CN112111797A

CN112111797A - Method and device for melt spinning a plurality of filaments

Info

Publication number: CN112111797A
Application number: CN202010553343.6A
Authority: CN
Inventors: P·云格; G·沃特伯格
Original assignee: Oerlikon Textile GmbH and Co KG
Current assignee: Oerlikon Textile GmbH and Co KG
Priority date: 2019-06-19
Filing date: 2020-06-17
Publication date: 2020-12-22
Anticipated expiration: 2040-06-17
Also published as: DE102020114761A1; CN112111797B

Abstract

The invention relates to a method and a device for melt-spinning a plurality of filaments from a polymer melt. For this purpose, the filaments are extruded through a plurality of nozzle openings of a spinneret and subsequently cooled. To assist cooling, the filaments are electrostatically charged during cooling and discharged by contact with the wetted contact surface according to the invention. It is therefore also possible to advantageously use the dispersion achieved by electrostatic charging to wet the filaments.

Description

Method and device for melt spinning a plurality of filaments

Technical Field

The invention relates to a method for melt-spinning/melt-spinning a plurality of filaments and to a device for melt-spinning a plurality of filaments according to the preamble of claim 7.

Background

In the case of melt-spinning synthetic filaments from a polymer melt, the filaments are usually cooled by means of cooling air after extrusion through a spinneret in order to solidify the polymer. During the cooling of the filaments, the so-called filament titer is formed by the solidification of the polymer melt. Here, a high uniformity of the fineness is desired for the quality of the monofilaments. Thus, the uniformity of the fineness of each filament and the uniformity of the fineness across all the filaments can be achieved equally. The transport of the cooling air is thus controlled such that as uniform a cooling of each filament as possible within the filament bundle/filament group (filcementschar) is obtained. However, a problem with a high number of filaments is that individual adhesion between the filaments occurs. In order to avoid such a connection and bundling of a plurality of filaments, it is known in the prior art to electrostatically charge/charge the filaments in order to thus avoid filament aggregation by homopolar charging.

Thus, EP 0949362a2 discloses a method and a device for melt spinning a plurality of filaments, in which a charge generator is arranged directly below the spinneret and by means of which an electrostatic charging of the filaments takes place. To charge the filaments, ionized air is delivered to the freshly extruded filaments. After cooling, the filament is discharged.

In the known method and device for melt-spinning a plurality of filaments, the problem is that the filaments are already subjected to electrostatic charging immediately after extrusion, which leads to an expansion of the filament bundle. However, this effect prevents the formation of a uniform single filament titer.

Disclosure of Invention

It is therefore an object of the present invention to provide a method and a device for melt spinning a plurality of filaments of the type mentioned, in which method and device a large number of filaments can be produced uniformly.

This object is achieved by a method having the features according to claim 1 and by a device having the features according to claim 7.

Advantageous developments of the invention are defined by the features and feature combinations of the respective dependent claims.

The invention has the particular advantage that the electrostatic charging of the filaments takes place only in the state in which at least one edge region of the filaments has already been cured. Thus, the filaments are electrostatically charged during cooling. For this purpose, the charge generator is arranged in the height range of the blowing part, preferably in the lower third. The repulsion between the individual filaments is thereby simultaneously used for a more uniform wetting of the individual filaments in addition to a better cooling. The discharge of the filaments is thus achieved by contact with the wetted contact surfaces. All the filaments can be individually wetted by spreading out the filaments.

In order to improve the cooling of the filaments and the wetting of the filaments, in the device according to the invention, the charge generator is arranged in the height region of the blowing part, wherein the subsequent discharging of the filaments is provided by a wetting device having a wetted contact surface on which the filaments are guided.

The method according to the invention and the device according to the invention thus enable the melt spinning of high numbers of filaments without the risk of forming individual bundles. In this regard, the method according to the invention and the device according to the invention are particularly suitable for high throughputs, as are often the case, for example, in the production of staple fibers.

In one process variant, the electrostatic charging of the filaments takes place during the pre-cooling of the filaments, at a distance from the spinneret. This variant of the method has the particular advantage that the monofilaments are sufficiently precured. In this respect, a concentrated electrostatic charging can be produced in the edge regions of the monofilaments. The core of the monofilament remains substantially unaffected.

In order to achieve targeted and rapid electrostatic charging, the following method variants have proven advantageous, namely: in order to charge the filaments, an electric field is generated at a high voltage in the range of maximally 30kV, through which the filaments are guided.

Preferably, the electric field is generated by a charging electrode spaced from the monofilament by a distance of 5mm to 30 mm. The spacing between the filaments and the charging electrode is substantially dependent on the filament density and filament arrangement.

In order to be able to produce a high number of filaments with the same properties, a method variant is preferably implemented in which the filaments are extruded in an annular arrangement and cooled by means of an internally located blowing candle/blowing cylinder (blasterrze), wherein the blowing candle acts as a counter electrode in conjunction with a charging electrode to generate an electric field. The annular monofilament curtain can thus be charged electrostatically in a targeted manner.

The wetting and discharging of the filaments is then preferably carried out by means of a method variant in which the filaments are wetted with a fluid on the circumference of a wetting ring on the holding end of the blower candle.

In the device according to the invention, a development is particularly advantageous in which the charge generator is arranged below the spinneret with a minimum spacing in which the pre-cooling of the filaments can be carried out. The cured edge regions of the monofilaments can thus be charged electrostatically in a targeted manner. The formation of a uniform and constant filament titer is prevented from being hindered.

In order to be able to vary the charging location in the cooling zone depending on the filament number and the respective polymer type, the development of the invention provides that the charge generator is designed to be adjustable in height. This makes it possible to adapt the distance to the spinneret and to the distance to the subsequent wetting device to the respective process and the corresponding filament.

For intensive electrostatic charging, the charge generator is preferably designed such that an electric field can be generated in the environment of the individual filaments by a high voltage in the range of maximally 30 kV. Thus, a strong charge can be generated in the relatively short passage area of the monofilament.

For this purpose, the charge carriers have a charging electrode which is arranged at a distance of 5mm to 30mm from the individual filaments.

For melt spinning very large quantities of filaments, preference is given to using apparatus variants in which the spinneret has nozzle openings arranged in a ring shape and the charging electrode is configured in a ring shape. Thus, the monofilament bundle extruded through the spinneret may be surrounded by the charging electrode so as to form uniform electrostatic charging over the entire circumference of the monofilament bundle.

The cooling is preferably carried out by a blower candle arranged centrally with respect to the spinneret, which blower candle is simultaneously designed as a counter electrode with respect to the charging electrode. In this regard, a stable electric field can be generated between the charging electrode and the blowing candle without additional components.

In order to be able to use the repelling effect of the electrostatic charge in the filament bundle directly, the wetting device is preferably formed by a wetting ring on the holding end of the blower candle, on the circumference of which wetting ring the filaments can be guided in a contacting manner. Thus ensuring uniform and intensive wetting of all the filaments.

However, in principle, there is also the possibility of generating an electric field through the charging electrode and the opposing counter electrode or the grounded metal member. In this regard, it is also possible to use a rectangular spinneret assembly with, for example, cross-flow blowing.

Drawings

The method according to the invention for melt spinning a plurality of filaments is explained in detail below with reference to the drawing with the aid of some embodiments of the device according to the invention for melt spinning a plurality of filaments.

The figures show:

fig. 1 schematically shows a front view of a first embodiment of an apparatus for melt spinning a plurality of monofilaments according to the invention.

Fig. 2 schematically shows a side view of the embodiment of fig. 1.

Fig. 3 schematically shows a cross-sectional view of another embodiment of an apparatus for melt spinning a plurality of monofilaments according to the invention.

Detailed Description

A first embodiment of an apparatus for melt spinning a plurality of filaments from a polymer melt according to the present invention is schematically illustrated in fig. 1 and 2. This embodiment is shown in front view in fig. 1 and in side view in fig. 2. The following description applies to both figures, as long as it is not specifically referred to which figure.

This embodiment has a spinneret 1, which is typically arranged in a heated spinning beam. The spinneret 1 has on its underside a nozzle plate/nozzle plate 2 with a plurality of nozzle bores 3. The spinneret 1 is connected via a melt inlet 4 to a melt pump, not shown here.

The cooling device 6 is arranged below the spinneret 1. The cooling device 6 has a blowing part 7 which generates a cooling air flow which blows onto the freshly extruded filament bundle 5 through the nozzle bores 3. For this purpose, the blowing part 7 has a blowing wall 8 arranged laterally next to the filament bundle 5, which is connected to a blowing chamber 9. The cooling air is supplied to the blowing chamber 9, which is blown transversely to the filament bundle 5 by a blowing wall 8.

On the side opposite the cooling device 6, a charge generator 10 is arranged. In this embodiment, the charge generator 10 is formed by a charging electrode 11 which is held on a holder 13 at a distance from the filament bundle 5. The spacing between the charging electrode 11 and the monofilament tuft 5 is indicated by the letter a in fig. 2. The pitch a is in the range of 5mm to 30mm depending on the process, number of filaments and denier of the filaments.

The charging electrode 11 is designed in the form of a stick and is connected to a power supply, not shown here. The charging electrode 11 is adapted to generate an electric field at a high voltage of maximally 30kV around the monofilament tuft 5. The blowing wall 8 opposed to the charging electrode 11 can be used as a counter electrode according to its characteristics. Alternatively, however, there is also the possibility, as indicated by the dashed line in fig. 2, of: a counter electrode 12 is arranged opposite to the charging electrode 11 in order to generate an electric field around the monofilament tuft 5.

The charging electrode 11 is embodied to be height-adjustable on the support 13. In this case, however, the charging electrode 11 can only be set at a minimum distance from the spinneret 1. The minimum distance between the upper position of the charging electrode 11 and the spinneret is denoted by reference numeral V in fig. 2. The minimum distance V is the cooling zone of the filament bundle, which enables a pre-cooling in which solidification of the edge regions of the filaments occurs.

The moistening device 14 is arranged directly below the cooling device 6. In this exemplary embodiment, the wetting device 14 has a driven roller 16, which is wetted with fluid in a bath 17. The periphery of the roller 16 forms a contact surface 15 on which the filament bundle 5 is guided in contact. The roller 16 is grounded via line 18.

In the exemplary embodiment shown in fig. 1 and 2, the spinneret 1 is of rectangular shape and has a plurality of nozzle bores 3, preferably arranged in a plurality of rows, on a nozzle plate 2. A polymer melt, for example polyester, supplied under pressure to a spinneret 1 is extruded through nozzle holes 3 in a nozzle plate 2 into very fine monofilaments. The filaments 5.1 are cooled by a cooling air flow below the spinneret 1. The monofilaments 5.1 first pass through a pre-cooling zone, in which at least a sufficient solidification of the edge regions of the monofilaments takes place. A defined titer of filaments is formed on each filament of the filaments 5.1. In the further course of the cooling, the filaments of the filament bundle 5 are passed through an electric field generated by the charging electrode 11. In this case, homopolar electrostatic charging occurs at the edge regions of the individual filaments, which prevents the individual filaments from merging into one another and from bundling one another. This repulsion between the filaments propagates not only against the spinning direction but also along the spinning direction. A defined separation by electrostatic charges is achieved, so that the filaments of the filament bundle contact the contact surface 15 of the wetting apparatus 4 in this state. On the one hand, each of the filaments is wetted with fluid and, on the other hand, an electrical discharge is achieved at the contact surface 15, which is formed in this embodiment by the circumference of the roller 16. For this purpose, the moistening device 14 is grounded. After wetting the filaments, the filaments may be combined into filaments or fiber bundles/tows.

To make staple fibers, a plurality of filaments, which may include tens of thousands of filaments, are extruded through a spinneret. Such a high number of filaments in a filament bundle is preferably extruded through a spinneret with nozzle holes arranged in a loop. Such an embodiment is schematically shown in a cross-sectional view in fig. 3.

In the embodiment of the apparatus according to the invention for melt-spinning a plurality of monofilaments shown in fig. 3, the spinneret 1 has a nozzle plate 2, on the underside of which a plurality of rows of annularly arranged nozzle bores 3 are formed. The spinneret 1 is connected via a melt inlet 4 to a melt pump, not shown here, in order to feed the polymer melt under pressure into the spinneret 1.

Below the spinning nozzle 1, a cooling device 6 is provided, which has a cylindrical blowing candle 19 as the blowing part 7. The blower candles 19 are arranged centrally with respect to the spinneret 1, so that the blower candles 19 are located within the filament curtain of the filament bundle 5. The blower candle 19 has an air-permeable candle outer circumference, wherein the blower candle 19 is connected to a cooling air source, not shown here, via a candle holder 23. In this connection, a cooling air flow flowing radially from the inside to the outside is generated by the blowing candles 19, which flows through the filament bundle 5.

Directly below the spinneret 1, a suction device 20 is arranged outside the filament bundle 5 opposite the blowing candles 19. This makes it possible to achieve a very uniform laminar air flow directly on the freshly extruded filament bundles, which leads to a pre-cooling of the filaments.

A wetting ring 21 is arranged on the holding end 22 of the blowing candle 19. The wetting ring 21 has a contact surface 15, which is wetted with a fluid. For example, the contact surface 15 may have an outlet channel in the upper region for conveying the fluid. Alternatively, however, it is also possible for the contact surface 15 of the wetting ring 21 to be porous and to be coupled internally to a fluid source.

The wetting ring 21 is connected to the candle holder 23 and is connected to ground via the candle holder.

At the level of the blowing part 7, an annular charging electrode 11 is arranged outside the filament bundle 5. The charging electrode 11 is spaced from the outer filament bundle 5. The spacing is indicated by the letter a and is in the range of 5mm to a maximum of 30 mm. The distance a depends on the density and width of the filament bundles 5 to be guided.

In the exemplary embodiment shown in fig. 3, the outer circumference of the blower candle 19 is made of metal and serves as a counter electrode. The ground connection of the blowing candles 19 is realized by means of a candle holder 23. Accordingly, an electric field can be generated between the charging electrode 11 and the outer circumferential surface of the blowing candle 19. For this purpose, the charging electrode is operated at a high voltage of maximally 30 kV. The charging electrode 11 is designed to be adjustable in its height, based on the characteristics of the blowing candles 19. Therefore, the electric field is preferably generated in the lower third of the cooling zone. The width of the charging electrode 11 is selected in advance according to the number, density and fineness of the monofilaments. The width of the charging electrode 11 extends in the travelling direction of the monofilament and thus determines the magnitude of the electric field.

The function of the embodiment of the device for electrostatically charging and for discharging monofilaments according to the invention shown in fig. 3 is the same as in the previous embodiment. Thus, an electrostatic charge is generated on the filaments of the filament bundle 5 by the electric field of the charging electrode 11. The dispersion of the filaments achieved here serves to moisten the filaments of the moistening device 14 directly after cooling. For this purpose, the entire filament bundle is guided in contact with the contact surface 15 of the wetting ring 21. The discharge process is simultaneously activated by the contact, so that the filaments no longer have an electrostatic charge after wetting. The filaments are preferably collected after wetting and drawn off as a fiber bundle from a drawing roll.

By means of the method according to the invention, in particular in the apparatus shown in fig. 3, undesired filament bunching during cooling can be avoided. Even in a multi-row arrangement, the filaments are cooled and wetted discretely.

In the embodiments of the device according to the invention shown in fig. 1 to 3, electrostatic charging can also be supported by distributing ionized particles into a monofilament tuft by means of an air flow. However, in principle, it is also possible to replace the charging electrode by an ionizer.

In principle, it is also possible in the above-described exemplary embodiments to separate the discharge of the filament from the wetting of the filament by means of an additional thread guiding element. It is important in this case, however, that the cooling of the filaments and the wetting of the filaments take place as far as possible in the charged state of the filaments.

Claims

1. A process for melt spinning a plurality of filaments in the steps of:

1.1 extruding a monofilament from a polymer melt through a plurality of nozzle orifices of a spinneret;

1.2 cooling the filaments by means of cooling air;

1.3 electrostatically charging the filaments during cooling;

1.4 discharge the filaments by contact with the wetted contact surface.

2. The method of claim 1, wherein the electrostatic charging of the monofilament is performed after pre-cooling of the monofilament, spaced apart from the spinneret.

3. A method as claimed in claim 1 or 2, characterized in that for electrostatically charging the filaments an electric field is generated with a high voltage of maximally 30kV, through which the filaments are guided.

4. A method according to claim 3, wherein the electric field is generated by a charging electrode spaced from the monofilament by a distance of from 5mm to 30 mm.

5. A method according to claim 3 or 4, characterized in that the monofilaments are extruded in an annular arrangement and cooled by means of a blowing candle located inside, so that the blowing candle interacts as a counter electrode with the charging electrode to generate the electric field.

6. The method of claim 5, wherein the monofilaments are wetted with a fluid over the circumference of a wetting ring at the holding end of the blow candle.

7. An apparatus for melt spinning a plurality of filaments, the apparatus having: a spinneret (1) having a nozzle plate (2) comprising a plurality of nozzle holes (3) on a bottom side; a cooling device (6) having a blowing part (7) for generating a cooling air flow below the spinneret (1); and a charge generator (10) for charging the monofilaments,

it is characterized in that the preparation method is characterized in that,

the charge generator is arranged in the height range of the blowing part (7), and a wetting device (14) with a wetted contact surface (15) is provided for discharging the monofilaments, and the monofilaments are guided on the contact surface.

8. The apparatus according to claim 7, characterized in that the charge generator (10) is arranged below the spinneret (1) with a minimum pitch (V) in which pre-cooling of the monofilaments can be carried out.

9. Device according to claim 7 or 8, characterized in that the charge generator (10) is designed to be height-adjustable.

10. An apparatus according to any one of claims 7 to 9, characterized in that the charge generator (10) is designed such that an electric field can be generated around the monofilament with a high voltage of at most 30 kV.

11. The device according to claim 10, characterized in that the charge generator (10) has charging electrodes (11) which are arranged at a distance of 5mm to 30mm from the monofilament.

12. Device according to claim 11, characterized in that the spinneret (1) has nozzle bores (3) arranged in an annular manner, the charging electrode (11) being designed in an annular manner.

13. The apparatus according to claim 11, characterized in that the blowing means (7) is a blowing candle (19) arranged centrally with respect to the spinneret (1), the blowing candle (19) being designed as a counter electrode with respect to the charging electrode (11).

14. Apparatus according to claim 12 or 13, characterized in that the wetting device (14) has a wetting ring (21) at the holding end (22) of the blowing candle (19), on the circumference of which wetting ring the monofilaments can be guided in a contacting manner.

15. The device according to any of claims 11 to 14, characterized in that the charging electrode (11) is provided with an opposing counter electrode (12) or a grounded metal component (8) for generating an electric field.