Method and apparatus for producing a felt

Abstract

The invention relates to a method and to a needle-punching apparatus for producing a felt, in particular a press felt for a paper machine, the method comprising the following steps: a. providing a base structure, in particular a woven base structure, b. arranging at least one first nonwoven layer on one side of the base structure, c. needle-punching the first nonwoven layer to the base structure in a first needle-punching operation, d. needle-punching the first nonwoven layer to the base structure in a second needle-punching operation, forming a nonwoven support, wherein the first needle-punching operation is performed by means of mechanical needling, and the second needle-punching operation is performed by means of water jet needling.

Description

[0001] METHOD AND DEVICE FOR PRODUCING A FELT

[0002] The invention relates to a method for producing a felt, in particular a press felt for a paper machine, and to a device for carrying out such a method.

[0003] In the production of felts, especially press felts for paper machines, it is common practice to provide a base structure with a layer of nonwoven fibers. The base structure is usually a woven base structure.

[0004] For attachment, the nonwoven fibers are arranged on the base structure and attached to it by needling. This needling of nonwoven fibers has long been known and is described, for example, in EP 0 480 868 B1.

[0005] For needling, special needles are used, which are described, for example, in documents EP1069224 A1 or DE102004037716 A1, and which are used in large numbers in so-called needle boards. Such needle boards are shown as an example in EP1953287 A1.

[0006] Although the needling process has been proven successful for decades, it does have several disadvantages. On the one hand, these needles wear out with continued use and must be replaced. This, in addition to the costs, leads to extended downtime of production facilities.

[0007] Another disadvantage is that needling causes a certain amount of damage to the nonwoven fibers. The more deeply the felt is needled, the more noticeable this damage becomes. This can lead to the technologically desired higher density of the nonwoven layer not being achieved, as the damage to the fibers caused by the needles is no longer within the tolerable range.

[0008] The surface of the felt is also influenced to some extent by needling. So-called "needle craters" can often be observed where the fibers have been pierced into the structure. This can lead to an inhomogeneous paper side of the felt and uneven drainage, or even to undesirable effects on the paper surface.

[0009] Finally, needling also limits the thickness of nonwoven fibers that can be used for felt.

[0010] To avoid these disadvantages, some attempts have been made to dispense with the mechanical needling process and instead use water jet needling, which is known from nonwoven fabric production.

[0011] Patent applications DE102009024057 A1 and WO12098223 A1 describe processes for this. However, these processes have not yet been widely adopted in the industry. One of the reasons for this is certainly the fact that the application of heavier nonwoven layers, e.g., 500 g / m 2 and more, is only possible with difficulty.

[0012] The object of the invention is to propose an alternative method for fastening the nonwoven layer and a corresponding felt which overcome the problems known from the prior art.

[0013] The object is achieved according to the invention by an embodiment according to the independent claims. Further advantageous embodiments of the present invention can be found in the subclaims.

[0014] The object is achieved by a method for producing a felt, in particular a press felt for a paper machine, wherein the method comprises the following steps: a. Providing a basic structure, in particular a woven basic structure b. Arranging at least one first nonwoven layer on one side of the basic structure C. Needling the first nonwoven layer with the basic structure in a first

[0015] Needling d. Needling the first nonwoven layer with the basic structure in a second needling, forming a nonwoven layer, wherein the first needling is carried out by means of mechanical needling and the second needling is carried out by means of water jet needling.

[0016] In advantageous embodiments, it can be provided that in step b. one or more further nonwoven layers are arranged, and the further nonwoven layer or the further nonwoven layers are needled to the basic structure together with the first nonwoven layer to form a nonwoven overlay in steps c. and d.

[0017] In a further variant of the method, it can be provided that between steps c.) and d.) the following steps are carried out: b1) arranging at least one further nonwoven layer c1) needling the further nonwoven layer with the basic structure in a mechanical needling process.

[0018] Steps b1 ) and c1 ) can be carried out several times in order to mechanically needle several additional nonwoven layers.

[0019] This process variant makes it possible to mechanically bond several or all nonwoven layers to the base structure. This can be done on a conventional mechanical needle loom, which does not necessarily require modification. The base structure with the attached nonwoven layer can then be completed in a final step using waterjet needling.

[0020] The waterjet needling unit can be located separately from the mechanical needling frame. After attachment, the base structure can be easily transported together with the fleece overlay. Unlike a design in which the waterjet needling unit and the mechanical needling unit are integrated into the same device, this creates an additional work step. However, existing machines such as a mechanical needling frame and a conventional waterjet needling unit can potentially be reused. Furthermore, this prevents the felt, which has become damp during the waterjet needling, from running through the mechanical needling unit again.

[0021] Alternatively or additionally, it can also be provided that after step c., at least one further nonwoven layer is arranged, wherein the at least one further nonwoven layer is needled together with the first nonwoven layer to form a nonwoven layer in step d. In this case, it can therefore be provided that the further nonwoven layer is needled exclusively by means of water jets, while the first nonwoven layer is also mechanically needled. This once again exemplifies that the combination of mechanical and water jet needling described in this application can be implemented in a variety of ways.

[0022] In addition to the nonwoven layers, additional functional layers can also be incorporated into the felt. These functional layers can be, for example, a film, a foam, a membrane, or a spun web. Such functional layers can, for example, include or consist of a polyurethane.

[0023] The additional functional layers can be incorporated into the felt, for example, by mechanical needling and / or water jet needling.

[0024] The water jet needling of a nonwoven fabric can be carried out using a nozzle bar, which has a strip of nozzles with outlet openings, usually in two or more parallel rows. Accordingly, the water jets are arranged in two or more parallel rows and act on the nonwoven fabric. The outlet openings, and thus the emerging water jets, are advantageously arranged offset from one another. The water jets usually emerge as continuous water jets, but can in principle also be pulsed. For needling, the base structure, together with the arranged nonwoven fabric, is moved relative to the nozzle bar. Either the base structure can move with a fixed nozzle bar, or the nozzle bar with a fixed base structure. Alternatively, both the nozzle bar and the base structure can move.

[0025] For the purposes of this application, the term "fleece overlay" refers to the entire fiber fleece attached to one or both sides of the felt. This fleece overlay can, in turn, be constructed from several "fleece layers." Such fleece layers can be available as rolls or in another suitable form.

[0026] If several nonwoven layers are used, the additional nonwoven layers can be arranged on a previous nonwoven layer or on the second side of the basic structure.

[0027] The nonwoven fibers in the nonwoven layers are usually staple fibers (also called batt fibers). Such staple fibers are currently used as standard for the production of press felts. However, in principle, the use of other nonwoven fibers is also possible.

[0028] A structure consisting of multiple nonwoven layers can be advantageous, for example, for applying a larger quantity of nonwoven fibers to a felt than is reasonably possible with a single nonwoven layer. In this case, several similar nonwoven layers with the same nonwoven fibers can be used.

[0029] Alternatively or additionally, the nonwoven fibers of the various nonwoven layers can be different, for example, in material or linear density. In this way, the nonwoven layer can be adapted to the requirements of the felt by selecting and arranging the individual nonwoven layers.

[0030] A single nonwoven layer can be homogeneous, meaning it consists only of fibers of the same material and / or denier. A single nonwoven layer can also be heterogeneous, consisting of nonwoven fibers of different materials and / or deniers. Nonwoven layers consisting solely of nonwoven fibers are common. However, a nonwoven layer can also contain additional components in addition to the nonwoven fibers, such as polymer material to improve the properties of the resulting felt.

[0031] Woven base structures are preferably used as the base structure. These can be endless fabric loops or fabric loops made endless by means of a seam, such as a pintle seam. In advantageous embodiments, this base structure can be constructed from simple flat fabrics, as described, for example, in documents EP 0425 523 B1 or EP2788546 B1.

[0032] Alternatively or additionally, the base structure can also contain or consist of layers of threads. One possible embodiment of such a base structure is described, for example, in WO23110220 A1. Other textile fabrics, such as knitted or spacer fabrics, can also be present in the base structure.

[0033] An important feature of the invention is the combination of conventional mechanical needling and water jet needling. This allows one or more nonwoven layers to be attached to the base structure by mechanical needling. Even heavier nonwoven layers can be easily attached to the base structure. This avoids the problem of water jet needling, where heavy nonwoven layers cannot be needled or can only be needled with great effort. In general, a wide range of felts can be produced using the processes proposed here. The nonwoven layers can be used in a weight range between 300 g / m 2 and 3000g / m 2 , preferably between 400 g / m 2 and 1600 g / m 2 lay.

[0034] A single fleece layer usually has a weight in the range between 50 g / m 2 and 500 g / m 2 , preferably between 100 g / m 2 and 400 g / m2 . Nonwoven layers with lower weights, and especially nonwoven layers with weights higher than 500 g / m 2 are difficult to process. The final needling is then carried out using waterjet needling. This effectively prevents the effects on the felt surface, such as the formation of needle craters, that are common with mechanical needling.

[0035] Furthermore, the specialist has many new possibilities at his disposal when designing the felt using the water jet needling tool, which are described in more detail below.

[0036] Within the scope of the procedure, it is possible that steps c. and d. can be carried out multiple times.

[0037] In general, it is advantageous to perform step d after step c. The final needling should preferably be performed using waterjet needling, as this is a particularly effective way to avoid the adverse effects of mechanical processes such as needle craters, etc.

[0038] In a particularly advantageous embodiment of the method, it can be provided that the needling in step d. - i.e. the water jet needling - is carried out until the material density of the nonwoven layer is at least 60%, in particular between 70% and 90%.

[0039] The specification of [xx%] material density refers to the fact that xx% of the volume of the nonwoven layer consists of the nonwoven fiber material and, if applicable, other solid components of the nonwoven layer, while the remaining 100-xx% is formed by hollow spaces ("void volume"). The material density / void volume can be determined using known methods, such as mercury porosimetry or p-CT scanning. To determine the material density, the sample is subjected to a pressure of 5 MPa.

[0040] This reveals another advantage of the process proposed here. To increase the material density in the nonwoven layer to values ​​of 60% and more, the nonwoven fibers must be densified through long and intensive needling. If this is achieved by mechanical needling, surface defects due to mechanical damage to the fibers increase significantly. Such material densities are almost impossible to achieve using conventional processes and are generally only possible with felts where surface quality is not particularly relevant to the product being manufactured. However, if this densification is achieved entirely or at least partially through waterjet needling, these defects do not occur.

[0041] Alternatively or additionally, it can be provided that at least one nonwoven layer consists of more than 50%, in particular entirely, of coarse nonwoven fibers with a titer of at least 67 dtex, in particular 100 dtex and more. Even higher titers of 200 dtex, 250 dtex, 300 dtex, or 400 dtex are also possible. For each individual fiber type and thickness, at least 50 g / m 2 preferably at least 100 g / m 2 in the fleece layer or even in a single fleece layer.

[0042] Such thick nonwoven fibers cannot be needled, or only very poorly, using conventional mechanical needling. The needles damage the thick fibers. However, since a significant portion of the needling is done using waterjet needling, these fibers can also be used.

[0043] Here it is also very time-consuming to use appropriate needles, because the barb size would have to be adjusted and with very large barbs too many fine fibers are needled at once.

[0044] In addition, the classic mechanical needling is inevitably a timed process due to the up and down movement of the needle board.

[0045] Waterjet needling, on the other hand, is significantly more flexible. It can be performed as a nearly continuous needling process, especially when continuous water jets are used. However, if desired or necessary, waterjet needling can also be performed intermittently. For this purpose, the water jets can be appropriately pulsed. By varying this pulsation, even the timing can be largely freely adjusted. This is not easily possible with conventional mechanical needling. The proposed process can be designed very flexibly with regard to the weighting of steps c. and d., i.e., the proportions of the two needling types.

[0046] Does the felt have a rather heavy fleece layer of 500 g / m 2 and more, especially 1000 g / m 2 and more or 1500 g / m 2and more, it will be advantageous to perform a significant portion of the entire needling process using mechanical needling in addition to waterjet needling to ensure good attachment to the base structure. For lower nonwoven weights, mechanical needling may be limited to lightly attaching the nonwoven layer. The optimal coordination of these two process steps will be determined by a specialist depending on the specific product.

[0047] One possible adjustment is the pressure of the water jets used in waterjet needling. This pressure can be up to 400 bar, for example, but is often chosen in the range between 20 bar and 250 bar.

[0048] The speed at which the web is moved through the waterjet needling unit is also a control variable for the needling process. With waterjet needling, speeds of 400 m / min are quite common. However, this speed can be increased depending on the application, so that speeds of 600 m / min and more are also possible. In the applications described here, however, lower speeds can also be advantageous, especially when thicker fibers and larger application quantities are to be used. For example, speeds of 100 m / min, 50 m / min, 30 m / min, 20 m / min, 10 m / min, 5 m / min, or less can be advantageous in individual cases.

[0049] In particularly advantageous embodiments, it can be provided that the water jet needling in step d. is not carried out uniformly across the width direction of the felt, so that in particular the material density of the fleece layer varies in the width direction of the felt.

[0050] In contrast to conventional mechanical needling, the effect of waterjet needling on the nonwoven backing can be easily and precisely influenced by varying the water jets. In this way, for example, a predefined profile of the material density or other properties of the nonwoven backing can be created with waterjet needling. In particular, the properties of the nonwoven backing at the edges of the felt can differ from those in the center. This opens up entirely new possibilities in felt design, allowing the felt to be optimally adapted to the application conditions.

[0051] In general, the individual steps of a method according to one of the preceding aspects can be carried out on different systems. However, for a particularly fast and economical implementation of such a method, a needling device for producing a felt, in particular a press felt for a paper machine, is proposed. The device comprises means for guiding a material web, as well as a mechanical needling unit and a water jet needling unit.

[0052] It is advantageous if the water jet needling unit is arranged behind the mechanical needling unit in the running direction of the material web.

[0053] Such a needling device essentially requires the same amount of space as a conventional (mechanical) needle loom. It is often also possible to convert an existing mechanical needle loom to waterjet needling by adding a unit.

[0054] The invention is explained below with reference to figures. The invention is not limited to the embodiments shown in the figures.

[0055] Figures 1 to 3 each show a needling device according to various aspects of the invention.

[0056] Figure 1 shows a needling device 10 for carrying out a method for producing a felt according to aspects of the present invention. A series of rollers 6 are provided for guiding a material web 1, 3. Some of these rollers 6 can be provided with drives. The basic structure 1 can initially be inserted into the needling device 10 as the material web. During the course of the method, this is converted into a basic structure with a nonwoven layer 3 or a finished press felt. In this embodiment, the arrangement of the first nonwoven layer 2 on the basic structure 1 is carried out exemplarily by unwinding the first nonwoven layer 2 from a roll and depositing it onto the basic structure 1 by means of a feed roller 9. However, the arrangement can also be realized in other ways.

[0057] After the first nonwoven layer 2 has been arranged, a mechanical needling unit 4 is provided in the needling device 10. This unit serves to needling the first nonwoven layer 2 to the base structure 1 in a first needling process. This mechanical needling attaches the first nonwoven layer 2 to the base structure 1. The base structure with the resulting nonwoven overlay 3 is then guided directly or via further guide rollers 6 to a water jet needling unit 5. There, the first nonwoven layer 2 is further needled to the base structure 1 in a second needling process. The water jets can be operated at a pressure of up to 400 bar, preferably between 20 bar and 250 bar.

[0058] In addition to the water jet nozzles, the water jet needling unit 5 can also have a support element 7 for supporting the material web during needling.

[0059] Needling, especially waterjet needling, can be continued until the material density of the nonwoven layer reaches at least 60%, particularly between 70% and 90%. (The material density is determined using a sample subjected to a pressure of 5 MPa.)

[0060] The needling device 10 in Figure 2 corresponds to the variant in Figure 1 except that a further nonwoven layer 2b is arranged after the first nonwoven layer 2. The further nonwoven layer 2b is arranged on the first nonwoven layer 2 before the mechanical needling unit 4 and is then needled together with it.

[0061] Figure 3 shows a further needling device 10. Similar to Figure 1, here the first nonwoven layer 2 is arranged on the base structure 1 before the mechanical needling unit 4. In addition, a further nonwoven layer 2b is provided. However, in contrast to Figure 2, this further nonwoven layer 2b is only arranged after the mechanical needling unit 4 and is needled together with the base structure 1 and the first nonwoven layer 2 only in the water jet needling unit 5. In the water jet needling unit 5 shown in Figure 3, the support element 7 is designed, for example, as a support roller 8.

[0062] The devices shown in Figures 1 and 3 are intended to give an impression that the inventive idea of ​​combining mechanical needling and water jet needling can be realized in a wide variety of ways.

[0063] List of reference symbols

[0064] 1 Basic structure

[0065] 2 first fleece layer 2b further fleece layer

[0066] 3 Basic structure with fleece layer

[0067] 4 mechanical needling unit

[0068] 5 Water jet needling unit

[0069] 6 Guide roller 7 Support element

[0070] 8 support roller

[0071] 9 Feed roller

[0072] 10 needling device

Claims

Patent claims (combination) 1 . Method for producing a felt, in particular a press felt for a paper machine, the method comprising the following steps: a. Providing a basic structure, in particular a woven basic structure b. Arranging at least one first nonwoven layer on one side of the basic structure c. Needling the first nonwoven layer to the basic structure in a first needling d. Needling the first nonwoven layer to the basic structure in a second needling, to form a nonwoven layer, the first needling being carried out by means of mechanical needling and the second needling being carried out by means of water jet needling, and the following steps are also carried out between steps c.) and d.): b1) Arranging at least one further nonwoven layer c1) Needling the further nonwoven layer to the basic structure in a mechanical needling. And / or after step c. at least one further nonwoven layer is arranged, wherein the at least one further nonwoven layer is needled together with the first nonwoven layer to form a nonwoven overlay in step d.

2. Method according to claim 1, characterized in that in step b. one or more further nonwoven layers are arranged, and the further nonwoven layer or the further nonwoven layers together with the The first nonwoven layer is needled to the basic structure in steps c. and d. to form a nonwoven layer.

3. Method according to one of the preceding claims, characterized in that steps c. and / or d. are carried out several times.

4. Method according to one of the preceding claims, characterized in that step c. takes place at least partially before step d.

5. Method according to one of the preceding claims, characterized in that the needling in step d. is carried out until the material density of the nonwoven layer is at least 60%, in particular between 70% and 90%.

6. Method according to one of the preceding claims, characterized in that at least one nonwoven layer consists of more than 50%, in particular completely, of coarse nonwoven fibers with a titre of at least 67 dtex, in particular 100 dtex and more.

7. Method according to one of the preceding claims, characterized in that in step d. the water jets are operated at a maximum pressure of 400 bar, preferably between 20 bar and 250 bar.

8. Method according to one of the preceding claims, characterized in that the water jet needling in step d. is not carried out uniformly across the width direction of the felt, so that in particular the material density of the nonwoven layer varies in the width direction of the felt.

9. Needling device for carrying out a method according to one of the preceding claims, wherein the device comprises means for Guiding a material web, as well as a mechanical needling unit and a water jet needling unit.

10. Needling device according to claim 9, characterized in that the water jet needling unit is arranged behind the mechanical needling unit in the running direction of the material web.

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