Natural, biodegradable rheology modifiers

Abstract

The present invention relates to a biodegradable rheology modifier comprising bacterial cellulose for use in a formulation or fluid product, the bacterial cellulose being surface-modified to comprise at least one carboxyl group or derivative thereof. The biodegradable rheology modifier further comprises at least one natural gum, and the surface-modified bacterial cellulose and the natural gum interact to increase the viscosity of the fluid product. In a further aspect, the present invention relates to a liquid product comprising the biodegradable rheology modifier and a method for making the biodegradable rheology modifier.

Description

[Technical field]

[0001] The present invention relates to a novel biodegradable rheology modifier for use in fluid products. The biodegradable rheology modifier comprises bacterial cellulose, where the bacterial cellulose is surface-modified to comprise at least one carboxyl group or derivative thereof. The biodegradable rheology modifier further comprises at least one natural gum, where 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, preferably a cosmetic product, a pharmaceutical product, an ink, a paint, a coating or a food product. The present invention further relates to a method of making the biodegradable rheology modifier, 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 a natural gum. [Background technology]

[0002] The safety, shelf life, applicability, aesthetic properties, and tactile properties of various fluid or semi-solid products depend on the viscosity, density, and flow properties of the product. Many such everyday products include, for example, suspensions of inorganic or polymeric materials. In the case of inorganic materials, for example, wall paints often include suspensions of titanium dioxide (TiO2) particles that contribute to the opacity and are used to adjust the color of the paint. Such paints are often stored for months or years before use, during which the suspended particles may settle, thereby causing inconsistencies in the color and opacity of the paint. Furthermore, the adhesion of the paint to the surface and the avoidance of undesirable dripping during the period required for the paint to dry depend on the flow behavior, i.e., rheology, of the paint. This rheology is often adjusted by adding additives, which may include thinners or thickeners. Examples of such additives include synthetic approaches such as polymers, e.g., polyacrylates, that contribute to the desired shear-thinning behavior of wall paints.

[0003] Similarly, cosmetic products often contain suspended ingredients, such as ZnO particles in the case of sunscreens, oil-based droplets in the case of moisturizers, or microbeads in many hygiene products. Due to gravity, these ingredients tend to settle to the bottom of cosmetic products over time, which significantly shortens their shelf life. This is often regulated by thickening additives, which modify the rheological properties of the suspension so that settling behavior is dramatically slowed down. However, for such products, the use of inorganic and / or non-renewable rheology adjusting additives may be inappropriate and may also involve health risks.

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

[0005] The term "natural" as used herein preferably refers to a compound or composition that occurs in nature. The term "natural" also preferably refers to a compound or composition that occurs 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, arabic gum, tara gum, gellan gum, pectin, dextrin, cyclodextrin, polysaccharides and carrageenan.

[0006] The term "semi-synthetic" as used herein preferably refers to naturally occurring compounds that have been processed by artificially initiated chemical and other processes. Semi-synthetic rheology modifiers include modified celluloses such as carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose and related derivatives.

[0007] The term "synthetic" as used herein is preferably defined to mean referring to compounds formed by artificially initiated chemical and other processes, as opposed to compounds formed by natural sources. Synthetic rheology modifiers include polyethylene glycol derivatives (PEG), maleic anhydride copolymers, carbomers, polyacrylamides, copolymers of acrylic acid, N-vinylpyrrolidone, cationic monomers (preferably N-vinylimidazole), and hydrophobic monomers which may be long chain esters of methacrylic acid with ethoxylated spacer chains, and the like.

[0008] Rheology modifiers are used in fluid or semi-solid formulations, such as cosmetics and personal care products, home care products, health care products, food products, inks, paints and coatings. As used herein, the term "formulation" preferably refers to the composition of the final product, preferably a fluid product. These formulations include aqueous solutions or suspensions, and are therefore considered aqueous systems. As used herein, the term "aqueous system" preferably describes any system containing water in any physical state, including water containing one or more dissolved or dispersed substances. Rheology modifiers maintain the stability of the formulation against settling over storage time, and also thicken the aqueous system in which they are used. These formulations benefit from improved storage stability, ease of application, working life / wet edge and sagging.

[0009] In recent years, consumers and regulations have driven the replacement of synthetic ingredients with ingredients of natural origin or the development of formulations composed partly or entirely of natural ingredients, not just in cosmetics but in all consumer products. Natural cosmetic ingredients have the advantage of being biocompatible, less toxic and more easily biodegradable compared to their synthetic counterparts.

[0010] Examples of natural raw materials used in place of synthetic rheology modifiers include various natural gums such as 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, as well as modified starches. For example, natural gums are used to impart shear-thinning properties to ketchup (Non-Patent Document 1). These raw materials are often not considered suitable replacements for synthetic materials, as they often have poor functionality and their use in known compositions often leads to formulation instability. These gums also vary in their behavior in water with respect to their solubility, water-holding capacity, rheology, thermodynamic properties, angle of repose, bulk density and coefficient of friction. Furthermore, the use of natural gums has been found to have a detrimental effect on the sensory profile of the final formulation. Stabilization and suspension of active ingredients in personal and home care product formulations can be difficult. Without the necessary stabilization, the product may be subject to formulation degradation phenomena such as aggregation and coalescence.

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

[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 to form a weak gel. This weak gel does not show the long stringy rheology of an entangled network and does not flow smoothly when subjected to shear. However, locust bean gum forms viscous, shear-thinning weak gels and can easily form elastic gels by interacting with other hydrocolloids such as carrageenan. This synergistic gelation is due to the stabilization of the K-carrageenan network by the mannan chains of locust bean gum. Furthermore, the interface with other macromolecules prevents gel syneresis during storage. The inventors have recognized that there is a need for a rheology modifier that provides the benefits of locust bean gum while allowing for the smooth flow of fluids for easily controllable applications, such as cosmetics.

[0013] Konjac gum, a traditional agricultural food ingredient, has a high molecular weight, which is responsible for the high viscosity in solution, and therefore is a good thickener for food and cosmetic products. High concentrations of konjac gum combined with other natural gums form strong elastic gels that are freeze-thaw stable and have low syneresis. The present inventors have recognized that there is a need for a rheology modifier that provides the benefits of konjac even when used at relatively low concentrations.

[0014] Researchers have used konjac gum, which forms high viscosity dispersions unaffected by salt, to form thermally irreversible gels using alkali (Non-Patent Document 2). This has been applied in food applications, such as noodles and jellied desserts (Patent Document 1). At least one study has shown stimuli-responsive behavior modification by the effects of temperature, pH, NaCl, and ethanol on the swelling properties of a mixture of natural gums forming a complex gel. Both the degree and speed of swelling were found to decrease as the temperature increased in the range of 20°C to 40°C (Non-Patent Document 3). Research has revealed an exemplary body scrub formulation containing Konjac flour and H. macroloba (3%) that retains 58.49% to 75.15% moisture, has a viscosity of 10106.67 cPas to 14900.00 cPas, a pH of 6.48 to 6.93, a whiteness of 67.74% to 95.96%, and a spreadability of 1.63 cm to 2.17 cm (Non-Patent Document 4). Natural gums can provide some important rheological properties, but the viscosity effects are often highly functional or dependent on electrolyte concentration and temperature. Thus, the properties of these gums alone are not suitable for adjusting the rheology of a wide variety of fluid products to aid in controlled flow and stability without being overly sensitive to system conditions such as the presence or absence of local electrolytes.

[0015] In addition to functional limitations, rheology modifiers provide formulators with a high degree of control over the viscosity, suspension and texture of advanced personal and home care fluid products. Rheology modifiers, such as thickening and suspending polymers, can provide and actually ensure long-term shelf-life stability for formulators and manufacturers. Nevertheless, when it comes to personal care products, consumers are increasingly skeptical about the presence of unfamiliar ingredients and additives in these products. There is an increasing need for personal care products that are highly biocompatible and have a low risk of irritation, especially for consumers with sensitive skin. There is an increasing awareness of the risks associated with carcinogens, metallic opacifiers and potential allergens. As a result, various brands have emerged to meet this need, providing personal care products labeled as natural, pure or simple.

[0016] However, consumers may not be fully aware that common and beneficial natural ingredients, such as honey, tea tree oil, peppermint oil, etc., are irritating to the skin when used in pure form. Such ingredients must be mixed with a carrier or diluent, and the stability of the mixture should be maintained throughout the shelf life of the product. Personal care products that contain these ingredients tend to use non-natural additives to adjust the rheology of diluted solutions and emulsions, thereby compromising on the promise of being completely natural, or failing to achieve the high viscosity and stability of their non-natural competitors. Thus, natural alternatives are often much more runny than consumers expect, difficult to apply evenly to the skin, and have a short shelf life. The watery texture can further give the impression of being diluted, low quality, and not worth the price. Thus, it is recognized that there is a strong need for products that are completely or to a high extent natural and biocompatible, while at the same time achieving the desired viscosity and stability of their non-natural counterparts.

[0017] In recent years, there has also been an increasing demand for rheology modifiers of sustainable origin that can also be safely disposed of in a biodegradable manner. Consumers and regulatory authorities are now increasingly taking a cradle-to-grave approach to assessing the environmental impact of a product, including the harvesting method of its raw materials as well as its processing, distribution, use and disposal. Commercially available natural raw materials are attractive alternatives to synthetic rheology modifiers due to their improved biocompatibility as well as their easy biodegradability and low environmental impact compared to synthetic compounds.

[0018] As an example of the background art, Patent Document 2 identifies the use of fermented cellulose to improve the emulsifying properties of oil-in-water cosmetic emulsions. Fermented cellulose offered the environmental advantage of being harvestable in vitro without deforestation over plant cellulose. It was also found to offer improved functional properties that were believed to be at least in part due to the longer length and higher purity of the polymer. However, it was found that fermented cellulose only offered a relatively low viscosity of 1000 mPas at 25°C. The inventors of the patent further propose using both fermented cellulose and a gum, such as xanthan gum, to improve the homogeneity and stability of the emulsion. The achieved viscosity and solubility of cellulose in the emulsion remained low. In particular, the suitability of the composition as a rheology modifier was low for application to viscous products such as toothpaste and skin cream. Generally, various fluid formulations require a viscosity of 10,000 mPas or more for application, and therefore prior art emulsifiers based on fermented cellulose have only limited functionality as rheology modifiers.

[0019] For cosmetics, it has been found that product pH affects biocompatibility and user experience. It is highly desirable for cosmetic products to have stable pH in addition to stable textural and rheological properties. Rheology modifiers available on the market are natural, biodegradable, and provide a wide range of viscosities in various aqueous systems, but do not provide sufficient pH stability. Therefore, there is a need for natural rheology modifiers that overcome the functionality problems of the prior art, while also being biodegradable, having a low overall environmental impact, and having a stable pH. [Prior art documents] [Patent documents]

[0020] [Patent Document 1] Toba S.; Yoshida H.; Tokita T., "Konjac Mannan Containing Reversible Gel" (1987), U.S. Patent No. 4,676,976 [Patent Document 2] Patent Publication No. 2017-222594 [Non-patent literature]

[0021] [Non-Patent Document 1] Sahin, H., & Ozdemir, F., Effect of Some Hydrocolloids on The Rheological Properties of Different Formulated Ketchups. Food Hydrocolloids, 2004, 18, 1015-1022 [Non-Patent Document 2] William, PA; Phillips, Gyln O.; "Overview of the Hydrocolloids", In Gums and Stabilizer for the Food Industry, Vol 13. RSC publ, Oxford, p13-30 [Non-Patent Document 3] Dan, H.; Yinglong, W., Modern Food Science and Technology, 2006 [Non-Patent Document 4] Formulation and characterization of body scrub using marine alga Halimeda macroloba, chitosan and konjac flour, Ervina, A.; Santoso, J.; Prasetyo, BF; Setyaningsih, I.; Tarman, T., IOP Conf. Ser.: Earth Environ. Sci. 2020, 414, 012004 Summary of the Invention

[0022] The object of the present invention was to overcome the disadvantages of the prior art and to provide a biodegradable rheology modifier that can be produced in various viscosities, is pH stable, and is made from renewable materials. A further object of the present invention is to provide a fluid product comprising the biodegradable rheology modifier, where the fluid product is preferably a cosmetic product, a pharmaceutical product, an ink, a paint, a coating, or a food product. The fluid product may further preferably be or include a personal care composition, a home care composition, a health care composition, or a pharmaceutical composition, merely by way of example. Furthermore, the object of the present invention is to provide an improved method for producing the biodegradable rheology modifier and the fluid product, where the improved method is more sustainable than the prior art methods.

[0023] The problem is solved by the features of the independent claims. Preferred embodiments of the invention are presented in the dependent claims.

[0024] The present invention relates to a biodegradable rheology control agent for use in a fluid product or formulation, the agent comprising bacterial cellulose, the bacterial cellulose being surface-modified to contain at least one carboxyl group or a derivative thereof, the agent further comprising at least one natural gum, the surface-modified bacterial cellulose and the natural gum interacting to increase the viscosity of the fluid product.

[0025] The term "rheology modifier", as used herein, preferably refers to an additive that affects the viscosity at high and / or low shear rates and also contributes to adjusting the consistency of the coating composition. The term "biodegradable", as used herein, preferably refers to the property of being chemically, physically or biologically degradable in a biological environment without leaving behind toxic residues. Preferably, the term "biodegradable" refers to the kind of decomposition effected by living organisms, usually microorganisms such as bacteria and fungi.

[0026] As used herein, a "carboxyl group" (-COOH) is preferably an organic functional group consisting of a carbon atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group. The term "carboxyl group" as used herein may also refer to a carboxylate anion, preferably COO - The organic compounds containing a carboxyl group (RCOOH) are preferably called carboxylic acids. A "derivative of a carboxyl group" is preferably a carboxyl group in which the hydroxyl group has been modified or replaced. Preferably, the newly formed group contains an acyl group (RCOOH) in addition to the ion or group that has replaced the hydroxyl group. - Examples of derivatives of the carboxyl group are carboxylates, amides, thioesters, esters, anhydrides and salts of carboxylic acids. Particularly preferred derivatives of the carboxyl group form salts or esters. Examples include -COO - Na + As in the example of (1), the hydrogen atom of the hydroxyl group may be substituted with a carboxyl group.

[0027] As used herein, a "fluid" is preferably a substance that deforms continuously when subjected to a shear stress of any magnitude. A "fluid" is also preferably a substance that deforms continuously when subjected to a shear stress above a critical value. Fluids preferably encompass substances such as liquids, including (non-)aqueous solutions, (non-)aqueous suspensions, deformable gels, semi-solids, and materials that flow only when subjected to a stress above their associated yield stress.

[0028] As used herein, a "fluid product" is preferably a substance or composition that is in fluid form during manufacture, transportation, storage, sale or use. For example, a "fluid product" may be a skin cream, toothpaste, paint or shampoo, ketchup, mayonnaise or any other product to which a rheology modifier is applied. A "fluid product" may also be a product that is sold in a non-fluid form but is intended to be used in a fluid form, at least temporarily, in the sense of the present invention. For example, a paint that is provided as a powder at the point of sale can be considered as a fluid product if it is intended to be suspended or dissolved in water or oil when used and then dried to a solid after use. Similarly, a shampoo that is sold as a solid bar but is 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.

[0029] A "fluid product" in the sense of the present invention may preferably belong to the group of personal care products, home care products, laundry or detergent products, agricultural formulation products, pharmaceutical products, inks, paints, coatings or foods.

[0030] The term "personal care composition", as used herein, preferably means compositions including, but not limited to, cosmetics, toiletries, cosmeceuticals, beauty aids, personal hygiene and cleansing compositions, applied to the body, including the skin, hair, scalp, and nails of humans and animals.

[0031] The term "home care compositions", as used herein, preferably refers to compositions including, but not limited to, compositions used in the home for cleaning surfaces or maintaining hygiene, for example, in the kitchen and bathroom, and laundry products for the care and cleaning of fabrics.

[0032] The term "health care composition", as used herein, preferably means compositions including, but not limited to, pharmaceuticals, pharmacosmetics, oral care compositions such as oral suspensions, mouthwashes, toothpastes, and the like, for improving a health-related or medical condition or for generally maintaining hygiene or well-being, as well as over-the-counter compositions applied externally to the body, including the skin, scalp, nails, and mucous membranes of humans and animals.

[0033] The term "food composition" as used herein preferably means a composition including, but not limited to, food applications in which the rheology modifier is used to enhance function, flavor, improved shelf life and color. The product is preferably stable over a wide range of temperatures and pH, including freeze-thaw conditions (where the food is placed at room temperature from a frozen state). However, the growing focus on health and nutrition, especially the growing need to reduce the global burden of obesity, diabetes, and food allergies, has stimulated a demand for fat substitutes. Currently, some hydrocolloid-based stabilizers are manufactured solely as texturizers and emulsifiers in food formulations. Hydrocolloids are widely used in food to keep foods fresh even after freezing and to prevent deterioration. These chemicals aid in storage by increasing water retention capacity and preventing the formation of ice crystals during frozen storage. Hydrocolloids are also added to formulations to prepare emulsions such as mayonnaise, to stabilize food particles, especially in dairy and juice formulations, and to control the rheology of products such as creams, sauces, soups, etc. Such hydrocolloids can preferably be replaced in whole or in part by the rheology modifiers of the present invention.

[0034] As used herein, "bacterial cellulose" is preferably cellulose synthesized by bacteria, and is also referred to as "microbial cellulose". Suitable bacteria known to those skilled in the art include, but are not limited to, Gluconacetobacter xylinus and Acetobacter xylinum. Bacterial cellulose is preferably characterized by a crystalline nanofiber structure, which preferably results in a large surface area to mass ratio and can retain more fluid than plant cellulose. Preferably, the diameter of the bacterial cellulose nanofiber is between 20 nm and 100 nm. The crystalline cellulose nanofiber structure is also referred to herein indifferently as "cellulose nanocrystals".

[0035] As used herein, "surface modification" is a method of changing the chemical structure and / or state of a particle, particularly a nanoparticle or microparticle, preferably by chemical reaction or chemical adsorption. Surface modification can preferably be used to change the hydrophobicity, hydrophilicity, electrical conductivity, reflectivity and other properties of the nanoparticle. "Surface modification" can preferably introduce functional groups into the structure of the particle, for example by substitution reactions. Examples of surface modifications are esterification, sulfonation, oxidation, carboxylation, silylation and polymer grafting. Some of these examples are illustrated diagrammatically in FIG. 5.

[0036] As used herein, "surface-modified bacterial cellulose" is preferably cellulose synthesized by bacteria and subjected to surface modification, and therefore the cellulose molecules preferably contain functional groups resulting from said surface modification.

[0037] As used herein, "natural gum" preferably refers to a naturally occurring polysaccharide, one of the properties of which is the ability to thicken a solution or suspension, i.e. to cause a measurable increase in the viscosity of a solution or suspension to which it is 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 and carrageenan (both derived from seaweed), beta-glucan (derived from oat or barley bran), chicle gum (derived from sapods), okra (derived from the pods of a plant native to Africa), galbanum resin (a gum resin derived from a perennial herb), xanthan gum (both derived from bacterial fermentation), glucomannan (derived from the konjac plant), guar gum (derived from guar beans), gum arabic (derived from the sap of Acacia trees), ghatti gum (derived from the sap of Anogeissus trees), tragacanth gum (derived from Astragalus shrubs). Natural gums include gum tragacanthus (derived from the sap of Sterculia shrubs), karaya gum (derived from the sap of Sterculia trees), etc. The natural gums are preferably used in substantially the same chemical form as they occur in nature, e.g., having the chemical structure produced by the relevant organism from which they are harvested.

[0038] As used herein, the "interaction" between components, for example, the interaction between the surface-modified bacterial cellulose and the natural gum, preferably refers to the occurrence of intermolecular or electrostatic forces between the molecules of the components. Examples of such interactions preferably include dipole-dipole interactions, van der Waals forces, London dispersion forces, and the introduction, increase or decrease in the number or strength of hydrogen bonds between the components. It may be preferable that the interaction between the components results in an intermolecular attraction between the components, particularly an increase in the strength of hydrogen bonds.

[0039] As used herein, the term "viscosity" preferably refers to a measure of the resistance of a fluid to deformation. Viscosity preferably quantifies the internal frictional forces between adjacent layers of a fluid moving relative to one another. Unless otherwise specified, as used herein, the term "viscosity" preferably refers to dynamic viscosity, also known as absolute viscosity.

[0040] The preparation of formulations by adding natural gums (guar, arabic, konjac, locust, xanthan, carrageenan, etc.) or combinations thereof to the surface-modified bacterial cellulose contributes to an increase in viscosity. The components (natural gums and surface-modified bacterial cellulose) contribute synergistically to increase the viscosity of the final formulation. That is, the increase in viscosity observed when using a mixture of both components exceeds the sum of the increases in viscosity observed when each component is used alone. Surprisingly, it has been found that the addition of the resulting rheology modifiers containing these components in small amounts can dramatically increase the viscosity of the formulation. This not only reduces the manufacturing cost of the formulation, but also allows the formulation to have a smaller proportion of additives compared to the active ingredient. Such formulations can be used in products such as personal care or food, where end users tend to be skeptical of additives and prefer products labeled as "simple", "free of harsh chemicals" or a given percentage of "pure".

[0041] Bacterial cellulose, the raw material for biodegradable rheology control agents, can be surface-modified to meet the requirements of green chemistry, ultimately realizing the goal of replacing non-biodegradable product components.

[0042] The use of bacterial cellulose in the rheology modifier can make the manufacturing process of the rheology modifier more sustainable when taking a cradle-to-grave approach. This eliminates the need for plant cellulose, so no trees need to be cut down to make the rheology modifier of the present invention. Furthermore, bacterial cellulose can be biodegraded much faster than plant cellulose and does not leave any residue. In fact, it has been found that 100% biodegradation of carboxylated bacterial cellulose can be achieved within 60 days. Therefore, the production and disposal of bacterial cellulose can be configured as a zero waste cycle.

[0043] Surprisingly, it was also found that the use of bacterial cellulose can provide very fine fibers with a higher surface area and therefore higher reactivity. As shown in FIG. 1, the fibers also tended to form a network that increased the stability and water retention of the bacterial cellulose. The use of carboxylated bacterial cellulose was found to significantly increase the solubility in aqueous media, which in turn increased the contact and intermolecular interactions with other components, such as natural gums. Natural gums are at least partially soluble in water due to functional groups, such as carboxyl groups, in their polymer chains. Without wishing to be limited by any theory, it is believed that hydrogen-hydrogen bonds occur between the carboxylated bacterial cellulose and the natural gums, which increases the homogeneity and stability of suspensions containing these components. Thus, the suspensions remain well mixed for extended periods of time. Furthermore, when used in solutions or suspensions, especially in aqueous systems, the interactions between these components result in a dramatic increase in viscosity, most likely due to the interpenetrating network formed between the bacterial cellulose and the natural gums.

[0044] Bacterial cellulose is highly biocompatible and provides various benefits to the skin, such as increased skin hydration due to its high water-holding capacity. Direct contact of bacterial cellulose with human skin did not result in irritation or allergic reactions. Surprisingly, it was found that bacterial cellulose retains its high biocompatibility when carboxylated and used as a rheology modifier in the present invention together with natural gums. No adverse effects could be detected from the use of bacterial cellulose in this modified form.

[0045] The rheology modifiers of the present invention were very effective in increasing the viscosity and stability of formulations. When used in fluid products, they can provide a much longer shelf life due to the reduced tendency of suspended components to settle. Furthermore, increasing the viscosity can improve the tactile properties of the formulation. For example, a skin cream can be made more viscous, thus facilitating its application on the skin and giving the impression of a concentrated, "rich", high-quality product. It was further found that the biodegradable rheology modifiers significantly slow down the destabilization of emulsions. Formulations with different phases (o / w emulsions or w / o emulsions) remained stable for longer periods when rheology modifiers were used as additives. This allows the development of personal care products that can match the textural and tactile properties of conventional products and meet the market demand for safe biodegradable and biocompatible ingredients.

[0046] In a preferred embodiment of the present invention, the natural gum is selected from the group including 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. These gums have been found to interact surprisingly well with the surface-modified bacterial cellulose and to synergistically increase the viscosity of aqueous solutions to which they are added. Furthermore, these gums have been found to be safe, particularly when used on human skin.

[0047] Furthermore, these natural gums can be harvested in a sustainable manner, increasing the overall sustainability of the final product. Harvesting natural gums does not generally require felling or deforestation. Instead, many gums, such as gum arabic, can be harvested from acacia trees using traditional methods that discourage tree felling in the respective communities.

[0048] Preferably, the natural gums are selected because they are responsive to stimuli. Preferably, the stimuli belong to the group including temperature, pH, light, electric field, electrostatic force and combinations thereof. A person skilled in the art will understand which gums are responsive to the relevant stimuli. These gums advantageously form stimuli-responsive hydrogels in aqueous systems. The properties of such hydrogels can change depending on local environmental conditions such as temperature and pH. Stimuli-responsive hydrogels have a wide variety of special applications including drug delivery, gene delivery and tissue regeneration, and are particularly advantageous when used in pharmaceutical or cosmeceutical products or food products.

[0049] In a further preferred embodiment of the present invention, the biodegradable rheology modifier comprises at least one natural gum selected from the group including xanthan gum, konjac gum, guar gum, locust bean gum, carrageenan gum, etc. In a further preferred embodiment of the present invention, the biodegradable rheology modifier comprises at least two gums, at least one of which is preferably selected from the group including xanthan gum, konjac gum, guar gum, and locust bean gum. It has been found that by using at least two gums, the rheological properties of the rheology modifier can be synergistically improved. For example, the viscosity of konjac gum is synergistically enhanced by adding xanthan gum. Without intending to be limited to a particular theory, it is believed that this synergistic effect is due to an increase in hydrogen bonds between these types of gums and the surface-modified bacterial cellulose.

[0050] In a further preferred embodiment of the invention, the surface modification is obtained by carboxylation of one or more primary alcohol groups of bacterial cellulose, preferably the primary alcohol group at the C6 position. Cellulose is preferably characterized as a high molecular weight linear homopolysaccharide of β-1,4 linked anhydro-D-glucose units (hereinafter: monomers), where every monomer is rotated 180° with respect to the neighboring monomer. Each monomer contains three hydroxyl ("-OH" or "alcohol") groups. As shown in Figure 7, these groups are present at the C2, C3 and C6 positions. The alcohol groups at the C2 and C3 positions are considered to be "secondary alcohol" groups, since they are bonded to two carbon atoms. The alcohol group at the C6 position is considered to be a "primary alcohol" group, since it is bonded to only a single carbon atom. In a preferred oxidation of the primary alcohol group at the C6 position, the alcohol group is replaced by a carboxyl group or a derivative thereof. Preferably, a position-selective oxidation technique is used to oxidize the primary alcohol group at the C6 position in a targeted manner.

[0051] In a further preferred embodiment of the present invention, the bacterial cellulose comprises a plurality of monomers, and at least 70%, preferably at least 80%, 90% or more of the monomers of the bacterial cellulose have at least one carboxyl group or a derivative thereof. In some embodiments, at least 95%, at least 99% or 100% of the monomers of the bacterial cellulose have at least one carboxyl group. It has been found that such a degree of carboxylation allows for high solubility of the cellulose in water and also allows for a synergistic increase in the viscosity of the aqueous solution by interacting with at least one natural gum.

[0052] In a further 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 around 1:1. A ratio of surface-modified bacterial cellulose to natural gum of 6:5 to 5:6 may be preferred. Surprisingly, it has been found that in the above mentioned ratios, the synergy between the two components can be maximized, increasing the interaction between the two components when used in a fluid formulation.

[0053] In a further preferred embodiment of the present invention, the biodegradable rheology modifier further comprises an antimicrobial agent, preferably selected from the group comprising alkali metal salts or alkaline earth metal salts, more preferably comprising sodium benzoate, sodium metabisulfite, antioxidants and mixtures thereof. The antimicrobial agent also increases the shelf life of the final product in which it is used, especially after opening the package containing the product. Furthermore, the selected antimicrobial agent was also useful for adjusting the pH of the rheology modifier. Preferably, the concentration of the antimicrobial agent in the biodegradable rheology modifier was such that its concentration in the fluid product was up to 1% by weight. In some cases, it may be preferred to add the antimicrobial agent directly to the fluid product, rather than making it part of the rheology modifier.

[0054] In a further preferred embodiment of the present invention, the pH of the biodegradable rheology modifier is set to a value in the range of 3 to 13, preferably 4 to 10, even more preferably 5 to 10, using a buffer. The buffer is preferably a phosphate buffer, a citrate buffer, a carbonate buffer, a bicarbonate buffer, a combination thereof or any buffer of the prior art known to control pH. In some cases, it may be preferred that the buffer comprises citric acid or sodium hydroxide. The buffer can advantageously stabilize the pH of the formulation in which the rheology modifier and the buffer are used. The buffer may be part of the composition of the rheology modifier of the present invention, for example by being present together with the remaining components in powder form or as a suspension. Alternatively or additionally, the buffer may be added directly to the fluid product. Preferably, the concentration of the buffer in the fluid product is up to 1% by weight.

[0055] In a further preferred embodiment of the invention, the cellulose is milled prior to surface modification. Milled bacterial cellulose is more reactive and can be carboxylated to a higher extent. At the same time, the ability of cellulose to form a network in an aqueous system was preserved. This increases the interaction of the cellulose with the natural gums when used in the formulation. Finely milling the cellulose also allows the formulation to be visually and texturally uniform, thereby resulting in a good user experience. In a further preferred embodiment of the invention, the biodegradable rheology modifier is provided in a granular or suspended form having a particle size of 1 μm to 1000 μm, preferably 1 μm to 500 μm, more preferably 1 μm to 100 μm. By providing the rheology modifier in granular form, e.g. as a powder, it can be easily stored and measured for use in the various applications described elsewhere herein. In contrast, a suspended form of the rheology modifier, a solution or suspension thereof, is advantageous to allow for a more rapid homogenization of the formulation. Alternatively, in production, the suspension can be pumped or flowed directly into the manufacturing site where the formulation is prepared.

[0056] In a further preferred embodiment of the present invention, the bacterial cellulose is milled to a particle size of up to 1000 μm, preferably 1 μm to 500 μm, more preferably 1 μm to 100 μm, before being surface-modified and mixed with the natural gum to form the rheology modifier. Milling to these sizes advantageously maximizes the solubility and dispersibility of the bacterial cellulose. As used herein, the term "granular" preferably means a powder. Carboxylation and mixing are preferably carried out in aqueous conditions.

[0057] In a further aspect, the present invention relates to a fluid product comprising the biodegradable rheology control agent described above.

[0058] In a preferred embodiment of the present invention, the concentration of the surface-modified cellulose in the fluid product is 0.2% to 5% by weight, preferably 0.5% to 2% by weight, more preferably 1% to 1.5% by weight. As used herein, the concentration expressed in "wt%" preferably refers to the mass of the component as a percentage of the total mass of the composition. At these concentrations, high viscosities can be achieved, as demonstrated by the experimental examples shown herein. Thus, the concentration of the surface-modified cellulose in the fluid product is kept low, while allowing the viscosity of the fluid product to be adjusted over a wide range of viscosities. Thus, very viscous fluid products can be produced cheaply and sustainably using only small amounts of biodegradable rheology modifier. This also allows greater freedom in adjusting other qualities of the fluid product, such as color and opacity.

[0059] In a further preferred embodiment of the invention, the concentration of gum in the fluid product is between 0.2% and 5% by weight, preferably between 0.5% and 2% by weight, more preferably between 1% and 1.5% by weight. These gum concentrations have also been found to be suitable for providing the desired high viscosity at low concentrations, as demonstrated by the experimental examples presented herein.

[0060] In a further preferred embodiment of the present invention, the fluid product is a personal care product, a cosmetic product, a pharmaceutical product, a health care product, a home care product, a laundry or detergent product, an agricultural formulation product, an ink, a paint, a coating or a food product. In a preferred embodiment of the present invention, the fluid product is a personal care product, preferably selected from the group comprising lotions, creams, body washes, shampoos, serums, leave-on cosmetic products, fluids in wipes and emulsions. In a particularly preferred embodiment of the present invention, the fluid product is a skin care product.

[0061] In a preferred embodiment of the present invention, the fluid product further comprises one or more solvents, emollients, active pharmaceutical ingredients, dermatologically active ingredients, opacifiers, dyes, fragrances and / or preservatives.

[0062] In a further aspect, the present invention relates to a method for making a biodegradable rheology modifier comprising surface modifying cellulose by carboxylation to form carboxyl groups or derivatives thereof in the cellulose polymer and blending the surface modified cellulose with a natural gum, the cellulose being preferably bacterial cellulose.

[0063] In a preferred embodiment of the present invention, the method for preparing the biodegradable rheology modifier includes grinding the cellulose before surface modification. Furthermore, the ground bacterial cellulose was more reactive and could be carboxylated to a higher degree. At the same time, the ability of cellulose to form a network in an aqueous system was maintained. This increased the interaction of cellulose with natural gums when used in a formulation. Finely grinding the cellulose also allowed the formulation to be visually and texturally uniform, which provided a good user experience.

[0064] Preferably, the carboxylation and mixing are carried out under aqueous conditions. In a preferred embodiment of the present invention, the method further comprises milling the cellulose prior to surface modification so that the granular cellulose has an average particle size of 1 μm to 1000 μm, preferably 1 μm to 500 μm, more preferably 1 μm to 100 μm.

[0065] In a further preferred embodiment of the present invention, the milling of the cellulose is carried out in the presence of hydrogen peroxide (HPO), thus further bleaching the cellulose. This allows the rheology modifier to be used in a wide variety of fluid products with minimal impact on the color of the final product. Furthermore, for many fluid products, a neutral color, such as white, is desired.

[0066] In a further preferred embodiment of the present invention, the surface modification of cellulose is preferably N-oxyl compounds, preferably TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl) or TEMPO derivatives (T1 to T4) having at least one functional group at the C4 position; 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; The reaction is carried out in the presence of at least one catalyst selected from the group comprising:

[0067] Particularly preferably, the catalyst comprises TEMPO, the above-mentioned TEMPO derivatives, hydrogen peroxide (HPO) or ammonium persulfate. As used herein, the abbreviation "TEMPO" preferably refers to 2,2,6,6-tetramethylpiperidine-1-oxyl radical. TEMPO has the advantage of being position selective, so that oxidation occurs mainly at the C6 position of the cellulose monomer, as well as being highly soluble in aqueous systems and highly efficient.

[0068] In some preferred embodiments, the surface modification is carried out in the presence of TEMPO, NaBr and NaClO, where TEMPO and NaBr act as co-catalysts and NaClO functions as the primary oxidant. In some cases, it may be preferable to use ammonium persulfate as a catalyst. Ammonium persulfate has also been found to be a good oxidant for bleaching cellulose, which may be desirable in some applications.

[0069] By carrying out the surface modification under alkaline conditions, it was possible to increase the dissociation of primary alcohol groups in aqueous systems. In cellulose chains, primary alcohol groups are more likely to dissociate than secondary alcohol groups and therefore tend to react to a greater extent to form carboxyl groups (or their derivatives) than secondary alcohol groups.

[0070] Advantageously, the above reaction conditions accelerate the desired carboxylation of the C6 primary alcohol group without the need for very high temperatures or concentrations, thus making the reaction commercially viable.It has also been found advantageously that the reaction conditions do not substantially result in undesirable side reactions, toxicity, or undesirable by-products.

[0071] Terms such as substantially, approximately, about, etc. preferably describe a tolerance range of less than ±20%, preferably less than ±10%, particularly preferably less than ±5%, in particular less than ±1%, and include the exact value.

[0072] Detailed description and examples of the invention 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 falling within the scope of these claims and their equivalents be covered thereby.

[0073] The examples presented herein demonstrate that a rheology modifier comprising a blend of surface-modified bacterial cellulose and natural gums can achieve high viscosity (5000 cP-110000 cP) and exhibit shear-thinning behavior while maintaining a stable viscosity over a wide range of pH values. Thus, the rheology modifier according to the present invention was able to meet high standards of stability, viscosity and haptic properties while being natural, biocompatible and sustainable throughout its life cycle.

[0074] Without intending to be limiting, the invention will now be explained in more detail with reference to exemplary embodiments and the following drawings, in which: [Brief description of the drawings]

[0075] [Figure 1a] SEM images showing morphological observations of bacterial cellulose-based structures according to an embodiment of the present invention. The image on the left (a) is an SEM image of bacterial cellulose (×5000). The image on the right (b) is an SEM image of bacterial cellulose (×10000). These images show intact fibrous structures and 3D networks with micro-level diameters of 10 μm (a) and 1 μm (b). [Figure 1b] Same as above [Diagram 2] 1 is a graph showing the viscosity of surface-modified cellulose at various concentrations at neutral pH. [Diagram 3] 1 is a graph showing the rheological properties of a bacterial cellulose-based composite according to one embodiment of the present invention, measured using a cone and plate rheometer, showing non-Newtonian viscosity versus shear rate, indicating shear thinning behavior. [Figure 4] 1 is a graph showing the viscosity and pH for several samples of bacterial cellulose-based composites according to two embodiments of the present invention, showing the stability of the formulated composites in acidic to basic media. [Diagram 5] FIG. 1 is a schematic diagram of various known surface modification reactions for cellulose. [Figure 6] FIG. 2 is a schematic diagram of the reaction mechanism for three preferred surface modification reactions of cellulose to produce the rheology modifier of the present invention. [Figure 7] FIG. 1 is a schematic diagram of a single monomer unit that is part of a cellulose chain, with the C1 to C6 carbons of the unit labeled with numbers. [Figure 8] 1 is a graph showing the viscosity of rheology modifiers without natural gums at different shear rates and different pH values. [Figure 9] 1 is a graph showing the viscosity of rheology modifiers according to the present invention containing natural gums, measured at various shear rates and pH values. [Figure 10] 1 is a graph showing the complex shear modulus of rheology modifiers containing no natural gum at various shear strains and various pH values. [Figure 11] 1 is a graph showing the complex shear modulus of a rheology modifier according to the present invention comprising a natural gum, the complex shear modulus being measured at various shear strains and pH values. [Figure 12] 1 is a graph showing the particle size distribution of a rheology modifier without natural gum (curve I) and with natural gum (curve II) according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0076] All of the exemplary methods for preparing the rheological modifiers of the present invention use bacterial cellulose as a raw material. Figures 1a and 1b show the surface morphology of the material as investigated using a scanning electron microscope. As observed, bacterial cellulose forms fine fibers with a diameter of up to 10 μm. The freeze-dried samples were coated with a thin layer of evaporated gold by sputtering. The micrographs were taken at magnifications of 5000 and 10000 and an accelerating voltage of 25 kV. An intact fibrous structure is shown, with the solid materials in the composite remaining in a 3D fibrous network with a non-uniform distribution. They are particularly suitable for improving the stability of slurries, suspensions, emulsions or solutions, since the network counteracts the tendency of the components of the system to settle. The network structure also increases the water retention of bacterial cellulose, thereby improving the performance of skin care products in which it is used.

[0077] In a preferred embodiment of the present invention, the surface modification of cellulose is preferably carried out in the presence of at least one catalyst selected from the group including TEMPO (T1), 2,2,6,6-tetramethylpiperidinooxy radical and its derivatives, i.e., 4-(acetamino)-2,2,6,6-tetramethylpiperidinooxy (T2), 2,2,6,6-tetramethyl-4-oxopiperidinooxy (T3), 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinooxy (T4), hydrogen peroxide (HPO), and ammonium persulfate. TEMPO has the advantage of being position selective, so that oxidation occurs mainly at the C6 position of the cellulose monomer, as well as being highly soluble in aqueous systems and highly efficient. In some preferred embodiments, the surface modification is carried out in the presence of TEMPO, NaBr, and NaClO, where TEMPO and NaBr act as cocatalysts and NaClO functions as the main oxidizing agent.

[0078] In some cases, it may be preferable to use ammonium persulfate as a catalyst. Ammonium persulfate (APS) has also been found to be a good oxidizing agent for bleaching cellulose, and is likewise desirable in some applications. Ammonium persulfate has also been found to be particularly advantageous, since it is harmless from a toxicity point of view. Ammonium persulfate can also be produced from natural materials and safely disposed of, and therefore is highly sustainable. In some cases, it may be preferable to use hydrogen peroxide (HPO). HPO is also a strong oxidizing agent, and at the same time, it provides a bleaching action. Several catalysts and co-catalysts are known in the art of surface modification of cellulose. However, the reaction yield, the characteristics of the product, and the porous or fibrillar structure vary depending on the conditions used for the modification. In the present invention, the process is optimized for each category of desired application, preferably rheology modifiers or polymer modifiers. Bacterial cellulose (BC) was chemically surface modified according to a catalytic oxidation reaction with different modifiers. This reaction converts the primary alcohol group (-CH2OH) at position 6 of the bacterial cellulose structure into a -COOH group (carboxylation), while the rest of the bacterial cellulose structure remains the same, and therefore the presence of the -COOH group can be defined as a surface modification. Surface modification of bacterial cellulose was carried out by the oxidation technique described 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 basicity of the reaction medium, and therefore the -COOH group is seen as -COONa in the aqueous system, as shown in Figure 7.Various TEMPO-mediated surface modification reactions of mono-, oligo- and polysaccharides for the regioselective conversion of primary hydroxyl groups to carboxylate groups have 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 (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- and halogen-free aerobic oxidation of alcohols in water. Chem. Eur. J. 17, 6056-6060 (2011)) and polymerized 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 alcohols with hypochlorite. Chem. Commun. 271-272 (2000)) and the modification of bacterial cellulose using TEMPO derivatives grafted to other water-soluble polymers has also shown promise.

[0079] Comparative Example 1 In a preferred embodiment of the present invention, the surface modification or carboxylation of bacterial cellulose was additionally or alternatively mediated by TEMPO (T1), a 2,2,6,6-tetramethylpiperidinooxy radical. A schematic is illustrated in FIG. 6. In a typical laboratory experiment, a bacterial cellulose suspension (5 g) in water (500 mL) containing TEMPO (0.50 mmol) and sodium bromide (5 mmol) were thoroughly mixed in an Erlenmeyer flask. The contents of the flask were maintained at 50° C. and the pH was adjusted to 10. TEMPO-mediated surface modification was initiated by adding the desired amount of NaClO solution (10 mmol to 16 mmol NaClO per gram of cellulose) as an oxidizing agent. The reaction mixture was maintained at the defined conditions for an additional 30 to 60 min and quenched by adding ethanol. The surface-modified cellulose was thoroughly washed, dried, and stored at 4° C. The reaction yield was found to be greater than 80%. The carboxylic acid content of the surface-modified cellulose was determined using a titration method, as shown in Table 2.

[0080] Comparative Example 2 In a preferred embodiment of the present invention, a schematic of the surface modification of bacterial cellulose, the process of carboxylation, when mediated by APS, is illustrated in Figure 6. The mixture obtained by this method was also found to be homogeneous, without fibrous strings or precipitates. No color change was observed over the storage period of the mixture. In a typical laboratory experiment, a 1% aqueous suspension of bacterial cellulose, 20 mL to 50 mL of 1 M aqueous ammonium persulfate solution, was transferred to a 2 L Erlenmeyer flask. The temperature of the mixture was then raised to 60°C and kept stirring for 1.5 hours, during which the pH of the mixture was maintained at 1.0 to 2.0. The modified bacterial cellulose was thoroughly washed, dried, and stored at 4°C. The yield of modified cellulose was found to be greater than 50%.

[0081] Table 1: Analysis results of surface-modified bacterial cellulose (powder) [Table 1]

[0082] Table 2: Yield and carboxyl content of surface-modified bacterial cellulose [Table 2] a :Gravity method, b : Modified titration based on the TAPPI method (T 237 cm-98)

[0083] Comparative Example 3 In a preferred embodiment of the present invention, the carboxylation of bacterial cellulose was additionally or alternatively mediated by HPO. A schematic is illustrated in FIG. 6. The mixture obtained by this method was also found to be homogeneous, without fibrous lumps or precipitates. This process caused bleaching of the cellulose. No further color change was observed over the storage period of the mixture. In a typical laboratory experiment, 10 g of bacterial cellulose was suspended at 2.0% (166.67 mL) with 12% hydrogen peroxide solution. Then, 22.2 mL of 1 M NaOH was added to the suspension (pH=11) and the temperature was increased to 80° C. for 1.0 h. The modified bacterial cellulose was thoroughly washed, dried, and stored at 4° C. until neutral. The yield of modified cellulose was found to be greater than 50%.

[0084] As can be seen from Table 1, the surface modified bacterial cellulose was converted by an in-house invented process into a powder in the size range required for further processing. The 2.5% suspension was shown to have a very high viscosity. It was observed that the viscosity of the modified cellulose increased with increasing concentration of the modified cellulose. The modified bacterial cellulose was found to be 100% biodegradable according to the OECD 301F method. In Table 2, the yield and carboxylation value of the modified bacterial cellulose by the TAPPI method (T237 cm-98) are shown. The details of the TAPPI (Technical Association of the Pulp and Paper Industry) method are known and readily available to those skilled in the art. On average, the yield was 70%-90%, depending on the TEMPO derivative used.

[0085] Viscosity and pH dependence: Measurements of the dynamic viscosity of the mixtures were carried out using an NDJ-8S Rotational Viscometer with spindle series S1-S4. The measurements were carried out under standard conditions. The mixtures were found to be homogeneous with no fibrous lumps or sediments. No color change was observed during the recording of the measurements.

[0086] Preparation of the composite: In a preferred embodiment of the invention, the product obtained by modifying bacterial cellulose in the formulation (described in the section below) behaved as a biodegradable rheological modifier with a natural content of more than 95%. Composites of different compositions with natural gums were prepared and investigated for viscosity. The modified bacterial cellulose was found to be insensitive to electrolytes over a pH range of 4 to 10, thus indicating its importance for personal and home care applications where the effect of electrolytes (especially alkali metal halides, e.g. sodium chloride or potassium chloride, concentrations 0.1 M to 0.5 M) is constant. It was also found that this sample can be used to enhance the appearance of the formulation and to further improve the rheological properties according to the requirements.

[0087] Table 3: Composites using different surface-modified bacterial cellulose [Table 3] Rheology modifier 1: Bacterial cellulose and natural gum with TEMPO; Rheology modifier 2: Bacterial cellulose and natural gum with APS; Rheology modifier 3: Bacterial cellulose and natural gum with HPO

[0088] Compounds: Rheology Modifiers (1-7) Finely ground modified 1.25%-3.0% bacterial cellulose suspensions (Comparative Examples 1-3) were mixed with at least one of natural gums 1-4 (including any of guar, arabic, konjac, locust, xanthan, carrageenan and other gums or combinations thereof) as received or in aqueous solution with a total concentration of 1.25%-3.0% to form a mixture. The prepared mixture or slurry was homogenized (20000 rpm-30000 rpm) for another 15 minutes. The pH of the slurry was maintained at 4-5 using weak acid. A uniform texture and high viscosity slurry was obtained to which the preservative / stabilizer sodium benzoate was added to a concentration of 0.5% in the mixture to avoid microbial contamination and antioxidant was also added for long term stability.

[0089] Table 4: Composites with different surface modified bacterial cellulose and natural gums [Table 4] 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

[0090] Application preparation: The prepared rheology modifiers were used in various applications to understand and evaluate their effectiveness for personal care, coatings, and other applications in agriculture, as shown below. The application fields are endless and are not limited to those shown below in this application.

[0091] Table 5: Various applications using rheology modifiers [Table 5]

[0092] Table 6: Results of various applications using rheology modifiers [Table 6]

[0093] Table 7: Food Applications Using Rheology Modifiers [Table 7]

[0094] Table 8: Agricultural Applications Using Rheology Modifiers [Table 8]

[0095] Viscosity and pH dependence: Measurements of the dynamic viscosity of the mixtures were carried out using an NDJ-8S Rotational Viscometer with spindle series S1-S4. The measurements were carried out under standard conditions. The mixtures were found to be homogeneous with no fibrous lumps or sediments. No color change was observed during the recording of the measurements.

[0096] Table 4 shows the viscosity values ​​obtained in a wide range of pH values ​​(3-11). In general, the lower the pH, the more viscous the modified bacterial cellulose and the higher the viscosity of the resulting mixture. The composite products showed a smooth, uniform texture, without fibrous lumps / squishy morphology, no phase separation, no sedimentation and no color change with temperature. The viscosity building effect results in the formation of a stable cream with easily adjustable thickening. The samples were found to be suitable for the range of 3-11 and to be electrolyte insensitive (tested at 0.1 M NaCl). The samples were almost entirely bio-based with a natural content of more than 95%. Hence, these samples can be applied as premixes such as powders. It was also found that these samples can be used to enhance the appearance of the formulation and further improve the rheological properties according to the requirement.

[0097] In Figure 3, the performance of the rheology modifier according to the embodiment of the present invention at various shear rates is shown. As can be observed in Figure 3, the viscosity tended to decrease dramatically with increasing shear rate. Thus, the rheology modifier could provide a shear-thinning effect. They are particularly beneficial in terms of improving the user experience, as they make the fluid product easier to remove from the container, and easier to spread and apply. At the same time, shear-thinning fluids tend to become more viscous when shear forces are not actively applied. This allows them to remain stable on a surface, for example, on a wall while drying in the case of paint, or on the end user's skin in the case of skin care products. Thus, the undesirable dripping effect is avoided, improving the user experience. Thus, the rheology modifier can be used to produce a natural biodegradable fluid product that can be comparable to conventional products in terms of tactile properties, texture, and user experience.

[0098] In Figure 4, the stability of two different composites of rheology modifiers (rheology modifier 1 and rheology modifier 4) with natural gum according to the present invention is shown. The samples belong to two groups with two compositions according to two embodiments of the present invention. The results for the samples belonging to the first group are shown with filled circles, and the results for the samples belonging to the second group are shown with open circles. As shown in Figure 4, the performance of the rheology modifiers was good in terms of producing high viscosity in a wide range of pH values. The viscosity of the samples of both groups remained substantially the same in acidic and alkaline conditions. This indicates that the rheology modifiers of the present invention are suitable for use in a wide variety of applications ranging from food products, which tend to be acidic, to cleaning products, which tend to be alkaline.

[0099] Further analysis of the viscosity of rheology modifier samples under various conditions is shown in Figures 8-11. Figure 8 shows the viscosity of the rheology modifier without natural gum (Comparative Example 1, Table 1). The viscosity was measured at various shear rates [s -1 ] and various pH values. The measurements are presented for comparison. As can be seen in FIG. 8, the dynamic viscosity of such rheology modifiers is nearly pH independent (pH dependent) throughout the entire range of shear rates tested. At a given pH, the higher the shear rate, the lower the viscosity. This tendency of decreasing viscosity with increasing shear rate is observed throughout the entire pH range. For example, at a shear rate of 0.01 s -1 The dynamic viscosity of the rheology modifier at pH 5 (shown by the open circles) significantly exceeds the dynamic viscosity at pH 9 (shown by the filled circles) at the same shear rate. Thus, 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 taking into account the exact pH of the composition.

[0100] Similarly, Fig. 9 shows the results of various shear rates [s -19] and the dynamic viscosity of a rheology modifier according to the present invention (Rheology Modifier 1, Table 3) at various pH values. The rheology modifier comprises at least one natural gum. As can be seen in the graph of FIG. 9, the curves representing all tested pH values ​​(3-11) show a shear rate of 1 s -1 The viscosity curves are almost exactly the same from 0.01 to 0.05. The viscosity drop is not significant from rheology modifier (without natural gum) to the composite of rheology modifier containing at least one natural gum. At the same time, a surprisingly strong pH independence is realized. The overlap of the rheology curves at different pH indicates 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.

[0101] A further advantage of the rheology modifiers of the present invention is that they are pH insensitive while remaining sensitive to changes in shear rate. The change in dynamic viscosity with shear rate (i.e., thixotropy or shear thinning behavior) is present and quite constant over the entire range of shear rates tested, 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 viscosity can be achieved, a highly desirable property in various products, e.g., for spreading paint, squeezing compositions from tubes, etc. In contrast to the small predictable relationship between dynamic viscosity and shear rate for the gum-free rheology modifiers (Figure 8), the thixotropy of the rheology modifiers of the present invention is highly predictable. A smooth thickening effect can be achieved. This indicates that the inclusion of preferably at least one natural gum in the rheology modifiers of the present invention surprisingly results in a much more stable, predictable thixotropy and a much more pH insensitive material.

[0102] These results were further confirmed by comparing the complex shear modulus (G*) at various shear strains and pH values ​​for the rheology modifiers with and without natural gums. In FIG. 10, the results for the rheology modifiers without natural gums are shown. These results are presented for comparison. It can be seen that at all pH values, the complex shear modulus [Pa] decreases with increasing shear strain [%]. By changing from pH 5 (indicated by open circles) to pH 7 (indicated by filled diamonds) at 0.1% shear strain, the complex shear modulus is more than halved. Note that the y-axis is on a logarithmic scale. Thus, a pH change of only 2 dramatically changes the rheological properties of the rheology modifiers. Moreover, the rheology modifiers show a plateau at lower shear strains (less than 1%) at a given pH, thereby indicating stable behavior. Therefore, depending on the target application, appropriate shear strain values ​​can be applied to result in stable formulations.

[0103] In contrast, FIG. 11 shows the effect of shear strain and pH value on the complex shear modulus of a rheology modifier comprising at least one natural gum according to the present invention. As can be seen in FIG. 11, the points representing pH values ​​from 5 to 11 overlap almost exactly across all shear strains tested. pH 3 only affects the complex shear modulus up to 10% shear strain. Furthermore, at higher shear strains, complex shear modulus well below 10 can be achieved. Furthermore, at pH values ​​higher than 3, the width of the plateau increases, thereby indicating an extension of the stability of the rheology modifier composite at slightly higher shear strains. This data further confirms that the rheology modifiers of the present invention are highly stable and pH independent. The rheology modifiers can be dosed and incorporated in the same manner to produce the same effect in completely different compositions, from foods to shampoos to household cleaners. This is significantly improved by the inclusion of natural gums, as evidenced by contrasting the results shown in FIG. 10.

[0104] The particle size distribution of the rheology modifier with and without natural gum was also investigated. The particle size distribution of the rheology modifier without natural gum is shown in curve I (Comparative Example 1, Table 1) of Figure 12. This curve is presented for comparison. The curve shows a very broad distribution of particle size classes with multiple peaks. Thus, the rheology modifier contains non-uniform particles. The particles are also particularly large, with the largest peak being over 1000 (μm) in size. Such large particles make the rheology modifier prone to undesirable settling and reduce its effectiveness. Non-uniform particle size is disadvantageous during mixing and may result in a non-smooth composition. However, this rheology modifier provides stability in various ranges of pH when used in any formulation.

[0105] For comparison, curve II in FIG. 12 (Rheology Modifier 1, Table 3) shows the particle size distribution of a rheology modifier according to the invention comprising at least one natural gum. A narrow particle size distribution with a single peak at a much lower particle size class can be observed. The small particle size reduces the risk of settling, which is further reduced by the networking behavior of the natural gums, which interact synergistically with the particle size. Thus, a high viscosity with strong thixotropy can be achieved using very small particle sizes. Thus, the rheology modifier of the invention has a much smoother texture compared to other rheology modifiers. [Explanation of symbols]

[0106] Drawing translation Figure 2 Viscosity surface modified BC solid surface modified BC solid Figure 3 Effective Viscosity Shear rate Figure 4 Viscosity Sample Figure 5 Phosphate Esters Sulfate Esters Carboxylate Esters Esterification Silanisation Etherification Oxidation Carboxylic Acid Aldehyde Figure 6 TEMPO-mediated Oxidation Ammonium Persulfate Oxidation 1h 1 hour Peroxide Oxidation 48h 48 hours Figure 8 Viscosity Shear rate Figure 9 Viscosity Shear rate Figure 10 Complex Shear Modulus Shear Strain Figure 11 Complex Shear Modulus Shear Strain Figure 12 Volume Density Size Classes Curve

Claims

1. A biodegradable rheological modifier containing bacterial cellulose, used in pharmaceutical formulations or fluid products, A biodegradable rheology modifier wherein the bacterial cellulose is surface-modified and comprises at least one carboxyl group or a derivative thereof, and the biodegradable rheology modifier further comprises at least one natural gum, thereby increasing the viscosity of the formulation or fluid product through interaction between the surface-modified bacterial cellulose and the natural gum.

2. The biodegradable rheology modifier according to claim 1, wherein the surface modification is obtained by oxidation of one or more primary alcohol groups of bacterial cellulose.

3. The biodegradable rheology modifier according to claim 1, wherein the bacterial cellulose comprises a plurality of monomers, and the at least one carboxyl group or its derivative is present in at least 70% of the monomers of the bacterial cellulose.

4. The biodegradable rheology modifier according to claim 1, wherein the biodegradable rheology modifier is provided in granular or suspension form having a particle size of 1 μm to 1000 μm, and / or bacterial cellulose is surface-modified and pulverized to a particle size of up to 1000 μm before being mixed with the natural gum to form the rheology modifier.

5. The biodegradable rheology modifier according to any one of claims 1 to 4, wherein the natural gum is selected from the group comprising 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 claim 1, comprising at least two types of gum, wherein at least one of the gums is selected from the group comprising xanthan gum, konjac gum, guar gum, and locust bean gum.

7. The biodegradable rheology modifier according to claim 1, wherein the ratio of surface-modified bacterial cellulose to gum is 4:1 to 3:

7.

8. The biodegradable rheology modifier according to claim 1, wherein the pH of the biodegradable rheology modifier is set to a range of 3 to 13 using a buffer solution.

9. The biodegradable rheological modifier according to claim 1, wherein the biodegradable rheological modifier further comprises an antibacterial agent.

10. A fluid product comprising the biodegradable rheological modifier described in claim 1, wherein the fluid product is a personal care product, a home care product, a laundry or detergent product, an agricultural formulation product, a pharmaceutical product, an ink, a paint, a coating, or a food product.

11. The fluid product according to claim 10, wherein the concentration of surface-modified cellulose in the product is 0.2% to 5% by weight, and / or the concentration of gum in the fluid product is 0.2% to 5% by weight.

12. A method for producing a biodegradable rheological modifier according to claim 1, Surface modification of cellulose by carboxylation to form carboxyl groups and / or derivatives thereof within the cellulose polymer, Mixing surface-modified cellulose with natural gum, Methods that include...

13. The method according to claim 12, further comprising grinding the cellulose before surface modification so that the average particle size of the granular cellulose is 1 μm to 1000 μm.

14. The method according to claim 12 or 13, wherein the pulverization of the cellulose is carried out in the presence of hydrogen peroxide, and as a result the cellulose is further bleached.

15. The surface chromatin of the cellulose is N-oxyl compounds, Alkali metal halides, and Oxidizing agent, The method according to claim 12, carried out in the presence of at least one catalyst selected from the group consisting of the following.

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