Crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid

Abstract

The present invention relates to a crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° degrees 2-theta (+ / - 0.1°).

Description

Title of the invention: Crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid. Field of the invention

[0001] The present invention relates to a crystalline form of 2-acrylamido-2-methylpropane sulfonic acid. More specifically, the present invention relates to a crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid. The invention also relates to the process for obtaining the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid, as well as the polymers obtained from this crystalline form. Prior state of the art

[0002] 2-Acrylamido-2-methylpropane sulfonic acid, also known as ATBS, is widely used as an additive in acrylic fibers, or as a raw material to obtain polymers used as a dispersant, thickener, friction reducer, flocculant or superabsorbent in various sectors such as the oil and gas industry, the mining industry, construction, textiles, water treatment (seawater desalination, mineral industry, etc.) or cosmetics.

[0003] The reaction carried out in the process for preparing 2-acrylamido-2-methylpropanesulfonic acid follows the reaction scheme below, in which acrylonitrile is present in excess so as to be both the solvent and a reactant of the reaction. The acrylonitrile is contacted with fuming sulfuric acid (oleum) and isobutylene.

[0004] [Chem.l]

[0005] A by-product that can be generated during this synthesis is acrylamide.

[0006] 2-Acrylamido-2-methylpropane sulfonic acid is not soluble in the acrylonitrile solvent. Therefore, the reaction product is in the form of a crystalline suspension in the reaction solvent.

[0007] By way of example, US patents 6,448,347 and CN 102351744 describe a process for manufacturing 2-acrylamido-2-methylpropane sulfonic acid in mode continuous. 2-Acrylamido-2-methylpropane sulfonic acid is subsequently separated from acrylonitrile, usually by filtration, and then dried.

[0008] Drying the 2-acrylamido-2-methylpropanesulfonic acid is necessary to reduce the amount of acrylonitrile and acrylamide remaining in the crystal. These two compounds are classified as carcinogenic, mutagenic, or toxic to reproduction (CMR). Therefore, efficient filtration is necessary to remove as much acrylonitrile as possible, followed by drying the 2-acrylamido-2-methylpropanesulfonic acid to obtain low levels of acrylonitrile and acrylamide.

[0009] It is known to those skilled in the art that the crystals of 2-acrylamido-2-methylpropane sulfonic acid have a crystallographic arrangement which produces a needle-shaped solid.

[0010] Needle-shaped crystals are known to those skilled in the art to have macroscopic properties which pose difficulties in the handling and transport of the solid (poor flowability of the solid, clumping, low resistance to shear stress), and in processing (poor filterability, difficulty in drying, attrition).

[0011] In the context of 2-acrylamido-2-methylpropane sulfonic acid, the additional problems that are encountered are generally the small particle size of the needle-like crystals, the density of the solid encountered, and the explosive nature of the fine dust.

[0012] These macroscopic properties are directly related to the morphology of the crystals and their specific surface area. In the case of a needle-shaped crystal, the specific surface area is high.

[0013] It is described in patents WO 2009 / 072480, JP 2008 / 307822 and JP 2003 / 137857 that the crystals of 2-acrylamido-2-methylpropane sulfonic acid obtained are in the form of needles.

[0014] Applicant's document WO2018172676 describes a new crystal form of 2-acrylamido-2-methylpropane sulfonic acid designated "hydrated crystalline form of 2-acrylamido-2-methylpropane sulfonic acid". This new crystalline form has different physicochemical properties than the needle form and also gives polymers comprising 2-acrylamido-2-methylpropane sulfonic acid in this new form improved properties.

[0015] However, regardless of the form of 2-acrylamido-2-methylpropane sulfonic acid, it remains a strong acid due to its sulfonic acid function, which exhibits a pronounced corrosive character towards metals. Due to the powdery nature of 2-acrylamido-2-methylpropane sulfonic acid powder, there is also a risk of chemical burns through skin, eye, or lung contact via inhalation. fine particles suspended in the air during powder handling operations.

[0016] When 2-acrylamido-2-methylpropane sulfonic acid is used in a polymerization process, the latter must be in aqueous form. The aqueous phase can be used as is, i.e., in its acidic form, or after neutralization with an alkali metal, an alkaline earth metal, or a molecule containing an unsubstituted or substituted amine function.

[0017] The shelf life of this aqueous solution is generally limited due to auto-polymerization phenomena caused by exposure to temperature, UV radiation, or pollutants such as iron or its oxidized forms. These oxidized forms can be generated by the corrosion of pipes or metal containers caused by the acidic form of 2-acrylamido-2-methylpropanesulfonic acid. Furthermore, the temperature rise generated by the auto-polymerization of 2-acrylamido-2-methylpropanesulfonic acid is significantly higher than the boiling point of water, which can lead to a pressure increase in the container and cause an explosion. Consequently, auto-polymerization phenomena present a significant risk to the safety of personnel and equipment.

[0018] The Applicant has discovered a new form of 2-acrylamido-2-methylpropanesulfonic acid designated "crystalline form of the potassium salt of 2-acrylamido-2-methylpropanesulfonic acid." This new form offers improved physicochemical and application properties (similar to the "hydrated crystalline form"), while eliminating the need for a neutralization step. The risks of burning, corrosion, and self-polymerization are also reduced. Finally, the crystalline form of the potassium salt has a longer shelf life than an aqueous solution of the potassium salt of 2-acrylamido-2-methylpropanesulfonic acid.

[0019] The use of the crystalline form of the potassium salt of 2-acrylamido-2-methylpropanesulfonic acid according to the invention reflects a principle of environmental awareness and a concern for the impact of industry and humankind on the planet. The new form of the product offers a safer product for handlers and reduces energy consumption due to the elimination of the neutralization step during the polymerization of 2-acrylamido-2-methylpropanesulfonic acid, and due to the powder form, which allows for the transport of more active material (100% for the powder versus a maximum of 50% for a solution). The improved shelf life of the product also reduces waste associated with increased product dosage resulting from the reduced performance of an aging product.Furthermore, the superior performance of polymers obtained from the crystalline form of the potassium salt of the invention allows for a reduction in the quantity of product required for the applications in which they are used. used to reduce overall water consumption and greenhouse gas emissions such as CO2. Description of the invention

[0020] The present invention relates to a specific form of 2-acrylamido-2-methylpropane sulfonic acid, hereinafter referred to as "crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid".

[0021] The present invention also relates to a method for manufacturing the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0022] The present invention also relates to the use of the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid for the manufacture of water-soluble, hydro-swelling or super-absorbent polymers.

[0023] The present invention also relates to a method for treating a suspension of solid particles in water, comprising contacting said suspension with at least one water-soluble polymer obtained at least in part from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° degrees 2-theta (+ / - 0.1°).

[0024] The present invention also relates to a method for flocculating a suspension of solid particles in water, comprising bringing said suspension into contact with at least one water-soluble polymer obtained at least in part from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° degrees 2-theta (+ / - 0.1°).

[0025] The present invention also relates to a method for enhanced recovery of hydrocarbons (oil and / or gas) comprising the following steps: a) Preparation of an injection fluid comprising at least one water-soluble polymer of 2-acrylamido-2-methylpropane sulfonic acid, with water or brine; the 2-acrylamido-2-methylpropane sulfonic acid being, prior to polymerization, at least partly in crystalline form of the potassium salt having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° degrees 2-theta (+ / - 0.1°); b) Injection of the injection fluid into an underground formation; c) Scanning of the underground formation using the injected fluid; d) Recovery of an aqueous and hydrocarbon mixture (mixture comprising water and hydrocarbons).

[0026] The present invention also relates to a fracturing fluid comprising at least one propping agent and at least one water-soluble polymer obtained at least in part from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° degrees 2-theta (+ / -0.1°).

[0027] The present invention also relates to a method for manufacturing a fracturing fluid with at least one water-soluble polymer obtained at least in part from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° degrees 2-theta (+ / - 0.1°).

[0028] The present invention also relates to a method of hydraulic fracturing of an unconventional underground reservoir using the fracturing fluid according to the invention.

[0029] The present invention also relates to a friction reduction method using a fracturing fluid in a hydraulic fracturing operation of an unconventional underground reservoir using the fracturing fluid according to the invention.

[0030] The present invention also relates to the use of a polymer obtained at least in part from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid in: drilling or cementing wells; conformance, diversion; open, closed or semi-closed circuit water treatment; fermentation must treatment; sludge treatment; construction; paper or cardboard manufacturing; battery manufacturing; wood processing; hydraulic composition processing (concrete, cement, mortar and aggregates); cosmetic product formulation; detergent formulation; textile manufacturing; geothermal energy; sanitary diaper manufacturing; or in agriculture.

[0031] Finally, the present invention also relates to the use of a polymer obtained at least in part from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid as a coagulant, binding agent, viscosity-reducing agent, thickening agent, absorbent, draining agent, charge-retaining agent, dehydrating agent, conditioning agent, stabilizing agent, agent fixative, film-forming agent, sizing agent, superplasticizing agent, clay inhibitor or dispersant. Description of the invention

[0032] The term "polymer" refers to a homopolymer or a copolymer. A copolymer is defined as a polymer obtained from at least two different monomers. It can therefore be a copolymer of at least two monomers chosen from among hydrophilic anionic monomers, hydrophilic cationic monomers, hydrophilic nonionic monomers, hydrophilic zwitterionic monomers, hydrophobic monomers and mixtures thereof.

[0033] By "hydrophilic monomer" is meant a monomer which has an octanol / water partition coefficient, Kow, of less than 1, in which the partition coefficient Kow is determined at 25°C in an octanol / water mixture having a volume ratio of 1 / 1, at a pH between 6 and 8.

[0034] By "hydrophobic monomer" is meant a monomer which has an octanol / water partition coefficient, Kow, greater than 1, in which the partition coefficient Kow is determined at 25°C in an octanol / water mixture having a volume ratio of 1 / 1, at a pH between 6 and 8.

[0035] The octanol / water partition coefficient, Kow, represents the ratio of the concentrations (g / L) of a monomer between the octanol phase and the aqueous phase. It is defined as follows:

[0036] [Math.l] _ [moïwmère]ocfanoj r * 1 [mûnomere je?au

[0037] By definition, a water-soluble polymer is a polymer which gives an aqueous solution when dissolved under stirring at 25°C and with a concentration of 10 gL 1 in water.

[0038] By "X and / or Y" means "X", or "Y", or "X and Y".

[0039] Also part of the invention are all possible combinations between the The disclosure includes various embodiments, whether preferred or given by way of example. Furthermore, when ranges of values ​​are specified, the bounds are included within those ranges. The disclosure also encompasses all combinations of the bounds within those ranges. For example, the value ranges "1-20", preferably "5-15", imply the disclosure of the ranges "1-5", "1-15", "5-20", and "15-20", as well as the values ​​1, 5, 15, and 20.

[0040] Crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid

[0041] The present invention relates to a crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° 2-theta degrees. The uncertainty of these peaks is generally on the order of + / - 0.1°.

[0042] X-ray crystallography, radiocrystallography, or X-ray diffractometry is an analytical technique that allows the study of the structure of crystalline matter at the atomic scale. It is based on the physical phenomenon of X-ray diffraction. A diffractometer with a copper source can be used.

[0043] A powder formed from a particular crystalline phase always exhibits diffraction peaks in the same directions. This diffraction pattern thus forms a true signature of the crystalline phase. It is therefore possible to determine the nature of each crystalline phase within a mixture or a pure product.

[0044] This signature is specific to each organic or inorganic compound, and takes the form of a list of position peaks at an angle of 20 (2-theta).

[0045] This technique is used to characterize matter, in particular the different crystalline forms that can exist for the same chemical molecule, also called polymorphs.

[0046] Another aspect of the invention relates to a crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a Fourier transform infrared spectrum comprising peaks at 3293cm1, 3075cm1, 3000cm*, 2979cm1, 1655cm1, 1625cm1, 1550cm1, 1405cm1, 1209cm1, 1190cm1, 1162cm1, 1048cm1, 979cm*, 824cm1, 803cm*, 756cm1, 633cm1, 523cm1. The uncertainty of these peaks is generally on the order of + / - 8cm'.

[0047] Infrared measurement is carried out by Fourier transform, for example by means of a Perkin Elmer Spectrum 100 type spectrometer equipped with a single reflection ATR Polarization accessory, the accuracy of which is 8cm'.

[0048] Fourier transform infrared spectroscopy is the analysis of vibrations emitted, absorbed, or scattered by molecules. This technique is sensitive to so-called short interactions (influence of the unit cell on the bonds). In most cases, the Fourier transform infrared spectra of different crystal systems differ significantly. The Fourier transform infrared spectrum therefore reflects the details of the crystal structure of a chemical compound.

[0049] Generally, and unless otherwise indicated, the X-ray diffraction pattern and the infrared spectrum are obtained at 20°C and at a pressure of 1 absolute atmosphere (101,325 Pa).

[0050] Another aspect of the invention relates to a crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a minimum ignition energy greater than 500 mJ, preferably greater than 1000 mJ.

[0051] The minimum ignition energy represents the minimum energy that must be supplied to a product (chemical compound) to cause it to ignite. The energy can be electrical or thermal. The minimum ignition energy is an essential factor for considering the risk of explosion during the handling of the product (transfer, storage, reaction, shaping, etc.).

[0052] The minimum ignition energy depends on the properties of the powder (composition) as well as its macromolecular structure (particle size, crystalline shape, specific surface area).

[0053] In the case of solids, this energy is the minimum energy of an electrical spark capable of igniting a dust cloud. The higher the value of the minimum ignition energy, the lower the risk posed by the solid during its use, handling, and storage.

[0054] The measurement of the minimum ignition energy is carried out according to the standard NF EN 13821.

[0055] Another aspect of the present invention relates to a crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid exhibiting two thermal phenomena with the differential scanning calorimetry technique, at 79.4°C and 207°C. The uncertainty in observing these phenomena is generally on the order of 10°C (+ / -10°C), advantageously 5°C or less.

[0056] Thermal phenomena are measured by differential scanning calorimetry (DSC). This technique exploits the measurement of the heat variation associated with the thermal denaturation of the compound when it is heated at a constant rate, for example with a heating ramp of 10°C / minute.

[0057] Process for manufacturing the crystalline form of potassium salt

[0058] The present invention also relates to the process for manufacturing the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid comprising at least the following successive steps: 1) mixing of 2-acrylamido-2-methylpropane sulfonic acid with an aqueous solution SAi and at least one potassium salt, advantageously for at least 1 minute, in order to form an aqueous solution or aqueous suspension SA2; 2) distillation at a pressure lower than atmospheric pressure of the aqueous solution or aqueous suspension SA2 in order to form a suspension Si; 3) solid / liquid separation of the Si suspension and isolation of the Si suspension crystals obtained at the end of step 2) in the form of a Cp composition The crystals obtained are in crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0059] By potassium salt(s) in step 1), means at least one inorganic salt(s), for example potassium hydroxide, potassium carbonate, potassium bicarbonate or mixtures thereof.

[0060] The temperature and mixing time in step 1) may vary depending, in particular, on the concentration of 2-acrylamido-2-methylpropane sulfonic acid. Those skilled in the art will know how to adjust the temperature variation and mixing time to optimize crystal formation.

[0061] The process for manufacturing the crystalline form of the potassium salt can be carried out on any form of 2-acrylamido-2-methylpropane sulfonic acid, such as the needle form or the hydrated form.

[0062] The manufacturing process can be carried out on any degree of purity of 2-acrylamido-2-methylpropane sulfonic acid.

[0063] Thus, the process can be carried out downstream of any type of manufacturing process for 2-acrylamido-2-methylpropane sulfonic acid. It can also be carried out on crystals of 2-acrylamido-2-methylpropane sulfonic acid already obtained.

[0064] Step 1) of the process for manufacturing the crystalline form of potassium salt:

[0065] 2-Acrylamido-2-methylpropane sulfonic acid is produced by a manufacturing process as described above (acrylonitrile, fuming sulfuric acid, and isobutylene). 2-Acrylamido-2-methylpropane sulfonic acid may be in the form of a fine powder or shaped in a controlled manner by a process such as compaction, granulation, or extrusion.

[0066] 2-Acrylamido-2-methylpropane sulfonic acid can be added to an aqueous solution S Ai before, after or in parallel with potassium salt, preferably the addition is done in parallel.

[0067] Advantageously, the concentration of the aqueous solution or aqueous suspension SA2 in potassium salt is between 1% by weight and saturation, preferably between 10% by weight and saturation, more preferably between 20% by weight and saturation, more preferably between 30% by weight and saturation, more preferably between 40% by weight and saturation, and even more preferably between 50% by weight and saturation, by weight relative to the weight of the aqueous solution or aqueous suspension SA2.

[0068] 2-Acrylamido-2-methylpropane sulfonic acid and potassium salt can be added all at once or in several stages. Preferably they are added in several stages.

[0069] When the addition is made in several stages, the 2-acrylamido-2-methylpropane sulfonic acid and the potassium salt are added in fractions.

[0070] When 2-acrylamido-2-methylpropane sulfonic acid and potassium salt are added in fractions, there is no limit to the number of fractions, advantageously there are at least two fractions, preferably at least three fractions.

[0071] There is no limitation as to the order of addition between 2-acrylamido-2-methylpropane sulfonic acid and the potassium salt. They can be added at the same time (i.e. in parallel), one after the other (2-acrylamido-2-methylpropane sulfonic acid first then the potassium salt, or vice versa), or alternately (a first fraction of 2-acrylamido-2-methylpropane sulfonic acid, then a first fraction of the potassium salt, followed by a second fraction of 2-acrylamido-2-methylpropane sulfonic acid then a second fraction of the potassium salt and so on), preferably they are added at the same time.

[0072] When adding one after the other or alternately, the start of the addition of the second compound (whether it be 2-acrylamido-2-methylpropane sulfonic acid or potassium salt) can start before the end of the addition of the first compound.

[0073] A first fraction Fl of 2-acrylamido-2-methylpropane sulfonic acid advantageously represents at least 1 mol% of the total 2-acrylamido-2-methylpropane sulfonic acid present in the aqueous solution or aqueous suspension SA2, preferably at least 5 mol%, more preferably at least 10 mol%, even more preferably at least 15 mol% and even more preferably at least 20 mol%.

[0074] A second fraction F2 of 2-acrylamido-2-methylpropane sulfonic acid advantageously represents at least 1 mol% of the total 2-acrylamido-2-methylpropane sulfonic acid present in the aqueous solution or aqueous suspension SA2, preferably at least 5 mol%, more preferably at least 10 mol%, even more preferably at least 15 mol% and even more preferably at least 20 mol%.

[0075] A third fraction F3 of 2-acrylamido-2-methylpropane sulfonic acid advantageously represents at least 1 mol% of the total 2-acrylamido-2-methylpropane sulfonic acid present in the aqueous solution or aqueous suspension SA2, preferably at least 5 mol%, more preferably at least 10 mol%, even more preferably at least 15 mol% and even more preferably at least 20 mol%.

[0076] In a particular mode, the process is carried out continuously; in this case, 2-acrylamido-2-methylpropane sulfonic acid and potassium salt are added continuously.

[0077] The amount of 2-acrylamido-2-methylpropane sulfonic acid in the aqueous solution or aqueous suspension SA2 is advantageously between 10 and 90% by weight relative to the total weight of the aqueous solution or aqueous suspension SA2, preferably between 20 and 85% by weight, more preferably between 30 and 80% by weight.

[0078] The mixing in step 1) is advantageously carried out at a temperature between 0 and 90°C, preferably between 5 and 60°C, more preferably between 10 and 40°C, in order to obtain the aqueous solution or aqueous suspension SA2.

[0079] In a particular mode, the aqueous solution or the SA2 suspension may comprise one or more organic solvents.

[0080] The amount of organic solvent can vary depending on the temperature, the amount of 2-acrylamido-2-methylpropanesulfonic acid, or the potassium salt. This amount is not limited as long as it does not prevent the formation of the crystalline form of the potassium salt of 2-acrylamido-2-methylpropanesulfonic acid. A person skilled in the art will be able to determine this limit, which remains a routine task. Generally, the aqueous solution or aqueous suspension SA2 contains more water (by volume) than organic solvent.

[0081] The organic solvent(s) are advantageously chosen from the following compounds: - organic acids, advantageously carboxylic acids comprising 1 to 8 carbons; - amides advantageously comprising from 1 to 8 carbon atoms; - alcohols advantageously comprising from 1 to 8 carbon atoms; - ketones advantageously comprising 3 to 8 carbon atoms; - ethers advantageously comprising from 2 to 8 carbon atoms; - esters advantageously comprising from 2 to 8 carbon atoms; - alkanes advantageously comprising 4 to 8 carbon atoms; - halogenated hydrocarbon compounds advantageously comprising from 2 to 8 carbon atoms; - nitriles advantageously comprising from 1 to 8 carbon atoms; or - their mixtures.

[0082] When an organic solvent is used in the context of the invention, the temperature can be adjusted so that the solvent + water mixture remains in liquid form.

[0083] These compounds can be linear or branched. They can be saturated or include unsaturations, an unsaturation corresponding to a double or triple bond (for example C=C or C=C).

[0084] Preferably, the organic solvent is chosen from acrylonitrile, isopropanol, acetic acid, or mixtures thereof. Preferably, the organic solvent is acrylonitrile.

[0085] The organic solvent is generally in liquid form at the temperature at which steps 2) and 3) are carried out. In addition, it is advantageously partially miscible in water, preferably completely miscible in water.

[0086] The organic solvent may, where appropriate, allow the solubilization of any impurities or by-products present with the 2-acrylamido-2-methylpropane sulfonic acid used to form the aqueous solution or aqueous suspension SA2. However, 2-acrylamido-2-methylpropane sulfonic acid is not necessarily soluble in the solvent.

[0087] In a preferred mode according to the invention, the aqueous solution or aqueous suspension SA2 does not contain any organic solvent.

[0088] The mixing time between the aqueous solution SAb and 2-acrylamido-2-methylpropane sulfonic acid is advantageously at least 1 minute, preferably between 1 minute and 600 minutes, more preferably between 5 minutes and 400 minutes, and even more preferably between 10 minutes and 240 minutes.

[0089] The mixing of the compounds in step 1) can be carried out by various technologies. By way of example and without limitation, we can mention reactors with agitators, loop reactors, static mixers, microreactors, plug flow reactors, agitated filter-dryer reactors, for example Nutsche, paddle mixers, twin-cone mixers, plowshare mixers, and disc mixers.

[0090] The pH of step 1) is advantageously controlled between 6 and 14, preferably between 8 and 14, more preferably between 10 and 14, even more preferably between 12 and 14, even more preferably between 13 and 14.

[0091] Step 2) of the process for manufacturing the crystalline form of potassium salt:

[0092] The distillation of the aqueous solution or aqueous suspension SA2 is carried out at a pressure lower than atmospheric pressure. It is generally carried out in a vacuum distillation device, which is typically an evaporator. It is therefore also referred to here as "vacuum distillation".

[0093] When the aqueous solution or aqueous suspension SA2 is distilled, typically by passing it through an evaporator, crystals of the potassium salt of acrylamido-2-methyl-2-propanesulfonic acid begin to form. There is then coexistence of the aqueous solution or aqueous suspension SA2 comprising acrylamido-2-methyl-2-propane sulfonic acid, at least one potassium salt, and crystalline solid particles of the potassium salt of acrylamido-2-methyl-2-propane sulfonic acid.

[0094] The distillation of the aqueous solution or aqueous suspension SA2 can be carried out using an evaporator. This can be a falling film evaporator, a rising film evaporator, a scraped thin-film evaporator, a short-path evaporator, a forced-circulation evaporator, a spiral-tube evaporator, or a flash-cooling evaporator. It can also be a continuously stirred reactor. Preferably, the distillation takes place in a scraped thin-film evaporator, a short-path evaporator, or a forced-circulation evaporator. Even more preferably, the distillation takes place in a scraped thin-film evaporator.

[0095] Generally, an evaporator is a device comprising an inlet for the solution to be treated (aqueous solution or aqueous suspension SA2), an outlet for removing the distilled solvent (water and any organic solvents), and an outlet for removing the Sp suspension.

[0096] The residence time of the aqueous solution or aqueous suspension SA2 in the distillation device (advantageously under vacuum), which is advantageously an evaporator, in other words, the distillation time at a pressure below atmospheric pressure, is advantageously between 1 second and 600 seconds, preferably between 3 seconds and 300 seconds, and more preferably between 30 seconds and 100 seconds. The residence time corresponds to the time required to carry out step 2), that is, the time required to prepare the suspension Si by distilling the aqueous solution or aqueous suspension SA2. In other words, in the case of an evaporator, it is the residence time of the acrylamido-2-methyl-2-propanesulfonic acid (and / or its crystalline form of potassium salt) between the inlet and outlet of the device.This residence time depends on the amount of water (and any organic solvents), 2-acrylamido-2-propanesulfonic acid, and potassium salt present in the aqueous solution or aqueous suspension SA2. A person skilled in the art will be able to adjust this residence time in order to obtain 2-acrylamido-2-propanesulfonic acid in crystalline form of potassium salt according to the quantity of the constituents of the aqueous solution or aqueous suspension SA2.

[0097] Distillation can be carried out in a vertical or horizontal evaporator. Preferably, it is carried out in a vertical evaporator.

[0098] The aqueous solution or aqueous suspension SA2 can flow in co-current or counter-current with respect to the vapors generated by evaporation. Preferably, It flows in the opposite direction to the vapors in the distillation device. In other words, the aqueous solution or aqueous suspension SA2 is preferentially introduced into the distillation device, advantageously an evaporator, in a co-current or counter-current manner with respect to the distilled solvent.

[0099] The aqueous solution or aqueous suspension SA2 can circulate in one or more evaporators in series before obtaining the Sp suspension. Preferably, it circulates in a single evaporator.

[0100] The pressure during distillation is advantageously between 1 and less than 1000 mbar absolute (1 mbar = 100 Pa). It is preferably less than 900 mbar absolute, more preferably less than 800 mbar absolute, more preferably less than 700 mbar absolute, more preferably less than 600 mbar absolute, more preferably less than 500 mbar absolute, more preferably less than 400 mbar absolute, more preferably less than 300 mbar absolute, more preferably less than 200 mbar absolute, more preferably less than 100 mbar absolute, and even more preferably less than 50 mbar absolute, and advantageously greater than 1 mbar absolute. The absolute pressure corresponds to the pressure relative to zero pressure (vacuum).

[0101] In a particular mode, step 2) includes an optional step 2') to facilitate solvent evaporation. Step 2') then consists of increasing the temperature of the aqueous solution or aqueous suspension SA2; in other words, the distillation according to step 2') is carried out at high temperature.

[0102] Heating during distillation can be achieved using various technologies. By way of example, and without limitation, we can mention heating with steam, hot water, electricity, vapor compression, or a heat pump. Thus, the distillation apparatus can be of the double-walled type, with a hot heat transfer fluid circulating between the two walls.

[0103] The aqueous solution or aqueous suspension SA2 is advantageously heated to a temperature between more than 5°C and 95°C, preferably between more than 10°C and 60°C, more preferably between more than 20°C and 40°C.

[0104] When the aqueous solution or aqueous suspension SA2 is heated, the temperature is advantageously higher than the temperature of step 1).

[0105] The temperature rise of the SA2 solution is advantageously carried out at a rate of between 0.1 and 10°C / hour, preferably between 0.2 and 9°C / hour, more preferably between 0.3 and 8°C / hour, and even more preferably between 0.5 and 5°C / hour.

[0106] The temperature rise may not be constant throughout the process. For example, the aqueous solution or aqueous suspension SA2 may be heated by 5°C per hour for the first three hours, and then be heated at a rate of 10°C per hour until the final temperature is reached.

[0107] According to another particular embodiment of the invention, step 2) may include an optional step 2"), following or instead of step 2"), which increases the productivity and profitability of the process of the invention by accelerating the crystallization of acrylamido-2-methyl-2-propanesulfonic acid in the crystalline form of potassium salt. Step 2") then consists of lowering the temperature of the aqueous solution or aqueous suspension SA2.

[0108] The aqueous solution or aqueous suspension SA2 is advantageously cooled to a temperature between 5 and less than 95°C, preferably between 10 and less than 60°C, more preferably between 20 and less than 40°C.

[0109] When the aqueous solution or aqueous suspension SA2 is cooled, the temperature is advantageously lower than the temperature of steps 1), 2) and optionally 2').

[0110] The temperature decrease of the aqueous solution or aqueous suspension SA2 is advantageously carried out at a rate of between 0.1 and 10°C / hour, preferably between 0.2 and 9°C / hour, more preferably between 0.3 and 8°C / hour, and even more preferably between 0.5 and 5°C / hour.

[0111] The temperature decrease may not be constant throughout the process. For example, the aqueous solution or aqueous suspension SA2 may be cooled by 5°C per hour for the first three hours, and then cooled at a rate of 10°C per hour until the final temperature is reached.

[0112] During the cooling of the aqueous solution or aqueous suspension SA2, crystals of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid are formed and a suspension Si is obtained.

[0113] In a particular mode, previously obtained potassium salt crystals of 2-acrylamido-2-methylpropanesulfonic acid can be added during this step to modify the formation of the Sp II suspension. This involves crystallization seeding, which allows for better control of the crystallization temperature, crystal particle size, particle size distribution, purity of the final product, and, potentially, yield. The potassium salt crystals of 2-acrylamido-2-methylpropanesulfonic acid thus added advantageously have a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° degrees 2-theta (+ / - 0.1°).

[0114] According to a particular embodiment of the invention, the solvent distilled in step 2) can be partially or totally recycled to form the aqueous solution SAi of step 1). In other words, the distilled solvent is advantageously recycled at least partially into the aqueous solution SAb

[0115] According to another particular embodiment of the invention, the distilled solvent can be recycled partially or totally, generally to wash the potassium salt crystals of acrylamido-2-methyl-2-propane sulfonic acid obtained after liquid / solid separation step 3), in an optional step 4), with or without a pretreatment step.

[0116] The suspension Si obtained advantageously comprises between 30 and 80% by weight of 2-acrylamido-2-methylpropane sulfonic acid in crystalline form of potassium salt, relative to the total weight of the suspension Si, preferably between 50 and 60% by weight.

[0117] During step 2), the pH is advantageously greater than 10, preferably greater than 11, more preferably greater than 12, even more preferably the pH is between 13 and 14.

[0118] Step 3 of the process for manufacturing the crystalline form of potassium salt

[0119] The potassium salt crystals of 2-acrylamido-2-methylpropane sulfonic acid contained in the Si suspension obtained at the end of step 2) are isolated by a liquid / solid separation step and are in the form of a composition Cp

[0120] The liquid / solid separation step can be carried out using various technologies. By way of example, and without limitation, we can mention the use of a centrifuge, a decanter, a filter press, a stirred smoother filter, a belt filter, a disc filter, or a rotary drum filter. Preferably, the liquid / solid separation is carried out using a centrifuge. The liquid / solid separation can also be carried out by gravity settling.

[0121] Step 3) is advantageously carried out at a temperature between -20 and 40°C, preferably between -5 and 30°C.

[0122] Preferably after step 3) of liquid / solid separation, the potassium salt crystals of 2-acrylamido-2-methylpropane sulfonic acid are not dried.

[0123] The isolated composition Ci has a potassium salt crystal content of 2-acrylamido-2-methylpropanesulfonic acid advantageously between 40 and 99%, preferably between 60 and 99% by weight, more preferably between 60 and 98%, by weight relative to the weight of composition Ci. The remainder of composition Ci may be water and / or solubilized potassium salt of 2-acrylamido-2-methylpropanesulfonic acid, and / or potassium salt introduced in step 1).

[0124] At the end of this step 3), the crystals are characterized as being crystals of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0125] In a particular mode, the liquid phase obtained as a result of the liquid / solid separation is used totally or partially in the aqueous solution S Ai of step 1).

[0126] During step 4) the pH is advantageously controlled between 6 and 14, preferably between 8 and 14, more preferably between 10 and 14, even more preferably between 12 and 14, even more preferably between 13 and 14.

[0127] Step 4) of the process for manufacturing the crystalline form of potassium salt:

[0128] In an optional step 4), the composition Ci containing the crystals obtained at the end of step 3) is washed using a washing solution.

[0129] The washing solution may be water, an aqueous solution of potassium salt (saturated or unsaturated), or a solution (saturated or unsaturated) of potassium salt of 2-acrylamido-2-methylpropane sulfonic acid (advantageously in the crystalline form of potassium salt of 2-acrylamido-2-methylpropane sulfonic acid), preferably it is a saturated solution of a potassium salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0130] Examples of potassium salt solutions include solutions of potassium hydroxide, potassium carbonate, potassium bicarbonate, or mixtures thereof.

[0131] The washing solution may comprise one or more organic solvents.

[0132] The amount of organic solvent may vary depending on the temperature, the amount of potassium salt of 2-acrylamido-2-methylpropane sulfonic acid or the amount of potassium salt.

[0133] Advantageously, the washing solution does not include any organic solvent.

[0134] As already indicated in relation to step 1), the organic solvent is advantageously chosen from organic acids, amides, alcohols, ketones, ethers, esters, alkanes, halogenated hydrocarbon compounds, nitriles, or mixtures thereof. Preferably, the organic solvent is chosen from acrylonitrile, isopropanol, acetic acid, or mixtures thereof. More preferably, the organic solvent is acrylonitrile.

[0135] In a particular mode, the washing of the composition Ci obtained at the end of step 3) is carried out by spraying the washing solution onto said composition Ci.

[0136] In a particular mode, the washing of the composition Ci obtained at the end of step 3) is carried out by suspending the composition Ci in the washing solution.

[0137] The weight ratio between the aqueous washing solution and the composition Ci obtained at the end of step 3) is advantageously between 0.05:1 and 10:1 and more preferably between 0.1:1 and 5:1.

[0138] This washing step is advantageously carried out at a temperature between -5 and 40°C, preferably between 0 and 30°C. A person skilled in the art will know how to adjust the temperature so as not to solubilize the crystals of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0139] The potassium salt crystals of 2-acrylamido-2-methylpropane sulfonic acid obtained at the end of this optional step 4) can be isolated from the washing solution by a liquid / solid separation step, in the form of a C2 composition.

[0140] The liquid / solid separation step can be carried out using various technologies. By way of example, and without limitation, we can mention the use of a vertical or horizontal centrifuge, a decanter, a filter press, a belt filter, a disc filter, a pusher filter, or a rotary drum filter. Liquid / solid separation can also be carried out by gravity settling.

[0141] In a particular mode, the recovered washing solution can be used, totally or partially, again in step 4), with or without a prior treatment step.

[0142] In a particular mode, the recovered washing solution can be used, totally or partially, in the aqueous solution SAi in step 1), with or without a prior treatment step.

[0143] The pH of the washing solution in step 5 is advantageously controlled between 6 and 14, preferably between 8 and 14.

[0144] Step 5) of the process for manufacturing the crystalline form of potassium salt:

[0145] In an optional step 5), the composition Ci obtained at the end of step 3) or the composition C2 obtained at the end of step 4) is dried.

[0146] The drying stage can be carried out by various technologies. By way of example and without limitation, we can cite the use of all drying technologies by convection, conduction or radiation (fluidized bed dryer, flow bed dryer, conveyor belt drying, microwave drying, heated agitated smoothing filter drying, high frequency radiation drying, infrared, spray drying).

[0147] The drying operation can be carried out at atmospheric pressure or under vacuum.

[0148] The drying step can be carried out discontinuously (batch) or continuously.

[0149] Other steps in the process of manufacturing the crystalline form of potassium salt:

[0150] During the manufacturing process, i.e. during steps 1) to 5), and regardless of the step, it is possible to introduce at least one polymerization inhibitor so as to prevent the possible polymerization of 2-acrylamido-2- methylpropane sulfonic acid or its salt. This inhibitor may be chosen without limitation from hydroquinone, paramethoxyphenol, phenothiazine, 2,2,6,6-tetramethyl(piperidin-l-yl)oxyl, 4-hydroxy-2,2,6,6-tetramethyl(piperidin-l-yl)oxyl, phenylenediamine derivatives, or mixtures thereof.

[0151] Preferably, the inhibitor is paramethoxyphenol or 4-hydroxy-2,2,6,6- tetramethyl(piperidin-1-yl)oxyl.

[0152] The amount of inhibitor introduced relative to the amount of 2-acrylamido-2-methylpropane sulfonic acid introduced in step 1) is advantageously between 0.001% and 5% by weight, more preferably between 0.01% and 1% by weight.

[0153] The inhibitor can be introduced during any one or more steps of the process. Preferably, it is introduced in additional quantity during step 1). More preferably, the inhibitor is part of the aqueous solution SAi introduced in step 1).

[0154] The manufacturing process (steps 1) to 5)) can be carried out continuously or discontinuously (in batch). Polymer

[0155] The present invention also relates to the use of the new crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid for the manufacture of polymers.

[0156] The present invention therefore also relates to a polymer obtained at least from 2-acrylamido-2-methylpropane sulfonic acid, at least part of which is in crystalline form of the potassium salt having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° degrees 2-theta (+ / - 0.1°).

[0157] The polymer is obtained at least in part from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid, and advantageously from at least one other monomer selected from: hydrophilic nonionic monomers, hydrophilic anionic monomers (distinct from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid), hydrophilic cationic monomers, hydrophilic zwitterionic monomers and hydrophobic monomers.

[0158] It can therefore be a polymer of several distinct monomers or a homopolymer.

[0159] The 2-acrylamido-2-methylpropane sulfonic acid used to obtain the polymer is advantageously at least 10 mol% in the crystalline form of the potassium salt, preferably at least 30 mol%, more preferably at least 50 mol%, even more preferably at least 70 mol%. Even more preferably, 100 mol% of 2-acrylamido-2-methylpropane sulfonic acid is in the crystalline form of the potassium salt.

[0160] The polymer advantageously comprises between 1 and 100 mol% of 2-acrylamido-2-methylpropanesulfonic acid, preferably between 2 and 60 mol%, more preferably between 3 and 25 mol%, with advantageously at least 10 mol% in the crystalline form of the potassium salt, preferably at least 30 mol%, more preferably at least 50 mol%, and even more preferably at least 70 mol%. Even more preferably, 100 mol% of the 2-acrylamido-2-methylpropanesulfonic acid used is in the crystalline form of the potassium salt.

[0161] In a particular mode, the polymer advantageously comprises at least 10 mol% of 2-acrylamido-2-methylpropane sulfonic acid, preferably at least 20 mol%, more preferably at least 30 mol%, more preferably at least 40 mol%, more preferably at least 50 mol%, more preferably at least 60 mol%, more preferably at least 70 mol%, more preferably at least 80 mol%, more preferably at least 90 mol%, with advantageously at least 10 mol% in the crystalline form of the potassium salt, preferably at least 30 mol%, more preferably at least 50 mol%, even more preferably at least 70 mol% and even more preferably 100% of the 2-acrylamido-2-methylpropane sulfonic acid used is in the crystalline form of the potassium salt.

[0162] In a particular mode, the polymer is a homopolymer of 2-acrylamido-2-methylpropane sulfonic acid, advantageously with at least 10 mol% in the crystalline form of the potassium salt, preferably at least 30 mol%, more preferably at least 50 mol%, even more preferably at least 70 mol%, and even more preferably 100% of the 2-acrylamido-2-methylpropane sulfonic acid used is in the crystalline form of the potassium salt.

[0163] In a particular mode, the polymer is a homopolymer of the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0164] In a particular embodiment, the polymer is a polymer obtained from 2-acrylamido-2-methylpropane sulfonic acid (of which advantageously at least 10 mol% is in the crystalline form of the potassium salt) and at least one non-ionic monomer. Polymer composition

[0165] The polymer is obtained from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid, and advantageously from at least one other monomer which may be selected from hydrophilic nonionic monomers and / or hydrophilic anionic monomers and / or hydrophilic cationic monomers and / or hydrophilic zwitterionic monomers and / or hydrophobic monomers and their mixtures. It can be a polymer of several distinct monomers or a homopolymer.

[0166] Advantageously, the hydrophilic nonionic monomer(s) that may be used in the context of the invention are chosen, in particular, from the group comprising water-soluble vinyl monomers, such as acrylamide, methacrylamide, N-alkylacrylamides, N-alkylmethacrylamides, N,N-dialkyl acrylamides (for example, N,N-dimethylacrylamide or N,N-diethylacrylamide), N,N-dialkylmethacrylamides, alkoxylated esters of acrylic acid, alkoxylated esters of methacrylic acid, N-vinylpyrrolidone, N-methylolacrylamide, N-vinylformamide (NVF), N-vinyl acetamide, N-vinyl imidazole, N-vinyl succinimide, and acryloyl morpholine. (ACMO), acryloyl chloride, glycidyl methacrylate, glyceryl methacrylate, diacetone acrylamide, hydroxyalkyl (meth)acrylate, aminoalkyl (meth)acrylate, thioalkyl (meth)acrylate, hydroxyalkyl acrylates, hydroxyalkyl methacrylates, and mixtures thereof.Among these non-ionic monomers, the alkyl groups are advantageously Cr C5, more advantageously C1-C3. They are preferentially linear alkyls. Preferably, the hydrophilic non-ionic monomer is acrylamide.

[0167] The polymer advantageously comprises between 0 and 99 mol% of hydrophilic non-ionic monomer(s), preferably between 40 and 98 mol%, more preferably between 75 and 97 mol%.

[0168] Advantageously, the hydrophilic anionic monomer(s), other than 2-acrylamido-2-methylpropane sulfonic acid in crystalline form as a potassium salt, that may be used in the context of the invention may be selected from a wide range. These monomers may have vinyl functional groups (advantageously acrylic, maleic, fumaric, malonic, itaconic, or allylic), and contain a carboxylate, phosphonate, phosphate, sulfate, sulfonate, or other anionically charged group.Examples of suitable monomers include acrylic acid; methacrylic acid; dimethylacrylic acid; itaconic acid; crotonic acid; maleic acid; fumaric acid; acrylamidoundecanoic acid; 3-acrylamido-3-methylbutanoic acid; maleic anhydride; strong acid monomers exhibiting, for example, a sulfonic acid or phosphonic acid function such as vinylsulfonic acid, vinylphosphonic acid, allylsulfonic acid, methallylsulfonic acid, 2-methylidenepropane-1,3-disulfonic acid, 2-sulfoethyl methacrylate, sulfopropyl methacrylate, sulfopropylacrylate, allylphosphonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid (ATBS), 2-acrylamido-2-methylpropane disulfonic acid; water-soluble salts of these monomers such as their alkali metal salts (distinct from the crystalline form of the . potassium salt of 2-acrylamido-2-methylpropane sulfonic acid), alkaline earth metals, or ammonium; and mixtures thereof. Preferably, the hydrophilic anionic monomer(s) is / are acrylic acid and / or its salts.

[0169] The polymer advantageously comprises between 0 and 99 mol% of hydrophilic anionic monomer(s) (distinct from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropanesulfonic acid), preferably between 5 and 70 mol%, more preferably between 10 and 50 mol%. From 5 mol% onwards, these percentages also include the monomer in the crystalline form of the potassium salt of 2-acrylamido-2-methylpropanesulfonic acid according to the invention.

[0170] In a particular mode, the hydrophilic anionic monomer(s), other than 2-acrylamido-2-methylpropane sulfonic acid in crystalline form of the potassium salt, can be salified.

[0171] By "salified," it is understood that at least one acid function of the anionic monomer is replaced by a salt that neutralizes the negative charge of the acid function. In other words, the unneutralized (unsalified) form corresponds to the acidic form of the monomer, for example -C(=O)-OH in the case of the carboxylic acid function, while the neutralized (salified) form of the monomer corresponds to the form -C(=O)-O X+, where X+ is a positively charged counterion (for example, a metal salt or an ammonium compound). The neutralization of the acid functions of the polymer may be partial or total.

[0172] The salt form advantageously corresponds to the salts of alkali metals (Li, Na, K...), alkaline earth metals (Ca, Mg...) or ammonium (for example the ammonium ion or a tertiary ammonium). The preferred salt is the potassium salt.

[0173] Salification can take place before, during or after polymerization.

[0174] In a particular embodiment, the polymer advantageously comprises between 1 and 100 mol% of hydrophilic anionic monomer(s) in salt form, preferably between 50 and 100 mol%. These percentages include the crystalline form monomer of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid according to the invention.

[0175] Advantageously, the hydrophilic cationic monomer(s) that can be used in the context of the invention are chosen from among monomers derived from vinyl-type motifs (advantageously acrylamide, acrylic, allyl, or maleic), these monomers having a quaternary phosphonium or ammonium function. Examples include, in particular and without limitation, quaternized dimethylaminoethyl acrylate (ADAME), quaternized dimethylaminoethyl methacrylate (MADAME), and dimethyldiallylammonium chloride (DADMAC). acrylamido propyltrimethyl ammonium chloride (APTAC), and methacrylamido propyltrimethyl ammonium chloride (MAPTAC).

[0176] A person skilled in the art will know how to prepare the quaternized monomers, for example using an alkyl halide of the type R*-X, where R* is an alkyl group and X is a halogen (in particular methyl chloride). The quaternizing agent may be selected from alkyl chlorides, dialkyl sulfates, or alkyl halides. Preferably, the quaternizing agent is selected from methyl chloride and diethyl sulfate.

[0177] In addition, the present invention also covers DADMAC, APTAC, and MAPTAC type monomers in which the halide counterion is fluoride, bromide, or iodide instead of chloride.

[0178] In a preferred mode, the hydrophilic cationic monomer is selected from diallyldialkyl ammonium salts such as diallyl dimethyl ammonium chloride (DADMAC); acidified or quaternized dialkyl-aminoalkylacrylamides; acidified or quaternized dialkyl-aminoalkylmethacrylamides, such as methacrylamido-propyl trimethyl ammonium chloride (MAPTAC), acrylamido-propyl trimethyl ammonium chloride (APTAC), and mixtures thereof. Advantageously, the alkyl groups are in the C1-C3 configuration.

[0179] The polymer advantageously comprises between 0 and 20 mol% of hydrophilic cationic monomer(s), preferably between 0 and 6 mol%.

[0180] Advantageously, the hydrophilic zwitterionic monomer(s) may be a derivative of a vinyl-type motif (advantageously acrylamide, acrylic, allyl or maleic), this monomer having a quaternary amine or ammonium function and an acid function of the carboxylic (or carboxylate), sulfonic (or sulfonate) or phosphoric (or phosphate) type. Examples include, but are not limited to, derivatives of dimethylaminoethyl acrylate, such as 2-((2-(acryloyloxy)ethyl) dimethylammonio) ethane-1-sulfonate, 3-((2-(acryloyloxy)ethyl) dimethylammonio) propane-1-sulfonate, 4-((2-(acryloyloxy)ethyl) dimethylammonio) butane-1-sulfonate, [2-(acryloyloxy)ethyl] (dimethylammonio) acetate, and derivatives of dimethylaminoethyl methacrylate such as 2-((2-(methacryloyloxy) ethyl) dimethylammonio) ethane-1-sulfonate and 3-((2-(methacryloyloxy) ethyl) dimethylammonio) propane-1-sulfonate.4-((2-(methacryloyloxy)ethyl)dimethylammonio)butane-1-sulfonate, [2-(methacryloyloxy)ethyl](dimethylammonio)acetate, dimethylamino propylacrylamide derivatives such as 2-((3-acrylamidopropyl)dimethylammonio)ethane-1-sulfonate, 3-((3-acrylamidopropyl)dimethylammonio)propane-1-sulfonate, 4-((3-acrylamidopropyl)dimethylammonio)butane-1-sulfonate, [3-(acryloyloxy)propyl](dimethylammonio)acetate, dimethylamino propyl methylacrylamide derivatives, such as 2-((3-methacrylamidopropyl) dimethylammonio) ethane-l-sulfonate, 3-((3-methacrylamidopropyl) dimethylammonio) propane-1-sulfonate, 4-((3-methacrylamidopropyl) dimethylammonio) butane-1-sulfonate and [3-(methacryloyloxy)propyl] (dimethylammonio) acetate and mixtures thereof.

[0181] The polymer advantageously comprises 0 and 20 mol% of hydrophilic zwitterionic monomer(s), more preferably between 0 and 10 mol%.

[0182] Hydrophobic monomers with a Kow partition coefficient greater than 1 may also be used in the preparation of the polymer according to the invention. They are preferably selected from the following list: alkyl, arylalkyl, and / or ethoxylated and / or propoxylated (meth)acrylamide esters; alkyl, arylalkyl, or dialkyl and / or ethoxylated and / or propoxylated (meth)acrylamide derivatives; cationic allyl derivatives having an alkyl, arylalkyl, or dialkyl chain and / or an ethoxylated and / or propoxylated chain; hydrophobic anionic or cationic (meth)acryloyl derivatives; and anionic or cationic monomeric (meth)acrylamide derivatives bearing a hydrophobic chain. The hydrophobic monomers may include halogen atoms, for example, chlorine.

[0183] Among these hydrophobic monomers: - Alkyl groups are preferably located at C3-C20, more preferably at C3-C8. Alkyls at C6-C20 are preferably linear alkyls, while alkyls at C3-C5 are preferably branched. - the arylalkyl groups are preferably at C7-C25, more preferably at C7-C15, - the ethoxylated chains preferably comprise 6 to 100 -CH2-CH2-O- groups, more preferably 10 to 40, - the propoxylated chains preferably comprise 1 to 50 -CH2-CH2-CH2-O- groups, more preferably 1 to 20.

[0184] When the polymer is water-soluble, it advantageously comprises less than 5 mol% of hydrophobic monomers and their quantity is adjusted so that the polymer remains soluble in water.

[0185] Monomers exhibiting a fluorescent function can also be used within the scope of the invention. A monomer exhibiting a fluorescent function can be detected by any suitable method, for example, by fluorometry with a fixed-wavelength fluorometer. Generally, detection of the monomer exhibiting a fluorescent function occurs at the excitation and emission maxima, which can be determined using a scanning fluorometer.

[0186] Monomers exhibiting a fluorescent function are chosen, for example, from the following monomers: sodium or potassium styrene sulfonate, styrene sulfonic acid, vinylimidazole and its derivatives, 9-vinyl anthracene and its derivatives, pyranine and its derivatives, coumarin and its derivatives, quinolaxin and its derivatives, pinacyanol and its derivatives, xanthydrol and its derivatives, luminol and its derivatives, dabsyl and its derivatives, 3-hydroxy-2-methylene-3-(l-naphthyl)propionic acid and its derivatives, rhodamine and its derivatives, N-dibenzosuberenylamide and its derivatives, N-9-xanthenylacrylamide and its derivatives, naphthalic derivatives, fluorescein and its derivatives, pyrene and its derivatives, carbostyril and its derivatives, pyrazoline and its derivatives, allyl dibenzosuberenol and its derivatives, chinconicine and its derivatives, quininone and its derivatives, luminol and its derivatives, and cinchoninone and its derivatives, and mixtures thereof.

[0187] In a particular mode, the polymer may comprise at least one cyclic monomer having a hydrolyzable function. Advantageously, the cyclic monomer(s) having a hydrolyzable function are chosen from among cyclic ketene acetals, thionolactones and mixtures thereof.

[0188] The cyclic ketene acetal is advantageously chosen from: 2-methylene-1,3-dioxepane (MDO), 5,6-benzo-2-methylene-1,3-dioxepane (BMDO), 2-methylene-4-phenyl-1,3-dioxolane (MPDL), 2-methylene-1,3,6-trioxocane (MTC), and mixtures thereof. Preferably, it is 2-methylene-1,3-dioxepane (MDO).

[0189] The thionolactone is advantageously chosen from: Dibenzo[c,e]oxepine(7H)-5-thione (DOT), e-thionocaprolactone, 3,3-dimethyl-2,3-dihydro-5Hbenzo[e] [1,4]dioxepine-5-thione (DBT) and mixtures thereof. Preferably, it is 3,3-dimethyl-2,3-dihydro-5Hbenzo[e] [1,4]dioxepine-5-thione.

[0190] In a particular embodiment, the polymer may comprise at least one LCST group.

[0191] According to the general knowledge of those skilled in the art, a LCST group is a group whose solubility in water, for a given concentration, changes above a certain temperature and depending on the salinity. It is a group exhibiting a heating transition temperature that defines its lack of affinity for the solvent medium. This lack of affinity for the solvent results in opacification or loss of transparency, which can be due to precipitation, aggregation, gelation, or viscosification of the medium. The minimum transition temperature is called the "LCST" (Lower Critical Solution Temperature). For each concentration of an LCST group, a heating transition temperature is observed. This temperature is higher than the LCST, which is the minimum point on the curve.Below this temperature, the polymer is soluble in water; above this temperature, the polymer loses its solubility in water.

[0192] In a particular embodiment, the polymer may comprise at least one UCST group.

[0193] According to the general knowledge of those skilled in the art, a UCST group corresponds to a group whose solubility in water, for a given concentration, changes below a certain temperature and depending on the salinity. It is a group exhibiting a cooling transition temperature that defines its lack of affinity for the solvent medium. This lack of affinity for the solvent results in opacification or a loss of transparency, which can be due to precipitation, aggregation, gelation, or viscosification of the medium. The maximum transition temperature is called the "UCST" (Upper Critical Solution Temperature). For each concentration of a UCST group, a cooling transition temperature is observed. This temperature is lower than the UCST, which is the maximum point on the curve.Above this temperature, the polymer is soluble in water; below this temperature, the polymer loses its solubility in water.

[0194] The quantities of the different monomer(s) will be adjusted by a person skilled in the art so as not to exceed 100% molar during the preparation of the polymer according to the invention.

[0195] According to the invention, the polymer can have a linear, branched, cross-linked, star-shaped or comb-shaped structure. This structure can be obtained, according to the general knowledge of a person skilled in the art, for example by selection of the initiator, the transfer agent, the polymerization technique such as reversible addition-fragmentation chain transfer polymerization (RAFT), nitroxide-mediated polymerization (NMP) or atom transfer radical polymerization (ATRP), the incorporation of structural monomers, or the concentration.

[0196] The polymer can further be structured by a branching agent. A structured polymer is defined as a non-linear polymer that has side chains such that, when this polymer is dissolved in water, it exhibits a high state of entanglement leading to very high low-gradient viscosities.

[0197] The branching agent is advantageously chosen from: - structural agents, which may be chosen from the group comprising polyethylene unsaturation monomers (having at least two unsaturated functions), such as vinyl, allylic, acrylic and epoxy functions, and examples include methylene bisacrylamide (MBA), triallyamine, or tetraallylammonium chloride or 1,2-dihydroxyethylene bis-(N-acrylamide), and / or - monomers having at least two epoxy functional groups, - monomers having at least one unsaturated function and one epoxy function, - macroinitiators such as polyperoxides, polyazo and polytransfer agents such as polymer-capturing polymers, and polyols, - functionalized polysaccharides.

[0198] The amount of branching agent in the polymer is advantageously less than 40,000 ppm by weight relative to the total weight of the monomers in the polymer, preferably less than 10,000 ppm by weight, more preferably less than 5,000 ppm by weight.

[0199] In a particular mode, the amount of branching agent is at least equal to 0.1 ppm by weight relative to the total weight of the monomers of the polymer, preferably at least 1 ppm by weight, more preferably at least 10 ppm by weight, more preferably at least 100 ppm by weight and even more preferably at least 1,000 ppm by weight.

[0200] When the polymer is water-soluble and includes a branching agent, the polymer can remain soluble in water. A person skilled in the art will know how to adjust the amount of branching agent, and possibly the amount of transfer agent, to achieve this result.

[0201] In a preferred mode, the polymer is a water-soluble polymer not comprising a branching agent.

[0202] In a particular mode, the polymer may comprise a transfer agent.

[0203] The transfer agent is advantageously chosen from methanol, isopropyl alcohol, sodium, calcium, magnesium, potassium, or ammonium hypophosphite; 2-mercaptoethanol; 3-mercaptopropanol; dithiopropylene glycol; thioglycerol; thioglycolic acid; thiohydracrylic acid; thiolactic acid; thiomalic acid; cysteine; aminoethanethiol; sodium, calcium, magnesium, potassium, or ammonium methallysulfonate; and mixtures thereof. Preferably, it is sodium hypophosphite.

[0204] The amount of transfer agent in the polymer is advantageously between 0 and 100,000 ppm by weight relative to the total weight of the polymer monomers, preferably between 0 and 10,000 ppm by weight, more preferably between 0 and 1,000 ppm by weight, and even more preferably between 0 and 100 ppm by weight. When present, the transfer agent represents at least 0.1 ppm by weight relative to the total weight of the polymer monomers, preferably at least 1 ppm by weight.

[0205] In a particular mode, the polymer does not comprise a transfer agent.

[0206] In general, the polymer does not require the development of a particular polymerization process. Indeed, it can be obtained using all techniques polymerizations well known to those skilled in the art. These may include solution polymerization; gel polymerization; precipitation polymerization; emulsion polymerization (aqueous or reverse); suspension polymerization; reactive extrusion polymerization; water-in-water polymerization; or micellar polymerization.

[0207] Polymerization is generally a radical polymerization, preferably by inverse emulsion polymerization or gel polymerization. By radical polymerization, we include free radical polymerization using UV, azo, redox, or thermal initiators, as well as controlled radical polymerization (CRP) techniques or matrix polymerization techniques.

[0208] Examples of controlled radical polymerization techniques include, but are not limited to, iodine transfer polymerization (ITP), nitroxide-mediated polymerization (NMP), atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer polymerization (RAFT), which includes MADIX technology (macromolecular design by interchange of xanthates), various organometallic-mediated radical polymerization (OMRP), and organoheteroatom-mediated radical polymerization (OHRP).

[0209] The polymer can be partially or totally post-hydrolyzed.

[0210] Post-hydrolysis is the hydrolysis reaction of the polymer after its formation by monomer polymerization. This step consists of the reaction of hydrolyzable functional groups of advantageously non-ionic monomers, more advantageously amide or ester groups, with a hydrolyzing agent. This hydrolyzing agent can, for example, be an enzyme, an ion-exchange resin, or a Brønsted acid (e.g., a hydrohalic acid) or a Brønsted base (e.g., an alkali hydroxide or an alkaline earth hydroxide). Preferably, the hydrolyzing agent is a Brønsted base. During this post-hydrolysis step of the polymer, the number of carboxylic acid groups increases. Indeed, the reaction between the base and the amide or ester groups present in the polymer produces carboxylate groups.

[0211] The polymer can be in liquid, gel or solid form when its preparation includes a drying step such as spray drying, drum drying, radiation drying such as microwave drying, or fluidized bed drying.

[0212] The polymer advantageously has a molecular weight of at least 0.5 million g / mol, preferably between 0.5 and 40 million g / mol, more preferably between 5 and 30 million g / mol. Molecular weight is understood to be the average molecular weight by weight. The polymer may also have a molecular weight between 5,000 and 100,000 g / mol or between 100,000 and 500,000 g / mol.

[0213] The molecular weight is determined by the intrinsic viscosity of the polymer. The intrinsic viscosity can be measured by methods known to those skilled in the art and can be calculated from the reduced viscosity values ​​for different polymer concentrations by a graphical method consisting of plotting the reduced viscosity values ​​(ordinate axis) against the concentration (abscissa axis) and extrapolating the curve down to zero concentration. The intrinsic viscosity value is plotted on the ordinate axis or using the least squares method. The molecular weight can then be determined by the Mark-Houwink equation: [q] = KM“ where [q] represents the intrinsic viscosity of the polymer determined by the method of measuring viscosity in solution. K represents an empirical constant. M represents the molecular weight of the polymer, and a represents the Mark-Houwink coefficient. K and a depend on the specific polymer-solvent system. Polymer properties

[0214] The polymer, when water-soluble, advantageously has a filtration ratio (FR) of less than 1.5, preferably less than 1.3, more preferably less than 1.1.

[0215] The term filtration quotient (FR) is used in this document to refer to a test used to determine the performance of a polymer solution under conditions approximating reservoir permeability. This test consists of measuring the time taken by given volumes / concentrations of the solution to pass through a filter. The FR generally compares the filterability of the polymer solution for two consecutive equivalent volumes, indicating the solution's tendency to clog the filter. Lower FRs indicate better performance.

[0216] The test used to determine the FR consists of measuring the time it takes for given volumes of a solution containing 1000 ppm (by weight) of polymer to flow through a filter. The solution is contained in a cell pressurized to two bars, and the filter is 47 mm in diameter with a defined pore size. Generally, the FR is measured with filters having a pore size of 1.2 µm, 3 µm, 5 µm, or 10 µm.

[0217] The times required to obtain 100 ml (t200mi); 200 ml (t200mi) and 300 ml (t300mi) of filtrate are measured, and a FR is then defined, expressed as:

[0218] [Math.2] 300 mJ - ml FK = ---------- tzoo ml — ml

[0219] Times are measured to the nearest 0.1 seconds.

[0220] The FR thus represents the capacity of the polymer solution to clog the filter for two consecutive equivalent volumes.

[0221] The polymers used according to the invention exhibit improved resistance to chemical and thermal degradation compared to polymers of equivalent molecular weight obtained from 2-acrylamido-2-methylpropane sulfonic acid not being in crystalline form of the potassium salt.

[0222] The test used to determine resistance to chemical degradation consists of preparing a polymer solution at a given concentration in a given brine under aerobic conditions and bringing it into contact with a chemical contaminant such as iron or hydrogen sulfide. The viscosity of the polymer solution is measured before and after 24 hours of exposure to the contaminant. The viscosity measurements are carried out under the same temperature and shear gradient conditions.

[0223] The test used to determine resistance to mechanical degradation consists of preparing a polymer solution at a given concentration in a brine of a given composition under anaerobic conditions (using an inert glove box, for example, with nitrogen) and allowing it to age in a stainless steel cell placed at a given temperature for a predetermined time. At the end of this period, the stainless steel cell is cooled to room temperature, and then the viscosity of the polymer solution it contains is measured and compared to its initial value. Any handling of the stainless steel cell is carried out inside the glove box to avoid any exposure to oxygen. The stainless steel cells are sealed to prevent any oxygen from entering the solution during temperature aging.Viscosity measurements before and after aging are performed in a glove box under the same temperature and velocity gradient conditions.

[0224] Resistance to chemical and thermal degradation is quantified by the viscosity loss value expressed as a percentage and determined at maturity by:

[0225] [Math.3] Viscosity loss (%) =--, ■------- X 100

[0226] Process for treating a suspension of solid particles in water

[0227] The Applicant has surprisingly discovered that the use of a water-soluble polymer obtained from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid improves the performance of suspension treatments such as: - the increase in sludge concentration at the outlet of a thickener, - the dewatering stage and the drying and solidification stages of the suspensions when they are discharged onto the ground, and - the mechanical treatment of the treated suspensions.

[0228] The invention therefore relates to a method for treating a suspension of solid particles in water, comprising contacting said suspension with at least one water-soluble polymer, said polymer being obtained from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid. This method therefore involves mixing said suspension with the water-soluble polymer.

[0229] Such treatment can be carried out in a thickener, which is a retention zone, generally in the form of a tube section several meters in diameter with a conical bottom in which the particles can settle. According to a specific embodiment, the aqueous suspension is conveyed by means of a pipe (pipeline) to a thickener, and the water-soluble polymer is added to said pipe.

[0230] In a particular mode, the water-soluble polymer is added to a thickener that already contains the suspension to be treated. In a typical mineral processing operation, suspensions are often concentrated in a thickener. This results in a higher-density slurry exiting the bottom of the thickener, and an aqueous fluid released from the treated suspension (called liquor) exiting by overflow from the top of the thickener. The addition of the water-soluble polymer increases the concentration of the slurry and increases the clarity of the liquor.

[0231] In a particular embodiment, the water-soluble polymer is added to the particle suspension during the transport of said suspension, by means of a pipe, to a deposition zone. Preferably, the water-soluble polymer is added in the pipe that transports said suspension to a deposition zone. It is on this deposition zone that the treated suspension is spread for dehydration and solidification. The deposition zones may be open, such as an unbounded area of ​​soil, or closed, such as a basin or a cell.

[0232] An example of these treatments during the transport of the suspension is the spreading of the suspension treated with the water-soluble polymer on the ground for dehydration and solidification, and then the spreading of a second layer of the treated suspension on the first solidified layer.

[0233] Another example is the continuous spreading of the suspension treated with the water-soluble polymer such that the treated suspension falls continuously onto the suspension previously discharged in the deposition zone, thus forming a mass of treated material from which the water is extracted.

[0234] In a particular mode, the water-soluble polymer is added to the suspension, and then a mechanical treatment is carried out, such as centrifugation, pressing, or filtration.

[0235] The water-soluble polymer can be added simultaneously in different stages of the suspension treatment, i.e. for example in the pipe (pipeline) transporting the suspension to a thickener and in the slurry exiting the thickener which will be conveyed either to a settling area or to a mechanical treatment device.

[0236] The water-soluble polymer can be added to the aqueous suspension to be treated in liquid or solid form. It can be added as an emulsion (advantageously water-in-oil), an aqueous or oily polyphasic particulate suspension, or a powder. The water-soluble polymer is preferably added as an aqueous solution obtained from a concentrated form of the water-soluble polymer, such as a powder, a water-in-oil emulsion, or an aqueous or oily polyphasic particulate suspension.

[0237] In a particular mode, the aqueous polyphasic particulate suspension preferably comprises: - 15 to 60% by mass of at least one water-soluble polymer in the form of a solid particle with an average size between 5 and 500 pm; - 15 to 45% by mass of at least one salt of an alkali metal and / or at least one salt of an alkaline earth metal; - at least one thickening agent other than the water-soluble polymer; - at least 10% water by mass; and said suspension having a Brookfield viscosity between 500 and 20,000 cps at a temperature of 20°C, and said suspension having a density between 1.1 and 2 kg.L *.

[0238] In a particular embodiment, the oily particulate polyphasic suspension preferably comprises: - 15 to 60% by mass of at least one water-soluble polymer in the form of a solid particle with an average size between 5 and 500 pm; - at least one viscosifying agent other than the water-soluble polymer; - at least 10% oil by mass; and said suspension having a Brookfield viscosity between 500 and 20,000 cps at a temperature of 20°C, and said suspension having a volumetric mass between 0.6 and 1.4 kg.L *.

[0239] Brookfield viscosity is measured with a Brookfield apparatus, fitted with an LV module, the module being able to rotate at a speed of 30 revolutions per minute for example, the measurement being advantageously carried out at 20°C. The density is measured at 20°C, at a pressure of 1 atm i.e. 101,325 Pa.

[0240] When the water-soluble polymer is in solid form, it can be partially or totally dissolved in water using a polymer preparation unit such as the Polymer Slicing Unit (PSU) disclosed in document EP 2 203 245.

[0241] In a particular embodiment, the water-soluble polymer is added to the suspension in combination with at least one other polymer, synthetic or natural. These polymers may be added simultaneously or separately (before or after the addition of the water-soluble polymer). The other polymer may be water-soluble or swellable in water. It may be a dispersant, a coagulant, or a flocculant.

[0242] In a particular embodiment, the water-soluble polymer is added to the suspension in combination with a salt such as a calcium and / or magnesium salt. The water-soluble polymer and the salt may be added simultaneously or separately. The salts may be inorganic or organic. Suitable salts include calcium chloride, calcium acetate, calcium sulfate, calcium nitrate, calcium hydroxide, calcium carbonate, magnesium chloride, magnesium acetate, magnesium sulfate, magnesium nitrate, magnesium hydroxide, magnesium carbonate, calcium formate, calcium gluconate, calcium propionate, tricalcium phosphate, and calcium succinate.

[0243] The quantity of water-soluble polymer added to the aqueous suspension is advantageously between 50 and 5000 g per tonne of solid particles, by dry weight, of the suspension, preferably between 250 and 2000 g / t, more preferably between 500 and 1500 g / t. The quantity depends on the nature and composition of the suspensions to be treated; those skilled in the art will know how to adjust this quantity, which remains a routine adjustment for them.

[0244] According to the invention, the process makes it possible to efficiently treat a suspension of solid particles and more particularly of mineral particles.

[0245] Suspensions of solid particles in water include all types of sludge, residues, or waste materials. These suspensions originate particularly from ore extraction and take the form of suspensions of mineral particles. They may, for example, consist of industrial sludge or residues and all mine washing and waste products from mining operations, such as coal mines, diamond mines, phosphate mines, and metal mines (aluminum, platinum, etc.). iron, gold, copper, silver, etc.). Suspensions can also originate from oil sands extraction, for example, from sludge or extraction residues derived from oil sands processing. These suspensions generally comprise organic and / or mineral particles, such as, for example, clays, sediments, sand, metal oxides, petroleum, etc., mixed with water.

[0246] Generally, the suspensions of solid particles are concentrated and contain between 5% and 60% by weight of solid particles, preferably between 20% and 50% by weight of solid particles, relative to the total weight of said suspensions.

[0247] The process according to the invention can also be useful for treating residues from oil sands extraction: so-called "fine tailings," that is, tailings containing a large quantity of clay, and for treating so-called "mature" fine tailings, or Mature Fine Tailings (MFT), that is, these same fine tailings after several years of sedimentation, and containing an even greater quantity of clay. The process according to the invention can also be used to treat so-called "fresh" tailings, that is, tailings coming directly from the operation of separating the bitumen from the soil from which it (the bitumen) is extracted.

[0248] Method for flocculating a suspension of solid particles in water

[0249] The present invention also relates to a method for flocculating a suspension of solid particles in water, comprising bringing said suspension into contact with at least one water-soluble polymer obtained from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° degrees 2-theta (+ / - 0.1°).

[0250] All embodiments previously described concerning the process of treating a suspension of solid particles in water are also applicable to the process for flocculating a suspension of solid particles in water.

[0251] Enhanced hydrocarbon recovery process (oil and / or gas)

[0252] The invention relates to a process for enhanced recovery of hydrocarbons (oil and / or gas) comprising the following steps: a) Preparation of an injection fluid comprising at least one water-soluble polymer of 2-acrylamido-2-methylpropane sulfonic acid, with water or brine; the 2-acrylamido-2-methylpropane sulfonic acid being, before polymerization, in the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° 2-theta degrees (+ / - 0.1°); b) Injection of the injection fluid into an underground formation; c) Sweeping of the underground formation using the injected fluid; d) Recovery of an aqueous and hydrocarbon mixture.

[0253] When the water-soluble polymer used in the preparation of the injection fluid is in powder form, the average size of the water-soluble polymer particles is advantageously less than 1.5 millimeters, preferably less than 850 micrometers. The average size of the water-soluble polymer particles is advantageously greater than 5 µm.

[0254] The average particle size of water-soluble polymer is the average size of the largest dimension, for example, the diameter for spherical particles. It is advantageously measured with a laser measuring device using conventional techniques that are part of the knowledge of those skilled in the art. For example, a Mastersizer-type device from Malvern, such as the MS2000, can be used for this purpose. This type of device allows the particle size distribution of particles in liquid or solid form to be measured by laser diffraction.

[0255] When the water-soluble polymer is in granular form, it can be dissolved in an aqueous medium in a dispersion device. An example of a dispersion device is the polymer slicing unit (PSU) described in US patent 8,186,871, which allows the preparation of a concentrated aqueous polymer solution.

[0256] The water or brine used for preparing the injection fluid may be production water. "Production water" means any salt or non-salt water, brine, seawater, or aquifer water originating from a hydrocarbon reservoir. This production water may be pre-treated before preparing the injection fluid as described in patent application WO 2018 / 020175.

[0257] Water-soluble polymers can be combined with stabilizing compounds. Stabilizing compounds (stabilizing agents) can be compounds that adequately protect polymers, for example, against thermal, chemical, and / or mechanical degradation. Examples of suitable stabilizing agents are given in patent application WO 2010 / 133258.

[0258] The injection of the injection fluid comprising the water-soluble polymer, depending on the technique employed, is carried out alone or in conjunction with one or more chemical compounds useful for the enhanced recovery of hydrocarbons (oil and / or gas). These chemical compounds include the use of weak, strong, or superstrong mineral or organic bases capable of saponifying crude oils and producing in-situ surfactants that solubilize hydrocarbons, particularly petroleum. Examples include sodium or potassium carbonate, Caustic soda, borate and metaborate compounds, amines, and basic polymeric species are commonly injected. Another family of compounds widely injected with polymers is that of surfactants, often anionic, zwitterionic, cationic, and sometimes nonionic. These compounds are rarely injected undiluted, but generally with a co-surfactant and a co-solvent to improve their compatibility and effectiveness in the reservoir (underground formation).

[0259] The injection fluid advantageously comprises between 10 and 15,000 ppm by weight of water-soluble polymer, preferably between 50 and 10,000 ppm by weight, more preferably between 100 and 5,000 ppm by weight.

[0260] Quite surprisingly, the Applicant discovered that water-soluble polymers obtained from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropanesulfonic acid have better filterability and better resistance to chemical and thermal degradation compared to polymers of equivalent molecular weight obtained from 2-acrylamido-2-methylpropanesulfonic acid not in the crystalline form of the potassium salt. Furthermore, it is known that filterability deteriorates as the molecular weight of the polymer increases. One of the advantages of the invention lies in the possibility of obtaining water-soluble polymers of very high molecular weight that, at the same time, exhibit good filterability.Furthermore, the concentration of water-soluble polymer required to achieve a target injection fluid viscosity is reduced, which improves the economic conditions for recovering hydrocarbons (oil and / or gas) contained in the underground formation.

[0261] The water-soluble polymers according to the invention have the function of viscosifying the waters injected into reservoirs (underground formations) containing hydrocarbons (oil and / or gas) to ensure mobility control without the need for crosslinking, i.e. chemical bridging between chains.

[0262] In a particular embodiment, the enhanced hydrocarbon (oil and / or gas) recovery process comprises the following steps: a) Preparation of an injection fluid comprising a water-soluble polymer having a molecular weight greater than 5 million g / mol: - the injection fluid having a salt concentration greater than 100 g / l of which at most 50 g / l of divalent salt(s); - the polymer comprising at least 80 mol% of 2-acrylamido-2-methylpropane sulfonic acid of which advantageously at least 50 mol% of 2-acrylamido-2-methylpropane sulfonic acid is, before polymerization, in the crystalline form of the potassium salt, preferably at least 70 mol%, more preferably 100 mol%; - the concentration of water-soluble polymer in the injection fluid being less than 3,000 ppm by weight, - the injection fluid before the shearing step b) having a viscosity Vj; b) Shearing of the injection fluid to obtain a viscosity reduction of more than 25% compared to Vj with:

[0263] [Math.4] V2 - Calf ----------> 3 <J Veau

[0264] where, Vi corresponds to the viscosity of the injection fluid before the shearing step at the formation temperature; V2 is the viscosity of the injection fluid after the shearing step at the formation temperature; Veau is the viscosity of the water used for preparing the injection fluid at the formation temperature; c) Injection of the injection fluid into an underground formation, the underground formation being a carbonate formation, having a permeability of less than 300 millidarcy and a temperature greater than 100°C; d) Scanning of the underground formation using the injected fluid; e) Recovery of an aqueous and hydrocarbon mixture (oil and / or gas).

[0265] The shearing step can be carried out, for example, using a valve, an orifice or a pump.

[0266] Preferably, the concentration of divalent salt(s) in the injection fluid is between 3 and 50 g / l.

[0267] Carbonate formations are sedimentary rock formations whose carbonate composition is at least 50%. Fracking fluid

[0268] The present invention relates to a fracturing fluid comprising an aqueous phase, at least one propping agent and at least one water-soluble polymer obtained from 2-acrylamido-2-methylpropane sulfonic acid in the crystalline form of the potassium salt having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° degrees 2-theta (+ / -0.1°).

[0269] The aqueous phase is advantageously chosen from: seawater, brine, fresh water, advantageously it is brine.

[0270] Brine is defined as a solution comprising water and organic or inorganic salts. The salts may include monovalent salts, divalent salts, trivalent salts, and mixtures thereof. Advantageously, the brine comprises at least 1,000 mg / L of salts, preferably at least 5,000 mg / L, more preferably at least 10,000 mg / L, even more preferably at least 50,000 mg / L, and even more preferably the brine is saturated with salts.

[0271] The support agent may be chosen without restriction from sand, ceramics, bauxite, glass beads, and resin-impregnated sand.

[0272] Advantageously, the amount of propping agent in the fracturing fluid is between 0.5 and 40% by weight relative to the total weight of the fracturing fluid, preferably between 1 and 25%, more preferably between 1.5 and 20%.

[0273] Advantageously, the fracturing fluid comprises between 0.001% and 1% by weight of water-soluble polymer obtained from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid relative to the total weight of the fracturing fluid, preferably between 0.002% and 0.2%.

[0274] The fracturing fluid may comprise other compounds known to those skilled in the art, such as those mentioned in document SPE 152596, for example: - Anti-swelling agents for clays such as potassium chloride, or choline chloride, and / or - Biocides to prevent the growth of bacteria, particularly sulfate-reducing bacteria, which can form viscous masses that reduce surface area. Examples include glutaraldehyde, the most commonly used, as well as formaldehyde, isothiazolinones, and / or - Oxygen reducers such as ammonium bisulfite to prevent the destruction of other components by oxidation and corrosion of the injection tubes, and / or - Anti-corrosion additives to protect the tubes against oxidation by residual oxygen, with N,N dimethylformamide being preferred, and / or - Lubricants such as oil distillates, and / or - Iron chelating agents such as citric acid, EDTA (ethylenediaminetetraacetic acid), phosphonates, and / or - Anti-scale products such as phosphates, phosphonates, polyacrylates or ethylene glycol.

[0275] Before its use in the fracturing fluid, the water-soluble polymer according to the invention may be in various solid or liquid forms. Preferably, it is in the form of a powder, a water-in-oil inverse emulsion, an aqueous polyphasic particulate suspension, or an oily polyphasic particulate suspension.

[0276] Method for preparing a fracturing fluid

[0277] The present invention also relates to a method for preparing a fracturing fluid by adding, in water or brine, at least one water-soluble polymer obtained from 2-acrylamido-2-methylpropane sulfonic acid in the crystalline form of the potassium salt (described above), and in which the water-soluble polymer is, before formation of the fracturing fluid: - either in powder form; - either in the form of a reverse water-in-oil emulsion; - either in the form of a polyphasic aqueous or oily particulate suspension.

[0278] The process for preparing a fracturing fluid according to the invention preferably includes a step of adding to said fluid at least one propping agent as described above.

[0279] When the water-soluble polymer added to the fracturing fluid is, before the formation of the fracturing fluid, in powder form, the average size of the polymer particles is advantageously less than 1.5 millimeters, preferably less than 850 micrometers, and more preferably less than 200 micrometers. The average size of the water-soluble polymer particles is advantageously greater than 5 µm.

[0280] The average particle size of water-soluble polymer is the average size of the largest dimension, for example, the diameter for spherical particles. It is advantageously measured with a laser measuring device using conventional techniques that are part of the knowledge of those skilled in the art. For example, a Mastersizer-type device from Malvern, such as the MS2000, can be used for this purpose. This type of device allows the particle size distribution of particles in liquid or solid form to be measured by laser diffraction.

[0281] When the water-soluble polymer according to the invention is in solid form, it can be partially or totally dissolved in water using a polymer preparation unit such as the Polymer Slicing Unit (PSU) disclosed in document EP 2 203 245.

[0282] When the water-soluble polymer added to the fracturing fluid is, before formation of the fracturing fluid, in the form of a reverse water-in-oil emulsion, the concentration of water-soluble polymer in the emulsion is preferably between 5 and 60% by weight, more preferably between 15 and 40% by weight relative to the weight of the emulsion.

[0283] In a preferred embodiment according to the invention, the water-in-oil inverse emulsion may comprise between 0.01% and 70% by weight of an organic salt and / or an inorganic salt relative to the weight of the emulsion, preferably between 5% and 20%. The salts may be chosen without restriction from sodium chloride, sodium sulfate, sodium bromide, ammonium sulfate, ammonium chloride, lithium chloride, lithium bromide, potassium chloride, potassium bromide, magnesium sulfate, aluminum sulfate and mixtures thereof. Ammonium chloride and ammonium sulfate are the preferred salts.

[0284] When the water-soluble polymer added to the fracturing fluid is, before formation of the fracturing fluid, in the form of an aqueous particulate polyphasic suspension comprising: - 15 to 60% by weight of at least one water-soluble polymer in the form of solid particles with an average size between 5 and 500 pm; - 15 to 45% by weight of at least one salt of an alkali metal and / or at least one salt of an alkaline earth metal; - at least one viscosifying agent other than the water-soluble polymer; - at least 10% water by weight; and said suspension having a Brookfield viscosity between 500 and 20,000 cps at a temperature of 20°C; and said suspension having a density between 1.1 and 2 kg.L *.

[0285] When the water-soluble polymer added to the fracturing fluid is, before formation of the fracturing fluid, in the form of an oily particulate polyphasic suspension, said suspension preferably comprises: - 15 to 60% by weight of at least one water-soluble polymer in the form of solid particles with an average size between 5 and 500 pm; - at least one viscosifying agent other than the water-soluble polymer; - at least 10% oil by weight; and said suspension having a Brookfield viscosity between 500 and 20,000 cps at a temperature of 20°C, and said suspension having a density between 0.6 and 1.4 kg.L *.

[0286] Brookfield viscosity is measured with a Brookfield apparatus, fitted with an LV module, the module being able to rotate at a speed of 30 revolutions per minute for example, the measurement being advantageously carried out at 20°C. The density is measured at 20°C, at a pressure of 1 atm i.e. 101,325 Pa.

[0287] Unconventional underground oil or gas hydraulic fracturing process

[0288] The present invention also relates to a method of hydraulic fracturing of an unconventional underground oil or gas reservoir comprising the preparation of a fracturing fluid as described above, and the injection of said fracturing fluid into the underground reservoir.

[0289] The injection is carried out under pressure so as to create fractures distributed throughout the production well.

[0290] Optionally, before, during or after the creation of the fractures, at least one oxidizing compound and / or at least one surfactant compound is injected into the reservoir.

[0291] The injection of surfactant makes it possible to eliminate the viscosity generated by the polymer in Inhibiting interchain hydrophobic interactions, while the injection of the oxidizing compound destroys the polymer. In both cases, the injection restores a fluid viscosity close to that of water.

[0292] Examples of oxidizing compounds include bleach (aqueous solution of a hypochlorite salt), hydrogen peroxide, ozone, chloramines, persulfates, permanganates or perchlorates.

[0293] The chemical nature of the surfactant compound(s) is not critical. They may be anionic, nonionic, amphoteric, zwitterionic, and / or cationic. Preferably, the surfactant compound(s) of the invention carry anionic charges.

[0294] Preferably, the surfactant compounds used are chosen from anionic surfactants and their zwitterions selected from the group comprising derivatives of alkyl sulfates, alkyl ethersulfates, arylalkyl sulfates, arylalkyl ethersulfates, alkylsulfonates, alkyl etherssulfonates, arylalkylsulfonates, arylalkyl etherssulfonates, alkyl phosphates, alkyl ethersphosphates, arylalkyl phosphates, arylalkyl ethersphosphates, alkylphosphonates, alkyl ethersphosphonates, arylalkyl phosphonates, arylalkyl ethersphosphonates, alkyl carboxylates, alkyl ethers carboxylates, arylalkyl carboxylates, arylalkyl ethers carboxylates, alkyl polyethers, arylalkyl polyethers...

[0295] An alkyl chain is defined as a chain of 6 to 24 carbons, branched or unbranched, with or without multiple units, which may optionally contain one or more heteroatoms (O, N, S). An arylalkyl chain is defined as a chain of 6 to 24 carbons, branched or unbranched, comprising one or more aromatic rings and which may optionally contain one or more heteroatoms (O, N, S).

[0296] The most commonly used surfactants, for reasons of cost, stability, and availability, are of the sulfonate or sulfate type, presented in the form of alkali metal or ammonium salts.

[0297] Method for reducing friction of a fracturing fluid in a hydraulic fracturing operation of an unconventional underground oil or gas reservoir

[0298] The present invention also relates to a method for reducing friction of a fracturing fluid in a hydraulic fracturing operation of an unconventional underground oil or gas reservoir, comprising the preparation of a fluid of fracturing as described above, and the injection of said fracturing fluid into the underground reservoir.

[0299] Friction reduction makes it possible to decrease or eliminate losses (pressure) related to friction during the injection of the fracturing fluid. Other uses of the polymer

[0300] Another aspect of the invention relates to the use of polymers obtained from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0301] The present invention also relates to the use of this polymer in: well drilling or cementing; conformance; diversion; open, closed or semi-closed circuit water treatment; fermentation must treatment; sludge treatment; construction; paper or cardboard manufacturing; battery manufacturing; wood processing; hydraulic composition processing (concrete, cement, mortar and aggregates); cosmetic product formulation; detergent formulation; textile manufacturing; geothermal energy; sanitary diaper manufacturing; or agriculture.

[0302] The invention also relates to the use of this polymer as a coagulant, binding agent, absorbent agent, draining agent, charge retention agent, dehydrating agent, conditioning agent, stabilizing agent, fixing agent, film-forming agent, sizing agent, superplasticizing agent, clay inhibitor or dispersant.

[0303] The invention and its advantages will become clearer from the following figures and examples, which are given to illustrate the invention and not to limit it. Description of figures

[0304] [Fig-1] Fig. 1 illustrates the proton NMR spectrum of acid 2- crystals acrylamido-2-methylpropane sulfonic obtained according to example 1.

[0305] [Fig.2] Fig.2 illustrates the proton NMR spectrum of 2- acid crystals acrylamido-2-methylpropane sulfonic obtained according to example 2.

[0306] [Fig.3] Fig.3 illustrates the X-ray diffraction pattern of the crystals obtained according to example 1.

[0307] [Fig.4] Fig.4 illustrates the X-ray diffraction pattern of the crystals obtained according to example 2.

[0308] [Fig. 5] [Fig. 5] illustrates the Fourier transform infrared spectrum of the crystals obtained in example 1.

[0309] [Fig.6] Fig.6 illustrates the Fourier transform infrared spectrum of the crystals obtained according to example 2.

[0310] [Fig.7] Fig.7 illustrates the thermogram of the crystals obtained according to example 1.

[0311] [Fig.8] Fig.8 illustrates the thermogram of the crystals obtained according to example 2.

[0312] [Fig.9] Fig.9 illustrates the grain size distribution graph of the crystals obtained according to Example 1.

[0313] [Fig. 10] The [Fig. 10] illustrates the grain size graph of the crystals obtained according to example 2.

[0314] [Fig. 11] The [Fig. 11] corresponds to the observation under the optical microscope of the crystals obtained according to example 1.

[0315] [Fig. 12] The [Fig. 12] corresponds to the observation under the optical microscope of the crystals obtained according to example 2.

[0316] [Fig. 13] The [Fig. 13] corresponds to the demonstration of the corrosion of ATBS at 50°C, after 15 days on carbon steel plates, following its production according to examples 1 and 2.

[0317] [Fig. 14] The [Fig. 14] represents the percentage reduction in friction as a function of time for polymers.

[0318] [Fig. 15] The [Fig. 15] represents the percentage reduction in friction as a function of time for homopolymers.

[0319] [Fig. 16] The [Fig. 16] represents the percentage reduction in friction as a function of time for ter-polymers.

[0320] [Fig. 17] The [Fig. 17] represents the percentage reduction in friction as a function of time for post-hydrolyzed polymers.

[0321] [Fig. 18] The [Fig. 18] illustrates the loss of viscosity of polymers as a function of the shape of the ATBS and the iron content.

[0322] [Fig. 19] The [Fig. 19] illustrates the loss of viscosity of polymers as a function of the shape of ATBS during aging at 90°C.

[0323] [Fig.20] Figure [Fig.20] illustrates the viscosity loss of homopolymers as a function of the form of ATBS and iron content. Examples

[0324] Example 1: Synthesis of 2-acrylamido-2-methylpropane sulfonic acid

[0325] In a 2000 mL double-jacketed stirred reactor, 1522 grams of acrylonitrile containing 0.4% water by weight and 180 grams of fuming sulfuric acid containing 104% H2SO4 (18% oleum) are added. The mixture is stirred for 1 hour and cooled by the reactor's double jacket, which maintains the temperature of the sulfonant mixture at -20°C.

[0326] 97 grams of isobutylene are added to the previous sulfonant mixture, at a flow rate of 1.6 grams / minute.

[0327] The temperature of the mixture is controlled at 45°C during the introduction of isobutylene. The particles of 2-acrylamido-2-methylpropane sulfonic acid precipitate in the mixture, and the solids content is approximately 20% by weight. The reaction mixture is filtered through a Buchner filter and dried under vacuum at 50°C. The resulting solid is 2-acrylamido-2-methylpropane sulfonic acid and is a very fine white powder.

[0328] According to observations made under the optical microscope ([Fig. 11]) the crystals have a needle-like morphology.

[0329] Example 2: Formation of the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid

[0330] In a 1000 mL double-jacketed stirred reactor, 477 grams of a 28% potassium hydroxide solution (by weight in water) are added. To the preceding mixture are added 452 grams of 2-acrylamido-2-methylpropanesulfonic acid (white powder obtained from Example 1).

[0331] The mixture is stirred for 30 minutes, at 10°C, to form an aqueous solution SA2.

[0332] The aqueous solution SA2 is heated to a temperature of 40°C under a vacuum of 50 mbar for 20 minutes, then the temperature is maintained for 30 minutes under a vacuum of 50 mbar, and then cooled to a temperature of 10°C. The cooling time between 40°C and 10°C is 6 hours. A suspension Si of potassium salt crystals of 2-acrylamido-2-methylpropanesulfonic acid is obtained. The suspension Si is filtered using a Robatel vertical centrifuge. A solid of composition Ci is obtained, containing 80% by weight of potassium salt crystals of 2-acrylamido-2-methylpropanesulfonic acid.

[0333] According to observations made under the optical microscope ([Fig. 12]) the crystals have a column and platelet type morphology.

[0334] Counterexample 21: Failure to obtain the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0335] In a 1000 mL double-jacketed stirred reactor, 477 grams of a 28% potassium hydroxide solution (by weight in water) are added. To the preceding mixture, 452 grams of 2-acrylamido-2-methylpropanesulfonic acid (white powder from Example 1) are added.

[0336] The mixture is stirred for 30 minutes, at 10°C, to form an aqueous solution SA2.

[0337] Solution SA2 is heated to a temperature of 40°C for 20 minutes at atmospheric pressure, then the temperature is maintained for 30 minutes at atmospheric pressure. The solution is then cooled to a temperature of 10°C. The cooling time between 40°C and 10°C is 6 hours. After the cooling step, solution SA2 does not allow the formation of a Si suspension; therefore, no filtration or centrifugation operation is possible to isolate any crystals of 2-acrylamido-2-methylpropane sulfonic acid in their crystalline form of potassium salt.

[0338] Example 3: NMR analysis of the products from examples 1 and 2

[0339] The solid of 2-acrylamido-2-methylpropane sulfonic acid obtained in the example 1 and its crystalline form of the potassium salt obtained in example 2 are analyzed by proton nuclear magnetic resonance (NMR).

[0340] The samples are dissolved in D2O. The NMR instrument has a frequency of 400 MHz, is a Bruker brand, and is equipped with a 5mm BBO BB-'H probe.

[0341] The two proton spectra ([Fig.1] and [Fig.2]) are similar and the assignment of the peaks is consistent with the molecular structure of 2-acrylamido-2-methylpropane sulfonic acid or its potassium salt. Example 4: X-ray diffraction analysis

[0342] The solids obtained in examples 1 and 2 are first ground into powders and are analyzed by X-ray diffraction over an angular range of 10 to 90°. The equipment used is a Rigaku miniflex II diffractometer equipped with a copper source.

[0343] We can observe that the solid obtained at the end of Example 2 ([Fig.4]) has an X-ray diffraction pattern having the following characteristic peaks: 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° degrees 2-theta (+ / - 0.1°).

[0344] The X-ray diffraction pattern of the solid according to Example 1 ([Fig.3]) does not show the same peaks.

[0345] Example 5: Fourier Transform Infrared Measurement

[0346] The Fourier transform infrared measuring equipment is the Perkin Elmer Spectrum 100 equipped with a single reflection ATR polarization accessory, the accuracy of which is 8cm'.

[0347] The solids obtained in examples 1 and 2 are sieved at 100 µm. The particles remaining on the sieve are dried and placed in an oven at 60°C for at least 4 hours.

[0348] A few hundred milligrams of solid are placed on the diamond of the ATR accessory and pressure is applied manually using the accessory.

[0349] We can observe that the following bands ([Fig.6]) are characteristic of the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid: 3293cm*, 3075cm1, 3000cm*, 2979cm1, 1655cm1, 1625cm1, 1550cm*, 1405cm1, 1209cm1, 1190cm1, 1162cm1, 1048cm1, 979cm1, 824cm1, 803cm1, 756cm1, 633cm*, 523cm1.

[0350] The infrared spectrum of the solid according to example 1 ([Fig.5]) does not show the same peaks.

[0351] Example 6: Differential Calorimetric Analysis (DSC)

[0352] The equipment used is a Mettler brand DSC 3.

[0353] The solids obtained in Examples 1 and 2 are analyzed with a heating ramp of 10°C / minute under a nitrogen flow. The initial temperature is 30°C, the product is heated up to 350°C.

[0354] The thermogram of the crystals of Example 1 ([Fig.7]) shows a thermal effect at a temperature of 195.15°C, which is generally considered to be the melting / degradation point of 2-acrylamido-2-methylpropane sulfonic acid.

[0355] The thermogram of the crystals of example 2 ([Fig.8]) shows 2 thermal phenomena at 79.4°C; 207°C.

[0356] In comparison, the thermogram of the crystals in Example 1 shows only one degradation peak at 195.15°C followed by two exothermic degradation phenomena at 212.8°C and 288.4°C ([Fig.7]).

[0357] Example 7: Measurement of minimum ignition energy (MIE)

[0358] The measurement of the minimum ignition energy is carried out according to the standard NF EN 13821.

[0359] The explosimeter is a vertical Hartmann tube. The dust dispersion system is of the mushroom type.

[0360] The total induction is less than 25 microhenries. The discharge voltage is between 5kV and 15kV. The electrodes are made of brass and spaced at a minimum distance of 6mm.

[0361] Different dispersed energies and masses were tested and summarized in the following tables.

[0362] It is clear that the crystalline form of potassium salt presents a much lower risk of explosion than the needle form obtained in Example 1.

[0363] [Tables 1] Energy (mJ) Mass of dispersed solid (g) Dispersion number Ignition? Yes (O) No (N) Flame Pressure 1000 0.5 2 O Small Low 500 0.5 3 O Medium Medium 300 0.5 3 O Medium Medium 100 0.5 20 N - - 200 0.5 20 N 200 1 20 N - - 200 2 20 N - - 200 3 7 O Medium Low 100 3 20 N - - 100 5 20 N - - 100 7 20 N 100 10 20 N - - 100 1 20 N - - 100 2 20 N

[0364] Table 1: Determination of the solid EMI of Example 1

[0365] [Tables2] Energy (mJ) Mass of dispersed solid (g) Dispersion number Ignition? Yes (O) No (N) Flame Pressure 1000 0.5 20 N - - 1000 1 20 N - - 1000 2 20 N - - 1000 3 20 N - - 1000 3 20 N - - 1000 5 20 N - - 1000 7 20 N - - 1000 10 20 N - - 1000 15 20 N - 1000 20 20 N - - High energy 0.5 3 O Small Low

[0366] Table 2: Determination of the solid EMI of example 2 Example 8: Particle size measurement

[0367] The solids obtained in examples 1 and 2 are analyzed by laser diffraction in order to determine their particle size distribution.

[0368] The equipment used in laser diffraction is a Cilas 1190.

[0369] For the crystals in Example 1, the value of d50 is about 40pm and 90% of the particles have a size less than 100pm ([Fig.9]).

[0370] For the crystals in Example 2, the value of d50 is approximately 600 pm and 90% of the particles have a size less than approximately 1500 pm ([Fig. 10]). The crystals of Example 2 contains less than 10% of particles with a size smaller than 325pm.

[0371] Example 9: Evaluation of the corrosivities on carbon steel of different forms of ATBS

[0372] 20 grams of crystals from example 1 or 2 are deposited on two steel plates Carbon plates measuring 20 x 50 mm² are used. These coated plates are placed in an oven at 50°C for two weeks. Simultaneously, a control plate is left uncoated but placed under the same temperature conditions.

[0373] Photographs of the plates thus placed in situ ([Fig. 13]) show visually more pronounced corrosion on the plate that was in contact with 2-acrylamido-2-methylpropane sulfonic acid according to Example 1, compared to Example 2 of the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid (ATBS.K). The weighings of the plates before and after the contact period confirm these observations.

[0374] [Tables3] Initial mass (g) Final mass (g) t+15 days 50°C % loss Control plate 9.5032 9.5020 0.012 Plate + ATBS example 1 9.3560 8.6582 7.46 Plate + ATBS.K example 2 9.5231 9.3526 1.79

[0375] Table 3: Corrosivity of different forms of ATBS on carbon steel

[0376] Example 10: Protocol for preparing a solution of a potassium salt of 2-acrylamido-2-methylpropane sulfonic acid from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid

[0377] In a 2000 mL double-jacketed reactor equipped with a condenser, a pH meter, and a stirrer, 1000 grams of the crystalline form of the potassium salt of acrylamido-2-methylpropanesulfonic acid of Example 2 and 1000 grams of water are introduced. The mixture has a pH greater than 12.

[0378] The mixture obtained is a potassium salt solution of 2-acrylamido-2-methylpropane sulfonic acid at a concentration of 50% by weight in water.

[0379] Example 11: Protocol for preparing a solution of a potassium salt of 2-acrylamido-2-methylpropane sulfonic acid from the acidic form

[0380] In a 2000 mL double-jacketed reactor equipped with a condenser, a pH meter, and a stirrer, 800 grams of acrylamido-2-methylpropane sulfonic acid of Example 1 and 650 grams of water are introduced. The mixture has a pH less than 1.

[0381] A 50% by weight potassium hydroxide solution in water is prepared in a dropping funnel. The caustic solution is added to the reaction mixture over 120 minutes. The temperature is controlled to be below 30°C.

[0382] The final pH of the solution is at a pH between 8 and 10.

[0383] 451 grams of 50% by weight potassium hydroxide solution in water are added together.

[0384] The mixture obtained is a potassium salt solution of 2-acrylamido-2-methylpropane sulfonic acid at a concentration of 50% by weight in water.

[0385] Example 1 2: Evolution of the quality of ATBS potassium salt stored in solid or liquid form

[0386] 500 g of 50% (by weight in water) solutions of potassium salt of 2- acid acrylamido-2-methylpropane sulfonic acid prepared according to examples 10 and 11 were stored for 12 months in order to compare their stability over time by measuring and monitoring the appearance of potassium salt homopolymers of 2-acrylamido-2-methylpropane sulfonic acid.

[0387] In parallel, 2-acrylamido-2-methylpropane sulfonic acid in crystalline form of potassium salt prepared according to example 2 and 2-acrylamido-2-methylpropane sulfonic acid prepared according to example 1 are stored in solid form for the same duration.

[0388] Every three months, 500 g of a potassium salt solution of 2-acrylamido-2-methylpropanesulfonic acid is freshly prepared according to Example 10 or 11 with the crystals of Example 2 or 1 stored. The level of potassium salt homopolymers of 2-acrylamido-2-methylpropanesulfonic acid present is then measured in order to compare the solid storage of this new form.

[0389] The solutions are analyzed by liquid-phase size exclusion chromatography with an Agilent 1260 chromatograph equipped with AquagelOH -20 -30, -40 and -50 columns allowing the analysis of anionic polymer up to 600,000 g / mol in PEG equivalent.

[0390] Potassium salt solutions of 2-acrylamido-2-methylpropane sulfonic acid are diluted to 2000 ppm (by weight in water) before injection. The integration of the 250 nm UV signal at the column outlet is performed for the polymer peaks before being reported in Table 4 below. The stronger the signal, the greater the polymer content, and therefore the lower the product's long-term stability.

[0391] [Tables4] Sampling time after production Solution according to Example 10 stored (mV.s) Solution according to Example 11 stored (mV.s) Newly prepared solution from the stored crystals of Example 2 (mV.s) Newly prepared solution from the stored crystals of Example 1 (mV.s) T0 0 0 0 T0 + 3 months 653 7533 200 250 T0 + 6 months 15326 423236 6532 7702 T0 + 9 months 25631 653126 9532 10503 T0 + 12 months 65231 1523621 25631 256300

[0392] Table 4: Stability of solutions of the salt of 2-acrylamido-2-methylpropane sulfonic acid

[0393] It can be seen that the new crystalline form of potassium salt of 2-acrylamido-2-methylpropane sulfonic acid makes it possible to obtain more time-stable solutions of 2-acrylamido-2-methylpropane sulfonic acid salt.

[0394] In addition to better preservation in liquid form, the new crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid allows storage in solid form offering improved storage time.

[0395] Example 1 3: Preparation of an acrylamide / 2-acrylamido-2-methylpropane sulfonic acid (75 / 25 mol%) polymer

[0396] In a 2000 mL beaker are added 628.3 g of deionized water, 500 g of acrylamide in 50% solution (by weight in water), 16.2 g of urea and 288.7 g of potassium salt crystals of 2-acrylamido-2-methylpropane sulfonic acid obtained according to Example 2.

[0397] The solution thus obtained is cooled to between 0 and 5°C and transferred to an adiabatic polymerization reactor, nitrogen bubbling is carried out for 30 minutes in order to eliminate any trace of dissolved oxygen.

[0398] The following are then added to the reactor: - 0.75 g of 2,2'-azobisisobutyronitrile, - 1.5 ml of a 5 g / L (in water) solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane dihydrochloride], - 1.5 ml of a 3 g / L (in water) solution of sodium hypophosphite, - 2.25 ml of a 1 g / L (in water) solution of tert-butyl hydroperoxide, - 2.25 ml of a 1 g / L (in water) solution of ammonium sulfate and iron(II) hexahydrate (Mohr's salt).

[0399] After a few minutes the nitrogen supply is closed and the reactor is shut down. The polymerization reaction proceeds for 1 to 5 hours until a peak of temperature. The resulting rubbery gel is chopped into particles with a size between 1 and 6 mm.

[0400] The gel is then dried and ground to obtain the polymer in powder form. This yields the PL polymer

[0401] P2 and P3 polymers are obtained according to the process of obtaining the PI polymer by varying the amount of sodium hypophosphite.

[0402] A PI' polymer is obtained according to the process for obtaining the PI polymer, but replacing the crystalline form of 2-acrylamido-2-methylpropane sulfonic acid of potassium salt with 243g of 2-acrylamido-2-methylpropane sulfonic acid not being in crystalline form of potassium salt (example 1) and 131.7 g of potassium hydroxide at 50% by weight in water.

[0403] P2' and P3' polymers are obtained according to the process for obtaining the PI polymer, but replacing the crystalline form of 2-acrylamido-2-methylpropane sulfonic acid of potassium salt with 243g of 2-acrylamido-2-methylpropane sulfonic acid not being in crystalline form of potassium salt (example 1) and 131.7 g of potassium hydroxide at 50% by weight in water and varying the amount of sodium hypophosphite.

[0404] Example 1 4: Preparation of homopolymers from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid

[0405] In a 2000 mL beaker, 562.1 g of deionized water and 418.3 g of crystals of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid obtained according to Example 2 are added.

[0406] The solution thus obtained is cooled to between 5 and 10°C and transferred to an adiabatic polymerization reactor; nitrogen bubbling is carried out for 30 minutes to eliminate any trace of dissolved oxygen.

[0407] The following are then added to the reactor: - 0.45 g of 2,2'-azobisisobutyronitrile, - 1.5 ml of a 2.5 g / L (in water) solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane dihydrochloride], - 1.5 ml of a 1 g / L (in water) solution of sodium hypophosphite, - 1.5 ml of a 1 g / L (in water) solution of tert-butyl hydroperoxide, - 1.5 ml of a 1 g / L (in water) solution of ammonium sulfate and iron(II) hexahydrate (Mohr's salt).

[0408] After a few minutes, the nitrogen supply is closed and the reactor is shut down. The polymerization reaction proceeds for 2 to 5 hours until a temperature peak is reached. The resulting rubbery gel is chopped into particles with a size between 1 and 6 mm.

[0409] The gel is then dried and ground to obtain the polymer in powder form. This yields polymer P4.

[0410] A P5 polymer is obtained according to the process of obtaining the P4 polymer by varying the amount of sodium hypophosphite.

[0411] A P4' polymer is obtained according to the process for obtaining polymer P4, but replacing the crystalline form of 2-acrylamido-2-methylpropane sulfonic acid of potassium salt with 352.1 of 2-acrylamido-2-methylpropane sulfonic acid not being in crystalline form of potassium salt (example 1) and 190.8 g of potassium hydroxide at 50% by weight in water.

[0412] A P5' polymer is obtained according to the process for obtaining polymer P4 but by replacing the crystalline form of 2-acrylamido-2-methylpropane sulfonic acid of potassium salt with 243g of 2-acrylamido-2-methylpropane sulfonic acid not being in crystalline form of potassium salt (example 1) and 190.8 g of potassium hydroxide at 50% by weight in water and by varying the amount of sodium hypophosphite.

[0413] Example 1 5: Preparation of an acrylamide / 2-acrylamido-2-methylpropane sulfonic acid / acrylic acid (71 / 9 / 20 mol%) terpolymer

[0414] In a 2000 mL beaker are added 1022g of deionized water, 558.7g of acrylamide in 50% solution, 124.6g of 50% sodium hydroxide, 80g of glacial acrylic acid, 15.3g of urea and 125g of 2-acrylamido-2-methylpropane sulfonic acid crystals (crystalline form of the potassium salt) from Example 2.

[0415] The solution thus obtained is cooled to between 0 and 5°C and transferred to an adiabatic polymerization reactor; nitrogen bubbling is carried out for 30 minutes to eliminate any trace of dissolved oxygen.

[0416] The following are then added to the reactor: - 1.13 g of 2,2'-azobisisobutyronitrile, - 1.5 mL of a 15 g / L solution of 2,2'-azobis[2-(2-imidazolin-2-ylpropane] dihydrochloride, - 1.5 ml of a 3 g / L sodium hypophosphite solution, - 0.75 ml of a 1 g / L tert-butyl hydroperoxide solution, - 2.25 ml of a 1 g / L sodium persulfate solution, - 1.5 ml of a 2 g / L solution of ammonium sulfate and iron(II) hexahydrate (Mohr's salt).

[0417] After a few minutes, the nitrogen supply is closed and the reactor is shut down. The polymerization reaction proceeds for 1 to 5 hours until a temperature peak is reached. The resulting gel is chopped into particles with a size between 1 and 6 mm.

[0418] The gel is then dried and ground to obtain the polymer in powder form. This yields polymer P6.

[0419] A P6' polymer is obtained according to the process for obtaining polymer P5, but replacing the crystalline form of 2-acrylamido-2-methylpropane sulfonic acid of potassium salt with 105.2 of 2-acrylamido-2-methylpropane sulfonic acid not being in crystalline form of potassium salt (example 1) and 181.4 g of potassium hydroxide at 50% by weight in water.

[0420] Example 16: Preparation of a post-hydrolyzed (90 / 10 mol%) acrylamide / 2-acrylamido-2-methylpropane sulfonic acid polymer

[0421] In a 2000 mL beaker are added 761.9 g of deionized water, 574.2 g of acrylamide in 50% solution, 11.7 g of urea and 110 g of 2-acrylamido-2-methylpropane sulfonic acid crystals (crystalline form of potassium salt).

[0422] The solution thus obtained is cooled to between 0 and 5°C and transferred to an adiabatic polymerization reactor; nitrogen bubbling is carried out for 30 minutes to eliminate any trace of dissolved oxygen.

[0423] The following are then added to the reactor: - 0.45 g of 2,2'-azobisisobutyronitrile, - 1.5 mL of a 5 g / L solution of 2,2'-azobis[2-(2-imidazolin-2-ylpropane] dihydrochloride, - 1.5 ml of a 1 g / L sodium hypophosphite solution, -2.25 ml of a 1 g / L tert-butyl hydroperoxide solution, -3.0 ml of a 1 g / L solution of ammonium sulfate and iron(II) hexahydrate (Mohr's salt).

[0424] After a few minutes, the nitrogen supply is closed and the reactor is shut down. The polymerization reaction proceeds for 2 to 5 hours until a temperature peak is reached. The resulting gel is chopped into particles with a size between 1 and 6 mm.

[0425] 500.0 g of previously chopped gel are then mixed with 22.5 g of lye using 50% sodium hydroxide, the mixture is brought and maintained at a temperature of 90°C for a period of 90 minutes.

[0426] The gel is then dried and ground to obtain the polymer in powder form. This yields polymer P7.

[0427] Polymer P7' is obtained according to the process for obtaining polymer 4, but replacing the 110 g of 2-acrylamido-2-methylpropane sulfonic acid in crystalline form of potassium salt with 93.1 g of 2-acrylamido-2-methylpropane sulfonic acid not in crystalline form of potassium salt (example 1) and 50.1 g of potassium hydroxide at 50% concentration. Example 17: Measuring Viscosity

[0428] The reduced viscosity of the polymers prepared in Examples 13 and 14 is measured at 25°C in an aqueous solution of 0.5 M sodium chloride using a Brookfield type LVT viscometer equipped with a UL adapter at 60 rpm.

[0429] Preparation of polymer solutions: 500 mg of dried polymers are dissolved in a beaker containing 290 mL of deionized water at a stirring speed of 500 rpm. 29.25 g of sodium chloride are added to the prepared solutions. The solutions are left under agitation for 10 min at 700 rpm to completely dissolve the salt. The solutions thus prepared are filtered through a cloth with 200 pm pores.

[0430] 16 mL of the prepared solutions are transferred into a cylindrical tube and used to perform a viscosity measurement.

[0431] [Tables5] Polymer Viscosity (cps) PI (invention) 7.1 P1' (counterexample) 4.5 P2 (invention) 5.0 P2* (counterexample) 3.2

[0432] Table 5: Viscosity of polymer solutions of salified 2-acrylamido-2-methylpropane sulfonic acid

[0433] Polymers comprising the new crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid have a higher viscosity than polymers prepared from the classical form of salified 2-acrylamido-2-methylpropane sulfonic acid (potassium).

[0434] Example 18: Preparation of fracturing fluids

[0435] The polymers PI, PI', P4, P4', P6, P6', P7 and P7' in powder form are dissolved under stirring at a concentration of 10 OOppm by weight in a brine composed of water, 85 g of sodium chloride (NaCl) and 33.1 g of calcium chloride (CaCl2, 2H2O) per liter of brine.

[0436] The resulting polymer saline solutions are then injected at a concentration of 0.05 pptg (parts per thousand gallons; 1 gallon = 3.78541 litres) into the brine recirculated for the following Flow Loop tests.

[0437] Example 19: Flow Loop Friction Reduction Tests

[0438] To evaluate the friction reduction of each of the polymers PI, PI', P4, P4', P6, P6', P7 and P7', the reservoir of the Flow Loop was filled with 20 L of brine (brine described in Example 18).

[0439] The brine is then recirculated in the Flow Loop at a rate of 24 gallons per minute. The polymer is added at a concentration of 0.5 pptg to the recirculating brine.

[0440] The percentage reduction in friction is thus determined by measuring pressure variations measured inside the Flow Loop.

[0441] Figures 14 to 17 are graphs showing the percentage reduction in friction as a function of time for each type of polymer. ([Fig. 14]: PI, PI' polymers; [Fig. 15]: homopolymers, P4, P4'; [Fig. 16]: ter-polymers P6, P6'; [Fig. 17]: post-hydrolyzed P7, P7').

[0442] These figures demonstrate that the injection fluids according to the invention allow for improved friction reduction. Indeed, when the polymers contain ATBS in the crystalline form of the potassium salt, the friction reduction is better.

[0443] Example 20: Measurement of the filtration quotient of polymer solutions

[0444] Filtration tests were carried out on 3 polymers obtained from the non-crystalline form of 2-acrylamido-2-methylpropane sulfonic acid PI', P2' and P3', obtained as described in Example 13, and on 3 polymers obtained from the crystalline form as potassium salt of 2-acrylamido-2-methylpropane sulfonic acid PI, P2, P3, obtained as described in Example 13.

[0445] The polymer solutions were obtained at an active concentration of 1,000 ppm in a brine containing water, 30,000 ppm NaCl, and 3,000 ppm CaCl2·2H2O (ppm by weight). The filtration quotient (FR) was measured on filters with a pore size of 1.2 pm, representative of low-permeability deposits.

[0446] [Tableauxô] Form of ATBS potassium salt used Molecular weight (in millions of Da) Filtration quotient PI Crystalline 6.7 1.08 P2 Crystalline 9.2 1.06 P3 Crystalline 11.5 1.07 PI' Non-crystalline 6.6 1.13 P2' Non-crystalline 9.2 1.17 P3' Non-crystalline 11.4 1.45

[0447] Table 6: Polymers tested for filterability quotient

[0448] We can observe in Table 6 that, at equivalent molecular weights, the polymers obtained from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid (PI, P2 and P3) always exhibit a FR lower than that of polymers obtained from the non-crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid (PI', P2' and P3'). This difference becomes increasingly significant as the molecular weight of the polymer increases.

[0449] Example 21: Measurement of the resistance to chemical degradation of solutions of polymers of equivalent molecular weight

[0450] Chemical degradation resistance tests of polymers P3 and P3' were carried out under aerobic conditions in the presence of different iron(II) concentrations (2, 5, 10, and 20 ppm) in a brine composed of water, 37,000 ppm NaCl, 5,000 ppm Na2SO4, and 200 ppm NaHCO3 (ppm by weight). These tests were performed on a polymer obtained from the non-crystalline form of the potassium salt of 2-acrylamido-2-methylpropanesulfonic acid (P3') and on a polymer obtained from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropanesulfonic acid (P3). Both polymers have the same chemical composition. The results obtained after 24 hours of contact between the polymer solution and the contaminant are shown in [Fig. 18].

[0451] We can observe that, for each concentration of iron(II), the P3 polymer undergoes a less significant loss of viscosity than that of the equivalent P3' polymer.

[0452] Example 22: Measurement of the resistance to thermal degradation of solutions of polymers of equivalent molecular weight

[0453] Thermal degradation resistance tests of polymers P3 and P3' were carried out under anaerobic conditions at an active concentration of 2,000 ppm in a brine composed of 30,000 ppm NaCl and 3,000 ppm CaCl2·2H2O (ppm by weight). These tests were performed on a polymer obtained from the non-crystalline form of the potassium salt of 2-acrylamido-2-methylpropanesulfonic acid (P3') and on a polymer obtained from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropanesulfonic acid (P3). Both polymers have the same chemical composition. The polymer solutions were aged for 6 months at 90°C. The results obtained are presented in [Fig. 19] in terms of viscosity loss. We can observe that P3 loses less viscosity than the equivalent polymer P3'.

[0454] Example 23: Measurement of the filtration quotient of polymer solutions

[0455] Filtration tests were carried out on 2 polymers obtained from the non-crystalline form of 2-acrylamido-2-methylpropane sulfonic acid P4', P5', obtained as described in Example 14, and on 2 polymers obtained from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid P4 and P5, obtained as described in Example 14.

[0456] The polymer solutions were obtained at an active concentration of 1,000 ppm in a brine containing water, 30,000 ppm NaCl, and 3,000 ppm CaCl2·2H2O (ppm by weight). The filtration quotient (FR) was measured on filters with a pore size of 1.2 pm, representative of low-permeability deposits.

[0457] [Tables?] Potassium salt form of ATBS used Molecular weight (in millions of Da) Filtration quotient P4 Crystalline 3.1 1.07 P5 Crystalline 5.5 1.10 P4' Non-crystalline 3.0 1.18 P5' Non-crystalline 5.4 1.63

[0458] Table 7: Polymers tested for filterability quotient

[0459] We can observe in Table 7 that, at equivalent molecular weights, polymers obtained from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid (P4, P5) always exhibit a lower FR than polymers obtained from the non-crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid (P4', P5'). This difference becomes increasingly significant as the molecular weight of the polymer increases.

[0460] Example 24: Measurement of the resistance to chemical degradation of solutions of P6 and P6' polymers

[0461] Chemical degradation resistance tests of polymers P5 and P5' were carried out under aerobic conditions in the presence of different iron(II) concentrations (2, 5, 10, and 20 ppm) in a brine composed of water, 37,000 ppm NaCl, 5,000 ppm Na2SO4, and 200 ppm NaHCO3 (ppm by weight). These tests were performed on a polymer obtained from the non-crystalline form of the potassium salt of 2-acrylamido-2-methylpropanesulfonic acid (P5') and on a polymer obtained from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropanesulfonic acid (P5). Both polymers have the same chemical composition. The results obtained after 24 hours of contact of the polymer solution with the contaminant are shown in [Fig. 20].

[0462] We can observe that for each concentration of iron(II) the polymer P5 loses less viscosity than the equivalent polymer P5'.

[0463] Example 25: Measurement of the filtration quotient of polymer solutions

[0464] Filtration tests were carried out on a polymer obtained from the non-crystalline form of 2-acrylamido-2-methylpropane sulfonic acid P7', obtained as described in Example 16, and on a polymer obtained from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid P7, obtained as described in Example 16.

[0465] The polymer solutions were obtained at an active concentration of 1,000 ppm in a brine containing water, 30,000 ppm NaCl, and 3,000 ppm CaCl2·2H2O (ppm by weight). The filtration quotient (FR) was measured on filters with a pore size of 3 µm, representative of low-permeability deposits.

[0466] [Tables8] Form of potassium salt of ATBS used Molecular weight (in millions of Da) Filtration quotient P7 Crystalline 26 1.09 P7' Non-crystalline 7? 1.14

[0467] Table 8: Polymers tested for filterability quotient

[0468] We can observe in Table 8 that, despite a higher molecular weight, the polymer obtained from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid (P7) has an equivalent FR to that of the polymer obtained from the non-crystalline form of 2-acrylamido-2-methylpropane sulfonic acid (P7'). Example 26: Treatment of a mining effluent

[0469] The polymers PI and PI' are dissolved in tap water to obtain aqueous solutions having a polymer concentration of 0.4% by weight relative to the total weight of the solution. Both solutions are mechanically stirred at 500 rpm until the polymers are completely dissolved and clear, homogeneous solutions are obtained.

[0470] A series of flocculation tests is carried out on a mining effluent from a coal mine, and having a solids content of 18.2% by weight.

[0471] A quantity of each solution, corresponding to a polymer dosage of 280 g of polymer per tonne of dry matter of the mine effluent, is added to 200 g of mine effluent and then a complete mixing is carried out manually until optimal flocculation and water release is observed.

[0472] The result is expressed using the LNE (Net Water Release), which corresponds to the total amount of water recovered 1 hour after the flocculation test less the amount of water unduly added during the incorporation of the aqueous polymeric solution into the suspension. The same LNE is calculated after 24 hours, providing a good indication of the maximum water release.

[0473] The LNE with polymer PI' is 55 mL versus 80 mL with polymer PL. The LNE after 24h with polymer PI' is 65 mL versus 85 mL with polymer PL. The water released during flocculation with polymer PI' is clearer than that released during flocculation with polymer PL.

[0474] The results of this experiment clearly demonstrate that the use of 2-acrylamido-2-methylpropane sulfonic acid in crystalline form potassium salt according to The invention makes it possible to obtain a more efficient polymer for flocculating a mining effluent from a coal mine. Example 27: Treatment of an alumina effluent

[0475] Another series of tests is carried out with the PI and PI' polymers on a red mud from a Bayer process, and having a solids content of 22.8% by weight.

[0476] The same test protocol as that used for Example 25 is applied, with the difference that the quantity of polymer added is here 740 g of polymer per tonne of dry red mud.

[0477] The LNE with the PI' polymer is 35 mL versus 48 mL with the PL polymer. The LNE after 24h with the PI' polymer is 40 mL versus 55 mL with the PL polymer. The water released during flocculation with the PI polymer is clearer than that released during flocculation with the PI' polymer.

[0478] The results of this experiment clearly demonstrate that the use of 2-acrylamido-2-methylpropane sulfonic acid in crystalline form according to the invention makes it possible to obtain a more effective polymer for flocculating red mud from a Bayer process. Prepared polymers

[0479] Table 9 summarizes the composition and molecular weight of the prepared polymers.

[0480] [Tables9] Polymer Monomers (moEo) Molecular weight (in millions of Da) Filtration quotient AM ATBS.K ATBS-exl AA.Na PI 75 25 - - 6.7 1.08 PT 75 - 25 - 6.6 1.13 P2 75 25 - 9.2 1.06 P2' 75 25 - 9.2 1.17 P3 75 25 - 11.5 1.07 P3' 75 - 25 - 1L4 1.45 P4 100 3.1 1.07 P4' - - 100 - 3.0 1.18 P5 - 100 - - 5.5 1.10 P5' - - 100 - 5.4 1.63 P6 71 9 - 20 Not measured Not measured P6' 71 - 9 20 Not measured Not measured P7 71 9 - 20 26 1.09 P7' 71 - 9 20 22 1.14

[0481] Table 9: Nature of the polymers prepared

[0482] In Table 9, the following abbreviations are used: - AM = acrylamide - ATBS.K = crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid - ATBS-exl = non-crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid (according to example 1) - AA.Na = sodium acrylate

Claims

Demands

1. Crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° 2-theta degrees (+ / - 0.1°).

2. Crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid according to claim 1, characterized in that it exhibits a Fourier transform infrared spectrum comprising peaks at 3293cm 3075cm 3000cm *, 2979cm 1655cm1, 1625cm1, 1550cm1, 1405cm1, 1209cm1, 1190cm1, 1162cm1, 1048cm ', 979cm1, 824cm1, 803cm1, 756cm ', 633cm1, 523cm1 (+ / - 8cm ').

3. Crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid according to claim 1 or 2, characterized in that it has a minimum ignition energy greater than 500 mJ.

4. Crystalline form of potassium salt of 2-acrylamido-2-methylpropane sulfonic acid according to any one of claims 1 to 3, characterized in that it exhibits 2 thermal phenomena with the differential scanning calorimetry technique, at 79.4°C; 207°C (+ / -10°C).

5. A process for manufacturing the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid according to any one of claims 1 to 4, comprising at least the following successive steps; 1) mixing 2-acrylamido-2-methylpropane sulfonic acid with an aqueous solution SA1 and at least one potassium salt to form an aqueous solution or aqueous suspension SA2; 2) distilling at a pressure below 700 mbar absolute of the aqueous solution or aqueous suspension SA2 to form a suspension Si; 3) solid / liquid separation of the suspension Si and isolation of the crystals of the suspension Si obtained at the end of step 3) in the form of a composition Ci.

6. A method according to claim 5, characterized in that the concentration of the aqueous solution or aqueous suspension SA2 in potassium salt is between 1% by weight and saturation, relative to the weight of the aqueous solution or aqueous suspension sa2.

7. A process according to claim 5 or 6, characterized in that, in step 1), 2-acrylamido-2-methylpropane sulfonic acid and potassium salt are added in several stages.

8. A process according to any one of claims 5 to 7, characterized in that the aqueous solution or aqueous suspension SA2 comprises between 10 and 90% by weight of 2-acrylamido-2-methylpropane sulfonic acid relative to the total weight of the aqueous solution or aqueous suspension SA2.

9. A method according to any one of claims 5 to 8, characterized in that the potassium salt is selected from potassium hydroxide, potassium carbonate, potassium bicarbonate or mixtures thereof.

10. Polymer obtained at least in part from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° 2-theta degrees (+ / - 0.1°).

11. A process for treating a suspension of solid particles in water, comprising contacting said suspension with at least one water-soluble polymer obtained at least in part from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° 2-theta degrees (+ / - 0.1°).

12. A process for flocculating a suspension of solid particles in water, comprising contacting said suspension with at least one water-soluble polymer obtained at least in part from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks of 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° degrees 2-theta (+ / - 0.1°).

13. A process for enhanced hydrocarbon recovery comprising the following steps: a) Preparation of an injection fluid comprising at least one water-soluble polymer of 2-acrylamido-2-methylpropane sulfonic acid, with water or with brine, the 2-acrylamido-2-methylpropane sulfonic acid being, prior to polymerization, at least partly in the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° degrees 2-theta (+ / - 0.1°); b) Injection of the injection fluid into a subsurface formation; c) Sweeping of the subsurface formation using the injected fluid; d) Recovery of an aqueous and hydrocarbon mixture.

14. Fracture fluid comprising at least one aqueous phase, a propping agent and at least one water-soluble polymer obtained at least in part from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° 2-theta degrees (+ / - 0.1°).

15. A method for preparing a fracturing fluid according to claim 14, by adding, in water or brine, at least one water-soluble polymer obtained at least in part from the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid, and in which the water-soluble polymer is, before formation of the fracturing fluid: - either in powder form; - or in the form of a water-in-oil inverse emulsion; - or in the form of an aqueous or oily particulate polyphasic suspension, the crystalline form of the potassium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 13.1°; 14.4°; 16.3°; 19.8°; 23.5°; 24.3°; 26.9°; 27.6°; 29.3°; 30.6°; 31.6°; 34.3°; 36.1°; 41.7°; 44.6°; 46.7° degrees 2-theta (+ / - 0.1°).

16. A method for hydraulically fracturing an unconventional underground oil or gas reservoir, comprising preparing a fracturing fluid according to claim 14, and injecting said fracturing fluid into an underground reservoir.

17. A method for reducing friction of a fracturing fluid in a hydraulic fracturing operation of an unconventional underground oil or gas reservoir, comprising the preparation of a fracturing fluid according to claim 14, and the injection of said fracturing fluid into an underground reservoir.

18. Use of the polymer according to claim 10 in well drilling; well cementing; conformance; diversion; open, closed or semi-closed circuit water treatment; fermentation must treatment; sludge treatment; construction; paper or cardboard manufacturing; battery manufacturing; wood processing; hydraulic composition processing; cosmetic formulation; detergent formulation; textile manufacturing; geothermal energy; sanitary diaper manufacturing; or agriculture.

19. Use of the polymer according to claim 10 as a coagulant, binding agent, absorbent, draining agent, charge retention agent, dehydrating agent, conditioning agent, stabilizing agent, fixing agent, film-forming agent, sizing agent, superplasticizing agent, clay inhibitor or dispersant.

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