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

Abstract

The present invention relates to a crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 11.7°; 12.2°; 13.2°; 13.5°; 15.6°; 16.8°; 17.8°; 18.5°; 19.1°; 20.6°; 21.4°; 23.3°; 25.1°; 25.8°; 26.9°; 29.1°; 29.5°; 31.0°; 33.0°; 33.6°; 34.4°; 35.2°; 35.9°; 37.1°; 38.4°; 39.6°; 41.1°; 42.9°; 45.1°; 46.0°; 47.2°; 47.6°, degrees 2-theta (+ / - 0.1°).

Description

Title of the invention: Crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid Scope 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 sodium salt of 2-acrylamido-2-methylpropane sulfonic acid. The invention also relates to the process for obtaining the crystalline form of the sodium 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 the continuous manufacture of 2-acrylamido-2-methylpropane sulfonic acid. The 2-acrylamido-2-methylpropane sulfonic acid is subsequently separated from acrylonitrile, usually by filtration, 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-methylpropanesulfonic 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-methylpropanesulfonic acid powder, there is also a risk of chemical burns through skin, eye, or lung contact by inhaling fine particles suspended in the air during handling operations. powder.

[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 sodium 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 sodium salt has a longer shelf life than an aqueous solution of the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid.

[0019] The use of the crystalline form of the sodium 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 improved performance of polymers obtained from the crystalline form of the sodium salt of the invention allows for a reduction in the quantity of product required for the applications in which they are used, thereby reducing 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 sodium salt of 2-acrylamido-2-methylpropane sulfonic acid".

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

[0022] The present invention also relates to the use of the crystalline form of the sodium 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 the use of a polymer obtained at least in part from the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid 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; the battery field; wood processing; hydraulic composition processing (concrete, cement, mortar and aggregates); cosmetic product formulation; detergent formulation; textile manufacturing; geothermal energy; sanitary diaper manufacturing; or agriculture.

[0024] Finally, the present invention also relates to the use of a polymer obtained at least in part from the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid as a coagulant, binding agent, absorbent, draining agent, charge retention agent, conditioning agent, stabilizing agent, fixing agent, film-forming agent, sizing agent, superplasticizing agent, clay inhibitor or dispersant. Description of the invention

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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:

[0029] [Math.l] [monomerl^j [mono mother] left

[0030] 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.

[0031] By "X and / or Y" means "X", or "Y", or "X and Y".

[0032] 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.

[0033] Crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid

[0034] The present invention relates to a crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 11.7°; 12.2°; 13.2°; 13.5°; 15.6°; 16.8°; 17.8°; 18.5°; 19.1°; 20.6°; 21.4°; 23.3°; 25.1°; 25.8°; 26.9°; 29.1°; 29.5°; 31.0°; 33.0°; 33.6°; 34.4°; 35.2°; 35.9°; 37.1°; 38.4°; 39.6°; 41.1°; 42.9°; 45.1°; 46.0°; 47.2°; 47.6° degrees 2-theta. The uncertainty of these peaks is generally on the order of + / - 0.1°.

[0035] X-ray crystallography, also known as X-ray diffractometry, is an analytical technique used to study the structure of crystalline matter at the atomic scale. It relies on the physical phenomenon of X-ray diffraction. A diffractometer with a copper source can be used.

[0036] A powder formed from a given crystalline phase will always give rise to diffraction peaks in the same directions. This diffraction pattern thus forms a 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.

[0037] 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).

[0038] This technique is used to characterize matter, in particular the different crystalline forms that can exist for the same chemical molecule, also called polymorphs.

[0039] Another aspect of the invention relates to a crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid having a Fourier transform infrared spectrum comprising peaks at 3576 cm⁻¹, 3485 cm⁻¹, 3310 cm⁻¹*, 3079 cm⁻¹, 2975 cm⁻¹, 1658 cm⁻¹*, 1629 cm⁻¹*, 1543 cm⁻¹, 1403 cm⁻¹, 1321 cm⁻¹, 1301 cm⁻¹*, 1205 cm⁻¹, 1187 cm⁻¹, 1163 cm⁻¹, 1046 cm⁻¹*, 980 cm⁻¹*, 629 cm⁻¹. The uncertainty of these peaks is generally on the order of + / - 8 cm⁻¹.

[0040] Infrared measurement is carried out by Fourier transform, for example using a Perkin Elmer Spectrum 100 type spectrometer equipped with a single reflection ATR polarization accessory, the accuracy of which is 8 cm1.

[0041] 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 an organic compound.

[0042] In general, 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).

[0043] Another aspect of the invention relates to a crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid having a minimum ignition energy greater than 500 mJ, preferably greater than 1000 rnJ.

[0044] The minimum ignition energy represents the minimum energy that must be supplied to a compound to cause ignition. The energy can be electrical or thermal. The minimum ignition energy is essential information for considering the risk of explosion during the handling of the product (transfer, storage, reaction, shaping, etc.).

[0045] 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).

[0046] In the context of solids, this energy is the minimum energy of a spark electrical potential to ignite a dust cloud. The higher the minimum ignition energy value, the lower the risk posed by the solid during use, handling, and storage.

[0047] The measurement of the minimum ignition energy is carried out according to the standard NF EN 13821.

[0048] Another aspect of the present invention relates to a crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid exhibiting four thermal phenomena with the differential scanning calorimetry technique, at 49.8°C; 144.8°C; 169.8°C and 254.3°C. The uncertainty in observing these phenomena is generally on the order of 10°C (+ / -10°C), advantageously 5°C or less.

[0049] 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.

[0050] Process for manufacturing the crystalline form of sodium salt

[0051] The present invention also relates to the process for manufacturing the crystalline form of the sodium 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 sodium 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 sodium salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0052] By sodium salt(s) in step 1), means at least one inorganic salt(s), for example sodium hydroxide, sodium carbonate, sodium bicarbonate or mixtures thereof.

[0053] 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.

[0054] The process for manufacturing the crystalline form of the sodium salt can be carried out on any form of 2-acrylamido-2-methylpropane sulfonic acid, such as the needle form or the hydrated form.

[0055] The manufacturing process can be carried out on any degree of purity of 2-acrylamido-2-methylpropane sulfonic acid.

[0056] 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.

[0057] Step 1) of the process for manufacturing the crystalline form of sodium salt:

[0058] 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.

[0059] 2-Acrylamido-2-methylpropane sulfonic acid can be added to an aqueous solution S Ai before, after or in parallel with sodium salt, preferably the addition is done in parallel.

[0060] Advantageously, the concentration of the aqueous solution or aqueous suspension SA2 in sodium 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.

[0061] 2-Acrylamido-2-methylpropane sulfonic acid and the sodium salt can be added all at once or in several stages. Preferably, they are added in several stages.

[0062] When the addition is made in several stages, the 2-acrylamido-2-methylpropane sulfonic acid and the sodium salt are added in fractions.

[0063] When 2-acrylamido-2-methylpropane sulfonic acid and sodium 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.

[0064] There is no limitation as to the order of addition between 2-acrylamido-2-methylpropane sulfonic acid and the sodium 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 sodium salt, or vice versa), or alternately (a first fraction of 2-acrylamido-2-methylpropane sulfonic acid, then a first fraction of the sodium salt, followed by a second fraction of 2-acrylamido-2-methylpropane sulfonic acid then a second fraction of the sodium salt and so on), preferably they are added at the same time.

[0065] 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 sodium salt) can start before the end of the addition of the first compound.

[0066] 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%.

[0067] 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%.

[0068] 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%.

[0069] In a particular mode, the process is carried out continuously; in this case, 2-acrylamido-2-methylpropane sulfonic acid and sodium salt are added continuously.

[0070] 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.

[0071] 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.

[0072] In a particular mode, the aqueous solution or aqueous suspension SA2 may comprise one or more organic solvents.

[0073] The amount of organic solvent may vary depending on the temperature, the amount of 2-acrylamido-2-methylpropanesulfonic acid, or the sodium salt. This amount is not limited as long as it does not prevent the formation of the crystalline form of the sodium 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. In general, the aqueous solution or aqueous suspension SA2 comprises more water (by volume) than organic solvent.

[0074] 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.

[0075] 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.

[0076] 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).

[0077] Preferably, the organic solvent is chosen from acrylonitrile, isopropanol, acrylic acid, acetic acid, or mixtures thereof. Preferably, the organic solvent is acrylonitrile.

[0078] 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.

[0079] 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.

[0080] In a preferred mode according to the invention, the aqueous solution or aqueous suspension SA2 does not contain any organic solvent.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] Step 2) of the process for manufacturing the crystalline form of sodium salt:

[0085] 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".

[0086] When the aqueous solution or aqueous suspension SA2 is distilled, typically by passing through an evaporator, crystals of the sodium 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-propanesulfonic acid, at least one sodium salt, and crystalline solid particles of the sodium salt of acrylamido-2-methyl-2-propanesulfonic acid.

[0087] 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.

[0088] 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 suspension Si.

[0089] 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 lower than atmospheric pressure, is advantageously between 1 second and 600 seconds, Preferably between 3 and 300 seconds, more preferably between 30 and 100 seconds. The residence time corresponds to the time required to complete step 2), that is, the time required to prepare the Si suspension by distilling the aqueous solution or aqueous suspension SA2. In other words, in the case of an evaporator, it is the residence time of 2-acrylamido-2-methyl-2-propanesulfonic acid (and / or its crystalline form of sodium 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 sodium salt present in the aqueous solution or aqueous suspension SA2.A person skilled in the art will know how to adjust this residence time in order to obtain 2-acrylamido-2-propanesulfonic acid in crystalline form of sodium salt depending on the quantity of the constituents of the aqueous solution or aqueous suspension SA2.

[0090] Distillation can be carried out in a vertical or horizontal evaporator. Preferably, it is carried out in a vertical evaporator.

[0091] The aqueous solution or aqueous suspension SA2 can flow co-currently or counter-currently with the vapors generated by evaporation. Preferably, it flows counter-currently with the vapors in the distillation apparatus. In other words, the aqueous solution or aqueous suspension SA2 is preferably introduced into the distillation apparatus, advantageously an evaporator, co-currently or counter-currently with respect to the distilled solvent.

[0092] 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.

[0093] 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).

[0094] In a particular embodiment, 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.

[0095] Heating during distillation can be achieved using various technologies. As Examples, but not limited to, include heating with steam, hot water, electricity, vapor compression, or a heat pump. The distillation unit itself can be a double-walled type, with a hot heat transfer fluid circulating between the two walls.

[0096] 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.

[0097] When the aqueous solution or aqueous suspension SA2 is heated, the temperature is advantageously higher than the temperature of step 1).

[0098] The temperature rise of the 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.

[0099] 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 heated at a rate of 10°C per hour until the final temperature is reached.

[0100] 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 crystalline sodium salt form. Step 2") then consists of lowering the temperature of the aqueous solution or aqueous suspension SA2.

[0101] 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.

[0102] 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').

[0103] 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.

[0104] 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.

[0105] During the cooling of the aqueous solution or aqueous suspension SA2,

[0106]

[0107]

[0108]

[0109]

[0110] [YES] Crystals of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid form and a Sp suspension is obtained In a particular method, previously obtained sodium salt crystals of 2-acrylamido-2-methylpropane sulfonic 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, final product purity, and potentially, yield. The sodium salt crystals of 2-acrylamido-2-methylpropane sulfonic acid thus added advantageously exhibit a powder X-ray diffraction pattern with peaks at 11.7°. 12.2°; 13.2°; 13.5°; 15.6°; 16.8°; 17.8°; 18.5°; 19.1°; 20.6°; 21.4°; 23.3°; 25.1°; 25.8°; 26.9°; 29.1°; 29.5°; 31.0°; 33.0°; 33.6°; 34.4°; 35.2°; 35.9°; 37.1°; 38.4°; 39.6°; 41.1°; 42.9°; 45.1°; 46.0°; 47.2°; 47.6° degrees 2-theta (+ / - 0.1°). 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 SAp According to another particular embodiment of the invention, the distilled solvent can be recycled partially or totally, generally to wash the sodium 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. The resulting Sp suspension advantageously comprises between 30 and 80% by weight of 2-acrylamido-2-methylpropane sulfonic acid in crystalline sodium salt form, relative to the total weight of the Sp suspension preferably between 50 and 60% by weight. During step 2), the pH is advantageously greater than 10, preferably greater than 11, more preferably greater than 12, and even more preferably the pH is between 13 and 14. Step 3 of the process for manufacturing the crystalline form of sodium salt:

[0112] The sodium 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

[0113] 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 se- Liquid / solid separation can also be carried out by gravity settling.

[0114] Step 3) is advantageously carried out at a temperature between -20 and 40°C, preferably between -5 and 30°C.

[0115] Preferably after step 3) of liquid / solid separation, the sodium salt crystals of 2-acrylamido-2-methylpropane sulfonic acid are not dried.

[0116] The isolated composition Ci has a sodium salt crystal content of 2-acrylamido-2-methylpropane sulfonic 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 Cp. The remainder of composition Ci may be water and / or solubilized sodium salt of 2-acrylamido-2-methylpropane sulfonic acid, and / or sodium salt introduced in step 1).

[0117] At the end of this step 3), the crystals are characterized as being crystals of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0118] 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).

[0119] 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.

[0120] Step 4) of the process for manufacturing the crystalline form of sodium salt:

[0121] In an optional step 4), the composition Ci containing the crystals obtained at the product from step 3) is washed using a washing solution.

[0122] The washing solution may be water, an aqueous solution of sodium salt (saturated or unsaturated), or a solution (saturated or unsaturated) of sodium salt of 2-acrylamido-2-methylpropane sulfonic acid (advantageously in the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid), preferably it is a saturated solution of a sodium salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0123] Examples of sodium salt solutions include a solution of sodium hydroxide, sodium carbonate, sodium bicarbonate, or mixtures thereof.

[0124] The washing solution may comprise one or more organic solvents.

[0125] The amount of organic solvent may vary depending on the temperature, the amount of sodium salt of 2-acrylamido-2-methylpropane sulfonic acid or the amount of sodium salt.

[0126] Advantageously, the washing solution does not include any organic solvent.

[0127] 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 their mixtures. Preferably, the organic solvent is chosen from acrylonitrile, isopropanol, acetic acid, or mixtures thereof. More preferably, the organic solvent is acrylonitrile.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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 sodium salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0132] The sodium 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] The pH of the washing solution in step 5 is advantageously controlled between 6 and 14, preferably between 8 and 14.

[0137] Step 5) of the process for manufacturing the crystalline form of sodium salt:

[0138] 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.

[0139] The drying step can be carried out using 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 dryer, microwave dryer, heated agitated smoothing filter dryer, high-frequency radiation dryer, infrared dryer, atom- (misation).

[0140] The drying operation can be carried out at atmospheric pressure or under vacuum.

[0141] The drying step can be carried out discontinuously (batch) or continuously.

[0142] Other steps in the process of manufacturing the crystalline form of sodium salt

[0143] 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 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.

[0144] Preferably, the inhibitor is paramethoxyphenol or 4-hydroxy-2,2,6,6-tetramethyl(piperidin-l-yl)oxyl.

[0145] 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.

[0146] 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).

[0147] The manufacturing process (steps 1) to 5)) can be carried out continuously or discontinuously (in batch). Polymer

[0148] The present invention also relates to the use of the new crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid for the manufacture of polymers.

[0149] The present invention therefore also relates to a polymer obtained at least from 2-acrylamido-2-methylpropane sulfonic acid, at least a portion of which is in crystalline form of the sodium salt having a ray diffraction pattern X on powder including peaks at 11.7°; 12.2°; 13.2°; 13.5°; 15.6°; 16.8°; 17.8°; 18.5°; 19.1°; 20.6°; 21.4°; 23.3°; 25.1°; 25.8°; 26.9°; 29.1°; 29.5°; 31.0°; 33.0°; 33.6°; 34.4°; 35.2°; 35.9°; 37.1°; 38.4°; 39.6°; 41.1°; 42.9°; 45.1°; 46.0°; 47.2°; 47.6° degrees 2-theta (+ / - 0.1°).

[0150] The polymer is obtained at least in part from the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid, and advantageously from less one other monomer selected from: hydrophilic nonionic monomers, hydrophilic anionic monomers (distinct from the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid), hydrophilic cationic monomers, hydrophilic zwitterionic monomers, and hydrophobic monomers.

[0151] It can therefore be a polymer of several distinct monomers or a homopolymer.

[0152] The 2-acrylamido-2-methylpropane sulfonic acid used to obtain the polymer is advantageously at least 10 mol% in the crystalline form of the sodium 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 the 2-acrylamido-2-methylpropane sulfonic acid is in the crystalline form of the sodium salt.

[0153] 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 sodium 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 sodium salt.

[0154] 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 sodium 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 sodium salt.

[0155] 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 sodium 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 sodium salt.

[0156] In a particular mode, the polymer is a homopolymer of the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0157] In a particular embodiment, the polymer is a polymer obtained from 2-acrylamido-2-methylpropane sulfonic acid (advantageously at least 10 mol% of which is in the crystalline form of the sodium salt) and at least one non-ionic monomer. Polymer composition

[0158] The polymer is obtained from the crystalline form of the sodium 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 mixtures thereof. It may be a polymer of several distinct monomers or a homopolymer.

[0159] 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, 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 in the C1-C5 position, more advantageously in the C1-C3 position. They are preferably linear alkyls. Preferably, the hydrophilic non-ionic monomer is acrylamide.

[0160] 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%.

[0161] Advantageously, the hydrophilic anionic monomer(s), other than 2-acrylamido-2-methylpropane sulfonic acid in crystalline sodium salt form, that may be used in the context of the invention may be selected from a wide range. These monomers may have vinyl functionalities (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 the acid acrylic; methacrylic acid; dimethylacrylic acid; itaconic acid; crotonic acid; maleic acid; fumaric acid; acrylamido-undecanoic acid; 3-acrylamido-3-methylbutanoic acid; maleic anhydride; strong acid monomers having, 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 sodium 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.

[0162] The polymer advantageously comprises between 0 and 99 mol% of hydrophilic anionic monomer(s) (distinct from the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic 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 sodium salt of 2-acrylamido-2-methylpropane sulfonic acid according to the invention.

[0163] In a particular mode, the hydrophilic anionic monomer(s), other than 2-acrylamido-2-methylpropane sulfonic acid in crystalline form of the sodium salt, can be salified.

[0164] 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.

[0165] 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 sodium salt.

[0166] Salification can take place before, during or after polymerization.

[0167] In a particular mode, the polymer advantageously comprises between 1 and 100 mol% of hydrophilic anionic monomer(s) in salified form, preferably between 50 and 100 mol%. These percentages include the monomer in the form crystalline of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid according to the invention.

[0168] 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), dimethyldiallylammonium chloride (DADMAC), acrylamido propyltrimethyl ammonium chloride (APTAC), and methacrylamido propyltrimethyl ammonium chloride (MAPTAC).

[0169] 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.

[0170] 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.

[0171] In a preferred embodiment according to the invention, the hydrophilic cationic monomer is selected from diallyldialkyl ammonium salts such as diallyl dimethyl ammonium chloride (DADMAC); acidified or quaternized dialkylaminoalkylacrylamides; acidified or quaternized dialkylaminoalkylmethacrylamides, such as methacrylamidopropyl trimethyl ammonium chloride (MAPTAC), acrylamidopropyl trimethyl ammonium chloride (APTAC), and mixtures thereof. Advantageously, the alkyl groups are in the C1-C3 configuration.

[0172] The polymer advantageously comprises between 0 and 20 mol% of hydrophilic ca-tionic monomer(s), preferably between 0 and 6 mol%.

[0173] 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 the me dimethylaminoethyl thacrylate such as 2-((2-(methacryloyloxy)ethyl)dimethyl-ammonio)ethane-l-sulfonate, 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-l-sulfonate, 3-((3-acrylamidopropyl)dimethylammonio)propane-1-sulfonate, 4-((3-acrylamidopropyl)dimethylammonio)butane-1-sulfonate, [3-(acryloyloxy) propyl] (dimethylammonio) acetate, derivatives of dimethylamino propyl methylacrylamide 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.

[0174] The polymer advantageously comprises 0 and 20 mol% of hydrophilic zwitterionic monomer(s), more preferably between 0 and 10 mol%.

[0175] 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.

[0176] Among these hydrophobic monomers: - Alkyl groups are preferably located at C3-C2O, more preferably at C3-C8. Alkyls at C6-C2O are preferably linear alkyls, while alkyls at C3-C5 are preferably branched. - the arylalkyl groups are preferably in C7-C25, more preferably in C7-C15, - 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.

[0177] 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.

[0178] Monomers having 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.

[0179] 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, larhodamine and its derivatives, N-dibenzosuberenylacrylamide and its derivatives, N-9-xanthenyllacrylamide and its derivatives, naphthalic derivatives, fluorescein and its derivatives, pyrene and its derivatives, carbostyril and its derivatives, pyrazoline and its derivatives, allyl dibenzo-suberenol and its derivatives, chinconicine and its derivatives, quininone and its derivatives, luminol and its derivatives, and cinchoninone and its derivatives, and mixtures thereof.

[0180] 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 cyclic ketene acetals, thionolactones and mixtures thereof.

[0181] 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).

[0182] The thionolactone is advantageously chosen from: Dibenzo[c,e]oxepine(7H)-5-thione (DOT), e-thionocaprolactone, 3,3-dimethyl-2,3-dihydro-5Hbenzo[e][l,4]dioxepine-5-thione (DBT) and mixtures thereof. Preferably, it is 3,3-dimethyl-2,3-dihydro-5Hbenzo[e][l,4]dioxepine-5-thione.

[0183] In a particular embodiment, the polymer may comprise at least one LCST group.

[0184] According to the general knowledge of those skilled in the art, an LCST group corresponds to a group whose solubility in water, for a given concentration, is modified 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 a loss of transparency, which may be due to A precipitation, aggregation, gelation, or viscosification of the medium can occur. The minimum transition temperature is called the LCST (Lower Critical Solubility Temperature). For each group concentration at the LCST, 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.

[0185] In a particular embodiment, the polymer may comprise at least one UCST group.

[0186] 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.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] The branching agent is advantageously chosen from: - Structuring agents, which may be chosen from the group comprising monomers with polyethylene unsaturation (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 functions, - monomers having at least one unsaturated function and one epoxy function, - macroinitiators such as polyperoxides, polyazo compounds, and polytransfer agents such as polymer-capturing polymers and polyols, - functionalized polysaccharides.

[0191] 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.

[0192] 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.

[0193] When the polymer is water-soluble and includes a branching agent, the polymer remains 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.

[0194] In a preferred mode, the polymer is a water-soluble polymer not comprising a branching agent.

[0195] In a particular mode, the polymer may comprise a transfer agent.

[0196] 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 methylsulfonate; and mixtures thereof. Preferably, it is sodium hypophosphite.

[0197] 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 monomers in the polymer, 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 it is present, the transfer agent represents at least 0.1 ppm by weight, relative to the total weight of the monomers of the polymer, preferably at least 1 ppm by weight.

[0198] In a particular mode, the polymer does not comprise a transfer agent.

[0199] In general, the polymer does not require the development of a specific polymerization process. Indeed, it can be obtained using all polymerization techniques well known to those skilled in the art. These may include, in particular, solution polymerization; gel polymerization; precipitation polymerization; emulsion polymerization (aqueous or inverse); suspension polymerization; reactive extrusion polymerization; water-in-water polymerization; or micellar polymerization.

[0200] 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.

[0201] 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), and various polymerization variations with organometallic compounds. Organometallic-Mediated Radical Polymerization (OMRP) is radical polymerization controlled by heteroatomic compounds. (“OrganoHeteroatom-mediated Radical Polymerization” in English (OHRP)).

[0202] The polymer can be partially or totally post-hydrolyzed.

[0203] 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 metal (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.

[0204] 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.

[0205] 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. The 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.

[0206] 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 solution viscosity measurement method. K represents an empirical constant. M represents the molecular weight of the polymer. a represents the Mark-Houwink coefficient. K and a depend on the particular polymer-solvent system. Use of the polymer

[0207] Another aspect of the invention relates to the use of polymers obtained from the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0208] 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.

[0209] The invention also relates to the use of this polymer as a coagulant, agent binder, 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.

[0210] The invention and its advantages will be more clearly illustrated by the following figures and examples, which are given to illustrate the invention and not by way of limitation. Description of figures

[0211] [Fig-1] The [Fig. 1] illustrates the proton NMR spectrum of 2-acrylamido-2-methylpropane sulfonic acid crystals obtained according to example 1.

[0212] [Fig.2] Fig.2 illustrates the proton NMR spectrum of 2-acrylamido-2-methylpropane sulfonic acid crystals obtained according to example 2.

[0213] [Fig.3] The [Fig.3] illustrates the X-ray diffraction pattern of the crystals obtained according to example 1.

[0214] [Fig.4] The [Fig.4] illustrates the X-ray diffraction pattern of the crystals obtained according to example 2.

[0215] [Fig.5] The [Fig.5] illustrates the Fourier transform infrared spectrum of the crystals obtained in example 1.

[0216] [Fig.6] Fig.6 illustrates the Fourier transform infrared spectrum of the crystals obtained according to example 2.

[0217] [Fig.7] Fig.7 illustrates the thermogram of the crystals obtained according to example 1.

[0218] [Fig.8] Fig.8 illustrates the thermogram of the crystals obtained according to example 2.

[0219] [Fig.9] Fig.9 illustrates the grain size distribution graph of the crystals obtained according to Example 1.

[0220] [Fig. 10] The [Fig. 10] illustrates the grain size graph of the crystals obtained according to example 2.

[0221] [Fig. 11] The [Fig. 11] corresponds to the observation under the optical microscope of the crystals obtained according to example 1.

[0222] [Fig. 12] The [Fig. 12] corresponds to the observation under the optical microscope of the crystals obtained according to example 2.

[0223] [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.

[0224] Example 1: Synthesis of 2-acrylamido-2-methylpropane sulfonic acid

[0225] In a 2000 mL stirred reactor having a double jacket, 1522 grams of acrylonitrile containing 0.4% water by weight are added, the medium is stirred for 1 hour and cooled by the double jacket of the reactor which maintains the temperature of the sulfonant mixture at -20°C, then 180 grams of fuming sulfuric acid titrating 104% H2SO4 (18% Oleum) are added.

[0226] 97 grams of isobutylene are added to the previous sulfonant mixture, at a flow rate of 1.6 grams / minute.

[0227] The temperature of the mixture is controlled at 45°C during the introduction of isobutylene. Particles of 2-acrylamido-2-methylpropanesulfonic acid precipitate in the mixture, and the solids content is approximately 20% by weight. The reaction mixture is filtered through a Buchner funnel and dried under vacuum at 50°C. The resulting solid is 2-acrylamido-2-methylpropanesulfonic acid and is a very fine white powder.

[0228] According to observations made under an optical microscope ([Fig. 11]) the crystals have a needle-like morphology.

[0229] Example 2: Formation of the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid

[0230] In a 1000 mL double-jacketed stirred reactor, 439 grams of a 22% sodium 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).

[0231] The mixture is stirred for 30 minutes at 10°C to form an aqueous solution SA2.

[0232] 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 sodium 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 sodium salt crystals of 2-acrylamido-2-methylpropanesulfonic acid.

[0233] According to observations made under the optical microscope ([Fig.12]) the crystals have a column and platelet type morphology.

[0234] Counterexample 2': Failure to obtain the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0235] In a 1000 mL double-jacketed stirred reactor, 439 grams of a 22% sodium 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.

[0236] The mixture is stirred for 30 minutes at 10°C to form an aqueous solution SA2.

[0237] The aqueous 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 the atmospheric pressure. The solution is cooled to a temperature of 10°C. The cooling time between 40°C and 10°C is 6 hours. After the cooling step, the aqueous solution SA2 does not allow the formation of a Si suspension; therefore, no filtration or centrifugation operation is feasible to isolate 2-acrylamido-2-methylpropanesulfonic acid crystals in their crystalline form from the sodium salt.

[0238] Example 3: NMR analysis of products from examples 1 and 2

[0239] The solid of 2-acrylamido-2-methylpropane sulfonic acid obtained in Example 1 and its crystalline form of sodium salt obtained in example 2 are analyzed by proton nuclear magnetic resonance (NMR).

[0240] 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.

[0241] The two proton spectra ([Fig.1] and 2) are similar and the assignment of the peaks is consistent with the molecular structure of 2-acrylamido-2-methylpropane sulfonic acid or its sodium salt. Example 4: X-ray diffraction analysis

[0242] 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.

[0243] We can observe that the solid obtained from example 2 ([Fig.4]) has an X-ray diffraction pattern with the following characteristic peaks: 11.7°; 12.2°; 13.2°; 13.5°; 15.6°; 16.8°; 17.8°; 18.5°; 19.1°; 20.6°; 21.4°; 23.3°; 25.1°; 25.8°; 26.9°; 29.1°; 29.5°; 31.0°; 33.0°; 33.6°; 34.4°; 35.2°; 35.9°; 37.1°; 38.4°; 39.6°; 41.1°; 42.9°; 45.1°; 46.0°; 47.2°; 47.6° degrees 2-theta (+ / -0.1°).

[0244] The X-ray diffraction pattern of the solid according to Example 1 ([Fig.3]) does not show the same peaks.

[0245] Example 5: Fourier Transform Infrared Measurement

[0246] The Fourier transform infrared measurement equipment is the Spectrum 100 from the Perkin Elmer brand equipped with a single reflection ATR polarization accessory, the accuracy of which is 8cm1.

[0247] 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.

[0248] A few hundred milligrams of solid are placed on the diamond of the ATR accessory and pressure is applied manually using the accessory.

[0249] We can observe that the following bands ([Fig.6]) are characteristic of the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid: 3576cm1, 3485cm1, 3310cm*, 3079cm*, 2975cm1, 1658cm1, 1629cm*, 1543cm1, 1403cm1, 1321cm1, 1301cm1, 1205cm1, 1187cm1, 1163cm1, 1046cm*, 980cm*, 629cm1.

[0250] The infrared spectrum of the solid according to example 1 ([Fig.5]) does not show the same peaks.

[0251] Example 6: Differential Calorimetric Analysis (DSC)

[0252] The equipment used is a Mettler brand DSC 3.

[0253] 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.

[0254] 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, followed by two exothermic degradation phenomena at 212.8°C and 288.4°C.

[0255] The thermogram of the crystals of Example 2 ([Fig.8]) shows 4 thermal phenomena at 49.8°C; 144.8°C; 169.8°C and 254.3°C.

[0256] Example 7: Measurement of minimum ignition energy (MIE)

[0257] The measurement of the minimum ignition energy is carried out according to the standard NF EN 13821.

[0258] The explosimeter is a vertical Hartmann tube. The dust dispersion system is of the mushroom type.

[0259] 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.

[0260] Different dispersed energies and masses were tested and summarized in the following tables.

[0261] It is clear that the crystalline form of sodium salt presents a much lower risk of explosion than the needle form obtained in Example 1.

[0262] [Tables 1] Energy (ml) Mass of dispersed solid (g) Dispersion number Ignition? Yes (O) No (N) Flame Pressure 1000 0.5 2 O Small Small 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 Small 100 3 20 N - - 100 5 20 N - - 100 7 20 N — - 100 10 20 N - - 100 1 20 N - - 100 2 20 N - -

[0263] Table 1: Determination of the solid EMI of Example 1

[0264] [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 7 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 1 O Small Small

[0265] Table 2: Determination of the solid EMI of Example 2 Example 8: Particle size measurement

[0266] The solids obtained in examples 1 and 2 are analyzed by laser diffraction in order to determine their particle size distribution.

[0267] The equipment used in laser diffraction is a Cilas 1190.

[0268] 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]).

[0269] For the crystals in Example 2, the value of d50 is approximately 600 pm and 90% of the particles are smaller than approximately 1500 pm ([Fig. 10]). The crystals in Example 2 contain less than 10% of particles smaller than 325 pm.

[0270] Example 9: Evaluation of the corrosivity of different forms of ATBS on carbon steel

[0271] 20 grams of crystals from example 1 or 2 are deposited on two steel plates Carbon plates measuring 20 x 50 mm 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.

[0272] Photographs of the plates thus placed ([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 (ATBS), compared to Example 2 of the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid (ATBS.Na). The weighings of the plates before and after the contact period confirm these observations.

[0273] [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.Na example 2 9.4562 9.4302 0.275

[0274] Table 3: Corrosivity of different forms of ATBS on carbon steel

[0275] Example 10: Protocol for preparing a solution of a sodium salt of 2-acrylamido-2-methylpropane sulfonic acid from the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid

[0276] 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 sodium salt of acrylamido-2-methylpropane sulfonic acid of Example 2 and 1000 grams of water are introduced. The mixture has a pH greater than 12.

[0277] The mixture obtained is a sodium salt solution of 2-acrylamido-2-methylpropane sulfonic acid at a concentration of 50% by weight in water.

[0278] Example 11: Protocol for preparing a solution of a sodium salt of 2-acrylamido-2-methylpropane sulfonic acid from the acidic form

[0279] 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.

[0280] A 50% by weight sodium 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.

[0281] The final pH of the solution is at a pH between 8 and 10.

[0282] 310 grams of 50% by weight sodium hydroxide solution in water are ad edited.

[0283] The mixture obtained is a sodium salt solution of 2-acrylamido-2-methylpropane sulfonic acid at a concentration of 50% by weight in water.

[0284] Example 12: Evolution of the quality of ATBS sodium salt stored in solid or liquid form

[0285] 500 g of 50% (by weight in water) sodium salt solutions of the acid 2-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 sodium salt homopolymers of 2-acrylamido-2-methylpropane sulfonic acid.

[0286] In parallel, 2-acrylamido-2-methylpropane sulfonic acid in crystalline form of the sodium 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.

[0287] Every three months, 500 g of a sodium salt solution of 2-acrylamido-2-methylpropane sulfonic acid is freshly prepared according to Example 10 or 11 with the crystals of Example 2 or 1 stored. The level of sodium salt homopolymers of 2-acrylamido-2-methylpropane sulfonic acid present is then measured in order to compare the solid storage of this new form.

[0288] 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.

[0289] Sodium salt solutions of 2-acrylamido-2-methylpropane sulfonic acid are diluted to 2000 ppm (by weight in water) before injection. The integration of the A 250 nm UV signal at the column outlet is applied to the polymer peaks before being reported in Table 4 below. The larger the signal area, the more polymer there is, and therefore the lower the product's long-term stability.

[0290] [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 0 T0 + 3 months 550 6326 230 250 T0 + 6 months 12536 311326 5263 7702 T0 + 9 months 23564 562143 7593 10503 T0 + 12 months 52364 1252230 10235 256300

[0291] Table 4: Stability of solutions of the salt of 2-acrylamido-2-methylpropane sulfonic acid

[0292] It can be seen that the new crystalline form of sodium 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.

[0293] In addition to better preservation in liquid form, the new crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid allows storage in solid form offering improved storage time.

[0294] Example 13: Preparation of the PI acrylamide / 2-acrylamido-2-methylpropane sulfonic acid copolymer in crystalline form of the sodium salt (75 / 25 mol%)

[0295] 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 268.8 g of sodium salt crystals of 2-acrylamido-2-methylpropane sulfonic acid obtained according to Example 2.

[0296] 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.

[0297] 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).

[0298] 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 rubbery gel is chopped into particles with a size between 1 and 6 mm.

[0299] The gel is then dried and ground to obtain the polymer in powder form.

[0300] Example 14: Preparation of the P'1 acrylamide / 2-acrylamido-2-methylpropane sulfonic acid copolymer in non-crystalline form of the sodium salt (75 / 25 mol%)

[0301] In a 2000 mL beaker, 535.1 g of deionized water are added, the solution is cooled to 5°C, and 243.0 g of 2-acrylamido-2-methylpropane sulfonic acid crystals obtained according to example 1 are added.

[0302] In a dropping funnel, 93.90 g of 50% sodium hydroxide solution (by weight in water) is prepared. Once the crystals have completely dissolved, the caustic solution is added to the reaction mixture over 120 minutes. The temperature is controlled to remain below 30°C. The final pH of the solution is between 8 and 10.

[0303] 500 g of acrylamide in a 50% solution (by weight in water) and 16.2 g of urea are in introduced to complete the mixture.

[0304] 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.

[0305] 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) sodium hypophosphite solution, - 2.25 ml of a 1 g / L (in water) solution of tert-butyl hydroperoxide, - 2.25 ml of a 1 g / L solution (in water) of ammonium sulfate and iron(II) hexahydrate (Mohr's salt).

[0306] 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 rubbery gel is chopped into particles with a size between 1 and 6 mm.

[0307] The gel is then dried and ground to obtain the polymer in powder form.

[0308] Example 15: Preparation of P2 homopolymers from the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid

[0309] In a 2000 mL beaker, 562.1 g of deionized water and 389.4 g of crystals of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid obtained according to Example 2 are added.

[0310] 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.

[0311] 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 dihydrochloride 2,2'-azobis[2-(2-imidazolin-2-yl)propane], - 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).

[0312] 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 and dried to obtain a coarse powder, which is then ground and sieved to obtain the polymer in powder form.

[0313] Example 16: Preparation of P'2 homopolymers from 2-acrylamido-2-methylpropane sulfonic acid in non-crystalline form of the sodium salt

[0314] In a 2000 mL beaker, 427.5 g of deionized water are added, the solution is cooled to 5°C, and 352.1 g of 2-acrylamido-2-methylpropane sulfonic acid crystals obtained according to example 1 are added with stirring.

[0315] In a dropping funnel, 136.1 g of 50% sodium hydroxide solution (by weight in water) is prepared. The caustic solution is added to the reaction mixture over 120 minutes. The temperature is controlled to remain below 30°C. The final pH of the solution is between 8 and 10.

[0316] 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.

[0317] 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 dihydrochloride 2,2'-azobis[2-(2-imidazolin-2-yl)propane], - 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 solution (in water) of ammonium sulfate and iron(II) hexahydrate (Mohr's salt).

[0318] 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 and dried to obtain a coarse powder, which is then ground and sieved to obtain the polymer in powder form. Example 17: Viscosity Measurement

[0319] The reduced viscosity of the polymers prepared in Examples 13 to 16 is measured at 25°C in an aqueous solution of 0.5 M sodium chloride using a Brookfield type LVT viscometer equipped with a 60 rpm UL adapter.

[0320] 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. 9.75 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 pores of 200 pm.

[0321] 16 mL of the prepared solutions are transferred into a cylindrical tube and used to perform a viscosity measurement.

[0322] [Tables5] Polymer Viscosity (EPS) PI (invention) 7.2 P'1 (counterexample) 4.8 P2 (invention) 5.2 P'2 (counterexample) 3.5

[0323] Table 5: Viscosity of polymer solutions of salified 2-acrylamido-2-methylpropane sulfonic acid

[0324] Polymers comprising the new crystalline form of the sodium 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 (sodium).

Claims

Demands

1. Crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 11.7°; 12.2°; 13.2°; 13.5°; 15.6°; 16.8°; 17.8°; 18.5°; 19.1°; 20.6°; 21.4°; 23.3°; 25.1°; 25.8°; 26.9°; 29.1°; 29.5°; 31.0°; 33.0°; 33.6°; 34.4°; 35.2°; 35.9°; 37.1°; 38.4°; 39.6°; 41.1°; 42.9°; 45.1°; 46.0°; 47.2°; 47.6°, degrees 2-theta (+ / - 0.1°).

2. Crystalline form of the sodium 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 3576cm1, 3485cm1, 3310cm*, 3079cm*, 2975cm1, 1658cm1, 1629cm1, 1543cm1, 1403cm1, 1321cm1, 1301cm1, 1205cm1, 1187cm1, 1163cm1, 1046cm1, 980cm1, 629cm'(+ / - 8cm1).

3. Crystalline form of sodium 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 sodium salt of 2-acrylamido-2-methylpropane sulfonic acid according to any one of claims 1 to 3, characterized in that it exhibits 4 thermal phenomena with the differential scanning calorimetry technique, at 49.8°C; 144.8°C; 169.8°C and 254.3°C (+ / -10°C).

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

6. A process according to claim 5, characterized in that the concentration of the aqueous solution or aqueous suspension SA2 in salt of sodium 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 sodium 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 sodium salt is selected from sodium hydroxide, sodium carbonate, sodium bicarbonate or mixtures thereof.

10. Polymer obtained at least in part from the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid having a powder X-ray diffraction pattern comprising peaks at 11.7°; 12.2°; 13.2°; 13.5°; 15.6°; 16.8°; 17.8°; 18.5°; 19.1°; 20.6°; 21.4°; 23.3°; 25.1°; 25.8°; 26.9°; 29.1°; 29.5°; 31.0°; 33.0°; 33.6°; 34.4°; 35.2°; 35.9°; 37.1°; 38.4°; 39.6°; 41.1°; 42.9°; 45.1°; 46.0°; 47.2°; 47.6°, degrees 2-theta (+ / - 0.1°).

11. Polymer according to claim 10, characterized in that the polymer is obtained at least in part from the crystalline form of the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid, and from at least one other monomer selected from: hydrophilic nonionic monomers, hydrophilic anionic monomers, hydrophilic cationic monomers, hydrophilic zwitterionic monomers and hydrophobic monomers.

12. Use of the polymer according to claim 10 or 11 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.

13. Use of the polymer according to claim 10 or 11 as a coagulant, binding agent, absorbent agent, draining agent, agent of charge retention, dehydrating agent, conditioning agent, stabilizing agent, fixing agent, film-forming agent, sizing agent, superplasticizing agent, clay inhibitor or dispersant.

Images