Method of making a spunbond web from filaments

Abstract

A spunbond nonwoven from thermoplastic filaments is made by spinning the filaments from at least one spinner, cooling and stretching the spun filaments, depositing the cooled and stretched filaments on a surface to form a nonwoven fleece web, and moving the fleece web in a travel direction. A liquid medium is introduced into the moving fleece web and it is then mechanically needled. The mechanically needled web is then subject to a hydraulic or hydrodynamic final consolidation by hydroentanglement to a basis weight of more than 80 g/m.sup.2 from a top side as well as from a lower side of the nonwoven fleece web by high-pressure water-jet bars above and below the nonwoven fleece web. O of the bars is upstream of the other bar and has a hpi density that is smaller than that of the other bar and that is equal to at most 40.

Claims

1. A method of making a spunbond nonwoven from thermoplastic filaments, the method comprising the steps of sequentially: spinning the filaments from at least one spinner; cooling and stretching the spun filaments; depositing the cooled and stretched filaments via at least one diffuser on a surface to form a nonwoven fleece web; moving the fleece web in a travel direction; introducing a hydrophilic liquid medium into the moving fleece web in an amount of 0.2% to 25% based on the weight of the dry nonwoven fleece web or the weight of a dry area section of the nonwoven fleece web; mechanically needling the moving fleece web into which the liquid medium was introduced; premoistening the needled and moving fleece; and hydraulically or hydrodynamically final consolidating by hydroentanglement the mechanically needled and moving fleece web to a basis weight of more than 80 g/m.sup.2 from a top side as well as from a lower side of the nonwoven fleece web by high-pressure water-jet bars above and below the nonwoven fleece web, one of the bars being upstream of the other bar, being operated at a higher pressure than the other bar, and having a hpi density that is smaller than that of the other bar and that is equal to at most 40.

2. The method defined in claim 1, wherein the basis weight after final consolidation is more than 100 g/m.sup.2.

3. The method defined in claim 1, wherein the amount is 0.3 to 20%.

4. The method defined in claim 1, wherein the amount is 0.4 to 15%.

5. The method defined in claim 1, wherein the mechanical needling of the nonwoven fleece web is performed with a puncture density of less than 70 E/cm.sup.2.

6. The method defined in claim 1, wherein the hydraulic final consolidation is effected by a plurality of high-pressure water-jet bars with the bar doing the most hydraulic consolidation work having at least a 33% share of the total consolidation work.

7. The method defined in claim 6, wherein one of the water-jet bars carries out at least a 40% share of the total hydraulic consolidation work.

8. The method defined in claim 1, wherein the total hydraulic consolidation work is less than 1 kWh/kg.

9. The method defined in claim 8, wherein the total hydraulic consolidation work is less than 0.8 kWh/kg.

10. The method defined in claim 1, wherein the hole density of the one bar is less than 30 hpi.

11. The method defined in claim 1, wherein the one high-pressure water-jet bar has a hole diameter of 0.08 to 0.25 mm.

12. The method defined in claim 11, wherein the hole diameter is from 0.10 to 0.16 mm.

13. The method defined in claim 1, wherein the one upstream high-pressure water-jet bar is operated at a water pressure of more than 220 bar and the other downstream high-pressure water-jet bar is operated at a water pressure between 130 and 220 bar.

14. The method defined in claim 1, wherein the final consolidated fleece web has a basis weight of more than 130 g/m.sup.2.

15. The method defined in claim 14, wherein the basis weight is more than 150 g/m.sup.2.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The invention is explained in greater detail below on the basis of figures that illustrate only one illustrated embodiment. Therein:

(2) FIG. 1 is a schematic a vertical section through an upstream part of the inventive apparatus,

(3) FIG. 2 is a schematic a vertical section through a downstream part of the inventive apparatus and

(4) FIG. 3 is a view like to FIG. 2 of a different embodiment.

DETAILED DESCRIPTION OF THE INVENTION

(5) The figures show an apparatus for making a spunbond nonwoven from filaments that preferably consist of thermoplastic material. The filaments are spun using a spinner or spinneret 1 and are then introduced into a cooling chamber 2 where the filaments are cooled with cool air. The cooling chamber 2 in this embodiment is subdivided into two cooling subchambers 2a and 2b. In addition to the cooling chamber 2, there is an air supply means 8 that has an upper supply compartment 8a and a lower supply compartment 8b. Cooling air having different convective heat dissipation capacities is advantageously supplied from the two supply compartments 8a and 8b. Cooling air of different temperatures can preferably be supplied from the two compartments 8a and 8b. The filaments may be acted upon by cooling air of different temperatures and/or different quantities and/or different atmospheric humidities in the two cooling subchambers 2a and 2b.

(6) A stretcher 4 that advantageously and in this embodiment consists of an intermediate passage 3 and a lower passage 5 connected to the intermediate passage 3 is connected to the cooling chamber 2. According to a preferred embodiment and in this embodiment, a spreader 6 having at least one diffuser 13, 14 is connected to the stretcher 4. In this embodiment, two diffusers are provided, namely an upstream diffuser 13 and a downstream diffuser 14 connected to the former. According to a recommended embodiment and in the embodiment according to FIG. 1, an ambient air inlet gap 15 is provided between the upstream diffuser 13 and the downstream diffuser 14.

(7) Advantageously and in this embodiment, a continuously moving foraminous belt 7 for deposition of the filament to form a nonwoven fleece web 11 is provided underneath the spreader 6. According to an especially preferred embodiment and in the embodiment according to FIG. 1, no air supply from the outside is provided in the area of the cooling chamber 2 and the stretcher 4 apart from the supply of cooling air to cool the filaments in the cooling chamber 2. Preferably and in the embodiment according to FIG. 1, except for the above-described air supply there is no additional air supply from the outside throughout the entire system comprised of the cooling chamber 2 and the stretcher 4. This is a so-called closed system. According to one variant and in the embodiment according to FIG. 1, there is no additional supply of air in the entire system consisting of the cooling chamber 2, stretcher 4 and spreader 6, apart from the air supply described above and the air supply through the ambient air inlet gap 15.

(8) In the embodiment according to FIG. 1, the filaments emerging from the downstream diffuser 14 are deposited on the screen belt 7 to form the nonwoven fleece web 11. Advantageously and in the embodiment, a suction device 19 that draws air from underneath down through the screen belt 7 is provided in this deposition area for the filaments underneath the air permeable screen belt 7. According to the embodiment shown in FIG. 1, downstream from the above-described deposition area and/or suction area in the travel direction of the nonwoven fleece web there is compacting means 9 that here consists of two driven rollers 10, 12 that are advantageously heated. The rollers 10, 12 are not absolutely necessary, however.

(9) FIG. 2 shows a downstream section of the inventive apparatus. After deposition of the filaments on the screen belt and optionally after passing through the compactor 9, the nonwoven fleece web leaves the screen belt 7 and then is passed through a needler 16 (needle loom) where the nonwoven fleece web 11 is mechanically preconsolidated by needling. The nonwoven fleece web 11 preconsolidated in this way is then sent to a water-jet unit 17, where the nonwoven fleece web 11 is final consolidated hydraulically and/or hydrodynamically. Before the final consolidation, the nonwoven fleece web 11 is prewetted with a premoistener 18. The premoistener 18 is advantageously and in the embodiment according to FIG. 2 designed as a water-jet bar extending across the travel direction of the nonwoven fleece web 11. The water-jet bar is operated only at a low water pressure in contrast with downstream high-pressure water-jet bars 20, 21, 25 and 26.

(10) The embodiment according to FIG. 2 operates using one water-jet bar as the premoistener 18 and four high-pressure water-jet bars 20, 21, 25 and 26 as the water-jet unit 17 for the hydrodynamic and/or hydraulic final consolidation. The water-jet bars of the premoistener 18 advantageously have a nozzle bore diameter of 0.08 to 0.15 mm, preferably 0.10 to 0.14 mm and, for example, a nozzle bore diameter of 0.12 mm. Preferably, this water-jet bar has a hole density or hole bore density of 35 to 45 hpi, in particular a hole density of 40 hpi. The water-jet bar of the premoistener 18 is advantageously operated at a water pressure of 5 to 120 bar, preferably with a water pressure of 20 to 110 bar and with a water pressure of 100 bar, for example. The two high-pressure water-jet bars 20, 21 of the water-jet unit 17 each preferably has a nozzle bore diameter of 0.08 to 0.16 mm. The upstream high-pressure water-jet bar 20 is characterized according to a preferred embodiment of the invention by a hole density or a nozzle bore density of less than 40 hpi, preferably less than 30 hpi, for example, of 25 hpi. The downstream high-pressure water-jet bar 21 has a higher hole density in comparison with that, namely preferably a hole density greater than 25 hpi for example a hole density of 30 hpi. The upstream and downstream high-pressure water-jet bars 20, 21 are advantageously operated at a water pressure of more than 220 bar. The water pressure of the two downstream high-pressure water-jet bars 25 and 26 is preferably between 130 and 220 bar. The two high-pressure water-jet bars 25 and 26 act primarily on filaments near the surface and serve to subsequently smooth the nonwoven fleece web surface.

(11) After the hydraulic final consolidation, the nonwoven fleece web 11 is advantageously dried. During this process, the residual water content from the water-jet final consolidation is removed.

(12) FIG. 3 shows another embodiment of the inventive apparatus, where a liquid medium is applied to the nonwoven fleece web between the deposition of the filament and are between the discharge rollers 10, 12 and the needler 16. To do so a device 22 is provided with which the liquid medium is applied from above to the nonwoven fleece web 11. An intake device 23 that sucks the liquid medium applied by the device 22 into the nonwoven fleece web 11 is provided underneath the nonwoven fleece web 11 and/or underneath the screen belt 7. Preferably and in the embodiment, this suction device 23 has a suction slot 24 extending across the travel direction of the nonwoven fleece web 11. In this embodiment, with the application of a liquid medium, premoistening before the hydrodynamic final consolidation may also omitted. Therefore, in FIG. 3 the optional premoistener 18 is shown with dash-dot lines.