Method for producing spunbonded fabric

Description

[0001] The invention relates to a method for producing spunbond nonwoven fabric in which a spinning mass is extruded through a plurality of nozzle holes of at least one spinneret to form filaments and the filaments are each stretched in the extrusion direction, wherein the filaments are deposited on a perforated conveying device to form a spunbond nonwoven fabric and wherein the nozzle holes of the spinneret are arranged along a main axis oriented in a transverse direction to the conveying direction of the conveying device, so that the spunbond nonwoven fabric formed on the conveying device extends in this transverse direction. State of the art

[0002] The production of spunbond nonwovens is known from the prior art, using both spunbond and meltblown processes. In the spunbond process (e.g., GB 2 114 052 A or EP 3 088 585 A1), the filaments are extruded through a die and drawn off and stretched by a drawing unit below. In the meltblown process (e.g., US 5,080,569 A, US 4,380,570 A, or US 5,695,377 A), the extruded filaments are drawn and stretched by hot, high-speed process air as they exit the die. In both technologies, the filaments are laid down in a random orientation on a storage surface, such as a perforated conveyor belt, to form a nonwoven fabric, transported to post-processing steps, and finally wound onto rolls.

[0003] Equipment for the production of spunbond nonwovens is typically designed for a specific product width or spinning width. All system components are also designed for this product width. In the production of spunbond nonwovens, for example, for hygiene applications, the nonwoven web is usually cut across its width into numerous narrow strips. The design is pre-arranged to minimize edge trimming. Depending on the number and width of the strips to be cut, significant amounts of waste can be generated for various technical applications. To avoid large amounts of waste, it is advisable to reduce the spinning width.

[0004] CN 101550611 B describes a modular arrangement of spinnerets for spunbond nonwoven production, in which each spinneret module has its own melt feed line. This allows the total spinning width to be reduced or increased, at least by the width of a module, by switching the respective module's spinning pump on or off. However, as mentioned, for example, in EP 1 486 591 A1, practical experience shows that switching off the modules leads to thermal damage to the melt in the respective module, clogging of the spinneret holes by the damaged melt, and making switching the modules on and off problematic in everyday production.

[0005] Based on EP 1 486 591 A1, the spinning width can be changed by means of distribution plates and subsequent shorter or longer extrusion plates. However, this can only be done by removing the spinneret and not during operation. The downtime for changing the plates and spinnerets, as well as the mechanical engineering effort, negatively impacts the economic viability of such systems.

[0006] US patent 7,438,544 describes a device for adjusting the spin widths of meltblown spinnerets, in which the melt and primary air can be switched on and off modularly. Shut-off devices are used for this purpose, preventing the melt from flowing further. However, this variant also suffers from a deterioration in melt quality, as it is trapped at high temperatures for extended periods. Experience has shown that thermal degradation occurs at these points, affecting the melt, the distributor block, and the spinneret material. Furthermore, the extrusion holes become clogged, and restarting the previously shut-off modules is problematic. Especially in the production of cellulose spunbond nonwovens, e.g., with lyocell spinning compound, long residence times or even a standstill of the spinning compound should be avoided, as the spinning compound could otherwise react exothermically.

[0007] It is also known from the prior art to produce cellulosic spunbond nonwovens according to the spund bonding technology (e.g., US 8,366,988 A) and according to the meltblown technology (e.g., US 6,358,461 A and US 6,306,334 A). In these processes, a lyocell spinning mass is extruded and drawn according to the known spund bonding or meltblown methods. Before being laid down to form a nonwoven, however, the filaments are additionally brought into contact with a coagulant to regenerate the cellulose and produce dimensionally stable filaments. The wet filaments are then laid down in random order as a nonwoven fabric.

[0008] Since the spinning media used have a cellulose content of 3 to 17%, cellulosic spunbond technologies require a larger quantity of spinning media than thermoplastic spunbonds to achieve the same productivity. This necessitates the use of larger spinning pumps, piping, manifold blocks, and primary air lines compared to thermoplastic spunbond plants to maintain the same productivity. While a modular design, such as that described in CN 101550611 B and already known from other publications, could be implemented, it would result in very high costs for the spinning pumps, spinning media piping, manifold blocks, primary air lines, and spinnerets. Furthermore, the thermal decomposition and exothermic reaction of the lyocell spinning media cannot be reliably prevented in the shut-down module.

[0009] With the aforementioned state of the art, the question remains how one of the main characteristics of a nonwoven fabric, its basis weight, can be uniformly adjusted even after changes in the spinning width. Distributing the melt across multiple modules, as described in CN 101550611 B, means that more melt must be conveyed through the remaining modules if, for example, one module is switched off. Similarly, EP 1 486 591 and US 7,438,544 raise the question of how the melt mass flow can be evenly distributed across the remaining spinning width and how this affects the basis weight and basis weight distribution of the spunbond nonwoven. Particularly in the case of cellulosic spinning stock produced using the Lyocell process, it becomes apparent that even with a constant spinning stock mass flow rate, a homogeneous distribution of the cellulose content in the spinning stock across the entire spinning width is hardly achievable.This also inevitably leads to a non-constant basis weight of the product, and adjusting the basis weight is also significantly more difficult than, for example, with thermoplastic spunbond nonwovens.

[0010] Further relevant information can be found in documents US 2003 / 234464 A1, US 2007 / 237849 A1 and US 5 361 466 A.

[0011] The current state of the art therefore does not offer a reliable solution, particularly for the production of cellulose spunbond nonwovens, for adjusting the spinning width of the spunbond during operation and at the same time keeping the basis weight of the spunbond constant in the event of fluctuations in the spinning mass. Disclosure of the invention

[0012] The object of the present invention is therefore to provide a method of the type mentioned at the outset which enables a reliable adjustment of the spinning width and the basis weight distribution of the spunbond nonwoven, or a constant maintenance of the basis weight distribution during ongoing operation.

[0013] The invention solves the problem by variably adjusting the spinning mass throughput of the nozzle holes along the transverse direction.

[0014] It has been found that by variably adjusting the spinning mass flow rate through the die holes along the transverse direction, any desired basis weight distribution of the spunbond can be achieved across the entire width of the spinneret along its main axis. Such a controlled basis weight distribution enables the production of a spunbond with several advantages, as described below. Firstly, the basis weight distribution of the spunbond can be kept uniformly constant across its entire width by changing and adjusting the spinning mass flow rate. This allows for a reliable response to fluctuations in the spinning mass or in the permeability of the spinnerets, thereby improving the quality of the spunbond.On the other hand, by varying the spinning mass throughput along the transverse direction of the spunbond, several areas with different basis weights can be created, resulting in a very versatile spunbond suitable for a large number of possible applications.

[0015] For example, a spunbond nonwoven can be created that has several parallel, thicker strips with a high basis weight in the transverse direction and thinner strips with a lower basis weight interspersed between them. Alternatively, a spunbond nonwoven with a thickness that increases uniformly from the edge in the transverse direction can also be created. Of course, the inventive method can also be used to create a spunbond nonwoven that incorporates several of the aspects described above. A versatile and reliable method for producing a spunbond nonwoven with an adjustable basis weight distribution can thus be provided.

[0016] Particularly in the production of cellulosic spunbond nonwovens, the process according to the invention offers numerous improvements and advantages with regard to the economic efficiency and operation of the manufacturing process, as well as the product quality of the spunbond nonwoven. Both the costs and the complexity of the equipment used to carry out the process can be significantly reduced. In particular, such a system does not need to rely on the complex and error-prone use of numerous small, interconnected spinneret modules with a multitude of associated spinning mass pumps to adjust the basis weight distribution of the cellulosic spunbond nonwoven. By using spinnerets that allow for a change in the spinning mass throughput in the transverse direction, structurally simple and cost-effective processes for the production of the spunbond nonwoven can be provided.

[0017] Furthermore, by altering the temperature distribution in the spinneret, the variable spinning mass throughput through the nozzle holes can be reliably and easily controlled from a process engineering perspective. Surprisingly, it has been shown that by selectively cooling and / or heating areas of the spinneret, the spinning mass throughput in the cooled or heated areas can be selectively reduced or increased without negatively affecting the stability and accuracy of the spinning process, the deposition of the spun web, or the spinning mass quality.

[0018] The production of cellulosic spunbond nonwovens from lyocell spinning compound takes place at relatively low temperatures of around 100 °C compared to thermoplastic melts. It has been found that even small temperature changes within the spinneret are sufficient to increase or decrease the viscosity at the cooled or heated area, thus causing less or more spinning compound to flow out. Surprisingly, a continuous flow of spinning compound through the spinneret holes can still be maintained, preventing an increased occurrence of spinning defects and ensuring a high-quality finished spunbond nonwoven.

[0019] The aforementioned circumstance is therefore particularly surprising, since in conventional melt spinning processes according to the state of the art, for example for the production of polyethylene terephthalate or polyamide nonwovens, a reduction of the temperature in a part of a spinneret, under otherwise constant operating conditions, inevitably leads to the clogging or blockage of the affected spinneret holes and thus to fatal spinning defects, up to and including the failure of the entire spinneret.

[0020] The reliability of the process can be further improved by varying the pressure distribution of the spinning mass in the spinneret to control the transversely variable spinning mass flow rate through the nozzle holes. Thus, in addition to varying the temperature distribution in the spinneret, it is also possible to vary the pressure of the spinning mass transversely across the spinneret and thereby set a desired pressure distribution. This allows the process to reliably control the spinning mass flow rate in a wide variety of situations depending on several parameters.

[0021] If several spinning mass pumps are assigned to the spinneret along the transverse direction in order to adjust the pressure of the spinning mass in the spinneret, a pressure distribution that varies along the transverse direction can be set in a process-engineering simple way.

[0022] The aforementioned advantages can be further improved if the spinneret is designed in multiple parts in the transverse direction, with each part of the spinneret having at least one spinning mass pump assigned to it.

[0023] If the spunbond nonwoven has at least one edge cut area with a lower basis weight, the economic efficiency of the process can be further improved. The process according to the invention makes it possible, in particular, to minimize the amount of edge cut while maintaining the same spinning width of the spunbond nonwoven, for example, if a spunbond nonwoven with a narrower width is to be produced.

[0024] To produce narrower spunbond nonwovens, conventional methods typically involve cutting the finished spunbond web, which has the same basis weight across its entire width, to the desired width. This results in significant waste and thus reduces the yield of the process. This can be avoided, in particular, by ensuring that the basis weight in the edge cut area is lower or significantly reduced compared to the basis weight of the rest of the spunbond, so that no significant amount of waste is generated. Furthermore, with the same spinning mass throughput, the production speed for the spunbond can be increased, further improving the economic efficiency of the process.

[0025] Furthermore, the reduction of the basis weight in the edge cut area can be carried out during ongoing operation in the process according to the invention, without having to change spinnerets, spinneret parts, spinning mass pumps or spinning mass distributors. In particular, no shut-off devices need to be installed, which create dead spaces and which, in the case of cellulosic spunbond nonwovens, can lead to thermal degradation of the spinning mass and possibly to exothermic reactions.

[0026] According to the invention, it has been shown that the reduction of waste in the edge cutting area can be controlled by means of a temperature profile in such a way that the basis weight of the edge cutting can be radically reduced and thereby, although not the edge cutting width, the edge cutting quantity is significantly reduced over time.

[0027] Preferably, the basis weight of the spunbond nonwoven in the edge cut area can be reduced by at least 80%, and particularly preferably by at least 90%, compared to the basis weight of the spunbond nonwoven in the usable area.

[0028] The aforementioned advantages are particularly evident when the basis weight of the spunbond nonwoven fabric in the edge-cut area is less than or equal to 5 g / m². This allows for a further improvement in the reliability of the process, as a constant flow of spinning material through the spinnerets can be maintained despite the significantly reduced basis weight in the edge-cut area.

[0029] In one example, a spunbond nonwoven fabric with a total width of 300 cm is to be reduced to a usable area of ​​260 cm. The basis weight in the edge trimming area can be reduced to less than 5 g / m² over a width of 40 cm, with the basis weight of the spunbond nonwoven fabric in the usable area being 50 g / m². Without the method according to the invention, a 40 cm wide strip with a basis weight of 50 g / m² would be produced as edge trimming. Using the method according to the invention, the amount of edge trimming in this example can be reduced by 90%, from 50 g / m² to 5 g / m².

[0030] It has been found that, according to the invention, adjusting the basis weight distribution to minimize the amount of waste generated at the edges, particularly in the production of cellulosic spunbond nonwovens, can be done both faster and more accurately than with a purely modular spinneret (in which modules can be switched on and off). Furthermore, the inventive solution also increases the productivity of the system.

[0031] Furthermore, the inventive method makes it possible to produce cellulosic spunbond nonwovens with basis weights of 5 g / m³ to 1000 g / m², preferably 10 g / m² to 500 g / m², and particularly preferably 15 g / m² to 250 g / m², and to adjust and control the basis weight distribution. The basis weight of the edge cut areas can be reduced to as low as 5 g / m², and the proportion of the edge cut areas can be between 1% and 50%, preferably between 2% and 30%, and particularly preferably between 3% and 20% of the spinneret width.

[0032] The reliability of the process can be further improved by measuring the actual surface weight distribution of the spunbond nonwoven, determining the difference between the actual surface weight distribution and a predefined target surface weight distribution, and adjusting the spinning mass throughput of the die holes in the transverse direction as a function of the determined difference.

[0033] If the actual basis weight distribution of the spunbond nonwoven is measured, the inventive adjustment of the spinning mass throughput in the transverse direction of the spinneret can subsequently be used to adapt the actual basis weight distribution to a predetermined target basis weight distribution in the nonwoven and to keep it constant using the inventive method. For this purpose, the actual basis weight distribution of the spunbond nonwoven is continuously determined and compared with a (time-varying) target basis weight distribution. Depending on the difference between the measured actual basis weight distribution and the predetermined target basis weight distribution, the spinning mass throughput of the spinneret holes is then set or adjusted. This can be done, for example, as described above, by changing the temperature of the spinneret or by changing the spinning mass pressure.

[0034] Furthermore, the conveying speed of the conveying system can be adjusted depending on the difference between the actual basis weight distribution and the predefined target basis weight distribution. This is particularly advantageous when the basis weight of the spunbonded nonwoven fabric needs to be increased or decreased without changing the spinning mass throughput. For example, the production speed can also be adapted to the spinning mass throughput.

[0035] The actual surface weight distribution of the spunbond nonwoven can advantageously be measured using a detection device. Such a detection device can consist of, for example, a number of cameras, optical sensors (e.g., lasers), mechanical sensors, and / or non-contact and non-destructive measuring sensors (e.g., ultrasonic sensors).

[0036] Furthermore, a control unit connected to the detection device can determine the difference between the actual basis weight distribution measured by the detection device and the target basis weight distribution stored in the control unit. Depending on the determined difference, the control unit can then output at least one control signal to a spinning mass control unit, which regulates the temperature and / or pressure distribution of the spinnerets, to change the variable spinning mass throughput of the spinnerets. The process can thus be equipped with an automatic control system that enables reproducible and precise control of the basis weight distribution of the spunbond.

[0037] Furthermore, depending on the determined difference, the control unit can output at least one control signal to a conveyor belt control device to change the conveying speed of the conveyor belt. In this way, in addition to the basis weight distribution, the throughput of the process can also be varied, and thus all parameters of the manufacturing process can be automatically controlled.

[0038] Since the basis weight distribution is measured continuously during operation, an advantage of the method according to the invention is that even the smallest fluctuations can be detected and compensated for by means of the control unit. This allows a spunbond nonwoven fabric according to the invention, in particular a cellulosic spunbond nonwoven fabric, to be produced with a coefficient of variation of the basis weight of 0% to 3%, preferably from 0% to 2%, and most preferably from 0% to 0.5%, measured according to the standard "Determination of basis weight (ISO 9073-1: 1989)".

[0039] Maintaining a consistent basis weight offers advantages in further processing. For example, if products containing lotions, such as wipes, cleaning wipes, or facial sheet masks, are to be manufactured from the cellulosic spunbond nonwoven, then both the application and distribution of the lotion within the final product are not only easier during production, but also visually and tactilely noticeable to the end customer. A uniform basis weight is a clear and measurable quality characteristic for nonwovens, which can be reliably achieved using the inventive method.

[0040] The advantages of the process according to the invention described above are particularly relevant for the production of cellulosic spunbond nonwovens, wherein the spinning mass is a lyocell spinning mass, i.e. a solution of cellulose in a direct solvent for cellulose.

[0041] It has been shown that, unlike thermoplastic melts where the spinning mass pumps are operated at a constant speed, the rotational speed of the spinning mass pumps in the production of cellulose spunbond nonwovens must be continuously adjusted to control the basis weight and basis weight distribution, as the cellulose content in the spinning mass constantly varies. Furthermore, it has been shown that the temperature of the spinning mass varies across the spinneret width, and this variation, which would lead to different spinning mass throughput along the transverse direction of the spinneret, can be compensated for, for example, by targeted adjustment of the temperature distribution. It has also been shown that the conveying speed of the perforated conveying unit must be constantly adjusted due to the fluctuations in the cellulose content of the spinning mass in order to maintain an approximately constant basis weight over time.The inventive method allows such a variation in cellulose content to be reliably compensated by targeted adjustment of the spinning mass throughput via temperature and pressure profile.

[0042] A direct solvent for cellulose is defined as a solvent in which the cellulose is dissolved in its non-derivatized form. This is preferably a mixture of a tertiary amine oxide, such as NMMO (N-methylmorpholine N-oxide), and water. Alternatively, ionic liquids or mixtures with water are also suitable as direct solvents.

[0043] The cellulose throughput per spunbond nozzle can range from 5 kg / h / m nozzle width to 500 kg / h / m nozzle width.

[0044] The cellulose content in the spinning mass can be between 3 wt.% and 17 wt.%, preferably between 5 wt.% and 15 wt.%, and particularly preferably between 6 wt.% and 14 wt.%.

[0045] The temperature of the spinning mass before entering the spinneret can be between 60 °C and 160 °C, preferably between 80 °C and 140 °C, and particularly preferably between 100 °C and 120 °C.

[0046] The temperature profile of the spinneret can be set so that the temperature of the spinning mass upon exiting the nozzle holes is between 60 °C and 160 °C, preferably between 80 °C and 140 °C, and particularly preferably between 100 °C and 120 °C.

[0047] The temperature of the stretching airflow can be between 20 °C and 200 °C, preferably between 60 °C and 160 °C, and particularly preferably between 80 °C and 140 °C.

[0048] The air pressure of the stretching airflow can be 0.05 bar to 5 bar, preferably 0.1 bar to 3 bar, particularly preferably 0.2 bar to 1 bar.

[0049] The internal structure of the spunbond nonwoven can also be reliably controlled if the filaments extruded and stretched from the spinneret are partially coagulated.

[0050] The spinneret can be equipped with a coagulation air stream containing a coagulation fluid for at least partial coagulation of the filaments, thereby allowing targeted control of the internal structure of the spunbond. This coagulation air stream can preferably be a fluid containing water and / or a coagulant, e.g., gas, mist, vapor, etc.

[0051] If NMMO is used as a direct solvent in the lyocell spinning mass, the coagulation fluid can be a mixture of fully demineralized water and 0 wt.% to 40 wt.% NMMO, preferably 10 wt.% to 30 wt.% NMMO, and particularly preferably 15 wt.% to 25 wt.% NMMO. This allows for particularly reliable coagulation of the extruded filaments.

[0052] The spunbond nonwoven fabric according to the inventive method can also consist of several spunbond layers, wherein the basis weights and properties can differ for each layer. For example, in the development of new gas and liquid filters, the combination of several spunbond layers with different basis weights and / or air permeabilities can be used to produce high-performance filters.

[0053] In one embodiment, these individual spunbond layers can be produced simultaneously by means of spinnerets positioned one behind the other and laid on top of each other in such a way as to form a multi-layered spunbond. The spunbond layers are then bonded by water jet bonding. It has been shown that while water jet bonding and drying can influence the basis weight due to some shrinkage of the spunbond, this effect can be compensated for by the method according to the invention. For example, if a threshold value of the basis weight is exceeded after drying, the control system according to the invention can compensate for this by adjusting the spinning mass throughput of the individual spunbond layers laid on top of each other.

[0054] The multiple spinnerets for producing the multilayer spunbond nonwoven can be connected in series in the production direction, with each spinneret having at least one coagulation unit assigned to it.

[0055] The spinnerets used according to the invention can be single-row slit spinnerets, multi-row needle spinnerets, or preferably column spinnerets with a width of, in particular, between 0.1 m and 6 m, as known from the prior art (US 3,825,380, US 4,380,570, WO 2019 / 068764).

[0056] According to the invention, the spinnerets can consist of several spinneret modules. Preferably, at least one spinning pump is provided for each spinneret or spinneret module.

[0057] Furthermore, it is preferred that at least one spinneret control unit is provided for each spinneret and / or spinneret module, which controls the temperature distribution in the spinneret or spinneret module. Depending on the desired accuracy of the temperature distribution control, a varying number of spinneret control units can be provided.

[0058] The setting and control of the temperature of the spinnerets, or subsequently the temperature distribution, can be achieved, for example, by means of infrared, ultrasound, electricity, steam, oil or other fluids or technologies for heat transfer known to those skilled in the art.

[0059] For example, Qualiscan QMS-12 type basis weight measuring devices from the manufacturer Mahlo GmbH & Co. KG, Saal an der Donau, Germany, are suitable as detection devices for detecting the basis weight distribution of the spunbond nonwoven. Brief description of the characters

[0060] Preferred embodiments of the invention are described in more detail below with reference to the drawings. They show: Fig. 1 a schematic representation of the method according to the invention according to a first embodiment, Fig. 2 a schematic representation of the control of the area weight distribution according to the invention in the method according to Fig. 1 Fig. 3 shows a schematic representation of the local distribution of the spinning mass throughput as a function of the temperature profile according to the first embodiment, Fig. 4 shows a schematic representation of the local distribution of the spinning mass throughput as a function of the temperature profile according to a second embodiment with modular spinnerets, and Fig. 5 shows a schematic representation of the local distribution of the spinning mass throughput as a function of the temperature profile according to a third embodiment with modular spinnerets. Ways to implement the invention

[0061] Fig. 1 Figure 1 shows a schematic representation of a process 100 for the production of cellulose spunbond nonwoven fabric 1 according to a first embodiment of the invention. In a first process step, a spinning mass 2 is produced from a cellulosic raw material and fed to a spinneret 3. The cellulosic raw material for the production of the spinning mass 2, the production of which is not shown in detail in the figures, can be a pulp suitable for the production of lyocell filaments from wood or other plant-based raw materials. However, it is also conceivable that the cellulosic raw material consists at least partially of production waste from spunbond nonwoven fabric production or recycled textiles. The spinning mass 2 is a solution of cellulose in NMMO and water, wherein the cellulose content in the spinning mass is between 3 wt.% and 17 wt.%.

[0062] In a next step, the spinning mass 2 is extruded through a plurality of nozzle holes 4 of the spinning nozzle 3 to form filaments 5, the nozzle holes 4 of the spinning nozzle 3 being arranged along a main axis 6. The main axis 6 of the spinning nozzle 3 is aligned along a transverse direction 12 to the conveying direction 11 of the spun web, as can be seen in particular in the schematic representation of process 100 in Fig. 2 shown in detail. The spinning mass throughput of the nozzle holes 4 along the transverse direction 12 is variably adjusted in the spinning nozzle 3, so that the individual nozzle holes 4 have a different spinning mass output in the transverse direction 12.

[0063] The extruded filaments 5 are then accelerated and stretched by a stretching airflow. A stretching device is provided in the spinneret 3 to generate the stretching airflow. Stretching air 7 is supplied to this device, and it ensures that the stretching airflow exits the spinneret 3 to accelerate the filaments 5 after extrusion.

[0064] In one embodiment, the drawing airflow can exit between the nozzle holes of the spinneret 3. In another embodiment, the drawing airflow can alternatively exit around the nozzle holes. This is not shown in detail in the figures. Such spinnerets 3 with drawing devices for generating a drawing airflow are known from the prior art (US 3,825,380 A, US 4,380,570 A, WO 2019 / 068764 A1).

[0065] The extruded and stretched filaments 5 are also exposed to a coagulation air stream 8, which is supplied by a coagulation device 9. The coagulation air stream 8 typically contains a coagulation fluid, for example in the form of vapor, mist, etc. Through contact of the filaments 5 with the coagulation air stream 8 and the coagulation fluid contained therein, the filaments 5 are at least partially coagulated, which in particular reduces adhesion between the individual extruded filaments 5.

[0066] The stretched and at least partially coagulated filaments 5 are then placed in a tangled position on a conveyor belt 10 as a conveying device 10 and form the spunbond nonwoven 1 there. The conveyor belt 10 then transports the formed spunbond nonwoven 1 away in the conveying direction 11, whereby the spunbond nonwoven 1 formed on the conveyor belt 10 extends on the conveyor belt 10 in a transverse direction 12 to the conveying direction 11.

[0067] Due to the variable spinning mass throughput of the spinneret 3 in the transverse direction 12, a spunbond 1 with a variable basis weight in the transverse direction 12, i.e., a basis weight distribution in the transverse direction 12, is obtained on the conveyor belt 10, which in Fig. 2 This is shown in more detail below. The spunbond nonwoven fabric has several areas 13, 14, 15 with different basis weights, with the edge cut areas 13, 15 having a lower basis weight than the usable area 14. The basis weight of the edge cut areas 13, 15 is less than 5 g / m² and is reduced by at least 90% compared to the usable area 14.

[0068] To reliably control the spinning mass throughput of the spinneret 3 in the transverse direction 12 and thus the basis weight distribution of the spunbond 1, or to obtain a spunbond 1 with a defined target basis weight distribution 19, the actual basis weight distribution 18 of the spunbond 1 is measured by means of a detection device 16 and transmitted to a control unit 17 connected to the detection device 16. The control unit 17 then determines a difference between the measured actual basis weight distribution 18 and the target basis weight distribution 19, whereby control signals 20, 21, 22 are output based on the difference.

[0069] In Fig. 2 The control of the actual surface weight distribution 18 by means of the control unit 17 and control signals 20, 21, 22 is shown in detail. Control signal 20 is used to control the pressure distribution of the spinning mass 2 in the spinneret 3. For this purpose, control signal 20 is output to a spinning mass control unit 23, which controls the spinning mass pumps 24 assigned to the spinneret 3 in order to control the pressure distribution of the spinning mass 2 and thus adjust the spinning mass throughput of the spinneret 3. Control signal 21, in turn, is used to control the temperature distribution of the spinneret 3 and is output to a spinneret control unit 25, which changes the temperature of the spinneret 3 in the transverse direction 12 so that the spinning mass throughput of the spinneret 3 in the transverse direction 12 is adjusted.Finally, the control signal 22 is output to a conveyor belt control device 26 to regulate the conveying speed of the conveyor belt 10, and thus to adjust the basis weight of the spunbond nonwoven fabric 1.

[0070] In Fig. 3 The local spinning mass throughput distribution 34 and the temperature distribution 35 in the spinneret 3 are shown, wherein the spinning mass throughput distribution 34 and the temperature distribution 35 each represent the course of the spinning mass throughput 31 and the temperature 32, respectively, as a function of the expansion 33 of the spinneret 3 in the transverse direction 12. The temperature distribution 35 exhibits in the corresponding edge section regions 13, 15, as shown in Fig. 2 As shown on the spunbond 1, a decrease in temperature 32 towards the edges occurs, while the temperature 32 is kept essentially constant in the usable area 14. Following the temperature distribution 34, a lower spinning mass throughput 31 also occurs in the edge cut areas 13, 15, which is then reflected in the lower basis weight in the edge cut areas 13, 15 - as shown in Fig. 2 shown - strikes down.

[0071] What's next from the Fig. 2 A feedback loop is evident between the control devices 23, 25, 26 and the detection device 16, which can achieve and maintain a target basis weight distribution 19 in the finished spunbond 1 fully automatically by controlling the spinning mass throughput of the spinneret 3 and the conveying speed of the conveyor belt 10. Such constant basis weight distribution can serve both to compensate for fluctuations in the cellulose raw material and to produce a spunbond 1 with a predefined basis weight profile.

[0072] As in Fig. 1 As shown, after the formation of the spunbond nonwoven 1, it is subjected to washing 27 and water jet bonding 28. The washed and water jet bonded spunbond nonwoven 1 is then dried in a dryer 29 to remove any remaining moisture and obtain a finished spunbond nonwoven 1. Finally, the process 100 is completed by optionally winding 30 and / or packaging the finished spunbond nonwoven 1.

[0073] The detection device 16 for measuring the actual surface weight distribution 18 of the spunbond nonwoven fabric 1 is advantageously provided between the dryer 29 and the winding unit 30, since the properties of the finished spunbond nonwoven fabric 1 can be determined after the dryer 29, thereby achieving a high reliability of the method 100.

[0074] In another embodiment, not shown in detail in the figures, the spunbond nonwoven fabric 1 is trimmed around the edge cutting areas 13, 15 before winding 30, so that only the usable area 14 is fed to the winding 30.

[0075] In Fig. 4 A multi-part spinneret 40 with several spinneret modules 41, 42, 43, 44 is shown according to a further embodiment of the inventive method 101. Each spinneret module 41, 42, 43, 44 is assigned a spinning mass pump 45, 46, 47, 48 in order to adjust the pressure distribution in the spinneret 40 in addition to the temperature distribution 37. In the present embodiment, the spinning mass pumps 45-48 each produce the same pressure in the spinneret modules 41-44 and thus ensure a uniform pressure distribution in the spinneret 40. As shown in Fig. 4 As shown, the spinning mass throughput distribution 36 also exhibits a drop in the edge areas, so that edge cut areas 61, 63 are formed again on the spunbond 1, in which the basis weight is reduced compared to the usable area 62.

[0076] In Fig. 5 A further multi-part spinneret 50 with four spinneret modules 51, 52, 53, 54 is shown according to a further embodiment of the inventive method 102. As already described for Fig. 4 As shown, each spinneret module 51, 52, 53, 54 is assigned a spinning mass pump 55, 56, 57, 58. In contrast to Fig. 4In the present embodiment, the spinning mass pump 58 conveys spinning mass 2 at only low or minimal pressure. Thus, the pressure distribution in the spinneret 50 in the area of ​​the spinneret module 54 is very low, resulting in only a minimal spinning mass throughput 31 in the spinneret module 54. Furthermore, a temperature distribution 39 is provided in the spinneret 50, which is reflected in a spinning mass throughput distribution 38. This, in turn, leads to edge cut zones 64, 66 in the spunbond 1 with a lower basis weight than the usable area 65. In this embodiment, the edge cut zone 66 is composed of the basis weight drop due to the temperature distribution 39 and the uneven pressure distribution, thereby creating an extensive edge cut zone 66 with a very low basis weight in the spunbond 1.The amount of waste after trimming the spunbond nonwoven 1 to the usable area 65 can therefore be kept to a minimum.

[0077] In another embodiment, the offcuts from the edge cutting areas 14, 16, 61, 63, 64, 66 can again be used as cellulosic raw material for the production of spinning mass 2, which, however, has not been shown in more detail in the figures.

Claims

1. A process for the production of a spunbonded nonwoven (1), wherein a spinning mass (2) is extruded through a plurality of nozzle holes (4) of at least one spinneret (3, 40, 50) to form filaments (5), and the filaments (5) are drawn, in each case, in the extrusion direction, wherein the filaments (5) are deposited on a perforated conveying device (10) to form a spunbonded nonwoven (1), and wherein the nozzle holes (4) of the spinneret (3, 40, 50) are arranged along a main axis (6) oriented in a transverse direction (12) to the conveying direction (11) of the conveying device (10) such that the spunbonded nonwoven (1) formed on the conveying device (10) extends in this transverse direction (12), characterized in that the spinning mass throughput (31) of the nozzle holes (4) is adjusted variably along the transverse direction (12).

2. A process according to claim 1, characterized in that the temperature distribution (35, 37, 39) in the spinneret (3, 40, 50) is changed in order to control the spinning mass throughput (31) of the nozzle holes (4) variable in the transverse direction (12).

3. A process according to claim 1 or 2, characterized in that the pressure distribution of the spinning mass (2) in the spinneret (3, 40, 50) is changed in order to control the spinning mass throughput (31) of the nozzle holes (4) variable in the transverse direction (12).

4. A process according to claim 3, characterized in that several spinning mass pumps (45, 46, 47, 48, 55, 56, 57, 58) are allocated to the spinneret (40, 50) along the transverse direction (12) in order to adjust the pressure of the spinning mass (2) in the spinneret (40, 50).

5. A process according to claim 4, characterized in that the spinneret (40, 50) is designed in multiple parts in the transverse direction (12), with at least one spinning mass pump (45, 46, 47, 48, 55, 56, 57, 58) being allocated to each part (41, 42, 43, 44, 51, 52, 53, 54) of the spinneret (40, 50).

6. A process according to any of claims 1 to 5, characterized in that the spunbonded nonwoven (1) has at least one edge cutting area (13, 15, 61, 63, 64, 66) with a lower basis weight.

7. A process according to claim 6, characterized in that the basis weight of the spunbonded nonwoven in the edge cutting area (13, 15, 61, 63, 64, 66) is less than or equal to 5 g / m2.

8. A process according to claim 6 or 7, characterized in that after forming the spunbonded nonwoven (1) is trimmed from the edge cutting area (13, 15, 61, 63, 64, 66).

9. A process according to any of claims 1 to 8, characterized in that the actual basis weight distribution (18) of the spunbonded nonwoven (1) is measured, the difference between the actual basis weight distribution (18) and a predefined target basis weight distribution (19) is determined, and the spinning mass throughput (31) of the nozzle holes (4) in the transverse direction (12) is variably adjusted as a function of the determined difference.

10. A process according to claim 9, characterized in that the conveying speed of the conveying device (10) is adjusted as a function of the difference between the actual basis weight distribution (18) and the predefined target basis weight distribution (19).

11. A process according to any of claims 1 to 10, characterized in that the actual basis weight distribution (18) of the spunbonded nonwoven (1) is measured using a detection device (16).

12. A process according to claim 11, characterized in that, by means of a control unit (17) connected to the detection device (16), the difference between the actual basis weight distribution (18) measured by the detection device (16) and the target basis weight distribution (19) stored in the control unit (17) is determined.

13. A process according to claim 12, characterized in that, for changing the variable spinning mass throughput (31) of the nozzle holes (4), the control unit (17) outputs at least one control signal (21) to a spinneret control device (25) regulating the temperature distribution (35, 37, 39) and / or at least one control signal (20) to a spinning mass control device (23) regulating the pressure distribution of the spinnerets (3, 40, 50), depending on the determined difference.

14. A process according to claim 12 or 13, characterized in that, depending on the determined difference, the control unit (17) outputs at least one control signal (22) for changing the conveying speed of the conveyor belt (10), to a conveyor belt control device (26).

15. A process according to any of claims 1 to 14, 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, particular a tertiary amine oxide in aqueous solution.