Biodegradable water-dispersible and swellable structures, their preparation and use as suspensions

Abstract

The invention relates to a new easily biodegradable water-dispersible polymeric structure of limited size, its method of production, and its use as a suspending additive in flowable formulations for home and personal care, agriculture, paints, metal treatment and oilfield markets. No drawing.

Description

[0001] This application claims priority to application US 63 / 618739, filed 08.01.2024, and application EP 24154453.5, filed 29.01.2024, the entire contents of each of these applications are incorporated herein by reference for all purposes. Technical Field

[0002] This invention relates to a novel readily biodegradable water-dispersible polymer structure with finite size, a method for producing it, and its use as a suspending additive in flowable formulations for the home and personal care, agriculture, coatings, metal processing, and oilfield markets. Background Technology

[0003] A wide variety of household and personal care products, as well as agricultural products, coatings, metal processing products, and products used in the oilfield market, are shear-thinning fluids. Shear-thinning fluids exhibit non-Newtonian behavior, meaning their viscosity decreases under shear stress. This behavior is sometimes considered synonymous with pseudoplastic behavior.

[0004] Shear thinning is considered to be an effect of small structural changes within a fluid, causing a rearrangement of the fluid's microscale geometry, thereby promoting shearing. For example, in colloidal systems, phase separation during flow leads to shear thinning. In polymer systems such as polymer melts and solutions, shear thinning is caused by the detangling of polymer chains during flow. At rest, high molecular weight polymers are tangled and randomly oriented. However, when subjected to sufficiently high stirring rates, these highly anisotropic polymer chains begin to detangle and align along the direction of the shear force. This results in weakened molecular / particle interactions and a greater amount of free space, thus reducing viscosity.

[0005] An example of shear-thinning formulations is latex paint. When these paints are applied to a surface, the shear created by the brush or roller thins them and evenly wets the surface. Once applied, these paints regain their higher viscosity, thus preventing dripping and sagging. Another example is whipped cream. When whipped cream is sprayed from its container, it flows smoothly from the nozzle due to its low viscosity at high flow (shear) rates. After application, whipped cream stops flowing, and its increased viscosity makes it rigid. The same behavior can be observed in cosmetic products such as bath foam formulations.

[0006] Furthermore, common household and personal care formulations, agricultural formulations, coatings, metal treatment products, and oilfield market products are dispersions in which objects such as beads, bubbles, oil droplets, or solid particles (e.g., pigment particles) are suspended. These suspended objects tend to flocculate / sediment and / or aggregate in formulations. However, for the effective use of such formulations, it is essential to ensure that the objects remain suspended in the continuous phase of the formulation (e.g., an aqueous solution). Therefore, formulations typically contain suspending agents to prevent flocculation, sedimentation, and / or aggregation of suspended objects.

[0007] One currently commercially available example of such suspending agents is microgels, particularly carbomer microgels. Microgels are objects of finite size (typically minute) that can disperse in liquids (e.g., water), swelling and filling the entire volume of the liquid. This property of microgels allows suspended objects to be maintained in the continuous phase of a formulation. Carbomer is a high molecular weight polymer crosslinked with allyl ethers of acrylic acid and polyols. In addition to its excellent suspension properties, carbomer microgels do not affect the shear-thinning behavior of liquid formulations. This functionality of microgels has made their application in shear-thinning fluids a focus of interest.

[0008] However, as is known in the art, there are problems with using such carbomer microgels in, for example, home and personal care formulations, because they are generally non-biodegradable.

[0009] Compared to these carbomer microgels, biodegradable gels or hydrogels are known in the art. However, such biodegradable gels or hydrogels do not provide sufficient suspension properties and / or cause macroscopic gelation of the formulation, rendering it non-flowable. Therefore, by using these biodegradable gels or hydrogels, it is impossible to suspend the object in the continuous phase of the formulation while maintaining its shear-thinning behavior.

[0010] Therefore, there is a need for a biodegradable suspending additive that has the same function as known non-biodegradable suspending additives in the art (e.g., carbomer microgels), i.e., that enables the suspension to remain in the continuous phase of the formulation while maintaining the shear-thinning behavior of the formulation. Summary of the Invention

[0011] This invention relates to cross-linked polysaccharide particles having a particle size between 0.1 and 150 µm, a degree of cross-linking between 0.00001 and 0.001, and being biodegradable according to OECD 301F standards.

[0012] Furthermore, the present invention provides a method for obtaining the cross-linked polysaccharide particles of the present invention, wherein the polysaccharide is contacted with water, alkali and a bifunctional cross-linking agent in an amount resulting in a cross-linking degree of 0.00001 to 0.001.

[0013] Furthermore, the present invention relates to an aqueous formulation comprising cross-linked polysaccharide particles of the present invention, wherein the cross-linked polysaccharide particles preferably constitute 0.5 to 10.0 wt.% based on the total weight of the composition, and wherein the formulation preferably has a yield stress of at least 0.1 Pa and / or preferably a ratio (pol / par) of less than 60%, preferably less than 50%, of free polysaccharide chains to cross-linked polysaccharide particles by weight. This formulation can be used for various purposes, such as in household and personal care products, agricultural products, coatings, metal treatments, and products for the oilfield market. Detailed Implementation

[0014] Before describing the problems of the present invention in detail, the following should be considered:

[0015] Unless the context clearly indicates otherwise, as used herein, the singular forms “a / an” and “the” include both the singular and plural indicators. For example, “a compound” means one or more compounds.

[0016] As used herein, the terms “comprising,” “comprises,” and “comprisedof” are synonymous with “including,” “includes,” “containing,” and “contains,” and are inclusive or open-ended, not excluding additional, unlisted members, elements, or method steps. It will be understood that the terms “comprising,” “comprises,” and “comprisedof” as used herein include the terms “consisting of,” “consists,” and “consists of.”

[0017] Throughout this application, the term “about” is used to indicate a value that includes the standard deviation of the error of the apparatus or method used to determine that value.

[0018] As used herein, unless otherwise indicated, the term "average" refers to the exponential average.

[0019] As used herein, the terms “% by weight,” “wt.-%,” “weight percentage,” or “percentage by weight,” and the terms “% by volume,” “vol.-%,” “volume percentage,” or “percentage by volume” are used interchangeably.

[0020] The range of values ​​listed by endpoints includes all integers and fractions contained within that range, including the endpoints themselves (e.g., 1.0 to 10.0 includes 1.0 and 10.0, as well as all values ​​greater than 1.0 and less than 10.0, such as 1.1, 1.2, ... 2.0, 2.1, ... 9.9).

[0021] As used herein, the terms "suspending power," "suspending property," "suspension power," and "suspension property" refer to the characteristics of an additive that prevent dispersed particles from settling in a formulation that is originally a liquid. In contrast, "suspension" is a general term used to describe a class of liquid formulations in which particles, objects, etc., are dispersed. These particles, objects, etc., may or may not settle, depending on the presence of an additive with suspending power. Therefore, according to the present invention, the term "suspension" is distinct from a formulation with suspending power.

[0022] As used herein, the terms “yield” and “yield stress” refer to a rheological characteristic, which is a quantitative measure of an additive’s ability to suspend in a given aqueous medium. It corresponds to the critical stress required for such a formulation to begin flowing under shear.

[0023] As used herein, the term "shear-thinning" refers to a liquid formulation whose viscosity decreases with increasing shear rate. "Newtonian" refers to a liquid formulation whose viscosity is constant and unaffected by shear rate (deformation rate).

[0024] As used herein, the term "microgel" refers to an object of finite size, typically small (micrometer-scale), that can be dispersed in water, swell, and fill the entire volume of a liquid formulation. In contrast, a "gel" refers to a macroscopic, monolithic system prepared as is. A gel is not a collection of objects of finite size; it is a single object. A "hydrogel" is a type of gel prepared in the presence of water as a solvent. Hydrogels typically contain a high concentration of water.

[0025] As used herein, the term "DS" refers to the degree of crosslinking of the polysaccharide. This property is typically determined using nuclear magnetic resonance (NMR) and corresponds to the number of crosslinking points, i.e., the number of moles of crosslinking agent per mole of crosslinked polysaccharide. However, since the DS of the products of this invention is very low, it is generally impossible to measure it. However, it can be calculated given the crosslinking efficiency of the crosslinking agent used. This efficiency can be determined by measuring the DS (by NMR) of a product with a much higher DS (i.e., a product crosslinked with the same crosslinking agent but in a much higher amount).

[0026] As used in this article, the term “DD” refers to the degree of derivatization of a polysaccharide, that is, the degree to which it is replaced by functional groups (i.e., the number of substituents).

[0027] As used in this article, the terms “functionalized,” “grafted,” and “substituted” are interchangeable.

[0028] If any disclosure of any patent, patent application, or publication incorporated herein by reference conflicts with this specification to the extent that it may obscure the terminology, this specification shall prevail.

[0029] Unless otherwise defined, all terms used in disclosing this invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Further guidance is provided, including definitions of terms, to better understand the teachings of this invention.

[0030] In the following paragraphs, various alternatives, embodiments, and variations of the invention are defined in more detail. Each of the alternatives and embodiments thus defined can be combined with any other alternative and embodiment, and this applies to each variation unless expressly stated to the contrary, or clearly incompatible when the value ranges of the same parameter do not intersect. In particular, any feature indicated as preferred or advantageous can be combined with one or more other features indicated as preferred or advantageous.

[0031] Furthermore, in one or more embodiments, the specific features, structures, or characteristics described herein can be combined in any suitable manner, as will be understood by those skilled in the art based on this disclosure. Additionally, while some embodiments described herein include features that are not included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments, as will be understood by those skilled in the art.

[0032] This invention relates to cross-linked polysaccharide particles having a particle size between 0.1 and 150 µm, a degree of cross-linking between 0.00001 and 0.001, and being biodegradable according to OECD 301F standards.

[0033] Cross-linked polysaccharides are known in the art (see, for example, US 11,365,371 B2 or US 10,414,960). However, none of these documents address cross-linked polysaccharide particles (hereinafter referred to as microgels) with a finite-sized, readily biodegradable, water-dispersible polymer structure that provide suspension properties while maintaining the shear-thinning behavior of formulations in which they are used.

[0034] HONGBO TANG et al., “Synthesis, Optimization, Property, Characterization, and Application of Dialdehyde Cross-Linking Guar Gum,” INTERNATIONAL JOURNAL OF POLYMER SCIENCE, Vol. 2016, January 1, 2016, disclosed the use of phosphoryl chloride as a cross-linking agent to cross-link guar gum. The degree of cross-linking obtained and the properties of the cross-linking agent (an inorganic cross-linking agent with a small molecular size) prevented the acquisition of microgels as described in this invention.

[0035] EP 2088994 B1 relates to the use of glyoxal as a crosslinking agent for guar gum. This is also a small molecule, and the resulting crosslinked product does not form any gel upon contact with water, but rather a dispersion of discrete particles.

[0036] WO 2013077620 relates to a method for preparing a water-insoluble gel based on a water-soluble polysaccharide, wherein the water-insoluble gel remains unbiodegraded for at least several months or longer.

[0037] Polysaccharides are long chains of monosaccharides linked by glycosidic bonds, such as fructose, galactose, glucose, mannose, xylose, arabinose, rhamnose, and their stereoisomers and derivatives.

[0038] According to the present invention, the preferred polysaccharide is selected from the group consisting of: dextran, starch, amylose, amylopectin, glycogen, dextran, cellulose, mannan, xylan, lignin, arabinogalactan, galactan, polygalacturonic acid, chitin, chitosan, glucuronic acid xylan, arabinoxylan, xyloglucan, glucomannan, pectin, arabinogalactan, carrageenan, agar, gum arabic, tragacanth gum, ghatti gum, karaygum, carob gum, polygalactomannan, or mixtures thereof. More preferably, the polysaccharide is galactomannan (polygalactomannan). Galactomannan is a polysaccharide mainly composed of galactose and mannose units, wherein the mannose units are linked by 1-4-β-glycosidic bonds and galactose branching occurs by means of 1-6-α-bonds to the mannose units. Naturally occurring galactomannans can be obtained from many sources, including guar gum, guar split, locust bean gum, resurrection tree gum, and cassia gum. Additionally, galactomannans can also be obtained through chemical modification of naturally occurring galactomannans. In a preferred embodiment, the galactomannan is guar gum.

[0039] In a more preferred embodiment of the invention, galactomannan and its derivatives are selected from the group consisting of: fenugreek gum, mesquite gum, guar gum, tara gum, locust bean gum, cassia gum, daincha gum, konjac gum, and their derivatives such as hydroxyalkyl guar gum, carboxylalkyl guar gum, carboxylhydroxyalkyl guar gum, cationic guar gum, hydrophobically modified guar gum, hydrophobically modified hydroxyalkyl guar gum, hydrophobically modified carboxylalkyl guar gum, hydrophobically modified carboxylhydroxyalkyl guar gum, hydrophobic cationic guar gum, and mixtures thereof. Most preferably, the polysaccharide is guar gum or a guar gum derivative. As used herein, the terms "polysaccharide," "galactomannan," and "guar gum" also refer to their derivatives, such as those listed above.

[0040] In other words, the polysaccharide of the present invention can be derivatized, that is, the polysaccharide can be grafted with one or more functional (substituent) groups. The functional group can be a nonionic, anionic, or cationic hydrophobic substituent, or a combination thereof.

[0041] Suitable nonionic (neutral) substituents are hydroxyalkyl groups, such as hydroxypropyl.

[0042] Suitable anionic substituents are carboxyl alkyl, such as carboxymethyl, or sulfonic acid alkyl, such as 2-acrylamido-2-methylpropanesulfonic acid (AMPS).

[0043] Suitable cationic substituents are primary amino, secondary or tertiary amino or quaternary ammonium, sulfonyl or phosphonium (e.g. hydroxypropyltrimethylammonium), or amide amine, and combinations thereof.

[0044] Particularly preferred is that the functionalized / grafted polysaccharide is anionic or cationic substituted polysaccharide; more preferably, the substituent is carboxymethyl, sulfonic alkyl, or hydroxypropyltrimethylammonium.

[0045] In a preferred embodiment of the present invention, the polysaccharide is functionalized guar gum, preferably carboxyl alkyl, sulfonic acid alkyl or quaternary ammonium guar gum, more preferably carboxymethyl, 2-acrylamido-2-methylpropanesulfonic acid or hydroxypropyltrimethylammonium guar gum.

[0046] The cross-linked polysaccharide particles of the present invention have a particle size of 0.1 to 150 µm, particularly 0.2 to 150 µm, preferably 2 to 100 µm, and more preferably 5 to 25 µm, as determined by bright-field microscopy and dynamic light scattering (DLS).

[0047] The degree of crosslinking of the crosslinked polysaccharide particles of the present invention is 0.00001 to 0.001, preferably 0.00002 to 0.0005.

[0048] If the degree of crosslinking is too low, a certain percentage of the biopolymer will not crosslink, which will reduce / impair the suspension properties of the solution. On the other hand, if the degree of crosslinking is too high, the particles will have very high rigidity and will no longer be able to swell sufficiently in water.

[0049] According to OECD 301F standard, the cross-linked polysaccharide particles of this invention are biodegradable, meaning that the cross-linked polysaccharide exhibits a biodegradability of 60% or greater within 28 days. This standard is a solution aerobic biodegradation test, which determines the biodegradability of the material by measuring oxygen consumption.

[0050] Furthermore, the present invention relates to a method for obtaining cross-linked polysaccharide particles as described above.

[0051] In the method, the polysaccharide as defined above is contacted with water, alkali and a bifunctional crosslinking agent in an amount resulting in a degree of crosslinking (DS) of 0.00001 to 0.001, more preferably 0.00002 to 0.0005.

[0052] In the method of the present invention, it is preferable to use water in an amount between 0.1 and 2 mass equivalents, or more preferably about 1 mass equivalent, for 1 mass equivalent of polysaccharide.

[0053] In the method of the present invention, the base used as a catalyst for deprotonating polysaccharides can be used in stoichiometric amounts. However, according to the present invention, it is preferable to use the base in amounts below stoichiometric levels to maintain good functionalization and minimize molecular weight degradation of the polysaccharide. Preferably, the base is used in amounts of 0.1 to 1.0 mol / mol polysaccharide, especially 0.1 to 0.5 mol / mol polysaccharide, and particularly 0.15 to 0.25 mol / mol polysaccharide.

[0054] The bifunctional agent is preferably used in an amount of 0.00002 to 0.003 mol / mol polysaccharide, and particularly 0.00004 to 0.001 mol / mol polysaccharide. In the method of the present invention, the polysaccharide as defined above is used.

[0055] Preferably, in the method of the present invention, the polysaccharide is galactomannan, more preferably guar gum, most preferably functionalized guar gum, and especially carboxymethyl guar gum.

[0056] The functionalization (derivation) of the polysaccharide can be carried out before or after the cross-linking reaction of the present invention. Preferably, the polysaccharide is functionalized before reacting with a bifunctional cross-linking agent. Functional nonionic, anionic, and / or cationic functional groups can be introduced into the polysaccharide chain via a series of reactions or by simultaneously reacting with a suitable corresponding derivatizing agent as known in the art. Suitable methods are described in WO 94 / 24169 or WO 2021 / 072012.

[0057] The degree of derivatization (DD) of the polysaccharide is preferably between 0.01 and 3.0, more preferably between 0.05 and 1.0, and even more preferably between 0.1 and 0.3, which is achieved through... 1 Determined by 1H NMR spectroscopy. The degree of derivatization refers to the average number of substituents attached to each monomer unit of the polysaccharide due to the reaction between the polysaccharide and the reactants.

[0058] Furthermore, the polysaccharide used in the method of the present invention preferably has a high average molecular weight (M). w ), that is, M w Preferably, it is 20,000 g / mol to 3,000,000 g / mol, more preferably 20,000 g / mol to 2,000,000 g / mol, more preferably 50,000 g / mol to 1,800,000 g / mol, or 80,000 g / mol to 1,500,000 g / mol, 100,000 g / mol to 1,500,000 g / mol, or even more preferably 500,000 g / mol to 1,500,000 g / mol.

[0059] The average molecular weight (Mw) of polysaccharides, particularly grafted polysaccharides, can be measured using SEC-MALS (size exclusion chromatography with multi-angle light scattering detection). For molecular weight measurements, a dn / dc value of 0.140 was used. The Wyatt MALS detector was calibrated using a 22.5 kDa polyethylene glycol standard. All calculations of the molecular weight distribution were performed using Wyatt's ASTRA software. For cationic polysaccharides, particularly cationic guar gum, samples were prepared as 0.05% solutions in a mobile phase (100 mM NaNO3, 200 ppm NaN3, 20 ppm pDADMAC) and filtered through a 0.45 µm PVDF filter prior to analysis. 100 µL of the filtered solution was injected and then passed through a pre-column with three OH pak SB-806 M columns at 35°C. For nonionic and anionic polysaccharides, particularly nonionic and anionic guar gum, the sample was prepared as a 0.05% solution in the mobile phase (100 mM NaNO3, 200 ppm NaN3) and filtered through a 0.45 µm PVDF filter before analysis. 100 µL of the filtered solution was injected and passed through a pre-column at 35°C with three OH pak SB-806HQ columns.

[0060] The base used in the method of the present invention is preferably a strong base and soluble in water. Suitable bases for carrying out the method of the present invention are selected from the group consisting of: sodium hydroxide, potassium hydroxide, sodium methoxide, 1,4-diazabicyclo[2.2.2]octane (DABCO), triethylamine (TEA), sodium carbonate (Na2CO3), pyridine (C5H5N), sodium bicarbonate (NaHCO3), potassium carbonate (K2CO3), potassium bicarbonate (KHCO3), sodium ethoxide, and potassium tert-butoxide. More preferably, the base is sodium hydroxide.

[0061] The bifunctional crosslinking agent is preferably selected from the group consisting of bisacrylamide, bisepoxides, bis(acid anhydride), biscarboxylic acids, bis(amino) derivatives, or mixtures thereof. Preferably, the bifunctional crosslinking agent is bisacrylamide because this molecule can build bridges between polysaccharide molecules when crosslinking them, thereby facilitating swelling. Therefore, according to this embodiment of the invention, the degree of crosslinking can be expressed as the number of moles of bisacrylamide per mole of polysaccharide. In other words, this embodiment of the invention relates to crosslinked polysaccharide particles as described above, which contain 0.00001 to 0.001 moles of bisacrylamide (particularly MBA: see below) per mole of polysaccharide.

[0062] Therefore, the present invention particularly relates to cross-linked polysaccharide particles having a particle size between 0.1 and 150 µm, typically between 2 and 150 µm, which are biodegradable according to OECD 301F standards and contain 0.00001 to 0.001, more preferably 0.00002 to 0.0005 moles of bisacrylamide per mole of cross-linked polysaccharide.

[0063] The bisacrylamide molecules that can be used in the framework of this invention are N,N'-methylenebisacrylamide (MBA), N,N'-ethylidenebisacrylamide (EBA), N,N'-bis(acryloyl)cystamine (BAC) and N,N'-bis(acryloyl)piperazine (BAP).

[0064] More preferably, the bifunctional crosslinking agent is methylenebisacrylamide (MBA), as it is a water-soluble molecule that helps form a stable (irreversible) insoluble gel. Furthermore, it provides a linear bridge of nine atoms between the crosslinked polysaccharide molecules, allowing for a flexible structure and making swelling particularly easy. MBA is known to have a crosslinking efficiency of 40%, meaning that 0.000025 to 0.0025 moles of MBA must be used per mole of polysaccharide.

[0065] The crosslinking reaction according to the invention is preferably Michael addition, as exemplified below:

[0066]

[0067] The duration of cross-linking of polysaccharides is preferably between 1 and 10 hours, more preferably between 1 and 6 hours.

[0068] Furthermore, it is preferred that the crosslinking reaction be carried out at a temperature between 20°C and 80°C, more preferably between 50°C and 80°C.

[0069] According to the present invention, after the crosslinking reaction is completed, the reaction mixture can be neutralized, washed to remove unreacted reagents, and optionally dried.

[0070] The neutralization of the mixture, preferably to a pH between 6 and 7, can be obtained by any suitable acid known in the art, such as acetic acid.

[0071] The washing step can be performed using a mixture of water and alcohol (such as isopropanol).

[0072] The drying step can be carried out in a vacuum oven at a temperature between 45°C and 55°C, preferably at about 50°C.

[0073] After drying, the obtained powder can be ground and sieved for further use.

[0074] Cross-linked polysaccharide particles obtained by the methods of this invention typically comprise a mixture of free (unattached / uncross-linked) polysaccharide chains (hereinafter referred to as polymer free chains or free chains). The free chain population may originate from (a) polymer chains that have never been attached, i.e., for example, when the degree of cross-linking is very low; and / or (b) thermal degradation over time due to prolonged reaction at high temperatures. The amount of free chains can be determined by suspending the microgel in water and subsequently centrifuging to separate the remaining solids (microgel) and the supernatant. The solid content of the supernatant is then determined to be the free polymer.

[0075] According to a preferred embodiment of the invention, the amount of free polymer chains (pol) present in the cross-linked polysaccharide particles (par) obtained by the method of the invention is controlled. That is, the inventors have found that, in order for the microgel particles to exhibit their optimal suspension properties in formulations, a ratio (pol / par) of less than 60%, preferably less than 50%, by weight of free polysaccharide chains to cross-linked polysaccharide particles is preferred. In other words, preferably, the cross-linked polysaccharide particles of the invention contain less than 60%, preferably less than 50%, preferably less than 20% by weight of free polysaccharide chains. Preferably, the pol / par ratio is 0% to 50%, more preferably 0% to 20%.

[0076] By carrying out the method of the present invention, microgel particles with a desired degree of crosslinking and a preferred ratio (pol / par) between free polysaccharide chains and crosslinked microgel particles can be obtained.

[0077] The present invention also relates to an aqueous formulation comprising the cross-linked polysaccharide particles of the present invention, wherein the concentration of the cross-linked polysaccharide particles is preferably 0.5 to 10.0 wt.- based on the total weight of the aqueous formulation.

[0078] The aqueous formulation of the present invention can be obtained by dispersing microgel particles obtained by the method of the present invention as described above in water.

[0079] Preferably, the concentration of cross-linked polysaccharide particles present in the aqueous formulation of the present invention is 0.5 to 10.0 wt%, preferably 0.5 to 5.0 wt.-%, or even more preferably 0.5 to 2.0 wt.-%, based on the total weight of the aqueous formulation.

[0080] Furthermore, preferably, the yield stress of the formulation is at least 0.1 Pa, preferably between 0.1 and 30 Pa, more preferably between 1.0 and 25 Pa, and even more preferably between 2.0 and 20 Pa. The yield stress of the formulation is determined by means of a Malvern Kinexus Pro rheometer at 25°C and at 10°C. -3 Up to 10 1 s -1The shear rate was measured under conditions of a steep increase.

[0081] The pol / par ratio of the aqueous formulation according to the invention is preferably within the range defined above to ensure that the formulation is a suitable suspending agent for shear-thinned formulations. If necessary, this ratio can be adjusted by centrifugation.

[0082] Formulations containing the cross-linked polysaccharide particles of the present invention can be used in home and personal care applications, agricultural applications, coatings, metal treatments, and products for the oilfield market. Preferably, the formulation is used in home and personal care applications (e.g., as a bath and shower product, cream, lotion, or hair care composition) or in agricultural applications, preferably for suspending objects such as beads or bubbles.

[0083] By using the formulation of the present invention, a final product formulation can be provided, wherein the object is stably suspended, i.e., the object remains in a continuous phase of the formulation. The resulting suspension is stable for at least 1 week, at least 2 weeks, at least 3 weeks, at least 5 weeks, at least 8 weeks, or at least 12 weeks, or at least 18 weeks. More preferably, the resulting suspension is stable for at least 30 months.

[0084] If any disclosure of any patent, patent application, or publication incorporated herein by reference conflicts with this specification to the extent that it may obscure the terminology, this specification shall prevail.

[0085] The invention will be further illustrated by the following examples. It should be understood that the following examples are for illustrative purposes only and are not intended to limit the invention thereto.

[0086] Example 1: Synthesis of cross-linked carboxymethyl guar gum (CMG) microgels

[0087] Introduce 20 g of CMG (carboxymethyl guar gum) into the mortar.

[0088] Add 18.1 g of distilled water and then mix it with the powder using a pestle to obtain swollen guar gum powder.

[0089] Add 1.78 g of NaOH aqueous solution (50% wt in water) to the swollen guar gum powder and mix with a pestle.

[0090] Add an amount m of N,N'-bis-methyleneacrylamide (MBA) to the swollen powder. The amount m of MBA depends on the target degree of crosslinking.

[0091] The mixture was transferred from the mortar to a 250 mL round-bottom flask with an integrated reverse blade and heated at 70°C for 6 hours. At the end of the reaction, the solid was transferred to a beaker and a solution (200 mL) of isopropanol and water (isopropanol / water = 3 / 1; v, v) was added. The pH of the mixture was adjusted to approximately 6–7 using acetic acid. The solid was washed with a solution (200 mL x 3 times) of isopropanol and water (isopropanol / water = 3 / 1; v, v) and then dried in an oven at 50°C under atmospheric pressure. The formation of cross-linked particles with particle sizes between 0.1 and 150 µm was confirmed using bright-field microscopy and dynamic light scattering (DLS).

[0092] 0.2 g of dried microgel was suspended in 19.8 g of water in a centrifuge tube. The tube was centrifuged at 14,500 rpm for 1 hour. The solid content of the supernatant was determined, and this solid content corresponds to the free polymer.

[0093] Example 2: Synthesis of cross-linked hydroxypropyl guar gum (HPG) microgels

[0094] Introduce 20 g of HPG (hydroxypropyl guar gum) into the mortar.

[0095] Add 18.1 g of distilled water and then mix it with the powder using a pestle to obtain swollen guar gum powder.

[0096] Add 1.78 g of NaOH aqueous solution (50% wt in water) to the swollen guar gum powder and mix with a pestle.

[0097] Add an amount m of N,N'-bis-methyleneacrylamide (MBA) to the swollen powder. The amount m of MBA depends on the target degree of crosslinking.

[0098] The mixture was transferred from the mortar to a 250 mL round-bottom flask with an integrated reverse blade and heated at 70°C for 6 hours. At the end of the reaction, the solid was transferred to a beaker and a solution (200 mL) of isopropanol and water (isopropanol / water = 3 / 1; v, v) was added. The pH of the mixture was adjusted to approximately 6–7 using acetic acid. The solid was washed with a solution (200 mL x 3 times) of isopropanol and water (isopropanol / water = 3 / 1; v, v) and then dried in an oven at 50°C under atmospheric pressure. The formation of cross-linked particles with particle sizes between 0.1 and 150 µm was confirmed using bright-field microscopy and dynamic light scattering (DLS).

[0099] 0.2 g of dried microgel was suspended in 19.8 g of water in a centrifuge tube. The tube was centrifuged at 14,500 rpm for 1 hour. The solid content of the supernatant was determined, and this solid content corresponds to the free polymer.

[0100] Example 3: Synthesis of cross-linked hydroxypropyltrimethylammonium chloride guar gum (cationic guar gum) microgels

[0101] Introduce 20 g of hydroxypropyltrimethylammonium chloride guar gum (cationic guar gum) into a mortar.

[0102] Add 18.1 g of distilled water and then mix it with the powder using a pestle to obtain swollen guar gum powder.

[0103] Add 1.78 g of NaOH aqueous solution (50% wt in water) to the swollen guar gum powder and mix with a pestle.

[0104] Add an amount m of N,N'-bis-methyleneacrylamide (MBA) to the swollen powder. The amount m of MBA depends on the target degree of crosslinking.

[0105] The mixture was transferred from the mortar to a 250 mL round-bottom flask with an integrated reverse blade and heated at 70°C for 6 hours. At the end of the reaction, the solid was transferred to a beaker and a solution (200 mL) of isopropanol and water (isopropanol / water = 3 / 1; v, v) was added. The pH of the mixture was adjusted to approximately 6–7 using acetic acid. The solid was washed with a solution (200 mL x 3 times) of isopropanol and water (isopropanol / water = 3 / 1; v, v) and then dried in an oven at 50°C under atmospheric pressure. The formation of cross-linked particles with particle sizes between 0.1 and 150 µm was confirmed using bright-field microscopy and dynamic light scattering (DLS).

[0106] 0.2 g of dried microgel was suspended in 19.8 g of water in a centrifuge tube. The tube was centrifuged at 14,500 rpm for 1 hour. The solid content of the supernatant was determined, and this solid content corresponds to the free polymer.

[0107] Example 4: Synthesis of cross-linked anionic guar gum-AMPS microgels

[0108] 20 g of anionic guar gum-AMPS was introduced into the mortar.

[0109] Add 18.1 g of distilled water and then mix it with the powder using a pestle to obtain swollen guar gum powder.

[0110] Add 1.78 g of NaOH aqueous solution (50% wt in water) to the swollen guar gum powder and mix with a pestle.

[0111] Add an amount m of N,N'-bis-methyleneacrylamide (MBA) to the swollen powder. The amount m of MBA depends on the target degree of crosslinking.

[0112] The mixture was transferred from the mortar to a 250 mL round-bottom flask with an integrated reverse blade and heated at 70°C for 6 hours. At the end of the reaction, the solid was transferred to a beaker and a solution (200 mL) of isopropanol and water (isopropanol / water = 3 / 1; v, v) was added. The pH of the mixture was adjusted to approximately 6–7 using acetic acid. The solid was washed with a solution (200 mL x 3 times) of isopropanol and water (isopropanol / water = 3 / 1; v, v) and then dried in an oven at 50°C under atmospheric pressure. The formation of cross-linked particles with particle sizes between 0.1 and 150 µm was confirmed using bright-field microscopy and dynamic light scattering (DLS).

[0113] 0.2 g of dried microgel was suspended in 19.8 g of water in a centrifuge tube. The tube was centrifuged at 14,500 rpm for 1 hour. The solid content of the supernatant was determined, and this solid content corresponds to the free polymer.

[0114] Test 1: Swelling Capacity

[0115] This test is used as a screening technique to find the optimal parameters for producing the most efficient synthetic products. In fact, the greater the degree of swelling of the microgel particles, the greater their potential to act as efficient suspending agents.

[0116] Therefore, the CMG microgel particles obtained as described above were introduced into water at 2 wt.% and the resulting suspension was adjusted to a pH of approximately 6.5 using acetic acid. The suspension was allowed to stand on the lab bench for 12 hours to allow the microgel particles to swell to their maximum extent in the water. When fully swollen in such a dilute solution, the microgel particles may settle to the bottom of the glass vial. The degree of swelling (expansion) was calculated by measuring the height of the microgel particles relative to the total height of the suspension.

[0117] Tables 1 and 2 summarize the swelling behavior of different suspensions.

[0118]

[0119]

[0120] Test 2: Method for measuring the ratio of free chains to microgel particles

[0121] A 1 wt.% suspension of cross-linked guar gum in water was prepared by dissolving 0.2 g of cross-linked guar gum in 19.8 g of water. The suspension was then placed in centrifuge tubes and centrifuged at 14,500 rpm for 1 hour. The supernatant was observed to become clear after centrifugation. This was considered to contain free polymer chains, and the sediment fraction was considered to contain cross-linked guar gum particles. 1 g of the supernatant and 1 g of the sediment fraction were placed on a glass slide of known weight. The slide was heated to 200°C, and the remaining solids were weighed. The percentages of free polymer chains and cross-linked guar gum particles were calculated based on the remaining solids in the supernatant and sediment fractions. The results are shown in Tables 1 and 2 above.

[0122] Test 3: Evaluation of Suspension Properties

[0123] Prepare 2 and 4 wt.% suspensions of microgel particles in water, and then adjust the pH to 6.5 using acetic acid. Add beads with a diameter of 1 mm (approximately 2.2 for glass beads, 1.7 for silica beads, and 1.05 for acrylic beads) to the suspensions. Visually monitor the height of the beads to check for any settling. Note that all beads should remain suspended at room temperature for at least 8 weeks.

[0124] Test 4: Biodegradability

[0125] The biodegradability of the cross-linked guar gum samples (DS 0.001) synthesized as described in Example 1 was tested using the OECD 3O1F standard test, and 60% of the samples showed biodegradability in less than 28 days, indicating that the samples are readily biodegradable. This demonstrates that cross-linked CMG-MBA guar gum with a DS below 0.001 is also readily biodegradable.

Claims

1. A cross-linked polysaccharide particle having a particle size between 0.1 and 150 µm, a cross-linking degree of 0.00001 to 0.001, and being biodegradable according to OECD 301F standards.

2. The cross-linked polysaccharide particles according to claim 1, wherein, The polysaccharide is galactomannan, preferably guar gum.

3. The cross-linked polysaccharide particles according to claim 1 or 2, wherein, The polysaccharide is a derivatized polysaccharide having nonionic, anionic, cationic, hydrophobic substituents, or combinations thereof, more preferably a carboxymethyl modified polysaccharide, a 2-acrylamido-2-methylpropanesulfonic acid (AMPS) modified polysaccharide, or a hydroxypropyltrimethylammonium chloride modified polysaccharide.

4. The cross-linked polysaccharide particles according to any one of claims 1 to 3, comprising less than 50% by weight of free polysaccharide chains.

5. The cross-linked polysaccharide particles according to any one of claims 1 to 4, comprising 0.00001 to 0.001 moles of bisacrylamide per mole of polysaccharide.

6. A method for obtaining cross-linked polysaccharide particles according to any one of claims 1 to 5, wherein, The polysaccharide is brought into contact with water, alkali and a bifunctional crosslinking agent in an amount resulting in a crosslinking degree of 0.00001 to 0.

001.

7. The method according to claim 6, wherein, The polysaccharide has an average molecular weight of 20,000 g / mol to 3,000,000 g / mol.

8. The method according to claim 6 or 7, wherein, This polysaccharide is a functionalized polysaccharide with a degree of derivatization between 0.01 and 3.

0.

9. The method according to any one of claims 6 to 8, wherein, Water is used in amounts of 0.1 to 2 mass equivalents for 1 mass equivalent of the polysaccharide.

10. The method according to any one of claims 6 to 9, wherein, The alkali is used in amounts of 0.1 to 1.0 mol / mol of the polysaccharide, especially 0.1 to 0.5 mol / mol of the polysaccharide, and particularly 0.15 to 0.25 mol / mol of the polysaccharide.

11. The method according to any one of claims 6 to 10, wherein, The bifunctional cross-linking agent is used in amounts of 0.00002 to 0.003 mol / mol of the polysaccharide, and particularly 0.00004 to 0.001 mol / mol of the polysaccharide.

12. The method according to any one of claims 6 to 11, wherein, The bifunctional crosslinking agent is selected from the group consisting of bisacrylamide, bisepoxide, bisanhydride, biscarboxylic acid, bisamino derivative, or mixtures thereof; preferably bisacrylamide, more preferably methylenebisacrylamide.

13. The method according to any one of claims 6 to 12, wherein, The polysaccharide is contacted with water, the alkali and the bifunctional crosslinking agent for 1 to 10 hours, preferably at a temperature between 30°C and 80°C for 1 to 10 hours.

14. An aqueous formulation comprising cross-linked polysaccharide particles according to any one of claims 1 to 5, wherein the cross-linked polysaccharide particles preferably constitute 0.5 to 10.0 wt.% based on the total weight of the composition, and wherein, The aqueous formulation preferably has a yield stress of at least 0.1 Pa, and / or preferably has a ratio of less than 50% by weight of free polysaccharide chains to cross-linked polysaccharide particles.

15. Use of the aqueous formulation according to claim 14, wherein the aqueous formulation is used in home and personal care applications, agricultural applications, coatings, metal treatment, and oilfield market products, preferably for suspending objects such as beads or bubbles.

16. A cross-linked polysaccharide particle having a particle size between 0.1 and 150 µm, being biodegradable according to OECD 301F standards, and containing 0.00001 to 0.001 moles of bisacrylamide per mole of cross-linked polysaccharide.

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