EP0443390B1 - Process for the production of an air-textured yarn - Google Patents

Description

The invention relates to a method for producing an air-textured thread according to the preamble of claim 1 and an air texturing machine. Process and machine are the subject of European patent application EP-A 0 373 519. According to this older invention, a pre-oriented, thermoplastic thread is presented as the thread to be textured. This thread is drawn in a drawing zone and then blown into loops, loops, arches and the like in an air blowing nozzle. The thread produced has residual shrinkage. According to the older invention, an air-textured thread is produced which is low in shrinkage, i.e. that has a low residual shrinkage.

This invention is based on the knowledge that the problem of residual shrinkage also exists in those air-textured threads which are presented to the air-texturing machine as fully stretched, fully oriented thermoplastic threads.

The object of the invention is therefore to produce an air-textured thread from a fully oriented, fully stretched thermoplastic thread - just as in the older invention - which is low-shrinkage, i.e. that has a low residual shrinkage.

The solution results from the characteristics of claims 1 and 4, respectively.

The invention is based on the finding that the air texturing machine with a heating zone, which is designed as a heating godet and which is directly upstream of the texturing zone, not only when presenting pre-oriented threads that are still drawn on the air texturing machine, but also when presenting fully drawn Threads is a suitable means for eliminating the residual shrinkage, this means being superior to all other known means in terms of its effect, but also because of the low technical complexity and the good classification in the process sequence.

With this solution, the tendency towards residual shrinkage can be reduced much more than in the known processes previously discussed. The particular advantage is that there is no impairment of the texturing. It is particularly important that the heating of the thread is intense. Therefore, the thread can be heated to a temperature above the 2nd order transition point, so that the previously firmly anchored crystal structure softens and internal stresses are relieved. With particular advantage, the godet is heated to a temperature which is just below the melting temperature of the thread to be processed, i.e. for polyamide 6.6 and polyethylene terephthalate approx. 240 °, for polypropylene approx. 150 °. On the other hand, however, the thread in the air texturing nozzle is cooled down very much, so that the shrinkage comes to a standstill and the texturing takes place on the cold thread.

The solution represents a happy integration of the relaxation process into the air texturing process. The heating of the thread can take place in the entrance of the texturing zone. The use of the heating godet allows intensive heating and very low thread tensions in the texturing zone and thus a good shrinking effect.

Compared to threads which have been treated according to the known methods described for reducing residual shrinkage, the residual shrinkage of the threads treated according to the invention is less than half. This is due to the fact that the method according to the invention does not have the limitations of the known methods mentioned. Because according to the invention the shrinkage to be set does not depend on the speed difference of the relaxation zone (feed speed minus take-off speed) and the thread tension does not increase due to the triggering of the shrinkage. Rather, the thread tension to be set and thus the shrinkage are based solely on the tensile force of the air texturing nozzle.

The method according to this invention is of particular superiority over all known methods in the texturing of multifilament threads of high titer, the method and device according to this invention being proposed in particular for the air texturing of carpet yarn, in particular carpet yarn made of polypropylene, in particular in the usual titer range of 130 dtex.

It should be taken into account that, in contrast to all known methods for reducing the residual shrinkage, the process according to this invention, contrary to expectations, occurs particularly with strong titers, whereas with the known methods the removal of the residual shrinkage in threads with strong titers is only possible to a limited extent .

The method is particularly favored in that the low thread tensions of the texturing zone - as stated in claim 2 - are set differently in front of and behind the air texturing nozzle. The thread at the outlet of the air texturing nozzle is deflected strongly, preferably at approximately 90 °. This measure is in contrast to the straight thread run, which is common with tangling (interlacing, entangling) and is also possible with air texturing nozzles.

The heat and shrinkage treatment according to the invention makes it possible to eliminate irregularities in the previous stretching by means of the intensive shrinkage treatment even before the actual texturing. Threads with high strength and the desired properties with regard to elongation and residual shrinkage can be produced.

The thread tension relevant for the shrinkage arises from the tensile force of the texturing nozzle. The tensile force of the texturing nozzle depends on the thread speed. The thread speed is determined by the peripheral speed of the godet, which is upstream of the texturing nozzle. The difference in the peripheral speed of the godet and the delivery mechanism, which follows the texturing nozzle, is not decisive for the shrinkage. Because according to the invention this difference - as stated in claim 3 - is always greater than the amount of the desired shrinkage. The amount of shrinkage required is determined solely by the tensile force of the nozzle and by the temperature of the godet. In other words, the overfeed of the thread in the texturing zone is always greater than the shrinkage set by the tensile force of the nozzle and the temperature of the godet. Here is the tradition
0 = (v5 - v10) x 100 / v10 with
v10 = peripheral speed of the supplying plant, which is connected downstream of the texturing nozzle,
v5 = peripheral speed of the godet.

The shrinkage is expressed by the relationship
S = (L1 - L2) x 100 / L1 with
L1 = original length of the thread
L2 = length of thread after shrinking.

The fact that the tradition is greater than the set shrinkage means that the thread can be crimped in the desired manner. The difference between delivery and set shrinkage is 1 to 10% for technical threads, for which the texturing serves in particular the purpose of roughening the thread, e.g. to improve its running ability (sewing threads) or to improve its adhesion to other materials (technical fabrics, tire cord) .

The difference between tradition and set shrinkage is 10 to 300% for textile threads. In the case of textile threads, it is important to influence the appearance, the feel, the fullness and other properties in a way that is desired for clothing and other textile applications.

This invention makes it possible to change the conventional air texturing machine only slightly, as follows from claim 4.
Because of the disadvantages of the prior art and further advantages of this invention, reference is made to the earlier application EP-A 0 373 519, which in this respect is also made the subject of this application.

Exemplary embodiments of the invention are described below.

Fig. 1

eine schematische Darstellung zur Ausführung des Verfahrens;

Fig. 2

eine Einrichtung zur Messung des Restschrumpfes.

Show it

Fig. 1

a schematic representation of the execution of the method;

Fig. 2

a device for measuring the residual shrinkage.

An air texturing process in the sense of this application means a process in which an endless, synthetic thread, which consists of a large number of individual filaments, is subjected to the action of an air texturing nozzle. An unheated air jet is blown onto the thread in the air texturing nozzle. This creates the single filaments deformed into loops, loops, arches and the like, without the chemical-physical structure of the filaments being significantly changed thereby. The filaments, which are initially essentially parallel, are therefore only geometrically displaced into an irregular shape. In particular, loops, loops, arches are created. A particularly suitable and suitable process for the production of high-quality threads results from the German patent DE-A 27 49 867 (Bag. 1045) = US patent Re 32047. Suitable nozzles are, for example, in the doctoral thesis by Bock "Texturing of filament yarns in an air stream ", Aachen 1984/1985.

As usual, the following terminology is used in this application:
Residual shrinkage is the tendency of the thread to shrink when heated, for example by hot air or hot water.
Shrinkage is the shortening of the thread that actually occurs when heated, expressed by the formula (L1 - L2) x 100 / L1%, where L1 is the original length and L2 is the shortened length of the thread. The shrinkage cannot be greater than the previous shrinkage. Despite shrinkage, a residual shrinkage may still remain.

If the known method is used, the residual shrinkage, ie the tendency to shrink, can only be reduced by a suitable aftertreatment following the method. It is indeed possible to reduce the residual shrinkage of the thread by such post-treatment measures for shrinking treatment. However, these post-treatment measures have considerable disadvantages. This applies in particular to textured threads, since the post-treatment subsequently affects or even damages the crimp. Above all, the shrinking treatment can only be carried out intensively if the thread is "contact heated", ie if the thread is over a hot plate or hot godet is performed. However, this is generally not advisable for textured threads because this results in an ironing effect. This means that the thread texture that was previously inserted is partially removed by contact with the hot surface, especially on one side of the thread.

An aftertreatment process for reducing the shrinkage of an air-textured thread is known from US Pat. No. 3,892,020 = DE-A 24 59 102. In this process, the air-textured thread is wound on a very soft spool under a low thread tension of less than 3.532 cN / dex (0.4 g / den). This coil is then dyed in a heated dye bath. This triggers the shrinkage and accordingly the residual shrinkage remaining in the thread is reduced. With this method, the treatment for reducing residual shrinkage cannot take place on the air texturing machine. It is particularly disadvantageous that the bobbin must be wound up with a low thread tension. Because this affects the transportability of the coil. In addition, the bobbin and the thread are damaged by the increased thread tension that builds up when the shrinkage is triggered.

The residual shrinkage could also be reduced before texturing. For this purpose, it is known from EP-A 0 032 067 that the thermoplastic drawing of thermoplastic threads can be followed by a treatment to reduce the shrinkage in a relaxation zone. This relaxation zone adjoins the actual stretching zone. The relaxation zone is formed between two godets or delivery units, the thread being heated in the relaxation zone. This would increase the length of the thread and thus the height of the air texturing machine. Above all, this relaxation treatment always has the problem that the reduction in shrinkage in such a relaxation zone is limited bumps because the thread tension of a thread running between godets cannot be reduced arbitrarily and because of this the shrinkage depends on the limited speed difference of the godets.

This is based on the fact that a thread between two supply plants always runs in a straight line and therefore must be under a certain minimum thread tension. The actual shrinkage results from the state of equilibrium between the tendency to shrink on the one hand and the thread tension on the other.

Such a method for reducing the residual shrinkage, in which interlacing (entangling) of the multifilament thread takes place at the same time, is known from US Pat. No. 3,069,836. The thread previously stretched between two godets with the help of an unheated stretching pin is passed through a relaxation zone, the delivery speed being greater than the take-off speed. In the relaxation zone, the thread is passed through a nozzle which is fed with a heated gas. The shrinkage achieved here depends - as I said - on the difference in this speed. The blowing up of hot air serves on the one hand to trigger the shrinkage and on the other hand to produce a yarn whose filaments are entangled. The method is not suitable for producing a crimp. This creates a yarn whose filaments have been chemically and physically altered in their internal structure by exposure to heat during air texturing. Even if loops and loops were produced in the filaments, such a crimping of this yarn would not be stable: That means that this crimping would be removed from the yarn again by applying tensile forces. However, tensile forces that are sufficient to remove this crimp occur as a result of the shrinkage in the relaxation zone, but also during the aftertreatment through subsequent stabilization and heat fixation, which are provided according to US Pat. No. Re 32047 to improve the length stability of the yarn, and in particular during weaving and knitting. Therefore, such a yarn would not be useful as a crimped yarn.

As shown in FIG. 1, a completely stretched and oriented thread is drawn off from the supply spool 1 via the head thread guide 2 by a heated godet 5. Behind the heated godet 5, the thread passes through the air texturing nozzle 7. Unheated compressed air is fed to the air texturing nozzle 7. The thread is never heated until it softens during the air texturing treatment. The deformations caused by the air jet treatment are therefore not imprinted on the chemical-physical thread structure. When it hits the thread, the air expands and cools down further. The expanding filament blows the individual filaments of the multifilament chemical thread into loops, loops, arches and the like. These are merely geometrical deformations, which intertwine and get caught together, resulting in the texture of the thread.

It should therefore be emphasized that the air with which the texturing nozzle is fed is unheated and has a temperature which is below the temperature at which the crystal structure of the thread freezes and therefore any shrinkage stops. The air temperature is usually below 40 ° C. This air is further cooled by the expansion. The air leaving the nozzle has a temperature of less than 10 °. It should be noted that the texturing nozzle is operated with compressed air at a pressure between 6 and 10 bar. Therefore, the thread, which was previously heated by the godet 5, is also very strongly quenched in the texturing nozzle, so that its temperature also falls below the temperature at which the crystal structure freezes. It can therefore be assumed that the thread is cooled by the air texturing nozzle and the shrinkage is thereby brought to a standstill. This has the advantage that the texturing by forming the loops, loops, arches and the like only takes place when the shrinkage has come to a standstill. Therefore, the texturing is no longer affected or affected by the shrinkage. This is of great importance because in order to produce an air-textured thread with good length stability after the texturing, a tensile force must first be applied to the thread before the thread is further compacted by a further heat and shrinking treatment. In this respect, reference is made to the already cited patents DE 27 49 867 = US Re 32047. The method according to the invention therefore represents an important addition to the known method.

It is indicated schematically that the air channels 8, which are directed towards the thread channel 9 in the texturing nozzle 7, have a directional component in the thread running direction. As a result, the air texturing nozzle 7 also exerts a conveying action and a tensile force on the thread. The thread leaves the air texturing nozzle 7 essentially without thread tension, the thread being deflected and guided to the delivery mechanism 10. The deflection is 30 to 90 °, preferably 90 °. The deflection is achieved in that the delivery mechanism 10 is not offset on the axis of the thread channel 9 of the texturing nozzle 7, but laterally to it. The deflection does not take place in that the thread is drawn over a thread guide, but in that the thread is initially conveyed straight ahead by the air jets when it exits the thread channel 9 and then has to change its direction to the feed mechanism 10. This type of deflection results in a substantial reduction in the thread tension. Therefore, the thread tension between the godet 5 and the texturing nozzle 7 is higher than the thread tension behind the texturing nozzle 7 and after the deflection in front of the delivery unit 10 builds up again. The thread tensions in front of and behind the air texturing nozzle were, for example, 6 cN and 5 cN.

A suitable thread treatment, such as in particular e.g. is shown by German Patent 27 49 867 = US Patent Re 32047 (Bag. 1045). In particular, the thread can be warped in a stabilizing zone between two godets without elastic or plastic deformation without heating. Alternatively or preferably after the stabilization, the thread can be passed through a fixing zone at temperatures up to 245 ° C. The series connection of the stabilizing zone and the fixing zone creates a particularly compact thread with low instability. The thread is then moved back and forth through the traversing device 11 transversely to its running direction and wound on the spool 12. The spool 12 is driven by the drive roller 13 at a constant peripheral speed.

According to the invention, the godet 5 is heated. When polyamide, polyester or polyethylene terephthalate threads are relaxed, the temperature of the godet 5 is between 200 ° and 245 ° C, and around 150 ° for polypropylene.

In the case of polyamide threads, that is to say nylon and perlon threads, cold drawing has already been possible and customary. The threads are wrapped around a drawing pin, to which no heat is applied from the outside. With the method according to the invention, the treatment of such cold-drawn threads is possible in particular. The method has proven to be so effective that cold-drawn polyester threads, in particular made of polyethylene terephthalate, can also be placed on the supply spool. With the method according to the invention, even with cold-drawn polyester threads, the very bad ones after drawing have textile properties, good strength and elongation properties and thereby achieve residual shrinkage behavior that cannot be achieved with other processes. The process proves to be particularly effective if the cold drawing is carried out on pre-oriented threads which have been drawn out of the spinning zone at high spinning speeds.

The tests according to the earlier application were also carried out analogously for the discounting process according to this invention.

The test parameters and the test results are shown in the table below. The threads initially had a diter of 410 dtex and a yield point of 180% before they were fully oriented by drawing with a drawing ratio of 1: 1.95 or for the technical thread of 1: 2.3 and wound up to the supply spool 1 were.

A suitable device for rapid measurement of the residual shrinkage is shown schematically in FIG. Such a device is commercially available under the trade name testrite. This device is used in particular for comparison tests. The device determines what percentage (L1 - L2 / L1 x 100) of a pretreated thread shrinks when it is subjected to shrinkage treatment on the testrite device with the same clamping length, the same heating length, the same heating temperature and heating time and the same thread tension becomes.

The thread is firmly clamped at one end 15 and passed over a measuring roller 16 at the other end. The thread end behind the measuring roller 16 is loaded by a weight 17. The measuring roller 16 is connected to a pointer 18 so that the change in the thread length is displayed on a scale. The Thread is heated by a heater 19 with a thread slot 20. It follows from general experimental principles that when carrying out an experiment, the treatment time, the clamping length of the thread between the clamping 15 and the measuring roller 16, the length of the heater 19, the temperature of the heater 19 and the weight 17 remain constant.

REFERENCE SIGN LISTING

1

Supply spool

2nd

Head thread guide

5

Godet

6

Drawing pin

7

Texturing nozzle

8th

Air duct

9

Thread channel

10th

Delivery plant

11

Traversing device

12th

Kitchen sink

13

Drive roller

14

15

End, gripping

16

Measuring roller

17th

Weight

18th

pointer

19th

Stoker

20th

Thread slit

21

Delivery plant

22

Stoker

23

Heating pipe

24th

Delivery plant

25th

Stabilization zone

26

Fixing zone

27

Water nozzle

28

Water box

Claims (4)

1. Method of manufacturing an air-textured yarn, wherein a yarn is withdrawn from the feed spool (1) and then fed into an air-texturing zone,
   is conveyed in said zone through an air-texturing nozzle (7) and is fed as well as blown without thermoplastic softening into snarls, loops, curves and the like by means of said air-texturing nozzle (7),
   is withdrawn by a delivery mechanism (10) from the air-texturing zone and wound after a suitable intermediate treatment,
   having the following characterizing process steps :
   a feed spool (1) is supplied with fully stretched yarn;
   the yarn is withdrawn from the feed spool (1) by a heated galette (5) and fed into the air-texturing zone, the yarn being looped several times around the galette (5);
   the galette (5) is heated up to a temperature which is suitable for initiating shrinking for the purpose of reducing the residual shrinkage and lies above the second-order transition point, preferably above 80°C;
   the yarn is withdrawn from the galette (5) with the aid of the air-texturing nozzle (7) at a tension lower than 0.1 cN/dtex, with the yarn tension not increasing as a result of the initiation of shrinking, and is cooled down in the texturing nozzle to below the second-order transition point, preferably down to below 40°C;
   downstream of the air-texturing nozzle (7) the yarn is deflected from the axis of the yarn channel (8) of the nozzle (7) and withdrawn from the region of the air-texturing nozzle (7) at a low yarn tension of less than 0.08 cN/dtex by a delivery mechanism (10) downstream of the air-texturing nozzle, the difference between the speed at which the yarn is fed into the air-texturing nozzle and the speed at which the yarn is withdrawn from the air-texturing nozzle (7) being greater than the value of the initiated shrinkage.
2. Method according to claim 1,
   characterized in that
   the yarn is withdrawn from the region of the air-texturing nozzle (7) at a yarn tension of less than 0.05 cN/dtex.
3. Method according to claim 1 or 2,
   characterized in that
   the overfeed with which the yarn is fed by the galette (5) into the texturing zone is at least 1% greater, preferably in the case of yarns to be used for industrial purposes 1 to 10%, in the case of yarns to be used for textile purposes 10 to 300% greater than the shrinkage desired in the texturing zone through adjustment of the tensile force of the nozzle and the temperature of the galette.
4. Air-texturing machine, having a feed spool (1), a heated galette (5) and a texturing zone with an air-texturing nozzle (7), as well as a delivery mechanism (10) downstream of the air-texturing nozzle (7), for effecting the method according to claim 1,
   characterized in that
   disposed between the feed spool (1) and the texturing zone is a single heated galette (5), around which the yarn is looped and by means of which the yarn is withdrawn from the feed spool (1) and fed into the texturing zone.

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