Preparation and
Characterization of
Cellulose Dopes in NMMO
Frank Meister, Birgit Kosan
Thuringian Institute for Textile and Plastics Research,
Breitscheidstraße 97, 07407 Rudolstadt, Germany
1
TITK, F. Meister 15.04.2015 2
Thuringia
Germany
Rudolstadt
Where TITK is localised ?
District Saalfeld-
Rudolstadt
TITK, F. Meister 15.04.2015 3
1954 Prof. Dr. Böhringer constitutes the Institute for Textile Technology of man-made Fibres
(ITC) in fact and law independent from the man-made fibre mill Schwarza 1970 ITC looses its independence and becomes a part of the central textile research of the
man-made fibre mill (R&D activities on all fields of Textile Research; up to 480 employees
at the end of 1980’s) 1991 re-foundation of the TITK as a first private, non-profit R&D institute of Thuringia strong
linked to business interests of SME (55 employees) 1992 formation of the OMPG as a 100 % subsidiary of the TITK 1997 TITK/OMPG transferred together with Zimmer Corp. results of self-contained Lyocell
technology (ALCERU process) into pilot plant scale 300 t/y of textile staple fibres and 10
t/y textile filaments
2002 Competence centre for Polysaccharide Research Jena–Rudolstadt is founded.
2005 TITK becomes an “Associate Institute” at the Technical University of Ilmenau;
2006 1,000 t/a pilot plant for textile Lyocell staple fibres manufacturing is launched at Shanghai
by Chinese Partner and TITK
2009 TITK became a member European Centre of Excellence for Polysaccharide Research
(EPNOE), TITK is awarded with Thuringian R&D Price for Transfer of Lyocell fibres
2011 installation of centre of excellence for direct dissolution and dry-jet-wet technologies
named Hugo-Richard-Küttner Centre
2014 Smartpolymer Ltd. is launched as 100 % subsidiary of OMPG
A brief history
15.04.2015 4
- since 1991 the TITK has taken its textile expertise to become a
modern institute for materials research,
- whereby TITK's R&D activities are primarily focussed on studies
with natural and synthetic polymers.
The Research Departments:
The fields of expertise:
• Synthesis of polymers and functional additives
• Characterisation, forming and functionalisation of polysaccharides, particularly
cellulose and proteins
• Technical textiles
• Fibre-reinforced composites
• Polymer nano composites
• Polymer electronics,
• Polymer photovoltaic,
• Roll to roll coating,
• Materials modified by photo-chromic, thermo-chromic, electro-chromic and
solvato-chromic additives
• Native Polymers and Chemical Research
• Textile and Materials Research
• Plastics Research
• Functional Polymers Systems
TITK, F. Meister 15.04.2015 5
OMPG East Thuringian Material Testing
Company for Textiles and Plastics
(100 % subsidiary of TITK)
Employees: 31
analytical services (chemical, physical)
polymer and material testing
exclusive R&D orders
product commercialisation and technology
transfer
TITK Group
TITK Thuringian Institute for Textile and
Plastics Research
Employees: 125
Members: about 90
Research and development projects
on polymer materials, processing and
technologies (50 R&D projects each
year)
smartpolymer GmbH
(100 % subsidiary of OMPG)
Employees: 30
product commercialisation and technology transfer
TITK, F. Meister 15.04.2015 6
Cell SolutionTM protection
Smartpolymer GmbH
Cell SolutionTM skin care
Cell SolutionTM hygienic
Cell SolutionTM ceramic
Cell SolutionTM bioactive
Cell SolutionTM filaments
Cell SolutionTM clima
TITK, F. Meister 15.04.2015 7
Outline
1. Pulp characterisation and impact of pulp impurities
1.1. General view
1.2. Effects of pulp impurities
2. Dope characterisation
2.1. Dope inhomogeneities
2.2. Rheological measurements of dope characteristics
3. Fibres spinning
4. Conclusions
TITK, F. Meister 15.04.2015 8
Fibres and spinning procedures
Fibres are materials, what: - possess a huge length to thickness ratio
- molecules are preferentially oriented into MD
animal, like silks, wools or hairs
mineral, like asbestos
vegetable, like cotton or bast fibres
natural
Fibres
man-made
modified natural synthetics,
like PP, PA, PET, PAN, PVC, PU
inorganic, like carbon, glass, metal,
basalt organic, like cellulose CV, CLY, CUP, CA, CAB, CC
TITK, F. Meister 15.04.2015 9
Varieties of fibres spinning processes
spinnability - is the capability to form mechanical stable liquid filaments
cooling, consolidating,
drafting, crimping
Solution spinning
polymer pellets
molten mass
melt spinning
Melt spinning
fibres, filaments
polymer powder
spinning dope
dry spinning wet spinning dry-wet spinning
cooling, consolidating
drafting, coagulating
drafting, crimping
washing, crimping
fibres, filaments
solvent h0 = 80 - 20,000 Pa s
200 - 2,000 mm hole diameter,
50 - 6,000 m/min take-up speed
10 – 60,000 spinning holes 40 - 250 mm
hole diameter,
80 - 120 m/min
take-up speed,
2,000 up to
200,000
spinning holes
h0 = 20 - 20,000 Pas
TITK, F. Meister 15.04.2015 10
Dissolving Pulp
(enzymatically activated)
N-methylmorpholine-
N-oxide solution
Pre-dope
preparation
Dissolving
Spinning
After-treatment
washing, bleaching,
finishing, drying
Shaped bodies,
like fibres, filaments, MB-non-woven, films
Textile
processing
Textile use
Biodegradation
© holz.bayern.de
recycled solvent
and process water
What is the Lyocell Process cycle ?
TITK, F. Meister 15.04.2015 11
Analytical methods for pulp characterisation at TITK
Determination of ash content, Fe, Cu, Mn, Cr, Ni, Na, K, Mg and Ca
= important for process safety in the case of NMMO and the
contamination of spinning bathes because of solvent recovery
Determination of Cuoxam-DP by capillary viscometry
= average degree of polymerisation for estimation of usable
cellulose concentration for dissolution tests, evaluation of cellulose degradation at dissolution and shaping processes
Molecular weight distribution (MWD) by size exclusion
chromatography (SEC)
= MWD of the pulp influences the solution properties, the spinning behaviour and attainable fibre properties
Content of carbonyl and carboxyl groups
= influenced by pulp cooking processes and MWD of the pulp
a-cellulose content
= important for solution properties and attainable fibre properties
TITK, F. Meister 15.04.2015 12
Main solvent degradation effects in the system cellulose /
N-methylmorpholine-N-oxide (NMMO)
References: Lukanoff, B., Philip, B., Schleicher, H.: Acta Polymerica 35, (1984), 339-343
Taeger, E., Franz, H., Mertel, H.: Formeln, Fasern, Fertigware 4, (1985), 14-22
Buijtenhuijs, F.A., Abbas, M., Witteveen, A.J.; Papier 12, (1986), 615-619
Rosenau, T., Potthast, A., Sixta, H., Kosma, P. Prog. Polym. Sci. 26, (2001), 1763-1837
Hydrogen bond system
between cellulose and NMMO
O
OH
OH
HOCell-O
O-Cell
ON
O
O
OH
OH
HOCell-O
O-Cell
temperature
and
pressure
O
OH
OH
HO
OH
O
OH NO
O
Cell-O
+
NO
OHOCell-
HO
OH
OH
Thermal degradation
Oxidation of cellulose, deoxygenation of NMMO
Radical reaction
Polonovski type reaction
NO
OAA
NO
O-Acyl
NOB
CH2 + O-Acyl H-B+
OH-
NO CH2OH
NO H
+ HCHO
AA = acylating agent
B = Base
NO
O
Fe(II)+ +.
Fe(III)NO2 H+
- H2O
O
NO HNO H2O+
_
+NO 1/3 1/3 1/32/3 + + CO2
NMMO
labile oxidant
Cellulose end groups
sugar acids
radicals
Impurities especially iron
or copper ions
Properties of
additives
pH value,
proton
donating
groups like
carboxyl, or
amino,
pore size,
particle size ,
porosity
O
OO
O
OO
RO
HO
OH
OR
OR
OH
OH
HO
O
N
CH3
O
HO
H
O HO
H
H
OH
OH
OH
HORO
O
H
OH
ON
CH3
O
TITK, F. Meister 15.04.2015 13
Dope preparation tests in laboratory scale 3
by preparation of about 250 g cellulose solution it will be possible to test most suitable dissolution conditions, to characterise solution properties and to realise a first laboratory spinning test
modified laboratory kneading system, Haake Rheocord 900
TITK, F. Meister 15.04.2015 14
Protocol for cellulose dope characterisation 4
Refractive index: determination of water contents in solvents and in cellulose dopes with known cellulose content, important for the completion of the water removing in the case of NMMO monohydrate
Solids content: precipitation, washing, drying and weighing of the cellulose from a definite dope sample
DP and MWD: determination of the cellulose DP in cuoxam solution and molecular weight distribution of precipitated cellulose from dopes or fibres
Microscopy: monitoring of fibre residuals in cellulose dopes by polarising microscope
Particle analysis: particle content in dopes, particle size distribution between 0.5 and 175 μm by laser diffraction
Rheometry: zero shear viscosity, storage and lost moduli, master curves and mean relaxation time of cellulose dopes
Helos Particle Analyser
Haake Rheostress RS 100
TITK, F. Meister 15.04.2015 15
Polarising microscopy 5
visualisation of discrete particles with diameters greater than 10 μm
(not perfect dissolved fibre residuals, pulp or solvent impurities)
incomplete dissolving state a few fibre residuals of 10 to
30 μm
dope without visible particles
TITK, F. Meister 15.04.2015 16
Particle analysis by laser diffraction
detection of particle sizes between 0.5 and 175 μm; particle content is based
on basic calibration using spherical particles
verification of gel particles with minor differences in the refraction index by
means of Fraunhofer diffraction
measurements only possible at low particle contents
Helium-Neon laser working with wave length at 632 nm
temperature controlled measuring cell
0
20
40
60
80
100 Q
3(x
) / %
0
20
40
60
80
100
120
de
nsity q
3*(
x)
/ %
0.5 1 5 10 50 100 particle size / µm
TITK, F. Meister 15.04.2015 17
Rheological evaluation of polymer solutions 7
1. Determination of zero shear viscosity h0 by means of creep and creep recovery
is one of the most important rheological parameter in polymer industry
it permits to give relative information for change of molecular weight
may be determined (a) by rotation test at controlled shear stress (90 Pa) or (b) frequency sweep (oscillation test) from h*, if angular velocity w 0
2. Characterisation of the viscoelastic flow behaviour and stress relaxation
oscillation tests (frequency sweeps between 0.046 and 14.7 Hz) at
different temperatures for calculation of master curves (storage and loss
moduli as well as the complex viscosity depending on frequency
respectively angular rate, referring to a reference temperature, i.e. 85 or
95 °C)
determination of the cross over between storage and loss modulus and
the plateau moduli (plateau value of the storage modulus)
calculation of the weighted relaxation spectra (relaxation time lm,
information on the molecular mass distribution of the polymers which
are involved in the solution state by rheological methods
TITK, F. Meister 15.04.2015 18
Rheometric evaluation of polymer dopes is realised by 2 different
experimental approaches: 1. Creep (and creep recovery trial) - shear stress steps
determination of the linear viscoelastic behaviour of meltable or of dissolved polymers above two shear stress steps (1) t = 0 t0 between t0 and t2 and (2) t0 t = 0 between t2 and t4
calculation of zero shear viscosity h0 and molecular weight M (h0 M3.4); at begin of the trial a constant shear stress t0 is impressed until the end of reading
h0 = t0 / tan b = t0 / [g3 / (t2 – t1)] = t0 / g 0
t
t
t0
t2 t4 t0 t0 t1 t2 t3 t4 t
g
g3
g2
g1
ge
gv
TITK, F. Meister 15.04.2015 19
2. Relaxation trial - deformation steps
- by dynamic-mechanical measurements (deformation steps) complex material characteristics like complex viscosity 𝜼∗(𝝎)
storage modulus G’(w) and
loss modulus G”(w)
are detected at exactly allowed shearing amplitudes (amplitude sweep) or frequencies (frequency sweep) and temperatures (commonly 85 °C)
TITK, F. Meister 15.04.2015 20
Dope 1: 11.8 % cotton linters in NMMO Cuoxam-DP pulp: 584 DPL: 570 h0 (85°C): 8,211 Pas h0 could also be calculated
from the plateau value of the complex viscosity
cross over 2.9 rad/s // 4,255 Pa
plateau modulus 31,700 Pa
G’’
G’
h*
100
1,000
10,000
100,000
0,01 0,1 1 10 100 1,000
w [rad/s]
Sto
rage
/ L
oss
Mo
du
lus
[Pa]
10
100
1,000
10,000
Co
mp
lex
Vis
cosi
ty [
Pas
]
storage modulus loss modulus complex viscosity
WLF = Williams, Landel, Ferry
TITK, F. Meister 15.04.2015 21
Dope 2:
12.1 % spruce pulp dissolved in NMMO
DP pulp: 615
DPL: 564
h0 (85°C): 12,760 Pas
Plateau Modulus
27200 Pa
Cross over
1.3 rad/s // 2390 Pa
G’
G’’
h*
Master curve of spruce pulp in NMMO
(reference temperature: 85°C)
100
1000
10000
100000
0,01 0,1 1 10 100 1000
w [rad/s]
Sto
rag
e / L
os
s M
od
ulu
s [
Pa
]
10
100
1000
10000
Co
mp
lex
Vis
co
sit
y [
Pa
s]
12.1 % SP - Storage modulus 12.1 % SP - Loss Modulus 12.1 % SP - Complex Viscosity
TITK, F. Meister 15.04.2015 22
0
500
1000
1500
2000
2500
3000
0,001 0,01 0,1 1 10 100 1000
Relaxation time l [s]
H(l
) *
l [
Pa
s]
11.8% CL in NMMO
12.1% SP in NMMO
Shear stress relaxation relaxation is a specific material function and controls time-dependent deformation and
back-deformation of polymer fractions of defined molecular weight and molecule
structure
such specific functions aren’t directly detectable, but could be calculated by means
of linear viscoelastic (LVE) theory - generalised Maxwell model
relaxation = f(h*(w), G(t)) (1), because validity of Boltzmann super positioning principle
at LVE region t(t) = 𝝉𝒊 𝒕 = 𝜸𝟎 ⋅ 𝑮𝒊 𝒊 ⋅𝒊 exp (-t / li) (2)
t(t) = tmax , if t = 0, t(l) = 0.368 ⋅tmax , if t = l and t(t) = tmax 1/e = 0, if t = (3)
H(l)l ...
- represents the collectivity of similar
molecules of a polymer
- indicates the frequency of
occurrence of macro molecules
exhibiting a low or a high relaxation
time l
TITK, F. Meister 15.04.2015 23
complex viscosity at cross over :h
wco Mw (as lower wco as higher Mw, if PDI (Uh) is more or less identic )
Gco‘ PDI (as lower Gco‘ as higher PDI (broader MWD), if DP=const.)
lm important value for spinning safety (viscoelastic dope behaviour)
(as higher lm as higher safety of use of a longer air gap)
h0 Mw (as higher h0 as higher Mw, h0 Mw3.4)
References (German language, only):
Schrempf, Ch.; Schild, G.; Rüf, H.: „Pulp-NMMO-Dopes and their Flow Behaviour“ Das Papier 12/1995, 748-757
Michels, Ch. et al.: About Determination of Molecular Mass Distribution in Cellulose from Rheometric Data,
Das Papier 1/1998, 3-8
Haake Mars II rheometer
Rheometric parameter and its structural relevance
Rheological dopes data: 11.8% CL (584)
in NMMO
12.1% SP (615)
in NMMO
zero shear viscosity (85°C) Pas 8,211 12,760
angular rate w at cross over rad/s 2.9 1.3
storage modulus G' at cross over Pa 4,255 2,390
plateau modulus Pa 31,700 27,200
rheological polydispersity Uh 3.0 3.7
relaxation time lm at H(l)m s 2.4 11.6
: rheological poly-
dispersity 𝑈𝜂 =
𝜂0
𝜂+# - 1,
TITK, F. Meister 15.04.2015 24
Final examination: Laboratory spinning tests 13
dry-wet spinning tests for preparation staple fibres using available
laboratory spinning equipment
testing of suitable spinning parameters (temperature, air gap length,
take-up velocity, conditioned air gap clima, …)
detection of textile-physical values of the prepared fibres using
defined ambient atmosphere (fineness, elongation, tenacity, loop
tenacity, fibrillation behaviour, modulus)
TITK, F. Meister 15.04.2015 25
Continuous dry-wet spinning testing plant at TITK
bobbin
winding-up
filament
dryer
filament
washing
dope
preparation
dry-jet-wet
spinning bar
fibre
staples
cutter
fibre after-
treatment
and fibre
finishing
fibres dryer
and
baling press
TITK, F. Meister 15.04.2015 26
Conclusion - air-gap spinning of cellulose is among solution spinning and needs a lot
of additional knowledge toward polymer properties in dissolved state
- analytical protocol of pulp and dope characterisation is a very suitable instrument to guarantee save and optimal solvation and spinning procedures
- rheological properties of polymer solutions are influenced by: properties of the polymer (DP, MWD, a-cellulose content) chemical -physical behaviour of the solvent (NMMO, different ILs) polymer concentration dissolving state
- dope characteristics are important criteria for most secure air-gap spinning procedure adjustment of intended fibre properties (fineness, tenacity,
elongation, …)
- all the properties of pulp and cellulose dopes have always to be adapted for the shaping process, shaped product and intended application
TITK, F. Meister 15.04.2015 27
Contact:
Thuringian Institute for Textile and Plastics Research
Chemical Research Department
Breitscheidstraße 97, 07407 Rudolstadt
Phone: +49(0)3672 37 92 00 Fax: +49(0)3672 37 93 79
E-mail: [email protected], [email protected] http://www.titk.de
Thank you very much for your kind attention !
Comments or any questions ?
Acknowledgement
Research activities presented
were financial supported by the
Federal Ministry of Economy
and Energy and the Thu-
ringian Ministry of Economy,
Labour and Development.
We also wish to express our
thanks to company partners for
cooperation and support and
textile research institutes
(STFI, HIT, TITV) for
processing and application
studies complementing the
TITK‘s R&D-activities.
TITK, F. Meister 15.04.2015 28
Agenda 04/08/2015 at TITK
14.15 Arrival of participants at TITK, walk to IUK 14.20 – 14.50 Presentation „Preparation and Characterization of Cellulose Dopes in NMMO“, Dr. Meister 14.55 – 16.20 Activity centres for explanation and demonstration in following topics
1. Characterisation of cellulose dopes in NMMO Dr Meister 2. Dry-jet-wet (air-gap) sping of cellulose dopes at laboratory scale Mrs Dr Kosan 3. Demonstration electrospinning Mrs Dr Römhild
Three groups (about 10 persons) are guided by TITK staff. Group 1 begins at Station 1 and ends up at Station 3, Dr. Schaller Group 2 begins at Station 2 and ends up at Station 1, Dr. Schulze Group 3 begins at Station 3 and ends up at Station 2, Hr. Schmuck
about 16.20 every group immediately adjourns to the bus 16.25 Trip to the smartpolymer pilot plant at Prof.-Hermann-Klare-Straße 23 16.30 Round tour through the pilot plant, Dr. Meister 17.00 End of the course at TITK, return to Jena, Dr. Koschella
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