Method of making a spunbond from filaments

Abstract

The invention relates to a device for producing a spun-bonded web from filaments, comprising spinnerets, a cooling chamber into which process air can be introduced in order to cool the filaments, a monomer suction device arranged between the spinnerets and the cooling chamber, a stretching unit, and a placing device for placing the filaments so as to form the spun-bonded web. The cooling chamber is divided into two cooling chamber portions. Process air can be suctioned out of a first upper cooling chamber portion to the monomer suction device with a volumetric flow rate V.sub.m, and process air exits the first upper cooling chamber portion into a second lower cooling chamber portion with a volumetric flow rate V.sub.1. The volumetric flow rate ratio V.sub.M/V.sub.1 is 0.1 to 0.3.

Claims

1. A method of making a spunbond web, the method comprising the steps of: providing a spinneret having a nozzle plate forming a plurality of nozzle holes that are homogeneously distributed across the entire nozzle plate; heating polypropylene having an average isotactic sequence length of at least 65 to an onset temperature of at least 120; extruding filaments of the heated polypropylene by the spinneret through the homogeneously distributed nozzle holes such that the filaments travel in a flow direction and are spaced apart homogeneously in a direction transverse to the flow direction; moving the homogeneously spaced and extruded filaments in the flow direction downstream from the nozzle plate through a monomer suction device into a cooling chamber divided into upper and lower cooling compartments; feeding cool process air into the cooling chamber to cool the filaments in the compartments thereof; sucking a portion of the process air by the monomer suction device from the upper cooling compartment and drawing the sucked out portion of the process air into the monomer suction device at a volumetric flow rate V.sub.M; feeding another portion of the process air from the upper compartment at a volumetric flow rate V.sub.1 into the lower cooling compartment; setting the flow rates relative to each other such that a volumetric flow-rate ratio V.sub.M/V.sub.1 is 0.1 to 0.3; and feeding the filaments from the lower cooling compartment into a stretcher; and then depositing the filaments from the stretcher onto a deposition device for the spunbond web.

2. The method defined in claim 1, further comprising the steps of: providing next to the cooling chamber an air supply cabin divided into upstream and downstream cabin sections respectively connected to the upper and lower compartments, the introducing process air into the upper cooling compartment from the upstream cabin section, and into the lower cooling compartment from the downstream cabin section.

3. The method in accordance claim 1, further comprising the step of: withdrawing process air at a volumetric flow rate V.sub.2 from the lower cooling compartment such that a volumetric flow-rate ratio V.sub.1/V.sub.2 is 0 to 0.5.

4. The method in accordance claim 1, further comprising the step of: emitting process air at a volumetric flow rate V.sub.1 from the upper cooling compartment into the lower cooling compartment and withdrawing process air at a volumetric flow rate V.sub.2 from the lower cooling compartment such that a volumetric flow-rate ratio V.sub.1/V.sub.2 is 0.2 to 0.5.

5. The method in accordance with claim 1, further comprising the step of: varying a distance between the spinneret and the upper compartment of the cooling chamber.

6. The method in accordance with claim 1, further comprising the step of: excluding entry of process air from outside into the compartments of the cooling chamber and at a transition area between the cooling chamber and the stretcher.

7. The method in accordance with claim 1, further comprising the step of: providing at least one diffuser between the stretcher and the deposition unit for separating the filaments transversely of the flow direction.

8. The method in accordance with claim 1, wherein the polypropylene has a melting flow rate of 10 dg/min to 40 dg/min.

9. The method in accordance with claim 1, wherein the filaments are monocomponent filaments.

10. The method in accordance with claim 1, wherein the filaments are stretched in the stretcher to 0.3 to 2 den.

11. The method defined in claim 1, wherein the portion of process air sucked from the upper compartment into the monomer suction device moves opposite to the flow direction of the filaments.

12. The method defined in claim 1, wherein the other portion flowing from the upper compartment into the lower cooling compartment moves in the flow direction of the filaments.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) In the following, the invention is explained in greater detail based on a drawing illustrating only one sample design. It shows the following in schematic drawing:

(2) FIG. 1 a vertical section through the apparatus in accordance with the invention and

(3) FIG. 2 an enlarged section A from the object of FIG. 1.

SPECIFIC DESCRIPTION OF THE INVENTION

(4) The figures show an apparatus for continuous production of a spunbond web of filaments of thermoplastic. The apparatus exhibits, first of all, a spinneret 1 with a nozzle plate 2 and nozzle holes therein for spinning the filaments that are not depicted. The spun filaments are then run past a monomer suction device 3 positioned below spinneret 1. This monomer suction device 3 is used to remove objectionable gasses from the system during the spinning process. The monomer suction device 3 exhibits a sucking chamber 4 as well as an exhaust ventilator 5 connected to the sucking chamber 4. A sucking slit 6 for sucking up the gasses is included in the lower region of the sucking chamber 4. Most practically, the sucking chamber 4 will be positioned both to the right and left of the filament formation space, as shown in the design example. The left half of the sucking chamber 4 is also connected to sucking ventilator 5.

(5) A cooling chamber 7 into which process air for cooling the filaments can be introduced is positioned below the spinneret 1 and below the monomer suction device 3. Preferably, the cooling chamber 7 will be divided into an initial, upper cooling chamber 7a and a second, lower cooling chamber 7b, as shown in the design example. Most practically, and as shown in the design example, an air supply chamber 8 will be positioned next to the cooling chamber 7 that advisably and as shown in the design example, will be divided into an upper compartment 8a and a lower compartment 8b. Preferably and as shown in the design example, process air of various volumetric flow rates can be fed in from the two compartments 8a and 8b. Most practically and as shown in the design example, a blower 9a and 9b for feeding in process air will be connected to the compartments 8a and 8b. The scope of the invention includes that the infed volumetric flow rates of process air can be controlled. The scope of the invention also includes that the compartments 8a and 8b be positioned both to the right and left of the cooling chamber 7. The left halves of compartments 8a and 8b are also connected to the corresponding blowers 9a and 9b.

(6) The invention is based on the recognition that process air can be or is sucked from the first, upper cooling compartment 7a at a volumetric flow rate V.sub.M via the monomer suction device 3 positioned above the cooling chamber 7. The process air leaves the first, upper cooling compartment 7a toward the second cooling compartment 7b at a volumetric flow rate V.sub.1. According to the invention, the ratio of the volumetric flow rates V.sub.M/V.sub.1 is 0.1 0.3 and preferably 0.12 to 0.25. The process air leaves the second, lower cooling compartment 7b at a volumetric flow rate V.sub.2. The flow volume ratio V.sub.1/V.sub.2 is preferably 0.1 to 0.5.

(7) It can be seen in FIG. 1 that the cooling chamber 7 is connected to the intermediate passage 10, as shown in the design example. This intermediate passage 10 reaches to pulling under passage 11 of the stretcher 12. Most practical and as shown in FIG. 1 of the design example, the intermediate passage 10 runs together in a vertical, wedge-shaped cut from the outlet of cooling chamber 7 to the inlet of the pulling under passage 11, and preferably and as shown in the design example with the entry width of the pulling under passage 11. Preferably and as shown in the design example, a laying unit 13 is positioned below the stretcher 12. In the design example, this laying unit 13 has two diffusers 14 and 15. It can be seen that each of these diffusers 14 and 15 has a diverging shape or is designed with diverging walls in the lower area. Preferably and as shown in the design example, a continuous, moving conveyor belt 16 for depositing the filaments and/or the spunbond web is provided below the laying unit 13.

(8) It can be seen in FIG. 1 that, with the exception of the infeed of process air to the cooling chamber 7, no air supply takes place in the area of the cooling chamber 7, the intermediate passage 10, and the laying unit 13. This means that operations are performed in a closed system. FIG. 1 also shows that the distance between the spinneret 1 and/or between the nozzle plate 2 and the cooling chamber 7 can be set and varied in accordance with the recommended design form. Most practical and as shown in the design example, the vertical height of spinneret 1 can be set.