Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B15/00—Preparation of other cellulose derivatives or modified cellulose, e.g. complexes
  • C08B15/02—Oxycellulose; Hydrocellulose; Cellulosehydrate, e.g. microcrystalline cellulose
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B1/00—Preparatory treatment of cellulose for making derivatives thereof, e.g. pre-treatment, pre-soaking, activation
  • C08B1/003—Preparation of cellulose solutions, i.e. dopes, with different possible solvents, e.g. ionic liquids
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/001—Modification of pulp properties
  • D21C9/002—Modification of pulp properties by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives
  • D21C9/004—Modification of pulp properties by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives inorganic compounds
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/001—Modification of pulp properties
  • D21C9/002—Modification of pulp properties by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives
  • D21C9/005—Modification of pulp properties by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives organic compounds
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/001—Modification of pulp properties
  • D21C9/007—Modification of pulp properties by mechanical or physical means
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
  • D21H11/16—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only modified by a particular after-treatment
  • D21H11/18—Highly hydrated, swollen or fibrillatable fibres
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/03—Non-macromolecular organic compounds
  • D21H17/05—Non-macromolecular organic compounds containing elements other than carbon and hydrogen only
  • D21H17/07—Nitrogen-containing compounds
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/64—Alkaline compounds
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/66—Salts, e.g. alums
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
  • D21H21/22—Agents rendering paper porous, absorbent or bulky

Definitions

• the present invention is directed towards a low energy method for the preparation of non- derivatized nanocellulose via a swollen intermediate.
• the present invention is directed towards a low energy method for the preparation of nanocellulose using selected organic or inorganic swelling agents.
• the use of these swelling agents allows opening up the intercrystalline structure and only partially but not fully opening up the intracrystalline structure of the cellulosic material thereby achieving a reduction in the energy required to subsequently process the resultant swollen cellulose material into nanocellulose.
• low energy method or energy efficient method (or method of the invention) refers to a method which is characterized by a significantly reduced energy consumption of the mechanical processing devices applied compared to the known energy intensive prior art methods in this area of technology.
• a low energy method suitable for the present invention is based on a mechanical comminution processing method, which typically requires less than 2000 kWh/t, preferably less than 1500 kWh/t and more preferably less than 500 kWh/t.
• Mechanical comminution processing methods include any effective mechanical comminution processing step which achieves a breaking up (or breakdown) into small particles (see also hereinafter).
• nanocellulose as used herein encompasses the (interchangeably used) term "nanofibrillated cellulose” and refers to cellulose particles which are characterized by having an elongated form, having an aspect ratio of >1, and having an average length in the range of 15-900 nm, preferably in the range of 50-700 nm, more preferably 70-700nm.
• the average thickness is preferably in the range of 3-200 nm, preferably in the range of 5-100 nm, more preferably in the range of 5-30 nm (for example, see Figure 1(A).
• cellulosic material includes but is not limited to the following type: microcrystalline cellulose, microbial cellulose, cellulose derived from marine or other invertebrates, mechanically generated wood pulp, chemical (dissolving) pulp, native biomass (in the form of plant fibres, stems or husks) and cellulosic man-made fibres such as tyre cord and other cellulose II sources such as mercerised cellulose.
• the cellulosic material may further be chemically derivatized by for example carboxylation, oxidation, sulphation or esterification.
• Preferred cellulose sources are derived primarily from wood pulp and other cellulosic biomass fibres and micro-crystalline cellulose, as for example Avicel PH-101, from FMC Corporation and also textile or technical textile fibres, for example as supplied by Cordenka GmbH under the trade name of Cordenka 700 (Super 3) can be used as a starting source of cellulosic material.
• Preferred sources of wood pulp include ground wood fibres, recycled or secondary wood pulp fibres, bleached and unbleached wood fibres. Both softwoods and hardwoods can be utilised.
• suitable biomass materials such as bagasse and bamboo based cellulose can be utilised.
• swelling agent is defined as being an agent that can disrupt either the intercrystalline bonding or which can disrupt both the intercrystalline and partially (i.e. not fully) the intracrystalline bonding normally present in cellulosic material. Agents that will only disrupt intercrystalline bonding (and at most will minimally affect intracrystalline structure), will only lead to swelling independent of the reaction conditions used. Such agents will never lead to full solvation (which is a result of significant or full disruption of intracrystalline bonding). The extent of swelling is dependent on the interaction conditions.
• reaction conditions that are able to disrupt both intercrystalline bonding and intracrystalline bonding may lead to either swelling (at most partial but not full disruption of intracrystalline bonding) or solvation (full disruption of of intracrystalline bonding) depending on the reaction conditions.
• suitable reaction conditions e.g. concentration, temperature, reaction time have to be chosen for obtaining swelling only (i.e. either achieving disruption of the intercrystalline bonding only or achieving disruption of the intercrystalline bonding and only partial (but not full) disruption of the intracrystalline bonding), but preventing complete solvation.
• full disruption of intracrystalline bonding is not desired and has to be prevented.
• a suitable swelling agent is an organic or inorganic swelling agent or a mixture thereof (in pure form or a solution thereof). It is understood that a swelling agent may be a solid or a liquid. A solid swelling agent may be dissolved or suspended in one or more suitable solvents, a liquid swelling agent may be used in pure form or further diluted with one or more suitable solvents to form a swelling agent solution. Thus the term "swelling agent" includes all of the above forms (pure and in solution).
• a typical inorganic swelling agent includes inorganic bases such as an inorganic halide, which is an inorganic metal halide or inorganic pseudo metal halide or an inorganic hydroxide.
• a typical organic swelling agent may include any organic swelling agents disclosed in the art, see, e.g. as cited in The Polymer Handbook 3 rd edition, 1989 (published by J Wiley & Sons, edited by J Brandrup & EH Immergut), more specifically within the section “Properties of Cellulose Materials”, specifically in the section “Solvents for Cellulose”.
• N-methyl morpholine N-oxide N-methyl morpholine N-oxide
• ionic liquids e.g. l-ethyl-3- methylimidazolium acetate
• urea urea and mixtures thereof.
• zinc ammonium complex zinc chloride, copper ammonium complex, silver ammonium complex, strontium hydroxide, barium hydroxide and the like, or mixtures thereof.
• Suitable mixtures of swelling agents include a mixture of an organic swelling agent and an inorganic metal halide or pseudo metal halide, e.g. a mixture of sodium thiocyanate and ethylenediamine,
• swelling agents for use in the present invention are any acid halides, e.g. hydrochloric acid, and conventional mineral acids, e.g. sulphuric, phosphoric and nitric acids.
• acid halides e.g. hydrochloric acid
• mineral acids e.g. sulphuric, phosphoric and nitric acids.
• the swelling agent is a liquid organic swelling agent, preferably morpholine, piperidine or mixtures thereof.
• a aqueous mixture comprising >1% morpholine, piperidine or mixtures thereof (by volume) , preferably >50% morpholine, piperidine or mixtures thereof,and most preferably at a ratio of from 80% morpholine, piperidine or mixtures thereof to 20% water to 90% morpholine, piperidine or mixtures thereof to 10% water.
• the swelling agent is an aqueous mixture of morpholine, piperidine or mixtures thereof comprising of from 60 to 99% (by volume) morpholine, piperidine or mixtures thereof, or of from 70 to 95% (by volume) of morpholine, piperidine or mixtures thereof.
• the liquid organic swelling agent is N-methyl morpholine N-oxide.
• N-methyl morpholine N-oxide is used at a concentration of higher than 50 %, preferably higher than 70 %, but less than 81 %, at temperatures of higher than 80 °C, preferably higher than 85°C.
• N-methyl morpholine N-oxide Most preferred conditions for N-methyl morpholine N-oxide (NMMO) are at a concentration of 78 % w/w and 85 °C. Above these conditions (82 % w/w and 85 °C) it behaves as a solvent for cellulosic material.
• suitable reaction conditions such as concentration of the swelling agent depends on the choice of swelling agent and its potential as a cellulose swelling agent.
• concentration of the swelling agent depends on the choice of swelling agent and its potential as a cellulose swelling agent.
• a swelling agent which is also a recognised cellulose solvent, it is necessary to use it at below its dissolution concentration and temperature (which are known in the art, see e.g. The Polymer Handbook 3 rd edition, 1989 (published by J Wiley & Sons, edited by J Brandrup & EH Immergut), more specifically within the section “Properties of Cellulose Materials", specifically in the section "Solvents for Cellulose”) such that it acts as a cellulose swelling agent, i.e. prior to the stage of full disruption of all intracrystalline bonding in the cellulosic material and its resultant dissolution.
• Solvation should be preferably avoided, as complete disruption of the intracrystalline bonding will lead to destruction of the crystalline structure that is required as the product from the swelling process as disclosed herein.
• the extent of swelling may be determined in various ways. In the context of the present invention, the extent of swelling has been found to be conveniently defined in terms of the apparent increase in the phase volume fraction of the cellulosic material in the system, relative to the phase volume fraction of the same cellulosic material suspended in water the cellulose being in a powdered form amenable to processing via the intended mechanical technique.
• the cellulosic material in powdered form (1.0 g) was weighed into a 20 ml glass scintillation vial and the liquid swelling agent of interest (9.0 ml) added by means of a micropipetting device. The system was then mixed via manual agitation and allowed to equilibrate for 24 hours at 20 °C. Alternatively, the extent of swelling may be determined following incubation at a temperature greater than ambient, as appropriate to the swelling agent of interest. In each case, an identical standard sample was also prepared using deionized water in place of the liquid swelling agent.
• the cellulosic material is expected to not enter into a true solution of molecularly dispersed chains - rather to absorb a proportion of the fluid of the continuous phase, facilitated via disruption of intermolecular and intramolecular hydrogen bonding.
• the apparent phase volume fraction of the resultant swollen cellulose particles (and the associated interstitial fluid) is then estimated visually/macroscopically by means of a ruler with 1mm graduations, with the heights of the upper (liquid supernatant, hupper) and lower (swollen cellulosic particles, liLower) phases being estimated to the nearest 0.01 mm.
• nanofibrillation of cellulosic materials via mechanical comminution processing means may be afforded in liquid media characterized by a swelling index, S, as defined above, of between 1 and 10, with a value between 1.5 and 3 being most preferred.
• S swelling index
• Swelling increases to reach a maximum in systems where the volume fraction of morpholine in the continuous medium is between 80% and 90%.
• an aqueous mixture of morpholine and piperidine may be used, where the volume fraction of morpholine in the continuous medium may be kept below or equal to 78%, or from 60 to 78%, while the remaining volume fraction is made up of water and piperidine, thereby combining a safety advantage with dramatic energy reduction.
• Exemplary swelling agents are aqueous mixtures of morpholine and piperidine comprising, preferably consisting of, from 60 to 78% (by volume) of morpholine, of 1 to 39 (by volume) of piperidine, and at least 1% water, and more preferably aqueous mixtures of morpholine and piperidine comprising, preferably consisting of, from 70 to 78% (by volume) of morpholine, of 1 to 29 (by volume) of piperidine, and at least 1% water.
• Mechanical comminution processing may be performed using conventional technologies known in the art, such as high shear forces, microfiuidization, (e.g. a M110-EH Microfluidizer Processor fitted with two chambers in series), high pressure homogenization (e.g. a NanoDeBee high pressure homogenizer (BEE International Inc), a ConCor high pressure/high shear homogenizer (Primary Dispersions Ltd)), controlled hydro-dynamic cavitation (eg. using an Arisdyne Systems controlled flow cavitation device) and high friction forces (e.g. a Super MassColloider colloid/friction mill (Masuko)), and combinations thereof.
• high shear forces e.g. a M110-EH Microfluidizer Processor fitted with two chambers in series
• high pressure homogenization e.g. a NanoDeBee high pressure homogenizer (BEE International Inc)
• ConCor high pressure/high shear homogenizer
• controlled hydro-dynamic cavitation
• Apparatus of the type classified as a high pressure or high shear homogenizer relies on the generation of high mechanical stresses within the fluid to achieve break down of the cellulosic feedstock into the desired nanocellulose. This is achieved by pumping the fluid formulation through a well-defined microfluidic interaction chamber - effectively a situation corresponding to a confined flow, as defined in the field of fluid dynamics.
• microfluidic in the context of the present invention, refers to a confined flow geometry or interaction chamber, where the width orthogonal to the direction of flow is less than 500 microns, preferably between 400 and 50 microns.
• Commonly encountered interaction chamber designs include abrupt contractions (either axisymmetic or rectangular slots), Z-geometries (abrupt inflections in the path of the flow) and Y-geometries (where the flow is split and recombined as impinging/opposing jets).
• geometries involving convergence of the streamlines/acceleration of the fluid are characterised by a high tensile or extensional component within the flow field - which makes a major contribution to the efficiency of mechanical fibrillation and dispersive mixing (but also further complicates defining a characteristic shear rate for the process).
• the term 'high shear' in the context of use of a high shear homogenizer within the scope of the present invention, is best clarified via an illustrative example of the shear rate in a 50 micron radius ( R) axisymmetric capillary (which may be considered as part of e.g.
• Shear rate ( ⁇ ) in capillary (Poiseuille) flow may be conveniently estimated via the following expression:
• the operating range of processing apparatus of the high shear homogenizer type is between 8.5 x 10 6 s "1 and 102 x 10 6 s “1 (defined as above) and 5000 psi to 60000 psi, most preferably between 34 x 10 6 s "1 and 72 x 10 6 s "1 (defined as above) and 20000 psi to 42500 psi.
• An alternative technology that could be employed would be a colloid or friction mills.
• This technology relies on the generation of high shear rates between two coaxially mounted cone-shaped members separated by a narrow gap (the term narrow, in the context of the present invention would be defined by a distance of less than 500 microns).
• one member is fixed (stator) and the other rotated at high speed (rotor).
• Sections of the rotor and stator may have increasingly fine serrations or grooves, which aid fibrillation of the cellulosic feedstock.
• typical rotortip speeds of up to 50 ms "1 are used.
• the apparent shear rate is conveniently estimated from the velocity gradient across the gap. In the above case, the apparent shear rate is therefore typically 1 x 10 6 s "1 .
• the degree of disruption of the intercrystalline and the intracrystalline structure of the cellulosic materials can be determined using X-Ray diffraction or 13 C NMR. It can be seen by these techniques that swelling agents that only affect the intercrystalline structure of the cellulosic materials retain all or most of their original, pre-swelling crystallinity. In the case of swelling agents that disrupt both intercrystalline and partially (but not fully) the intracrystalline bonding that the measured crystallinity of the cellulosic material will be reduced as a function of the extent of the degree of intracrystalline swelling induced by the agent used and by the processing conditions.
• the relative proportions of amorphous and crystalline material is readily ascertained by consideration of the double peak corresponding to the resonance of the carbon nucleus at C4 (chemical shift typically 80 - 93 ppm), which is split into two components as the amorphous (80 - 87 ppm) and crystalline (87 - 93 ppm) regions correspond to different chemical environments. Loss of crystallinity post-swelling is manifested as a significant reduction in the area of the downfield peak of the C4 resonance signal, relative to the area of the upfield component.
• the fraction of crystalline cellulose is most simply estimated by comparison of the relative intensity of the peak corresponding to diffraction from the 002 plane in the cellulose I unit cell (I 002 taken at a Bragg angle 2 ⁇ of ⁇ 22.7°) to the intensity (I AM ) measured at the trough between the 002 and 101 diffraction peaks (corresponding to diffraction from the less ordered amorphous regions).
• I AM intensity measured at the trough between the 002 and 101 diffraction peaks (corresponding to diffraction from the less ordered amorphous regions).
• More complex analyses based on a full peak deconvolution of the diffractogram are available in e.g. Park et al - 'Cellulose crystallinity index: measurement techniques and their impact on interpreting cellulase performance' (Biotechnology for Biofuels, 2010, 3, 10) and references cited therein.
• the native cellulose polymorph At high levels of intracrystalline swelling the native cellulose polymorph, cellulose I is partially or fully converted to another polymorph when the swelling agent is removed from the cellulosic material. This is commonly encountered where alkali metal hydroxides (e.g. potassium hydroxide, sodium hydroxide) in aqueous media are employed as swelling agents.
• alkali metal hydroxides e.g. potassium hydroxide, sodium hydroxide
• the native cellulose, present in the natively occurring cellulose I polymorph is regenerated into the more thermodynamically stable (for use in the present invention less preferred) cellulose II polymorph - a process commonly referred to as 'Mercerisation' in the field of textile fibre science.
• the cellulose I and cellulose II polymorphs are readily distinguished by their characteristically different wide angle x-ray diffraction patterns.
• Both cellulose I and cellulose II are characterised by a monoclinic crystal habit, but differ in the relative directional orientation of adjacent polymer chains and pattern of associated intra- and intermolecular hydrogen bonding - the chains in cellulose I being parallel, whilst those in cellulose II are antiparallel.
• Figure 2 (A) Quantification of the extent of swelling of microcrystalline cellulose (Avicel PH-101 ) in various water/morpholine mixtures (x-axis represents vol % morpholine in continuous medium (water); y-axis represents the swelling index S). (B): Image of samples used for generation of graph A, the numbers indicate % morpholine in water as the swelling agent. (C) Replicate quantification of the extent of swelling of microcrystalline cellulose (Avicel PH-101) in various water/morpholine mixtures (x-axis represents vol % morpholine in continuous medium (water); y-axis represents the swelling index S). (D): Image of samples used for generation of graph A, the numbers indicate % morpholine in water as the swelling agent
• Figure 3 (A) Quantification of the extent of swelling of microcrystalline cellulose (Avicel PH-101) in various water/piperidine mixtures (x-axis represents vol % piperidine in continuous medium (water); y-axis represents the swelling index S). (B): Image of samples used for generation of graph A, the numbers indicate % piperidine in water as the swelling agent
• the mechanical comminution processing has been performed here using a Ml 10-EH Microfluidizer Processor fitted with two chambers in series.
• the first chamber is the Auxiliary processing Module ( APM) and comprises a ceramic module with a 200 micron diameter channel and the second is called the Interaction chamber (IXC) and has a diamond channel with a 100 micron diameter channel.
• APM Auxiliary processing Module
• IXC Interaction chamber
• a range of channel geometries and channel sizes can be used with this equipment. The operational limits are not defined by this example.
• Example 1 Processing of microcrystalline cellulose in aqueous morpholine (organic swelling agent).
• Microcrystalline cellulose (Avicel PH-101, 5.0g) was added to morpholine:water (80:20 vol%, 500 ml) by gradual introduction into the vortex created by a rotorrstator mixer (UltraTurrax), mixing being continued for a further 10 minutes at room temperature.
• This slurry was then introduced into the feed hopper of a Ml 10-EH Microfluidizer (Microfluidics Corp) and recirculated for 8.5 minutes through two Z-shaped interaction chambers arranged in series [200 micron diameter (ceramic) followed by 100 micron diameter (diamond)], setting the operating pressure of the apparatus at 25000 psi.
• the resultant nanostructured cellulose was then separated from the swelling agent via centrifugation and the upper level of continuous phase removed via decantation.
• the system was then made up to its original volume by addition of an appropriate amount of deionized water and the system mixed thoroughly via manual agitation to afford re-suspension of the cellulose.
• Two more centrifugation, decantation, re- suspension operations were performed, prior to further purification of the system via dialysis against deionized water for 3 days (with frequent replacement of the dialysate).
• the cellulose was then isolated in solid form by means of freeze-drying. The morphology of the cellulose was conveniently characterized via scanning electron microscopy.
• a polyvinyl alcohol [PVOH] film was cast from a 10% aqueous solution on a glass microscope slide and allowed to dry under ambient conditions in a covered petri dish.
• a small aliquot of the dialysed cellulose suspension ( ⁇ 1 microlitre) was then dispensed onto the PVOH and spread into a thin layer with the micropipette tip, before being allowed to dry.
• a small square ( ⁇ 3mm x 3mm) of the PVOH was then cut from the polymer film and placed sample side down on an SEM stub covered with conducting tape. The PVOH layer was then removed via dissolution in hot deionized water and the exposed particles sputter coated with Au prior to imaging.
• Example 2 Processinfi of cellulose pulp in aqueous morpholine
• Cellulose pulp (92% a-cellulose, viscose/dissolving grade from Sappi Saiccor) was shredded in a standard office paper shredder (cross-cut configuration). The shredded pulp (5.0 g) was then suspended in morpholine: water (80:20 vol%, 500 ml) and allowed to swell for 2 hours. The swollen pulp suspension was then homogenized using a rotor-stator mixer (UltraTurrax) and processed, purified and dried as in Example 1. SEM analysis as above indicated that the pulp fibres has been extensively broken down into an entangled web of fibres of diameter ⁇ 30 nm. Under these conditions, the generation of such a nanocellulose product required approximately 1500kWh/t.
• Example 3 Processing of microcrystalline cellulose in aqueous calcium thiocyanate
• Microcrystalline cellulose (Avicel PH-101, 5.0g) was suspended in aqueous calcium thiocyanate solution (45 % by weight, 500 ml) at 50 °C (corresponding to conditions which afford swelling as disclosed hereinabove) and the system homogenized using a rotor stator mixer. The hot cellulose slurry was then transferred into the feed hopper of an M110-EH Microfluidizer and processed, purified and dried as in Example 1. SEM analysis as above indicated the mechanical breakdown of the microcrystalline cellulose in the presence of the swelling agent into separate needle-like particles of length 200-400 nm, although extensively aggregated.
• Example 4 Processing of cellulose pulp in aqueous calcium thiocyanate.
• Cellulose pulp (prepared as in Example 2, 5.0 g) was suspended in aqueous calcium thiocyanate solution (45% by weight, 500 ml) at 50 °C and allowed to swell for 1 hour. The pulp suspension was then homogenized by means of a rotor-stator mixer (UltraTurrax) for 10 minutes and the hot slurry introduced into the feed hopper of a M110-EH Microfluidiser (Microfluidics Corp). The cellulose slurry was then processed, purified and dried as in Example 1. SEM analysis indicated the mechanical breakdown of the pulp into extensively fibrillated and entangled structures of diameter ⁇ 100 nm.
• Example 5 Processing of microcrystalline cellulose in aqueous potassium hydroxide
• Microcrystalline cellulose (Avicel PH-101, 5.0g) was suspended in aqueous potassium hydroxide solution (27 % by weight, 500 ml) at 20 °C (corresponding to conditions which afford swelling as disclosed hereinabove) and the system homogenized using a rotor stator mixer. The hot cellulose slurry was then transferred into the feed hopper of an M110-EH Microfluidizer and processed, purified and dried as in Example 1. SEM analysis as above indicated the mechanical breakdown of the microcrystalline cellulose in the presence of the swelling agent into separate needle-like particles of length 200-400 nm, although extensively aggregated.
• Example 6 Processing of cellulose pulp in aqueous potassium hydroxide
• Cellulose pulp (prepared as in Example 2, 5.0 g) was suspended in aqueous potassium hydroxide solution (27% by weight, 500 ml) at 20 °C and allowed to swell for 30 minutes. The pulp suspension was then homogenized by means of a rotor-stator mixer (UltraTurrax) for 10 minutes and the slurry introduced into the feed hopper of an M110-EH Microfluidiser (Microfluidics Corp). The cellulose slurry was then processed, purified and dried as in Example 1. SEM analysis indicated the mechanical breakdown of the pulp into extensively fibrillated and entangled structures of diameter ⁇ 100 nm.
• Example 7 Processing of microcrystalline cellulose in aqueous N-methylmorpholine-N- oxide
• Microcrystalline cellulose (Avicel PH-101, 5.0g) was suspended in aqueous N- methylmorpholine-N-oxide [ MMO] solution (78 % by weight, 500 ml - prepared by mixing appropriate amounts of NMMO monohydrate and water) at 85 °C (corresponding to conditions which afford swelling as disclosed hereinabove) and the system homogenized using a rotor stator mixer (UltraTurrax).
• MMO N- methylmorpholine-N-oxide
• the cellulose slurry was then transferred into the feed hopper of an M110-EH Microfluidizer (Microfluidics Corp) and processed, purified and dried as in Example 1.
• SEM analysis as above indicated the mechanical breakdown of the microcrystalline cellulose in the presence of the swelling agent into separate needlelike particles of length 200-400 nm, width 20-50 nm, which had a loosely aggregated structure.
• Example 8 Processing of cellulose pulp in aqueous N-methylmorpholine-N-oxide
• Cellulose pulp (prepared as in Example 2, 5.0 g) was suspended in aqueous N- methylmorpholine-N-oxide solution (78% by weight, 500 ml - prepared by mixing appropriate amounts of NMMO monohydrate and deionized water) at 85 °C and allowed to swell for 1 hour.
• the pulp suspension was then homogenized by means of a rotor-stator mixer (UltraTurrax) for 10 minutes and the hot slurry introduced into the feed hopper of an M110-EH Microfluidiser (Microfluidics Corp).
• the cellulose slurry was then processed, purified and dried as in Example 1.
• Example 10 Processing of cellulose pulp in aqueous piperidine
• Cellulose pulp (92% a-cellulose, viscose/dissolving grade from Sappi Saiccor) was shredded in a standard office paper shredder (cross-cut configuration). The shredded pulp (5.0 g) was then suspended in piperidine:water (90:10 vol%, 500 ml) and allowed to swell for 30 minutes.
• the swollen fibre suspension was then homogenised using a rotor-stator mixer (UltraTurrax) at 4000 rpm for 10 minutes at room temperature and then further processed, purified and dried as described in Example 1.
• SEM analysis as above indicated that the fibres had been extensively broken down into an entangled web of fibres of diameter ⁇ 3-30nm. Under these conditions, the generation of a mixture of 80% nanocellulose product required approximately 1600kWh/t.

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