IE912743A1 - Deep-drawable textile material and shaped articles produced¹therefrom - Google Patents

Abstract

There is described an isotropic, readily deep-drawable nonwoven which has been formed as a filament nonwoven and consists of low-orientation, coarse-denier filaments to an extent of not less than 30% by weight and which has been consolidated with a fusible binder. Furthermore, a resinated, sheetlike prepreg produced from the nonwoven; a three-dimensional shaped textile structure produced using the resinated or unresinated deep-drawable nonwoven; and a sandwich material with a core comprising said three-dimensionally shaped, resinated textile structure. There are also described processes for manufacturing the abovementioned objects.

Description

HOECHST AKTIENGESELLSCHAFT HOE 90/F 233 Dr. VA/Le Description Deep-drawable textile material and shaped articles produced therefrom The present invention relates to a deep-drawable nonwoven, a resinated sheetlike prepreg produced therefrom, a three-dimensionally shaped textile structure produced using the resinated or unresinated deep-drawable nonwoven, and a sandwich material having a core made of said three-dimensionally shaped resinated textile structure.

The present invention further relates to processes for producing the above-designated objects.

EP-A-247 232 describes nonwovens of filaments of low preorientation as evidenced by a breaking extension of above 100 % or a birefringence of from 0.01 to 0.07.

These nonwovens are thermally preconsolidated with hot embossing rolls, moistened and then heat-set under tension. This results in consolidated areas, which greatly restrict the mobility of the filaments within the nonwoven, and the subsequent setting under tension results in an anisotropy of the thermomechanical properties, which greatly impairs the formability of such nonwovens, at least in the tension direction.

DE-A-3 029 752 discloses a process for producing a deep25 drawn article from a staple fiber web containing at least 10 % by weight of drawable fibers having a breaking extension at 150°C below the melting point of at least 100 %, which has been consolidated by needling and which is deep-drawn at a temperature between 150 °C and the melting point of the drawable fibers.

The web can be additionally reinforced by a thermoplastic or thermosetting binder.

The staple fibers used for this material can consist of a very wide range of synthetic polymers and according to the examples have staple lengths of about 50 - 80 mm and - 2 individual filament deniers of from 1.5 to 20.

The shaped articles produced are suitable for use as self-supporting filters. However, owing to the exclusive use of staple fibers, they lack mechanical strength. The reference gives no indication that a deep-drawable web might also be constructed from continuous fibers; on the contrary, the person skilled in the art is led to think that the deep-drawability of this known web is due to the use of short fibers which can slide relatively easily past one another during deep-drawing.

A formable spunbonded web which consists exclusively of partially oriented continuous synthetic fibers is known from DE-B-1 560 797. The fiber material of these webs can consist of polyamides, polyesters or polyolefins. To consolidate the web, it is compacted in a pattern and impregnated with locally varying binder concentrations. This specific form of consolidation is said by this reference to be of pivotal importance for the formability of the web. However, as with the spotwise consolidation effected in EP-A-247 232 the result here too is an anisotropy in the mobility of the filaments within the nonwoven, which impairs the three-dimensional formability of the nonwoven.

It is already known from EP-A-250 005 to produce three25 dimensional structures from woven fabrics and normal webs by deep drawing. The gain in area achieved in the process of deep-drawing is said by this reference to be due only to the inherent stretchability of this sheet material and accordingly is small.

The present invention provides an isotropic, readily deep-drawable nonwoven which under normal processing conditions, In particular in the course of impregnation, shows very good dimensional stability and which at the same time makes possible a sufficiently large deep-draw ratio for all practical purposes.

The Isotropic, readily deep-drawable nonwoven of the - 3 present invention is constructed as a filament nonwoven which contains at least 30 % by weight of low-orientation, coarse-denier filaments having a linear density of more than 7 dtex and has been consolidated with a fusion binder which may have been introduced for example in powder form but preferably has been introduced in the form of binding fibers.

Suitable fusion binders are in particular polymers whose melting points are lower than the melting point of the low-orientation, coarse-denier filaments which form the spunbonded web.

Advantageously, the melting point of the fusion binder is about 10°C, preferably about 30°C, below the melting point of the coarse-denier, low-orientation filaments.

The melting point of the binder can be above or below the shaping temperature of the deep-drawing process to which the nonwoven is subjected when being processed into shaped articles.

If the melting temperature of the binder is lower than the shaping temperature, the binding points of the nonwoven loosen in the course of deep-drawing and its filaments become substantially freely movable; this results in virtually unhindered shapeability.

Particularly suitable fusion binders consist of poly25 esters, preferably polybutylene terephthalate, or of modified polyesters having an appropriately lowered melting point, preferably a polyethylene terephthalate which has been modified for example by incorporation of isophthalic acid radicals. The fusion binder share of the nonwoven weight is advantageously from 5 to 25% by weight, preferably from 10 to 15% by weight.

Within this range the fusion binder content is made as low as possible and adapted to the remaining composition of the nonwoven and the intended degree of shaping.

If the fusion binder is present in the nonwoven in the form of binding fibres, it generally has a linear density within the range from 1 to 20 dtex. - 4 If of advantage, for example for the convenience of the manufacturing process, the webs of the present invention can also have been preconsolidated mechanically, for example by needling or other known mechanical processes.

The orientation of the low-orientation coarse-denier filaments contained in the nonwovens of the present invention is advantageously such that it corresponds to an ultimate tensile strength extension of at least 80 %, preferably of at least 100 %. The ultimate tensile strength extension of the low-orientation, coarse-denier filaments is basically limited at the upper end only by whether they can be produced. However, it is advantageous to select a filament orientation which results in an ultimate tensile strength extension of between 100 and about 350 %. It is particularly preferable to adapt the degree of orientation of the low-orientation, coarsedenier filaments, i.e. their ultimate tensile strength extension, to the intended purpose, i.e. to the threedimensional shape to be achieved by deep drawing, in such a way that, in the drawn areas, the coarse-denier filaments cannot break but, on the other hand, do not have any excessive residual drawability left either. It is therefore particularly preferable to adjust the orientation of the coarse-denier filaments, i.e. their ultimate tensile strength extension, in such a way that, following the deep drawing of the web of the present invention, the coarse-denier filaments in the drawn areas still have a residual drawability of from about 10 to 50 %, in particular 10 to 30 %.

The coarse-denier filaments contained in the nonwovens of the present invention generally have individual linear densities of from 7 to 30 dtex, preferably from 10 to 25 dtex. Even linear densities outside these advantageous linear density limits are possible, provided that the abovementioned conditions concerning the orientation of the filament material can be complied with. - 5 For specific purposes the deep-drawable nonwovens of the present invention are made 100 % of the low-orientation, coarse-denier filaments. However, it has been found that it is possible, surprisingly, also to produce readily deep-drawable webs according to the present invention which contain up to 70 % of other fibers.

These other fibers can correspond to any type of fiber known to be suitable for webmaking. They preferably have a normal to high degree of orientation and can according10 ly have a normal to high tensile strength and they can be staple fibers or, preferably, continuous fibers. Therefore, hereinafter the term other fibers is always to be understood as meaning all these types of fiber.

It is surprising that such webs of the present invention which contain only about 30 % of low-orientation, coarsedenier filament are still readily deep-drawable while known webs exhibit only a moderate deep-drawability tearing in the drawn zones at high deep-draw ratios. The deep-drawability of webs of the present invention which contain a predominant proportion of other fibers is likely to be due to the fact that the proportion of loworientation, coarse-denier filaments present in the web perform a surprisingly good supporting and stabilizing function which is surprisingly effective in preventing breaking of the other fiber portions of the web of the present invention. Preferred nonwovens of the present invention contain a proportion of from 40 to 85 % by weight of the low-orientation, coarse-denier filaments or, as mentioned earlier, they are 100 % low-orientation, coarse-denier filaments.

Neither the low-orientation, coarse-denier filaments nor the other fibers of the nonwoven of the present invention need all have the same linear density. On the contrary, it is also possible for two or more groups of low-orien35 tation, coarse-denier filaments having different linear densities above 7 dtex to be present in the same nonwoven, or the linear densities of the low-orientation, - 6 coarse-denier filaments can be randomly distributed in a range above 7 dtex, provided their orientation corresponds to the ultimate tensile strength extension of at least 80 %. The same applies of course also to the other fibers of the nonwoven of the present invention. They too can be present in one and the same nonwoven in various linear densities or in a linear density spectrum in which the linear densities are randomly distributed, but they are not subject to the linear density restriction to values above 7 dtex.

The linear densities of these other fibers therefore can also be less than 7 dtex, and in general they range from 1 to 30 dtex.

The linear density mix of the filaments and fibers makes 15 it possible to vary the character of the nonwovens of the present invention within fairly wide limits. For instance, a higher proportion of coarse-denier filaments and fibers leads for example to increased stiffness and lower opacity; a higher proportion of fine deniers below dtex is particularly preferred when the opacity of the nonwoven of the present invention is to be increased and/or made more uniform.

There are various ways of distributing the low-orientation, coarse-denier filaments and the other fibers in the deep-drawable nonwovens of the present invention. The low-orientation, coarse-denier filaments and the other fibers can be present in the deep-drawable nonwovens in a virtually homogeneous mixture, so that on average the distribution of low-orientation, coarse-denier filaments and other fibers is approximately the same in every volume element of the web. However, the deep-drawable nonwoven of the present invention can also have a layered structure in which the low-orientation, coarse-denier filaments and the other fibers are present in different layers. These layers of low-orientation, coarse-denier filaments and layers of other fibers alternate. With such a structure it is preferable that at least one outer surface of the layered nonwoven, but in particular both - 7 outer surfaces, are layers of low-orientation, coarsedenier filaments. The layers of such a nonwoven of the present invention are likewise bonded together by the permeating fusion binder, in particular binding fibers.

However, they can also be, if necessary additionally, bonded together mechanically, for example by needling.

The excellent support offered by the deep-drawable nonwovens of the present invention can also be utilized by combining a nonwoven of the present invention with other, known nonwovens by local or uniform bonding. This once again results in a layered structure, which, owing to the presence of at least one layer of a nonwoven of the present invention, exhibits good deep-drawability. When a layered material of the present invention is combined with other, known layered materials, the number of layers is in principle not limited but is determined by the intended use. Such a combination generally comprises in alternation nonwovens according to the invention and conventional nonwovens, and can have as an outer layer on one or both sides a nonwoven according to the invention or a conventional nonwoven.

The basis weight of the nonwovens of the present invention is likewise essentially determined by the use intended for the material, and generally ranges from 50 to 500 g/m2, preferably from 100 to 300 g/m2.

The excellent formability of the nonwoven of the present invention is due not only to the good formability of the low-orientation, coarse-denier filaments present therein but also due to the good mobility of the filaments, which are bonded together by the fusion binder only at their points of contact.

The coarse-denier individual filaments contained in the nonwoven of the present invention confer good self-stability on the deep-drawn articles even if they do not or not as yet contain any stabilizing resin. - 8 The deep-drawable spunbonded of the present invention is produced in a conventional manner by forming the filaments on a moving perforated surface into a random-laid web, and comprises using at least 30 % by weight of low5 orientation, coarse-denier filaments having a linear density of more than 7 dtex. The blasting jets for extruding the filaments are adjusted here in such a way as to confer on these coarse-denier filaments a relatively low degree of preorientation which corresponds to an ultimate tensile strength extension of at least 80 %, preferably at least 100 %. It is particularly advantageous to adjust the take-off jets in such a way that, depending on the intended use for the deep-drawable web of the present invention, the low-orientation, coarse15 denier filaments have ultimate tensile strength extensions within the range from 100 to 350 %. Preferably, the individual linear density of the coarse-denier loworientation filaments is within the range between 8 and 30 dtex and their share of the total weight of the web is between 80 and 100 % by weight. The amount of filament laid down per m2 is determined in accordance with the above-specified criteria; in general, from 50 to 500 g, preferably from 100 to 300 g, of filaments are laid down per m2.

The filaments are preferably laid down using a rotating impingement plate and in particular a downstream guiding surface as described for example in German Patent 2,713,241. To produce the deep-drawable spunbondeds of the present invention with the preferred layered structure in which the low-orientation, coarsedenier filaments and the other fibers are present in different layers, the filaments are laid down through a plurality of successive (in the transport direction of the perforated surface) rows of depositing elements, from which low-orientation, coarse-denier filaments and other fibers are deposited alternately.

The freshly laid spunbonded is consolidated in a conventional manner with a fusion binder. - 9 The fusion binder is introduced into the laid web in powder or filament form in the abovementioned amount. The web is then consolidated into a nonwoven by heating, in particular by means of a calender, which may have smooth or profiled rolls, for example engraved rolls. The process of consolidation may be effected exclusively with a calender or by means of a calender (consolidation) and subsequent further heat treatment, for example hot air or radiative energy. In the course of this heat treatment the binders, preferably the binding filaments, melt to some extent and form the desired bonding points at the crossing points of the load-bearing coarse-denier, loworientation filaments. Consolidation with the fusion binder can also be combined with a known form of mechanical consolidation, for example needling. This produces, in particular in the case of thick and/or heterogeneous nonwovens, an appreciable gain in stability.

The filaments and fibers of the deep-drawable spunbonded of the present invention can in principle consist of any spinnable polymer material. The polymer material of which the low-orientation, coarse-denier filaments are made, however, must permit the production of filaments which have an ultimate tensile strength extension of at least 80 %, preferably 100 %, in particular from 100 to 350 %.

The other fibers optionally present in the webs of the present invention are not subject to any such restrictions .

Preferred polymer raw materials for preparing the deep30 drawable nonwovens of the present invention are polyesters, polyamides and polyacrylonitrile. Particular preference is given to polyesters, in particular those comprising at least 80 % terephthalic acid and ethylene glycol units. Preference is given in particular to a polymer raw material comprising pure polyethylene terephthalate or polyethylene terephthalate containing not more than 5 % of modifying units. - ίο Polyester building blocks which can be present in the polyesters to be used, as well as terephthalic acid and ethylene glycol, are those customarily used in spinnable polyesters, for example isophthalic acid, sulfoiso5 phthalic acid, naphthalenecarboxylic acids, aromatic hydroxycarboxylic acids, for example p-hydroxybenzoic acid, aliphatic dicarboxylic acids of about 4 to 10 carbon atoms, for example adipic acid, glycols of from 3 to 10 carbon atoms, diglycol, triglycol and polyglycol.

The present invention also provides a deep-drawable nonwoven of the above-described kind which has been additionally impregnated with a thermoplastic or thermosetting resin. The thermoplastic or thermosetting resin used is preferably such as to stiffen the nonwoven to such an extent as to render it self-supporting. Particular preference is given to a nonwoven of the present invention which has been impregnated with a known thermosetting resin, in particular a phenolic or melamine resin. The resin addon, i.e. the amount of resin applied per m2 of textile material, depends on the intended use and is preferably determined in such a way as to produce an essentially open-pored web network. An open-pored web network is for the purposes of the present invention a material which has essentially retained the open-pored structure of the original web and where the resin completely or partially envelopes only the individual filaments and forms binding points at the crossover points of the filaments.

Suitable addon levels for the resin are within the range from 20 to 80, preferably from 40 to 50, % by weight of the semi-finished product. Within the stated ranges, the amount of resin may advantageously be further adapted to the square meter weight of the nonwoven of the present invention. If a heavyweight nonwoven of the present invention is used, the amount of resin is preferably within the upper half of the stated range, whereas if a lightweight textile material is used it is in the lower half. For specific applications it can also be - 11 advantageous to raise the resin addon level to such an extent as to leave a resin film between the threads of the web network even in the extended state.

The resin-impregnated deep-drawable nonwovens of the 5 present invention are simple to produce by subjecting the above-described nonwoven to a conventional resin impregnation process. The resin can be applied in a conventional manner by brushing, rubbing, knife-coating, padding or dipping. The nonwoven is then advantageously passed through a pair of squeeze rollers to squeeze it off to the desired resin pickup. In a preferred embodiment, the resin is applied by a reverse process, wherein the resin is first applied uniformly to a transfer material. The resinated transfer is then brought into close uniform contact with the deep-drawable nonwoven of the present invention and the resin is sucked from the transfer to the nonwoven by virtue of the capillary forces of the latter.

It is certainly not necessary that the resin must be applied uniformly over the entire area of the nonwoven.

On the contrary, the resin can also be applied in the form of a regular pattern or in an irregular but statistically uniform distribution. However, it must be borne in mind here to limit the extent of the nonresinated areas so as to ensure still adequate stiffening of the entire three-dimensionally formed or unformed sheet material.

An effective random distribution of the resin is obtained for example on applying the resin by the above-described reverse process to a nonwoven of the present invention which has a layered structure in which one side contains predominantly coarse fibers of low orientation and the other side contains predominantly finer filaments of normal or high orientation. In this case the resin is applied from the coarse-denier side and the coarse-denier filaments attract the predominant portion of resin and, after deep-drawing and hardening of the resin, form a particularly effectively stiffened support network. - 12 Thermoplastic resins for the impregnation process are advantageously applied in the form of solutions or preferably emulsions; thermosetting resins are advantageously applied in commercial form as highly concentrated aqueous solutions or dispersions.

The deep-drawable nonwoven of the present invention with or without resin impregnation can be used with particular advantage for producing three-dimensionally shaped textile sheet materials. These three-dimensional structures likewise form part of the subject-matter of the present invention. They comprise a three-dimensionally shaped, open-pored nonwoven wherein at least 30 % by weight of the filaments are low-orientation, coarsedenier filaments which even in the shaped areas have only been stretched to below their ultimate tensile strength extension, i.e. have not been broken.

They contain a relatively coarse-pored support network which is formed by the low-orientation, coarse-denier filaments, more highly stretched within the areas of the deformations, and which may additionally be stiffened by a thermoplastic or thermosetting resin. In the case of the three-dimens ional ly shaped textile sheet materials of the present invention which do not consist exclusively of the low-orientation, coarse-denier filaments, the space between the relatively coarse openings of the support network is taken up by the optionally likewise resinstiffened porous web with its numerous fine openings, formed by the other, possibly finer filaments.

In a specific, but - owing to the higher weight - less preferable embodiment, the pores of the formed nonwoven can also be filled out by the thermosetting or thermoplastic resin.

Figure 1 shows in schematic form a possible shape into which a sheet material of the present invention (3) can be three-dimensionally shaped: a multiplicity of wells (5) drawn out of a textile base surface (4) (nonwoven). - 13 Figure 2 is a schematic enlargement of one of the wells (5) of the structure of Figure 1.

For clarity Figures 1 and 2 show schematically only the support network formed by the low-orientation, coarse5 denier filaments and in each case only the structure of the surfaces of the wells facing the observer, but not the far sides visible through the open-pored nonwoven structure. Figure 2 shows schematically particularly clearly open spaces between the fibers of the open-pored nonwoven structure.

In a specific embodiment which is particularly useful with regard to the later use as a core material for the manufacture of layered materials, the three-dimensionally shaped sheetlike textile material of the present inven15 tion exhibits a multiplicity of elevations in a regular pattern on a base area. In a further embodiment, the three-dimensionally shaped material of the present invention exhibits a multiplicity of elevations and depressions in a regular pattern on the plane of the base area. The elevations and depressions can take the form of wells having a round or angular base area or for example lands, which advantageously have a flat top and a flat bottom respectively and which are preferably all situated within one plane and parallel to the base area.

The three-dimensionally shaped sheetlike textile material of the present Invention is produced either by subjecting a resinated nonwoven of the present invention to a conventional deep-drawing process or by deep-drawing a nonresinated nonwoven of the present invention and then resinating the resulting three-dimensionally shaped structure, or by subjecting a nonresinated nonwoven according to the present invention together with a resin film of appropriate sheet weight to a process of deepdrawing .

The present invention further provides a sheetlike - 14 sandwich article comprising two outer firm cover layers which are connected to one another via a core comprising the above-described three-dimensionally shaped, resinreinforced, sheetlike textile material of the present invention. The bonding between the cover layers and the top surfaces of the elevations or the bottom surfaces of the depressions of the core material of the present invention can be effected using conventional laminating techniques involving the use of adhesives, in particular cold- or hot-curing adhesives, for example epoxy resins or thermosetting resins. Owing to the large area of contact between the core material and the cover layers, the adhesive joint proves to be remarkably stable. Despite the open-pored nonwoven structure of the core material of the present invention, the sandwich articles produced therewith combine a surprisingly high compressive strength with an extremely low weight. They are therefore highly suitable for use as material for the interior construction of vehicle cells, in particular aircraft cells. Particular preference is given here to three-dimensionally shaped textile nonwovens of the present invention made of a flame-retardant filament material.

Figure 3 shows a sandwich structure (6) with the cover surfaces (7) and (8) and a core (9) comprising a threedimensionally shaped sheet material of the present invention.

Claims (19)

1. HOE 90/F 233 What is claimed is: 5 1. An isotropic, readily deep-drawable nonwoven, constructed as a filament nonwoven which contains at least 30 % by weight of low-orientation, coarsedenier filaments having a linear density of more than 7 dtex and has been consolidated with a fusion binder. 10 2. The nonwoven of claim 1, wherein the orientation of the low-orientation, coarse-denier filaments corresponds to an ultimate tensile strength extension of at least 80 %, preferably at least 100 %. 15 3. The nonwoven of at least one of claims 1 and 2, wherein the low-orientation, coarse-denier filaments have an individual linear density of from 7 to 30 dtex. 4. The nonwoven of at least one of claims 1 to 3, wherein the proportion of low-orientation, coarsedenier filaments is from 40 to 85 % by weight. 20 5. The nonwoven of at least one of claims 1 to 4, consisting exclusively of low-orientation, coarse- denier filaments. 25 6. The nonwoven of at least one of claims 1 to 5, wherein low-orientation, coarse-denier filaments and other filaments are present in a virtually homogeneous mixture. 30 7. The nonwoven of at least one of claims 1 to 5, wherein low-orientation, coarse-denier filaments and other filaments are predominantly present in different layers of the nonwoven which have been joined together mechanically. 8. The nonwoven of at least one of claims 1 to 7, - 16 having a basis weight within the range from 50 to 500 g per m 2 , preferably from 100 to 300 g per m 2 . 9. The nonwoven of at least one of claims 1 to 8, additionally combined with another, known nonwoven by

2. 5 local or uniform bonding. 10. A process for producing the spunbonded of claim 1 by forming the filaments into a random-laid web in a conventional manner, which comprises using at least 30 % by weight of low-orientation, coarse-denier 10 filaments whose individual linear density is above

3. 7 dtex and consolidating the web by introducing a fusion binder and a subsequent heat treatment.

4. 11. The process of claim 10, wherein the filaments are laid down through a plurality of successive (in the 15 transport direction of the web transport means) rows of depositing elements which alternately deposit low-orientation, coarse-denier filaments and other filaments.

5. 12. The isotropic, readily deep-drawable nonwoven of at 20 least one of claims 1 to 9, additionally impregnated with a thermoplastic or thermosetting resin.

6. 13. The deep-drawable nonwoven of claim 12, wherein the resin addon has been determined in such a way as to produce an essentially open-pored nonwoven network. 25

7. 14. A process for producing the deep-drawable resinimpregnated nonwoven of claim 12, which comprises producing a deep-drawable nonwoven as per claim 10 and then impregnating said nonwoven with a thermoplastic or thermosetting resin.

8. 15. A three-dimensionally shaped, open-pored nonwoven, wherein at least 30 % by weight of the filaments are low-orientation, coarse-denier filaments which even in the deformed areas have been stretched only to below their ultimate tensile strength extension. - 17

9. 16. The three-dimensionally shaped open-pored nonwoven of claim 15, additionally stiffened with a thermoplastic or thermosetting resin. 5

10. 17. A process for producing the three-dimensionally shaped nonwoven of claim 15, which comprises providing a deep-drawable nonwoven of claim 1 with a regular arrangement of a multiplicity of elevations and depressions by a deep-drawing process.

11. 18. A process for producing the three-dimensionally shaped resin-stiffened nonwoven of claim 16, which comprises providing a deep-drawable nonwoven of claim 1 together with a resin film with a regular arrangement of a multiplicity of elevations and depressions using a deep-drawing process.

12. 19. A process for producing the three-dimensionally shaped nonwoven of claim 16, which comprises producing a three-dimensionally shaped nonwoven by the process of claim 17 and then impregnating this

13. 20 nonwoven with a thermoplastic or thermosetting resin and curing as reguired. 20. A process for producing the three-dimensionally shaped nonwoven of claim 16, which comprises providing a deep-drawable resin-impregnating non25 woven of claim 12 with a regular arrangement of a multiplicity of elevations and depressions by a deep-drawing process.

14. 21. A sheetlike sandwich article comprising two outer firm cover layers joined together via a core of 30 lightweight material, wherein the core comprises the three-dimensionally shaped, resin-stiffened web of claim 16.

15. 22. A process for producing the sandwich article of

16. 23. 23.

17. 24. 24.

18. 25. 25.

19. 26. 26. claim 21, which comprises producing a three-dimensionally shaped, resin-stiffened web as per any one of claims 17 to 20 and then laminating the cover layers onto it on both sides in a conventional manner. A nonwoven according to claim 1, substantially as hereinbefore described. A process according to claim 10, substantially as hereinbefore described. A nonwoven according to claim 1, whenever produced by a process claimed in claim 10, 11 or 24. A three-dimensionally shaped, open-pored nonwoven according to claim 15, substantially as hereinbefore described with particular reference to and as illustrated in Figures 1 and 2 of the accompanying drawings . A sheetlike sandwich article according to claim 21, substantially as hereinbefore described with particular reference to and as illustrated in Figure 3 of the accompanying drawings.