Date post: | 16-Apr-2017 |
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Content The improvement of paper’s strength through refining
Cellulose nanofibres (definition, sources and production)
Addition of CNF into papermaking suspensions
Experiments
Results Conclusions
Why CNF in papermaking?
˃ Compatibility ˃ Large specific surface area (great bonding capacity) ˃ High strength and stiffness ˃ Transparency
EXPERIMENTS:
TEMPO-mediated oxidation
(bleached euc pulp)
TEMPO-CNF (surface
application)
Enz-CNF bulk application
(1.5, 3 and 4.5%)
Enzymatic treatment
(bleached euc pulp)
Mechanical and physical
characterization
Solution A (0.45wt% CNF)
Solution B (0.45 wt% CNF+2.5wt%
starch size press)
Density, porosity, opacity, breaking length, scott bond, burst index
Catiotic demand, surface area, yield, transmittance, diametre
Sample
Cationic
demand
(µeq·g/g)
Surface
area
(m2/g)
Diametre
(nm)
Yield
(%)
Transmittance
(800nm, %)
Degree
of polym.
Enzymatic CNF
(4 h contact time, 240 g/ton) 258 105.2 23.8 34.0 38.9 307
TEMPO-oxidized CNF
(15 mmol HClO, alkaline pH) 1988 323 8.3 >95 84.7 197
Bulk application: non-chemical CNF have lesser impact on pulp’s drainability
Surface application: shorter fibres penetrate better into the paper’s structure
RESULTS
High carboxylic content
Lower polymerization degree
Shorter nanofibres
TEMPO-oxidized CNF are better for surface application because:
RESULTS
Achieved without mechanical refining!!!, preserving fibre’s original length and properties.
Increase of 273%!!!!
RESULTS
Bulk (cm3/g)
Opacity (%)
Gurley Porosity (s)
1,91 88,6 1,1 1,81 88,2 2,1
1,76 87,6 3,0 1,70 87,0 3,8
Effect of enzymatic CNF on physical properties added in masse to bleached kraft hardwood pulp
CNF content Thickness (μm)
0 145,52 1,5 138,64 3 133,88
4,5 129,34
ºSR
15 21
24 29
RESULTS
Costs of CNF production: a pending task
Type of CNF Pretreatment Nanofibrillation Process at 2wt% fiber Total
Cost (€/kg CNF) Treatment Conditions Chemicals
(€/kg CNF) Energy
(€/kg CNF)
Enzymes (€/kg CNF)
Energy consumption
(kW·h/kg)
Energy cost* (€/kg CNF)
Enzymatic hydrolysis
T=50ºC, pH=5, 240g/t, 4h and
5wt% fiber 0,01** 0,07 0,48 19,1 1,53 2,09
TEMPO oxidation 15 mmols 303,06** 0,03 0,00 19,1 1,53 304,62
RESULTS
CNF are an interesting alternative over mechanical beating.
CNF improve mechanical and physical properties of paper by
increasing the amount of hydrogen bonds between fibres.
CNF can be applied as bulk additives or as coatings.
Addition of CNF as bulk and surface additive increase paper’s strength in 273%.
TEMPO-oxidized CNF have high fabrication costs in comparison to enzymatic CNF.
CONCLUSIONS