PROCESS FOR MANUFACTURING A BAND-SHAPED NON-WOVEN PRODUCT WITH INCREASED TENSILE STRENGTH

Abstract: The invention relates to a process for manufacturing a band-shaped non-woven product with increased tensile strength longitudinally and/or in the cross direction of the band-shaped product, characterized in that, in the direction in which the tensile strength of the non-woven is to be increased, strengthening wires and/or filaments are applied to it, and joined to the fleece of which the non-woven consists, by application of one of the following techniques, namely needling, hydrolace glueing, or application of heat when the materials of which the non-woven and/or the strengthening wires and/or filaments consist, lend themselves to that.

Description: Process for manufacturing a band-shaped non-woven product with increased tensile strength This invention relates to a process for manufactur- ing a band-shaped non-woven product with increased tensile strength, longitudinally and/or in the cross direction of the band-shaped product, as well as to the band-shaped non-woven products manufactured according to this process. It is the aim of the invention to realize a band- shaped non-woven product of the above discussed type, the tensile strength (according to DIN 53857) of which is increased longitudinally, in the cross direction, or in both directions. Non-woven products of the kind referred to, and having such characteristics, find a remarkable application as a geo- textile or as a carrier for bituminous roofing bands. The strengthening of non-woven products has already been proposed in the following documents: GB 2 169 930 A and US 5,219,633. In the former reference, essentially the elasticity of the product is considered, and not the application of the process on band- shaped products essentially intended as a carrier for bituminous roofing bands is suggested. The increase of the tensile strength of such band- shaped non-woven products presents very specific requirements, especially when the tensile strength is considered exclusively longitudinally and/or in the cross direction of the product. In the latter reference, the production of a non- woven material as a raw material for diapers, among others, is described, so it will be immediately clear that the process described in this reference complies with very specific requirements, and does not in any way provide any indication to the issue discussed here, i.e. the realisation of carriers for asphalt bands and geotextiles by strengthening of the tensile strength of the band-shaped product, specifically longitudinally and/or in the cross direction. In order to achieve the proposed aim, the process according to the invention is primarily characterized in that, in the direc- tion in which the tensile strength of the non-woven is to be increased, strengthening wires and/or filaments are applied to it, and are joined to the fleece of which the non-woven consists, by application of one of the following techniques, namely needling, gluing, high water pressure hydrolace, application of heat when the materials of which the non- woven and/or strengthening wires and/or filaments consist, lend themselves to that. Still according to the invention, above mentioned fleece with the strengthening wires and/or filaments applied to it, are thermofixed. In a first embodiment, for manufacturing the fleece of the non-woven, natural, synthetic or mineral staple fibres are used, or a combination thereof. According to another possible embodiment, for manufacturing the fleece of the non-woven, continuous synthetic fila- ments are used. Other details and advantages of the invention will appear from the following description of a process for manufacturing a non-woven product with increased tensile strength and of the thus obtained non-woven according to the invention. This description is exclusively given as an example en does not limit the invention. The current non-wovens are built up, either of staple fibres, or of continuous filaments. In these non-wovens, the ratio of the strength longitudinally and in the cross direction is dertermined by the ratio of the number of fibres or filaments which are found longitudi- nally or in the cross direction, and by their respective tensile strength. It will immediately be noticed, that the band- shaped products according to the invention are clearly distinguished from the products described in the two references referred to in the preamble, because the strengthening wires are both present longitudi- nally and in the cross direction, when the band-shaped product is to be strengthened in both these directions, and these strengthening wires or filaments are needled together, which is not the case with the products described in these references. In patent application GB 2 169 930 A, very clearly an elastic non-woven is described, while US Patent 5,219,633 describes disposable, non-woven products, a.o. diapers, the requirements and specifications of which are not connected with the band-shaped non-wovens according to this application. The fleece on which the non-woven material according to the invention is based, may be composed of synthetic, natural or mineral staple fibres, or a combination of these fibres. It may also be composed of several non-wovens, also based on the same synthetic, natural or mineral fibres, or mixtures thereof. The fleece may also be built up of continuous synthetic filaments, either in combination with another non-woven or not. The wires or filaments used for strengthening the fleece, may be described as follows: a) wire composed of synthetic fibres or of a mixture or combination of these synthetic fibres with natural and/or mineral fibres. The wires may also be twined with synthetic and/or mineral filaments. b) when using filaments, one may call upon synthetic filaments, or filaments which are twined with wires and/or mineral filaments. The wires which are used for twining, in turn, may consist of synthetic fibres, natural fibres, mineral fibres, or a mixture thereof. Preferably, PES filaments having a thickness of 1100 dtex, a tensile strength of ± 7 kg per filament, an elasticity between 15 and 25 %, a torsion of ± 60 and a weight of 0.11 g/current metre, are used. When a non-woven based on staple fibres is considered, the fleece is built up of synthetic, natural or mineral staple fibres, or a combination of these fibres. The whole is converted into a fleece by using a card, or the technique known as "air- lay". When the use of filaments (spunbounds) is considered, it is built up of continuous filaments, which in turn are needled, or when thermally bound fleeces are concerned, are compressed by means of a calender, and this at a temperature which is sufficiently high to be able to melt filaments with a lower melting point. When in a non-woven based on staple fibres, the highest tensile strength is to be realized in the cross direction, the basic fleeces coming from a card, or by application of the technique known as "air-lay", are brought together by means of a cross laying device, until the desired weight is obtained, whereby the speed of the cross laying device is adjusted such, that the rectilinearity of the staple fibres is preserved as much as possible. Only afterwards, the fleece is pre-needled on a pre-needling machine. Preferably, PES fibres will be used, with a thickness varying between 3 and 6 deniers, or with a mixture thereof. Fibres with a length of 125 and 150 mm are preferred. When in a non-woven based on staple fibres, the highest tensile strength of the non-woven is to be created longitudinally, the card fleece, of which the staple fibres are parallel to a high degree, is simply rolled up after a light pre-needling or calendering. When staple fleeces are to be produced in which the difference in tensile strength longitudinally and in the cross direction is to be reduced to a minimum, the process described above with reference to obtaining a non-woven with the highest tensile strength in the cross direction, is applied, but prior to the final needling, the non-woven is stretched by means of a draw bench, so that the fibres will take up a less parallel position. By doing so, the difference in tensile strength longitudinally and in the cross direction is smaller. If continuous filaments are used, the division of the tensile strength longitudinally and in the cross direction is determined by the degree of rectilinearity or non-rectilinearity of the filament. The longitudinal tensile strength is increased in case of a clear excess of parallel filaments found together. The tensile strength is increased in the cross direction when less rectilinear filaments are found. In order to guarantee the specifications of the final product, the strengthening wires and/or filaments are laid tensionless onto the fleece, whereby a) wires and/or filaments winded onto bobbins, or b) bobbins and/or filaments which are winded, or a combination of both may be used. The adhesion of the strengthening wires and/or filaments to the fleece may be realized by needling, by gluing with acrylic resins, among others by hydrolace, or by application of heat, when the fusible and/or bicomponent fibres or filaments, or their combination are present in the overall structure. It is important that during needling the wires and/or filaments are damaged as little as possible, so as not to harm the tensile strength of the finished product. When using acrylic resins, the wires and/or filaments are impregnated with an acrylic resin and subsequently attached to the non-woven by application of heat and pressure. The attachment of wires and/or filaments may also be realized on an already thermostabilised fleece. The fleece is stabil- ised by a calender or hot air drum. It is important that the process enables the elasticity, in the direction in which the wires and/or filaments are found, to be varied within certain limits, and this by adapting the ratio of feed rate and speed of thermostabilising element. The finishing comprises: a) the thermostabilisation b) the binding of the fibres and/or filaments. If the basic non-woven is not yet thermally stabilised (by calender or hot air drum), the whole of non-wovens, with its wires or filaments, or a combination of both, is thermally stabilised. This may be done with a calender (of the Stork type), or a drum to which hot air is blown (e.g. of the Fleissner type). If in the mixture or composition of the filaments fusible fibres or bicomponent fibres or fusible filaments or bicomponent filaments have been used, the product is herewith finally finished. If no fusible or bicomponent fibres, or fusible or bicomponent filaments have been used, for the binding of the fibres or filaments together, resins are used, preferably acrylic resins, because of their good temperature resistance. These acrylic resins are applied to the non-woven and squeezed out by means of a sizing machine to the required amount. The whole of non-woven and acrylic resin is then dried up to a temperature of 210 °C, or until the resin is dried. By applying the above described process, a final product is obtained with application possibilities both as bituminous roofing bands and as a geotextile.

Claims: CLAIMS 1. Process for manufacturing a band-shaped non-woven product with increased tensile strength longitudinally or in the cross direction of the band-shaped product, characterized in that, in the direction in which the tensile strength of the non-woven is to be increased, strengthening wires and/or filaments are applied to it, and joined to the fleece of which the non-woven consists, by application of one of the following techniques, namely needling, hydrolace gluing, or application of heat when the materials of which the non-woven and/or the strengthening wires and/or filaments consist, lend themselves to that. 2. Process according to claim 1 , characterized in that above mentioned fleece with the strengthening wires and/or filaments applied onto it, are thermofixed. 3. Process according to any one of claims 1 and 2, characterized in that, when applying the strengthening wires longitudinally and in the cross direction of the band-shaped product, these strengthening wires are needled together. 4. Process according to any one of claims 1-3, characterized in that above mentioned strengthening wires and/or filaments are applied tensionless onto the fleece. 5. Process according to any one of claims 2-4, characterized in that, for the manufacturing of the fleece of the non- woven, natural, synthetic or mineral staple fibres are used, or a combination thereof. 6. Process according to any one of claims 1-5, characterized in that, for the manufacturing of the fleece of the non- woven, continuous synthetic filaments are used. 7. Process according to any one of claims 1-6, characterized in that a fleece built up of one single layer is used. 8. Process according to any one of claims 1-6, characterized in that a fleece built up of at least two layers is used. 9. Band-shaped non-woven having at least in one direction increased tensile strength, characterized in that it consists of at least one fleece on which strengthening wires and/or filaments are applied in the direction in which the tensile strength is to be increased, and are needled together in both directions in strengthening the tensile strength. 10. Non-woven according to claim 9, character- ized in that above mentioned fleece consists of natural, mineral, or synthetic staple fibres, or a combination thereof. 11. Non-woven according to any one of claims 9 and 10, characterized in that above mentioned fleece consists of continuous synthetic filaments. 12. Non-woven according to any one of claims 9- 11 , characterized in that above mentioned strengthening wires and/or filaments are synthetic filaments. 13. Non-woven according to claim 11 , characterized in that above mentioned synthetic strengthening filaments are twined with wires and/or mineral filaments, whereby the wires used for twining belong to one or several of the following groups: synthetic, natural, mineral fibres, or mixtures thereof, as well as wires twined with filaments. 14. Non-woven according to any one of claims 12-13, characterized in that above mentioned strengthening filaments and/or wires are PES filaments or wires, having a thickness of 1100 dtex, a tensile strength of ± 7 kg per filament, an elasticity between 15 and 25 %, a torsion of ± 60 and a weight of almost 0.11 g per current metre.

Inventors: BAERT LOUIS, BAERT PAUL, BAERT, LOUIS, BAERT, PAUL
Applicants: BAERT LOUIS, BAERT PAUL, WATTEX, BAERT, LOUIS, BAERT, PAUL
Application year: 1997
Main classification: D04H1
IPC codes: B32B5, D04H1, D04H5, D04H13