EP0752020B1 - Process and device for cooling melt-extruded filaments - Google Patents

Abstract

PCT No. PCT/DE96/00089 Sec. 371 Date Dec. 2, 1996 Sec. 102(e) Date Dec. 2, 1996 PCT Filed Jan. 17, 1996 PCT Pub. No. WO96/22409 PCT Pub. Date Jul. 25, 1996For the cooling of melt-extruded filaments of fiber-forming polymers spun from nozzle in molten form, said filaments are exposed to a medium prepared in foam form. The filaments emerging from the spinning nozzle are taken to the cooling area through said foam before passing on to a further process. The cooling medium, consisting of a liquid, is prepared by the addition of a gas.

Description

The invention relates to a method for cooling melt-spun Filaments made of thread-forming polymers and a Device for performing the method.

Filament yarns and staple fibers made of thread-forming polymers such as Polyesters, polyamides or polyolefins are commonly used produced by the melt spinning process. With this procedure a polymer melt is fed to a spinning pump, which melt through the spinnerets in the so-called spinning beam promotes. Those from the nozzles in the form of liquid filaments escaping melt solidifies in a cooling shaft. Then a preparation is carried out at the same time, i.e. Humidification and anti-static treatment and the like before the filaments go through another process be fed. The cooling of those emerging from the spinneret liquid filaments is of great influence the titer uniformity (Uster value) and the textile technology Properties of fibers and threads in the end product. In some applications, e.g. with high single titers, decreases with increasing production speed (g / min / hole) the yarn strength from (US PS 4 973 236). The cause is insufficient cooling of the exiting from the nozzle hole Melt flow.

Air, but also water, are generally used as cooling media.

Air cooling has the advantage that the air is low Exerts friction on the emerging filaments and therefore no unwanted stretching occurs. The disadvantage is, however low cooling effect of the air, so that a long cooling distance is required. However, a long cooling section also means a slow cooling. A slow cooling favors the crystallite formation in the thread, which is the result of the subsequent stretching Causing problems. A high throughput (g / min / hole) or thicker single filaments require one especially long cooling distance, because the cooling speed is low. Thus, as already mentioned above, there is this Spun material particularly the risk of crystallite formation.

The cooling usually takes place by blowing the filaments crosswise. The air flow must be low in turbulence and the same Have speed across the chute width so every filament experiences exactly the same cooling in time and place. Perforated sheets or screen mesh in connection with honeycomb rectifiers are used to meet the required flow conditions to create. Also can be about the height of the cooling shaft if necessary, a speed profile can be provided. Despite this partly elaborate measures will be taken at high Number of filaments per surface no uniform cooling of all Single filaments guaranteed. From filament to filament arises a transverse temperature gradient, so that the number of rows of holes arranged one behind the other in the air flow is limited.

Through U.S. Patent 4,425,293 it is also known to be water Use coolant. The advantage of water cooling is a quick dissipation of heat and thereby avoidance of spin crystallization. A disadvantage of water cooling is however, high water / filament friction. This can cause it to unwanted stretching of the filaments. Indeed has also been tried, the unwanted stretching to calculate and design for water cooling that a Desired stretching takes place (US 5 268 133 and WO 91/181 133). However, such measures have been complicated and proved to be not without problems.

From SU-PS 386 034 it is known to cool the foam to use filaments emerging from the spinneret, whereby the foam by blowing air through a water solution is generated with surface-active material. With that an increase in the uniformity of the physical-mechanical Properties of the fibers and an intensification of the Process of cooling can be achieved.

It has now been shown that the use of foam instead of water as a cooling medium did not bring the expected benefits Has. The handling of the foam is easier than that of water passing through the nozzles Spinning melt, but here too there are repeated delays or also spin crystallization.

The object of the present invention is to provide a method create, which the cooling of the emerging from the nozzles Spinning melt improved by means of foam and thus also that Spinning thicker filaments at high speed allows without crystallite formation in these filaments comes, which adversely affects the subsequent stretching / texturing process influenced. This task is characterized by the features of the claim 1 and the device claim 10 solved.

It has been shown that, surprisingly, by using foam the cooling effect is increased significantly without the great hydrodynamic friction force known from water To produce filaments. By forming a liquid film on the filament surface, however, approximates achieved the cooling effect of the water. The disadvantages of cross-blowing are also by the inventive method avoided. Further advantages of the invention result from the fact that because of the drastically reduced cooling section Execution of spinning systems with a very low overall height possible becomes. This leads to considerable cost savings. Further Details of the invention are described with reference to the figures.

Figur 1 -

schematisch eine Anlage zum Spinnen von schmelzgesponnenen Filamenten aus fadenbildenden Polymeren, wobei die Teile der Anlage, die für die Erfindung unwesentlich sind, weggelassen wurden.

Figur 2 -

eine andere Ausführungsform der Schaumanlage

Figur 3 -

eine graphische Darstellung des Abkühlungsvorganges gemäß dem Stand der Technik und gemäß der Erfindung

Show it:

Figure 1 -

schematically a plant for spinning melt-spun filaments from thread-forming polymers, the parts of the plant which are not essential to the invention have been omitted.

Figure 2 -

another embodiment of the foam system

Figure 3 -

a graphic representation of the cooling process according to the prior art and according to the invention

Spinning nozzles 2, from which the filaments F emerge, are arranged on a spinning beam 1. Before these filaments F, which leave the nozzles 2 in liquid form, can be fed to any further processing, they have to be solidified by cooling, for example to wind them up into bobbins or to deposit them in bundles in cans. They therefore pass through a so-called cooling section SK, on which the threads are guided freely without touching themselves or other objects and are cooled from the usual melting temperature of approximately 300 ° C. to a limit temperature t _g , which is approximately 70 ° C. . Only when this limit temperature t _{g is} reached or fallen below, the filaments F may have contact. 3 shows the temperature t of the spinning material in ° C. over the distance SK in m, which the spinning material has to pass through until it has cooled to a certain temperature. The line t _g indicates the temperature to which the spinning material must have cooled at least before each contact (limit temperature). The cooling conditions are shown, for example, for a polyester POY monofilament with a titer of 22-35 dtex by curve A. The cooling takes place as usual with air, which has an intrinsic temperature corresponding to the room temperature of about 20 ° C. The course of the cooling shows that with this type of cooling and a production speed of 3600 m / min, the limit temperature of approximately 70 ° C. is only reached after a cooling section SA of approximately 3.5 m. Only at this distance from the nozzle have the filaments achieved such strength through cooling that they may be in contact with each other or with thread guide elements or the like.

Is the production speed increased or one more stronger titer spun, so an even larger cooling section SK required, which can be up to 5 or 6 m. The disadvantages of such a long cooling section have already been mentioned already mentioned. After a first contact of the filaments F may only follow the nozzles at this distance this means that the whole plant reaches a great height. By these dimensions make the system complex and expensive, apart from the fact that the filaments F on the cooling section too are exposed to uncontrolled influences.

The use of water would certainly cool the cooling section shorten the most because of the good heat transfer. However There are major disadvantages due to the strong friction between water and filament on. Surprisingly, it has now been shown that through Foam a similarly strong cooling can be achieved as with water. However, the harmful friction does not occur between Filament and foam like with water.

Curves B and C show the cooling conditions for foam with different volume fractions of liquid. It follows that in the case of a foam with a liquid volume fraction of 5% under the same conditions as for curve A, the cooling distance is shortened to approximately 1.1 to 1.2 m in order to reach the limit temperature t _g . If the volume fraction is higher, the cooling distance is further shortened, since the heat transfer also increases greatly depending on the volume fraction of liquid in the foam. For example, curve C shows the cooling process for a foam with about 10% liquid volume. The cooling section SK is reduced to the section SC, which is less than 1 m, in order to reach the limit temperature.

FIG. 3 shows the entire cooling process from the exit from the spinnerets to the preparation for the next treatment process. In the air gap S between the nozzle plate 2 and the foam container 3, a relatively flat course of the temperature decrease can be seen first. With the entry into the foam, the cooling curve is considerably steeper than if the cooling were only carried out by air and thus reaches the limit temperature t _g after a short distance.

Needless to say that this is significant Shortening the cooling section SK not only the technological Properties and production conditions for strong titers considerably improved, but it will also be significantly lower Dimensions of the spinning system reached. The heights can smoothly be reduced to half to a third of what when installing such systems to significant cost savings leads.

As can be seen from Figures 1 and 2, is under the spinning beam 1 and the nozzle plate 2 at a distance S a foam container 3 or 30 arranged. The distance S can be very small be, e.g. only 1 - 2 cm. Its size depends on the Filament thickness and production speed. after the Filaments F emerge in liquid form from the nozzles 3 some solidification is necessary before going into the foam immerse yourself. This solidification occurs with fine filaments much faster than with coarser titles, where this Distance from the foam depending on the production speed can be up to 1.5 m.

The foam container 3 is supported by a frame 32 and has a wide inlet opening 31 at its upper end so that the filaments F cannot touch the walls of the foam container 3, while a narrow opening 35 is provided at its lower end through which the Filaments F leave the foam container. Due to the widening cross section of the foam container 3, the flow rate of the foam is reduced and the regression and separation of the liquid is promoted and the spinning material passed through the foam in countercurrent is wetted and cooled intensively. Since the filaments F largely fill this narrow opening 35 and thus contact contacts occur, the limit temperature t _g must be reached with certainty up to this point. As can be seen from Figure 3, this also determines the overall height of the foam container 3.

At the lower end, close to the outlet opening 35, there is a Foam generator 5 arranged, the air supply 51 and has a liquid supply 52 and the foam immediately supplies in the lower part of the foam container 3. While the foam by the continuous foam generation upwards increases, the filaments F countercurrently from top to bottom passed down through the foam container 3 and occur at the Exit opening 35 from the foam container 3 to then to be sent to another processing process. The rising foam is controlled by a sensor 4, which, if necessary, the fill level via Level controller 41 regulates. The edge of the upper entry opening 35 of the foam container 3 is designed as an overflow, so that re-forming liquid, if necessary, over the Edge can run off. The overflowing liquid as well as in Foam container 3 resulting from regression and down draining liquid is collected in a drip pan 33 and returned to the circulation pump 7 via drain lines 36.

The foam generator 5 is continuously fed by the Circulation pump 7, which is also the circuit of the returned liquid caused by the foam container 3. By the metering pump 72 water is added to this cycle to the extent that foam generation and cooling of the filaments F liquid is consumed. A second pump 71 removes the liquid Preparation oil added. The circulation pump then does both 7 pumped through a mixer 6 and thereby to the Prepared liquid that the foam generator 5 on the Line 52 is supplied. In the foam generator 5 is by Feed 51 air added to the liquid and so the foam generated, which is delivered in the lower part of the foam container 3 becomes.

When piecing, the foam container 3 is initially empty. From the filaments F emerging from the nozzle 2 fall down into the Foam container 3 and are inserted into the outlet opening 35. For this purpose, a flap 34 is used, which covers the lower part of the Foam container 3 makes accessible. After filament insertion F the flap 34 is closed again and foam is added. The sensor 4 controls the rising foam and regulates the motor 42, which controls the metering pump, via a controller 41 72 drives for the water supply. Through the over the Sensor 4 controlled level in the foam container 3 is thus also determines the cooling section SK, which the filaments at Need to go through the foam.

In the filament cooling process according to the invention due to foam, the bubble bath is used at the same time to Apply the preparation solution to the filaments F. The invention The system therefore also includes the required one Preparation device. Below the foam container 3, the emerging filaments through two electrodes 8 scanned. With a resistance measurement the constancy of the preparation pad is measured and if necessary through a target / actual value comparison in the concentration controller 81 and a frequency converter 82, the motor 83 for drives the metering pump 71 for the preparation oil.

In the embodiment according to Figure 2, the foam container is something designed differently than in Figure 1. The foam container 30 is as rectangular or cylindrical shaft formed on the itself in continuation of its external form, but separated through a joint 38, the foam generator 50, 50 ', connects. The narrow outlet opening 35 of the foam container 3 is here in the foam generator 50, 50 ', so that the foam container 3 open at the parting line 38 in full cross section is.

The foam generator consists of two half-shells 50, 50 ' are movable apart in the horizontal direction along the Parting line 38. This makes the lower part for piecing of the foam container 30 accessible so that the falling Filaments F captured and in yarn guides for further processing can be inserted. If this has happened, they will the two half-shells 50, 50 'of the foam generator are reassembled, so that they enclose the filaments F and the Foam container 30 is closed except for the outlet opening 35 for filaments F.

Each of the two half-shells 50, 50 'is independent Foam generator designed and both to an air supply 51st as well as connected to a liquid supply 52. This Supply lines are expediently elastic to the two half-shells 50, 50 'to be able to move apart. The two Half-shells 50, 50 'are expediently on one for this Axis mounted perpendicular to the parting line 38 at one end, so that the half-shells 50, 50 'unfolded can be used for inserting the filaments F. In each of the Half shells 50, 50 'are arranged sintered metal candles 53, through which the air is fed into the liquid. Instead of through the sintered metal candles 53 can also for the air supply over a plate or some other form of sintered metal manufactured body are supplied. Preferably however, are commercially available sintered metal candles for the air supply used. By using sintered material an exceptionally good treatment of the liquid with gas, preferably air to foam. Of course you can other fine-pored elements for the gas supply in the Liquid can be used, such as strainers, nozzle plates and Like ..

The liquid level 54 in the foam generator 50, 50 'is controlled by a level limiter 37 to a to guarantee even foam production. The easiest The type of such a sensor 37 is shown in FIG represented an overflow. Instead of the overflow 37 a probe can also be provided which monitors the fluid supply controls each. The foam generated in this way increases up into the foam container 30, while the filaments F in Counter current flow through the foam container 30 and through the Leave outlet opening 35.

The upper part of the foam container 30 is in the same way designed as in the described embodiment according to the figure 1. Here too, the edge of the opening 31 is designed as an overflow, so that regressive liquid collect and over can drain this edge to catch again and the Circuit to be fed again for foam generation.

The sensor 4 regulates the level of the foam within of container 30, however, additional may be required Take measures to ensure that the foam level is even and thus all filaments F through the same cooling section SB go through the foam. To avoid being at the entry opening 31 of the foam container 30 forms a foam mountain, can also have a device for smoothing the foam level be provided. In the embodiment shown a suction channel 21 is provided, which is such a foam mountain transported away or the formation of such a foam mountain prevented by a slight air flow.

The distance S to the nozzle plate 2 is much smaller here shown as in Figure 1. As mentioned above, this is Distance depending on the filament speed and the titer the filaments F. However, a certain distance S must be maintained as the foam should not touch the nozzle plate 2, to undesirably cool the foam avoid. Such a device 21 for smoothing the Foam level makes a certain distance from the nozzle plate required.

Reference list

Spinning beam

1

Nozzle plate

2nd

Air duct

21

Foam container

3, 30

Entrance opening

31

frame

32

Drip pan

33

flap

34

Outlet opening

35

procedure

36

Level limiter

37

Parting line

38

Level sensor

4th

Foam generator

5; 50, 50 '

Air supply

51

Coolant supply

52

Sintered candles

53

Liquid level

54

mixer

6

Circulation pump

7

Dosing pump prep. Oil

71

Dosing pump water

72

Drive motors

42, 83

Electrodes

8th

Concentration regulator

81

Frequency converter

R2

Cooling section

SK

Air gap

S

Limit temperature

t _G

Cooling sections to reach Limit temperature

SA, SB, SC

Filaments

F

Claims (24)

1. A process to cool down melt-spun filaments made from thread-forming polymers where the melt, in the form of liquid filaments, exits from spinnerets and said filaments are then fed to a zone in which the spun material is subjected to a medium prepared as a foam for quenching and the spun material exiting from said spinnerets (2) is passed countercurrently through said foam in the quenching zone before the spun material is passed on to undergo another process, characterized in that the spun material (F) exiting from the spinneret (2) is contacted with the foam after its passage through a free distance (S) which is as short as possible to cause the spun material (F) to reach a certain set before entering the foam.
2. The process according to claim 1, characterized in that said foam is prepared in a foam generator (5; 50, 50') and is led directly from it to a vessel (3) through which the spun material (F) is passed.
3. The process according to one of claims 1 or 2, characterized in that the foam vessel (3) is kept to a certain filling level.
4. The process according to one or more of claims 1 to 3, characterized in that the foam level undergoes smoothing.
5. The process according to claim 4, characterized in that smoothing is performed by means of an air stream passed over the foam level.
6. The process according to claim 5, characterized in that a suction air stream is passed over the foam level.
7. The process according to one or more of claims 1 to 6, characterized in that foam generation is continuos and the liquid produced during foam disintegration is collected and recycled for foam generation.
8. The process according to one or more of claims 1 to 7, characterized in that the speed of the foam flow is reduced towards the point of filament entry into the vessel.
9. The process according to one or more of claims 1 to 8, characterized in that the foam is prepared preferably from about 5 to 10 per cent by volume of liquid.
10. Device to cool down melt-spun filaments using a bath of foam where a melt of polymers exits, in the form of liquid filaments (F), from spinnerets (2) mounted in a spinning manifold (1) and is passed through a quenching zone before said filaments (F) are passed on to undergo another process, and a foam vessel (3) is disposed in the quenching zone through which said filaments (F) are passed for a cool-down, characterized in that means are provided to maintain a free distance (S) which is as short as possible between the spinnerets (2) and the foam level in the foam vessel (3) to cause the spun material (F) to reach a certain set before entering the foam.
11. The device according to claim 10, characterized in that a foam generator (5, 50, 50') is directly associated with the foam vessel (3).
12. The device according to claim 11, characterized in that the foam generator (5, 50, 50') is disposed at the lower end of the foam vessel (3).
13. The device according to claim 12, characterized in that the foam generator (5, 50, 50') opens directly into the foam vessel (3).
14. The device according to one or more of claims 11 to 13, characterized in that the foam generator (5, 50, 50'), in continuation of the foam vessel (3), is disposed at the lower end thereof.
15. The device according to one or more of claims 11 to 14, characterized in that the foam generator (5, 50, 50') is connected to a liquid supply (52) and an air supply (51).
16. The device according to claim 14, characterized in that the foam generator (5, 50, 50') comprises two cup halves (50, 50'), which may be swivelled apart in a radial direction so as to release the filaments (F) enclosed by the cup halves (50, 50') which then exit from the foam vessel (3).
17. The device according to claim 16, characterized in that the cup halves (50, 50') each comprise a self-contained liquid vessel in which air feed members (53) are disposed.
18. The device according to one or more of claims 11 to 17, characterized in that the air feed members (53) are made up of sintered metal.
19. The device according to claim 18, characterized in that the air feed members (53) are formed as sintered metal candles.
20. The device according to one or more of claims 11 to 19, characterized in that the foam generator (50, 50') includes a level limiter (37) for the liquid.
21. The device according to claim 20, characterized in that the level limiter (37) is formed as an overflow.
22. The device according to one or more of claims 11 to 21, characterized in that the foam vessel (3) includes a wide inlet port (31) at is upper end for the filaments (F) to prevent the filaments from touching the walls of the foam vessel (3), and includes a narrow outlet port (35) at its lower end, which is largely filled by the filaments, and that the cross-section of the foam vessel widens in the direction of foam flow.
23. The device according to one or more of claims 11 to 22, characterized in that a device to smooth the foam level is disposed at the inlet side (31) of the foam vessel (3).
24. The device according to claim 23, characterized in that the device to smooth the foam level comprises a suction duct (21).

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