EP0586630B1 - Process and device for producing continuous synthetic filaments - Google Patents

Abstract

A process and device for spinning and cooling synthetic, multi-strand, spin-oriented continuous filaments with a spinning device with nozzle plates containing spinning heads and cooling shafts with permeable walls through which a stream of air is inducted inside the cooling shaft purely through the frictional transport of the air by the filaments. The stream of air is continuously taken in directly beneath the spinning heads and then over the entire length of the cooling shafts at filament speeds of the least 2400 m/min.

Description

The invention relates to a method and a device for spinning and cooling synthetic, multifilament, spin-oriented continuous filaments by means of a spinning device with spinnerets containing nozzle plates and cooling shafts with an air-permeable wall, through which an air flow into the interior of the cooling shafts solely due to a frictional entrainment of the air by the filaments is sucked.

Continuous filaments made of synthetic polymer are produced from the melt having the spinning temperature by means of a spinning device. The melt is pressed through bores in a nozzle plate, the extruded melt streams are then cooled and combined to form a filament bundle which is provided with a spin finish and drawn off with a thread take-off device and is finally wound up.

Cooling is of particular importance. The uniformity of the cooling is directly transferred to the physical characteristics of the filaments, such as the uniformity of the filament thickness (Uster) or the coloration. Disturbances are transmitted by non-laminar or turbulent flow of the cooling air. Before the melt streams pressed out at high spinning temperature have not cooled below the solidification point they must not collide or be touched by thread guides, otherwise they will stick together.

Systems with cooling air conditioning in an air conditioning system, supply via air ducts to cooling shafts and blowing in by means of the pre-pressure generated by fans into the area of the melt flows below the nozzle plates have proven themselves. Elaborate air distribution, control and homogenization devices must be used to supply the turbulent cooling air in a directed and laminarized manner.

Embodiments are those with cross flow, ie. H. essentially right-angled blow-through of the filaments and direct removal of the heat of fusion leeward side (US-A 4529368), as well as those with radial blowing, d. H. Air direction directed from the outside into the filament bundle and heat dissipation essentially in the filament running direction (US-A 4712988 and DE-A 3406347).

Another method of generating a cooling air flow is to pass the filaments through negative pressure systems in which the cooling air flow is generated due to the negative pressure (US-A 4496505 and WO 90-02222A).

In any case, blowing melt streams either through overpressure or underpressure is the customary technique today for cooling the melt streams in order to subsequently combine them into a bundle of filaments and to process them further.

From DE-A 1914556 a device for spinning and cooling synthetic continuous filaments has become known, in which the required cooling air flow within a tube provided with a plurality of perforations, through which a from a nozzle plate squeezed out bundle of melt flows is generated. It is the arrangement according to Figures 5 and 6 of this document. The tube is deliberately designed in such a way that it has no perforation in its area adjoining the spinning head over a length of at least 300 mm, as a result of which outside air is expressly excluded from the area behind the tube. The melt streams should therefore initially not be subjected to any cooling immediately after leaving the spinning head. The consequence of this is a corresponding extension of the required cooling section, which is also expressly mentioned in DE-A 3406347, page 5, paragraph 1 above.

The invention has for its object to provide a method and an apparatus for spinning and cooling synthetic continuous filaments, which or gets along with a minimum of equipment and control technology and is particularly suitable for high take-off speeds. This object is achieved on the basis of the method described at the outset in that the air flow is drawn in directly at the underside of the spinning heads and continuously over the length of the cooling shafts at take-off speeds of at least 2400 m / min.

In deviation from the teachings of DE-A 1914556 cited above, cooling air is supplied from the outside air directly to the melt streams directly on the underside of the spinning heads, namely sucked in by the friction between the air and the filaments guided through the cooling shaft in question, which in a certain way Way to compare with an injector effect. This injector effect extends over the entire length of the cooling shaft and in particular also on the area directly on the underside of the spinning heads, so that the melt streams to be cooled are subjected to cooling immediately after leaving the spinning head. The cooling shaft causes one Channeling of the air flowing in through its wall along the direction of the filaments, which thus create an air flow that closes evenly around the filaments and thus causes a uniform cooling throughout.

Surprisingly, it has been shown that cooling generated by the above-described injector action and extending in particular to the area directly on the underside of the spinning heads in the sense of the invention leads, particularly at high take-off speeds, to filaments which, on the one hand, have a spinning orientation due to the high take-off speed, which cannot occur when using the device according to DE-A 1914556 because of the pull-in speed of 1000 m / min, which is preferred in this document, and on the other hand have a filament uniformity which occurs when using the device of DE-A 1914556 in connection with take-off speeds of over 2400 m / min because of the deliberate exclusion of the area below the spinning head from the cooling, which is prescribed in this publication. The uniform cooling resulting from the perforated shafts according to the invention also leads to the area immediately below the spinning heads, which leads to the fact that the individual filaments thus produced have a high uniformity over the length and from individual filament to individual filament.

In addition, there is the essential advantage in practice that compared to the conventional cooling systems with blowing by positive or negative pressure, which require considerable technical effort, in particular fans, this effort is completely avoided, so that the inventive method, which is more practical and advantageous Way allows the production of filaments, a particularly high economy is made possible. Separate and energy-consuming air conditioning systems to process the Cooling air, feed channels and homogenization devices for laminarizing the turbulent air can be omitted.

When using the method according to the invention, the average spacing of the individual filaments of a filament bundle at the outlet of the cooling shaft can be less than 6 mm due to the resulting particular uniformity of the air flow.

The device for carrying out the method according to the invention is designed so that the wall of the cooling shafts is provided with openings for air access over the entire length, so that even in the event of a connection of the cooling shafts directly to the underside of the spinning heads, air enters the cooling shaft at this point can be sucked in. In addition, it is also possible to arrange the cooling shaft at a distance from the underside of the spinning head, so that a particularly large cross section for the entry of air results at this particularly critical point. Here, the gap formed by the distance between the cooling shaft and spinning head is expediently chosen so large that only air is sucked into the cooling shaft through the gap and no countercurrent occurs in the gap, thus avoiding the occurrence of turbulence inside the cooling shaft.

The device is advantageously designed so that the access of cooling air can be regulated in the area immediately below the spinning head. In the case of a connection of the cooling shaft directly to the underside of the spinning head, this is done by making the cross-sections of the openings adjustable. If a gap is arranged between the cooling shaft and the underside of the spinning head, the width of this gap can be adjusted accordingly.

The cooling shaft can be designed as a metal sieve, in which case relatively large passages are present over its entire surface in close proximity.

It is also possible to design the cooling shaft as a perforated shaft which is perforated over its entire surface. The holes advantageously have a diameter between 1 to 5 mm and extend in total over an area which does not exceed 50% of the total surface.

The shape of the cooling shafts is expediently based on the shape of the nozzle plates, which can be round, oval or rectangular. Accordingly, the cooling shafts have a circular, oval or rectangular cross section, which is preferably 10 to 60 mm larger than that of the perforated field of the nozzle plate. The cross section of the cooling shaft is expediently constant over the entire length. In an alternative embodiment, the area with a constant cross section in the vicinity of the exit zone is followed by a short area with a decreasing cross section, the lower opening for the passage of the filament bundle having a minimum diameter or a minimum dimension of more than 10 mm.

The cooling shafts can expediently be cylindrical and each can be assigned a second cylinder concentrically at a distance, both cylinders being provided with perforations. In this case, the outer cylinder has the effect of a certain calming of the air flow, so that the air sucked in through the cooling shaft (inner cylinder) then comes from an air-calming zone and accordingly flows evenly inside the cooling shaft.

In order to be able to easily adapt the cross-section of the perforation in the cooling shaft to the respective requirements, the cooling shaft can be made cylindrical and another cylinder can be slid onto this cylinder, both cylinders being provided with perforations and a more or less strong overlap due to mutual rotation the perforations can be achieved. In this way, the desired cross section of the air passages can then be set.

The method according to the invention is preferably suitable for the production of single filament titers from 0.3 to 3.0 dtex at take-off speeds of 2400 to 7000 m / min, particularly preferably 0.3 to 1.5 dtex at 2400 to 5000 m / min, but with consideration of the following ratio of take-off speed to spinning titer.

Particularly advantageous conditions exist when filament titers are produced at certain speed ranges. It has been shown that the ratio of take-off speeds and spinning titer of the single filament, calculated in the dimensions m / min and dtex, is advantageous with at least 1800. Ratios greater than 8000 lead to filament tears and ratios greater than 10,000 increasingly lead to filament tears. The ratio is advantageously chosen to be less than 6000.

The speed of the first driven godet after the point of convergence is defined as the take-off speed (also spinning speed). The speed of the winding unit applies to godetless filament draw-off. The single filament titer, also known as the spin titer, on the take-off device is calculated in a known manner based on the defined take-off speed.

Fig. 1 - 6

schematisch, verschiedene Ausführungen der erfindungsgemäßen Vorrichtung zeigen, und zwar

Fig. 1

einen mit einstellbarem Abstand zur Spinnkopf-Unterseite angeordneten Abkühlschacht mit perforierter Wandung,

Fig. 2

einen mit einstellbarem Abstand zur Spinnkopf-Unterseite angeordneten Abkühlschacht mit doppelter, mit festem Abstand konzentrisch zueinander angeordneter, perforierter Wandung,

Fig. 3

einen unmittelbar an den Spinnkopf anschließenden Abkühlschacht mit im Bereich nahe dem Spinnkopf einstellbarer Größe der Perforierungen,

Fig. 4

einen mit einstellbarem Abstand zur Spinnkopf-Unterseite angeordneten Abkühlschacht mit über die gesamte Länge des Schachtes einstellbarer Größe der Perforierungen,

Fig. 5

den konisch ausgeführten unteren Bereich eines Abkühlschachtes,

Fig. 6

einen Abkühlschacht, wie in Fig. 1 dargestellt, jedoch mit rechteckigem Querschnitt.

The invention is discussed below with reference to Figures 1 to 7, the

1-6

schematically show different versions of the device according to the invention, namely

Fig. 1

a cooling shaft with a perforated wall, which is arranged at an adjustable distance from the underside of the spinner head,

Fig. 2

a cooling shaft arranged at an adjustable distance from the underside of the spinning head with double perforated walls arranged concentrically to one another at a fixed distance,

Fig. 3

a cooling shaft directly adjoining the spinning head with a size of the perforations that can be set in the area near the spinning head,

Fig. 4

a cooling shaft arranged at an adjustable distance from the underside of the spinning head with a size of the perforations which can be adjusted over the entire length of the shaft,

Fig. 5

the conical lower area of a cooling shaft,

Fig. 6

a cooling shaft, as shown in Fig. 1, but with a rectangular cross section.

FIG. 7 shows the speed of the air carried by the filament bundle as a function of the distance from the spinneret in a spinning device without forced supply of air.

Fig. 1 shows schematically, as an example, a cooling shaft arranged at a distance (2) to the underside of the spinning head (1), which concentrically surrounds the filaments (5) emerging from the spinning head and essentially consists of a metal cylinder (3). A gap adjustment (4) makes it possible to arrange the metal cylinder (3) with a more or less large gap (2) to the spinning head.

The gap (2) should at most only be so large that an air flow directed in the direction of the filaments forms. If the opening was too large, warm air would escape, and there would be a risk of eddies from the differently directed air streams near the thread. In addition, the gap (2) minimizes heat transfers from the spinning head to the cooling device.

The metal cylinder (3) has openings distributed uniformly over the entire wall, the air permeability being selectable in wide ranges. However, the air resistance should not be too high so as not to impair the suction effect. Openings that are too large should also be avoided in order to buffer air movements in the area. A proportion of free openings (holes) of up to 50% of the total area has proven itself. Instead of the metal perforated cylinder shown here, a metal sieve cylinder can also be used.

Since each bundle of threads is surrounded separately by the air-permeable wall (3) of the cooling shaft, the cooling air (arrows) drawn in by the suction of the filaments is directed essentially radially from the outside inwards. It is taken from the environment and therefore has a temperature corresponding to that of the spinning room.

Below the cooling shaft is a thread oiler device, not shown here, or another thread guide for bundling the cooled filaments into a thread, which is then fed to a take-off device.

The cooling shaft shown schematically in FIG. 2 is constructed similarly to that of FIG. 1. A second metal cylinder (6) arranged concentrically to the first (3) at a fixed distance makes it possible to prevent any air movements in the spinning chamber, e.g. B. when opening and closing doors, in addition to buffering. A distance between the walls of the two metal perforated cylinders of a maximum of 20 mm is recommended.

Another embodiment of the device according to the senses is shown in FIG. 3. The air-permeable wall begins here directly below the spinning head (1). The metal hole cylinder forming the cooling shaft is surrounded in the area near the spinning head by a second, movable metal hole cylinder (7) lying directly on the first. Both metal hole cylinders have the same perforation, so that the holes of the first cylinder are either completely released or more or less covered by rotary movements of the second metal hole cylinder (7). It is therefore possible to regulate the passage of air in this area near the spinning head. The metal hole cylinder (3) adjoining at the bottom is designed similarly to that of FIG. 1, but without gap adjustment.

Another embodiment is shown in FIG. 4. This cooling shaft is initially constructed similarly to that of FIG. 1, with a (4) shaft with perforated wall (3) which is arranged at a distance (2) from the underside of the spinner head (1) and is adjustable in height. A second perforated shaft of the same shape (8) resting on the first perforated shaft (3) enables regulation of the air passage over the entire height of the shaft.

The setting is made by rotating or moving the two perforated shafts (3 and 8) towards each other. An optimal setting of the air passage both in the area near the spinning head and over the entire shaft height is possible.

As an alternative to the discharge shafts with a constant cross-section shown schematically in FIGS. 1, 2 and 4, FIG. 5 shows a cooling shaft according to the invention, the perforated outlet zone (9) of which is conical with a decreasing cross-section. This improves the injector effect.

Fig. 6 is an example of a cooling shaft with a rectangular cross section, which is used in spinning heads with rectangular nozzle plates. Otherwise, the structure corresponds to that of the device in FIG. 1.

FIG. 7 shows measurements of the speed of the air carried by the filament bundle at different distances from the nozzle plate as a function of the filament titer. The measurements were carried out during the spinning of polyethylene terephthalate (PET) with an intrinsic viscosity (IV) of 0.67 dl / g using a spinning device without forced supply of air (ie without a conventional blowing shaft and without a cooling device according to the invention) at a winder speed of 3200 m / min. The vertical component of the air flow was measured using an ALNOR anemometer, measuring range 0.1 - 30 m / sec. The air speed is a measure of the amount of air moved by the suction effect of the filament bundle. The lower air velocity with a higher titer in relation to the same nozzle spacing characterizes its slower cooling. It can be seen from the figure that by increasing the distance of the bundling point from the nozzle plate, the amount of cooling air can be increased as desired and to a desired value, thereby preventing the filaments from sticking together.

However, the distance of the convergence thread guide from the nozzle plate and thus the cooling shaft should not be too great. The entrained air increases the filament air friction and thus the thread tension of the filament bundle. With fine filaments and high take-off speeds, these could reach the range of the tensile strength of the filaments and result in filament tears.

example 1

PET chips with a viscosity of I.V. = 0.67 dl / g are melted and the melt is pressed at a temperature of 300 ° C. through the bores of a nozzle plate used in a conventional spinning head. The nozzle plate has a diameter of 70 mm; the hole field diameter is 55 mm; the 61 holes have a diameter d = 0.25 mm and a capillary length of L = 2 D.

The delivery rate was 17.3 g / min, the nominal titer dtex 33f61, the spinning titer per filament being 0.89 dtex.

The threads then passed into a cooling shaft consisting of a sieve cylinder with a length of L = 350 mm, φ = 100 mm, 600 meshes / cm ² . The distance between the bottom edge of the spinning head and the top edge of the cylinder was varied between 0 and 15 mm, so that a correspondingly free gap was created. The screen cylinder is surrounded by the room air at a temperature of 23 ° C.

A thread oiler for applying an aqueous emulsion was attached at a distance of 530 mm from the lower edge of the spinning head, the dosage amount corresponding to a coating on the filament bundle of 0.8%. The oiler is the first point of convergence of the thread bundle. The thread was then wound up using a winder with a tension reducing device at a speed of 3200 m / min.

The best uster-half inert values of 0.80% were achieved with a gap of 0 - 5 mm. With a 15 mm gap, the U value was 7.2%.

Example 2:

The design was carried out as in Example 1, but with an additional sieve cone at the outlet of the sieve cylinder, the opening for the thread passage being φ = 30 mm. The Uster value improved to U = 0.60%.

Example 3:

PET chips with a viscosity of I.V. = 0.67 dl / g are melted, and the melt is pressed at a temperature of 294 ° C. through the holes in a nozzle plate. The nozzle plate has a diameter of 80 mm; the hole field diameter was 70 mm, the bore diameter = 0.17 mm, L = 2 D.

In a first experiment the number of holes in the nozzle plate was 72, in a second experiment 144. The delivery rate was 16.0 g / min and 31.0 g / min, respectively, so that a nominal titer of 36f72 and 72f144 dtex, respectively a comparable spin titer per filament of 0.8 dtex resulted.

Directly after the spinning head was a perforated cylinder with a length of L = 500 mm, φ = 100 mm, hole diameter = 5 mm, evenly distributed over the wall. The free area was 34% (39 x 70 holes).

The cylinder is surrounded by room air at a temperature of 28 ° C. The convergence point is formed by a thread oiler, which was 250 mm from the cooling cylinder. The average distance between the individual filaments at the cylinder outlet is between 1.7 and 2.5 mm, depending on the number of capillaries. The filament bundle was then drawn off and wound up at 2800 m / min using godets and a winding unit. Of the Degree of spinning orientation, characterized by the elongation at break, as well as further characteristic data and their uniformity are summarized in Table 1. Table 1 Blowing - perforated tube Nominal titer dtex 36f72 72f144 Spin fineness dtex 56.4 109.4 Tear load cN 156.9 301.8 Tear load - CV % 2.5 2.1 Tensile strength cN / tex 27.8 27.6 Elongation at break % 126.8 125.5 Elongation at break - CV % 3.8 3.1 Uster, helped inertly % 0.26 0.66

Example 4:

The design was carried out as in Example 3, but varying the distance between the thread oiler and the perforated cylinder between 50 and 850 mm, corresponding to a distance of 550 to 1350 mm from the spinning head. The investigations were carried out on the nominal titer 36f72 dtex. Spinning breaks occurred at a distance of 850 mm, triggered by a relatively high thread tension due to the open length of the filament bundle being too long. At distances below 850 mm, the Uster value remained good at 0.39 - 0.58%.

Example 5:

PET chips with a viscosity of I.V. = 0.63 dl / g were melted and the melt was pressed at a temperature of 294 ° C. through the holes in a nozzle plate. The nozzle plate had a diameter of 80 mm; the hole field diameter was 70 mm, the hole diameter = 0.25 mm, L = 2 D. The number of holes in the nozzle plate was 34.

The delivery rate was 18.5 g / min, so that a nominal titer of dtex 50f34 resulted in a spinning titer per filament of 1.47 dtex.

The perforated cylinder described in Example 3 was at a distance of 50 mm from the spinning head.

The cylinder is surrounded by ambient air at a temperature of 29 ° C. The convergence point is formed by a thread oiler, which was 600 mm from the cooling cylinder. The average distance between the individual filaments at the cylinder outlet was approximately 5.9 mm.

The filament bundle was then drawn off and wound up directly from a winding unit, which was equipped with a grooved roller operated with a lead of 6% for tension compensation, at a speed of 3700 m / min. The degree of spinning orientation is characterized by an elongation at break of the wound filament bundle of 95%, the tensile strength was 28.8 cN / tex.

The Uster uniformity was excellent and was Uster helped inert = 0.39%.

Example 6:

The design was carried out as in Example 5, but with the measure that the take-off speed was varied from 4200 to 5700 m / min, with an advance of the grooved roll of up to 10%. Furthermore, the delivery rate was increased and readjusted at every speed in such a way that the dtex 76f34 titer was kept constant corresponding to a single filament titer of 2.24 dtex.

The thread characteristics and uniformity values are summarized in Table 2. Table 2 Speed (m / min) 4200 4700 5200 5700 Delivery rate (g / min) 31.9 35.7 39.5 42.9 Titer (dtex) 76.1 76.2 76.1 76.9 Tear load (cN) 232.5 243.8 249.1 258.9 CV tear load (%) 2.3 1.8 1.8 1.7 Tensile strength (cN / tex) 30.6 32.0 33.0 33.7 Elongation at break (%) 85.5 72.5 60.4 54.3 CV elongation at break (%) 2.9 3.7 5.1 3.9 Uster-half inert (%) 0.35 0.62 0.32 0.41

The preceding examples show that when the method and the device according to the invention are used, filament characteristics are obtained which at least correspond to those of the conventional systems and in certain sensitive applications, such as Production of microfilaments at take-off speeds of more than 2400 m / min, improve them, and this with extremely little equipment.

Claims (11)

1. A method for spinning and cooling synthetic, multifilament, spinning-oriented endless filaments (5) by means of a spinning device with spinning heads comprising spinneret plates and cooling chutes having air-permeable walls through which an air stream is sucked into the interior of the cooling chutes exclusively as a result of the frictional entrainment of the air by the filaments, characterized in that the air stream is sucked in at draw-off speeds of the filaments (5) of at least 2,400 m per minute directly at the lower side (1) of the spinning heads and without interruption further over the length of the cooling chutes (3; 3, 6; 3, 7; 3, 8; 3, 9).
2. A method as claimed in claim 1, characterized in that the mean distance of the filaments (5) of a filament bundle at the exit of the cooling chute (3; 3, 6; 3, 7; 3, 8; 3, 9) is under 6 mm.
3. A method as claimed in one of the claims 1 to 2, characterized in that the air stream is adjustable in the zone near the spinning head.
4. An apparatus for carrying out the method as claimed in one of the claims 1 to 3, with a spinning device having spinning heads comprising spinneret plates and cooling chutes with air-permeable walls (3; 3, 6; 3, 7; 3, 8; 3, 9), through which an air stream can be sucked into the interior of the cooling chutes exclusively as a result of the frictional entrainment of the air by the filaments (5), characterized in that the wall (3; 3, 6; 3, 7; 3, 8; 3, 9) is provided with breakthroughs over its entire length for the access of air.
5. An apparatus as claimed in claim 4, characterized in that the cooling chute (3; 3, 6; 3, 8; 3, 9) is arranged at a distance (2) from the lower side (1) of the spinning head.
6. An apparatus as claimed in claim 5, characterized in that the gap (2) formed by the distance between the cooling chute (3; 3, 6; 3, 8; 3, 9) and the spinning head (1) is so large that only air is sucked into the cooling chute (3; 3, 6; 3, 8; 3, 9) through the gap (2).
7. An apparatus as claimed in one of the claims 5 and 6, characterized in that the distance (2) of the cooling chute (3; 3, 6; 3, 8; 3, 9) is adjustable from the lower side (1) of the spinning head for the purpose of regulating the air passage.
8. An apparatus as claimed in claim 4, characterized in that the size of the breakthroughs in the zone (7) near the spinning head (1) is adjustable for the purpose of regulating the air passage.
9. An apparatus as claimed in one of the claims 4 to 7, characterized in that the size of the breakthroughs is adjustable over the entire length of the wall (3, 8) for the purpose of regulating the air passage.
10. An apparatus as claimed in one of the claims 4 to 7, characterized in that the cooling chute consists of two concentrically arranged cylinders (3, 6; 3, 8) with a wall distance of up to 20 mm, which cylinders are both provided with breakthroughs for the inlet of air.
11. An apparatus as claimed in one of the claims 4 to 9, characterized in that the lower opening of the cooling chute (3, 9) is formed by a cone (9) which narrows downwardly and leaves an opening for the passage of the filament bundle of at least 10 mm.

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