GB2163462A - Producing crimped, staple fibres - Google Patents

Abstract

The invention relates to the production of spinable fibres which are preferably continuously spun as filament threads (1) in a fibre process, folded and collectively stretched. The stretched filament cable (9) is compression chamber-crimped and then cut to spinning fibres (19) in a fibre cutter (18). The filament cable (9) which is more than 5000dtex is crimped in a blast nozzle (12) with a compression tube connected thereto and a thermal after-treatment apparatus (15) for the formed thread stopper. The spinning fibres (19) have excellent crimp values owing to their 3-dimensional crimp of the filament threads (1) and a greater covering capacity. <IMAGE>

Description

SPECIFICATION A process and an apparatus for the production of spinnable fibres This invention relates to a process for the production of spinnable fibres from synthetic high-polymer plastics materials forming filament threads which are folded to a filament cable having a titre of more than 5,000 dtex, and to an apparatus for carrying out the process.

According to the known processes for the production of spinnable fibres, a polymer melt is pressed through spinning nozzles and the spun filament yarns are cooled in a flow of blast air and compacted and dampened with a spinning avivage.

The filament threads are then collectively stretched in one or more stages on stretching devices and immediately folded to a filament cable or tow and crimped in a compression crimping apparatus/compression chamber. The filament cable is then converted into spinnable fibres by cutting or parting. The spinnable fibres are pressed into packs.

The known compression crimping apparatus have proved worthwhile for many years in crimping filament cables with a high titre and the twodimensional crimp thereby produced seemed acceptable with respect to the production costs of the spinnable fibres.

High quality spinnable fibres should, however, have a 3-dimensional crimp which is comparable with the crimp of wool and particularly cotton. So as to obtain spinnable fibres with such a 3-dimensional crimp, up until now filament threads with a titre of less than 1000 dtex had to be crimped. The filament threads could only be folded to fibres cable after crimping. This process is, however, very costly.

The invention aims to provide a process for the production of spinning fibres, of the type described at the beginning, in which a continuous process spinnable fibres having a 3-dimensional crimp can be produced.

According to the invention there is provided a process for the production of spinnable fibres from high-polymer, synthetic plastics material by spinning filament threads, by subsequent stretching, compression crimping of the filament threads folded to a filament cable of more than 5000 dtex, and by converting the filament cable into spinnable fibres in a continuous operation, wherein the speed of the filament cable on leaving the stretching device is less than 500 m!min and the compression crimping takes place by using a blast nozzle which is charged with hot air, whereby the filament cable is drawn into the blast nozzle by the hot air and is transported into the compression chamber surbordinate to the blast nozzle and is combined into a compact fibre stopper, and whereby the fibre cable is again released to a filament cable after cooling and then converted into spinnable fibres.

Thus, filament cables with titres which are usual in apparatus for the production of spinnable fibres can be successfully, and in an unexpected manner, compression chamber-crimped by using a blast nozzle and nevertheless processed at relatively low speeds as are usual in such fibre processes. This was surprising in that the crimp during compression chamber-texturizing using a blast nozzle is based on the change in dimension which the high speed starting filaments undergo when colliding with the thread stopper arranged in the compression chamber. It was thus generally assumed that the hot air flow transported through the blast nozzle could only give a sufficiently high kinetic energy to threads which have a relatively low titre of less than 3000 dtex.It was likewise suprising that the production of a high quality crimp was at all possible with relatively low speeds of the pressure fluid in the blast nozzle.

In the invention, it is most preferable for the filament cable on running into the blast nozzle to be spread out in a band-shape in a suction funnel so that twisting of the filament cable in the blast nozzle is avoided and the blasting medium can take effect in advantageous manner on all filament threads.

It was moreover advantageous if on the blast nozzle a suction funnel is placed which is sealed in relation to the blast nozzle and is rotatable and movable such that the feed cross-section of the filament cable in the blast nozzle can be adjusted directly. This is particularly advantageous since, on supplying the cable, a large cross-section exists into which the filament cable is absorbed, while the feed cross-section can be reduced in size during operation so as to have to carry as little "false air", and additionally heat, as possible to the filament cable.

For spreading the filament cable, it is particularly advantageous for a reversing device for the filament cable to be arranged at the side above the suction funnel of the blast nozzle, and for the filament cable running from the side to be flattened at the edge of the feed funnel before being absorbed into the blast nozzle.

For the thermal after-treatment of the filament cable, the cable is passed along a substantially straight or helical path. This path can be defined by a supporting surface under suction, which is formed, for example, as a perforated or porous guide rail. There may also be a drum over which the thread stopper is placed in helical turns and is moved forward in the axial direction of the drum by a suitable advance device (c.f. for example DE 26 32 082).

In the process of the invention, filament cables with a strength of more than 5000 dtex, particularly more than 40,000 dtex and preferably from 40,000 to 120,000 dtex, are in each case compressioncrimped in a blast nozzle, whereby the speed of the filament cable at the inlet of the crimping stage is more than 50 mimin and is particularly from 60 to 300 mimic, preferably from 60 to 200 m/min. In the upper speed range, the process is superior to the known process which operates with a cable crimping apparatus, not only with respect to the crimp result, but also with respect to the production speed.

With the proposed process 3-dimensional crimped spinnable fibres of synthetic, linear polymers, preferably of polyolefins such as polypropylene or polypropylene: polyethylene mixtures, can be produced. By observing the appropriate conditions during stretching, fibres processes for the production of spinnable fibres from polyamides, particularly PA6 or PA66, or for polyesters, such as polyethylene terephthalate, can be operated.

A device for carrying out the process of the invention is characterised in that the apparatus for crimping the filament cable is formed as a blast nozzle with a compression tube connected to the mixing channel, at the end of which a speed-adjustable supply device and a supporting surface preferably under suction are connected. The novelty thereby particularly lies in the design of the blast nozzle for crimping the filament cable which distinguishes itself from the known blast nozzles particularly by the adjustable feed cross-section of the filament cable, the suction funnel placed on the blast nozzle and by the guiding of the flow medium.

The apparatus for the thermal after-treatment of the thread stopper at the outlet of the compression tube takes into account the valuable principles of the known spinning-stretching-crimping apparatus of DE 26 32 082 and DE 26 32 083A. It can be formed as a guide rail under section, or as a perforated drum which is rotatable about its axis, having a suitable advance device around which the thread stopper is passed in narrow turns, in a helical manner, to increase the residence time, and is released at the end of the outlet.

A preferred embodiment of the invention is described in detail below, by example only, with reference to the accompanying drawings, wherein: Figure 1 is a schematic representation of an apparatus for the continuous production of spinnable fibres; Figure 2 is a schematic representation of a detail of the blast nozzle and thermal after-treatment apparatus of the apparatus according to Figure 1; and Figure 3 shows an enlarged longitudinal section through the suction funnel and the mixing channel of the blast nozzle with the supply channel for the blasting medium.

The apparatus according to Figure 1 consists of an apparatus part for melt-spinning a large number of filament threads 1 of linear high-polymer plastics materials, which are melted in an extruder (not shown) and are pressed through the nozzle bores of the spinning nozzle plates 2. The filament threads which are blasted with blasting air, perpendicular to the run of the thread, below the spinning nozzle plates 2, are cooled to below the melting point of the polymer so that they do not adhere to each other during further treatment. The filament threads 1 spun from one or more spinning nozzles, with a total titre of in each case for example 20 000 dtex, are passed over avivage rollers 3 on which they are dampened with a spinning preparation, and after being combined at reversing devices 4 are passed in the form of filament bundles 5 to the inlet supply device 6 of the stretching device.The inlet supply device 6 consists of several rollers, the first group 7 of which is unheated and the second group 8 of which is heated. It is surrounded in a meandering manner by the folded filament bundles 5 which are spread out next to each other in a band-shape and the whole of which forms the filament cable 9. To the inlet supply device 6 are connected, at a spacing, a heat treatment section, for example a hot air furnace 10 for hot stretching, and a further supply device 11, the rollers 7.1, 8.1 of which are driven at a relatively high speed around the factor of the stretching ratio 1 and which are similarly surrounded in a meandering manner by the filament cable 9.The filament cable 9 is stretched as a whole in the stretching device such that the individual filaments 1 have a strength which is sufficient for textile purposes, but do not break, so as to avoid the danger of the formation of thread windings on one of the rollers 7.8 The filament cable 9 produced up until now in a substantially conventional manner is now crimped in a blast nozzle 12 with a compression tube 13 and thereby receives a 3-dimensional crimp. The stopper 14 of the filament cable 9 formed in the tube 13 is positively pushed forward after emerging from the compression tube 13 and reaches a thermal after-treatment apparatus 15 (see Figure 2) where the crimped structure of the filaments is fixed by cooling.At the end of the after-treatment apparatus 15, the stopper 14 is again released from a supply device 16 which is driven at a faster pace and the crimped filament cable is transported to a secondary cooling zone 17 which simultaneously operates as a storage area before the fibres are cut. The spinnable fibres 19 are cut at the fibre cutter 18 into substantially constant staple lengths and are drawn off by suction from the collecting container surrounding the fibre cutter 18 and are finally compressed to fibre bales 21 on a bale press 20.

Figure 2 is a schematic representation of the blast nozzle 12 for compression chamber-crimping, the filament cable 9 and the thermal after-treatment apparatus 15. Above and to the side of the suction funnel 22, a supply device 23 is arranged from which the stretched fibre assemblage spread out on the rollers of the stretching device (6,10,11) are drawn together to form a filament cable 9 and are introduced to the blast nozzle 12 at a defined speed. The suction funnel 22 is formed at the inlet of the filament cable 9 such that this cable is flattened there in an oval manner and on being introduced to the feed channel 24 of the blast nozzle 12 is not twisted about its longitudinal axis. Moreover, the suction funnel 22 can be swung around on a horizontal journal 25 which is attached in a plane perpindicular to the plane of projection (drawn displaced by 90o), so that by adjusting the eccentricity of the thread channel at the outlet of the suction funnel 22 opposite the feed channel 24 of the blast nozzle 12, the inlet cross-section for the filament cable 9 can be changed from a maximum crosssection (on supplying the filament cable 9 to the blast nozzle 12) to a smaller cross-section (in production operation, see Figure 3).

The feed channel 24 ends in the mixing chamber 26 of the blast nozzle 12 in which the blasting medium heated to an elevated temperature, for example from 140 to 150 C, and flowing out at high flowing speed, meets the filament cable 9 in order to carry it through the mixing channel 29. The blasting medium is preferably compressed air which is brought to the desired treatment temperature by a heating device 27 on the blast air supply 28. At the end of the mixing channel 29, the flow channel widens conically and verges into the compression tube 13 in which openings 30 are provided through which the blast air flows off and in which the filament threads 1 of the filament cable 9 are deposited in a tangled state to a stopper 14. The blast air collects in the ring space 31 and is carried off via the outlet supports 32, substantially without pressure.

The stopper 14 formed in the compression tube 13 is grasped by a speed-adjustable driven roller pair 33 and transported to the after-treatment apparatus 15, where the crimp is fixed. The drawingoff speed of the roller pair 33 is freely adjustable so as to control the consistency and the air-permeability of the stopper 14. The after-treatment apparatus is, according to Figure 2, a guide rail 34 which is formed as supporting surface and has a porous or perforated surface and an arched crosssection. On the back, a low-pressure chamber 46 is arranged to which a suction ventilator 35 is connected and through which surrounding air 36 is drawn off by suction in a flow transverse to the thread stopper 14.The guide rail 34, seen in the drawing-off direction 37 of the released stopper 14, has a J-shaped outlet arc 38 along which the stopper 14 is passed and is released, while as a result of friction on the outlet arc 38 and the consistency of the stopper 14 a condition of equilibrium is set for the looping angle, which determines the release position of the stopper.

Figure 3 shows an enlarged view of a longitudinal section through the suction funnel 22 with the feed channel 24 of the blast nozzle 12, as well as the mixing chamber 26 with connecting mixing channel 29 and the supply of the blasting medium.

The suction funnel 22 is thereby twisted in relation to the feed channel 24 of the blast nozzle 12 (for example during production), such that the absorbed filament cable 9 is relatively strongly pressed and can hardly entrain "false air". Morever, between the suction funnel 22 and the blast nozzle inlet 39, a seal 40 is arranged which likewise prevents the drawing-off by suction of "false air" and increases the suction performance of the blast nozzle 12.

The hot air is passed through the air supply tube 28 and first reaches a ring channel. This ring channel is connected by bores 42 to a radial slit channel 43 lying in a plane. The bores 42 are positioned around the thread channel at equal spacings and at the same spacing in each case from the thread channel. The slit channel connects to the upper end of a ring gap 45. The ring gap 45 likewise lies concentrically to the thread channel and tapers conically in the running direction of the thread until it leads into the mixing chamber 29. The mixing chamber 26 is penetrated by the thread run and lies concentrically to the inlet channel 24 and the mixing channel 26.

With the described apparatus, a good texturizing result can be achieved by which a filament cable 9 with a strength up to 120,000 dtex can be perfectly crimped at an operational speed of 120 m/min, and the produced, cut spinnable fibres 19 have a 3-dimensional crimp.

N.B. The word "compression" as used herein is a translation of the word "stauch".

Claims (22)

1. A process for the production of spinnable fibres from high-polymer, synthetic plastics materials by spinning filament threads, by subsequent stretching, compression crimping of the filament threads folded to a filament cable of more than 5000 dtex, and by converting the filament cable into spinnable fibres in a continuous operation, wherein the speed of the filament cable on leaving the stretching device is less than 500 mimin, and the compression crimping takes place by using a blast nozzle which is charged with hot air, whereby the filament cable is drawn into the blast nozzle by the hot air and is transported into the compression chamber surbordinate to the blast nozzle and is combined into a compact fibre stopper, and whereby the fibre cable is again released to a filament cable after cooling and then converted into spinnable fibres.

2. A process according to claim 1, wherein the spinning of the filament threads and stretching also takes place in a continuous operation.

3. A process according to claim 1 or 2, wherein the filament cable on entry into the blast nozzle is spread out in a band-shape in a suction funnel.

4. A process according to claim 3, wherein the filament cable is supplied to the blast nozzle at an angle of inclination against the nozzle axis of preferably greater than 30 .

5. A process according to any of the preceding claims, wherein the hot air is at a temperature of from 140 to 150'C.

6. A process according to any of the preceding claims, wherein the fibre stopper, on leaving the compression chamber, is passed on to a gaspermeable supporting surface and is cooled by a cooling medium transversely drawn off by suction through the fibre stopper.

7. A process according to claim 6, wherein the cooling medium is ambient air.

8. A process according to any of the preceding claims wherein the filament cable after stretching has a titre of greater than 40 000 dtex.

9. A process according to claim 8, wherein the titre is from 40 000 to 120 000 dtex.

10. A process according to any of the preceding claims, wherein the speed of the folded filament cable on entering the blast nozzle is less than 300 m;min.

11. A process according to claim 10, wherein the speed is from 60 to 200 mimin.

12. A process according to any of the preceding claims, wherein the synthetic polymer is a polyolefin, particularly a spinnable polypropylene or a polypropylene!polyethylene mixture, and the filament cable is stretched before crimping with a ratio of from 2.5:1 to 3.2:1.

13. A process according to any of claims 1 to 11, wherein the synthetic polymer is a polyamide, particularly PA6 or PA66, or a spinnable polyester, particularly polyethylene terephthalate.

14. A process for producing spinnable fibres substantially as herein described, with or without reference to the accompanying drawings.

15. An apparatus for carrying out the process of any of claims 1 to 13, comprising a melt-spinning device having a melting device and a spinning nozzle with an air flow and an apparatus for collectively stretching, crimping and converting a filament cable into spinnable fibres, wherein the apparatus for crimping the filament cable is blast nozzle with a compression tube connected thereto, at the end of which a speed-adjustable supply device and a supporting surface are connected.

16. An apparatus according to claim 15, wherein the supporting surface is under suction.

17. An apparatus according to claim 15 or 16, wherein on the blast nozzle a suction funnel is placed which is sealed off in relation to the blast nozzle and can be rotated or moved such that the inlet cross-section of the filament cable can be adjusted directly.

18. An apparatus according to claim 17, wherein above the suction funnel of the blast nozzle, a reversing device for the filament cable is arranged to the side, such that the filament cable flattens out in an oval manner as the inlet of the blast nozzle or is spread out in a band-shape.

19. An apparatus according to claim 17, wherein the outlet of the suction funnel is radially displaced opposite the inlet channel in the blast nozzle inlet and the coaxial mixing channel.

20. An apparatus according to any of claims 15 to 19 wherein, the blast nozzle has a mixing chamber which is penetrated by the thread channel (inlet channel and mixing channel) and into which a conical ring gap leads which is connected to the hot air supply via a slit which is positioned radially to the thread channel as weil as bores parallel to the thread channel, which are arranged on a circle surrounding the thread channel.

21. An apparatus according to any of claims 17 to 20, wherein the supporting surface connected to the suction chamber is a guide rail with a perforated or porous track, whereby the profile of the track is substantially adapted to the cross section of the compression chamber and the fibre stopper formed therein, and that the supporting surface has an outlet arc with a centring angle of greater than 90 .

22. An apparatus for producing spinnable fibres substantially as herein described and as illustrated in the accompanying drawings.