Israel González Tovar
LEPAMAP Group
University of Girona (Spain)
Content
 The improvement of paper’s strength through refining
 Cellulose nanofibres (definition, sources and production)
 Addition of CNF into papermaking suspensions
 Experiments
 Results
 Conclusions
Mechanical refining (beating) is the main
method to improve paper’s strength
Refined fibres present better properties
than normal fibres, however…
What are cellulose nanofibres (CNF)?
Source: Isogai 2010
Why CNF in papermaking?
˃
˃
˃
˃
Compatibility
Large specific surface area (great bonding capacity)
High strength and stiffness
Transparency
EXPERIMENTS:
How do we release the microfibrils?
Chemical pre-treatment (TEMPO-mediated
oxidation)
EXPERIMENTS:
How do we release the microfibrils?
Enzymatic pre-treatment
EXPERIMENTS:
Enzymatic
treatment
(bleached euc pulp)
Enz-CNF bulk
application
(1.5, 3 and 4.5%)
TEMPO-mediated
oxidation
(bleached euc pulp)
Catiotic demand, surface area,
yield, transmittance, diametre
Solution A
(0.45wt% CNF)
Solution B
(0.45 wt% CNF+2.5wt%
starch size press)
TEMPO-CNF
(surface
application)
Mechanical and
physical
characterization
Density, porosity, opacity, breaking
length, scott bond, burst index
RESULTS
Bulk application: non-chemical CNF have lesser impact
on pulp’s drainability
Sample
Enzymatic CNF
(4 h contact time, 240 g/ton)
TEMPO-oxidized CNF
(15 mmol HClO, alkaline pH)
Cationic
Surface
demand
area
(µeq·g/g)
2
(m /g)
258
1988
Diametre Yield Transmittance
Degree
(nm)
(%)
(800nm, %)
of polym.
105.2
23.8
34.0
38.9
307
323
8.3
>95
84.7
197
Surface application: shorter fibres penetrate better
into the paper’s structure
RESULTS
TEMPO-oxidized CNF are better for surface application
because:
High carboxylic content
Lower polymerization
degree
Shorter nanofibres
RESULTS
CNF-reinforced papers show improved strength
RESULTS
Increase of 273%!!!!
Achieved without mechanical refining!!!, preserving fibre’s
original length and properties.
RESULTS
Effect of enzymatic CNF on physical properties added in masse to
bleached kraft hardwood pulp
CNF content
0
1,5
3
4,5
Thickness
(μm)
145,52
138,64
133,88
129,34
Bulk
(cm3/g)
1,91
1,81
1,76
1,70
Opacity
(%)
88,6
88,2
87,6
87,0
Gurley Porosity
(s)
1,1
2,1
3,0
3,8
ºSR
15
21
24
29
RESULTS
Papers become denser after CNF addition (more compact structure)
RESULTS
CNF-reinforced papers present also improved internal cohesion
RESULTS
Costs of CNF production: a
pending task
Type of CNF
Pretreatment
Energy
(€/kg CNF)
Enzymes
(€/kg
CNF)
Nanofibrillation
Process at 2wt% fiber
Energy
Energy
cost*
consumption
(€/kg
(kW·h/kg)
CNF)
Total
Cost
(€/kg
CNF)
Treatment
Conditions
Chemicals
(€/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
15 mmols
303,06**
0,03
0,00
19,1
1,53
304,62
TEMPO
oxidation
CONCLUSIONS
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.
Thank you for your attention!!
We’re waiting for your visit in
Girona!!
Girona