WO2006003089A2

WO2006003089A2 - Fiber medium comprising non bond fibers

Info

Publication number: WO2006003089A2
Application number: PCT/EP2005/052837
Authority: WO
Inventors: Thomas Beirnaert; Stefaan De Bondt
Original assignee: Nv Bekaert S.A.; VANDEMAELE, Noël
Priority date: 2004-06-29
Filing date: 2005-06-17
Publication date: 2006-01-12
Also published as: WO2006003089A3; EP1761350A2

Abstract

A fiber medium as subject of the invention comprises a fiber web having a first outer surface and a second outer surface, the fiber web comprising non bond fibers having an average fiber length L. The medium comprises further a first group of essentially parallel filamentary objects and a second group of essentially parallel filamentary objects, which first group of filamentary objects is present at the first outer surface, the second group of filamentary objects is present at the second outer surface and the filamentary objects of the first group of filamentary objects crosses at least some of the filamentary objects of the second group of filamentary objects at overlap points. At least at some of these overlap points, the crossing filamentary objects are attached to each other through the fiber web providing attached overlap points. The medium as subject of the invention is characterized in that the average fiber length L is larger than the shortest distance between adjacent attached overlap points.

Description

FIBER MEDIUM COMPRISING NON BOND FIBERS

Field of the invention.

The present invention relates to a fiber medium comprising non bond or

"individual" fibers and filamentary objects, and more in particular to a heat resistant fiber medium comprising heat resistant fibers and filamentary objects, such as metal and/or ceramic fiber medium comprising metal and/or ceramic fibers and filamentary objects such as metal wires.

Background of the invention.

Fiber media are well known in the art nowadays. Fiber media which comprise individual fibers, being fibers not incorporated in the medium by means of yarns used to provide media, have been subjected to a mechanical or chemical treatment in order to anchor the fibers to each other, so providing a fiber medium.

A disadvantage of such fiber medium, is that its mechanical strength, either in thet>lane of the medium, or perpendicular to the surface of the medium, is determined to a large extent by the type and performance of this anchoring of the fibers in the medium.

In case the fibers are anchored to each other in the medium by means of mechanical treatment, such as e.g. air jet or water jet felting, or needle punching, such treatments usually cause spots where less fiber material is present, or where even holes are made in the fiber web. In order to provide additional strength to the medium, woven , braided or knitted fabrics may be incorporated in the medium, e.g. during the needling operation as an insert between stacked layers of fiber web prior to needling. The medium can be however significantly porous and permeable to air or liquid.

Metal fiber media comprising non thermally connected metal fibers are known in the art, e.g. from WO9918393A1.

Metal fiber media comprising non thermally connected metal fibers typically comprise discontinuous fibers or "staple" fibers, connected though each other by using textile processes and therefore have a reduced mechanical strength as compared to the strength of continuous fibers. The strength of the medium is determined by the degree of mechanical anchoring of the fibers. Due to the mechanical action necessary to anchor the metal fibers in the metal fiber fleece, some sort of perforation is created, causing holes with varying dimensions to the fleece. Due to these holes or perforations, the porosity of such non sintered metal fiber web typically becomes too large and/or too inhomogeneous. The latter is especially a disadvantage in case the medium is to be used as a filter material.

Inhomogeneous porosity may cause a filter rating out of the desired range.

It is also a disadvantage for fiber media comprising metal fibers, as well as fiber media comprising ceramic fibers, that the mechanical treatments on the fiber webs may cause severe damage, e.g. fracture of the fibers and thus shortening of the fiber length, during mechanical treatment.

An other example of a fiber web comprising not bond fibers is described in EP1143055. a metal fiber web is positioned between two woven wire meshes, which meshes are connected to each other. A disadvantage is however that still fiber migration may occur, as well as that bending of such is product is complicated by the presence of two parallel layers of woven metal mesh As an example, thermally treated metal fiber media are widely known in the art, such as from EP329863B1. As an example, sintered metal fiber media are well known for a very diverse range of applications, such as filter media, acoustic muffling and many more.

Alternatively, fiber web may be provided by chemically or thermally bonding the fibers to each other in the fiber medium. As an example, rolling between heated drums, applying adhesive liquids and many more treatments may be used to anchor the fibers to each other and thus in the medium.

A disadvantage of such thermally or chemically bonded media, is the decrease in permeability to air or liquid due to the increase of the density of the fiber media. Also, in case of thermal treatment of the fibers, the fibers may loose to some extent their resilient behavior due to relaxation of the fibers under increased temperature..

Thermally treated metal fiber media with additional metal grids are also known, such as from US5679441 and DE10250716.

When compared to metal fiber media comprising non thermally connected metal fibers, metal fiber media with thermally connected metal fibers have the disadvantage that the metal fibers have a less resilient behavior. Further, the metal fiber medium is made more dense and heavier, as the metal fibers are to be sufficiently bound to each other in order to make the medium mechanically stable. As an other disadvantage, in case a metal fiber medium is envisaged having metal fibers being coated with a coating, e.g. a catalytic coating, such coatings usually do not withstand the sintering operation. As a result, a much more difficult coating operation of the sintered metal fiber medium is required.

Summary of the invention.

It is a subject of the present invention to provide an alternative fiber medium which is more resilient than comparable thermally bond fiber media. It is a subject of the present invention to provide fiber media which have an improved homogeneity of porosity and air permeability as compared to comparable mechanically anchored fiber media. It is a subject of the present invention to provide a fiber medium which has mechanical properties which are substantially independent from the fiber characteristics and the anchoring of the fibers in the fiber medium. It is also a subject of the present invention to provide a fiber medium having improved filter rating homogeneity in case the fiber medium is used as filter media for filtering fluids. It is an other subject of the present invention to provide a fiber medium which has reduced risk on fiber migration.

It is further a subject of the present invention to provide such fiber medium out of heat resistant fibers, such as glass fibers and/or ceramic fibers and/or metal fibers. It is also a subject of the present invention to provide a fiber medium out of heat resistant fibers which enables the use of coated heat resistant fibers and avoids a sintering step to provide a stable fiber medium.

It is a subject of the present invention to provide a metal fiber medium comprising non sintered metal fibers, which medium is less expensive and more easy to produce than prior art media comprising sintered or non sintered metal fibers. A fiber medium as subject of the invention has the features as set out in the first claim. Advantageous embodiments are further set out in the dependent claims.

A fiber medium as subject of the invention comprises a fiber web having a first outer surface and a second outer surface. The medium further comprises a first group of essentially parallel filamentary objects and a second group of essentially parallel filamentary objects, which filamentary objects of the first group of filamentary objects cross at least some of the filamentary objects of the second group of filamentary objects at overlap points. The first group of filamentary objects is present at the first outer surface, the second group of filamentary objects is present at the second outer surface, and at least at some of the overlap points, the crossing filamentary objects are attached to each other through the fiber web creating attached overlap points. Preferably the filamentary objects are attached to each other at all of the overlap points.

According to the present invention, the term "filamentary object" is to be understood as an object consisting of one or more filaments, being a long thin flexible object having a relatively small cross section as compared to its length. As an example which is not to be understood as limiting, a filamentary object may be a metal wire, a cord or strand of metal wires, a polymer filamentary object such as a polymer monofilament, a multifilament yarn comprising metal filaments or polymer filaments or a yarn comprising metal or polymer staple fibers. According to the present invention, the term "essentially parallel" is to be understood as that the filamentary objects extend in substantially the same direction.

According to the present invention, the term "attach" is to be understood in its broadest sense. It means that two filamentary objects are joined or made fast one to the other at the overlap point where they cross, in such a way that they are immobilized one relative to the other. This may be done by tying them to each other using a tie wire, by gluing, soldering, brazing, welding or any similar means to join the filamentary objects.

With the term "overlap point" is meant the point where a filamentary object from the first group of filamentary objects crosses a filamentary object from the second group of filamentary objects.

The term "fiber web" is to be understood as a web of non bond fibers. The web may be obtained by carding operation, air laid down, wet laid down or any other known technique as known in the art. An untreated web of random oriented fibers is preferred. Alternatively, the web may be provided by laying bundles of fibers one beside the other. It is understood that the fiber web may be provided as a stack of several layers of fibers. In case in some of the layers the fibers have a preferred orientation, this preferred orientation may vary between the different layers.

The thickness of the fiber web may vary over a large extent, e.g. between 0.05mm and 10mm. Preferably the thickness of the web is between 0.2mm and 5mm. The web thickness is measured according to the standard EN ISO 9073-2. The weight of the fiber web may vary over a large extent, e.g. between 50 g/m² and 5000 g/m². Preferably the weight of the web is between 100 g/m² and 3000 g/m².

The porosity of the fiber web may vary over a large extent, e.g. between 50% and 99%. Preferably the porosity of the web is between

64% and 90%.

The term "porosity" P is to be understood as

P = 100 - d wherein d = (weight of 1 m³ metal fiber medium) / (SF) wherein

SF = specific weight per m³ of alloy out of which the metal fibers of the metal fiber medium are provided.

According to the present invention, at the overlap point where filamentary objects present a the first surface of the fiber web, cross with filamentary objects present a the second surface of the fiber web, the filamentary objects are attached to each other through the fiber web. Dependent on the nature of the filamentary objects, this tying may be done in many different ways.

As an example and not to be understood as limiting, at the overlap points, the filamentary objects may be glued to each other, e.g. using contact adhesive, thermosetting adhesive, hot-setting adhesive or alike. It is understood that possibly some pressure may be used in order to bond the filamentary objects one to the other , through the fiber web. Alternatively they may be thermally bond, e.g. by melting the polymer material in case the filamentary objects are polymer filamentary objects. Also in this case it is understood that possibly some pressure may be used in order to bond the filamentary objects one to the other , through the fiber web. As an other alternative, the two filamentary objects may be attached to each other using a tie wire. In case the filamentary objects are provided using metal material, e.g. metal wires, strands, cords filamentary yarns or staple yarns, tying can be done by means of e.g. spot welding or by soldering, in case the type of fibers in the web allow the use of such applicable temperatures. In case of heat resistant fibers such as metal fibers, glass fibers or ceramic fibers, such tying is possible.

As a result, the fibers of the fiber web are so-to-say squeezed between the filamentary objects from the first and second group of filamentary objects.

An other advantage of the fiber medium as subject of the invention is that the product can be made very cost-effective, providing a medium in which the fibers are prevented to leave the medium during use.

Other advantages are a homogeneous filter rating over the fiber media surface in case the media are used for filtration applications, the possibility to provide a fiber medium comprising coated fibers, which fibers are coated prior to production of the fiber medium as subject of the invention and reliable and tunable strength and stiffness, independent from the fiber characteristics.

To provide the fiber web, any type of fibers may be used, either as staple fibers or filamentary fibers. As an example, organic or inorganic fibers such as polymer fibers, ceramic fibers, C-fibers, metal fibers or glass fibers may be used. Preferably , heat resistant fibers such as glass fibers, metal fibers or ceramic fibers such as Nextel®-fibers may be used.

In case of a metal fiber web , being part of the fiber medium as subject of the invention, any type of metal or metal alloy may be used to provide the metal fibers.

The metal fibers are for example made of steel such as stainless steel. Preferred stainless steel alloys are AISI 300 or AISI 400-serie alloys, such as AISI 316L or AISI 347, or alloys comprising Fe, Al and Cr, and 0.05 to 0.3 % by weight of Yttrium, Cerium, Lanthanum, Hafnium or

Titanium, such as e.g. DIN 1.4767 alloys or Fecralloy^® are used. Also Copper or Copper-alloys, or Titanium or Titanium alloys may be used. The metal fibers can also be made of Nickel or a Nickel alloy or Aluminum or Aluminum-alloys.

Metal fibers may be made by any presently known metal fiber production method, e.g. by bundle drawing operation, by coil shaving operation as described in JP3083144, by wire shaving operations (such as steel wool) or by a method providing metal fibers from a bath of molten metal alloy. The fibers may be chopped or broken, and may be substantially straight or provided with undulation or so-called 'crimp'.

As a non sintered metal fiber web is used, the metal fibers are not subjected to a thermal treatment to bind them to each other. This results in a metal fiber medium, which has a resilient and usually voluminous metal fiber layer between the bound places of the filamentary objects. The metal fiber medium as subject of the invention has on the other hand a mechanical strength determined by the mechanical properties of the filamentary objects used to provide the metal fiber medium as subject of the invention. As an other advantage, the fibers used to provide the fiber web, may be coated with substantially any coating, prior to be integrated in the product. Preferably, a coating with catalytic active substance is used, such as coatings comprising Pt, Pd, Au, Ag, other noble metals, Cu , Ni and alike materials and combinations of such materials. As no thermal treatment over the whole of the fiber web is to be applied, the coating will not be subjected to degradation or migration of the coating material in the fiber material.

It is understood that coating may be applied to the fiber medium as subject of the invention, after such fiber medium as subject of the invention is provided.

The fibers used to provide the fiber web are characterized in having an equivalent diameter D and an average fiber length L. With "equivalent diameter" of a fiber is meant the diameter of an imaginary circle having the same surface as the surface of a radial cross section of the fiber.

Preferably the equivalent diameter D of the fibers is less than 100μm such as less than 65μm, more preferably less than 36μm such as 35μm, 22μm or 17μm. Possibly the equivalent diameter of the fibers is less than 15μm, such as 14μm, 12μm or 11μm, or even more less than 9μm such as e.g. 8μm, 7μm, 6μm, 5μm, or even less.

The fibers all have an individual fiber length. As some distribution on these fiber lengths may occur, due to the method of manufacturing the fibers, the fibers have an average fiber length L. This length is determined by measuring a significant number of fibers, according to appropriate statistical standards. Possibly, the fibers used are filamentary as well, having an L being endlessly large, this is more than 10000 times the equivalent diameter. The average fiber length of the fibers may be however be smaller than 200mm, e.g. smaller than 100mm.

The fiber medium as subject of the invention is characterized in that the average fiber length L is larger than the shortest distance between adjacent attached overlap points. Advantageously, L is more than 1.5 the shortest distance between adjacent attached overlap points. It was found that this decreases the possible fiber migration of the fiber medium to a large extent.

It is understood that in case a metal fiber web is used, comprising several metal fiber layers, the properties of the metal fibers from a particular metal fiber layer may differ from the metal fibers from the other metal fiber layers.

The filamentary objects as part of the metal fiber medium as subject of the invention, may be provided using e.g. polymer or metallic material.

For example, the filamentary objects may be provided of steel such as stainless steel, low carbon steel of high carbon steel. Possible stainless steel alloys are AISI 300 or AISI 400-serie alloys, such as AISI 316L or AISI 347, or alloys comprising Fe, Al and Cr, and 0.05 to 0.3 % by weight of Yttrium, Cerium, Lanthanum, Hafnium or Titanium, such as e.g. DIN 1.4767 alloys or Fecralloy^®. Also Copper or Copper-alloys, Aluminum or Aluminum alloys, Nickel or a Nickel alloys or Titanium or

Titanium alloys may be used.

Possibly, filamentary objects being provided out of a steel alloy with a relatively low carbon content, i.e. smaller than 0.20 weight%, which possibly has been annealed may be used. Alternatively, filamentary objects being provided out of a steel alloy with a relatively higher carbon content, i.e. higher than 0.60 weight%, and which may have been subjected to a final stress-relieving treatment may be used.

In case the filamentary objects are provided using polymer material, the polymer material may be polyamide, polyester, polyether, polyethylene, polypropylene, polyactrilonitrile, polyacrylate, polyvinilchlodide, polyethyleneterephtalate, or any other known polymer material .

The dimensions of the filamentary objects may be chosen in function of the required strength and other mechanical properties. It is understood that the dimensions and properties, such as composition, mechanical and surface properties, of the filamentary objects present on the first surface of the fiber medium may be different from the dimensions and properties of the filamentary objects present on the second surface of the fiber medium. Also within the first or second group of filamentary objects, the dimensions and properties may differ.

In case the filamentary objects are metal cords or strands, or yarns comprising filaments or staple fibers, the cord-, strand - or yarn construction, thickness, fineness and composition can be chosen and may vary to a large extent.

The filamentary objects may have a cross section which can vary to a large extent. Such cross section may be substantially circular, or profiled, e.g. square, rectangular, l-profiled, oval, or any other shape.

The presence of profiled filamentary objects may influence the bending behavior and mechanical properties in a given direction of the fiber medium as subject of the invention. In case of circular cross sections, the diameter of the filamentary objects may vary over a large extent, e.g. between 0.05mm and 2mm. Preferably the diameter of the circular cross section is between 0.1mm and 1mm.

The filamentary objects may be provided as substantially straight filamentary objects, or they may be provided with a deformation, such as an undulation.

In case the web is provided by laying bundles of fibers one beside the other care is to be taken that the main direction of the bundles is not parallel to the direction of one of the groups of filamentary objects, in case the filamentary objects are substantially straight.

In case of undulated filamentary objects, this undulation may be coplanar with the surfaces of the fiber medium, or the undulation may be substantially perpendicular to the surface of the fiber medium. As an example, the filamentary objects of one group of filamentary objects may be provided with a number of bulges, pointing away from the surface of the fiber web at which side it is present. The bulges may have a dimension which corresponds with the dimension of the filamentary object present at the opposite side of the fiber web. The filamentary objects are attached to each other trough the fiber web is such a way that the second filamentary object is so-to-say sunk in the bulge of the first filamentary object. This results in a more firm clamping of the fibers at the overlap point between the two filamentary objects.

Even more, both filamentary objects may be provided with a bulge, which corresponds to each other, so the bulge of the first filamentary object is sunk in the bulge of the second filamentary object and vice versa, which even further increases the clamping of the fibers. As an other example, the filamentary objects from the first and second group may be provided with a bulge at the overlap points, in such a way that the bulges points towards the surface of the fiber web. The filamentary objects can be attached to each other at the locations of the bulges, which provides more space for the fibers in the fiber medium.

Alternatively, the bulged filamentary objects may be attached to the overlapping filamentary object at other locations than the bulge.

Each of the groups of filamentary objects comprises filamentary objects being substantially parallel to each other. The distances between the filamentary objects of one group of filamentary object may vary between filamentary objects of this group. The distances between the filamentary objects of the first group of filamentary object may be different from the distances between the filamentary objects of the second group.

The filamentary objects of the first and the second group cross each other at the overlap points. The angle^" between the direction of the filamentary objects of this first and second group may range from 0° to

90°. The use of angles smaller from 90° may provide anisotropic properties to the fiber medium as subject of the invention. In case the angle between the direction of the filamentary objects of the first and second group is 0°, the filamentary objects may cross over their whole length, or may cross only at particular overlap points in case at least one of the filamentary objects comprises an undulation. It is understood that in case the filamentary objects cross over their whole length, and substantially parallel fiber bundles are used as web, the orientation of the parallel fiber bundle and the direction of the filamentary objects is not to be identical. Possibly, additional filamentary objects may be present in the fiber medium, which are not attached to the fiber web.

The fiber medium as subject of the invention may be used for may different applications, such as e.g. filtration purposes, for filtering solid particles from fluids such as gasses or liquids, separating liquids from gas streams (so-called demisting), as carrier of catalytic material, for use in catalytic converters, as burner membranes, noise damping or EMI-shielding applications, or as electrodes such as e.g. in fuel cells or batteries

Brief description of the drawings.

The invention will now be described into more detail with reference to the accompanying drawings wherein

FIGURE 1a and FIGURE 1b, FIGURE 2a, FIGURE 2b, FIGURE 3a, FIGURE 3b, FIGURE 4, FIGURE 5a, FIGURE 5b, FIGURE 6, FIGURE 7, FIGURE 8 and FIGURE 9 are schematically views of fiber media as subject of the invention.

Description of the preferred embodiments of the invention.

A schematically view of a fiber medium 100 as subject of the invention is shown in FIGURE 1a and FIGURE 1b. FIGURE 1a is a top view of the fiber medium 100, whereas FIGURE 1b is a cross section of the fiber medium according to the plane AA'.

The fiber medium 100 comprises a fiber web 101, e.g. a web with a weight of 500 g/m² provided out of coil shaved metal fibers from Fecralloy ® alloy, this is an alloy comprising Fe, Al , Cr and Yt. The fibers have a substantially rectangular cross section and are characterized by an equivalent diameter of 35μm. the fibers have an average fiber length of approximately 50mm.. The metal fiber web is provided by means of an air laid down process. The fibers may be coated with a noble metal coating layer, e.g. being provided with a Pt-coating having a thickness of less than 1μm.

At the first outer surface 120 of the metal fiber medium 100, a group of filamentary objects 121 are present, spaced one from the other using a distance D1 of 5mm. At the second outer surface 130 of the metal fiber medium 100, a group of filamentary objects 131 are present, spaced one from the other using a distance D2 of 5mm. The filamentary objects 121 and 131 are e.g. low carbon steel wires, having a substantially circular cross section with a diameter of 0.1mm.

At least at a part of the overlap points 140, the filamentary objects 121 and 131 are attached to each other by spot welding the wires through the metal fiber web. As shown in FIGURE 1a, in this embodiment at all overlap points, the filamentary objects are attached to each other by spot welding.

It is understood that at the locations of the spot welds, the coating may no longer have its original appearance. However, on the surface of the fibers not located in the welding zone, the coating remains unchanged.

As an alternative embodiment, a fiber web comprising metal fibers and ceramic fibers may be used, e.g. fiber web comprising 50% volume metal fibers, and 50% volume ceramic Nextel®-fibers. As an other alternative, both filamentary objects 121 and 131 are polyamide monofilaments having a diameter of 0.1 mm . At the overlap points 140, the polyamide filaments are thermally fused to each other.

As alternatives for the above mentioned embodiments, filamentary objects 121 and 131 may be a high carbon or low carbon steel metal cord with an optical diameter of 0.1mm, a stainless steel metal multifilament fiber yarn with fibers of equivalent diameter 12μm and a yarn fineness of 1000 Tex or a stainless steel spun yarn with fibers of equivalent diameter 12μm and a yarn fineness of 1000 Tex. Such filamentary objects may be attached by spot welding provided a fiber web is used which may resist the temperatures as occurs during spot welding.

As an other alternative for the above mentioned embodiments, filamentary objects 121 and 131 being a polymer, e.g. polyamide or polyester, multifilament yarn or spun yarn with fineness of 120 Tex may be used. Such filamentary objects may be attached by thermo fusing.

A schematically view of a fiber medium 200 as subject of the invention is shown in FIGURE 2a and FIGURE 2b. FIGURE 2a is a top view of the fiber medium 200, whereas FIGURE 2b is a cross section of the fiber medium according to the plane BB'.

The fiber medium 200 comprises a fiber web 201, being similar as the ones in the embodiments as shown in FIGURE 1a and FIGURE 1b.

At the first outer surface 220 of the fiber medium 200, a group of filamentary objects 221 are present, spaced one from the other using a distance D1 of 5mm. At the second outer surface 230 of the fiber medium 200, a group of filamentary objects 231 are present, spaced one from the other using a distance D2 of 10mm. The filamentary objects 221 and 231 are Sn-coated low carbon steel wires, having a substantially circular cross section with a diameter of 0.1mm.

At the overlap points 240, the filamentary objects 221 and 231 are attached to each other by soldering the wires through the fiber web using a soldering material as indicated 241, e.g. a Sn-alloy, provided a fiber web is used which may resist the temperatures as occurs during soldering.

As an alternative, both filamentary objects 221 and 231 are polyamide monofilaments having a diameter of 0.1mm . At the overlap points 240, the filamentary objects 221 and 231, either polymer or metal objects, may be glued to each other through the fiber web 201 are to each other, using a contact glue, e.g. cyanoacrylate.

An other embodiment of a fiber medium 300 of the present invention is shown in FIGURE 3a (top view) and FIGURE 3b (cross section according to the plane CC). The filamentary objects 331 and 321, each present at a side 330, respectively 320, of the fiber web 301 may be attached to each other at the overlap points 340 by means of a tie wire 350. The fiber web 301 and the filamentary objects 321 and 331 may be similar to the ones as in the embodiments shown in FIGURE 1a and FIGURE 1 b or FIGURE 2a and FIGURE 2b.

An other embodiment of a fiber medium 400 as subject of the invention is shown in FIGURE 4, being a top view of the fiber medium 400. Also here, at both sides 420 and 430 of a fiber web 401, a group of filamentary objects 421 , respectively 431 are present. At the overlap points 440 of the filamentary objects 431 and 421, the filamentary objects 431 and 421 are attached to each other by a means as described for the embodiments as shown in FIGURE 1a and FIGURE 1b, FIGURE 2a and FIGURE 2b or FIGURE 3a and FIGURE 3b. The filamentary objects 431 and 421 may be similar to the filamentary objects as described for the embodiments as shown in FIGURE 1a and FIGURE 1b, FIGURE 2a and FIGURE 2b or FIGURE 3a and FIGURE 3b.

In contrast to the embodiments of FIGURE 1a, FIGURE 1b, F2a,

FIGURE 2b , FIGURE 3a and FIGURE 3b, where the filamentary objects are essentially perpendicular or under an angle α equal to 90°, in the embodiment of FIGURE 4, the directions of first group of filamentary objects 421 and the second group of filamentary objects 431 at overlap points 440 are under an angle α smaller than 90°, e.g.

81°. In a direction as indicated with arrow 460, the fiber medium 400 appears to be somewhat less stiff.

An other embodiment of a fiber medium 500 as subject of the invention is shown in FIGURE 5a, being a top view of the fiber medium 500. Also here, at both sides 520 and 530 of a fiber web 501, a group of filamentary objects 521, respectively 531 are present. Both groups of filamentary objects are substantially parallel. Due to the undulation of the filamentary objects, overlap points 540 are obtained. At the overlap points 540 of the filamentary objects 531 and 521 , the filamentary objects 531 and 521 are attached to each other by a means as described for the embodiments as shown in FIGURE 1a and FIGURE 1b, FIGURE 2a and FIGURE 2b or FIGURE 3a and FIGURE 3b. The filamentary objects 531 and 521, and the fiber web 501 may be similar to the ones as described for the embodiments as shown in FIGURE 1a and FIGURE 1b, FIGURE 2a and FIGURE 2b or FIGURE 3a and FIGURE 3b. In the fiber medium 500, the overlap points between filamentary objects 521 and 531 are provided due to the undulated shape of the filamentary objects. The undulations and the location of the filamentary objects is chosen in such a way that the undulations of filamentary objects 521 and filamentary objects 531 cross each other. It is understood that the undulations are coplanar with the surface of the medium 500.

In FIGURE 5b, an other embodiment of the present invention is shown.

Also here, at both sides 520 and 530 of a fiber web 501, a group of filamentary objects 521, respectively 531 are present. Both groups of filamentary objects are substantially parallel. As the filamentary objects are all substantially parallel, filamentary objects of the first and the second group overlap over substantially the whole length. At several points, the filamentary objects 531 and 521 are attached to each other by a means as described for the embodiments as shown in FIGURE 1a and FIGURE 1b, FIGURE 2a and FIGURE 2b or FIGURE 3a and FIGURE 3b. The filamentary objects 531 and 521, and the fiber web^* 501 may be similar to the ones as described for the embodiments as shown in FIGURE 1a and FIGURE 1b, FIGURE 2a and FIGURE 2b or FIGURE 3a and FIGURE 3b.

An other embodiment of a fiber medium 600, 700 and 800 as subject of the invention are shown in FIGURE 6, FIGURE 7 respectively

FIGURE 8, being a top view of the fiber medium, and a detail of an overlap point. Also for these embodiments, at both sides of a fiber web, a group of filamentary objects is present. At the overlap points of the filamentary objects, the filamentary objects are attached to each other by a means as described for the embodiments as shown in FIGURE 1a and FIGURE 1b, FIGURE 2a and FIGURE 2b or FIGURE 3a and FIGURE 3b. The filamentary objects and the fiber webs may be similar to ones as described for the embodiments as shown in FIGURE 1a and FIGURE 1 b, FIGURE 2a and FIGURE 2b or FIGURE 3a and FIGURE 3b.

In the fiber medium 600 as shown in FIGURE 6, at a first side 620 substantially straight filamentary objects 621 are present. At the second side 630, filamentary objects 631 are present, which have a bulge 670 pointing away from the surface of this side 630 of the fiber web 601. At the overlap points 640, the filamentary object 621 is so-to-say sunk in the concave curve of the bulge 670 of filamentary object 631. As a result, the fibers of the fiber web 601 are clamped to a larger extent between the filamentary objects 621 and 631. It was found that the fiber web 601 may be densified to some extent.

In the fiber medium 700 as shown in FIGURE 7, at a first side 720, filamentary objects 721 are present, which have a bulge 780 pointing away from the surface of this side 720 of the fiber web 701. At the second side 730, filamentary objects 731 are present, which have a bulge 770 pointing away from the surface of this side 730 of the fiber web 701. At the overlap points 740, the concave curve of the bulge 780 of filamentary object 721 is so-to-say sunk in the concave curve of the bulge 770 of filamentary object 731. As a result; the fibers of the fiber web 701 are clamped to a larger extent between the filamentary objects 721 and 731. It was found that the fiber web 701 may be densified to some extent. In the fiber medium 800 as shown in FIGURE 8, at a first side 820, filamentary objects 821 are present, which have a bulge 880 pointing towards the surface of this side 820 of the fiber web 801. At the second side 830, filamentary objects 831 are present, which have a bulge 870 pointing towards the surface of this side 830 of the fiber web 801. At the overlap points 840, the convex curve of the bulge 880 of filamentary object 821 is attached to the convex curve of the bulge 870 of filamentary object 831. The bulges are attached to each other so-to- say 'top-to-top'. As a result, the fibers of the fiber web 801 are clamped to a less extent between the filamentary objects 821 and 831. It was found that the fiber web 801 has more the tendency to keep its resiliency.

An other embodiment of a fiber medium 900 of the present invention is shown in FIGURE 9a (top view), FIGURE 9b (cross section according to the plane DD') and FIGURE 9c (cross section according to the plane EE'). The filamentary objects 931 and 921, each present at a side 930, respectively 920, of the fiber web 901 may be attached to each other at the overlap points 940 by a^" means as described for the embodiments as shown in FIGURE 1a and FIGURE 1b, FIGURE 2a and FIGURE 2b or FIGURE 3a and FIGURE 3b. the metal fiber web 901 may be similar to the fiber webs as described for the embodiments shown in FIGURE 1a and FIGURE 1b, FIGURE 2a and FIGURE 2b or FIGURE 3a and FIGURE 3b.

The filamentary objects 921 present at the first outer surface 920 of the fiber web 901 are rectangular profiled filamentary objects, such as rectangular profiled metal wires, out of low carbon steel and having a long side of approximately 2mm and a shortest side of about 0.2mm. The filamentary objects 931 present at the first outer surface 930 of the metal fiber web 901 are l-profiled filamentary objects, such as l-profiled metal wires, out of low carbon steel and having outer dimensions of 3mm by 2mm, and a flange thickness of 0.3mm. As a result of this choice of profiled filamentary objects, the metal fiber medium 900 has the possibility of bending to in the direction according to the plane DD', as shown in FIGURE 9b and indicated with arrow 970. In the opposite direction, this is according to the plane EE' as shown in FIGURE 9c, the metal fiber medium 900 is substantially stiff due to the presence of l-profiled filamentary objects 921.

It is understood for the embodiments as shown in the FIGURES one to nine, it is not necessary, although preferred, to attach the overlap filamentary objects at all overlap points. Possibly the filamentary objects are attached to each other at a given selection of overlap points.

Claims

CLAlMS

1. A fiber medium comprising a fiber web having a first outer surface and a second outer surface, said fiber web comprising non bond fibers having an average fiber length L, said medium comprising a first group of essentially parallel filamentary objects and a second group of essentially parallel filamentary objects, said first group of filamentary objects is present at said first outer surface, said second group of filamentary objects is present at said second outer surface, said filamentary objects of said first group of filamentary objects crossing at least some of said filamentary objects of said second group of filamentary objects at overlap points, at least at some of said overlap points, said crossing filamentary objects are attached to each other through said fiber web providing attached overlap points, characterized in that said average fiber length L is larger than the shortest distance between adjacent attached overlap points..

2. A fiber medium as in claim 1 , wherein said crossing filamentary objects are attached to each other at all of said overlap points.

3. A fiber medium as in any one of the claims 1 or 2, wherein said fibers comprises metal fibers.

4. A fiber medium as in claim 3, wherein said fiber web consists of metal fibers.

5. A fiber medium as in any one of the claims 1 to 3, wherein said fibers comprises ceramic fibers and/or glass fibers.

6. A fiber medium as in any one of the claims 1 to 5, wherein said filamentary objects are metal wires.

7. A fiber medium as in any one of the claims 1 to 5, wherein said filamentary objects are metal cords or metal strands.

8. A fiber medium as in any one of the claims 1 to 5, wherein said filamentary objects are metal filament yarns.

9. A fiber medium as in any one of the claims 1 to 5, wherein said filamentary objects are metal yarns comprising metal staple fibers.

10. A fiber medium as in any one of the claims 1 to 5, wherein said filamentary objects are polymer filamentary objects.

11. A fiber medium as in any one of the claims 1 to 5, wherein said filamentary objects are polymer monofilaments.

12. A fiber medium as in any one of the claims 1 to 5, wherein said filamentary objects are polymer multifilament yarns.

13. A fiber medium as in any one of the claims 1 to 5, wherein said filamentary objects are polymer yarns comprising polymer staple fibers.

14. A fiber medium as in any one of the claims 6 to 9, said filamentary objects are spot welded to each other.

15. A fiber medium as in any one of the claims 6 to 9, said filamentary objects are soldered to each other.

16. A fiber medium as in any one of the claims 1 to 13, said filamentary objects are attached to each other by thermal fusion.

17. A fiber medium in any one of the claims 1 to 13, said filamentary objects are bound to each other by means of a tie wire.

18. A fiber medium in any one of the claims 1 to 13, said filamentary objects are glued to each other.

19. A fiber medium in any one of the claims 1 to 18, said filamentary objects have a non-circular cross section.

20. A fiber medium in any one of the claims 1 to 19, said filamentary objects are substantially straight filamentary objects.

21. A fiber medium in any one of the claims 1 to 19, said filamentary objects are undulated filamentary objects.

22. A fiber medium in clam 21, said undulating is coplanar with the surface of said medium.

23. A fiber medium in clam 21, said undulating is substantially perpendicular to the surface of said medium

24. A fiber medium in any one of the claims 1 to 23, the directions of said first group of filamentary objects and said second group of filamentary objects at overlap points are under an angle α smaller than 90°.

25. A fiber medium in any one of the claims 1 to 23, the directions of said first group of filamentary objects and said second group of filamentary objects at overlap points are under an angle α equal to 90°.

26. A fiber medium in any one of the claims 1 to 23 said first group of filamentary objects and said second group of filamentary objects are substantially parallel to each other.

27. A fiber medium in any one of the claims 1 to 26, wherein said average fiber length L is larger than 1.5 times the shortest distance between adjacent attached overlap points.

28. A fiber medium in any one of the claims 1 to 27, wherein said fibers of said fiber web are coated.