METHOD AND DEVICE FOR SOLVENT SEPARATION

FROM THE PROCESS AIR IN SPINNOVWOVEN PRODUCTION

The invention relates to a device for depositing filaments to form a spunbond, dehumidifying the spunbond and extracting the process air laden with solvents and coagulants, comprising a conveying device which has a conveyor belt for transporting spunbond in a transport direction, with one on the upper side of the conveyor belt Storage surface for the filament is arranged, the conveyor device being permeable to gases and liquids at least in the area of ​​the storage surface, a dehumidifying device being provided on the underside of the conveyor belt at least below the storage surface, with at least one suction device being provided above the conveyor belt next to the storage surface. The invention also relates to a method for depositing filaments to form a spunbond,

BACKGROUND OF THE INVENTION

For several decades, spunbonded nonwovens have been manufactured using the spunbond or meltblown process. In the spunbond process, as described, for example, in GB 2 1 14 052 and EP 3 088 585, filaments are extruded through a nozzle and drawn off and drawn by an underlying drawing unit.

In contrast, in the meltblown process, as described for example in US Pat. No. 5,080,569, US Pat. No. 4,380,570 and US Pat. No. 5,695,377, the extruded filaments are already entrained and stretched by hot, fast process air when they exit the nozzle. With both technologies, the filaments are placed on a storage surface, for example a perforated conveyor belt, in a random layer to form a nonwoven, transported to post-processing steps and finally wound up as nonwoven rolls.

Known suction units are described, for example, in US Pat. No. 7,001,567, EP 1 079 012, EP 1 340 844 or US Pat. No. 6,331,268.

The known methods and devices have mainly been developed for the deposition of plastic filaments such as polypropylene (PP). These filaments are easy to move on the storage surface and can lead to poor web formation if the suction is poor. Therefore, all of the process air is sucked through the shelf to prevent the process air from being reflected.

In contrast to the already well-known spunbond and meltblown processes for thermoplastics, the suction unit for the production of cellulosic spunbonded webs, for example from Lyocell spinning mass, has to perform additional tasks. The production of cellulosic spunbonded nonwovens using spunbond technology is described, for example, in US Pat. No. 8,366,988 and according to meltblown technology in US Pat. No. 6,358,461 and US Pat. No. 6,306,334. The lyocell spinning mass is stretched in the same way as in the known spundbond and meltblown processes, but the filaments are also brought into contact with a coagulant before the fleece is deposited in order to regenerate the cellulose and produce dimensionally stable filaments. Due to the turbulence of the air, the wet filaments are laid down in a random layer as a non-woven fabric.

Since the spinning masses used have a pulp content of 3 to 17%, cellulosic spunbond technologies require more process air per kg of product than the production of thermoplastic spunbonded fabrics. This means that with the same productivity compared to thermoplastic spunbond systems, more process air has to be conveyed through the nozzle and the coagulant and solvent must be extracted. So more process air hits the same storage surface at a higher speed and this process air is also loaded with a lot of liquid.

Subsequently, the solvent and coagulant, which is present in fine droplets in the exhaust air flow, must also be separated. Especially in the production of spunbonded fabrics from Lyocell spinning mass, the loss of the solvent NMMO should be reduced as far as possible and the recovery maximized. This not only improves the profitability of the production plant, but also ensures compliance with regulatory requirements in the area of ​​exhaust air limit values.

Due to the increased process air flow in the production of cellulosic spunbonded fabrics and the high quantities of solvents and coagulants that must first be sucked off and then separated, the previously known spunbonded nonwovens cannot be used because neither the productivity and recovery of the necessary for economic operation Solvent, nor the official requirements for the purity of the exhaust air can be complied with.

BRIEF DESCRIPTION OF THE INVENTION

In the prior art it is stated that in the production of cellulosic spunbonded nonwovens, the process air is sucked off through the storage area in order to enable the filaments to be deposited to form a nonwoven fabric. The extraction unit must extract the process air as evenly and economically as possible through the storage surface, without the deposited filaments being displaced by reflecting air and creating an unevenness in the nonwoven. The reflection of the process air should be avoided as far as possible.

Due to the already described differences between the production of spunbonded nonwovens from thermoplastics and from cellulose, the known devices can neither extract nor recover the entire amount of solvent and coagulant-laden process air in an energy-saving manner. In order to meet the increased requirements and to enable a commercial and environmentally sensible operation of a spunbonded nonwoven plant for cellulosic spunbonded webs, it is the object of the present invention to meet the demands placed on economy and environmental protection.

The aim of the present invention is to remove the solvent and coagulant-laden process air in the production of cellulosic spunbonded webs as economically as possible without negatively affecting the web deposition.

According to the invention, this object is achieved by a device for depositing filaments on a spunbond, dehumidifying the spunbond and extracting the process air laden with solvents and coagulants, comprising a conveying device for transporting the spunbond in a transport direction, the conveying device having a storage area for the filament , the conveying device being permeable to gases and liquids at least in the area of ​​the storage surface, a primary dehumidifying device being provided below the storage surface of the conveying device, characterized in that at least one upper suction device is arranged in front of and / or after and / or to the side of the storage surface.

The device therefore has at least one upper suction device in front of or after the storage surface in the machine direction, or laterally next to the storage surface, which sucks process air reflected from the storage surface.

The task is also achieved by a method for depositing filaments into a spunbond, dehumidifying the spunbond, suctioning off the process air laden with solvents and / or coagulants, separating and recovering the coagulant or solvent from the process air, with filaments being discharged from a spinning system and deposited on a storage surface of a conveyor device to form a spunbonded nonwoven fabric and then transported further, the filaments on the storage surface being dehumidified from the underside of the conveyor device by reducing the pressure, characterized in that process air reflected by the conveyor device is at least in a section in front of and / or is suctioned after and / or to the side of the storage area above the conveyor.

Furthermore, in a next step it can be provided that the coagulation agent or solvent is separated from the exhaust air stream and recovered.

In one aspect of the invention, an arrangement comprising a device for producing cellulosic spunbonded nonwoven and a device of the aforementioned type is also provided.

In the following, the device, the method and the arrangement are described in more detail in parallel and advantageous design variants are discussed.

In the device for depositing filaments into a spunbonded nonwoven, dehumidifying spunbonded nonwoven and discharging the process air laden with solvents and coagulants, filament, which comes from a spinning system, for example, is guided onto the depositing surface. To regenerate cellulose from the spinning mass filaments extruded from the spinning system to form a spunbonded web, the extrudate is sprayed with coagulation liquid, for example via nozzles. The now moist spunbonded fleece is placed on the storage surface. At the same time, the process air required for stretching flows onto the storage area. The storage surface is located on a conveyor device, which preferably has a conveyor belt for transporting spunbonded nonwoven in one transport direction. The storage area for the filament is now arranged on the top of the conveyor belt, wherein the conveying device is permeable to gases and liquids at least in the area of ​​the depositing surface. On the underside of the conveyor belt, a primary dehumidifying device is provided, at least below the storage area, which has a vacuum box, for example. At least one upper suction device is provided above this section. According to the invention is mainly through the primary dehumidifying device

Solvents and coagulants removed and only as much process air as is required for a stable and faultless fleece deposit. The remaining part of the process air is reflected and caught and sucked off by at least one suction device above the conveying device. The conveying device can also be gas and liquid-permeable at least in a section in the machine direction before or after the depositing surface. This area can have a secondary dehumidifying device with which, on the one hand, solvents and coagulants are removed from the spunbonded nonwoven and, on the other hand, the spunbonded nonwoven is held in place so that it is not lifted off the conveyor belt and sucked off by the suction device located above.

In one embodiment it is provided that the upper suction device has a suction direction during operation in the transport direction or against the transport direction or in and against the transport direction, in the direction of the storage surface.

One embodiment variant provides that, during operation, the upper suction device has a suction direction transverse to the transport direction, in the direction of the storage area.

The term that the device has at least one upper suction device above this section is understood within the scope of the invention to mean that process air previously reflected from the storage surface is suctioned off above the conveyor belt.

Regardless of the exact design of the upper suction device (s), each suction device is preferably assigned a secondary dehumidifying device below the storage area. As a result, the spunbonded nonwoven is on the one hand fixed and dehumidified on the conveyor device and, on the other hand, the reflected process air is sucked off.

It is preferably provided that both the dehumidifying devices and the suction devices are followed by a moisture separator or droplet separator. As a result, solvents or coagulants can be separated from the process air and / or from the spunbonded nonwoven and recovered.

In one embodiment it is provided that the upper suction device is arranged in the transport direction of the conveyor device in front of the storage area.

In another embodiment it is provided that the upper suction device is arranged in the transport direction of the conveyor device after the depositing surface.

In one embodiment it is provided that the upper suction device is arranged laterally next to the storage area in the transport direction of the conveyor device.

Particularly preferably, an upper suction device is arranged in front of the storage surface in the transport direction and an upper suction device is arranged after the storage surface in the transport direction.

Even more preferably, an upper suction device is arranged in front of and after the storage surface in the transport direction and an upper suction device is arranged laterally next to the storage surface.

In a preferred embodiment variant, the upper suction devices form a square around the storage area and thus suck off the reflected process air at a 360 ° angle.

DETAILED DESCRIPTION OF THE INVENTION

In the present invention, a method is provided which allows the storage area to be used mainly for dehumidifying the spunbonded nonwoven and to allow the process air to bounce off the storage area, to suck out the reflected process air and then, if necessary, to separate the solvent and coagulant and return it to the coagulation storage container or subsequently to be fed to the solvent work-up.

The device according to the invention enables the dehumidification of the spunbonded fleece, the reflection of the process air and the suction of the reflected process air next to the storage area above the conveyor belt.

In order to better illustrate the invention, the essential features are shown in the following figures using preferred embodiments of the method according to the invention and the device according to the invention.

Fig. 1 shows schematically a device according to the invention

Fig. 2 shows an oblique view of the device according to FIGS. 1 and

Fig. 3 shows a plan view of this device.

4 shows a diagram of an embodiment variant of the invention.

FIG. 1 shows the device 1 according to the invention, with which the spinning mass filaments 3 extruded and drawn by the spinning system 2 can be deposited to form a spunbonded nonwoven 8 and dehumidified. The filaments 3 are sprayed with coagulation liquid 4 in order to regenerate the cellulose and stabilize the shape of the filaments 3 before the process air 5 and the filaments 3 hit the storage surface 6 and the spunbond 8 is formed.

In the case of the Lyocell process, the coagulation liquid can be a mixture of fully demineralized water and NMMO, with a weight fraction of 0% to 40% NMMO, preferably 10% to 30% NMMO, even more preferably 15 to 25% NMMO. The spunbond 8 is dewatered by the storage surface 6 and the dehumidifying device 9 and the proportion of coagulant and solvent in the spunbond 8 is significantly reduced.

It has been shown that with high productivity of the spinning system 2 between 10 kg / h / m and 1000 kg / h / m cellulose throughput, the primary dehumidifying device 9 is already so stressed by the high amount of coagulation and solvent that the amount of process air is not as high in the devices and methods corresponding to the state of the art, it can be completely suctioned off and reflected in all directions after it has hit the support surface 6. Surprisingly, however, the cellulosic filaments 3 adhere so well to the depositing surface 6 that the nonwoven depositing is still possible.

According to the invention, this reflection effect is used to the extent that the storage surface 6 is mainly used to remove the coagulation and solvent mixture from the spunbond 8 by the primary dehumidifying device 9 and the reflection of the coagulation and solvent-laden, hot and fast air flow is allowed. One advantage of the device according to the invention is the high energy saving, since not the entire amount of process air 5 is sucked off by the primary dehumidifying device 9 with high energy expenditure, but can be removed above the conveying device 7 with significantly less pressure loss.

According to the invention, the reflective process air 5 could be intercepted by upper suction devices 11 in and against the direction of the conveyor belt (MD boxes) and by upper suction devices 10 transversely to the direction of the conveyor belt (CD boxes)

be sucked off. This prevented the coagulation and solvent-laden process air 5 from being distributed in the plant room. This enabled both the solvent to be recovered and the exhaust air limit values ​​to be complied with.

This has resulted in a further advantage of the device according to the invention: Since the reflected process air flows at high speed into the upper suction devices 10, 11 and the pressure loss is very low, very little energy is required for the further transport of the process air 5. The suction effect of the upper suction device is so strong that a secondary dehumidifying device 12 can be used according to the invention so that the spunbonded nonwoven 8 is not entrained into the suction devices 10, 11. In the exemplary embodiment, two secondary dehumidifying devices 12 are shown.

According to the invention, part of the amount of coagulation and solvent is extracted from the spunbond 8 via the primary dehumidifying device 9 and the secondary dehumidifying devices 12 and the other part from the reflected coagulation and solvent-laden process air 5 via the upper suction devices 10, 11. Part of the amount of coagulation and solvent is separated from the dehumidifying devices 9, 12 via the drainage lines 15, while the coagulation and solvent droplets are removed from the exhaust air by mist separators 16. The deposited amount of coagulation and solvent can be collected in the coagulation storage container 17 and either pumped back to the coagulation liquid spray system or conveyed to the solvent processing 19. The solvent cycle can thus be closed as shown in FIG. 4 and the solvent can be recovered and reused. The exhaust air 18 can be fed to further cleaning steps after the droplet separators 16.

The economic and environmental advantages are achieved firstly through the use of the device 1 according to the invention for dehumidifying the spunbond 8 and the extraction of the process air 5, since the extraction performance can be reduced and secondly through the use of the method according to the invention for solvent separation and recovery shown in FIG. 4 enables.

The spunbonded web 8 is either transported on the conveyor belt of the conveyor device 7 to the next spinning system 2 in order to produce multi-layered spunbonded webs, or

washed, if necessary solidified, dried, if necessary post-treated and finally wound up into fleece rolls.

The process according to the invention can be used for the recovery of a wide variety of solvents and ionic liquids which can be used for the production of cellulosic spunbonded nonwovens, preferably tertiary amine oxides, even more preferably NMMO.

The present invention can be used for the dehumidification and the suction of process air in the production of cellulosic spunbonded nonwovens by the spunbond process and by the meltblown process. The pulp throughput per spinning system 2 can be in the range from 10 kg / h / m to 1000 kg / h / m, preferably 20 kg / h / m to 500 kg / h / m, even more preferably from 30 kg / h / m to 300 kg / h / m. The specific amount of process air per kg of pulp can be in the range from 30 Nm 3 / kg to 1000 Nm 3 / kg, preferably 50 Nm 3 / kg to 700 Nm 3 / kg, even more preferably 70 Nm 3 / kg to 400 Nm 3 / kg (The unit "Nm 3 " means "standard cubic meter").

The extruded filaments 3 which are deposited on the support surface 6 can have diameters in the range from 0.1 μm to 100 μm, preferably 1 μm to 40 μm, even more preferably 3 μm to 30 μm.

The specific coagulation liquid throughput per kg of pulp through the spray system 4 can be in the range from 2 L / kg to 300 L / kg, preferably 10 L / kg to 200 L / kg, even more preferably 20 L / kg to 150 L / kg. The coagulant can be atomized via single-fluid nozzles, two-fluid nozzles, or other types known to the person skilled in the art.

The further the distance between the spinning system 2 and the depositing surface 6, the lower the impact speed, but the higher the amount of air that has to be sucked out, since ambient air is drawn in with it. The distance between the spinning system 2 and the storage surface 6 can be between 0.1 and 5 m, preferably 0.3 and 4 m, even more preferably between 0.5 and 3 m. The speed of the process air 5 upon impact can be between 5 m / s and 250 m / s, preferably between 10 m / s and 150 m / s, even more preferably between 15 m / s and 50 m / s.

The storage surface 6 forms, for example, a woven conveyor belt which is suitable for drainage. The conveyor belt rests on vacuum plates 14 and is

thereby supported in order to be able to withstand the back pressure of the process air 5. The vacuum plates 14 can have a wide variety of hole shapes in order to reinforce the drainage effect and to stabilize the spunbond 8 (not shown in more detail). The deposited nonwoven 8 can have weights per unit area in the range from 5 g / m 2 to 500 g / m 2 , preferably 10 g / m 2 to 300 g / m 2 , even more preferably 15 g / m 3 to 200 g / m 2exhibit. With higher weights per unit area, finer filament diameters, high amounts of coagulation liquid, high amounts of process air, small distance between the spinning system 2 and storage area 6, conveyor belts with low air permeability and several layers of nonwoven fabric on top of one another, more and more process air 5 is reflected and captured and extracted by the suction devices 10, 11.

Most of the coagulant and solvent is sucked off by the primary dehumidifying devices 9. The moisture content of the spunbond 8 is reduced to such an extent that the proportion of liquid in the spunbond 8 after the dehumidifying device 9 is in the range from 0.1 kg / kg to 10 kg / kg, preferably 1 kg / kg to 8 kg / kg, even more preferred is between 3 kg / kg and 6 kg / kg.

A small part of the amount of coagulation and solvent is also sucked off via the secondary dehumidifying device 12. The solvent collects both in the primary dehumidifying device 9 and in the secondary dehumidifying devices 12 at the lowest point and is drained off via the drainage line 15 to the coagulation storage tank 17.

Most of the process air 5 is reflected and discharged via the suction devices (MD / CD boxes) 10.1 1. The MD / CD boxes 10, 11 have, for example, specially shaped baffles that make it possible to better discharge the reflected process air (not shown in more detail). There is a gap between the MD boxes 11 and the conveyor belt 7 so that the conveyor belt 7 and the spunbond 8 can be transported between them. The secondary dehumidifying devices 12 are located under the MD boxes 11 and hold the spunbond 8 in place.

The primary dehumidifying device 9 and the secondary dehumidifying device 12 can be implemented as one apparatus or separately.

The upper suction devices 10, 11 can be designed as one apparatus or separately.

The primary dehumidifying device 9, the secondary dehumidifying device 12 and the suction devices can each be supplied by a separate suction line 13 with separator 16 and vacuum fan or by a common vacuum line. Other variations are also possible in between.

The separators used can be, for example, droplet separators, but other separator variants are also possible.

Several devices according to the invention can be positioned one behind the other in order to produce multi-layer spunbonded nonwovens. The first secondary dehumidifying device 12 serves to fix the spunbonded web 8 that has already been laid down in the conveying direction so that it is not damaged by the reflected process air 5 from the next spinning system 2.

In an embodiment variant, the conveying device 7 can have a rotating, perforated vacuum drum in order to deposit, dehumidify and transport the spunbonded nonwoven. According to the invention, the reflection effect can then be used to remove the process air from the vacuum drum by appropriate adaptation of the suction devices 10, 11. The rotating vacuum drum can have a storage surface with a primary dehumidifying device and fleece holding areas under the suction devices with secondary dehumidifying devices (not shown).

EXPECTATIONS

1. Device for depositing filaments (3) to form a spunbond (8), dehumidifying the spunbond (8) and extracting the process air laden with solvents and coagulants, comprising a conveying device (7) for transporting the spunbond (8) in a transport direction ,

wherein the conveying device (7) has a storage surface (6) for the filament (3),

wherein the conveying device (7) is permeable to gases and liquids at least in the area of ​​the depositing surface (6),

a primary dehumidifying device (9) being provided below the storage surface (6) of the conveying device (7),

characterized in that at least one upper suction device (10, 11) is arranged in front of and / or after and / or to the side of the storage surface (6).

2. Device according to claim 1, characterized in that the upper suction device (11) in operation has a suction direction in the transport direction or against the transport direction or in and against the transport direction, in the direction of the storage surface (6).

3. Device according to claim 1 or claim 2, characterized in that the upper suction device (10) in operation has a suction direction transverse to the transport direction, in the direction of the storage surface (6).

4. Device according to one of claims 1 to 3, characterized in that a secondary dehumidifying device (12) is assigned to each suction device in the machine direction (11).

5. Device according to one of claims 1 to 4, characterized in that the secondary dehumidifying device (12) can be operated under vacuum.

6. Device according to one of claims 1 to 5, characterized in that the upper suction device (1 1) is arranged in the transport direction in front of the storage surface (6).

7. Device according to one of claims 1 to 6, characterized in that the upper suction device (1 1) is arranged in the transport direction after the storage surface (6).

8. An arrangement comprising an apparatus for the production of cellulosic

Filaments and a device according to any one of claims 1 to 7.

9. A method for depositing filaments (3) to form a spunbond (8), dehumidifying the spunbond (8), suctioning off the process air laden with solvents and / or coagulants, separating and recovering the coagulant or solvent from the process air, wherein Filaments (3) are discharged from a spinning system (2) and deposited on a storage surface (6) of a conveying device (7) to form a spunbonded non-woven fabric and then transported further, the filaments (3) on the storage surface (6) from the underside of the conveying device ( 7) are dehumidified by reducing the pressure, characterized in that process air reflected by the conveying device (7) is sucked off at least in a section in front of and / or after and / or to the side of the storage surface (6) above the conveying device (7).

10. The method according to claim 9, characterized in that the coagulation or. Solvent is separated from the exhaust air stream and recovered.