EP0393422A2 - Spinning in water-vapour of segmented polyurethane-urea elastomers - Google Patents

Abstract

The invention provides a process for spinning segmented polyurethane-urea elastomers into dry spinning cells by introducing certain amounts of superheated steam. The process makes possible a remarkable increase in the productivity per cell and also in the spin speed, in particular in the case of medium and high deniers, at high spinning cell temperatures and without undesirable alteration, in fact in some instances with distinct improvement, in the properties of the knitting filament yarns. The novel process more particularly also prevents decomposition tendencies of the spinning solvent at high temperatures (otherwise necessary for substantial spinning solvent removal at high spinning speeds) in air without having to use inert gases as spinning atmosphere. The novel process further makes it possible to produce (multi)filament yarns having higher filament linear densities, which helps to improve the stability of the filament yarns to external influences and degradation effects.

Description

The invention relates to a method for spinning segmented polyurethane urea elastomers in dry spinning chimneys while introducing certain amounts of superheated steam. The process allows an extraordinary increase in the spinning performance per shaft as well as an increase in the spinning speed, in particular in the case of medium and coarse titers, at high spinning shaft temperatures and without undesired change, in some cases even with a significant improvement in the thread properties of the filament yarns obtained. The new process in particular also prevents tendencies of the spinning solvents to decompose at high temperatures in air (otherwise necessary for extensive spinning solvent removal at high spinning speeds) without the use of inert gases as spinning air media. The new process also enables the spinning of (multi) filament yarns with higher single filament titers, which contributes to improving the stability of the filament yarns against external influences and degradation influences.

Highly elastic PU elastomer threads (spandex or spandex threads) are mainly manufactured using wet and, in particular, dry spinning processes. For this purpose, highly viscous solutions of the elastomers in dimethylformamide or dimethylacetamide are spun through multi-hole nozzles into heated spinning shafts, to which hot air is additionally fed (cf. H. Oertel, in synthetic fibers, publisher: B. v Falkai, Verlag Chemie Weinheim 1981, pp. 180 to 190 and H. Gall / KH Wolf in Kunststoff Handbuch, Vol. 7, Polyurethane, 1983, C. Hanser Verlag, pp. 611 to 627).

The temperature of the spinning solution, the temperature in the spinning shaft, the temperature of the additionally supplied hot air and the take-off speed, and the geometric dimensions of the spinning shafts essentially determine the drying out of the filaments with extensive removal of the solvents.

However, it has been found that there are various technological limits to the complete removal of the solvents. If the temperatures near the nozzles are too high - whether due to the solution temperature being too high or the ambient temperature too high - the solution spinning jets will tear off just below the spinneret outlet holes, especially if the take-off speeds are high. An increase in the take-off speed is fundamentally highly desirable for economic reasons, however this measure has so far been limited by a too high pre-orientation of the threads, which among other things results in very steep force expansion stress diagrams with (too) strong reduction in the elongation at break limits.

An increase in the temperature of the spinning air is limited in practice for reasons previously discussed, but also because of thermal discoloration of the threads and because of a thermal instability of the spinning solvent. It has been shown that dimethylacetamide, but also dimethylformamide, increasingly decomposes in the shaft at spinning air temperatures of above approximately 300 ° C. to 350 ° C., increasingly above 350 ° C., and the yield of recoverable solvents decreases. This means that the temperatures are inevitably capped. If nitrogen or combustion gases ("Kemp" gas) are used instead of air as the hot spinning air component, the (oxidative) degradation reaction can be reduced, but the costs and effort increase considerably.

Another problem that is technically and environmentally technologically important is that too much solvent remains in the spun elastomer thread, especially for medium and coarse titers.

Japanese Patent 44-896 (1969) describes a dry spinning process for glycol chain-extended polyurethane elastomers based on higher molecular weight polyesters, diisocyanates and ethylene glycol, dissolved in a mixture of methyl isobutyl ketone / DMF or tetrahydrofuran as a solvent, these polyurethanes being spun in a spinning shaft of at least 150 ° C with introduction above the spinneret from 1 to 30 m³ / h superheated steam at 150 to 400 ° C and at moderate take-off speeds (low spinning performance). Such threads show practically the same properties in comparison to threads spun without water vapor. Volatile solvents such as tetrahydrofuran are used or are also used. Glycol-extended polyurethane elastomers of this type cannot be spun at elevated shaft temperatures and at the same time high temperatures of gaseous spinning media; they tear off or are stretched thermoplastic with an undesirable change in the elastic properties. The spinning performance described by the Japanese process still remains very unsatisfactory for such glycol-extended polyurethanes.

The object of the invention is to provide an improved dry spinning process, according to which the polyurethane urea (PUH -) elastomers, based on diamine chain extension of NCO prepolymers, are made practically completely from highly polar solvents such as dimethylformamide and especially dimethylacetamide, with high spinning performance and without the risk can be spun from decomposition of the spinning solvent at high temperatures to PUH elastomer threads, which now have only a low content of spinning solvent, have a good raw color and also have improved elastic properties compared to threads spun from hot air. The inventive task should be as possible without changing the existing which spinning shafts (especially their length) can be achieved. With the steam quantities of 1 to 30 m³ / h specified in the above-cited Japanese Patent 44 896, corresponding to approximately 0.5 kg / h at 150 ° C. to 13.6 kg / h at 150 ° C. of superheated steam from 150 to 400 ° C, spinning was not possible with the PUH elastomer solutions to be used according to the invention and with the shaft geometry present in our experiments (shaft cross-sectional area 0.0615 m² - shaft diameter = 28 cm). According to the invention, significantly higher amounts of steam are required, preferably more than 50 m³ / h, corresponding to at least 20 kg / h, preferably more than 30 kg / h steam from 250 to 400 ° C. Only with this drastic increase in the amount of steam introduced, preferably 30 up to 45 kg / h of superheated steam from 240 to 400 ° C, accordingly
30 kg / h at 250 ° C = 75 m³ / h (at the appropriate temperature)
45 kg / h at 250 ° C = 112.5 m³ / h
30 kg / h at 400 ° C = 96 m³ / h
45 kg / h at 400 ° C = 144 m³ / h
The polyurethane-ureas to be used according to the invention can be effectively spun, in contrast to the amounts of 1 to 30 m³ / h mentioned in the Japanese patent specification at 150 ° C. to 400 ° C., maximum 0.3 to 13.6 kg / h steam .

The invention relates to an improved dry spinning process of polyurethane elastomer fibers using superheated steam as the spinning medium, characterized in that
Polyurethane urea elastomers which have been produced by diamine chain extension of NCO prepolymers,
from their solutions in dimethylformamide or (preferably) dimethylacetamide
via a spinneret hot at least 100 ° C at spinning solution temperatures in the nozzle of at least 100 ° C, preferably 105 to 125 ° C,
in a heated spinning shaft of at least 160 ° C shaft wall temperature, for example 160 to 238 ° C, preferably 170 to 230 ° C, and in particular 175 to 225 ° C,
and in the case of shaft diameters up to 28 cm at least 20 kg / h, preferably 25 to 50 kg / h, particularly preferably 30 to 45 kg / h, superheated steam of greater than 250 ° C., preferably 275 to 400 ° C., in particular 280 to 325 ° C (measured at the level of the spinneret in the middle of the shaft with free flow) as a hot spinning medium, and for larger shaft diameters preferably with amounts of steam which are around the ratio H of the shaft cross sections, especially only 0.1 H to 0.8 H, in particular only 0.2 to 0.6 H increased amounts of steam, introduced as hot spinning medium,
at the end of the spinning shaft, spin medium and spinning solvent are fed for recovery, and a withdrawal speed of the threads from the shaft of at least 250 m / min, for example at least 400 m / min and preferably 500 to 1500 m / min, in particular 500 to 1200 m / min,
be respected.

According to the method according to the invention, polyurethane urea elastomer threads (PUH threads) can be spun with excellent economy, spinning shaft performance and quality. Despite the sometimes very high spinning speeds (for example zB 500, for example up to 1500 m / min), these polyurethane urea elastomer threads surprisingly do not show the sharp decrease in extensibility and undesirably high module values of the threads in comparison to the usual spinning speeds (for example of about 200 m / min), but surprisingly rather an increase in the elongation at break compared to similar spinning conditions in hot air (if such a spinning is possible at all with hot air). One of the causes may be the interaction between water (steam) and the polyurea hard segments in the PUH elastomers at the high spinning temperatures, while the residual solvent contents remaining at the same time have a reduced solvation effect, but this is only a tentative interpretation of the unexpected results.

The steam spinning process according to the invention is very particularly advantageous for coarser titers (about ≧ 500 dtex, preferably ≧ 1000 dtex) and for relatively coarser filament individual titers (from about 10 to 25 dtex of the weak in the final state of the elastomer filament yarns glued ("coalesced") single filaments (see literature). Until now, such coarse titers had to be spun at a relatively slow speed and reduced power (see comparative example) in order on the one hand to obtain sufficient drying out and on the other hand not to be too strong a prior orientation (reduced extensibility).

Despite the slow spinning speeds in prior art dry spinning processes with coarser titers, however, undesirably high contents (e.g. 1.5 to 3% by weight DMA) of solvents remained in the threads and had to be reduced if necessary by further post-treatment steps.

As can be seen from comparative experiments, according to the process claimed according to the invention, for example in the case of the particularly critical coarse titers (approx. 1300 dtex), the take-off speed can be increased to at least twice (!) The take-off speed (for example from about 250 to 280 m / min to 500 to 600 m / min and thus with at least twice the shaft capacity), the same type of spinning equipment (shaft length equal, shaft diameter equal, spinning hot air media quantity approximately the same, spinning solution temperature identical), the same PUH elastomer solutions are spun without the thread characteristics being undesirably changed if a sufficient amount is overheated Steam is used as hot spinning medium instead of hot air. In addition, the residual content of spinning solvent dimethylacetamide compared to hot air is from about 1.5 to 3% by weight or higher, to ≦ 1.5% by weight, mostly even ≦ 1.0% by weight, although the spinning performance was increased considerably and although high filament single titer or total titer was spun.

It is particularly surprising that the thermal decomposition of the solvents, e.g. Dimethylacetamide, are considerably reduced and the content and the number of different decomposition products (to about 1/3) and the amount of decomposition products is extremely greatly reduced (e.g. by a factor of 50 less), although it was actually to be expected that water (steam ) should cause a very noticeable hydrolysis of dimethylformamide or dimethylacetamide at these high temperatures.

Examinations of the spinning exhaust air behind the spinning cooler, in which the spinning gas and the spinning solvent evaporated in the spinning shaft are condensed, led in the case of the comparative example with spinning air of 400 ° C. (without steam) as spinning gas medium and dimethylformamide as spinning solvent to the following amounts (in mg / l spinning cooler mixture , ie in the solvent condensate) on decomposition products:
Formaldehyde = 2 to 3 mg / l
Formic acid = 170 to 172 mg / l
Dimethylamine = 12 to 13 mg / l
plus other modification products.

In the case of superheated steam (40 kg / h at 400 ° C), instead of air of the same temperature as spinning gas medium, the following quantities of decomposition products are detected analytically:
Formaldehyde = ≦ 2 mg / l
Formic acid = 9 to 17 mg / l
Dimethylamine = ≦ 1 mg / l
practically without further modification products.

As can be seen from the comparative measurements, the number of decomposition products in the case of spinning with superheated steam is reduced by at least a factor of 10 compared to air spinning. This is of considerable ecological importance.

As already stated, the method according to the invention is particularly suitable for medium and coarse titers (approx. 250 to 560 dtex; or> 560 dtex, in particular> 800 dtex) and in particular for thicker single filaments, e.g. ≧ 8 dtex, advantageous because threads with a low residual solvent content are obtained even under these difficult conditions.

However, the process according to the invention is also of great advantage for the fine titer elastomer threads, whereby it turns out to be essential to spin such fine titer at relatively high temperatures - without risk of decomposition of the solvents dimethylformamide and especially dimethylacetamide - and thus to achieve economical production performance and a substantially increased spinning speed . This is particularly the case with spinning processes, where 4, 8, 16 or even 24 thread groups (for example each of 3 to 6 individual filaments) from a single dry spinning shaft. In addition to the high economic effect of spinning performance, the new process also enables product-saving and ecologically better spinning conditions to be achieved.

All diamine chain-extended, segmented PUH elastomers (see literature cited at the beginning) are suitable as polyurethane urea elastomer threads. They are made from NCO prepolymers with about 1.5 to 4% by weight of the NCO end groups and diamines as chain extenders. Aliphatic, cycloaliphatic or araliphatic diamines or their mixtures are used as diamines in the narrower sense, e.g. Ethylene diamine, 1,2-propylene diamine, trimethylene diamine, H₂N.CH₂.C (CH₃) ₂.CH₂.NH₂, 1,3-diaminocyclohexane, isophorone diamine, m-xylylenediamine and many other diamines, but preferably ethylenediamine as the main component, optionally in a mixture of about 30 mol% of 1,2-propylenediamine, 1,3-diaminocyclohexane, piperazine etc. Monoamines can also be used in small amounts as chain terminators / chain regulators. The diamines in the broader sense also include hydrazine and dihydrazide compounds, e.g. Carbodihydrazide, hydrazide semicarbazide, semicarbazide carbazine ester and the like. Links.

The NCO prepolymers are made from higher molecular weight diols, e.g. polyesters (including polylactones), polyethers, preferably polyoxytetramethylene diols, polyether esters etc., with a molecular weight of about 1000 to 4000, by reaction with excess amounts (e.g. 1.5 to 2.5 mol) of diisocyanates such as 4,4'-diphenylmethane diiso cyanate (MDI), tolylene diisocyanate or 1,3-cyclohexane diisocyanate, produced in the melt or preferably in solvents. NCO prepolymers with about 1.5 to 2.9% NCO, or 1.6 to 2.5% NCO and MDI as diisocyanate are preferred.

If necessary, further components can be used in the formation of the NCO prepolymer, e.g. N-methyldiethanolamine or N-methyl-bis- (β-hydroxypropyl) amine.

The NCO prepolymer (solution) s can be reacted continuously or batchwise with the diamine compounds in highly polar solvents such as dimethylformamide or dimethylacetamide, the NCO / NH₂ equivalent ratios being approximately between 0.9 and 1.1.

Starting materials and processes are known from a large number of publications and patents on elastomer threads and can be used to produce the polyurethane urea elastomer solution in the sense of the process. The polyurethane urea elastomer spinning solutions generally have viscosities of about 50 to 250, preferably 70 to 180 Pas at room temperature. The concentrations are generally between 20 to 35% by weight, preferably 22 to 30% by weight.

The spinning solutions can contain customary additives and stabilizers, e.g. white pigments such as titanium dioxide (rutile or anatase), zinc oxides of any purity, zinc sulfide, color pigments or dyes, stabilizers and anti-aging agents, UV stabilizers, non-stick agents such as magnesium stearate and / or zinc stearate (e.g. 0.1 to 0.8% by weight - or any mixtures thereof), zinc oxides, optionally containing up to 4% other oxides such as magnesium oxide, or magnesium carbonate, flow improvers such as silicone oils (polydimethylsiloxanes) or soluble polyoxyalkylene / dimethylsiloxane copolymers. Suitable substances are often named here in the literature.

The elastomer solutions are filtered and fed to the individual spinning chutes. Before being introduced into the spinnerets, the solutions have to be preheated to such an extent that they heat up to at least 100 ° C within the spinnerets, although temperatures of 90 to 95 ° C are sufficient when the solution is supplied and the remaining heat supply exceeds that in the high temperature range ( Spinnluft / steam / shaft heating) is effective to keep the solution temperature and nozzle surface temperature to over 100 ° C to just below the boiling point of the solvent dimethylformamide / dimethylacetamide, preferably 105 to 135 ° C, it is more reliable to process the solution temperature during the supply Einzustellen 100 ° C. This can e.g. happen via short preheating sections and circulation via static mixer elements. The nozzles to be used are also installed in a preheated state ≧ 100 ° C to prevent condensation of water vapor during spinning.

Conventional heated shafts with a length of 5 to 15 m, preferably 7 to 12 m, and diameters of 25 to 70, preferably 27 to 55 cm, are used as spinning shafts. The spinning chutes can be heated over their entire length or on partial lengths, if necessary with different temperatures.

The steam is supplied by a steam heater, which is located at a certain distance from the spinning chimneys. There, in general, somewhat higher temperatures are generated in the steam in order - depending on the insulation / removal etc. - to have the temperatures mentioned on the spinning shaft. The quantities are e.g. certain about pinholes. The temperatures of the steam are determined approximately at the level of the spinnerets. The amount of steam that is introduced into the spinning shaft depends on the cross section of the spinning shaft and, to some extent, on the amount of spinning solution introduced (the amount of spinning solvent in the shaft). With a shaft with a cross section (d = 28 cm) of 615 cm², e.g. the amount of 50 m³ / h superheated steam has a flow rate of 812 m / h (0.225 m / sec). When changing to other shaft cross-sections, the amount of steam may have to be adjusted according to the ratio (H) of the shaft cross-sections, if this appears necessary. The ratio H represents the quotient from the enlarged shaft cross-section to the shaft cross-section of 615 cm² (28 cm shaft diameter). The amount of steam is preferred only to a part of this ratio H, e.g. 0.1 H to 0.8 H (i.e. only a 10% to 80% increase above the amount of steam for the "normal" spinning shaft diameter of 28 cm). In particular, the increase in the amount of steam is only 0.2 H to 0.6 H. The smaller value of x.H is selected especially for the larger shaft diameters.

For economic reasons, the amount of steam is generally reduced to the lowest value necessary for the process set. If the elastomer solution throughput (shaft capacity) and the shaft cross-section are increased at the same time, more steam will tend to be used than if only the shaft cross-section was increased.

Preparation of a polyurethane urea elastomer spinning solution

A polyester with terminal hydroxyl groups and an average molecular weight of 2,000 (OH number of 56) was obtained by reacting 10 kg of adipic acid with 8.1 kg of 1,6-hexanediol and 7.1 kg of 2,2-dimethyl-propanediol-1. 3 (neopentyl glycol) prepared in the usual way. 10 kg of this polyester together with 190 g of N, N-bis (β-hydroxypropyl) methylamine, 2,600 g of 4,4-diphenylmethane diisocyanate (containing 0.6% 2,4-diphenylmethane diisocyanate) and 3.2 kg of dimethylacetamide with stirring for 100 min heated to 50 to 54 ° C until the NCO content of the prepolymer was 2.66% by weight (based on solids). 245 g of ethylenediamine were dissolved in 43.45 kg of dimethylacetamide, placed in a kettle and mixed with 270 g of solid CO₂, so that a carbamate suspension was formed. 16 kg of prepolymer solution (as prepared above) were added to this freshly formed suspension with vigorous stirring. A homogeneous, clear elastomer solution with a solids content of 22% by weight and a solution viscosity of 92.6 Pas was obtained. 4% by weight of titanium dioxide, 0.3% by weight of magnesium stearate and 1% of the silicone oil Baysilon® M100 (Bayer AG) were added to the viscous polymer solution. The solution was further treated with 1% Cyanox® 1790 (stabilizer of the formula 2,4,6-tris (2,4,6-trimethyl-3-hydroxybenzyl) isocyanurate).

Comparative example

A 22% by weight polyurethane urea elastomer solution in dimethylacetamide (see production instructions) was spun on a 8.8 m long spinning shaft with an inner diameter of 28 cm from a 96 hole nozzle with a 0.3 mm hole diameter to give elastomer threads with 1200 dtex fineness. The threads were drawn off under the spinning shaft on a first godet at 375 m / min, taken over from a second godet at 390 m / min and wound onto bobbins at a winding speed of 450 m / min. The spinning shaft (wall heating) temperature was 200 ° C. It was spun with 56 Nm³ / h hot air at 380 ° C. Solution lines and spinning head were preheated to 110 ° C.

The following fiber technology values were determined on the spun elastomer filament yarns:

In a further part of the experiment, attempts were made to increase the temperature of the shaft from 200 to 220 ° C. and in further parts of the experiment to further increase the temperature temperature of 380 ° C to 400 ° C (measured at the outlet of the air heater) to expel the spinning solvent more completely. In all cases, the threads broke after the temperature rises and showed the beginning of yellowing. Obviously the limit of the thermal resistance of the threads was exceeded.

example 1

The 22% by weight PUH elastomer solution in dimethylacetamide described above was spun into threads on an 8.8 m long spinning shaft with a cross section of 28 cm from a 96 hole nozzle with a hole diameter of 0.3 mm. 300 cm³ of spinning solution (approx. 100 ° C.) per minute were pressed through the nozzle. The speed of godet 1) was 415 m / min, of godet 2) 435 m / min and the winding speed was 500 m / min. The spinning shaft temperature (shaft heating) was 200 ° C. It was spun with 40 kg / h superheated steam from 400 ° C (measured on the steam heater / 310 to 320 ° steam temperature near the nozzle). Solution lines and spinning head were preheated to 110 ° C.

The following fiber technology values were determined on the spun elastomer filament yarns: Thread count 1323 dtex Maximum tensile force (based on DIN 53 835, part 2) - simple tensile test) 1397 CN Maximum tensile force expansion (based on DIN 53 835, part 2) - simple tensile test) 487% Elongation force of the thread with delay 1: 4 in rolling take-off 185 cN Residual solvent content dimethylacetamide 0.85% Spinning shaft performance 4.0 kg elastomer filament yarn / h.

Example 2

The 22% by weight solution, as described, was spun on the above-mentioned shaft and with the same nozzles. 325 cm³ of spinning solution at approx. 110 ° C per minute were pressed through the nozzle. The speed of godet 1) was again 415 m / min, of godet 2) 435 m / min. However, the winding speed was increased to 550 m / min. All other spinning data were kept unchanged according to Example 1.

The following fiber technology values were measured on the spun elastomer filament yarns: Thread count 1308 dtex Maximum traction 1216 cN Maximum tensile strength expansion 437% Elongation force of the thread with delay 1: 4 in rolling take-off 262 cN Residual content of solvent dimethylacetamite 0.86% Spinning shaft performance 4.31 g elastomer filament yarn / h.

As can be seen from the examples, with the spin medium superheated steam instead of air, higher spinning speeds can be achieved with significantly lower levels of residual solvent in the elastomer threads with improved fiber technology data. With the method shown here, it can be made clear Realize higher spinning shaft outputs. An increase in the maximum tensile force of the elastomer threads by 30 to 50% compared to the comparative example is obtained. The cause is not exactly known, but must be based on the changed mechanisms of solvent removal. The significantly better residual solvent removal from the elastomer filament threads despite shorter dwell times in the spinning shaft is of great practical / technological importance. In addition to the economic advantages, as already mentioned, significant ecological advances are also made in terms of the type and amount of decomposition products in the spinning exhaust air.

Example 3

As in Examples 1 and 2, the PUH elastomer solution mentioned was spun in dimethylacetamide with 353 cm 3 of spinning solution at 110 ° C. per minute. The speed of godet 1) was 410 m / min, of godet 2) 545 m / min and the winding speed was increased to 600 m / min. It was spun with 45 kg / h steam at 400 ° C (on a steam heater / correspondingly 320 ° near the nozzle). The shaft temperature was 225 ° C. The following fiber technology values were determined on the elastomer filament yarns spun in this way: Thread count 1217 dtex Maximum traction 1208 cN Maximum tensile strength expansion 400% Elongation force of the thread with delay 1: 4 in rolling take-off 401 cN Residual content of dimethylacetamide 0.95% Spinning shaft performance 4.3 kg elastomer filament yarn / h.

In a test variant, the speed was increased from godet 1) to 585 m / min, from godet 2) to 610 m / min and the winding speed to 700 m / min and the amount of elastomer solution passed through was increased to 414 cm 3 / min. The other spinning parameters were kept unchanged. Threads of 916 dtex fineness were obtained. The fiber technology properties largely corresponded to the values from Example 3 / first part of the experiment, the residual spinning solvent content in the threads was only 0.96% by weight, despite the increased spinning performance.

Claims (1)

1. Improved dry spinning process for the production of polyurethane elastomer fibers using superheated steam as the spinning medium, characterized in that
Polyurethane urea elastomers which have been produced by diamine chain extension of NCO prepolymers,
from their solutions in dimethylformamide or (preferably) dimethylacetamide
via a spinneret hot at least 100 ° C at spinning solution temperatures in the nozzle of at least 100 ° C, preferably 105 to 125 ° C,
are spun into a heated spinning shaft of at least 160 ° C shaft wall temperature, preferably 160 to 238 ° C,
and in the case of shaft diameters up to 28 cm, at least 20 kg / h, preferably 25 to 50 kg / h, particularly preferably 30 to 45 kg / h, superheated steam at a temperature of greater than 250 ° C., preferably 275 to 400 ° C., in particular 280 to 325 ° C, and at higher shaft diameters, if necessary, by the ratio H of the shaft cross sections, preferably only by the factor 0.1 H to 0.8 H, in particular only 0.2 to 0.6 H, increased amounts of steam as hot spinning medium be introduced
at the end of the spinning shaft, spin medium and spinning solvent are fed for recovery,
and a withdrawal speed of the threads from the shaft of at least 250 m / min, preferably at least 400 m / min,
be respected.