Making a nonwoven from filaments

Abstract

An apparatus for making a nonwoven fabric from thermoplastic plastic filaments has an air permeable deposit conveyor having a horizontal face displaceable in a horizontal travel direction and a spinneret above the conveyor for spinning the filaments and depositing the spun filaments on the deposit conveyor in a deposit area of the conveyor as a nonwoven web for conveyance in the travel direction. An extractor beneath the conveyor draws air or process air through the deposit conveyor in the deposit area in a main extraction area below the deposit conveyor and is delimited by, relative to the travel direction, upstream and downstream suction partitions. One of the partitions has an upper edge set at a predetermined vertical spacing below the conveyor equal to between 10 mm and 250 mm.

Claims

1. An apparatus for making a nonwoven fabric from thermoplastic plastic filaments, the apparatus comprising: a conveyor that is air permeable and has a horizontal face displaceable in a horizontal travel direction; a spinneret above the conveyor for spinning the filaments and depositing the spun filaments on the face of the conveyor in a deposit area of the conveyor as a nonwoven web for conveyance in the travel direction; and an extractor beneath the conveyor that draws air or process air through the conveyor in the deposit area in a main extraction area below the conveyor and delimited by, relative to the travel direction, upstream and downstream suction partitions, one of the partitions having an upper end with an upper edge set at a predetermined vertical spacing below the conveyor equal to between 10 mm and 250 mm, the one suction partition having an upper end formed by a partition section that is angled from the rest of the one suction partition and forms a spoiler, the upper edge of the spoiler with the shortest vertical spacing from the conveyor having the predetermined vertical spacing from the conveyor, the spoiler being more angled relative to the vertical extending perpendicular to the face than an upper partition section of the other suction partition and/or in its projection onto the conveyor face having a greater length than the corresponding projection of an upper, angled or bent upper partition section of the other suction partition and/or having a greater spacing from the conveyor relative to its upper end than an upper edge of the upper partition section of the other suction partition.

2. The apparatus according to claim 1, wherein the one suction partition has at its upper end a spoiler in the form of an angular element with two spoiler parts arranged at an angle to one another, and an upper end edge of this spoiler has the predetermined vertical spacing from the conveyor.

3. The apparatus according to claim 2, wherein the spoiler has a spoiler part that is oriented transversely or substantially perpendicularly to the face of the conveyor, and the spoiler also has a spoiler part oriented parallel or substantially parallel to the face.

4. The apparatus according to claim 1, wherein only the downstream suction partition has the spoiler.

5. The apparatus according to claim 1, wherein the spoiler is aligned or angled to a side of the respective suction partition facing away from a center of the main extraction area or the spoiler is aligned or angled toward a center of the main extraction area.

6. The apparatus according to claim 1, wherein at least two of the spinnerets are provided spaced in the direction above the conveyor for spinning the filaments and therefore being upstream and downstream spinnerets, respective upstream and downstream main suction areas in which air or process air is sucked through the conveyor being associated with the respective upstream and downstream spinnerets, each of these main suction areas being delimited by two respective upstream and downstream suction partitions, at least one suction partition of each main suction area having a spoiler, the spoiler of the upstream suction area is aligned or angled to the side of the respective suction partition facing away from the center of the upstream suction area, and the spoiler of the downstream main extraction area is aligned or angled toward the center of the downstream main suction area.

7. The apparatus according to claim 1, further comprising: a cooler downstream of the spinneret and above the conveyor; a stretcher downstream of the cooler and above the conveyor; and a diffuser downstream of the stretcher and above the conveyor.

8. The apparatus according to claim 7, wherein the cooler and the stretcher form a subassembly closed to the admission of outside air other than cooling air in the cooler.

9. The apparatus according to claim 7, wherein the diffuser has relative to the direction upstream and downstream diffuser walls having respective lower diverging diffuser wall sections that are asymmetrical relative to a center plane of the diffuser or of the apparatus with the upstream diffuser wall section forming a smaller angle with the center plane of the diffuser or of the apparatus than the downstream diffuser wall section.

10. The apparatus according to claim 7, wherein the diffuser has relative to the direction upstream and downstream diffuser walls forming respective upstream and downstream secondary air inlet gaps at an upper end of the diffuser such that lower secondary air streams enter through the secondary air inlet gaps.

11. The apparatus according to claim 1, wherein the extractor has second upstream and downstream partition walls spaced in the direction from the main extraction area and forming a second extraction area where air or process air is drawn through the conveyor, when the second extraction area is downstream of the main extraction area, the extractor draws air through it at extraction speed v.sub.2 lower than an extraction speed V.sub.H in the main extraction area, and/or when the second extraction area is upstream of the main extraction area, the extractor draws air through it at an extraction speed lower V.sub.v than the extraction speed in the main extraction area.

12. The apparatus according to claim 11, wherein the downstream partition wall of the main extraction area and the second downstream partition wall of the second extraction area are spaced differently from the face of the conveyor such that there is a continuous uniform transition between the extraction speed v.sub.H of the main extraction area and the extraction speed v.sub.2 of the second extraction area.

13. The apparatus according to claim 11, further comprising: a preconsolidater for preconsolidating the nonwoven fabric on or above the second extraction area.

14. The apparatus according to claim 13, wherein a spacing in the direction between a center plane of the diffuser and the preconsolidater is 100 mm to 1000 mm.

15. A method of making a nonwoven fabric, the method comprising the steps of: displacing an air-permeable conveyor belt in a horizontal travel direction; delimiting a main extraction area below the conveyor belt by, relative to the direction, a downstream suction partition and by an upstream suction partition; spinning filaments and depositing the spun filaments on an air-permeable conveyor belt at the main extraction area to form a nonwoven web; delimiting below the conveyor belt a second extraction area spaced upstream or downstream from the main extraction area; drawing air through the belt at the main extraction area at a greater extraction speed in the main extraction area than in the second extraction area, the extraction speed in the main extraction area being 1.5 to 4 times greater than the extraction speed in the second extraction area; and when the second extraction area is upstream of the main extraction area, spacing an upper end of the upstream suction partition below the belt or, when the second extraction area is downstream of the main section area, spacing an upper end of the downstream suction partition below the belt such that the extraction speed of the air flow through the belt decreases uniformly between the main extraction area and the second extraction area.

16. The method according to claim 15, wherein the filaments are continuous multicomponent filaments.

17. The method according to claim 15, wherein a change in the extraction speed between the speed in the main extraction area and the speed in the second extraction area has a gradient of 1 to 8 m/s.

18. The method according to claim 17, wherein the extraction speed changes uniformly and continuously from the extraction speed in the main extraction area to the extraction speed in the second extraction area in a transition zone of a length in the direction of at least 10 cm.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

(2) FIG. 1 is a vertical section through an apparatus according to the invention for making a nonwoven fabric,

(3) FIG. 2 is an enlarged detail from FIG. 1 at the deposit conveyor,

(4) FIG. 3 shows the structure according to FIG. 2 in an alternative embodiment,

(5) FIG. 4 is a graph showing the dependence of the extraction speed on the position in the transition area between the main extraction area and the second extraction area,

(6) FIG. 5 is a vertical section through a two-beam system or multibeam system with two parts according to the invention for making a nonwoven fabric and

(7) FIG. 6 is a section through a filament preferably used for the nonwoven fabrics made according to the invention with an eccentric core-sheath configuration.

SPECIFIC DESCRIPTION OF THE INVENTION

(8) FIG. 1 shows an apparatus according to the invention for making a nonwoven fabric 1 from filaments of thermoplastic material, where preferably and here the filaments are continuous filaments 2, and specifically as recommended and according to this embodiment the filaments are bicomponent filaments with an eccentric core-sheath configuration. Continuous filaments 2 with an eccentric core-sheath configuration that are particularly preferred in the context of the invention are described in more detail below. As recommended and according to this embodiment, the apparatus according to the invention is designed as a spunbond apparatus for making spunbond nonwoven fabric.

(9) FIG. 1 shows a spinneret 10 for spinning the continuous filaments 2. Preferably and according to this embodiment, the spun endless filaments 2 are introduced into a cooler 11 with a cooling chamber 12. Expediently and according to this embodiment, air supply compartments 13 and 14 are one above the other on two opposite sides of the cooling chamber 12. Air at different temperatures is expediently introduced into the cooling chamber 12 from these air supply compartments 13 and 14 arranged one above the other. According to the recommended embodiment and here, a monomer extractor 15 is between the spinneret 10 and the cooler 11. With this monomer extractor 15, disruptive gases occurring during the spinning process can be removed from the apparatus. These gases can be, for example monomers, oligomers or decomposition products and the like.

(10) In the filament flow direction, a stretcher 16 for drawing the continuous filaments 2 is provided downstream of the cooler 11. Preferably and according to this embodiment, the stretcher 16 has an intermediate passage 17 that connects the cooler 11 to a shaft 18 of the stretcher 16. According to a particularly preferred embodiment and here, the subassembly consisting of the cooler 11 and the stretcher 16 or the subassembly consisting of the cooler 11, the intermediate passage 17 and the shaft 18 is designed as a closed unit and, apart from the supply of cooling air in the cooler 11, further air entry from the outside into this subassembly is blocked.

(11) As recommended and according to this embodiment, a diffuser 19 through which the continuous filaments 2 pass adjoins the stretcher 16 in the filament flow direction. Preferably and according to this embodiment, after passing through the diffuser 19, the continuous filaments are deposited on a deposit conveyor designed as a mesh belt 20. Preferably and according to this embodiment, the mesh belt 20 is designed as an endlessly circulating mesh belt 20. It is within the scope of the invention that the mesh belt 20 is air-pervious, so that process air can be extracted from below through the mesh belt 20.

(12) According to the recommended embodiment and here, the diffuser 19 directly above the depositing belt 20 has upstream and downstream diffuser walls forming respective upstream and downstream lower diverging diffuser wall sections 21 and 22 that, preferably and according to this embodiment flank a center plane M of the diffuser 19. Expediently and according to this embodiment, the upstream diffuser wall section 21 at its lower edge has a smaller spacing e.sub.1 from the center plane M of the diffuser 19 or of the apparatus than the spacing e.sub.2 of the downstream diffuser wall section 22 or the lower edge of the downstream diffuser section 22. As recommended and according to this embodiment, the upstream diffuser wall section 21 forms a smaller angle β with the center plane M of the diffuser 19 or of the apparatus than the downstream diffuser wall section 22.

(13) According to a recommended embodiment of the invention, two opposite secondary air inlet gaps 24 and 25, each of which is on a respective one of the two opposite diffuser walls, are provided at the inflow end 23 of the diffuser 19. A smaller secondary air stream can preferably be introduced through the secondary air inlet gap 24 upstream relative to the travel direction of the mesh belt 20 than through the downstream secondary air inlet gap 25.

(14) Preferably and according to this embodiment at least one extractor is provided that can draw air or process air through the mesh belt 20 in the deposit area or in the main deposit area 26 of the filaments 2 in a main extraction area 27. The main extraction area 27 is delimited below the mesh belt 20 in an inlet area of the mesh belt 20 and in an outlet area of the mesh belt 20 by a upstream and downstream suction partitions 28.1 and 28.2.

(15) It is within the scope of the invention that at least one of the suction partitions 28.1 and 28.2 has at its upper end turned toward the conveyor a partition section designed as a spoiler 30. Here according to FIGS. 1 and 2, the downstream suction partition 28.2 has at upper end a partition section angled from the rest of the suction partition 28.2 and designed as a spoiler 30. Here shown in FIGS. 1 and 2, the spoiler 30 is, as it were, an integral part of the downstream suction partition 28.2 and is merely designed as an angled section of this partition 28.2. Preferably and according to this embodiment, the vertical spacing A of the upper end of the spoiler 30 from the mesh belt 20 is between 10 mm and 250 mm, in a preferred embodiment between 18 mm and 120 mm. Preferably and here according to FIGS. 1 and 2, the spoiler 30 is angled on the side of the respective suction partition 28.2 facing away from the center of the main extraction region 27.

(16) FIG. 3 shows a further embodiment of a spoiler 30. The spoiler 30 is connected here as a separate L-shaped element to the downstream suction partition 28.2. Preferably and according to this embodiment, the L-shaped element is composed of only two spoiler parts 34, 35 that are angled relative to one another. Expediently and according to this embodiment, the two spoiler parts 34, 35 are oriented at a right angle to one another. Preferably, one spoiler part 34 of the spoiler 30 is perpendicular to the deposit conveyor face F of the mesh belt 20 and the other spoiler part 35 is oriented parallel to the deposit conveyor face F. Here, the end of the spoiler 30 on the conveyor side also has the spacing A according to the invention from the deposit conveyor or the mesh belt 20.

(17) Preferably and here according to FIG. 1, a second extraction area 29 in which air or process air is sucked through the mesh belt 20 is connected downstream of the main extraction area 27 in the travel direction of the mesh belt 20. Preferably and according to this embodiment, the extraction speed v.sub.2 of the process air through the mesh belt 20 in the second extraction area 29 is lower than the extraction speed v.sub.H in the main extraction area 27.

(18) It is within the scope of the invention that downstream of the deposit area 26 or downstream of the main extraction area 27 in the travel direction of the nonwoven web there is at least one thermal preconsolidater for thermal preconsolidation of the nonwoven web. Furthermore, it is within the scope of the invention that this thermal preconsolidater is on or above the second extraction region 29. According to a particularly preferred embodiment, the thermal preconsolidater works with hot air, and particularly preferably this thermal preconsolidater connected downstream of the main extraction region 27 is a hot-air knife 31. In principle, however, another preconsolidater or hot-air preconsolidater could also be used. Bonds between the filaments 2 of the nonwoven web can be formed in a simple manner with the thermal preconsolidater or hot-air preconsolidater. The spacing B (FIGS. 2 and 3) between the center plane M of the diffuser 19 or of the apparatus and the first hot-air preconsolidater, in particular in the form of the hot-air knife, is expediently 31-120 mm to 550 mm.

(19) According to one embodiment of the invention, at least two thermal preconsolidaters are provided for preconsolidating the nonwoven web. FIG. 1 shows a preferred embodiment here. The first thermal preconsolidater in the travel direction of the nonwoven web is a hot-air knife 31 and a second thermal preconsolidater in the form of a hot-air oven 32 is preferably connected downstream of this hot-air knife 31 in the travel direction of the mesh belt 20. It is within the scope of the invention that air is also sucked through the mesh belt 20 at the hot-air oven 32. Furthermore, it is within the scope of the invention that the extraction speed of the air sucked through the mesh belt 20 decreases from the main extraction area 27 to the further extraction areas in the travel direction of the mesh belt 20.

(20) The spoiler 30 according to the invention ensures a continuous and more or less smooth transition of the extraction speeds from the main extraction area 27 to the second extraction area 29. In the embodiment according to FIGS. 1 to 3, the spoiler 30 is aligned or angled to the side of the respective suction partition 28.2 facing away from the center of the main extraction region 27 or to the side facing away from the center plane M.

(21) In the preferred embodiment of the spoiler 30 shown in FIG. 2, the spoiler 30 is more strongly angled relative to a vertical V extending perpendicular to the deposit conveyor face F than a dividing wall section of the upstream partition 28.1 facing the mesh belt 20. FIG. 2 also shows that, according to a preferred embodiment, the spoiler 30 has a greater length L in its projection onto the deposit conveyor face F than the corresponding projection of an angled or bent partition section of the further upstream partition 28.1 facing the mesh belt 20. Furthermore, FIG. 2 shows that, according to a particularly preferred embodiment, the spoiler 30 has a greater vertical spacing A from the mesh belt 20 relative to its end on the mesh belt side than the end of the partition section of the upstream partition 28.1 facing the mesh belt 20. A vertical height h of the spoiler 30 (projection onto the center plane M) is preferably 5 mm to 110 mm, in particular 15 mm to 100 mm.

(22) As mentioned above, a spoiler 30 according to the invention ensures a very uniform and continuous transition of the extraction speeds from the main extraction area 27 to the area following it in the travel direction of the mesh belt 20 and in particular to the second extraction area 29. Due to the orientation of the spoiler 30 a gradual, continuous and steady decrease in the extraction speed can be achieved. This will be described below with reference to FIG. 4. The gradual continuous decrease in the extraction speed makes it possible to avoid defects that can be caused by abrupt changes in extraction speed in the nonwoven web or in the spunbond nonwoven fabric 1 according to the invention. Above all, the so-called blow-back effects in the transition area between the main extraction area 27 and the second extraction area 29, which lead to disadvantageous inhomogeneities in the nonwoven web in apparatuses known from the prior art and in particular to disruptive filament agglomerates, can be avoided.

(23) FIG. 4 shows schematically the extraction speed v through the mesh belt 20 at various positions along the mesh belt 20 in the transition area between the main extraction area 27 and the second extraction area 29. For the profiles shown, the extraction speed was measured in a 10 cm grid with an impeller anemometer with a diameter of 80 mm, spaced directly above the mesh belt 20 by 0 mm to 5 mm. The maximum on the left corresponds to the high extraction speed v.sub.H in the main extraction area 27 and the more or less horizontal curves on the right show the extraction speed v.sub.2 in the second extraction area 29. The drop in the curves between the maximum and the horizontal outlet corresponds to the transition of the extraction speeds v between the main extraction area 27 and the second extraction area 29. The curves K1 and K2 correspond to the drop in the extraction speed in conventional spunbond apparatuses without a spoiler 30 according to the invention. The curves K3 illustrate the drop in the extraction speed for a spunbond apparatus according to the invention with a spoiler 30, specifically at different extraction speeds v.sub.2. An angled spoiler 30 according to FIG. 2 was used here. It can be seen that the extraction speeds for the conventional spunbond apparatuses (curves K1 and K2) drop very abruptly in the transition area between the main extraction area 27 and the second extraction area 29. In contrast, in a spunbond apparatus according to the invention with a spoiler 30 the extraction speed drops less abruptly and rather gradually and continuously here in a transition area or over a mesh belt section of approximately 20 cm. In comparison to the conventional spunbond apparatuses without a spoiler 30, there is therefore a much smoother continuous decrease in the extraction speeds. The invention is based on the discovery that this is associated with the considerable advantage that disadvantageous blow-back effects in the transition area between the main extraction area 27 and the second extraction area 29 can be largely avoided. Therefore, compared to the conventional spunbond apparatuses, nonwoven webs can be made according to the invention that are made much more homogeneous over their face or surface and in particular have no disruptive filament agglomerates. In this respect, a spunbond apparatus according to the invention with a spoiler 30 is characterized by considerable advantages.

(24) FIG. 5 shows a two-bar system with two spunbond apparatuses according to the invention connected in series that preferably and according to this embodiment deposit endless filaments 2 on the same mesh belt 20 for the nonwoven web. To this extent, this system produces a laminate of two nonwoven webs or two spunbond nonwoven fabrics 1. In principle, this system could also be part of a multibeam system with further spinnerets 10.

(25) For the sake of simplicity, the complete spunbond apparatuses were not shown in FIG. 5, but only the lower part with the diffuser 19 above the mesh belt 20. It is within the scope of the invention that both spunbond apparatuses have a structure corresponding to the spunbond apparatus according to FIG. 1 above the mesh belt 20. In the first bar or in the first spinneret 10 on the left in FIG. 5, a first spoiler 30 is connected to the downstream suction partition 28.2 of the main extraction area 27, and preferably and according to this embodiment this spoiler 30 is angled to the side of the connected suction partition 28.2 facing away from the center of this left main extraction area 27. As a result, a smooth continuous transition of the extraction speeds from the extraction speed v.sub.H in the main extraction area to the extraction speed v.sub.2 in the second extraction area 29 is achieved. The first deposited nonwoven web then preferably runs through two thermal hot-air preconsolidaters that are preferably designed as a hot-air knife 31 and as a hot-air oven 32 downstream of this hot-air knife 31. The preconsolidaters are not shown in FIG. 5.

(26) Subsequently, a further nonwoven web is deposited on the second bar or on the second spinneret 10 on the right side. This second nonwoven web is deposited on the first nonwoven web. In this second bar, the orientation of the spoiler 30 differs from the first bar. Here, the second spoiler 30 is also connected to the downstream suction partition 28.2 of the main extraction area 27. However, in contrast to the first bar, this second spoiler 30 of the second bar is angled toward the center of the second main extraction area 27. Here, a further extraction area 33, in which process air is sucked through the mesh belt 20 at an extraction speed v.sub.V, is connected upstream of the main extraction area 27. This extraction speed v.sub.V of the upstream extraction area 33 is lower or significantly lower than the extraction speed v.sub.H of the subsequent main extraction area 27. In order to ensure continuous transition of the extraction speed from the upstream extraction area 33 to the main extraction area 27 here, in this second bar the spoiler 30 is angled toward the center of the main extraction area 27 in the manner described. This also ensures a smooth continuous transition of the extraction speeds from the upstream extraction area 33 to the main extraction area 27.

(27) FIG. 6 shows a cross section through an endless filament 2 with a special core-sheath configuration. The manufacture of nonwoven fabrics 1 from these continuous filaments 2 has proven particularly useful in connection with the apparatus according to the invention and the method according to the invention. In the case of these continuous filaments 2, the sheath 3 has a constant thickness d in the filament cross section and, here, preferably over more than 50%, preferably over more than 55% of the filament circumference. Preferably and according to this embodiment, the core 4 of the filaments 2 occupies more than 65% of the area of the filament cross section of the filaments 2. As recommended and according to this embodiment, the core 4, seen in the filament cross section, is designed in the form of a segment of a circle. Expediently and here, this core 4 has a circularly arcuate surface region 5 and a straight surface region 6 with regard to its circumference. Preferably and according to this embodiment, the circular arcuate surface region of the core 4 takes up over 50%, preferably over 55% of the circumference of the core 4. Expediently and here, the sheath 3 of the filaments 2, seen in the filament cross section, is formed outside the sheath area with the constant thickness d in the form of a segment of a circle. This circular segment 7 of the casing 3 has, as recommended and according to this embodiment, a circular arcuate surface region 8 and a straight surface region 9 with regard to its circumference. The thickness d or the average thickness d of the sheath 3 in the region of its constant thickness is preferably 1% to 8%, in particular 2% to 10% of the filament diameter D. Here, the thickness d of the sheath 3 in the region of its constant thickness may be 0.2 μm to 3 μm.

(28) FIG. 6 shows the spacing a of the centroid of the core 4 from the centroid of the surface of the sheath 3 of the endless filament 2. For a given mass ratio of core and sheath material, this spacing a of the centroid of the core 4 from the sheath 3 is generally greater in the case of the continuous filaments 2 preferred here than in the case of conventional continuous filaments 2 with an eccentric core-sheath configuration. The spacing a of the centroid of the core 4 from the centroid of the sheath 3 is preferably 5% to 40% of the filament diameter D or of the largest filament diameter D in the present filaments 2.