Process for the Production of a Nanocellulose Material

(19) TZZ¥Z__T

(11) EP 3 409 691 A1

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication: (51) Int Cl.: 05.12.2018 Bulletin 2018/49 C08B 1/00 (2006.01) C08B 15/02 (2006.01) D21C 9/00 (2006.01) D21H 11/18 (2006.01) (21) Application number: 17173805.7

(22) Date of filing: 31.05.2017

(84) Designated Contracting States: (72) Inventors: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB • ENGLISH, Robert GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO Isle of Harris, Eilean Siar HS5 3UE (GB) PL PT RO RS SE SI SK SM TR • HEATON, John Designated Extension States: 6211 SN Maastricht (NL) BA ME Designated Validation States: (74) Representative: Schmitz, Joseph MA MD Isler & Pedrazzini AG Giesshübelstrasse 45 (71) Applicant: SAPPI Biochemtech B.V. Postfach 1772 6211 AA Maatricht (NL) 8027 Zürich (CH)

(54) PROCESS FOR THE PRODUCTION OF A NANOCELLULOSE MATERIAL

(57) Aprocess forthe productionof anon-derivatized non-derivatized nanocellulose material from the swollen nanocellulose material from a cellulosic fibrous material, and optionally refined cellulosic fibrous material and such comprising the steps of providing a suspension of cellu- as to form a dispersion of non-derivatized nanocellulose losic fibrous material in a continuous phase of amaterial in a continuous phase of a processing solvent; non-aqueous process liquid comprising a swelling agent contacting the dispersion of non-derivatized nanocellu- and a processing solvent; allowing the cellulosic fibrous lose material in a continuous phase of a processing sol- material to swell such as to form a suspension of swollen vent with a supercritical fluid such as to remove the cellulosic fibrous material in a continuous phase of processing solvent and isolate the non-derivatized na- non-aqueous process liquid; optionally refining said sus- nocellulose material, wherein the supercritical fluid is pension of swollen cellulosic fibrous material in a contin- preferably supercritical carbon dioxide or ammonia; char- uous phase of non-aqueous process liquid to increase acterized in that the swelling agent is a low-transi- the fineness of the swollen cellulosic fibrous material; tion-temperature mixture (LTTM) and in particular a deep removing the swelling agent from the rocess liquid such eutectic solvent and said low-transition-temperature mix- as to form a suspension of cellulosic fibrous material in ture and in particular said deep eutectic solvent is soluble a continuous phase of processing solvent; subjecting the in the processing solvent and wherein the processing swollen and optionally refined cellulosic fibrous material solvent is non-solubilizing for the cellulosic fibrous ma- to high-shear comminution such as to release of the terial and the non-derivatized nanocellulose material. EP 3 409 691 A1

Printed by Jouve, 75001 PARIS (FR) 1 EP 3 409 691 A1 2

Description crofluidisation, the pre-treated wood cellulose is first washed with deionized water in order to remove the deep TECHNICAL FIELD eutectic solvent after the pre-treatment and only then is the thus obtained aqueous suspension of pre-treated [0001] The present invention relates to a process for 5 wood cellulose microfluidized. The thus obtained aque- the production of a nanocellulose material from a cellu- ous suspension of nanofibrillated cellulose (NFC) is then losic precursor material. freeze-dried to prepare samples for further analysis. The removal of water from the nanocellulose by freeze-drying PRIOR ART however yields nanocellulose that cannot easily be re- 10 dispersed and having inferior rheological properties. [0002] Cellulose is a material that is widely available [0006] It is thus desirable to provide a simplified proc- from renewable sources suchas plant material. Cellulose ess for the manufacture of nanocellulose in which the is present asa fiber inthe primarycell wall of greenplants, overall energy can be reduced preferably without resort- where it is usually found in a mixture with hemicellulose, ing to hazardous chemicals. lignin, pectin and other substances. The cellulose fiber 15 itself consists of crystalline and amorphous regions, and SUMMARY OF THE INVENTION the crystalline regions are known as cellulose nanofibers (CNF) and nanocrystalline cellulose (NCC), which can [0007] The present invention provides for a process in both be separated from the amorphous regions, and ex- which the energy consumption of the overall process for hibit mechanical properties that make them highly suita- 20 the production of a non-derivatized or derivatized nano- ble for reinforcing use in material applications and other cellulose material from a cellulosic fibrous material as applications where CNF or CNC gels are of use such as raw material can be reduced and in which the process in cosmetics, for example as gels. liquids used allow safer processing of the raw material [0003] However, the production of either cellulose na- and furthermore allows subsequent spray-drying with nofibers (CNF) or nanocrystalline cellulose (NCC) from 25 commonly used supercritical fluids without chemical re- cellulosic material such as wood pulp is technically de- action between the supercritical fluids and the liquid to manding and energy-intensive, which is why there is a be removed. The process yields a nanocellulose material constant desire in the field of producing either cellulose in the form of a solid such as for example solid particulate nanofibers (CNF) or nanocrystalline cellulose (NCC) in material that can easily be re-dispersed in aqueous so- both an uncomplicated and an energy-efficient manner 30 lutions to yield a homogenous dispersion of nanocellu- which does involve a minimum of hazardous chemicals. lose material, thereby forming for example a liquid or gel [0004] EP 2 712 364 proposes that the swelling of the and which disperion is nearly identical with a freshly (i.e. cellulosic precursor material in an aqueous solution of a never-dried) prepared nanocellulose dispersion in morpholine, piperidine or mixtures thereof can reduce terms of rheological properties. This can be achieved by the energy consumption by reducing the number of mi- 35 using a swelling agent that is a low-transition-tempera- crofluidisation steps required to release the nanocellu- ture mixture (LTTM) such as to form for example a deep lose material from the cellulosic precursor by relying on eutectic solvent which is soluble in a processing solvent the swelling agent property of aqueous morpholine and where the processing solvent is non-solubilizing for and/or piperidine. However, the obtained aqueous sus- both the cellulosic fibrous material that is used as raw pension of nanocellulose must be further processed in 40 material and the derivatized or non-derivatized nanocel- order to yield a re-dispersible nanocellulose powder, lulose material. which can be technically challenging. For instance, in the [0008] It is an object of the present invention to provide case where the nanocellulose obtained through said a process for the production of a non-derivatized or deri- process is to be dried using supercritical fluids, the mor- vatized nanocellulose material from a cellulosic fibrous pholine and piperidine must be removed beforehand be- 45 material, comprising the steps of: cause they tend to chemically react with the most commonly used supercritical fluids such as carbon dioxide a. providing a suspension of cellulosic fibrous mate- and must be replaced by another inert processing fluid. rial in a continuous phase of a non-aqueous process In addition, morpholine and piperidine are hazardous liquid comprising a swelling agent and a processing substances which must be handled with care and which 50 solvent; must be thoroughly removed from the nanocellulose ma- b. allowing the cellulosic fibrous material to swell terial before commercialization, especially for pharma- such as to form a suspension of swollen cellulosic ceutical or food applications of nanocellulose. fibrous material in a continuous phase of non-aque- [0005] In Green Chem., 2015, 17, 3401-3406, Sirviö ous process liquid; et al. describe a pre-treatment of wood cellulose with55 c. optionally refining said suspension of swollen cel- choline chloride/urea as swelling agent before microflu- lulosic fibrous material in a continuous phase of non- idisation to release the nanofibrillated cellulose (NFC) aqueous process liquid to increase the fineness of from the pre-treated wood cellulose. However, before mi- the swollen cellulosic fibrous material;

2 3 EP 3 409 691 A1 4

d. removing the swelling agent from the process liq- represent the re-dispersed nanocellulose spray uid such as to form a suspension of cellulosic fibrous dried from a suspension of nanocellulose in materialin acontinuous phase ofprocessing solvent; ethyl lactate according to the present invention e. subjecting the swollen and optionally refined cel- and the open symbols represent the re-dis- lulosic fibrous material to high-shear comminution 5 persed nanocellulose when spray dried from an such as to release of the non-derivatized nanocellu- aqueous suspension of nanoncellulose. lose material from the swollen and optionally refined cellulosic fibrous material and such as to form a dis- DESCRIPTION OF PREFERRED EMBODIMENTS persion of non-derivatized nanocellulose material in a continuous phase of a processing solvent; 10 [0012] In the context of the present application, the f. contacting the dispersion of non-derivatized nano- term "low transition temperature mixture" or "LTTM" re- cellulose material in a continuous phase of a fers to a liquid mixture of at least one hydrogen bond processing solvent with a supercritical fluid such as donor (HBD) and one hydrogen bond acceptor (HBA) to remove the processing solvent and isolate the counterpart that results in the formation of liquid mixture non-derivatized nanocellulose material, wherein the 15 showing an unusually low freezing/melting point or glass supercritical fluid is preferably supercritical carbon transition point. dioxide or ammonia; [0013] In the context of the present application, the term "deep eutectic solvents" or "DES" refers in particular characterized in that the swelling agent is a low-transi- to liquid mixtures of quaternary ammonium salts such as tion-temperature mixture (LTTM) and in particular a deep 20 for example quaternary ammonium halide salts or gua- eutectic solvent and said low-transition-temperature mix- nidinium salts such as for example guanidinium halide ture and in particular said deep eutectic solvent is soluble salts, as hydrogen bond acceptor (HBA) in combination in the processing solvent and wherein the processing with one or more hydrogen bond donors (HBD) such as solvent is non-solubilizing for the cellulosic fibrous ma- for example urea showing an unusually low freez- terial and the non-derivatized nanocellulose material. 25 ing/melting point. [0009] It is another object of the present invention to [0014] Exemplary hydrogen bond acceptors (HBA) are provide the use of a non-aqueous process liquid com- quaternary ammonium salts which are suitable for the prising a swelling agent and a processing solvent in a formation of a deep eutectic solvent in combination with process for the production of a derivatized or non-deri- one or more hydrogen bond donors (HBD). Suitable qua- vatized nanocellulose material according to the above, 30 ternary ammonium salts are in particular quaternary am- characterized in that the swelling agent is a low-transi- monium halide salts such as choline chloride, (2-hydrox- tion-temperature mixture (LTTM) and in particular a deep yethyl)dimethylethylammonium chloride, trimethylgly- eutectic solvent and said low-transition-temperature mix- cine and 2-(chlorocarbonyloxy)-N,N,N-trimethylethan- ture (LTTM) and in particular said deep eutectic solvent aminium chloride or N-benzyl-2-hydroxy-N,N-dimethyl- is soluble in the processing solvent and wherein the35 ethanaminium chloride. processing solvent is non-solubilizing for the cellulosic [0015] Suitable hydrogen bond donors (HBD) that may fibrous material and the non-derivatized nanocellulose be used for the formation of a deep eutectic solvent with material. quaternary ammonium halide salts are urea and deriva- [0010] It is yet another object of the present invention tives thereof such as 1-methyl urea, 1,3-dimethyl urea or to provide a derivatized or non-derivatized nanocellulose 40 1,1-dimethyl urea; thiourea and derivatives thereof, material obtained by a process according the above, hav- amides such as benzamide or acetamide and derivatives ing an aspect ratio of at least 100 and wherein the deri- thereof;polyols suchas glycerol, ethylene glycerol orpro- vatized or non-derivatized nanocellulose material is pref- pylene glycol, benzoic acid and derivatives thereof, di- erably in the form of a solid such as for example solid carboxylic acids such as malonic acid, adipic acid, oxalic particulate material like a powder. 45 acid, succininc acid or citric acid, α-hydroxy carboxylic acid alkyl esters and derivatives thereof such as ethyl BRIEF DESCRIPTION OF THE DRAWINGS lactate. [0016] In the context of the present invention, low tran- [0011] Preferred embodiments of the invention are de- sition temperature mixtures and deep eutectic solvents scribed in the following with reference to the drawings, 50 which are liquids at room temperature, i.e. which have a which are for the purpose of illustrating the present pre- freezing/melting points below 25°C, are preferred for rea- ferred embodiments of the invention and not for the pur- sons of energy consumption of the process, since no pose of limiting the same. In the drawings, energy is needed in this case to melt and keep the low transition temperature mixtures and deep eutectic sol- Fig. 1 shows a graph in which the shear stress is55 vents in a liquid state. It is however possible to use low shown in dependency of the shear rate for two transition temperature mixtures and deep eutectic sol- samples of re-dispersed nanocellulose at con- vents having a freezing/melting points of between 25°C sistency of 1% by weight. The filled symbols and 95°C, and preferably between 25°C and 50°C.

3 5 EP 3 409 691 A1 6

It is an object of the present invention to provide a process efficiently and preferably as a closed circuit with respect for the production of a non-derivatized or derivatized na- to swelling agent and processing solvent. Because in the nocellulose material from a cellulosic fibrous material, present invention, the processing solvent is chosen such comprising the steps of: as to not chemically react with the supercritical fluid such 5 as carbon dioxide and ammonia, the mixture of process- a. providing a suspension of cellulosic fibrous mate- ing solvent and supercritical fluid that is removed can be rial in a continuous phase of a non-aqueous process easily separated by returning the mixture to a pressure liquid comprising a swelling agent and a processing and temperature at which the supercritical fluid returns solvent; to a gas state, thereby boiling off, and at which the b. allowing the cellulosic fibrous material to swell 10 processing solvent returns to a liquid state. Thus, also such as to form a suspension of swollen cellulosic the fluid in a gas state can be used, i.e. recycled, to pro- fibrous material in a continuous phase of non-aque- vide the supercritical fluid in step f. ous process liquid; [0020] In a preferred embodiment of the process ac- c. optionally refining said suspension of swollen cel- cording to the present invention, the low-transition-tem- lulosic fibrous material in a continuous phase of non- 15 perature mixture (LTTM) and in particular the deep eu- aqueous process liquid to increase the fineness of tectic solvent is a binary low-transition-temperature mix- the swollen cellulosic fibrous material; ture (LTTM) and in particular a binary deep eutectic sol- d. removing the swelling agent from the process liq- vent, and preferably is a binary deep eutectic solvent of uid such as to form a suspension of cellulosic fibrous a quaternary ammonium salt with a hydrogen bond do- materialin acontinuous phase ofprocessing solvent; 20 nor, more preferably of a quaternary ammonium halide e. subjecting the swollen and optionally refined cel- salt such as a choline halide with a hydrogen bond donor lulosic fibrous material to high-shear comminution chosen from urea or ethanolamine. such as to release of the non-derivatized nanocellu- [0021] In a more preferred embodiment of the process lose material from the swollen and optionally refined according to the present invention, the swelling agent is cellulosic fibrous material and such as to form a dis- 25 a binary deep eutectic solvent of choline chloride and persion of non-derivatized nanocellulose material in urea or choline chloride and ethanolamine, wherein the a continuous phase of a processing solvent; choline chloride and urea or ethanolamine are present f. contacting the dispersion of non-derivatized nano- in a molar ratio of 1:2. cellulose material in a continuous phase of a [0022] In a preferred embodiment of the process ac- processing solvent with a supercritical fluid such as 30 cording to the present invention, the swelling agent is a to remove the processing solvent and isolate the ternary deep eutectic solvent, and preferably is a ternary non-derivatized nanocellulose material, wherein the deep eutectic solvent of a quaternary ammonium salt supercritical fluid is preferably supercritical carbon such as choline halide with a binary hydrogen bond donor dioxide or ammonia; chosen from glycerol/DBN or glycerol/DBU in a molar 35 ratio of 1:2:6 characterized in that the swelling agent is a low-transi- [0023] In a preferred embodiment of the process action-temperature mixture (LTTM) and in particular a deep cording to the present invention, the cellulosic fibrous eutectic solvent and said low-transition-temperature mix- material has a cellulose content of at least 90% by weight ture and in particular said deep eutectic solvent is soluble or is bleached chemical pulp preferably having a lignin in the processing solvent and wherein the processing 40 content of less than 5% by weight and preferably has a solvent is non-solubilizing for the cellulosic fibrous ma- lignin content of less than 1% by weight. terial and the non-derivatized nanocellulose material. [0024] In a preferred embodiment the nanocellulose [0017] In a preferred embodiment of the process ac- material obtained from the process according to the cording to the present invention, the swelling agent represent invention may be in solid particulate form. This moved from the process liquid in step d. is used, i.e. re- 45 allows for simpler storage and dosing of the nanocellu- cycled, to form the non-aqueous process liquid suspen- lose material. sion of cellulosic fibrous material in step a.. [0025] In a preferred embodiment, the process accord- [0018] In a preferred embodiment of the process ac- ing to the present invention yields a non-derivatized na- cording to the present invention, the processing solvent nocellulose material from a cellulosic fibrous material or removed in step f. is used, i.e. recycled, to form the non- 50 a derivatized nanocellulose material, depending on the aqueous process liquid suspension of cellulosic fibrous chemical nature of the swelling agent and/or the process- material in step a.. ing solvent. It is however preferred that the chemical na- [0019] In a more preferred embodiment of the process ture of the swelling agent and/or the processing solvent according to the present invention, the swelling agent are such as to yield a non-derivatized nanocellulose ma- removed in step d. and the processing solvent removed 55 terial. in step f. are used, i.e. recycled, to form the non-aqueous [0026] In a preferred embodiment of the process ac- process liquid suspension of cellulosic fibrous material cording to the present invention, the non-aqueous proc- in step a.. This way, the process can be carried out more ess liquid comprises of, or consists of, from 50 to 95

4 7 EP 3 409 691 A1 8 weight percent, preferably of from 75 to 95 weight percent sample to a reference sample. As the cellulose material of swelling agent and/or from 5 to 50 weight percent, swells, the volume of the cellulose increases and the preferably of from 5 to 25 weight percent of processing height of the swollen cellulose in a vial after gravitational solvent, based on the weight of the non-aqueous process setting increases and can be compared to a reference liquid. By including 50 or more weight percent of swelling 5 sample. One such example may be found in the specifi- agent in the non-aqueous process liquid, the swelling of cation of EP 2 712 364 where a swelling index is com- the cellulosic fibrous material can be increased whereas puted. In a preferred embodiment of the process accord- the addition of the processing solvent helps to reduce ing to the present invention, the suspension of cellulosic the viscosity of the non-aqueous process liquid which fibrous material in non-aqueous process liquid compris- allows for better refining in the ensuing refining step.10 ing a swelling agent and a processing solvent can be Therefore, in a preferred embodiment of the process ac- agitated in order to reduce the time needed to achieve a cording to the present invention, the processing solvent certain degree of swelling. For instance, such agitation has a viscosity at 25°C that is inferior to the viscosity of may be achieved in a hydropulper. the swelling agent and wherein preferably the processing [0031] In the process according to the present inven- solvent has a viscosity of less than 500 mPa s at 25°C. 15 tion, suspension of swollen cellulosic fibrous material in [0027] In a preferred embodiment of the process ac- a continuous phase of non-aqueous process liquid can cording to the present invention, the cellulosic fibrous optionally be refined to increase the fineness of the swol- material is allowed to swell in the non-aqueous process len cellulosic fibrous material. Increasing the fineness of liquid for no more than four hours at 50°C. the swollen cellulosic fibrous material ensures a more [0028] In the process according to the present inven- 20 robust operation of the microfluidizer in the ensuing proc- tion, a suspension of cellulosic fibrous material is provid- ess step, since in some cases the particle size of the ed in a continuous phase of a non-aqueous process liquid swollen cellulosic fibrous is such that the processing comprising a swelling agent and a processing solvent. module of the microfluidizer may become clogged after The swelling agent and a processing solvent are prefer- a certain time. In addition, most refiners such as disc ably freely miscible and the non-aqueous process liquid 25 refiners are optimized for accepting cellulose material forms a continuous phase of liquid in which the solid cel- having a particles size that is similar to the particle size lulosic fibrous material is suspended. The suspension of of the swollen cellulosic fibrous material and thus, the cellulosic fibrous material can be provided by for example increase in fineness of the swollen cellulosic fibrous ma- combining either the swelling agent, the processing sol- terial is particularly energy efficient. Suitable refiners are vent or the non-aqueous process liquid with the cellulosic 30 for example refiners having disk-shaped, cylindrical or fibrous material in a vessel. The cellulosic fibrous mate- conical refiner elements. rial may for example be bleached hardwood sulphite pulp [0032] In the process according to the present inven- in sheet form which is first pulverized in a knife mill to a tion, theswelling agent from theprocess liquid is removed particle size of less than 1 mm and then inserted together such as to form a suspension of cellulosic fibrous material with the non-aqueous process liquid in a heated hydro- 35 ina continuous phaseof processingsolvent. The removal pulper in which the suspension of cellulosic fibrous ma- of the swelling agent from the process liquid is removed terial in a continuous phase of a non-aqueous process before further processing of the cellulosic fibrous material liquid is formed through agitation. can preferably be achieved by washing the suspension [0029] In a preferred embodiment of the process ac- of swollen cellulosic fibrous material in a continuous cording to the present invention, the suspension of cel- 40 phaseof non-aqueous process liquidwith processing sol- lulosic fibrous material in a continuous phase of a non- vent until the swelling agent is removed and a suspension aqueous process liquid comprises of from 1 weight per- of cellulosic fibrous material in a continuous phase of cent of cellulosic fibrous material to 6 weight percent of processingsolvent is formed. The processing solvent can cellulosic fibrous material and/or the suspension of swol- wash away the swelling agent because the swelling len cellulosic fibrous material in a continuous phase of a 45 agent is chosen such as to be miscible with the swelling process solvent comprises of from 1 weight percent of agent. It is understood that the processing solvent is cellulosic fibrous material to 4 weight percent of cellulosic processing solvent essentially free of water, i.e. a dry fibrous material and preferably comprises of from 0.1 processing solvent, as water would be detrimental to ob- weight percent of cellulosic fibrous material to 2 weight taining an easily re-dispersable nanocellulose material. percent of cellulosic fibrous material. 50 [0033] In a preferred embodiment of the process ac- [0030] In the process according to the present inven- cording to the present invention, the processing solvent tion,the cellulosic fibrousmaterial isallowed to swell such is chosen from esters of a hydroxyalkanaoic acids and as to form a suspension of swollen cellulosic fibrous ma- from lower mono- or polyhydric alcohols such as propyl- terial in a continuous phase of non-aqueous process liq- ene glycol. In the case where the processing solvent is uid. The time required to achieve a certain degree of55 chosen from esters of a hydroxyalkanaoic acids, it is pref- swelling may vary depending on the swelling agent. The erably chosen from esters of α-hydroxycarboxylic acids amount of swelling may be monitored by for example by such as for example esters of lactic acid. An example of visual inspection of a sample in vial and comparing the an ester of lactic acid is ethyl lactate, preferably food-

5 9 EP 3 409 691 A1 10 grade or pharmaceutically acceptable ethyl lactate. [0039] It is yet another object of the present invention [0034] In the process according to the present inven- to provide a derivatized or non-derivatized nanocellulose tion, the swollen and optionally refined cellulosic fibrous material obtained by a process according the above, hav- material is subjected to high-shear comminution such as ing an aspect ratio of at least 100 and wherein the non- to release of the non-derivatized or derivatized nanocel- 5 derivatized nanocellulose material is preferably in the lulose material from the swollen and optionally refined form of a powder. cellulosic fibrous material and such as to form a dispersion of non-derivatized or derivatized nanocellulose ma- EXAMPLES terial in a continuous phase of a processing solvent. A suitable apparatus for subjecting the swollen and option- 10 [0040] 12.9 kg of urea and 15.1 kg of choline chloride ally refined cellulosic fibrous material to high-shear com- were mixed in a rotary drum blender and then transferred minution can be a microfluidizer such as Microfluidizer to a vessel equipped with a heating jacket and a mixing Processor M-110-EH equipped with a 200 mm ceramic impeller. The mixture of urea and choline was then stirred processor module arranged in series with a 100 mm dia- at 20 rpm and heated to a temperature of 70 °C, during mond interaction chamber and operating at 25 000 psi, 15 which a single liquid swelling agent was obtained. To available from the Idex Corp. this, 7.0 kg of ethyl lactate as processing liquid were add- [0035] In the process according to the present inven- ed gradually while continuously stirring. tion, the dispersion of non-derivatized nanocellulose ma- [0041] To the thus obtained non-aqueous processing terial in a continuous phase of a processing solvent is liquid, 750 g bleached hardwood sulphite dissolving pulp contacted with a supercritical fluid such as to remove the 20 was added and the mixture was transferred into a hydro- processing solvent and isolate the non-derivatized na- pulper operating at 50 °C where the mixture of cellulose nocellulose material, wherein the supercritical fluid is materialand non-aqueous processing liquid was agitated preferably supercritical carbon dioxide or ammonia. As for 4 hours in order to swell the cellulose material. an example, the dispersion of non-derivatized nanocel- [0042] The resultant suspension of swollen cellulose lulose material in a continuous phase of a processing 25 material in non-aqueous processing liquid was then solvent is contacted with a supercritical fluid such as to transferred into the holding vessel of a laboratory disc remove the processing solvent by spray-drying the dis- refiner and recirculated continuously. The calculated cu- persion of non-derivatized nanocellulose material in a mulative refining energy was equivalent to 800 continuous phase of a processing solvent with supercrit- kWh/tonne of cellulose and the processing gap was 100 ical carbon dioxide or ammonia in suitable spray-drying 30 microns. apparatus. The processing solvent is chosen such that [0043] To an aliquot of the resultant swollen and re- the processing solvent it is not only miscible with the fined swollen cellulose material (500 g) was added ethyl swelling agent but it is also miscible with the supercritical lactate (250 g), with stirring until visually homogeneous. fluid, and in particular with supercritical carbon dioxide This mixture was then filtered under reduced pressure in or supercritical ammonia. 35 a large sintered filter funnel (diameter 300 mm), before [0036] In a preferred embodiment of the process ac- washing the filter cake carefully with further aliquots of cording to the present invention the dispersion of deriva- ethyl lactate (5 x 250g). tized or non-derivatized nanocellulose material in a con- [0044] A sample of the above filter cake was resus- tinuous phase of a processing solvent is contacted with pended in the processing solvent ethyl lactate (1000 g) a supercritical fluid to remove the processing solvent in 40 using a laboratory rotor-stator mixer to give a final cellu- a spray drying apparatus. lose solids content of 1% by weight. This suspension of [0037] In a preferred embodiment of the process ac- cellulose material in processing solvent was then passed cording to the present invention the derivatized or non- twice at 10000 psi through a M-110-EH Microfluidizer derivatized nanocellulose material is cellulose nanofiber Processor (Idex Corp) fitted with a 200 micron ceramic (CNF). 45 auxillary processing module. The sample was then given [0038] It is another object of the present invention to a further 3 passes through the 200 micron ceramic aux- provide a use of a non-aqueous process liquid compris- illary processing module arranged in series with a 100 inga swellingagent and a processing solvent ina process micron diamond interaction chamber at 25000 psi. for the production of a derivatized or non-derivatized na- [0045] The resultant suspension of nanocellulose in nocellulose material according to the above, character- 50 ethyl lactate was dried in a benchtop spray drying appa- ized in that the swelling agent is a low-transition-temper- ratus (Feyecon Development and Implimentation BV) us- ature mixture (LTTM) and in particular a deep eutectic ing supercritical carbon dioxide. The nanocellulose sus- solvent and said low-transition-temperature mixture pension and pressurized carbon dioxide were metered (LTTM) and in particular said deep eutectic solvent is separately into a chamber, prior to being conveyed soluble in the processing solvent and wherein the55 through a capillary into an enclosed chamber, where the processing solvent is non-solubilizing for the cellulosic solid nanocellulose was collected. fibrous material and the non-derivatized nanocellulose The nanocellulose used as comparative was prepared material. by first treating bleached softwood pulp in a mixture of

6 11 EP 3 409 691 A1 12 urea/choline chloride (2:1 mol), washing with water and such as to form a dispersion of non-derivatized re-suspending in water, high shear processing as above nanocellulose material in a continuous phase of and finally also spray drying directly from the water sus- a processing solvent; pension. f. contacting the dispersion of non-derivatized [0046] The respectively obtained nanocellulose pow- 5 nanocellulose material in a continuous phase of ders were re-dispersed into de-ionized water at a con- a processing solvent with a supercritical fluid sistency of 1% by weight by mixing with a laboratory rotor- such as to remove the processing solvent and stator (Ultra Turrax IKA) for 15 mins at 12000 rpm. Vis- isolate the non-derivatized nanocellulose mate- cometric data were collected using a TA Instruments AR- rial, wherein the supercritical fluid is preferably G2 rotational rheometer, fitted with a serrated concentric 10 supercritical carbon dioxide or ammonia; cylinder measuring geometry. A decelerating stress ramp experiment was performed. characterized in that the swelling agent is a low- [0047] The nanocellulose of the present invention was transition-temperature mixture (LTTM) and in partic- seen to produce a homogeneous structured gel on re- ular a deep eutectic solvent and said low-transition- dispersion, whilst the nanocellulose obtained from spray 15 temperature mixture and in particular said deep eu- drying the aqueous suspension was a mobile, low vis- tectic solvent is soluble in the processing solvent and cosity fluid which exhibited phase separation on stand- wherein the processing solvent is non-solubilizing ing. for the cellulosic fibrous material and the non-deri- [0048] As can be seen from the viscometric data pre- vatized nanocellulose material. sented in Fig. 1, the nanocellulose of the present inven- 20 tion (filled symbols) displays enhanced low shear viscos- 2. The process according to claim 1, wherein the sus- ity and apparent yield stress when compared to the na- pension of cellulosic fibrous material in a continuous nocellulose obtained from spray drying the aqueous sus- phase of a non-aqueous process liquid comprises pension (open symbols). of from 1 weight percent of cellulosic fibrous material 25 to 6 weight percent of cellulosic fibrous material LIST OF REFERENCE SIGNS and/or wherein the suspension of cellulosic fibrous material in a continuous phase of a process solvent [0049] none comprises of from 0.1 weight percent of cellulosic fibrous material to 4 weight percent of cellulosic fi- 30 brous material and preferably of from 0.1 weight per- Claims cent of cellulosic fibrous material to 2 weight percent of cellulosic fibrous material. 1. A process for the production of a non-derivatized nanocellulose material from a cellulosic fibrous mate- 3. The process according to claim 1 or 2, wherein the rial, comprising the steps of: 35 non-aqueous process liquid comprises of from 50 to 95 weight percent, preferably of from 75 to 95 weight a. providing a suspension of cellulosic fibrous percent of swelling agent and/or from 5 to 50 weight materialin a continuousphase of a non-aqueous percent, preferably of from 5 to 25 weight percent of process liquid comprising a swelling agent and processing solvent, based on the weight of the non- a processing solvent; 40 aqueous process liquid. b. allowing the cellulosic fibrous material to swell such as to form a suspension of swollen cellu- 4. The process according to any preceding claim, losic fibrous material in a continuous phase of wherein the non-derivatized nanocellulose material non-aqueous process liquid; has an aspect ratio of at least 100. c. optionally refining said suspension of swollen 45 cellulosic fibrous material in a continuous phase 5. The process according to any preceding claim, of non-aqueous process liquid to increase the wherein the cellulosic fibrous material is allowed to fineness of the swollen cellulosic fibrous mate- swell in the non-aqueous process liquid for no more rial; than four hours. d. removing the swelling agent from the process 50 liquid such as to form a suspension of cellulosic 6. The process according to any preceding claim, fibrous material in a continuous phase of wherein the processing solvent has a viscosity at processing solvent; 25°C that is inferior to the viscosity of the swelling e. subjecting the swollen and optionally refined agent and wherein preferably the processing solvent cellulosic fibrous material to high-shear commi- 55 has a viscosity of less than 500 mPa s at 25°C. nution such as to release of the non-derivatized nanocellulose material from the swollen and op- 7. The process according to any preceding claim, tionally refined cellulosic fibrous material and wherein the low-transition-temperature mixture

7 13 EP 3 409 691 A1 14

(LTTM) and in particular the deep eutectic solvent is ical fluid to remove the processing solvent in a spray a binary low-transition-temperature mixture (LTTM) drying apparatus. and in particular a binary deep eutectic solvent, and preferably is a binary deep eutectic solvent of a qua- 15. The use of non-aqueous process liquid comprising ternary ammonium salt with a hydrogen bond donor, 5 a swelling agent and a processing solvent in a proc- more preferably of a quaternary ammonium halide ess for the production of a non-derivatized nanocel- salt such as a choline halide with a hydrogen bond lulose material according to any of the preceding donor chosen from urea or ethanolamine. claims, characterized in that the swelling agent is a low-transition-temperature mixture (LTTM) and in 8. The process for the production of a non-derivatized 10 particular a deep eutectic solvent and said low-tran- nanocellulose material according to any of the pre- sition-temperature mixture (LTTM) and in particular ceding claims, wherein the swelling agent is a binary said deep eutectic solvent is soluble in the process- deep eutectic solvent of choline chloride and urea or ing solvent and wherein the processing solvent is choline chloride and ethanolamine, wherein the non-solubilizing for the cellulosic fibrous material choline chloride and urea or ethanolamine are15 and the non-derivatized nanocellulose material. present in a molar ratio of 1:2. 16. A non-derivatized nanocellulose material obtained 9. The process for the production of a non-derivatized by a process according to any of claims 1 to 14, hav- nanocellulose material according to any of the pre- ing an aspect ratio of at least 100 and wherein the ceding claims, wherein the swelling agent is a ternary 20 non-derivatized nanocellulose material is preferably deep eutectic solvent, and preferably is a ternary in the form of a powder. deep eutecticsolvent ofa quaternaryammonium salt such as choline halide with a binary hydrogen bond donor chosen from glycerol/DBN or glycerol/DBU in a molar ratio of 1:2:6. 25

10. The process for the production of a non-derivatized nanocellulose material according to any of the preceding claims, wherein the high-shear comminution imparts a shear of at least 8 x 10 6 s-1, preferably of 30 from 34 x 106 to 62 x 106 s-1.

11. The process for the production of a non-derivatized nanocellulose material according to any of the preceding claims, wherein the cellulosic fibrous material 35 has a cellulose content of at least 90% by weight or is bleached wood pulp and preferably has a lignin content of less than 5% weight and preferably has a lignin content of less than 1% by weight. 40 12. The process for the production of a non-derivatized nanocellulose material according to any of the preceding claims, wherein the processing solvent is an ester of a hydroxyalkanaoic acid and an preferably an ester of a α-hydroxy carboxylic acid such as for 45 example ethyl lactate or is a lower mono- or polyhydric alcohol such as propylene glycol.

13. The process for the production of a non-derivatized nanocellulose material according to any of the pre- 50 ceding claims, wherein the non-derivatized nanocellulose material is cellulose nanofiber (CNF).

14. The process for the production of a non-derivatized nanocellulose material according to any of the pre- 55 ceding claims, wherein the dispersion of non-derivatized nanocellulose material in a continuous phase of a processing solvent is contacted with a supercrit-

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• EP 2712364 A [0004] [0030]

Non-patent literature cited in the description

• Green Chem., 2015, vol. 17, 3401-3406 [0005]