Shear responsive colloidal cellulose composition

Abstract

The present invention relates to a colloidal composition comprising unmodified, discrete cellulose microparticles, such as a colloidal emulsion or colloidal gel, a method of preparing the colloidal composition and uses of the colloidal composition and cellulose particles The colloidal composition comprises a continuous phase and a dispersed phase, wherein the continuous phase is a liquid; wherein the dispersed phase comprises cellulose microparticles which are dispersed in the continuous phase of the colloidal composition, wherein the cellulose microparticles have a mean average particle length of from 0.1 to 20 µm a mean average particle width from 0.05 to 1.3 µm, and a maximum thickness not exceeding 0.2 µm determined by scanning electron microscopy; and an aspect ratio of length / width of 1 to 25, and wherein the colloidal composition has a flow index n of ≤ 1 determined by a rheometer at NTP (normal temperature (25°C) and pressure (1 atm)).

Description

[0001] Shear Responsive Colloidal Cellulose Composition

[0002] Field of the Invention

[0003] The present invention relates to a shear responsive colloidal composition comprising cellulose microparticles, such as a colloidal emulsion or colloidal gel, a method of preparing the colloidal composition and uses of the colloidal composition and cellulose microparticles.

[0004] Background

[0005] Emulsions are heterogeneous systems normally including two immiscible phases, one of which is dispersed in the other one. In emulsions there is a liquid which is present as droplets and is called a 'dispersed phase', and the base liquid surrounding the droplets is called the 'continuous phase'. In gels, the dispersed phase may be a solid particle or a polymer network, which the continuous phase surrounds. In emulsions, the dispersed phase, or internal phase, is typically stabilized by emulsifiers, such as surfactants. Traditionally, the liquid droplets, or the dispersed phase, are stabilized by small-molecule surfactants or surface-active polymers, which can be adsorbed onto the interface, thereby reducing the interfacial free energy.

[0006] Emulsions can also be stabilised solely by solid particles, such as fine solid particles to form solid-stabilised emulsions. These emulsions are often referred to as Pickering emulsions.

[0007] The formation of oil-in-water (o / w) or water-in-oil (w / o) emulsions depends on the three-phase contact angle at the interface, which affects the bending of the fluid-fluid interface. If the three- phase contact angle is less than 90°, the particles will cause the fluid-fluid interface to bend towards the oil phase, leading to the formation of o / w emulsions; otherwise w / o emulsions will be formed. If the particles are completely wetted by one of the phases, they may remain dispersed in that phase and no stable emulsion will form.

[0008] The stability of Pickering emulsions is related to the particle concentration and particle-particle interactions. At high particle concentrations, the irreversibly adsorbed particles at the interface and the formation of a 3D particle network can prevent the coalescence of dispersed droplets. At low particle concentration, however, the limited coalescence and bridging of droplets by a monolayer of particles become the major stabilisation mechanism. The emulsion stability can be dramatically improved when the stabilising particles are weakly flocculated.

[0009] A wide variety of solid particles have been investigated to prepare either o / w or w / o Pickering emulsions, including inorganic particles such as silica, silicate, montmorillonite, calcium carbonate, carbon graphite and polymer particles, for instance, polystyrene, poly(vinylidene difluoride) and poly(tetrafluoroethylene).

[0010] Traditional surfactants, such as small-molecule surfactants, surface-active polymers or solid particles have various draw backs. These surfactants are typically not renewable or have energy intensive production processes. The surfactants can also display toxicity, to animals and aquatic life. This makes the use of these known surfactants for food, healthcare and cosmetic applications undesirable.

[0011] Traditional emulsions also often require colourants and / or opacifiers to be included to enhance the visual appearance of the emulsion. This is especially the case in food, healthcare and cosmetic applications, where the appearance of the emulsion is important. Known emulsions may use traditional opacifiers such as titanium dioxide (TiO2).

[0012] Again, these traditional colourants and / or opacifiers are undesirable because they are typically not renewable, have energy intensive production processes, and may display toxicity.

[0013] Moreover, existing surfactant and colourant technology requires that emulsions require separate components to act as colourants and surfactants. This increase the formulation complexity of emulsions. Not only are more components required, which increases the formulation cost, but the components also need to be carefully selected so as not to effect the stability of the emulsion. Emulsions are often unstable and may phase separate, e.g., during long term storage. The choice of components for the emulsion is important for ensuring stability, and the effects on stability can be difficult to predict.

[0014] Thus, the addition of any extra components, such as colourants and / or opacifiers, can have a detrimental effect on emulsion stability. This necessitates additional testing and refinement of the formulation to ensure the stability needed for commercial applications.

[0015] GICQUEL ERWAN ET AL ("Impact of sonication on the rheological and colloidal properties of highly concentrated cellulose nanocrystal suspensions”, CELLULOSE, SPRINGER NETHERLANDS, NETHERLANDS, vol. 26, no. 13, 25 July 2019 (2019-07-25), pages 7619- 7634, XP036875593, ISSN: 0969-0239, DOI: 10.1007 / 510570-019-02622-7) discloses the rheological behavior of CNC suspensions. In Fig. 8, the relationship between viscosity and shear rate is explored for CNC aqueous suspensions at various concentrations. For concentrations below 5 w%, the viscosity remains constant regardless of the shear rate, indicating Newtonian behavior. However, at concentrations between 6 and 8 w%, there is a slight decrease in viscosity as shear rates increase, suggesting the onset of shear-thinning behavior. As concentrations exceed 10 w%, viscosity decreases significantly, pointing to the presence of aggregation or agglomeration of the CNC particles. Notably, the response changes after sonication, particularly at low shear rates for concentrations above 10 w%; this likely results from instability in the particle aggregates, which indicates that these suspensions do not exhibit good long-term stability at higher concentrations. Further it is suggested that before sonication, CNC particles may form clusters that alter their rheological properties. Following sonication, the particles are smaller and more stable, exhibiting consistent viscosity at lower concentrations. However, at concentrations above approximately 10 w%, their behavior becomes erratic, reinforcing the notion of compromised long-term stability. In Fig. 7, the elastic (G1) and viscous (G") moduli of CNC particles before and after sonication are presented. For sonicated particles, G' and G" are similar in magnitude, revealing a liquid-like behavior. This shows that the suspension behaves more like a fluid than a gel, which would exhibit greater viscoelastic properties. Thus, the significant changes in CNC particles' behavior postsonication, demonstrating stable, liquid-like characteristics at lower concentrations, while at higher concentrations, the behavior becomes complex and inconsistent due to potential aggregation, highlighting the lack of long-term stability in these suspensions.

[0016] US 11 028307 B2 discloses a drilling fluid comprising an aqueous suspension of clay particles, sodium hydroxide for pH control, lignite as a deflocculant, polyanionic cellulose as a solid control agent, and a finely-ground calcium montmorillonite clay / silica mixture as a viscosifier. In addition, the fluid comprises cellulose nanocrystals (CNCs) that are chemically modified via covalent bonding of functional groups to the hydroxyl moieties on the CNC surface. Thus, the CNCs are modified with tailored surface charges or with tailored levels of salt-tolerant polymer grafting, and combined with bentonite nanoplatelets in an aqueous suspension. This surface modification is essential to enhance the compatibility of the CNCs with the fluid matrix, to prevent aggregation, and to tailor their rheological behavior. The modified CNCs contribute to the overall stability and performance of the drilling fluid by improving dispersion, optimizing viscosity, and ensuring functional integration with other fluid components.

[0017] US 2021 / 069378 A1 discloses a bioink composition for 3D bioprinting, comprising nanocellulose in the form of nanocellulose crystals, nanofibrils, or a combination thereof; alginate in the form of alginic acid and / or an alginate salt; and water, wherein said alginate is ionically crosslinkable in the presence of an ionic crosslinking agent. Cellulose nanofibrils are entangled, flexible, and elongated nanostructures that typically form continuous, web-like networks. Their high aspect ratio and strong tendency to interact via hydrogen bonding enable the formation of interconnected fibrillar structures. The bioink has a pseudoelastic behavior rapid flow through a nozzle and instant recovery after deposition, thereby reducing the mechanical stress exerted on cells.

[0018] OGUZLU HALE ET AL (Colloidal behavior of aqueous cellulose nanocrystal suspensions", CURRENT OPINION IN COLLOID & INTERFACE SCIENCE, LONDON, GB.vol. 29, 12 February 2017 (2017-02-12), pages 46-56, XP085046638, ISSN: 1359-0294, DOI:10.1016 / J. COCIS.2017.02.002) discloses the colloidal microstructure of sulfonated cellulose nanocrystal (CNC) suspensions and connect to their rheological behavior in the presence of electrolyte, by changing its surface chemistry and also in dilute water soluble polymer solutions. It was shown that the presence of electrolyte has a significant effect depending both on the concentrations of CNC and electrolyte.

[0019] NIGMATULLIN RINAT ET AL (Thermosensitive supramolecular and colloidal hydrogels via self-assembly modulated by hydrophobized cellulose nanocrystals", CELLULOSE, SPRINGER NETHERLANDS, NETHERLANDS, vol. 26, no. 1 ,8 January 2019 (2019-01-08), pages 529-542, XP036704029) discloses a study on thermosensitive hydrogels formed via hydrophobic interactions between water-soluble macromolecules and nanoparticles. These hybrid hydrogels, made from octyl-modified cellulose nanocrystals (CNCs) and hydroxypropyl methylcellulose (HPMC), exhibit tunable rheological properties, resulting in increased stiffness and viscosity compared to standard HPMC and hydrophilic CNC hydrogels. NMR spectroscopy showed that heating increases network-bound water, enhancing the hydrogels' mechanical properties. The study demonstrates that the rheological characteristics of these hybrid hydrogels can be finely adjusted to meet specific application needs.

[0020] US 2024 / 067759 A1 discloses a process for producing dried colloidal microcrystalline cellulose (colloidal MCC), to colloidal MCC producible by the said process and to colloidal MCC.

[0021] COSTA ANA LETICIA RODRIGUES ET AL ("Cellulose nanofibers from banana peels as a Pickering emulsifier: High-energy emulsification processes", CARBOHYDRATE POLYMERS, vol. 194, 1 August 2018 (2018-08-01), pages 122-131) discloses Cellulose nanofibers (CNFs) from banana peels was evaluated as stabilizer for oil-in-water emulsions.

[0022] WO 2023 / 135261A1 discloses cellulose particles having a length of from 1 ,000 to 10,000 nm and an aspect ratio of from 2 to 18 and a method for preparing cellulose particles comprising hydrolysing a cellulose material to provide hydrolysed cellulose particles, washing the hydrolysed cellulose particles, and fractioning the hydrolysed cellulose particles using differential centrifugation.

[0023] The problem of the present invention is therefore to provide a colloidal composition that offers excellent long term stability, improved texture, and good processablity.

[0024] The problem is solved by the colloidal composition according to claim 1. Further preferred embodiments are subject of claims 2 to 21 .

[0025] Surprisingly, it was found that the colloidal composition according to the present invention has an excellent long term stability and and improved texture. The colloidal composition comprises a continuous phase and a dispersed phase, wherein the continuous phase is a liquid; and wherein the dispersed phase comprises native, discrete cellulose microparticles which are dispersed in the continuous phase of the colloidal composition, and wherein the cellulose microparticles have a mean average particle length of from 0.1 to 20 pm, a mean average particle width from 0.05 to 1 .3 pm, and a maximum thickness not exceeding 0.2 pm, determined by scanning electron microscopy; and an aspect ratio (length / width) of 1 to 25, wherein the colloidal composition has a flow index n of < 1 determined by a rheometer at NTP (normal temperature (25°C) and pressure (1 atm)). Unexpectedly, it was discovered that a variety of compositions with cellulose microparticles have a flow index of < 1. This finding is surprising, as such compositions usually do not exhibit this behavior. With its shear-thinning characteristics, the composition facilitates easier flow under stress, making it ideal for several applications such as lubricants and food products. Additionally, enhanced viscosity control enables thixotropic behavior, where the viscosity decreases under shear stress but recovers over time once the stress is removed. This thixotropic behaviour means their viscosity decreases over time under constant shear stress and gradually recovers once the shear is removed, indicating a time-dependent structural breakdown and rebuilding process, rather than an immediate, reversible response to shear rate. Thus, the longer the shear is applied, the more the internal structure breaks down, resulting in a gradual drop in viscosity. Once the shear is removed, the structure slowly rebuilds, and viscosity gradually increases again. The compositions of the present invention show in fact a thixotropic behavior at any concentration until they become a gel. Due to their thixotropic, shear-thinning properties they combine intelligent flow behavior with exceptional control over setting dynamics. When subjected to shear, it becomes fluid and easy to handle, enabling precise application through injection, spreading, or coating. Once the shear is removed, the material gradually rebuilds its internal structure, ensuring it remains exactly where placed without dripping or deformation. A major advantage of this composition is its controlled recovery and delayed setting. Unlike materials that harden or solidify too rapidly, it provides an extended working time, allowing flexibility during handling, adjustment, or positioning. This balance ensures the material stays adaptable throughout application while reliably transitioning into a stable, form-retaining state once at rest. Thus, a significant benefit of this composition is its improved processability, which enhances the ease of pumping, mixing, and handling during manufacturing. Furthermore, the composition allows for precise application in adhesives and sealants, as it can be easily applied under shear yet sets within minutes once the shear is removed. Enhanced stability and storage are also achieved by preventing sedimentation and maintaining stable suspensions, thereby avoiding phase separation. The reason for this surprising rheological behavior lies in the morphology and geometry of the cellulose microparticles. Not only are the ranges of their mean length, mean width, and maximal thickness relevant, but especially their aspect ratio, that is, the ratio of their mean length to mean width. The particles must therefore fall within a certain range of lengths and widths, but at the same time, the length-to-width ratio must not be too large, i.e. in the range of 1 to 25.

[0026] In addition to its excellent shear-responsive properties, the composition according to the present invention is also color-tunable. This feature allows for precise customization of color, enhancing its versatility and appeal for a wide range of uses. The color-tunable nature of the composition complements its mechanical properties without compromising performance.

[0027] In the context of the present invention, the term "native, discrete cellulose microparticles" refers to individual, i.e., non-interconnected particles obtained through hydrolysis. These particles are considered virgin ("unmodified" or “native”) in the sense that they are not covalently or otherwise bonded to any larger molecule or polymer. The surface half-ester sulfate groups introduced during cellulose hydrolysis, post-treatments to increase the anionic charge density, as well as the hydroxyl groups originating from the structure of cellulose itself are regarded as natural components and do not constitute modifications. It is crucial that the microparticles remain unmodified, as their overall behavior changes significantly if any molecules are grafted or crosslinked onto them. Furthermore, to ensure that the shear-thinning properties remain effective across a wide range of concentrations, it is essential that the particles exist as discrete entities.

[0028] With the term shear-thinning the phenomenon of a viscosity drop with increased shear rate is addressed. Such decrease of viscosity is considered reversible if viscosity reaches the original value when the shear rate is decreased to its original value. The composition comprises cellulose microparticle populations, each population having a specific concentration-to-size relationship. Outside this specific range, the composition exhibits a shear-thickening behavior, meaning its viscosity increases as the shear rate rises. As illustrated in Table 1 below, the composition according to the present invention includes the cellulose microparticle population CMPLS at a concentration of 1 to 10 wt.%, the cellulose microparticle population CMPXat a concentration of 5 to 20 wt.%, and the cellulose microparticle population CMPZat a concentration of 10 to 20 wt.% or a mixture thereof.

[0029] In the context of the present invention, the cellulose microparticle populations (CMP) are characterized as follows:

[0030] - CMPZhas an average particle length of 7 pm to 12 pm, a mean average particle width from 0.05 to 0.5 pm, and a maximum thickness not exceeding 0.2 pm ; the CMPZparticles, exhibit an aspect ratio (length / width) of 1 to 25, preferably in the range of 15 to 25, with the most preferred range being 20;

[0031] - CMPLShas an average particle length ranging from 1 pm to less than 7 pm, a mean average particle width from 0.05 to 0.5 pm, and a maximum thickness not exceeding 0.2 pm, the CMPLSparticles, or cellulose white pigments, exhibit an aspect ratio (length / width) of 1 to 25, preferably in the range of 15 to 25, with the most preferred range being 20; and

[0032] - CMPXhas an average particle length of 0.1 pm to less than 1 pm a mean average particle width from 0.05 to 0.5 pm, and a maximum thickness not exceeding 0.2 pm the CMPXparticles, exhibit an aspect ratio (length / width) 1 to 25, preferably in the range of 15 to 25, with the most preferred range being 20. Contrary to CNCs known from the prior art, which are spindle-like particles (similar to a grain of rice) and possess length and width, the particles contained in the composition according to the present invention, specifically the CMPLS, CMPZ, or CMPX, are 3D platelets with three physical dimensions: length, width, and thickness. The length is greater than the width, and the width is greater than the thickness. Thus, CNCs have a pronounced thickness that makes it a three-dimensional elongated body, whereas a the particles contained in the composition according to the present invention have a very small thickness relative to its length and width gives it a flat, platelet-like shape. This difference in morphology and geometry has a notable impact on the rheological behavior, as it allows to control the viscosity and shear stress over a wide range of shear rates (0.1 to T000 s-1).

[0033] One aspect of the present invention relates to a preferred composition comprising one of the following cellulose microparticle populations (CMP):

[0034] - particle population CMPX, having an average particle length of 0.1 pm to less than 1 pm, a mean average particle width from 0.05 to 0.5 pm, and a maximum thickness not exceeding 0.2 pm at a concentration of 1 wt% to 12 wt%, or

[0035] - particle population CMPLS, having an average particle length ranging from 1 pm to less than 7 pm, a mean average particle width from 0.05 to 0.5 pm, and a maximum thickness not exceeding 0.2 pm at a concentration of 5 wt% to 20 wt%, or

[0036] - particle population CMPZ, having an average particle length ranging from 7 pm to 12 pm, a mean average particle width from 0.05 to 0.5 pm, and a maximum thickness not exceeding 0.2 pm at a concentration of 10 wt% to 20 wt%, or

[0037] - a mixture thereof,

[0038] - whereby all particle populations have an aspect ratio of 1 to 25.

[0039] A further aspect of the present invention relates to a preferred composition comprising one of the following cellulose microparticle populations:

[0040] - particle population CMPX, having an average particle length of 0.1 to less than 1 pm and a mean average particle width of 0.05 pm to less than 0.5 pm at a concentration of 1 wt% to 12 wt%, or

[0041] - particle population CMPLS, having an average particle length ranging from 1 pm to less than 7 pm and a mean average particle width of 0.05 pm to less than 0.35 pm at a concentration of 5 wt% to 20 wt%, or

[0042] - particle population CMPZ, having an average particle length ranging from 7 pm to 12 pm and a mean average particle width of 0.35 pm to less than 0.5 pm at a concentration of 10 wt% to 20 wt%, or

[0043] - a mixture thereof

[0044] - whereby all particle populations have an aspect ratio of 1 to 25.

[0045] The thickness of said cellulose microparticle populations is preferably is one order of magnitude smaller than the width. In a second aspect of the invention there is provided a method of preparing a colloidal composition of the first aspect, the method comprising: mixing a liquid and cellulose microparticles to form a continuous phase and a dispersed phase, wherein the dispersed phase comprises cellulose microparticles which are dispersed in the continuous phase.

[0046] In a related aspect, there is also provided a colloidal composition which is obtained or obtainable by the method of the second aspect.

[0047] In another aspect of the invention there is provided a use of cellulose microparticles as a dispersed phase in the colloidal composition of the first aspect.

[0048] A further aspect of the present invention relates to compositions, wherein the concentration of the cellulose microparticles is below the gel point. Particle population CMPXreaches its gel point at 6 wt%, particle population CMPLSat 14 wt%, and particle population CMPZat 12 wt%, all based on the total mass of the colloidal composition at NTP. These compositions are powerlaw fluids, meaning they become thinner and flow more easily as they are stirred or mixed faster, without requiring any specific amount of force to start flowing. This characteristic offers several advantages, particularly in applications where minimal force is preferred or available. The ease of flow under low stress makes the compositions according to the present invention user-friendly, simplifying processes and reducing the energy needed for operations. Their predictable behavior under varying shear rates further simplifies the design of equipment and processes, leading to more consistent and reliable performance. Consequently, they are ideal for applications such as coatings and sprays, where uniform application with minimal energy input is beneficial.

[0049] A further aspect of the present invention relates to compositions, wherein the concentration of the cellulose microparticles is equal or above of the gel point. Particle population CMPXreaches its gel point at 6 wt%, particle population CMPLSat 14 wt%, and particle population CMPZat 12 wt%, all based on the total mass of the colloidal composition at NTP. These compositions are yield stress fluids that behave like solids until a certain force threshold is met, after which they flow like liquids and become thinner with increased stirring. This property provides distinct advantages, especially in situations where the composition needs to remain stable until intentionally moved. For example, these compositions according to the present invention are valuable in products like toothpaste and food items, ensuring they stay in place until used. This stability prevents unwanted flow or leakage. Once the yield stress is surpassed, these fluids flow smoothly, allowing for controlled application and processing. The combination of stability and controlled flow makes said compositions also particularly useful in construction materials like concrete and in personal care products, where precise and consistent application is essential.

[0050] In some embodiments, the cellulose microparticles are used as an opacifier, an emulsifier and / or a rheology modifier, in the colloidal composition. In another aspect of the invention there is provided a use of a colloidal composition of the first aspect as a personal care composition, a cosmetic composition, a pharmaceutical composition, a food composition, a microfluidics composition, or a drilling fluid.

[0051] In general, cellulosic materials are beneficial due to their renewability and non-toxicity, which is desirable for food, healthcare and cosmetic applications. The present invention provides a renewal and non-harmful alternative to known emulsifiers, rheology modifiers and opacifiers.

[0052] Unlike known cellulose materials, which have a different morphology (i.e. a rice grain-like shape or fiber-like shape), the cellulose microparticles used in this invention with a platelet-like shape are uniquely capable of simultaneously acting as both emulsifiers and opacifiers in colloidal compositions. Within the context of the present invention, the term “platelet” means a particle resembling a flat plate or flake. T raditional cellulose materials lack the morphological properties required to function as efficient light-scattering particles. To the inventors' knowledge, no particle, whether cellulose-based or otherwise, has been previously explored for its ability to serve both roles of emulsifier and opacifier concurrently. Additionally, this work demonstrates that MCC particles having a particle length of more than 20 pm and CNC particles having a particle length of less than 100 nm and / or particles having an aspect ratio of more than 25 are incapable of delivering the same rheological and structural responses necessary for gel and network formations as achieved by the cellulose microparticles used in the present invention.

[0053] Especially good results could be achieved with particles or particle populations having the length, width, and thickness ranges described above and an aspect ratio of 15 to 25, in particular with

[0054] - cellulose microparticles having a mean average particle length of from 13 to 20 pm, a mean average particle width of from 0.5 to 0.8 pm and a maximum thickness not exceeding 0.2 pm, and / or

[0055] - cellulose microparticles having an average particle length of 0.1 to less than 1 pm and a mean average particle width of 0.05 pm to less than 0.5 pm, and / or

[0056] - cellulose microparticles having an average particle length ranging from 1 pm to less than 7 pm and a mean average particle width of 0.05 pm to less than 0.35 pm, and / or

[0057] - cellulose microparticles having an average particle length ranging from 7 pm to 12 pm and a mean average particle width of 0.35 pm to less than 0.5 pm.

[0058] Within the context of the present invention, the term 'flow index' refers to a measure of how viscosity changes with increasing shear rates. It is determined by measuring shear stress and shear rate using a rheometer at NTP (normal temperature (25°C) and pressure (1 atm)), plotting the data on a log-log scale, and calculating the slope of the resulting linear plot. A fluid with a flow index greater than 1 is classified as a Newtonian fluid, indicating that its viscosity remains constant across varying shear rates. Conversely, a fluid with a flow index of less than or equal to 1 is classified as a shear-thinning fluid, as its viscosity decreases with higher shear rates. The present invention provides a new approach to stabilise and opacify colloidal compositions, such as an emulsion or gel. The present invention also provides a new approach to providing a texturizing, smoothening and / or emulsifying effect to a colloidal composition while also opacifying the composition.

[0059] The simultaneous stabilisation and opacification, using renewable and non-harmful cellulose microparticles, is particularly suited to use in food, healthcare and cosmetic applications.

[0060] The colloidal composition according to the present invention demonstrates excellent long-term stability, preferably remaining stable for at least 12 months. In this context, “stability” means that no phase separation can be observed.

[0061] The cellulose microparticles can be used on their own or in combination with surfactants or copolymers of low molecular weight to stabilise mixtures, gels, or emulsions. Each system has different stability requirement and may require different amounts of cellulose microparticles. However, in a preferred embodiment, the composition according to the present invention is free of additional stabilizers, such as the aforementioned surfactants or low molecular weight copolymers.

[0062] The cellulose microparticles can provide a white colour (opacity) to the composition, while different shades of colours can be provided by the addition of further colorants (e.g., dyes or pigments). If other colourants are used, then CMPs can be used to modulate the specific colour tints in the colloidal compositions. In one embodiment of the present invention, the composition is free of additional opacifiers such as titanium dioxide.

[0063] The colloidal composition may provide long-term storage stability (including at elevated temperatures up to 80°C) controlled rheological behaviour and, in the case of emulsion, rapid release of the dispersed phase by changing the shearing rates exerted on the emulsion. These tunable systems can be used in cosmetics, personal care products, biomedical, engineering, food, pharmaceutical, microfluidics and drilling fluid applications.

[0064] In particular, the cellulose microparticles can be used to emulsify highly stable high-internal phase emulsions (HIPE) as well as medium-internal phase Pickering emulsions (MIPE).

[0065] Emulsions stabilized by cellulose microparticles can change their rheological behaviour in response to externally applied shear forces. Additionally, the emulsions according to the invention also demonstrate remarkable stability, in the absence of any additional surfactant. Consequently, another key aspect of this invention pertains to emulsions that are entirely free from supplemental surfactants.

[0066] There is a distinct advantage in using cellulose microparticles over surfactants because of their renewability, nontoxicity, and low environmental impact owing to very low CO2emissions associated with the production of cellulose microparticles vis-a-vis surfactant synthesis, especially from petrochemical sources.

[0067] When applied on a surface, the compositions according to the present invention (e.g., gels or emulsions) can first be evenly spread on the desired area under low shear, and the film remains intact as the external force is removed. This is akin, for instance, to applying a cream on a hand or any other surface. As rubbing begins (shear force), the cream evenly spreads. Once rubbing stops, the cream remains as a uniform film over the area indicating good coverage. This could also emulate painting, where the flow properties change as external forces are applied and released. Similarly, when blending colloidal compositions stabilised by cellulose microparticles into food, cosmetic or other formulations, then applying and releasing external shear forces to the entire mix via homogenisation or stirring can modulate the rheological properties. This process not only positively influences the texture, but also enhances the consistency, thereby improving stability and overall performance of the final product.

[0068] The threshold value for the applied shear forces can be regulated by the ratio of components, such as the ratio of the continuous phase and dispersed phase, and the cellulose microparticle content, or the ionic strength of the cellulose microparticles. These tunable, shear-responsive colloidal compositions (e.g., emulsions) are well suited to a wide variety of applications in personal care products, cosmetics, pharmaceuticals, food, biomedical applications, microfluidics, and drilling fluids.

[0069] Summary of the Figures

[0070] The present invention is described with reference to the figures listed below.

[0071] FIG. 1 shows a scanning electron microscopy (SEM) image of cellulose microparticles with unique light scattering capability, CMPLS, also known as cellulose white pigments (CWP). Thus, CMPLSand CWP are used as synonyms.

[0072] FIG. 2 shows particle length distributions (indicated as particle size on the x-axis) for three regimes of cellulose microparticles obtained via sulphuric acid hydrolysis or direct sonication and centrifugation of the starting cellulose material. (2A) CMPZhas average particle length of more than 7 pm to 12 pm; (2B) 1 pm > CMPLS> 7 pm; and (2C) CMPX0.1 pm to less than 1 pm.

[0073] FIG. 3 shows flow curves for aqueous suspensions containing different concentrations of CMPLSor CMPZmicroparticles. The curves illustrate the shear stress response (3A) and viscosity (3B) vs. varying shear rate.

[0074] FIG. 4 shows amplitude (4A) and frequency (4B) sweeps for aqueous suspensions containing different concentrations of CMPLSor CMPZmicroparticles. FIG. 5 shows flow curves for aqueous suspensions containing different concentrations of CMPXmicroparticles and cellulose nanocrystals (CNCs).

[0075] FIG. 6 shows amplitude sweeps for aqueous suspensions containing different concentrations of CMPXmicroparticle and CNC suspensions.

[0076] FIG. 7 shows the relaxation behaviour of microparticle (CMPX) and nanoparticle (CNC) aqueous suspensions by measuring how the shear stress changes over time.

[0077] FIG. 8 shows Amplitude sweeps depicting the storage moduli (G’ and G”) vs. strain for CMPLSand microcrystalline (MCC) aqueous suspensions at different concentrations.

[0078] FIG. 9 shows paraffin-in-water emulsions (60 vol% oil and 40 vol% water stabilized by CMPLs at various concentrations (9A1)-(9C2). Fig. (9D) shows the paraffin-in-water emulsions and a commercial cream after centrifuging at 2000g.

[0079] FIG. (10A) shows photographs of mixtures of hydrophilic oil (glycerine) and water including a cellulose white pigment (CMP) at various concentrations from 0.1 to 9 wt%. Fig. (10B) shows a photograph of mixtures of lipophilic oil (paraffin) and water including a CMP at various concentrations from 0.1 to 7 wt% and a nonionic surfactant at 0.1 wt%.

[0080] FIG. (11 A) shows a polarized light image depicting the uniform dispersion of cellulose microparticles within a mixture of glycerine and water stabilized by 5 wt% CMP. The scale bar is 100 pm. Fig. (11 B) shows a SEM image of a paraffin and water emulsion stabilized by 5 wt% CMP. The scale bar is 50 pm.

[0081] FIG. 12 shows images of a red dye (D&C Red #7 Calcium Lake Dye) mixed at different concentration with CMP-stabilized emulsion to produce a red emulsion (12A) and a pink emulsion (12C). The emulsion and dye before mixing is shown in (12B).

[0082] FIG. 13 shows images of lignin containing (13A) and melanin containing (13B) emulsions prepared without CMP (left side of each image, marked “Ref”) and with 5 wt% cellulose white pigments (CMP) (right side of each image, marked “CMP”).

[0083] FIG. 14 shows images of (14A1-14A4) Cellulose white pigments, CMP, in coffee at different concentrations; and (14B1-14B3) CMP based coffee creamers with hot coffee over 60 minutes.

[0084] FIG. 15 shows image of eye shadow formulations including (15A1-15A4) TiO2(comparative), CMPLS, a combination of CMPLSand CMPX, and a combination of CMPLSand CMPZ(left to right) shown in a dish (top) and on skin (bottom); and (15B1-15B4) shows TiO2(comparative), 12.5 wt.% CMPLS, 25 wt.% CMPLSand 50 wt.% CMPLS(left to right) shown in a dish (top) and on skin (bottom). Detailed Description of the Invention

[0085] Colloidal Composition

[0086] In a first aspect of the invention there is provided a colloidal composition comprising a continuous phase and a dispersed phase, wherein the continuous phase is a liquid; wherein the dispersed phase comprises native, discrete cellulose microparticles which are dispersed in the continuous phase of the colloidal composition, wherein the cellulose microparticles have a mean average particle length of from 0.1 to 20 pm, a mean average particle width from 0.05 to 1.3 pm, and a maximum thickness not exceeding 0.2 pm determined by scanning electron microscopy and an aspect ratio of length / width of 1 to 25; and wherein the colloidal composition has a flow index n of < 1 determined by a rheometer at NTP.

[0087] A colloidal composition is a composition in which one substance is dispersed throughout another substance. A colloidal composition comprises a dispersed phase and a continuous phase. The dispersed phase is typically dispersed within the continuous phase.

[0088] The continuous phase is typically continuous. For example, the continuous phase may be a liquid, which surrounds the dispersed phase. It forms an unbroken phase that extends throughout the entire colloidal system, allowing for the uniform suspension and distribution of the dispersed phase within it. This continuous nature ensures stability and homogeneity in the colloidal composition.

[0089] The dispersed phase is typically non-continuous. For example, the dispersed phase may be particle or droplets, which are separated from each other by the continuous phase. These individual entities are scattered throughout the continuous phase, making the dispersed phase discontinuous. This non-continuous nature of the dispersed phase is essential for creating the specific properties and behaviors of the colloidal composition. The colloidal composition may include multiple phases (e.g., multiple dispersed phases).

[0090] The dispersed phase may include cellulose microparticles. The cellulose microparticles are described in more detail herein. The dispersed phase may also include a liquid dispersed phase.

[0091] Where the continuous phase is a liquid and the dispersed phase is a solid, the colloidal composition may be known as a colloidal gel. The solid dispersed phase may comprise cellulose microparticles.

[0092] Where the continuous phase comprises a liquid and the dispersed phase comprises a liquid, the colloidal composition may be known as a colloidal emulsion. A colloidal emulsion may also include solid components, such as cellulose microparticles. The cellulose microparticles may be dispersed in the emulsion, and so may still be known as a dispersed phase. The cellulose microparticles are preferably present at the interface of the dispersed liquid phase and the continuous phase. In this way, the cellulose microparticles act as an emulsifier for the emulsion.

[0093] The colloidal gel or the colloidal emulsion has a flow index n of < 1 at NTP. Preferably, the colloidal gel or the colloidal emulsion comprises a cellulose microparticle population CMPXat a concentration of 1 to 12 wt.% based on the total mass of the colloidal composition, a cellulose microparticle population CMPLs at a concentration of 5 to 20 wt.%, or a cellulose microparticle population CMPZat a concentration of 10 to 20 wt.% or a mixture thereof.

[0094] The continuous phase is a liquid. In some embodiments, the amount of liquid compared to the total mass of the final colloidal composition is from 70 to 95 wt.% of the colloidal composition, based on the total mass of the colloidal composition. Preferably, the liquid is present at from 80 to 90 wt.%, more preferably from 85 to 90 wt.%.

[0095] The colloidal composition may further comprise a liquid dispersed phase. The total mass of the liquid in the continuous phase and the liquid dispersed phase may be from 70 to 95 wt.% of the colloidal composition, based on the total mass of the colloidal composition. Preferably, the liquid is present at from 80 to 90 wt.%, more preferably from 85 to 90 wt.%.

[0096] Cellulose Microparticles

[0097] The dispersed phase comprises cellulose microparticles.

[0098] The cellulose microparticles may provide opacity to the colloidal composition. The cellulose microparticles may be adapted to provide opacity to the colloidal composition. Thus, the cellulose microparticles may function as an opacifier.

[0099] The cellulose microparticles may modify the rheological properties of the colloidal composition. The cellulose microparticles may be adapted to modify the rheological properties of the colloidal composition. Thus, the cellulose microparticles may function as a rheology modifier.

[0100] The cellulose microparticles may assist in emulsification to the colloidal composition. The cellulose microparticles may be adapted to assist in emulsification to the colloidal composition. Thus, the cellulose microparticles may function as an emulsifier.

[0101] The cellulose microparticles may provide opacity and modify the rheological properties to the colloidal composition. The cellulose microparticles may be adapted to provide opacity and modify the rheological properties to the colloidal composition Thus, the cellulose microparticles may function as an opacifier and rheology modifier. The cellulose microparticles may provide opacity, modify the rheological properties and assist in emulsification to the colloidal composition. The cellulose microparticles may be adapted to provide opacity, modify the rheological properties and assist in emulsification to the colloidal composition. Thus, the cellulose microparticles may function as an opacifier, rheology modifier and emulsifier.

[0102] Particle characterization

[0103] The cellulose microparticles have a mean average particle length of from 0.1 to 20 pm, a mean average particle width from 0.05 to 1.3 pm, and a maximum thickness not exceeding 0.2 pm determined by scanning electron microscopy; and an aspect ratio of length / width of 1 to 25.

[0104] Preferably, the cellulose microparticles have a mean average particle length of from 0.1 to

[0105] 12 pm, more preferably 1 to 7 pm, a mean average particle width from 0.05 to 0.5 pm, and a maximum thickness not exceeding 0.2 pm determined by scanning electron microscopy and an aspect ratio of length / width of 1 to 25.

[0106] In some embodiments the dispersed phase comprises a first portion of cellulose microparticles having a mean average particle length of from 1 to 7 pm, and a second portion of cellulose microparticles have a mean average particle length of 1 pm or less or 7 pm or more and the mean width, maximum thickness, and aspect ratio are the same as indicated above.

[0107] In some embodiments the first portion of cellulose microparticles (having a mean average particle length of from 1 to 7 pm) and the second portion of cellulose microparticles (having a mean average particle length of 1 pm or less or 7 pm or more) are present at a weight ratio of 70:30 to 30:70, such as 60:40 to 40:60, such as about 50:50.

[0108] In some embodiments the cellulose microparticles have a mean average particle length of from

[0109] 13 to 20 pm, a mean average particle width of from 0.5 to 0.8 pm and a maximum thickness not exceeding 0.2 pm determined by scanning electron microscopy.

[0110] Cellulose microparticles of the dimensions disclosed herein provide for excellent scattering of I R, UV and Visible light. Colour emanates from the interaction of light waves with the electrons in molecules comprising an object. Structural colour, on the other hand, is colour by reflection off a specified geometry, and hence is permanent for as long as the geometry of the identified material is unchanged.

[0111] White colour is obtained through appropriate light scattering off a specific particle, dependent on the refractive index, which is a material-dependent property. Titanium dioxide, TiO2, for instance, has a refractive index of 2.87 at 632.8 nm. All polymeric materials, including cellulose, have lower refractive indices than such metal oxides. Thus, to produce a white colour using cellulose, cellulose microparticles of a specific geometry that permits efficient light scattering are used. The cellulose microparticles used in the present invention have the required geometry and morphology to efficiently scatter I R, UV and / or visible light.

[0112] The length of the particle is typically the longest lateral dimension. The lateral dimension is the dimension observable when viewing a particle in plan view. The particles in plan view appear to be two dimensional. For example, if the particle is measured from a top down (or plan) image, then length is the longest dimension measurable from the top down image of the particle.

[0113] The length, the width and the thickness of the particles may be measured using standard techniques. For example, scanning electron microscope (SEM) may be used. Suitable systems include a Mira3 FEG-SEM system (TESCAN) operated at 30 kV and a working distance of 5 mm. The length and the width of the microparticles may then be analysed by Imaged. Within the context of the present invention, the length, the width and the thickness of the particles is measured using SEM. The aspect ratio of the particles is then calculated by dividing the mean length by the mean width of the particles. mean length aspect ratio = - — — mean width

[0114] The length and width of the microparticles are determined by taking multiple measurements, typically ranging from 100 to 1 ,000. The length or the width is the mean average value of the respective measurements taken. The mean average is a number average. By calculating a mean average value for these values, the effect of anomalous values is reduced, and the representative length and / or width of the particle is indicated.

[0115] This particle length of the cellulose microparticle provides the appropriate physical dimensions to scatter light efficiently in the visible range and, gives rise to producing white colour in coatings. The particle lengths can also be used to control the flow properties of suspensions and can therefore be used to tune the rheological properties of the coating composition and coatings.

[0116] Typically, the length of the particles gives a particle length distribution having a log-normal distribution. Generally, the particles have a monomodal particle length distribution, which has only one peak or maxima in the particle length distribution. The peak or maximum of the monomodal distribution corresponds to the median average particle diameter by number for all particles in the distribution.

[0117] In some embodiments, the length of the particles gives a multimodal particle length distribution, which has two or more peak or maxima in the particle length distribution. In other embodiments, the length of the particles gives a bimodal particle length distribution, which has exactly two peaks or maxima in the particle length distribution. In other embodiment, the length of the particles gives a trimodal particle length distribution, which has exactly three peaks or maxima in the particle length distribution.

[0118] The cellulose microparticle is typically a primary particle, i.e. a single, distinct entity. That is, the cellulose microparticle is not an agglomeration of smaller particles. It retains its individual identity and properties.

[0119] Herein, the dimensions of the cellulose microparticles refers to the separately divisible particle. In other words, where the particles are provided as primary particles then the dimensions refer to the primary particles.

[0120] The cellulose microparticles have excellent optical properties. The cellulose microparticles scatter incident light. In particular, the cellulose microparticles can provide high reflectance and low transmittance. As result, the cellulose microparticles provide good opacity.

[0121] The optical properties of the particles can be measured using standard techniques, such as using a light source coupled with a spectrometer and an integrating sphere. The signal can be normalized with respect to the intensity in the absence of sample. Typically, a white diffuser standard is used, such as a Labsphere SRS-99-010. The background can be recorded when no light is applied, and the background noise can be subtracted from the measurements. The optical properties are measured in the visible range (e.g., from 400 nm to 800 nm). Typically, the optical properties are measured in air. Transmittance may be measured, and reflectance calculated from the obtained transmittance values assuming that there is no absorption by the particles. Typically, five spectra were taken for each sample and averaged.

[0122] In some embodiments the total transmittance and reflectance measurements were performed with an integrating sphere (Labsphere). A light source (Ocean Optics HPX-2000) was coupled into an optical fibre (600 pmThorlabs FC-UV100-2-SR) via a collimator (Thorlabs) and the signal was collected by a spectrometer (Avantes HS2048), as shown in Figure 8 (T-, and T2). The signal was normalized with respect to the intensity when no sample was mounted. The background was recorded when no light was applied. The range of wavelengths was between 400 and 700 nm. Five spectra were taken for each sample and averaged to reduce the signal- to-noise ratio. Each spectrum was recorded using an integration time equal to 3 s.

[0123] L* (45 / 0) refers to an incidence angle of 45° to the normal of the surface and a reflectance angle at 0° to the normal of the surface. The measurement is taken for a 0.1 wt.% CMP suspension in a 1 cm cuvette.

[0124] In some embodiments, the cellulose microparticles have a L* (4570°) of 38 or more, preferably from 38 to 42, wherein L* (4570°) is a CEILAB colour-space coordinate measured for a 1 wt.% suspension of the cellulose microparticles in water. If the suspension concentration is 2 wt.% then the L*(45 / 0) should be around 52. The relationship is not linear, and these are experimentally validated numbers.

[0125] In some embodiments, the cellulose microparticles have a reflectance of 50% or more, preferably 55% or more, more preferably 60% or more of incoming light at a wavelength of from 400 to 700 nm, wherein reflectance is measured for a 1 wt.% suspension of the cellulose microparticles in water.

[0126] The cellulose microparticle may be prepared by acid hydrolysis. During acid hydrolysis, it is thought that the cellulose chain backbone of the cellulose microparticle is modified at the molecular level to provide colloidal stability to the cellulose microparticle. For example, sulfuric acid hydrolysis is thought to be provided the cellulose chains with sulfate half ester groups.

[0127] Cellulose microparticles typically incorporate 20 to 400 mmol / kg, preferably 40-250 mmol / kg, more preferably 40 to 60 mmol / kg of half-ester sulfate groups on their surfaces as a result of the acid hydrolysis process. The mass contribution of the half-ester group (e.g., -SO3H) corresponds to 5 wt.% or less based on the total mass of the cellulose microparticles, preferably 1 wt.% or less.

[0128] The density of the half-ester sulfate groups is measured by conductometric titration, such as according to ISO 21400:2018.

[0129] The half-ester group may contribute to the anionic charge on the cellulose microparticles. Thus, in some embodiments, the cellulose microparticles are anionic. In some embodiments, the cellulose microparticles are surface modified with anionic sulfate half ester groups.

[0130] The cellulose microparticles have an anionic charge density of from 50 mmol / kg or more, preferably 100 mmol / kg or more, more preferably 150 mmol / kg or more. The cellulose microparticles may have an anionic charge density of from 40 to 60 mmol / kg.

[0131] The cellulose microparticles may be further modified to increase the negative charge. For example, the cellulose microparticles may be modified by reaction with sulfamic acid as part of a reactive deep eutectic solvent. Urea can be used to increase the reactivity of sulfamic acid. The highly sulphated cellulose nanoparticles can then be mixed in the manner described in this patent application with the family of surfactants outlined herein.

[0132] A post-treatment may increase the anionic charge density to reach 2000 mmol / kg. This can be useful for highly charged mixtures to ensure stability and maintain the same functionality.

[0133] The cellulose microparticles may have an anionic charge density of 2000 mmol / kg or less. Cellulose microparticles typically have 40-60 mmol / kg half-ester sulfate groups on their surfaces because of the acid hydrolysis process. They can be tailored to have higher sulfation levels using a suitable post-treatment protocol. Such a post-treatment may include treatment with sulfamic acid. Urea may be added to increase the reactivity of sulfamic acid.

[0134] Alternatively, the cellulose microparticles can be dispersed in a suitable sulfuric acid concentration of about 20-50 wt%, for a period ranging from 30 to 240 min at temperatures not exceeding 50 °C. Additional charge (sulfates) can be imparted on the surfaces of the cellulose microparticles in this way.

[0135] The charge density of the particles is measured by conductometric titration, such as according to ISO 21400:2018.

[0136] The charge may depend on the pH of the solution in which the particles are present. The charge of the particles is determined at the pH of the coating composition or opacifier in the invention. This is typically a pH of 7.

[0137] It is also possible that the cellulose microparticles are prepared without any surface change. They will maintain the same optical and rheological behaviour.

[0138] Preparation of Cellulose Microparticles

[0139] Example 1 [CMPZ]

[0140] The cellulose microparticles used in the present invention may be obtained using the methods described in WO2023 / 135261. For example, the particles can be prepared as follows: Cellulose microcrystalline powder (1g) was hydrolysed with sulfuric acid (50 wt. %, 60 mL) for 5 hours at 50 °C, and then quenched by adding 300 mL milli-Q water. The acid supernatant was removed by centrifugation. The hydrolysed cellulose particles were dispersed by adding 100 mL milli-Q water and then centrifuged. This process was repeated three times to remove most of the acid and the suspension of hydrolysed cellulose particles were dialyzed against milli-Q water (MWCO 12-14 kDa) for one week while changing water two times a day. The dialyzed suspension of hydrolysed cellulose particles (0.5% wt, 30 mL) was tip sonicated in an ice bath (Fisher brand ultrasonic disintegrator 500 W, 20 kHz, tip diameter 12.7 mm, amplitude 30%, 2 seconds on and 2 seconds off). The suspension was centrifuged at 2000 rpm for five minutes, and then the supernatant was collected and centrifuged at 3000 rpm for five minutes to get the cellulose nanoparticles.

[0141] Example 2 [CMP-LS]

[0142] Cellulose microparticles with a slightly smaller width and length than Example 1 , and a slightly higher aspect ratio than Example 1 , were obtained by adjusting the concentration of sulfuric acid and temperature. The CMPs of Example 2 were obtained using the same method as for Example 1 , except the cellulose microcrystalline powder (1g) was hydrolysed with sulfuric acid (55 wt. %, 60 mL) for 5 hours at 60 °C.

[0143] Comparative Example 3 [CMPX]

[0144] Cellulose microparticles with a much smaller width and length than Examples 1 and 2 were prepared by adjusting the concentration of sulfuric acid, reaction time and temperature, and by using an alternative source of cellulose.

[0145] The CMPs of Comparative Example 3 were obtained using the same method as for Example 1 , except that the cellulose microcrystalline powder was replaced by cellulose filter paper (Whatman No. 1). The cellulose filter paper (Whatman No. 1) was hydrolysed with sulfuric acid (55 wt. %, 60 mL) for 0.5 hours at 50 °C.

[0146] In general, the cellulose microparticles may be obtained using sulphuric acid hydrolysis of cellulose-containing biomass, e.g., wood pulp fibres, followed by purification and size separation to produce particles suspended in water and can subsequently be dried using spray or freeze drying.

[0147] Typically, the cellulose microparticles are obtained via sulfuric acid hydrolysis of biomass using particular acid concentration, temperature, and reaction time to control the morphology and physical dimensions.

[0148] This stable CMP-containing colloidal suspension can be incorporated into other mixtures or blends to form a stable system for a variety of end-use applications spanning coatings, paints, cosmetic creams, and personal care products - such as shampoo, sunscreen, and body lotion. Pristine cellulosic microparticles form oil-in-water (o / w) emulsions owing to their hydrophilic nature. Different surface treatments, such as silylation or esterification, can be used to render cellulose hydrophobic in order to prepare water-in-oil (w / o) emulsions or oil-water-oil (o / w / o) double emulsions.

[0149] Generally, the cellulose microparticles are prepared by a method comprising:

[0150] (a) adding acid to a cellulose material to hydrolyse the cellulose microparticles;

[0151] (b) removing the acid from the hydrolysed cellulose microparticles; and

[0152] (c) isolating a particular size of hydrolysed cellulose microparticles.

[0153] The step (a) of “Adding acid to the cellulose microparticles” may be referred to as the hydrolysing step. The step (b) of “removing acid from the hydrolysed cellulose microparticles” may be referred to as the washing step. The step (c) of “isolating a particular size of hydrolysed cellulose microparticles” may be referred to as the fractioning step. The application also provides a method of preparing a cellulose microparticle, the method comprising:

[0154] (a) hydrolysing a cellulose material to provide hydrolysed cellulose microparticles;

[0155] (b) washing the hydrolysed cellulose microparticles; and

[0156] (c) fractioning a suspension of the hydrolysed cellulose microparticles.

[0157] The method is suitable for preparing the cellulose microparticles for use in the coating composition and opacifier of the invention. However, cellulose microparticles prepared by alternative methods may also be used, provided such particles have properties required by the opacifier.

[0158] The conditions used for hydrolysis step, washing step, and fractioning step can be adjusted to prepare a cellulose microparticle having the size and shape described herein.

[0159] Any suitable cellulose material may be used. Suitable cellulose material may be prepared from bacterial, vegetal or animal sources (e.g. chitin), including plant-based and biomass source such as cotton and wood along with subsequent processed products such as paper, filter-paper cotton linters, cellulose powder and wood pulp.

[0160] Preferably, the cellulose material is a microcrystalline cellulose powder. Suitable microcrystalline cellulose powder is commercially available (e.g. from SERVA Electrophoresis GmbH)

[0161] The cellulose material may be provided in the form of a suspension. Preferably a microcrystalline cellulose powder is dispersed in water to form an aqueous suspension.

[0162] A suspension is a heterogeneous mixture of a fluid that contains solid particles that are typically sufficiently large for sedimentation to occur if the suspension is left undisturbed for extended periods of time. The cellulose microparticles are suspended in the liquid. The suspension may be mixed, for example by sonification, to avoid settling of the cellulose microparticles.

[0163] Any suspension medium suitable for holding cellulose material may be used. Suitable suspension media are typically aqueous solvents, such as water. Acidic and basic media may be used. Typically, acid is used, and suitable acids are set out below.

[0164] The method of preparing a cellulose microparticle comprises hydrolysing a cellulose material to provide hydrolysed cellulose microparticles. This may be known as the hydrolysis step. The hydrolysis step takes place before the washing step.

[0165] The hydrolysis is typically carried out in aqueous solvent (e.g. water).

[0166] In the hydrolysis step, the cellulose material is typically hydrolysed with an acid. Acid hydrolysis is a hydrolysis process in which a protic acid is used to catalyse the cleavage of a chemical bond via a substitution reaction with the addition of water. During acid hydrolysis, it is also proposed that the cellulose chain backbone of the cellulose microparticle is modified at the molecular level to provide colloidal stability to the cellulose microparticle. For example, sulfuric acid hydrolysis is thought to modify the cellulose chains with sulfate half ester groups.

[0167] The hydrolysis step may comprise contacting the cellulose material, such as the suspension of cellulose material, with acid.

[0168] The acid may be an organic acid or an inorganic acid. Typically, the acid is an inorganic acid (a mineral acid). Suitable inorganic acids include hydrobromic acid (HBr), hydrochloric acid (HCI), hydrofluoric acid (HF), hydroiodic acid (HI), nitric acid (HNO3), perchloric acid (HCIO4), phosphoric acid (H3PO4), sulfuric acid (H2SO4) or a combination thereof. Preferably the inorganic acid is sulfuric acid or hydrochloric acid. More preferably the inorganic acid is sulfuric acid.

[0169] Suitable organic acids include formic acid (HCOOH) and acetic acid (CH3COOH). Preferably the organic acid is formic acid.

[0170] Preferably the acid is sulfuric acid or hydrochloric acid. More preferably the acid is sulfuric acid.

[0171] The strength of an (aqueous) acid can be specified using the pH scale. Methods for determining the pH of an aqueous solution are known and include, for example, electrochemical methods (using a pH probe) and titration against an indicator compound such as universal indicator. Typically, the pH refers to the pH of the hydrolysis solution at the end of the hydrolysis step.

[0172] The acid used in the hydrolysis step is highly acidic. Typically, the acid has a pH of 1.0 or lower, preferably, 0.5 or lower, more preferably or 0.0 or lower.

[0173] The strength of the acid is proportional to the concentration of the acid. The concentration of an aqueous acid can be specified using weight percentage (wt.%).

[0174] Typically, the concentration of the acid is from 30 to 60 wt.%, preferably from 35 to 58 wt.%, more preferably from 45 to 58 wt.%, yet more preferably from 48 to 55 wt.%. The wt.% is typically calculated with water as the solvent.

[0175] The amount of acid is selected to allow a desirable quantity of cellulose material to be suspended. The amount of aqueous acid can be specified by stating the volume aqueous acid in mL per gram of cellulose material used (the ratio of acid to cellulose material).

[0176] Typically, the hydrolysis step uses a mass ratio of acid to cellulose material of 100:1 preferably 80:1 , more preferably 60:1. In addition or alternatively, the hydrolysis step may use a mass ratio of acid to cellulose material of 4: 1 , preferably 10: 1 . For example, the hydrolysis step may use a mass ratio of acid to cellulose material of from 100: 1 to 4: 1 , preferably from 80: 1 to 10: 1. A higher ratio of cellulose to acid make the process more efficient as less acid is required for the hydrolysis step and less solvent is required for the washing step.

[0177] The hydrolysis step may be performed for a sufficient time to allow a desirable quantity of cellulose material to be hydrolysed. Typically, the hydrolysis is performed for from 1 to 10 hours, preferably from 2 to 8 hours, more preferably from 3 to 7 hours, such as about 5 hours.

[0178] The hydrolysis takes place from the addition of the acid until the reaction is quenched. The reaction may be quenched by any suitable means, such as by adding water to dilute the acid, adding base to neutralise the acid, removing the acid (e.g. by washing such as by dialysis), or reducing the temperature.

[0179] The hydrolysis step may be performed at elevated temperature (above ambient temperature; approximately 25°C). Methods for providing heat during the hydrolysis step are known and include, for example, using a reaction vessel having an external heating jacket or using microwave heating.

[0180] Typically, the hydrolysis step is performed at a temperature of from 30 to 60°C, preferably from 35 to 58°C, more preferably from 48 to 55°C, such as about 50°C.

[0181] Preferably, the cellulose material is hydrolysed with 50 wt.% sulfuric acid at a temperature of about 50°C for 40 min to 180 min.

[0182] In some embodiments, in step (b) the cellulose material is hydrolysed with 50 wt.% sulfuric acid 2 hours at a temperature of 50°C. In some embodiments, in step (b) the cellulose material is hydrolysed with 55 wt.% sulfuric acid 1 .5 hours at a temperature of 45°C.

[0183] The hydrolysis may be stopped by quenching the acid hydrolysis. Typically, the hydrolysis is quenched by the addition of water, such as an excess of water. For example, if 60 mL of sulfuric acid is used to hydrolyse cellulose microparticles, then 300 mL of water may be added to quench the acid hydrolysis.

[0184] It is thought that using a higher concentration of acid, a higher temperature or a longer time period increases the rate of acid hydrolysis. Typically, a greater degree of hydrolysis results in a smaller cellulose microparticle length.

[0185] The hydrolysed cellulose microparticles may be collected by any suitable method. Typically, the hydrolysed cellulose microparticles are collected by centrifugation. Centrifugation can separate the hydrolysed cellulose microparticles from the acid supernatant, and optionally the water added to quench the acid hydrolysis. The supernatant can then be removed, for example using a pipette. The method of preparing a cellulose microparticle comprises: washing the hydrolysed cellulose microparticles.

[0186] This may be known as the washing step. The washing step takes place after the hydrolysis step and before the fractionation step.

[0187] The hydrolysed cellulose microparticles may be washed by adding water. The water may then be removed. Thus, the washing step may comprise contacting the hydrolysed cellulose microparticles with water.

[0188] The washing step typically quenches the hydrolysis reaction, and so ends the hydrolysis step. The washing step may dilute the acid from the cellulose microparticles, thus quenching the hydrolysis reaction.

[0189] Typically, the washing step may add sufficient water to provide a concentration of 1 wt.% of cellulose microparticles. For example, for 1 g of hydrolysed cellulose microparticles, around 100 mL of water may be added per wash. This may be repeated one or more times, preferably two or more times, more preferably three or more times to remove the acid. The washing water may then be removed by centrifugation.

[0190] Preferably, the washing step may alternatively or additionally comprise dialyzing the hydrolysed cellulose microparticles with water, such as distilled water. The dialysis may take place after washing with water as set out above. Dialysis comprises resuspending the hydrolysed cellulose microparticles in distilled water and purifying them from dissolved ions (e.g. the acid used in the hydrolysis step) by means of their unequal rates of diffusion through the pores of semipermeable (dialysis) membrane. Any suitable dialysis membrane may be used. Suitable dialysis membranes have molecular weight cut off of 12 kDa or more, such as from 12 to 40 kDa.

[0191] The distilled water may be replaced during the dialysis process. For example, the distilled water may be replaced every 12 hours during dialysis. The distilled water may be replaced 5 or more times, preferably 10 or more times.

[0192] In some embodiments, the hydrolysed cellulose material is dialyzed against distilled water for 7 days, replacing the distilled water every 12 hours.

[0193] In some embodiments, the hydrolysed cellulose material is dialyzed until the pH of the hydrolysed cellulose material has stabilized. The pH may be measured each time the distilled water is replaced during the dialysis process, such as every 12 hours. Typically, the pH of the hydrolysed cellulose material has stabilized once the pH is constant for at least two consecutive measurements, preferably four consecutive measurements, more preferably six consecutive measurements. Alternatively, the pH may be measured once per day, and the pH has stabilized once the pH is constant for at least two consecutive days, preferably three consecutive days, more preferably four consecutive days. The constant pH indicates that the acid or base has been substantially removed from the hydrolysed cellulose material. Methods for determining the pH of an aqueous solution are known, as set out above.

[0194] In some embodiments, the washing step may comprise removing the acid from the cellulose microparticles by centrifugation, washing with water and removing the water by centrifugation, and dialyzing the hydrolysed cellulose material.

[0195] The method of preparing a cellulose microparticle comprises: fractioning a suspension of the hydrolysed cellulose microparticles.

[0196] This may be known as the fractionation step. The fractionation step takes place after the washing step.

[0197] The hydrolysed cellulose microparticles may be fractioned by any suitable method. Suitable methods include filtration and centrifugation. Preferably the hydrolysed cellulose microparticles are separated from the liquid by differential centrifugation.

[0198] The fractioning takes place on a suspension of the hydrolysed cellulose microparticles. For the fractioning step, the suspension of hydrolysed cellulose microparticles is typically a suspension of individual cellulose microparticles. That is, the hydrolysed cellulose microparticles are not significantly aggregated, or aggregated, in the suspension of hydrolysed cellulose microparticles. This is beneficial, since it avoids the fractioning step removing aggregations of cellulose microparticles having the desired size and shape. This improves the yield of cellulose microparticles having the desired size and shape.

[0199] The fractioning (such as centrifugation) is carried out on a suspension of the cellulose microparticles. Typically, a suspension of the cellulose microparticles in water, such as Millipore water, is used. Any suitable concentration may be used. Suitable concentrations comprise from 0.1 wt% to 5.0 wt% cellulose microparticles, such as 0.2 wt% to 2.0 wt%, such as 0.2 wt% to 1.0 wt%. Preferably, the concentration of hydrolysed cellulose microparticles is 0.5 wt%.

[0200] The suspension of the cellulose microparticles may be prepared by any suitable method. The hydrolysed cellulose microparticles may be mixed or agitated prior to separation. Typically, the hydrolysed cellulose microparticles are sonicated prior to separation, such as by tip sonication or ultrasonification.

[0201] In some embodiments, a 30 mL suspension with 0.5 wt% particle concentration of the hydrolysed cellulose microparticles is ultrasonicated at an Amplitude of 30 % for 2 min in 2s on 2s off cycles. Ultrasonification may be performed using any suitable apparatus, such as a Fisherbrand Ultrasonic disintegrator, 20 kHz, tip diameter 12.7 mm. Typically, the differential centrifugation comprises a first centrifugation and a second centrifugation. The first centrifugation is at a different speed than the second centrifugation. The first centrifugation is at a lower speed than the second centrifugation. The second centrifugation is typically carried out on the supernatant from the first centrifugation.

[0202] The first centrifugation may be at a speed of from 1 ,000 to 3,000 rpm, preferably from 1 ,500 to 2500 rpm, more preferably from 1 ,800 to 2200 rpm, such as around 2,000 rpm.

[0203] The second centrifugation may be at a speed of from 2,000 to 4,000 rpm, preferably from 2500 to 3500 rpm, more preferably from 2,800 to 3,200 rpm, such as around 3,000 rpm.

[0204] Centrifugation speed may also be quantified using relative centrifugal force (RCF). RCF is a measure of the force acting on the particles during centrifugation. RCF is generally expressed as multiples of the earth's gravitational field (g). RCF may be calculated by the following equation, where radius (cm) is the distance from the centre of the centrifuge to the extremity of the sample and rotation speed (rotation per minute) is the rotation speed of the centrifuge. The radius is typically about 15 cm.

[0205] RCF = 11.2 x radius x (rotation speed / 1000)2.

[0206] The RCF of the first centrifugation may be different to the second centrifugation. The RCF of the first centrifugation may be less than the second centrifugation.

[0207] The first centrifugation may be at a RCF of from 50 to 1 ,500, preferably 150 to 1 ,500, more preferably from 300 to 1 ,100, yet more preferably from 500 to 900, even more preferably from 600 to 800. The first centrifugation may be at a RCF of about 650.

[0208] The second centrifugation may be at a RCF of from 600 to 2,600, preferably from 1 ,000 to 2,000, more preferably from 1 ,300 to 1 ,700, yet more preferably from 1 ,400 to 1 ,600. The second centrifugation may be at a RCF of about 1 ,500.

[0209] The first centrifugation may be at a RCF of from 168 to 1 ,512, preferably from 378 to 1 ,150, more preferably from 544 to 813. The first centrifugation may be at a RCF of about 672.

[0210] The second centrifugation may be at a RCF of from 671 to 2,688, preferably from 1 ,050 to 3,058, more preferably from 1 ,317 to 1 ,720. The second centrifugation may be at a RCF of about 1 ,512.

[0211] The first centrifugation may be carried out for a time of from 1 to 20 minutes, preferably from 2 to 15 minutes, preferably from 3 to 10 minutes, more preferably from 4 to 6 minutes, such as around 5 minutes. The second centrifugation may be carried out for a time of from 1 to 20 minutes, preferably from 2 to 15 minutes, preferably from 3 to 10 minutes, more preferably from 4 to 6 minutes, such as around 5 minutes.

[0212] Preferably the first centrifugation is carried out at 2000 rpm for five minutes and the second centrifugation is carried out at 3000 rpm for five minutes, and the second centrifugation is carried out on the supernatant from the first centrifugation.

[0213] It is thought that a two-step differential centrifuging process results in a narrower particle length distribution for the cellulose microparticles. The first centrifugation at a lower speed sediments the larger cellulose microparticles. The supernatant from the first centrifugation thus still includes the desired size particles and smaller particles. This supernatant from the first centrifugation is then centrifuged again at a high speed so as to sediment the desired particles. The smaller particles remain in the supernatant from the second centrifugation. As a result, the sedimented particles from the second centrifugation do not include a large proportion of larger or smaller particles, so the particle length distribution is narrower.

[0214] The sedimented cellulose microparticles may be collected by any suitable method. Typically, the cellulose microparticles are collected by filtration.

[0215] The cellulose microparticles are typically collected as a slurry or a suspension. The slurry or suspension may be with water, ethanol or acetone. Preferably, the slurry or suspension is with water.

[0216] The sedimented larger cellulose microparticles from the sediment fraction of the first centrifugation may be recirculated and reprocessed by repeating the sonication and fractionation steps described above. This may improve the yield of the fraction containing the desired particle lengths.

[0217] The method of preparing a cellulose microparticle may also comprise: drying the fractionated cellulose microparticles.

[0218] This may be known as the drying step. The drying step typically takes place after the fractionation step. The drying step is typically carried out on the slurry or suspension of cellulose microparticles prepared by the fractionation step.

[0219] Typically, the drying step comprises removing a solvent from the fractionated cellulose microparticles. The drying step typically comprises removing water, ethanol or acetone from the fractionated cellulose microparticles. Preferably, the drying step comprises removing water from the fractionated cellulose microparticles.

[0220] The fractionated cellulose microparticles may be dried by any suitable method. Suitable methods include evaporation, freeze-drying, spray-drying or spray-freeze drying. Preferably, the method is freeze-drying, spray-drying or spray-freeze drying. More preferably, the method is freeze-drying.

[0221] Any suitable freeze-drying apparatus may be used. Suitable freeze-drying apparatus include Scanvac and Coolsafe freeze driers by LaboGene A / S, or VirTis freeze dryer by SP Scientific.

[0222] Any suitable spray-drying apparatus may be used. Suitable spray-drying apparatus include a PrecisionCoat spray coater by Specialty Coating Systems (SCS).

[0223] Any suitable spray-freeze drying apparatus may be used. Suitable spray-freeze drying apparatus include a PrecisionCoat spray coater by SCS and Scanvac and Coolsafe freeze driers by LaboGene A / S.

[0224] Typically, the drying step provides a dry powder of cellulose microparticles. Freeze drying or spray-drying may provide a dry powder of cellulose microparticles. Preferably, freeze drying provides a dry powder of cellulose microparticles.

[0225] The drying step may provide clusters of cellulose microparticles. Preferably, spray drying or spray-freeze drying provides clusters of cellulose microparticles.

[0226] The shape and size of the dried cellulose microparticles are generally the same as the cellulose microparticles before drying.

[0227] The dry powder of cellulose microparticles is useful for many applications. Several applications require the cellulose microparticles to be provided as a dry powder, such that the cellulose microparticles can be redispersed in different media.

[0228] The dry powder also minimizes storage and transportation cost due to a reduced mass of solvent. The dry powder also inhibits fungal and bacterial growth in the cellulose microparticles. The dry powder further allows the cellulose microparticles to be redispersed in a different polarity solvent to that used for the preparation of the cellulose microparticles. For example, if the cellulose microparticles are prepared in a polar solvent (e.g. water), the dry powder can be redispersed in a non-polar solvent (e.g. organic solvent). The dry powder may also undergo further chemical modifications. The dry powder may be redispersed in an organic solvent prior to further chemical modifications.

[0229] Optionally, the method of preparing cellulose microparticles may further comprise: modifying the surface of the cellulose microparticles.

[0230] This may be known as the surface modification step. Typically, the surface modification step is carried out after fractionation of the cellulose microparticles. The surface modification may be carried out on any cellulose microparticles. Typically, the surface modification is carried out on the cellulose microparticles obtained in the fractionation step or the drying step described above.

[0231] The surface modification step typically comprises transforming a hydroxyl group on the surface of the cellulose microparticle into a different functional group. The hydroxyl group is preferably converted into an ester (esterification) or an ether (etherification). For example, the hydroxyl groups may be converted into an ether group, such as a silylether group.

[0232] In some embodiments, the surface modification step comprises contacting the cellulose microparticles with an esterification agent or an etherification agent. Preferably, the surface modification step comprises contacting the cellulose microparticles with a hydrophobic agent.

[0233] Any suitable reagent may be used to perform the surface modification. Preferably, the reagent is an esterification reagent or an etherification reagent. Preferably, the surface modification step involves treating the cellulose microparticle with anhydrite, acyl chloride or epoxy bearing reagents. The hydrophobic agent includes any suitable hydrophobic agent, such as trimethylchlorosilane (TCMS) and chlorotrimethoxysilane. Preferably the hydrophobic agent is TCMS.

[0234] The reagent may be liquid or a vapour (gas). Typically, the reagent agent is a vapour.

[0235] The surface modification may be carried out in a solution or in a gas phase reaction. The solution may be an aqueous solution or a non-aqueous solution. The surface modification may be carried out under an inert atmosphere, such as a nitrogen or an argon atmosphere.

[0236] Emulsions

[0237] In some embodiments the colloidal composition is a colloidal emulsion. Within the context of the present invention the term “colloidal emulsion” stands for a system where the continuous phase comprises a liquid and the dispersed phase comprises a liquid.

[0238] The cellulose microparticles may be considered part of the dispersed phase. The dispersed phase may comprise a liquid dispersed phase and the cellulose microparticles.

[0239] The cellulose microparticles are preferably present at the interface of the dispersed liquid phase and the continuous phase. In this way, the cellulose microparticles act as an emulsifier for the emulsion.

[0240] Accordingly, in a specific aspect of the invention there is provided a colloidal emulsion comprising a continuous phase and a dispersed phase, wherein the continuous phase is a liquid; wherein the dispersed phase comprises a liquid dispersed phase and cellulose microparticles, wherein at least a portion of the cellulose microparticles are at the interface of the continuous phase and the liquid dispersed phase, wherein the cellulose microparticles have a mean average particle length of from 0.1 to 20 pma mean average particle width from 0.05 to 1.3 pm, and a maximum thickness not exceeding 0.2 pm determined by scanning electron microscopy,; and an aspect ratio of length / width of 1 : 25; and wherein the colloidal composition has a flow index n of < 1 at NTP.

[0241] Preferably, the cellulose microparticles in said colloidal emulsion have a mean average particle length of from 0.1 to 12 pm, a mean average particle width from 0.05 to 0.5 pm, and a maximum thickness not exceeding 0.2 pm, even more preferably a mean average particle length of from 1 to 7 pm, a mean average particle width of from 0.05 to 0.35 pm and a maximum thickness not exceeding 0.2 pm.

[0242] In some embodiments, the cellulose microparticles disperse the dispersed phase in the continuous phase. That is, the cellulose microparticles act as an emulsifier between for the dispersed phase and the continuous phase. The cellulose microparticles may act as an emulsifier by stabilising the interface between the dispersed liquid phase and the continuous phase.

[0243] In some embodiments more than 90% of the cellulose microparticles are at the interface of the continuous phase and liquid dispersed phase, preferably more than 95%. It is evident from the uniform distribution of oil droplets as well as the small oil droplet size that all of the cellulose microparticles of the composition according to the present invention are at the oil / water interface thus creating a very stable emulsion.

[0244] The colloidal emulsion may be a solid-stabilised emulsion. A solid-stabilised emulsion is also known as a Pickering emulsion. A solid-stabilised emulsion is where a solid (e.g., cellulose microparticle) is adsorbed on the interface of droplets of the dispersed phase. This has the advantage that the cellulose microparticles create a robust barrier at the oil-water interface, leading to increased stability and reduced sensitivity to changes in temperature, pH, and ionic strength. Additionally, these emulsions have improved viscosity and texture, beneficial in food and cosmetic products.

[0245] In some embodiments, the cellulose microparticles are present instead of surfactants. The colloidal composition may be substantially free of surfactants. Indeed, Fig. 11 indicates that the CMP can effectively and efficiently stablise the oil / water interface on their own without the need to use any surfactants. The uniform distribution of oil droplets and the small oil droplet size indicate that the CMPs act as good emulsifiers. The colloidal composition can be free of surfactants. In some embodiments, the cellulose microparticles are the only emulsifier in the colloidal composition. In some embodiments the colloidal composition is substantially free of additional emulsifiers, such as free of additional emulsifiers.

[0246] In some embodiments the emulsion is a medium internal phase emulsions (MIPE). Typically, a MIPE refers to the volume content the dispersed phase can accommodate, which is from 50 to 74 vol. % based on the total volume of the colloidal composition. The colloidal composition may comprise the dispersed phase at from 50 to 74 vol.% based on the total volume of the colloidal composition. This creates a structure where the dispersed phase droplets are closely packed but not excessively deformed, leading to a moderately viscous consistency.

[0247] In some embodiments the emulsion is high internal phase emulsions (HIPE). Typically, a HIPE refers to the volume content of the dispersed phase accommodating 74 vol. % or more based on the total volume of the colloidal composition. The colloidal composition may comprise the dispersed phase at 74 vol.% or more based on the total volume of the colloidal composition. This creates a structure where the dispersed phase droplets are densely packed and often deformed, leading to a highly viscous consistency.

[0248] Preferably, the colloidal emulsion is a high-internal phase emulsion, because the high volume fraction of the dispersed phase results in unique rheological properties, such as high viscosity and gel-like behavior, which can be advantageous for applications requiring stability and controlled release. Additionally, the densely packed and often deformed droplets in HIPEs create a robust structure that enhances the mechanical strength and durability of the resulting material, making it ideal for uses in areas like polymer foams, cosmetics, and biomedical scaffolds.

[0249] The emulsion may include any suitable continuous phase. The continuous phase is a liquid. In some embodiments the continuous phase is water or an organic solvent. The organic solvent may be ethanol, acetone, ethyl acetate or limonene. The organic solvent may be a renewablebased solvents, such as limonene. Preferably the dispersed phase is water.

[0250] The continuous phase may be 2-propanol, 1 ,2-dichloroethane, 1 ,4-dioxane, 18-crown-6, 2-propanol, 2-ethoxyethanol, acetic acid, acetone, acetonitrile, ammonia, benzene, n-butanol, n-butyl acetate, chloroform, cyclohexane, dichloromethane, diethyl ether, diglyme, dimethyl formamide, Dimethyl sulfoxide, DME, ethane, ethanol, ethyl acetate, ethylene, ethylene glycol, formic acid, glycerine, heptane, hexane, hexamethylbenzene, HMDSO, HMPA, Hydrogen, Imidazole, isobutanol, isopropyl alcohol, methane, methanol, n-hexane, nitromethane n- pentane, propane, propylene, propylene carvonate, pyridine, pyrrole, pyrrolidine, silicone grease, tert -butyl alcohol, tetrahydrofuran, toluene, triethylamine, water, white spirit and xylene or a mixture thereof.

[0251] The emulsion may include any suitable dispersed liquid phase. The dispersed liquid phase is a liquid which is different to the continuous phase. Typically, the dispersed liquid phase is a liquid which is immiscible in the continuous phase. The dispersed liquid phase may be 2-propanol, 1 ,2-dichloroethane, 1 ,4-dioxane, 18-crown-6, 2-propanol, 2-ethoxyethanol, acetic acid, acetone, acetonitrile, ammonia, benzene, n-butanol, n-butyl acetate, chloroform, cyclohexane, dichloromethane, diethyl ether, diglyme, dimethyl formamide, Dimethyl sulfoxide, DME, ethane, ethanol, ethyl acetate, ethylene, ethylene glycol, formic acid, glycerine, heptane, hexane, hexamethylbenzene, HMDSO, HMPA, Hydrogen, Imidazole, isobutanol, isopropyl alcohol, methane, methanol, n-hexane, nitromethane n- pentane, propane, propylene, propylene carvonate, pyridine, pyrrole, pyrrolidine, silicone grease, tert -butyl alcohol, tetrahydrofuran, toluene, triethylamine, water, white spirit and xylene or a mixture thereof.

[0252] In some embodiments the continuous phase is a hydrophobic liquid and the dispersed liquid phase is a hydrophilic liquid. For example, the emulsion may be a water-in-oil emulsion.

[0253] In some embodiments the continuous phase is a hydrophilic liquid and the dispersed liquid phase is a hydrophobic liquid. For example, the emulsion may be an oil-in-water emulsion.

[0254] In such embodiments, the hydrophilic liquid may be water or glycerine.

[0255] In such embodiments, the hydrophobic liquid may be an organic solvent, such as paraffin oil.

[0256] In some embodiments the continuous phase is water and / or glycerine, and the dispersed liquid phase is a hydrophobic liquid, such as paraffin oil.

[0257] In some embodiments the continuous phase is paraffin oil, and the dispersed liquid phase is a hydrophilic liquid, such as water and / or glycerine.

[0258] The emulsion may be is a double emulsion. A double emulsion is typically an emulsion where a first dispersed liquid is dispersed in a continuous phase, and a second dispersed liquid is dispersed within the first dispersed liquid. In other words, droplets of the first dispersed liquid comprise droplets of the second dispersed liquid.

[0259] In some embodiments the ratio of the dispersed phase to the continuous phase is from 20:80 to 80:20 by weight, preferably from 30:70 to 70:30, more preferably from 40:60 to 60:40.

[0260] In some embodiments the ratio of a hydrophobic continuous phase to a hydrophilic dispersed liquid phase is from 20:80 to 80:20 by weight, preferably from 30:70 to 70:30, more preferably from 40:60 to 60:40.

[0261] In some embodiments the ratio of a hydrophilic continuous phase to a hydrophobic dispersed liquid phase is from 20:80 to 80:20 by weight, preferably from 30:70 to 70:30, more preferably from 40:60 to 60:40. Gefs

[0262] In some embodiments the colloidal composition is a colloidal gel. Within the context of the present invention, the term "colloidal gel" stands for a composition wherein the continuous phase comprises a liquid and the dispersed phase comprises solid colloidal particles that assemble to form into a three-dimensional network, resulting in a semi-solid structure with unique rheological properties. Due to the specific particle size (length, width, thickness and aspect ratio) and shape of the cellulose microparticles, this three-dimensional network is highly stable. The cellulose microparticles form a hydrogen-bonded solid, where the cellulose surface hydroxyl groups interact to stabilize the macroscopic gel structure.

[0263] The cellulose microparticles may be considered part of the dispersed phase. Thus, the dispersed phase may comprise cellulose microparticles, such as consist of cellulose microparticles.

[0264] The cellulose microparticles may be arranged as a gel network, and the continuous phase surrounds the gel network of cellulose microparticles. These gels are effective structural materials because the dispersed cellulose microparticles create an inter-percolated network within the solvent. In essence, the particles interconnect and interlock, forming a web-like structure throughout the solvent. This interconnected network endows the gel with stability and mechanical strength, enabling it to maintain its shape and resist deformation under stress. The inter-percolated network is vital for the gel's properties, ensuring a uniform distribution of the dispersed phase and enhancing the gel's overall integrity and functionality.

[0265] Accordingly, in a specific aspect of the invention there is provided a colloidal gel comprising a continuous phase and a dispersed phase, wherein the continuous phase is a liquid; wherein the dispersed phase comprises cellulose microparticles, wherein the cellulose microparticles are dispersed in the continuous phase, wherein the cellulose microparticles have a mean average particle length of from 0.1 to 20 pm, preferably 0.1 to 12 pm, more preferably 1 to 7 my, a mean average particle width from 0.05 to 1.3 pm, and a maximum thickness not exceeding 0.2 pm determined by scanning electron microscopy; and an aspect ratio of length / width of 1 to 25, and wherein the colloidal composition has a flow index n of < 1 determined by a rheometer at NTP (normal temperature (25°C) and pressure (1 atm)).

[0266] Preferably, the cellulose microparticles in said colloidal emulsion have a mean average particle length of from 0.1 to 12 pm, a mean average particle width from 0.05 to 0.5 pm, and a maximum thickness not exceeding 0.2 pm, even more preferably a mean average particle length of from 1 to 7 pm, a mean average particle width of from 0.05 to 0.35 pm and a maximum thickness not exceeding 0.2 pm. The emulsion may include any suitable continuous phase. The continuous phase is a liquid. In some embodiments the continuous phase is water or an organic solvent. The organic solvent may be ethanol, acetone, ethyl acetate or limonene. The organic solvent may be a renewablebased solvents, such as limonene. Preferably the continuous phase is water.

[0267] The continuous phase may be 2-propanol, 1 ,2-dichloroethane, 1 ,4-dioxane, 18-crown-6, 2-propanol, 2-ethoxyethanol, acetic acid, acetone, acetonitrile, ammonia, benzene, n-butanol, n-butyl acetate, chloroform, cyclohexane, dichloromethane, diethyl ether, diglyme, dimethyl formamide, Dimethyl sulfoxide, DME, ethane, ethanol, ethyl acetate, ethylene, ethylene glycol, formic acid, glycerine, heptane, hexane, hexamethylbenzene, HMDSO, HMPA, Hydrogen, Imidazole, isobutanol, isopropyl alcohol, methane, methanol, n-hexane, nitromethane n- pentane, propane, propylene, propylene carvonate, pyridine, pyrrole, pyrrolidine, silicone grease, tert -butyl alcohol, tetrahydrofuran, toluene, triethylamine, water, white spirit and xylene or a mixture thereof.

[0268] The cellulose microparticles may impart rheological properties to the gel. In particular, the type and amount of cellulose microparticles may affect the rheological properties of the gel.

[0269] A colloidal gel typically has a gel point. The gel point is the point at which the gel undergoes an abrupt change in viscosity. In other words, the gel point is the point at which the rate of change of viscosity is at a maximum. In some examples, the gel point defines the point a gel changes from a viscoelastic liquid to a viscoelastic solid. The gel point may be defined in terms of the concentration of the dispersed phase, such as the concentration of the cellulose microparticles. The gel point may be determined based on cellulose microparticles in water as the continuous phase, at ambient temperature and pressure. In the context of the present invention, the gel point is determined by the point at which the storage modulus (G') and the loss modulus (G") from dynamic mechanical analysis become equal according to ISO 6721-10 unless otherwise indicated. This gel point indicates the cellulose microparticle concentration necessary to achieve structural integrity within the system.

[0270] The gel point may depend on the morphology of the cellulose microparticles, such as the cellulose microparticle length. Particle population CMPXreaches its gel point at 6 wt%, particle population CMPLSat 14 wt%, and particle population CMPZat 12 wt%, all based on the total mass of the colloidal composition.

[0271] The colloidal gel may have particular rheological characteristics, imparted by the cellulose microparticles. The rheological characteristics may be measured as described in the Examples section. In some embodiments, the colloidal gel is a yield stress fluid. Preferably, the colloidal gel is a yield stress fluid above the gel point. A yield stress fluid is a fluid which does not flow unless the stress applied to the fluid exceeds a threshold value.

[0272] The threshold value for the yield stress fluid to flow is known as the ‘yield stress’ (T0). In some embodiments the colloidal gel has a yield stress (T0) of 0.4 to 71 Pa, preferably 0.4 to 15 Pa. Preferably the colloidal gel has a yield stress of from 0.1 to 1 Pa, such as about 0.4 Pa. Such a yield stress allows the colloidal gel to flow easily under low stress for practical application while maintaining stability and shape when at rest, preventing unwanted spreading or sagging.

[0273] Flow coefficient may also be determined for the colloidal gel. The flow coefficient is indicative of how efficiently a fluid can flow. The flow coefficient may be determined based on the following formula:

[0274] In the formula,vis the flow coefficient (expressed in m3 / h), Q is the flowrate (in m3 / h), SG is the specific gravity of the fluid, and AP is the differential pressure across the device (in bar). The flow coefficient may be determined at ambient temperature and for example pressure with a flow meter and a differential pressure sensor.

[0275] In some embodiments, the colloidal gel has a flow coefficient ( ) of from 0.1 to 7 Pas ensuring a balance between ease of flow and sufficient viscosity for stability, making the gel versatile, stable, and suitable for various applications

[0276] The flow index is indicative of how viscosity changes with increasing shear rates. If a fluid has a flow index of 1 it is a Newtonian fluid - meaning that viscosity is the same at all shear rates. If a fluid has a flow index of less than or equal to 1 , it is a shear thinning fluid, as the viscosity of the fluid decreases at higher shear rates. The composition according to the present invention has a flow index of less than or equal to 1 .

[0277] The colloidal gel according to the present invention has a flow index (n) of 1 or less, preferably 0.4 to 0.6 has excellent application properties, providing smooth and uniform coverage with minimal dripping and sagging, leading to a superior finish.

[0278] In some embodiments the colloidal gel is a viscoelastic solid. A viscoelastic solid is a substance displaying the viscosity of a fluid and the elasticity of a solid. In particular, the colloidal gel may be a viscoelastic solid above the gel point. The gel point is as described above.

[0279] The storage modulus (G’) and loss modulus (G”) in viscoelastic materials represents the stored elastic energy in the elastic solid and the energy lost as heat in the viscous fluid, respectively. The storage module and loss modulus may be determined by any suitable method, such as dynamic mechanical analysis (DMA), rheometry, oscillatory shear tests, torsional oscillation tests, and broadband dielectric spectroscopy.

[0280] In some embodiments the colloidal gel has a storage modulus of from 15 to 1 ,000 Pa, preferably from 15 to 40 Pa. This range ensures the gel has enough elasticity to maintain its structure and recover after deformation, providing stability and durability, while still being soft and flexible enough for comfortable use in applications like cosmetics.

[0281] In some embodiments the colloidal gel has a loss modulus of from 4 to 80 Pa, preferably from 4 to 20 Pa, resulting in a balance between energy dissipation and structural integrity.

[0282] Additives

[0283] The colloidal composition may comprise additives. The additives refer to components in addition to the continuous phase, cellulose microparticles (dispersed phase) and, where present, a dispersed liquid phase.

[0284] The colloidal emulsion may comprise additives. The colloidal gel may comprise additives. The additives may be added for the colloidal compositions to be used as a personal care composition, a cosmetic composition, a pharmaceutical composition, a food composition, a microfluidics composition, or a drilling fluid.

[0285] In some embodiments, the colloid composition further comprises additives at from 0.1 to 30 wt.% based on the total weight of the composition, preferably from 1 to 25 wt.%, more preferably from 5 to 20 wt.%, yet more preferably from 10 to 15 wt.%.

[0286] Any suitable additive may be used. The additives may include colourants, emollients, oils, polymers, waxes and gelling agent. The additives are typically suited for the intended application and use. The composition may comprise one or more additives, such as two or more additives, or three or more additives.

[0287] The additives may comprise organic molecules or organic polymers.

[0288] In some embodiments, the additives are melanin or lignin. Suitable polymers may include stabilisers, plasticizers and flame retardants. Polymer stabilisers refer to any polymer suitable for inhibit or retard the degradation of the opacifier, coating composition or coating. The polymer stabiliser may be a UV absorber, anti-oxidant and biocides. Plasticizers refer to polymers which increase the plasticity of the coating. This may include a phthalate-based plasticisers, DMP, DEP, DIBP, DBP, DINP, Terephthalates, Trimellitates and organophosphates.

[0289] The additive may comprise gelling agents. Suitable gelling agents includes cellulose-derivative thickener, such as hydroxyethyl cellulose, as well as acacia gum, agar, aloe gel, gelatin, guar gum, gum arabic, gum tragacanth, pectin, alginates, starches, carrageenan, and xanthan gum. Preferably the gelling agent is a cellulose derived gelling agent, such as hydroxyethyl cellulose.

[0290] The additive may comprise a surfactant, such as a non-ionic surfactant.

[0291] A non-ionic surfactant has a net zero charge at the head / hydrophilic group. Suitable non-ionic surfactants may include ethoxylate surfactants, polyethylene glycol monododecyl ether surfactants, alkylphenol ethoxylates, Nonoxynols, polyethoxylated tallow amine, cocamide monoethanolamine, cocamide diethanolamine, terminally blocked ethoxylates, poloxamers, fatty acid esters of polyhydroxy compounds, fatty acid esters of glycerol, glycerol monostearate, glycerol monolaurate, fatty acid esters of sorbitol, fatty acid esters of sucrose, alkyl polyglucosides, and alkyl polyglycosides.

[0292] The additive may comprise a colourant.

[0293] In some embodiments the colloidal composition further comprises a colourant. If a specific colourant is added to the colloidal composition, then compositions of specific colours can be produced. It is apposite to note that the individual cellulose microparticles retain their ability to scatter light and form a white composition, but colour (i.e., absorption of specific bands of visible light) may be provided for by a colourant.

[0294] The colourant may include any suitable dye or pigment. The colourant may be an organic or inorganic colourant, preferably an organic colourant. The colourant may absorb narrow bands of light (specific wavelengths of light), to impart colour to the coating. This differs from the opacifying function of the cellulose microparticles, which reflect light across a broad range of wavelengths. Preferably the colourant is a dye.

[0295] The colourant may be a Beta-naphthol, BON arylamides, Benzimidazolone, Disazo condensation, Quinacridone, Perylene, Anthraquinone, Dibromanthrone, Pyranthrone, Diketopyrrolo-pyrrole pigments (DPP), Copper phthalocyanine, Indanthrone, Phthalocyanine green, Dioxazine violet, Perinone orange, Pyrazolone orange, Carbon Black, Graphite, Aniline Black, Anthraquinone Black, Benzimidazolone, Disazo condensation, or combinations thereof.

[0296] The colourant may be present at 1wt.% or less, such as 0.2 to 0.8 wt.%, such as 0.4 to 0.6 wt.%, based on the total mass of the colloidal composition.

[0297] The colloidal composition can also be mixed with any colourant to modulate shades of a particular colour. The colourant is preferably provided in the carrier liquid. For example, the carrier liquid may be a paint. In some embodiments, the colloidal composition is free of surfactant. In particular, where the colloidal composition is a colloidal emulsion, the emulsion may be free of surfactant. In this way, the cellulose microparticles may be the main component of the composition which stabilises the emulsion.

[0298] In some embodiments, the colloidal composition is free of additional opacifier. In this way, the cellulose microparticles may be the main component of the composition which provides opacity to the colloidal composition.

[0299] In some embodiments, the colloidal composition is free of additional rheology modifier. In this way, the cellulose microparticles may be the main component of the composition which changes the rheological properties of the colloidal composition.

[0300] Method of Preparing Colloidal Compositions

[0301] In a second aspect of the invention there is provided a method of preparing a colloidal composition of the first aspect, the method comprising: mixing a liquid and cellulose microparticles to form a continuous phase and a dispersed phase, wherein the dispersed phase comprises cellulose microparticles which are dispersed in the continuous phase.

[0302] In some embodiments the method further comprises a step of providing a liquid and cellulose microparticles. This may be referred to as the ‘preparation’ step. This step refers to making a suitable cellulose microparticle and a suitable liquid available. The preparation step typically takes place before the mixing step.

[0303] Any suitable cellulose microparticle may be used, as described herein. The cellulose microparticles may be provided as a powder. The cellulose microparticles may be provided as a suspension or solution in a solvent. The suspension may also take the form of a slurry.

[0304] Any suitable liquid may be used, as described herein. The liquid may be provided as a single liquid or a mixture of liquids.

[0305] The liquid and cellulose microparticles may be provided in particular proportions.

[0306] The amount of cellulose microparticles compared to the total mass of the final colloidal composition is as described herein. For example, the cellulose microparticles may be provided at from 5 to 20 wt.% of the colloidal composition, based on the total mass of the colloidal composition. Preferably, the cellulose microparticles are present at from 10 to 20 wt.%, more preferably from 10 to 15 wt.%.

[0307] The amount of liquid compared to the total mass of the final colloidal composition is as described herein. For example, the liquid may be provided at from 70 to 95 wt.% of the colloidal composition, based on the total mass of the colloidal composition. Preferably, the liquid is present at from 80 to 90 wt.%, more preferably from 85 to 90 wt.%.

[0308] The method comprises a step of mixing a liquid and cellulose microparticles. This may be referred to as the ‘mixing’ step. This step refers to mixing the liquid and cellulose microparticles to form a continuous phase and a dispersed phase. After the mixing step, the cellulose microparticles are dispersed in the continuous phase.

[0309] The mixing may be carried out by any suitable means. Preferably, gels are prepared by mechanical mixing of cellulose microparticle population CMPLSat a concentration of 14 wt.% to 20 wt.%, the cellulose microparticle population CMPXat a concentration of 6 wt.% to 12 wt.%, and the cellulose microparticle population CMPZat a concentration of 12 wt.% to 20 wt.%and the suitable solvent, e.g., water. The gel is formed instantaneously as external mechanical force is applied at low shear force ca. 100-300 rpm. Emulsions are, however, prepared by first mixing the cellulose microparticles, at concentrations less than 10 wt.%, and water using low shear force, ca. 100-300 rpm, to ensure proper dispersion of the cellulose microparticles in water. This is then followed by the addition of the oil phase under high shear force, ca. 7000 rpm or higher. A stable emulsion is then formed whereby the cellulose microparticles are lodged at the oil / water interface resulting in a uniform distribution of oil droplets and a very small size of the oil droplet - see Fig. 11. Alternatively, emulsions may be prepared by simultaneously mixing the cellulose microparticles, water phase and oil phase via sonication ca. 30 kJ / g for several minutes, ideally 5 min.

[0310] The sonication may be tip sonification or ultra-sonification. The sonication may be at an energy of from 10 to 70 kJ / g, preferably from 20 to 40 kJ / g, more preferably from 25 to 35 kJ / g. The sonication energy refers to the energy per total mass of the suspension being sonicated. The sonication may be performed by any suitable apparatus, such as a Fisherbrand Ultrasonic disintegrator.

[0311] In some embodiments mixing comprises sonicating the liquid and the cellulose microparticles, such as sonicating at 30 kJ / g.

[0312] The method may further comprise mixing a second liquid with the liquid and cellulose microparticles, wherein the second liquid is different from the liquid. The second liquid may be mixed with the liquid and cellulose microparticles to form a continuous phase and a dispersed phase, wherein the dispersed phase comprises cellulose microparticles and the second liquid, which are dispersed in the continuous phase liquid.

[0313] The liquid corresponds to the continuous phase. The liquid component is as described herein, such as in the emulsions section.

[0314] The second liquid corresponds to the dispersed liquid phase. The second liquid component is as described herein for the dispersed liquid phase, such as in the emulsions section. The dispersed liquid is a liquid which is different to the continuous phase liquid. Typically, the dispersed liquid phase is a liquid which is immiscible in the continuous phase liquid.

[0315] In some embodiments the method is a method of preparing a colloidal emulsion.

[0316] In some embodiments, the method is a method of preparing a colloidal emulsion according to the first aspect, the method comprising: mixing a liquid, a second liquid and cellulose microparticles to form a continuous phase and a liquid dispersed phase, wherein at least a portion of the cellulose microparticles are at the interface of the continuous phase and the liquid dispersed phase.

[0317] In some embodiments, the method is a method of preparing a colloidal emulsion according to the first aspect, the method comprising: mixing a liquid and cellulose microparticles to form a continuous phase and a dispersed phase, wherein the dispersed phase comprises cellulose microparticles which are dispersed in the continuous phase mixing the continuous phase and a dispersed phase with a second liquid to form a dispersed liquid phase in the continuous phase, wherein at least a portion of the cellulose microparticles are at the interface of the continuous phase and the liquid dispersed phase.

[0318] The method including a first mixing step and a second mixing step may be used where the cellulose microparticles are present at 10 wt.% or more, based on the total weight of the colloidal composition. Preferably, the method including a first mixing step and a second mixing step is used where the cellulose microparticles are present at 15 wt.% or more, based on the total weight of the colloidal composition. The two step mixing process provides improved distribution of the cellulose microparticles in the continuous phase, prior to addition of the liquid dispersed phase. This in turn assists with dispersion of the liquid dispersed phase.

[0319] The first mixing step comprises mixing a liquid and cellulose microparticles to form a continuous phase and a dispersed phase. In this step, the dispersed phase comprises cellulose microparticles. The cellulose microparticles are dispersed in the continuous phase.

[0320] The first mixing step may comprise mixing a hydrophilic liquid and cellulose microparticles to form a continuous phase and a dispersed phase. The hydrophilic liquid is preferably an aqueous liquid, such as water.

[0321] The first mixing step typically occurs at a low shear rate. For example, the first mixing step may occur at a mixing speed of 100-300 rpm. The first mixing step may take place at a lower shear rate than the second mixing step.

[0322] The second mixing step comprises mixing the product of the first mixing step (continuous phase and a dispersed phase of cellulose microparticles) with a second liquid to form a dispersed liquid phase in the continuous phase. In this step, the dispersed phase comprises a liquid dispersed phase and cellulose microparticles. The liquid dispersed phase is dispersed in the continuous phase. At least a portion of the cellulose microparticles are at the interface of the continuous phase and the liquid dispersed phase. The cellulose microparticles act to stabilise the emulsion formed of the continuous phase and liquid dispersed phase.

[0323] The second mixing step typically occurs at a high shear rate. For example, the second mixing step may occur at a mixing speed of 2000-10,000 rpm. The first mixing step may take place at a higher shear rate than the second mixing step.

[0324] In some embodiments the method is a method of preparing a colloidal gel. In some embodiments, the method is a method of preparing a colloidal gel of the first aspect, the method comprising: mixing a liquid and cellulose microparticles to form a continuous phase and a dispersed phase, wherein the dispersed phase comprises cellulose microparticles which are dispersed in the continuous phase.

[0325] The method may further comprise adding one or more additives to the colloidal composition.

[0326] The step of adding one or more additives may be carried out sequentially with the preparation step. The step of adding one or more additives may be carried out after the mixing step. Preferably, the step of adding one or more additives is carried out before the mixing. Thus, the additives may also be mixed during the mixing step.

[0327] Where the method includes a first mixing step and a second mixing step (as described above), the step of adding one or more additives may be carried out before the first mixing step. Preferably the step of adding one or more additives is carried out after the first mixing step and before the second mixing step.

[0328] Where multiple additives are added, the additives may be added separately or together.

[0329] The additives are as described herein.

[0330] In a related aspect, there is also provided a colloidal composition which is obtained or obtainable by the method of the second aspect.

[0331] In some embodiments, the colloidal composition is a colloidal emulsion which is obtained or obtainable by the method of the second aspect.

[0332] In some embodiments, the colloidal composition is a colloidal gel which is obtained or obtainable by the method of the second aspect. Uses and Applications

[0333] In another aspect of the invention there is provided a use of cellulose microparticles in the colloidal composition of the first aspect, wherein the cellulose microparticles are used as an opacifier, an emulsifier and / or a rheology modifier.

[0334] In some embodiments, the cellulose microparticles are used as an opacifier in the colloidal composition.

[0335] An opacifier typically provides some degree of opacity, such as when incorporated into the colloidal composition. The opacity may primarily be provided by the cellulose microparticle component. The opacity may be in the I R, UV or visible region of the spectrum, preferably in the visible region of the spectrum. The opacifier has good light scattering properties, and poor light transmittance, across a broad range of wavelengths. The opacifier may be a visible light opacifier, which opacifies in the visible region (e.g., 400 to 1000nm). The opacifier may be a UV opacifier, which opacifies in the UV region (e.g., 100 to 400nm). The opacifier may be an IR opacifier, which opacifies in the IR region (e.g., 1000 to 2500nm).

[0336] The cellulose microparticles may be used as an opacifier, such that they provide a transmittance of 20% or less, preferably 18% or less, more preferably 15% or less for incoming light at a wavelength of from 400 to 800 nm, for a layer of the colloidal composition having a thickness of 20 pm.

[0337] The cellulose microparticles may be used as an opacifier, such that they provide a reflectance of 50% or more, preferably 55% or more, more preferably 60% or more of incoming light at a wavelength of from 400 to 800 nm, for a layer of the colloidal composition having a thickness of 20 pm.

[0338] The cellulose microparticles may be used as an opacifier, such that they provide a L* of 70 or more, such as 75 or more, such as 80 or more, wherein L* is a CEILAB colour-space coordinate (determined according to ISO 11664-4), and is measured for a layer of the colloidal composition having a thickness of 20 pm.

[0339] The transmittance, reflectance and L* may be measured using any suitable method, such as with an integrating sphere (Labsphere), a light source (Ocean Optics HPX-2000) coupled into an optical fibre (600 pmThorlabs FC-UV100-2-SR) via a collimator (Thorlabs) and the signal collected by a spectrometer (Avantes HS2048). The signal may be normalized with respect to the intensity when no sample was mounted. The background is typically recorded when no light is applied. The range of wavelengths may be between 400 and 800 nm. Five spectra may be taken for each sample and averaged to reduce the signal-to-noise ratio. Each spectrum may be recorded using an integration time equal to 3 s. In some embodiments, the cellulose microparticles are used as an emulsifier in the colloidal composition. In particular, the cellulose microparticles may be used as an emulsifier in the colloidal emulsion.

[0340] Typically, an emulsifier assists in dispersion a liquid dispersed phase in a continuous phase. The cellulose microparticles may be present at the interface of the dispersed liquid phase and the continuous phase, and in this way, the cellulose microparticles act as an emulsifier for the colloidal emulsion.

[0341] The use of the cellulose microparticles as an emulsifier are as described in the emulsion section, herein.

[0342] In some embodiments, the cellulose microparticles are used as a rheology modifier in the colloidal composition.

[0343] Typically, a rheology modifier is a component which alters the rheological properties of a composition. The rheological properties may include the gel point, yield stress (T0), flow coefficient ( ), flow index (n), storage modulus (G’) and / or loss modulus (G”).

[0344] The use of the cellulose microparticles as a rheology modifier are as described in the colloidal composition, emulsion and gel sections, herein. In particular, where the colloidal composition is a colloidal gel, the cellulose microparticles may act as a rheology modifier.

[0345] In another aspect of the invention there is provided a use of a colloidal composition of the first aspect as a personal care composition, a cosmetic composition, a pharmaceutical composition, a food composition, a microfluidics composition, or a drilling fluid.

[0346] The colloidal composition of the first aspect may be a personal care composition, a cosmetic composition, a pharmaceutical composition, a food composition, a microfluidic composition, or a drilling fluid.

[0347] The method of preparing a colloidal composition of the second aspect may be a method of preparing a personal care composition, a cosmetic composition, a pharmaceutical composition, a food composition, a microfluidic composition, or a drilling fluid.

[0348] Definitions

[0349] The following common definitions are used herein, as determined by the relevant context. Other Preferences

[0350] Each and every compatible combination of the embodiments described above is explicitly disclosed herein, as if each and every combination was individually and explicitly recited.

[0351] Various further aspects and embodiments of the present invention will be apparent to those skilled in the art in view of the present disclosure.

[0352] “and / or” where used herein is to be taken as specific disclosure of each of the two specified features or components with or without the other. For example “A and / or B” is to be taken as specific disclosure of each of (i) A, (ii) B and (iii) A and B, just as if each is set out individually herein.

[0353] Unless context dictates otherwise, the descriptions and definitions of the features set out above are not limited to any particular aspect or embodiment of the invention and apply equally to all aspects and embodiments which are described.

[0354] Certain aspects and embodiments of the invention will now be illustrated by way of example and with reference to the figures described above.

[0355] Examples

[0356] The following examples are provided to further illustrate the present invention and are not intended to limit the scope of the invention.

[0357] Experimental Methods and Materials

[0358] Materials

[0359] Microcrystalline cellulose powder (MCC) having a mean average length of 20 pm was purchased from SERVA Electrophoresis.

[0360] Cellulose nanocrystals (CNCs) having an average length of 150 to 200 nm were prepared by Seprify.

[0361] Sulfuric acid (concentration > 95%) was purchased from Sigma Aldrich (Merck).

[0362] ECOSURF SA-9 was obtained from Dow.

[0363] Paraffin oil was purchased from Sigma Aldrich (Merck).

[0364] Glycerine was purchased from Sigma Aldrich . Lignin from Sigma Aldrich (Merck).

[0365] Melanin was purchased from Avantor (VWR).

[0366] Measurement Methods

[0367] The SEM images are obtained using an FEI Nanolab 650 FIB-SEM operated at 5.0 kV and a working distance of 6.9 mm.

[0368] All rheological characterization was performed using an Anton Paar MCR502 rheometer. Amplitude sweeps were conducted using 0.005 to 5 with timestep = 10 s and frequency = 1 Hz; frequency sweeps were run as reverse amplitude sweeps 5 to 0.005 and same timestep and frequency, then amplitude = 0.001 for frequency 100 to 0.1 rad / s with log spacing. Flow curves were carried out for shear rates 300 to 0.1 s-1with log-spacing timesteps from 5 to 50 s.

[0369] The rheological characterisation was carried out at shear rates of from 0.1 to 1000 s-1.

[0370] The rheological examples were modelled as a Power Law fluid and above the gelling point as a yield stress fluid using the Hershel-Bulkley law.

[0371] The following two equations represent the Power Law fluid and Hershel-Bulkley law, respectively:

[0372] The model fitting parameters are defined as: K = flow coefficient, n = flow index (if n<1 , then shear thinning, n>1 , shear thickening, and T0= yield stress.

[0373] All rheology characterizations, including measurement of the viscosity, were performed with a discovery hybrid rheometer from TA instruments (Model: HR-2). The measurements were conducted using a parallel plate geometry with a gap distance of 1 mm. The diameters of plates were 25 mm for CMP emulsions. After closing the gap, emulsion samples were set to rest for 750 s to reach equilibration before starting the test, except for the time sweep. Amplitude sweep was carried out first for each sample to determine the linear viscoelastic (LVE) region, in which all follow- ing oscillation tests were completed. The swept stain range was from 0.01 to 1000% at an angular frequency of 6.28 rad / s. All frequency sweeps were performed between 0.1 and 100 rad / s at a constant strain of 0.08%. For time sweep, data acquisition was started immediately after gap closing and proceeded for 30 min at an angular frequency of 6.28 rad / s with a strain of 0.08%. In the flow measurements, all samples were swept in the shear rate range of 0.001 to 100 s-1. At each shear rate, the samples were allowed to reach equilibrium for 60 s and the measurement time was 30 s. In the constant shear rate tests, the response at three shear rates, 0.1 , 1 , and 10 s"1 were measured for 10 min for each emulsion sample. All measurements were conducted at 25°C.

[0374] The emulsions were observed (see Fig. 11) using an optical microscope (Nikon Microphot-FX) equipped with a charge-coupled device dig- ital camera (SPOT RT Slider; Diagnostic Instruments Inc.). The samples were prepared by gently smearing a small amount of the emulsion on a glass slide and placing a glass cover on top. In this process, no pressure was applied on the glass cover to avoid influencing the oil droplets in the emulsions. The oil droplet size was analysed on the microscopic images using ImagePro software.

[0375] Preparation of CMPs

[0376] Cellulose microparticles, CMP-LS, CMP-X and CMP-Z, of different sizes (Fig. 2) are prepared using acid hydrolysis, specifically sulphuric acid, followed by washing and separating solids from the liquid.

[0377] Characterization of CMPs

[0378] CMP-LS was characterised by Scanning electron microscopy (SEM). Figure 1 shows an SEM image of the cellulose microparticles with unique light scattering capability. The scale bar is 5 pm.

[0379] The size distribution of CMP-LS, CMP-X and CMP-Z was measured by scanning electron microscope (SEM). A dilute suspension of CMPs (0.001 wt.%) was dropped on a carbon coated copper grid (300 mesh) for 2 minutes and removed by a piece of filter paper, then a drop of uranyl acetate solution (2%) was applied as stain for 1 minute before being removed by a piece of filter paper. The length of the particles was analysed by Imaged. The length refers to the largest diameter of the particle which is visible in the SEM image. The number of measurements taken to give the size distribution is typically from 100 to 1 ,000. Generally, over 100 measurements of the length are taken.

[0380] The size distribution of the particle length of CMP-LS, CMP-X and CMP-Z is shown in Figure 2(a)-(c) (the term “particle size” on the x-axis refers to the particle length). The size distribution is quantified by volume of the particles. CMPZhas average particle length of more than 7 pm. The CMPLShas an average particle length of from 1 to 7 pm. The CMPXhas an average particle length of less than 1 pm.

[0381] Preparation of Gels

[0382] Gel compositions were prepared by mechanically mixing the required cellulose microparticles (CMPLS, CMP-X or CMP-Z) with solvent in the proportions specified. Further details of the CMP, solvent and proportion are provided for each example below. Preparation of Emulsions

[0383] Emulsion compositions were prepared by mechanically mixing the required cellulose microparticles (CMP-LS, CMP-X or CMP-Z) with a continuous phase solvent and a liquid phase solvent in the proportions specified to form an emulsion. The emulsions were sonicated at 30 kJ / g.

[0384] Preparation of Mixtures

[0385] Mixtures were prepared by mechanically mixing the required cellulose microparticles (CMPLS, CMP-X or CMP-Z) with solvents in the proportions specified. Further details of the CMP, solvent and proportion are provided for each example below.

[0386] Rheological Characterisation of Gels

[0387] Flow curves were obtained for aqueous gels containing different concentrations of CMPLSor CMPZmicroparticles. Gel compositions were prepared including CMPLs as the dispersed phase and water as the continuous phase, at a CMP concentration of 10 wt.%, 15 wt.% and 20 wt.% based on the total weight of the composition. Further gel compositions were prepared including CMPZand water at a CMP concentration of 10 wt.%, 15 wt.% and 20 wt.% based on the total weight of the composition.

[0388] The shear stress was measured at various shear rates, as described above. The results are shown in Figure 3(a).

[0389] The viscosity was measured at various shear rates, as described above. The results are shown in Figure 3(b).

[0390] The curves indicate the shear thinning behaviour for gels of CMPLSand CMPZand water at CMP concentrations from 10 to 20 wt.%.

[0391] Aqueous suspensions of cellulose microparticles exhibit a unique and distinct rheological behaviour. CMPLSand CMPZsuspensions (Figure 3) exhibit shear-thinning behaviour at low and high concentrations. CMPLSmicroparticles, which are smaller than CMPZparticles, show a more fluid-like behaviour for all concentrations, whereas the CMPZparticles exhibit a more pronounced stress behaviour (see Figure 3(a)).

[0392] Amplitude and frequency sweeps were carried out to identify the gelation concentration for CMP aqueous gels.

[0393] Aqueous gels containing different concentrations of CMPLSor CMPZmicroparticles were prepared and tested. Gel compositions were prepared including CMPLSas the dispersed phase and water as the continuous phase, at a CMP concentration of 10 wt.%, 15 wt.% and 20 wt.% based on the total weight of the composition. Further gel compositions were prepared including CMPZand water at a CMP concentration of 10 wt.%, 15 wt.% and 20 wt.% based on the total weight of the composition.

[0394] The amplitude sweep was measured for each gel at different strain amplitudes. The results are shown in Figure 4(a).

[0395] The amplitude sweep was measured for each gel at different angular frequencies. The results are shown in Figure 4(b).

[0396] Based on the data shown in Figure 4 it was observed that gelation occurs for microparticle concentrations between 10 and 15 wt% with gels formed by CMPZ(15 wt%) indicating stronger networks than those formed by CMPLs (20 wt%) for low deformation, while the reverse is true for high deformations.

[0397] We can gain further insights into the structural build-up in these colloidal systems by acknowledging the stronger network formation within CMPZmicroparticles, which indicates longer time for CMPZto generate a network relative to CMPLS. This can translate into practical aspects, namely, CMPLSwill have less sagging compared to CMPZin, for instance, paint applications. Furthermore, both CMPLSand CMPZaqueous suspensions exhibit a nonlinear response above 1 % strain, and gelation occurs between 10 and 15 wt% for both microparticle suspensions (see Figure 4(a)). CMPLSnetworks can form stronger gels at higher deformations (> 50% strain), whereas CMPZcan form stronger gels at low deformations (< 10% strain) for all similar concentrations (see Figure 4(a)). There are low moduli variations for all formed gels.

[0398] Further flow curves were obtained for aqueous suspensions containing different concentrations of CMPXmicroparticles and comparative cellulose nanocrystals (CNCs).

[0399] Aqueous gel compositions were prepared including CMPXas the dispersed phase and water as the continuous phase, at a CMP concentration of 1 wt.%, 5 wt.% and 10 wt.% based on the total weight of the composition. Further gel compositions were prepared including comparative CNCs and water at a CNC concentration of 5 wt.% and 10 wt.% based on the total weight of the composition.

[0400] The shear stress was measured at various shear rates, as described above. The results are shown in Figure 5.

[0401] The flow curves illustrate the shear stress response vs. varying shear rate. Gelation starts at concentrations ca. 5 wt% for both particle suspensions. A distinct response is observed for CMPx as the concentration is increased. Similarly, distinctly comparable responses are observed for CMPz and CMPLS when the concentration is increased from 10 to 20 wt%. It is important to note that the shear stress increases by nearly two orders of magnitude at higher concentrations. Thus, at the same concentration (5 wt.% and 10 wt%) the CMPXsuspensions exhibit higher shear stresses at the same shear rate, indicating that the CMPXmicroparticles have better gelation properties than CNC nanoparticles.

[0402] Further amplitude sweeps were carried out to identify the gelation concentration for CMP aqueous gels.

[0403] Aqueous gels containing different concentrations of CMPXmicroparticles and comparative CNC nanoparticles were prepared and tested. Gel compositions were prepared including CMPXas the dispersed medium and water as the continuous phase, at a CMP concentration of 5 wt.% and 10 wt.% based on the total weight of the composition. Further gel compositions were prepared including comparative CNC and water at a CNC concentration of 5 wt.% and 10 wt.% based on the total weight of the composition.

[0404] The amplitude sweep was measured for each gel at different strain amplitudes. The results are shown in Figure 6.

[0405] The storage moduli (G’ and G”) vs. strain amplitude for CMPXmicroparticles indicate a larger linear region up to 10 wt% relative to aqueous suspensions of CMPLSor CMPZ(see Figure 4). The results also indicate that high storage moduli can be reached for CMPXmicroparticle suspensions, thereby indicating these microparticle suspensions can create a more stable gelation network relative to the nanoparticles, CNCs, at the same concentration.

[0406] Relaxation behavior of microparticle (CMPX) and nanoparticle (CNC) aqueous gels were tested by measuring the shear stress over time, as described above. Aqueous gels containing 10 wt.% CMPXmicroparticles and 10 wt.% comparative CNC nanoparticles were prepared as described above.

[0407] The relaxation behaviour was measured for each gel by measuring the shear stress over time. The results are shown in Figure 7. Relaxation relates to how a material relieves internal stress over time after being suddenly deformed and then held at constant strain. In the case of the shear stress vs. time response for CNC based gels shown in Figure 7, the shear stress is practically unchanged over time. This indicates that the CNC particles behave elastically. The response for CMPx particles is characteristically different. The shear stresses abruptly increase at lower times, then slowly increase over a longer period. This is attributed to the thixotrpic behaviour characteristic of the CMPx particles (as discussed above). The CMPx shear stress vs time behaviour is characteristic of a time-dependent structural build-up. Initially, the CMPx systems reflect initial resistance to defomation (initial abrupt stress increase), then shear- induced structural formation kicks in or slow relaxation or yielding occurs (subsequent gradual increase in shear stress over longer periods). In summary, the CMPx particles start aligning in the gel after a short period of applying stress and form a more resistant structure relative to CNC particles under the application of continued shear. Yet further amplitude sweeps were carried out to identify the gelation concentration for CMP aqueous gels and comparative MCC gels.

[0408] Aqueous gels containing different concentrations of CMPLSmicroparticles and comparative MCC particles were prepared and tested. Gel compositions were prepared including CMPLSas the dispersed phase and water as the continuous phase, at a CMP concentration of 10 wt.%, 15 wt.% and 20 wt.% based on the total weight of the composition. Further gel compositions were prepared including comparative MCC and water at a MCC concentration 10 wt.%, 15 wt.% and 20 wt.% based on the total weight of the composition.

[0409] The amplitude sweep was measured for each gel at different strain amplitudes. The results are shown in Figure 8.

[0410] The results illustrate that MCC gelation networks are much less stable than those by CMPLSregardless of the concentration. Even at 10 wt% concentration, the MCC gel network is noticeably weak compared to the CMPLSgel network.

[0411] Overall, cellulose nanocrystals (CNCs) exhibit very fast relaxation, whereas the larger CMPXmicroparticles require some time, at least 100 s, to fully re-structure (see Figure 7). In contrast to the larger microparticles, the CMPXshow no gelation below 5 wt% and they exhibit a more stable gelling behaviour when compared to the CNCs (see Figure 5). The linear viscoelastic region for CMPXand CNCs is much bigger than that for CMPLS(see Figure 6 and Figure 4(a)). All microparticle suspensions, including CMPX, show more stable gelling networks than CNC nanoparticles and gels formed by microparticles (CMPLS, CMPZor CMPX) can reach high storage moduli before turning into gel. The much larger MCC particles exhibit very weak network structures at all concentrations. This gives unique and systematic evidence how the tailored cellulose microparticles, CMPLS, CMPXand CMPZ, can create tunable gel and network structures with a distinct opacifying feature for the CMPLSmicroparticles. Neither the larger MCC particles or much smaller CNC particles can deliver similar rheological and structural responses for gel and network formations.

[0412] Calculation of Rheological parameters

[0413] The rheological characterisation of the gels described above was used to calculate various rheological parameters (as detailed in the Measurement Methods section).

[0414] The flow behaviour of CMP gels were determined at different concentrations (cf. FIG. 3 and 5) fitted above (yield stress fluid) and below (Power Law) the gel point. Table 1 indicates the calculated model fitting parameters, namely: K = flow coefficient, n = flow index (if n<1 , then shear thinning, n>1 , shear thickening, and T0= yield stress.

[0415] The parameters were calculated as set out in the Measurement Methods section, above.

[0416] The yellow cells (left side) indicate gels fitted as a “Power-Law fluid”. The blue cells (right side) indicate gels fitted as a “Yield Stress fluid”.

[0417] The Table also indicates the gel point for each of the CMP types.

[0418] The storage moduli vs. shear rate of CMP aqueous gels (at different concentrations) subjected to amplitude sweeps (cf. FIG. 4(a), FIG. 6 and FIG. 8) were also determined, as the results are shown in Table 2. The table presents values for G' = storage modulus in linear viscoelastic regime (describes how “solid” the system is), G" = loss modulus in linear viscoelastic regime (describes how dissipative the system is), and yf= flow point at G'= G" (indicative of the stability of the gel network).

[0419] 1) gels fitted as a “Viscoelastic liquid”.

[0420] 2) gels fitted as a “Viscoelastic solid”.

[0421] Table 2 - Storage Moduli, Loss Modulus and Flow Point for CMP Gels

[0422] These results indicate that CMPLs, CMPXand CMPZaqueous suspensions behave as perfect viscoelastic liquids at concentrations below 5 wt%, and this behaviour can be extended to concentrations ca. 10 wt% for the relatively larger microparticles CMPLs and CMPZ. Gelation for CMPLSand CMPZsuspensions occurs at concentrations > 12 wt%. The much smaller CMPXmicroparticles gel at much lower concentrations, ca. 6 wt%. This makes possible the ability to tune structural features using these microparticles to create gels and emulsions of variable and controllable performance.

[0423] Characterisation of Emulsions

[0424] Oil in water emulsions were prepared including 60 vol% paraffin oil and 40 vol% water. The emulsions were sonicated at 30 kJ / g. The emulsions were prepared including CMPLSat a concentration of from 1 wt.% to 10 wt.%, at 1wt.% increments, where the wt.% is based on the total mass of the compositions.

[0425] The resulting emulsions were visually inspected. Photographs of the emulsions are provided in Figure 9.

[0426] Figure 9(a) shows a photograph of emulsions including 1 wt.%, 2 wt.%, 3 wt.% and 4 wt.% CMPLS(left to right) in a glass vial. The left hand image shows the emulsions pre-inversion of the vial. The right hand image shows the emulsions post-inversion of the vial.

[0427] Figure 9(b) shows a photograph of emulsions including 5 wt.%, 6 wt.% and 7 wt.% of CMPLS(left to right) in a glass vial. The left hand image shows the emulsions pre-inversion of the vial. The right hand image shows the emulsions post-inversion of the vial. Figure 9(c) shows a photograph of emulsions including 8 wt.%, 9 wt.% and 10 wt.% of CMPLS(left to right) in a glass vial. The left hand image shows the emulsions pre-inversion of the vial. The right hand image shows the emulsions post-inversion of the vial.

[0428] As the CMP concentration increase the viscosity of the emulsion increases. At CMP concentrations of 4wt.% or less the emulsions are stable fluids. For CMP concentrations between 5 and 7wt% the emulsions are stable creams. For CMP concentrations between 8 and 10 wt% the emulsions flow resembles a viscous paste. This shows that the CMP can operate as a viscosity modifier when used in such emulsions.

[0429] All of the emulsions were formed successfully using only a CMP as the emulsifier. All of the emulsions were observed to have a white appearance. The diffuse white appearance of the emulsions is thought to be provided by the CMP.

[0430] The stability of the emulsions was tested by centrifuging. The emulsions including 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.% and 10 wt.% of CMPLSwere centrifuged for 10-20 min at 2000g. A commercial cream was also centrifuged under the same conditions.

[0431] Figure 9(d) shows a photograph of the emulsions after centrifuging compared to the commercially available cream.

[0432] All the emulsions tested showed excellent stability (no phase separation) at all concentrations from 6 to 10 wt.% CMPLS. The stability observed was comparable to the commercial cream, which also showed good stability following centrifuging.

[0433] This example illustrates that the CMP can simultaneously function as opacifier, emulsifier and rheology modifier for oil-in-water emulsions.

[0434] This example (see Figure 9) pertains to paraffin oil-in-water emulsion (60 vol% oil and 40 vol% water and sonicated to 30 kJ / g) stabilized by CMPLSat the concentrations shown. For concentrations below 5 wt%, the emulsions are stable fluids; between 5 and 7 wt% they are stable creams (b); and between 8 and 10 wt% their flow resembles a viscous paste. The oil volume can be increased to 80% and a variety of mineral or vegetable oils, possessing different densities and polarities, can be used to construct CMPLS-stabilised emulsions.

[0435] All the test emulsions show great stability after centrifugation using 2000 g (see Figure. 9(d) and Figure 11(b)) which illustrates the uniform and small-size oil droplets in this specific emulsion indicating excellent emulsion stability (no phase separation). Characterization of Oil-Water Mixtures and Emulsions

[0436] Glycerine and Water

[0437] Oil and water mixtures were prepared including 60 vol% glycerine and 40 vol% water. Glycerine is a relatively hydrophilic oil. The mixtures were mixed by hand for ~10 min. A range of mixtures were prepared including CMPLSat a concentration of from 0.1 wt.% to 9 wt.%, where the wt.% is based on the total mass of the compositions.

[0438] The resulting mixtures were visually inspected. Photographs of the mixtures are provided in Figure 10(a).

[0439] Figure 10(a) shows a photograph of mixtures including 0.1 wt.% up to 9 wt.% CMPLs (left to right) in glass vials. Mixtures of hydrophilic oils and water can be stabilized using CMP at various concentrations. The image shows that as the concentration of CMPLs increases the whiteness and opacity of the mixture increases. This is consistent with the CMPLSacting as an opacifier when stabilizing the oil-water mixtures.

[0440] The mixture including 5 wt% CMP was also analysed by taking a polarized light image. The image is shown in Figure 11(a). This shows the uniform dispersion of cellulose microparticles within the mixture of glycerine and water.

[0441] Paraffin and Water

[0442] Further Oil and water mixtures were prepared including 60 vol% paraffin and 40 vol% water. Parrafin oil is a relatively hydrophobic oil. A range of mixtures were prepared including CMPLSat a concentration of from 0.1 wt.% to 7 wt.%, where the wt.% is based on the total mass of the compositions. A nonionic surfactant (ECOSURF) was added at 0.1 wt.% to improve affinity between CMP and the hydrophobic oil.

[0443] The resulting mixtures were visually inspected. Photographs of the mixtures are provided in Figure 10(b).

[0444] Figure 10(b) shows a photograph of mixtures including 0.1 wt.% up to 7 wt.% CMPLS(left to right) in glass vials. Mixtures of hydrophobic oils and water can be stabilized using CMP at various concentrations. The image shows that as the concentration of CMPLSincreases the whiteness and opacity of the mixture increases, and the viscosity of the mixture also increases. This is consistent with the CMPLSacting as an opacifier and rheology modifier when stabilizing the oil-water mixtures.

[0445] Mixtures of hydrophilic polyols (e.g. glycerine) and water can be stabilised using cellulose microparticles at various concentrations (see Figure10(a)). Mixtures of lipophilic oil (e.g. paraffin) and water can also be stabilised with CMP and a non-ionic surfactant at low dosage (ca. 0.1 wt% of ECOSURF) to improve the affinity between CMP and the lipophilic oil (see Figure 10(b)).

[0446] The mixtures including 5 wt% CMP was also analysed using SEM. The SEM image is shown in Figure 11 (b). The SEM image was taken after the mixture was sonicated at 30 kJ / g and formed an emulsion. The image shows uniform and very small oil droplet sizes, indicating excellent stability of the emulsions provided by the cellulose microparticles.

[0447] The excellent dispersion of CMP in these oil / water mixtures is illustrated via polarised optical imaging (see Figure 11 (a)), indicating the uniform dispersion of the CMP in the mixture. These mixtures or emulsions can be used as additives in, for instance, food and drink applications to produce completely natural coffee creamers based on CMP.

[0448] Example Applications

[0449] It is possible to physically mix the CMP-stabilised emulsions with a dye to create stable shades of any colour (see Figure 12). In yet another example, cellulose white pigments can also be used as both opacifier and emulsifier for a wide variety of demanding systems. The CMP can clearly tune the dark colour of the emulsion as well as simultaneously produce stable emulsions. Figure 13 depicts emulsions (a) prepared without and with 5 wt% CMP in addition to 70 wt% water, 10 wt% oil, 5 wt% glycerine and 10 wt% lignin; whereas (b) illustrates emulsion ingredients that are similar except for lignin is replaced with melanin.

[0450] Coloured Compositions

[0451] A red coloured emulsion was prepared. A CMP-stabilized emulsion of water and paraffin oil in a ratio of 40 / 60 by volume was prepared with CMPLSat 5 wt% based on the total mass of the emulsion. 0.2 g of 25 wt.% red dye (D&C Red #7 Calcium Lake Dye) was physically mixed with 8.1 g of the CMP-stabilized emulsion to produce a red emulsion.

[0452] A pink coloured emulsion was also prepared using 0.05 g of red dye (D&C Red #7 Calcium Lake Dye) which was physically mixed with 8 g of the CMP-stabilized emulsion. The final composition included 0.4 g of CMP.

[0453] The resulting compositions were visually inspected and photographed. An image of the red emulsion is shown in Figure 12(a). An image of the pink emulsion is shown in Figure 12(c).

[0454] The resulting emulsions display an excellent appearance. The emulsions have good opacity provided by the CMP, which simultaneously acts as an opacifier as well as a emulsifier and rheology modifier for the emulsion. The compositions are colour tuneable.

[0455] Figure 12(b) also shows a small amount of emulsion added to the red due solution. The image shows the colour of the two compositions and how the combination of dye and CMP can be used to produce controllable colour tuned composition, at the desired tinting strength. The CMPs were also tested as opacifiers in more complex and demanding systems.

[0456] A lignin emulsion was prepared including 70 parts water, 10 parts oil (such as for example paraffin) , 5 parts glycerine and 10 parts lignin by weight. One portion of the emulsion was left unstabilised (comparative) and another portion was stabilised with 5 parts CMPLSby weight.

[0457] A melanin emulsion was prepared including 70 parts water, 10 parts oil (such as for example paraffin), 5 parts glycerine and 10 parts melanin by weight. One portion of the emulsion was left unstabilised (comparative) and another portion was stabilised with 5 parts CMPLSby weight.

[0458] The resulting compositions were visually inspected and photographed.

[0459] An image of the lignin emulsions is shown in Figure 13(a). The unstabilised (comparative) emulsion is shown on the left and the CMP-stabilised stabilised emulsion is shown on the right.

[0460] An image of the melanin emulsions is shown in Figure 13(b). The unstabilised (comparative) emulsion is shown on the left and the CMP-stabilised stabilised emulsion is shown on the right.

[0461] It was observed that the comparative emulsions were unstable, easily separated and had low viscosity. In contrast, the CMP-stabilised emulsions had improved texture, viscosity and stability. In particular, the CMP-stabilised emulsions were more homogeneous and less prone to separation. This demonstrates that the CMP can tune the dark colour of the emulsion as well as simultaneously produce stable emulsions for complex, multi-component emulsions.

[0462] Coffee Creamers

[0463] The CMPs were further tested as a a coffee whitener or coffee creamer.

[0464] A coffee creamer is a product intended to substitute for milk or cream as an additive to coffee, tea, hot chocolate or other beverages. The coffee creamer is intended to have a whitening effect on the coffee, as well as effect the rhelogical properties, mouth feel and taste.

[0465] CMPLSwere added to hot black coffee at concentrations of 1 wt.%, 5 wt.% and 10 wt.% based on the total weight of the composition.

[0466] The resulting compositions were visually inspected and photographed. The image is shown in Figure 14(a). The CMPLSprovides a white colour to the coffee. The whiteness increases with the CMP concentration (left to right, in the image). The coffee including CMPLShas a similar appearance to a coffee with milk.

[0467] A coffee creamer composition was prepared including 10 parts glycerine to 90 parts water by volume, along with an additional 5 wt% CMPLSand a 0.2 wt% xanthan gum based of the weight of the composition. This coffee creamer composition was added to hot black coffee. The resulting compositions were visually inspected and photographed immediately after adding to the coffee, as well as after 30 minutes and after 60 minutes. The images are shown in Figure 14(b). The coffee creamer was found to be stable in the hot coffee as a dispersion for at least 30 min.

[0468] While CMP powder alone can be dispersed in various food applications (see Figure 14 (a)), the advantage of using the CMP-based oil / water mixture in demanding food or liquid applications is to improve dispersion over time at temperatures above room temperature. The dispersion of this formulation was stable in hot coffee for at least 30 min.

[0469] Cosmetic Formulations

[0470] Cosmetic eye shadows formulations were prepared. A comparative eye shadow formulation was prepared with 12.5 wt.% TiO2. Formulations of the invention were also prepared including 76wt.% CMPLS, a combination of 36 wt.% CMPLs and 36 wt.% CMPXand also a combination of 36 wt.% CMPLSand 36 wt.% CMPZ. Typical eyeshadow formulations include the white pigment, oil (e.g., coco-caprylate), the colour pigment (red, black, etc.) and additives (e.g., mica and magnesium stearate). The ratio of ingredients are adjusted to suit the desired end effect.

[0471] The resulting compositions were visually inspected and photographed. The image is shown in Figure 15(a). The top image shows the formulations in a dish. The bottom image shows the formulations spread onto skin. The comparative formulation is on the left.

[0472] The images show how the tune texture, whiteness, and coverage in cosmetic formulations. The results show how the metal oxide can be completely replaced with bio-sourced cellulose white particles (CMP) in cosmetic formulations to create a uniform and intense white colour with excellent coverage and texture when spread on a human skin.

[0473] It was found that using a combination of CMPLSand CMPXcan be used to maintain colour but improve texture and feel, or smoothness on the skin.

[0474] Further eye shadow formulations were prepared including 12.5wt.% CMPLS, 25 wt.% CMPLSand 50 wt.% CMPLS.

[0475] The resulting compositions were visually inspected and photographed. The image is shown in Figure 15(b). The top image shows the formulations in a dish. The bottom image shows the formulations spread onto skin. The comparative formulation is on the left, with increasing CMPLSconcentration moving left to right. This shows that one-to-one replacement of TiO2with CMP is possible and the colour can be tuned along with the texture and sensoriality using the CMP.

[0476] The TiO2can completely be replaced with bio-sourced cellulose white pigments in cosmetic formulations to create a uniform and intense white colour with excellent coverage and texture when spread on a human skin.

[0477] To produce the desired colour tuning, CMPLScan solely be used to replace TiO2as shown in FIG. 15 (b). However, in order to tune colour, texture and coverage, combinations of CMPLs and CMPXor CMPLSand CMPZcan be used (see Figure 15). Using equal amounts of CMPLSand CMPX(36 wt% each) was found to maintain a similar colour effect and improve coverage. Alternatively, CMPLSand CMPXcan be used in equal amounts (36wt% each) to maintain colour but improve texture and feel, or smoothness and sensoriality on the skin.

Claims

Claims1. A colloidal composition comprising a continuous phase and a dispersed phase, wherein the continuous phase is a liquid; wherein the dispersed phase comprises native, discrete cellulose microparticles which are dispersed in the continuous phase of the colloidal composition, wherein the cellulose microparticles have a mean average particle length of from 0.1 to 20 pm a mean average particle width from 0.05 to 1.3 pm, and a maximum thickness not exceeding 0.2 pm determined by scanning electron microscopy; and an aspect ratio of length / width of 1 to 25, and wherein the colloidal composition has a flow index n of < 1 determined by a rheometer at NTP (normal temperature (25°C) and pressure (1 atm)).

2. The colloidal composition according to claim 1 , wherein the cellulose microparticles have a mean average particle length of from 0.1 to 12 pm, a mean average particle width from 0.05 to 0.5 pm, and a maximum thickness not exceeding 0.2 pm determined by scanning electron microscopy.

3. The colloidal composition according to any of the preceding claims, wherein the cellulose microparticles have a mean average particle length of from 1 to 7 pm, a mean average particle width of from 0.05 to 0.35 pm and a maximum thickness not exceeding 0.2 pm determined by scanning electron microscopy.

4. The colloidal composition according to any of the preceding claims, wherein the cellulose microparticles have a mean average particle length of from 13 to 20 pm, a mean average particle width of from 0.5 to 0.8 pm and a maximum thickness not exceeding 0.2 pm determined by scanning electron microscopy.

5. The colloidal composition according to any of the preceding claims, wherein the cellulose microparticles have an aspect ratio in the range of 15 to 25.

6. The colloidal composition according to any of the preceding claims, wherein the cellulose microparticles have a platelet-like shape.

7. The colloidal composition according to any of the preceding claims, wherein the concentration of the cellulose microparticles is below the gel point.

8. The colloidal composition according to any claims 1 or 6, wherein the concentration of the cellulose microparticles is equal or above the gel point.

9. The colloidal composition according to any of the preceding claims, comprising one of the following cellulose microparticle populations:- particle population CMPX, having an average particle length of 0.1 to less than 1 pm at a concentration of 1 wt% to 12 wt%, or- particle population CMPLS, having an average particle length ranging from 1 pm to less than 7 pm at a concentration of 5 wt% to 20 wt%, or- particle population CMPZ, having an average particle length ranging from 7 pm to 12 pm at a concentration of 10 wt% to 20 wt%, or- a mixture thereof.

10. The colloidal composition according to any one of claims 1 to 9, wherein the composition is a colloidal emulsion, and the dispersed phase is dispersed in a continuous phase, optionally wherein the colloidal emulsion is a solid-stabilised emulsion.

11. The colloidal composition according to claim 10 wherein at least a portion of the cellulose microparticles are present at the interface of the dispersed phase and the continuous phase, optionally wherein at least 90 wt.% of the cellulose microparticles are present at the interface of the dispersed phase and the continuous phase based on the total mass of the cellulose microparticles.

12. The colloidal composition according to claim 9 to 11 , wherein the colloidal emulsion is a high-internal phase emulsion or a medium-internal phase emulsion, preferably wherein the colloidal emulsion is a high-internal phase emulsion.

13. The colloidal composition according to any one of claims 1 to 6 and 8 to 9, wherein the composition is a colloidal gel.

14. The colloidal composition according to claim 13, wherein the cellulose microparticles are arranged as a gel network which is dispersed in the continuous phase.

15. The colloidal composition according to claim 13 or 14, comprising one of the following cellulose microparticle populations:- particle population CMPX, having an average particle length of 0.1 to less than 1 pm at a concentration of 6 wt% to 12 wt%, or- particle population CMPLS, having an average particle length ranging from 1 pm to less than 7 pm at a concentration of 14 wt% to 20 wt%, or- particle population CMPZ, having an average particle length ranging from 7 pm to 12 pm at a concentration of 12 wt% to 20 wt%,16. The colloidal composition according to any one of claims 1 to 15, wherein the colloidal composition has in addition to the flow index (n) of 1 or less, one or more rheological properties selected from:- a flow coefficient ( ) of from 0.1 to 7 Pas;- a yield stress (T0) of 0.4 to 71 Pa, preferably 0.4 to 15 Pa determined by a rheometer at NTP;- a storage modulus of from 15 to 1 ,000 Pa, preferably from 15 to 40 Pa determined by a rheometer at NTP; and- a loss modulus of from 4 to 80 Pa, preferably from 4 to 20 Pa determined by a rheometer at NTP.

17. The colloidal composition according to any of the preceding claims, wherein the cellulose microparticles incorporate 20 to 400 mmol / kg, preferably 40-250 mmol / kg of half-ester sulfate groups on their surface.

18. A method of preparing a colloidal composition according to any one of claims 1 to 17, the method comprising: mixing a liquid and cellulose microparticles to form a continuous phase and a dispersed phase, wherein the dispersed phase comprises cellulose microparticles which are dispersed in the continuous phase.

19. The method of claim 18, wherein the method is a method of preparing a colloidal emulsion, the method comprising: mixing a liquid and cellulose microparticles to form a continuous phase and a dispersed phase, wherein the dispersed phase comprises cellulose microparticles which are dispersed in the continuous phase- mixing the continuous phase and a dispersed phase with a second liquid to form a dispersed liquid phase in the continuous phase, wherein at least a portion of the cellulose microparticles are at the interface of the continuous phase and the liquid dispersed phase.

20. Use of cellulose microparticles in a colloidal composition according to any one of claims 1 to 17, as an opacifier, an emulsifier and / or a rheology modifier.

21. Use of a colloidal composition of any one of claims 1 to 17 as a personal care composition, a cosmetic composition, a pharmaceutical composition, a food composition, a microfluidics composition, or a drilling fluid.

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