supply of cooling air.

The measures mentioned here can of course also be used for partial thickness, double-sided adhesive fiber consolidation by first applying them to one side and then, at a later time or location, to the opposite side of the fleece.

Finally, it should be noted that commercially available flatbed laminating machines can also be used for partial thickness bonding of nonwovens with adhesive fibers if the process parameters of the heating arranged on one side of the material to be treated on the one hand and those of the cooling arranged opposite on the other hand are set in a suitable manner.

In connection with the nonwoven fabric 20 according to Figure 6, which is particularly intensively "tangled" in the middle, it has already been mentioned that this is advantageously partially bonded with adhesive fibers in the fiber-rich middle layer, for which purpose a dielectric or capacitive heating of the nonwoven fabric in a high-frequency field was considered.

With regard to certain uses of a nonwoven fabric, it can be quite sensible to use a nonwoven fabric that is mechanically mesh-bonded on both sides and has a high proportion of standing fibers, e.g. one as shown in Figure 5, to additionally bond it with adhesive in the thickness in part only in the area of the centrally standing fibers. The central zone of the standing fibers would then be highly elastic and would have good resilience, while the meshed outer zones would remain soft and fluffy. A nonwoven fabric of this type that is highly elastic in the direction of thickness could, for example, be used excellently as a base material for upholstery purposes. Such uses or applications are not only found in seat cushions, e.g. for car seats, train or airplane seats or upholstered furniture in the living area, but the high thickness elasticity of the nonwoven fabric with a soft surface can also be used advantageously in the interior lining or cladding of car bodies, airplane cabins, travel compartments in rail vehicles or ship cabins, and also in room linings in the living area. The high thickness elasticity with soft outer layers makes the nonwoven fabric an ideal insulating material that is soft and supple. It can be rolled up tightly.

len, but springs back to its full thickness after unrolling, i.e. in the stretched position.

For partial thickness bonding of adhesive fibers in the middle layer of a nonwoven fabric, a variant of the device shown in Figure 8 can be used, which is indicated in dash-dotted lines. In this variant, the upper cooling plate 42 can take on the function of one plate electrode, which is connected to a suitable high-frequency alternating voltage source 43, indicated in dash-dotted lines. In this case, it would have to be held and guided within the machine in a well-insulated electrical manner. The metal running screen 25, which is located at the bottom of the nonwoven fabric, and the air box that comes into contact with it are electrically grounded via the connection 44, indicated in dash-dotted lines, and in this case would take on the function of the opposite plate electrode. In addition, if the air box is operated with forced-cooled circulating air, the nonwoven fabric can be cooled from below by forced convection.

The nonwoven fabric, which is to be partially strengthened by adhesive fibers in the middle area, is heated most strongly in the middle by the high-frequency alternating electric field that is maintained between the cooling plate on the one hand and the running screen or the air box on the other. By cooling the nonwoven fabric on the top and bottom and by using suitable process control parameters, e.g. energy density of the electric field, frequency level, etc., the activation temperature of the adhesive fibers is only exceeded in the middle area of the nonwoven fabric, but not in the cooled outer layers. This means that only the middle of the nonwoven fabric is partially strengthened by adhesive fibers.

.oOo.

Claims (15)

1. A nonwoven fabric mechanically consolidated by meshing, which is also adhesive-fiber-consolidated by embedded adhesive fibers, characterized in that the adhesive fiber consolidation of the nonwoven fabric ( 12 , 21 ) is limited to a partial region ( 10 ) of the thickness extension (D) of the nonwoven fabric ( 12 , 21 ). 2. Nonwoven fabric according to claim 1, characterized in that the nonwoven fabric ( 12 ) is formed in at least two layers with at least one layer ( 5 ) with essentially longitudinally oriented fibers ( 3 ') and a further layer ( 1 ') consisting of a zigzag-shaped pile with essentially transversely oriented fibers ( 3 ). 3. Nonwoven fabric according to claim 1, characterized in that the nonwoven fabric ( 16 ) consists of a zigzag-shaped pile ( 2 ) in which the fibers ( 3 ) are aligned essentially transversely to the longitudinal direction of the nonwoven fabric and to the wales ( 9 ') of the fiber mesh ( 14 , 15 ). 4. Nonwoven fabric according to claim 1, characterized in that the nonwoven fabric ( 12 ) is stitch-bonded ( 8 ) only on one flat side. 5. Nonwoven fabric according to claim 1, characterized in that the nonwoven fabric ( 16 ) is mechanically strengthened on both opposite flat sides by meshing ( 14 , 15 ) fibers close to the surface. 6. Nonwoven fabric according to claim 1, characterized in that the adhesive fiber-bonded portion ( 10 ) is arranged close to the surface in the nonwoven fabric. 7. Nonwoven fabric according to claim 1, characterized in that the thickness-partial adhesive fiber consolidation of the nonwoven fabric is limited to the partial region ( 10 ) mechanically consolidated by meshing. 8. Nonwoven fabric according to claim 1, characterized in that the nonwoven fabric ( 12 , 16 ) contains a portion of standing fibers which extend substantially transversely between the two opposite flat sides. 9. Nonwoven fabric according to claim 8, characterized in that at least a proportion of about 15% by weight of the fibers are arranged upright in the nonwoven fabric ( 12 , 16 ). 10. Nonwoven fabric according to claim 1, characterized in that - the nonwoven fabric ( 12 ) is mechanically strengthened only on one flat side by a mesh ( 8 ) of the fibres close to the surface, - that the nonwoven fabric ( 12 ) contains a proportion of standing fibres which extend essentially transversely to the meshed ( 8 ) flat sides of the nonwoven fabric ( 12 ) and protrude from this in the form of pile fibres in the manner of a velour, - that the adhesive fibre consolidation of the nonwoven fabric ( 12 ) is limited to the near-surface portion ( 10 ) of the thickness (D) of the nonwoven fabric ( 12 ) which is mechanically consolidated by the mesh ( 8 ) and - that the pile fibres ( 11 ) which are not bonded with adhesive fibres are mechanically finished, e.g. sheared and brushed in the manner of a loden or otherwise refined. 11. Nonwoven fabric according to claim 1, characterized in that - the nonwoven fabric ( 20 ) is mechanically strengthened on both opposite flat sides by intermeshing ( 18 , 19 ) of fibres close to the surface, - the thickness of the nonwoven fabric (S) being less than the common size (2 × h) of the meshes ( 18 , 19 ) of one and the other side, measured in the thickness direction, and - that fibres for the meshes ( 18 ) of one flat side and fibres for the meshes ( 19 ) of the other flat side lie in a common plane lying approximately centrally in the nonwoven fabric ( 20 ), - whereby the fibres of this central plane are particularly strongly bound to one another, i.e. they have a higher degree of binding than in the area close to the surface and are preferably aligned parallel to the flat sides. 12. Nonwoven fabric according to one of the preceding claims, characterized in that the adhesive fiber consolidation of the nonwoven fabric ( 20 ) is limited to the region lying approximately in the middle of the nonwoven fabric ( 20 ). 13. Nonwoven fabric according to one of the preceding claims, characterized in that thermally activatable hot melt adhesive fibers or bicomponent binding fibers are contained as adhesive fibers in a proportion of 2 to 20 wt.%, preferably 5 to 12 wt.% in the nonwoven fabric. 14. Nonwoven fabric according to one of the preceding claims, characterized by the use of the nonwoven fabric ( 12 , 16 , 20 , 21 ) for outer clothing, in particular as visible outer material of clothing items. 15. Nonwoven fabric according to claims 8 and 12, characterized by the use of the nonwoven fabric ( 16 ) as a base material for seat cushions or for interior linings or paneling of rooms.