DE20102639U1 - Isotropic nonwoven, in particular as an outer fabric for clothing - Google Patents

Description

Textile service I. Schmidt February 14, 2001

Emmendingen

Isotropic nonwoven fabric, especially as outer fabric for clothing purposes

The invention is based on a nonwoven fabric consisting exclusively of unspun fibers, as is known, for example, from DE 195 46 430 Cl.

Nonwovens can be used in various 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 for use as visible, tensile-loaded carrier materials for items of clothing.

Such nonwovens, which can be 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 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 designed as needle punched nonwovens, in which the fibers are needled onto a carrier web. The carrier web - a woven or knitted fabric made of spun threads - provides the required longitudinal and transverse strength, while the needled fibers provide the volume and fluffiness of the nonwoven. The needle punched nonwovens produced or constructed in this way are suitable for outerwear purposes and are therefore also widely used by the population at least for clothing for sports and leisure activities. The well-known

However, the needle-punched nonwovens do not consist exclusively of unspun fibers. Rather, the carrier web made of woven threads is an intermediate product produced in several processing stages - fiber production, spinning, weaving/knitting - and is therefore relatively expensive. Due to the complex production process, these needle-punched nonwovens are not particularly cheap.

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 should be partially designed as chemically or thermally activated adhesive fibers which bond the contact points to other fibers. In order to achieve a certain longitudinal stability, - only - one side of the voluminous nonwoven fabric is at least partially meshed, with the mesh wales lying in the longitudinal direction of the nonwoven fabric and in the direction of the fiber orientation. A 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 items.

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, with the web thus produced being mechanically strengthened with a high proportion of standing fibers on the top and bottom by intermeshing the fibers. This technology can be used to produce a voluminous nonwoven fabric in a rational and cost-effective manner. It is stated that the nonwoven fabric intended for insulation purposes can also

013

should have a high dimensional and volume stability. Experience with nonwovens of this type, however, suggests 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 in the outerwear sector that is subject to tensile stress in all directions.

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 therefore 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.

Based on this state of the art, the object of the invention is to provide an improved nonwoven fabric which can be produced more cost-effectively than a needle-punched nonwoven fabric with an integrated carrier web, but at the same time at least

: ₄ ·

approximately has its strength values and low values of permanent elongation in the longitudinal and transverse directions. This object is achieved according to the invention by a nonwoven fabric with the features of claim 1.

The mutual adhesive bonding of the mechanically interwoven nonwoven fibers achieves a sufficiently high strength and a low permanent stretch. By using at least a two-layer template nonwoven with a zigzag pile in which the fibers are predominantly transversely oriented and at least one further fiber layer with longitudinally oriented fibers, the longitudinal and transverse strength of the nonwoven is equalized. The invention combines several measures or features to create a novel whole with a surprising effect: Firstly, several fiber layers, each with predominantly longitudinally and predominantly transversely oriented fibers, are combined in the nonwoven; secondly, the nonwoven is mechanically strengthened by stitches with longitudinally oriented wales; finally, the fibers of the nonwoven are additionally strengthened by gluing. This combination of measures creates a fiber structure that is elastic but spatially stable and can only be torn apart with considerable resistance and has a high level of elasticity. These properties provide the high longitudinal and transverse strength as well as dent resistance of the nonwoven fabric according to the invention.

Appropriate 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 a fleece layer formed by zigzag laying of a pile as an intermediate product for the formation of a multi-layer template fleece, which fleece layer has essentially transversely oriented fibers,

·

·

Fig. 2 and 3 show a two-layer (Figure 2) or three-layer (Figure 3) template fleece for producing a nonwoven fabric, which is formed from at least one fleece layer with longitudinally oriented fibers and a further fleece layer according to Figure 1 with transversely oriented fibers,

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 that is reinforced on one side by meshes and only partially adhesively reinforced in the thickness direction and

Fig. 8 shows a cross-section through a production device for the 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 strengthened at least on one flat side by intermeshing the fibers close to the surface and which is also adhesively strengthened by chemical finishing or - preferably - by admixed, thermally activated adhesive fibers at mutual contact points of the fibers of the nonwoven fabric.

The nonwoven fabric according to the invention is intended to be more cost-effective than a needle-punched nonwoven fabric, but at the same time, despite dispensing with an integrated carrier web, it is at least

013

approximately have strength values as well as low values of permanent elongation in the longitudinal and transverse directions, i.e. be highly elastic.

For this purpose, a new nonwoven fabric structure and a modified method of manufacturing it are used. According to the invention, the nonwoven fabric contains, on the one hand, several nonwoven layers with longitudinally and transversely oriented fibers, on the other hand, mechanical stitch reinforcement with longitudinally oriented wales and, thirdly, adhesive reinforcement of the fibers, all combined in a sensible manner. This creates a fiber structure that is elastic but spatially stable and can only be torn apart with considerable resistance, with high longitudinal and transverse strength and a high dent resistance of the nonwoven fabric. Due to these mechanical properties, the nonwoven fabric according to the invention does not warp under load and is dent-resistant, so that it can be used without further ado for outerwear, in particular as a visible carrier material for outerwear.

In the production of the nonwoven fabric according to the invention, a nonwoven layer 1 shown in perspective in Figure 1 is used as an intermediate product for a multi-layer template nonwoven, which is formed by laying a pile 2 in a zigzag shape. The fibers 3, which are initially mainly aligned lengthwise in the pile, are aligned essentially transversely to the longitudinal direction of the nonwoven layer 1 and to the wales of the fiber mesh that are attached later due to the zigzag arrangement.

The nonwoven fabric according to the invention can be constructed or manufactured in different variants. In any case, 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, such as

This is shown in perspective in Figure 2 for a two-layer template fleece and in Figure 3 for a three-layer template fleece. In the two-layer template fleece 4 according to Figure 2, the upper fleece layer 1 with transversely oriented fibers 3 consists of the zigzag-shaped pile, whereas the lower, "straight" fleece layer 5 contains predominantly longitudinally oriented fibers 3'. The three-layer template fleece 6 shown in Figure 3 has a "straight" fleece layer 5' or 5" with predominantly longitudinally oriented fibers 3' on the bottom and top, whereas the "zigzag" fleece layer 1 arranged in between contains predominantly transversely oriented fibers 3'.

In order to be able to bond the nonwoven fabric in a later step of production, in a preferred variant of the invention, a certain proportion of adhesive fibers must be mixed into 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. It is advisable to contain thermally activated hot melt adhesive fibers or bicomponent binding fibers in the nonwoven fabric in a proportion of 2 to 20% by weight, whereby the optimal content of adhesive fibers depends very much on the specific application or intended use of the nonwoven fabric to be produced. If the nonwoven fabric is to have a very soft drape, similar to a clothing fabric, a lower content of adhesive fibers is mixed in and/or the adhesive strength in the thickness direction is limited to a portion of the nonwoven thickness. If the nonwoven fabric is to have a

013

On the other hand, if the adhesive has a certain inherent rigidity, more adhesive fibres will be added and/or the adhesive will be strengthened throughout the thickness.

In connection with the adhesive bonding of the nonwoven fabric, it should be mentioned that basically every single method from the entire range of known adhesive bonding methods can be considered here. In particular, reference is made to the book publication "Nonwoven fabrics - raw materials, production, application, properties, testing", published by W. Albrecht, H. Fuchs, W. Kittelmann, Wiley-VCH, Weinheim, 2000, ISBN 3-527-29535-6. In Chapter 3, "Binders" (pages 119-135), this textbook first looks at the various binders as such from various perspectives and in Chapter 6, "Nonwoven bonding", in subsections 6.4: "Thermal methods" (pages 340-369) and 6.5: "Chemical methods" (pages 369-388), it deals with all known methods of adhesive bonding of nonwoven fabrics.

At this point, it should simply be mentioned that as an alternative to the thermally triggered adhesive fiber bonding method that is most common today, the fibers of the nonwoven fabric can be treated with binding agents after mechanical bonding by dipping (wet) or dusting (dry, powdered). Another way of treating the fabric with binding agents, which can be of particular interest for partial thickness bonding close to the surface, is to so-called slapping the nonwoven fabric, whereby it is passed over a roller that is constantly wetted with binding agent. During adhesive fiber bonding, the adhesive in the nonwoven fabric collects primarily at the contact gussets or intersection points of the fibers, so that after the adhesive has set, a spatially stabilized fiber structure remains.

The multi-layer template fleeces 4 or 6 shown in Figures 2 or 3 are preferably made from a fiber mixture enriched with adhesive fibers.

013

In nonwoven fabrics, there is at least one nonwoven layer 1 with fibers 3 aligned transversely to the nonwoven web. The template nonwovens 4 or 6 formed in this way are then first mechanically consolidated by stitch formation, for which various known processes are available. In this context, reference is also made to the above-mentioned book "Nonwovens", subsection 6.2 "Stitch formation processes" (pages 302-325). At this point, a stitch consolidation process will be briefly discussed in general terms, i.e. without reference to an example.

In the case of one-sided consolidation by forming stitches, 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 pre-prepared fleece to be processed and another device for pulling loops out of the fibers and for creating stitches. The voluminous nonwoven fabric formed with a Kunit machine consists on its upper side of fleece pile folds that are perpendicular to the nonwoven surface and on its underside exclusively of fiber stitches lying in the nonwoven 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 by another Multiknit® device. The voluminous nonwoven fabric formed with such a combination machine consists exclusively of fiber meshes on the top side and predominantly of fiber meshes on the bottom side in the nonwoven fabric surface. The layer in between contains fibers,

i ^: "&iacgr;&ogr;&idigr; IV · &eegr; ·&Igr;

which 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 bonded, which in the case of mixed adhesive fibers is achieved by radiant heating of the nonwoven fabric, by contact heating and/or forced convective heating using hot air. Due to the heating of the mixed adhesive fibers integrated in the nonwoven fabric, they are thermally activated, i.e. melted, so that clumps of melted adhesive accumulate at the points of contact and crossing of fibers. 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 its 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 2 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 transversely to the meshed flat side and protrude from there in the manner of a velour. The adhesive bonding of the nonwoven fabric, e.g. by admixed, thermally activated adhesive fibers, is limited to a partial area 10 (thickness t) of the nonwoven fabric close to the surface with the total thickness D. In fact, only the side of the nonwoven fabric that is already mesh-bonded is also partially (relative to the total thickness) adhesive-bonded. The thickness-partial adhesive bonding will be discussed in more detail below in connection with Figures 7 and 8. The pile folds 7 or pile fibers extending in the direction of the opposite side of the nonwoven fabric are neither mechanically mesh-bonded nor adhesive-bonded; rather, they protrude softly and loosely from the doubly bonded side of the nonwoven fabric. These loose pile fibers 11 are mechanically treated, e.g. sheared and flat-brushed in the manner of 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 fleece can be produced inexpensively, which can be processed into coats, traditional suits, traditional costumes or the like.

1 11'* &Lgr;2. · · ·

1 11'* · * ♦ ·

In the embodiment shown in cross-section in Figure 5, a similar template fleece 4' is further processed into a nonwoven fabric 16. The template fleece 4', 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 top-side (14) and bottom-side intermeshing 15, with the mesh wales 9' lying parallel to the nonwoven fabric 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 also bonded with adhesive across its entire cross-section. In the case of mixed-in adhesive fibers, this can be done, for example, in a forced convective manner by passing hot air through the nonwoven fabric and by subsequent, preferably also forced convective, cooling using cold air. The voluminous 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 an elastically 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 clothing.

The embodiment of a further nonwoven fabric 20 shown in cross section in Figure 6 is also based on a similar template fleece 4" 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 of one and the other, measured in the thickness direction,

whose side is larger than the thickness S of the nonwoven fabric. Relatively large stitches are therefore created. As a result, the stitches of the opposite sides overlap each other in the middle of the nonwoven fabric (overlap zone u). As a result of this overlapping of the opposite meshes 18 and 19, fibers from the stitches on one flat side and fibers from the stitches on the other flat side are particularly closely interwoven (also known as entangled in regional parlance), which results in a higher degree of integration of these in a common plane located approximately in the middle of the nonwoven fabric. At the same time, these centrally located fibers are preferably pulled or aligned parallel to the flat sides. In the case of extremely uneven mesh heights, the overlap zone with an increased degree of integration is offset off-center in the direction of the nonwoven fabric side with the smaller stitches. The overlapping mesh, the increased fiber integration there and the additional adhesive strengthening of the nonwoven give the nonwoven a high elastic stretch and good flexibility at the same time. The thin and flexible nonwoven, which has a knitted texture on both sides, is easy to process for lightweight clothing.

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 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 and the adhesive fibers are thereby activated, 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 area 22 form

the 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 gussets corresponding to the crossed fibers and thereby bind the fibers firmly to one another.

The device shown in cross-section in Figure 8 serves for the partial thermal consolidation of a nonwoven fabric, e.g. that according to Figure 7, 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 thick bonding, 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 embodiment shown, 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 blow chambers 33 are connected to the pressure line of a blower 36 via a branching blow line 35. In a similar way, the suction chambers 32 are also connected to the pressure line of a blower 36 via a

branched suction line 34 is connected to the suction port of this blower. A controllable heat exchanger 37 is also installed in the blower line 35 to heat the air being conveyed, whereby the heating energy from a temperature sensor 38 installed downstream of the heat exchanger in the blower line can be controlled via a control line 39 extending from it and the air being conveyed can be heated to predeterminable temperatures within narrow limits. An adjustable suction flow throttle 41 is also installed in the suction line in front of the blower 36 and a blower flow throttle 40, which is also adjustable, is installed in the blower's pressure port.

By adjusting and coordinating the blowing (40) and suction quantity throttle 41, not only the absolute delivery rate of the blower can be adjusted at a given drive speed, but also whether the conveyed warm air is pressed more or less strongly into the transport screen 25 and the nonwoven fabric 21 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 is blown in more than sucked out, the heated air penetrates deeper into the nonwoven fabric and the area 22 of adhesive 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 adhesive consolidation is then relatively thin.

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 horizontally in a fixed position or guided vertically in a horizontal direction to prevent it from drifting away 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. Secondly, its constant low temperature and constant contact with the top of the fleece prevent the upper zones of the fleece cross-section from heating up.

It can be advantageous if the cooling plate is longer in the direction of transport than the warm air box and extends beyond the latter on the inlet side and/or outlet side. This can be used to pre-cool and/or post-cool the nonwoven fabric on its upper side if required. If the cooling plate is cooled using 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 advantageous for particularly thin nonwoven fabrics and/or for very small percentage areas of adhesive fiber consolidation. In other cases, it may be sufficient to keep the upper side of the nonwoven fabric approximately at 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 upper side, which is kept at room temperature on the upper side by a cooling fan using room 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 activate the fleece on one side by contact heating.

temperature of the adhesive fibers and to prevent the heat from penetrating too deeply on the opposite flat side of the nonwoven fabric 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 nonwoven fabric to be heated. In the case of contact heating, an air-impermeable, superficially smooth Teflon tape would be used as the transport belt, which moves the nonwoven fabric over a heating plate under a predefined contact pressure. Another design alternative for the "contact heating" procedure is to guide the nonwoven fabric to be partially bonded with the side to be bonded over a heatable roller or drum and to cool the exposed back side by intensively supplying cooling air.

Finally, it should be noted that commercially available flatbed laminating machines can also be used for continuous or partial thickness bonding of nonwovens. Particularly when releasing the adhesive in partial thickness, the process parameters of the heating arranged on one side of the material to be treated and the cooling arranged opposite must be 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 may be quite sensible to use a nonwoven fabric that is mechanically stitch-bonded on both sides and has a high proportion of standing fibres, e.g. one such as that shown in Figure 5.

to additionally consolidate the central fibers with an adhesive in some parts of the thickness. The central zone of the central fibers would then be highly elastic and would have good spring-back properties, while the meshed outer zones would remain soft and fluffy. A nonwoven fabric with this kind of high thickness elasticity could, for example, be used primarily in the clothing sector as interlining or 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 advantageous for the interior lining or cladding of car bodies, airplane cabins, travel compartments in rail vehicles or ship cabins, and also for room linings in the living area. The high thickness elasticity and soft outer layers make the nonwoven fabric an ideal insulating material that is soft and supple. It can be rolled up tightly, but after unrolling, i.e. in the stretched position, it springs back up to its full thickness.

For the sake of completeness, a variant of a nonwoven fabric with a high proportion of standing fibers that is stitch-bonded on both sides should also be mentioned in this context. This nonwoven fabric is partially bonded with adhesives in the thickness, in particular bonded with adhesive fibers, but in which the adhesive bonding covers both the stitch bonding on the other side and the relatively strong central region with the standing fibers; only the stitch-bonded visible side of this nonwoven fabric would not be bonded with adhesives and would therefore still be soft and fluffy. An upholstery nonwoven fabric that is partially bonded with adhesives in the thickness direction to at least two-thirds or more would be of particular interest for lining purposes in the applications mentioned above. Due to the fact that the adhesive bonding extends deep into the nonwoven fabric on one side up to the outer surface of the nonwoven fabric,

is sufficient, it can be triggered thermally with simpler equipment and can be controlled more reliably in terms of process control.

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 (12)

1. A nonwoven fabric ( 12 , 16 , 20 , 21 ) consisting exclusively of unspun fibers, which is mechanically strengthened at least on one flat side by a mesh ( 8 , 14/15 , 18/19 , 23 ) of the fibers close to the surface and is also adhesively strengthened due to adhesive fibers or other binding agents, wherein the nonwoven fabric ( 12 , 16 , 20 , 21 ) 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 ). 2. 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. 3. 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. 4. Nonwoven fabric according to claim 3, characterized in that at least a proportion of about 15% by weight of the fibers are arranged upright in the nonwoven fabric ( 12 , 16 ). 5. 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 strengthening of the nonwoven fabric ( 12 ) is limited to the near-surface portion ( 10 ) of the thickness (D) of the nonwoven fabric ( 12 ) mechanically strengthened by the mesh ( 8 ) and - that the non-adhesive pile fibres ( 11 ) are mechanically finished, e.g. sheared and brushed like a loden or otherwise mechanically finished. 6. 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. 7. Nonwoven fabric according to claim 1, characterized in that the adhesive strengthening of the nonwoven fabric ( 12 , 21 ) is limited to a partial region ( 10 ) of the thickness (D) of the nonwoven fabric ( 12 , 21 ). 8. Nonwoven fabric according to claim 7, characterized in that the adhesive fiber-bonded portion ( 10 ) is arranged close to the surface in the nonwoven fabric. 9. Nonwoven fabric according to claim 7, 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 ). 10. 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 ( 12 , 16 , 20 , 21 ). 11. Nonwoven fabric according to one of the preceding claims, characterized by the use of the nonwoven fabric ( 12 , 16 , 20 , 21 ) for outerwear, in particular as a visible carrier material of clothing items. 12. Nonwoven fabric according to claims 3 and 9, characterized by the use of the nonwoven fabric ( 16 ) as a base material for seat cushions or for interior linings or paneling of rooms.