Note: Descriptions are shown in the official language in which they were submitted.
'~1372~'~
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PROCESS FOR THE PRODUCTION OF CELLULOSE FIBRES aAVING A REDUCED ~-~
TENDENCY TO FIBRILLATION
The invention is concerned with a process for the production of
cellulose fibres having a reduced tendency to fibrillation.
As an alternative to the viscose process, in recent years there
has been described a number of processes in which cellulose,
without forming a derivative, is dissolved in an organic
solvent, a combination of an organic solvent and an inorganic
,. ~, ,, . .~ .- .
salt, or in aqueous saline solutions. Cellulose fibres made;~
from such solutions have received by BISFA (The International
Bureau for the Standardisation of man made Fibres) the géneric
name Lyocell. As Lyocell, BISFA define~ a cellulose fibre
obtained by a spinning process from an organic solvent. By
"organic solvent", BISFA understands a mixture of an organic
chemical and water. "Solvent-spinning" ist considered to mean
disgolving and spinning without the forming of a derivative. ~.
So far, however, only one process for the production of a ;-~-
cellulose fibre of the Lyocell type has achieved industrial~
scale realization. In this process, a tertiary amine-oxide, -
particularly N-methylmorpholine-N-oxide (NMMO), is used as a ;
~olvent. Such a process is described for instance in US-A - ~ <-
4,246,221 and provides fibres which present a high tensile ',.,"~.,':!'~;,~.'~,"~
~trength, a high wet-modulus and a high loop strength.
However, the usefulness of plane fibre assemblies, for example
fabrics, made from the above fibres, is significantly ; ~ ~;
restricted by;~the pronounced,tendency of such fibres to ! :`' ~ ~''i';'."'
fibrillate when wet. Fibrillation means the breaking up of the
wet fibre in longitudinal direction at mechanical stress in a
wet condition, so that the fibre gets hairy, furry. A fabric
made from these fibres and dyed significantly loo~es colour
intensity as it is washed several times. Additionally, light
~tripes are formed at the abrasion and crease edge3. The reason
may be that the fibres consist of fibrils which are arranged in
the longitudinal direction of the fibre axis and that the
crosslinking between these is reduced. ~ J
- 2137 2? 2
-2- -:~
wo 92/14871 describe~ a process for the production of a fibre ~ i
having a reduced tendency to fibrillation. The reduced tendency -
to fibrillation is attained by providing all the baths with
which the freshly spun fibre is contacted before the first
drying with a maximum pH of 8,5.
wo 92to7l24 also describes a proce~s for the production of a
fibre having a reduced tendency to fibrillation, according to ~ ~j
which the freshly spun, i.e. not yet dried, fibre is treated
with a cationic polymer. As such a polymer, a polymer with
imidazole and azetidine groups is mentioned. Additionally,
there may be carried out a treatment with an emulsifiable ~ ;
polymer, such as polyethylene or polyvinylacet~te, or a
crosslinking with glyoxal.
In a lecture given by S. Mortimer at the CELLUCON conference in ~-
1993 in Lund, Sweden, it was mentioned that the tendency to
fibrillation rises as drawing is increased.
It is the objective of the invention to provide a process which
can be carried out in an easy way, allowing the production of i ~ -;
cellulose fibres of the Lyocell type having a reduced tendency
to fibrillation.
The process according to the invention for the production of "'''~',',~'~'''1`'',~'!'~'','~
cellulose fibres having a reduced tendency to fibrillation
con~ist~ in that the freshly spun, not yet dried fibres are
contacted with a textile agent, which carries at least two
reactive groups, and are washed with an aqueous buffer,
provided glyoxal is not used,a~ textile agent. :
A~ textile agent~, especially dyes having two reactive groups
have shown good result~. According to the invention, however, ~-
textile agents which are colourless, i.e. do not absorb visible
light, may al~o be used.
According to the invention, the use of textile agents which ~ ji
carry one or two vinylsulfone groups as reactive groups is ~ '
preferred. ~
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2137232
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A convenient embodiment of the process according to the ~;
invention is charactPrized in that the freshly spun fibres are
contacted with the textile agent in an aqueous alkaline medium. ~ t
It was shown that the tendency to fibrillation is especially
reduced when an alkali carbonate and an alkali hydroxide is ;
chosen as the alkaline medium.
Another preferred embodiment of the process according to the
invention consists in that the fibres contacted with the
textile agent are heat-treated. The heat treatment drastically
reduces the impregnation time.
EP-A - O 538 977, published on April 28, 1993, describes heat
treatment of cellulose fibres impregnated with a dye. It was i~ ~ ^
shown, however, that heating of the fibres impregnated with the ~ ',.`;4:''~'.
textile agent by means of hot air may reduce the impregnation
time, but that this carries the risk of the fibres not being
heated uniformly. Thus for example, the fibres on the outside
of a fibre bundle to be dried may already be partly dried, 2;
while the fibres inside the bundle have not yet reached the
required temperature. This has a negative effect on the quality
of the fibree produced.
It has been f ound that thi~ drawback occurring in a simple heat
treatment can be overcome by irraidiating the fibres with
electromagnetic waves, particularly microwaves. When irradiated
with microwaves, on the one hand the fibres are heated ~;
uniformly and on the other hand premature drying of the fibres j;
can be avoided, since irradiation with electromagnetic waves
provides the po~sibility to weld the fibre bundle for example
into a plastic wrapping and expose it in a welded condition to
the electromagnetic field. -~
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The above advantages are also given when the fibres, for ~;~
example lying a~ plane fibre assembly on a conveyor, are moved
through a narrow channel, in which they are exposed to
electromagnetic waves. This channel can be designed in a way
that only little air space above the fibres is left, thereby
.:'
2137232
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preventing a partial drying of the outer fibres of the bundle.
Simultaneously, this way of fixation of the textile agent also
offers the possibility of a large-scale production easy to put
into practice.
Thus, the invention further refers to a process for the
production of cellulose fibres having a reduced tendency to
fibrillation, in which a solution of cellulose in a tertiary
amine-oxide is spun into fibres, and the freshly spun fibres
are contacted with a textile agent which carries at least two
reactive groups and are heat-treated, characterized in that the
heat treatment is carried out by irradiation with
electromagnetic waves. ~-
Also according to this embodiment of the process according to
the invention, the use of a textile agent which carries
vinylsulfone groups as the reactive groups, is preferred, ;~
preferably being a dye. However, textile agents which are `;i;~
colourless, i.e. do not absorb visible light, can also be used.
Another preferred embodiment of the process according to the ,~
invention consists in carrying out the heat treatment by means
of microwaves.
The invention will be explained in more detail by the following
example~. All references to % are to be understood as weight %.
Production of the cellulose fibres
According to the process!described in EP-A - 0 356 419, a ! ~ ~ ""~''" ~' ~'
~olution of cellulose in NMM0 was prepared and extruded through
a spinneret. The filaments thereby obtained were conducted
through an air gap into an aqueous precipitation bath, in which
the cellulose coagulated. The fibres obtained in the
precipitation bath were washed, presenting a titer of 1,7 dtex.
The wa~hed fibres were used for the examples hereinafter
described and represent those fibres which in the present
description and in the present claims are referred to as fibres
freshly spun, not yet dried.
' ' ''~;
2~372~
-5-
1) Treatment with textile agents without subsequent heat
treatment -
A) General procedure
1 g of each of the fibres produced according to the above
process were impregnated in 190 ml of an aqueous solution
(bath), which contained a textile agent comprising two reactive
groups and Na2SO4, at 40C for 30 minutes. Then NaOH (3%), -~
Na2CO3 (4%) or a mixture of NaOH, Na2CO3 (4% Na2CO3 and 0,2 g/1 - -
NaOH) were added for the fixation of the textile agent. After
another 60 minutes at 40C the fibres were washed several
times, in order to remove the textile agent not fixed to the '~
fibre. Then the washed fibres were treated for 30 minutes with
an aqueous buffer, then again washed with water (for 15
minutes) and dried at 60C. Afterwards the fibres were examined
to determine their tendency to fibrillation and to determine ;~
other fibre parameters.
Evaluation of fibrillation
The abrasion of the fibres among each other in washing
processes and finishing processes in wet condition was ~
~imulated by the following test: 8 fibres with a length of 20 j ~ ;
mm e~ch were put into a 20 ml sample bottle with 4 ml of water
and ~haken during 9 hours in a laboratory mechanical shaker of
the RO-10 type of the company Gerhardt, Bonn (Germany), at
atage 12. Afterwards the fibrillation behaviour of the fibres ~ ;
was evaluated by microscope, by means of counting the number of ;~;
fibril~ per 0,276 mm fibre length.
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1372
Further fibre parameters
The fibre tensile strength and fibre elongation at break were ~ ~ -
te~ited following the BISFA rule on "Internationally agreed
methods for tei3ting vi~cose, modal, cupro, lyocell, acetat and -~;
triacetat staple fibres and tows", edition 1993. ~ `~; o
B) Examples
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According to the above process, fibres were treated with the
dye Remazol Black B and Remazol Red RB as textile agent (made ;
by Hoechst AG). The dye Remazol Black B carries two -
vinylsulfone groups and the dye Remazol Red B earries one
vinylsulfone group and one monochlorotriazine group.
The bath contained 3~ Remazol Black B and 0,5% Remazol Red RB
respectively. The pH of the bath was 4,6 in each example. The ~ ~
used aqueous buffer was an aqueous solution which contained 3% ~ ~ -
acetic acid and 7~ sodium acetate. The p~ value of this
solution was 4,6. After the treatment with the buffer, the
fibres were washed with water for 15 minutes and afterwards ~ ~-
examined. Table la indicates the fixing agent used in each
case, the fibrillation (number of fibrilsi), the titer (dtex),
the fibre strength ~cN/tex) and the fibre elongation at break
(%). Examples 1, 2 and 3 were carried out with the dye Remazol `~
Black B and Example 4 with the dye Remazol Red RB.
Table lb show~ the results of comparative tests carried out i
without dye.
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21~7232 ~;
Table la (Textile Agent)
Ex. Fixing agent Fibrils Titer Tensile Strength Elongation
1 NaOH 22 1,82 28,81 11,14
. , .;.
2 Na2CO~ 2 2,07 26,39 10,67
3 NaOH+Na~CO~ 0 2,34 24,94 10,04
_ , .. ~ . .. .
4 NaOH+Na~CO3 5 2,34 30,00 11,74 . ~ ~ .
Table lb (Comparative Examples) ~ ~ ~
. -. ~
Ex. Fixing agent Fibrils Titer Tensile Strength Elongation ;~
5 NaOH >60 1,80 33,76 12,71 ~ b.
6 Na~CO3 60 1,56 33,78 12,15 :~
7 NaOH+Na~CO3 >60 1,72 30,18 12,14
8 NaOH+Na2CO3 >60 1,72 32,00 12,70 ~ .
A comparison of the results of Tables la and lb shows that the ~. '`~'
textile agent, in the present case the dyes Remazol Black B and
Remazol Red RB, drastically reduces the tendency to
fibrillation and that the combination of NaOH+Na2CO3, which is
used for the fixation of the textile agent, also drastically
further reduce~ the tendency to fibrillation.
It was shown that the above results are obtained also when
u~ing other textile agents which comprise two reactive groups.
Thu~, Remazol Black B and Remazol Red RB may represent other :.
textile agents which also carry at least two reactive groups.
2) Treatment with textile agents and subsequent heat treatment ~:;
1 g of each of the fibres produced according to the above
process was impregnated in 190 ml of a bath (containing 0,2% ~ :
Remazol Black B, 2% Na2CO3, 0,2% NaOH, pH a 11,53 three times
for 30 ~econds each, the fibres being squeezed off after each
impregnation. Afterwards, each sample was heat-treated twice
for 40 seconds in each case in a circulating-air oven at 180C. ; `~`
Subsequently, each heat-treated sample was treated for 30
minutes with the above mentioned acetate buffer (pH = 4,6), : .
''. '.,';:'';,~,' ,'.
2137222
-8-
washed with water for 15 minutes, dried at 60C and examined.
The results are shown in Table 2, Example 10 representing a
Control Sample (for Example 10, Example 9 was repeated without
using a textile agent).
Table 2
¦ Ex. ¦ Fibrils ¦Titer¦Tensile Strength¦Elongation~
9 24 1,S6 33,78 I 12,15 ~`
10 >57 1,80 33,76 1 12,71 3
From table 2 it can be seen that a heat treatment of the fibres
impregnated with the textile agent drastically reduces the
impregnation time, a~ well as the tendency to fibrillation is -
reduced.
With the dye Remazol Red RB, similarly good results could be j~
attained.
3. Treatment with textile agents and subsequent irradiation
with microwaves ~ ~H
10 g of the fibres produced according to the above process were -~ .,`",,:":~:,,!,~"j~",
lmprognated in a 900 ml bath (10% Remazol Black B, 10% Na2SO4,
8% Na2CO3; the pH wa~ adjusted with NaOH to 11,5) for 9
minutes. Afterwards, the fibres were squeezed off and divided
into 2 parts of equal amount (Examples 12, 13). Example 11 was
a Control Sample, indicating the properties of the fibres not
treated with a textile agent. For Examples 12 and 13, the
fibrés were ~quéezed offlafterlimpregnation with the bath,land
they either were heated to 180C for 180 seconds (Example 12) ;;~
or irradiated with 90 watt microwave~ for 50 seconds (Example
13). Afterward~, the fibres were treated for 30 minutes in the ~ -
above acetate buffer at a pH of 4,6, washed with water for 15 ~;~
minutes and dried at 60C. The results of the tests are Yhown
ln Table 3. ~
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21372~2
9 ..~. ,: ,.
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Table 3
- .- ~ ~ .
Ex.Heating Fibrils Titer Tensile Strength Elongation
11 ___ 56 1,83 31,98 11,52
_ .
12 180 sec.;180C 11 1,91 23,70 9,77 ~ ;
, .,
13 50 sec.; 90 W 7 1,92 31,23 11,34
From Table 3 it can be seen that the irradiation with
microwaves further reduces the heating time, the tendency to
fibrillation being still further reduced. Similarly good
results in terms of a reduced tendency to fibrillation were
obtained, when instead of Remazol Black B other textile agents
with at least two reactive groups were used. Particularly it
was shown that the positive effect upon the tendency to - ,~;-
fibrillation is similarly pronounced as with glyoxal. ~ ~
Furthermore it was shown that the above positive effect brought - ~ ;
about by irradiation with microwaves can also be observed with ~ ~ -
: , .-. ..
glyoxal and other dialdehydes, as can be deduced from the ; ~-
following example.
2 g of fibres produced according to the process described in
section 1 were impregnated twice for 3 minutes each with 140 ml
of a bath, containing 2% glyoxal and 0,66% crosslinking
catalyst (for example Condensol FB, a mixture of ZnCl2 and
MgClz, made by BASF). Afterwards, the fibres were squeezed off
4nd divided into 2 parts (Examples 15, 16). Example 14 was a
Control Sample, for Example 15 the fibres were treated for 10
minutes in a circulating-air oven at 100C, and for Example 16
the fibres were subjected to a power of 500 watt by means of a
microwave. The fibrillation results are indicated in the i ;
following Table 4. -
The above methode was repeated, using glutardialdehyde ~3,4%)
instead of glyoxal. The fibrillation results of the obtained
fibres are also reflected in Table 4 (Examples 17, 18 and 19
corre~pond to Examples 14, 15 and 16 respectively). ;
:: ~ ;.:
-` 21~7232 ;
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Table 4
Exam~leTextile agent Treatment Fibrils
. ,.
_14 ____ ____ 35,5
15 _Glyoxal 10 min.; 100C 24,0 -~
~ - . . - -
16 Glvoxal 60 sec.; 500w 8,5
17 _ ____ 35,5
_
18Glutardialdehyde10 min.; 100C 10,5
19Glutardialdehyde60 sec.; 500 w _ 21,0 ~
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