Influence of mechanico-enzymatic and chemical

pre-treatment methods on NFC preparation

Valerie Meyer, Centre Technique du Papier

S. Tapin-Lingua, D. da Silva Perez, Institut Technologique FCBA

Tiemo Arndt, Papiertechnische Stiftung

Ulf Germgård, Karlstad University

SUNPAP Workshop 5.10.2011

Context

• Fibre pre-treatment prior to homogenization = key factor for energy

efficient preparation of nanocellulose

• Weakening the fibres and increasing the initial specific surface before

the mechanical disintegration starts is essential

• Several pulp pre-treatments : chemical, enzymatic or mechanical

methods, alone or in combination

• The energy demand can be influenced, but also the structure of

the final NFC product.

• Another important issue for papermaking applications of NFC :

• Reduction of the water content of NFC suspension (96-98%) and

the decrease of the gel-like product viscosity.

• Chemical pre-treatments • Controlled acid hydrolysis

• Peroxide oxidation

• Surface cellulose chemical modifications

(TEMPO)

• Enzymatic pre-treatments

• Endoglucanases

• Hemicellulases

• Mechanical treatments

• Fibers refining/beating/grinding

• “Homogenizers”

Micro/nanofibrillated cellulose production

Pääkkö et al., Biomacromolecules, 2007, 8, 1934-1941

Context

Objectives

• To develop a method of pulp pre-treatment combining mechanical and

enzymatic/chemical effects

• To reduce the fibre size

• To limit the energy consumption

• To facilitate the NFC production (diameter < 200 nm)

• To modify surface energy and properties of NFC for optimized applications

in paper production processes

• To control viscosity for application purpose

• To confer specific functions

Objectives

• To develop a method of pulp pre-treatment combining mechanical and

enzymatic/chemical effects

• To reduce the fibre size

• To limit the energy consumption

• To facilitate the NFC production (diameter < 200 nm)

• To modify surface energy and properties of NFC for optimized applications

in paper production processes

• To control viscosity for application purpose

• To confer specific functions

• Chemical pre-treatments • Controlled acid hydrolysis

• Peroxide oxidation

• Surface cellulose chemical modifications

(TEMPO)

• Enzymatic pre-treatments

• Endoglucanases

• Mechanical treatments

• Fibers refining/beating/grinding

• “Homogenizers”

Micro/nanofibrillated cellulose production from softwood dissolving pulp

Preliminary results

Optimisation of a combined mechanical/enzymatic pre-

treatment of pulps before NFC production

Softwood

dissolving Pulp

Pre-Refined pulp

~25°SR

Enzymatic treatment

Bio-treated pulp

Refining

Refining

Bio-treated

refined pulp

~ 80 °SR

NFC-CTP

Homogenizing through

Microfluidizer

• 2 refining conditions

• 2 commercial endoglucanases tested (3 reaction times, 3

charges, 2 pulp consistencies)

• Optimisation of the number of passes

Measurements performed

• Energy consumption during refining

• Fibre chemical composition (enzymatic treatment)

• Intrinsic viscosity and LODP

• Fibre morphology of refined pulps (MorFi analyzer)

• NFC morphology was visualised using

• Light microscopic images

• Scanning electron microscopy (SEM)

• Transmisson Electron Microscopy (TEM)

Pulp pre-refining

Objective: to improve cellulose accessibility

to enzyme

• Low consistency refining (3.5%)

• Smooth refining easy to control

• Energy consumption between 60 and 150 kWh/t

All the refinings were carried out at low consistency

• High consistency refining (20%)

Too intensive for chemical pulp fibres preparation

• Difficulty to be reproducible to reach 25 °SR

• High energy consumption

• Risk of pulp darkening

Softwood

dissolving Pulp

Pre-Refined pulp

~25°SR

Mechanical pre-refining

HC LC

Enzymatic pre-treatment

Objective: to weaken the fibre to facilitate the refining

Conditions tested:

• Iogen DP318 and Novozym 476: 2 endoglucanases with different purity level

• Enzyme charge: 0.1, 1 and 5 kg/t

• Reaction time: 30 to 120 min

• Best enzymatic pretreatment conditions :

• Novozym 476

• Consistency 3.5%, 50 °C, pH 5 for 1 hour

• Enzyme charge: 0.1 kg/t

• Effects observed

• Drastic intrinsic viscosity reduction

• Fibre modifications: highlighted after refining

Softwood

dissolving Pulp

Pre-Refined pulp

~25°SR

Enzymatic treatment

Bio-treated pulp

Refining

Refining

Objective: to cut fibres and improve fibrillation to facilitate NFC production

• Two refining conditions tested (refining intensity)

• 1 condition promoting fibre cutting (high intensity)

• 1 allowing a better fibrillation (low intensity)

• Continuous refining until the highest freeness (without pulp darkening)

Fibrillation conditions led to the best homogenization to produce NFC

Softwood

dissolving Pulp

Pre-Refined pulp

~25°SR

Enzymatic treatment

Bio-treated pulp

Refining

Refining

Bio-treated

refined pulp

~ 80 °SR

Impact of mechanical/enzymatic pre-treatment on

softwood dissolving pulps properties

Pre-treatment Viscosity [cm3/g] LODP [cm

3/g] Fine content [%]

Starting pulp 550 123 7.0

Pre-refined pulp 520 117 14.1

Abiotic pulp 500 - 20.2

Endoglucanase X 450 105 24.8

Endoglucanase Z 330 104 25.3

Softwood

dissolving Pulp

Pre-Refined pulp

~25°SR

Enzymatic treatment

Bio-treated pulp

Refining

Refining

Bio-treated

refined pulp

~ 80 °SR Impact of endoglucanase

• 30% energy savings

• Reduction of macrostructure (fibres)

and microstructure (cellulose chains)

• Creation of fine elements

400

500

600

700

800

900

1000

1100

1200

Avera

ge le

ngth

weig

hte

d in

are

a (

µ

m)

100 150 200 250 300 350 400

SEC (kW.h/t)

Control

Endoglucanase

MorFi analysis:

275 385

NFC production at laboratory scale

Objective: to produce NFC at laboratory scale to

evaluate the impact of pre-treatment prior to

homogenization

• Possibility to reduce number of passes into the

microfluidizer reduction of energy consumption

during NFC processing

Optimised sequence for the production of NFC from

spruce dissolving pulp • 1 pass at 400 µm • 3 passes at 200 µm • 5 passes at 100 µm

Homogenization through

Microfluidizer:

1 to 3 times through 400 µm

1 to 5 times : 200 µm

+/- 5 times : 100 µm

Softwood

dissolving Pulp

Pre-Refined pulp

~25°SR

Bio-treated pulp

Refining

Refining

Bio-treated

refined pulp

~ 80 °SR

NFC-CTP

Enzymatic treatment

NFC-CTP production from spruce dissolving pulp

Light microscopy MFC produ ced by Microfluidizer using :

400 µm*1 + 200 µm*3 passes

NFC produced by Microfluidizer using : 400 µm*1 + 200 µm*3 +100 µm*5 passes

Abio

tic

En

zym

e Z

D

E

NFC-CTP from spruce dissolving pulp

SEM examination

• Heterogeneous suspension

• A majority of elements with a diameter below 200 nm

Control E

Endoglucanase

NFC-CTP from Spruce dissolving pulp

TEM examination

1 µm

Partially

microfibrillated fibre

NFC Diameter 20-30 nm

Length 1-10 µm

• Determination of an optimised protocol to produce pulps for NFC production

• Pre-refining at low consistency up to 25°SR

• Optimised enzymatic pretreatment with endoglucanase

• LC Refining with fibrillating conditions :

• 20-40% energy saving

• Good fibre preparation for homogeneisation

• Drastic decrease in fibre length and fibrillation development

• Almost all particles were in the desired nano-scale region with a diameter < 200 nm

• Scale up with 250 kg of pre-treated pulps validated

Summary

Objectives

• To develop a method of pulp pre-treatment combining mechanical and

enzymatic/chemical effects

• To reduce the fibre size

• To limit the energy consumption

• To permit the NFC production (diameter < 200 nm)

• To modify surface energy and properties of NFC for optimized applications

in paper production processes

• To control viscosity for application purpose

• To confer specific functions

TEMPO

NaOCl, NaBr

• Hydrophobisation of NFC by Carboxylation/Amidation

• Aqueous system

• Oxidation conditions (fibres): pH 10, room temperature, 0.1 to 1 mols of

oxidant per OH in C6 group, 2 % TEMPO, 5 min – 2 h reaction time

• Amidation conditions (fibres) : pH 8, room temperature, 2 moles EDAC,

2 moles NHS, 0.1-1 mole amine per COOH group, 1-3 h reaction time

O

O H

O H O H

O O

O N a

O H O H

O

O OH

O NX

O H O H

O

O NX

NHS, EDAC

NHS = N-hydroxysuccinimide

EDAC = N-(3-Dimethylaminopropyl)-N’-ethyl-carbodiimide

MFC/NFC Functionalisation

Strategies for hydrophobisation of NFC by carboxylation/amidation

Bleached pulps

(Pre-refining) /

Enzymatic treatment

NFC production

Post-refining 80°SR

Chemical modification NFC production

Post-refining 80°SR

Chemical modification

NFC production

Post-refining ??

Chemical modification

Strategy 1A Strategy 1B Strategy 1C

COOH = 0.40 to 1.65

Yield = 26.9 to 48 %

Min viscosity = 0.2 Pa.s

COOH = 0.6 to 1.38

Yield = 31.0 to 60.7 %

Min viscosity = 0.2 Pa.s

COOH = 0.6 to 1.42

Yield = 55.6 to 85.2 %

Viscosity = 0.4 Pa.s

TE

MP

O-o

xid

ized

NF

C

Am

idate

dN

FC

Dispersion of modified

NFC in acetone

Gel viscosity decreased

after amidation

Amidation of oxidized NFC with aniline

1 min later

NFC TEMPO-ox

NFC Amidated

NFC

NFC TEMPO-ox

NFC Amidated

NFC

TEMPO-oxidation / amidation

• NFC production

• Equipment : Microfluidizer

• Only 5 passes in the100 µM chamber

• 2 % consistency

• Both TEMPO-oxidized and amidated NFC produced

TEMPO oxidized NFC Aniline-amidated NFC

NFC-TE/CTP NFC-TEA/CTP

• NFC surface modifications by oxydation/amidation should be done directly on the bleached pulp prior to homogenization

• Production of NFC oxidized and amidated successfully achieved

• Amidation led to a decrease in NFC viscosity

• Scale up of the pulp pre-treatment with TEMPO oxidation prior to NFC production validated with 5 Kg

• Measurement of rheological properties of NFC still under progress

• Tests aiming at increasing solid content prior to homogenization scheduled

Conclusions & Perspectives

Acknowledgment

• The research leading to these results received funding from the

European Community’s Seventh Framework Programme under

Grant Agreement No 228802.