Israel Gonzalez Tovar, University of Girona (LEPAMAP). This was presented during the New Ideas for the Paper Industry: Young Researchers' Presentations session, organised as part of European Paper Week 2015. More at http://www.cepi.org/epw

1. Israel González Tovar
LEPAMAP Group
University of Girona (Spain)

2. Content
 The improvement of paper’s strength through refining
 Cellulose nanofibres (definition, sources and production)
 Addition of CNF into papermaking suspensions
 Experiments
 Results
 Conclusions

3. Mechanical refining (beating) is the main
method to improve paper’s strength

4. Refined fibres present better properties
than normal fibres, however…

5. What are cellulose nanofibres (CNF)?
Source: Isogai 2010

6. Why CNF in papermaking?
˃ Compatibility
˃ Large specific surface area (great bonding capacity)
˃ High strength and stiffness
˃ Transparency

7. How do we release the microfibrils?
Chemical pre-treatment (TEMPO-mediated
oxidation)
EXPERIMENTS:

8. How do we release the microfibrils?
Enzymatic pre-treatment
EXPERIMENTS:

9. 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

10. 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

11. High carboxylic content
Lower polymerization
degree
Shorter nanofibres
TEMPO-oxidized CNF are better for surface application
because:
RESULTS

12. CNF-reinforced papers show improved strength
RESULTS

13. Achieved without mechanical refining!!!, preserving fibre’s
original length and properties.
Increase of 273%!!!!
RESULTS

14. 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

15. Papers become denser after CNF addition (more compact structure)
RESULTS

16. CNF-reinforced papers present also improved internal cohesion
RESULTS

17. 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

18. 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

19. Thank you for your attention!!
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