METHOD AND APPARATUS FOR MAKING NONWOVEN FROM CONTINUOUS FILAMENTS

Abstract

An apparatus for making nonwoven has a spinning device for spinning continuous filaments and moving the spun filaments in a vertical travel direction along a vertical travel path and a mesh belt below the spinning device, traveling in a horizontal direction, and having a multiplicity of vertically throughgoing openings distributed generally uniformly over its surface and of which a portion are plugged. A cooler and a stretcher are provided along the path downstream of the spinning device and above the belt for cooling and stretching the filaments and depositing the cooled and stretched filaments at a predetermined deposition location on the belt. A blower underneath the belt at the deposition location aspirates air through the openings and thereby holds the deposited filaments down on the belt.

Claims

1. An apparatus for making nonwoven, the apparatus comprising: a spinning device for spinning continuous filaments and moving the spun filaments in a vertical travel direction along a vertical travel path; a mesh belt below the spinning device, traveling in a horizontal direction, and having a multiplicity of vertically throughgoing openings distributed generally uniformly over its surface and of which a portion are plugged; a cooler and a stretcher along the path downstream of the spinning device and above the belt for cooling and stretching the filaments and depositing the cooled and stretched filaments at a predetermined deposition location on the belt; means underneath the belt below the cooling and stretching devices for aspirating air through the openings and thereby holding the deposited filaments down on the belt, the openings being dimensioned and the air being aspirated through the belt such that, if none of the openings were plugged, air would pass through the belt at 300 to 1100 cfm, but actually so many of the openings are plugged that air passes through the belt at 150 to 700 cfm.

2. The apparatus defined in claim 1, wherein the mesh belt is formed by a textile having warp filaments and weft filaments that define the mesh belt openings.

3. The apparatus defined in claim 2, wherein the textile of the mesh belt has a web density of 20 to 75 warp filaments per 25 mm and 10 to 50 weft filaments per 25 mm.

4. The apparatus defined in claim 1, wherein a minimum diameter of a plugged opening of the mesh belt amounts to at least 1.5 mm and a maximum of 8 mm.

5. The apparatus defined in claim 1, wherein a ratio of air permeability of an unplugged mesh belt to an air permeability of the partly plugged mesh belt amounts to 1.2 to 4.

6. The apparatus defined in claim 1, wherein the plugged belt openings are plugged by a sealing compound that is in or below a surface of the mesh belt and does not project past the mesh-belt surface more than a maximum of 1.5 mm.

7. The apparatus defined in claim 1, wherein the plugged openings are arrayed in punctate or linear fashion.

8. The apparatus defined in claim 7, wherein the plugged openings are arrayed uniformly in a regular pattern on the mesh belt.

9. The apparatus defined in claim 1, wherein the cooler and stretcher together form a closed subassembly such that, except for a supply of cooling air in the cooler, no further air enters this closed subassembly.

10. The apparatus defined in claim 1, further comprising, downstream of the stretcher and upstream of the deposition location: a diffuser through which the filaments can be guided to the deposition location prior to being deposited.

11. The apparatus defined in claim 1, further comprising, downstream in the belt-travel direction from the deposition location: a compacting roller for preconsolidating the nonwoven deposited on the deposition device or on the mesh belt; and means for heating the compacting roller.

12. A method of making nonwoven comprising the steps of: spinning continuous filaments from a spinneret to move along a vertical travel path in a vertical travel direction; cooling and stretching the filaments downstream from of the spinneret in a cooler and a stretcher; depositing the cooled and stretched filament at a deposition location on a mesh belt moving horizontally underneath the cooler and stretcher and having an array of openings of which a portion are plugged; drawing air downward through the unplugged openings in the mesh belt to stabilize the filaments deposited on the mesh belt, the air being aspirated through the mesh belt at the location at a rate forming a ratio to a rate if none of the openings were plugged of 1.2 to 4.

13. The method defined in claim 12, wherein the nonwoven is produced as spunbond nonwoven.

14. The method defined in claim 12, wherein the air is aspirated through deposition location at an aspiration speed of 5 to 25 m/s.

15. The method defined in claim 12, further comprising the step of: preconsolidating the deposited nonwoven into final form.

16. The method defined in claim 12, further comprising the step, to separate the nonwoven from the mesh belt, of blowing air through the mesh belt from below or against the underside of

17. A spunbond nonwoven comprising continuous filaments of thermoplastic made by the method of claim 12, the continuous filaments have a titer of 0.9 to 10 denier.

18. A melt-blown nonwoven of continuous thermoplastic filaments made by the method of claim 12. wherein the continuous filaments have a diameter of 0.1 to 10 μm.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0039] 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:

[0040] FIG. 1 is a vertical section through an apparatus of the invention;

[0041] FIG. 2 is an enlarged view of the detail shown at A in FIG. 1;

[0042] FIG. 3a is a top view of a first embodiment of a mesh belt used according to the invention;

[0043] FIGS. 3b, 3c, and 3d are views like FIG. 3a of second, third, and fourth embodiments of the invention; and

[0044] FIG. 4 is an enlarged detail of FIG. 1 in a first embodiment; and

[0045] FIG. 5 is the same detail as FIG. 4 but in a second embodiment.

SPECIFIC DESCRIPTION OF THE INVENTION

[0046] The drawings shows an apparatus according to the invention for making nonwoven 1 from continuous filaments 2. In a particularly preferred embodiment and in this illustrated embodiment, this is a spunbond apparatus for making spunbond nonwoven 1 or spun nonwoven 1. The continuous filaments 2 preferably are of thermoplastic or essentially of thermoplastic. In the apparatus of the invention, the continuous filaments 2 are spun with the aid of a spinning device a spinneret 3. After that, the continuous filaments 2 are cooled in a cooler 4. This cooler 4 preferably and in the illustrated embodiment has two compartments 4a and 4b, one above the other or one after the other in the filament-travel direction, and that introduce cooling air of a variable temperature into the filament flow chamber. Downstream of the cooler 4 in the filament-travel direction is a stretcher 5 that preferably and in the illustrated embodiment has both an intermediate passage 6 that narrows in the flow direction of the continuous filaments 2 and a stretching passage 7 at the downstream end of the intermediate passage. Preferably and in the illustrated embodiment, the unit comprising the cooler 4 and the stretcher 5 is a plugged system. In this plugged system, except for the supply of cooling air or processing air, there is no further air supply in the cooler 4.

[0047] In a preferred embodiment of the invention and in the illustrated embodiment, a diffuser 8, 9 is connected to the stretcher 5 downstream in the filament-travel direction. Advantageously and in the illustrated embodiment, two diffusers 8, 9 are provided, located either one below the other or one after the other. It is recommended that an ambient air inlet gap 10 be provided between the two diffusers 8, 9 for the entry of ambient air. It is within the scope of the invention that the continuous filaments 2, downstream of the diffusers 8, 9, are deposited on a deposition device in the form of a mesh belt 11. It is furthermore within the scope of the invention that this is a continuously circulating mesh belt 11.

[0048] The mesh belt 11 has a mesh belt surface 12 with many mesh belt openings 13 distributed over the surface 12. According to the invention, air is aspirated through the mesh belt surface 12, or in other words through the (open) mesh belt openings 13. For that purpose, at least one suction blower, not shown in detail in the drawings, is located below the mesh belt 11. Preferably and in the illustrated embodiment, in the travel direction of the belt there are three separate suction areas 14, 15, 16 one after the other. In the suction area 17 of the continuous filaments 2, a main suction area 15 is preferably provided in which air is aspirated through the mesh belt 11, for instance at a suction speed or a mean suction speed of 5 to 30 m/s. Advantageously, the suction speed in the main suction area 15 is set such that it is higher than the suction speed in the remaining suction areas 14 and 16. A first suction area 14 is provided upstream of the main suction area 15, and a second suction area 16 is downstream of the main suction area 15. Advantageously and in the illustrated embodiment, a compacting device 18 with two compacting rollers 19, 20 is provided along the second suction area 16 for compacting or preconsolidating the nonwoven 1. As recommended and in the illustrated embodiment, at least one of the compacting rollers 19, 20 is a heated compacting roller 19, 20.

[0049] According to the invention, some of the mesh belt openings 13 of the mesh belt 11 are plugged. To that extent, the result is plugged mesh belt openings 21 or plugged points 22 in the mesh belt that are formed by a single plugged mesh belt opening 21 or a plurality of adjoining plugged mesh belt openings 21. It is understood that the air permeability of the unplugged mesh belt 11 (solely open mesh belt openings 13) is greater than the air permeability of the mesh belt 11 that is provided with plugged mesh belt openings 21. For instance, the air permeability of the unplugged mesh belt amounts to 600 cfm, and the air permeability of the plugged mesh belt 11—that is, the air permeability of the mesh belt 11 with some plugged mesh belt openings 21—is only 350 cfm. The ratio of the air permeability of the unplugged mesh belt 11 to the air permeability of the partly plugged mesh belt 11 is preferably 1.2 to 3. The air permeability is measured in particular crosswise to the mesh belt surface 12 in a circular surface of the mesh belt that is 38.3 cm.sup.2 in area, at a pressure difference of 125 Pa.

[0050] Preferably and in the illustrated embodiment, the mesh belt 11 has a textile that comprises warp filaments 23 and weft filaments 24 that define the mesh belt openings 13. The diameter D or the minimum diameter D of a mesh belt opening 13 may amount to 0.5 mm in the illustrated embodiment. Advantageously, this is the diameter D with respect to filaments or woven filaments located on the surface or in a surface layer of the mesh belt or mesh belt textile. It is recommended that the textile of the mesh belt 11 have a web density of 20 to 75 warp filaments per 25 mm and 10 to 50 weft filaments per 25 mm.

[0051] In a preferred embodiment of the invention, the plugged openings 22 in the mesh belt 11 are arrayed in punctate and/or linear form. FIG. 3a shows the punctate embodiment of plugged openings 22 in the mesh belt 11. The (least) diameter d of such a punctate plugged opening 22 may amount to 2 mm in the illustrated embodiment. In the illustrated embodiment of FIG. 3b, plugged-opening lines 22 are shown. The least width b of the plugged-opening lines 22 may amount to 2 mm as well in the illustrated embodiment. FIG. 3c shows a further embodiment with interrupted plugged-opening lines 22. The plugged-opening lines 22 can furthermore, in a manner not shown, also be curved or bowed lines. In FIG. 3d, an additional illustrated embodiment is shown with intersecting plugged-opening lines 22. This embodiment, too, has proved itself. FIGS. 3a, 3b and 3d furthermore show embodiments in which the plugged openings 22 are symmetrical to the longitudinal direction or travel direction of the belt 11. The travel direction F of the mesh belt 11 is indicated in FIGS. 3a through 3d by an arrow. Conversely, the embodiment of FIG. 3c is not symmetrical to the longitudinal direction or travel direction F of the mesh belt 11. The embodiments that are symmetrical with respect to the longitudinal direction or travel direction F are preferred in the context of this invention.

[0052] In FIG. 4, an especially recommended embodiment of the apparatus of the invention is shown. The continuous filaments 2 emerging from the diffuser 9 are deposited on the mesh belt surface 12 in the deposition area 17 of the mesh belt 11. The main suction area 15 for aspirating the processing air through the mesh belt 11 or through the mesh belt surface 12 is located below the deposition area 17. Downstream of the main suction area 15 is the second suction area 16 in which processing air is aspirated at what in comparison to the main suction area 15 is a lower air speed. The compacting device 18 with the two compacting rollers 19, 20 is provided above the second suction area 16. A separation area 25 is then downstream in the travel direction of the nonwoven 1. In this separation area, the nonwoven 1 or the preconsolidated nonwoven 1 is released/separated from the mesh belt 11 or in other words from the mesh belt surface 12. To that end, air is blown from below, or in other words against the underside of the nonwoven 1 and up through the mesh belt 11. This has been indicated in FIGS. 4 and 5 by arrows 26. In a recommended embodiment and in the illustrated embodiment of FIG. 4, the nonwoven 1 subjected to the separating air is braced by an air-permeable drum 27 co-rotating in the travel direction of the belt 11. The drum can be positioned at a spacing of 0.5 to 5 mm, for instance, above the mesh belt surface 12. The surface of the drum 27 can be for example a metal textile. Instead of the drum, an additional mesh belt (not shown) jointly rotating in the travel direction of the belt 11 could also be used.

[0053] FIG. 5 shows a further embodiment of a drum 27 provided for bracing the nonwoven 1 subjected to the separation air. In this illustrated embodiment, the drum 27 has a suction area 28 for receiving the separation air, and supporting air is additionally blown in, in the direction of the mesh belt 11 or of the nonwoven 1, in order to prevent the continuous filaments 2 or nonwoven 1 from sticking to the drum 27. The supporting air is symbolized in FIG. 5 by an arrow 29