Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Pulp and lyocell articles with reduced cellulose content
[0001] The present invention describes special cellulose compositions which
allow the large-
scale stable production of a lyocell fibre with a reduced cellulose content,
as well as the lyocell
fibre produced from it.
State of the art
[0002] Lyocell fibers are used in a variety of applications. Purified
cellulose is often used as a
raw material, with a very small proportion of various end parts made of
cellulose.
[0003] Pulp is obtained from wood consisting only of 40-44 % cellulose by
weight. Since a high
cellulose content of over 95 % by weight is generally required in pulp for the
production of
lyocell mouldings, a large proportion of the raw material for material use is
lost during cooking
and bleaching. There are a number of known ways of reducing the proportion of
hemicelluloses
in particular, both in pulp production on the way from wood to pulp or to the
lyocell end product:
(a) digestion: A large proportion of hemicelluloses are lost in
sulphite cooking, whereas in
alkaline digestion prehydrolysis is used to remove hemicelluloses prior to
cooking.
b) Bleaching: usually for elimination of residual lignin and/or optical
brightening, but also
destroys hemicellulose components
c) Partial insolubility of branched hemicellulose fractions in the lyocell
solvent
d) degradation in DOPE with subsequent dissolution in the spinning bath
[0004] There are indeed strong efforts to use these other components as by-
products.
However, implementation is only carried out in small quantities due to known
technical
restrictions. In the waste liquors from pulp production, these further wood
components are
present in the form of a large number of different degradation products, in
addition mixed with
strong acids or bases, which makes separation and further processing extremely
difficult. WO
98/16682 describes a production process for a cellulose composition suitable
for fibre
production. A starting mixture which is not considered suitable for fibre
production (but only for
paper production) is processed in such a way that the hemicellulose content,
in particular the
xylan content, is reduced. The WO 99/47733 describes Lyocell fibers and the WO
2010/132151 A2 reveals a pulp with a cellulose with a low degree of
polymerization.
[0005] Nevertheless, efforts have been made in recent years to broaden the raw
material base
for Lyocell products through the use of celluloses with increased levels of
lignin and/or
hemicelluloses.
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US 6440523 and US 6444314 describe such approaches as examples:
[0006] The approach taken in these papers is essentially to describe either
the pulp and/or the
lyocell products made from it, which, in addition to the cellulose content,
also have a
hemicellulose content of more than 5 % by weight. However, it is considered
essential in all
these writings that the higher hemicellulose contents described there are only
possible if a
number of other essential conditions are fulfilled at the same time. These
are, for example, a
certain viscosity of the pulp, a maximum copper number and/or a maximum kappa
number.
[0007] Although lyocell products are described in these papers, it is
remarkable that the
developments based on these intellectual property rights have not yet been
realized on a large
scale, although the use of cellulose with a higher hemicellulose content in
particular should
bring significant cost and thus competitive advantages. This may well be due
to the difficulties
in up-scaling from laboratory scale and the achievable fibre properties, which
do not meet the
expectations of the textile and nonwovens market. The US 2015/0184338 Al
reveals force
pulp with a low content of hem icelluloses.
Task of the invention
[0008] In the interests of maximum resource utilisation, it would be desirable
to be able to use
as many material components as possible from the raw material wood to produce
a lyocell
fibre. The primary goal in the quest for the most comprehensive sustainability
possible and a
truly effective biorefinery concept must be to use the natural raw material
wood as
comprehensively as possible for the main product, namely Lyocell moulded
bodies, from the
outset. The extraction of by-products remains of great importance, but overall
this remains of
secondary importance. The previous efforts to this end have failed because the
reduction of
the cellulose content in the fibre either led to a massive change in the
material and property
parameters of the resulting (Lyocell) fibre (or other variants of moulded
bodies) or, on the other
hand, no stable large-scale production was possible. On the contrary, a large
number of
patents and publications require that the content of lignin, hemicelluloses
and accessory
components should be extremely low for the large-scale application of a
chemical pulp in the
Lyocell process.
[0009] For these reasons, it is desirable to provide technologies that can be
used on a large
2
scale to reduce the proportion of cellulose in the finished fibre by
increasing the proportion of
other wood components, in particular hemicelluloses, but also 'join, without
significant
restrictions with regard to the resulting material parameters. Despite the
large number of
state-of-the-art approaches, there are currently no known processes that can
be used on a
large scale to manufacture such Lyocell products with a reduced cellulose
content.
Short description of the invention
[1)0101 The aforementioned prior art problems are overcome by this invention,
The present
invention provides a pulp, a lyocell product, and the methods having
properties or features
described herein. Preferred forms of the invention are indicated in the
following detailed
description of the invention. ,
[00111 In particular, the present invention provides the following non-
limiting aspects, as well
as the preferred embodiments recited in the description.
1. Pulp suitable for the production of shaped lyocell bodies, having a
cellulose content of
90 wt.% or less, preferably 85 wt.% or less, and a hemicelluloses content of
at least 7
wt.%, characterized in that the ratio of the C5/Xylan to C6/ mannan fraction
(C5/C6
ratio) present in the hemicellulose is in the range from 125:1 to 1:3.
2. A cellulose of embodiment 1, wherein the C5/C6 ratio is in the range of
25:1 to 1:2.
3. A pulp according to embodiment 1 and/or 2, wherein the proportion of
hemicelluloses
is 10% by weight or more.
4. Pulp according to at least one of the abovementioned embodiments, the
hemicelluloses
of which are present in a native state, have been chemically modified by
processing
processes or have been chemically modified or functionalized in a separate
process
step.
5. A pulp according to at least one of the above embodiments, having a lignin
content of
more than 1% by weight.
6. Pulp according to at least one of the above embodiments, wherein the
cellulose content
is further reduced by the presence of lignin, accessory constituents from the
wood
and/or the addition of metallic compounds.
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7. A pulp according to at least one of the above embodiments, having a xylan
content of
9% by weight or more and/or a mannan content of 6% by weight or more.
8. Pulp according to embodiment 7 having a xylan content of 9% or more by
weight and
a mannan content of 1% or less by weight.
9. Lyocell shaped bodies prepared by using the pulp according to any of
the embodiments
Ito 8.
10. Lyocell shaped body according to embodiment 9, wherein the shaped body is
selected
from fibres, filaments, staple fibres, nonwoven knitted fabrics, films and
powders in
spherical form.
11. Lyocell shaped body according to at least one of the embodiments 9 and/or
10, wherein
the shaped body is a fibre, a filament or a staple fibre, having a cellulose
content of
less than 90% by weight, a hemicellulose content of more than 5% by weight and
a
C5/C6 ratio of 125:1 to 1:3, preferably 25:1 to 1:2.
12. Lyocell shaped bodies according to at least one of the embodiments 9 to
11, wherein
the hemicellulose content is more than 10% by weight.
13. Lyocell shaped body according to at least one of the embodiments 9 to 12,
wherein the
shaped body is a fibre, a filament or a staple fibre with a WRV of greater
than 70%,
preferably greater than 75%, in particular greater than 80%.
14. Lyocell shaped bodies according to at least one of the embodiment s 9 to
13, wherein
the shaped body has a crystallinity of 40% or less.
15. Lyocell shaped bodies of at least one of the embodiments 9 to 14, having a
lignin
content of more than 0% by weight up to 5% by weight.
16. A process for producing a shaped lyocell body comprising dissolving a pulp
having a
cellulose content of 90 wt.% or less, preferably 85 wt.% or less, and a
hemicellulosis
content of at least 7 wt.%, characterized in that the ratio of the C5/Xylan to
C6/ Mannan
fraction (C5/C6 ratio) present in the hemicellulose is in the range of 125:1
to 1:3, in a
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suitable solvent, and forming the solution into a shaped lyocell body.
17. Process according to embodiment 16, wherein the lyocell shaped body is
obtained by
a lyocell spinning process.
18. A process for producing a pulp according to any of the embodiments 1 to 8,
said
process comprising at least one of the following steps:
a) Mixing a pure pulp with xylan and/or mannan;
b) Treating a pulp having a hemicellulose content including mannan by chemical
andor physical methods to modify the hemicellulose content and/or the
composition of the hemicellulose contained therein;
c) Production of a pulp using coniferous and/or deciduous woods;
d) Mixing a mannan-free pulp with a hemicellulose-rich pulp and optionally
subsequent
chemical and/or physical treatment of the mixture to adjust the hemicellulose
content and/or composition of the hemicellulose moiety;
e) Mixing two pulps having different hemicellulose content and/or
hemicellulose
composition, and optionally subsequent chemical and/or physical treatment of
the
mixture -to adjust the hemicellulose content and/or the composition of the
hem icell ulose moiety.
19. A method according to embodiment 18, wherein the different pulps are
selected from
hardwood and softwood based pulps.
[0012] In another aspect, the present invention resides in a pulp for use in
the production of
shaped lyocell bodies, having a cellulose content of 50 to 85 wt.% and a
hemicellulosis content
of at least 7 wt.%, wherein a ratio of C5/Xylan to 06/ Mannan fraction (C5/06
ratio) present in
the hemicellulose is in the range from 125:1 to 1:3.
[0012a] In a further aspect, the present invention resides in a process for
producing a shaped
!wooll body comprising dissolving a pulp having a cellulose content of 50 to
85 v.ft.% and a
hemicelluloses content of at least 7 wt.0/0, wherein a ratio of C5/Xylan to
C6/ Mannan fraction
(C5/C6 ratio) present in the hemicellulose is in the range of 125:1 to 1:3, in
a suitable solvent,
and forming the solution into the shaped lyocell body.
Short description of the figures
Fig. 1 shows the correlation of crystallinity and water retention capacity of
lyocell fibres of the
present invention and of standard lyocell fibres
Date recue / Date received 2022-02-02
Fig. 2 shows the ratio of xylan to mannan in sulphite pulp as a function of
the I-1 factor when
beech wood is used.
Fig. 3 shows the ratio of xylan to mannan in sulphite pulp as a function of
the H-factor when
using spruce wood.
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Detailed description of the invention
[0013] If the proportion of cellulose in the lyocell process is reduced, this
means that the
savings are to be offset by other substances from the wood raw material. This
poses the
problem of process stability or property change when the cellulose content is
reduced, as
explained above. The main components of non-cellulosic material in the raw
material wood are
hemicelluloses (essentially polyoses from the sugar monomers xylose,
arabinose, mannose,
galactose, glucose and rhamnose), lignin and accessory components.
[0014] Cellulose: It is the structural substance of the cell walls in wood and
is mainly used for
tensile strength. The long molecule chains of glucose units are stored
together in so-called
fibrils several times in a helical structure. This helical arrangement in the
cell wall ensures good
bending strength of the tree, e.g. in the event of wind loading or of the
wood, e.g. in a roof
construction. Cellulose is hydrophilic, but not water-soluble due to its high
crystallinity.
[0015] Lignin: binder for the solid bond of cellulose in the form of an
amorphous matrix. Thus
lignin is mainly responsible for the compressive strength, on the other hand
it is less flexible
and in contrast to cellulose hydrophobic. It is responsible for the stamina of
the tree. Plants
that do not store lignin reach only low growth heights. Lignin is biologically
relatively stable and
biodegradable only slowly.
[0016] Hemicellulose in the sense of the present invention means components
present in wood
in the form of short-chain polymers of C5 and/or C6 sugars. In contrast to
cellulose, they have
side groups and can therefore only form crystals to a much lesser extent.
Their basic building
blocks are mannose, xylose, glucose, rhamnose and galactose. The side groups
preferably
consist of arabinose groups, acetyl groups and galactose residues as well as 0-
acetyl groups
and 4-0-methylglucuronic acid side groups. It is known that mannans prefer to
be associated
with cellulose, while xylans tend to associate with lignin. The composition of
hemicelluloses
varies greatly depending on the type of wood used. During the manufacturing
process of pulp,
side chains are partially separated and the polymer chains split. In the
context of this invention,
the term hemicelluloses includes those in their native structure as well as
those which have
been altered by their processing and also those which have been adjusted for
their intended
use by specific chemical modification. Also included are short-chain
celluloses and other
polyoses with a DP of up to 500.
[0017] Accessory components: Accessoric constituents are organic and inorganic
wood
components other than lignin, cellulose and hemicellulose, and usually include
salts and low
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molecular organic compounds of up to about 100 atoms, such as tannins, resins,
fats and
waxes, tannins and humins, terpenes, terpenoids and phenolic compounds,
pectins, suberins,
polyphenols and polyoses.
[0018] If the cellulose content in a cellulose material is to be reduced as
desired and other
components of the raw material wood are to compensate for this reduction, it
has surprisingly
been shown that only the combination of different types of sugar in a certain
ratio makes it
possible to indicate a cellulose which, despite its reduced cellulose content,
allows the safe
large-scale production of lyocell products, whereby these products also have a
reduced
cellulose content, but nevertheless have satisfactory product properties.
[0019] According to the invention, it is essential that a reduced cellulose
content in the pulp of
less than 90% by weight has a hemicelluloses content of at least 7% by weight,
the ratio of
sugars with five carbon atoms such as xylan to sugars with six carbon atoms
such as mannan
(hereinafter referred to as C5/C6 ratio) being in the range from 125:1 to 1:3.
[0020] Surprisingly, the large-scale production of lyocell products can be
safely realized with
such a pulp, even though the cellulose content in the pulp is lowered.
[0021] The cell materials used here, which are preferably used in the context
of the present
invention, show, as already explained, a relatively high content of
hemicelluloses with the
composition defined here. In comparison with standard pulps with a low
hemicellulose content,
used especially in the state of the art for the production of standard lyocell
fibers, the preferred
pulps used in the context of this invention also show further differences,
which are listed below.
In comparison with standard cell materials, the cell materials preferably used
in the present
invention show a rather fluffy view. After grinding (during the production of
starting materials
for the production of spinning solutions for the Lyocell process), this
results in a particle size
distribution with a high proportion of larger particles. As a result, the bulk
density is much lower
compared to standard pulps with a low hem icellulose content. Such a low bulk
density requires
adaptations with regard to dosing parameters (e.g. dosing using at least two
storage tanks)
during the production of the spinning solutions. In addition, the cell
materials preferably used
in the present invention show an impregnation behaviour towards NMMO, which in
comparison
with standard cell materials shows that impregnation is more difficult here.
This can be checked
by evaluating the impregnation behaviour with the Cobb evaluation. While
standard pulps
typically show a Cobb value of more than 2,8 g/g (determined in accordance
with DIN EN ISO
535 with adaptations for the use of an aqueous solution of 78% NMMO at 75 C
with an
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impregnation time of two minutes), the pulps preferably used in the present
invention show
Cobb values of approximately 2,3 g/g. This requires adaptations during the
preparation of
spinning solutions, such as increased solution time (e.g. explained in WO
94/28214 and WO
96/33934) and/or temperature adaptation and/or increased shear during
dissolution (e.g. WO
96/33221, WO 98/05702 and WO 94/8217). This makes it possible to produce
spinning
solutions that allow the pulp described here to be used in a standard lyocell
process).
[0022] In a preferred form of the present invention, the pulp used for the
manufacture of lyocell
products, preferably fibres as described here, shows a SCAN viscosity in the
range 300 to 440
ml/g, in particular 320 to 420 mUg, more preferably 320 to 400 ml/g. The SCAN
viscosity is
determined in accordance with SCAN-CM 15:99 using a cupriethylenediamine
solution, a
method known to the professional and which can be performed with commercially
available
devices, such as the Auto PulpIVA PSLRheotek device, available from PSL-
Reotek. The
SCAN viscosity is an important parameter which influences the processing of
pulp during the
production of spinning solutions. Even if two pulps show a large agreement in
terms of
composition etc., different SCAN viscosities lead to a completely different
behaviour during
processing. In a direct solution spinning process, such as the Lyocell
process, the pulp is
dissolved in NMMO as such. There is no maturing step, comparable for example
with the
viscose process, where the degree of polymerization of the cellulose can be
adapted to the
needs of the process. Therefore, the viscosity specifications of a raw pulp
are typically for the
lyocell process in a small target window. Otherwise, problems may occur during
production. In
accordance with the present invention, it was found that the pulp viscosity is
preferably as
described above. Lower viscosities lead to a deterioration of the mechanical
properties of the
Lyocell products. Higher viscosities can in particular lead to an increased
viscosity of the
spinning solution, so that spinning becomes slower overall. Lower spinning
speeds also result
in lower tensile ratios, which again can have a significant influence on the
fiber structure and
fiber properties (Cabohydrate Polymers 2018, 181, 893-901). This would require
procedural
adaptations leading to a capacity reduction. The use of cellulose with the
viscosities defined
here, on the other hand, enables simple processing and the manufacture of high-
quality
products.
[0023] The term "lyocell process", or the terms "lyocell technology" and
"lyocell process" as
used herein, designate a direct dissolution process of wood cellulose pulp or
other cellulose
based starting materials in a polar solvent (e.g. N-methylmorpholine-n-oxide
(NMMO, NMO)
or ionic liquids). Commercially, this technology is used to produce a group of
cellulose staple
fibers commercially available from Lenzing AG, Lenzing, Austria under the
brand names
TENCELOD or TENCELTM), which are widely used in the textile industry or the
nonwoven
industry. Other shaped cellulose bodies obtained by lyocell technology have
also already been
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produced. In accordance with this process, the cellulose solution is usually
extruded in a so-
called dry wet spinning process using a forming tool and the formed solution
is obtained e.g.
after passing an air gap into a precipitation bath where the formed body is
obtained by
precipitating the cellulose. The moulded body is washed and optionally dried
after further
treatment steps. A process for the production of lyocell fibres is described
in US 4246221, WO
93/19230, WO 95/02082 or WO 97/38153. As far as the present invention
discusses the
disadvantages of the state of the art and discusses the unique properties of
the new products,
disclosed and claimed here, in particular in the context of the use of
laboratory equipment
(especially in the state of the art) or in the context of (semi-commercial)
pilot plants and
commercial fibre spinning units, the present invention is to be understood as
referring to units
which can be defined as follows with respect to their respective production
capacities:
Semi-commercial pilot plant: about 1 kt/a
Commercial unit greater than 30 kt/a
[0024] In the context of the present invention, it has been shown that,
especially in fibre
production in the context of a lyocell process, orientation in the direction
of production and
stretching of the fibres takes place. From an initial more or less
orientationless mix of different
polymers and other components in the dope
the strong narrowing of the cross-section at the spinneret results in an
initial orientation of the
polymers in the direction of production. The additional stretching in the air
gap after the
spinneret and during the following process steps results in a stretched
oriented fiber structure
of the polymers. These processes are well known from specialist literature.
[0025] The fiber properties are strongly influenced by the type and
composition of the
polymers. It is also known that cellulosic fibres produced by the Lyocell
process have a very
high crystallinity of about 44 to 47%, while fibres from the viscose process
have a crystallinity
of about 29 to 34%. The crystallinity describes the orientation of the
cellulose polymers towards
each other and thus, for example, their ability to absorb, swell and store
water. In addition, the
polymer chains in the non-crystalline areas of the lyocell fibers are more
ordered than in the
viscose fibers. As a result, ordinary lyocell fibers swell less and are less
suitable for highly
absorbent products than viscose fibers.
[0026] The use of cellulose with a reduced cellulose content in accordance
with the invention
unexpectedly enables a completely different type of aggregation of the
polymers and thus a
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different structure of the lyocell fibres. Their crystallinity is
significantly lower, typically 40% or
less, such as 39% or less, and for example in the range 38% to 30%, such as in
the range
37% to 33%.
[0027] The values for WRV for fibres in accordance with the present invention,
isolated or in
combination with the other preferred designs described here, preferably in
combination with
the values for the crystallinity of the fibre described here, are preferably
70% or more, in
particular 75% or more, such as 80% or more, e.g. from 70 to 85%.
[0028] It is known from literature that xylans also form a crystal structure
if their side chains
have been split off during the production process and they are precipitated
from a pure xylane
solution (Fengel, Wegener p. 113; Fengel D, Wegener G (1989): Wood, Chemistry,
Ultrastructure, Reactions; Walter de Gruyter Verlag). The same applies to
Mannan (ibid.;
p.119). In the present invention, however, opposite effects can be seen. The
polymers including
the cellulose are present in dope in a mixture and are thus also spun out and
precipitated.
Furthermore, the hemicelluloses still have side groups, since the glucuronic
acid side groups
of )rylans are comparatively stable under the conditions of acid digestion
(Sixta H (Ed.) (2006):
Handbook of Pulp Vol. 1; Wiley VCH p.418). The hemicelluloses thus fulfil all
the conditions
required to disrupt the crystallization of the cellulose and thus form a more
disordered structure
than standard Lyocell fibres. Thus, the expert would expect that with a higher
hemicellulose
content and reduced cellulose content, useless products, in particular fibres,
would result.
However, it has been shown unexpectedly that the hemicelluloses content in
combination with
the C5/C6 ratio can be used to selectively control product properties. This
mixture of different
sugar polymers still achieves crystallinity values above those of viscose
fibers, but the overall
accessibility of the fiber to water is now increased, so that the water
retention capacity (WRV)
can be significantly increased. This improved absorbency is a decisive
advantage for various
applications, e.g. nonwovens. This relationship between decreasing
crystallinity and increasing
water retention capacity for Lyocell fibers is shown in Figure 1 and can be
adjusted by reducing
the cellulose content in the fiber as described above.
[0029] As shown in the examples, the qualities of the new Lyocell fibers with
reduced cellulose
content are similar to those of conventional TENCEL fibers. It becomes clear
that the fiber
strengths are slightly below those of TENCEL fibers, measured in the examples
as strength
and working capacity. At the same time, the cellulose content could be
significantly reduced,
recorded in the examples as a glucan value. By absorbing other wood
components, the
crystallinity decreases by up to 21% and the absorbency increases
significantly by up to 27%,
measured in the examples as crystallinity index and water retention capacity.
Interestingly, the
crystallinities of the new Lyocell fibers according to the invention lie
between those of
conventional TENCEL fibers and nonwovens Lenzing Viscose fibers; at the same
time, the
WRV is in the range of Lenzing Viscose. The WRV thus rises more strongly than
it could be
explained by the decreasing crystallinity of the fibres. This is a clear sign
of the unexpected
properties that can be realized with this invention. The other components such
as in particular
hemIcelluloses, but also lignin and accessory components from the wood not
only provide a
significant increase in yield, i.e. improved sustainability, but also a
significant improvement in
product properties such as water retention capacity.
Embodiments
[0030] As described, the pulp according to the invention is characterized by a
reduced
cellulose content, a minimum of hemicelluloses and a certain C5/C6 ratio with
respect to the
composition of the hemicellulose.
[0031] In a preferred form, the pulp, which may also be a mixture of different
pulps (as long as
the essential conditions are met), is a pulp having a hemicellulose content of
from 7 to 50% by
weight, preferably from 7 to 30% by weight, more preferably from 16 to 25% by
weight, such
as from 10 to 20% by weight.
[0032] The pulp to be used in accordance with the invention is also preferably
a pulp containing
at least 9 % xylan by weight, preferably at least 10 % xylan by weight. The
proportion of
mannan can be chosen, in combination or independently, in a wide range, as
long as the ratio
defined in the invention is fulfilled. Suitable man contents lie in the range
from 0.1 to 10 wt.%,
such as from 0.1 to 9 wt.%, and in the form of 0.1 to 6 wt.%, from 0.1 to 4
wt.%, from 5 to 10
wt.%, from 6 to 10 wt.%, etc., from 0.1 to 9 wt.%. In forms of execution, the
mannan content is
in the range from 0.1 to 1 wt.%, preferably in combination with a xylan
content of at least 9
wt.%, preferably at least 10 wt.%. In other designs, the manganese content is
higher, preferably
in the range of 6 % or more by weight.
[0033] In a preferred form, isolated or in combination with the forms
described above and
below, the cellulose content in the pulp is in a range of equal to or less
than 90 wt.% to 50
wt.%, preferably in a range of 90 wt.% to 60 wt.%, such as from 85 wt.% to 70
wt.%.
[0034] The weight ratio of cellulose to hemicellulose may range from 1:1 to
20:1. The
proportion of accessory components can be more than 0.05 wt.%, preferably more
than 0.2
wt.%, more preferably more than 0.5 wt.%. Unexpectedly, it has been shown that
with such
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CA 03092615 2020-08-24
proportions of accessory components in the pulp according to the invention,
the effect can be
supported that the C5/C6 ratio in the produced lyocell products, especially
fibers, is stable and
the hemicellulose content does not change significantly (i.e. the content in
the lyoceff product
does not decrease or only decreases to a minor extent compared to the pulp).
[0035] In another preferred design, the C5/C6 ratio in accordance with the
invention achieves
such a high retention capacity that at the same time a proportion of metal
compounds, usually
present as their oxides and hydroxides, of up to 25% by weight, based on the
weight of the
lyocell product (e.g. Mg(OH)2or Al(OH)3for flame retardant purposes) is made
possible, which
further substantially reduces the cellulose proportion. Such metal compounds
are in particular
T102, A120 3, MgO, SiO2, Ce02, Mg(OH)2, Al(OH)3, BN, ZnO and originate partly
from the
mineral components of the wood or can be added to the cellulose solution as
functional
additives (flame retardants, matting agents, biocides...).
In another preferred design, lyocell fibres with a cellulose content reduced
to less than 70%
can be produced, which not only meet the practical requirements compared with
the known
lyocell fibres (mechanical strength etc.), but are also even more suitable for
some applications
due to the new properties resulting from the invention. The relevant studies
have shown that
fibres in the proposed composition show in particular an increased water
retention capacity
and rapid biodegradability during composting.
[0037] According to the invention, the ratio of C5/C6 sugars of non-cellulosic
polymers has
been shown to be an important factor in adjusting the fibre composition and
its resulting
properties. By adjusting this ratio, also in combination with the content of
hemicelluloses, the
desired product properties can be adjusted.
[0038] In this context, the expert knows how to control or adjust the C5/C6
ratio. This can be
achieved by mixing various pulps such as softwood pulps with a higher mannan
content with
hardwood pulps with a higher xylan content. Trials have confirmed another very
effective way
to adjust the setting. The ratio of C5 to C6 sugars can be controlled by
setting specific cooking
parameters such as the H factor. This is illustrated in Figures 2 and 3. The H-
factor is regarded
as an essential parameter for controlling sulphite cooking (Sixta (Vol. 1
2006) p. 432). It
summarizes cooking temperature and cooking time as one size.
Figure 2 shows the influence of the H factor in sulfite boiling on the
hemicellulose ratio in
hardwood using beech as an example. The content of xylan in hardwoods is
naturally higher.
With increasing H-factor, Xylan is degraded more than Mannan. The ratio C5/C6
decreases.
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= CA 03092615 2020-08-24
[0040] When using softwood, the hemicellulosis ratio is the other way around.
The proportion
of mannan in wood and pulp is higher. Here, contrary to expectations, Mannan
is dismantled
faster than Xylan as can be seen in Figure 3.
[0041] Another way to adjust the pulp composition according to the invention
is to add C5
and/or C6 sugars previously obtained in other processes or process steps, such
as an alkaline
extraction, be it a cold alkaline extraction or an E step or the like. For the
production of viscose,
the addition of hemicelluloses in dissolved form to the spinning mass and the
subsequent joint
spinning are known (W02014086883). This allows viscose fibres with a reduced
cellulose
content to be produced. This is only possible because the viscose process
takes place in an
aqueous medium and the hemicelluloses are correspondingly alkali-soluble, so
the cellulose
exanthate and the dissolved hemicelluloses can be mixed together and spun out
together. In
contrast, the pulp is dissolved in NMMO or similar solvents in the Lyocell
process, which means
that no alkaline or aqueous solutions can be added. They would dilute the
solvent and reduce
solubility or even lead to unwanted precipitation. Hemicellu loses cannot
therefore be added in
the form of solutions in the production of spinning solutions, but must be
introduced differently
into the process. One possibility is the addition in the pulp production
process, so that the
mixture can then be dried with the pulp.
[0042] Surprisingly, it was found that close attention to the hemicellulose
composition is a
crucial point for the technical production of lyocell mouldings, in particular
fibres. A large-scale
use of hemicellulose in the fiber structure is only possible if the proportion
of the C5 fraction is
correlated with the proportion of the C6 fraction. The ratio of xylan to
mannan is preferred
between 18:1 to 1:3, preferably 9:1 to 1:2. At the same time such a mixing
ratio allows the
incorporation of 0.5-5 wt.% lignin (and/or other accessory components) into
the fibre structure
without impairing the desired properties to an adverse extent.
[0043] The fibres provided by the invention have common fibre titres, such as
7 dtex or less,
for example 2,2 dtex or less, such as 1,3 dtex, or less, or even less, such as
0,9 dtex or less,
depending on the desired application, For applications in the nonwoven sector,
titers of 1.5 to
1.8 dtex are typical, while lower titers such as 1.2 to 1.5 dtex are suitable
for textile applications.
This invention also includes fibres with even lower titers as well as fibres
with significantly
higher titers, such as 10 dtex or less, such as 9 dtex or less, or even 7 dtex
or less. Suitable
lower limits for fibre titres are values of 0,5 dtex or more, such as 0,8 dtex
or more, and 1,3
dtex or more in the forms. The upper and lower limits revealed here can be
combined and the
resulting ranges, such as from 0.5 to 9 dtex, are also included. Surprisingly,
the earth discovery
13
== CA 03092615 2020-08-24
at hand enables the production of fibers with titers that can be used in the
entire spectrum of
fiber applications, including textile applications as well as nonwoven
applications.
[0044] If reference is made in this application to parameters, these are
determined as
described here. It is essential that these parameters are obtained with the
fibres as such,
comprising a maximum of 1% by weight of additives, such as matting agents,
etc., and that the
fibres are not affected by the process. However, the fibres described here can
of course contain
conventional additives in normal quantities, provided that this does not
impair the production
of spinning solutions and/or the production process of the fibres.
The following examples illustrate aspects of this invention.
Methods
[0045] Determination of the crystallinity index [%]
The crystallinity index is determined by Raman spectroscopy. This method is
calibrated with
data from the X-ray wide-angle method (WAX) and was published by Rider et al.
(2009)
(Roder T, Moosbauer J, Kliba G, Schlader S, Zuckerstatter G, and Sixta H
(2009): Comparative
Characterisation of Man-Made Regenerated Cellulose Fibers. Lenzing Reports
Vol. 87, p. 98
ff.).
Determination of the water retention capacity [70].
Allow the sample to swell overnight at 20 0,1 C. After further dilution, the
sample is
centrifuged in accordance with Zellcheming Leaflet IV/33/57 at 3000 times
acceleration due to
gravity. The water retention capacity is then calculated as follows:
WRV = (weight of wet sample ¨ weight of dry sample)/weight of dry sample x 100
Examples
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[0046] Xylan-Mannan ratio settina example
Table 1 shows the results of the adjustment of the C5/C6 ratio, for two wood
species, using the
example of the variation of the H-factor in magnesium bisulphite digestion.
test number H factor Xyl/Man Xylan/% Mannan/%
sylvatica fagus
wood 0 17,7:1 19,5 1,1
Mg433 18 13,1:1 14,5 1,1
Mg434 37 8,5:1 9,4 1,1
Mg435. 60 7,6:1 6,9 0,9
Mg436 90 6,4:1 5,1 0,8
Mg437 130 6,6:1 4,0 0,6
Mg438 160 6,4:1 3,2 0,5
Mg439 180 5,8:1 2,9 0,5
Mg420 210 5,8:1 2,3 0,4
Mg408 249 4,3:1 1,3 0,3
Picea abies
wood 0 1:2,4 5,6 13,6
Mg673 78 1:1,6 4,1 6,7
Mg674 116 1:1,5 3,4 5,2
Mg675 166 1:1,4 2,9 4,0
Mg678 180 1:1,4 2,5 3,4
Mg676 193 1:1,4 2,0 2,8
Mg677 201 1:1,6 1,7 2,7
Table 1: Adjustment of the xylan-mannan ratio in magnesium bisulfite cooking
of Fagus
sylvatica (beech) and Picea abies (spruce) using the H factor.
[0047] Example of a eucalyptus fuel Pulp
In the pilot plant, a new Kraft chemical pulp was produced from eucalyptus
wood using the
VisCBC process in accordance with the invention. The H-factor was 1200, the
effective
alkalinity in the cooking liquor was 25 g/I. Bleaching was performed after a
TCF sequence.
Relevant process information and product properties are given in Table 2.
Eucalyptus raw pulp Bleached Cellulose-
reduced
analysis unit Wood cellulose Lyocell fibre
pilot
plant trial
test number Clone "D" Ka_CBC689698 81438
E33_2017_0572
Klason lignin % 24,9 - - -
Acid soluble lignin % 3,4 - - -
Kappa number 9,6 0,3 -
degree of whiteness %ISO - 40,8 92,2 -
intrinsic viscosity ml - /g 1025 385 -
R10 % - 92,7 88,3 -
R18 % - 94,9 94,0 -
acetone extract % 0,76 0,19 0,04 0,46
,
. . ,
CA 03092615 2020-08-24
ash % 0,20 0,33 0,20 _
Fe ppm 6,4 6,3 6,9 -
Mn ppm - 0,8 <0,38 -
Cu ppm - 1,0 <1,3 -
Ni ppm - 0,7 <1,2 -
Mg ppm - 12,0 130,0 -
Si ppm - 24,7 31,3 -
Ca ppm - 78,0 12,0 -
SiO2 ppm - 52,8 67,0 -
CaO ppm - 109,1 16,8 -
glucan % 44,3 79,8 82,3 85,4
xylan % 13,1 15,1 14,0 12,1
Mannan % 0,8 <0,2 <0,2 0,1
Xylan / Mannan - 16,4 - - 121
arabinane % 0,3 <0,1 <0,1 <0,1
Rhamnan % 0,2 <0,1 <0,1 <0,1
galactan % - <0,1 <0,1 <0,1
Crl % - - 39
WRV % - - - 78
Table 2: Properties from wood to pulp to finished cellulose-reduced lyocell
fibre.
In this new chemical pulp with reduced cellulose content, the xylan-to-mannan
ratio has been
extremely increased to 121 in the finished fiber, while the cellulose content
has been kept very
low at about 85%. This new pulp fully meets the requirements of the Lyocell
process for the
production of the new Lyocell fibre with reduced cellulose content.
[0048] Example of fibre properties when using new cellulose-reduced MIPS
Table 3 summarizes the salaries of the sugar monomers of the starting pulps
for the production
of Lyocell fibers.
Pulp for cellulose-
Pulp for standard Pulp for cellulose-
sugar
reduced Lyocell fibre
Lyocell fiber reduced lyocell fiber
"pilot plant" trial
Glucan (%) 95.5 82.2 82.3
Xylan (%) 2.3 8.3 14.0
Mannan (%) 0.2 5.7 <0.2
Table 3: Sugar contents of cellulose-reduced pulps compared to a standard
Lyocell pulp
Table 4 shows mechanical properties for standard fibers (lyocell and viscose)
compared to
properties achieved with lyocell fibers produced with invention pulp. The
results impressively
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CA 03092615 2020-08-24
demonstrate the advantages of this invention.
Both in pilot plant trials and in large-scale production of lyocell fibres in
accordance with the
present invention, it has been shown that acceptable values for strength and
working capacity
can be achieved for commercially relevant titres, despite a considerably lower
cellulose
content. At the same time, the WRV increases drastically, so that such fibers
become
interesting for new areas of application, which were previously occupied by
viscose fibers.
Compared to commercially available viscose fibers, however, significantly
higher mechanical
properties can be achieved with the Lyocell fibers invented.
The new, inventive lyocell fibers thus combine the advantageous properties of
previously
commercially available lyocell and viscose fibers.
rehearsal Titer Strength Working capacity Crystallinity Glucan WRV
[dtex] [cNitex] [cN/tex"./0] Pk] [%]
TENCELO NW 1,8 32,1 408 47 94,3 65,3
(Standard)
TENCELO textile 1,3 36,1 455 44 95,8 69,6
(standard)
Cellulose-reduced 1,8 28,1 323 40 85,6 82,5
lyocell
Cellulose-reduced 1,7 28,9 370 39 81,6
lyocell fiber
Cellulose-reduced 1,3 30,9 374 37 86,6 82,8
lyocell fiber
Lenzing Viscose0 1,7 22,0 429 33 78-85
NW (Standard)
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Cellulose-reduced 1,7 27,6 315 39 85,4 78,0
Lyocell fibre pilot
plant trial
Table 4: Properties of conventional and cellulose-reduced Lyocell fibers
compared to a
standard viscose fiber.
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