DE19705113C2 - Stretching device and method for producing stretched plastic filaments - Google Patents

Description

Technical field

The invention relates to an apparatus and a method for producing stretched Plastic filaments, after which melt-spun filaments with a Individual titers of greater than 1 dtex at least behind a spinning device Solidification temperature cooled and by means of a pneumatic Take-off device are stretched, for the production of plastic threads, Staple fibers or nonwovens.

State of the art

The production of plastic filaments by melt spinning consists in essentially from three process steps. First the polymer is by means of of an extruder melted, followed by spinning the filaments by means of a spinneret provided with capillary holes or several spinnerets. Finally, the spun is stretched Filaments to achieve a reduction in cross-section. The Reducing the cross section of the spun filament is for many technical and textile applications an essential requirement.  

The drawing process is a crucial step in the process Possible uses of these filaments can be immediate continuously and / or automatically, be integrated into the spinning process or as an independent process step in the manufacturing process.

The filaments are stretched by means of a draw-off device mechanically via godets or pneumatically via a Jet.

Regardless of the type of integrated trigger device, pneumatic or mechanically, they have at high spinning speed, i.e. H. larger than 3500 m / min clearly spun filaments on a single-stage system poorer mechanical properties, such as strength and Young's modulus than that of the lower spinning speed, i.e. H. smaller than 3500 m / min filaments spun in an additional Process step have undergone post-stretching.

In the one-step process, a high spinning speed favors the Training of improved mechanical properties compared to a lower spinning speed, but at the same time also in the filament even structural differences between the surface and the interior of the Filaments created for a reduction in strength or Modulus of elasticity of the filaments compared to a re-drawn filament are responsible.

US 2 604 667 teaches the manufacture of oriented threads without special ones Stretching device for post-stretching by using a Take-off speed of at least 4700 m / min. This high Speed is required to achieve high strength. Will the  If the speed falls below, the filaments produced have a high Strain. To achieve this pull-off speed, you can driven rollers or an air nozzle can be used. U.S. 2,604,667 deals primarily with the production of yarns, but is also mentioned the production of staple fibers when using an air nozzle as Trigger device.

For the production of spunbonded fabrics from spun, endless filaments it is known to stretch the exits from the spinneret Filaments by means of a pneumatic nozzle operated in the supersonic area a trigger device. Several solidified filaments each are by means of the nozzle of a storage device for the production of Spunbond supplied. The one exerted on the filaments by air friction Force enables the trigger speed to be adjusted and thus the Influencing the mechanical properties of the filaments. Here has It has been shown that the influencing of the properties of the filaments limits are set. Despite increasing the take-off speed, what by the Increasing the pressure of the air supplied to the nozzle can happen Strength hardly increased any further and the elongation hardly decreased any further become.

From DE-OS 21 17 659 is a method for producing threads and Fibers by melt spinning capillaries from synthetic, linear Known polymers that works at take-off speeds up to 3500 m / min. The withdrawal speed is by the speed of one Specified pair of godets. To influence the stretch is between a spinneret and the withdrawal godets arranged a heating element, in which is a plastic filament consisting of 50 filaments at temperatures above the solidification point and below the melting temperature  is heated, whereby a stretch ratio of up to 1: 2 is achieved. Farther becomes the production of spunbonded nonwovens from filaments with a fine single titer and specifically adjusted strength and elongation mentioned, but without this to elaborate.

DE 29 25 006 A1 describes the effect of stretching on the Strength on the one hand and on the stretch and shrink on the other received. It is stated that the filaments are stretched get higher strength while stretching and shrinking can be reduced. The higher compared to DE-OS 21 17 659 Take-off speeds of 4100 to 6000 m / min are achieved by the Use slightly red-hot heating elements in direct contact with the Filaments reached.

For the production of plastic fibers from polymers, especially polyamide, Polyester or polypropylene by melt spinning is made from DE 40 21 545 A1 a system with at least one spinneret, a blow shaft, a heating shaft, a preparation device, godet and one Coil device known, the heating shaft generating countercurrent Blow devices, e.g. B. has blowing nozzles. With this system you can fully stretched plastic threads or fibers are produced, the individual fibers or filaments have a single titer less than 1 dtex. On this system and according to this process, are fully drawn Plastic threads produced without after-treatment, which turned into a special let fine and supple goods be processed. Whether the facility for higher titer ranges has sufficient stretching properties not executed.  

DE-OS 22 05 273 describes a process for producing a nonwoven fabric known, in which the threads emerging from the spinneret by means of Cooling air can be cooled and at a distance from the spinneret Arranged contact surface are passed, the threads on a Temperature below the melting point were heated. With this The threads continue to be moved by a pressurized air Injector guided so that the threads of the flowing through the injector Compressed air can be subjected to tension. The threads are stretched. The disadvantage here is that due to the touch of the thread with the Contact surface only one-sided frictional stresses are formed by the thread.

In DE-Z: Chemical Fibers International, Volume 46, January 1996, pages 37 to 40 describes a process for producing drawn yarn, in which the yarn before spinning the filaments into a thread and the subsequent winding on a godet through a heating channel with in Counter current to the direction of movement of the individual filaments Air is passed through. Due to the entire outer surface of the The air friction acting on individual filaments can be used to stretch and Affect the strength of the yarn produced.

The object of the invention is to provide a device and a To provide methods which are suitable for the production of stretched plastic filaments with a titer greater than 1 dtex To produce filaments with increased strength and reduced elongation.  

Presentation of the invention

According to the invention, the stretching device has one between the spinning device and the extraction device arranged heating device with a countercurrent to the Plastic filaments listed heating medium flow.

With the method according to the invention for the production of stretched plastic filaments, after which melt-spun filaments behind a spinning device cooled at least to the solidification temperature and by means of a pneumatic take-off device are stretched with a subsequent heating in a heater for the purpose of Drawing, the filaments in the heater being made by one gaseous fluid heated to a temperature above the solidification point Plastic filaments can be blown in counterflow are generated which have a higher strength with less elongation with respect to the prior art.

These filaments require no further post-stretching and enable the process to be carried out at lower take-off speeds than before. The process is carried out in such a way that post-drawing takes place between the heating device and the take-off device in a drawing ratio of 1.1 to 1.5. Furthermore, the filaments are blown in countercurrent at a temperature of 200 ° C to 350 ° C, in the case of PET or PA 66 preferably 225 ° C to 300 ° C. The air volume will vary from 5 m ³ / h to 25 m ³ / h.

With this process, endless filaments can be made from thermoplastic Plastic, for example polyester, polyamide, polypropylene, polyethylene etc., by single or multiple spinning (two-layer, segmented, coaxial, etc.) for technical or textile applications. The mechanical properties of those produced by melt spinning Filaments improve significantly. In particular with the same titer, the improves  Tensile strength, elongation, modulus of elasticity and thermal Shrinkage.

The heating device can be supplied with hot air or in countercurrent another hot, preferably neutral gas, but also with additives staggered gas mixtures. The air gets to temperature heated, which is above the solidification temperature of the filaments.

The operation of the heater is based on the fact that between the Spinning device and the take-off device by countercurrent led heating means an area for "holding" or "braking" the heated Filament bundle is created. This is attacking another Stretching force by means of the downstream of the area Trigger device possible and there is an additional stretching. The Elongation is due to the difference in the rate of entry Filaments in the heater and the rate of entry of the filaments defined in the trigger device.

Surprisingly, it has been shown that the pneumatic Extraction device, which works on the principle of air friction, also with can be combined with a heating device that works in countercurrent. The filaments thus obtained experience one at the same take-off speed Increase in strength and decrease in elongation. A Another major advantage is that for the production of filaments With certain properties, the pull-off speed is drastically reduced can be.  

To achieve a significant improvement in strength and elongation it is sufficient if the filaments with a take-off speed of 2000 m / min to 4700 m / min through the counterflow. Nevertheless the improvement in properties occurs even at higher speeds on.

With the method, the properties of the to be manufactured Plastic filaments are affected. So it is possible to change the amount of air and the Adjust the temperature of the countercurrent flow so that a thread stretch less than 60%. It is possible to change the speed of the filaments Set the air volume and the temperature of the counterflow air so that at same pull-off speed a relative increase in the tensile strength of the post-drawn filaments of at least 20% compared to a simple drawn filament is achieved, preferably a tensile strength of Filaments of at least 32 cN / tex, particularly preferably 34 to 45 cN / Tex is achieved. It is also possible to determine the amount of air and the temperature of the counterflow air Set so that a hot air shrinkage of at most 6% (at 180 ° C, 15 min) is achieved. This applies in particular if PES is used as the material.

It is also advantageous to determine the rate at which the filaments are drawn off Set the air volume and the temperature of the counterflow air so that the Transition of the area of elastic deformation to the area of plastic Deformation only takes place under a force that is at least 20% higher.

Although the filaments are stretched, it is possible to remove the filaments in the Connection to the countercurrent treatment continuously or in a redraw separate treatment stage again.  

As a further process step, the plastic filaments can be used for production a fleece are placed on a support or for the production of Staple fibers are cut, the cut filaments for Processing can be filled in further processes.

The use of plastic filaments for production is particularly advantageous of a fleece, the filaments having a tensile strength of at least 32 cN / tex and an elongation less than 60%. To make a Spunbond, the plastic filaments can be deposited as continuous threads, to produce a nonwoven fabric, the plastic filaments can be used as Staple fibers are placed.

The use of plastic filaments for production is also advantageous of yarns, the filaments having a tensile strength of at least 32 cN / tex and have an elongation less than 60%. The yarns can be made endless plastic filaments or made of staple fibers be spun.

Brief description of the drawing

In the drawing is a stretching device for the production of stretched plastic filaments shown schematically. It shows the:

Fig. 1 shows the essential components of the system, the

Fig. 2 shows a curve of the speed of a filament bundle according to the invention in comparison to conventional systems and

Fig. 3 shows the characteristics of various mechanical properties.

Implementation of the invention

The drawing device shown in FIG. 1 for the production of drawn plastic fibers comprises a spinning device 1 , which is supplied with melted plastic in a known manner. A number of filaments 2 , which together form a bundle of filaments 3 , emerges via spinnerets arranged in the spinning device 1 and corresponds to the number of openings in the spinnerets. Usually 16, 32 or 64 filaments are combined into a filament bundle. After emerging from the spinneret, the filaments 2 are cooled below the solidification temperature, and an additional cooling device 4 can be provided. Crystalline and amorphous zones form in the individual filament.

The cooled filaments 2 are now fed to a heating device 5 and bundled there so that the heating device 5 runs in parallel. The heating device 5 has a heating shaft 6 , at the lower end 7 of which hot air 8 is fed in relation to the spinning device and at the upper end 9 of which the air emerges again. In the heating shaft 6 , the air 8 is consequently guided in countercurrent to the filament bundle 3 .

At a certain distance from the heating shaft 6 , the take-off device 10 is arranged, with which a pulling force is exerted on the filament bundle 3 . This is done pneumatically via a Venturi nozzle 11 , which is supplied with air 12 under high pressure, so that the narrowest cross-section the speed of sound is reached and the speed of sound is exceeded in the further course.

The filament bundle 3 emerging from the take-off device 10 can be processed in a known manner into a plastic thread, cut to produce staple fibers or used to produce a spunbonded nonwoven. The latter is described for example in FR 74 20 254.

In FIG. 2, an overview of the speed curve of the spun filaments for various systems and methods is shown. Under the usual conditions of direct spinning and stretching of the filaments in one step and at high speed, here a take-off speed of 6000 m / min, the filaments experience a shock-like cooling due to the very high speed gradients in the longitudinal and transverse directions, see curve A. Along The speed gradient of the spinning path is greater than 2 × 10 ⁴ 1 / s, and the cooling rate is of the order of 26,000 ° C./s. These extreme conditions create a different, heterogeneous structure in the filament between the sheath and the core of the filament. Compared to the filaments post-drawn in a multi-stage process, this results in a drop in certain mechanical properties.

A reduction in speed to 4400 m / min take-off speed reduces the speed gradient and the cooling speed clear how can then be read from curve B. However, takes also the breaking load and the elongation at break.

In order to increase the despite the advantageous low take-off speeds To obtain breaking load and a reduction in elongation at break uses two-stage mechanical processes that have a first range with a high speed gradient and a second area have high speed gradients. The speed course curve C shows a two-stage mechanical process.  

By using a heating device with filaments blown by countercurrent, heated air between the spinneret and the take-off device, the course according to the invention shown in curve D is achieved at a take-off speed of 4400 m / min. The filaments heated above the solidification point are stretched over a length L of the heating device 5 .

Table 1 shows various test results with and without Heater for different mass flow rates from Polyethylene terephthalate (PET) with a melting point of 256 ° C and one Viscosity of 190 Pa s at 290 ° C compared.

In a first test arrangement T, a drawing device consisting of spinning device 1 and take-off device 10 was used for the production of filaments.

The second experimental arrangement V differs from the first in that a heating device 5 was provided between the spinning device 1 and the take-off speed 10 , in which the filaments were heated with air which was conducted in countercurrent and heated to a temperature above the solidification temperature. It is possible that the filaments 3 are heated above their solidification temperature, but that the melting temperature is nevertheless not reached.

The tests were carried out for both test arrangements on the one hand Mass flow of 1 g / min per capillary opening of the spinneret (T1, V1.1, V1.2) and on the other hand with a mass throughput of 0.62 g / min each Capillary opening of the spinneret (T2, V2) performed.  

When comparing the essential properties of the first Test series produced filament can be found first that the Pull-off speed of the filament in tests V1.1 and V1.2 has decreased significantly compared to T1. This can be explained by that the frictional forces in the heater due to the pressure increase in the Trigger device were not fully compensated. A direct one Comparison of the mechanical properties of two with the same Take-off speed according to the two test arrangements T, V Filaments produced are therefore not possible here.

But you can see that despite one decreased from 4770 m / min to 3330 m / min Peel speed the strength from 30.3 cN / tex to 39.7 cN / tex increased and the elongation was reduced from 72.6% to 57.1% (T1 and V1.2). This makes it possible to produce high strength filaments in an area of medium take-off speed. An increase in Speed in the test setup with heater to 4000 m / min leads to a further improvement in strength of 39.7 cN / tex to 42.5 cN / tex and a reduction in elongation from 57.1% to 43.7% (V1.2 compared to V1.1).

In the second test series V2, T2, a mass throughput polymer / hole was of 0.62 g / min. Also decreased in the finer titer range the take-off speed. The strength improved considerably Measurements from 27.7 cN / tex to 36.6 cN / tex and the elongation was also from Significantly reduced from 82.6% to 47.6%.  

Table 1

In FIG. 3, the force-elongation curve is that of experiments T1, V1, V1.1, V1.2; T2, V2 resulting filaments compiled. One can see the extraordinarily large influence of the heating device on both the strength and the elongation. Of particular importance is the substantial improvement in elongation in the range of forces higher than 10 cN / tex. The improved filaments can take significantly more load here without experiencing excessive stretching. This behavior is still largely the case even with filaments produced with reduced take-off speed in accordance with V1.2 or V2.

The filaments emerging from the approximately 300 ° C. hot spinning device were cooled by air flow at room temperature, the filaments in the heating device were heated with a volume flow of air heated to 270-300 ° C. between 10 and 15 m ³ / h. It goes without saying that the temperature of the gaseous fluid 8 for polyolefins must be adjusted according to the respective melting temperature. The mass flow rate of gaseous fluid 8 depends, among other things, on the amount of filaments to be drawn, the polymer or polymers used, the degree of drawing and the pre-drawing between the spinning device 1 and the heating device 5 .

The filaments are suitable due to their improved mechanical Properties particularly for the production of nonwovens, being used as a material thermoplastics, especially PET, but also polyester (PES), Polyamide (PA), polyamide 6.6 (PA 6.6), polypropylene (PP) or Polybutylene terephthalate (PBT) come into question. The filaments can too be made from several different materials, known ones Spinning techniques are used.

Claims (21)

1. stretching device for the production of stretched plastic filaments ( 2 , 3 ), comprising a spinning device ( 1 ), and a pneumatic means ( 11 ) for generating a tensile force on the plastic filaments ( 2 , 3 ) comprising withdrawal device ( 10 ), characterized in that between the spinning device ( 1 ) and the take-off device ( 10 ) is arranged a heating device ( 5 ) with a heating medium flow ( 8 ) which is conducted in counterflow to the plastic filaments ( 2 , 3 ). 2. Stretching device according to claim 1, characterized in that Means for producing a spunbonded fabric are provided. 3. Stretching device according to claim 1, characterized in that means for producing staple fibers, for example for the Manufacture of non-woven fabrics are provided. 4. A process for the production of stretched plastic filaments ( 2 , 3 ), according to which melt-spun filaments ( 2 , 3 ) with a single titer greater than 1 dtex are cooled behind a spinning device ( 1 ) at least to the solidification temperature and stretched by means of a pneumatic take-off device ( 10 ), characterized in that the filaments after cooling and prior to entry into the trigger mechanism for the purpose of stretching are heated in a heating device (5), wherein the filaments in the heating device (5) from a gaseous to a temperature above the solidification point of heated fluid ( 8 ) be blown in counterflow. 5. The method according to claim 4, characterized in that between the heating device ( 5 ) and the take-off device ( 10 ) is post-stretching in a stretching ratio of 1.1 to 1.5. 6. The method according to claim 4 or 5, characterized in that the filaments ( 2 , 3 ) at a temperature of 200 ° C to 350 ° C, preferably 225 ° C to 300 ° C, are blown in countercurrent. 7. The method according to any one of claims 4 to 6, characterized in that the filaments are blown in counterflow with an amount of air from 5 m ³ / h to 25 m ³ / h. 8. The method according to any one of claims 4 to 7, characterized in that the filaments with a take-off speed of 2000 m / min 4700 m / min through the counterflow. 9. The method according to any one of claims 4 to 8, characterized in that the amount of air and the temperature of the counterflow air are set so be that a thread stretch less than 60% is achieved. 10. The method according to any one of claims 4 to 9, characterized in that that the withdrawal speed of the filaments, the amount of air and the Temperature of the counterflow air can be set so that at the same Take-off speed a relative increase in the tensile strength of the post-drawn filaments of at least 20% compared to one simply drawn filament is obtained, preferably one Tensile strength of the filaments of at least 32 cN / tex, especially preferably 40 to 50 cN / tex is achieved.   11. The method according to any one of claims 4 to 10, characterized in that that the withdrawal speed of the filaments, the amount of air and Temperature of the counterflow air are set so that the transition of the Range of elastic deformation in the range of plastic deformation only under a force increased by at least 20%. 12. The method according to any one of claims 4 to 11, characterized in that that the amount of air and the temperature of the counterflow air are set so that a hot air shrinkage of at most 6% (at 180 ° C, 15 min) is achieved. 13. The method according to any one of claims 4 to 12, characterized in that that the filaments following the counter current treatment post-stretched continuously or in a separate treatment stage become. 14. The method according to any one of claims 4 to 13, characterized in that the plastic filaments ( 2 , 3 ) for producing a nonwoven are placed on a carrier. 15. The method according to any one of claims 4 to 13, characterized in that the plastic filaments ( 2 , 3 ) are cut to produce staple fibers. 16. Fleece comprising using a stretching device one of claims 1 to 3 or by a method according to one of the Claims 4 to 15 produced stretched plastic filaments, thereby  characterized in that the filaments have a tensile strength of at least 32 cN / Tex and an elongation less than 60%. 17. Fleece according to claim 16, characterized in that the Plastic filaments are stored as filaments. 18. Fleece according to claim 16, characterized in that the Plastic filaments are available as staple fibers. 19. Yarn comprising using a drawing device after one of claims 1 to 3 or by a method according to one of the Claims 4 to 15 produced stretched plastic filaments, thereby characterized in that the filaments have a tensile strength of at least 32 cN / tex and an elongation less than 60%. 20. Yarn according to claim 19, characterized in that the Plastic filaments are filaments. 21. Yarn according to claim 19, characterized in that the Plastic filaments are available as staple fibers.