PROCESS AND APPARATUS FOR PRODUCING ELECTROSTATICALLY CHARGED FIBRES AND AN ELECTRET PRODUCT

Abstract

Techniques produce electrostatically charged fibres, and in particular produce an electret fibre construct, where fibres are produced from a plastics and/or natural-origin material, where a polar liquid is atomized using a gaseous pressure medium to produce a treatment aerosol and where the fibres are treated with the treatment aerosol for electrostatic charging, wherein the atomizing is undertaken with a quotient of the volume flow of the polar liquid in litres per second and the positive pressure of the gaseous pressure medium in hectopascals of 0.004 to 0.008.

Claims

1. Process for producing electrostatically charged fibres, in particular for producing an electret fibre construct, where fibres are produced from a plastics and/or natural-origin material, where a polar liquid is atomized using a gaseous pressure medium to produce a treatment aerosol and where the fibres are treated with the treatment aerosol for electrostatic charging, wherein the atomizing is undertaken with a quotient of the volume flow of the polar liquid in litres per hour and the positive pressure of the gaseous pressure medium in hectopascals of 0.004 to 0.008 and/or with a quotient of the mass flow of the polar liquid and the mass flow of the gaseous pressure medium of 1.4 to 3 and/or with a quotient of the volume flow of the polar liquid and the volume flow of the gaseous pressure medium of 0.001 to 0.004.

2. (canceled)

3. (canceled)

4. Process according to claim 1, wherein the atomizing of the polar liquid is undertaken via at least one two-fluid nozzle, in particular with a plurality of two-fluid nozzles.

5. Process according to claim 4, wherein the atomizing may be undertaken in a two-fluid nozzle or per two-fluid nozzle at a volume flow of the polar liquid of 3.2 litres per hour to 5.2 litres per hour, in particular at a volume flow of the polar liquid of 4.2 litres per hour or about 4.2 litres per hour.

6. Process according to claim 1, wherein the atomizing of the polar liquid is undertaken at a positive pressure of the gaseous pressure medium of 500 to 900 hectopascals, in particular at a positive pressure of the gaseous pressure medium of 700 hectopascals or about 700 hectopascals.

7. Process according to claim 4, wherein the atomizing is undertaken in a two-fluid nozzle or per two-fluid nozzle at a mass flow of the gaseous pressure medium of 2.1 to 2.7 kilograms per hour, in particular at a mass flow of the polar liquid of 2.1 to 2.5 kilograms per hour or 2.3 to 2.7 kilograms per hour.

8. Process according to claim 4, wherein the atomizing may be undertaken in a two-fluid nozzle or per two-fluid nozzle at a volume flow of the gaseous pressure medium of 1.5 to 2.5 cubic metres per hour, in particular at a volume flow of the polar liquid of 0.002-0.008 cubic metres per hour.

9. Process according to claim 1, wherein the fibres are sprayed with the treatment aerosol before consolidation to afford a fibre construct and/or fibre nonwoven and/or before laydown on a collecting apparatus and/or before capture by a vacuum source.

10. Process according to claim 1, wherein the fibres are produced by melt blowing and/or in that the fibres are sprayed with the treatment aerosol immediately after exiting a melt blowing die apparatus and/or in that the treatment aerosol is supplied to the outlet opening of a melt blowing die apparatus for spraying of the fibres.

11. Process according to claim 1, wherein after spraying with the treatment aerosol the fibres are consolidated to afford a fibre construct and/or a fibre nonwoven and/or laid down on a collecting apparatus and/or in that the fibres consolidated to afford a fibre construct and/or fibre nonwoven and/or laid down on a collecting apparatus have a residual moisture content of less than 6%, in particular of less than 5%, without active drying.

12. Apparatus for producing electrostatically charged fibres, in particular for performing a process, with a spinning apparatus for producing fibres from a plastics and/or natural-origin material and with a nozzle apparatus for producing a treatment aerosol by atomizing a polar liquid using a gaseous pressure medium and for electrostatic charging of the fibres by spraying the fibres with the treatment aerosol, wherein the nozzle apparatus is configured for undertaking the atomizing with a quotient of the volume flow of the polar liquid in litres per hour and the positive pressure of the gaseous pressure medium in hectopascals of 0.004 to 0.008 and/or with a quotient of the mass flow of the polar liquid and the mass flow of the gaseous pressure medium of 1.4 to 3 and/or with a quotient of the volume flow of the polar liquid and the volume flow of the gaseous pressure medium of 0.001 to 0.004.

13. Apparatus according to claim 12, wherein the nozzle apparatus comprises a two-fluid nozzle or a plurality of two-fluid nozzles, wherein a plurality of two-fluid nozzles is preferably arranged at a distance of 4 cm to 10 cm, in particular a distance of 5 cm to 8 cm or a distance of 7 cm or about 7 cm to one another and/or in that the openings of the two-fluid nozzles are arranged at an angle relative to the horizontal , in particular at an angle of 1° to 30°, preferably of 5° to 20°.

14. Apparatus according to claim 12, wherein spinning apparatus is in the form of a melt blowing apparatus, in the form of a melt spinning apparatus, in particular with an Exxon die or single- or multi-row coaxial dies or spunbond dies, or in the form of a solvent spinning apparatus.

15. Electret article, in particular electret fibre and/or an electret fibre nonwoven, produced by a process where fibres are produced from a plastics and/or natural-origin material, where a polar liquid is atomized using a gaseous pressure medium to produce a treatment aerosol and where the fibres are treated with the treatment aerosol for electrostatic charging, wherein the atomizing is undertaken with a quotient of the volume flow of the polar liquid in litres per hour and the positive pressure of the gaseous pressure medium in hectopascals of 0.004 to 0.008.

Description

[0062] The invention will now be described by way of example with reference to the accompanying figures. In the figures:

[0063] FIG. 1 shows a section of an inventive apparatus according to an example embodiment of the present invention,

[0064] FIG. 2 shows a section of an inventive apparatus according to a further example embodiment of the present invention,

[0065] FIG. 3 shows a section of an inventive apparatus according to yet a further example embodiment of the present invention,

[0066] FIG. 4 shows a section of an inventive apparatus according to yet a further example embodiment of the present invention,

[0067] FIG. 5 shows a side view of a nozzle apparatus of an inventive apparatus for producing electrostatically charged fibres.

[0068] FIG. 1 shows a section of an inventive apparatus 10 according to one example embodiment of the present invention. The apparatus 10 is configured for producing electrostatically charged fibres 12, in particular for producing an electret fibre construct 14.

[0069] The apparatus 10 according to the example embodiment in FIG. 1 includes a spinning apparatus 16 for producing fibres 12 from a polymer material 18. The spinning apparatus 16 may be in the form of a melt blowing apparatus/meltblown apparatus according to FIG. 1 and to this end include a melt blowing die apparatus 20. The melt blowing die apparatus 20 may in particular be a so-called Exxon die.

[0070] The apparatus 10 may thus be a melt blowing plant/a meltblown plant.

[0071] Inside the melt blowing die apparatus 20 the polymer material 18 may be in the form of polymer melt/introduced into the melt blowing die apparatus 20 in the form of polymer melt.

[0072] The apparatus 10 according to FIG. 1 further includes a nozzle apparatus 22 for producing a treatment aerosol 24 for atomizing a polar liquid using a gaseous pressure medium. The nozzle apparatus 22 is configured for electrostatically charging the fibres 12 by spraying the fibres 12 with the treatment aerosol 24.

[0073] The nozzle apparatus 22 is configured for undertaking the atomizing with a quotient of the volume flow of the polar liquid of 3.2 to 5.2 litres per hour and the positive pressure of the gaseous pressure medium in hectopascals of 0.004 to 0.008. Alternatively or in addition the nozzle apparatus 22 may be configured for undertaking the atomizing with a quotient of the mass flow of the polar liquid and the mass flow of the gases pressure medium of 1.4 to 3. The nozzle apparatus 22 may be likewise be configured for undertaking the atomizing with a quotient of the volume flow of the polar liquid and the volume flow of the gases pressure medium of 0.001 to 0.004.

[0074] Using such a quotient/such a ratio allows a relatively large amount of charges to be produced and applied to the fibres 12. Such a quotient/such a ratio likewise allows the amount of the produced treatment aerosol 24 to be sufficiently limited or minimized. This ensures that an only relatively slight moistening of the fibres 12 or of the fibre construct 14 is effected. An active drying of the electrostatically charged fibres 12/of the fibre construct 14 can accordingly be avoided, thus reducing the production costs and the energy costs required for production. The sufficient electrostatic charge simultaneously ensures a high filtration efficiency of the fibre construct 14 produced from fibres 12 produced in such a way.

[0075] The melt blowing die apparatus 20 according to FIG. 1 includes at least one air channel 26 through which an air stream is directed onto the produced fibres 12, in particular acts tangentially on the fibres 12, in order to stretch the fibres.

[0076] After treatment of the fibres 12 with the treatment aerosol 24 the fibres are laid down on a collecting apparatus 28. The collecting apparatus 28 may be a laydown belt for example. An air stream 30 for vacuum aspiration/vacuum extraction may be used for the laydown or consolidation of the fibres 12 on the collecting apparatus 28. The air stream 30 may be provided by a vacuum aspiration and/or vacuum extraction apparatus (not shown here). The vacuum aspiration/vacuum extraction and laydown of the fibres 12 makes it possible to achieve sufficient drying of the fibres 12 treated with the treatment aerosol 24 since the nozzle apparatus 22 effects only limited moistening. The laydown or consolidation of the fibres 12 on the collecting apparatus 28 makes it possible to produce a fibre construct 14, for example a fibre nonwoven.

[0077] FIG. 2 shows a section of an inventive apparatus 10 according to a further example embodiment of the present invention. The apparatus 10 according to FIG. 2 is also configured for producing electrostatically charged fibres 12, in particular for producing an electret fibre construct 14.

[0078] The apparatus 10 according to FIG. 2 includes a spinning apparatus 16 for producing fibres 12 from a polymer material 18. The apparatus 10 according to FIG. 2 differs from the apparatus according to FIG. 1 in the configuration of the spinning apparatus 16. The spinning apparatus 16 according to FIG. 2 may be in the form of a melt spinning apparatus and to this end include a melt spinning die apparatus 21. The melt spinning die apparatus 21 may include for example single- or multi-row coaxial dies.

[0079] The apparatus 10 according to FIG. 2 may thus be a melt spinning plant.

[0080] According to FIG. 2 the spinning apparatus 16 produces a plurality of rows of strands of fibres 12/rows of fibre jets. The nozzle apparatus 22 may be adapted or arranged for treating all fibres 12 or all rows of fibres 12 with the treatment aerosol 24.

[0081] FIG. 3 shows a section of an inventive apparatus 10 according to yet a further example embodiment of the present invention. The apparatus 10 according to FIG. 3 is also configured for producing electrostatically charged fibres 12, in particular for producing an electret fibre construct 14.

[0082] Different embodiments of the apparatus 10 are shown in FIG. 3. Either compacting rollers 56, represented by a solid line, may be arranged in the conveying direction of the collecting apparatus 28 or sealing rollers 56, represented by a dotted line, may be arranged counter to the conveying direction of the collecting apparatus 28. In one embodiment both compacting rollers 56 and sealing rollers 56 may be provided. The compacting rollers 56 compact the fibre construct and to the sealing rollers have a sealing function.

[0083] The apparatus 10 according to FIG. 3 likewise includes a spinning apparatus 16 for producing fibres 12 from a polymer material 18. The apparatus 10 according to FIG. 3 in turn differs from the apparatus according to FIG. 1 or FIG. 2 in the configuration of the spinning apparatus 16. The spinning apparatus 16 according to FIG. 3 may be in the form of a melt spinning apparatus and to this end include a melt spinning die apparatus 21. The melt spinning die apparatus 21 may in particular include single- or multi-row spunbond dies.

[0084] The apparatus 10 according to FIG. 3 may thus be a melt spinning plant in which a stretching is carried out after employing a fibre/filament cooling as described below.

[0085] According to FIG. 3 the spinning apparatus 16 produces a plurality of rows of strands of fibres 12/rows of fibre jets. The nozzle apparatus 22 may be adapted or arranged for treating all fibres 12 or all rows of fibres 12 with the treatment aerosol 24.

[0086] Before the fibres 12 are subjected to a treatment with the treatment aerosol 24 an oligomer and/or spinning fume vacuum extraction 32 may optionally be undertaken using a vacuum extraction apparatus (not shown here).

[0087] Following the treatment with the treatment aerosol 24 via the nozzle apparatus 22 the fibres 12 are subjected to a cooling 34, in particular an air cooling/a so-called air quenching. A cooling apparatus (not shown here) may be employed to this end.

[0088] Following the cooling 34 the fibres 12 are stretched by a primary air 36/stretching air. The primary air 36/stretching air may be supplied via an air supply 38. In the further course of the fibres 12 these may optionally be supplied with a secondary air 40 via the air supply 42 and a tertiary air 44 via an air supply not shown here.

[0089] The primary air is conducted in a spinning shaft 58 together with the fibres 12. The spinning shaft 58 may be circular and/or rectangular and be formed from a continuous spinning/58 or from spinning shaft portions spaced apart from one another.

[0090] After the treatment of the fibres 12 with the treatment aerosol 24 and also the cooling 34, the stretching by means of the primary air 36 and optionally the supplying of a secondary air 40 and tertiary air 44 the fibres 12 may be laid down/consolidated on a collecting apparatus 28 as described hereinabove in respect of the example embodiment in FIG. 1.

[0091] FIG. 4 shows a section of an inventive apparatus 10 according to yet a further example embodiment of the present invention. The apparatus 10 according to FIG. 4 is also configured for producing electrostatically charged fibres 12, in particular for producing an electret fibre construct 14.

[0092] The apparatus 10 according to FIG. 4 likewise includes a spinning apparatus 16 for producing fibres 12 from a polymer material 18. The apparatus 10 according to FIG. 4 in turn differs from the apparatus according to FIG. 1, FIG. 2 or FIG. 3 in terms of the configuration of the spinning apparatus 16. The spinning apparatus 16 according to FIG. 4 is thus configured as a solvent spinning apparatus and to this end may include a solvent die apparatus 23. Inside the solvent die apparatus 23 the polymer material 18 may be in the form of a polymer solution.

[0093] The apparatus 10 according to FIG. 4 may thus be a solvent spinning plant.

[0094] Before the fibres 12 are subjected to a treatment with the treatment aerosol 24 a stretching of the fibres 12 by a primary air 36/stretching air may optionally be carried according to the embodiment in FIG. 4. The primary air 36/stretching air may be supplied via an air supply not shown here. After the optional stretching by the primary air 36/stretching air the fibres 12 the fibres are treated with the treatment aerosol 24 for electrostatic charging via the nozzle apparatus 22.

[0095] In the further course of the fibres 12 these may optionally be passed through an electric field 46. The electric field 46 may in particular be a high-voltage field. The passage through the electric field 46 may likewise or additionally effective a stretching of the fibres 12. In the example embodiment according to FIG. 4 a stretching of the fibres 12 may alternatively or in addition be brought about by a centrifugal force.

[0096] In the example embodiment in FIG. 4 too, the fibres 12 may be laid down/consolidated on a collecting apparatus 28 as described hereinabove in respect of the example embodiment in FIG. 1.

[0097] FIG. 5 shows a side view of a nozzle apparatus 22 of an inventive apparatus 10 for producing electrostatically charged fibres 12. The nozzle apparatus 22 may include a plurality of two-fluid nozzles 48. The two-fluid nozzles 48 may in particular be arranged along a horizontal 50 shown in schematic form. The two-fluid nozzles 48 may in particular be in the form of flat jet nozzles.

[0098] The openings of the two-fluid nozzles 48 may be arranged at an angle 52 relative to the horizontal 50, in particular at an angle 52 of 1° to 30°, preferably of 5° to 20°. As a result, the treatment aerosol 24 can exit the opening of the respective two-fluid nozzle 48 in a flat jet 54 which is likewise at an angle 52 to the horizontal 50. A plurality of such flat jets 54 allow the treatment aerosol 24 to be relatively well distributed in the space.

LIST OF REFERENCE DESIGNATIONS

[0099] 10 Apparatus [0100] 12 Fibres [0101] 14 Fibre constructs [0102] 16 Spinning apparatus [0103] 18 Polymer material [0104] 20 Melt blowing die apparatus [0105] 21 Melt spinning die apparatus [0106] 22 Nozzle apparatus [0107] 23 Solvent die apparatus [0108] 24 Treatment aerosol [0109] 26 Air channel [0110] 28 Collecting apparatus [0111] 30 Air stream [0112] 32 Oligomer and/or spinning fume vacuum extraction [0113] 34 Cooling [0114] 36 Primary air [0115] 38 Air supply [0116] 40 Secondary air [0117] 42 Air supply [0118] 44 Tertiary air [0119] 46 Electric field [0120] 48 Two-fluid nozzles [0121] 50 Horizontal [0122] 52 Angle [0123] 54 Flat jet [0124] 56 Sealing roller/compacting roller [0125] 58 Spinning shaft