Cellulose Fibre
The present invention relates to a cellulosic fibre of the Lyocell type.
In consequence of the environmental problems associated with the known viscose process
for the production of cellulosic fibres, intense efforts have been made in recent decades to
provide alternative and more environmentally friendly methods. A particularly interesting
possibility which thereby has arisen in recent years is to dissolve cellulose in an organic
solvent without a derivative being formed and to extrude moulded bodies from said solution.
Fibres spun from such solutions have received the generic name Lyocell from BISFA (The
International Bureau for the Standardization of man made fibers), wherein an organic solvent
is understood to be a mixture of an organic chemical and water.
Furthermore, such fibres are also known by the term "solvent-spun fibres".
It has turned out that in particular a mixture of a tertiary amine oxide and water is perfectly
suitable as an organic solvent for the production of Lyocell fibres and other moulded bodies,
respectively. Thereby, N-methylmorpholine-N-oxide (NMMO) is predominantly used as the
amine oxide. Other suitable amine oxides are disclosed in EP-A 553 070.
In EP 0 356 419 A, a technical implementation of the method of producing a solution of a
pulp in an amine oxide is described. In doing so, a suspension of the crushed pulp is
conveyed in an aqueous tertiary amine oxide in the form of a thin layer across a heating
surface, water is evaporated and, thereby, a spinnable cellulose solution is produced.
A method of spinning cellulose solutions in amine oxides is known from US 4,246,221.
According to said method, filaments extruded from a spinneret are guided through an air
gap, drawn therein and, subsequently, the cellulose is precipitated in an aqueous spinning
bath. The method is known as a „dry/wet spinning process“ or also as an „air-gap spinning
process“.
The entire method of producing fibres from solutions of cellulose in a tertiary amine oxide is
referred to in the following as an "amine oxide process", with the abbreviation "NMMO"
denoting hereinafter all tertiary amine oxides which are able to dissolve cellulose. Fibres
produced according to the amine oxide process are characterized by a high fibre strength in
the conditioned state as well as in the wet state, a high wet modulus and a high loop strength.
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The conditions within the air gap such as temperature, humidity, cooling rate of the filaments
as well as draft dynamics are of great significance for the properties of the resulting fibres
(see, in this connection, the publication by Volker Simon in „Transactions of the American
Society of Mechanical Engineers (ASME) 118 (1996) No. Feb., p. 246-249“).
Technical embodiments of the spinning process have been described in numerous
documents:
WO 93/19230 describes a method wherein the extruded filaments are cooled just beneath the
nozzle by being blasted with air. WO 94/28218 describes a nozzle design and a blowing
method. WO 95/01470 claims a laminar flow of the cooling gas stream described in WO
93/19230. WO 95/04173 describes a further technical implementation of blowing. In
WO 96/17118, the moisture content of the blowing air is defined. In WO 01/68958, the
blowing air stream is directed downwards toward the extruded filaments at an angle of from
0° to 45°. WO 03/014436 describes a blowing device comprising a suction of the blowing
air. WO 03/057951 claims the shielding of part of the air gap from the blowing air. In WO
03/057952, a turbulent gas stream for cooling the filaments is described. WO 05/116309
likewise describes the shielding of part of the air gap from the blowing air.
The fibres/filaments obtained according to the air-gap spinning process differ in structural
terms from known viscose fibres. While the crystalline orientation is approximately at the
same high level both in viscose fibres and in Lyocell fibes (a largely parallel arrangement of
the cellulose chains located in the structured areas of the fibre relative to the fibre axis),
considerable differences exist in the amorphous orientation (a higher parallelism of the
random portions in Lyocell fibres).
The particularities of the Lyocell fibre such as a high crystallinity, long and thin crystallites
and a high amorphous orientation prevent an adequate bond of the crystallites transversely to
the fibre axis. In the wet state, the swelling of the fibres additionally reduces the bonding
forces transversely to the fibre axis and thus leads to the separation of fibre fragments under
mechanical strain. This behaviour is referred to as wet fibrillation and causes quality losses
in the form of greying and hairiness in the final textile product.
Surveys of the state of research in this field are provided by the works of Josef Schurz,
Jürgen Lenz: „Investigations on the structure of regenerated cellulose fibers“ in
Macromolecular Symposia, Volume 83, Issue 1, pages 273–289, May 1994, and Fink H-P,
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Weigel P, Purz H-J, Ganster J „Structure formation of regenerated cellulose materials from
NMMO-solutions“ Prog.Polym.Sci. 2001 (26) p. 1473-1524.
Previous efforts to improve the wet-fibrillation resistance of Lyocell fibres were aimed in
two directions:
- varying the manufacturing conditions, or
- introducing a step of chemical cross-linking during the production process
However, it is hardly possible to evaluate the success of the measures of reducing fibrillation
which have been described in each case. There is no standardized method of measuring the
fibrillation behaviour, and all the methods applied in the patent literature are proprietary.
The second procedure, chemical cross-linking, is associated with a number of drawbacks
such as
- additional chemicals/costs of chemicals/waste water problems during the production of the
fibre
- environmental pollution during the production of the cross-linking chemicals
- inadequate hydrolysis stability of cross-linking under the conditions of textile processing.
Examples of the procedure of chemical cross-linking are described in EP 0 53 977 A, EP 0
665 904 A and EP 0 943 027 A, respectively.
Numerous documents have been published with regard to the first procedure, varying the
manufacturing conditions. However, the described methods have either brought about only a
slight improvement in the fibrillation behaviour, which has not been reflected in a lasting
improvement of processability, or the methods have failed to be feasible on a large scale as a
result of the costs/technical expenditures.
In SU 1,224,362, a dope is spun from a single pulp into a bath containing NMMO in amyl
alcohol or isopropanol, respectively. WO 92/14871 claims a fibre with a reduced fibrillation,
characterized in that the pH of the spinning bath and of subsequent washing baths is below
8.5. No details are given about the type of the pulp or the spinning conditions.
WO 94/19405 describes a method wherein a pulp mixture is used. However, no reference is
made to the tendency toward fibrillation of the fibres which have been spun.
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WO 95/02082 describes a combination of process parameters, illustrated in a mathematical
expression, for the production of a fibre with a low tendency toward fibrillation. Said process
parameters are the diameter of the spinning hole, the output of spinning mass, the titre of the
filaments, the width of the air gap and the humidity in the air gap. The pulp used is not
described in detail, the spinning temperature is only 115°C.
In WO 95/16063, the extruded filaments are contacted in the spinning bath or in the
aftertreatment baths, respectively, with a surfactant in a dissolved form. The type of the pulp
used is not specified, the spinning temperature is 115°C.
WO 96/07779 uses an organic solvent, preferably polyethylene glycol, as a spinning bath.
No details are given about the pulp used or the textile-mechanical properties of the obtained
fibres. 110°C is indicated as the spinning temperature.
In WO 96/07777, the extruded filaments are contacted in the air gap with an aliphatic
alcohol provided in a gaseous form. The type of the pulp used is not specified, the spinning
temperature is 115°C.
WO 96/20301 describes a method wherein the moulded solution is guided consecutively
through at least two precipitation media, with a slower coagulation of the cellulose occurring
in the first precipitation medium as compared to the latter precipitation medium. In the
examples, a higher alcohol is preferably used as the first precipitation medium. The pulp
used is not indicated, the spinning temperature amounts to 115°C.
WO 96/21758 describes a method wherein the moulded solution is blasted in the air gap in
an upper zone with air having a higher moisture content and in a lower zone with air having
a lower moisture content. Single pulps of various degrees of polymerization are used as
pulps, the spinning temperature amounts to 115°C.
EP 0 853 146 describes a two-stage method wherein the dwell time of the fibres in the first
precipitation stage is adjusted such that merely the stickiness of the surface of the solution
moulded into fibres is prevented and the fibres are coagulated without tension in a later
precipitation stage. In the examples, the spinning temperature amounts to 109 – 112°C.
In WO 97/23669, spinning takes place into a spinning bath having a content of NMMO of
more than 60%. A single pulp is used.
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In WO 97/35054, a combination of parameters for obtaining a fibre low in fibrillation is
described, namely the concentration of the dope, the draft in the air gap as well as the
diameter of the nozzle hole. A single pulp is used, the spinning temperature ranges from 80
to 120°C.
In WO 97/38153, a combination of parameters for obtaining a fibre low in fibrillation is
likewise described, namely the length of the air gap, the spinning rate, the dwell time in the
air gap, the speed of the blowing air in the air gap, the moisture content of the blowing air as
well as the product of the dwell time in the air gap times the moisture content of the blowing
air. A single pulp is used as the pulp.
In WO 97/36028, the fibres are treated with a solution of 40 – 80% NMMO, optionally with
an additive being added, upon leaving the precipitation bath.
In WO 97/36029, the fibres are treated with a solution of zinc chloride upon leaving the
precipitation bath.
In WO 97/46745, the fibres are treated with a solution of NaOH upon leaving the
precipitation bath.
In WO 98/02602, the fibres are treated with a solution of NaOH upon leaving the
precipitation bath in a relaxed state.
In WO 98/06745, a pulp mixture is used which is obtained by mixing solutions of pulps of
different degrees of polymerization. No details are given with regard to the spinning
temperature.
In WO 98/09009, the addition of additives (polyalkylenes, polyethylene glycols,
polyacrylates) to the spinning mass is described. A single pulp is used as the pulp.
In WO 98/22642, a pulp mixture having a low degree of polymerization is used. The
spinning temperature amounts to 110 - 120°C.
Also in WO 98/30740, a pulp mixture is used, the spinning mass is spun according to a
centrifugal spinning process. The spinning temperature amounts to 80 – 120°C.
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In WO 98/58103, details about the molecular weight distribution of the pulp in a spinning
mass from a pulp mixture are indicated, which lead to stable spinning. However, no
reference is made to the fibrillation behaviour of the obtained fibres/filaments.
In DE 19753190, the fibres are treated with a concentrated NMMO solution upon leaving the
precipitation bath.
In GB 2337990, a co-solvent is used for dissolving the single pulp. The nascent solution is
spun at 60 – 70°C.
In US 6471727, a spinning mass from a single pulp with a high content of hemicellulose and
lignin is processed according to a dry/wet or meltblown spinning process, respectively.
In WO 01/81663, a spinneret is described in which the spinning capillary is directly heated
close to the outlet cross-section. Said measure is supposed to reduce the tendency toward
fibrillation of Lyocell fibres, however, no test conditions are specified for this.
WO 01/90451 describes a spinning method characterized by a mathematical relationship
including the heat flux density in the air gap and the ratio of length to diameter of the
extrusion channel. Fibres spun according to the invention are proposed to display a lower
tendency toward fibrillation, however, no further details are given in this connection.
In US 6773648, a meltblown process for the production of a fibrillation-reduced fibre is
made public. Due to their irregular titres, meltblown fibres are unsuitable for textile use.
In DE 10203093, a fibre with a low fibrillation is produced by spinning two dopes of
different cellulose concentrations from a single pulp from a biocomponent nozzle. No
example is given.
In DE 10304655, polyvinyl alcohol is added to the NMMO in order to improve the quality of
the solution. The conditions for spinning the claimed less fibrillating fibre are not indicated.
The specific structure of the Lyocell fibre leads, on the one hand, to excellent textilemechanical
properties such as a high strength in both the dry and wet states as well as to a
very good dimensional stability of the planar assemblies produced therefrom and, on the
other hand, to little flexibility (high brittleness) of the fibres, which manifests itself in a
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decrease in the abrasion resistance in comparison to viscose fibres within the planar
assembly.
The term flexibility (compliance) is defined, according to Hooke’s Law, as the quotient from
the elongation of the test body and the load causing the elongation. Increasing the flexibility
of Lyocell fibres is the object of a number of publications:
A flexible Lyocell fibre is described in EP 0 686 712. The patent claims a fibre with a
reduced NMR degree of order, obtained by adding nitrogenous substances such as urea,
caprolactam or aminopropanol to the polymer solution or into the precipitation bath,
respectively. However, a fibre with a very low wet strength is obtained; thus, the fibre differs
distinctly from the fibres according to the invention as described below.
In WO 97/25462, a method for the production of a flexible and fibrillation-reduced fibre is
described, wherein, after the precipitation bath, the moulded fibre is guided through a
washing and aftertreatment bath containing an aliphatic alcohol, in addition, optionally, with
an additive of sodium hydroxide. The properties of the obtained fibres are described only
very insufficiently. In particular data about the dry and wet strengths are missing, which
would allow classification in the „Höller chart“, as described in further detail below.
It may be said, however, that, in the examples of the present application, the fiber shows
considerable differences in a comparison of the fibre elongations indicated in said document
with the corresponding data of the fibres according to the invention and that, due to the low
values of elongation as indicated in said document, the flexibility of the fibre cannot be very
high according to the above-mentioned definition of flexibility. The improvement in the
fibrillation behaviour as mentioned in the text of the document is not confirmed by any data
whatsoever.
Documents EP 1 433 881, EP 1 493 753, EP 1 493 850, EP 1 841 905, EP 2 097 563 and EP
2 292 815 describe fibres and filaments, respectively, preferably for the application tyre
cord, produced by adding polyvinyl alcohol to the NMMO/dope. The fibres/filaments are
characterized by high strength, but little elongation. Accordingly, their flexibility can only be
minor according to the above-mentioned definition.
Further publications which indicate that, by adding additives to the spinning mass, influence
can be exerted on the fibrillation behaviour and/or the flexibility of the fibre, are
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Chanzy H, Paillet m, Hagege R „Spinning of cellulose from N-methylmorpholine N-oxide in
the presence of additives“ Polymer 1990, 31, p 400-5
Weigel P, Gensrich J, Fink H-P „Strukturbildung Cellulosefasern aus Aminoxidlösungen“
Lenzinger Berichte 1994; 74(9), p 31-6 and
Mortimer SA, Peguy AA „Methods for reducing the tendency of lyocell fibers to fibrillate“
J.appl.Polym.Sci. 1996, 60, p 305-16.
WO 2014/029748 (not pre-published) discloses the manufacture of solvent-spun cellulosic
fibres, especially from solutions in ionic liquids. Further state of the art in this regard is
known from DE 10 2011 119 840 A1, AT 506 268 A1, US 6,153,136, CN 102477591A,
WO 2006/000197, EP 1 657 258 A1, US 2010/0256352 A1, WO 2011/048608 A2, JP
2004/159231 A and CN 101285213 A.
The invention of viscose fibres (Cross and Bevan 1892, GB 8700) occurred more than a
hundred years ago. Despite weaknesses in the production (environmental problems) and the
properties (poor washing behaviour of the standard type), more than one million tons of said
fibre type is produced each year.
The further development of the old process after the second world war (polynosic and modal
fibres) resulted in fibres with a better washing behaviour and a higher dimensional stability,
but was unable to change the intrinsic properties of the method (environmental relevance as
well as, due to the large number of process steps, an extremely complicated method).
Conversely, it became apparent during the development of the new fibre type „Lyocell“ that,
due to its varying structure, the fibre places special demands on the processing conditions
and, thus, the established methods of processing a viscose or modal fibre cannot be applied
in the textile chain. Special machines and processing adjustments which are adapted to the
fibre are required especially for dyeing and wet finishing. Today, more than 20 years after
the Lyocell fibre was placed on the market, this is still regarded as a disadvantage.
Now it would be desirable to impart particular properties of the viscose fibre such as
- a lower tendency toward fibrillation in the wet state
- higher flexibility (less brittleness)
to the Lyocell fibre while maintaining the excellent properties of the Lyocell fibre (such as,
e.g., a high wet strength, a high wet modulus and, hence, a washability and a dimensional
stability which, in comparison to viscose fibres, are substantially improved).
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It is thus an object of the present invention to provide a Lyocell fibre with properties more
similar to viscose by means of which processing of the fibre according to the well-known
and established methods of viscose processing is rendered possible.
The change in properties should be achieved solely by choosing suitable process parameters
for the production of the fibre, without having to fall back on chemicals extraneous to the
process as additives to either the spinning mass, the spinning bath or during the
aftertreatment. Every additional chemical in the system, be it as an additive to the spinning
mass or to the spinning bath, necessitates increased efforts for the recovery and constitutes a
cost factor.
The object of the present invention is achieved by a cellulosic fibre of the Lyocell type
which has a titre of from 0.8 dtex to 3.3 dtex and is characterized by the following
relationships:
Höller factor F2 ≥ 1, preferably ≥ 2
Höller factor F1 ≥ -0.6
Höller factor F2 ≤ 6 and
Höller factor F2 minus 4.5*Höller factor F1 ≥ 1, preferably ≥ 3.
Short description of the figures
Fig. 1 shows a Höller chart of commercially available fibres from regenerated cellulose prior
to the development of the Lyocell fibre.
Fig. 2 shows the area in the Höller chart in which the fibres according to the invention are
located.
Fig. 3 shows a Höller chart in which the fibre according to the invention is contrasted to a
common Lyocell fibre.
Detailed description of the invention
In the following, the new Lyocell fibres according to the invention are described by
reference to the so-called „Höller factors“ F1 and F2 and are distinguished from known
cellulosic man made fibres of the prior art.
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While the basic chemical structure of man made cellulosic fibres such as, e.g., viscose fibres,
but also of Lyocell fibres, is essentially the same (cellulose), the fibres differ in factors such
as, e.g., the crystallinity or also the orientation in particular of amorphous areas. It is difficult
to quantitatively distinguish those factors from each other.
It is also apparent to a person skilled in the art that a Lyocell fibre differs, for example, from
a viscose fibre in textile-mechanical parameters (such as, e.g., strength values), but also in
properties which can be defined less clearly, e.g., the textile “grip”. Likewise, there are
considerable differences between the different types of cellulose fibres produced according
to the viscose process such as, e.g., a (standard) viscose fibre, a modal fibre or a polynosic
fibre.
In the essay by R. Höller „Neue Methode zur Charakterisierung von Fasern aus
Regeneratcellulose“ Melliand Textilberichte 1984 (65) p. 573-4, a clear differentation
between the different fibre types made of regenerated cellulose known at the time, i.e., the
fibres produced according to the viscose process, could be presented on the basis of
quantitative features.
According to this suggestion the complexity of the comparison of a greater number of fibre
properties could be simplified significantly by way of formation of few parameters splitting
fibres into groups of similar properties and by factor analysis. Factor analysis is a
multivariate statistical method which makes it possible to reduce a group of correlated
features to a smaller number of uncorrelated factors.
The textile-mechanical properties used by Höller for factor analysis were the maximum
tensile force conditioned (FFk) and wet (FFn), the maximum tensile force elongation
conditioned (FDk) and wet (FDn), the wet modulus (NM), the loop strength conditioned
(SFk) as well as the knot strength conditioned (KFk).
All those measurands as well as their determination are known to a person skilled in the art,
see, in particular, BISFA regulation „Testing methods viscose, modal, lyocell and acetate
staple fibers and tows“ Edition 2004 Chapters 6 and 7, and will be described in further detail
below.
In the fibre collective available to Höller, 87% to 92% of the variance between the samples
could be detected by merely two factors (see Fig. 1). Those two factors are calculated as
follows:
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Höller factor F1 = -1.109 + 0.03992xFFk – 0.06502xFDk + 0.04634xFFn – 0.04048xFDn +
0.08936xNM + 0.02748xSFk + 0.02559xKFk
Höller factor F2 = -7.070 + 0.02771xFFk +0.04335xFDk + 0.02541FFn + 0.03885FDn –
0.01542xNM + 0.2891xSFk + 0.1640xKFk.
As can be seen in Fig. 1, a clear differentiation between the different fibre types could be
illustrated by way of this analysis – drawn up on the basis of clearly measurable parameters.
Fig. 1 shows in the coordinate system of Höller factors F1 and F2 the fibre collective made
up of 70 samples of commercially available fibres of regenerated cellulose which has been
examined by Höller. Along factor F1, it is possible to identify the division into (standard)
viscose fibres and modal fibres, which are also listed by BISFA as different fibre types
(although they are produced according to the same basic method, namely the viscose
process). To the left of the ordinate, the region of (standard) viscose fibres is shown
(designated as “V” in figure 1). Essentially to the right of the ordinate the region of modal
fibres is shown, which are further structured in two sub-groups, i.e. fibres of the HWM-type
(“HWM” – high wet modulus) and fibres of the polynosic type (“PN”). In addition, a
(dashed) boundary is plotted in the graph, beyond which none of the fibres made of
regenerated cellulose and examined at the time were located. However, at the time of this
publication, Lyocell fibres were still in the trial stage and not commercially available.
Lyocell fibres which currently are commercially available have Höller F1 values of 2 to 3
and F2 values of 2 to 8. In the „Höller chart“ according to Fig. 1, such fibres would therefore
be located beyond the above-mentioned boundary, from which the considerable difference
between the fibres of the viscose group and the Lyocell fibres is apparent already purely
visually.
The fibre according to the invention is now located in an area of the Höller chart which can
be illustrated by a square.
The sides of the square correspond to the following values or relationships, respectively:
Lower boundary F2 = 1
Left-hand boundary F1 = -0.6
Upper boundary F2 = 6
Right-hand boundary defined via the relationship:
Höller factor F2 minus 4.5*Höller factor F1 ≥ 1, preferably ≥ 3
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The arrangement of the Lyocell fibre according to the invention in the Höller chart resulting
from said relation is shown in Fig. 2. Loosely speaking, the fibre according to the invention
thus occupies in the Höller chart the space above the abscissa and around the ordinate as well
as to the left thereof and is clearly distinguished from Lyocell fibres which are currently
commercially available and, in the Höller chart, are located, loosely speaking, (considerably)
to the right of the ordinate.
Conversely, the Lyocell fibre according to the invention is located in the Höller chart close
to the area of the (standard) viscose. Actually, it has been shown that the Lyocell fibre
according to the invention has, with regard to its processability, properties which are by far
“more similar to viscose” than those of Lyocell fibres which are currently commercially
common.
In textile practice, these “more viscose-like” properties lead to the following property
changes:
- The fibre according to the invention can be dyed as a planar assembly like viscose in a
strand (conventional Lyocell fibres are only suitable for open-width dyeing).
- Planar assemblies (such as knitted fabrics) made of the fibre according to the invention,
which have not been subjected to high-grade finishing with a resin finish, will keep an
unchanged fabric appearance for a longer time when being washed.
- Planar assemblies made of the fibre according to the invention exhibit an abrasion
resistance similar to planar assemblies made of viscose and hence display an improvement
by the double in comparison to conventional Lyocell fibres.
However, the fibre according to the invention retains during washing processes the high
dimensional stability which is characteristic of the Lyocell fibre.
Although the areas of the fibre according to the invention and of (standard) viscose fibres as
well as, partially, of modal fibres overlap in the Höller chart, the fibre types can, however,
clearly be differentiated from each other based on basic differences in the manufacturing
process, since the fibre according to the invention can be analytically distinguished
unambiguously from fibres produced according to the viscose process such as (standard)
viscose fibres and modal fibres:
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- A residual amount of solvent associated to the fibre type Lyocell is detectable (in particular
residues of NMMO in case of fibres produced according to the amine oxide process).
- Unlike a fibre produced according to the viscose process, the fibre contains no sulphur.
According to the method described below, the wet abrasion behaviour of the fibre according
to the invention ranges between 300 and 5000 revolutions up to the point of fibre breakage,
preferably between 500 and 3000 revolutions.
The flexibility (i.e., the quotient FDk/FFk) of the fibre according to the invention preferably
ranges between 0.55 and 1.00, preferably between 0.65 and 1.00.
It has been shown that the dry abrasion according to Martindale of a single jersey 150 g/m2
made of a ring yarn Nm 50/1 of the fibre according to the invention may range between
30 000 and 60 000 tours up to the point of hole formation.
The fibre according to the invention is preferably characterized in that it is produced
according to the amine oxide process.
The fibre according to the invention is preferably provided as a staple fibre, i.e., as cut fibres.
The property change according to the invention of Lyocell fibres toward a Lyocell fibre
similar to viscose and hence the repositioning of the fibre data in the Höller chart is
achieved, according to the present invention, by carefully adjusting the raw material and the
process conditions:
1) Pulp
A defined molecular weight distribution of the raw material used is required for the
production of the fibre according to the invention. This is achieved in particular by mixing
two or more single pulps. Accordingly, the fibre according to the invention is preferably
characterized in that it is produced from a mixture of at least two different pulps.
The molecular weight distribution is characterized by the following parameters:
a) The amount of celluloses or accompanying substances of cellulose (polymeric pentosans
and hexosans such as xylan, glucomannan, low-molecular beta-1,4-glucan) with a degree of
polymerization of less than 50 is below 2% (based on the pulp mixture), preferably below
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1.5 % (determination of the molecular weight distribution with GPC/SEC by MALLS
detection in DMAC/LiCl, Bohrn, R., A. Potthast, et al. (2004). "A novel diazo reagent for
fluorescence labeling of carboxyl groups in pulp." Lenzinger Berichte 83: 84-91).
b) An amount of 70% to 95% of the pulp mixture has a limiting viscosity number ranging
from 250 to 500 ml/g, preferably from 390 to 420 ml/g (measured according to SCAN-CM
15:99), in the following referred to as the „low-molecular component“.
c) An amount of 5% to 30% of the pulp mixture has a limiting viscosity number of from
1000 to 2500 ml/g, preferably of 1500 – 2100 ml/g, in the following referred to as the „highmolecular
component“.
d) Preferably, the amount of the low-molecular component is 70 - 75%, if the high-molecular
component has a limiting viscosity number of 1000 – 1800 ml/g, and, respectively, 70 -
95%, if the high-molecular component has a limiting viscosity number of > 2000 ml/g.
e) Furthermore, the purity of the pulps used is important: The purity is defined as the mean
value of alkali resistances R10 and R18 according to DIN 54355 (1977), i.e. the
determination of the resistance of pulp against caustic soda (alkali resistance). Said value
approximately corresponds to the content of alpha cellulose according to TAPPI T 203 CM-
99.
The purity of the low-molecular component is > 91%, preferably > 94%, the purity of the
high-molecular component is > 91%, preferably > 96%.
It has been shown that, in particular by using high-purity pulps such as cotton linter pulps, it
is possible more easily to produce fibres displaying the properties according to the invention.
Furthermore, it has been shown that pulps made from reclaimed cotton textiles (“reclaimed
cotton fibres” – RCF) are suitable for the manufacture of the fibres according to the
invention. Such pulps can be produced according to the teaching of the publication „Process
for pretreating reclaimed cotton fibres to be used in the production of moulded bodies from
regenerated cellulose “ (Research Disclosure, www.researchdisclosure.com, database
number 609040, published digitally December 11, 2014).
2) Spinning conditions
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In addition to choosing the appropriate pulp composition, the spinning conditions for
producing the fibre according to the invention are of particular importance:
i) The throughput of spinning mass should range between 0.01 and 0.05 g/nozzle hole/min,
preferably between 0.015 and 0.025 g/nozzle hole/min.
ii) Air gap length: The procedure of producing the fibre according to the invention differs
from the prior art (WO 95/02082, WO 97/38153) in that the air gap length does not
constitute a relevant parameter. Fibres according to the invention are obtained already with
an air gap length starting from 20 mm.
iii) Climate within the air gap: The production of the fibre according to the invention also
differs from the prior art (WO 95/02082, WO 97/38153) in that the humidity and the
temperature of the blowing air do not constitute relevant parameters. Humidity values of the
blowing air of between 0 g/kg air and 30 g/kg air are applicable, and the temperature of the
blowing air may range between 10°C and 30°C (it is known to a person skilled in the art that,
for a given humidity setpoint of the blowing air, a minimum air temperature corresponding
to a relative humidity of 100% cannot be fallen short of).
The speed of the blowing air in the air gap is lower than for the production of Lyocell fibres
which currently are commercially available and should be below 3 m/sec, preferably at about
1 - 2 m/sec.
iv) Draft in the air gap: The value of the draft in the air gap (quotient of the haul-off speed
from the spinning bath to the extrusion speed from the nozzle) should be below 7. Given a
defined titre of the fibre, a small draft is achievable by using nozzles with small hole
diameters. Nozzles having a hole diameter of ≤ 100 μm are usable, nozzles having a hole
diameter of between 40 μm and 60 μm are preferred.
v) Spinning temperature: Spinning must occur at a temperature as high as possible, which is
limited only by the thermostability of the solvent. However, it must not fall short of a value
of 130°C.
vi) The spinning bath temperature may range between 0°C and 40°C, values of from 0°C to
10°C are preferred.
17
vii) During the transport of the fibre from the spinning bath into the aftertreatment and
during the aftertreatment, the filaments should be exposed, according to WO 97/33020, to a
tensile load in the longitudinal direction of not more than 5.5 cN/tex.
It has been shown that, if the above parameters are met, Lyocell fibres which comply with
the relations according to the invention with regard to the two Höller factors F1 and F2 and
thus have more “viscose-like” properties are obtained in a reproducible way.
The present invention also relates to a fibre bundle comprising a plurality of fibres according
to the invention. A "fibre bundle" is understood to be a plurality of fibres, for example, a
plurality of staple fibres, a strand of continuous filaments or a bale of fibres.
Measuring methods:
Testing of textile-mechanical properties:
The determination of the titre of the fibres (linear density) was carried out according to
BISFA regulation „Testing methods viscose, modal, lyocell and acetate staple fibers and
tows“ Edition 2004 Chapter 6 by means of a vibroscope, type Lenzing Technik.
The determination of the maximum tensile force (breaking tenacity), of the maximum tensile
force elongation (elongation at break) in the conditioned and wet state, and of the wet
modulus was carried out, according to the above-mentioned BISFA regulation, Chapter 7, by
means of a tensile testing device Lenzing Vibrodyn (device for tensile tests on single fibres
at a constant deformation speed).
The loop strength was determined on the basis of DIN 53843, Part 2, in the following way:
The titres of the two fibres used for the test are determined on the vibroscope. For
determining the loop strength, the first fibre is formed into a loop and clamped with both
ends into the pre-load weight (size of the pre-load weight according to the above-mentioned
BISFA regulation, Chapter 7). The second fibre is drawn into the loop of the first fibre and
the ends are placed into the upper clamp (measuring head) of the tensile testing device in
such a way that the interlacing is located in the middle of the two clamps. After the pre-load
has levelled out, the lower clamp is closed and the tensile test is started (clamping length 20
mm, traction speed 2 mm/min). It should be made sure that the breakage of the fibre occurs
at the loop arc. As a titre-related loop strength, the measured maximum tensile force value,
which has been obtained, is divided by the smaller one of the two fibre titres.
18
The knot strength was determined on the basis of DIN 53842, Part 1, in the following way:
A loop is formed from the fibre to be tested, one end of the fibre is drawn through the loop
and, thus, a loose knot is formed. The fibre is placed into the upper clamp of the tensile
testing device in such a way that the knot is located in the middle between the clamps. After
the pre-load has levelled out, the lower clamp is closed and the tensile test is started
(clamping length 20 mm, traction speed 2 mm/min). For the evaluation, only results are used
in which the fibre has actually broken at the knot.
Determination of the fibrillation behaviour according to the wet abrasion method:
The method described in the publication by Helfried Stöver: „Zur Fasernassscheuerung von
Viskosefasern“ Faserforschung und Textiltechnik 19 (1968) Issue 10, p. 447-452, was
employed.
The principle is based on the abrasion of single fibres in the wet state using a rotating steel
shaft coated with a viscose filament hose. The hose is continuously moistened with water.
The number of revolutions until the fibre has been worn through and the pre-load weight
triggers a contact is determined and related to the respective fibre titre.
Device: Abrasion Machine Delta 100 of Lenzing Technik Instruments
Departing from the above-cited publication, the steel shaft is continuously shifted in the
longitudinal direction during the measurement in order to prevent the formation of grooves
in the filament hose.
Source of supply of the filament hose: Vom Baur GmbH & KG. Marktstraße 34, D-42369
Wuppertal
Test conditions:
Water flow rate: 8.2 ml/min
Speed of rotation: 500 U/min
Abrasion angle: 40° for titre 1.3 dtex, 50° for titre 1.7 dtex, 50° for titre 3.3 dtex
Pre-load weight: 50 mg for titre 1.3 dtex, 70 mg for titre 1.7 dtex, 150 mg for titre 3.3 dtex
Determination of the abrasion resistance of planar assemblies according to Martindale:
Methods according to the standard „Determination of the Abrasion Resistance of Planar
Textile Assemblies by means of the Martindale Method - Part 2: Definition of the
19
Destruction of Samples (ISO 12947-2:1998+Cor.1:2002; German version EN ISO 12947-
2:1998+AC:2006).
Examples:
The pulps and pulp mixtures, respectively, described below in Table 1 were processed into
spinning masses of the composition indicated in Table 2 and spun into fibres having a titre of
approx. 1.2 to approx. 1.6 dtex by a spinning method according to WO 93/19230 under the
conditions of Table 2.
Constant parameters not indicated in the table are:
- the spinning mass output of 0.02 g/hole/min
- the air gap of 20 mm
- the humidity of the blowing air of 8 - 12 g H2O/kg air
- the temperature of the blowing air of 28 – 32°C
- the speed of the blowing air in the air gap of 2 m/sec
The textile-mechanical data of the obtained fibres are indicated in Table 3. The Höller
factors calculated from the textile data, the wet abrasion value and the flexibility of the fibres
can be seen in Table 4. The results clearly show the impact of the pulp and the particular
importance of the spinning temperature.
Table 1:
Pulp code
limiting
viscosity
number
alpha
content
amount of
DP <50 DP>2000
ml/g % %
Solucell 250 So 250 270 91.8 1.3 2.8
Borregard Derivative HV Bo HV 1030 n.b. 1.4 49.1
Saiccor Sai 383 90.4 6.6 14.9
Borregard Derivative VHV Bo VHV 1500 92.7 n.b. n.b.
Solucell 400 So 400 415 94.9 1.9 11.8
Cotton Linters low MW Co LV 396 97.1 0.6 0
Cotton Linters high MW Co HV 2030 99.1 0 98.3
20
Pulp code
limiting
viscosity
number
alpha
content
amount of
DP <50 DP>2000
Reclaimed cotton fibers,
low MW RCF LV 423 97.1 0.45 7.7
Reclaimed cotton fibers,
high MW RCF HV 1840 97.8 0 68.7
The pulps “RCV LV” and “RCV HV” were produced according to the teaching of the
publication „Process for pretreating reclaimed cotton fibres to be used in the production of
moulded bodies from regenerated cellulose “ (Research Disclosure,
www.researchdisclosure.com, database number 609040, published digitally December 11,
2014).
Table 2:
pulp or pulp mixture,
respectively
ratio high-molecular
amount/lowmolecular
amount
cellulose in spinning
mass
water in spinning
mass
nozzle
draft
spinning temperature
spinning bath
temperature
%
%
μ
°C
°C
Example 1 Co HV/Co LV 10 / 90 11 12 40 1.54 131 0
Example 2 Co HV/Co LV 10 / 90 11 12 50 2.41 131 0
Example 3 Co HV/Co LV 10 / 90 11 12 60 3.47 130 0
Example 4 Co HV/Co LV 10 / 90 11 12 80 6.17 130 0
Example 5 Co HV/Co LV 10 / 90 11 12 60 3.47 130 20
Example 6 Co HV/Co LV 10 / 90 11 10.5 50 2.41 132 0
Example 7 Co HV/Co LV 10 / 90 11 10.5 50 2.41 132 20
Example 8 Co HV/Co LV 10 / 90 13 11.7 50 2.85 131 0
Example 9 Co HV/Co LV 5 / 95 13.5 10 50 2.96 130 20
Example 10 Co HV/Co LV 5 / 95 13.5 10 50 2.96 131 0
Example 11 Bo HV/So 250 30 / 70 11 12 40 1.54 130 20
Example 12 Bo HV/So 250 30 / 70 11 12 50 2.41 130 20
Example 13 Bo HV/So 250 30 / 70 11 12 60 3.47 130 20
21
pulp or pulp mixture,
respectively
ratio high-molecular
amount/lowmolecular
amount
cellulose in spinning
mass
water in spinning
mass
nozzle
draft
spinning temperature
spinning bath
temperature
%
%
μ
°C
°C
Example 14 Bo HV/So 250 30 / 70 11 12 70 4.73 130 20
Example 15 Bo VHV/So 400 24 / 76 11 12 50 2.41 132 20
Example 16
RCF HV /
RCF LV 10 / 90 11 12 50 2.41 130 0
Example 17
Bo VHV /
RCF LV 10 / 90 11 12 50 2.41 132 0
Comparative
Example 1 Co HV/Co LV 5 / 95 13.5 10 50 2.96 122 0
Comparative
Example 2 Co HV/Co LV 10 / 90 11 12 100 9.64 130 20
Comparative
Example 3 Sai 12.8 10.5 40 1.80 132 20
Comparative
Example 4
(commercial
Lyocell fibre) Sai 13 10.5 100 11.4 124 20
Table 3:
titre FFk FDk FFn FDn NM SFk KFk
dtex cN/tex % cN/tex % cN/tex, 5% cN/tex cN/tex
Example 1 1.37 21.8 15.2 16.7 22.8 4.2 14.8 21.3
Example 2 1.37 25.1 21.5 17.8 28.2 3.9 15.7 23.3
Example 3 1.37 26.4 17.4 19.0 22.2 4.8 16.3 23.3
Example 4 1.37 26.3 16.5 20.8 22.8 5.4 17.5 25.1
Example 5 1.36 26.0 14.0 17.5 20.5 4.7 14.5 22.7
Example 6 1.23 24.5 19.0 18.7 25.5 4.4 16.1 22.5
Example 7 1.34 24.7 17.5 20.0 24.4 5.5 16.7 24.1
Example 8 1.54 26.4 16.1 19.5 21.7 4.7 17.4 23.6
Example 9 1.29 27.5 14.9 20.5 21.0 5.8 20.6 24.9
Example 10 1.37 24.8 17.8 19.4 24.2 4.5 19.1 23.6
Example 11 1.34 21.3 14.1 14.9 22.8 3.6 11.5 19.2
22
titre FFk FDk FFn FDn NM SFk KFk
dtex cN/tex % cN/tex % cN/tex, 5% cN/tex cN/tex
Example 12 1.30 24.1 15.2 15.4 19.2 4.4 10.2 19.4
Example 13 1.37 22.9 15.9 18.1 22.7 4.4 11.1 20.3
Example 14 1.30 25.3 14.6 19.4 21.8 5.0 12.0 20.5
Example 15 1.30 27.5 16.9 22.7 22.8 6.0 13.2 23.8
Example 16 1.36 24.6 16.0 18.5 23.9 4.2 14.8 22.4
Example 17 1.32 23.1 16.5 17.9 24.5 4.0 14.1 20.9
Comparative
Example 1 1,30 28.8 15.0 21.1 23.6 5.3 20.9 25.2
Comparative
Example 2 1.43 27.7 11.1 21.6 16.1 8.1 16.7 25.0
Comparative
Example 3 1.31 30.1 13.5 22.3 16.4 6.9 11.3 21.1
Comparative
Example 4
commercial
Lyocell fibre 1.37 39.3 13.6 34.9 18.6 10.6 18.9 31.7
Table 4:
Höller
factor
Höller
factor
wet abrasion
value flexibility
F 1 F 2
revolutions until
breakage FDk/FFk
Example 1 -0.05 3.20 1951 0.70
Example 2 -0.45 4.39 1947 0.86
Example 3 0.27 4.22 664 0.66
Example 4 0.51 4.88 370 0.63
Example 5 0.40 3.33 244 0.54
Example 6 -0.12 4.16 1427 0.78
Example 7 -0.07 5.02 1455 0.71
Example 8 0.42 4.53 511 0.61
Example 9 0.84 5.61 303 0.54
Example 10 0.17 5.15 635 0.72
Example 11 -0.28 1.82 336 0.66
Example 12 -0.04 1.45 585 0.63
Example 13 -0.09 2.06 410 0.70
23
Höller
factor
Höller
factor
wet abrasion
value flexibility
F 1 F 2
revolutions until
breakage FDk/FFk
Example 14 0.27 2.36 312 0.58
Example 15 0.52 3.49 443 0.62
Example 16 0.08 3.59 1153 0.65
Example 17 -0.14 3.13 821 0.71
Comparative
Example 1 1.21 5.94 332 0.52
Comparative
Example 2 1.45 4.16 125 0.40
Comparative
Example 3 1.05 2,17 30 0.45
Comparative
Example 4
commercial
Lyocell fibre 2.72 6.17 40 0.34
Fig. 3 shows the position of the examples/comparative examples in the Höller chart as well
as the area of the chart which is claimed according to the invention. Therein, examples 1 to
17 (according to the invention) are designated with their respective numbers, while the
comparative examples 1 to 4 are designated with a pre-fix “V”, respectively.
Comparative Example 1 demonstrates that the object according to the invention is not
achieved if the spinning temperature, which, at 122°C, is below the required value of at least
130°C even if all remaining manufacturing parameters correspond to the parameters for the
production of the fibre according to the invention.
Comparative Example 2 demonstrates that the object according to the invention is not
achieved if the draft, which, at 9.64, is above the required value of less than 8.00, even if all
remaining manufacturing parameters correspond to the parameters for the production of the
fibre according to the invention.
Comparative Example 3 demonstrates the significance of the pulp. The object according to
the invention is not achieved if the pulp composition, which, with a single pulp, fails to
exhibit the necessary proportion of a very high and a low molecular weight, even if all
remaining manufacturing parameters correspond to the parameters for the production of the
fibre according to the invention.
24
Comparative Example 4 shows the properties and the position in the Höller chart of a
commercial Lyocell fibre (Tencel® of Lenzing AG).
Processing example:
A 130 kg bale of a fibre of 1.3 dtex/38 mm according to Example 11 was processed into a
ring yarn Nm 50. A single jersey with a mass per unit area of 150 g/m2 was produced from
said yarn. A sample of this single jersey was dyed with 4% Novacronmarine FG, bath ratio
1:30, at 60°C in a laboratory jet for 45 min and subsequently subjected to 15 household
washings at 60°C.
Table 5 shows the abrasion and washing behaviour of this single jersey in comparison to a
planar assembly of the same structure made of a commercial viscose or Lyocell fibre,
respectively.
Table 5:
Fibre according to
Example 11
viscose 1.3
dtex
Lyocell
standard 1.3
dtex
Abrasion Martindale
tours until hole formation 57 500 58 750 15 500
Washing test
Grey scale*
Grade after 1st washing 4-5 4 3-4
Grade after 5th washing 4-5 4 1
Grade after 10th washing 3 4-5 2
Grade after 15th washing 2-3 4-5 1
* Grades from 1 to 5, the best grade is 5
25
Claims:
1) A cellulosic fibre of the Lyocell type which has a titre of from 0.8 dtex to 3.3 dtex and is
characterized by the following relationships:
Höller factor F2 ≥ 1, preferably ≥ 2
Höller factor F1 ≥ -0.6
Höller factor F2 ≤ 6 and
Höller factor F2 minus 4.5*Höller factor F1 ≥ 1, preferably ≥ 3.
2) A fibre according to claim 1, characterized by a wet abrasion resistance amounting to
between 300 and 5000 revolutions.
3) A fibre according to claim 1 or 2, characterized by a flexibility of between 0.55 and 1.00.
4) A fibre according to any of the preceding claims, wherein a single jersey 150 g/m2
produced from a ring yarn Nm 50/1 of said fibre exhibits an abrasion resistance according
to Martindale of between 30 000 and 60 000 tours up to the point of hole formation.
5) A fibre according to any of the preceding claims, characterized in that it is produced
according to the amine oxide process.
6) A fibre according to any of the preceding claims, characterized in that it is produced from
a mixture of at least two different pulps.
7) A fibre bundle comprising a plurality of fibres according to any of the preceding claims.