Biodegradable water-dispersible and swellable structures, preparation and uses thereof as suspending agents

Abstract

The invention relates to a new readily biodegradable water-dispersible polymer structures of finite size, a production process thereof, and their use as suspending additives in flowable formulations for home and personal care, agricultural, coatings, metal treatment, and oil field market. No figure

Description

[0001] BIODEGRADABLE WATER-DISPERSIBLE AND SWELLABLE STRUCTURES, PREPARATION AND USES THEREOF AS SUSPENDING AGENTS

[0002] This application claims priority to application US 63 / 618739 filed on 08.01.2024 and to application EP 24154453.5 filed on 29.01.2024, the whole content of each of these applications being incorporated herein by reference for all purposes.

[0003] TECHNICAL FIELD

[0004] The invention relates to a new readily biodegradable water-dispersible polymer structures of finite size, a production process thereof, and their use as suspending additives in flowable formulations for home and personal care, agriculture, coatings, metal treatment, and oil field markets.

[0005] TECHNICAL BACKGROUND

[0006] A wide variety of home and personal care formulations, but also of agricultural formulations, coatings, metal treatment products and products of oil field market are shear-thinning fluids. Shear-thinning fluids have a non-Newtonian behaviour, i.e., their viscosity decreases under shear stress. This behaviour is sometimes considered a synonym for pseudo-plastic behaviour.

[0007] The shear thinning effect is regarded to be an effect of small structural changes within the fluid, such that microscale geometries within the fluid rearrange to facilitate shearing. For example, in colloid systems, phase separation during flow leads to shear thinning. In polymer systems such as polymer melts and solutions, shear thinning is caused by the disentanglement of polymer chains during flow. At rest, high molecular weight polymers are entangled and randomly oriented. However, when undergoing agitation at a high enough rate, these highly anisotropic polymer chains start to disentangle and align along the direction of the shear force. This leads to less molecular / particle interaction and a larger amount of free space, decreasing the viscosity.

[0008] An example for shear thinning formulations are latex paints. When these paints are applied on a surface, the shear created by the brush or roller will allow them to thin and wet out the surface evenly. Once applied, the paints regain its higher viscosity, which avoids drips and runs. Another example is whipped cream. When the whipped cream is sprayed out of its canister, it flows out smoothly from the nozzle due to its low viscosity at high flow (shear) rates. After application, the whipped cream does no longer flow, and its increased viscosity allows it to be rigid. The same behaviour can be observed in cosmetic products, like shower foam formulations.

[0009] Furthermore, commonly home and personal care formulations, agricultural formulations, coatings, metal treatment products and products for the oil field market are dispersions in which objects like beads, air bubbles, oil droplets or solid particles, e.g., pigment particles, are suspended. These suspended objects have the tendency to flocculate / sediment and / or to coalesce in the formulation. However, for an effective use of the formulations, it has to be ensured that objects are remained suspended in the continuous phase of the formulation, such as, for example in the aqueous solution Therefore, usually the formulations include suspending agents to avoid flocculation, sedimentation and / or agglomeration of the suspended objects.

[0010] One currently commercially available example for such suspending agents are microgels, especially carbomer microgels. Microgels are objects of a finite size, in general of micro size, which can be dispersed in a liquid, for example water, swell and fill up the whole volume of the liquid. Due to this property of the microgels, the suspended objects can be maintained in the continuous phase of the formulation. Carbomers are high molecular weight polymers of acrylic acid crosslinked with allyl ethers of polyalcohols. In addition to their good suspending properties, carbomer microgels do not influence the shear-thinning behaviour of the liquid formulation. This functionality of the microgels make their use in shearthinning fluids interesting.

[0011] However, the use of such carbomer microgels as known in the art, for example in home and personal care formulations, is problematic, because generally they are not biodegradable.

[0012] In contrast to these carbomer microgels, gels or hydrogels are known in the art, which are biodegradable. However, such biodegradable gels or hydrogels either do not bring sufficient suspending properties and / or cause formulations to gel macroscopically so that they no longer flow. Hence, by using these biodegradable gels or hydrogels, it is not possible to suspend an object in the continuous phase of a formulation while maintaining the shear-thinning behaviour of the formulation.

[0013] Therefore, there was the need to provide a biodegradable suspending additive, which has the same functionality as non-biodegradable suspending additives as known in the art, e.g., carbomer microgels, i.e., which makes it possible to maintain suspended objects in the continuous phase of the formulation while maintaining the shear-thinning behaviour of the formulation. SUMMARY OF THE INVENTION

[0014] The present invention relates to crosslinked polysaccharide particles having a particle size between 0. 1 and 150 pm, a degree of crosslinking from 0.00001 to 0.001 and which are biodegradable according to the OECD 301F standard.

[0015] Furthermore, the invention provides a process for obtaining the crosslinked polysaccharide particles of the invention, wherein a polysaccharide is contacted with water, a base and a bifunctional crosslinking agent in amounts leading to a degree of crosslinking from 0.00001 to 0.001.

[0016] Moreover, the invention relates to an aqueous formulation comprising the crosslinked polysaccharide particles of the invention, preferably in an amount of from 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 of polysaccharide free chains to crosslinked polysaccharides particles (pol / par) of less than 60%, preferably less than 50% in weight. This formulation can be used for different purposes, for example as home and personal care products, agricultural products, coatings, metal treatment, and products for the oil field market.

[0017] DETAILED DESCRIPTION OF THE INVENTION

[0018] Before the issues of the invention are described in detail, the following should be considered:

[0019] As used herein, the singular forms "a", "an", and "the" include both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a compound" means one compound or more than one compound.

[0020] The terms "comprising", "comprises" and "comprised of' as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. It will be appreciated that the terms "comprising", "comprises" and "comprised of as used herein comprise the terms "consisting of', "consists" and "consists of.

[0021] Throughout this application, the term "about" is used to indicate that a value includes the standard deviation of error for the device or method being employed to determine the value.

[0022] As used herein, the term "average" refers to number average unless indicated otherwise. 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.

[0023] The recitation of numerical ranges by end points includes all integer numbers and fractions comprised within that range, including the end points themselves (e.g., from 1.0 to 10.0 includes both 1.0 and 10.0, and all values higher than 1.0 and lower than 10.0, e.g. 1.1, 1.2....2.0, 2.1, ....9.9).

[0024] The terms “suspending power”, “suspending property”, “suspension power”, “suspension property”, as used herein, refer to the characteristic of an additive that prevents sedimentation of dispersed particles in an otherwise liquid formulation. In contrast, a “suspension” is a general term to describe a type of liquid formulation in which particles, objects etc. have been dispersed. These may, or may not, sediment depending on the presence of an additive with suspending power. Hence, according to the invention, the term “suspension” differs from a formulation with suspension power.

[0025] The terms “yield” and “yield stress”, as used herein, refer to a rheological feature that is a quantitative measurement of the suspension power of an additive in a given aqueous medium. It corresponds to the critical stress that is needed to make such formulation start flowing under shear.

[0026] The term “shear thinning”, as used herein refers to a liquid formulation whose viscosity is lower as the shear rate is increased. “Newtonian” refers to a liquid formulation whose viscosity is constant regardless of the shear rate (deformation rate).

[0027] The term “microgel”, as used herein, refers to an object of finite size, in general of small (micronic) size, which can be dispersed in water, swells and fills up the whole volume of a liquid formulation. In contrast thereto, a “gel” refers to a monolithic system prepared as is, macroscopically. A gel is not an assembly of objects of finite size, it is one object. A “hydrogel” is one type of said gel that is prepared in the presence of water as solvent. It typically contains a high concentration of water.

[0028] The term “DS”, as used herein, refers to the degree of crosslinking of the polysaccharide. This property can usually be determined using nuclear magnetic resonance (NMR) and corresponds to the number of crosslinking points i.e. to the number of moles of crosslinking agent per mole of crosslinked polysaccharide. However, since the DS of the product of the invention is very low, it can generally not be measured. Instead, it can be calculated knowing the crosslinking efficiency of the crosslinking agent used. This efficiency can be determined by measuring the DS (by NMR) on products with a much higher DS i.e. crosslinked with the same crosslinking agent but in much higher amounts.

[0029] The term “DD”, as used herein, refers to the degree of derivatization of the polysaccharide i.e. the degree of substitution with functionalized groups i.e. the number of substituents.

[0030] The terms "functionalized", "grafted" and “substituted” as used herein are interchangeable.

[0031] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

[0032] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

[0033] In the following passages, different alternatives, embodiments and variants of the invention are defined in more detail. Each alternative and embodiment so defined may be combined with any other alternative and embodiment, and this for each variant unless clearly indicated to the contrary or clearly incompatible when the value range of a same parameter is disjoined. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

[0034] Furthermore, the particular features, structures or characteristics described in the present description may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art.

[0035] The present invention relates to crosslinked polysaccharide particles having a particle size between 0.1 and 150 pm, a degree of crosslinking from 0.00001 to 0.001, and which are biodegradable according to the OECD 301F standard.

[0036] Crosslinked polysaccharides are known in the art (see e.g. US 11,365,371 B2 or US 10,414,960). However, none of these documents refers to crosslinked polysaccharide particles having a readily biodegradable water-dispersible polymer structure of finite size, herein after referred to as microgels, which provides suspending properties while maintaining the shear-thinning behaviour of the formulation, in which they are used.

[0037] HONGBO TANG ET AL: "Synthesis, Optimization, Property, Characterization, and Application of Dialdehyde Cross-Linking Guar Gum", INTERNATIONAL JOURNAL OF POLYMER SCIENCE, vol. 2016, 1 January 2016, discloses to crosslink guar using phosphorus oxychloride as a crosslinking agent. The degree of crosslinking obtained, and the nature of the crosslinking agent (an inorganic one of small molecular size) are such that no microgel can be obtained as in the present invention.

[0038] EP 2088994B1 relates to the use of glyoxal as crosslinking agent for guar. This is again a small size molecule, and the obtained crosslinked product does not form any gel after contact with water but rather a dispersion of discrete particles.

[0039] WO 2013077620 relates to a method for preparing a water-insoluble gel based on a water-soluble polysaccharide which is not biodegraded for a period of at least several months or more.

[0040] Polysaccharides are long chains of monosaccharides, such as, for example, fructose, galactose, glucose, mannose, xylose, arabinose, rhamnose, and stereoisomers and derivatives thereof, linked by glycosidic bonds.

[0041] According to the invention, it is preferred that the polysaccharide is selected from the group consisting of glucan, starch, amylose, amylopectin, glycogen, dextran, cellulose, mannan, xylan, lignin araban, galatan, galacturonan, chitin, chitosan, glucuronoxylan, arabinoxylan, xyloglucan, glucomannan, pectin, arabinogalactan, carrageenan, agar, gum Arabic, gum tragacanth, ghatti gum, karay gum, carob gum, polygalactomannan, or mixture thereof. More preferably, the polysaccharide is a galactomannan (polygalactomannan). Galactomannans are polysaccharides composed principally of galactose and mannose units, wherein the mannose units are linked in a 1-4-P-glycosidic linkage and the galactose branching takes place by means of a 1 -6-a-linkage to mannose units. Naturally occurring galactomannans are available from numerous sources, including guar gum, guar splits, locust bean gum, flame tree gum and casein gum. Additionally, galactomannan may also be obtained by chemical modification of naturally occurring galactomannans. In a preferred embodiment the galactomannan is guar.

[0042] In a more preferred embodiment of the invention, the galactomannan and derivatives thereof is 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, carboxyalkyl guar, carboxyalkyl hydroxyalkyl guar, cationic guar, hydrophobically modified guar, hydrophobically modified hydroxyalkyl guar, hydrophobically modified carboxyalkyl guar, hydrophobically modified carboxyalkyl hydroxyalkyl guar, hydrophobically cationic guar and mixtures thereof. Most preferably, the polysaccharide is a guar or a guar derivative. The terms “polysaccharide”, “galactomannan” and “guar” as used herein also refers to their derivatives as for example listed above.

[0043] It is namely so that the polysaccharides of the invention may be derivatized, i.e., the polysaccharides may be grafted with one or more functional (substituent) groups. The functional groups may be non-ionic, anionic, cationic, hydrophobic substituent groups, or a combination thereof.

[0044] Suitable non-ionic (neutral) substituent groups are hydroxyalkyl groups, such a hydroxypropyl groups.

[0045] Suitable anionic substituent groups are carboxyalkyl groups, for example carboxymethyl groups or sulfonic alkyl groups such as 2-Acrylamido-2- methylpropane sulfonic acid (AMPS).

[0046] Suitable cationic substituent groups are primary, secondary, or tertiary amino groups or quaternary ammonium, sulfonium, or phosphonium groups, for example hydroxypropyltrimonium or amido amine, and combinations thereof

[0047] Especially, it is preferred that the functionalized / grafted polysaccharide is an anionic or cationic substituted polysaccharide; more preferably, the substituent group is carboxymethyl, sulfonic alkyl or hydroxypropyltrimonium.

[0048] In a preferred embodiment of the invention, the polysaccharide is a functionalized guar, preferably carboxyalkyl, sulfonic alkyl or quaternary ammonium guar, more preferably carboxymethyl, 2-acrylamido-2-methylpropane sulfonic acid or hydroxypropyltrimonium guar.

[0049] The crosslinked polysaccharide particles of the invention have a particle size of from 0.1 to 150 pm, in particular from 0.2 to 150 pm, preferably of from 2 to 100 pm, more preferably of from 5 to 25 pm, determined by Bright Field microscopy and dynamic light scattering (DLS).

[0050] The degree of crosslinking of the crosslinked polysaccharide particles of the invention is from 0.00001 to 0.001, preferably from 0.00002 to 0.0005.

[0051] If the degree of crosslinking is too low, a percentage of the biopolymer will not be crosslinked, which will decrease / harm the suspending property of the solution. On the other hand, if the degree of crosslinking is too high, the particles will be very rigid and no longer be able to swell enough in water. The crosslinked polysaccharide particles of the invention are biodegradable according to OECD 301F standard, meaning the crosslinked polysaccharides have a biodegradability of 60% or greater within 28 days. This standard is a solution aerobic biodegradation test that determines the biodegradability of a material by measuring oxygen consumption.

[0052] Furthermore, the invention relates to a method for obtaining the crosslinked polysaccharide particles as described above.

[0053] In said method, a polysaccharide as defined above is contacted with water, a base and a bi-functional crosslinking agent in amounts leading to a degree of crosslinking (DS) from 0.00001 to 0.001, more preferably from 0.00002 to 0.0005.

[0054] It is preferred to use an amount of water between 0.1 and 2 eq., or more preferred of about 1 eq. in mass of water for 1 eq. in mass of the polysaccharide in the method of the invention.

[0055] The base, used in the method of the invention as catalyst to deprotonate the polysaccharide, may be used in stoichiometric amounts. However, according to the invention, the base is used preferably in amounts lower than stoichiometric amounts to keep a good functionalization and to minimize the molecular weight degradation of the polysaccharide. Preferably, the base is used in an amount of from 0.1 to 1.0 mol / mol, notably from 0.1 to 0.5 mol / mol, and particularly from 0.15 to 0.25 mol / mol of the polysaccharide.

[0056] The bifunctional agent is preferably used in an amount of from 0.00002 to 0.003 mol / mol, and particularly from 0.00004 to 0.001 mol / mol of the polysaccharide. In the method of the invention, polysaccharides as defined above are used.

[0057] Preferably in the method of the invention the polysaccharide is a galactomannan, more preferably a guar, most preferably a functionalized guar, especially carboxymethyl guar.

[0058] The functionalisation (derivatization) of the polysaccharide may be conducted prior to the crosslinking reaction of the invention or afterwards. Preferably, the polysaccharide is functionalized before reacting with a bifunctional crosslinking agent. The functional non-ionic, anionic and / or cationic functional groups may be introduced to the polysaccharide chains via a series of reactions or by simultaneous reactions with the respective appropriate derivatizing agent as known in the prior art. In WO 94 / 24169 or WO 2021 / 072012 suitable methods are described.

[0059] The degree of derivatization (DD) of the polysaccharide is preferably between 0.01 and 3.0, more preferably between 0.05 and 1.0, more preferably between 0.1 and 0.3, determined by 'H NMR spectroscopy. The degree of derivatization refers to the average number of substituents groups attached to each monomeric unit of the polysaccharide as result of the reaction between the polysaccharide and the reactant.

[0060] Additionally, the polysaccharide used in the method of the invention has preferably a high average molecular weight (Mw), i.e., the Mwis preferably from 20,000 g / mol to 3,000,000 g / mol, preferably from 20,000 g / mol to 2,000,000 g / mol, more preferably, from 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 preferred from 500,000 g / mol to 1,500,000 g / mol.

[0061] The average molecular weight Mw of the polysaccharides, in particular of the grafted polysaccharides, may be measured by SEC-MALS (Size Exclusion Chromatography with Multi-Angle Light-Scattering detection). A value of 0.140 for dn / dc is used for the molecular weight measurements. A Wyatt MALS detector is calibrated using a 22.5 kDa polyethylene glycol standard. All calculations of the molecular weight distributions are performed using Wyatt's ASTRA software. For cationic polysaccharides, in particular for cationic guars, the samples are prepared as 0.05% solutions in the mobile phase (100 mM NaNCh, 200 ppm NaNs, 20 ppm pDADMAC) and filtered through 0.45 pm PVDF filters before analysis. 100 pL of the filtered solution are injected and then go through a pre-column plus 3 columns OH pak SB-806 M at 35°C. For non-ionic and anionic polysaccharides, in particular for non-ionic and anionic guars, the samples are prepared as 0.05% solutions in the mobile phase (lOOmM NaNOs, 200 ppm NaNs) and filtered through 0.45 pm PVDF filters before analysis. 100 pL of the filtered solution are injected and go through a pre-column plus 3 columns OH pak SB-806 HQ at 35°C.

[0062] The base used in the method of the invention is preferably a strong base and soluble in water. Suitable bases for carrying out the method of the invention are selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium methoxide, l,4-diazabicyclo[2.2.2]octane (DABCO), tri ethylamine (TEA), sodium carbonate (TSfeCCE), pyridine (C5H5N), sodium bicarbonate (NaHCOs), potassium carbonate (K2CO3), potassium bicarbonate (KHCO3), sodium ethoxide, and potassium / c / V-butoxide. More preferably, the base is sodium hydroxide.

[0063] The bifunctional crosslinking agent is preferably selected from the group consisting of Zh -acrylamide, -epoxide, -anhydride, -carboxylic acid, -amino derivatives or mixtures thereof. Preferably, the bifunctional crosslinking agent is a bis-acrylamide since this kind of molecule enables building bridges between the polysaccharide molecules when crosslinking them, which favours swelling. Hence, according to this embodiment of the invention, the degree of crosslinking can be expressed as the number of moles of bis-acrylamide per mole of polysaccharide. In other words, this embodiment of the present invention relates to crosslinked polysaccharide particles as described above which comprise from 0.00001 to 0.001 mole of bis-acrylamide (in particular MBA: see below) per mole of polysaccharide.

[0064] Therefore, the present invention relates in particular to crosslinked polysaccharide particles having a particle size between 0.1 and 150 pm, typically between 2 and 150 pm, which are biodegradable according to the OECD 301F standard and which comprise from 0.00001 to 0.001, more preferably from 0.00002 to 0.0005 mole of bis-acrylamide per mole of crosslinked polysaccharide.

[0065] Bis-acrylamide molecules that can be used in the frame of the invention are

[0066] N,N' -Methylenebisacrylamide (MBA), N,N' -Ethylenebisacrylamide (EBA), N,N'- Bis(acryloyl)cystamine (BAC) and N,N'-Bis(acryloyl)piperazine (BAP).

[0067] More preferably, the bifunctional crosslinking agent is methylene bis- acrylamide (MBA) because this is a water-soluble molecule that helps forming an insoluble gel that is stable (non-reversible). Besides, it provides linear bridges comprising 9 atoms between the crosslinked polysaccharide molecules, which allows reaching a flexible structure which makes swelling particularly easy. Knowing that the crosslinking efficiency of MBA is 40%, this means that from

[0068] O.000025 to 0.0025 mole of MBA must be used per mole of polysaccharide.

[0069] The crosslinking reaction according to the invention is preferably a Michael addition, as exemplified below:

[0070] The duration time for crosslinking the polysaccharide is preferably between 1 and 10 hours, more preferably between 1 and 6 hours.

[0071] Furthermore, it is preferred that the crosslinking reaction is carried out at temperature between 20 and 80°C, more preferably between 50 and 80°C. According to the invention, after finishing the crosslinking reaction, the reaction mixture may be neutralized, washed to remove unreacted reagents, and optionally dried.

[0072] The neutralisation of the mixture, preferably to a pH between 6 to 7, can be obtained through any suitable acid known in the art, for example through acetic acid.

[0073] The washing step may be performed using a mixture of water and alcohol, e.g. isopropanol.

[0074] The drying step may be carried out in a vacuum oven at temperature between 45 and 55°C, preferably at about 50°C.

[0075] After drying the obtained powder may be ground and sieved for further use.

[0076] The crosslinked polysaccharide particles obtained by carrying out the method of the invention commonly comprise a mixture of free (unattached / non crosslinked) polysaccharide chains, herein after referred to as polymer free chains or free chains. The population of free chains can originate from either (a) that the polymer chains have never attached, i.e., for instance when the degree of crosslinking is very low; and / or (b) thermal degradation caused over time by prolonged reaction at high temperature. The amount of free chains can be determined by suspending the microgel in water, followed by centrifugation to separate the remaining solid (microgel) and a supernatant. The solid content of the supernatant is then the free polymer.

[0077] According to a preferred embodiment of the invention, the amount of polymer free chains (pol) present in the crosslinked polysaccharide particles (par) obtained by carrying out the method of the invention is controlled. The inventors have namely found that in order for the microgel particles to show their optimal suspending properties in a formulation, it is preferable to have a ratio of polysaccharide free chains to crosslinked polysaccharides particles (pol / par) which is less than 60%, preferably less than 50% in weight. In other words: it is preferable that the crosslinked polysaccharide particles of the invention comprise less than 60%, preferably less than 50% in weight of polysaccharide free chains, preferably less than 20% in weight. Preferably, the pol / par ratio is from 0 to 50%, more preferably from 0 to 20%.

[0078] By carrying out the method of the invention, it is possible to obtain microgel particles having the desired crosslinking degree, and the preferred ratio between free polysaccharide chains and crosslinked microgel particles (pol / par). The present invention also relates to an aqueous formulation comprising the crosslinked polysaccharide particles of the invention, preferably in a concentration of from 0.5 to 10.0 wt.-%, based on the total weight of the aqueous formulation.

[0079] The aqueous formulation of the invention can be obtained by dispersing the microgel particles obtained by the method of the invention as described above in water.

[0080] Preferably the concentration of the crosslinked polysaccharide particles present in the aqueous formulation of the invention is from 0.5 to 10.0 wt%, preferably 0.5 to 5.0 wt.-%, even more preferably from 0.5 to 2.0 wt.-%, based on total weight of the aqueous formulation.

[0081] Furthermore, it is preferred that the yield stress of the formulation is of at least 0.1 Pa, preferably between 0.1 to 30 Pa, more preferably between 1.0 to 25, even more preferred 2.0 to 20 Pa. The yield stress of the formulation is determined with the aid of a Malvern Kinexus Pro Rheometer at 25°C and a shear Rate Ramp from 10'3to 101s'1.

[0082] The pol / par ratio of the aqueous formulation according to the invention is preferably in the range as defined above to ensure that the formulation is a suitable suspending agent for shear-thinning formulations. This ratio can if needed be adapted by centrifugation.

[0083] The formulation including the crosslinked polysaccharide particles of the invention can be used for home and personal care applications, agricultural applications, coatings, metal treatment, and products for the oil field market. Preferably, the formulation is used in home and person care applications, for example as bath and showering formulation, cream, lotion or hair care composition, or in agricultural applications, preferably for suspending objects, like beads or air bubbles.

[0084] By using the formulation of the invention, it is possible to provide an endproduct formulation wherein an object is stably suspended, i.e., the object remains in the continuous phase of the formulation. This formed suspension is stable at least for 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 formed suspension is stable for at least 30 months.

[0085] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence. The present invention is further illustrated by the following examples. It should be understood that the following examples are for illustration purposes only and are not used to limit the present invention thereto.

[0086] Example 1: Synthesis of a crosslinked carboxymethyl guar (CMG) microgel

[0087] In a mortar were introduced 20 g of CMG (Carboxymethyl guar).

[0088] 18.1 g of distilled water was added and then mixed with the powder with a pestle to obtain a swollen guar powder.

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

[0090] An amount m of N,N" - / v.s-methylene acrylamide (MBA) was added to the swollen powder. The amount m of MBA depends on the degree of crosslinking that is targeted.

[0091] The mixture was transferred from the mortar to a 250 mL round bottom flask with an integrated counter-blade then heated at 70°C for 6 hours. At the end of reaction, the solid was transferred to a beaker and a solution composed of isopropanol and water (isopropanol / water=3 / l; v,v) (200 mL) was added. The pH of the mixture was adjusted to pH~6-7 using acetic acid. The solid was washed by a solution composed of isopropanol and water (isopropanol / water=3 / l; v,v) (200 mL X 3 times) then dried in an oven at 50°C under atmospheric pressure. The formation of crosslinked particles with a particle size between 0.1 and 150 pm 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 corresponds to the free polymer.

[0093] Example 2: Synthesis of a crosslinked hydroxypropyl guar (HPG) microgel

[0094] In a mortar were introduced 20 g of HPG (Hydroxypropyl guar).

[0095] 18.1 g of distilled water was added and then mixed with the powder with a pestle to obtain a swollen guar powder.

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

[0097] An amount m of N,N" - / v.s-methylene acrylamide (MBA) was added to the swollen powder. The amount m of MBA depends on the degree of crosslinking that is targeted. The mixture was transferred from the mortar to a 250 mL round bottom flask with an integrated counter-blade then heated at 70°C for 6 hours. At the end of reaction, the solid was transferred to a beaker and a solution composed of isopropanol and water (isopropanol / water=3 / l; v,v) (200 mL) was added. The pH of the mixture was adjusted to pH~6-7 using acetic acid. The solid was washed by a solution composed of isopropanol and water (isopropanol / water=3 / l; v,v) (200 mL X 3 times) then dried in an oven at 50°C under atmospheric pressure. The formation of crosslinked particles with a particle size between 0.1 and 150 pm was confirmed using Bright Field microscopy and dynamic light scattering (DLS).

[0098] 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 corresponds to the free polymer.

[0099] Example 3: Synthesis of a crosslinked hydroxypropyltrimonium chloride guar (Cationic guar) microgel

[0100] In a mortar were introduced 20 g of hydroxypropyltrimonium chloride guar (Cationic guar).

[0101] 18.1 g of distilled water was added and then mixed with the powder with a pestle to obtain a swollen guar powder.

[0102] 1.78 g of NaOH aqueous solution (50%wt in water) was added to the swollen guar powder and mixed with a pestle.

[0103] An amount m of N,N" - / v.s-methylene acrylamide (MBA) was added to the swollen powder. The amount m of MBA depends on the degree of crosslinking that is targeted.

[0104] The mixture was transferred from the mortar to a 250 mL round bottom flask with an integrated counter-blade then heated at 70°C for 6 hours. At the end of reaction, the solid was transferred to a beaker and a solution composed of isopropanol and water (isopropanol / water=3 / l; v,v) (200 mL) was added. The pH of the mixture was adjusted to pH~6-7 using acetic acid. The solid was washed by a solution composed of isopropanol and water (isopropanol / water=3 / l; v,v) (200 mL X 3 times) then dried in an oven at 50°C under atmospheric pressure. The formation of crosslinked particles with a particle size between 0.1 and 150 pm was confirmed using Bright Field microscopy and dynamic light scattering (DLS).

[0105] 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 corresponds to the free polymer. Example 4: Synthesis of a crosslinked anionic Guar-AMPS (Guar-AMPS) microgel

[0106] In a mortar were introduced 20 g of anionic Guar-AMPS (Guar-AMPS).

[0107] 18.1 g of distilled water was added and then mixed with the powder with a pestle to obtain a swollen guar powder.

[0108] 1.78 g of NaOH aqueous solution (50%wt in water) was added to the swollen guar powder and mixed with a pestle.

[0109] An amount m of N,N" - / v.s-methylene acrylamide (MBA) was added to the swollen powder. The amount m of MBA depends on the degree of crosslinking that is targeted.

[0110] The mixture was transferred from the mortar to a 250 mL round bottom flask with an integrated counter-blade then heated at 70°C for 6 hours. At the end of reaction, the solid was transferred to a beaker and a solution composed of isopropanol and water (isopropanol / water=3 / l; v,v) (200 mL) was added. The pH of the mixture was adjusted to pH~6-7 using acetic acid. The solid was washed by a solution composed of isopropanol and water (isopropanol / water=3 / l; v,v) (200 mL X 3 times) then dried in an oven at 50°C under atmospheric pressure. The formation of crosslinked particles with a particle size between 0.1 and 150 pm was confirmed using Bright Field microscopy and dynamic light scattering (DLS).

[0111] 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 corresponds to the free polymer.

[0112] 1stTest: Swelling Capability

[0113] This test was used as a screening technique to find the optimal parameters leading to the most efficient synthesized product. Indeed, the higher the degree of swelling, the better the chances of the microgel particles to be efficient suspending agents.

[0114] Therefore, CMG microgel particles obtained as described above were introduced at 2 wt.-% in water and the obtained suspensions were adjusted to a pH of ~6.5 using acetic acid. The suspensions were left on the bench for 12 hours to allow the microgel particles to swell in water to their maximum. When fully swollen in such a dilute solution, microgel particles could sediment to the bottom of the glass bottle. The degree of swelling (expansion) was calculated by measuring the height occupied by the microgel particles, over the total height of the suspension. In Tables 1 and 2, the swelling behaviours of different suspensions are summarized.

[0115]

[0116] Table 1

[0117]

[0118] Table 2

[0119] 2ndTest: Methodology to measure the ratio of Free Chains to Microgel Particles

[0120] 1 wt.-% suspensions of crosslinked guar in water was prepared by dissolving 0.2 g of crosslinked guar in 19.8 g water. Then the suspension was installed in a centrifugal tube. The suspension was centrifuged at 14,500 rpm for 1 hour. It was observed that the supernatant becomes clear after the suspension was centrifuged. It was considered that the supernatant contains polymer free chains and the sediment part contains crosslinked guar particles. 1 g of the supernatant and 1 g of the sediment part were put on known weight of glass slides. The glass slides were heated to 200°C and the remaining solids were weighted. The percentage of polymer free chains and crosslinked guar particles were calculated from the remaining solids of the supernatant and the sediment parts. The results are shown in Tables 1 and 2 above.

[0121] 3rdTest: Assessment of Suspending properties

[0122] 2 and 4 wt.-% suspensions of microgel particles in water were prepared, and then the pH was adjusted to 6.5 using acetic acid. 1-mm diameter beads (glass bead density-2.2, silica bead density-1.7, acrylic bead density-1.05) were added into the suspensions. The level of beads was visually monitored to see if the beads have any sedimentation. It was noticed that all beads remained suspended for at least 8 weeks at room temperature.

[0123] 4thtest: Biodegradability

[0124] A crosslinked guar sample obtained via the synthesis described in example 1 (DS 0.001) was tested for biodegradability using the OECD 3O1F standard test, and 60% of the sample appeared to biodegrade in less than 28 days, meaning the sample is readily biodegradable. This proves that crosslinked CMG-MBA guars with a DS below 0.001 are readily biodegradable as well.

Claims

CLAIMS1. Crosslinked polysaccharide particles having a particle size between 0.1 and 150 pm, a degree of crosslinking from 0.00001 to 0.001 and which are biodegradable according to the OECD 301F standard.

2. Crosslinked polysaccharide particles of claim 1, wherein the polysaccharide is a galactomannan, preferably guar.

3. Crosslinked polysaccharide particles according to claim 1 or 2, wherein the polysaccharide is a derivatized polysaccharide having nonionic, anionic, cationic, hydrophobic substituent groups, or a combination thereof, more preferably a carboxymethyl modified polysaccharide, a 2-acrylamido-2-methylpropane sulfonic acid (AMPS) modified polysaccharide or a hydroxypropyltrimonium chloride modified polysaccharide.

4. Crosslinked polysaccharide particles according to any one of claims 1 to 3, comprising less than 50% in weight of polysaccharide free chains.

5. Crosslinked polysaccharide particles according to any one of claims 1 to 4, comprising from 0.00001 to 0.001 mole of bis-acrylamide per mole of polysaccharide.

6. A method for obtaining the crosslinked polysaccharide particles as defined in any one of claims 1 to 5, wherein a polysaccharide is contacted with water, a base and a bifunctional crosslinking agent in amounts leading to a degree of crosslinking from 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 claims 6 or 7, wherein the polysaccharide is a functionalized polysaccharide having a degree of derivatization of between 0.01 and 3.0.

9. The method according to any one of claims 6 to 8, wherein water is used in an amount of 0.1 to 2 eq. in mass for 1 eq. in mass of the polysaccharide.

10. The method according to any one of claims 6 to 9, wherein the base is used in an amount of from 0.1 to 1.0 mol / mol, notably from 0.1 to 0.5 mol / mol, and particularly from 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 crosslinking agent is used in amount of from 0.00002 to 0.003 mol / mol, and particularly from 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 Z -acrylamide, -epoxide, -anhydride, -carboxylic acid, -amino derivative, or mixtures thereof; preferably bis-acrylamide, more preferably methylene / v.s-acrylamide.

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

14. An aqueous formulation comprising the crosslinked polysaccharide particles as defined in any one of claims 1 to 5, preferably in an amount of from 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 free polysaccharide chains to crosslinked polysaccharide particles of less than 50% in weight.

15. Use of the aqueous formulation as defined in claim 14, for home and personal care applications, agricultural applications, coatings, metaltreatment, and products for the oil field market preferably for suspending objects, like beads or air bubbles.

16. Crosslinked polysaccharide particles having a particle size between 0.1 and 150 pm, which are biodegradable according to the OECD 301F standard and which comprise from 0.00001 to 0.001 mole of bisacrylamide per mole of crosslinked polysaccharide.

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