EP1644565B1 - Method for reinforcing a web of nonwoven fabric by means of needling - Google Patents

Abstract

A system and method for reinforcing a textile web of a fiber web or a fiber fleece by needling in a plurality of directly successive steps are provided, in which the web is needed from both sides with a high needle density in an alternating manner and in the state of the needles stitched into the web is transported through a movement of the needles which extends in the longitudinal direction of the web, where each needle in a stitching-in movement grasps merely a single fiber, having a gauge of 1 to 2 dtex, from the web. By the aid of the invention very thin fleeces can be produced without damaging same during their processing.

Description

In order to achieve sufficient strength in very thin fiber webs, as used for example in the field of hygiene, a very close bond of the webs forming fibers is required. For the needling technique as one of the possibilities for the production of nonwovens from batt and for the consolidation of nonwovens this means that the pile or the nonwoven must be needled with very high density of the punctures.

Thin fiber batt and nonwoven fabric of the aforementioned type are very sensitive before their solidification. They easily lose their cohesion even at low mechanical stress and tear. Their processing in needle machines is therefore very delicate, which is why a reduction in the basis weight of the needled products were previously set relatively high limits that did not meet the wishes of users.

The sensitivity of the machined material also meant that the working speeds were very low and the nonwoven web had to be processed in a very large number of steps in order to obtain the necessary number of needle punctures per unit area of the product for solidification, resulting in a correspondingly low productivity.

The invention is therefore based on the object of specifying a method and a device with which a gentle processing of fiber webs and fiber webs is possible, which makes it possible to produce very thin and lightweight needled products.

To solve this problem, the invention provides a method for solidifying a textile material web of a batt or non-woven fabric by needling in a plurality of immediately successive steps, in which the material web in each case needled alternately from both sides and in the material web pierced state of the needles exclusively is moved by a running in the longitudinal direction of the web movement of the needles.

Such a method is also known from US-6,161,269.

According to the invention, each needle now only takes up a single fiber of a stitch of 1-2 dtex during its insertion movement.

The invention achieved by the use of a high needle density already at the individual needling steps high productivity. When using needle boards of, for example, 350 to 400 mm width, it enables a loading density of up to 40,000 needles per meter of needle board length. The pitch of the needles is then for example about 3 mm or less, which necessitates the use of small diameter special needles. The production speed can reach 200 m / min with working widths of up to 6 m, just to give examples. It can thus produce lightweight products with a weight per unit area of up to 10 g / m ² , for example, from a single carding board. The fibers can be very fine down to about 1 dtex. Also fiber fibrils of less than 1 dtex are processable. The puncture densities are, for example, about 2,500 per cm ² , but may possibly be even higher. With a needle loading density of the aforementioned type and an effective horizontal stroke of the needles of 1 cm, the nonwoven web of six needle boards must be needled on both sides in order to achieve said stitch density.

The processing of even such lightweight products, as explained above, is possible by the measures according to the invention, according to which the material web is advanced in the pierced state of the needles within the needle machine exclusively by a longitudinal movement of the web extending movement of the needles. Because the needles of the two needle assemblies, which are combined in a double needle machine, in the invention alternately pierce the nonwoven web, ie the working cycles of these needle assemblies are offset by 180 ° from each other, there is an almost continuous transport of the nonwoven web through the needle machine through solely by the effect the needles. Furthermore, this mode allows a dense placement of the needle boards, since the needles of two opposing needle boards from home can not collide with each other.

It thus acts on the material web substantially no train acting from external transport devices, which would be braked in the pierced into the material web state of the needles of these, rather, get the needle aggregates the feed of the material web itself.

Depending on the type of material being processed, a change in length of the material web may occur during operation of the needling machines due to the individual needling processes. To avoid compression or distortion of the material web between the needle machines, the feed rates with which the individual needling machines transport the material web, must be adapted to each other in a suitable manner. In each case the same horizontal and vertical strokes of the needle bar per puncture movement in the individual needling machines, the adjustment of the feeds can be made by changing the stitch frequencies of the individual needle machines. This solution is particularly useful when horizontal stroke and vertical stroke of the needle bar are firmly coupled together. However, it is also possible to make the penetration depths of the needles different in each case with the same horizontal and vertical strokes of the individual needling machines, because thereby the time period during which the needles are inserted into the material web and transport it by the horizontal movement of the needle bar is influenced, which has some effect on the transport stroke in the horizontal direction per needle penetration. If needle machines of the type described in EP 0 892 102 B1 are used, the horizontal feed per needle penetration can be influenced within wide limits by appropriate control of the needle machines.

The co-movement of the needles with the material web in the inserted into this state of the needles is already known from DE 196 15 697 A1. It has the goal there, a disturbance of the surface of the web, which could be caused by a delay when the transport speed of the fibrous web through the needle machine is high, to avoid. The speed of the horizontal drive component of the needle bar is adapted to the conveying speed with which the material web of feeding and withdrawal devices is moved by the needle machine. In this case, the present invention utilizes the oscillating component of movement of the needles running in the longitudinal direction of the material web to actively transport the material web without the need for other transport devices. With the help of the invention can be even consolidate one-ply, but also multi-ply fibrous webs delivered directly from a card to a fleece. But it is also possible to solidify cross-laid nonwovens with the inventive measures. Also aerodynamically placed, possibly very thin card webs can be solidified by means of the invention by needling.

The fibers may, for example, be cotton fibers, with staple lengths of 20 mm to 40 mm being considered. Endless fibers of spunbonded nonwovens, smooth fibers and textured fibers may also form the material webs which can be processed by means of the invention.

When processing the material webs, needles are used whose notches are so fine that they grip only a single fiber of a thickness of 1-2 dtex. For example, such a needle has a shaft diameter of 1.85 mm and reduces its diameter over its length to 0.5 mm in two steps. The notch depth of the needles is 0.02 mm and preferably only one notch is formed on one edge of the needle. Because only a single fiber is pushed into the fleece by the needle and the needle has an extremely small diameter, no puncture holes remain visible. Therefore, and because of the high puncture density, a mark-free surface of the needle-punched product with high abrasion resistance is obtained.

The spacing of the notches from the needle tip should preferably be small in order to work with a small needle stroke. A preferred distance between notch and needle tip is for example 2 mm. A small needle stroke allows for higher working speeds. It can also be used with fork needles, crown needles or wreath needles, for example, with fork widths and depths of 2/100 mm. The needles can have standard lengths of 2.5, 3 or 3.5 inches, but may also be shorter, which benefits their stability and weight reduction. A weight reduction advantageously further contributes when the needles are made of plastic. One as small as possible Diameter of the needle shaft improves the strength of the needle board, because then remains at the same Nadelbestückungsdichte more board material.

Since the needle boards are very heavy due to the high needle assembly density, plastic needles are also considered whose weight is about 1/8 that of steel needles. In order to prevent fluttering of the needle boards on the needle bar carrying them, it is possible to attach the needle boards under low elastic deformation to the needle bar as described in DE 102 38 063 A1. This technique also allows the use of very wide needle boards.

It is also advantageous when working with a laminated down holder, which consists of a slotted plate on which a plurality of mutually parallel slats are formed, which extend transversely to the longitudinal extent of the plate. In this way, a hold-down plate can be realized, on the one hand has a small thickness in the slot area and is accordingly less prone to blockages by fiber fly, on the other hand, has a high stability with low weight. This hold-down device can also be used conversely with lamellas directed against the nonwoven web to be needled, but also vice versa, if necessary. Such a hold-down comes against the fact that due to the small needle shank diameter, the needles are more prone to bending than thick needles. A lame-on hold-down facilitates threading the needle into the slits of the slat bearing plate, or makes threading quite unnecessary if the needles do not leave the slits in the slab throughout their lifting movement.

Instead of using a plurality of sequentially arranged needle machines through which a nonwoven web is passed successively, one can also provide the fleece through one and the same needle machine multiple forward and backward forward and edit with this needle machine multi-stage, where necessary between the individual passes Needle boards can be changed if different needling in the different stages of processing, besipielsweise with different needles and different needle assembly densities.

With the help of the invention smooth webs can be produced on both sides, in which case the penetration depths of the needles from the processing step, ie needle aggregate, to processing step, ie the next needle aggregate, can decrease. Thus, then needled through the needles through the web through needled fibers on the side of the puncture projecting side of the material web, pierced by the needling from the other side back into the web, and with the help of the gradual reduction of the puncture density can finally achieve that no longer protruding fibers from the material web. The double needle technique, in which the material web is needled simultaneously or altematively from both sides in a needling zone, causes a doubling of the puncture density in a narrow space.

On the other hand, it is also possible to produce hairy nonwovens in which fibers protrude on one side. Such nonwovens are used, for example, for lamination onto a substrate, in which case the hair promotes the anchoring of the nonwoven on the substrate. '

Furthermore, it is possible with the aid of the invention to produce light nonwovens having a structured surface, for example wipes which have a hole pattern pierced in them. Such wipes are popular in the household because of their dirt holding capacity. For this purpose, only a corresponding operation with suitable smooth needles enlarged stem diameter and low insertion density of the needle board is inserted into the process flow. Because of the elastic returnability of the fibers, which could lead to a closing of the holes produced, this process may be carried out in stages with needles from stage to stage of increasing diameter, paying attention to the alignment of the holes of the semi-finished product on the needles of each subsequent processing stage must become. With the help of modern synchronizers this can be achieved without difficulty. The use of a Bürtsenbandes as underlay, which is guided through all processing stages, is advantageous in this case, because the fleece adheres well to the brush belt and thus retains its position on the surface. After the holes have been formed, thermal fixation may optionally take place by passing the perforated material through a screen drum oven or through a ribbon dryer to achieve thermofusion of the fibers at their points of intersection, provided that they are made of a suitable material such as e.g. a thermoplastic.

Other structures are conceivable. The needling on a grid, or better on a slotted plate or a laminated plate as stitch backing, especially using needles with multiple notches per edge or multiple edges with notches and with a higher notch depth allows structuring of the fleece, which occurs on both sides when needling from both sides of the web. Tufts are pulled out of the preconsolidated web or pushed out and transported to the nonwoven surface. Using a multiple array of needle looms, this patterning is done in the last needle looms or the last needle looms of the chain of machines, or in a separate operation within a single machine operated outside the machine chain for the purpose of patterning and structuring.

Depending on the advance of the material web or per stroke and needle arrangement in the needle board known patterns can be produced, such as longitudinal strips, horizontal stripes, diagonals or stitch patterns.

It is essential that at least the horizontal drives, which are assigned to the different Nadelungszonen, are independent of each other, so that an adaptation to different transport speeds, which are caused by shortening and extensions of the material web, is possible. Unless it is intended for a synchronous vertical drive of all needle bars, which is preferable in terms of the smoothest possible transport of the nonwoven web through the device, can also be considered, the transport speeds, which are caused by the individual needle machines, by changing the stroke frequencies of the individual Needle machines to influence.

The invention will be explained in more detail with reference to an apparatus shown in the drawing for the consolidation of a fiber web.

Figs. 1 and 2 together show a plant for producing a needled nonwoven fibrous web. 1 shows an aerodynamic web forming machine with feed, feeder and pickup, a transfer device and the lead-in area of a multi-stage needling machine, while FIG. 2 shows further needling machines of a pickling line. Instead of an aerodynamic web-forming device, a roll card, a card or other pile or nonwoven fabric producers can also be provided.

The plant of FIGS. 1 and 2 comprises a fiber feeder 1, which is connected via an infeed 2 to an aerodynamic web-forming device 3. Of the web forming 3 performs a transfer device 4, which has an endless circulating conveyor belt 5, the inlet area The conveyor belt 5 is in the inlet region of the needling 6 an endlessly rotating pressure belt 7 opposite, which serves to compress a discharged from the roller card 3 nonwoven web 8, which is located on the endless circulating conveyor belt 5.

Within the needling 6, a plurality of double needle machines 9 are arranged, of which in each case schematically the needle bar 10, which needles the nonwoven web 8 alternately from above and below, are shown schematically by hatched triangles. The needle bars 10 each carry a needle board which is densely populated with needles or a needle board group densely populated with needles (not shown). Of the needling machines 9, only the drive motors 91 for the vertical stitch drive and horizontal drive units 11 are schematically shown, which are coupled via connecting rods 12 with the needle bar 10 to this a horizontal, parallel to the direction of extension of the nonwoven web 8 extending, back and forth to give walking movement component. The coupling between the connecting rods 12 and the needle bar 10 is not shown here for reasons of clarity. For details, reference may be made, for example, to the already mentioned DE 196 15 697 A1 and also to EP 0 892 102 B1, the latter also disclosing devices which are to be adjusted elegantly to steplessly change the stroke size of the horizontal movement of the needle bar. It should be noted in this context that it is advantageous if the penetration depth of the needles is adjustable, because this determines the residence time during which the needles are in the nonwoven inserted into the nonwoven state. For further explanations in this context, reference is made to DE 196 15 697 A1.

The arrangement of the needle bar 10 and its drives 11 and 91 is the same for all needle machines 9. The vertical drives of the individual needling machines 9 can be controlled independently of each other and independently of one another in order to be able to influence the stroke frequencies individually, with which the transport speeds of the nonwoven web at the individual needling machines can be changed. But they can also be synchronous with each other, in particular driven by a common drive means, which helps to avoid stretching and compression of the nonwoven web within the Vemadelungsanlage. But at least then the horizontal drives should be individually adjustable in their stroke size to make local transport speed adjustments can.

On the outlet side of the needling machine 6, a pair of take-off rollers 13 is arranged, which discharges the finished non-woven fabric web, now designated as the end product with 81, from the system.

In the needle machine 6 each two double needle machines 9 can be combined in a common machine frame to a twin unit, the common upper and lower stitch pads (not shown) for the material to be processed web. Possibly. For example, all upper needle bars, i. the upper needle bar group of the twin arrangement can be driven together, and the same applies to all lower needle bar.

Since the horizontal drives 11 for the needle bar 10 occupy a certain space, the gaps Z between adjacent twin units, where the horizontal drives are housed, each bridged by endless circulating conveyor belts 14 which support the processed nonwoven web 8 from below, so they are not under their own weight sags and thereby possibly undesirably stretched. As an alternative, smooth support plates with low surface friction can be considered, over which the nonwoven web can easily slip.

Since in the invention, the web 8 is needled from both sides and therefore the invention uses double needle machines, which face each other in a Nadelungszone two mutually needling needle aggregates whose needles pierce alternately into the nonwoven web, the stitch pads are on both sides of the nonwoven web 8 against the the latter 8 is pressed by the needle movement, each lamellar slats with longitudinal slots or slotted plates whose slots allow the horizontal movement of the needles for the transport of the nonwoven web 8 in the inserted into this state. Details are not shown here, it can be made to the already mentioned documents. The use of lamellar grates is already known per se from the needling technique, in particular in the case of the formation of pile loops on needle felts, which are to be used, for example, as a floor covering.

The needles may be disposed on the needle boards in packages, respectively, wherein packages are offset transversely from each other by less than one pitch in the longitudinal direction to increase the puncture density on the nonwoven web. The slots in a slotted plate as stitch backing must then also in accordance with each other in the transverse direction be offset. It is also possible to adjust the lateral guide on the individual needle machines in coordination with one another such that the punctures created by the needles of a subsequent needle machine are transversely offset in the nonwoven web from the punctures produced by the needles of a preceding needle machine in the same nonwoven web become.

The horizontal strokes that have to perform the individual horizontal drives 11 must be adjustable depending on the material properties of the nonwoven web. As already mentioned, EP 0 892 102 B1 discloses devices with which the horizontal stroke, even during operation of the machine, can be infinitely adjusted. As an alternative comes, as already mentioned, a change in the stroke frequency into consideration. The expansion or shrinkage of the nonwoven web 8 which may occur as a result of the processing can be determined, for example, contactlessly with the aid of electronic cameras and autocorrelation of the images taken by them, and with the aid of which the horizontal drives can be adjusted. The necessary facilities for this purpose are not shown in the drawing for reasons of clarity. It is understood that such devices are provided at each needle machine, where the nonwoven web can undergo changes, wherein a central control unit can be provided for the entire system.

Claims (12)

1. A method for reinforcing a textile web composed of a fibre web or a fibre fleece by means of needling in a plurality of steps, wherein said web (8) is alternately needled from both sides and in a state of the needles stitched into the web (8) is moved in the longitudinal extension of the web exclusively by a movement of the needles which extends in the longitudinal extension of the web, characterized in that said web (8) is needled in a plurality of directly successive steps each with a high needle density, wherein each needle in a stitching-in movement grasps merely a single fiber having a gage of 1 to 2 dtex from the web (8).
2. The method as claimed in claim 1, characterized in that the stitching depth of the needles decreases from step to step.
3. The method as claimed in claim 1, characterized in that in at least late steps of the method the stitching depth of the needles on a first side of the web (8) is smaller than a stitching depth of the needles on the other side of the web (8).
4. The method as claimed in one of the preceding claims, characterized in that the web (8) consists of a single-layered or multi-layered card non-woven web.
5. The method as claimed in one of the preceding claims, characterized in that the vertical stitching movements of needle bars (10) are synchronized with one another.
6. The method as claimed in one of the preceding claims, characterized in that the web (8) is supported between at least some of the needling steps by smooth rest surfaces or by support surfaces moved in unison with the web (8) and contacted by the web (8).
7. The method as claimed in one of the preceding claims, characterized in that the plurality of successive steps are performed by a plurality of double needle looms (9) arranged in a transport direction of the web (9).
8. The method as claimed in one of the preceding claims, characterized in that the horizontal movement components of the needles in the individual steps are differently large.
9. The method as claimed in one of the preceding claims, characterized in that permanent holes are generated in the needled web (8) by the aid of needles, and the web (8) is subsequently subjected to a fixing process.
10. The method as claimed in one of the preceding claims, characterized in that needles made from plastics are used.
11. The method as claimed in one of the preceding claims, characterized in that needles having a notch depth of 0.02 mm are used.
12. The method as claimed in one of the preceding claims, characterized in that the needles are arranged at a needle board in groups which, seen in the transport direction of the web, are transversely offset with respect to one another by less than one needle pitch.

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