SE1951496A1 - Foam granulation method - Google Patents

Abstract

The present disclosure relates to a foam granulation method comprising:a) preparing an aqueous mixture comprising nanocellulose and a foaming agent,b) foaming said mixture to obtain a foam,c) adding solid particles to said foam,d) mixing and drying said foam with added particles to obtain a granulate comprising the solid particles.

Description

FOA|\/I GRANULATION I\/IETHOD Technical fieldThe present disclosure relates to methods for granulation of powdery or solidsubstances into larger granules.

BackgroundGranulation is the process of forming grains or granules from a powdery or solid substance, producing a granular material. lt is applied in several technologicalprocesses in the chemical and pharmaceutical industries. Typically, granulationinvolves agglomeration or coating of fine particles to form larger granules, typically of size range between 0.2 and 4.0 mm depending on their subsequent use.

Granulation is carried out for various reasons, one of which is to prevent thesegregation of the constituents of a powder mix. Segregation is due to differencesin the size or density of the components of the mix. Normally, the smaller and/ordenser particles tend to concentrate at the base of the container with the largerand/or less dense ones on the top. An ideal granulation will contain all theconstituents of the mix in the correct proportion in each granule and segregation ofgranules will not occur. Furthermore, many powders, because of their small size,irregular shape or surface characteristics, are cohesive and do not flow well.Granules produced from such a cohesive system will be larger and moreisodiametric, both factors contributing to improved flow properties.

There are two main types of granulation: dry granulation and wet granulation. Themain difference between dry and wet granulation is that dry granulation is theformation of granules without using any liquid solution whereas wet granulation is the formation of granules by adding a granulation liquid. ln wet granulation, granules are typically formed by the addition of a granulationliquid onto a powder bed which is under the influence of an impeller (in a high-shear granulator), screws (in a twin screw granulator) or air (in a fluidized bed granulator). The agitation resulting in the system along with the wetting of the 2 components within the formulation results in the aggregation or coating of theprimary powder particles to produce wet granules. The granulation liquid containsa liquid carrier which must be volatile so that it can be removed by drying. Theliquid carrier can be either aqueous based or solvent-based. Aqueous solutions have the advantage of being safer to deal with than other solvents.

Drying of the granules drives off the liquid but a network of solid bridges andpolymeric chains give strength and cohesion to the new granules. Drying andgranulating particles is sometimes very difficult since it might lead to uncontrolledagglomeration and formation of lumps. Also, spray drying for example is verysensitive to clogging issues and requires low solids and low viscosity.

These problems may be even more relevant when adding functional additivessuch as a rheology modifier, reinforcement agent or binder. Drying and granulationof such materials might lead to loss of the performance of the additives or to the formation of very large agglomerates.Accordingly, there is a need for improved solutions to solve the problems derivedfrom the granulation of materials comprising additives such as a rheology modifier, reinforcement agent or binder.

Description of the invention lt is an object of the present disclosure to provide a granulation method forgranulating particles with functional additives such as a rheology modifier, reinforcement agent or binder. lt is another object of the present disclosure to provide a granulation method forgranulating particles with nanocellulose, which is cost efficient and requires less water than a conventional wet granulation method. lt is another object of the present disclosure to provide a granulation method forgranulating particles with nanocellulose, which enables fast re-dispersion of the granulates formed. 3 The above-mentioned objects, as well as other objects realized by the skilledperson in the light of the present disclosure, are achieved by the various aspectsof the present disclosure.

Foam granulation refers to a type of wet granulation, in which the granulation liquidis an aqueous foam. The liquid foam is obtained by foaming an aqueousgranulation liquid comprising a foaming agent, e.g. a surfactant, and optionallyother additives. Foam granulation typically requires less water than conventionalwet granulation. However, foam behavior is complex and additives to the foamliquid may affect foam formation and stability in ways that are difficult to predict.

The present inventors have surprisingly found that the use of a foam granulationtechnique solves the problems of uncontrolled agglomeration and formation oflumps when drying and granulating particles, especially in the presence of reinforcement agents or binders such as nanocellulose.

According to a first aspect illustrated herein, there is provided a foam granulationmethod comprising: a) preparing an aqueous mixture comprising nanocellulose and a foaming agent, b) foaming said mixture to obtain a foam, c) adding solid particles to said foam, d) mixing and drying said foam with added particles to obtain a granulatecomprising the solid particles.

The term ”foam granulation” as used herein refers to a type of wet granulation, inwhich the granulation liquid is in the form of an aqueous foam. The inventivemethod thus involves first preparing an aqueous foam comprising a mixture ofnanocellulose and a foaming agent, followed by adding solid particles in saidfoam. The foam with added solid particles is then subjected to mixing and drying to obtain a granulate comprising the solid particles.

The term foam, as used herein, refers to a Substance made by trapping air or gasbubbles inside a solid or liquid. Typically, the volume of gas is much larger thanthat of the liquid or solid, with thin films separating gas pockets. Threerequirements must be met in order for foam to form. l\/lechanical work is needed toincrease the surface area. This can occur by agitation, dispersing a large volumeof gas into a liquid, or injecting a gas into a liquid. The second requirement is thata foam forming agent, typically an amphiphilic substance, a surfactant or surfaceactive component, must be present to decrease surface tension. Finally, the foammust form more quickly than it breaks down.

The term solid, as used herein, refers to a material that is not liquid or fluid, butfirm and stable in shape. A solid is a sample of matter that retains its shape anddensity when not confined. The solid may be rigid, or susceptible to plastic and/orelastic deformation. The adjective solid describes the state, or condition, of matterhaving this property. A solid material may be porous or non-porous. Accordingly, the term solid particles refers to porous or non-porous particles in solid form.

Nanocellulose can be effectively dispersed in the liquid phase of the foam and hasbeen found to bind to the solid particles, for example by adsorption or absorption,upon drying of the foam with added solid particles to obtain a granulate. ln some embodiments, the nanocellulose comprises cellulosic nanofibers havingan average diameter in the range of 1 - 1 000 nm. The diameter may for examplebe determined from environmental scanning electron microscope (ESEl\/l) or scanning electron microscope (SEM) images.

Nanocellulose comprises partly or totally fibrillated cellulose or lignocellulosefibers. The liberated fibrils or bundles of fibrils have a diameter less than 1 000 nm,whereas the actual fibril diameter or particle size distribution and/or aspect ratio(length/width) depends on the source and the manufacturing methods. Thesmallest fibril is called elementary fibril and has a diameter of approximately 2-4nm (see e.g. Chinga-Carrasco, G., Cellulose fibres, nanofibrils and microfibrils: The morphological sequence of l\/IFC components from a plant physiology and fibre technology point of view, Nanoscale research letters 2011, 6:417), while it iscommon that the aggregated form of the elementary fibrils, also defined asmicrofibril, is the main product that is obtained when making l\/IFC e.g. by using anextended refining process or pressure-drop disintegration process (Fengel, D.,Uitrastructural behavior of cell wall polysaccharides, Tappi J., l\/larch 1970, Vol 53,No. 3). Depending on the source and the manufacturing process, the length of thefibrils can vary from around 1 to more than 10 micrometers. A coarsenanocellulose grade might contain a substantial fraction of fibrillated fibers, i.e.protruding fibrils from the tracheid (cellulose fiber), and with a certain amount offibrils liberated from the tracheid (cellulose fiber).

There are different acronyms for nanocellulose such as cellulose microfibrils,fibrillated cellulose, nanofibrillated cellulose (NFC), fibril aggregates, nanoscalecellulose fibrils, cellulose nanofibers, cellulose nanofibrils, nanocrystallinecellulose, cellulose microfibers, cellulose fibrils, cellulose nanofilaments,microfibrillar cellulose, microfibrillated cellulose (MFC), microfibril aggregrates and cellulose microfibril aggregates.

Nanocellulose can also be characterized by various physical or physical-chemicalproperties such as its large surface area or its ability to form a gel-like material atlow solids (1 -5 wt°/>) when dispersed in water. The cellulose fiber is preferablyfibrillated to such an extent that the final specific surface area of the formednanocellulose is from about 1 to about 500 m2/g, such as from about 1 to about200 m2/g, or more preferably 50-200 m2/g when determined for a solventexchanged and freeze-dried material with the BET method.

Various methods exist to make nanocellulose, such as single or multiple passrefining, pre-hydrolysis or enzymatic treatment followed by refining or high sheardisintegration or liberation of fibrils.

One or several pre-treatment steps are usually required in order to makenanocellulose manufacturing both energy efficient and sustainable. The cellulosefibers of the pulp to be utilized may thus be pre-treated, for example enzymatically or chemically, for example to hydrolyse or swell the fibers or to reduce the quantity 6 of hemicellulose or lignin. The cellulose fibers may be chemically modified beforefibrillation, such that the cellulose molecules contain other (or more) functionalgroups than found in the original or native cellulose. Such groups include, amongothers, carboxymethyl (Cl\/l), aldehyde and/or carboxyl groups (cellulose obtainedby N-oxyl mediated oxidation, for example "TEl\/lPO"), quaternary ammonium(cationic cellulose) or phosphoryl groups. After being modified or oxidized in one ofthe above-described methods, it is easier to disintegrate the fibers intonanocellulose or nanofibrillar size fibrils.

The nanocellulose may contain some hemicelluloses, the amount of which isdependent on the plant source and the pulping and bleaching process. l\/lechanicaldisintegration of the fibers is carried out with suitable equipment such as a refiner,grinder, homogenizer, colloider, friction grinder, single- or twin-screw extruder,ultrasound sonicator, fluidizer such as microfluidizer, macrofluidizer or fluidizer-type homogenizer. Depending on the nanocellulose manufacturing method, theproduct might also contain fines, or nanocrystalline cellulose. The product mightalso contain various amounts of micron size fiber particles that have not been efficiently fibrillated.

Nanocellulose can be produced from wood cellulose fibers, both from hardwoodand softwood fibers. lt can also be made from microbial sources, agricultural fiberssuch as wheat straw pulp, bamboo, bagasse, or other non-wood fiber sources. lt ispreferably made from pulp including pulp from virgin fiber, e.g. mechanical,chemical and/or thermomechanical pulps. lt can also be made from broke orrecycled paper. The term nanocellulose includes parenchymal nanocellulose andBNC (bacterial nanocellulose). Nanocellulose can also be obtained from vegetable fibers, e.g. sugar beet or potato based nanocellulose.

The above described definition of nanocellulose includes, but is not limited to, thedefinition of nanocellulose in the ISO/TS 20477:2017 standard.

The nanocellulose of the aqueous mixture may be unmodified nanocellulose orchemically modified nanocellulose, or a mixture thereof. ln some embodiments, the nanocellulose is an unmodified nanocellulose.

Unmodified nanocellulose refers to nanocellulose made of unmodified or nativecellulose fibers. The unmodified nanocellulose may be a single type ofnanocellulose, or it can comprise a mixture of two or more types of nanocellulose, differing e.g. in the choice of cellulose raw material or manufacturing method.

Chemically modified nanocellulose refers to nanocellulose made of cellulose fibersthat have undergone chemical modification before, during or after fibrillation. lnsome embodiments, the nanocellulose is a chemically modified nanocellulose. Thechemically modified nanocellulose may be a single type of chemically modifiednanocellulose, or it can comprise a mixture of two or more types of chemicallymodified nanocellulose, differing e.g. in the type of chemical modification, thechoice of cellulose raw material or the manufacturing method. ln someembodiments, the chemically modified nanocellulose is microfibrillated dialdehydecellulose (DA-l\/IFC). DA-MFC is a dialdehyde cellulose treated in such way that itis microfibrillated. Dialdehyde cellulose can be obtained by oxidation of cellulose.l\/licrofibrillated dialdehyde cellulose can be obtained by treating dialdehydecellulose for example by a homogenizer or in any other way such that fibrillationoccurs to produce microfibrillated dialdehyde cellulose.

The aqueous mixture may comprise nanocellulose and foaming agent only, or itcan comprise nanocellulose and foaming agent combined with other ingredients oradditives. Depending of the purpose of the granules, a lower amount ofnanocellulose can be used as a foam stabilizing agent, or a higher amount ofnanocellulose can be used as a functional additive in the final granules. Theaqueous mixture preferably includes nanocellulose as its main component basedon the total dry weight of the aqueous mixture. ln some embodiments, theaqueous mixture in step a) comprises in the range of 5-99.5 wt°/>, preferably in therange of 30-99.5 wt°/-.~, preferably in the range of 50-99.5 wt°/-.~, preferably in therange of 60-995 wt°/-.~, more preferably in the range of 65-98 wt% of nanocellulose,based on the total dry weight of the aqueous mixture.

The foaming agent is a compound capable of forming and/or stabilizing a foam in an aqueous composition. The foaming agent is typically an amphiphilic substance, 8 i.e. a chemical compound possessing both hydrophilic and hydrophobic (Iipophilic)properties. A foaming agent reduces the work needed to create the foam byreducing the surface tension of the liquid and increases the colloidal stability of thefoam by inhibiting coalescence of bubbles.

The foaming agent of the solid composite may be any foaming agent suitable forfacilitating the formation of a foam in an aqueous nanocellulose dispersion and forstabilizing the formed foam. ln other words, the foaming agent should be capable of forming a stable foam in an aqueous nanocellulose dispersion. ln some embodiments, the foaming agent is a non-ionic surfactant.

Certain polymeric foaming agents have been found to be particularly useful in thepresent invention. ln addition to acting as foaming agents, polymeric foamingagents may also improve the stability and mechanical properties of the solidcomposite formed when the water of the aqueous foam has evaporated. The useof a polymeric foaming agent may therefore reduce or completely dispense withaddition of an optional additional polymeric binder. Thus, in some preferredembodiments the foaming agent is a polymeric foaming agent.

The polymeric foaming agent is preferably an amphiphilic polymer, i.e. a polymerpossessing both hydrophilic and hydrophobic (Iipophilic) properties. ln someembodiments, the at least one foaming agent is water-soluble. The polymericfoaming agent may for example be a water-soluble polymer with hydrophobicmoieties, such as a hydrophilic polymeric backbone provided with hydrophobicsidechains, or a block copolymer comprised of hydrophilic and hydrophobicsections. ln some embodiments, the at least one foaming agent is selected from the groupconsisting of optionally hydrophobically modified polysaccharides, proteins,polyvinyl alcohol, polyvinyl acetate and mixtures thereof. The optional hydrophobicmodification typically comprises one or more hydrophobic groups, e.g. alkylgroups, covalently attached to the foaming agent. 9 ln some embodiments, the at least one foaming agent is an optionallyhydrophobically modified polysaccharide selected from the group consisting ofoptionally hydrophobically modified cellulose, starch, hemicellulose and mixturesthereof. ln some embodiments, the at least one polymeric foaming agent is an optionallyhydrophobically modified polysaccharide selected from the group consisting ofoptionally hydrophobically modified cellulose acetate (CA),ethyl(hydroxyethyl)cellulose (EHEC), methy|ce||u|ose (l\/IC), ethylcellulose (EC),hydroxyethylcellulose (HEC), hydroxypropylcellulose (HPC), sodiumcarboxymethylcellulose (Cl\/IC), hydroxypropylmethy|ce||u|ose (HPl\/IC),sulfoethylcellulose, starch, and mixtures thereof. ln some embodiments, the at least one polymeric foaming agent is selected fromthe group consisting of ethyl(hydroxyethyl)cellulose, hydrophobically modifiedethyl(hydroxyethyl)cellulose (Hl\/I-EHEC), hydroxyethylcellulose, hydrophobicallymodified hydroxyethyl cellulose (Hl\/I-HEC), methy|ce||u|ose (l\/IC), hydrophobicallymodified methy|ce||u|ose (Hl\/I-l\/IC), hydrophobically modifiedcarboxymethylcellulose (Hl\/I-Cl\/IC), and hydrophobically modified starch (Hl\/l-starch). Examples of useful hydrophobically modified starch derivatives include,but are not limited to dialdehyde starch, hydroxypropylated starch, octenyl succinicanhydride (OSA) starch, and dodecyl succinic anhydride (DDSA) starch. ln some embodiments, the at least one polymeric foaming agent is an optionally hydrophobically modified methyl cellulose. ln some embodiments, the at least one polymeric foaming agent is ahydrophobically modified polyvinyl alcohol (PVOH), such as ethylene modifiedPVOH. ln some embodiments, the polymeric foaming agent is a polyvinyl alcoholcontaining at least 2% acetate groups, more preferably at least 10% acetategroups, and even more preferably at least 15% acetate groups.

The at least one polymeric foaming agent may also be a charged amphiphilic polymer. The charge may facilitate the retention of the polymer.

The at least one polymeric foaming agent may also be a mixture of different amphiphilic polymers or derivatives of the above-mentioned amphiphilic polymers. ln some embodiments, the polymeric foaming agent has a molecular weight above5 OOO g/mol, preferably above 10 OOO g/mol. ln some embodiments, the aqueous mixture in step a) comprises in the range of0.1 -80 wt%, preferably in the range of 0.5-50 wt°/>, preferably in the range of O.5-1O wt°/>, preferably in the range of O.5-5 wt°/>, more preferably in the range of 2-5 wt°/> of foaming agent, based on the total dry weight of the aqueous mixture. ln some applications, such as in materials intended for contact with foodstuff, lowmolecular components which could potentially migrate or be leached from thematerial, are preferably avoided. Thus, in some embodiments the aqueous mixtureand the resulting granulate is free from surface active chemicals having amolecular weight below 1 OOO g/mol. lnstead the foaming agent is comprised of polymeric foaming agent(s) less prone to migration or leaching.

The foaming agent may optionally be combined with one or more polymericdispersing and/or rheology modifying agents. The inventors have found that theaddition of a polymeric dispersing and/or rheology modifying agent can furtherimprove the foam formation and the stability of the formed aqueous foam. Apolymeric dispersing and/or rheology modifying agent may also improve thestability and mechanical properties of the granulate formed when the water of the aqueous foam has evaporated.

A polymeric dispersing and/or rheology modifying agent may be especially usefulwhen the foaming agent is not a polymeric foaming agent. However, a polymericdispersing and/or rheology modifying agent may also be useful when the foamingagent is a polymeric foaming agent, but additional modification of the foam 11 properties is desired. The polymeric dispersing and/or rheology modifying agentmay be a dispersing agent, a rheology modifying agent or a combination of both.

Examples of dispersing agents useful in the aqueous mixture include, but are notlimited to, polycarboxylates such as polyacrylates or carboxyiatedpolysaccharides, and polyphosphates, and sa|ts, e.g. metal sa|ts, thereof.

Examples of rheology modifying agents useful in the aqueous mixture include, butare not limited to, cellulosic polymers, starch, alginate, proteins, polyacrylates andother acrylic polymers and ethoxylated polyurethanes.

Examples of polymeric dispersing and/or rheology modifying agents useful in theaqueous mixture include, but are not limited to, polycarboxylates such aspolyacrylates or carboxyiated polysaccharides. ln some embodiments, the polymeric dispersing and/or rheology modifying agent is a carboxymethyl cellulose (Cl\/IC).

The concentration of the polymeric dispersing and/or rheology modifying agent issuitably selected depending on the type and molecular weight of the polymer. lnsome embodiments, the aqueous mixture comprises in the range of 0.1 -20 wt°/>,preferably in the range of 0.3-10 wt°/>, more preferably in the range of O.5-5 wt% ofthe polymeric dispersing and/or rheology modifying agent, based on the total dry weight of the aqueous mixture.

The formulation of the aqueous mixture may vary depending on the intended usefor the granulate. The aqueous mixture may include a wide range of ingredients invarying quantities to improve the end performance of the granulation process orthe formed granulate.

The aqueous mixture may further comprise additives such as starch, a filler,retention aids, flocculation additives, deflocculating additives, dry strengthadditives, softeners, humectants, antistatic agents, or mixtures thereof. 12 ln some embodiments, the aqueous mixture further comprises a polymeric binder.ln some preferred embodiments, the aqueous mixture further comprises PVOH.The PVOH may be a single type of PVOH, or it can comprise a mixture of two ormore types of PVOH, differing e.g. in degree of hydro|ysis or viscosity. The PVOHmay for example have a degree of hydro|ysis in the range of 80-99 mol°/>,preferably in the range of 88-99 mol°/>. Furthermore, the PVOH may preferablyhave a viscosity above 5 mPa> aqueous solution at 20 °C DIN 53015/JIS K 6726. ln some embodiments, the aqueous mixture further comprises a pigment. Thepigment may for example comprise inorganic particles of talcum, silicates,carbonates, alkaline earth metal carbonates and ammonium carbonate, or oxides,such as transition metal oxides and other metal oxides. The pigment may alsocomprise nano-size pigments such as nanoclays and nanoparticles of layeredmineral silicates, for instance selected from the group comprising montmorillonite,bentonite, kaolinite, hectorite and hallyosite. ln some embodiments, the pigment is selected from the group consisting ofnanoclays and nanoparticles of layered mineral silicates, more preferablybentonite. ln some embodiments, the total solid content of the aqueous mixture prior tofoaming is preferably in the range of 1-50 wt°/>. ln some embodiments, the foaming in step b) is achieved by high speed mixing. ln some embodiments, the amount of solid particles added to the foam in step c) isabove 20 wt°/-.~, preferably above 30 wt°/>, and more preferably above 40 wt°/>, based on the total weight of the foam with added particles. ln some embodiments, the amount of solid particles added to the foam in step c) isin the range of 20-95 wt°/-.~, preferably in the range of 30-90 wt°/>, and morepreferably in the range of 40-80 wt°/>, based on the total weight of the foam with added particles. 13 ln order to facilitate the granulation process, the solid particles preferably have lowor zero solubility in water. This allows for mixing of the particles in the aqueousfoam without any substantial dissolution of the particles occurring duringpreparation of the granulate. Low solubility in the context of this disclosure meansthat less than 20%, preferably less than 10%, more preferably less than 5%, mostpreferably less than 1%, of the dry weight of the particles is lost into solution (i.e. into the aqueous mixture) during preparation of the granulate.

The solid particles may for example comprise cork, wood, other biomass orStyrofoam. Preferably however, the particulate material is a bio-based material,such as cork, wood or other biomass. ln some embodiments, the solid particlescomprise a particulate material selected from the group consisting of cork particlesand wood particles. ln preferred embodiments, the solid particles are bio-based and/or renewableand/or compostable particles. Using bio-based and/or renewable and/orcompostable particles allows for preparation of a granulate which is based entirelyor at least mainly on renewable and/or compostable materials. ln some embodiments, the solid particles are selected from the group consisting of polysaccharide, lignin and protein based particles. ln some embodiments, the solid particles are polysaccharide particles selectedfrom the group consisting of starch, hemicellulose or cellulose based particles, or mixtures thereof. ln some embodiments, the solid particles are polysaccharide particles selectedfrom the group consisting of hornificated cellulose beads, microcrystalline cellulose(l\/ICC) particles, starch granules, chemically modified starch particles orchemically modified cellulose particles. ln some embodiments, the solid particles comprise a superabsorbent polymer(SAP). 14 The solid particles may be chemically and/or physically crosslinked in order toreduce their solubility in water. ln some embodiments, the solid particles are hydrophobized.

The formation of a foam allows for low-density particles, more specifically particleshaving a density of less than 1.2 kg/dms, to be effectively dispersed in liquid mixture comprising nanocellulose and a foaming agent. ln some embodiments, the solid particles have a density of less than 1.2 kg/dm3,preferably less than 1.0 kg/dm3, less than 0.9 kg/dms, less than 0.8 kg/dms, lessthan 0.7 kg/dms, less than 0.6 kg/dm3, less than 0.5 kg/dms, less than 0.4 kg/dms,less than 0.3 kg/dms or less than 0.2 kg/dm3. ln some embodiments, the solid particles are porous particles. Porous particlesmay be of particular interest for their low weight and thermal insulation properties.The porous particles may comprise closed pores, open pores, or a combination ofclosed and open pores. ln some embodiments, the solid particles are porous withclosed pores or have a combination of closed pores and open pores. ln someembodiments, the solid particles have a specific surface area above 50 m2/g, preferably above 70 m2/g, and more preferably above 100 m2/g.

The average particle size can be analyzed using an air-jet sieve analyzer. Resultsare then presented as a particle-size distribution and as the particle size at which50 wt% of the particles were below the given size denoted as the median particlediameter, or d50. ln some embodiments, the solid particles have a d50 average particle size in therange of 5 - 10 000 um, preferably in the range of 5 - 1 000 um, preferably in therange of 5 - 800 um, and more preferably in the range of 5 - 600 um. ln some embodiments, the total solid content of the foam with added particlesbefore drying is at least 30 wt°/-.~, preferably at least 40 wt°/-.~, and more preferably atleast 50 wt°/°. ln some embodiments, the drying in step d) is performed at a temperature below240 °C, preferably below 220 °C and more preferably below 200 °C. ln some embodiments, the drying in step d) is performed at a temperature in therange of 40-180 °C, preferably in the range of 60-160 °C. ln some embodiments, the drying in step d) is performed until the total solidcontent of the granulate is at least 50 wt°/>, at least 60 wt°/>, at least 70 wt°/-.~, atleast 80 wt°/-.~, at least 90 wt°/-.~, at least 95 wt°/>, or at least 99 wt°/-.~. ln some embodiments, the granulate is further subjected to milling, pulverization, micronization, size classification, screening, and/or blending.

The granulate may also be subjected to further processing, such as compacting,briquetting or pelletizing, to bring it into a suitable form for further use.

According to a second aspect illustrated herein, there is provided a granulate obtainable by the foam granulation method according to the first aspect.

According to another aspect illustrated herein, there is provided a granulateobtained by the foam granulation method according to the first aspect.

The granulate may advantageously be used in pharmaceuticals, food, personal and home care such as cosmetics, composites, papermaking and packaging.

While the invention has been described with reference to various exemplaryembodiments, it will be understood by those skilled in the art that various changesmay be made and equivalents may be substituted for elements thereof withoutdeparting from the scope of the invention. ln addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention 16 without departing from the essential scope thereof. Therefore, it is intended thatthe invention not be limited to the particular embodiment disclosed as the bestmode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (27)

17 CLAIIVIS

1. Foam granulation method comprising: a) preparing an aqueous mixture comprising nanocellulose and a foaming agent, b) foaming said mixture to obtain a foam, c) adding solid particles to said foam, d) mixing and drying said foam with added particles to obtain a granulatecomprising the solid particles.

2. The method according to claim 1, wherein said nanocellulose comprisescellulosic nanofibers having an average diameter in the range of 1-1000 nm.

3. The method according to claim any one of the preceding claims, wherein theaqueous mixture in step a) comprises in the range of 5-99.5 wt°/>, preferably in therange of 30-99.5 wt°/-.~, preferably in the range of 50-99.5 wt°/-.~, preferably in therange of 60-995 wt°/>, more preferably in the range of 65-98 wt% of nanocellulose,based on the total dry weight of the aqueous mixture.

4. The method according to any one of the preceding claims, wherein the atleast one foaming agent is a polymeric foaming agent.

5. The method according to any one of the preceding claims, wherein the atleast one foaming agent is an amphiphilic polymer.

6. The method according to any one of the preceding claims, wherein the atleast one foaming agent is selected from the group consisting of optionallyhydrophobically modified polysaccharides, proteins, polyvinyl alcohol, polyvinylacetate and mixtures thereof. 18

7. The method according to any one of the preceding claims, wherein the atleast one foaming agent is an optionally hydrophobically modified polysaccharideselected from the group consisting of cellulose, starch, hemicellulose and mixtures thereof.

8. The method according to any one of the preceding claims, wherein the atleast one foaming agent is an optionally hydrophobically modified polysaccharideselected from the group consisting of optionally hydrophobically modified celluloseacetate (CA), ethyl(hydroxyethyl)cellulose (EHEC), methylcellulose (l\/IC),ethylcellulose (EC), hydroxyethylcellulose (HEC), hydroxypropylcellulose (HPC),sodium carboxymethylcellulose (GMC), hydroxypropylmethylcellulose (HPl\/IC),sulfoethylcellulose, starch, and mixtures thereof.

9. The method according to any one of the preceding claims, wherein the atleast one foaming agent is an optionally hydrophobically modified methyl cellulose.

10. The method according to any one of the preceding claims, wherein thefoaming agent has a molecular weight above 5 000 g/mol, preferably above 10000 g/mol.

11. The method according to any one of the preceding claims, wherein theaqueous mixture in step a) comprises in the range of 0.1 -80 wt°/>, preferably in therange of 0.5-50 wt°/>, preferably in the range of 0.5-10 wt°/>, preferably in the rangeof 0.5-5 wt%, more preferably in the range of 2-5 wt% of foaming agent, based on the total dry weight of the aqueous mixture.

12. The method according to any one of the preceding claims, wherein thegranulate is free from surface active chemicals having a molecular weight below 1000 g/mol.

13. The method according to any one of the preceding claims, wherein the aqueous mixture in step a) further comprises a polymeric binder. 19

14. The method according to any one of the preceding claims, wherein theamount of solid particles added in step c) is above 20 wt°/>, preferably above 30wt%, and more preferably above 40 wt°/>, based on the total weight of the foamwith added particles.

15. The method according to any one of the preceding claims, wherein the solidparticles have a d50 average particle size in the range of 5 - 10 000 pm, preferablyin the range of 5 - 1 000 pm, preferably in the range of 5 - 800 pm, and morepreferably in the range of 5 - 600 pm.

16. The method according to any one of the preceding claims, wherein the solid particles have low or zero solubility in water.

17. The method according to any one of the preceding claims, wherein the solidparticles are bio-based and/or renewable and/or compostable particles.

18. The method according to any one of the preceding claims, wherein the solidparticles are selected from the group consisting of polysaccharide, lignin and protein based particles.

19. The method according to claim 18, wherein the solid particles arepolysaccharide particles selected from the group consisting of starch,hemicellulose or cellulose based particles, or mixtures thereof.

20. The method according to claim 19, wherein the solid particles arepolysaccharide particles selected from the group consisting of hornificatedcellulose beads, microcrystalline cellulose (l\/ICC) particles, starch granules,chemically modified starch particles and chemically modified cellulose particles.

21. The method according to any one of the preceding claims, wherein the solid particles are porous particles.

22. The method according to any one of the preceding claims, wherein the solidparticles have a density of less than 1.2 kg/dms, preferably less than 1.0 kg/dms,less than 0.8 kg/dms, less than 0.6 kg/dms, or less than 0.4 kg/dms.

23. The method according to any one of the preceding claims, wherein the totalsolid content of the foam with added particles before drying is at least 30 wt°/-.~,preferably at least 40 wt°/-.~, and more preferably at least 50 wt°/>.

24. The method according to any one of the preceding claims, wherein thedrying in step d) is performed at a temperature below 240 °C, preferably below220 °C and more preferably below 200 °C.

25. The method according to any one of the preceding claims, wherein thedrying in step d) is performed at a temperature in the range of 40-180 °C,preferably in the range of 60-160 °C.

26. The method according to any one of the preceding claims, wherein thedrying in step d) is performed until the total solid content of the granulate is at least50 wt°/-.~, at least 60 wt°/-.~, at least 70 wt°/-.~, at least 80 wt°/-.~, at least 90 wt°/>, at least95 wt%, or at least 99 wt°/-.~.

27. A granulate obtainable by the foam granulation method according to any one of the preceding claims.