US20230020186A1

US20230020186A1 - Method for producing a spunbond nonwoven

Info

Publication number: US20230020186A1
Application number: US17/785,481
Authority: US
Inventors: Ibrahim Sagerer-Foric
Original assignee: Lenzing AG
Current assignee: Lenzing AG
Priority date: 2019-12-17
Filing date: 2020-12-11
Publication date: 2023-01-19
Also published as: PT4077789T; ES2987702T3; CN114787440A; JP2023506903A; CN114787440B; EP4077789B1; EP4077789A1; TW202140884A; WO2021122379A1; KR20220111706A; FI4077789T3; BR112022011701A2

Abstract

The invention relates to a process (100) for the production of spunbonded nonwoven (1) wherein a spinning mass (2) is extruded through the nozzle holes (4) of at least one spinneret (3, 30) to form filaments (5, 50), the filaments (5, 50) are drawn in the extrusion direction and deposited on a first conveying device (9) to form the spunbonded nonwoven (1), and wherein the spunbonded nonwoven (1) is subjected to at least one washing (10). For increasing the throughput of the process without losses of quality, it is suggested that the spunbonded nonwoven (1) is subjected to the washing (10) at least partially on a perforated second conveying device (13) with a lower conveying speed with respect to that of the first conveying device (9), wherein the spunbonded nonwoven (1) is sprayed with washing liquid during the washing (10) and the washing liquid is discharged at least partially through the perforated second conveying device (13).

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a process for the production of spunbonded nonwoven wherein a spinning mass is extruded through the nozzle holes of at least one spinneret to form filaments, the filaments are drawn in the extrusion direction and deposited on a first conveying device to form the spunbonded nonwoven, and wherein the spunbonded nonwoven is subjected to at least one washing.

Prior Art

The production of spunbonded nonwovens and, respectively, nonwoven fabrics by the spunbond process, on the one hand, and by the meltblown process, on the other hand, is known from the prior art. In the spunbond process (e.g., GB 2 114 052 A or EP 3 088 585 A1), the filaments are extruded through a nozzle and pulled off and drawn by a drawing unit located underneath. By contrast, in the meltblown process (e.g., U.S. Pat. No. 5,080,569 A, 4,380,570 A or 5,695,377 A), the extruded filaments are entrained and drawn by hot, fast process air as soon as they exit the nozzle. In both technologies, the filaments are deposited in a random orientation on a deposit surface, for example, a perforated conveyor belt, to form a nonwoven fabric, are carried to post-processing steps and finally wound up as nonwoven rolls.
It is also known from the prior art to produce cellulosic spunbonded nonwovens according to the spunbond technology (e.g., U.S. Pat. No. 8,366,988 A) and according to the meltblown technology (e.g., U.S. Pat. Nos. 6,358,461 A and 6,306,334 A). A lyocell spinning mass is thereby extruded and drawn in accordance with the known spundbond or meltblown process, however, prior to the deposition into a nonwoven, the filaments are additionally brought into contact with a coagulant in order to regenerate the cellulose and produce dimensionally stable filaments. The wet filaments are finally deposited in a random orientation as a nonwoven.
The advantages of the process may become evident especially in case of a washing. For the manufacture of thermoplastic spunbonded nonwovens, a washing is generally not necessary, as so-called “dry” spinning processes are involved in which any solvents that may be used evaporate by themselves from the spunbonded nonwoven downstream of the calender or dryer. In the simplest case, the spunbonded nonwoven is wound up into rolls directly after the extrusion and the deposition in such processes. However, in case of spinning processes that require a washing, such as for cellulosic spunbonded nonwovens, the throughput is usually limited by the duration of the washing, since the spunbonded nonwovens have to achieve certain dwell times in the washing so that the solvent can be washed out. Especially in the production of spunbonded nonwovens and, respectively, nonwoven fabrics with very low weights per unit area, the above-mentioned processes exhibit the disadvantage that increasing the throughput in a cost-efficient way and without impairing the quality of the spunbonded nonwovens is possible only to a very limited extent, since, in particular, very long washing systems have to be employed in order to achieve the same throughput and/or the same quality as with higher weights per unit area.
Since the spinning masses in cellulosic spunbond technologies merely have pulp contents of 3 to 17%, an amount of spinning mass larger than in the production of thermoplastic spunbonded nonwovens is required for achieving a comparable throughput. As a result, more spinnerets have to be provided for the same productivity as compared to thermoplastic spunbond systems or, respectively, a greater spinning mass throughput per spinneret must be achieved. The spunbonded nonwovens are then washed, solidified, dried and wound up. In WO 2018/071928 A1, a process for washing cellulosic spunbonded nonwovens is described. Therein, the relationship between dwell time, effectiveness of the washing and impact on the costs and the duration, respectively, of the washing is explained. Especially with high throughputs, which are important for the profitability of the process, and with low weights per unit area of up to 10 g/m², which are desirable for many applications, high conveying speeds are achieved. In this way, both the requirement in terms of the effectiveness of the washing and the necessary duration of the washing and, accordingly, the expenditure for mechanical and systems engineering and the costs for the system and the very long building are increased.
From US 2005/0056956 A1, a process for the production of cellulosic spunbonded nonwovens is known in which the filaments are deposited on a conveyor drum, hydroentangled, pressed and then deposited in the form of loops in a coagulation bath at a lower conveying speed. Subsequently, the loops are dissolved, and the spunbonded nonwoven is dried and wound up. However, such a method has several disadvantages when it is used in commercial production plants. For example, at high production speeds, the rotational speed of the deposit drum and the press rollers thus becomes very high, which, in the wet state of cellulosic spunbonded nonwovens, causes them to stick to the drum surface. This leads to tears and defects in the spunbonded nonwoven, or, respectively, the spunbonded nonwoven might wrap around the deposit drum and the press rollers, which is very disadvantageous for economic and safety reasons. In addition, the hydroentanglement of the spunbonded nonwoven immediately after the filaments have been deposited causes the freshly extruded filaments to be pressed and partly sucked into the drum under vacuum. Detaching the spunbonded nonwoven from the drum is thereby additionally hampered, which leads to further tears and defects in the spunbonded nonwoven. In addition, the structural changes introduced into the spunbonded nonwoven during the hydroentanglement are completely or partially removed by the subsequent coagulation baths and the associated swelling of the spunbonded nonwoven. A specific adjustment of the mechanical and structural properties of the produced spunbonded nonwoven is thus hampered significantly. In addition, the spunbonded nonwoven arranged in loops can be transported through the coagulation bath only at low conveying speeds, since, due to the buoyancy of the spunbonded nonwoven in the coagulation bath, a major resistance acts against the spunbonded nonwoven. Consequently, an increase in throughput is not possible without a drastic loss of quality.

DISCLOSURE OF THE INVENTION

Therefore, the invention has the object of improving a process for the production of spunbonded nonwoven of the initially mentioned type in such a way that the throughput of the process can be increased in a cost-effective and simple manner without impairing the quality of the spunbonded nonwoven.
The object is achieved in that the spunbonded nonwoven is subjected to the washing at least partially on a perforated second conveying device with a lower conveying speed with respect to that of the first conveying device, wherein the spunbonded nonwoven is sprayed with washing liquid during the washing and the washing liquid is discharged at least partially through the perforated second conveying device.
If the spunbonded nonwoven is subjected to the washing at least partially on a second conveying device with a lower conveying speed with respect to that of the first conveying device, i.e., if the conveying speed of the spunbonded nonwoven is reduced during at least part of the washing in comparison to the conveying speed of the spunbonded nonwoven before the washing, the dwell time of the spunbonded nonwoven in the washing can be increased in a simple manner without providing a cost-intensive longer washing. In this way, a spunbonded nonwoven with a predefined weight per unit area can be obtained, with a consistent spinning mass throughput of the spinneret and an appropriate conveying speed during the deposition of the spunbonded nonwoven, whereby the quality of the obtained spunbonded nonwoven, in particular its residual solvent contents after washing, is improved.
Alternatively, also by increasing the spinning mass throughput of the spinneret and adjusting the conveying speed appropriately when the spunbonded nonwoven is being deposited, a spunbonded nonwoven with the same weight per unit area and consistent quality can be obtained with a higher throughput.
With the process according to the invention, the conveying speed, which, as illustrated above, results from the spinning mass throughput and the desired weight per unit area, can thus be completely decoupled from the conveying speed of the washing. As a result, the duration of the washing, the length of the system or, respectively, the building and thus also the costs for setting up and operating a system for implementing the process can be reduced considerably.
If the spunbonded nonwoven is further sprayed with washing liquid during the washing and the washing liquid is discharged at least partially through the perforated second conveying device, the reliability and efficiency of the washing can be enhanced further.
The assisted transport of the spunbonded nonwoven through the second conveying device during the washing can, in fact, ensure a reliable and efficient washing even at high conveying speeds, since neither buoyancy nor water resistance will act on the spunbonded nonwoven, in comparison to a bath washing. In fact, such a buoyancy or, respectively, water resistance in a washing bath may lead to entanglements or agglutinations in the spunbonded nonwoven and thus render the spunbonded nonwoven unusable at high conveying speeds ranging approximately from 100 m/min to 500 m/min. This is the case especially if the spunbonded nonwoven has a lower conveying speed within the washing than before the washing, since the lower conveying speed results in an excess length of the spunbonded nonwoven in the washing and, due to the spraying with washing liquid, the overly long spunbonded nonwoven can be kept reliably on the second conveying device.
By directly discharging the washing liquid via the perforated second conveying device, on the one hand, bloating and, on the other hand, excessive swelling of the spunbonded nonwoven can be avoided. A spunbonded nonwoven completely soaked in washing liquid can, in fact, absorb 10 to 15 times as much liquid, based on its dead weight. However, since spunbonded nonwovens that have never been dried have very low strengths, such a complete soaking of the spunbonded nonwoven will lead to a further structural weakening and thus to increased tears, whereby a reliable further transport is prevented. Hence, due to the washing according to the invention, the throughput of the process can be enhanced without any negative impacts on the quality of the spunbonded nonwoven that is produced.
After the washing, the spunbonded nonwoven may preferably have a liquid content of less than 5 kg/kg, based on its dry weight. In a further embodiment, the liquid content may be less than 4 kg/kg, or, in yet another preferred embodiment, less than 3 kg/kg. Due to the low liquid content, the internal structure and the stability of the spunbonded nonwoven can be preserved, whereby a transport even at high conveying speeds remains possible.
For the purposes of the present invention, it is noted that, within the meaning of the present disclosure, a spunbonded nonwoven is understood to be a nonwoven fabric which is formed directly by depositing extruded filaments, wherein the filaments are essentially continuous filaments and are deposited in a random orientation to form the spunbonded nonwoven.
A conveying device within the meaning of the present invention may be understood as any device which is suitable for conveying or, respectively, transporting the spunbonded nonwoven at a specific conveying speed. Such a conveying device may be, for example, a conveyor belt, a conveyor drum, conveyor rollers or the like. In a preferred embodiment of the invention, the conveying devices are designed as conveyor belts.
The above-mentioned advantages can be achieved especially if the conveying speed of the second conveying device is reduced by a factor of between 1 and 1000 with respect to the first conveying device. For example, with a factor of 2, the throughput can be doubled with the weight per unit area remaining consistent and the duration of the washing remaining consistent, or the effectiveness of the washing can be enhanced considerably. It has been shown, for example, that doubling the dwell time in the washing increases the efficiency in an over-linear fashion and, for example, leads to a reduction in solvent residues in the finished spunbonded nonwoven by a factor of 4 to 8. Prior to the washing, the conveying speed is preferably reduced by a factor of between 1 and 100, or particularly preferably by a factor of between 1 and 25.
In addition, the reproducibility of the process can be improved further if the spunbonded nonwoven is deposited in loops on the second conveying device. In this way, it is namely particularly easy to procedurally respond to the reduction in the conveying speed within the washing. In doing so, the loops can have essentially parallel, superimposed sections on the spunbonded nonwoven, which enable efficient washing of the spunbonded nonwoven and can be pulled apart after the washing without any damage. Specifically, the loops can be pulled apart by a faster conveying device after the washing.
The spunbonded nonwoven can preferably be deposited on the second conveying device directly after the spunbonded nonwoven has been deposited and formed on the first conveying device. In this context, “directly after depositing” is understood to mean that, between the deposition and the formation of the spunbonded nonwoven on the first conveying device and the deposition on the second conveying device, no further treatment steps of the spunbonded nonwoven on the first conveying device are envisaged.
In doing so, the spunbonded nonwoven can be deposited on the second conveying device preferably before washing, particularly preferably directly before washing. Hence, a reduction in the conveying speed of the spunbonded nonwoven occurs before washing or, respectively, directly before washing. In this context, “directly before washing” is understood to mean that, before washing, no further treatment steps of the spunbonded nonwoven on the second conveying device are envisaged. Thus, the spunbonded nonwoven may preferably undergo the entire washing on the second conveying device.
Accordingly, between the deposition and the formation of the spunbonded nonwoven on the first conveying device and the washing on the second conveying device, preferably no further treatment steps of the spunbonded nonwoven may be envisaged.
In addition, after washing, the spunbonded nonwoven may undergo further treatment steps on a third conveying device at a conveying speed that is higher with respect to that of the second conveying device. For this purpose, the spunbonded nonwoven can be deposited on the third conveying device, whereby—as described above—the excess length of the spunbonded nonwoven or, respectively, any loops formed therein can be untangled, and the spunbonded nonwoven can be treated further again at a higher conveying speed. In doing so, the third conveying device preferably has essentially the same conveying speed as the first conveying device.
If the conveying speed of the third conveying device is again increased by a factor of between 1 and 1000 with respect to the second conveying device, a particularly versatile process can be provided, which permits direct further processing of the spunbonded nonwoven after the washing at a higher conveying speed. Thus, after washing, the spunbonded nonwoven can preferably be accelerated back to the same conveying speed as before the washing and may undergo further treatment steps. The conveying speed of the third conveying device is preferably increased by a factor of between 1 and 100, particularly preferably by a factor of between 1 and 25, with respect to the second conveying device.
The advantages mentioned above can thus be achieved in particular if the spunbonded nonwoven is subjected to hydroentanglement and/or drying after the washing. In fact, the hydroentanglement can, in this case, preferably be performed at the original conveying speed of the spunbonded nonwoven, as said speed does not depend on prolonged dwell times as compared to the washing.
In addition, providing hydroentanglement after the washing allows a particularly reliable control of the structural and internal properties of the spunbonded nonwoven. For example, in the course of hydroentanglement, patterns or, respectively, perforations that remain in the finished spunbonded nonwoven can be imprinted permanently.
After the hydroentanglement, the spunbonded nonwoven may also be subjected to drying in order to obtain a finished spunbonded nonwoven. The spunbonded nonwoven that has been treated to completion can then optionally be wound up into rolls in a winding device.
The efficiency of the washing can be improved further if the washing is a multi-stage countercurrent washing. Namely, in the countercurrent washing, the washing liquid used for washing, in particular water, circulates in several washing stages, wherein fresh washing liquid is supplied at the end of the washing and is discharged via the perforated second conveying device and is passed along successively in the same manner to the upstream washing stages, and wherein the spent washing liquid is discharged at the beginning of the washing.
The throughput of the process can be increased further if the spinning mass is furthermore extruded into filaments through at least a first spinneret and a second spinneret, wherein the filaments of the first spinneret are deposited on the first conveying device to form a first spunbonded nonwoven and the filaments of the second spinneret are deposited on the first conveying device to form a second spunbonded nonwoven, wherein the filaments of the second spinneret are deposited on the first conveying device to form the second spunbonded nonwoven over the first spunbonded nonwoven in order to obtain a multi-layered spunbonded nonwoven.
In fact, if the filaments of the second spinneret are deposited on the first conveying device to form the second spunbonded nonwoven over the first spunbonded nonwoven in order to obtain a multi-layered spunbonded nonwoven, the throughput of the process can be increased in a simple manner, since at least two spinnerets are provided for the simultaneous formation of at least two spunbonded nonwovens, but the multi-layered spunbonded nonwoven formed thereby can be processed further with the existing means instead of with a single spunbonded nonwoven. The second spinneret is preferably located downstream of the first spinneret in the conveying direction of the first conveying device.
The multi-layered spunbonded nonwoven formed thereby consists of the first and the second spunbonded nonwovens, with the second spunbonded nonwoven being arranged above the first one. The first and the second spunbonded nonwovens can, in this case, be interconnected in such a way (for example, by adhesion) that the multi-layered spunbonded nonwoven forms a unit which may undergo further process steps, but can be unravelled into the first and the second spunbonded nonwovens essentially without causing any structural damage to them.
If the multi-layered spunbonded nonwoven is unravelled into at least the first and the second spunbonded nonwovens in a subsequent step, at least two independent spunbonded nonwovens can again be obtained in the course of the process. A cost-efficient process for the production of spunbonded nonwoven with an increased throughput can thus be created.
Likewise, the spinning mass can also be extruded into filaments through a third and further spinnerets and the filaments can be drawn, in each case, in the extrusion direction, wherein the filaments of the third spinneret are deposited on the first conveying device to form a third spunbonded nonwoven over the second spunbonded nonwoven in order to obtain the multi-layered spunbonded nonwoven, or, respectively, the filaments of the further spinnerets are deposited on the first conveying device to form further spunbonded nonwovens over the respective preceding spunbonded nonwoven in order to obtain the multi-layered spunbonded nonwoven.
Such a multi-layered spunbonded nonwoven may comprise a plurality of spunbonded nonwovens, which can be separated from each other in a subsequent process step.
The aforementioned advantages of the process can become apparent especially if the multi-layered spunbonded nonwoven is subjected to at least one treatment step before it is separated into at least the first and the second spunbonded nonwovens. In this way, a joint treatment of the first and the second spunbonded nonwovens may, in fact, occur in the form of the multi-layered spunbonded nonwoven, and thus the throughput of the process can be increased considerably in comparison to the separate treatment of the spunbonded nonwovens.
This can become apparent especially if the at least one treatment step of the multi-layered spunbonded nonwoven is the washing according to the invention on the second conveying device with a conveying speed that is reduced with respect to that of the first conveying device. By means of the process according to the invention with a joint washing of the first and the second spunbonded nonwovens in the multi-layered spunbonded nonwoven, the duration of the washing can, in fact, be significantly reduced further and, respectively, the throughput can be increased.
The process according to the invention can be characterized by high flexibility if the spunbonded nonwoven is a multi-layered spunbonded nonwoven, wherein at least two consecutively arranged spinnerets are provided so that the filaments extruded from the respective spinnerets each form a layer of spunbonded nonwoven, which are deposited one on top of the other in such a way that the multi-layered spunbonded nonwoven is produced. The multi-layered spunbonded nonwoven can then still be washed reliably at a reduced conveying speed, using the process according to the invention.
The reliability of the process can be increased further if the filaments are drawn by means of a drawing air stream after they have been extruded from the spinneret. This allows the extrusion and drawing conditions of the filaments to be controlled specifically and, hence, the internal properties of the spunbonded nonwoven to be adapted. In doing so, the drawing air stream is directed from the respective spinneret onto the extruded filaments.
In particular, the drawing air stream can have a pressure ranging from 0.05 bar to 5 bar, preferably from 0.1 bar to 3 bar, particularly preferably from 0.2 bar to 1 bar. In particular, the drawing air stream can furthermore have a temperature ranging from 20° C. to 200° C., preferably from 60° C. to 160° C., particularly preferably from 80° C. to 140° C.
The process according to the invention may distinguish itself especially in terms of the production of cellulosic spunbonded nonwovens, with the spinning mass being a lyocell spinning mass, i.e., a solution of cellulose in a direct solvent for cellulose.
Such a direct solvent for cellulose is a solvent in which the cellulose is present in a state of having been dissolved in a non-derivatized form. Preferably, this may be a mixture of a tertiary amine oxide, such as NMMO (N-methylmorpholine-N-oxide), and water. Alternatively, however, also ionic liquids, or mixtures with water, are, for example, suitable as direct solvents.
In this case, the content of cellulose in the spinning mass may range from 3% by weight to 17% by weight, in preferred embodiment variants from 5% by weight to 15% by weight, and in particularly preferred embodiment variants from 6% by weight to 14% by weight.
In the production of cellulosic spunbonded nonwovens, numerous improvements and advantages with regard to the profitability of the production plant, the operation of the plant and the product quality arise as a result of the process according to the invention. Since several loops offset in parallel one on top of the other can be washed at the same time, the conveying speed of the spunbonded nonwoven can be reduced considerably during the washing. Due to the lower conveying speed, both the costs and the complexity of the production plant are reduced.
Surprisingly, it has been shown that the spunbonded nonwoven deposited at a reduced conveying speed in loops placed in parallel one on top of the other can be washed with greater efficiency than a spunbonded nonwoven with a higher and non-reduced conveying speed. Even after a multi-stage countercurrent washing, the loops can be dissolved without being destroyed and the spunbonded nonwoven can be accelerated back to the original conveying speed.
Even with low weights per unit area of up to 10 g/m²it has been shown that the spunbonded nonwovens are stable enough for being deposited in loops, being washed at a reduced speed and then being accelerated again in order to thereupon be optionally solidified, dried and wound up in further steps at the original conveying speed.
The throughput of cellulose per spinneret may preferably range between 5 kg/h per metre of spinneret length and 500 kg/h per metre of spinneret length.
The advantages according to the invention can become apparent especially if the weight per unit area of the spunbonded nonwoven is between 5 g/m²(gsm) and 500 g/m², preferably from 10 g/m²to 250 g/m², particularly preferably from 15 g/m²to 100 g/m².
The conveying speed of the spunbonded nonwoven when it is being deposited or, respectively, the conveying speed of the first conveying device may preferably range between 1 m/min and 2000 m/min, preferably from 10 m/min to 1000 m/min, particularly preferably from 15 m/min to 500 m/min.
In addition, the internal structure of the spunbonded nonwoven can be controlled reliably if the filaments that have been extruded from the spinneret and drawn are partly coagulated.
For this purpose, a coagulation air stream comprising a coagulation liquid for an at least partial coagulation of the filaments can be assigned to the spinneret, whereby the internal structure of the spunbonded nonwoven can be controlled specifically. In this case, a stream of coagulation air can preferably be a fluid containing water and/or a fluid containing coagulant, for example, gas, mist, vapour, etc.
A particularly reliable coagulation of the extruded filaments can thereby be achieved if the coagulation liquid is a mixture of water and a direct solvent for cellulose. In particular, the coagulation liquid may be a mixture of demineralized water and 0% by weight to 40% by weight of NMMO, preferably 10% by weight to 30% by weight of NMMO, particularly preferably 15% by weight to 25% by weight of NMMO.
The amount of coagulation liquid may, in this case, preferably range from 50 l/h to 10,000 l/h, furthermore preferably from 100 l/h to 5,000 l/h, particularly preferably from 500 l/h to 2,500 l/h per metre of coagulation nozzle.
With the spinnerets of the process according to the invention or, respectively, the device according to the invention, single-row slot nozzles, multi-row needle nozzles or preferably column nozzles with lengths of 0.1 m to 6 m as known from the prior art (U.S. Pat. Nos. 3,825,380 A, 4,380,570 A, WO 2019/068764 A1) may preferably be used.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiment variants of the invention are described in more detail below with reference to a drawing. FIG. 1 shows a schematic illustration of the process and a device according to a first embodiment variant.

WAYS OF IMPLEMENTING THE INVENTION

FIG. 1 shows a schematic illustration of the process 100 according to a first embodiment variant for the production of cellulosic spunbonded nonwoven 1 and a corresponding device 200 by means of which the process 100 is performed. In a first process step, a spinning mass 2 is produced from a cellulosic raw material and supplied to a spinneret 3 of the device 200. The cellulosic raw material for producing the spinning mass 2, which is not shown in further detail in the FIGURES, can be a conventional pulp made of wood or other plant-based starting materials. However, it is also conceivable that the cellulosic raw material consists of production waste from the production of spunbonded nonwoven or recycled textiles. In this case, the spinning mass 2 is a solution of cellulose in NMMO and water, with the cellulose content in the spinning mass 2 ranging between 3% by weight and 17% by weight.
The spinning mass 2 is then extruded in the spinneret 3 through a plurality of nozzle holes 4 to form the filaments 5. By supplying drawing air 6 to a drawing unit in the spinneret 3, the filaments 5 are drawn by means of a drawing air stream as they exit from the spinneret 3. In doing so, the drawing air 6 can emerge from openings in the spinneret 3 between the nozzle holes 4 and can be directed as a drawing air stream directly onto the extruded filaments 5, which is not shown in further detail in the FIGURES. After or already in the course of drawing, the extruded filaments 5 are charged with a coagulation air stream 7, which is generated by a coagulation device 8. The coagulation air stream 7 usually comprises a coagulation liquid, for example, in the form of vapour, mist, etc. Due to the contact of the filaments 5 with the coagulation air stream 7 and the coagulation liquid contained therein, the filaments 5 are coagulated at least partly, which, in particular, reduces adhesions between the individual extruded filaments 5. The filaments 5 that have been drawn and precipitated at least partly are then deposited in a random orientation on a first conveyor belt 9 as the first conveying device 9 to form the spunbonded nonwoven 1. By means of the conveyor belt 9, the spunbonded nonwoven 1 is then passed on to further treatment steps 10, 11, 12. In doing so, the spunbonded nonwoven 1 is subsequently subjected to at least one washing 10.
In order to increase the dwell time of the spunbonded nonwoven 1 in the washing 10, the spunbonded nonwoven 1 is deposited directly before the washing 10 on a second conveyor belt 13 as a second conveying device 13, which has a reduced conveying speed with respect to the first conveying device 9. The conveying speed of the spunbonded nonwoven 1 within the washing 10 is thus reduced in comparison to the conveying speed of the spunbonded nonwoven 1 before the washing 10, that is, while the filaments 5 are being deposited on the first conveyor belt 9. In doing so, the conveying speed is preferably reduced by a factor of between 1 and 1000. In another embodiment variant, the factor is between 1 and 100, and in yet another embodiment variant between 1 and 25. In order to accommodate the difference in the conveying speed between the first conveyor belt 9 and the second conveyor belt 13 in the spunbonded nonwoven 1, the spunbonded nonwoven 1 is deposited in loops 14 on the second conveyor belt 13. The spunbonded nonwoven 1 placed in loops 14 is then subjected to the washing 10, wherein it is essentially freed from solvent residues from the spinning mass 2.
After the washing 10, the spunbonded nonwoven 1 is deposited on a third conveyor belt 15, which has a higher conveying speed with respect to the second conveyor belt 13. In doing so, the third conveyor belt 15 preferably has the same conveying speed as the first conveyor belt 9, as a result of which the loops 14 are again pulled out completely. In a further embodiment variant, which is not shown in further detail, the third conveyor belt 15 can also have another conveying speed, which is different from the first conveyor belt 9 and which is increased by a factor of between 1 and 1000, preferably between 1 and 100, particularly preferably between 1 and 25, with respect to the second conveyor belt 13. On the third conveyor belt 15, the spunbonded nonwoven 1 is subjected to hydroentanglement 11, which is able to further adjust the internal structure of the spunbonded nonwoven 1. Besides, in the course of hydroentanglement 11, additional perforation patterns, embossing patterns or the like can be introduced into the spunbonded nonwoven 1, but this was not shown in further detail in the FIGURES.
Finally, the spunbonded nonwoven 1 is subjected to drying 12 in order to obtain a finished spunbonded nonwoven 1, wherein the process 100 is concluded by an optional winding 16 and/or packing process.
In a further embodiment variant, which is only indicated in the FIGURES, the device 100 or, respectively, the process 200 may have at least a first spinneret 3 and a second spinneret 30, with the spinning mass 2 being extruded simultaneously through the first spinneret 3 and the second spinneret 30 to form the filaments 5, 50. In doing so, the filaments 5, 50 are each drawn in the extrusion direction and coagulated at least partly, wherein the filaments 5 of the first spinneret 3 are deposited on the conveyor belt 9 to form a first spunbonded nonwoven 1 and the filaments 50 of the second spinneret 30 are deposited on the conveyor belt 9 to form a second spunbonded nonwoven. The filaments 50 of the second spinneret 30 are deposited on the conveyor belt 9 to form the second spunbonded nonwoven over the first spunbonded nonwoven 1 in order to obtain a multi-layered spunbonded nonwoven, which is not shown in further detail in the FIGURES.
Preferably, the first spunbonded nonwoven 1 and the second spunbonded nonwoven undergo the washing 10 jointly in the form of the multi-layered spunbonded nonwoven, wherein the multi-layered spunbonded nonwoven is deposited in loops 14 on the second conveyor belt 13 at a conveying speed that is lower with respect to that of the first conveyor belt 9. Preferably, the multi-layered spunbonded nonwoven can then be unravelled into at least the first spunbonded nonwoven 1 and the second spunbonded nonwoven in a step following the washing 10, with the first spunbonded nonwoven 1 and the second spunbonded nonwoven separately undergoing further steps, such as hydroentanglement 11 and/or drying 12, after unravelling.
Alternatively, the first spunbonded nonwoven 1 and the second spunbonded nonwoven may undergo the hydroentanglement 11 also jointly, whereby they are interconnected permanently to form the multi-layered spunbonded nonwoven.
Likewise, the first spunbonded nonwoven 1 and the second spunbonded nonwoven may each have different internal properties, for example, a different weight per unit area, and thus form a multi-layered spunbonded nonwoven with properties variable in cross-section.
In a further embodiment variant, which is not illustrated in the FIGURES, the first conveying device 9 is a conveyor drum and the second conveying device 13 is a conveyor belt.
In yet another embodiment, both the first conveying device 9 and the second conveying device 13 are a conveyor drum.

Claims

1. A process for the production of spunbonded nonwoven (1) wherein a spinning mass (2) is extruded through the nozzle holes (4) of at least one spinneret (3, 30) to form filaments (5, 50), the filaments (5, 50) are drawn in the extrusion direction and deposited on a first conveying device (9) to form the spunbonded nonwoven (1), and wherein the spunbonded nonwoven (1) is subjected to at least one washing (10), characterized in that the spunbonded nonwoven (1) is subjected to the washing (10) at least partially on a perforated second conveying device (13) with a lower conveying speed with respect to that of the first conveying device (9), wherein the spunbonded nonwoven (1) is sprayed with washing liquid during the washing (10) and the washing liquid is discharged at least partially through the perforated second conveying device (13).

2. A process according to claim 1, characterized in that the conveying speed of the second conveying device (13) is reduced by a factor of between 1 and 1000, in particular by a factor of between 1 and 100, particularly preferably by a factor of between 1 and 25, with respect to the first conveying device (9).

3. A process according to claim 1 or 2, characterized in that the spunbonded nonwoven (1) is deposited in loops (14) on the second conveying device (13).

4. A process according to any of claims 1 to 3, characterized in that, after washing (10), the spunbonded nonwoven (1) is subjected to further treatment steps (11, 12) on a third conveying device (15) at a conveying speed that is higher with respect to that of the second conveying device (13).

5. A process according to claim 4, characterized in that the conveying speed of the third conveying device (15) is increased by a factor of between 1 and 1000, in particular by a factor of between 1 and 100, particularly preferably by a factor of between 1 and 25, with respect to the second conveying device (13).

6. A process according to claim 4 or 5, characterized in that the third conveying device (15) has essentially the same conveying speed as the first conveying device (9).

7. A process according to any of claims 1 to 6, characterized in that the spunbonded nonwoven (1) is subjected to hydroentanglement (11) and/or drying (12) after the washing (10).

8. A process according to any of claims 1 to 7, characterized in that the washing (10) is a multi-stage countercurrent washing.

9. A process according to any of claims 1 to 8, characterized in that the spunbonded nonwoven (1) is deposited on the second conveying device (13) directly after it has been deposited and formed on the first conveying device (9).

10. A process according to any of claims 1 to 9, characterized in that the spunbonded nonwoven (1) is deposited on the second conveying device (13) directly before the washing (10).

11. A process according to any of claims 1 to 10, characterized in that the spinning mass (2) is extruded into filaments (5, 50) through at least a first spinneret (3) and a second spinneret (30), wherein the filaments (5) of the first spinneret (3) are deposited on the first conveying device (9) to form a first spunbonded nonwoven (1) and the filaments (50) of the second spinneret (30) are deposited on the first conveying device (9) to form a second spunbonded nonwoven, wherein the filaments (50) of the second spinneret (30) are deposited on the first conveying device (9) to form the second spunbonded nonwoven over the first spunbonded nonwoven (1) in order to obtain a multi-layered spunbonded nonwoven.

12. A process according to claim 11, characterized in that the multi-layered spunbonded nonwoven is unravelled into at least the first spunbonded nonwoven (1) and the second spunbonded nonwoven in a subsequent step, particularly after the washing (10).

13. A process according to any of claims 1 to 12, characterized in that the spunbonded nonwoven (1) is a cellulosic spunbonded nonwoven (1) and the spinning mass (2) is a solution of cellulose in a direct solvent, particularly a tertiary amine oxide.

14. A process according to any of claims 1 to 13, characterized in that the filaments (5, 50) are coagulated at least partly after the extrusion from the spinneret (3, 30), whereby in particular a coagulation air stream (7) comprising a coagulation liquid is assigned to the spinneret (3, 30) for the at least partial coagulation of the filaments (5, 50).

15. A process according to any of claims 1 to 14, characterized in that the coagulation liquid is a mixture of water and the direct solvent for cellulose, particularly a tertiary amine oxide.