Natural and biodegradable rheology modifiers

Abstract

The present invention relates to a biodegradable rheology modifier for a formulation or a fluid product, the biodegradable rheology modifier comprising bacterial cellulose wherein the bacterial cellulose is surface-modified and comprises at least one carboxyl group or a derivative thereof. The biodegradable rheology modifier further comprises at least one natural rubber wherein the surface-modified bacterial cellulose interacts with the natural rubber to increase the viscosity of the fluid product. In another aspect, the present invention relates to a liquid product comprising the biodegradable rheology modifier and to a process for the production of the biodegradable rheology modifier.

Description

Technical Field

[0001] The present invention relates to a novel biodegradable rheology modifier for fluid products. The biodegradable rheology modifier comprises bacterial cellulose, wherein the bacterial cellulose is surface-modified and comprises at least one carboxyl group or a derivative thereof. The biodegradable rheology modifier also comprises at least one natural gum, wherein the surface-modified bacterial cellulose interacts with the natural gum to increase the viscosity of the fluid product. The present invention also relates to a fluid product comprising the biodegradable rheology modifier, wherein the product is preferably a cosmetic, a medicine, an ink, a paint, a coating or a food. The present invention also relates to a method for producing a biodegradable rheology modifier, the method comprising surface-modifying cellulose by carboxylation to form carboxyl groups and / or derivatives thereof in the cellulose polymer, and mixing the surface-modified cellulose with the natural gum. Background Art

[0002] The safety, shelf life, applicability, aesthetic and tactile qualities of various fluid or semisolid products depend on their viscosity, density and flow characteristics. Many of these everyday products contain suspensions, such as minerals or polymers. For example, in the case of minerals, wall paints often contain suspended titanium dioxide (TiO 2 ) particles that contribute to opacity and are used to adjust the color of the paint. Such paints are often stored for months or years before use, during which time the suspended particles may settle, resulting in inconsistent paint color and opacity. In addition, the adhesion of the paint to the surface and the avoidance of unwanted dripping during the time it takes for the paint to dry depends on its flow behavior, i.e., its rheology. This rheology is often adjusted by adding additives, which can include diluents or thickeners. Examples of such additives include synthetic methods such as polymers, such as polyacrylates, which contribute to the desirable shear-thinning properties of wall paints.

[0003] Similarly, cosmetics often contain suspended ingredients, such as ZnO particles in sunscreens, oil-based droplets in moisturizers or microbeads in many hygiene products. Due to gravity, these ingredients tend to settle to the bottom of the cosmetic product over time. This significantly shortens its shelf life. This is usually adjusted by thickening additives, which change the rheological properties of the suspension and thus significantly slow down the sedimentation behavior. However, for such products, the use of inorganic and / or non-renewable rheology-modifying additives may not be suitable and may also pose health risks.

[0004] To improve the rheological properties, several rheology modifiers, which may contain organic or inorganic additives, are processed and added to aqueous or non-aqueous formulations to increase their viscosity, shear rate, yield stress, etc. Rheology modifiers can be classified as natural, semi-synthetic or synthetic.

[0005] As used herein, the term "natural" preferably refers to a compound or composition found in nature. The term "natural" also preferably refers to a compound or composition found in nature whose chemical structure has not been altered by human intervention. Natural rheology modifiers include casein, alginates, xanthan gum, locust bean gum, guar gum, tragacanth gum, konjac gum, gum arabic, tara gum, gellan gum, pectin, dextrin, cyclodextrin, polysaccharides and carrageenan.

[0006] As used herein, the term "semisynthetic" preferably refers to natural compounds that have been processed by chemical and other artificial processes. Semisynthetic rheology modifiers include modified celluloses such as carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and related derivatives.

[0007] The term "synthetic" as used herein is preferably defined as a compound formed by chemical and other artificial processes, rather than a compound formed from natural sources. Synthetic rheology modifiers include polyethylene glycol derivatives (PEG), maleic anhydride copolymers, carbomers, polyacrylamide, acrylic acid copolymers, N-vinyl pyrrolidone, cationic monomers (preferably N-vinylimidazole) and hydrophobic monomers (which may be long chain methacrylates with ethoxylated spacer chains, etc.).

[0008] Rheology modifiers are used in fluid or semisolid formulations, such as cosmetics and personal care products, home care products, health products, foods, inks, paints and coatings. The term "formulation" as used herein preferably refers to the composition of the final product, preferably a fluid product. Since these formulations contain aqueous solutions or water-based suspensions, they are considered to be aqueous systems. The term "aqueous system" as used herein is preferably intended to describe any system containing water in any physical state, including water containing one or more dissolved or dispersed substances. Rheology modifiers can maintain the stability of the formulation during storage, prevent precipitation, and thicken the aqueous system used. These formulations have better shelf stability, ease of use, open time / wet edge and droop.

[0009] In recent years, consumers and regulators have been pushing for the replacement of synthetic ingredients with natural raw materials (not only in cosmetics, but in all consumer products), or the development of formulations that are partly or entirely composed of natural ingredients. Natural cosmetic raw materials have the advantages of being more biocompatible, less toxic and more biodegradable than synthetic raw materials.

[0010] Examples of natural raw materials used to replace synthetic rheology modifiers include various natural gums, such as casein, alginate, xanthan gum, locust bean gum, guar gum, tragacanth gum, konjac gum, gum arabic, tara gum, gellan gum, pectin, dextrin, cyclodextrin, polysaccharides and carrageenan and modified starch. For example, natural gums can be used in ketchup to provide shear thinning properties (Sahin, H. and Ozdemir, F., Effect of Some Hydrocolloids on The Rheological Properties of Different Formulated Ketchups, Food Hydrocolloids, 2004, 18, 1015-1022). These raw materials are generally considered as suitable substitutes for synthetics because they are generally less functional and can cause formulation instability when used in known compositions. The solubility, water holding capacity, rheological properties, thermodynamic properties, response angle, bulk density and friction coefficient of these gums in water also vary. Additionally, the use of natural gums has been noted to adversely affect the sensory profile of the final formulation. Stabilization and suspension of active ingredients in personal care and home care product formulations can be challenging. Without the necessary stabilization, products may exhibit formulation disruptions such as flocculation and agglomeration.

[0011] For example, natural gums are soluble in water (miscible) and impart high viscosity to the fluid at low concentrations. However, viscosity is proportional to the temperature conditions of dissolution and the cooling rate. At low dissolution temperatures, the conformation is in an ordered state and vice versa. When the salt concentration is also low, the viscosity of the formulation decreases due to intermolecular ionic repulsion. However, above certain salt concentrations, e.g., >0.1%, viscosity becomes salt-independent. Therefore, for ion-containing solutions, xanthan gum is preferably used as a rheology modifier.

[0012] Locust bean gum is natural and partially soluble in cold water even at ambient temperature, and its polymer chains tend to aggregate into a 3D polymer network, forming a weak gel. This does not display the long, viscous rheology of an entangled network, nor does it flow smoothly when sheared. However, locust bean gum forms a viscous, shear-thinning weak gel and can easily form an elastic gel by interacting with other hydrocolloids such as carrageenan. The synergistic gelation stems from the stabilization of the K-carrageenan network by the mannan chains of locust bean gum. In addition, the interface with other macromolecules prevents the gel from syneresis during storage. The inventors have recognized that a rheology modifier is needed to provide the advantages of locust bean gum while enabling smooth flow of fluids that are intended for easy-to-control applications such as cosmetics.

[0013] Konjac gum is a traditional agricultural food ingredient with a large molecular weight and high viscosity in solution, making it a good thickener for food and cosmetics. When high concentrations of konjac gum are combined with other natural gums, a firm, resilient gel is formed that is freeze-thaw stable and has low syneresis. The inventors have recognized the need for a rheology modifier that can give full play to the advantages of konjac even at relatively low concentrations.

[0014] Researchers (William, PA; Phillips, Gyln O.; Overview of the Hydrocolloids, In Gums and Stabilizer for the Food Industry, Vol 13. RSCpubl, Oxford, p13-30) used konjac gum to form thermally irreversible gels with alkali, and konjac gum formed high viscosity dispersions without being affected by salt. This has been applied in the food industry, such as noodles and jelly desserts (Toba S.; Yoshida H.; Tokita T.; Konjac Mannan Containing Reversible Gel, 1987, US 4676976A). At least one study describes the effects of temperature, pH, NaCl, and ethanol on the swelling properties of natural gum mixtures forming composite gels, resulting in changes in stimulus-responsive behavior. It was found that both the degree and speed of swelling decreased with increasing temperature in the range of 20-40% (Dan, H.; Yinglong, W., Modern Food Science and Technology, 2006). The study revealed an exemplary body scrub formulation comprising konjac flour and H. macroloba (3%) (Formulation and characterization of body scrub using marine algae Halimeda macrolova, chitosan and konjac flour, Ervina, A.; Santoso, J.; Prasetyo, BF; Setyaningsih,I.; Tarman, T., IOP Conf. Ser.: Earth Environ. Sci. 2020, 414, 012004), with a moisturizing rate of 58.49-75.15%, a viscosity of 10,106.67-14,900.00 cPas, a pH of 6.48-6.93, a whiteness of 67.74%-95.96% and a spreadability of 1.63-2.17 cm.

[0015] While natural gums can provide some important rheological properties, the viscosity effects are often highly functional or dependent on electrolyte concentration and temperature. Therefore, the properties of these gums alone are not suitable for adjusting the rheology of various fluid products to help control flow and stability, nor are they overly sensitive to system conditions (such as the presence or absence of local electrolytes).

[0016] Beyond functional limitations, rheology modifiers provide formulators with a high degree of control over viscosity, suspension, and texture of advanced personal care and home care fluid products. For formulators and manufacturers, rheology modifiers such as thickening and suspending polymers can provide long-term stability or even ensure long-term stability for products that make it to the shelf. However, in personal care products, consumers are increasingly skeptical of the presence of unfamiliar ingredients and additives in these products. Especially for consumers with sensitive skin, the demand for personal care products with high biocompatibility and low irritation risk is increasing. People are becoming more aware of the risks associated with carcinogens, metal sunscreens, and potential allergens. As a result, various brands have emerged to meet this demand, offering personal care products that are advertised as natural, pure, or simple.

[0017] However, consumers may not be fully aware that popular and beneficial natural ingredients such as honey, tea tree oil, and peppermint oil can be irritating to the skin when used in pure form. These ingredients need to be mixed with a carrier or diluent, where the mixture should remain stable over the shelf life of the product. Personal care products containing these ingredients often use non-natural additives to adjust the rheology of dilute solutions and emulsions - thereby compromising their promise of being completely natural - or fail to achieve the high viscosity and stability of non-natural competitors. As a result, alternative natural products are often much thinner than consumers expect, more difficult to spread evenly on the skin, and have a shorter shelf life. A thin texture can give the impression of being diluted, low quality, and low cost-effective. As a result, there is a strong demand for products that are completely or highly natural and biocompatible, while achieving the ideal viscosity and stability of non-natural products.

[0018] In recent years, there has also been a high demand for sustainably sourced rheology modifiers that can also be safely disposed of in a biodegradable manner. Consumers and regulators are now more likely to take a cradle-to-grave approach to assessing the environmental impact of products, including the harvesting methods of raw materials as well as processing, distribution, use and disposal. Commercially available natural raw materials are excellent alternatives to synthetic rheology modifiers not only because they have improved biocompatibility, but also because they are readily biodegradable and have less impact on the environment than synthetic compounds.

[0019] As an example of background technology, JP2017222594A identifies the use of fermented cellulose to improve the emulsifying properties of water-in-oil cosmetic emulsions. Fermented cellulose is more environmentally friendly than plant cellulose and can be harvested in vitro without deforestation. It has also been found to provide improved functional properties, which is believed to be at least in part due to its longer polymer length and higher purity. However, it was found that fermented cellulose only provided a relatively low viscosity of 1000 mPas at 25 ℃. The inventors of the patent further proposed the use of fermented cellulose and gums (such as xanthan gum) to improve the uniformity and stability of the emulsion. The viscosity achieved and the solubility of cellulose in the emulsion are still low. In particular, for the application of thick products such as toothpaste and skin creams, the composition has low applicability as a rheology modifier. Generally, various fluid formulations require a viscosity of 10,000 mPas or higher to be applied, so the fermented cellulose-based emulsifiers of the prior art have only limited functionality as rheology modifiers.

[0020] It is well known that in cosmetics, the pH of the product affects biocompatibility and user experience. It is highly desirable for cosmetics to have a stable pH in addition to stable texture and rheological properties. Rheology modifiers on the market, while being natural, biodegradable, and offering a wide range of viscosities in various aqueous systems, do not adequately provide pH stability. Therefore, there is a need for a natural rheology modifier that can overcome the functional issues of the prior art while also being biodegradable, having a low overall environmental impact, and being pH stable. Summary of the invention

[0021] The object of the invention is to overcome the shortcomings of the prior art and provide a kind of biodegradable rheology modifier, it can provide a series of viscosities, pH value is stable, and is made of renewable materials. Another object of the present invention is to provide a kind of fluid product that comprises this biodegradable rheology modifier, wherein, this fluid product is preferably cosmetics, medicine, ink, paint, coating or food. Fluid product can also be preferably or comprise personal care composition, home care composition, health care composition or pharmaceutical composition, these are just examples. In addition, the object of the present invention is to provide a kind of improved biodegradable rheology modifier and the manufacture method of fluid product, this improved method is more sustainable than the method of prior art.

[0022] This problem is solved by the features of the independent claim. Preferred embodiments of the invention are provided by the dependent claims.

[0023] The present invention relates to a biodegradable rheology modifier for a fluid product or formulation, the biodegradable rheology modifier comprising bacterial cellulose. The bacterial cellulose is surface-modified and comprises at least one carboxyl group or a derivative thereof, wherein the biodegradable rheology modifier further comprises at least one natural gum. The surface-modified bacterial cellulose interacts with the natural gum to increase the viscosity of the fluid product.

[0024] As used herein, the term "rheology modifier" preferably refers to an additive that affects viscosity at high and / or low shear rates and may also help adjust the consistency of the coating composition. As used herein, the term "biodegradable" preferably refers to the property of being able to decompose chemically, physically or biologically in a biological environment without leaving toxic residues. Preferably, the term "biodegradable" refers to the type of degradability brought about by organisms, typically microorganisms such as bacteria and fungi.

[0025] As used herein, the term "carboxyl" refers to an organic functional group preferably consisting of a carbon atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group. The term "carboxyl" as used herein may also refer to a carboxylate anion, preferably abbreviated as COO - An organic compound containing a carboxyl group (RCOOH) is preferably referred to as a carboxylic acid. A "carboxyl derivative" is preferably a carboxyl group in which the hydroxyl group has been modified or substituted. Preferably, the new group formed contains an acyl group (RCOOH) in addition to the ion or group replacing the hydroxyl group. - ). Examples of carboxyl derivatives are carboxylates, amides, thioesters, esters, anhydrides and salts of carboxylic acids. It is particularly preferred that the carboxyl derivatives form salts or esters. For example, the hydrogen atom of the hydroxyl group may replace the carboxyl group, such as -COO - Na + Examples of salt formation.

[0026] As used herein, a "fluid" is preferably a substance that continuously deforms when subjected to a shear stress of any magnitude. A "fluid" is also preferably a substance that continuously deforms when subjected to a shear stress exceeding a critical value. Fluids preferably include substances such as liquids, including (non) aqueous solutions, (non) aqueous suspensions, deformable gels, semi-solids, and materials that flow only when a stress exceeding the relevant yield stress is applied.

[0027] As used herein, a "fluid product" is preferably a substance or composition in fluid form when manufactured, transported, stored, sold or used. For example, a "fluid product" can be a skin cream, toothpaste, paint or shampoo, ketchup, mayonnaise or any other product for applying a rheology modifier. A "fluid product" in the sense of the present invention can also be a product sold in a non-fluid form but intended to be used at least temporarily in a fluid form. For example, if a paint is intended to be suspended or dissolved in water or oil when used and then dried to a solid after use, the paint provided in powder form at the point of sale can be considered as a fluid product. Similarly, a shampoo sold in a solid stick form but intended to be used in a fluid form as an emulsion or foam is also preferably a fluid product in the sense of the present invention.

[0028] A "fluid product" in the sense of the present invention may preferably belong to the following groups: personal care products, household care products, laundry or detergent products, agricultural formulation products, pharmaceuticals, inks, paints, coatings or foods.

[0029] As used herein, the term "personal care composition" preferably refers to compositions including, but not limited to, cosmetics, toiletries, cosmeceuticals, beauty aids, personal hygiene and cleansing compositions for use on the human and animal body, including the skin, hair, scalp and nails.

[0030] As used herein, the term "home care composition" preferably refers to compositions including, but not limited to, those used for cleaning or maintaining sanitary conditions of household surfaces, such as in kitchens and bathrooms, as well as laundry products for fabric care and cleaning and the like.

[0031] The term "health care composition" as used herein preferably refers to, but is not limited to, pharmaceuticals, cosmeceuticals, oral care compositions, such as oral suspensions, mouthwashes, toothpastes, etc., and over-the-counter compositions for external application to the body (including the skin, scalp, nails and mucous membranes of humans and animals) for the improvement of health-related or medical conditions, or for the general maintenance of hygiene or health.

[0032] The term "food composition" as used herein preferably refers to a composition including, but not limited to, food applications, in which a rheology modifier is used to enhance functionality, flavor, improve shelf life and color. The product is preferably stable at a wide range of temperatures and pHs, including freeze-thaw conditions (food is restored from a frozen state to room temperature). However, the growing emphasis on health and nutrition, especially the growing demand to curb the global burden of obesity, diabetes and food allergies, is driving the demand for fat substitutes. Currently, several hydrocolloid-based stabilizers are produced only as texturizers and emulsifiers in food formulations. Hydrocolloids are widely used in foods to keep foods fresh even after freezing and prevent spoilage. These chemicals help storage because it increases water retention and prevents the formation of ice crystals during frozen storage. Hydrocolloids are also added to formulations to prepare emulsions (such as mayonnaise), stabilize food particles (especially in dairy and juice preparations) and control the rheology of products such as creams, sauces, soups, etc. This hydrocolloid is preferably completely or partially replaced by the rheology modifier of the present invention.

[0033] As used herein, "bacterial cellulose" is preferably cellulose synthesized by bacteria, also referred to as "microbial cellulose". Suitable bacteria known to experts in the field include, but are not limited to, Gluconacetobacter xylinus and Acetobacter xylinum. Bacterial cellulose is preferably characterized by a crystalline nanofiber structure that preferably produces a large surface area to mass ratio, thereby being able to retain more fluid than plant cellulose. Preferably, the diameter of the bacterial cellulose nanofibers is between 20-100 nm. The crystalline cellulose nanofiber structures are interchangeably referred to herein as "cellulose nanocrystals".

[0034] As used herein, "surface modification" is preferably a method of changing the chemical structure and / or state of a particle (particularly a nanoparticle or microparticle) by chemical reaction or chemical adsorption. Surface modification can preferably be used to change the hydrophobicity, hydrophilicity, conductivity, reflectivity and other properties of the nanoparticle. "Surface modification" can preferably introduce functional groups into the particle structure, for example by substitution reactions. Examples of surface modifications are esterification, sulfonation, oxidation, carboxylation, silanization and polymer grafting. Some of these examples are schematically shown in Figure 5.

[0035] As used herein, "surface-modified bacterial cellulose" is preferably cellulose synthesized by bacteria and is surface-modified such that the cellulose molecules preferably contain functional groups resulting from the surface modification.

[0036] As used herein, "natural gums" preferably refer to naturally occurring polysaccharides, one property of which is the ability to thicken solutions or suspensions, ie the ability to cause a measurable increase in the viscosity of a solution or suspension to which they are added. Non-limiting examples of such gums include agar, locust bean gum, sodium alginate, starch, locust bean gum, tara gum, curdlan, pullulan, welan gum, pectin, dextrin, cyclodextrin, rosin, sclerotium gum, dammar gum, gellan gum, and carrageenan (all from seaweed), beta homoglucan (from oat or barley bran), chicle gum (from the chicle tree), okra pods (from the pods of a plant native to Africa), galbanum (a gum resin from a perennial herb), xanthan gum (all from bacterial fermentation), glucomannan (from the konjac plant), guar gum (from guar beans), gum arabic (from the sap of the acacia tree), gum ghatti (from the sap of the anogeissus tree), gum tragacanth (from the sap of the astragalus shrub), gum karaya (from the sap of the sycamore tree), and the like. The natural gum is preferably used in a form substantially identical to the chemical form in which it occurs in nature, e.g. having the chemical structure produced by the relevant organism from which it was harvested.

[0037] As used herein, "interaction" between components, such as the interaction between surface-modified bacterial cellulose and natural gum, preferably refers to the intermolecular forces or electrostatic forces generated between the component molecules. Examples of such interactions preferably include introducing, increasing or decreasing the number or intensity of the following interactions: dipole-dipole interactions, van der Waals forces, London dispersion forces, and hydrogen bonds between components. The interaction between components preferably results in an increase in the intensity of the intermolecular attractive forces between the components, particularly hydrogen bonds.

[0038] As used herein, the term "viscosity" preferably refers to a measure of a fluid's resistance to deformation. Viscosity preferably quantifies the internal friction between adjacent fluid layers in relative motion. Unless otherwise indicated, the term "viscosity" as used herein preferably refers to dynamic viscosity, also known as absolute viscosity.

[0039] The formulations are made by adding natural gums (guar gum, gum arabic, konjac gum, acacia gum, xanthan gum, carrageenan, etc.) or combinations thereof to surface-modified bacterial cellulose, which helps increase viscosity. These ingredients (natural gums and surface-modified bacterial cellulose) work synergistically to increase the viscosity of the final formulation. That is, the increase in viscosity observed when a mixture of the two ingredients is used exceeds the sum of the viscosities observed when each ingredient is used alone. Surprisingly, it was found that rheology modifiers comprising these ingredients can significantly increase the viscosity of the formulation when added in small amounts. This not only reduces the manufacturing cost of the formulation, but also allows the proportion of additives in the formulation to be smaller compared to the active ingredient. Such formulations can be used in products such as personal care or food, where end users are often skeptical of additives and prefer products labeled "simple", "free of harsh chemicals" or "pure" to a certain percentage.

[0040] The raw material of the biodegradable rheology modifier, bacterial cellulose, has been surface-modified to meet the requirements of green chemistry. This ultimately achieves the goal of replacing non-biodegradable product ingredients.

[0041] By using bacterial cellulose in a rheology modifier, the manufacturing process of the rheology modifier can be made more sustainable in a cradle to grave approach. Since the need for plant cellulose can be eliminated, the production of the rheology modifier of the present invention does not require the felling of any trees. In addition, bacterial cellulose can biodegrade much faster than plant cellulose and does not leave any residue. In fact, studies have found that carboxylated bacterial cellulose can achieve 100% biodegradation within 60 days. Therefore, the production and disposal of bacterial cellulose can be configured as a zero waste cycle.

[0042] It is also surprisingly found that by using bacterial cellulose, very fine fibers with higher surface area and therefore higher reactivity can be provided.As shown in Figure 1, fiber also tends to form a network, thereby increasing the stability and water retention of bacterial cellulose.As is well known, using carboxylated bacterial cellulose, its solubility in aqueous media is greatly increased, and also increases its contact and intermolecular interaction with other components (such as natural gum).Natural gum is soluble in water at least in part due to functional groups such as carboxyl in its polymer chain.Not wishing to be restricted by any theory, it is believed that hydrogen-hydrogen bonds can be produced between carboxylated bacterial cellulose and natural gum, thereby increasing the uniformity and stability of the suspension containing these components.Therefore, suspension can keep well mixed for a long time.In addition, the interaction between these components causes a sharp increase in viscosity when used in solution or suspension, particularly in aqueous systems, which is likely due to the interpenetration network formed between bacterial cellulose and natural gum.

[0043] Bacterial cellulose is highly biocompatible and can provide various benefits to the skin, such as increased skin moisture due to its high water retention capacity. Bacterial cellulose does not cause irritation or allergic reactions in direct contact with human skin. Surprisingly, when bacterial cellulose is carboxylated and used in the rheology modifier of the present invention together with natural gum, its high biocompatibility is retained. No adverse effects were detected using this modified form of bacterial cellulose.

[0044] The rheology modifiers of the present invention are very effective in increasing the viscosity and stability of formulations. When used in fluid products, the shelf life can be extended because the sedimentation tendency of suspended ingredients is low. In addition, the tactile quality of the formulation can be improved by increasing the viscosity. For example, skin creams can be made thicker, making them easier to apply on the skin, giving the impression of a concentrated, "rich", high-quality product. It was further found that biodegradable rheology modifiers significantly slowed down the instability of emulsions. When rheology modifiers are used as additives, formulations containing different phases (o / w or w / o emulsions) remain stable for a longer period of time. This enables the development of personal care products that meet the market demand for safe, biodegradable and biocompatible ingredients, while being comparable to the texture and tactile quality of traditional products.

[0045] In a preferred embodiment of the present invention, the natural gum is selected from the group consisting of sodium alginate, starch, xanthan gum, locust bean gum, guar gum, tragacanth gum, konjac gum, gum arabic, tara gum, gellan gum, curdlan, pullulan, welan gum, pectin, dextrin, cyclodextrin, rosin, sclerotium gum, carrageenan and mixtures thereof. It is found that these gums interact surprisingly well with the surface-modified bacterial cellulose and synergistically increase the viscosity of the aqueous solution to which they are added. In addition, it is found that these gums are particularly safe when used on human skin.

[0046] Furthermore, these natural gums can be harvested in a sustainable manner, which improves the overall sustainability of the final product. Harvesting natural gums does not usually require felling trees or clearing forests. Instead, many gums, such as gum arabic, can be harvested from acacia trees through traditional methods that prevent individual local communities from cutting down trees.

[0047] Preferably, a natural glue is selected that responds to a stimulus. Preferably, the stimulus belongs to the group consisting of: temperature, pH, light, electric field, electrostatic force and combinations thereof. Those skilled in the art know which glues respond to the relevant stimulus. These glues advantageously form stimulus-responsive hydrogels in aqueous systems. The properties of such hydrogels can be altered depending on local environmental conditions, such as temperature and pH. Stimuli-responsive hydrogels have a wide range of special applications, including drug delivery, gene delivery and tissue regeneration, which makes them particularly advantageous when used in pharmaceuticals, cosmeceuticals or foods.

[0048] In another preferred embodiment of the present invention, biodegradable rheology modifier comprises at least one natural gum, selected from the group consisting of: xanthan gum, konjac gum, guar gum, locust bean gum, carrageenan etc. In another preferred embodiment of the present invention, biodegradable rheology modifier comprises at least one natural gum, selected from the group consisting of: xanthan gum, konjac gum, guar gum, locust bean gum, carrageenan etc. In another preferred embodiment of the present invention, biodegradable rheology modifier comprises at least two kinds of gum, preferably at least one kind of gum is selected from the group consisting of xanthan gum, konjac gum, guar gum and locust bean gum. It is found that the rheological properties of rheology modifier can be improved synergistically using at least two kinds of gum. For example, by adding xanthan gum to synergistically enhance the viscosity of konjac gum. Not limited to a particular theory, it is believed that the synergistic effect is due to the increase of hydrogen bonds between the type of gum and the surface-modified bacterial cellulose.

[0049] In another preferred embodiment of the present invention, the surface modification is obtained by carboxylating one or more primary alcohol groups of bacterial cellulose, preferably at the C6 position. Cellulose is preferably characterized as a high molecular weight linear homopolysaccharide of β-1,4 linked anhydrous-D-glucose units (hereinafter referred to as monomers), wherein each monomer is 180° helical relative to its adjacent monomers. Each monomer contains three hydroxyl ("-OH" or "alcohol") groups. As shown in Figure 7, they are located at the C2, C3 and C6 positions. The alcohol groups at the C2 and C3 positions are considered "secondary alcohol" groups because they are bound to two carbon atoms. The alcohol group at the C6 position is considered a "primary alcohol" group because it is only bound to a single carbon atom. Preferably, in the oxidation of the primary alcohol group at the C6 position, the alcohol group is replaced by a carboxyl group or a derivative thereof. Preferably, the primary alcohol group at the C6 position is oxidized in a targeted manner using a position selective oxidation technique.

[0050] In another preferred embodiment of the present invention, the bacterial cellulose comprises a plurality of monomers, and at least one carboxyl group or its derivative is present in at least 70%, preferably at least 80%, 90% or more of the monomers of the bacterial cellulose. In some embodiments, at least one carboxyl group is present in at least 95%, at least 99% or 100% of the monomers of the bacterial cellulose. It has been found that such a degree of carboxylation can achieve a high solubility of cellulose in water and can synergistically increase the viscosity of the aqueous solution by interacting with at least one natural gum.

[0051] In another preferred embodiment of the present invention, the ratio of surface-modified bacterial cellulose to natural gum is 4: 1 to 3: 7, preferably 3: 2 to 2: 3, more preferably about 1: 1. The ratio of surface-modified bacterial cellulose to natural gum is preferably 6: 5 to 5: 6. Surprisingly, at the above ratio, when used in a fluid formulation, the synergistic effect between the two ingredients can be maximized and the interaction between them is increased.

[0052] In another preferred embodiment of the present invention, the biodegradable rheology modifier also comprises an antimicrobial, preferably selected from the group consisting of an alkali metal salt or an alkaline earth metal salt, an antioxidant and mixtures thereof, and the alkali metal salt or the alkaline earth metal salt more preferably comprises sodium benzoate, sodium bisulfite. The antimicrobial also prolongs the service life of the final product using it, particularly after opening the package containing the product. In addition, the selected antimicrobial can also be used to adjust the pH value of the rheology modifier. Preferably, the concentration of the antimicrobial in the biodegradable rheology modifier is such that its concentration in the fluid product is as high as 1w / w%. The antimicrobial can also preferably be added directly to the fluid product without forming a part of the rheology modifier.

[0053] In another preferred embodiment of the present invention, the pH value of the biodegradable rheology modifier is set to 3-13, preferably 4-10, more preferably 5-10 by a buffer. The buffer is preferably a phosphate, citrate, carbonic acid, bicarbonate buffer, a combination thereof or any prior art known buffer that can control the pH value. The buffer can also preferably comprise citric acid or sodium hydroxide. The buffer can advantageously stabilize the pH value of the rheology modifier and its used formulation. The buffer can form a part of the rheology modifier composition of the present invention, for example, in a powder form or suspended with the remaining ingredients. Alternatively, or in addition, the buffer can be directly added to the fluid product. Preferably, the concentration of the buffer in the fluid product is up to 1w / w%.

[0054] In another preferred embodiment of the present invention, cellulose is ground before surface modification. Ground bacterial cellulose is more reactive and can be highly carboxylated. At the same time, the ability of cellulose to form a network in an aqueous system is retained. This increases the interaction between cellulose and natural gum when used in a formulation. By finely grinding the cellulose, the formulation can also become uniform visually and texture-wise, thereby providing a good user experience. In another preferred embodiment of the present invention, the biodegradable rheology modifier is provided in a granular form or a suspended form, and its particle size is 1µm-1000µm, preferably 1µm-500µm, and more preferably 1µm-100µm. By providing the rheology modifier in a granular form (e.g., a powder), it can be easily stored and measured for various applications mentioned elsewhere herein. In contrast, a suspended form of a rheology modifier, a solution thereof, or a suspension thereof is conducive to making the formulation uniform faster. In addition, during the production process, the suspension can be directly pumped or flowed to a manufacturing station for preparing the formulation.

[0055] In another preferred embodiment of the present invention, the bacterial cellulose is ground to a particle size of up to 1000µm, preferably 1µm-500µm, more preferably 1µm-100µm, before surface modification and mixing with natural gum to form a rheology modifier. By grinding to these sizes, the solubility and dispersibility of the bacterial cellulose can be advantageously maximized. As used herein, the term "granules" preferably refers to powders. Preferably, the carboxylation and mixing are carried out under aqueous conditions.

[0056] In another aspect, the present invention relates to a fluid product comprising the above-described biodegradable rheology modifier.

[0057] In a preferred embodiment of the present invention, the concentration of surface-modified cellulose in the fluid product is 0.2 w / w%-5 w / w%, preferably 0.5 w / w%-2 w / w%, and more preferably 1 w / w%-1.5 w / w%. As used herein, the concentration expressed as "as used herein preferably refers to the mass of the ingredient as a percentage of the total mass of the composition. At these concentrations, high viscosities can be achieved as shown in the experimental examples described herein. Therefore, the concentration of surface-modified cellulose in the fluid product can be kept low while allowing the viscosity of the fluid product to be adjusted over a wide viscosity range. Therefore, using only a small amount of a biodegradable rheology modifier, a very viscous fluid product can be manufactured inexpensively and sustainably. This also allows greater freedom in adjusting other qualities of the fluid product, such as its color and opacity.

[0058] In another preferred embodiment of the present invention, the concentration of the gum in the fluid product is 0.2w / w%-5w / w%, preferably 0.5w / w%-2w / w%, more preferably 1w / w%-1.5w / w%. It has also been found that these concentrations of gum are suitable for providing the desired high viscosity at low concentrations, as shown in the experimental examples described herein.

[0059] In another preferred embodiment of the present invention, the fluid product is a personal care product, cosmetics, medicine, health care products, household care products, laundry or detergent products, agricultural formulations, ink, paint, coating or food. In a preferred embodiment of the present invention, the fluid product is a personal care product, and is preferably selected from the group consisting of the liquid and the emulsion in emulsion, facial cream, shower gel, shampoo, essence, disposable cosmetics, wet wipes. In a particularly preferred embodiment of the present invention, the fluid product is a skin care product.

[0060] In a preferred embodiment of the present invention, the fluid product further comprises one or more solvents, emollients, active pharmaceutical ingredients, dermatologically active ingredients, sunscreens, dyes, fragrances and / or preservatives.

[0061] In another aspect, the present invention relates to a method for producing a biodegradable rheology modifier, comprising surface-modifying cellulose by carboxylation to form carboxyl groups or derivatives thereof in the cellulose polymer, and mixing the surface-modified cellulose with a natural gum. The cellulose is preferably bacterial cellulose.

[0062] In a preferred embodiment of the present invention, the method for producing a biodegradable rheology modifier includes grinding cellulose before surface modification. In addition, the ground bacterial cellulose is more reactive and can be highly carboxylated. At the same time, the ability of cellulose to form a network is retained in an aqueous system. This increases the interaction between cellulose and natural gum when used in a formulation. By finely grinding the cellulose, the formulation can also become uniform in vision and texture, thereby providing a good user experience.

[0063] Preferably, the carboxylation and mixing are carried out under aqueous conditions. In a preferred embodiment of the present invention, the method further comprises grinding the cellulose before surface modification so that the average particle size of the cellulose in the form of particles is 1µm-1000µm, preferably 1µm-500µm, more preferably 1µm-100µm.

[0064] In another preferred embodiment of the invention, the cellulose is ground in the presence of hydrogen peroxide (HPO) so that the cellulose is additionally bleached. This allows the rheology modifier to be used in a variety of fluid products with minimal impact on the color of the final product. In addition, in many fluid products, a neutral color (e.g. white) is desirable.

[0065] In another preferred embodiment of the present invention, the surface modification of cellulose is carried out in the presence of at least one catalyst, which is preferably selected from the group consisting of:

[0066] - an N-oxyl compound, preferably TEMPO (2,2,6,6-tetramethylpiperidinyl-N-oxyl) or a TEMPO derivative having at least one functional group at the C4 position (T1-T4),

[0067] - an alkali metal halide, preferably KBr, NaBr or LiBr, an oxidizing agent, preferably oxygen, ozone, hydrogen peroxide (HPO), ammonium persulfate, potassium persulfate, sodium persulfate or potassium permanganate.

[0068] Particularly preferably, the catalyst comprises TEMPO, the aforementioned TEMPO derivatives, hydrogen peroxide (HPO) or ammonium persulfate. As used herein, the abbreviation "ammonium persulfate. Preferably refers to 2,2,6,6-tetramethylpiperidin-1-oxyl free radical. TEMPO has the advantage of positional selectivity, so that oxidation occurs mainly at the C6 position of the cellulose monomer, and is highly soluble and efficient in aqueous systems.

[0069] In some preferred embodiments, the surface modification is carried out in the presence of TEMPO, NaBr and NaClO, wherein TEMPO and NaBr act as co-catalysts and NaClO acts as the primary oxidant. It may also be preferred to use ammonium persulfate as a catalyst. Ammonium persulfate has been found to be a good oxidant and it can also bleach cellulose, which may be desirable in certain applications.

[0070] By surface modification under alkaline conditions, the dissociation of primary alcohol groups in aqueous systems can be increased. Primary alcohol groups have a greater dissociation tendency than secondary alcohol groups, and therefore react to form carboxyl groups (or their derivatives) to a greater extent than secondary alcohol groups in the cellulose chain.

[0071] Advantageously, the above reaction conditions accelerate the desired carboxylation of the C6 primary alcohol group without requiring extremely high temperatures or concentrations, thus making the reaction commercially viable. It has also been found advantageous that the reaction conditions do not substantially result in unwanted side reactions or toxic or other undesirable byproducts.

[0072] Terms such as substantially, approximately, about and the like preferably describe a tolerance range of less than ± substantially, preferably less than ± preferably less, particularly preferably less than ± particularly, particularly preferably less than ± particularly, and include the exact value.

[0073] DETAILED DESCRIPTION AND EXAMPLES OF THE PRESENT INVENTION

[0074] It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the claims of the present invention define the scope of the invention and that methods and apparatus within the scope of these claims and their equivalents be covered thereby.

[0075] The examples described herein demonstrate that rheology modifiers consisting of a mixture of surface-modified bacterial cellulose and natural gum can achieve high viscosities (5,000-110,000 cP) that are stable over a wide pH range while exhibiting shear-thinning properties. Thus, the rheology modifiers according to the invention are able to meet high standards of stability, viscosity and tactile quality while remaining natural, biocompatible and highly sustainable throughout their lifecycle.

[0076] Without intending to limit the invention, the invention will be explained in more detail with reference to exemplary embodiments and the following drawings: BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figures 1a and 1b are morphological observations of bacterial cellulose-based structures according to an embodiment of the present invention by SEM, wherein the image on the left (a) is a SEM image (×5,000) of bacterial cellulose, and the image on the right (b) is a SEM image (×10,000) of bacterial cellulose. The images show a 3D network with a complete fiber structure and a microscopic diameter of 10µm (a) and 1µm (b).

[0078] Fig. 2 Viscosity of surface-modified cellulose at different concentrations at neutral pH.

[0079] Figure 3 shows the rheological properties of the bacterial cellulose-based composition according to an embodiment of the present invention measured by a cone-plate rheometer. The relationship between viscosity and shear rate is shown in a non-Newtonian form, showing shear-thinning properties.

[0080] FIG. 4 shows the viscosity and pH values ​​of a plurality of bacterial cellulose-based composition samples according to two embodiments of the present invention, showing the stability of the formulated compositions in acidic to alkaline media.

[0081] FIG. 5 is a schematic diagram of various known surface modification reactions of cellulose.

[0082] FIG. 6 is a schematic diagram of the reaction mechanisms of three preferred cellulose surface modification reactions for making the rheology modifier of the present invention.

[0083] Figure 7 Schematic representation of a single monomer unit that forms part of a cellulose chain. The C1-C6 carbon positions are labeled on the unit.

[0084] FIG. 8 shows a graph of the viscosity of a rheology modifier excluding natural gum at different shear rates and different pH values.

[0085] FIG. 9 shows a graph of the viscosity of a rheology modifier comprising a natural gum according to the present invention, wherein the viscosity is measured at different shear rates and pH values.

[0086] FIG. 10 shows a graph of the complex shear modulus of a rheology modifier that does not include a natural gum at different shear strains and different pH values.

[0087] 11 is a graph showing the complex shear modulus of a rheology modifier comprising natural gum according to the present invention, wherein the complex shear modulus is measured at different shear strains and pH values.

[0088] 12 is a graph showing the particle size distribution of a rheology modifier not containing natural gum (curve I) and a rheology modifier according to the invention containing natural gum (curve II). DETAILED DESCRIPTION

[0089] All exemplary methods for producing the rheology modifiers of the present invention use bacterial cellulose as a raw material. Figures 1a and 1b show the surface morphology of the materials examined using a scanning electron microscope. As observed, the bacterial cellulose forms fine fibers with a diameter of up to 10µm. The freeze-dried sample was sputter-coated with a thin layer of evaporated gold. The micrographs were taken at magnifications of 5000 and 10000 and an accelerating voltage of 25kV. It shows a complete fiber structure, with the solid materials in the composition forming a 3D fiber network in a non-uniform dispersion. These are particularly suitable for improving the stability of slurries, suspensions, emulsions or solutions, as the network counteracts the tendency of the system components to settle. The network structure also increases the water retention of the bacterial cellulose, thereby improving the performance of the skin care products in which it is used.

[0090] In a preferred embodiment of the present invention, the surface modification of cellulose is carried out in the presence of at least one catalyst, preferably selected from the group consisting of: TEMPO (T1), 2,2,6,6-tetramethylpiperidinyloxy radical and its derivatives, namely 4-(acetylamino)-2,2,6,6-tetramethylpiperidinyloxy (T2), 2,2,6,6-tetramethyl-4-oxopiperidinyloxy (T3), 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (T4), hydrogen peroxide (HPO) and ammonium persulfate. TEMPO has the advantage of position selectivity, for example, oxidation mainly occurs at the C6 position of the cellulose monomer, and is highly soluble and efficient in aqueous systems. In some preferred embodiments, the surface modification is carried out in the presence of TEMPO, NaBr and NaClO, wherein TEMPO and NaBr act as co-catalysts and NaClO acts as the main oxidant.

[0091] It may also be preferred to use ammonium persulfate as a catalyst. Ammonium persulfate (APS) has been found to be a good oxidant that can also bleach cellulose, which is also desirable in certain applications. Ammonium persulfate has also been found to be particularly advantageous because it is harmless from a toxicological point of view. It can also be made from natural materials and safely handled, making it highly sustainable. The use of hydrogen peroxide (HPO) may also be preferred. HPO also provides a bleaching effect while being a strong oxidant. Several catalysts and co-catalysts for surface modification of cellulose are known in the art. However, the reaction yield, product characteristics, and porous or fibril structure vary depending on the conditions used for the modification. Here, the process is optimized for the desired application of each category (preferably rheological or polymer modifiers). Surface chemical modification of bacterial cellulose (BC) is performed by catalytic oxidation reactions with different modifiers. The reaction converts the table alcohol group (-CH2OH) of 1 located at position 6 of the bacterial cellulose structure into a -COOH group (carboxylation) while keeping the rest of the bacterial cellulose structure unchanged, so this phenomenon can be defined as surface modification. The surface modification of bacterial cellulose was achieved using the oxidation technique set by Akira Isogai et al. (Akira Isogai, Tsuguyuki Saito and Hayaka Fukuzumi, TEMPO-oxidized cellulose fibers, Nannoscale, 2011, 3, 71-85; TEMPO-Mediated Environmentally Benign Oxidation of Primary Alcohols to Carboxylic Acids with Poly[4-(diacetoxyiodo)styrene, Yousuke Tashinoa, Hideo Togo, Synlett 2004(11): 2010-2012). In this case, NaOH was used to maintain the alkalinity of the reaction medium, so that the -COOH groups appeared as -COONa in the water system, as shown in Figure 7.TEMPO-mediated surface modification of monosaccharides, oligosaccharides, and polysaccharides for the regioselective conversion of primary hydroxyl groups to carboxylic acid groups has been reviewed elsewhere (AEJ de Nooy, AC Besemer, and H. van Bekkum, Selective oxidation of primary alcohols mediated by nitroxyl radical in aqueous solution, Kinetics and mechanism Tetrahedron, 1995, 51, 8023–8032; PL Bragd, H. van Bekkum, and AC Besemer, TEMPO-Mediated Oxidation of Polysaccharides: Survey of Methods and Applications, Top. Catal., 2004, 27, 49–66).In addition to the above, solid-supported TEMPO-modified bacterial cellulose (Fey, T., Fischer, H., Bachmann, S., Albert, K. & Bolm, C., Silica-supported TEMPO catalysts: synthesis and application in the Anelli oxidation of alcohols, J. Org. Chem. 66, 8154–8159 (2001); Karimi, B. & Farhangi, E., A highly recyclable magnetic core-shell nanoparticle-supported tempo catalyst for efficient metal- andhalogen-free aerobic oxidation of alcohols in water, Chem. Eur. J. 17, 6056–6060 (2011)) and polymeric TEMPO (Dijksman, A., Arends, IWCE & Sheldon, RA, Polymer immobilised TEMPO (PIPO): an efficient catalyst for the chlorinated hydrocarbon solvent-free and bromide-free oxidation of alcoholswith hypochlorite, Chem. Commun. 271–272 (2000), and TEMPO derivatives grafted onto other water-soluble polymers were found to be promising.

[0092] Comparative Example 1

[0093] In a preferred embodiment of the present invention, the surface modification or carboxylation of bacterial cellulose is additionally or alternatively mediated by TEMPO (T1), 2,2,6,6-tetramethylpiperidinyloxy radical. This is illustrated schematically in FIG6 . In a typical laboratory experiment, a bacterial cellulose suspension (5 g) was suspended in water (500 mL) containing TEMPO (0.50 mmol) and sodium bromide (5 mmol) and mixed thoroughly in a conical flask. The contents of the flask were kept at 50°C and the pH was adjusted to 10. The TEMPO-mediated surface modification was initiated by adding the required amount of NaClO solution (10-16 mmol NaClO per gram of cellulose) as an oxidant. The reaction mixture was kept under set conditions for a further 30-60 minutes and then quenched by adding ethanol. The surface modified cellulose was washed thoroughly, dried and stored at 4 °C. The reaction yield was found to be over 80%. The carboxylate content of the surface modified cellulose was determined using titration as shown in Table 2.

[0094] Comparative Example 2

[0095] In a preferred embodiment of the present invention, the surface modification of bacterial cellulose, i.e., the carboxylation process mediated by APS, is schematically illustrated in FIG6 . It was also found that the mixture obtained by the method was uniform, without streaks or precipitation. No color change was observed during storage of the mixture. In a typical laboratory experiment, a 1% aqueous suspension of bacterial cellulose was transferred to a 2L conical flask and 20-50 mL of a 1M aqueous ammonium sulfate solution was added. Thereafter, the temperature of the mixture was raised to 60°C and stirred continuously for 1.5 hours, while the pH value of the mixture was maintained at 1.0-2.0. The modified bacterial cellulose was thoroughly washed, dried and stored at 4°C. It was found that the yield of the modified cellulose exceeded 50%.

[0096] Table 1: Analysis results of surface modified bacterial cellulose (powder)

[0097]

[0098] Table 2: Yield and carboxyl content of surface modified bacterial cellulose

[0099]

[0100] a : Gravimetric method, b :Improved titration method based on TAPPI method (T 237cm-98)

[0101] Comparative Example 3

[0102] In a preferred embodiment of the present invention, the carboxylation of bacterial cellulose is additionally or alternatively mediated by HPO. This is illustrated in the form of a schematic diagram in FIG6 . It was also found that the mixture obtained by this method was homogeneous, without streaks or precipitation. The process resulted in bleaching of the cellulose. No further color change was observed during storage of the mixture. In a typical laboratory experiment, 10 g of bacterial cellulose was suspended in 2.0% (166.67 mL) of a 12% hydrogen peroxide solution. Thereafter, 22.2 mL of 1M NaOH was added to the suspension (pH=11), and the temperature was raised to 80 and maintained for 1.0 hour. The modified bacterial cellulose was thoroughly washed, dried and stored at 4 until neutral. The yield of the modified cellulose was found to be over 50%.

[0103] As can be seen from Table 1, the surface modified bacterial cellulose is converted into powder in the desired size range for further processing by an in-house invented process. The 2.5% liquid suspension shows a very high viscosity. It was observed that the viscosity of the modified cellulose increases with the increase in the concentration of the modified cellulose. The modified bacterial cellulose was found to be 100% biodegradable according to the OECD 301F method. Table 2 shows the yield and carboxylation value of the modified bacterial cellulose obtained by the TAPPI method (T237 cm-98). The details of the TAPPI (Technical Association of the Pulp and Paper Industry) method are well known and easily accessible to those skilled in the art. The average yield is between 70-90%, depending on the TEMPO derivative used.

[0104] Viscosity and pH dependence:

[0105] The dynamic viscosity of the mixture was measured using a NDJ-8S rotational viscometer with a series of spindles S1-S4. The measurements were performed under standard conditions. The mixture was found to be homogeneous with no filaments or sediments. No color change was observed while recording the measurements.

[0106] Preparation of the composition:

[0107] In a preferred embodiment of the present invention, the product obtained after modification of bacterial cellulose in a formulation (mentioned below) behaves as a biodegradable rheology modifier with a natural content of >95%. Compositions of different ingredients containing natural gum were prepared and their viscosity was examined. The modified bacterial cellulose was found to be insensitive to electrolytes in the pH range of 4-10, which indicates that it is important for personal care and home care applications, where the effect of electrolytes (especially alkali metal halides such as sodium chloride or potassium chloride at a concentration of 0.1-0.5M) will remain unchanged. It was also found that the use of this sample can enhance the appearance and further improve the rheological properties of the formulation as required.

[0108] Table 3: Compositions of bacterial cellulose using different surface modifications

[0109]

[0110] Rheology modifier 1: bacterial cellulose and natural gum from TEMPO; Rheology modifier 2: bacterial cellulose and natural gum from APS; Rheology modifier 3: bacterial cellulose and natural gum from HPO

[0111] Composition: Rheology modifier (1-7)

[0112] A finely ground, modified 1.25-3.0% bacterial cellulose suspension (Comparative Examples 1-3) was mixed with at least one of natural gums 1-4 (including guar gum, gum arabic, konjac, locust, xanthan gum, carrageenan and others or combinations thereof) to a total concentration of 1.25-3.0% (as is) or an aqueous solution of the mixture. The prepared mixture or slurry was further homogenized (20,000-30,000 rpm) for 15 minutes. The pH of the slurry was maintained between 4 and 5 using a weak acid. A uniform texture and highly thickened slurry was obtained, to which a preservative / stabilizer sodium benzoate was added to a concentration of 0.5% in the mixture to avoid microbial contamination, and an antioxidant was added to maintain long-term stability.

[0113] Table 4: Compositions of bacterial cellulose and natural gum using different surface modifications

[0114]

[0115] Rheology modifier 4: surface modified bacterial cellulose + natural gum-1; Rheology modifier 5: surface modified bacterial cellulose + natural gum-2; Rheology modifier 6: surface modified bacterial cellulose (APS) + natural gum-3; Rheology modifier 7: surface modified bacterial cellulose (APS) + natural gum-4

[0116] Application preparation:

[0117] The prepared rheology modifiers are used in various applications to understand and evaluate the efficacy of other applications in personal care, coatings and agriculture as shown below. The application areas are unlimited and not limited to the areas shown below in this application.

[0118] Table 5: Different applications using rheology modifiers

[0119]

[0120] Table 6: Results of different applications using rheology modifiers

[0121]

[0122] Table 7: Food applications using rheology modifiers

[0123]

[0124] Table 8: Agricultural applications using rheology modifiers

[0125]

[0126] Viscosity and pH dependence:

[0127] The dynamic viscosity of the mixture was measured using a NDJ-8S rotational viscometer with a series of spindles S1-S4. The measurements were performed under standard conditions. The mixture was found to be homogeneous with no filaments or precipitation. No color change was observed while recording the measurements.

[0128] Table 4 shows the viscosity values ​​obtained over a wide pH range (3-11). In general, the higher the consistency of the modified bacterial cellulose, the lower the pH and the higher the viscosity of the obtained mixture. The composite product showed a smooth, uniform texture, no filaments / limped forms, no phase separation, no precipitation, and no discoloration with temperature. The viscosity increasing effect formed a stable cream with easy adjustment of the thickening. The samples were found to be suitable for the pH range 3-11 and were not sensitive to electrolytes (0.1M NaCl test). The samples were almost completely bio-based with a natural content of >95%. Therefore, the samples can be used as premixes (e.g. powders). It was also found that the use of these samples could enhance the appearance and further improve the rheological properties of the formulation as required.

[0129] Fig. 3 shows the performance of rheology modifiers according to embodiments of the present invention at different shear rates. As can be seen from the figure, viscosity has a sharp downward trend as the shear rate increases. Therefore, rheology modifiers can provide a shear-thinning effect. These are particularly useful in improving user experience because they help release fluid products from containers and facilitate spreading and smearing. At the same time, shear-thinning fluids tend to have higher viscosities when shear forces are not actively applied. This allows them to stay on the surface and remain stable, such as paint on a wall during the drying process, or on the skin of an end user in the case of a skin care product. Therefore, unnecessary dripping effects are avoided and user experience is improved. In this way, rheology modifiers can be used to manufacture natural, biodegradable fluid products that are comparable to traditional products in terms of tactile quality, texture and user experience.

[0130] FIG4 shows the stability of two different compositions (rheology modifier 1 and rheology modifier 4) of the rheology modifier using the natural gum of the present invention. According to two embodiments of the present invention, the samples belong to two groups with two compositions. The results of the samples belonging to the first group are shown using solid circles, and the results of the samples belonging to the second group are shown using hollow circles. As shown in the figure, the rheology modifier performs well in providing high viscosity under a wide range of pH values. The viscosity of the two groups of samples remains essentially unchanged under acidic and alkaline conditions. This shows that the rheology modifier of the present invention is suitable for a variety of applications, from foods that tend to be acidic to cleaning products that tend to be alkaline.

[0131] Figures 8 to 11 show the further analysis results of the viscosity of the rheology modifier samples under different conditions. Figure 8 shows the viscosity of the rheology modifier without natural gum (Comparative Example 1, Table 1). -1 ] and different pH values ​​and are measured in mPas. The measured values ​​are provided for comparison purposes. As can be seen from the figure, the dynamic viscosity of this rheology modifier is almost independent of pH over the entire shear rate range tested. At a given pH, the higher the shear rate, the lower the viscosity. This trend of decreasing viscosity with increasing shear rate is observed in all pH ranges. For example, at a shear rate of 0.01 s -1 The dynamic viscosity of the rheology modifier at pH 5 (represented by open circles) significantly exceeds the dynamic viscosity at the same shear rate at pH 9 (represented by closed circles). Therefore, a change in pH from 5 to 9 significantly changes the behavior of the rheology modifier. Therefore, the effect of such a rheology modifier on a composition can only be predicted by considering the exact pH of the composition.

[0132] Similarly, FIG9 shows the rheology modifier according to the present invention (rheology modifier 1, Table 3) at different shear rates [s -1 ] and dynamic viscosity at different pH values. The rheology modifier comprises at least one natural gum. As can be seen from the figure, the curve representing all tested pH values ​​(3-11) varies from 1 s -1 The shear rate of the composite rheology modifier of the present invention almost completely overlaps. The viscosity decrease is not obvious from the rheology modifier (without natural gum) to the rheology modifier composition containing at least one natural gum. At the same time, surprisingly strong pH independence is achieved. The overlap of the rheological curves at different pHs shows the stability and versatility of the composite rheology modifier of the present invention. For almost all applications, the rheology modifier can be used to adjust the rheological properties of the composition in a precisely determined manner.

[0133] Another advantage of the rheology modifier of the present invention is that, while the rheology modifier is insensitive to pH, it is still sensitive to changes in shear rate. The change in dynamic viscosity with shear rate (i.e., thixotropy or shear thinning properties) is present throughout the shear rate range tested and is very constant, resulting in a regular relationship between viscosity and shear rate (note the logarithmic scale of the y-axis). At high shear rates, very low dynamic viscosities can be achieved. This is a very desirable property in a variety of products, such as for spreading paint, extruding compositions from tubes, etc. The thixotropy of the rheology modifier of the present invention is highly predictable, compared to the unpredictable relationship between dynamic viscosity and shear rate in rheology modifiers that do not contain a gum (Figure 8). A smooth thickening effect can be achieved. This preferably indicates that the inclusion of at least one natural gum in the rheology modifier of the present invention surprisingly leads to a more stable, predictable thixotropic and more pH-insensitive material.

[0134] These results were further confirmed by comparing the composite shear modulus (G*) of rheology modifiers with and without natural gum at different shear strains and pH values. Figure 10 shows the results for rheology modifiers without natural gum. These results are for comparison purposes. At all pH values, it can be seen that the composite shear modulus [Pa] decreases with increasing shear strain [%]. The composite shear modulus is reduced by more than half by changing the pH from 5 (represented by open circles) to pH 7 (represented by solid black diamonds) at a shear strain of 0.1%. It is worth noting that the y-axis scale is logarithmic. Therefore, a pH change of only 2 significantly changes the rheological properties of the rheology modifier. In addition, at a given pH value and low shear strain (less than 1%), the rheology modifier shows a plateau, indicating stable performance. Therefore, the correct shear strain value can be applied according to the target application to obtain a stable formulation.

[0135] In contrast, Figure 11 shows the influence of shear strain and pH value on the composite shear modulus of the rheology modifier comprising at least one natural gum according to the present invention. As can be seen from the figure, the points representing pH values ​​of 5-11 are almost completely overlapped on the shear strains of all tests. The influence of pH value of 3 on the composite shear modulus is only before the shear strain is 10%. In addition, under higher shear strains, the composite shear modulus can be much lower than 10. In addition, when the pH value is higher than 3, the width of the plateau increases, indicating that the stability of the rheology modifier composition is extended under slightly higher shear strains. The data further confirm that the rheology modifier of the present invention is highly stable and is not affected by pH value. The rheology modifier can be quantitatively added to very different compositions (from food to shampoo to household cleaners) in the same way to provide the same effect. By adding natural gum, the situation has been greatly improved, as shown in the comparative results shown in Figure 10.

[0136] The particle size distribution of the rheology modifier with and without natural gum was also studied. Curve I of Figure 12 (Comparative Example 1, Table 1) shows the particle size distribution of the rheology modifier without natural gum. This curve is provided for comparative purposes. The curve shows a very wide size grade distribution with multiple peaks. Therefore, the rheology modifier contains non-uniform particles. The particles are also particularly large, with the size of the largest peak being greater than 1000 (µm). Such large particles make the rheology modifier prone to unnecessary sedimentation, thereby reducing its effectiveness. The uneven particle size is a disadvantage during the mixing process and can result in a less smooth composition. However, the rheology modifier provides stability in different pH ranges when used in any formulation.

[0137] For comparison, curve II of Figure 12 (rheology modifier 1, Table 3) shows the particle size distribution of a rheology modifier according to the present invention comprising at least one natural gum. A narrower particle size distribution can be observed, with a single peak located at a lower size class. Small particle sizes reduce the risk of sedimentation. The network-building properties of natural gums further reduce this sedimentation risk, and natural gums act synergistically with particle size. Therefore, high viscosity and strong thixotropy can be achieved using very small particle sizes. Therefore, the rheology modifier of the present invention has a smoother texture compared to other rheology modifiers.

Claims

1. A biodegradable rheology modifier for a formulation or a fluid product, the biodegradable rheology modifier comprising bacterial cellulose, characterized in that: The bacterial cellulose is surface-modified and contains at least one carboxyl group or a derivative thereof, wherein the biodegradable rheology modifier further contains at least one natural gum, so that the surface-modified bacterial cellulose interacts with the natural gum to increase the viscosity of the formulation or fluid product.

2. The biodegradable rheology modifier according to claim 1, wherein The surface modification is obtained by oxidizing one or more primary alcohol groups of the bacterial cellulose, the primary alcohol group being preferably at the C6 position.

3. The biodegradable rheology modifier according to any one of the preceding claims, wherein The bacterial cellulose comprises a plurality of monomers, and at least one carboxyl group or a derivative thereof is present in at least 70%, preferably at least 80%, 90% or more of the monomers of the bacterial cellulose.

4. The biodegradable rheology modifier according to any one of the preceding claims, wherein The biodegradable rheology modifier is provided in a granular form or a suspended form, and has a particle size of 1µm-1000µm, preferably 1µm-500µm, more preferably 1µm-100µm, and / or wherein, Prior to surface modification and mixing with the natural gum to form the rheology modifier, the bacterial cellulose is ground to a particle size of up to 1000 µm, preferably 1 µm-500 µm, more preferably 1 µm-100 µm.

5. The biodegradable rheology modifier according to any one of the preceding claims, wherein The natural gum is selected from the group consisting of sodium alginate, starch, xanthan gum, locust bean gum, guar gum, tragacanth gum, konjac gum, gum arabic, tara gum, gellan gum, curdlan, pullulan, welan gum, pectin, dextrin, cyclodextrin, rosin, sclerotium gum, carrageenan and mixtures thereof.

6. The biodegradable rheology modifier according to any one of the preceding claims, wherein The biodegradable rheology modifier comprises at least two gums, preferably at least one gum is selected from the group consisting of xanthan gum, konjac gum, guar gum and locust bean gum.

7. The biodegradable rheology modifier according to any one of the preceding claims, wherein The ratio of surface modified bacterial cellulose to gum is 4:1 to 3:7, preferably 6:5 to 5:6, more preferably about 1:

1.

8. The biodegradable rheology modifier according to any one of the preceding claims, wherein The pH value of the biodegradable rheology modifier is set to 3-13, more preferably 4-10, by a buffer, wherein the buffer is preferably a phosphate buffer, a citrate buffer, a carbonate buffer, a bicarbonate buffer or a combination thereof.

9. The biodegradable rheology modifier according to any one of the preceding claims, wherein: The biodegradable rheology modifier further comprises an antimicrobial agent, preferably selected from the group consisting of alkali metal salts or alkaline earth metal salts, antioxidants or mixtures thereof, wherein the alkali metal salts or alkaline earth metal salts are particularly preferably sodium benzoate and sodium bisulfite.

10. A fluid product comprising a biodegradable rheology modifier according to any one of the preceding claims, wherein: The fluid product is preferably a personal care product, a household care product, a laundry or detergent product, an agricultural formulation product, a pharmaceutical product, an ink, a paint, a coating or a food.

11. Fluid product according to the preceding claim, wherein: The concentration of surface-modified cellulose in the product is 0.2 w / w%-5 w / w%, preferably 0.5 w / w%-2 w / w%, more preferably 1 w / w%-1.5 w / w%, and / or wherein, The concentration of the glue in the fluid product is 0.2 w / w%-5 w / w%, preferably 0.5 w / w%-2 w / w%, and more preferably 1 w / w%-1.5 w / w%.

12. A process for producing a biodegradable rheology modifier according to any one of the preceding claims, It is characterized in that The method comprises: - surface modification of cellulose by carboxylation to form carboxyl groups and / or their derivatives in the cellulose polymer, - Mixing surface modified cellulose with natural gum.

13. A method according to the preceding claim, wherein: The method further comprises grinding the cellulose before the surface modification so that the average particle size of the cellulose in the form of particles is 1 μm to 1000 μm, preferably 1 μm to 500 μm, more preferably 1 μm to 100 μm.

14. The method according to claim 12 or claim 13, wherein: The grinding of the cellulose is carried out in the presence of hydrogen peroxide, so that the cellulose is additionally bleached.

15. The method according to any one of claims 12 to 14, wherein: The surface modification of the cellulose is carried out in the presence of at least one catalyst, which is preferably selected from the group consisting of: - N-oxyl compounds, preferably TEMPO (2,2,6,6-tetramethylpiperidin-N-oxyl) or TEMPO derivatives having at least one functional group at the C4 position (T1-T4), - an alkali metal halide, preferably KBr, NaBr or LiBr, and - an oxidizing agent, preferably oxygen, ozone, hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate or potassium permanganate.

Images