METHOD FOR PRODUCING SPUNBONDED FABRIC

Abstract

A process for the production of spunbonded nonwoven (1) is shown, 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) so that the spunbonded nonwoven (1) formed on the conveying device (10) extends in this transverse direction (12). So as to enable the spinning width and the basis weight distribution of the spunbonded nonwoven to be adjusted reliably and, respectively, to allow the basis weight distribution to be kept constant during operation by means of the process, it is suggested that the spinning mass throughput (31) of the nozzle holes (4) is adjusted variably along the transverse direction (12).

Claims

1. A process for producing a spunbonded nonwoven comprising: extruding a spinning mass extruded through a plurality of nozzle holes of at least one spinneret to form filaments, and drawing the filaments, in each case, in an extrusion direction, wherein the filaments are deposited on a perforated conveying device to form the spunbonded nonwoven, wherein the plurality of nozzle holes of the at least one spinneret are arranged along a main axis oriented in a transverse direction to a conveying direction of the perforated conveying device so that the spunbonded nonwoven formed on the perforated conveying device extends in the transverse direction, wherein a spinning mass throughput of the plurality of nozzle holes is adjusted variably along the transverse direction.

2. The process according to claim 1, further comprising: changing temperature distribution in the at least one spinneret to control the spinning mass throughput of the plurality of nozzle holes variable in the transverse direction; and/or changing pressure distribution of the spinning mass in the at least one spinneret to control the spinning mass throughput of the plurality of nozzle holes variable in the transverse direction.

3. (canceled)

4. The process according to claim 2, wherein a plurality of spinning mass pumps is allocated to the at least one spinneret along the transverse direction for adjusting pressure of the spinning mass in the at least one spinneret.

5. The process according to claim 4, wherein the at least one spinneret is designed in multiple parts in the transverse direction, with at least one of the plurality of spinning mass pumps being allocated to each part of the at least one spinneret.

6. The process according to claim 1, wherein the spunbonded nonwoven has at least one edge cut area of a lower basis weight.

7. The process according to claim 6, wherein a basis weight of the spunbonded nonwoven in the at least one edge cut area is less than or equal to 5 g/m.sup.2.

8. The process according to claim 6, wherein after forming, the spunbonded nonwoven is trimmed from the at least one edge cut area.

9. The process according to claim 1, further comprising: measuring an actual basis weight distribution of the spunbonded nonwoven, determining a difference between the actual basis weight distribution and a predefined target basis weight distribution, and variably adjusting the spinning mass throughput of the plurality of nozzle holes in the transverse direction as a function of the difference that is determined.

10. The process according to claim 9, wherein a conveying speed of the perforated conveying device is adjusted as a function of the difference between the actual basis weight distribution and the predefined target basis weight distribution.

11. The process according to claim 9, wherein the actual basis weight distribution of the spunbonded nonwoven is measured by means of a detection device.

12. The process according to claim 11, wherein, by means of a control unit connected to the detection device, the difference between the actual basis weight distribution measured by the detection device and the predefined target basis weight distribution stored in the control unit is determined.

13. The process according to claim 12, wherein, for changing the spinning mass throughput of the plurality of nozzle holes, the control unit outputs at least one control signal to a spinneret control device regulating a temperature distribution and/or at least one control signal to a spinning mass control device regulating a pressure distribution of the spinnerets, depending on the difference that is determined.

14. The process according to claim 12, wherein, depending on the difference that is determined, the control unit outputs at least one control signal for changing a conveying speed of the perforated conveying device to a conveyor belt control device.

15. The process according to claim 1, wherein the spunbonded nonwoven is a cellulosic spunbonded nonwoven and the spinning mass is a solution of cellulose in a direct solvent, optionally a tertiary amine oxide in an aqueous solution.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0059] In the following, preferred embodiment variants of the invention are illustrated in further detail with reference to the drawings.

[0060] FIG. 1 shows a schematic illustration of the process according to the invention as per a first embodiment variant,

[0061] FIG. 2 shows a schematic illustration of the regulation according to the invention of the basis weight distribution in the process according to FIG. 1,

[0062] FIG. 3 shows a schematic illustration of the local distribution of the spinning mass throughput as a function of the temperature profile according to the first embodiment variant,

[0063] FIG. 4 shows a schematic illustration of the local distribution of the spinning mass throughput as a function of the temperature profile according to a second embodiment variant with modular spinnerets, and

[0064] FIG. 5 shows a schematic illustration of the local distribution of the spinning mass throughput as a function of the temperature profile according to a third embodiment variant with modular spinnerets.

DETAILED DESCRIPTION OF THE INVENTION

[0065] FIG. 1 shows a schematic illustration of a process 100 for the production of cellulosic spunbonded nonwoven 1 according to a first embodiment variant of the invention. In a first process step, a spinning mass 2 is produced from a cellulosic raw material and supplied to a spinneret 3. In this case, the cellulosic raw material for producing the spinning mass 2, which production is not shown in further detail in the figures, can be a pulp made of wood or other plant-based starting materials, which is suitable for the production of lyocell filaments. However, it is also conceivable that the cellulosic raw material consists at least partly 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 ranging between 3% by weight and 17% by weight.

[0066] In a following step, the spinning mass 2 is then extruded through a plurality of nozzle holes 4 in the spinneret 3 to form filaments 5, with the nozzle holes 4 in the spinneret 3 being arranged along a main axis 6. In this case, the main axis 6 of the spinneret 3 is aligned along a transverse direction 12 to the conveying direction 11 of the spunbonded nonwoven, which is shown in detail in particular in the schematic illustration of the process 100 in FIG. 2. In this case, the spinning mass throughput of the nozzle holes 4 along the transverse direction 12 is variably adjusted in the spinneret 3 so that the individual nozzle holes 4 have a differing spinning mass output in the transverse direction 12.

[0067] The extruded filaments 5 are then accelerated and drawn by a drawing air stream. For generating the drawing air stream, a drawing device is provided in the spinneret 3, which device is supplied with drawing air 7 and ensures that the drawing air stream exits the spinneret 3 in order to accelerate the filaments 5 after their extrusion.

[0068] In one embodiment variant, the drawing air stream can emerge between the nozzle holes of the spinneret 3. In a further embodiment variant, the drawing air stream may alternatively emerge around the nozzle holes. However, this is not illustrated in further detail in the figures. Such spinnerets 3 comprising drawing devices for generating a drawing air stream are known from the prior art (U.S. Pat. Nos. 3,825,380 A, 4,380,570 A, WO 2019/068764 A1).

[0069] Moreover, the extruded and drawn filaments 5 are charged with a coagulation air stream 8, which is provided by a coagulation device 9. The coagulation air stream 8 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 8 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.

[0070] The drawn and at least partially coagulated filaments 5 are then deposited in a random orientation on a conveyor belt 10 as a conveying device 10, forming the spunbonded nonwoven 1 there. The conveyor belt 10 then carries the formed spunbonded nonwoven 1 away in the conveying direction 11, with the spunbonded nonwoven 1 formed on the conveyor belt 10 extending on the conveyor belt 10 in the transverse direction 12 to the conveying direction 11.

[0071] As a result of the spinning mass throughput of the spinneret 3, which is variable in the transverse direction 12, a spunbonded nonwoven 1 with a basis weight variable in the transverse direction 12, i.e., a basis weight distribution in the transverse direction 12, is obtained on the conveyor belt 10, which is illustrated in further detail in FIG. 2. In this context, the spunbonded nonwoven has several areas 13, 14, 15 with different basis weights, with the edge cut areas 13, 15 having a lower basis weight than the useful area 14. In this case, the basis weight of the edge cut areas 13, 15 is less than 5 g/m2 and is reduced by at least 90% in comparison to the useful area 14.

[0072] In order to reliably control the spinning mass throughput of the spinneret 3 in the transverse direction 12 and thus the basis weight distribution of the spunbonded nonwoven 1 or, respectively, in order to obtain a spunbonded nonwoven 1 with a defined target basis weight distribution 19, the actual basis weight distribution 18 of the spunbonded nonwoven 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, wherein control signals 20, 21, 22 are output on the basis of the difference.

[0073] In FIG. 2, the regulation of the actual basis weight distribution 18 by means of the control unit 17 and control signals 20, 21, 22 are depicted in detail. In this case, the control signal 20 serves for regulating the pressure distribution of the spinning mass 2 in the spinneret 3. To this end, the control signal 20 is output to a spinning mass control device 23, which controls the spinning mass pumps 24 allocated to the spinneret 3 in order to control the pressure distribution of the spinning mass 2 and thus to adjust the spinning mass throughput of the spinneret 3. The control signal 21 in turn serves for regulating the temperature distribution of the spinneret 3 and, for this purpose, is output to a spinneret control device 25, which changes the temperature of the spinneret 3 in the transverse direction 12 in such a way that the spinning mass throughput of the spinneret 3 is adjusted in the transverse direction 12. Finally, the control signal 22 is output to a conveyor belt control device 26 for regulating the conveying speed of the conveyor belt 10 and, thus, for adjusting the basis weight of the spunbonded nonwoven 1.

[0074] In FIG. 3, the local spinning mass throughput distribution 34 and the temperature distribution 35 in the spinneret 3 are illustrated, wherein the spinning mass throughput distribution 34 and the temperature distribution 35 each represent the course of the spinning mass throughput 31 and, respectively, of the temperature 32 as a function of the expansion 33 of the spinneret 3 in the transverse direction 12. In this case, the temperature distribution 35 exhibits a drop in temperature 32 towards the edges in the corresponding edge cut areas 13, 15, as depicted on the spunbonded nonwoven 1 in FIG. 2, while the temperature 32 in the useful area 14 is kept essentially constant. Following the temperature distribution 34, a lower spinning mass throughput 31 will also appear 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.

[0075] As is also evident from FIG. 2, a feedback loop is provided between the control devices 23, 25, 26 and the detection device 16, which is able to achieve and keep constant a target basis weight distribution 19 in the finished spunbonded nonwoven 1 in a fully automatic fashion, by controlling the spinning mass throughput of the spinneret 3 and the conveying speed of the conveyor belt 10. Keeping the basis weight distribution constant in this way may serve both for levelling out fluctuations in the cellulose raw material and for producing a spunbonded nonwoven 1 with a predefined basis weight profile.

[0076] As illustrated in FIG. 1, after the spunbonded nonwoven 1 has been formed, it is finally subjected to washing 27 and hydroentanglement 28. In a following step, the washed and hydroentangled spunbonded nonwoven 1 is then subjected to drying in a dryer 29 in order to remove the remaining moisture and to obtain a finished spunbonded nonwoven 1. Finally, the process 100 is concluded by optionally winding 30 and/or packaging the finished spunbonded nonwoven 1.

[0077] In this case, the detection device 16 for measuring the actual basis weight distribution 18 of the spunbonded nonwoven 1 is advantageously provided between the dryer 29 and the winding 30, since, following the dryer 29, the properties of the finished spunbonded nonwoven 1 can be determined, whereby a high reliability of the process 100 is achieved.

[0078] In a further embodiment, which is not illustrated in further detail in the figures, the spunbonded nonwoven 1 is trimmed around the edge cut areas 13, 15 prior to winding 30 so that only the useful area 14 is supplied to winding 30.

[0079] In FIG. 4, a multi-part spinneret 40 with several spinneret modules 41, 42, 43, 44 according to a further embodiment variant of the process 101 according to the invention is shown. In this case, one spinning mass pump 45, 46, 47, 48 is allocated to each spinneret module 41, 42, 43, 44 in order to adjust the pressure distribution in the spinneret 40 in addition to the temperature distribution 37. In the exemplary embodiment forming the subject-manner, 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, the spinning mass throughput distribution 36 also exhibits, in each case, one drop in the edge areas so that edge cut areas 61, 63 are again formed on the spunbonded nonwoven 1, in which the basis weight is reduced in comparison to the useful area 62.

[0080] In FIG. 5, a further multi-part spinneret 50 with four spinneret modules 51, 52, 53, 54 according to a further embodiment variant of the process 102 according to the invention is shown. As already illustrated for FIG. 4, a spinning mass pump 55, 56, 57, 58 is again allocated to each spinneret module 51, 52, 53, 54. In contrast to FIG. 4, in the embodiment variant forming the subject-manner, the spinning mass pump 58 delivers spinning mass 2 at only a low or, respectively, minimal pressure, and, hence, the pressure distribution in the spinneret 50 exhibits a very low pressure in the area of the spinneret module 54, whereby the spinneret 50 also produces only a minimal spinning mass throughput 31 in the area of the spinneret module 54. In addition, a temperature distribution 39 is again provided in the spinneret 50, which is reflected in a spinning mass throughput distribution 38, which, in turn, leads to edge cut areas 64, 66 in the spunbonded nonwoven 1 with a lower basis weight than in the useful area 65. In the exemplary embodiment forming the subject-matter, the edge cut area 66 is now composed of the drop in basis weight due to the temperature distribution 39 and the uneven pressure distribution, whereby an extended edge cut area 66 with a very low basis weight is created in the spunbonded nonwoven 1. The waste after the trimming of the spunbonded nonwoven 1 to the useful area 65 can thus be kept to a minimum.

[0081] In a further embodiment variant, the wastes from the edge cut areas 14, 16, 61, 63, 64, 66 can be reused as a cellulosic raw material for the production of spinning mass 2, which, however, has not been illustrated in further detail in the figures.