WO2004088026A1

WO2004088026A1 - Method and device for producing a nonwoven composite

Info

Publication number: WO2004088026A1
Application number: PCT/EP2004/003175
Authority: WO
Inventors: Axel Nickel; Erwin Glawion
Original assignee: Rieter Automatik Gmbh
Priority date: 2003-03-31
Filing date: 2004-03-25
Publication date: 2004-10-14
Also published as: DE10314552A1

Abstract

The invention relates to a method for producing a nonwoven composite, in which a voluminous coarse-fibre nonwoven consisting of continuous or finite fibres of more than 6 dtex constitutes one component and a fine-fibre nonwoven comprising continuous or finite fibres that are significantly thinner than those of the coarse-fibre nonwoven constitutes the other component. According to the invention, a coarse-fibre nonwoven consisting of high-fusion fibres is laid on the fine-fibre nonwoven consisting of low-fusion fibres and a plurality of fluid jets are then directed onto the fine-fibre nonwoven with a pressure that is sufficiently high enough to force the fibres of the fine-fibre nonwoven between the fibres of the coarse-fibre nonwoven, thus merging the former fibres with the latter fibres to obtain the nonwoven composite. After drying in a heating stage, the nonwoven composite is further heated and subjected to temperatures that are high enough to fuse at least the surface fibres of the fine-fibre nonwoven, fusing them with the coarse-fibre nonwoven upon completion of the additional heating process.

Description

Method and device for producing a composite nonwoven

The invention relates to a method and a device for producing a composite nonwoven whose one component consists of a voluminous coarse fiber fleece consisting of endless fibers of more than ό dtex, and the other component consists of a fine fiber fleece with endless fibers which are substantially thinner than the coarse fiber fleece.

Such a composite nonwoven material is described in DE 41 14 839 C2, which consists of coarse filaments with respect to one component and fine microfibers with its other component. These two nonwoven materials are joined together in layers, the cohesion being generated by the microfibers, which are formed by components of an adhesive, being connected to the other nonwoven layer by heating.

It is also known from EP 0418493 to design a composite fleece from two layers, which are connected to one another in that water jets are directed onto one layer, and the fibers of the layer directly affected by the water jets into the other layer in the manner of needling pull it in and connect the two layers. This needling with water jets is only possible with fibers whose fineness does not exceed 6 dtex, which corresponds to a fiber diameter of approx. 25 micrometers mm. Because of the relatively low stiffness of fibers of such fineness, such nonwovens are compressed when needling, so that the layer thickness of such nonwovens is greatly reduced, which is undesirable in many cases. When using the two manufacturing methods of composite nonwoven described above, it has been shown that when two layers of nonwoven material are bonded as described above, only a connection between the two layers, but not a continuous internal strengthening and connection, is brought about. The possibility of such an internal strengthening of nonwoven material is particularly desirable in the production of stiff and deformation-resistant molded parts, such as are also used in automobiles, while tear resistance and softness are more important in hygiene applications. The method of needling by means of water jets, which is also described above, only works with a coarse fiber fleece with relatively thin fibers, which, however, leads, as said, to a reduction in the respective layer thickness. It is therefore an object of the invention to provide a method for producing a composite fleece which, on the one hand, leads to a particularly strong and durable bond between two fleece layers, the original thickness of the coarse fiber fleece being practically not reduced.

According to the invention, this is done by placing the fine fiber fleece consisting of low melting fibers on the coarse fiber fleece consisting of high-melting fibers and then directing a large number of fluid jets onto the fine fiber fleece at such high pressure that the fibers of the fine fiber fleece are forced between the fibers of the coarse fiber fleece and become mix with the latter to form the composite fleece, which after drying a heating stage is subjected to further heating at temperatures such that the fibers of the fine fiber fleece are melted at least on the surface and stick to the coarse fiber fleece after the further heating has ended.

Water jets, optionally tempered, and also superheated steam jets and air jets are primarily considered as fluid jets. By using the known needling of nonwoven fabric with fluid jets in combination with the bonding of fibers of a nonwoven fabric by heating, a particularly high dimensional stability is obtained even with a coarse fiber nonwoven fabric of more than 6 dtex, because one type of connection, namely the needling by means of Fluid jets, even in the case of the relatively thick fibers of more than 6 dtex, the stiffness of which largely counteracts a reduction in volume which occurs when needling, the other type of connection, namely the internal gluing, stabilizing the coarse fiber fleece, the combination of the two processes resulting in a high degree of mutuality Supporting the effect of both processes results in the result that the composite fleece produced according to the invention is a particularly dimensionally stable material. On the one hand, it is only necessary to practice the needling only to such an extent that no particular strength is generated by this alone, the particularly high dimensional stability of the composite fleece produced in this way then being achieved by the subsequent bonding. It may be necessary to first cut the fibers of the fine fiber fleece into short fibers using water jet nozzles in order to be able to press them better into the coarse fiber fleece.

The method can also be modified in such a way that the further heating is directed at the composite nonwoven with such temperature and duration that the fibers of the coarse fiber nonwoven are glued together when the fibers of the fine fiber nonwoven melt. This creates an effect on the fibers of the coarse fiber fleece in addition to the needling with fluid jets that previously took place, which results in a particular strength of this material.

It is also possible to adjust the exposure to the fine fiber fleece with fluid jets with regard to pressure and duration such that a layer of fibers of the fine fiber fleece remains over the coarse fiber fleece. When the composite nonwoven is heated, this results in an adhesive surface of the composite nonwoven, consisting of the layer of the melted fibers of the fine fiber nonwoven, with which another layer of nonwoven can then be adhered to the composite nonwoven it can be a simple non-woven layer, but it can also be another composite non-woven layer. In this way it is possible to produce a multiple layer of a composite nonwoven inexpensively by means of several composite nonwovens treated in this way.

The pressure and duration of the fluid jets directed onto the fine fiber fleece are advantageously set such that the mixing of the fibers of the fine fiber fleece with the fibers of the coarse fiber fleece decreases continuously with increasing depth in the coarse fiber fleece. This results in a composite fleece with a gentle strength transition from the outside to the inside of the composite fleece, the gradient of the mixing depending on the pressure and duration of the fluid jets being able to be set in each case, for example to a linear or exponential gradient.

It is also possible to place another fine fiber fleece on the side facing away from the fine fiber fleece and to glue this fine fiber fleece to the composite fleece by melting its fibers. In this way, a composite fleece is obtained which is of identical design on both sides.

The composite nonwoven can also be used to produce a material with a specially and attractively designed surface, for which purpose at least one further layer in the form of a further nonwoven, film or decorative material is placed on the composite nonwoven, which is bonded to the composite nonwoven in that the layers are melted by melting the Fine fiber fleece are glued together.

To create a particularly thick material, a plurality of composite nonwovens can be combined after each treatment by the fluid jets and exposed together to the heating stage, which leads to adhesion from layer to layer and ultimately results in a correspondingly thick material. An apparatus for carrying out the above-described method is expediently designed such that a nozzle arrangement in each case deposits the fibers for the coarse fiber fleece and the fine fiber fleece on a conveyor belt which, with the two fleeces, reaches a stage with pressurized fluid jets, to which a heating stage for drying, melting and cooling the fibers of the fine fiber fleece.

With such a device, the pressurized fluid jets can be guided in such a way that they perform a reciprocating transverse movement with respect to the conveyor belt, which due to the advance of the conveyor belt results in a meandering action on the fleece in question, the pressure of the fluid jets being adjusted so that the fine fibers are severed by the fluid jets to form small rhombic surface units.

Exemplary embodiments of the invention are shown in the figures. Show it:

Figure 1 shows a system for performing the method according to the invention with directly connected devices for generating the

Coarse fiber fleece and fine fiber fleece;

Figures la, b and c structures of the structural pattern of the given nonwoven fabric generated at the points designated in this regard in Figure 1;

Figure 2 shows a plant part for the production of coarse fiber fleece;

FIG. 3 shows the production of the composite fleece with a system that is fed with the result of the system according to FIG. 2;

FIG. 4 shows a system for producing a coarse fiber fleece coated on both sides with a fine fiber fleece; FIG. 5 shows a system for producing a composite nonwoven fabric that comes from composite nonwoven fabrics that are unwound from six coils and that are combined to form an overall composite nonwoven fabric;

FIG. 6 shows a fluid jet pattern drawn by the fluid jets on a coarse fiber fleece which is moved back and forth transversely to the conveying direction;

FIG. 7 shows an enlarged illustration of the pattern according to FIG. 6.

FIG. 1 shows a plant for carrying out the method according to the invention, in which two devices for producing a coarse fiber fleece and a fine fiber fleece are combined, namely the plant 1 for producing a coarse fiber fleece, shown in increased broken lines, with a granule hopper 2, an extruder 3 and a nozzle arrangement 4, from which a number of fibers 5 emerge, which form the coarse fiber fleece 7 on the advancing conveyor belt 6. The representation of the above-mentioned components 2, 3 and 4 is only a symbolic representation, since the components in question are known designs.

The system also contains the device 8 for producing a fine fiber fleece 9, shown in fine dashed lines, which, similar to the device 1, contains a granulate hopper 10, an extruder 11 and a nozzle arrangement 12. The fibers 13 emerge from the nozzle arrangement 12 and form the fine fiber fleece on the conveyor belt 6, which is deposited on the coarse fiber fleece 7.

The inner structure of the coarse fiber fleece 7 after the fibers 5 hit the conveyor belt 6 is shown in FIG. FIG. 1b shows the unfinished composite nonwoven transported at the marked point in FIG. 1 after the fibers 13 are deposited on the coarse fiber nonwoven 7, which together with the coarse fiber nonwoven 7 form the composite nonwoven. After depositing the fine fiber fleece 9 on the rough nonwoven fabric 7 (after the position in FIG. 1b in FIG. 1), the two superposed nonwovens are exposed to the water jet nozzles 14, 15 and 16, which direct their fluid jets onto the fine fiber nonwoven fabric 9 under high pressure (for example 200 bar). If necessary, it is possible that the fibers of the fine fiber fleece 9 are first cut into short fibers in a pattern according to FIG. 7 by the water jet nozzles 14 and 15, before they are forced into the coarse fiber fleece 7, whereby the two fleeces mix to form the composite fleece , For this purpose, either the water jet nozzles 14 and 15 are shifted in phase or the conveyor belt 6 with the composite fleece is moved back and forth with a corresponding offset of the water jet nozzles 14 and 15 (see FIG. 6). This produces lenticular sheets 24 and checkered sheets 25 according to FIG. 7.

The thickness of the fluid jets corresponds approximately to the thickness of the fibers of the coarse fiber fleece. The structure of this composite fleece is shown in FIG. 1c (see corresponding marking in FIG. 1), from which it can be seen that the thin fibers of the fine fiber fleece have mixed to a considerable extent between the fibers of the coarse fiber fleece.

The fibers of the coarse fiber fleece can be those which have a fiber fineness of about 6 to 30 dtex (g per 10000 m length). About 0.1 to 0.3 dtex apply to the fine fiber fleece. These values correspond approximately to a diameter of 25 - 60 micrometers for coarse fiber fleece and 3 - 6 micrometers for fine fiber fleece.

After leaving the conveyor belt 6, the composite fleece produced in this way is exposed to the heating stage 17, in which, on the one hand, the composite fleece is dried and the fibers of the fine fiber fleece 9 are melted, which gives them their adhesive properties and bonds with the coarse fiber fleece 7. A composite fleece is thus present as a compact material which, after cooling, can be wound up in a cooling section 23 on the winding 18 as finished material or can also be deposited in the form of a plate. A modification of the design of a plant for producing the composite fleece according to the invention is shown in FIGS. 2 and 3. Starting from the illustration in FIG. 1 relating to the device 1, the part of the installation shown in FIG. 2 contains only the production of the coarse fiber fleece 7, which after being formed on the conveyor belt 6a is first passed under the water jet nozzle 19 in order to be pre-consolidated there. The coarse fiber fleece 7 is then fed to the dryer 20, after which it is then wound up on the roll 21.

FIG. 3 goes back to the illustration of the device part 8 from FIG. 1. The device 8 is fed by the coarse fiber fleece 7 wound on the roll 21, onto which the fibers 13 forming the fine fiber fleece 9 are placed here, similar to the system according to FIG. The structure shown in FIG. 1b thus arises at the point in FIG. 1b according to FIG. The nonwovens placed one on top of the other then come under the influence of the water jet nozzles 14, 15 and 16, which, as described in connection with FIG. 1, press the fibers of the fine fiber nonwoven 9 into the fibers of the coarse fiber nonwoven 7, where they coexist with the fibers of the coarse fiber nonwoven 7 mix. After leaving the conveyor belt 6b, the composite nonwoven thus initially produced as a prefabricated product then passes into the heating stage 17, in which the composite nonwoven is dried and then the fibers of the fine fiber nonwoven 9 are melted, whereby the composite nonwoven is finally produced and after cooling in the cooling section 23 can be wound onto the winding 18.

FIG. 4 shows a system which contains the assemblies of the system according to FIG. 3 and which, however, is not fed with a coarse fiber fleece (winding 21 in FIG. 3), but rather is fed with a composite fleece 29 which, as in FIG shown, is wound on the winding 18 there. According to FIG. 4, the winding 18 is turned over in relation to its position in FIG. 3, so that the outermost layer with respect to the individual layers on the winding 18 is coated with the extruded fibers 27 for a fine-fiber fleece 28. After that then, as in the plant according to FIG. 3, the composite fleece, which here carries a fine fiber fleece on both sides, is transported further through the further stages of the plant 4, which correspond to those according to FIG. 3, and finally wound onto the winding 26 as a composite fleece coated on both sides with a fine fiber fleece ,

The method according to the invention can also be used to produce a composite nonwoven which consists of several layers of individual composite nonwovens, consisting of coarse fiber nonwoven and fine fiber nonwoven.

FIG. 5 shows six coils 21, each of which contains the composite fleece produced by the method according to the invention, preferably with the fine-fiber fleece not yet melted. These composite nonwovens are supplied in a known manner via deflection rollers to the heating stage 22, where, if necessary, the nonwovens supplied to them are also dried, provided that this drying has not already taken place beforehand. In this heating stage 22, the fine fiber fleece is heated in such a way that its fibers develop the required adhesive force and can bind to neighboring fibers. The consequence of this is that the individual composite nonwovens which are pulled off from the six windings 21 lie against one another within the heating stage 22, in order then to be glued together in the heating stage. The heating stage 22 then provides a particularly thick, stiff nonwoven.

It should also be pointed out that in the heating stage 22 the individual composite nonwovens can be subjected to a continuous or cyclical shaping and are glued to one another in this way, thus giving the composite nonwoven fabric emitted by the heating stage 22 a shape that is shaped by the heating stage 22 equivalent. It can e.g. to be a piece of a circular arc.

If the heating of the fine-fiber fleece takes place by means of the heating stages 17 and 22 shown in FIGS. 1, 3 and 4, such that it is largely in liquid form Mold penetrates into the coarse fiber fleece, then an internal strengthening of the coarse fiber fleece is achieved, since the individual fibers are then glued together in the coarse fiber fleece. The heating stages 17 and 22 can also be designed in the form of presses.

FIG. 6 shows the part of the installation according to FIG. 1 insofar as it comprises the area with the water jet nozzles 14 and 15 and water outlets 30 and 31 arranged below it. According to FIG. 6, the coarse fiber fleece 7 is moved back and forth during transport under the water jet nozzles 14 and 15, which can be brought about by a corresponding movement of the conveyor belt 6. This back and forth movement of the coarse fiber fleece 9 takes place under the water jet nozzles 14 and 15, with a stroke of only a few millimeters, so that the fluid jets of the water jet nozzles 14 and 15 each act on the fine fiber fleece 9 via a meandering track, due to the offset the water jet nozzles 14 and 15 touch these tracks, which, as shown in FIG. 6, leads to a diamond pattern according to which the fibers of the fine-fiber fleece 9 are cut at the respective crossing points of the tracks mentioned.

The relevant trace pattern is shown enlarged in FIG. When the coarse fiber fleece 7 moves back and forth with the fine fiber fleece 9 lying thereon, the intersecting traces of the water jet nozzles result, lenticular sheet-like structures 24 and square-shaped structures 25 being formed, each of which is encompassed by fibers of the fine fiber fleece 9. These structures are drawn into the coarse fiber fleece 7 by the fluid jets in addition to cutting the fibers of the fine fiber fleece 9 and here form a particularly uniform layer of the fine fiber fleece 9.

Claims

claims

1. A process for producing a composite nonwoven whose one component consists of a voluminous coarse fiber nonwoven (7), consisting of endless or finite fibers of more than 6 dtex, and the other component of a fine fiber nonwoven (9) with significantly thinner than the coarse fiber nonwoven (7) consists of endless or finite fibers, characterized in that on the coarse fiber fleece consisting of high-melting fibers

(7) the fine-fiber fleece (9) consisting of low-melting fibers is deposited and then a large number of fluid jets are directed onto the fine-fiber fleece (9) at such a high pressure that the fibers of the fine-fiber fleece (9) are forced between the fibers of the coarse-fiber fleece (7) and mix with the latter to form the composite fleece, which after drying a heating stage (17) is subjected to further heating at temperatures such that the fibers of the fine fiber fleece (9) are melted at least on the surface and, after the further heating has ended, coagulate with the coarse fiber fleece (7) stick together.

2. The method according to claim 1, characterized in that the further heating is directed to the composite nonwoven with such temperature and duration that when the fibers of the fine fiber nonwoven (9) melt, the fibers of the coarse fiber nonwoven (7) are glued together.

3. The method according to claim 1 or 2, characterized in that the application of the fine fiber fleece (9) with fluid jets in terms of pressure and duration is adjusted so that a layer of fibers of the fine fiber fleece (9) remains over the coarse fiber fleece.

4. The method according spoke 1 or 2, characterized in that the pressure and duration of the fluid jets directed onto the fine fiber fleece (9) is set such that, according to a gradient, the mixing of the fibers of the fine fiber fleece (9) with the fibers of the coarse fiber fleece (7) decreases continuously with increasing depth in the coarse fiber fleece.

5. The method according to any one of claims 1 to 4, characterized in that on the composite fleece (29) on its side facing away from the fine fiber fleece another fine fiber fleece (28) is placed and by melting the fibers of this fine fiber fleece (28) with the composite fleece (29) is glued.

6. The method according to claim 3, characterized in that at least one further layer in the form of a further non-woven fabric, film or decorative material is placed on the composite nonwoven, which is glued to the composite nonwoven in that the layers are glued together by melting the fine fiber nonwoven ,

7. The method according to any one of claims 1 to 6, characterized in that a plurality of composite nonwovens (21) are combined after treatment by the fluid jets and exposed together to the heating stage.

8. The device for carrying out the method according to one of claims 1 to 5, characterized in that in each case a nozzle arrangement (4, 12) deposits the threads for the coarse fiber fleece (7) and the fine fiber fleece (9) on a conveyor belt (6) with the two fleeces a stage (14, 15, 16) with pressurized fluid jets is reached, followed by a heating stage (17, 23) for drying, melting and cooling the threads of the fine fiber fleece (9). Device according to spoke 8, characterized in that the pressurized fluid jets are guided in such a way that they execute a reciprocating transverse movement with respect to the conveyor belt (6) which, due to the advance of the conveyor belt (6), meanders on the relevant fleece (7, 9), the pressure of the fluid jets being set such that the fine fibers are severed by the fluid jet to form small rhombic surface units (24, 25).