Note: Descriptions are shown in the official language in which they were submitted.
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Polymer fibre having improved long-term dispersibility
The invention relates to a polymer fibre having improved long-term
dispersibility, a
method for production thereof, and use thereof.
Polymer fibres, i.e. fibres based on synthetic polymers, are produced
industrially on a
large scale. In this case the underlying synthetic polymer is produced by
means of a
melt spinning process. To this end, the thermoplastic polymer material is
melted and
is conducted in the liquid state into a spinning beam by means of an extruder.
The
molten material is fed from this spinning beam to what are known as
spinnerets. The
spinneret usually has a spinneret plate provided with a number of holes, from
which
the individual capillaries (filaments) of the fibres are extruded. Besides the
melt .
spinning method, wet or solvent spinning methods are also used to produce
staple
fibres. In this case, instead of the melt, a highly viscous solution of a
synthetic
polymer is extruded through dies having fine holes. Both methods are referred
to by a
person skilled in the art as what are known as multi-position spinning
methods.
The polymer fibres produced in this way are used for textile and/or technical
applications. Here, it is advantageous if the polymer fibres have a good
dispersibility
in aqueous systems, for example for the production of wet-laid nonwovens. In
addition, it is advantageous for textile applications if the polymer fibres
have a good
and soft grip.
The modification or finishing of polymer fibres for the particular end
application or for
the necessary intermediate treatment steps, e.g. stretching and/or crimping,
is usually
accomplished by applying suitable finishes or layers which are applied to the
surface
of the finished polymer fibre or polymer fibre to be treated.
Another possibility for chemical modification can be accomplished on the
polymer
basic structure itself, for example, by incorporating compounds having a
flaming
action into the polymer main and/or side chain.
Furthermore, additives, for example, antistatics or dye pigments can be
introduced
into the molten thermoplastic polymer or introduced into the polymer fibre
during the
multi-position spinning process.
The dispersion behaviour of a polymer fibre is influenced, inter alia, by the
nature of
the synthetic polymers. In particular in the case of fibres of thermoplastic
polymer, the
dispersibility in aqueous systems is therefore influenced and adjusted by the
finishes
or layers applied to the surface.
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The dispersibility produced or improved by means of suitable finishes or
layers is
already sufficient for many textile applications.
For food-related applications, however, different requirements apply; the used
substances and materials must be approved for contact with food pursuant to EU
Reg. No. 231/2012. It is additionally desirable if the equipped polymer fibres
are
present in dispersed form for a relatively long time and/or under more extreme
conditions, e.g. high pressure, strong shear forces and elevated temperature,
in
particular also in aggressive, acidic, aqueous systems, and if this
dispersibility is
retained even after a relatively long storage time.
It is therefore the object to provide a polymer fibre with improved
dispersibility, in
particular long-term dispersibility, which has a good dispersibility even
after a
relatively long period of storage and additionally is approved for contact
with food
pursuant to EU Reg. No. 231/2012. In addition, the polymer fibre should be
readily
dispersible also under extreme conditions, i.e. high pressure, severe shear
forces
and elevated temperature, in particular also in aggressive aqueous systems
which
optionally have a pH of <7 and/or electrolytes, in particular saline-based
electrolytes,
and this good dispersibility should be retained, even after a relatively long
period of
storage.
The aforesaid object is solved by the polymer fibre according to the invention
comprising at least one synthetic polymer, preferably at least one synthetic
thermoplastic polymer, characterised in that the fibre on the surface has a
preparation comprising at least one cellulose ether selected from the group
carboxymethyl cellulose (CMC), methyl cellulose (MC), ethyl cellulose (EC),
hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), methylethyl
cellulose
(MEC), hydroxyethylmethyl cellulose (HEMC), hydroxypropylmethyl cellulose
(HPMC), ethylhydroxyethyl cellulose, carboxymethylhydroxyethyl cellulose, and
mixtures thereof.
Polymers
The synthetic polymers according to the invention which form the dispersion
medium
preferably comprise thermoplastic polymers, in particular thermoplastic
polycondensates, particularly preferably what are known as synthetic
biopolymers,
particularly preferably thermoplastic polycondensates based on what are known
as
biopolymers.
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The term "thermoplastic polymer" designates in the present invention a plastic
which
can be deformed (thermoplastically) in a specific temperature range,
preferably in the
range of 25 C to 350 C. This process is reversible, that is, it can be
repeated
arbitrarily frequently by cooling and re-heating as far as into the molten
state as long
as the so-called thermal decomposition of the material is not initiated by
overheating.
This is the difference between thermoplastic polymers and thermosetting
plastics and
elastomers.
Within the scope of the present invention, the following polymers are
preferably
understood by the term "thermoplastic polymer":
acrylonitrile ethylene propylene (diene) styrene copolymer, acrylonitrile
methacrylate
copolymer, acrylonitrile methyl methacrylate copolymer, acrylonitrile
chlorinated
polyethylene styrene copolymer, acrylonitrile butadiene styrene copolymer,
acrylonitrile ethylene propylene styrene copolymer, aromatic polyester,
acrylonitrile
styrene acryloester copolymer, butadiene styrene copolymer, cellulose acetate,
cellulose acetobutyrate, cellulose acetopropionate, hydrated cellulose,
carboxymethyl
cellulose, cellulose nitrate, cellulose propionate, cellulose triacetate,
polyvinylchloride,
ethylene acrylic acid copolymer, ethylene butylacrylate copolymer, ethylene
chlorotrifluoroethylene copolymer, ethylene ethylacrylate copolymer, ethylene
methacrylate copolymer, ethylene methacrylic acid copolymer, ethylene
tetrafluoroethylene copolymer, ethylene vinylalcohol copolymer, ethylene
butene
copolymer, ethylcellulose, polystyrene, polyfluoroethylene propylene,
methylmethacrylate acrylonitrile butadiene styrene copolymer,
methylmethacrylate
butadiene styrene copolymer, methylcellulose, polyamide 11, polyamide 12,
polyamide 46, polyamide 6, polyamide 6-3-T, polyamide 6-terephthalic acid
copolymer, polyamide 66, polyamide 69, polyamide 610, polyamide 612, polyamide
61, polyamide MXD 6, polyamide PDA-T, polyamide, polyarylether,
polyaryletherketone, polyamide imide, polyarylamide, polyamino-bis-maleimide,
polyarylate, polybutene-1, polybutylacrylate, polybenzimidazole, poly-bis-
maleimide,
polyoxadiazobenzimidazole, polybutylene terephthalate, polycarbonate,
polychiorotrifluoroethylene, polyethylene, polyestercarbonate,
polyaryletherketone,
polyetheretherketone, polyetherimide, polyetherketone, polyethylene oxide,
polyarylethersulfone, polyethylene terephthalate, polyimide, polyisobutylene,
polyisocyanurate, polyimide sulfone, polymethacrylimide, polymethacrylate,
poly-4-
methylpentene-1, polyacetal, polypropylene, polyphenylene oxide, polypropylene
oxide, polyphenylene sulfide, polyphenylene sulfone, polystyrene, polysulfone,
polytetrafluoroethylene, polyurethane, polyvinylacetate, polyvinylalcohol,
polyvinylbutyral, polyvinylchloride, polyvinylidene chloride, polyvinylidene
fluoride,
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polyvinylfluoride, polyvinylmethylether, polyvinylpyrrolidone, styrene
butadiene
copolymer, styrene isoprene copolymer, styrene maleic acid anhydride
copolymer,
styrene maleic acid anhydride butadiene copolymer, styrene methylmethacrylate
copolymer, styrene methylstyrene copolymer, styrene acrylonitrile copolymer,
vinylchloride ethylene copolymer, vinylchloride methacrylate copolymer,
vinylchloride
maleic acid anhydride copolymer, vinylchloride maleimide copolymer,
vinylchloride
methylmethacrylate copolymer, vinylchloride octylacrylate copolymer,
vinylchloride
vinylacetate copolymer, vinylchloride vinylidene chloride copolymer and
vinylchloride
vinylidene chloride acrylonitrile copolymer.
Within the scope of the present invention, the term "thermoplastic polymer" is
preferably understood to be a polymer that differs chemically and/or
physically from
the cellulose ethers used in the preparation. The thread-forming thermoplastic
polymers preferably do not comprise any cellulose ethers.
Particularly well-suited are high-melting thermoplastic polymers (Mp 100 C),
which
are very well suited for staple fibre production.
Suitable high-melting thermoplastic polymers are, for example, polyamides such
as
polyhexamethylene adipinamide, polycaprolactam, aromatic or partially aromatic
polyamides ("aramide"), aliphatic polyamides such as Nylon, partially aromatic
or fully
aromatic polyesters, polyphenylene sulfide (PPS), polymers with ether and keto
groups such as polyetherketone (PEK) and polyether etherketone (PEEK) or
polyolefins such as polyethylene or polypropylene.
Within the high-melting thermoplastic polymers, melt-spinnable polymers are
particularly preferred.
Melt-spinnable polyesters consist predominantly of building blocks which are
derived
from aromatic dicarboxylic acids and aliphatic diols. Common aromatic
dicarboxylic
acid building blocks are the divalent radicals of benzene dicarboxylic acids,
in
particular terephthalic acid and isophthalic acid; common diols have 2 to 4 C
atoms,
with ethylene glycol and/or propane-1,3-diol being particularly suitable.
Particularly preferred are polyesters having at least 95 mol (Yo polyethylene
terephthalate (PET).
Such polyesters, in particular polyethylene terephthalate, usually have a
molecular
weight corresponding to an intrinsic viscosity (IV) of 0.4 to 1.4 (dl/g),
measured for
solutions in dichloroacetic acid at 25 C.
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The term "synthetic biopolymer" designates in the present invention a material
which
consists of biogenic raw materials (renewable raw materials). A delimitation
is thus
made from the conventional petroleum-based materials or plastics such as, for
example, polyethylene (PE), polypropylene (PP) and polyvinylchloride (PVC).
According to the invention, particularly preferred synthetic biopolymers are
thermoplastic polycondensates based on what are known as biopolymers which
comprise repeating units of lactic acid, hydroxybutyric acid and/or glycolic
acid,
preferably of lactic acid and/or glycolic acid, in particular of lactic acid.
Polylactic
acids are particularly preferred in this case.
,
"Polylactic acid" is understood here as polymers which are constructed of
lactic acid
units. Such polylactic acids are usually produced by condensation of lactic
acids but
are also obtained by ring-opening polymerisation of lactides under suitable
conditions.
According to the invention, particularly suitable polylactic acids comprise
poly(glycolide-co-L-lactide), poly(L-lactide), poly(L-lactide-co-s-
caprolactone), poly(L-
lactide-co-glycolide), poly(L-lactide-co-D,L-lactide), poly(D,L-lactide-co-
glycolide) as
well as poly(dioxanone). Such polymers are available commercially for example
from
the company Boehringer Ingelheim Pharma KG (Germany) under the trade names
Resomer GL 903, Resomer L 206 S, Resomer L 207 S, Resomer L 209 S,
Resomer L 210, Resomer L 210 S, Resomere LC 703 S, Resomer LG 824 S,
Resomer LG 855 S, Resomer LG 857 S, Resomer LR 704 S, Resomer LR 706
S, Resomer LR 708, Resomer LR 927 S, Resomer RG 509 S and Resomer X
206 S.
For the purposes of the present invention, particularly advantageous
polylactic acids
are in particular poly-D-, poly-L- or poly-D,L-lactic acids.
In a particularly preferred embodiment the synthetic polymer is a
thermoplastic
condensate based on lactic acids.
The polylactic acids used according_to the invention have a number-average
molecular weight (Mn), preferably determined by gel permeation chromatography
against narrowly distributed polystyrene standards or by end-group titration,
of at
least 500 g/mol, preferably at least 1,000 g/mol, particularly preferably at
least 5,000
g/mol, expediently at least 10,000 g/mol, in particular at least 25,000 g/mol.
On the
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other hand, the number-average is preferably at most 1,000,000 g/mol,
expediently at
most 500,000 g/mol, more favourably at most 100,000 g/mol, in particular at
most
50,000 g/mol. A number-average molecular weight in the range from at least
10,000
g/mol to 500,000 g/mol has proved quite particularly successful within the
scope of
the present invention.
The weight-average molecular weight (Mw) of preferred lactic acid polymers, in
particular of poly-D-, poly-L- or poly-D,L-lactic acids, preferably determined
by gel
permeation chromatography against narrowly distributed polystyrene standards,
lies
preferably in the range from 750 g/mol to 5,000,000 g/mol, preferably in the
range
from 5,000 g/mol to 1,000,000 g/mol, particularly preferably in the range from
10,000
g/mol to 500,000 g/mol, in particular in the range from 30,000 g/mol to
500,000 g/mol,
and the polydispersity of these polymers is more favourably in the range from
1.5 to
5.
The inherent viscosity of particularly suitable lactic acid polymers, in
particular poly-D-
, poly-L- or poly-D,L-lactic acids, measured in chloroform at 25 C, 0.1%
polymer
concentration, lies in the range of 0.5 dl/g to 8.0 dl/g, preferably in the
range of 0.8
dl/g to 7.0 dl/g, in particular in the range of 1.5 dl/g to 3.2 dl/g.
Furthermore, the inherent viscosity of particularly suitable lactic acid
polymers, in
particular poly-D-, poly-L- or poly-D,L-lactic acids, measured in hexafluoro-2-
propanol
at 30 C, 0.1% polymer concentration, is in the range of 1.0 dl/g to 2.6 dl/g,
in
particular in the range of 1.3 dl/g to 2.3 dl/g.
Within the scope of the present invention, furthermore polymers, in particular
thermoplastic polymers, having a glass transition temperature higher than 20
C,
more favourably higher than 25 C, preferably higher than 30 C, particularly
preferably higher than 35 C, in particular higher than 40 C, are extremely
advantageous. Within the scope of a quite particularly preferred embodiment of
the
present invention, the glass transition temperature of the polymer lies in the
range of
35 C to 55 C, in particular in the range of 40 C to 50 C.
Furthermore, polymers having a melting point higher than 50 C, more favourably
of
at least 60 C, preferably higher than 150 C, particularly preferably in the
range of
160 C to 210 C, in particular in the range of 175 C to 195 C, are particularly
suitable.
In this case, the glass temperature and the melting point of the polymer are
preferably determined by means of Differential Scanning Calorimetry; or DSC
for
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short. In this connection, the following procedure has proved quite
particularly
successful:
Performing the DSC measurement under nitrogen on a Mettler-Toledo DSC 30S. The
calibration is preferably made with indium. The measurements are preferably
made
under dry oxygen-free nitrogen (flow rate: preferably 40 ml/min). The sample
weight
is preferably selected between 15 mg and 20 mg. The samples are initially
heated
from 0 C to preferably a temperature above the melting point of the polymer to
be
studied, then cooled to 0 C and heated a second time from 0 C to the said
temperature at a heating rate of 10 C/min.
Polyesters, in particular lactic acid polymers, are quite particularly
preferred as
thermoplastic polymers.
Polymer fibre
The polymer fibre according to the invention can be present as a finite fibre,
e.g. as
what is known as a staple fibre or as an infinite fibre (filament). For better
dispersibility the fibre is preferably present as a staple fibre. The length
of the
aforesaid staple fibres is not subject to any fundamental restriction but is
generally 1
to 200 mm, preferably 2 to 120 mm, particularly preferably 2 to 60 mm. In
particular
short fibres can be well cut from the fibres according to the invention. These
are
understood to be fibre lengths of 5 mm and less, in particular of 4 mm and
less.
The individual titre of the polymer fibres according to the invention,
preferably stable
fibres, is between 0.3 and 30 dtex, preferably 0.5 to 13 dtex. For some
applications
titres between 0.3 and 3 dtex and fibre lengths of <10 mm, in particular <8
mm,
particularly preferably <6 mm, in particular preferably <4 mm, are
particularly well
suited.
The polymer fibres according to the invention are preferably produced from
thermoplastic polymers, in particular thermoplastic organic polymers,
particularly
preferably from thermoplastic organic polycondensates, by means of melt
spinning
methods. In this case the polymer material is melted in an extruder and
processed by
means of spinnerets to form the polymer fibres. The polymer fibres according
to the
invention usually do not comprise any fibres that were produced by spinning
from
solution, in particular by means of electrospinning.
The polymer fibre can also be present as a bicomponent fibre, where the fibre
consists of a component A (core) and a component B (shell). In a further
embodiment
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the melting point of the thermoplastic polymer in component A is at least 5 C,
preferably at least 10 C, particularly preferably at least 20 C higher than
the melting
point of the thermoplastic polymer in component B. Preferably the melting
point of the
thermoplastic polymer in component A is at least 100 C, preferably at least
140 C,
particularly preferably at least 150 C.
The thermoplastic polymers used in the bicomponent fibres are the polymers
already
mentioned previously.
Preparation
The polymer fibre according to the invention has, on the surface, between 0.1
and 20
wt. %, preferably 0.5 to 3 wt. %, of a preparation which comprises at least
one
cellulose ether selected from the group carboxymethyl cellulose (CMC), methyl
cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC),
hydroxypropyl
cellulose (HPC), methylethyl cellulose (MEC), hydroxyethylmethyl cellulose
(HEMC),
hydroxypropylmethyl cellulose (HP MC), ethylhydroxyethyl cellulose,
carboxymethylhydroxyethyl cellulose, and mixtures thereof.
In a preferred embodiment the preparation comprises at least two cellulose
ethers
selected from the group carboxymethyl cellulose (CMC), methyl cellulose (MC),
ethyl
cellulose (EC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC),
methylethyl cellulose (MEC), hydroxyethylmethyl cellulose (HEMC),
hydroxypropylmethyl cellulose (HPMC), ethylhydroxyethyl cellulose,
carboxymethylhydroxyethyl cellulose, particularly preferred are preparations
from
methyl cellulose (MC) and hydroxypropylmethyl cellulose (HPMC), these being
present in amounts of from 0.1 and 20 wt. %, preferably 0.5 to 3 wt. %, on the
surface
of the polymer fibres according to the invention.
The preparation according to the invention covers at least 99 % of the total
surface of
the fibre, preferably at least 99.5 %, in particular at least 99.9 /0,
particularly
preferably 100% of the total surface of the fibre. The coverage of the surface
is
determined by means of microscopic methods. The preparation according to the
invention is preferably applied exclusively to the fibres, and not
subsequently to the
textile fabrics produced from the fibres.
The preparation according to the invention usually has a thickness of 5-10 nm
on the
fibres. The thickness is determined by means of microscopic methods.
The cellulose ether(s) used in accordance with the invention are substances
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approved in accordance with EU Reg. No. 231/2012 as additives. Substances of
this
kind are commercially obtainable, for example under the name VIVAPUR or
MethocelTM.
In a preferred embodiment the preparation comprises cellulose ether, but in
particular
carboxymethyl cellulose (CMC), methyl cellulose (MC), ethyl cellulose (EC),
hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), methylethyl
cellulose
(MEC), hydroxyethylmethyl cellulose (HEMC), hydroxypropylmethyl cellulose
(HPMC), ethyl hydroxyethyl cellulose, carboxymethylhydroxyethyl cellulose,
particularly preferred are preparations of methyl cellulose (MC) and
hydroxypropylmethyl cellulose (HPMC), which have a gelling temperature in the
range of 35 C to 90 C, preferably in the range of 40 C to 70 C, in particular
in the
range of 45 C to 60 C, particularly preferably in the range of 45 C to 55 C.
The cellulose ether(s) used in accordance with the invention usually have a
degree of
substitution (number of the substituted hydroxy groups per glucose molecule)
in the
range of from 1.3 to 2.6, preferably from 1.6 to 2Ø The degree of
substitution is
usually determined by means of gas chromatography.
The cellulose ether(s) used in accordance with the invention, but in
particular the
methyl celluloses, preferably have a methoxy group fraction of from 26 % to 33
%, in
particular of from 27 % to 32 %.
The hydroxypropyl celluloses used in accordance with the invention preferably
have
a hydroxypropyl group fraction of at most 5 %.
The hydroxypropyl celluloses used in accordance with the invention preferably
have
a hydroxypropyl group fraction of from 7 % to 12 %.
The cellulose ether(s) used in accordance with the invention, but in
particular the
methyl celluloses, preferably have a methoxy group fraction of from 26% to
33%, in
particular of from 27 % to 32 %, and a hydroxypropyl group fraction of at most
5 %.
The cellulose ether(s) used in accordance with the invention, but in
particular the
hydroxypropyl celluloses, preferably have a methoxy group fraction of from 26
% to
33 %, in particular of from 27 `)/0 to 32 %, and a hydroxypropyl group
fraction of from 7
% to 12%.
The cellulose ether(s) used in accordance with the invention usually have a
mean
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molecular weight Mn between 10,000 and 380,000 g/mol, preferably between
10,000
and 200,000 g/mol, in particular between 10,000 and 100,000 g/mol, in
particular
preferably between 12,000 and 60,000 g/mol, particularly preferably between
12,000
and 40,000 g/mol. The mean molecular weight Mn is usually determined by means
of
gel permeation chromatography (GPC).
The cellulose ether(s) used in accordance with the invention usually have a
degree of
polymerisation of from 50 to 1000.
The cellulose ether(s) used in accordance with the invention usually have a
viscosity
of from 10 to 40 mPas, measured as 2 wt. % solution in demineralised water
(demineralised water according to DIN standard EN50272-2:2001) at 20 C (30
seconds after activation of the solution (rest phase), measurements are taken
over a
further 30 seconds and the measured value is thus obtained after one minute),
for
example by means of Brookfield LVT.
The preparation according to the invention is usually applied as aqueous
preparation,
the solids content of cellulose ether(s) being 0.1 to 5.0 g/I. The aqueous
preparation
may also contain further constituents, for example anti-foaming agents, etc.
The polymer fibres finished in accordance with the invention demonstrate very
good
dispersibility of the fibres in water. On the one hand the fibres according to
the
invention disperse very quickly and remain dispersed over a relatively long
period of
time, and on the other hand polymer fibres finished in accordance with the
invention
also demonstrate good storage stability, i.e. even after storage of the fibres
prepared
in accordance with the invention of at least 1 month (at room temperature of
25 C
and a relative moisture in the range of from 20 to 70 `)/0), the fibres can
disperse
readily and are present very uniformly distributed in the form of dispersed
fibres. The
polymer fibres finished in accordance with the invention are also suitable for
stabilisation of aqueous dispersions, in which, besides the fibres according
to the
invention, solid particulate particles, for example mineral particles, are
additionally
present. Polymer fibres with a titre between 0.3 and 3 dtex and a fibre length
of
<10 mm, in particular <8 mm, particularly preferably <6 mm, in particular
preferably
<4 mm, are suitable for this embodiment.
The polymer fibres finished in accordance with the invention furthermore also
stabilise aqueous dispersions with other polymer fibres which are not finished
in
accordance with the invention. The other polymer fibres may differ in respect
of the
fibre-forming polymers or may also be identical, these other polymer fibres
not being
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finished in accordance with the invention. The fibres according to the
invention may
thus be well-suited for used in the production of wet-laid textile fabrics.
The addition
of the polymer fibres finished in accordance with the invention may be
performed in
the pulper or sheet former.
Polymer fibres with a titre between 0.3 and 3 dtex and a fibre length of <10
mm, in
particular <8 mm, particularly preferably <6 mm, in particular preferably <4
mm, are
suitable for this embodiment.
The synthetic polymer fibres according to the invention are produced by
conventional
methods. The synthetic polymer is firstly dried if necessary and fed to an
extruder.
The molten material is then spun by means of conventional apparatuses having
corresponding dies. The exit speed at the die outlet area is matched to the
spinning
speed, such that a fibre having the desired titre is created. The spinning
speed is
understood to be the speed at which the solidified threads are removed. The
threads
removed in this way may be fed either directly to stretching or may also be
wound
and stored and stretched at a later moment in time. The fibres and filaments
stretched in the usual manner may then be fixed by generally conventional
methods
and cut to the desired length to form staple fibres. In this case, the fibres
may be
uncrimped or crimped, and in the crimped version the crimping must be
configured
for the wet-laying method (low crimping).
The formed fibres may have round, oval and other suitable cross sections, or
also
other shapes, such as dumbell-shaped, kidney-shaped, triangular, or tri- or
multi-lobal
cross sections. Hollow fibres are also possible. Fibres formed from two or
more
polymers may also be used.
The fibre filaments thus produced are combined to form yarns and these in turn
to
form tows. The tows are initially laid down in cans for further processing.
The tows
stored intermediately in the cans are taken up and a large tow is produced.
Then, the large tow, these usually have 10-600 ktex, can be stretched using
conventional methods on a conveyor line, preferably at 10 to 110 m/min entry
speed
Here preparations can be applied which promote the stretching but do not
disadvantageously influence the subsequent properties.
The stretching ratios preferably extend from 1.25 to 4, particular from 2.5 to
3.5. The
temperature during the stretching lies in the range of the glass transition
temperature
of the tow to be stretched and for polyester, for example, is between 40 C and
80 C.
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The stretching can be executed as single-stage or if desired using a two-stage
stretching process (in this regard see for example US 3 816 486). Before and
during
the stretching one or more dressings can be applied using conventional
methods.
For the crimping/texturing of the stretched fibres which is to be carried out
optionally,
conventional methods of mechanical crimping using crimping machines known per
se
can be used. Preferred is a mechanical device for steam-assisted fibre
crimping,
such as a stuffer box. However, fibres crimped by other methods can also be
used,
thus for example three-dimensionally crimped fibres. In order to perform the
crimping
the tow is initially usually tempered to a temperature in the range of 500 to
100 C,
preferably 70 to 85 C, particularly preferably to about 78 C and treated with
a
pressure of the tow run-in rollers of 1.0 to 6.0 bar, particularly preferably
at about 2.0
bar, a pressure in the stuffer box of 0.5 to 6.0 bar, particularly preferably
1.5-3.0 bar,
with steam between 1.0 and 2.0 kg/min., particularly preferably 1.5 kg/min.
The preparation according to the invention is applied after the stretching,
and a
second time before the crimping machine, if a crimping is provided. The
preparation
according to the invention is usually heated and is applied to the fibre at an
application temperature in the range of from 30 to 110 C and is dried.
It has been found that the drying of the preparation according to the
invention and all
post-treatments of the fibres equipped with the preparation according to the
invention
are performed at a temperature of at most 120 C, since higher temperatures
have an
adverse effect on the dispersibility of the fibre. At temperatures of at most
120 C,
very homogeneous and uniform preparation applications are achieved, and
practically no settling is observed. Such an application is advantageous for
the
dispersibility according to the invention.
If the smooth or optionally crimped fibres are relaxed and/or fixed in the
furnace or
hot air stream, this occurs at temperatures of at most 130 C, since higher
temperatures have an adverse effect on the dispersibility of the fibres. At
temperatures above 130 C, the previously obtained homogeneous and uniform
preparation applications are damaged and the dispersibility according to the
invention
is reduced.
In order to produce staple fibres, the smooth or optionally crimped fibres are
taken
up, followed by cutting and optionally hardening and depositing in pressed
bales as
flock. The staple fibres of the present invention are preferably cut on a
mechanical
cutting device downstream of the relaxation. In order to produce tow types,
the
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cutting can be dispensed with. These tow types are deposited in bales in uncut
form
and pressed.
The fibres produced according to the invention in the crimped embodiment
preferably
have a degree of crimping of at least 2, preferably at least 3 crimps (crimp
arcs) per
cm, preferably 3 arcs per cm to 9.8 arcs per cm and particularly preferably
3.9 arcs
per cm to 8.9 arcs per cm. In applications to produce textile surfaces, values
for the
degree of crimping of about 5 to 5.5 arcs per cm are particularly preferred.
In order to
produce textile surfaces by means of wet-laying methods, the degree of
crimping
must be adjusted individually.
The aforesaid parameters spinning speed, stretching, stretching ratios,
stretching
temperatures, fixing, fixing temperature, run-in speeds, crimping/texturing
etc., are
determined according to the particular polymer. These are parameters which the
person skilled in the art selects in the usual range.
Textile fabrics can be produced from the fibres according to the invention,
which are
also the subject of the invention. As a result of the good dispersibility of
the fibres
according to the invention, such textile fabrics are preferably produced by
wet-laid
methods.
In addition to the improved dispersibility of the fibres in water, the polymer
fibre
according to the invention also exhibits a good pumpability of the dispersed
fibres in
water so that the polymer fibre according to the invention is particularly
well suited for
the production of textile fabrics using the wet-laying method. Since the
fibres
according to the invention promote the dispersibility of solid particulate
particles, for
example, mineral particles, textile fabrics with a mineral finish can also be
produced.
Polymer fibres with a titre between 0.3 and 3 dtex and a fibre length of <10
mm, in
particular <8 mm, particularly preferably <6 mm, in particular preferably <4
mm, are
suitable for this embodiment.
In addition to these wet-laying methods, what are known as melt-blowing
methods
(for example, as described in "Complete Textile Glossary, Celanese Acetate
LLC,
from 2000 or in "Chemiefaser-Lexikon, Robert Bauer, 10th edition, 1993) are
also
suitable. Such melt-blowing methods are suitable for producing fine-titre
fibres or
nonwovens, e.g. for applications in the hygiene sector.
The term "textile fabric" is therefore to be understood within the scope of
this
description in its broadest meaning. This can comprise all structures
containing the
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fibres according to the invention which have been produced by a surface-
forming
technique. Examples of such textile fabrics are nonwovens, in particular wet-
laid
nonwovens, preferably based on staple fibres or nonwovens produced by the melt-
blowing method.
The fibres according to the invention are characterised by significantly
improved
permanence of the dispersibility as compared with fibres without the additive
according to the invention. The fibres according to the invention have very
good
dispersibility, even after a relatively long period of storage, for example a
number of
weeks or months, in the form of bales or comparable structures.
In addition, the fibres according to the invention have an improved long-term
dispersion, i.e. with dispersion of the fibres according to the invention in
liquid media,
for example in water, the fibres remain dispersed for longer and only start to
settle
after a relatively long period of time.
In addition, the fibres according to the invention demonstrate a reduced fibre
fly,
which results in an improvement in occupational safety, since the preparation
ensures a significantly increased grip in the fibre composite. The reduced
fibre fly is
of great importance in particular for the formation of textile fabrics, for
example
nonwovens.
The textile fabrics produced by means of the fibres according to the invention
are in
particular wet-laid textile fabrics, in particular wet-laid nonwovens.
The textile fabrics produced by means of the fibres according to the invention
contain
the polymers according to the invention, to the surface of which between 0.1
and
20 wt. %, preferably 0.5 to 3 wt. % of a preparation is applied, which
preparation
comprises at least one cellulose ether selected from the group carboxymethyl
cellulose (CMC), methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl
cellulose
(HEC), hydroxypropyl cellulose (HPC), methylethyl cellulose (MEC),
hydroxyethylmethyl cellulose (HEMC), hydroxypropylmethyl cellulose (HPMC),
ethylhydroxyethyl cellulose, carboxymethylhydroxyethyl cellulose, and mixtures
thereof. The proportion of polymer fibres according to the invention in the
textile fabric
is usually at least 10 wt. %, in relation to the total weight of the textile
fabric,
preferably at least 20 wt. %, in particular at least 30 wt., %, particularly
preferably at
least 50 wt. %. In a particularly preferred embodiment, the textile fabric
consists
exclusively of the polymer fibres according to the invention.
Test methods:
Insofar as not already stated in the description above, the following
measurement
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and test methods are used:
Titre:
The titre was determined in accordance with DIN EN IS01973.
Dispersibility:
In order to assess the dispersibility, the following test method has been
developed
and is used in accordance with the invention.
The fibres according to the invention are cut to a length of 2-12 mm. The cut
fibres
are introduced at room temperature (25 C) into a glass vessel (dimensions:
length
150 mm; width 200 mm; height 200 mm), which is filled with demineralised water
(demineralised = completely desalinated). The amount of fibres is 0.25 g per
litre
demineralised water. For improved assessment, 1 g fibres and 4 litres
demineralised
water are usually used.
The fibre/demineralised water mixture is then stirred by means of a
conventional
laboratory magnetic stirrer (for example IKAMAG RCT) and a magnetic stirrer
bar (80
mm) for at least three minutes (rotational speed in the range of 750-1500 rpm)
and
the stirring unit is switched off. It is then assessed whether all fibres are
dispersed.
The dispersing behaviour of the fibres was assessed as follows:
not dispersed (-)
partially dispersed (o)
fully dispersed (+)
The above assessment was performed after defined time intervals.
A fibre not comprising the preparation according to the invention, but
otherwise
identical was used as a comparison.
Gelling temperature:
The gelling temperature was determined by means of an oscillation rheometer,
model
Physica MCR 301 from the company Anton Paar.
Insofar as not already specified in the above description, the following other
parameters were determined by means of the measurement or test methods
according to the publication "Methylcellulose, a Cellulose Derivative with
Original
Physical Properties and Extended Applications" in Polymers 2015, 7(5), 777-
803.
The invention is explained by the following example without its scope being
limited
. .
CA 03075545 2020-03-11
_
thereby.
Examples
Methyl cellulose solution was applied to melt-spun PLA fibres during
processing on
the conveyor line and was then dried. The produced PLA fibres thus have a
preparation on the surface comprising at least one methyl cellulose (MC).
The produced PLA fibres comprise the preparation according to the invention on
at
least 99 % of the total surface of the fibres.
The PLA fibres according to the invention were cut to a length of 6 mm, and 1
gram
of the cut PLA fibres was dispersed and examined at room temperature (25 C) as
described beforehand.
For comparison, 1 gram PLA fibres without the additive according to the
invention,
but otherwise identical, was dispersed and examined at room temperature (25 C)
as
described above.
The fibres according to the invention, in contrast to the comparison fibres
(without the
finish according to the invention), demonstrate a much improved long-term
dispersion, and a much improved permanence of the dispersibility following a
few
weeks storage.
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