Process of making fibers which give off troublesome gases and/or vapors during spinning

A process produces fibers from polymers which give off troublesome gases and/or vapors during spinning, comprising the steps of: PA0 a) extruding the molten polymer through a spinneret into a closed spinning shaft, PA0 b) quenching the resulting filaments in the spinning shaft with a gas, PA0 c) taking off the resulting filaments from the spinning shaft, PA0 d) conducting the quench gas away from the spinning shaft and introducing it into a gas purification system and PA0 e) purifying the used quench gas by contact with an adsorbent for said troublesome gases and/or vapors. It is possible by the present invention to keep hazardous gases occurring during the spinning of polymers away from the surroundings and to dispose of them. Suitable polymers are in particular polyphenylene sulfides.

Process and apparatus for producing fibers which give off troublesome gases 
and/or vapors during spinning. 
The present invention relates to a novel process for producing fibers which 
give off troublesome gases and/or vapors during spinning, in particular 
fibers based on polyarylene sulfides, and an apparatus adapted therefor. 
Melt-spinning processes of thermoplastic polymers, in which encapsulated 
spinning shafts are used, are known per se. 
Thus, in EP-A-143,173, a melt-spinning process of thermoplastic polymers is 
described in which the polymer is extruded into a spinning shaft which is 
under superatmospheric pressure and is cooled within this shaft. In 
addition, an adapted apparatus is described for carrying out the process, 
which apparatus is provided with a specially configured outlet orifice for 
the solidified filaments which are taken off at high speed and by which 
good sealing of the spinning shaft can be achieved. The apparatus and the 
process are intended especially for the production of a highly oriented 
multifilament yarn. 
In EP-A-205,694, a melt-spinning process of thermoplastic polymers is 
described, in which the polymer is extruded into a spinning shaft which is 
at a reduced pressure of less than 0.7 atm and is cooled within this 
shaft. The apparatus for carrying out this process relates essentially to 
the apparatus disclosed by EP-A-143,173, at the outlet side of which a 
vacuum pump is connected for the gas situated within the spinning shaft. 
In the description it is mentioned that monomers and oligomers evaporating 
from the spun filaments are removed from the spinning shaft by the gas 
conduction, so that problems with residues depositing in the spinning 
shaft can be avoided. The apparatus and the process are likewise intended 
for the production of a highly oriented multi-filament yarn. 
In the melt-spinning of polymers, troublesome gases and/or vapors are 
frequently liberated. In particular, when polymers containing 
sulfur-containing constituents are spun, strongly smelling and possibly 
even toxic gases or vapors are released. This problem is particularly 
pronounced when multifilaments are spun, since, as a consequence of the 
high surface area of the molten-liquid capillaries, they release large 
amounts of such hazardous gases. 
The object of the present invention is to keep troublesome gases, which are 
produced during the spinning of polymers, away from the surroundings and 
to dispose of them. 
This object is achieved by spinning such polymers into a closed spinning 
shaft, quenching the filaments formed and by subsequent special 
purification of the quench air conducted out of the shaft. 
The present invention relates to a process for producing fibers from 
polymers which give off troublesome gases and/or vapors during spinning, 
comprising the steps of: 
a) extruding the molten polymer through a spinneret into a closed spinning 
shaft, 
b) quenching the resulting filaments in the spinning shaft with a gas, 
c) taking off the resulting filaments from the spinning shaft, 
d) conducting the quench gas away from the spinning shaft and introducing 
it into a gas purification system and 
e) purifying the used quench gas by contact with an adsorbent for said 
troublesome gases and/or vapors. 
The term "fibers from polymers which release troublesome gases and/or 
vapors during spinning" in the context of this invention is taken to mean 
those fibers from which, during melt-spinning, gases and/or vapors are 
released in the spinning shaft, the escape of which into the surrounding 
air is not desired. These include, for example, the so-called "spinning 
fumes" and in particular gaseous and/or vaporous constituents which 
contain sulfur-containing or halogen-containing, in particular 
chlorine-containing, or sulfur- and halogen-containing components. The 
polymers which give off these latter gaseous and/or vaporous constituents 
include sulfur-containing polymers, such as polyarylene sulfides or 
polymers which are provided with halogen- and/or sulfur-containing 
additives before or during spinning. 
The process according to the invention is preferably used in the spinning 
of polyarylene sulfides or in the spinning of mixtures containing 
polyarylene sulfides and other thermoplastic polymers. Polyarylene 
sulfides which can be used in the process according to the invention are 
all filament-forming polymers which principally have the repeating 
structural unit of the formula I 
EQU --At--S--(I), 
in which Ar is a divalent mononuclear or polynuclear aromatic radical whose 
free valencies are in the p-position or m-position or in a parallel or 
angled position to each other comparable to these positions. The polymers 
can also be partially crosslinked structures if these can be spun under 
the above-defined spinning conditions. 
Mixtures of polyarylene sulfide polymers can also be used, or polyarylene 
sulfide polymers which have different repeating structural units of the 
formula I in one molecule. Examples of mixtures of polyarylene sulfides 
are listed in EP-A-407,887, whose contents are also a subject matter of 
the present description. 
Examples of thermoplastics which can be used in a mixture with polyarylene 
sulfides are polyesters, such as polyethylene terephthalate; 
poly-.alpha.-olefins, such as polyethylene or polypropylene; partially 
fluorinated or perfluorinated polymers, such as polytetrafluoroethylene; 
or a polyether ketone adapted to the melting characteristics of the 
polyarylene sulfide. 
The polyarylene sulfides used are preferably polyphenylene sulfides, in 
particular polymers in which Ar is a p-phenylene radical. 
Preferred polyphenylene sulfides have, at 320.degree. C., a melt viscosity, 
measured at a shear rate of 1000 sec.sup.-1 (.eta..sub.1000), of 60 to 150 
Pa*s and a melt viscosity, measured at a shear rate of 3000 sec.sup.-1 
(.eta..sub.3000), of more than 50 Pa*s, in which the difference between 
.eta..sub.1000 and .eta..sub.3000 is more than 20 Pa*s. 
The polyarylene sulfide, prior to spinning, is conventionally subjected to 
a drying process. For this purpose, the polymer, generally in a finely 
divided form, such as a powder form or granular form and in particular in 
the form of chips, is preferably dried under vacuum. Conventional drying 
times are between 6 and 10 hours. The drying temperature is conventionally 
120.degree. to 160.degree. C., preferably 120.degree. to 140.degree. C. 
However, the drying can also be performed under inert gas. 
A polyarylene sulfide is particularly preferably used whose water content 
is at most 0.01%, measured by the Karl-Fischer method. Using this raw 
material, particularly stable spinning conditions can be established. 
In the process according to the invention, filament-forming polymers are 
melt-spun, the molten polymer being spun by means of an extruder and a 
spinning pump through a spinneret into a closed spinning shaft. 
The minimum throughput of polymer through the spinneret is preferably 0.5 
g/(min*hole). Particularly preferred throughputs are in the range from 0.7 
to 1.3 g/(min*hole). 
In the case of the preferred polyphenylene sulfide, the temperatures in the 
spinneret are conventionally 280.degree. to 320.degree. C., preferably 
295.degree. to 315.degree. C. 
Any type of spinneret can be used. Typical numbers of holes in a spinneret 
are in the range from 50 to 500, in particular from 100 to 500. The shape 
of the spinneret holes can likewise be selected as desired, for example 
triangular or rectangular, multilobal, oval or, in particular, round. 
Typical diameters of the spinneret holes are in the range from 0.25 to 
0.65 mm. 
The spinneret holes in a ring spinneret are preferably arranged in the form 
of concentric circles. 
Spinning is carried out into a closed spinning shaft into a gas, in 
particular into air, or else into an inert gas, such as nitrogen. 
The term "closed spinning shaft" in the context of this invention is taken 
to mean a spinning shaft in which the intake and offtake of the quench gas 
is principally, for example up to more than 90%, achieved via the feedline 
and discharge line for the quench gas and in which only a small part of 
the quench gas leaves the spinning shaft through the outlet orifice for 
the filaments formed. 
This outlet orifice must therefore be configured in such a way that, in 
addition to the high rate of passage of the filaments formed, it also 
permits a good seal against an exit of the contaminated quench air in the 
interior of the spinning shaft. 
The freshly spun filaments can thus, for example, be conducted outwards 
through a labyrinth seal or through perforated end plates, below or 
between which an additional auxiliary extractor removes the entrained 
quench gas by suction. 
The spinning shaft can be operated at reduced pressure, external pressure 
or superatmospheric pressure. A slight reduced pressure is advantageously 
maintained in the spinning shaft, preferably a pressure reduced by between 
20 and 150 Pa with respect to the surroundings. This variant, in the case 
of leaks or pressure variations, prevents an immediate flowing-out of the 
contaminated quench air into the surroundings. 
The filaments produced, after the extrusion through the spinneret, are 
subjected to forced cooling in the spinning shaft by quenching with a gas. 
In this case, all quenching processes which are conventional per se can be 
used. In addition to the possible transverse quench, the central quench, 
in particular, is useful. Of these, in particular the quench from the 
inside to the outside is preferred. The gas used can be an inert gas, such 
as nitrogen. Air is preferred. 
The spinning take-off velocity of the filaments on leaving the spinning 
shaft can be more than 500 m/min, preferably between 800 and 5000 m/min, 
and in particular 1000 to 2000 m/min. 
Expediently, a conventional drawing preparation is applied to the filaments 
on leaving the spinning shaft. This can be carried out shortly before, 
during or shortly after leaving the spinning shaft. However, the 
preparation can alternatively be applied at other positions of the 
production plant. The application of the preparation can be carried out by 
all means known therefor, for example by spraying or by application with a 
preparation roll. 
The quench gas loaded with sulfur-containing gases and/or vapors is fed 
from the spinning shaft via one or more discharge lines to a gas 
purification system. It has been shown that the used quench air must be 
purified by contact with an adsorbent for said troublesome gases and/or 
vapors. 
Examples of suitable adsorbents are silica gel or, in particular, activated 
charcoal. 
The adsorbents are preferably used in drum-like containers furnished with 
an intake and outlet and preferably with the required ventilator. Such gas 
purification systems are obtainable commercially in a modular structure. 
After leaving the spinning shaft and, possibly, after application of the 
preparation, the spun filaments are further treated in a manner known per 
se. For this purpose, for example, they are subjected to application of a 
finishing, drawing which, if required, can also be multi-stage, and, if 
required, a fixing. The further processing can be performed continuously 
directly after the take-off from the spinning machine or after an 
intermediate storage of the freshly spun filaments. 
At the end of the further processing stage, the filaments obtained are 
either wound up or chopped in a manner known per se to form staple fibers.

The thermoplastic polymer to be spun is melted via an extruder (1) and 
transported to a spinning pump (2). The extruder is fed, for example, with 
polymer chips. The spinning pump (2) feeds the spin pack (3) which 
contains a filter (4) and spinnerets (5). The spinnerets (5) open out 
directly into a closed spinning shaft (6) which is provided with at least 
one feedline (7) and one discharge line (8) for the quench gas. In the 
representation of FIG. 1, two discharge lines (8) for the quench gas are 
depicted at the top and bottom end of the spinning shaft. In addition, in 
this FIG. 1, an auxiliary extraction line (12) for the quench gas is 
further provided, which is mounted at the bottom end of the spinning shaft 
next to the outlet orifice for the filaments. In the representation of 
FIG. 1, all discharge lines for the quench gas are equipped with a gas 
purification system (9). However, it is absolutely possible for all 
discharge lines to open out into one gas purification system. The purified 
quench air is withdrawn from the gas purification system via pumps (18). 
In addition, in FIG. 1, a central quench apparatus (11) is depicted from 
which the quench gas (10) flows radially from the inside to the outside 
through the filaments formed. Such quench apparatuses can be formed from 
tubes whose casing is provided with boreholes or other openings such as 
slots or screens or which is preferably composed of sintered metal. 
The central quench from inside to outside is particularly advantageous 
since with this embodiment, a particularly stable run of the filaments is 
made possible. 
After leaving the spinning shaft through the outlet orifice (13), the 
filaments (14) receive an application of preparation by application rolls 
(15), are conducted via a reversing godet (16) and wound up on a bobbin 
(17). The spun filaments can finally be supplied to further processing. 
To control the pressure within the spinning shaft, the quench gas is 
expediently blown in via a ventilator through the feedline (7) into the 
closed spinning shaft (6). At least one of the discharge lines (8) is 
equipped with a second ventilator, for example the extraction line at the 
bottom end of the spinning shaft in FIG. 1. In normal operation, the 
pressure in the interior of the spinning shaft can be regulated by the 
different output of the ventilators in the feedline and discharge line. 
To operate the spinning plant, the spinning shaft must be opened when the 
plant is operating. For this purpose, the spinning shaft is preferably 
provided beneath the spinneret with an apparatus which permits the 
spinning shaft to be opened during operation of the plant. In order to 
prevent exit of contaminated quench gas, it is expedient if a second 
powerful extractor is mounted in the region of the shaft opening beneath 
the spinneret, preferably on both sides beneath the spinneret, which is 
turned on when the shaft doors are opened and which prevents the exit of 
contaminated quench gas into the space in front of the shaft when the 
doors are open.