Apparatus for making spunbond

Abstract

An apparatus for making spunbond from continuous thermoplastic filaments has a spinneret for spinning the continuous filaments and advancing them in a filament-travel direction, a cooler for cooling the filaments, a stretcher for stretching the filaments, a depositing device including a foraminous belt extending in a machine direction transverse to the filament-travel direction for deposition of the filaments as a nonwoven web and conveyance away from the stretcher, a diffusor between the stretcher and the foraminous belt so that filaments and primary air from the stretcher enter into the diffusor, and a suction device for extracting air through the foraminous belt at an unobstructed extraction region underneath the diffusor outlet and having a width b in a machine direction that is greater than a width B of the diffusor outlet. The diffusor forms upstream and downstream secondary air-inlet gaps at opposite ends through which secondary air is aspirated into the diffusor.

Claims

1. An apparatus for making spunbond from continuous thermoplastic filaments, the apparatus comprising: a spinneret for spinning the continuous filaments and advancing them in a filament-travel direction; a cooler for cooling the filaments; a stretcher for stretching the filaments; a depositing device including a foraminous belt extending and traveling in a machine direction transverse to the filament-travel direction and defining a deposition region for deposition of the filaments as a nonwoven web and conveyance away from the stretcher in the machine direction; a diffusor between the stretcher and the foraminous belt and having relative to the filament-travel direction a downstream section that is of a predetermined length and that diverges in the filament-travel direction, an upstream section that is of a length equal to at most 60% of the predetermined length of the downstream section and that converges in the filament-travel direction, and a constriction between and connecting the sections so that filaments and primary air from the stretcher enter into the diffusor in the filament-travel direction, the diffusor forming relative to the machine direction upstream and downstream secondary air-inlet gaps at opposite ends of the diffusor through which secondary air is aspirated into the diffusor, the upstream and downstream secondary air-inlet gaps being oriented such that the secondary air flows in at an inflow angle α of less than 100° with respect to the filament-travel direction or with respect to a longitudinal central plane of the depositing device or of the diffusor, the downstream section having walls diverging in the filament-travel direction toward the depositing device and forming a diffusor outlet having an outlet width in the machine direction; and a suction device having two partitions spaced apart in the machine direction by an extraction width for extracting air or process air through the foraminous belt at an unobstructed extraction region underneath the diffusor outlet and free of further structures between the partitions, the extraction width in the machine direction being at least 1.5 times the outlet width in the machine direction of the diffusor outlet, the extraction by the suction device taking place such that at least in the region of the diffusor outlet tertiary air flows along outer surfaces of the diffusor walls toward the depositing device or the foraminous belt and the tertiary air flows substantially parallel to a mixed flow of the primary air and the secondary air flowing toward the diffusor outlet inside the diffusor, the tertiary air also being extracted through the foraminous belt by the suction device.

2. The apparatus defined in claim 1, wherein the unobstructed extraction region projects in the machine direction downstream and/or upstream of the deposition region of the filaments by an extraction section beyond the diffusor outlet.

3. The apparatus defined in claim 1, wherein a volume flow of tertiary air extracted with the suction device is at least 25% of a volume flow of the extracted primary and secondary air.

4. The apparatus defined in claim 1, wherein the cooler and the stretcher form a subassembly that is closed such that, apart from a supply of cooling air in the cooler, no further fluid medium or air flows into this closed subassembly.

5. The apparatus defined in claim 1, wherein at the secondary air-inlet gaps, a ratio of volume flows of the primary air to the secondary air is less than 5:1.

6. The apparatus defined in claim 1, wherein a ratio 1.sub.K/1.sub.D of a length 1.sub.k of the convergent upstream diffusor section to a length 1.sub.D of the divergent downstream diffusor section is 0.1:1.

7. The apparatus defined in claim 1, wherein an outlet angle β of the downstream diffusor section with respect to a longitudinal central axis M of the diffusor is a maximum of 30°.

8. The apparatus defined in claim 1, wherein a spacing between the diffusor or a lower edge thereof and the foraminous belt is 20 mm to 300 mm.

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, and

(3) FIG. 2 is an enlarged view of the detail shown at II in the lower region of the apparatus according to the invention.

SPECIFIC DESCRIPTION OF THE INVENTION

(4) The drawing shows an apparatus according to the invention for making spunbond of continuous filaments 1, in particular of continuous thermoplastic. The device has a spinneret 2 for spinning the continuous filaments 1 downward in a filament-travel direction FS as well as a cooler 3 downstream from the spinneret 2 for cooling the spun filaments 1.

(5) According to a particularly preferred embodiment of the invention, a monomer extractor 4 is provided between the spinneret 2 and the cooler 3. With this monomer extractor 4, perturbing gases produced during the spinning process can be removed from the device. These can be, for example, monomers, oligomers or decomposition products and similar substances. A gap 5 is formed between the monomer extractor 4 and the cooler 3 that usually runs around the entire filament formation space or filament flow space. According to a very preferred embodiment and here according to the figures (see in particular FIG. 1), at least one deformable seal 6 for sealing this gap 5 is between the monomer extractor 4 and the cooler 3. Advantageously the seal 6 runs in the gap 5 extends around the entire filament formation space or filament flow space.

(6) Here it lies within the scope of the invention that the installation properties, in particular the pressing force or the pressing pressure of the seal 6 relative to the boundary surfaces of the gap 5 can be varied or adjusted. A vertical height h of the gap 5 here may be 5 to 30 mm and the at least one deformable seal 6 seals the gap 5 over this vertical height h of the gap 5. Preferably and here, the at least one deformable seal 6 has a seal 6 that can be inflated with a fluid medium. By supplying or removing the fluid medium, preferably air, the installation properties, in particular the pressing force or the pressing pressure of the seal 6, can be varied.

(7) Here (see in particular FIG. 1), the cooler 3 has two cooling chambers provided one above the other or consecutively in which the filaments can be acted upon in particular with process air or cooling air at different temperature. In principle however, a cooler 3 with only one cooling chamber is possible within the scope of the invention.

(8) A stretcher 7 for elongating the filaments 1 is provided downstream of the cooler 3 in the filament-travel direction FS. Preferably and here, the cooler 3 opens into an intermediate passage 8 that connects the cooler 3 to a stretch passage 9 of the stretcher 7. According to a preferred embodiment and here, the subassembly comprising the cooler 3, the intermediate passage 8 and the stretch passage 9 is configured as a closed system. Apart from the supply of cooling air in the cooler 3, no further air is supplied to this subassembly 3, 8, 9. The air guided through the stretcher 7 or through the stretch passage 9 is here and subsequently designated as primary air P.

(9) According to the invention, downstream of the stretcher 7 in the filament-travel direction FS there is at least one diffusor 10. Preferably and here, two opposite secondary air-inlet gaps 11 and 12 for the introduction of secondary air S are provided between the stretcher 7 or its stretch passage 9 and the diffusor 10. Advantageously the secondary air-inlet gaps 11 and 12 extend over the entire transverse or CD width of the apparatus according to the invention.

(10) According to the invention the secondary air is supplied through the secondary air-inlet gaps at an inflow angle α that is less than 100°, advantageously less than or equal to 90°, preferably less than 80° and here less than 45°. According to a very recommended embodiment of the invention, the inflow angle α is between 0 and 60°, preferably between 2 and 50°. In order to achieve the inflow angle α, here (see in particular FIG. 2) suitable adapted inflow guides 13 are provided that here are configured as inflow passages 14 connected obliquely to the secondary air-inlet gaps 11 and 12. Here the inflow passages 14 form an angle with the filament-travel direction FS or with the longitudinal central axis M such that the secondary air can flow in at the specified inflow angle α. According to a particularly preferred embodiment, a quasi-parallel inflow of secondary air to the filament-travel direction FS takes place.

(11) According to a particularly recommended embodiment of the invention, the volume flow of secondary air supplied through the secondary air-inlet gaps 11 and 12 can be adjusted. This can be achieved in particular by adjusting the cross-sections of the secondary air-inlet gaps 11 and 12. In principle, different volume flows of supplied secondary air S can also be adjusted for the two opposite secondary air-inlet gaps 11 and 12. According to one embodiment of the invention, the secondary air volume flow flowing in through the secondary air-inlet gaps 11 and 12, preferably relative to each secondary air-inlet gap 11 and 12, can be adjusted or varied transversely to the machine direction or over the CD width. In this case, the supplied secondary air volume flow in the edge regions or the device or the secondary air-inlet gaps 11 and 12 is advantageously different compared with the central region of the device or the central region of the secondary air-inlet gaps 11 and 12.

(12) As a result of the entrance of secondary air S through the secondary air-inlet gaps 11 and 12, primary air P is mixed with secondary air S in the adjacent diffusor 10. According to a preferred embodiment of the invention, in the region of the secondary air-inlet gaps 11 and 12, the ratio of volume flows of primary air and secondary air VP/VS is less than 5:1 and preferably less than 4.5:1.

(13) Here according to the figures, only one diffusor 10 is provided in the filament-travel direction FS underneath the stretcher 7. In principle two or more diffusors 10 can be connected consecutively. The diffusor 10 provided here according to the figures has a convergent diffusor section 15 downstream of or underneath the secondary air-inlet gaps 11 and 12 in the filament-travel direction FS. Preferably and here, this convergent diffusor section 15 is followed by a constriction 16 of the diffusor 10. In the filament-travel direction FS downstream of or underneath the constriction 16, the diffusor 10 is preferably and here provided with a divergent diffusor section 17. It is here recommended that the divergent diffusor section 17 of the diffusor 10 in the filament-travel direction FS is longer or significantly longer than the convergent diffusor section 15. Preferably and here, the length 1.sub.k of the convergent diffusor section 15 is less than 50% of the length 1.sub.D of the divergent diffusor section 17.

(14) It is here recommended that the diffusor outlet angle β between a diffusor wall 18 of the divergent diffusor section 17 and the longitudinal central axis M of the diffusor 14 is a maximum of 25°. Advantageously and here, the width B of the diffusor outlet 19 is a maximum of 300%, preferably a maximum of 250% of the width VB of the outlet gap 20 of the stretch passage 9.

(15) The continuous filaments 1 emerging from the diffusor 10 are deposited on a deposition device configured as a foraminous belt 21 for filament deposition to form the nonwoven web 22. The deposited filament or nonwoven web 22 is conveyed or transported away by the depositing foraminous belt 21 in the machine direction MD. According to the invention, a suction device for extracting air or process air through the deposition device or through the depositing foraminous belt 12 is provided. To this end, an unobstructed extraction region 23 provided underneath the diffusor outlet 19 that preferably has a width b in the machine direction (MD). This width b of the unobstructed extraction region 23 is according to the invention greater than the width B of the diffusor outlet 19. The widths b and B are shown in FIG. 2. According to a preferred embodiment of the invention, the width b of the unobstructed extraction region 23 is at least 1.2 times, preferably at least 1.3 times the width B of the diffusor outlet 19. Here the width B of the diffusor outlet 19 is measured as the horizontal spacing of the lower edges of the diffusor walls 18. If the edges of the diffusor walls 18 of the divergent diffusor section 17 are at the same horizontal plane or do not end at the same vertical height, the distance of the end of the longer diffusor wall 18 from the end of a downward extension of the shorter diffusor wall 18 is measured.

(16) The unobstructed extraction region 23 located underneath the depositing foraminous belt 21 is delimited by two partitions 27 and 28 provided consecutively in the machine direction MD. The width b of the unobstructed extraction region 23, which is free of further structures between the partitions 27 and 28, is measured as the distance between the two partitions 27 and 28 and specifically as the spacing of the upper edges of the two partitions 27, 28. It can be particularly seen from FIG. 2 that relative to the machine direction MD downstream of the deposition region of the filaments 1 the unobstructed extraction region 23 projects by a first extraction section 24 beyond the diffusor outlet 19 or over the width B of the diffusor outlet 19. Furthermore, relative to the machine direction MD upstream of the deposition region of the filaments 1, the unobstructed extraction region 23 projects by a second extraction section 25 upstream (in direction MD) beyond the diffusor outlet 19 or beyond the width B of the diffusor outlet 19. FIG. 2 shows that the first extraction section 24 has a width b.sub.1 and the second extraction section 25 has a width b.sub.2. According to one embodiment and here, the widths b.sub.1 and b.sub.2 are the same. In principle however, they could also be different.

(17) In particular, as a result of the configuration of the unobstructed extraction region 23 according to the invention, the extraction by the depositing foraminous belt 21 takes place such that in the region of the diffusor outlet 19, tertiary air T flows along the outer surfaces 26 toward the foraminous belt 21 being deposited. According to a particularly preferred embodiment, the flows of the tertiary air T are aligned parallel or substantially parallel to the mixed flow of primary air P and secondary air S flowing toward the diffusor outlet 19 of the diffusor 10. Thus, according to a very preferred embodiment of the invention, primary air P and secondary air S as well as tertiary air T are sucked through the depositing foraminous belt 21. Advantageously the flows of primary air P, secondary air S and tertiary air T flow parallel or almost parallel through the depositing foraminous belt 12.