EP0468918A1 - Fluid-drawing system with variable breaking effect - Google Patents

Abstract

In a process for the hydrodynamic drawing of a synthetic monofilament or multifilament yarn, the yarn, if it is a multifilament yarn, is made into a ribbon and pulled through a brake fluid. Within the brake fluid, the yarn is heated to a temperature which corresponds to the glass transition point of the filament material and braked in such a way that the yarn tension at one point in the brake fluid corresponds to the drawing tension which is necessary to draw the filament or filaments. To be able to match process and apparatus to various materials and to various yarn speeds and to optimise process and apparatus in respect of the quality of the drawn product, the braking effect of the drawing arrangement is set and/or controlled via the length of travel of the ribbon in the brake fluid, the viscosity of the brake fluid, additional mechanical braking and/or the flow ratios in the drawing arrangement. The apparatus consists of a quasi-sealed main chamber (1) within which a brake fluid is circulated. The brake fluid also acts as a heat transfer medium. The main chamber (1) can have a prechamber (7) with a variable liquid level (14). The chambers are formed by two mutually fold-back parts, so that there is no problem with introducing the yarn. …<IMAGE>…

Description

The invention is in the field of textile technology and relates to a method and an apparatus for drawing synthetic filaments.

When producing synthetic filaments, more precisely linear polymer filaments (plain yarns), they have to be stretched shortly after extrusion in order to obtain an orientation of the molecules along the fiber axis. It is only after this stretching process that the synthetic thread works reach useful values in terms of strength and elongation at break. The elongation to stretch to align the polymers is considerable, as a rule it is several times their original length. The state of the art includes the knowledge that the stretching stretch must take place in a defined small stretching zone in order to obtain a filament characteristic that is uniform over the entire length (US Pat. No. 2,289,232 of 1942). Obviously, the same opinion is still widespread today, although this idea was questioned about 20 years later (US-3,002,804 from 1961) and a method for a non-mechanical stretching process was countered, which, however, only comes into effect at high thread speeds that were unreachable at the time. But despite the increasing thread speeds, today up to 6000 m / min, the stretching processes are still carried out mechanically with a considerable amount of effort.

Moving away from the technical constraint of the "smallest possible cut-in zone" allowed the introduction of the idea of a liquid brake between the spinneret and the automatic winder, in which the filament cannot be drawn off as "sharply" as on a mechanical braking device, but very evenly. However, there were limits to this early idea (1961), limits that until today have not allowed an industrially usable implementation. Thus, despite all the advantages, the process published in US Pat. No. 3,002,804 remained a laboratory process and unfortunately has not found its way into the industrial production processes for synthetic yarns. This has remained so to this day, which is confirmed, for example, by DE-35'34'079, according to which it was still believed in 1985 that the industrial introduction of this process is still prevented today by considerable disadvantages. In addition, it has now been found that the short notch zone can also be implemented in a liquid medium when braking.

If one looks at FIG. 5 of US Pat. No. 3,002,804, it can be seen that high thread speeds require shorter passage lengths in the liquid, which is desirable in and of itself, but it is also noticeable that this desired effect only occurs at yarn speeds of approx. 5000 m / min becomes noticeably noticeable and increases only slightly at higher speeds. This method could therefore offer advantages in terms of its dynamics. But if you know the requirements of the current high-speed yarn production, it does not look good for the adequate implementation of a liquid braking process. Too many questions remain unanswered today, e.g. the flow conditions in the liquid at high filament speed, and this method is associated with too many technical inadequacies, for example the introduction of the thread into the liquid and the corresponding execution through small eyelets (which must not be too small and not too large) for the realization to be within the range of the expert skill. The opposing constraints, namely: the greater the throughput speed, the smaller braking zones (throughput sections), are in contrast to the experience that higher thread speeds make the technical handling and, in addition, the parallel multi-thread stretching process disproportionately difficult.

In the above-mentioned DE-35'34'079, the use of a brake bath is considered to be so disadvantageous that stretching by means of a stretching pin is essentially maintained in this document and the solution is sought using liquid friction on a type of stretching pin. The main problem is the sufficient application of water to the thread, which this patent also had to solve. The solution to this wetting problem is that the stretched bundle of threads with the filaments running in parallel is passed through a liquid film which is metered onto cylindrical braking surfaces. The cylinder surfaces preferably have a thread running groove and the capillary force between the filament bundle additionally supports the wetting process. The liquid should not be thrown off the cylinder surface in order to collect in thread areas facing away from the braking surface. There is a great risk that the liquid film will still tear and the thread will run dry, completely unnoticed, with the hydrodynamic friction at least partially changing into the undesired mechanical friction. In addition, temperature control or temperature control in a thin liquid film is very difficult, so that it must also be expected that stretching below the glass transition point (at a brittle temperature) and it therefore brittle fractures can occur. This process seems technically delicate.

It is therefore a matter of concern for the applicant to clear the way for realizing the liquid bath process, that is, for implementing a process similar to the American patent mentioned, despite all existing prejudices. European patent application No. 90810061.3 (publication No. 0384886) by the same applicant also shows a corresponding method and devices for carrying out the method.

The invention described here sets itself the task of refining the above-mentioned method and the corresponding devices in such a way that they can be roughly and finely adjusted for different yarn qualities, for different yarn speeds and for different manufacturing processes, so that the stretching is optimal in every case Product can deliver. For this purpose, a method and device-like means are to be shown, with the help of which the hydrodynamic braking effect can be influenced in a targeted manner. The device used to carry out the method should be adjustable within the broadest possible limits, so that it can not only be used for the processing of different yarns at different speeds for optimal stretching, but also that possibilities open up for stretching into automatic monitoring and Integrate regulation of the manufacturing process.

This object is achieved by the invention specified in the characterizing part of the independent claims.

• Figur 1 (a bis d) eine graphische Darstellung des in-etwa-Verhaltens einer durch eine Flüssigkeits-Streckanordnung hindurchlaufenden Fibrille;
• Figur 2 eine schematisch dargestellte Ausführungsform der erfindungsgemässen Streckanordnung zur Erläuterung des Verfahrens;
• Figur 3 (a und b) zeigt als Schnitt parallel zur Fadenlaufrichtung und als Draufsicht auf den Basisteil eine weitere Ausführungsform mit einer verbreiterten Kammer, für den Durchlauf von zwei Garnfäden;
• Figur 4 (a und b) je einen Schnitt senkrecht zur Fadenlaufrichtung an verschiedenen Orten der Kammer gemäss Figur 3;
• Figur 5 eine graphische Darstellung entsprechend der Figur 1, für den Fall einer mechanischen Vorbremsung;
• Figur 6 eine längsgeschnittene Kammer mit zwei zum durchlaufenden Faden parallel verlaufenden Wandelementen, deren Abstand zum Faden von aussen verstellt werden kann.
• Figur 7 eine schematische Darstellung der erfindungsgemässen Vorrichtung, integriert in den Gesamtherstellungsprozess von synthetischen Glattgarnen.

The method and the device according to the invention are now discussed in detail with the aid of the figures listed below. Show:

• Figure 1 (a to d) is a graphical representation of the approximately behavior of a fibril passing through a fluid stretcher;
• FIG. 2 shows a schematically illustrated embodiment of the stretching arrangement according to the invention to explain the method;
• Figure 3 (a and b) shows a section parallel to the thread running direction and a plan view of the base part of a further embodiment with a widened chamber for the passage of two yarn threads;
• Figure 4 (a and b) a section perpendicular to the direction of thread at different locations in the chamber according to Figure 3;
• Figure 5 is a graphical representation corresponding to Figure 1, in the case of mechanical pre-braking;
• FIG. 6 shows a longitudinally cut chamber with two wall elements running parallel to the thread running through, the distance of which from the thread can be adjusted from the outside.
• Figure 7 is a schematic representation of the device according to the invention, integrated in the overall manufacturing process of synthetic plain yarns.

FIGS. 1a to 1d represent the temperature behavior and the mechanical tension behavior of a moving fibril in a fluid stretching arrangement in four types of representation depending on the distance that the fibril travels in the brake fluid. FIG. 1a shows schematically a liquid stretching arrangement S of length L, through which a fibrile F runs from left to right. A small zone Z = f (t) is indicated on the fibril near the entrance to the brake fluid, from which zone the temperature profile is observed during the passage through the brake fluid. The brake fluid is constantly circulated, in this representation from B _in to B _out in countercurrent. Of course, the arrangement can also be operated in co-current. Figure Ib shows the temperature profile of the small, limited fibril section Z on its passage through the brake fluid. T _x denotes various temperature sections with regard to the passage through the brake fluid. The temperature profile is essentially dependent on the throughput speed and the drawing or thread tension. Figure 1c shows the mechanical tension curve P of two different considerations, namely the stretching tension P _s , which is necessary to stretch the thread, and the tension P _f (thread tension), under which the thread is. P _sx and P _fy denote different sections of the voltage. FIG. 1d finally shows the geometrical change of the limited fibril zone Z on its way through the brake fluid, namely before and after a relatively well definable area G, the so-called stretching point. It is desirable that this constriction take place at a temperature corresponding to the glass transition point (English second order transition point) at which the yield stress drops sharply with increasing temperature. Below this temperature, the filament is brittle (brittle fractures), above that the achievable orientation and thus the strength of the stretched product decrease, so that the ideal stretching and thus chamber temperature is at the glass transition point.

In a first approximation, the stretching process in the brake fluid according to FIGS. 1a to 1d proceeds as follows. Before entering the drawing arrangement, the filament or fibril has a temperature which is at least 50 ° C. lower than the melting point (so-called quenching temperature) and which should preferably be below the temperature of the glass transition point. From the moment it enters the brake fluid, it warms up relatively quickly to the temperature of the brake fluid (approximately in the first half of the chamber). With increasing warming, the tensile stress necessary for the stretching of the polymer drops to approximately the same extent as the temperature in the fibril increases due to the warming in the brake fluid. This is particularly evident in the area of the so-called glass transition point.

The thread tension (P _f ) would increase steadily (P _f2 ) in the brake fluid if no stretching process would occur. At the (graphic) crossing point of the two functions of stretching tension (P _s ) and thread tension (P _f ), a spontaneous stretching occurs (P _f3 , P _s3 ). This leads to a sudden increase in the thread temperature (stretch energy, internal friction, release of internal tension). The energy released is quickly dissipated by the liquid surrounding the filament if the thread should be heated above the liquid temperature (temperature of the glass transition point), which is shown by the temperature curve (T₅). If the stretching begins at a thread temperature that is slightly below the temperature of the brake fluid (glass transition temperature), the heat generated by the stretching will quickly heat the thread to the desired temperature, so that the stretching will nevertheless take place at the desired temperature, which is caused by the temperature curve T is shown. Due to the small thermal source of the thread and the large thermal sink of the brake fluid, the stretching process can be carried out in such a way that an approximately isothermal stretching takes place. If necessary, the mass flow of the brake fluid (compared to the Mass flow of the thread material) can be adjusted by flow control so that the almost isothermal drawing takes place.

The thread tension (P _f ) also increases suddenly at the stretching point (P _f3 ), since the filament has to be accelerated to the higher speed. The higher thread speed after stretching therefore results in an even steeper increase in thread tension (P _f4 ), although the fibrils have become thinner after stretching (F _s ) and the friction surface between the fibril and the braking fluid has thus become somewhat smaller.

The steeper the two curves (functions), the stretching tension P _s and the thread tension P _f intersect (cross) and the closer this point of intersection is to the point where the thread has reached the chamber temperature, the more precisely the stretching point is fixed, it shifts locally of the chamber and will not extend to an undefined area. Such a thermally and mechanically controlled (controlled) stretching process results in high uniformity, high strength and gentle thread treatment at optimal temperatures.

The whole process is shown here on a single fibril. A basically identical stretching process can also be carried out with a thread consisting of a large number of fibrils, for example 30 to 50. It is crucial that all fibrils in the yarn are simultaneously exposed to the same physical condition as the sample fibril just discussed. This is preferably achieved by passing the thread in the form of a fibril band through the stretching arrangement, for which purpose the stretching device must be designed accordingly.

The drawing process therefore consists of heating the individual fibrils of the yarn in a quasi-closed chamber with the help of a liquid heat transfer medium as evenly as possible against the glass transition temperature and at the same time increasing the thread tension by hydrodynamic braking in such a way that it then achieves the drawing tension necessary for drawing the yarn reached when the yarn has reached the glass transition temperature or can just reach through the heat generated during stretching. Since the glass transition temperature and the drawing tension are different for different yarns, it is desirable that, in addition to this drawing process, processes are developed which allow a corresponding setting of other process parameters, especially the temperature and the braking action in the drawing arrangement. This is also desirable in terms of fine adjustment to optimize the stretching process and for automatic or manual regulation.

For a further description of the method according to the invention, FIG. 2 schematically shows an exemplary embodiment of a liquid drawing arrangement, the basic features of which correspond to the chamber of the cited application (EP-90810061), but which comprise additional means for setting the method parameters, so that the method and device are adapted to different yarn qualities and different yarn speeds can be adjusted.

• Da die Fibrillen, im Falle eines aus mehr als einer Fibrille bestehenden Fadens, in Form eines Fibrillenbändchens durch die Kammer laufen, ist eine regelmässige Benetzung der Fibrillen mit der Bremsflüssigkeit und damit eine gleichmässige Bremsung und eine gleichmässige Erwärmung aller Fibrillen gewährleistet.
• Da mit der vom Faden mitgeführten Luft beim Eingang in die Kammer eine unkontrollierbare Isolationsschicht vom Faden entfernt wird, wird die Erwärmung des Fadens besser kontrollierbar.
• Da die Bremsflüssigkeit einen hohen spezifischen Wärmeinhalt besitzt und zirkuliert wird, ist ein schneller Wärmeaustausch zwischen Fibrillen und Flüssigkeit und damit optimale Verhältnisse für einen isothermen Streckvorgang gewährleistet. Ist die Fibrille Wärmequelle (bei Überhitzung), so ist die Bremsflüssigkeit eine sehr grosse Senke zur Aufnahme der Energie. Ist die Fibrille Wärmesenke (bei Aufwärmen), so ist die Bremsflüssigkeit eine sehr grosse Quelle zur Abgabe der nötigen Energie. Der Energiefluss ist also immer in der richtigen Richtung gross, um eine hohe Dynamik in der Wärmeführung zu erzielen.
• Da die Eintauchlänge des Fadens in der Bremsflüssigkeit variiert werden kann, kann damit die Bremswirkung eingestellt und reguliert werden.
• Da die Zirkulation der Bremsflüssigkeit und die Geometrie der Kammer verstellbar sind, können die Strömungsverhältnisse in der Kammer und dadurch die hydrodynamische Bremswirkung auf den Faden verändert werden.
• Da auch verstellbare Mittel zur mechanischen Fadenbremsung eingesetzt sind, kann die Bremswirkung durch Kombination von hydrodynamischer und mechanischer Bremsung verändert werden.

In summary, the entire stretching process offers the following advantages:

• Since the fibrils, in the case of a thread consisting of more than one fibril, run in the form of a fibril ribbon through the chamber, the fibrils are regularly wetted with the brake fluid and thus ensuring uniform braking and uniform heating of all fibrils.
• Since the air carried by the thread at the entrance to the chamber removes an uncontrollable insulation layer from the thread, the heating of the thread becomes more controllable.
• Since the brake fluid has a high specific heat content and is circulated, a rapid heat exchange between fibrils and fluid and thus optimal conditions for an isothermal stretching process are guaranteed. If the fibril is a heat source (in the event of overheating), the brake fluid is a very large sink for absorbing the energy. If the fibril is a heat sink (when it is warming up), the brake fluid is a very large source for delivering the necessary energy. The energy flow is always large in the right direction in order to achieve high dynamics in heat management.
• Since the immersion length of the thread in the brake fluid can be varied, the braking effect can be adjusted and regulated.
• Since the circulation of the brake fluid and the geometry of the chamber are adjustable, the flow conditions in the chamber and thereby the hydrodynamic braking effect on the thread can be changed.
• Since adjustable means for mechanical thread braking are also used, the braking effect can be changed by combining hydrodynamic and mechanical braking.

If the thread F consists of more than one fibril, it is advantageous if it runs through the brake fluid in the form of a ribbon in which the individual fibrils are arranged next to one another as far as possible (in a plane perpendicular to the paper plane of FIG. 2). The brake fluid is traversed by the thread in a main chamber 1, which is closed except for a narrow, slit-shaped inlet opening 11 and an equally narrow, slit-shaped outlet opening 12 for the fibril bundle. A brake fluid is pumped through this main chamber 1 such that it enters the chamber through the inlet 2 and leaves it through the outlet 4. The main chamber is divided parallel to the thread running through two walls 5.1 and 5.2 into a thread channel 1.2 and two outer channels 1.1 and 1.3. These walls can be displaced parallel to the course of the thread in such a way that the thread channel can be set very closely, for example, and the outer channels become wider as a result. The two outer channels contain adjustable throttling means 6.1 and 6.2, through which their flow cross-section can be narrowed locally.

Before the thread runs into the main chamber, it passes through a prechamber 7, which can be open on the inlet side. The same brake fluid is pumped through this prechamber, namely through the inlet 8 into the prechamber, through the outlet 9 from the prechamber. The outlet 9 is provided with means which enable the liquid level 14 in the antechamber to be adjusted, for example with a displaceable pipe bend 10. Immediately in front of the entrance 11 into the main chamber, a cylindrical deflection element 13 is attached, the main task of which is to move into the main chamber 1 Arrange incoming fibril bundles in such a way that the individual fibrils run through the main chamber 1 in the form of a fibril ribbon as far as possible. Two further, for example cylindrical, deflection elements 15.1 and 15.2 are attached directly below the liquid level 14 and can be displaced with it, the main task of which is to squeeze out the air carried by the thread so that it is not carried into the chambers.

An arrangement as shown schematically in FIG. 2 allows the two most important parameters of the stretching process, the temperature of the brake fluid and its braking action to be set up and adjusted within wide limits.

The setting and regulation of the temperature of the brake fluid is achieved, for example, with a corresponding thermostatted reservoir for the brake fluid (not shown in FIG. 2), from which the brake fluid is pumped into the two chambers 1 and 7.

The hydrodynamic braking effect that the brake fluid exerts on the thread mainly depends on the length of the thread run in the liquid, on the viscosity of the liquid, on the flow conditions in the chambers and on the speed of the thread. The length of the thread course in the liquid is set and regulated by setting and regulating the liquid level 14 in the prechamber 7. Main chambers of different lengths can also be used. The viscosity of the fluid is adjusted by selecting the brake fluid accordingly. The flow conditions in the main chamber are set and regulated by setting and regulating the flow direction, the flow rate and flow rate of the brake fluid, by adjusting the position of the walls 5.1 and 5.2 and the restrictors 6.1 and 6.2 and by using walls 5.1 and 5.2 with various Thread-facing surfaces.

The flow conditions in the main chamber 1 are primarily given by the direction and strength of the circulation of the brake fluid. In the example of the method in FIG. 2, the brake fluid flows, for example, from the bottom up, that is, against the direction of the thread. The thread, however, especially when it is running at high speed, tears liquid with it, so that a flow in the thread running direction occurs in the thread channel 1.2, i.e. the circulating flow from bottom to top is a circular flow in the thread channel 1.2 down and in the outer channels 1.1 and 1.3 superimposed on top. Adjustable throttling points 6.1 and 6.2 installed in the outer channels 1.1 and 1.3 not only throttle the circulation flow and thus increase the pressure in the chamber part in the flow direction upstream of the throttling points, but also the circulating current generated by the thread and thus influence the braking effect. Strong throttling at throttling points 6.1 and 6.2 increase the braking effect without increasing the risk of turbulent disturbances in the thread channel. The width of the thread channel 1.2, which can be adjusted by the adjustability of the walls 5.1 and 5.2, can also act as a throttle for the circulating currents and thus, especially if it is chosen to be very small, influence the braking effect. Also in the case of a narrow thread channel 1.2, the nature of the surfaces of the walls 5.1 and 5.2 facing the thread will also influence the braking effect, since it depends, among other things, on how swirled the flow in the thread channel 1.2 is.

The variation of the braking effect by varying the distance between the thread and the chamber walls is based on the physical fact that the flow through a hollow body in the vicinity of the inner wall is not dependent on the pressure difference and the flowing medium, as far away from the inner wall as possible. In layers that are close to the inner wall, the friction of the medium on this wall also influences the flow, which in turn is influenced by parameters such as the surface quality the wall is dependent. In any case, the outermost layer of the medium has a very low speed compared to the inner regions. If the speed difference between inner and outer regions now becomes large, flow stalls can also occur in an intermediate region, which lead to local turbulence and thus to speed components perpendicular to the direction of flow. Such effects then cause much higher hydrodynamic resistances locally, which are experienced, for example, by a thread moving in or against the flow in a chamber according to the invention. The hydrodynamic braking effect will be different, depending on the distance from the chamber wall or another solid surface, and depending on the nature of this surface. It has been shown that such effects at distances between the thread and the wall in the region of 0.05 to 1 mm have an influence on the braking action of the brake fluid. For example, finely ground (Ra 0.05µm), roughly machined, edged or sand-coated (Ra 45µm) are used as variations in the surface quality.

The braking effect of the arrangement can also be changed by additional mechanical braking on the deflection elements 11, 15.1 and 15.2. Such mechanical braking in the area of the pre-chamber 7 then results in an increased thread tension when entering the main chamber 1. The deflection elements are arranged such that they can be adjusted parallel to their axes, so that the respective deflection angle can be set and regulated. Since the deflection elements are immersed in the brake fluid, their wetting is always ensured, which means that increases in the friction on these elements that are harmful to the thread due to dry running are excluded.

The schematic FIG. 2 represents an exemplary embodiment of the method and the device according to the invention. The advantages of this variant result from the division of the path of the thread in the brake fluid into the antechamber and main chamber. As a result, with an infinitely adjustable path length, an increased pressure in the main chamber is still possible, which further minimizes the introduction of air through the thread and increases the selection of brake fluids (boiling point). However, the device can only be used in the position shown, that is to say with a thread running vertically from top to bottom. There are no leakage problems at the inlet opening 11.

Further variants and their special advantages are briefly mentioned below.

The prechamber can be missing, which means that the use of the device is no longer restricted to a vertical thread running direction, but the path length can only be adjusted continuously by using chambers of different lengths. The inlet opening 11 must be designed in such a way that leakage through this opening is kept to a minimum. Such a chamber is advantageously operated with excess pressure, so that the walls of the inlet opening 11 always remain wetted and, in the event of any contact between these walls and the fibrils, there is no excessive mechanical friction.

The separation between the open antechamber and the quasi-closed main chamber can be missing, which means that the device can only be used vertically and no excess pressure can be generated in the chamber.

The main chamber can contain only one adjustable wall 5 or the adjustable walls can be missing at all, which means a simplification in terms of production technology.

The deflection elements directly below the liquid surface in the prechamber can be missing, as a result of which the air carried by the thread is not pressed out, which can lead to increased foaming of the brake fluid. Mechanical braking is then kept to a minimum, which can prove to be an advantage for sensitive yarns.

The means for forming a fibril band can be missing, which results in a simplified device for processing individual fibrils.

Further small chambers can follow the exit opening 12 in the thread running direction, in which the liquid discharged from the stretching chamber by the thread is thrown off and / or suctioned off. A similar drying effect can be achieved by connecting a liquid removal device to an arrangement according to FIG. 2 directly on the draw (main) chamber in the direction of the thread. A corresponding liquid removal device is described in Swiss Application No. 1,689 / 90-1 (May 18, 1990) by the same applicant. The use of means for throwing the entrained liquid out of the thread allows the use of more viscous brake fluids, through which a correspondingly higher braking effect can be generated.

The device can be designed such that it can be traversed by a plurality of threads running parallel to one another. The chambers must then be correspondingly wider and, at the entrance to the main chamber, additional guide elements are advantageously attached, which ensure a separate passage of the individual threads.

FIGS. 3a and 3b now show in detail an exemplary embodiment of the device according to the invention for carrying out the described method. The device is cut in FIG. 3a in the same way as the schematic device in FIG. 2 and in FIG. 3b as a top view of the base part. The device consists of a main chamber 1 and a prechamber 7 and is designed for the passage of two threads running in parallel (only the left thread is shown in FIG. 3b). For the passage of thread through the prechamber 7, two variants are shown, one (with a high level of liquid) with solid lines and position numbers corresponding to FIG. 2, the other (with a low level of liquid) with dashed lines and with apostrophized position numbers.

The device advantageously consists of two parts, a base part 21 and a cover part 22, which can be folded apart along the passage plane of the threads for the introduction of the thread or threads. The base part is arranged in a stationary manner, for example, and carries the inlet and outlet connections for the brake fluid, air, etc.

The thread F, which can be a single fibril or a bundle of fibrils, runs, as already described in connection with FIG. 2, through the prechamber 7, through which brake fluid flows (influence 8, outlet 9).

They are guided over at least one deflection element, for example two cylindrical ceramic pins 15.1 and 15.2, which are arranged directly below the liquid surface 14. The air entrained by the fibrils is squeezed out at these deflection elements, so that the foam formation is restricted to this area of the arrangement and an impairment of the stretching process by uncontrollable insulation pads between fibrils and brake fluid is avoided. Depending on the deflection angle on the two deflection elements 15.1 and 15.2, the threads are also braked more or less mechanically, with which the thread tension at the entrance to the main chamber 1 can be set, for example. Immediately before the entrance to the main chamber 1, the threads are shaped by the deflection element 13, for example a cylindrical ceramic rod, into fibril bands and separated by the guide elements 24.1, 24.2 and 24.3 and their width is restricted. Corresponding guide elements 24.4, 24.5 and 24.6 are also arranged at the thread exit of the device.

Mechanical braking of the threads before they enter the main chamber at the deflection elements 15.1 and 15.2 increases the tensile stress of the fibrils in the main chamber, so that the fibrils reach the level of the tensile stress faster, that is to say after a shorter distance in the brake fluid. The effect of such a "pre-braking" is shown in FIG. 5 : without pre-braking, the stretching point lies at point a, and the pre-braking shifts it towards the chamber entrance to point a. This makes it possible, for example, to use a stretching arrangement that is designed to be short for a high thread speed and also for smaller thread speeds at which the braking effect of the brake fluid is significantly smaller and the length of the passage through the brake fluid would therefore not be sufficient for sufficient braking without pre-braking . However, the braking effect of the "mechanical part" must never be so high that the one to be achieved Stretching takes place on the pins because the thread on the upstream pins has not yet reached the ideal stretching temperature, which roughly corresponds to the chamber temperature.

The same device can then be operated without pre-braking and with a reduced travel through the brake fluid if the input 8 for the brake fluid into the prechamber 7 is connected as its output. In the pre-chamber 7 then the brake fluid leaking from the inlet opening 11 into the main chamber 1 accumulates and rises to a level 14 ', which is designed such that the deflection element 13 is still covered with liquid. In this case, the threads F 'are not guided over the deflecting elements 15.1 and 15.2, but directly onto the deflecting element 13.

A very narrow channel (slot) 11, preferably only embedded in the base part 21, is provided for the entry of the threads into the main chamber 1. A drain pan 4 is formed at a distance from the inlet gap 11, through which the brake fluid operated in countercurrent flows. This drain pan 4, like the main chamber 1, is molded into both parts, base part 21 and cover part 22. An influence trough 2 is arranged against the thread exit of the main chamber 1, which is configured in the same way as the drain trough 4. Both troughs 2 and 4 are assigned their function according to the direction of flow, since the chamber can be operated in cocurrent or countercurrent. The actual stretching chamber is located between these two trays, and the threads run in the parting plane between the base and cover parts. In the main chamber 1, a wall 5 runs parallel to the threads with the aid of the adjusting means 23, for example adjusting screws, which divides the main chamber 1 into a thread channel 1.2 and an outer channel 1.1. The delivery is influenced by a certain, minimal distance between thread and wall 5 to the braking and thus the stretching effect. The effective distances are determined empirically, for example, and used in the process flow.

Short slit-shaped channels 12.1, 12.2, 12.3, separated from one another by further troughs or transverse chambers 25.1 and 25.2, are provided for the thread exit, in such a way that they form a kind of labyrinth in which the dragged-along brake fluid flows without pressure or under vacuum (pressure difference even above normal pressure) can. Adjoining this labyrinth, a pull-off edge 26 with a preferably small deflection radius is arranged, at which the thread is deflected and pressed off. An air outlet nozzle 27, just below the removal edge 26, supports the separation of entrained brake fluid and an opposite suction pan 28 serves to remove the spray which is being formed. In order to guide the threads separately as they pass through the drawing arrangement, guide elements 24.4, 24.5 and 24.6 are attached to the thread exit of the device, as at the entrance to the main chamber 1.

The device represented by FIGS. 3a and 3b is obviously small and can be used not only in the thread running direction after the spinnerets, but also, if appropriate, at other points in the production process.

The two FIGS. 4a and 4b show the stretching arrangement according to FIG. 3 in cross-section at the height of the inlet opening 11 or outlet opening 12 (FIG. 3a) and through the main chamber 1 (FIG. 3b). As already discussed above, 21 chamber recesses are embedded in the base part, which correspond to corresponding chamber recesses in the cover part 22.

Thanks to the deliverable wall, the cross section of the thread channel 1.2 on the one hand and the distance between filaments and wall 5 on the other hand can be adjusted. This gives, for example, the possibility of using differently shaped cover parts 22 with a single base part 21, for example with and without adjustable wall 5, and thus to vary the "chamber properties".

If only one level is spoken of in the discussion of the embodiments, in which the fibrils of a thread are arranged for the stretching, a general area, that is to say with a slight curvature, if necessary, can also be realized for order. The plane as an “order surface” can be brought about by a cylindrical pin (for example 13 in FIG. 2), whereas a corresponding “folder” must be provided for a curved surface.

The pulling-in process is very machine-friendly and simple with the described stretching device and can therefore also be easily automated. The inflow of liquid and the blown air are stopped and the chambers 1 and 7 are emptied, for example, by suction. The device is unfolded and the thread is placed in the thread guide at the inlet 11 and outlet 12 with a suction gun. He lays down in the ribbon arrangement of his fibrils. Possibly. Intersections disappear in the subsequent thread run. The cover part 22 can then be placed again on the base part 21 and fixed. The flow for the brake fluid is then released again and the blowing or suction air is started. The heat effect and the braking effect start slowly and in a controlled manner.

The thread section that extends beyond the exit of the stretching arrangement is placed with the suction gun on the subsequent thread supply unit (roll or bobbin winder). If the suction force of the pistol is too low to pull the thread that resists due to the excessive braking force of the brake fluid, it may be necessary that the thread must be placed on the subsequent delivery unit before the brake fluid is released. As soon as the thread finds enough entrainment there, the brake fluid can be released and the process started.

In the same way as shown in FIGS. 2 and 3, three or more threads running in parallel can also be processed in a correspondingly wider device. This saves a corresponding increase in "infrastructure", such as the pumps for the brake fluid and the suction air, by multiplying the "channels" and thus the device capacity. Due to the chamber pressure, the draw chamber is filled to the last corner, so that even relatively wide draw arrangements can be fed with four or more threads without any problems.

If the chamber recesses in the cover part 22 are shown as angular in FIGS. 3 and 4, this in no way means that they must be designed in this way. In the cover part (as well as in the base part), the chamber parts can be optimally shaped in terms of flow technology, depending on the brake fluid used, for which purpose a corresponding other cover part is then placed.

Ceramic pins are advantageously used for the deflection elements 13, 15.1 / 2 and guide elements 24.1 / 2/3/4/5/6 used in the antechamber and in the main chamber. These can be done using screws be fastened in corresponding threaded holes in the chamber walls. These screws can each carry an elastic insert, for example a small cylinder made of nylon, in a blind hole at their end and protruding from this blind hole. When installed, this insert acts as a transfer of the pressing force from the screw to the ceramic pin without damaging the ceramic pin.

FIG. 6 shows a further, exemplary embodiment of the stretching arrangement according to the invention. In contrast to the variant described in connection with FIG. 3, this comprises two sliding walls 5.1 and 5.2. This variant is characterized in particular by deflection elements 61.1, 61.2 ..., for example ceramic pins, which are alternately attached to the surfaces of the walls 5.1 and 5.2 facing the threads. These deflection elements not only influence the flow properties in the thread channel 1.2, but also deflect the thread and thereby brake it, depending on their mutual distance. Such an arrangement has the additional advantage that, as with very narrow walls, the liquid layers surrounding the threads are peeled off without increasing the risk of pinching the fibrils. Furthermore, the threads are repeatedly supported at short intervals by the deflecting elements, which effectively soothes a fluttering of the fibrils in the thread channel.

FIG. 7 shows schematically how the device according to the invention can be switched on in a manufacturing process. A synthetic material in the form of an extrudable liquid is pressed out through a spinneret arrangement 30 in the wall of a tank (not shown), the individual fibrils of a thread 31 being formed. For example, eight such filaments are shown in FIG. 7, in real application examples however, it is usually a large number of fibrils that are combined into a thread.

The individual spinnerets of the spinneret assembly can be arranged in any pattern. For the sake of simplicity it is assumed that in the example described the spinnerets are arranged equidistantly on a circle, in the center of which lies the axis of the thread formed from the filaments.

Following the spinneret arrangement 30, the thread is passed through a device 32 according to one of FIGS. 2, 3 or 6 and from there onto a tension roller 34 and an associated separating roller 36, both of which the thread revolves several times. Then the thread is wound up by a winding device, not shown, for example to a cylindrical bobbin 38. The pulling roller can be designed, for example, according to European Application No. 349829 and the winding device according to European Application No. 367253.

The pull roller 34 is driven so that it rotates about its axis perpendicular to the drawing plane of the figure. Due to the multiple wrapping of the tension roller 34 and the separation roller 36, the thread is "bound" to the rollers so that they exert a tensile force on the thread with which the fibrils are pulled out of the spinnerets of the device 30 and through the drawing bath 32 according to the invention.

The speed v₁ at which the material is pressed through the spinnerets and the speed v₃ at which the thread is drawn off the tension roller determine the titer of the thread created. The winding device is driven such that the speed at which the thread is wound corresponds to the speed v₃. The total stretch achieved with a stretch ratio of v₁: v₃ is divided by this arrangement into a spinning stretch of the still plastic fibrils with a stretch ratio v₁: v₂ and a hydrodynamic stretch with a stretch ratio v₂: v₃, where v₂ represents the speed at which the thread enters the stretching bath 32 according to the invention.

Claims (17)

Method for hydrodynamically stretching a thread consisting of one or more fibrils in a brake fluid surrounding the thread, through which the thread is pulled with a tensile force, characterized in that the thread, if it consists of more than one fibril, becomes one Fibril band is formed by fibrils arranged essentially side by side in such a way that the individual fibril or the fibril band in the brake fluid is heated to the temperature of the glass transition point of the fibril material and that the braking effect is set up in such a way that the thread tension (P _f ) corresponds to the height of the for the fibril or the fibril ribbon characteristic tensile stress (P _s ) within the brake fluid. A method according to claim 1, characterized in that the brake fluid is made to flow and is kept at a temperature which is in the region of the glass transition point of the fibril material to be stretched. A method according to claim 2, characterized in that the braking effect of the arrangement for the stretching of certain fibrils at a certain speed is adjusted and / or regulated by setting at least one of the following parameters: a) path length of the fibrils in the brake fluid, b) flow direction, quantity and speed of the brake fluid, c) additional mechanical braking, d) viscosity of the brake fluid, e) swirling the flow of the brake fluid, f) Distance between fibril or fibril ribbon and stationary elements that influence the hydrodynamics. Method according to one of claims 1 to 3, characterized in that more than one thread is passed through a common stretching arrangement. Method according to one of claims 2 to 4, characterized in that the chamber pressure is set so that the brake fluid used can be operated above its boiling point. Method according to one of claims 2 to 5, characterized in that the mass flow through the stretching arrangement is dimensioned at least so that an isothermal temperature control results. Method according to one of claims 1 to 6, characterized in that the thread is additionally mechanically braked, deflected and / or guided with corresponding mechanical braking, deflecting and / or guide elements and that these elements in the brake fluid are immersed or wetted with brake fluid. Device for stretching at least one synthetic thread consisting of at least one fibril in a brake fluid consisting of a delivery means, a means for generating a tensile force and a stretching arrangement arranged between the delivery means and means for generating the tensile force, characterized in that the plug-in arrangement comprises a base part (21 ) with at least one molded-in chamber part and a cover part (22) with at least one molded-in chamber part, that the base part (21) and cover part (22) can be brought into position in relation to one another in such a way that at least one chamber is created, and that the stretching arrangement can be adjusted for adjustment purposes the braking effect and appropriate adjustment means. Apparatus according to claim 8, characterized in that the stretching arrangement has an inlet device (13) for arranging threads from more than one fibril to form a fibril band arranged in a surface. Device according to one of claims 8 or 9, characterized in that in the main chamber (1) at least one partition (5) is mounted parallel to the thread running direction between the chamber wall and thread or threads, which the main chamber (1) into a thread channel (1.2) and divides at least one outer channel (1.1) and that the arrangement has adjustment means with which the distance of this partition and the passage area of the thread or threads is adjustable outside. Apparatus according to claim 10, characterized in that deflection elements (61) are attached to the surfaces of the partition walls facing the thread or threads. Apparatus according to claim 10, characterized in that throttle means (6) are attached in the outer channel (1.1) or in the outer channels (1.1, 1.3). Apparatus according to claim 8, characterized in that a prechamber (7) is arranged in the thread running direction in front of the main chamber (1). Device according to claim 13, characterized in that the prechamber (7) has an outlet (9) for brake fluid and order elements for arranging the fibrils in a ribbon and that the order elements are arranged such that they are immersed in the brake fluid. Apparatus according to claim 13, characterized in that the prechamber (7) is equipped with an inlet (8) and an outlet (9) for brake fluid and that these are connected to means for circulating the brake fluid. Device according to claim 13, characterized in that the pre-chamber (7) is provided with adjusting means for adjusting the liquid level. Device according to one of claims 8 to 16, characterized in that the closed main chamber (1) or the main chamber (1) and the prechamber (7) with means for circulating the brake fluid, with means for flow control and means for temperature control in the brake fluid is with which the chamber or chambers can be kept at positive pressure and a certain temperature.

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