U.S. patent application number 11/240993 was filed with the patent office on 2006-04-20 for method and device for producing post-stretched cellulose spun threads.
This patent application is currently assigned to ZIMMER AKTIENGESELLSCHAFT. Invention is credited to Lutz Glaser, Werner Schumann, Klaus Weidinger, Stefan Zikeli.
Application Number | 20060083918 11/240993 |
Document ID | / |
Family ID | 33038843 |
Filed Date | 2006-04-20 |
United States Patent
Application |
20060083918 |
Kind Code |
A1 |
Zikeli; Stefan ; et
al. |
April 20, 2006 |
Method and device for producing post-stretched cellulose spun
threads
Abstract
The invention relates to a method and device for producing
Lyocell fibres from a spinning solution containing water, cellulose
and tertiary amine oxide. The spinning solution is extruded to form
spun threads (10). The spun threads (10) are stretched and passed
through a precipitation bath (16) in order to precipitate the
cellulose. It has been surprisingly revealed that the tenacity of
the Lyocell fibres produced in this way can be increased when the
stretched fibres are subjected to post-stretching in a
post-stretching means. The post-stretched Lyocell fibres have a wet
modulus of at least 260 cN/tex.
Inventors: |
Zikeli; Stefan; (Regau,
AT) ; Weidinger; Klaus; (Lenzing, AT) ;
Glaser; Lutz; (Rudolstadt, DE) ; Schumann;
Werner; (Bad Blankenburg, DE) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH, LLP
100 E WISCONSIN AVENUE
MILWAUKEE
WI
53202
US
|
Assignee: |
ZIMMER AKTIENGESELLSCHAFT
Frankfurt
DE
|
Family ID: |
33038843 |
Appl. No.: |
11/240993 |
Filed: |
September 30, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP04/01268 |
Feb 11, 2004 |
|
|
|
11240993 |
Sep 30, 2005 |
|
|
|
Current U.S.
Class: |
428/364 ;
264/203; 264/210.8; 425/71 |
Current CPC
Class: |
Y10T 428/2913 20150115;
D02G 1/12 20130101; D01F 2/00 20130101 |
Class at
Publication: |
428/364 ;
264/203; 264/210.8; 425/071 |
International
Class: |
D02G 3/00 20060101
D02G003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 1, 2003 |
DE |
10314878.7 |
Claims
1. Method for the production of Lyocell fibres from a spinning
solution containing water, cellulose and tertiary amine oxide, the
method comprising: extrusion of the spinning solution to spun
threads; stretching of the spun threads; passage of the spun
threads through a precipitation bath; and post-stretching and
simultaneous heat treatment of the stretched spun threads after
passage through the precipitation bath.
2. Method according to claim 1, further comprising: coagulation of
the cellulose of the spun threads before stretching.
3. Method according to claim 1, further comprising: post-stretching
with a tensile stress of at least 0.8 cN/tex.
4. Method according to claim 3, further comprising: post-stretching
with a tensile stress of at least 3.5 cN/tex.
5. Method according to claim 1, further comprising: treatment of
the spun threads during heat treatment with hot inert gas.
6. Method according to claim 1, further comprising: treatment of
the spun threads during heat treatment with steam.
7. Method according to claim 1, further comprising: passage of the
spun threads through an air gap before the precipitation bath.
8. Method according to claim 7, further comprising: blowing of the
spun threads in the air gap with a flow of cooling gas.
9. Method according to claim 1, further comprising: conveyance of
the spun threads free of tensile stress between the stretching and
the post-stretching.
10. Method according to claim 1, further comprising: crimping of
the post-stretched spun threads.
11. Method according to claim 1, further comprising: cutting of the
post-stretched spun threads to form staple fibres.
12. Device (1) for the manufacture of spun threads from a spinning
solution containing cellulose, water and a tertiary amine oxide,
with a spinneret, through which the spinning solution can be
extruded in operation to form spun threads, with a precipitation
bath with a precipitating agent to precipitate cellulose, through
which the spinning threads are passed in operation, with a first
stretching means, through which the spun threads can be stretched
in operation, and with a second stretching means, through which the
spun threads stretched by the first stretching means can be
post-stretched in operation, and a heating device arranged in the
region of the second stretching means and by which the spun threads
can be heated in operation during the post-stretching, wherein the
spun threads can be stretched by the first stretching means in an
air gap before entering the precipitation bath.
13. Lyocell fibre, in particular manufactured by the method
according to claim 1, wherein a wet modulus of at least 250 cN/tex
and by a wet abrasion number per 25 fibres of at least 18.
14. Lyocell fibre according to claim 13, wherein a wet modulus of
at least 300 cN/tex.
15. Lyocell fibre according to claim 14, wherein a wet modulus of
at least 350 cN/tex.
16. Cellulose fibres according to claim 13, wherein a wet tensile
force elongation of at the most 12%.
17. Cellulose fibres according to claim 13, wherein a wet abrasion
number per 25 fibres of at the most 25.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of International
Application No. PCT/EP2004/001268 filed Feb. 11, 2004, which claims
priority to German Application No. 103 14 878.7 filed on Apr. 1,
2003. Priority to each of these applications is hereby claimed. The
subject matter of each of these applications is also hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] The invention relates to a method for the production of
Lyocell threads from a spinning solution containing water,
cellulose and tertiary amine oxide as well as the spun threads
produced by this method.
[0003] Furthermore, the invention relates to a device for the
manufacture of spun threads from a spinning solution containing
cellulose, water and tertiary amine oxide, with a spinneret,
through which the spinning solution can be extruded in operation to
form spun threads, with a precipitation bath with a precipitating
agent to precipitate cellulose, through which the spinning threads
are passed in operation, with a first stretching means, through
which the spun threads can be stretched in operation, and with a
second stretching means, through which the spun threads stretched
by the first stretching means can be post-stretched in operation,
and with a heating device arranged in the region of the second
stretching means and by which the spun threads can be heated in
operation during the post-stretching.
[0004] With the manufacturing method the spinning solution is first
extruded to spun threads, then the spun threads are stretched and
passed through a precipitation bath, and thereafter the cellulose
of the spun threads coagulates.
[0005] The method of producing spun threads (in the following the
terms "fibres" and "threads" are used synonymously) from cellulose
dissolved in a tertiary amine oxide such as
N-methyl-morpholine-N-oxide and water, also termed the Lyocell
method, goes back to the patent specifications U.S. Pat. No.
4,142,913, U.S. Pat. No. 4,144,080, U.S. Pat. No. 4,211,574, U.S.
Pat. No. 4,246,221, U.S. Pat. No. 4,261,943 and U.S. Pat. No.
4,416,698. In these patent publications, attributable to McCorsley,
the fundamental principle of the production of Lyocell fibres with
the three process steps of extruding the spinning solution to spun
threads in an air gap, stretching of the extruded spun threads in
the air gap and precipitation of the cellulose in a precipitation
bath was first described.
[0006] After the precipitation and coagulation of the cellulose,
the spun threads can be passed on for further processing steps.
Thus, the spun threads can be washed, dried and treated or
impregnated with additives. The spun threads can be cut for the
production of staple fibres.
[0007] The advantage of the Lyocell method lies in the good
environmental compatibility and in the excellent mechanical
properties of the spun threads or fibres. Through various further
developments of the method developed by McCorsley the efficiency
could be significantly improved.
[0008] The Lyocell fibres differ with regard to their structure and
their textile properties and in their manufacture from the other
cellulose fibres, such as described, for example, in DE-A-100 16
307, WO-A-01/58960, DE-A-197 53 806, DE-A-197 21 609, DE-A-195 11
151 and DE-A-43 12 219.
[0009] A special problem of the Lyocell method compared to the
methods described there lies in the high surface adhesion of the
freshly extruded spun threads. When the spun threads touch one
another in the air gap, they stick together, which either leads to
an unsatisfactory fibre quality or even to an interruption in the
spinning process and to a restart of spinning. As described in
DE-A-284 41 63, McCorsley used the spun threads in the air gap via
a roll with a precipitation bath solution. This arrangement is
however not practical at high spinning speeds. A series of further
developments of the McCorsley method therefore involves measures to
reduce the surface adhesion of the spun threads in the air gap and
to improve the operational reliability, also known as the spinning
reliability, of the production method.
[0010] One measure, which is widespread in the state of the art in
the production of Lyocell fibres or spun threads, is to blow with a
cooling gas onto the spun threads in the air gap in order to cool
the surface of the freshly extruded spun threads and to lower their
adhesion. This type of cooling blowing is for example described in
WO-A-93-9230, WO-A-94 2818, WO-A-95 01470 and in WO-A-95 01473.
According to these publications, various types and embodiments of
ventilation are used depending on the arrangement of the extrusion
openings through which the spinning solution is extruded.
[0011] A further problem in the production of Lyocell fibres is the
design of the precipitation bath. Due to the high extrusion speed
the spun threads are dipped into the precipitation bath solution at
a high speed and carry along the surrounding precipitation bath
solution. Consequently, a flow is generated in the precipitation
bath, which churns up the surface of the precipitation bath and
mechanically stresses the spun threads to the point of tearing them
when dipping into the precipitation bath.
[0012] In order to keep the surface of the precipitation bath as
calm as possible with extrusion openings arranged in an annular
shape, in DE-A-1 00 60 877 and DE-A-1 00 60 879 the spun threads
are passed through specially designed spinning funnels filled with
the precipitation bath. With the spinning funnels the precipitation
bath solution flows out together with the spun threads at the lower
end. This stream driven by the force of gravity can, as described
in DE-A-44 09 609, be exploited for stretching the spun
threads.
[0013] With extrusion openings arranged on a rectangular area,
according to DE-A-100 37 923 good results have been achieved when
the spun threads form an essentially flat curtain and are deflected
to the precipitation bath surface as a flat curtain in the
precipitation bath. A deflection element is arranged in the
precipitation bath in this design.
[0014] The further processing of Lyocell fibres after the extrusion
and coagulation of the cellulose for obtaining certain mechanical
properties of the spun threads is less well documented in the
patent literature.
[0015] In the basic article "Was ist neu an den neuen Fasern der
Gattung Lyocell?" (What is new in the new fibres of the Lyocell
type?), Lenzinger Berichte (Lenzinger Reports) 9/94, pgs. 37-40, it
is assumed that the fibre structure and the fibre properties are
determined by the molecular alignment during the extrusion and the
stretching which directly follows the extrusion. Here, the Lyocell
fibres differ crucially from the fibres as they are described in
DE-A-197 53 806, DE-A-197 21 609, DE-A-195 11 151, DE-A-100 16 307
and DE-A43 12 219.
[0016] This topic is taken up in the new patent literature and has
been implemented in practice. Thus, in EP-A-823 945, EP-A-853 146
and DE-A-100 23 391 devices are described in which, after
post-stretching of the extruded spun threads and after the
coagulation of the cellulose in the stretched spun threads, they
are maintained free of tensile stress during the further
processing. These developments are based on the idea that the
mechanical properties of the stretched and coagulated spun threads
can no longer be modified.
[0017] One way that initially appears to go in the opposite
direction is put forward only in EP-A-494 851. In this publication
a method is described in which the essentially stress-free extruded
and coagulated cellulose is stretched. The essential point in this
method is that no stretching of the freshly extruded spun threads
occurs. Through this method of EP-A494 851, which is unusual for
Lyocell processing and which has apparently also not been developed
further, a retrospective shaping of the spun threads is possible.
The method of EP-A-494 851 is therefore similar to a plastic
deformation process, whereby the starting material, the unstretched
Lyocell threads, exhibits a rubbery consistency. The mechanical
properties of the fibres produced according to the method of
EP-A-494 851 are however not commensurate with present-day
requirements.
[0018] In DE-A-102 23 268 it is described that a multi-stage
precipitation and at the same time a multi-stage stretching of the
spun threads can be realised if the wetting device is applied
simultaneously to the stretching of the spun threads. With this
measure the requirement on treatment medium is reduced and the
control of the precipitation process is improved, but the textile
properties are essentially unaffected by this type of retrospective
stretching.
[0019] In JP-A-03-076822 a method of producing fire-resistant
fibres is described. After coagulation of the unstretched fibres,
the filaments are stretched for the first time, then oil is applied
and they are dried. Then the filaments are post-stretched under
steam and dried again.
[0020] For modifying the mechanical properties, such as the loop
strength, tendency to fibrillation and tensile strength of Lyocell
fibres, currently essentially the repertoire is taken up, as
described in the article "Strukturbildung von Cellulosefasern aus
Aminoxidlosungen" (Structure formation of cellulose fibres from
amine oxide solutions), Lenzinger Berichte (Lenzinger Reports)
9/94, pgs. 31-35. Accordingly, the textile-related physical
properties of Lyocell fibres are set by modifying the cellulose
concentration in the spinning solution (cf. WO-A-96 18760), by
variation of the draw-off conditions (cf. DE-A42 19 658) and the
use of additives (cf. DE-A44 26 966, DE-A-218 121, WO-A-94 20656)
as well as by modifying the precipitation conditions (cf. AT-B-395
724). All of these methods however only permit an indirect control
of the mechanical properties of the Lyocell fibres or spun threads
which in the process management is very inaccurate.
SUMMARY OF THE INVENTION
[0021] The object of the invention is therefore to improve the
known methods and devices for the manufacture of Lyocell fibres
such that the mechanical properties such as loop strength and the
tensile strength of the Lyocell fibres can be selectively
influenced by a process which is easy to control.
[0022] This object is solved for the manufacturing method mentioned
in the introduction in that the stretched spun threads are
post-stretched and simultaneously heat treated.
[0023] For the device mentioned in the introduction this object is
solved in that the spun threads can be stretched by the first
stretching means in an air gap before entering the precipitation
bath.
[0024] Surprisingly, the mechanical properties--here in particular
the wet modulus--compared to the conventional Lyocell fibres can be
substantially improved by the post-stretching or elongation of the
spun threads which have already been stretched in the air gap and
then been coagulated. Due to the heat treatment during the
post-stretching, according to initial tests, the wet modulus is
slightly reduced and the fibre again becomes slightly more
elastic.
[0025] In contrast to the method and device of DE-A-102 23 268 the
heat treatment carried out during the post-stretching facilitates a
decisive improvement of the textile properties of the Lyocell
fibres.
[0026] Thus, Lyocell fibres produced with the method according to
the invention can achieve a wet modulus of at least 250 cN/tex and
a wet abrasion number per 25 fibres of at least 18. With the method
according to the invention wet modulus figures of at least 300
cN/tex or 350 cN/tex can be achieved. The wet maximum tensile force
elongation can here assume relatively low values, for example at
the most 12%.
[0027] Generally, higher figures for the wet modulus arise if the
spun threads are coagulated before the post-stretching.
[0028] The heat treatment can be carried out as a drying process in
a stage following a washing or impregnation process, i.e. so-called
stress drying. Alternatively, the heat treatment can take place in
a steam or dry steam atmosphere. The steam or dry steam can contain
impregnation agents which act on the spun threads and lead to a
chemical secondary treatment.
[0029] Preferably the heat treatment is carried out in an oven in
which the stretched and coagulated spun threads are post-stretched
with a specified tensile stress between two godets. Here, a hot
inert gas, such as hot air, or steam or dry steam can be passed
through the surfaces of the galettes and the spun threads lying on
them.
[0030] After the post-stretching the spun threads can be crimped,
since the natural crimping of the spun threads is significantly
reduced due to the post-stretching. Here, treatment with dry steam
at the same time as crimping is also possible.
[0031] Finally, the spun threads can be cut for the manufacture of
staple fibres.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] In the following the invention is explained in more detail
based on an embodiment and based on experimental results and
experimental examples with reference to the drawings.
[0033] The following are shown:
[0034] FIG. 1 a schematic overview of a system for the manufacture
of post-stretched Lyocell fibres;
[0035] FIG. 2 an embodiment of a means of post-stretching in a
schematic view;
[0036] FIG. 3 a further embodiment of a means of post-stretching in
a schematic view.
DETAILED DESCRIPTION
[0037] First, the basic structure of a system 1 for the manufacture
of Lyocell fibres is described based on the schematic
representation of FIG. 1. The system 1 of FIG. 1 is used for the
manufacture of staple fibres of Lyocell.
[0038] A highly viscous spinning solution containing water,
cellulose and tertiary amine oxide, for example
N-methyl-morpholine-N-oxide is passed through a pipe system 2. The
pipe system 2 is constructed in a modular manner from fluid pipe
sections 2a of a certain length, which are joined together via
standard flanges 2b.
[0039] The fluid pipe sections 2a are provided with an interior
temperature stabilisation device 3, which is fitted in the fluid
pipe sections 2 at the point of the core flow of the spinning
solution and through which the temperature of the spinning solution
in the pipe system 2 is closed-loop controlled.
[0040] A temperature controlled fluid is passed via feed modules 4
arranged between two adjacent fluid pipe sections through the
interior temperature stabilisation device, as indicated by the
arrows 5. The feed modules 4 essentially exhibit the dimension of
the standard flanges and can be fitted with such flanges for
connection.
[0041] At certain distances, burst modules 6, likewise arranged
between the fluid pipe sections 2a, are substituted for the feed
modules 4. The burst modules 6 essentially exhibit the same design
as the feed modules 4. They are fitted with burst elements which
are not shown in FIG. 1 and which burst when a certain pressure is
exceeded in the pipe system 2, permitting an outwards diversion of
pressure. Bursting can in particular occur during a spontaneous
exothermic reaction of the spinning solution due to over-ageing or
over-heating. The spinning solution emitted outwards during the
burst is caught in the collection containers 7, from where it can
be recycled or removed.
[0042] The spinning solution is passed to a spinning head 8 through
the pipe system 2. The spinning head 8 is fitted with a spinneret 9
which comprises a large number of extrusion openings (not
illustrated), normally many thousands of extrusion openings. The
spinning solution is extruded to spun threads 10 through the
extrusion openings. The arrangement of the extrusion openings in
the spinneret 9 can be of circular, annular or rectangular shape;
in the following reference is made only to a rectangular
arrangement as an example.
[0043] In order that optimum spinning conditions prevail at the
extrusion openings, apart from the temperature stabilisation device
3 in the pipe system 2, further installed devices can be provided
which similarly can be easily joined to the fluid pipe sections 2a
or to the feed modules 4 or burst modules 6 via the standard
flanges. Thus, a pressure equalisation container 11a can be
arranged in the pipe system 2 to compensate for pressure variations
and volume flow variations in the spinning solution in the pipe
system 2 by changing its internal volume, ensuring a constant
extrusion pressure at the extrusion openings of the spinning head
8.
[0044] Furthermore, a mechanical filter device 11b with a
back-purgable filter element (not shown) can be provided in the
pipe system 2. The filter element exhibits a fineness between 5
.mu.m and 25 .mu.m. Due to the filter device 11b a continuous
or--when using alternate operating buffer storage vessels (not
illustrated)--a discontinuous filtering of the spinning solution
occurs.
[0045] The extrusion openings border on an air gap 12 through which
the freshly extruded spun threads 10 pass and in which the spun
threads are stretched by tensile stress. In the air gap 12 a
cooling gas flow 13, produced by a blower device 14, is directed
onto the spun threads 10. The temperature, moisture and composition
of the cooling gas flow 13 can be controlled to predetermined or
variable specified values by a climatic device 15.
[0046] The cooling gas flow 13 acts at a distance from the
spinneret 9 on the spun threads 10 and exhibits a velocity
component in the extrusion direction E so that the spun threads are
stretched by the cooling gas flow 13. To facilitate good heat
transport the cooling gas flow 13 is turbulent.
[0047] After crossing the air gap 12, the spun threads 10 enter a
precipitation bath 16. In order to avoid churning up the surface of
the precipitation bath 16, the cooling gas flow 13 is spaced
sufficiently from the surface 17 of the precipitation bath, so that
it does not impinge on the surface.
[0048] In the precipitation bath 16 the spun threads 10 are
deflected by an essentially roll-shaped deflector 18 to a bundle
unit 19 outside the precipitation bath, so that they again pass
through the surface 17 of the precipitation bath. The deflector or
diverter can be configured rigidly or fixed or it can rotate with
the spun threads. The bundle unit 19 is rotary driven and as the
first means of stretching exerts a tensile stress, acting back up
to the extrusion openings of the spinneret 9, via the diverter 18
onto the spun threads 10, which stretches the spun threads. Of
course, the diverter 18 can also be driven as a means of
stretching.
[0049] In order to stretch the spun threads 10 as gently as
possible, the tensile stress can also be produced solely by the
cooling gas flow 13 as the first means of stretching. This has the
advantage that the tensile stress is transferred into the spun
threads 10 by a frictional stress acting distributed over the
surface of the spun threads.
[0050] From the bundle unit 19 the spun threads 10 are combined to
a spun thread bundle 20. Then, the spun threads 10, still wet with
the precipitation bath solution 16 and combined to a spun thread
bundle 20, are laid free of stress on a conveyor device 21 and
transported on it largely free of tensile stress. During the
transport of the spun threads on the conveyor device 21 the
complete or almost complete coagulation of the cellulose of the
spun threads takes place with as little effect from stress as
possible.
[0051] The conveyor device 21 can, as shown in FIG. 1, be
configured as a vibroconveyor, which transports the spun thread
bundle 20, or optionally a number of spun thread bundles 20
simultaneously, by vibrations in the conveying direction F. The
vibrations of the conveyor device 21 are indicated by the double
arrow 22. Due to the to and fro movement 21 the bundle of spun
threads 20 is placed in order on the conveyor device. Instead of
the vibroconveyor 22 other conveying devices such as a number of
consecutively arranged godets can be used with a circumferential
speed which is almost constant or which reduces in the conveying
direction.
[0052] During the transport on the conveying device 21 various
treatments of the spun thread bundle 20 can occur, for example the
spun thread bundle 20 can be washed once or many times, dried and
brightened, for example by a sprinkling system 23 from which a
treatment medium 24 is sprayed onto the spun thread bundle 20.
[0053] The spun thread bundle 20 is taken up by a godet 25 from the
conveyor device 21 and passed to a second post-stretching unit 26
through which the thoroughly coagulated spun threads 10 are
post-stretched.
[0054] In the embodiment of FIG. 1 the post-stretching takes place
during simultaneous heat treatment or drying in the form of stress
drying, because in this way the mechanical properties of the spun
threads 10 are most favourably influenced. Slightly worse
properties, which however are still excellent compared to the state
of the art, are obtained when the heat treatment during the
post-stretching is omitted.
[0055] The second post-stretching means 26 can also be provided
immediately after the bundling unit 19, i.e. between the conveyor
device 21 and the precipitation bath 16, so that first the
post-stretched spun threads are subjected to further treatment
steps.
[0056] For carrying out the heat treatment, the post-stretching
means 26 in the entry section of the spun thread 20 can comprise a
heating device 27 which brings the spun thread bundle 20 to a
certain temperature and at the same time dries the spun thread
bundle 20 at least on the surface.
[0057] In the post-stretching means 26 the spun threads are passed
over two godets 28, 29, which are driven such that the spun thread
bundle 20 is subjected to a predetermined post-stretching tensile
stress Z.sub.N between them. The spun thread bundle subjected to
this tensile stress is maintained at a specified high temperature
and during the post-stretching can be impregnated in particular
with a hot inert gas, such as air, or by steam, for example dry
steam and with swelling agents or other agents for chemical fibre
treatment, as indicated by the arrows 30. The godets 28, 29 can
also be heated to support the drying effect.
[0058] Due to the post-stretching, the spun thread bundle 20
exhibits reduced crimping compared to conventional fibres so that
it is crimped via a stuffer box 31. Then, the spun thread bundle 20
is cut by a cutting device 32. If an endless fibre is to be
produced, the crimping and/or cutting can of course be omitted.
[0059] After crimping and cutting the crimped staple fibres can be
transported in random orientation in the form of a crimped endless
cable 33 on a conveyor device 34 to further process steps.
[0060] FIG. 2 shows schematically an embodiment of a
post-stretching means 26. With this embodiment post-stretching in
the form of stress drying occurs.
[0061] As already described for FIG. 1, the post-stretching means
26 comprises two godets 28, 29 which are driven such that the spun
thread bundle 20 is tensioned or extended between them with a
predetermined tensile stress Z.sub.N of at least 0.8 cN/tex,
preferably at least 3.5 cN/tex. In this respect, the godet 29
following in the conveying direction F can be rotated at a
predetermined higher speed than the godet 28 preceding in the
conveying direction F, whereby a slippage, essentially determining
the tensile stress Z.sub.N, can prevail between the godet 29 and
the spun thread bundle 20 looped around the galette.
[0062] The shrinkage of the spun thread bundle 20 during drying can
also be exploited for stretching it: Since the spun thread bundle
shortens during the drying process, an elongation or
post-stretching also then takes place if this shortening is not
compensated by the rotational speed of the godets 28, 29. In this
way post-stretching can also occur when the galettes 28, 29 rotate
with essentially the same or only slightly different speeds.
[0063] One or both godets 28, 29 can be provided with a surface 30
which is at least permeable to gas and through which a hot inert
gas, steam or dry steam is pressed from the interior space of the
godets 28, 29 through the spun thread bundle 20 looped around the
godets 28, 29.
[0064] Alternatively or in addition to looping as illustrated in
FIG. 2, a roll 28a, 29a, also permeable to steam and actively or
passively rotating with the godet, can be arranged in a position
opposite each godet 28, 29, as schematically illustrated in FIG. 3.
The rolls 28a, 29a, also exhibit permeable surfaces through which
the inert gas or steam is drawn off. Large drums can also be
provided instead of rolls.
[0065] Instead of the godets 28, 29 also larger drums or suction
drums with a perforated surface can be used through which the hot
gas is drawn off.
[0066] In the region between the godets 28, 29 hot air or another
inert hot gas, steam or dry steam is passed through gas or the spun
thread bundles 20. The effectiveness of the post-stretching has
been proven in a series of tests.
[0067] The tests were carried out on a spun thread bundle of 79,270
single spun threads and a total titre of 110,978 dtex,
corresponding to a single titre of 1.4 dtex. Table I gives an
overview of the test results.
[0068] In a first series of tests (Tests 1 to 7) the spun thread
bundle was dried at 73.degree. C. over 15 min. under various
conditions.
[0069] In Test 1 the spun thread bundle was dried without
tension.
[0070] In Test 2 the spun thread bundle was dried without tension,
moistened again and dried under tension. To do this, the spun
thread bundle was passed through two eyes at a distance of 50 cm
and loaded at each end during drying with 19 kg.
[0071] In Test 3 the spun thread bundle was dried without tension,
moistened again and dried under tension. To do this, the spun
thread bundle was passed through two eyes at a distance of 50 cm
and loaded at each end during drying with 38 kg.
[0072] In Test 4 the spun thread bundle was clamped between two
clamps at a distance of 38 cm and then dried.
[0073] In Test 5 the moist spun thread bundle was dried under
tension. The spun thread bundle was passed through two eyes at a
distance of 50 cm and loaded at each end with a weight of 9 kg.
[0074] In Test 6 the moist spun thread bundle was dried under
tension. The spun thread bundle was passed through two eyes at a
distance of 50 cm and loaded at each end with a weight of 19
kg.
[0075] In Test 7 the moist spun thread bundle was dried under
tension. The spun thread bundle was passed through two eyes at a
distance of 50 cm and loaded at each end with a weight of 38
kg.
[0076] In a second series of tests the spun thread bundle was
subjected to treatment with caustic soda solution (NaOH) before the
drying. First, the spun thread bundle was treated with a 5% NaOH
solution for 5 min. and then washed with fully deionised water. The
NaOH solution was neutralised with 1% formic acid and again washed
with fully deionised water.
[0077] The spun thread bundle was then dried in the dryer at
73.degree. C. for 30 min.
[0078] In Test 8 the spun thread bundle was dried without
tension.
[0079] In Test 9 the spun thread bundle was dried without tension,
moistened again and dried under tension. To do this, the spun
thread bundle was passed through two eyes at a distance of 50 cm
and loaded at each end with 19 kg.
[0080] In Test 10 the spun thread bundle was dried without tension,
moistened again and dried under tension. To do this, the spun
thread bundle was passed through two eyes at a distance of 50 cm
and loaded at each end with 38 kg.
[0081] In Test 11 the spun thread bundle was clamped between two
clamps at a distance of 38 cm and then dried.
[0082] In Test 12 the moist spun thread bundle was dried under
tension. The spun thread bundle was passed through two eyes at a
distance of 50 cm and loaded at each end with a weight of 9 kg.
[0083] In Test 13 the moist spun thread bundle was dried under
tension. The spun thread bundle was passed through two eyes at a
distance of 50 cm and loaded at each end with a weight of 19
kg.
[0084] In Test 14 the moist spun thread bundle was dried under
tension. The spun thread bundle was passed through two eyes at a
distance of 50 cm and loaded at each end with a weight of 38
kg.
[0085] With the dried spun thread bundles the titre, the denier
related maximum tensile force, maximum tensile force elongation,
denier related wet maximum tensile force, wet maximum tensile force
strain, denier related loop maximum tensile force, the wet modulus
and the wet abrasion number were then determined. In doing this the
following test specifications were followed.
[0086] The titre was determined according to DIN EN ISO 1973. The
(wet) maximum tensile force and the (wet) maximum tensile force
elongation were determined according to DIN EN ISO 5079. The loop
maximum tensile force was determined according to DIN 53843 Part
2.
[0087] The wet modulus was determined on a fibre bundle which can
be used according to DIN EN 1973. The procedure followed the test
specification ASG N 211 from Alceru Schwarza GmbH. The tests for
the determination of the wet modulus were carried out on a tensile
testing machine with constant rate of elongation and
low-displacement electronic force measurement. The clamping length
of the fibre bundle was 10.0 mm.+-.0.1 mm. The denier related
pretension force for a titre of over 2.4 dtex was 2.5 mN/tex.+-.0.5
mN/tex. With a titre up to 2.4 dtex a pretension mass of 50 mg was
used. The rate of strain was 2.5 mm/min with a mean wet elongation
at tear of up to 10%, 5.0 mm/min with a mean wet elongation at tear
of over 10 to 20% and 7.5 mm/min with a mean wet elongation at tear
of over 20%.
[0088] Five spun thread bundles were placed into a flat dish with
wetting agent solution for at least 10 s, whereby previously the
pretension mass was clamped on one end of each spun thread bundle.
The test sample placed in for respectively the longest time was
removed from the dish and used for the tensile test and after each
test a new test sample was to be placed in the dish for
wetting.
[0089] The spun thread bundle to be clamped was clamped with its
end opposite the pretension mass in the tensile testing machine
while the pretension took effect and then the lower clamp was
closed and the dip tank with the wetting agent solution was raised
so that the liquid level reached as far as possible to the upper
clamp without however touching it. The distance between the clamps
must be continuously increased at the above stated strain rate
until a strain rate of 5% is obtained. At this point the movement
of the lower clamp was stopped and the wet tensile force determined
in mN to one decimal place.
[0090] The wet modulus M is calculated from the arithmetic mean of
the wet tensile force F in millinewtons and the mean denier T in
tex calculated for the tested spun fibres and stated in
millinewtons per tex rounded off to integers: M=F/(T0.05).
[0091] The wet abrasion number was determined with a fibre wet
abrasion testing device FNP from SMK Prazisionsmechanik Gera GmbH.
The wet abrasion number is the number of revolutions of the
abrasive shaft up to fracture of the fibre clamped under defined
pretension in the wet abrasion test device. The pretension weight
for a titre between 1.2 to 1.8 dtex was 70 mg. The rotational speed
of the abrasive shaft was 400 rpm, the angle of contact 45.degree..
The abrasive shaft is fitted with a textile tube.
[0092] From the tests according to Table 1 a surprising increase in
the wet modulus as well as in the wet abrasion number of the
post-stretched fibres can be seen compared to the conventional
fibres which were not post-stretched (Test 1). With stress-free
dried spun thread bundles, which were then moistened again and
dried under tension (Tests 2, 3 and 9, 10), at the loading with 38
kg (corresponds to 3.12 cN/tex) compared to the loading with 19 kg
(corresponding to 1.6 cN/tex), an increase in the wet modulus
occurred with a slight drop in the wet abrasion number. With the
heavier loading higher wet moduli can be obtained than with the
moist fibre bundles that were dried under tension in the Tests 5 to
7 and 12 to 14.
[0093] The maximum tensile force, measured both wet and dry, is
essentially unchanged compared to the fibres after Test 1, which
were not post-stretched. It can be concluded from the reduced
maximum tensile force elongation and the reduced loop maximum
tensile force in conjunction with the wet modulus and the wet
abrasion number that the post-stretched fibres are more brittle and
ductile than the fibres which have not been post-stretched.
[0094] Therefore, the tests show that fibres with an improved wet
modulus and an improved wet abrasion number can be produced by
post-stretching or by stress drying. TABLE-US-00001 TABLE 1 Denier
rel. Denier rel. wet max. tensile max. tensile Denier rel. loop Wet
Wet abrasion Titre force Max. tensile force Wet max. tensile max.
tensile force modulus number/25 dtex cN/tex force elongation %
cN/tex force elongation % cN/tex cN/tex fibres Test 1 1.378 42.1
11.5 33.4 12.2 11.8 244 22 Test 2 1.450 43.2 9.7 32.9 11.2 7.3 272
48 Test 3 1.379 46.2 8.7 38.8 11.7 5.5 366 42 Test 4 1.420 43.6
10.5 29.3 11.8 11.9 308 34 Test 5 1.538 42.3 10.1 32.5 11.6 9.3 260
56 Test 6 1.423 42.3 10.0 32.5 12.4 7.7 288 38 Test 7 1.434 42.2
10.8 31.7 11.7 7.5 286 31 Test 8 1.390 39.4 10.6 31.8 12.4 9.6 258
23 Test 9 1.415 41.3 9.5 30.5 10.6 4.5 308 48 Test 10 1.436 40.4
8.6 33.4 11.2 5.0 346 35 Test 11 1.441 42.3 10.4 31.0 12.9 11.9 278
47 Test 12 1.369 42.6 9.7 27.8 11.0 8.8 294 39 Test 13 1.425 41.2
8.5 33.4 10.7 6.7 356 38 Test 14 1.381 42.1 9.3 28.0 9.5 5.6 334
40
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