US20150218733A1

US20150218733A1 - Melt-spinning process and melt-spinning apparatus for producing a crimped yarn

Info

Publication number: US20150218733A1
Application number: US14/421,314
Authority: US
Inventors: Mathias Stündl; Friedrich Lennemann; Kirsten Prehn
Original assignee: Oerlikon Textile GmbH and Co KG
Current assignee: Oerlikon Textile GmbH and Co KG
Priority date: 2012-08-17
Filing date: 2013-08-08
Publication date: 2015-08-06
Also published as: CN104583471A; JP2015529287A; EP2885447A1; CN104583471B; WO2014026902A1

Abstract

A melt-spinning process and a melt-spinning apparatus produce a crimped yarn. By means of a spinning device, a filament bundle is generated from a thermoplastic polymer, is drawn after cooling and is compressed into a yarn plug in a stuffing chamber. The yarn plug is opened up into a crimped yarn and wound into a bobbin. In order to obtain as high a crimp resistance of the yarn as possible, amorphous fractions in the molecular structure of the yarn material are avoided after drawing. This is achieved by means of relaxation treatment after drawing and before compression, a minimum yarn pull force of >0.05 cN/dtex with a relaxation temperature in the range of 120° C. to 245° C. being maintained.

Description

The invention relates to a melt-spinning process for producing a crimped yarn, according to the preamble of claim 1, and to a melt-spinning apparatus for producing a crimped yarn, according to the preamble of claim 9.
A generic process and a generic apparatus are known from WO 2011/138 302 A1.
In the production of crimped yarns, preferably used for producing carpets, in a melt-spinning process, all the treatment steps for generating the desired physical properties of the yarn usually take place in succession. Thus, first, a multiplicity of filaments are extruded out of a melt of a polymer and, after cooling, are brought together as a filament bundle, prepared and drawn. After the drawing of the filament bundle, compression of the filament bundle takes place inside a stuffing chamber, so that the individual filaments are deposited in the form of arcs and loops within a yarn plug. The yarn plug is subsequently opened up into a yarn, the loops and arcs of the filaments not breaking down completely and giving the yarn a crimped structure. Depending on the respective polymer, the individual treatment steps are carried out under the influence of heat, particularly in order to influence the crystal morphology of the yarn material in the desired way. Thus, for example, a high crimp resistance of the yarn is desired. Crimp resistance is the ability of the yarn to preserve the existing crimping under mechanical load. Thus, low crimp resistance causes a large part of the loops and arcs preserved in the filaments to break down after being subjected to mechanical load.
In the known melt-spinning process and the known melt-spinning apparatus, the filament bundle is heated before drawing and after drawing, so that an oriented molecular structure can be formed within the yarn material. However, the heat treatment of the filament bundle which is carried out after drawing has the effect that uncontrolled expansion acts upon the filaments, causing partial restitution into non-oriented and amorphous fractions of the polymer material. However, such non-crystalline molecular structures in the yarn material have the disadvantage of very low crimp resistance.
In principle, it is known from the two-stage process for the production of textured and crimped yarns that these yarns have high crimp resistance. In this case, the crimping and drawing of the yarn take place in a superposed treatment step, and therefore attempts have also been made to apply this technique to the single-stage melt-spinning processes. Thus, for example, DE 199 20 177 A1 discloses a process and an apparatus for producing a crimped yarn, in which a conventional false-twist zone with a heating device, with a cooling device and with a false-twist assembly is arranged between a plurality of godet pairs. Consequently, although similar effects to a two-stage process can be simulated, there is the nevertheless the disadvantage that, at higher process speeds, the generation of twist on the filament bundle leads to considerable problems. The known process and the known apparatus have therefore not proved successful in the production of carpet yarns.
Furthermore, a process for producing a crimped yarn from a polytrimethylene terephthalate (PTT) is known from DE 10 2008 051 738 A1. In this, the filament bundle does not undergo heat treatment immediately before entry into the crimping chamber. Where conventional polyester materials are concerned, however, the unavoidable result of the absence of heat treatment is that the internal stresses which have occurred during drawing may not take effect until crimping takes place. To that extent, the PTT material is in a separate position with a special molecular structure.
The object of the invention, therefore, is to develop a melt-spinning process and a melt-spinning apparatus of the generic type for producing a crimped yarn, in such a way that crimped yarns can be produced with improved crimp resistance from conventional polymer materials, such as, for example, PET.
This object is achieved, according to the invention, for the melt-spinning process in that, after drawing and before compression, the filament bundle undergoes relaxation treatment at a relaxation temperature in the range of 120° C. to 245° C. and with a minimum yarn pull force of >0.05 cN/dtex.
The melt-spinning apparatus according to the invention offers the solution whereby the heated godets of the drawing godet pair have in each case a stepped or conical godet casing, by means of which relaxation treatment can be carried out on a filament bundle guided in a plurality of looping movements, with a minimum yarn tension of >0.05 cN/dtex and a relaxation temperature in the range of 120° C. to 245° C.
Advantageous developments of the invention are defined by the features and feature combinations of the respective subclaims.
The invention is based on the recognition that, in the conventional melt-spinning processes of the generic type, a complete collapse of yarn tension on the filament bundle occurs during the transition of the filament bundle from the drawing godet pair to the crimping device. Tension breakdowns of this kind on the filament bundle have the direct result that, during expansion, the yarn material is restructured into a state which is favorable in energy terms, so that amorphous and semi-amorphous fractions occur to an increased extent in the molecular structure. Such an absence of crystallinity is therefore conducive to a lack of crimp resistance. In the melt-spinning process according to the invention and the melt-spinning apparatus according to the invention, relaxation treatment is carried out on the filament bundle before entry into the crimping device and ensures a minimum yarn pull force of >0.05 cN/dtex. In this case, depending on the type of polymer, the relaxation temperatures lie in the range of between 120° C. and 245° C.
The melt-spinning apparatus according to the invention affords the great advantage, in particular, that relaxation treatment with a minimum yarn pull force can be carried out directly at the drawing godet pair. For this purpose, the godet casings of the godets of the drawing godet pair have a conical or stepped shape, so that a minimum yarn pull force is maintained each time the filament bundle is wound around on the circumference of the godet casings. Consequently, it is possible to heat the yarn material, in the tensioned state of the filament bundle, to the relaxation temperature in the range of between 120° C. and 245° C. Depending on the number of loopings around the godet casings, on the yarn speed and on the overall yarn titer of the filament bundle, the set surface temperature of the godet casings lies somewhat higher than the relaxation temperature. The temperatures at the godet surface are usually set at approximately 5° C. to 15° C. above the desired yarn temperatures.
In order to obtain sufficient expansion in spite of the yarn pull force acting on the filament bundle, an especially advantageous process variant is one in which, during relaxation treatment, the yarn pull force acting on the filament bundle lies in the range of 0.1 cN/dtex to 2.0 cN/dtex, preferably in the range of 0.2 cN/dtex to 0.7 cN/dtex. The desired expansion effects for reducing internal stresses on the filaments of the filament bundle can consequently be implemented.
In the melt-spinning process according to the invention, the relaxation treatment of the filament bundle immediately before compression can be carried out by means of all known devices for the generation of minimum yarn pull forces and for the heat treatment of the yarn. Especially advantageous, however, is the process variant in which, for relaxation treatment, the filament bundle is guided in a plurality of looping movements around a godet pair having heated godets and conical godet casings. The conicity of the godet casings ensures that, in the case of a plurality of windings of the filament bundle, a defined yarn pull force prevails during the heating of the yarn material.
It turned out to be especially advantageous that the transformation of the molecular structure of the yarn material during relaxation can also be stabilized by means of subsequent fixing treatment. In that regard, the process variant is preferably used in which the filament bundle, after relaxation treatment, undergoes fixing treatment with a fixing temperature in the range of 60° C. to 240° C., with a minimum yarn pull force of >0.05 cN/dtex being maintained. This operation is preferably achieved by guiding the filament bundle on cold godets of a godet pair. In principle, the fixing temperature should lie at least 5° C. below the relaxation temperature.
Depending on the type of polymer of the yarn material, alternatively or additionally, further heat treatment is carried out on the filament bundle immediately before compression. It is therefore necessary that the filaments as far as possible have ductility in order to be laid down in arcs and loops. For this purpose, the process variant is especially suitable in which, before compression, the filament bundle undergoes heat treatment at a temperature lying below the relaxation temperature, with a minimum yarn pull force of >0.05 cN/dtex being maintained. The treatment temperature should lie in the range of between 5 and 100° C. below the relaxation temperature previously set in each case. This ensures that undesirable restructurings in the molecular structure of the yarn material cannot occur.
This method step, too, is preferably carried out by means of heated godets of a godet pair on which the filament bundle is guided in the plurality of looping movements for heat treatment.
In order to assist the temperature control operation during the crimping of the filament bundle, for compression the filament bundle is preferably conveyed into the stuffing chamber by a hot air stream. Depending on the yarn material, however, there is also the possibility of guiding the filament bundle with a cold air stream.
In the melt-spinning apparatus according to the invention, flexibility for carrying out the melt-spinning process according to the invention is increased in that, according to an advantageous development, one or more godet pairs are arranged between the drawing device and the crimping device. Thus, in the case of an additional godet pair between the drawing device and the crimping device, fixing treatment or heat treatment can selectively be carried out on a filament bundle guided in a plurality of looping movements. For fixing treatment, the godet pair preferably has cold godets. By contrast, heat treatment is carried out by means of a heated godet pair.
In the event that the yarn material used in each case requires fixing treatment and heat treatment of the filament bundle before compression, the development of the melt-spinning apparatus according to the invention is provided in which a plurality of godet pairs are arranged between the drawing device and the crimping device. The fixing treatment and heat treatment can thus be carried out in succession.
To compress the filament bundle, the crimping device is preferably designed with a conveying nozzle which cooperates on the outlet side with a stuffing chamber. Such crimping devices have proved successful, particularly in the case of high process speeds, in order to generate continuous and uniform crimping of the filament bundle.
In order to fix the arcs and loops, generated under the influence of temperature, of the filaments, the yarn plug is preferably guided on the circumference of a cooling drum for cooling.
The melt-spinning process according to the invention and the melt-spinning apparatus according to the invention are suitable for producing crimped yarns in a single-stage process with high crimp resistance which can otherwise be achieved on yarns solely in a two-stage process.

The melt-spinning process according to the invention is explained in more detail below by means of some exemplary embodiments of the melt-spinning apparatus according to the invention, with reference to the accompanying figures in which:

FIG. 1 illustrates diagrammatically a view of a first exemplary embodiment of the melt-spinning apparatus according to the invention

FIG. 2 illustrates diagrammatically a view of a further exemplary embodiment of the melt-spinning apparatus according to the invention

FIG. 3 illustrates diagrammatically a view of a further exemplary embodiment of the melt-spinning apparatus according to the invention

FIG. 4 illustrates diagrammatically a view of a further exemplary embodiment of the melt-spinning apparatus according to the invention.

FIG. 1 illustrates diagrammatically a view of a first exemplary embodiment of the melt-spinning apparatus according to the invention for producing a crimped yarn. The exemplary embodiment of the melt-spinning apparatus according to the invention is shown by the example of one thread run, although such melt-spinning apparatuses are also used for producing a plurality of yarns next to one another in parallel.
The exemplary embodiment shown in FIG. 1 has a spinning device 1, a cooling device 5, a drawing device 11, a crimping device 15, a post-treatment device 20 and a winding device 24, which are arranged one behind the other to form a yarn run. In this exemplary embodiment, the spinning device 1 is illustrated merely by a spinning head 2. The spinning head 2 has at least one spinning pump (not illustrated here) and a spinnerette 3 which on the underside has a nozzle plate with a multiplicity of nozzle bores. The spinnerette 3 arranged inside the heated spinning head 2 is coupled to the spinning pump which is connected via a melt inflow 4 on the top side of the spinning head 2 to a melt source, not illustrated here, for example an extruder.
When a plurality of yarns are being produced next to one another in parallel, the spinning head 2, which is also designated by specialists as a spinning beam, carries a plurality of spinnerettes next to one another.
Underneath the spinning device 1, a cooling device 5 is provided, which forms a cooling shaft 6 for receiving freshly extruded filaments, the cooling shaft 6 being assigned a blowing means 7 for generating a cooling air stream. The cooling air may in this case be provided from the outside inward by means of cross-flow blowing or radial blowing. In principle, however, there is also the possibility of conducting a cooling air stream through the filament bundle radially from the inside outward.
After cooling, the filaments 8 generated by the spinnerettes 3 are brought together into a filament bundle 10. For this purpose, a preparation device 9 is provided underneath the cooling device 5. The preparation device 9 usually has a collecting yarn guide and a wetting means. Preparation pins or preparation rollers may be used as wetting means.
Underneath the preparation device 9, a drawing device 11 is provided, which is formed from a take-up godet pair 12 with two heated godets 12.1 and 12.2 and from a drawing godet pair 14 with the heated godets 14.1 and 14.2. The heated godets 12.1 and 12.2 of the take-up godet pair 12 and the heated godets 14.1 and 14.2 of the drawing godet pair 14 are arranged in each case in a godet box 13.
In contrast to the heated godets 12.1 and 12.2 of the take-up godet pair 12, which have a conventional cylindrical godet casing, the heated godets 14.1 and 14.2 of the drawing godet pair 14 are designed in each case with a conical godet casing. The conicity of the godet casings on the heated godets 14.1 and 14.2 is selected in such a way that, after the drawing of the filament bundle 10, a minimum yarn pull force of above 0.05 cN/dtex, preferably of 0.1 cN/dtex, acts on the filament bundle in each wind-around.
In this exemplary embodiment, the crimping device 15 is formed by a conveying nozzle 16 and a stuffing chamber 17 arranged on the outlet side of the conveying nozzle 16, said conveying nozzle and said stuffing chamber cooperating with a following cooling drum 19. The conveying nozzle 16 is coupled to a compressed air source in order to convey the filament bundle 10 by means of an air stream into the stuffing chamber 17 and compress it into a yarn plug. The yarn plug 18 is cooled on the circumference of the cooling drum 19 by cooling air.
The crimping device 15 is followed by a post-treatment device 20 which, on the one hand, opens up the yarn plug 18 by taking up a crimped yarn on the circumference of the cooling drum 19 and, on the other hand, carries out an intermingling of the yarn in order to increase the yarn strength. For this purpose, an intermingling nozzle 22 is arranged between two guide godet units 23.1 and 23.2. Each of the guide godet units 23.1 and 23.2 has a godet and an auxiliary roller.
At the end, the crimped yarn 21 is wound up into a bobbin 25 by means of the winding device 24. For this purpose, winding devices are usually used which have a winding turret 28 with two projecting winding spindles 29.1 and 29.2 which are guided successively into a winding region and thus lead to a continuous winding of the crimped yarn. Such winding devices are generally known and therefore not described in any more detail here.
In the exemplary embodiment, illustrated in FIG. 1, of the melt-spinning apparatus, a granulate of a polymer material, for example a polyester, is melted, for example via an extruder, and is fed to the spinning head 2 via the melt inflow 4. Inside the spinning head 2, the melt is conveyed under pressure to the spinnerette 3 by means of a spinning pump, so that a multiplicity of filaments 8 are extruded on the underside of the spinnerette 3. The freshly extruded filaments 8 are cooled inside the cooling device 5 by means of a cooling air stream and are brought together at the end into a filament bundle 10. For this purpose, the filaments 8 undergo wetting which is preferably an oil/water emulsion.
The filament bundle 10 is pulled out of the spinning device 1 by the take-up godet pair 12. The godets 12.1 and 12.2 of the take-up godet pair 12 have a surface temperature at the godet casings in order to heat the yarn material to a desired yarn temperature in the range of 80° C. to 120° C. In this case, the filament bundle is guided on the take-up godet pair 12 in 10 to 15 looping movements.
For drawing the filament bundle 10, the drawing godet pair 14 is driven with a speed difference, so that the filament bundle 10 is drawn in the yarn section between the take-up godet pair 12 and the drawing godet pair 13.
So that relaxation treatment can be carried out on the filament bundle 10 immediately after drawing, the godets 14.1 and 14.2 of the drawing godet pair 14 are heated in such a way that a yarn temperature on the filament bundle in the range of 120 to 245° C., preferably of 170 to 230° C., is reached. In order to compensate the length changes occurring during the heating of the yarn material, the two godet casings of the godets 14.1 and 14.2 may be designed to be slightly conical. The variation in the guide diameter of the godet casings of the godets 14.1 and 14.2 is selected as a function of the 8 to 12 loopings of the filament bundle, in such a way that at least one yarn pull force of 0.05 cN/dtex, preferably of 0.1 cN/dtex, acts in each looping. The diameter variation of the godet casings in the godets 14.1 and 14.2 is dimensioned in such a way that a maximum yarn pull force of 2.0 cN/dtex is not exceeded. It was shown that advantageous relaxation treatment is possible in a range of 0.2 to 0.7 cN/dtex. The relaxation temperature of yarn treatment, which is determined by the surface temperature of the godet casings of the godets 14.1 and 14.2, is set at a temperature of between 120° C. and 245° C. Relaxation treatment on the filament bundle 10 leads to uniform restructuring of the molecular structure without major fractions of amorphous or semi-amorphous regions. The high crystallinity of the yarn material ensures a stable crimping behavior with correspondingly high crimp resistance in the crimped yarn.
For crimping, the filament bundle 10 is conveyed through the conveying nozzle 16 into the stuffing chamber 17 and is compressed into a yarn plug. Depending on the temperature of relaxation treatment, the conveyance of the filament bundle may take place by means of a hot air stream or by means of a cold air stream. The crimped filaments of the filament bundle 10 are conveyed as a yarn plug 18 out of the stuffing chamber 17 and cooled on the circumference of the cooling drum 19. The opening up of the yarn plug 18 into the crimped yarn 21 takes place by means of the post-treatment device 20 which has a first guide godet unit 23.1. Further along, the crimped yarn 21 is intermingled in the intermingling nozzle 22 and is subsequently guided via the second guide godet unit 23.2 to the winding device 24. In the winding device 24, the crimped yarn 21 is wound into the bobbin 25.
The exemplary embodiment, illustrated in FIG. 1, of the melt-spinning apparatus according to the invention thus makes it possible to carry out the melt-spinning process according to the invention, the filament bundle running into the crimping device under the temperature control stipulated by the relaxation treatment. As already mentioned above, there is in this case the possibility of guiding the filament bundle 10 into the stuffing chamber 17 by means of a cold air stream. Consequently, in particular, the effects of the relaxation treatment can be fixed in the yarn material. In order nevertheless to obtain a pronounced crimping of the filament bundle, the yarn plug is preferably heated inside the stuffing chamber.
In order to obtain a temperature control of the filament bundle which is especially suitable for the crimping operation, in the apparatus and process illustrated in FIG. 1 the conveying nozzle 16 is alternatively operated by means of a hot air stream. In this case, however, only limited temperature changes of the yarn material can be achieved.
So that the relaxation of the filament bundle and the compression of the filament bundle can be set independently of one another, the exemplary embodiment of the melt-spinning apparatus according to the invention, as shown in FIG. 2, is especially suitable. The exemplary embodiment, illustrated in FIG. 2, of the melt-spinning apparatus according to the invention is essentially identical in set-up to the abovementioned exemplary embodiment according to FIG. 1, and therefore only the differences are explained at this juncture in order to avoid repetition.
In the exemplary embodiment, illustrated in FIG. 2, of the melt-spinning apparatus according to the invention, the spinning device 1, the drawing device 11, the crimping device 15, the post-treatment device 20 and the winding device 24 are designed identically to the exemplary embodiment according to FIG. 1. Reference may be made in that respect to the abovementioned description.
A further godet pair is provided between the drawing device 11 and the crimping device 15 and is designated in this case as a temperature control godet pair 27. The temperature control godet pair 27 has two heated godets 27.1 and 27.2 with cylindrical godet casings. The godets 27.1 and 27.2 are arranged in a godet box 13. For the temperature control of the filament bundle 10, the latter is likewise guided on the circumference of the godet casings of the godets 27.1 and 27.2 in a plurality of loopings, preferably 10 to 15 loopings.
By means of the exemplary embodiment, illustrated in FIG. 2, of the apparatus according to the invention, a variant of the process according to the invention can be operated in which, after the relaxation of the filament bundle, additional heat treatment takes place before the compression of the filament bundle. The godets 27.1 and 27.2 of the temperature control godet pair 27 are set at a treatment temperature which lies below the relaxation temperature. The selected difference must be between 5° C. and 100° C., depending on the type of polymer. It is essential in this case that the relaxation temperature set during relaxation is not exceeded. If the relaxation temperature is exceeded during subsequent heat treatment, there is the risk that renewed restructuring of the molecular structure of the yarn material commences. As a result of the heat treatment of the filament bundle immediately before compression, the production of the crimping can be carried out independently of the relaxation treatment. Thus, by means of the heat treatment, targeted temperature control can be carried out on the yarn material of the filament bundle, in order to obtain a uniform and intensive formation of filament loops.
In the selection of the treatment temperatures, however, care must be taken to ensure that the differences between the treatment temperature and the relaxation temperature are not too small, so that no fixing effects for the stability of the restructured molecular structure of the yarn material can occur. In order to fix the molecular structures of the yarn material which are generated after drawing and relaxation, the exemplary embodiment of the melt-spinning apparatus according to the invention, as shown in FIG. 3, has proved especially appropriate.
In the exemplary embodiment according to FIG. 3, two godet pairs are provided between the drawing device 11 and the crimping device 15. A first godet pair directly on the outlet side of the drawing device 11 is designated as a fixing godet pair 26. The fixing godet pair 26 has the godets 26.1 and 26.2, the godet casings of which are unheated. In this exemplary embodiment, the following godet pair is likewise a temperature control godet pair 27 with the heated godets 27.1 and 27.2. As compared with the exemplary embodiment according to FIG. 2, a further process step is provided between the relaxation and compression of the filament bundle. Thus, the fixing godet pair 26 with the cold godets 26.1 and 26.2 is used in order to cool the yarn material of the filament bundle 10. The surface temperatures of the godet casings of the godets 26.1 and 26.2 are set for this purpose at a yarn temperature of between 60 and 240° C. The material structure of the yarn material can consequently be fixed advantageously before compression.
In the additional process steps of fixing and temperature control, described in FIG. 2 and in FIG. 3, it is essential that a minimum yarn pull force of >0.05 cN/dtex, preferably of >0.1 cN/dtex, is maintained during the entire treatment. This ensures that the undesirable restitutions of the molecular structure which occur in the tension-free state are avoided. In the event that a reduction in tension takes place in the case of a large number of loopings of the filament bundle on the fixing godet pair 26 or the temperature control godet pair 27, there is likewise the possibility of designing the godets 26.1 and 26.2 of the fixing godet pair and the godets 27.1 and 27.2 of the temperature control godet pair 27 with a conical godet casing.
It may be mentioned expressly at this juncture that the diameter variations on the godet casings of the godets 14.1 and 14.2 of the drawing godet pair 14 may also be achieved by means of a different shaping of the godet casings. Thus, for example in the case of multiple looping by a plurality of yarns, a stepped shaping of the godet casings of the godets 14.1 and 14.2 could advantageously be used in order to ensure a minimum pull force. Likewise, zones of conical casing portions on the godet casings and of cylindrical casing portions may be used alternately in order to avoid a reduction in tension on the filaments of the filament bundle. Since stepped and conical godet casings in godets for the guidance of yarns are sufficiently known, a further explanation is dispensed with at this juncture.
In the exemplary embodiments according to FIGS. 1 to 3, the melt-spinning process according to the invention and the melt-spinning apparatus according to the invention are illustrated by the example of a crimped yarn which is generated from a filament bundle. Crimped yarns of this kind are preferably produced as single-color yarns. To generate multicolor yarns, which are preferably used for the production of carpets, preferably a plurality of filament bundles are generated from differently colored polymer melt or different cross-sectional shapes, numbers of filaments or filament titers and are combined before being wound up into a crimped composite yarn. Such an exemplary embodiment of the melt-spinning apparatus according to the invention is illustrated diagrammatically in FIG. 4.
In the exemplary embodiment, shown in FIG. 4, of the melt-spinning apparatus according to the invention, the spinning device 1 has a spinning head 2, on the underside of which three spinnerettes are held next to one another. Each of the spinnerettes 3 is connected to a spinning pump, not illustrated here, which is coupled in each case to a separate extruder via a separate melt inflow 4. The filaments 8 extruded by the spinnerettes 3 are guided jointly through a cooling shaft 6 of the cooling device 5 and are cooled by means of a cooling air stream.
Underneath the cooling device 5, a preparation device 9 is provided, which for each spinnerette 3 brings together in each case the extruded filaments to form a separate filament bundle 10. The filament bundles 10 are subsequently taken up from the spinning device 1 by a spinning godet unit 30 provided for each spinnerette 3 and are fed to a drawing device.
In the drawing device 11, the filament bundles 10 generated by the three spinnerettes 3 are guided next to one another in parallel and jointly drawn. For this purpose, the drawing device 11 has a take-up godet pair 12 and a drawing godet pair 14. The take-up godet pair 12 is in this case formed by a heated godet 12.1 and an auxiliary roller 12.3. the drawing godet pair 14 has the heated godets 14.1 and 14.2 which in each case possess a conical godet casing. In that respect, the drawing godet pair 14 is designed identically to the abovementioned exemplary embodiments and is arranged inside a godet box 13.
Underneath the drawing device 11, a temperature control godet pair 27 is provided, which is likewise designed identically to the abovementioned exemplary embodiment according to FIG. 2.
The subsequent devices 15, 20 and 24 are likewise identical to the exemplary embodiment according to FIG. 2, and therefore reference is made at this juncture to the abovementioned description.
In the exemplary embodiment, illustrated in FIG. 4, of the melt-spinning apparatus according to the invention, the filament bundles 10 are compressed jointly into a yarn plug 18 by means of the conveying nozzle 16. Thus far, the yarn plug 18 is generated from differently colored filament bundles and, after cooling, is opened up into the crimped yarn. In principle, however, there is also the possibility of compressing the differently colored filament bundles separately in each case into a separate yarn plug and of opening it up into a plurality of crimped yarns which are subsequently combined into a composite yarn in the post-treatment device 20 with the aid of the intermingling nozzle 22. In this case, the filament bundles could also have different individual titers and different filament cross sections and could additionally also be formed from different polymer materials.
The process according to the invention and the apparatus according to the invention therefore extend to crimped monocolor yarns and to crimped multicolor yarns. It is essential in this case that, after drawing and before compression, the filaments of the filament bundle undergo relaxation treatment with a minimum yarn pull force. The process according to the invention and the apparatus according to the invention are suitable, in principle, for all thermoplastic polymers which are used for fiber production. However, especially good crimp resistance results can be achieved particularly in the production of crimped polyester yarns.

LIST OF REFERENCE SYMBOLS

1 Spinning device
2 Spinning head
3 Spinnerette
4 Melt inflow
5 Cooling device
6 Cooling shaft
7 Blowing means
8 Filament
9 Preparation device
10 Filament bundle
11 Drawing device
12 Take-up godet pair
12.1, 12.2 Heated godets
12.3 Auxiliary roller
13 Godet box
14 Drawing godet pair
14.1, 14.2 Heated godets
15 Crimping device
16 Conveying nozzle
17 Stuffing chamber
18 Yarn plug
19 Cooling drum
20 Post-treatment device
21 Crimped yarn
22 Intermingling nozzle
23.1, 23.2 Guide godets
24 Winding device
25 Bobbin
26 Fixing godet pair
26.1, 26.2 Godets
27 Temperature control godet pair
27.1, 27.2 Godets
28 Winding turret
29.1, 29.2 Winding spindle
30 Spinning godet unit

Claims

1. A melt-spinning process for producing a crimped yarn, in which at least one filament bundle is generated from a thermoplastic polymer by the spinning of a plurality of filaments, in which the filament bundle is drawn after cooling and is compressed into a yarn plug in a stuffing chamber, and in which the yarn plug is opened up into a crimped yarn and wound into a bobbin, wherein, after drawing and before compression, the filament bundle undergoes relaxation treatment at a relaxation temperature in the range of 120° C. to 245° C. and with a minimum yarn pull force of >0.05 cN/dtex.

2. The process as claimed in claim 1, wherein, during relaxation treatment, the yarn pull force acting on the filament bundle lies in the range of 0.1 cN/dtex to 2.0 cN/dtex, preferably in the range of 0.2 cN/dtex to 0.7 cN/dtex.

3. The process as claimed in claim 1, wherein, for relaxation treatment, the filament bundle is guided in a plurality of loopings on a godet pair with heated godets and with conical godet casings.

4. The process as claimed in claim 1, wherein, after relaxation treatment, the filament bundle undergoes fixing treatment at a fixing temperature in the range of 60° C. to 240° C., with a minimum yarn pull force of >0.05 cN/dtex being maintained.

5. The process as claimed in claim 4, wherein, for fixing treatment, the filament bundle is guided in a plurality of loopings on a godet pair with cold godets.

6. The process as claimed in claim 1, wherein, before compression, the filament bundle undergoes heat treatment at a treatment temperature lying below the relaxation temperature, with a minimum yarn pull force of >0.05 cN/dtex being maintained.

7. The process as claimed in claim 6, wherein, for the heat treatment, the filament bundle is guided in a plurality of loopings on a godet pair with heated godets.

8. The process as claimed in claim 1, wherein, for the compression, the filament bundle is conveyed into the stuffing chamber by an air stream of hot air or cold air.

9. A melt-spinning apparatus for producing a crimped yarn, with a melt-spinning device, with a cooling device, with a drawing device, with a crimping device and with a winding device, the drawing device having a take-up godet pair with at least one heated godet and a drawing godet pair with two heated godets, wherein charactcrizcd in that the heated godets, of the drawing godet pair have in each case a stepped or conical godet casing, by means of which relaxation treatment can be carried out on a filament bundle guided in a plurality of loopings, with a minimum yarn tension of >0.05 cN/dtex and a relaxation temperature in the range of 120° C. to 245° C.

10. The apparatus as claimed in claim 9, wherein, between the drawing device and the crimping device, at least one further godet pair is arranged, by means of which fixing treatment or heat treatment can be carried out on a filament bundle guided in a plurality of loopings.

11. The apparatus as claimed in claim 9, wherein, between the drawing device and the crimping device a plurality of godet pairs are arranged, by means of which fixing treatment and heat treatment can be carried out on a filament bundle guided in a plurality of loopings.

12. The apparatus as claimed in claim 9, wherein the crimping device has a conveying nozzle and a stuffing chamber arranged on the outlet side of the conveying nozzle.

13. The apparatus as claimed in claim 12, wherein crimping device has a cooling drum for cooling a yarn plug guided out of the stuffing chamber.

14. A crimped yarn which is made from a thermoplastic polymer and which is produced by means of a single-stage melt-spinning process as claimed in claim 1.