Production methods of nanocellulose (CNF)- principles. Compiled by Tom Lindström Innventia

Transcription

1 Production methods of nanocellulose (CNF)- principles Compiled by Tom Lindström Innventia COST FP 1205 International Training Schol, April 2016

2 There are three different domains of Nanocellulosic materials: NFC NanoFibrillar Cellulose (=MFC) NCC NanoCrystalline Cellulose BC Bacterial Cellulose

3 Microfibrills in wood Courtesy: Geoff Daniels

4 Microfibrillar Cellulose (MFC) first produced by Turbak and co-workers at ITT in the beginning of the 80 s High Pressure Homogenizer Microfibrillated Cellulose MFC Turbak, A.F., Snyder, F.W. and Sandberg, K.R. J. Appl. Polym. Science. Applied Pol. Symp. 37 (1983) But: Very high energy consumption and clogging problems!

5 NFC generation 0 Energy consumption = kwh/tonne, 10 passes MFC Homogenisation Pulp

6 This is the graph, where the quoted KWh/tonne to make MFC came from.. Source: Lindström, T. and Winter, L. (1988).. STFI-meddelande C159 (internal STFI-report)

7 Comparison between STFI (Innventia) first MFC and Turbak (ITT Rayonier) MFC (1985)

8 TEM of early MFC (1984) Smallest fibrils 20 nm and up Source: Lindström, T. and Winter, L. (1988). Mikrofibrillär cellulosa som komponent vid papperstillverkning. STFI-meddelande C (Internal 8 STFI-report)

9 At this point in time (1990) we started to doubt that the machine construction was the secret as we had tried the Manton-Gaulin homogenizer, Ball mill machines and the Masuko supermasscollider and they all demanded very high energy inputs (in the order of kwh/tonne), the definition of MFC at this point in time was: A gelly type of substance with a very high fines content

10 One solution NFC generation 1 Energy consumption = 2000 kwh/tonne (2011) Nanocellulose Now:350 kwh/tonne! Homogenisation Mechanical & Enzyme treatment Pulp

11 Production method of NFC gen. 1 Bleached sulphite pulp E-W refiner to 30 SR Homogenisation in Microfluidizer Pretreatment Enzymatic treatment 1 pass small chambers E-W refiner to 94 SR NFC

12 NFC particle size, gen 1 Elementary fibril One elementary fibril: width 5 nm 5 nm 20 nm 5 nm MFC TEM-imaging: width 5-30 nm AFM-imaging: width 5-30 nm Solid state NMR: width 17 nm Light scattering: 20 nm Indicative length = 100 nm to > 1 m

13 Another solution NFC generation 2 Energy consumption = kwh/tonne Nanocellulose Homogenisation Carboxymethylation Pulp

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15 Different generations of NFC at Innventia Generation 0 (ITT-developments in the 80s ( kwh/tonne Generation 1 (Enzymatic pre-treat.) ( kwh/tonne papermaking wet-end appl.) Generation 2 (Carboxymethylation/ STFI 1987) Generation 3 (Tempo-oxidation) Generation 4 (g- CMC) Generation 5 (Cationic) Generation 6 (Acetylated NFC) Gen. 7 (Phosphated NFC) Gen. 8 (Sulphonated NFC)

16 16 MFC gen w-% MFC gen. 2 7 w-%

17 Our Basic concepts for the Estimation of Important Factors for Homogenizability Pulp Fibres Cell wall cohesion: Affected by enzymes by degrading fibres and the charge content/hemicellulose content Remedies: Enzymatic degradation of cellulose, while maintaining the hemicellulose, oxidative treatments/grafting technology Clogging of homogenizers affected by the tendency of fibres to flocculate Remedies: The use of thickeners, dispersion agents or grafting methods decreasing the surface friction of fibres

18 Fibres behave as Polyelectrolyte Gels, hence, the Charge Content is very Important for Cell Wall Cohesion

19 Charge density of kraft and sulphite fibres vs kappa number Lindström T, Carlsson G EUCEPA Symp. Chemistry in Papermaking, Warsaw, (1978)

20 Swelling vs ph and ionic strength for holocellulose fibres Carlsson G, Kolseth P, Lindström T, Wood 2014 Sci 20 Technol., 17:69-73 (1983)

21 Our Basic concepts for the Estimation of Important Factors for Homogenizability Pulp Fibres Cell wall cohesion: Affected by enzymes by degrading fibres and the charge content/hemicellulose content Remedies: Enzymatic degradation of cellulose, while maintaining the hemicellulose, oxidative treatments/grafting technology Clogging of homogenizers affected by the tendency of fibres to flocculate Remedies: The use of thickeners, dispersion agents or grafting methods decreasing the surface friction of fibres

22 Concept of Crowding Factor N (5 x C m x L 2 )/ω N= Crowding factor C m = Mass concentration of fibres (%) L= Fiber length in m ω = Fibre coarsness, kg/m The higher the crowding factor, the higher is the state of flocculation, But fibre-fibre friction, has not been taken into account in this formalism Kerekes, R. and Schell, C. (1992): J. Pulp Paper Sci. 18(1), J32-J

23 Charges affect surface friction

24 Colloidal Probe Microscopy

25 Comparison between 2.9 eq/g and 25 eq/g surface charge density of bleached kraft fibres F/2p r [N/m] Na + -form, 10-5 M NaCl 25 meq/g 2.9 meq/g Separation [nm] Horvath A E and Lindström T Journal of Colloid and Interface Science, (309) (2007)

26 Critical Strain ( c ), Storage Modulus (G ) and Yield Stress ( ) = G 0 c c

27 Effect of surface charge content on yield stress of pulp suspensions Apparent yield stress, t [Pa] meq/g 10 meq/g meq/g 21 meq/g Horvath A E and Lindström T Journal of Colloid and Interface Science, (309) (2007) Na + -form, de-ionized water 0,80, Consistency, C w [%]

28 Different generations of NFC at Innventia Generation 0 (ITT-developments in the 80s ( kwh/tonne)) Generation 1 (Enzymatic pre-treat.) (350 kwh/tonne papermaking wet-end appl.) Generation 2 (Carboxymethylation/ STFI 1987) Generation 3 (Tempo-oxidation) Generation 4 (g- CMC) Generation 5 (Cationic) Generation 6 (Acetylated NFC) Gen. 7 (Phosphated NFC) Gen. 8 (Sulphonated NFC)

29 Concept of physical grafting using carboxymethylcellulose (CMC) Chemical additives with two functionalities - One functionality for irreversible bonding to fibres - One functionality for aid interactions - Toposelectivity can be controlled by changing the M w of the polymer COO - R

30 Several parameters influence the attachment of CMC Time Ionic strength Type of electrolyte ph Temperature etc

31 Effect of temperature on the attachment of CMC CMC dosage 20 mg/g, 120 min, 0.05 M CaCl 2 Attached amount of CMC (mg/g) Ca-form Temperature ( C) Ca-form

32 Effect of ionic strength and form on the attachment of CMC Attached amount of CMC (mg/g) 10 8 Ads. CaCl2, Ca-form Ads. NaCl, Na-form ºC, 120 min Log electrolyte conc. (M)

33 Effect of ph on acid grafting Grafted amount CMC [mg/g] mg/g Amph.CMC A-CMC ph

34 Example: Results on sulphite pulps CMC Total charge ( eq./g) Adsorbed CMC (mg/g) Clogging? MFC gel? No CMC 50 0 Yes No Amphot Yes No Amphot No Yes Amphot No Yes Amphot No Yes Anionic (0.4) No Yes

35 Mikael Ankerfors MFC gels 89 ekv/g, amphoteric CMC 125 ekv/g, amphoteric CMC 231 ekv/g, amphoteric CMC 177 ekv/g, amphoteric CMC

36 Turbidity Results CNF CMC CNF Enzymatic/mechanical CNF - carboxymethylation

37 NFC Coatings and Films Assessment of NFC Quality from film strength

38 Oxygen and water vapour permeability of various materials Aulin and Lindström Biopolymer coatings.. Chapter 12 in Biopolymers-New materials for sustainable films and coatings, Ed. D. Placket, Wiley,

39 Cross-section of Nanocellulose Film

40 Important Considerations Density of amorphous cellulose= 1.48 g/cm 3 Chen W et al (2004), Polymer 45: Density of Cell I, crystals = 1.63 g/cm 3 Crystallinity of films= 60 %; Density= / g/cm 3 Aulin, C. et al, (2010) Cellulose 17: Density gradient column mesurements give g/cm 3 Thickness measurements: White-light interferometric profilometer (New View 5010, Zygo Corporation, USA) give 1.57 g/cm 3 NFC films are non-porous!

41 Tensile strength index (knm/kg) c NS (w/w) % Evolution of film strength for Gen. 2 CNF (carboxymethylated pulp) Energy (kwh/tonne)

42 Viscosity (Pa.s) G' (Pa) Evolution of the rheology for gen 2 CNF a) 400 bar 550 bar 850 bar 1700 bar 1000 b) 400 bar 550 bar 850 bar 1700 ba Energy (kwh/tonne) Energy (kwh/tonne)

43 Evolution of film strength for Gen. 4 (CMCmodified pulp Tensile strength index (knm/kg) Tensile stiffness index (MNm/kg) TEA index (knm/kg) Strain to break (%) 0.3 % 1 oass % 2 pass % 3 pass % 5 pass % 1 pass % 5 pass % 1 pass % 2 pass % 3 pass % 5 pass Naderi et al Cellulose

44 Summarizing film strength data for 3 CNF-generations CNF Type Tensile Index, Nm/g Reference Enzymatically liberated CNF (Gen. 1) Carboxymethyl ated liberated CNF (Gen. 2) CMC-grafted liberated cellulose (Gen. 4) Nm/g Unpublished Nm/g Naderi, A, Lindström, T, Sundström, J. Cellulose (2015) 22, Nm/g Naderi, A, Lindström, T, Sundström, J, Flodberg, G, Erlandsson, J. Cellulose (2015) 22,

45 Can the Page Equation for paper strength be of some help in assessing a theoretical film strength? A w T 8 w zero SBS P L RBA σ w T is the tensile index, Nm/kg σ w zero is the zero span breaking length, Nm/kg A is the average fibre cross section, m 2 r is the density of the fibres, kg/m 3 SBS is the Specific Bonding Strength, the shear bond strength per unit bonded area, Pa P is the perimeter of the fibre cross section, m L is the fibre length, m RBA is the relative bonded area in the sheet Derek Page Shear RBA SBS Page, D. H. Tappi 52(4), 674 (1969)

46 Basic factors responsible for Paper Strength Fibre Strength (relatively well understood factors) Fibre-Fibre bond strength (little is understood) Sheet structural features such as formation, fibre kinks (known to some extent) Residual stresses on different structural levels: z- direction gradients, microcomprerssions in bonding zones, free volume considerations (some features understood) Paper strength theories (e.g. Page) generally consider the first two factors

47 What is needed? In the Page equation the fibre cross section, fibre length, perimeter of the cross-section and fibre density are all quantities that can be determined If one pulp is used and strength additives are used, it s an advantage that these parameters are kept constant, because the parameters are associated with measuring errors The interlaminar shear strength needs to be measured RBA needs to be determined (krypton adsorption) Some good strength adjuvants should be used so the results are not blurred by changes in sheet formation or the general scattering in the experiments

48 Determination of interlaminar shear strength of paper A schematic view of the shear strength apparatus. Cross section of the shear instrument. The sample (A) is glued between the metal blocks (B and B). A hole in the block (C) makes it possible for the strain to be picked up in the center plane between the arm (D) and an arm via a sheet ball (E) on block (B). The movement is transferred via a link mechanism (F) to a transducer (G). The fine adjustment of zero of the transducer is provided by a micrometer (H). Fellers C (1977) Sv. Papperstidning, 80(3):

49 Page Equation 1 w T 9 8 w zero 12 A SBS P L RBA σ w T is the tensile index, Nm/kg σ w zero is the zero span breaking length, Nm/kg A is the average fibre cross section, m 2 (2.4 x ) r is the density of the fibres, kg/m 3 (1560) SBS is the Specific Bonding Strength, the shear bond strength per unit bonded area, Pa P is the perimeter of the fibre cross section, m (9 x 10-5 ) L is the fibre length, m (2.6 x 10-3 ) RBA is the relative bonded area in the sheet Derek Page Shear RBA SBS Page, D. H. Tappi 52(4), 674 (1969)

50 Calculated tensile index (knm/ kg) Page equation now proven from first principles! Measured tensile index (knm/ kg) Deviation at high tensile strengths can be explained by a shift to cohesive behaviour!

51 BET-area (m2/g) BET-area vs tensile index 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 What does it mean that all data points are on one line? What does it mean when the BET-area crosses zero BETarea? 0,2 0,1 0 Beating, Starch add. CMC-grapht. MFC add Tensile index (Nm/g)

52 BET-area (m2/g) Extrapolation of the graph to zero BETarea gives a value of 172 Nm/g 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0 Beating, Starch add. CMC-grapht. MFC add Tensile index (Nm/g)

53 Summarizing film strength data for 3 CNF-generations CNF Type Tensile Index, Nm/g Reference Enzymatically liberated CNF (Gen. 1) Carboxymethyl ated liberated CNF (Gen. 2) CMC-grafted liberated cellulose (Gen. 4) Nm/g Unpublished Nm/g Naderi, A, Lindström, T, Sundström, J. Cellulose (2015) 22, Nm/g Naderi, A, Lindström, T, Sundström, J, Flodberg, G, Erlandsson, J. Cellulose (2015) 22,

54 Extrapolation to zero BET-area? What does it mean? Extrapolation to zero BET-area (172 Nm/g) Tensile strength of an MFC-film ( Nm/g) short-span strength of paper, from which the CNF was made (174 Nm/g)

55 Innventia s pilot plant for NFC production (100 kg/day) Mikael Ankerfors, Innventia AB

56 Design of a transportable MFC-plant

57 Thank You for Your Attention Tom Lindström Mobile: