CN112111797B

CN112111797B - Method and apparatus for melt spinning a plurality of filaments

Info

Publication number: CN112111797B
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: 2023-07-11
Anticipated expiration: 2040-06-17
Also published as: DE102020114761A1; CN112111797A

Abstract

The present invention relates to a method and apparatus for melt spinning a plurality of filaments from a polymer melt. To this end, the filaments are extruded through a plurality of nozzle holes of a spinneret and then cooled. To aid in cooling, according to the invention, the filaments are electrostatically charged and discharged during cooling by contact with the wetted contact surface. The dispersion achieved by electrostatic charging can thus also be advantageously used to wet the filaments.

Description

Method and apparatus for melt spinning a plurality of filaments

Technical Field

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

Background

In the case of melt spinning filaments from a polymer melt, the filaments are typically cooled by cooling air after extrusion through a spinneret to solidify the polymer. During cooling of the filaments, a so-called filament number is formed by solidification of the polymer melt. Here, a high uniformity of the fineness is desired for the quality of the filaments. Thus, uniformity of fineness of each monofilament and uniformity of fineness on all monofilaments can be similarly achieved. The delivery of cooling air is thus controlled such that as uniform cooling of each filament as possible is obtained within the filament bundle/filament group (Filamentschar). However, when the number of monofilaments is high, there is a problem in that separate adhesion occurs between the monofilaments. In order to avoid such a connection and bundling of a plurality of filaments, it is known in the prior art that the filaments are electrostatically charged/electrostatically charged in order to thereby avoid a gathering of filaments by homopolar charging.

Thus, a method and a device for melt-spinning a large number of filaments are known from document EP 0949362A2, in which a charge generator is arranged directly below the spinneret, by means of which an electrostatic charge of the filaments is generated. To charge the filaments, ionized air is delivered to the freshly extruded filaments. The discharge of the filaments is performed after cooling.

In the known method and device for melt spinning a large number of filaments, the problem exists that the filaments are already electrostatically charged immediately after extrusion, which leads to expansion of the filament bundle. However, this effect prevents the formation of a uniform denier per filament.

Disclosure of Invention

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

This object is achieved by a method having the features of claim 1 and by an apparatus having the features of 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 occurs only in the state in which at least one edge region of the filaments has solidified. Thus, the filaments are electrostatically charged during cooling. For this purpose, the charge generator is arranged in the height range of the blowing component, preferably in the lower third. The repulsive effect formed between the individual filaments here is used in addition to better cooling also for uniform wetting of the individual filaments. The discharge of the filaments is thus achieved by contact with the wetted contact surface. All filaments can be individually wetted by spreading the filaments apart.

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 element, wherein a subsequent discharge of the filaments is provided by a wetting device having a wetted contact surface, over which the filaments are guided.

The method according to the invention and the device according to the invention thus enable melt spinning of a high number of filaments without the risk of forming individual bundles. In this regard, the method according to the invention and the apparatus according to the invention are particularly suitable for high throughput, as is often the case when producing short fibers.

In one method variant, the electrostatic charging of the filaments occurs during pre-cooling of the filaments at a distance from the spinneret. This variant of the method has the particular advantage that the filaments are sufficiently pre-cured. In this regard, concentrated electrostatic charging may be generated in the edge regions of the filaments. The core of the monofilament remains substantially unaffected.

In order to obtain targeted and rapid electrostatic charging, the following method variants prove advantageous, namely: 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 5mm to 30mm from the filaments. 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 variant of the method is preferably implemented in which the filaments are extruded in a ring-shaped arrangement and cooled by an internally located blowing candle/blowing cartridge (blowing cartridge), wherein the blowing candle acts as a counter electrode in conjunction with a charging electrode to generate an electric field. Thus, the endless filament curtain can be electrostatically charged in a targeted manner.

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

In the device according to the invention, it is particularly advantageous if the charge generator is arranged below the spinneret at a minimum distance in which pre-cooling of the filaments can be carried out. The cured edge regions of the filaments can thus be charged in a targeted manner. Avoiding the obstruction of the formation of a uniform and constant denier per filament.

In order to be able to change the charging point in the cooling zone as a function of the single-filament fineness and the corresponding polymer type, the development of the invention provides that the charge generator is configured to be adjustable in height. This allows the distance to be adapted to the respective process and the corresponding filaments, both with respect to the spinneret and with respect to the subsequent moistening device.

For strong electrostatic charging, the charge generator is preferably designed such that an electric field can be generated in the surroundings of the filament by means of a high voltage in the range of maximally 30 kV. As a result, a strong charge can be generated in the relatively short passage area of the filaments.

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

For melt spinning very large numbers of filaments, it is preferable to use a variant of the device in which the spinneret has nozzle openings arranged in a ring shape and the charging electrode is configured in a ring shape. Thus, the filament bundle extruded through the spinneret can be surrounded by a charging electrode so as to form uniform electrostatic charging over the entire circumference of the filament bundle.

The cooling is preferably effected here by a blower candle arranged centrally with respect to the spinneret, which blower candle is at the same time embodied 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 directly use the repulsive effect of electrostatic charging in the filament bundle, the wetting device is preferably formed by a wetting ring on the holding end of the blowing candle, on the circumference of which wetting ring the filaments can be guided in a contacting manner. Thus ensuring uniform and strong wetting of all filaments.

In principle, however, there is also the possibility of generating an electric field through the charging electrode and the opposing counter electrode or grounded metal member. In this regard, a rectangular spinneret assembly with, for example, cross-flow blowing may also be used.

Drawings

The method for melt spinning a plurality of filaments according to the present invention will be explained in detail below with reference to the accompanying drawings by means of some embodiments of the apparatus for melt spinning a plurality of filaments according to the present invention.

The drawings show:

fig. 1 schematically shows a front view of a first embodiment of an apparatus for melt spinning a plurality of filaments according to the present 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 filaments according to the present 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 shown 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, provided that it does not specifically indicate which figure is.

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

A cooling device 6 is arranged below the spinneret 1. The cooling device 6 has a blowing member 7 which generates a cooling air flow which is blown onto the filament bundle 5 freshly extruded through the nozzle holes 3. For this purpose, the blower part 7 has a blower wall 8 laterally arranged next to the filament bundle 5, which blower wall is connected to a blower chamber 9. Cooling air is supplied to the blower chamber 9, which is blown out transversely to the filament bundle 5 by the blower 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 at a distance from the filament bundle 5 on a support 13. The distance between the charging electrode 11 and the filament bundle 5 is indicated by the letter a in fig. 2. The spacing a is in the range of 5mm to 30mm depending on the process, the number of filaments and the denier per filament.

The charging electrode 11 is configured in the form of a rod and is connected to a power supply, not shown here. The charging electrode 11 is adapted to generate an electric field around the filament bundle 5 at a high voltage of maximally 30 kV. The blower wall 8 disposed opposite to the charging electrode 11 may be used as a counter electrode according to its characteristics. Alternatively, however, there is also the possibility as shown by the dashed line in fig. 2, namely: opposite the charging electrode 11, a counter electrode 12 is provided to generate an electric field around the filament bundle 5.

The charging electrode 11 is embodied to be height-adjustable on a support 13. However, the charging electrode 11 can only be adjusted to 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 area of the filament bundle, which enables 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 embodiment the moistening device 14 has a driven roller 16, which is moistened with a fluid in a bath 17. The circumference of the roller 16 forms a contact surface 15, on which the filament bundle 5 is guided in a contacting manner. The roller 16 is grounded by a line 18.

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

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

In the embodiment of the apparatus for melt spinning a plurality of filaments according to the invention shown in fig. 3, the spinneret 1 has a nozzle plate 2, on the underside of which a plurality of rows of nozzle holes 3 are formed in a ring-shaped arrangement. 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 spinneret 1, a cooling device 6 is arranged, which has a cylindrical blowing candle 19 as a blowing element 7. The blowing candles 19 are arranged centrally with respect to the spinneret 1 such that the blowing candles 19 are located within the filament curtain of the filament bundle 5. The blowing candle 19 has a gas-permeable candle outer circumferential surface, wherein the blowing 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 produced by the blowing candles 19, which cooling air flow passes through the filament bundle 5.

Immediately below the spinneret 1, a suction device 20 is arranged outside the filament bundle 5 opposite the blowing candles 19. A very uniform laminar air flow can thus be achieved directly on the freshly extruded individual filament bundles, which air flow results in pre-cooling of the filaments.

A moistening ring 21 is arranged on the holding end 22 of the blow 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 a discharge channel for conveying the fluid in the upper region. 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 dampening ring 21 is connected to a candle holder 23 and is grounded through the candle holder.

At the level of the blowing element 7, a ring-shaped charging electrode 11 is arranged outside the filament bundle 5. The charging electrode 11 is spaced from the outer filament bundle 5. The pitch is denoted by letter a and is in the range of 5mm to a maximum of 30 mm. The distance a is dependent on the density and width of the filament bundle 5 to be guided.

In the exemplary embodiment shown in fig. 3, the outer circumferential surface of the blower candle 19 is constructed of metal and serves as a counter electrode. Grounding of the blow candle 19 is accomplished by the candle holder 23. Accordingly, an electric field can be generated between the charging electrode 11 and the candle outer circumferential surface of the blow candle 19. For this purpose, the charging electrode is operated at a high voltage of maximally 30 kV. Based on the characteristics of the blowing candle 19, the charging electrode 11 is designed to be adjustable in its height. Thus, it is preferable to generate an electric field in the lower third of the cooling zone. The width of the charging electrode 11 is preselected according to the number, density, and fineness of the monofilaments. The width of the charging electrode 11 extends in the direction of travel of the filaments and thus determines the magnitude of the electric field.

The embodiment of the device for electrostatically charging and discharging filaments according to the invention shown in fig. 3 functions identically to the previous embodiment. Thus, electrostatic charging 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 in this way serves to wet the filaments of the wetting 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 bundled after wetting and are drawn off as fiber bundles from a drawing roll.

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

In the embodiment of the device according to the invention shown in fig. 1 to 3, electrostatic charging can also be supported by distributing ionized particles into the filament bundle by means of a gas flow. In principle, however, the possibility also exists that the charging electrode is replaced by an ionizer.

In principle, in the above-described embodiments, the possibility also exists of separating the discharge of the filaments and the wetting of the filaments by means of additional thread guiding elements. It is important here, however, that the cooling of the filaments and the wetting of the filaments take place as far as possible in the state in which the filaments are charged.

Claims

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

1.1 extruding filaments from a polymer melt through a plurality of nozzle holes of a spinneret;

1.2 cooling the filaments by means of cooling air;

1.3 electrostatically charging the filaments during cooling;

1.4 discharge filaments by contact with wetted contact surface.

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

3. A method according to claim 1 or 2, characterized in that, in order to electrostatically charge the filaments, an electric field is generated with a high voltage of maximally 30kV, through which field the filaments are led.

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

5. The method of claim 4, wherein the filaments are extruded in a circular arrangement and cooled by an internally located blow candle such that the blow candle interacts with the charging electrode as a counter electrode to create the electric field.

6. The method of claim 5, wherein the monofilament is wetted with a fluid on a perimeter of the 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 blower unit (7) for generating a cooling air flow below the spinneret (1); and a charge generator (10) for charging the filaments,

it is characterized in that the method comprises the steps of,

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 filaments, wherein the filaments 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 spacing (V) in which pre-cooling of the filaments can be carried out.

9. The device according to claim 7 or 8, characterized in that the charge generator (10) is designed to be highly adjustable.

10. The device according to claim 7 or 8, characterized in that the charge generator (10) is designed such that an electric field can be generated around the filaments by means of a high voltage of up to 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 filaments.

12. The apparatus according to claim 11, characterized in that the spinneret (1) has annularly arranged nozzle holes (3), and the charging electrode (11) is designed annular.

13. The apparatus according to claim 11, characterized in that the blowing component (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. The device according to claim 13, characterized in that the moistening device (14) has a moistening ring (21) at the holding end (22) of the blowing candle (19), on the circumference of which moistening ring the filaments can be guided in a contacting manner.

15. The device according to claim 11, characterized in that the charging electrode (11) is provided with opposing counter electrodes (12) or grounded metal members (8) for generating an electric field.