Apparatus for making spunbonded nonwoven from continuous filaments

Abstract

An apparatus for making spunbonded nonwoven has a spinneret for emitting the continuous filaments in a filament-travel direction, a cooling chamber downstream in the direction from the spinneret and receiving the filaments, and two air-supply manifolds flanking the chamber for feeding cooling air thereinto transverse to the direction. A flow straightener for equalizing flow of the cooling air on the filaments is provided in at least one of the air-supply manifolds and has passage walls forming a plurality of flow passages that extend transversely to a filament-travel direction. A flow cross section of the flow straightener is greater than 85% (preferably more than 90%) of a cross-sectional size of the straightener, a ratio of a length L of the flow passages to an inner diameter D.sub.i of the flow passages L/D.sub.i is 1 to 15.

Claims

1. An apparatus for making spunbonded nonwoven, the apparatus comprising: a spinneret for emitting continuous filaments in a filament-travel direction; a cooling chamber downstream in the direction from the spinneret and receiving the filaments; two air-supply manifolds flanking the chamber for feeding cooling air thereinto transverse to the direction and each subdivided relative to the direction into an upstream section and a downstream section that feed cooling air of different temperatures to the chamber; respective flow straighteners for equalizing flow of the cooling air on the filaments in each of the air-supply manifolds, the flow straighteners each extending in the direction along the upstream and downstream sections of the respective air-supply manifold and having passage walls extending between an intake side and an opposite outlet side of the respective straightener and forming a plurality of flow passages extending transversely to the filament-travel direction between the sides, a flow cross section of each flow straightener being greater than 85% of a cross-sectional size of the respective straightener, a ratio of a length L of the flow passages to an inner diameter Di of the flow passages L/Di of each flow straightener being 2.5:1 to 7.5:1; and a screen on each of the sides of each of the flow straighteners extending perpendicular to the passages and parallel to the direction and having a flow cross section equal to 20% to 50% of a cross-sectional size of the straightener.

2. The apparatus defined in claim 1, further comprising: a monomer extractor between the spinneret and the cooling chamber.

3. The apparatus defined in claim 1, wherein the screen has a mesh size of from 0.1 to 0.4 mm and a wire thickness of from 0.05 to 0.32 mm.

4. The apparatus defined in claim 1, wherein the flow cross section of the flow straightener is greater than 91% of a cross-sectional size of the straightener.

5. The apparatus defined in claim 1, wherein the flow passages of the flow straightener are of polygonal cross section.

6. The apparatus defined in claim 1, wherein the flow passages of the flow straightener have a round cross section.

7. The apparatus defined in claim 1, wherein the passage walls defining the passages or are wing or airfoil shaped and a spacing between two adjacent walls defining each passage is 3 to 12 mm.

8. The apparatus defined in claim 1, wherein an inner surface of the flow straightener through which the cooling air flows constitutes 5 to 50 m.sup.2 of the flow cross section of the flow straightener.

9. The apparatus defined in claim 1, wherein a length of the flow passages of the flow straightener is 15 to 65 mm.

10. The apparatus defined in claim 1, wherein a smallest inner diameter of the flow passages is 2 to 15 mm.

11. The apparatus defined in claim 1, wherein the spinneret is operated such that a speed of the filaments in the filament-travel direction is greater than 2000 m/min.

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 the apparatus according to the invention;

(3) FIG. 2 is an enlarge detail from FIG. 1 showing the cooler of the cooling chamber and the air-supply manifolds;

(4) FIG. 3 is a perspective view of an subassembly of a flow straightener with upstream and downstream flow screens;

(5) FIG. 4 is a cross section through a flow straightener section with hexagonal or honeycomb-shaped flow passages;

(6) FIG. 5 is a view like FIG. 4 with circular flow passages; and

(7) FIG. 6 is a view like FIG. 4 with airfoil-shaped passage walls of the flow passages of the flow straightener.

SPECIFIC DESCRIPTION OF THE INVENTION

(8) As seen in FIG. 1 an apparatus according to the invention for manufacturing spunbonded nonwovens from continuous filaments 1, particularly from continuous thermoplastic filaments 1 has a spinneret 2 for spinning the continuous filaments 1. These spun continuous filaments 1 are introduced in a vertical and downward filament-travel direction FS into a cooler 3 with a cooling chamber 4 flanked on opposite sides by air-supply manifolds 5 and 6. The cooling chamber 4 and the air-supply manifolds 5 and 6 are spaced transverse to a machine direction MD perpendicular to the direction FS and thus in the CD direction of the apparatus. Cooling air is introduced from the oppositely situated air-supply manifolds 5 and 6 into the cooling chamber 4. Preferably and here, a monomer extractor 7 is provided between the spinneret 2 and the cooler 3. With this monomer extractor 7, objectionable gases produced by the spinning process can be removed from the apparatus. These gases can be monomers, oligomers, or decomposition products and similar substances, for example.

(9) In the filament-travel direction FS, the cooler 3 is followed by a stretcher 8 in which the filaments 1 are elongated. Preferably and here, the stretcher 8 has an intermediate passage 9 that connects the cooler 3 to a tunnel 10 of the stretcher 8. According to an especially preferred embodiment and here, the subassembly of the cooler 3 and the stretcher 8 and/or the subassembly of the cooler 3, the intermediate passage 9, and the tunnel 10 are embodied as a closed system. “Closed system” means that, apart from the supply of cooling air by the manifolds 5 and 6 to the cooler 3, no further air is fed into this subassembly.

(10) Advantageously and here, a diffuser 11 through which the filaments 1 are guided adjoins the stretcher 8 in the filament-travel direction FS. According to one embodiment and here, secondary air inlet gaps 12 are provided between the stretcher 8 and/or between the tunnel 10 and the diffuser 11 for the introduction of secondary air into the diffuser 11. Preferably and here, after passing through the diffuser 11, the filaments 1 are deposited on a delivery device that is embodied as a mesh belt 13. The deposited filaments or the nonwoven web 14 is then conveyed or transported away by the mesh belt 13 in the horizontal machine direction MD. Recommendably and here, an extractor for sucking air, more particularly process air, through the delivery device or through the mesh belt 13 is provided beneath the delivery device or beneath the mesh belt 13. For this purpose, an aspiration zone 15 is preferably provided beneath the mesh belt 13 and here beneath the downstream end of the diffuser 11. The aspiration zone 15 extends at least over a width B of the diffuser outlet. Preferably and here, a width b of the aspiration zone 15 is greater than the width B of the diffuser outlet.

(11) According to a preferred embodiment and here, each air-supply manifold 5 and 6 is divided into upstream and downstream sections 16, 17, from each of which cooling air of different temperature can be supplied. Preferably and here, cooling air can thus be supplied from each of the upper sections 16 at a temperature T.sub.1, whereas cooling air can be supplied from each of the two lower sections 17 at a temperature T.sub.2 that is different from the temperature T.sub.1. According to one embodiment and here, a flow straightener 18 is provided in each air-supply manifold 5 and 6 on the cooling chamber side that, preferably and here, extends over both sections 16, 17 of each air-supply manifold 5 and 6.

(12) The two flow straighteners 18 serve to rectify the cooling air flow that is incident on the filaments 1. Preferably and here, each flow straightener 18 has a plurality of flow passages 19 for this purpose that are oriented perpendicular to the filament-travel direction FS. These flow passages 19 are each delimited by passage walls 20 and are preferably straight and each emit a perfectly horizontal substream of cooling air.

(13) According to a preferred embodiment and here, the flow cross section of each flow straightener 18 constitutes greater than 90% of the total area of the flow straightener 18. Recommendably and here, the ratio of the length L of the flow passages 19 to the smallest inner diameter D.sub.i of the flow passages 19 lies in the range between 1 and 10, advantageously in the range between 1 and 9.

(14) According to a very advantageous embodiment and here, each flow straightener 18 has a flow screen 21 both on its outer cooling-air intake side ES and on its inner cooling-air output side AS. Preferably and here, the two flow screens 21 of each flow straightener 18 are provided directly in front of or behind the flow straightener 18.

(15) Recommendably and here, the two flow screens 21 of a flow straightener 18, more particularly the surfaces of these flow screens 21 are aligned perpendicular to the longitudinal direction of the flow passages 19 of the flow straightener 18. It has proven advantageous for a flow screen 21 to have a mesh size w of from 0.1 to 0.5 mm, preferably from 0.1 to 0.4 mm, and more preferably from 0.15 to 0.34 mm. Furthermore, it is advantageous if the flow screen has a wire thickness of from 0.05 to 0.35 mm, preferably from 0.05 to 0.32 mm, and more preferably from 0.07 to 0.28 mm. It lies within the scope of the invention for the mesh size w of the flow screens 21 to be substantially smaller than the smallest inner diameter D.sub.i of the flow passages 19 of the flow straightener 18. The mesh size w of a flow screen 21 is preferably less than ⅙, very preferably less than ⅛, and especially preferably less than 1/10 of the smallest inner diameter D.sub.i of the flow passages 19. It is recommended that the flow cross section of a flow screen 21 that is not occupied by wire constitute up to 50% and preferably 25 to 45% of the total surface area of a flow screen 21.

(16) FIGS. 4 to 6 show typical cross sections of the flow passages 19 of a flow straightener 18 that is used according to the invention. According to a recommended embodiment and here according to FIG. 4, the flow passages 19 of a flow straightener 18 have a hexagonal or honeycomb-shaped cross section. Here, the smallest inner diameter D.sub.i is measured between opposite sides of the hexagon (see FIG. 4). In the embodiment according to FIG. 5, the flow passages 19 of the flow straightener 18 are of circular cross section. FIG. 6 shows an embodiment of a flow straightener 18 according to the invention with arcuate or airfoil-shaped passage walls 20. These airfoil-shaped passage walls 20 are advantageously separated from one another in the embodiment by spacers 22 that also form passage walls of these flow passages. The airfoil-shaped passage walls 20 are circularly arcuate segments in cross section (see right side of FIG. 6). In principle, the airfoil-shaped passage walls 20 can also be rectilinear, in which case the flow straightener 18 is a grid.