Influence of mechanico-enzymatic and chemical pre-treatment methods on NFC preparation

Transcription

1 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

2 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.

3 Micro/nanofibrillated cellulose production 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 Context Pääkkö et al., Biomacromolecules, 2007, 8,

4 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

5 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

6 Micro/nanofibrillated cellulose production from softwood dissolving pulp Chemical pre-treatments Controlled acid hydrolysis Peroxide oxidation Surface cellulose chemical modifications (TEMPO) Enzymatic pre-treatments Endoglucanases Mechanical treatments Fibers refining/beating/grinding Homogenizers Preliminary results

7 Optimisation of a combined mechanical/enzymatic pretreatment of pulps before NFC production Softwood dissolving Pulp Refining Pre-Refined pulp ~25 SR Enzymatic treatment Bio-treated pulp 2 refining conditions 2 commercial endoglucanases tested (3 reaction times, 3 charges, 2 pulp consistencies) Refining Bio-treated refined pulp ~ 80 SR Homogenizing through Microfluidizer Optimisation of the number of passes NFC-CTP

8 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)

9 Pulp pre-refining Objective: to improve cellulose accessibility to enzyme 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 Mechanical pre-refining HC Pre-Refined pulp ~25 SR LC 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

10 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 Softwood dissolving Pulp Refining Pre-Refined pulp ~25 SR Enzymatic treatment Bio-treated pulp Effects observed Drastic intrinsic viscosity reduction Fibre modifications: highlighted after refining

11 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) Softwood dissolving Pulp Refining Pre-Refined pulp ~25 SR Enzymatic treatment Bio-treated pulp Refining Bio-treated refined pulp ~ 80 SR Fibrillation conditions led to the best homogenization to produce NFC

12 Average length weighted in area ( µ m) Impact of mechanical/enzymatic pre-treatment on softwood dissolving pulps properties Pre-treatment Viscosity [cm 3 /g] LODP [cm 3 /g] Fine content [%] Starting pulp Pre-refined pulp Abiotic pulp Endoglucanase X Endoglucanase Z Softwood dissolving Pulp Refining Pre-Refined pulp ~25 SR Enzymatic treatment Bio-treated pulp MorFi analysis: Endoglucanase Control Impact of endoglucanase 30% energy savings Reduction of macrostructure (fibres) and microstructure (cellulose chains) Creation of fine elements Refining Bio-treated refined pulp ~ 80 SR SEC (kw.h/t)

13 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 Softwood dissolving Pulp Refining Pre-Refined pulp ~25 SR Enzymatic treatment Bio-treated pulp Refining Bio-treated refined pulp ~ 80 SR Homogenization through Microfluidizer: 1 to 3 times through 400 µm 1 to 5 times : 200 µm +/- 5 times : 100 µm NFC-CTP

14 Enzyme Z Abiotic NFC-CTP production from spruce dissolving pulp Light microscopy MFC produ ced by Microfluidizer using : 400 µm* µm*3 passes D NFC produced by Microfluidizer using : 400 µm* µm* µm*5 passes E

15 NFC-CTP from spruce dissolving pulp SEM examination Control E Endoglucanase Heterogeneous suspension A majority of elements with a diameter below 200 nm

16 NFC-CTP from Spruce dissolving pulp TEM examination NFC Diameter nm Length 1-10 µm Partially microfibrillated fibre 1 µm

17 Summary 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

18 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

19 MFC/NFC Functionalisation Hydrophobisation of NFC by Carboxylation/Amidation O H O O H O O H TEMPO NaOCl, NaBr O H O O OH O N a O O H NX NHS, EDAC O H O O NX O O H NHS = N-hydroxysuccinimide EDAC = N-(3-Dimethylaminopropyl)-N -ethyl-carbodiimide 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, mole amine per COOH group, 1-3 h reaction time

20 Strategies for hydrophobisation of NFC by carboxylation/amidation Bleached pulps (Pre-refining) / Enzymatic treatment Post-refining 80 SR Post-refining 80 SR Chemical modification NFC production Chemical modification Post-refining?? Chemical modification NFC production NFC production 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

21 TEMPO-oxidized NFC Amidated NFC Amidation of oxidized NFC with aniline NFC TEMPO-ox NFC Amidated NFC 1 min later Dispersion of modified NFC in acetone NFC TEMPO-ox NFC Amidated NFC Gel viscosity decreased after amidation

22 TEMPO-oxidation / amidation NFC production Equipment : Microfluidizer Only 5 passes in the100 µm chamber 2 % consistency Both TEMPO-oxidized and amidated NFC produced NFC-TE/CTP NFC-TEA/CTP TEMPO oxidized NFC Aniline-amidated NFC

23 Conclusions & Perspectives 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

24 Acknowledgment The research leading to these results received funding from the European Community s Seventh Framework Programme under Grant Agreement No