Patent Description:
<NUM>-acrylamido-<NUM>-methylpropanesulphonic acid, which is also referred to as ATBS, is widely used as an additive in acrylic fibers, or as a raw material for producing polymers used as dispersants, thickeners, friction reducers, flocculants or superabsorbents in various sectors including the oil and gas industry, mining, construction, textiles, water treatment (seawater desalination, mineral industry, etc.) or cosmetics.

The reaction carried out in the method for preparing ATBS corresponds to the reaction scheme below, in which acrylonitrile is present in excess so as to be both the reaction solvent and a reagent. The acrylonitrile is brought into contact with fuming sulphuric acid (oleum) and isobutylene.

One by-product that may be produced during this synthesis is acrylamide.

ATBS is not soluble in acrylonitrile solvent. As a result, the reaction product is in the form of a suspension of crystals in the reaction solvent.

For example, documents <CIT> and <CIT> describe a method for the continuous production of ATBS. The ATBS is then separated from the acrylonitrile, generally by filtration, and then dried.

It is necessary to dry ATBS in order to reduce the quantity of residual acrylonitrile and acrylamide present in the crystal. These two compounds are classified as carcinogenic, mutagenic or reprotoxic (CMR). It is therefore necessary to carry out effective filtration to dewater the acrylonitrile as thoroughly as possible, and then dry the ATBS in order to obtain low levels of acrylonitrile and acrylamide.

A person skilled in the art is aware that ATBS crystals have a crystallographic arrangement that produces a needle-shaped solid.

Needle-shaped crystals are known to a person skilled in the art to have macroscopic properties that pose difficulties in solid handling and transport operations (poor solid flowability, caking, low resistance to shear stress), and processing operations (poor filterability, drying difficulties, attrition).

In the case of ATBS, the additional problems encountered are generally the small particle size of the needle-shape crystals, the density of the solid in question, and the explosive nature of the fine dust.

These macroscopic properties are linked directly to the morphology of the crystals and to their specific surface area. Needle-shape crystals have a high specific surface area.

<CIT>, <CIT> and <CIT> describe that ATBS needle-shape crystals are obtained.

Document <CIT> filed by the Applicant describes a novel form of ATBS crystals referred to as a "hydrated crystalline form of ATBS". This novel crystalline form has physico-chemical properties that are different compared to the needle-shape ATBS and also gives improved properties to the polymers comprising ATBS in this novel form.

However, whatever the ATBS form, it remains a strong acid due to its sulphonic acid function, which is highly corrosive to metals. Due to the powdery nature of <NUM>-acrylamido-<NUM>-methylpropanesulphonic acid powder, there is also a risk of chemical burns due to fine airborne particles coming into contact with the skin or eyes or being breathed into the lungs during powder handling operations.

When ATBS is used in a polymerization method, it must be in aqueous form. The aqueous phase may be used as it is, i.e., in acid form, or in a salt form obtained by reaction of the acid with an alkali metal, an alkaline-earth metal or a molecule containing an unsubstituted or substituted amine function.

The shelf life of this aqueous solution is generally short because of self-polymerization phenomena caused by exposure to temperature, UV light or pollutants such as iron or its oxidized forms, which can be produced by the corrosion of metal pipes or containers caused by the acid form of ATBS. In addition, the increase in temperature generated by the self-polymerization of ATBS is well above the boiling point of water, which can lead to an increase in pressure in the container and cause an explosion. Therefore, self-polymerization phenomena present a certain risk to the safety of people and installations.

<CIT> and <CIT> describe the preparation of the sodium salt of ATBS, as discussed below in comparative examples 2b and 2c.

The Applicant has discovered a novel form of ATBS referred to as a "crystalline form of the <NUM>-acrylamido-<NUM>-methylpropanesulphonic acid sodium salt". This novel form offers improved physico-chemical and application properties (as with the "hydrated crystalline" form) while avoiding the intermediate step of forming the ATBS salt from the acid. 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 <NUM>-acrylamido-<NUM>-methylpropanesulphonic acid.

The sodium salt of <NUM>-acrylamido-<NUM>-methylpropanesulphonic acid is hereinafter referred to as ATBS.

Using the crystalline form of ATBS. Na according to the invention is in line with the principle of environmental awareness and the impact of industry and mankind on the planet. The novel form of the product means that it is safer for handlers to use and reduces the energy impact due to the salification step (salifying ATBS) that is no longer necessary during the polymerization of <NUM>-acrylamido-<NUM>-methylpropanesulphonic acid and due to the powder form, which allows more active ingredient to be transported (<NUM>% for the powder compared with a maximum of <NUM>% for a solution). The improved shelf life of the product also means less waste resulting from the increased product dosage required as a result of the reduced performance of a product that is too old. Moreover, the improved performances of the polymers obtained from the crystalline form of the sodium salt of the invention help reduce the quantity of product necessary for the applications in which they are used, reducing the overall water consumption and emissions of greenhouse gases such as the CO<NUM>.

The object of the present invention is a specific form of <NUM>-acrylamido-<NUM>-methylpropanesulphonic acid referred to hereinafter as a "crystalline form of the <NUM>-acrylamido-<NUM>-methylpropanesulphonic acid sodium salt".

The present invention also relates to a method for producing the crystalline form of the <NUM>-acrylamido-<NUM>-methylpropanesulphonic acid sodium salt (ATBS.

The term "polymer" should be understood to mean a homopolymer or a copolymer. The term "copolymer" should be understood to mean a polymer obtained from at least two different monomers. It may therefore be a copolymer of at least two monomers chosen from hydrophilic anionic monomers, hydrophilic cationic monomers, hydrophilic non-ionic monomers, hydrophilic zwitterionic monomers, hydrophobic monomers and the mixtures thereof.

The term "hydrophilic monomer" should be understood to mean a monomer that has an octanol-water partition coefficient, Kow, equal or less than <NUM>, in which the partition coefficient Kow is determined at <NUM> in an octanol-water mixture with a volume ratio of <NUM>/<NUM>, at a pH of between <NUM> and <NUM>.

The term "hydrophobic monomer" should be understood to mean a monomer that has an octanol-water partition coefficient, Kow, greater than <NUM>, in which the partition coefficient Kow is determined at <NUM> in an octanol-water mixture with a volume ratio of <NUM>/<NUM>, at a pH of between <NUM> and <NUM>.

The term "crystal" or "crystalline form" refers to a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. It does not encompass amorphous solid.

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

By definition, a water-soluble polymer is a polymer that gives an aqueous solution when it is dissolved while stirring at <NUM> and with a concentration of <NUM>. L-<NUM> in water.

"X and/or Y" should be understood to mean "X", or "Y", or "X and Y".

The invention also includes all possible combinations of the various embodiments disclosed, whether they are preferred embodiments or given by way of example. Furthermore, when ranges of values are indicated, the limit values are included in these ranges. The disclosure also includes all of the combinations between the limit values of these ranges of values. For example, the ranges of values "<NUM>-<NUM>, preferably <NUM>-<NUM>" imply disclosure of the ranges "<NUM>-<NUM>", "<NUM>-<NUM>", "<NUM>-<NUM>" and "<NUM>-<NUM>" and the values <NUM>, <NUM>, <NUM> and <NUM>.

The present invention relates to a crystalline form of the <NUM>-acrylamido-<NUM>-methylpropanesulphonic acid sodium salt having an X-ray powder diffraction pattern comprising peaks at <NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM><NUM>-theta angles. The uncertainty of these peaks is generally of the order of +/- <NUM>°.

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

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

This signature is specific to each organic or inorganic compound, and is in the form of a list of peaks positioned at an angle of 2θ (<NUM>-theta).

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

Another aspect of the invention relates to a crystalline form of ATBS. Na having a Fourier-transform infrared spectrum comprising peaks at <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. The uncertainty of these peaks is generally of the order of +/- <NUM>-<NUM>.

The infrared measurement is carried out by Fourier transform, for example using a Perkin Elmer Spectrum <NUM> spectrometer fitted with a single reflection ATR polarization accessory, with an accuracy of <NUM>-<NUM>.

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

Generally, and unless otherwise indicated, the X-ray diffraction pattern and the infrared spectrum are obtained at <NUM> and at a pressure of <NUM> atmosphere absolute (<NUM>,<NUM> Pa).

Another aspect of the invention relates to a crystalline form of ATBS. Na having a minimum ignition energy greater than <NUM> mJ, and preferably greater than <NUM> mJ.

The minimum ignition energy represents the minimum energy that must be supplied to a compound to cause an ignite. The energy may be electrical or thermal. The minimum ignition energy is an essential piece of information when considering the risk of explosion during product handling (transfer, storage, reaction, shaping, etc.).

The minimum ignition energy depends on the properties of the powder (composition) and its macromolecular structure (particle size, crystalline form, specific surface area).

In the case of solids, this energy is the minimum energy of an electric spark likely to ignite a cloud of dust. The higher the value of the minimum ignition energy, the less risk the solid presents when used, handled or stored.

The minimum ignition energy is measured in accordance with standard NF EN <NUM>.

Another aspect of the present invention relates to a crystalline form of ATBS. Na exhibiting <NUM> thermal phenomena with the differential scanning calorimetry technique, at <NUM>; <NUM>; <NUM> and <NUM>. The uncertainty relating to the observation of these phenomena is generally of the order of <NUM> (+/-<NUM>), advantageously <NUM> or less.

The thermal phenomena are measured by differential scanning calorimetry (DSC). This technique uses the measurement of the variation in heat associated with the thermal denaturation of the compound when it is heated at constant speed, for example with a heating ramp of <NUM>/minute.

The present invention also relates to the method for producing the crystalline form of ATBS. Na comprising at least the following successive steps:.

The crystals obtained are in the crystalline form of the sodium salt of <NUM>-acrylamido-<NUM>-methylpropanesulphonic acid.

"Sodium salt(s) base" in step <NUM>), should be understood to mean at least one inorganic sodium salt Brønsted base, for example sodium hydroxide, sodium carbonate, sodium bicarbonate or mixtures thereof.

The temperature and the mixing time of step <NUM>) may vary as a function, in particular, of the concentration of ATBS. A person skilled in the art knows how to adapt the temperature and the mixing time to optimize the formation of the crystals.

The method for producing the crystalline form of ATBS. Na can be carried out on any form of ATBS, such as, for example, the needle-shape form or the hydrated form.

The production method may be carried out on ATBS of any degree of purity.

Therefore, the method may be carried out downstream of any type of method for producing ATBS. It may also be carried out on any forms of ATBS i.e. amorphous or crystalline that have already been obtained.

ATBS is produced by a production method as previously described (acrylonitrile, fuming sulphuric acid and isobutylene). The ATBS may be in the form of fine powder or shaped in a controlled manner by a method such as compaction, granulation or extrusion.

The ATBS may be added to an aqueous solution SA1 before, after or in parallel with the sodium salt base, and preferably in parallel. Preferably, the aqueous solution SA1 is water.

The sodium salt base may be added as an aqueous solution, in this case, the aqueous solution of sodium salt base can be partially or totally the aqueous solution SA1.

Advantageously, the concentration of ATBS sodium salt in the aqueous solution or in the aqueous suspension SA<NUM> is between <NUM>% by weight and saturation, preferably between <NUM>% by weight and saturation, more preferably between <NUM>% by weight and saturation, more preferably between <NUM>% by weight and saturation, more preferably between <NUM>% by weight and saturation, and even more preferably between <NUM>% by weight and saturation, by weight relative to the weight of the aqueous solution or of the aqueous suspension SA<NUM>.

The ATBS and the sodium base may be added all at once or in several stages. They are preferably added all at once.

When they are added in several stages, the ATBS and the sodium salt base are added in fractions.

When the ATBS and the sodium salt base are added in fractions, there is no limit to the number of fractions, advantageously there are at least two fractions, and preferably at least three fractions.

There is no limitation to the order of addition of the ATBS and the sodium salt base. They may be added at the same time (i.e., in parallel), one after the other (the ATBS first, then the sodium salt base, or vice versa), or alternately (a first fraction of ATBS, then a first fraction of the sodium salt base, followed by a second fraction of ATBS then a second fraction of the sodium salt base, and so on); they are preferably added at the same time.

When they are added one after the other or alternately, the second compound (whether it is the ATBS or the sodium salt base) can start being added before the first compound has finished being added.

A first fraction F1 of ATBS advantageously represents at least <NUM> mol% of the total of the ATBS present in the aqueous solution or the aqueous suspension SA<NUM>, preferably at least <NUM> mol%, more preferably at least <NUM> mol%, even more preferably at least <NUM> mol% and even more preferably at least <NUM> mol%.

A second fraction F2 of ATBS advantageously represents at least <NUM> mol% of the total of the ATBS present in the aqueous solution or the aqueous suspension SA<NUM>, preferably at least <NUM> mol%, more preferably at least <NUM> mol%, even more preferably at least <NUM> mol% and even more preferably at least <NUM> mol%.

A third fraction F3 of ATBS advantageously represents at least <NUM> mol% of the total of the ATBS present in the aqueous solution or the aqueous suspension SA<NUM>, preferably at least <NUM> mol%, more preferably at least <NUM> mol%, even more preferably at least <NUM> mol% and even more preferably at least <NUM> mol%.

In one particular embodiment, the method is carried out continuously, in which case the ATBS and the sodium salt base are added continuously.

The quantity of ATBS in the aqueous solution or the aqueous suspension SA<NUM> is advantageously between <NUM> and <NUM>% by weight relative to the total weight of the aqueous solution or of the aqueous suspension SA<NUM>, preferably between <NUM> and <NUM>% by weight, more preferably between <NUM> and <NUM>% by weight.

The mixing of step <NUM>) (ATBS + sodium salt base) is advantageously carried out at a temperature of between <NUM> and <NUM>, preferably between <NUM> and <NUM>, more preferably between <NUM> and <NUM>, in order to obtain the aqueous solution or the aqueous suspension SA<NUM>.

In one particular embodiment, the aqueous solution or the aqueous suspension SA<NUM> may comprise one or more organic solvents.

In some embodiments, the aqueous solution SA<NUM> may comprise one or more organic solvents.

The quantity of organic solvent may vary as a function of the temperature and the quantity of ATBS or sodium salt base. This quantity is not limited, provided it does not prevent the crystalline form of the sodium salt of ATBS from being obtained. A person skilled in the art knows how to determine this limit, which is a routine task. Generally, the aqueous solution or the aqueous suspension SA<NUM> comprises more water (by volume) than organic solvent.

The organic solvent or solvents are advantageously chosen from the following compounds:.

When an organic solvent is used in the invention, the temperature may be adjusted so that the solvent + water mixture remains in liquid form.

These compounds may be linear or branched. They may be saturated or comprise unsaturated bonds. An unsaturated bond corresponds to a double or triple bond (for example C=C or C≡C).

The organic solvent is preferably chosen from acrylonitrile, isopropanol, acrylic acid, acetic acid or mixtures thereof. The organic solvent is preferably acrylonitrile.

The organic solvent is generally in liquid form at the temperature at which steps <NUM>) and <NUM>) are carried out. Furthermore, it is advantageously partially miscible in water, and preferably completely miscible in water.

The organic solvent may, if necessary, be used to solubilize any impurities or by-products present with the ATBS used to form the aqueous solution or the aqueous suspension SA<NUM>. However, ATBS is not necessarily soluble in the solvent.

In a preferred embodiment according to the invention, the aqueous solution or the aqueous suspension SA<NUM> does not contain organic solvent.

In a preferred embodiment according to the invention, the aqueous solution SA<NUM> does not contain organic solvent.

The time allowed for mixing the aqueous solution SA<NUM> and the ATBS is advantageously at least <NUM> minute, preferably between <NUM> minute and <NUM> minutes, more preferably between <NUM> minutes and <NUM> minutes, and even more preferably between <NUM> minutes and <NUM> minutes.

The compounds of step <NUM>) can be mixed using various technologies. Examples include, but are not limited to, reactors with stirrers, loop reactors, static mixers, microreactors, piston reactors, agitated filter dryers, for example by Nutsche, paddle mixers, twin-cone mixers, ploughshare mixers and disc mixers.

The pH in step <NUM>) is advantageously controlled between <NUM> and <NUM>, preferably between <NUM> and <NUM>, more preferably between <NUM> and <NUM>, even more preferably between <NUM> and <NUM>, and even more preferably between <NUM> and <NUM>.

The quantity of ATBS. Na in the aqueous solution or the aqueous suspension SA<NUM> is advantageously between <NUM> and <NUM>% by weight relative to the total weight of the aqueous solution or of the aqueous suspension SA<NUM>, preferably <NUM> and <NUM>%, preferably between <NUM> and <NUM>% by weight, preferably between <NUM> and <NUM>% by weight, preferably between <NUM> and <NUM>% by weight, more preferably between <NUM> and <NUM>% by weight.

The distillation of the aqueous solution or of the aqueous suspension SA<NUM> takes place at a pressure of <NUM> mbar or less. It generally takes place in a vacuum distillation device, which is typically an evaporator. It is therefore also referred to here as "vacuum distillation".

When the aqueous solution or the aqueous suspension SA<NUM> is distilled, typically by passing it through an evaporator, crystals of the sodium salt of ATBS begins to form. Thus ATBS, the at least one sodium salt base, and crystalline solid particles of the sodium salt of ATBS coexists in the aqueous solution or the aqueous suspension SA<NUM>.

The aqueous solution or the aqueous suspension SA<NUM> can be distilled using an evaporator. This may be a falling film evaporator, or a rising film evaporator, or a scraped thin film evaporator, or a short path evaporator, or a forced circulation evaporator, or a spiral tube evaporator, or a flash evaporator. It may also be a continuously stirred reactor. Preferably, distillation takes place in a scraped thin film evaporator, a short path evaporator or a forced circulation evaporator. Even more preferably, distillation takes place in a scraped thin film evaporator.

Generally, an evaporator is a device comprising an inlet for solution to be treated (aqueous solution or aqueous suspension SA<NUM>), an outlet for discharging the distilled solvent (the water and any organic solvents) and an outlet for discharging the suspension S<NUM>.

The residence time of the aqueous solution or of the aqueous suspension SA<NUM> in the distillation device (advantageously under vacuum), which is advantageously an evaporator, in other words the distillation time at a pressure of <NUM> mbar or less, is advantageously comprised between <NUM> second and <NUM> seconds, preferably between <NUM> seconds and <NUM> seconds, more preferably between <NUM> seconds and <NUM> seconds. The residence time corresponds to the time necessary to carry out step <NUM>), i.e., the time required to prepare the suspension S<NUM> by distillation of the aqueous solution or of the aqueous suspension SA<NUM>. In other words, when an evaporator is used, it is the residence time of the ATBS (and/or the crystalline form of its sodium salt) between the inlet and the outlet of the device. This residence time depends on the quantity of water (and any organic solvents), ATBS. Na and sodium salt base present in the aqueous solution or the aqueous suspension SA<NUM>. A person skilled in the art knows how to adapt this residence time in order to obtain ATBS. Na in the crystalline form depending on the quantity of the constituents of the aqueous solution or of the aqueous suspension SA<NUM>.

The distillation can be carried out in a vertical or horizontal evaporator. Preferably, it is carried out in a vertical evaporator.

The aqueous solution or the aqueous suspension SA<NUM> can circulate co-current or counter-current to the vapours generated by the evaporation. Preferably, it circulates counter-current to the vapours in the distillation device. In other words, the aqueous solution or the aqueous suspension SA<NUM> is preferably introduced into the distillation device, advantageously an evaporator, co-current or counter-current to the distilled solvent.

The aqueous solution SA<NUM> or the aqueous suspension SA<NUM> may circulate in one or more evaporators in series before obtaining the suspension S<NUM>. Preferably, it circulates in a single evaporator.

The pressure during distillation is advantageously between <NUM> and <NUM> mbar absolute (<NUM> mbar = <NUM> Pa). It is preferably less than <NUM> mbar absolute, more preferably less than <NUM> mbar absolute, more preferably less than <NUM> mbar absolute, more preferably less than <NUM> mbar absolute, more preferably less than <NUM> mbar absolute, more preferably less than <NUM> mbar absolute, more preferably less than <NUM> mbar absolute and even more preferably less than <NUM> mbar absolute, and advantageously greater than <NUM> mbar absolute. The absolute pressure corresponds to the pressure relative to zero pressure (vacuum).

In general, the pressure during distillation is preferably comprised between <NUM> and <NUM> mbar, preferably between <NUM> and <NUM> mbar, preferably between <NUM> and <NUM> mbar more preferably between <NUM> and <NUM> mbar, more preferably between <NUM> and <NUM> mbar, more preferably between <NUM> and <NUM> mbar, more preferably between <NUM> and <NUM> mbar, more preferably between <NUM> and <NUM> mbar, more preferably between <NUM> and <NUM> mbar.

In one particular embodiment, step <NUM>) comprises a step <NUM>') (optional) for helping the solvent to evaporate. Step <NUM>') consists in increasing the temperature of the aqueous solution or of the aqueous suspension SA<NUM>, in other words the distillation according to step <NUM>') is carried out under heat.

In some embodiments, in step <NUM>), the aqueous solution or the aqueous suspension SA<NUM> is heated, advantageously at a temperature of between <NUM> and <NUM>, preferably between more than <NUM> and <NUM>, more preferably between more than <NUM> and <NUM>.

The heating during distillation may be carried out by various technologies. Examples include, but are not limited to, heating with steam, with hot water, with electricity, by steam compression, or indeed by using a heat pump. Thus, the distillation device may be of the double-walled type, with a hot heat-transfer fluid circulating between the two walls.

The aqueous solution or the aqueous suspension SA<NUM> is advantageously heated to a temperature between more than <NUM> and <NUM>, preferably between more than <NUM> and <NUM>, more preferably between more than <NUM> and <NUM>.

When the aqueous solution or the aqueous suspension SA<NUM> is heated, the temperature is advantageously greater than the temperature of step <NUM>).

The temperature of the aqueous solution or of the aqueous suspension SA<NUM> advantageously increases at a ramp of between <NUM> and <NUM>/hour, preferably between <NUM> and <NUM>/hour, more preferably between <NUM> and <NUM>/hour, and even more preferably between <NUM> and <NUM>/hour.

In some embodiments, the temperature of the aqueous solution or of the aqueous suspension SA<NUM> advantageously increases at a ramp of between <NUM> and <NUM>/hour, preferably between <NUM> and <NUM>/hour, more preferably between <NUM> and <NUM>/hour, and even more preferably between <NUM> and <NUM>/hour.

The increase in temperature may not be constant throughout the whole process. For example, the aqueous solution or the aqueous suspension SA<NUM> may be heated by <NUM> per hour for the first three hours, and then heated at a speed of <NUM> per hour until the final temperature is reached.

According to another particular embodiment of the invention, step <NUM>) comprises a step <NUM>"), after step <NUM>'), or instead of step <NUM>'), that helps to increase the productivity and the profitability of the method of the invention by accelerating the crystallization of the ATBS into the crystalline form of its sodium salt. Step <NUM>") consists in decreasing the temperature of the aqueous solution or of the aqueous suspension SA<NUM> or the suspension S1.

The aqueous solution or the aqueous suspension SA<NUM> is advantageously cooled to a temperature of between <NUM> and less than <NUM>, preferably between <NUM> and less than <NUM>, more preferably between <NUM> and less than <NUM> and even more preferably between <NUM> and <NUM>.

Step <NUM>) further comprises a cooling step.

The cooling step is advantageously carried out at a temperature of between <NUM> and <NUM>, preferably between more than <NUM> and <NUM>, more preferably between more than <NUM> and <NUM>.

The temperature of the cooling step is decreased at a ramp of between <NUM> and <NUM>/hour, preferably between <NUM> and <NUM>/hour, more preferably between <NUM> and <NUM>/hour, and even more preferably between <NUM> and <NUM>/hour.

In some embodiments, the temperature of the cooling step is advantageously inferior to the temperature of heating of step <NUM>) and/or step <NUM>).

The cooling step is carried out on the aqueous solution or the aqueous suspension SA<NUM> and/or the concentrated aqueous solution or the aqueous suspension SA<NUM> and/or the suspension S<NUM>.

When the aqueous solution or the aqueous suspension SA<NUM> is cooled (step <NUM>")), the temperature is advantageously less than the temperature of step <NUM>) and optionally <NUM>').

According to a preferred embodiment, the temperature of step <NUM>") is the same or less than the temperature of step <NUM>).

In some embodiments, no organic solvent or aqueous solution is added in step <NUM>'' for obtaining the crystals of ATBS.

The temperature of the aqueous solution or of the aqueous suspension SA<NUM> decreases at a ramp of between <NUM> and <NUM>/hour, preferably between <NUM> and <NUM>/hour, more preferably between <NUM> and <NUM>/hour, and even more preferably between <NUM> and <NUM>/hour.

The decrease in temperature may not be constant throughout the whole process. For example, the aqueous solution or the aqueous suspension SA<NUM> may be cooled by <NUM> per hour for the first three hours, and then cooled at a speed of <NUM> per hour until the final temperature is reached.

While the aqueous solution or the aqueous suspension SA<NUM> is being cooled, crystals of the sodium salt of ATBS form and a suspension S<NUM> is obtained.

In one particular embodiment, previously obtained crystals of sodium salt of ATBS may be added during this step in order to modify the formation of the suspension S<NUM>, a process referred to as crystal seeding which makes it possible to better control the crystallization temperature, the particle size of the crystals, the particle size distribution, the purity of the end product and, possibly, the yield. The crystals of sodium salt of ATBS have advantageously an X-ray powder diffraction pattern comprising peaks at <NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>° <NUM>-theta angles (+/- <NUM>°).

According to one particular embodiment of the invention, the solvent distilled in step <NUM>) may be partially or totally recycled in order to form the aqueous solution SA<NUM> of ATBS in step <NUM>). In other words, the distilled solvent is advantageously at least partially recycled in the aqueous solution SA<NUM> of ATBS.

According to another particular embodiment of the invention, the distilled solvent may be partially or totally recycled, generally to wash the crystals of sodium salt of ATBS obtained after step <NUM>) of solid-liquid separation, in an optional step <NUM>), with or without a prior treatment step.

The obtained suspension S<NUM> advantageously comprises between <NUM> and <NUM>% by weight of crystalline form of ATBS. Na, relative to the total weight of the suspension S<NUM>, preferably between <NUM> and <NUM>% by weight, more preferably between <NUM> and <NUM>% by weight, and preferably between <NUM> and <NUM>% by weight.

During step <NUM>), the pH is advantageously greater than <NUM>, preferably greater than <NUM>, more preferably greater than <NUM>, and the pH is even more preferably between <NUM> and <NUM>.

The crystals ATBS. Na contained in the suspension S<NUM> obtained at the end of step <NUM>) are isolated in a solid-liquid separation step and are in the form of a composition C<NUM>.

The solid-liquid separation step can be carried out using various technologies. Examples include, but are not limited to, the use of a centrifuge, a decanter, a filter press, an agitated filter, a belt filter, a disc filter or a rotary drum filter. The solid-liquid separation is preferably carried out using a centrifuge. The solid-liquid separation may also be carried out by gravitational settling.

Step <NUM>) is advantageously carried out at a temperature of between -<NUM> and <NUM>, and preferably between -<NUM> and <NUM>.

After step <NUM>) of solid-liquid separation, the crystals of sodium salt of ATBS are preferably not dried.

The isolated composition C<NUM> has a content of crystals of sodium salt of ATBS advantageously between <NUM> and <NUM>%, preferably between <NUM> and <NUM>% by weight, more preferably between <NUM> and <NUM>% and even more preferably between <NUM> and <NUM>% by weight relative to the weight of the composition C<NUM>. The remainder of the composition C<NUM> may be water and/or solubilized sodium salt of ATBS, and possibly sodium salt base introduced in step <NUM>).

At the end of this step <NUM>), the crystals are characterized as being crystals of ATBS sodium salt (ATBS.

In one particular embodiment, all or part of the liquid phase obtained following the solid-liquid separation is used in the aqueous solution SA<NUM> of step <NUM>).

During step <NUM>), the pH is advantageously controlled between <NUM> and <NUM>, preferably between <NUM> and <NUM>, more preferably between <NUM> and <NUM>, even more preferably between <NUM> and <NUM>, and even more preferably between <NUM> and <NUM>.

In an optional step <NUM>), the composition C<NUM> containing the crystals of ATBS. Na obtained at the end of step <NUM>) is washed using a washing solution.

The washing solution may be water, an aqueous solution of a sodium salt base (which may or may not be saturated), or a solution (which may or may not be saturated) of ATBS sodium salt (advantageously in the crystalline form of ATBS. Na), and it is preferably a saturated solution of ATBS.

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

The washing solution may comprise one or more organic solvents.

Advantageously, the washing solution does not comprise organic solvent.

As already indicated for step <NUM>), the organic solvent is advantageously chosen from organic acids, amides, alcohols, ketones, ethers, esters, alkanes, halogenated hydrocarbon compounds, nitriles, or mixtures thereof. The organic solvent is preferably chosen from acrylonitrile, isopropanol, acetic acid or mixtures thereof. More preferably, the organic solvent is acrylonitrile.

In one particular embodiment, the composition C<NUM> obtained at the end of step <NUM>) is washed by spraying washing solution over said composition C<NUM>.

In one particular embodiment, the composition C<NUM> obtained at the end of step <NUM>) is washed by placing the composition C<NUM> in suspension in the washing solution.

The weight ratio of the aqueous washing solution to the composition C<NUM> obtained at the end of step <NUM>) is advantageously between <NUM>:<NUM> and <NUM>:<NUM> and more preferably between <NUM>:<NUM> and <NUM>:<NUM>.

This washing step is advantageously carried out at a temperature of between -<NUM> and <NUM>, and preferably between <NUM> and <NUM>. A person skilled in the art knows how to adjust the temperature so as not to solubilize the crystals of ATBS.

The crystals of ATBS. Na obtained at the end of this optional step <NUM>) can be isolated from the washing solution by a solid-liquid separation step, in the form of a composition C<NUM>.

The solid-liquid separation step can be carried out using various technologies. Examples include, but are not limited to, the use of a vertical or horizontal centrifuge, a decanter, a filter press, a belt filter, a disc filter, a push filter or a rotary drum filter. The solid-liquid separation may also be carried out by gravitational settling.

In one particular embodiment, all or part of the recovered washing solution may be used again in step <NUM>), with or without a prior treatment step.

In one particular embodiment, all or part of the recovered washing solution may be used in the aqueous solution SA<NUM> in step <NUM>), with or without a prior treatment step.

The pH of the washing solution of step <NUM> is advantageously controlled between <NUM> and <NUM>, and preferably between <NUM> and <NUM>.

In an optional step <NUM>), the composition C<NUM> obtained at the end of step <NUM>) or the composition C<NUM> obtained at the end of step <NUM>) is dried.

The drying step can be carried out using various technologies. Examples include, but are not limited to, the use of all convection, conduction or radiation drying technologies (fluidized bed dryer, through-bed dryer, drying by conveyor belt, microwave, heated agitated filter, high-frequency radiation, infrared radiation, spraying).

The drying operation may be carried out at atmospheric pressure or else under vacuum.

The drying step may be carried out discontinuously (batch drying) or continuously.

During the production method, i.e., during steps <NUM>) to <NUM>), and regardless of the step, at least one polymerization inhibitor may be introduced in order to prevent the possible polymerization of the ATBS or its salt. This polymerization inhibitor may be chosen, in a non-limiting manner, from hydroquinone, paramethoxyphenol, phenothiazine, <NUM>,<NUM>,<NUM>,<NUM>-tetramethyl(piperidin-<NUM>-yl)oxyl, <NUM>-hydroxy-<NUM>,<NUM>,<NUM>,<NUM>-tetramethyl(piperidin-<NUM>-yl)oxyl, phenylene diamine derivatives, or mixtures thereof.

The inhibitor is preferably paramethoxyphenol or <NUM>-hydroxy-<NUM>,<NUM>,<NUM>,<NUM>-tetramethyl(piperidin-<NUM>-yl)oxyl.

The quantity of polymerization inhibitor that is introduced relative to the quantity of ATBS introduced in step <NUM>) is advantageously between <NUM>% and <NUM>% by weight, and more preferably between <NUM>% and <NUM>% by weight.

The polymerization inhibitor may be introduced during any one or more of the steps of the method. An additional quantity of it is preferably introduced during step <NUM>). More preferably, the polymerization inhibitor is part of the aqueous solution SA<NUM> introduced in step <NUM>).

The production method (steps <NUM>) to <NUM>)) may be carried out continuously or discontinuously (batch production).

In some embodiments, the novel crystalline form of ATBS. Na is used for producing polymers.

The polymer is obtained at least from ATBS, which is at least partially in the crystalline form of ATBS. Na having an X-ray powder diffraction pattern comprising peaks at <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>° <NUM>-theta angles (+/- <NUM>°).

The polymer is obtained at least partially from the crystalline form of ATBS. Na, and advantageously from at least one other monomer chosen from: hydrophilic non-ionic monomers, hydrophilic anionic monomers (distinct from the crystalline form of ATBS. Na), hydrophilic cationic monomers, hydrophilic zwitterionic monomers and hydrophobic monomers.

It may therefore be a polymer of several distinct monomers or a homopolymer.

Advantageously, at least <NUM> mol%, preferably at least <NUM> mol%, more preferably at least <NUM> mol%, and even more preferably at least <NUM> mol% of the ATBS used to obtain the polymer is the crystalline form of ATBS. Na according to the invention. Even more preferably, <NUM> mol% of the ATBS is the crystalline form of ATBS. Na according to the invention.

The polymer advantageously comprises between <NUM> and <NUM> mol% of ATBS, preferably between <NUM> and <NUM> mol%, more preferably between <NUM> and <NUM> mol% and, advantageously, at least <NUM> mol%, preferably at least <NUM> mol%, more preferably at least <NUM> mol%, and even more preferably at least <NUM> mol% is the crystalline form of ATBS. Even more preferably, <NUM> mol% of the ATBS that is used is the crystalline form of ATBS. Na according to the invention.

In one particular embodiment, the polymer advantageously comprises at least <NUM> mol% of ATBS, preferably at least <NUM> mol%, more preferably at least <NUM> mol%, more preferably at least <NUM> mol%, more preferably at least <NUM> mol%, more preferably at least <NUM> mol%, more preferably at least <NUM> mol%, more preferably at least <NUM> mol%, more preferably at least <NUM> mol% and, advantageously, at least <NUM> mol%, preferably at least <NUM> mol%, more preferably at least <NUM> mol%, and even more preferably at least <NUM> mol% is the crystalline form of ATBS. Na and, even more preferably, <NUM>% of the ATBS that is used is the crystalline form of ATBS. Na according to the invention.

In one particular embodiment, the polymer is a homopolymer of ATBS and, advantageously, at least <NUM> mol%, preferably at least <NUM> mol%, more preferably at least <NUM> mol%, and even more preferably at least <NUM> mol% is in the crystalline form of ATBS. Na, and even more preferably <NUM>% of the ATBS that is used is the crystalline form of ATBS. Na according to the invention.

In one particular embodiment, the polymer is a homopolymer of the crystalline form of ATBS.

In one particular embodiment, the polymer is a polymer obtained from ATBS (at least <NUM> mol% of which is advantageously in the crystalline form of ATBS. Na ) and at least one non-ionic monomer.

The polymer is obtained from the crystalline form of ATBS. Na, and advantageously from at least one other monomer which may be chosen from hydrophilic non-ionic 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.

Advantageously, the hydrophilic non-ionic monomer or monomers that can be used in the invention are chosen, in particular, from the group comprising water-soluble vinyl monomers such as acrylamide, methacrylamide, N-alkylacrylamides, N-alkylmethacrylamides, N,N-dialkylacrylamides (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-vinyl caprolactam, N-vinylformamide (NVF), N-vinylacetamide, N-vinylimidazole, N-vinyl succinimide, acryloyl morpholine (ACMO), glycidyl methacrylate, glyceryl methacrylate, vinyl acetate, diacetone acrylamide, methacrylic anyhydride, acrylonitrile, maleic anydride, itaconamide, hydroxyalkyl (meth)acrylate, aminoalkyl (meth)acrylate, thioalkyl (meth)acrylate, hydroxy alkyl acrylates, hydroxy alkyl methacrylates, and mixtures thereof. Of these non-ionic monomers, the alkyl groups are advantageously C<NUM>-C<NUM>, and more advantageously C<NUM>-C<NUM>. They are preferably linear alkyls. Preferably, the hydrophilic non-ionic monomer is acrylamide.

The polymer advantageously comprises between <NUM> and <NUM> mol% of hydrophilic non-ionic monomer(s), preferably between <NUM> and <NUM> mol%, and more preferably between <NUM> and <NUM> mol%.

Advantageously, apart from the ATBS. Na in crystalline form, the hydrophilic anionic monomer or monomers which can be used in the invention can be chosen from a large group. These monomers may have vinyl functions (advantageously acrylic, maleic, fumaric, malonic, itaconic, or allylic), and contain a carboxylate, phosphonate, phosphate, sulphate or sulphonate group, or another anionically charged group. Examples of suitable monomers include acrylic acid; methacrylic acid; dimethylacrylic acid; itaconic acid; C<NUM>-C<NUM> hemiesters of itaconic acid, crotonic acid; maleic acid; fumaric acid; acryloyl chloride, <NUM>-acrylamido-<NUM>-methylbutanoic acid; maleic anhydride; strong acid monomers having, for example, a sulphonic acid or phosphonic acid function, such as vinylsulphonic acid, vinylphosphonic acid, allylsulphonic acid, methallylsulphonic acid, <NUM>-methylidenepropane-<NUM>, <NUM>-disulphonic acid, <NUM>-sulphoethylmethacrylate, sulphopropylmethacrylate, sulphopropylacrylate, allylphosphonic acid, styrene sulphonic acid, ethylene glycol methacrylate phosphate, <NUM>-acrylamido-<NUM>-methylpropanesulphonic acid (ATBS), <NUM>-acrylamido-<NUM>-methylpropane disulphonic acid, <NUM>-allyloxy-<NUM>-hydroxypropane sulfonic acid, diethylallylphosphonate; water-soluble salts of these monomers such as their alkali metal salts (distinct from the crystalline form of ATBS. Na), alkaline-earth metal salts or ammonium salts; and mixtures thereof. Preferably, the hydrophilic anionic monomer or monomers is acrylic acid and/or its salts.

The polymer advantageously comprises between <NUM> and <NUM> mol% of hydrophilic non-ionic monomer(s) (distinct from the crystalline form of ATBS. Na), preferably between <NUM> and <NUM> mol%, more preferably between <NUM> and <NUM> mol%. Above <NUM> mol%, these percentages also include the monomer in crystalline form of ATBS. Na according to the invention.

In one particular embodiment, the hydrophilic anionic monomer or monomers, apart from ATBS. Na in crystalline form, may be salified.

By salified, we mean the substitution of a proton of at least one acid function of the - Ra(=O)-OH type (with R representing P, S or C) of the anionic monomer by a metal or ammonium cation to form a salt of the -Ra(=O)-OX type (X being a metal cation or an organic cation). In other words, the non-salified form corresponds to the acid form of the monomer, for example Rb-C(=O)-OH in the case of the carboxylic acid function, while the salified form of the monomer corresponds to the Rb-C(=O)-O- X+ form, X+ corresponding to an alkaline cation or an organic cation. The salification of the acid functions of the branched water-soluble polymer can be partial or total. The salified form advantageously corresponds to the salts of alkali metals (Li, Na, K, etc.), alkaline-earth metals (Ca, Mg, etc.) or ammonium (for example the ammonium ion or a tertiary ammonium). The preferred salt is sodium salt.

The salification may take place before, during or after polymerization.

In one particular embodiment, the polymer advantageously comprises between <NUM> and <NUM> mol% of hydrophilic anionic monomer(s) in salified form, preferably between <NUM> and <NUM> mol%. These percentages include the monomer in crystalline form of ATBS. Na according to the invention.

Advantageously, the hydrophilic cationic monomer or monomers that can be used in the invention are chosen from monomers derived from vinyl-type units (advantageously acrylamide, acrylic, allylic or maleic), these monomers having a phosphonium or quaternary ammonium function. Mention may be made, in particular and in non-limiting manner, of diallyldialkyl ammonium salts such as diallyl dimethyl ammonium chloride (DADMAC); acidified or quaternized salts of dialkylaminoalkyl(meth)acrylamides, e.g. methacrylamido-propyl trimethyl ammonium chloride (MAPTAC), acrylamido-propyl trimethyl ammonium chloride (APTAC); acidified or quaternized salts of dialkylaminoalkyl acrylate, such as quaternized or salified dimethylaminoethyl acrylate (DMAEA); acidified or quaternized salts of dialkylaminoalkyl methacrylate, such as quaternized or salified dimethylaminoethyl methacrylate (DMAEMA); acidified or quaternized salts of N,N-dimethylallylamine; acidified or quaternized salts of diallylmethylamine; acidified or quaternized salts of diallylamine; polyvinylamine resulting from the hydrolysis (basic or acid) of an amide group -N(R2)-CO-R1 with R1 and R2 being, independently, a hydrogen atom or an alkylated chain of <NUM> to <NUM> carbons, for example polyvinylamine obtained from the hydrolysis of polyvinylformamide; polyvinylamine obtained by Hofmann degradation; and mixtures thereof. Advantageously, the alkyl groups are C<NUM>-C<NUM>, preferably C<NUM>-C<NUM>, and can be linear, cyclic, saturated or unsaturated chains. Preferably, quaternized dimethylaminoethyl acrylate.

A person skilled in the art knows how to prepare quaternized monomers, for example using a quaternizing agent of the R-X type, where R is an alkyl group and X is a halogen or sulfate.

The term "quaternizing agent" refers to a molecule capable of alkylating a tertiary amine.

The quaternizing agent may be chosen from dialkyl sulfates containing from <NUM> to <NUM> carbon atoms or alkyl halides containing from <NUM> to <NUM> carbon atoms. Preferably, the quaternizing agent is chosen from methyl chloride, benzyl chloride, dimethyl sulfate or diethyl sulfate.

In addition, the present invention also covers DADMAC, APTAC and MAPTAC monomers in which the counterion is a sulfate, fluoride, bromide or iodide instead of chloride.

The polymer advantageously comprises between <NUM> and <NUM> mol% hydrophilic cationic monomer(s), and preferably between <NUM> and <NUM> mol%.

Advantageously, the hydrophilic zwitterionic monomer or monomers may be a derivative of a vinyl-type unit (advantageously acrylamide, acrylic, allylic or maleic), this monomer having a quaternary amine or ammonium function and a carboxylic (or carboxylate), sulphonic (or sulphonate) or phosphoric (or phosphate) acid function. Mention may be made, in particular and in a non-limiting manner, of dimethylaminoethyl acrylate derivatives, such as <NUM>-((<NUM>-(acryloyloxy)ethyl) dimethylammonio) dimethylammonio) ethane-<NUM>-sulphonate, <NUM>-((<NUM>-(acryloyloxy)ethyl) dimethylammonio) propane-<NUM>-sulphonate, <NUM>-((<NUM>-(acryloyloxy)ethyl) dimethylammonio) butane-<NUM>-sulphonate, [<NUM>-(acryloyloxy)ethyl] (dimethylammonio) acetate, dimethylaminoethyl methacrylate derivatives, such as <NUM>-((<NUM>-(methacryloyloxy) ethyl) dimethylammonio) ethane-<NUM>-sulphonate, <NUM>-((<NUM>-(methacryloyloxy) ethyl) dimethylammonio) propane-<NUM>-sulphonate, <NUM>-((<NUM>-(methacryloyloxy) ethyl) dimethylammonio) butane-<NUM>-sulphonate, [<NUM>-(methacryloyloxy)ethyl] (dimethylammonio) acetate, dimethylamino propylacrylamide derivatives, such as <NUM>-((<NUM>-acrylamidopropyl) dimethylammonio) ethane-<NUM>-sulphonate, <NUM>-((<NUM>-acrylamidopropyl) dimethylammonio) propane-<NUM>-sulphonate, <NUM>-((<NUM>-acrylamidopropyl) dimethylammonio) butane-<NUM>-sulphonate, [<NUM>-(acryloyloxy) propyl] (dimethylammonio) acetate, dimethylamino propyl methylacrylamide derivatives such as <NUM>-((<NUM>-methacrylamidopropyl) dimethylammonio) ethane-<NUM>-sulphonate, <NUM>-((<NUM>-methacrylamidopropyl) dimethylammonio) propane-<NUM>-sulphonate, <NUM>-((<NUM>-methacrylamidopropyl) dimethylammonio) butane-<NUM>-sulphonate and [<NUM>-(methacryloyloxy)propyl] (dimethylammonio) acetate and mixtures thereof.

Other hydrophilic zwitterionic monomers can be used, in particular those described by the Applicant in document <CIT>.

The polymer advantageously comprises between <NUM> and <NUM> mol% hydrophilic zwitterionic monomer(s), more preferably between <NUM> and <NUM> mol%.

Hydrophobic monomers with a coefficient partition Kow greater than <NUM> can also be used in the preparation of the polymer according to the invention. They are preferably chosen from the following list: (meth)acrylic acid esters with a (i) C<NUM>-C<NUM> alkyl, or (ii) arylalkyl (C<NUM>-C<NUM> alkyl, C<NUM>-C<NUM> aryl), or (iii) propoxylated, or (iv) ethoxylated, or (v) ethoxylated and propoxylated chain; alkyl aryl sulfonates (C<NUM>-C<NUM> alkyl, C<NUM>-C<NUM> aryl) ; mono- or disubstituted (meth)acrylamide amides bearing a (i) C<NUM>-C<NUM> alkyl, or (ii) arylalkyl (C<NUM>-C<NUM> alkyl, C<NUM>-C<NUM> aryl), or (iii) propoxylated, or (iv) ethoxylated, or (v) ethoxylated and propoxylated chain; anionic or cationic monomer derivatives of (meth)acrylamide or (meth)acrylic acid bearing a hydrophobic chain; N-vinylpyridine and mixtures thereof. The hydrophobic monomers may comprise halogen atoms, for example chlorine.

Preferred hydrophobic monomers belonging to these classes are, for example:.

When the polymer is water soluble, it advantageously comprises less than <NUM> mol% of hydrophobic monomers and the quantity thereof is adjusted in order for the polymer to remain soluble in water.

Monomers having a fluorescent function can also be used in the invention. A monomer with a fluorescent function may be detected by any suitable method, for example by fluorometry with a fixed wavelength fluorometer. Generally, the monomer with a fluorescent function is detected at the excitation and emission maxima, which can be determined using a scanning fluorometer.

Monomers with a fluorescent function are chosen, for example, from the following monomers: sodium or potassium styrene sulfonate, styrene sulfonic acid, vinylimidazole and its derivatives, <NUM>-vinyl anthracene and its derivatives, N-<NUM>-xanthenylacrylamide and its derivatives, allyl dibenzosuberenol and its derivatives, chinconicin and its derivatives, quininone and its derivatives, cinchoninone and its derivatives, N,N-dimethyl-N-[<NUM>-[N'-(<NUM>-m'thoxy naphthalimide)]]propyl-N-(<NUM>-hydroxy-<NUM>-allyloxy)propyl ammonium hydroxide and mixtures thereof.

Other fluorescent compounds can be used when functionalized with an allyl, vinyl or acrylic double bond, such as pyranine and its derivatives, coumarin and its derivatives, quinolaxine and its derivatives, pinacyanol and its derivatives, xanthydrol and its derivatives, dabsyl and its derivatives, <NUM>-hydroxy-<NUM>-methylene-<NUM>-(<NUM>-naphthyl)propionic acid and its derivatives, rhodamine and its derivatives, N-dibenzosuberylacrylamide and its derivatives, naphthalic derivatives, fluorescein and its derivatives, pyrene and its derivatives, carbostyril and its derivatives, pyrazoline and its derivatives and mixtures thereof.

In a preferred mode, the polymer does not comprise a monomer with a fluorescent function.

In one particular embodiment, the polymer may comprise at least one cyclic monomer with a hydrolyzable function. Advantageously, the or the cyclic monomers with a hydrolyzable function are chosen from cyclic ketene acetals, thionolactones and mixtures thereof.

The cyclic ketene acetal is advantageously chosen from: <NUM>-methylene-<NUM>,<NUM>-dioxepane (MDO), <NUM>,<NUM>-benzo-<NUM>-methylene-<NUM>,<NUM>-dioxepane (BMDO), <NUM>-methylene-<NUM>-phenyl-<NUM>,<NUM>-dioxolane (MPDL), <NUM>-methylene-<NUM>,<NUM>,<NUM>-trioxocane (MTC), and mixtures thereof. Preferably, it is <NUM>-methylene-<NUM>,<NUM>-dioxepane (MDO).

The thionolactone is advantageously chosen from: dibenzo[c,e]oxepine(<NUM>)-<NUM>-thione (DOT), ε-thionocaprolactone, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-dihydro-<NUM>-benzo[e][<NUM>,<NUM>]dioxepine-<NUM>-thione (DBT) and mixtures thereof. Preferably, it is <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-dihydro-5Hbenzo[e][<NUM>,<NUM>]dioxepine-<NUM>-thione.

In one particular embodiment, the polymer may comprise at least one group with an LCST.

According to the general knowledge of a person skilled in the art, a group with an LCST corresponds to a group whose water solubility, for a given concentration, is modified above a certain temperature and as a function of salinity. It is a group with a heating transition temperature that defines its lack of affinity with the solvent medium. The lack of affinity with the solvent results in opacification or loss of transparency, which may be due to precipitation, aggregation, gelation or viscosification of the medium. The minimum transition temperature is known as the LCST (Lower Critical Solution Temperature). For each concentration a group with an LCST, a heating transition temperature is observed. It 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.

In one particular embodiment, the polymer may comprise at least one group with an UCST.

According to the general knowledge of a person skilled in the art, a group with a UCST corresponds to a group whose water solubility, for a given concentration, is modified below a certain temperature and as a function of salinity. It is a group with a cooling transition temperature that defines its lack of affinity with the solvent medium. The lack of affinity with the solvent results in opacification or loss of transparency, which may be due to precipitation, aggregation, gelation or viscosification of the medium. The maximum transition temperature is known as the UCST (Upper Critical Solution Temperature). For each concentration a group with a UCST, a cooling transition temperature is observed. It 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.

The quantities of the different monomer(s) will be adjusted by a person skilled in the art in order not to exceed <NUM> mol% when preparing the polymer according to the invention.

According to the invention, the polymer may 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 selecting the initiator, the transfer agent, the polymerization technique such as Reversible Addition Fragmentation chain Transfer (RAFT) polymerization, Nitroxide Mediated Polymerization (NMP) or Atom Transfer Radical Polymerization (ATRP), the incorporation of structural monomers, or the concentration.

The polymer may further by structured by a crosslinking agent. A structured polymer is a non-linear polymer that has side chains such that, when dissolved in water, the polymer has a high degree of entanglement leading to very high low-gradient viscosities.

The crosslinking agent is advantageously chosen from:.

The quantity of branching agent in the polymer is advantageously less than <NUM>,<NUM> ppm by weight relative to the total weight of the monomers of the polymer, preferably less than <NUM>,<NUM> ppm by weight, and more preferably less than <NUM>,<NUM> ppm by weight.

In one particular embodiment, the quantity of branching agent is at least equal to <NUM> ppm by weight relative to the total weight of the monomers of the polymer, preferably at least <NUM> ppm by weight, more preferably at least <NUM> ppm by weight, more preferably at least <NUM> ppm by weight and even more preferably at least <NUM><NUM> ppm by weight.

When the polymer is water soluble and comprises a branching agent, the polymer remains soluble in water. A person skilled in the art knows how to adjust the quantity of branching agent and, possibly, the quantity of transfer agent needed to obtain this result.

In a preferred embodiment, the polymer is a water-soluble polymer comprising no branching agent.

In one particular embodiment, the polymer may comprise a transfer agent.

The transfer agent is advantageously chosen from methanol; isopropyl alcohol; sodium hypophosphite; calcium hypophosphite; magnesium hypophosphite; potassium hypophosphite; ammonium hypophosphite; formic acid; sodium formate; calcium formate; magnesium formate; potassium formate; ammonium formate; <NUM>-mercaptoethanol; <NUM>-mercaptopropanol; dithiopropylene glycol; thioglycerol; thioglycolic acid; thiohydracrylic acid; thiolactic acid; thiomalic acid; cysteine; aminoethanethiol; thioglycolates; allyl phosphites; allyl mercaptans, such as n-dodecyl mercaptan; sodium methallysulfonate; calcium methallysulfonate; magnesium methallysulfonate; potassium methallysulfonate; ammonium methallysulfonate; alkyl phosphites such as trialkyl (C<NUM>-C<NUM>) phosphites, di-oleyl-hydrogen phosphites, dibutyl phosphite; dialkyldithiophosphates such as dioctyl phosphonate; tertiary nonylmercaptan; <NUM>-ethylhexyl thioglycolate; n-octyl mercaptan; n-dodecyl mercaptan; tertiary-dodecyl mercaptan; iso-octylthioglycolate; <NUM>-ethylhexyl thioglycolate; <NUM>-ethylhexyl mercaptoacetate; polythiols; and mixtures thereof. Preferably, the transfer agent is sodium hypophosphite or sodium formate.

The quantity of transfer agent in the polymer is advantageously between <NUM> and <NUM>,<NUM> ppm by weight relative to the total weight of the monomers of the polymer, preferably between <NUM> and <NUM>,<NUM> ppm by weight, more preferably between <NUM> and <NUM>,<NUM> ppm by weight, and even more preferably between <NUM> and <NUM> ppm by weight. When it is present, the transfer agent represents at least <NUM> ppm by weight relative to the total weight of the monomers of the polymer, and preferably at least <NUM> ppm by weight.

In one particular embodiment, the polymer comprises no transfer agent.

Generally speaking, the polymer does not require the development of any particular polymerization method. Indeed, it may be obtained using any of the polymerization techniques that are well known to a person skilled in the art. These include solution polymerization; gel polymerization; precipitation polymerization; emulsion polymerization (aqueous or inverse); suspension polymerization; reactive extrusion polymerization; water-in-water polymerization; or micellar polymerization.

The polymerization is generally radical polymerization, preferably by inverse emulsion polymerization or gel polymerization. Radical polymerization includes free radical polymerization using UV, azo, redox or thermal initiators, as well as controlled radical polymerization (CRP) or matrix polymerization techniques.

Controlled radical polymerization techniques include, but are not limited to, techniques such as Iodine Transfer Polymerization (ITP), Nitroxide Mediated Polymerization (NMP), Atom Transfer Radical Polymerization (ATRP), Reversible Addition Fragmentation chain Transfer (RAFT) Polymerization, which includes MADIX (MAcromolecular Design by Interchange of Xanthates) technology, various variations of Organometallic Mediated Radical Polymerization (OMRP), and OrganoHeteroatom-mediated Radical Polymerization (OHRP).

The polymer may be partially or totally post-hydrolyzed.

Post-hydrolysis is the hydrolysis reaction of the polymer after it has been formed by polymerization of the monomer(s). This step consists in reacting hydrolysable functional groups of monomers, advantageously non-ionic functional groups, more advantageously amide or ester functional groups, with a hydrolysis agent. This hydrolysis agent may, for example, be an enzyme, an ion-exchange resin, or a Brønsted acid metal (for example a hydrohalogenic acid) or a Brønsted base (for example an alkali hydroxide or an alkaline-earth hydroxide). Preferably, the hydrolysis agent is a Brønsted base. During this step of post-hydrolyzing the polymer, the number of carboxylic acid functions increases. Indeed, the reaction between the base and the amide or ester functions present in the polymer produces carboxylate groups.

The polymer may 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 drying in a fluidized bed.

The polymer advantageously has a molecular weight of at least <NUM> million g/mol, preferably between <NUM> and <NUM> million g/mol, more preferably between <NUM> and <NUM> million g/mol. Molecular weight is defined as weight-average molecular weight. The polymer may also have a molecular weight of between <NUM>,<NUM> and <NUM>,<NUM>/mol or between <NUM>,<NUM> and <NUM>,<NUM>/mol.

The molecular weight is determined by the intrinsic viscosity of the polymer. The intrinsic viscosity can be measured by methods known to a person skilled in the art and can be calculated from the reduced viscosity values for different polymer concentrations by a graphical method consisting in plotting the reduced viscosity values (y-axis) against the concentration (x-axis) and extrapolating the curve to zero concentration. The intrinsic viscosity value is plotted on the y-axis or using the least-squares method. The molecular weight can then be determined using the Mark-Houwink equation: <MAT>.

In some embodiments, the polymer may be used in: drilling or cementing wells; conformance, diversion; open, closed or semi-closed circuit water treatment; treatment of fermentation broth; sludge treatment; construction; paper or cardboard manufacture; batteries; wood treatment; treatment of hydraulic compositions (concrete, cement, mortar and aggregates); formulation of cosmetic products; formulation of detergents; textile manufacture; geothermal energy; manufacture of diapers; or agriculture.

In some embodiments, the polymer may be used as a coagulant, binding agent, absorbent agent, draining agent, filler retention agent, dehydrating agent, conditioning agent, stabilising agent, fixing agent, film-forming agent, sizing agent, superplasticizing agent, clay inhibitor or dispersant.

The invention and its advantages will be better understood in the light of the following figures and examples provided in order to illustrate the invention in a non-limiting manner.

<NUM> of acrylonitrile containing <NUM>% by weight of water are added to a stirred, double-jacketed <NUM> reactor, the mixture is stirred for <NUM> and cooled by the double jacket of the reactor, which keeps the temperature of the sulphonating mixture at -<NUM>, and then <NUM> of fuming sulphuric acid with a titre of <NUM>% H<NUM>SO<NUM> (<NUM>% oleum) are added.

<NUM> of isobutylene are added to the previous sulphonating mixture at a rate of <NUM>/min.

The temperature of the mixture is controlled at <NUM> when the isobutylene is added. The particles of the <NUM>-acrylamido-<NUM>-methylpropanesulphonic acid precipitate out of the mixture and the solids content is approximately <NUM>% by weight. The reaction mixture is filtered through a Büchner funnel and dried under vacuum at <NUM>. The solid obtained is <NUM>-acrylamido-<NUM>-methylpropanesulphonic acid (ATBS AH) in the form of a very fine white powder.

Optical microscope observation (<FIG>) shows that the crystals of ATBS AH have a needle-shape morphology.

<NUM> of a <NUM>% (by weight in water) sodium hydroxide solution are added to a stirred, double-jacketed <NUM> reactor. <NUM> of ATBS AH of example <NUM> are added to the previous mixture.

The mixture is stirred for <NUM>, at <NUM>, to form an aqueous solution SA<NUM>.

The aqueous solution SA<NUM> is heated to a temperature of <NUM> under vacuum of <NUM> mbar, for <NUM>, then the temperature is maintained for <NUM> under a vacuum of <NUM> mbar and cooled to a temperature of <NUM>. The cooling time between <NUM> and <NUM> is <NUM>. A suspension S<NUM> of crystals of the ATBS. Na is obtained. The suspension S<NUM> is filtered on a Robatel vertical centrifuge. A solid of composition C<NUM> is obtained, containing <NUM>% by weight of crystals of the ATBS.

Optical microscope observation (<FIG>) shows that the crystals ANa2a have a columnar and platelet morphology.

The crystals of ATBS. Na ANa2b are prepared according to the procedure described in Example 2a except that SA<NUM> is distilled under <NUM> mbar.

Optical microscope observations (<FIG>) show that the crystals ANa2b obtained in these conditions are identical to the crystals of ATBS. Na ANa2a prepared in example 2a.

The crystals of ATBS. Na ANa2c are prepared according to the procedure described in Example 2a except that the cooling time is reduced to 3h45.

Optical microscope observations (<FIG>) show that show that the crystals obtained in these conditions are identical to the crystals of ATBS.

The reaction is carried out according to the procedure described in Example 2a except that SA<NUM> is distilled under atmospheric pressure.

At the end of the cooling step, the aqueous solution SA<NUM> does not allow the formation of a suspension S1, and no filtration or centrifuging operation can be carried out to isolate crystals of ATBS sodium salt.

The reaction was carried out according to the conditions described in example <NUM> of patent application <CIT>.

<NUM> of sodium hydroxide and <NUM> of hydroquinone monomethyl ether are added to a stirred, double-jacketed <NUM><NUM> reactor with <NUM> of water. The medium is stirred until all the sodium hydroxide is dissolved.

<NUM> of ATBS AH are added to the previous mixture. The mixture is stirred for <NUM>, at <NUM>, to form an aqueous solution of sodium salt of <NUM>-acrylamido-<NUM>-methylpropanesulfonate.

The aqueous solution obtained is filtered in a <NUM><NUM> reactor equipped for distillation and containing an air purge tube. The content is heated and stirred while air is blown belon the surface at <NUM> cubic feet per h. The content is heated to <NUM> while under a vacuum of <NUM> mbar (~<NUM> millimeters of mercury). As the water is removed, a yellowish honeylike product forms. The product is then transfer to a Robatel vertical centrifuge, but no solid was recovered.

No optical microscope observation was possible as no solid was obtained (<FIG>).

The reaction was carried out according to the conditions described in example <NUM> of patent application<CIT>.

<NUM> of an ATBS. Na solution (<NUM>% by weight) is obtained according to example <NUM> of WO2013079507.

<NUM> of solvent (mixture of acrylonitrile and methanol) are removed from the ATBS. Na solution at room temperature under reduced pressure (less than <NUM> mbar) while introducing air into the ATBS. Na solution. A solid of ATBS. Na CE-ANa2c is formed and is filtered and washed with acrylonitrile/methanol and then dried at <NUM> overnight.

Optical microscope observation (<FIG>) shows that the dried solid of ATBS. Na CE-ANa2c does not correspond to the crystals of ATBS. Na according to the invention.

The reaction is carried out according to the procedure described in Example 2a except that SA<NUM> is distilled under <NUM> mbar.

A solid of composition C1 is obtained, containing <NUM>% by weight of crystals of the ATBS. Na CE-ANa2d.

Optical microscope observation (<FIG>) shows that the crystals of ATBS. Na CE-ANa2d does not correspond to the crystals of ATBS. Na according to the invention.

The reaction is carried out according to the procedure described in Example 2a except that the cooling time is 3h20.

A solid of composition C<NUM> is obtained, containing <NUM>% by weight of crystals of the ATBS. Na CE-ANa2e.

Optical microscope observation (<FIG>) shows that the crystals of ATBS. Na CE-ANa2e does not correspond to the crystals of ATBS. Na according to the invention.

ATBS AHand ATBS. Na ANa2a of are analysed by proton nuclear magnetic resonance (NMR).

The samples are dissolved in D<NUM>O. The NMR machine is a Bruker model with a frequency of <NUM> and is fitted with a <NUM> BBO BB-<NUM>H.

The two proton spectra (<FIG> and <FIG>) are similar and the peak assignments are consistent with the molecular structure of ATBS or the sodium salt.

ATBS AH and crystals of ATBS. Na ANa2a are ground beforehand to form powders to be analysed by X-ray diffraction over an angular range of <NUM> to <NUM>°. The equipment used is a Rigaku MiniFlex II diffractometer equipped with a copper source.

Crystals of ATBS. Na ANa2a (<FIG>) present an X-ray diffraction pattern with the following characteristic peaks:
<NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>°; <NUM>° <NUM>-theta angles (+/- <NUM>°).

The X-ray diffraction pattern of the ATBS AH (<FIG>) does not have the same peaks.

The equipment used for the Fourier transform infrared measurement is the Perkin Elmer Spectrum <NUM> fitted with a single reflection ATR polarization accessory, with an accuracy of <NUM>-<NUM>.

ATBS AH and crystals of ATBS. Na ANa2a are sieved to <NUM>. The particles remaining on the sieve are dried and placed in an oven at <NUM> for at least <NUM>.

A few hundred milligram of solid are placed on the diamond of the ATR accessory and pressure is applied manually using the accessory.

The following bands (<FIG>) are characteristic of the crystalline form of the ATBS. Na ANa2a:
<NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>.

The infrared spectrum of ATBS AH (<FIG>) does not have the same peaks.

The equipment used is a Mettler DSC <NUM>.

ATBS AH and crystals of ATBS. Na ANa2a are analysed with a heating ramp of <NUM>/min under a flow of nitrogen. The initial temperature is <NUM>, and the product is heated to <NUM>.

The thermogram of ATBS AH (<FIG>) shows a thermal effect at a temperature of <NUM>, which is generally considered to be the melting/degradation point of ATBS, followed by two exothermic degradation phenomena at <NUM> and <NUM>.

The thermogram of the crystals of ATBS. Na ANa2a (<FIG>) shows <NUM> thermal phenomena at <NUM>; <NUM>; <NUM>; and <NUM>.

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

Total induction is less than <NUM> microhenry. Discharge voltage is between <NUM> kV and <NUM> kV. The electrodes are made of brass and spaced apart by a minimum distance of <NUM>.

It is clear that the crystalline form of ATBS. Na ANa2a presents a much lower risk of explosion than the needle form of ATBS AH.

The ATBS AH and crystals of ATBS. Na ANa2a are analysed by laser diffraction to determine their particle-size distribution.

The laser diffraction equipment used is a Cilas <NUM>.

The crystals of ATBS AH have a d<NUM> value of approximately <NUM> and <NUM>% of the particles are smaller than <NUM> (<FIG>).

The crystals of ATBS. Na ANa2a have a d<NUM> value of approximately <NUM> and <NUM>% of the particles are smaller than approximately <NUM> (<FIG>). The crystals of ATBS. Na ANa2a contain less than <NUM>% of particles smaller than <NUM>.

<NUM> of each ATBS AH and ANa2a and ATBS CE-ANa2c to 2e are deposited on two carbon steel plates measuring <NUM> x <NUM>. The coated plates are placed in an oven at <NUM> for <NUM> days. At the same time, a control plate is left uncoated but placed under the same temperature conditions.

Photographs of the plates in this situation (<FIG>) show visually more pronounced corrosion on the plate that had been in contact with ATBS AH compared to the crystals of ANa2a. Weighing the plates before and after the contact period confirms these observations.

Solid ATBS sodium salts CE-ANa2c to 2e have also been tested.

<NUM> of the crystalline form of the ATBS. Na ANa2a and <NUM> of water are introduced into a double-jacketed <NUM> reactor fitted with a condenser, a pH meter and a stirrer.

The mixture has a pH greater than <NUM>.

The mixture obtained is a solution of ATBS. Na at a concentration of <NUM>% by weight in water.

The same protocol as in example <NUM>a is reproduced but using the crystal CE-ANa2c.

The same protocol as in example <NUM>a is reproduced but using the crystal CE-ANa2d.

The same protocol as in example <NUM>a is reproduced but using the ATBS. Na CE-ANa2e.

<NUM> of ATBS AH and <NUM> of water are introduced into a double-jacketed <NUM> reactor fitted with a condenser, a pH meter and a stirrer. The mixture has a pH less than <NUM>.

A <NUM>% by weight sodium hydroxide in water solution is prepared in a dropping funnel. The caustic solution is added to the reaction mixture over <NUM>. The temperature is controlled to less than <NUM>.

The final pH of the solution is between <NUM> and <NUM>.

<NUM> of <NUM>% by weight sodium hydroxide in water solution are added.

<NUM> of <NUM>% (by weight in water) of the solutions of ATBS. Na prepared according to examples 10a-d and <NUM> were stored for <NUM> months in order to compare their stability over time by measuring and monitoring the appearance of homopolymers of ATBS.

In parallel, the stability of the different ATBS (acid AH or sodium salt ANa2a) in solid form was also assessed over the same period of time.

In this case, every three months, <NUM> of a solution of ATBS. Na was freshly prepared according to the preparation process described in example <NUM>a or <NUM> using the stored ATBS products of AH, ANa2a and CE-ANa2c to 2e.

Stability of the solid products was also assessed by monitoring the amount of homopolymers of ATBS. Na present after that time.

The solutions were analysed by liquid-phase steric exclusion chromatography using an Agilent <NUM> chromatograph equipped with Aquagel-OH <NUM>, <NUM>, <NUM> and <NUM> columns allowing analysis of anionic polymers up to <NUM>,<NUM>/mol PEG equivalent.

The solutions of ATBS. Na were diluted to <NUM> ppm (by weight in water) before being injected. The UV signal at <NUM> at the column outlet was integrated for the polymer peaks and are detailed in tables <NUM>a and <NUM>b below. The larger the signal area, the more polymer is present, and therefore the lower the stability of the product over time.

These results demonstrate that, whether stored in solid or as a solution, the crystalline form of ATBS. Na of the present invention presents an improved stability on storage over time.

<NUM> of deionized water, <NUM> of <NUM>% (by weight in water) acrylamide solution, <NUM> of urea and <NUM> of crystals of ATBS. Na ANa2a are added to a <NUM> beaker.

The resulting solution is cooled to between <NUM> and <NUM> and transferred to an adiabatic polymerization reactor, where it is bubbled with nitrogen for <NUM> to remove all traces of dissolved oxygen.

The following are then added to the reactor:.

After a few min, the nitrogen inlet is shut off and the reactor is closed. The polymerization reaction takes place for <NUM> to <NUM> until a temperature peak is reached. The rubbery gel obtained is chopped into particles of between <NUM> and <NUM> in size.

The gel is then dried and ground to obtain polymer P1-ANa2a in powder form.

<NUM> of deionized water are added to a <NUM> beaker, the solution is cooled to <NUM>, and <NUM> of crystals of ATBS AH are added.

<NUM> of <NUM>% (by weight in water) sodium hydroxide solution are prepared in a dropping funnel. As soon as a complete dissolution of the crystals is obtained, the caustic solution is added to the reaction mixture over <NUM>. The temperature is controlled to be below <NUM>. The final pH of the solution is between <NUM> and <NUM>.

<NUM> of acrylamide in <NUM>% solution (by weight in water) and <NUM> of urea were added to complete the mixture.

The gel is then dried and ground to obtain the polymer P1-AH in powder form.

The same protocol as in example <NUM> is reproduced but using the ATBS. Na CE- ANa2c to produce polymer P1-CEANa2c.

The same protocol as in example <NUM> is reproduced but using the ATBS. Na CE- ANa2d to produce. polymer P1-CEANa2d.

The same protocol as in example <NUM> is reproduced but using the ATBS. Na CE- ANa2e to produce. polymer P1-CEANa2e.

<NUM> of deionized water and <NUM> of crystals of the ATBS. Na ANa2a are added to a <NUM> beaker.

After a few min, the nitrogen inlet is shut off and the reactor is closed. The polymerization reaction takes place for <NUM> to <NUM> until a temperature peak is reached. The rubbery gel obtained is chopped and dried to obtain a coarse powder which is itself ground and sieved to obtain the polymer P2-ANa2a in powder form.

<NUM> of deionized water are added to a <NUM> beaker, the solution is cooled to <NUM>, and <NUM> of crystals of ATBS AH are added under stirring.

<NUM> of <NUM>% (by weight in water) sodium hydroxide solution are prepared in a dropping funnel. the caustic solution is added to the reaction mixture over <NUM>. The temperature is controlled to be below <NUM>. The final pH of the solution is between <NUM> and <NUM>.

After a few min, the nitrogen inlet is shut off and the reactor is closed. The polymerization reaction takes place for <NUM> to <NUM> until a temperature peak is reached. The rubbery gel obtained is chopped and dried to obtain a coarse powder which is itself ground and sieved to obtain the polymer P2-AH in powder form.

The same protocol as in example <NUM> is reproduced but using the ATBS. Na CE-ANa2c to produce polymer P2-CEANa2c.

The same protocol as in example <NUM> is reproduced but using ATBS. Na CE-ANa2d to produce. polymer P2-CEANa2d.

The same protocol as in example <NUM> is reproduced but using the ATBS. Na CE-ANa2e to produce polymer P2-CEANa2e.

The experimental protocol of example <NUM> is reproduced except that the quantities of the different monomers are adjusted to reach the desired molar composition of acrylamide/acrylic acid/ATBS in the copolymer P3-ANa2a.

Polymers P3-AH is prepared using ATBS AH.

Polymers P3-CEANa2c is prepared using ATBS. Na CE-ANa2c.

Polymers P3-CEANa2d is prepared using ATBS. Na CE-ANa2d.

Polymers P3-CEANa2e is prepared using ATBS. Na CE-ANa2e.

Polymers P4-ANa2a, P'<NUM>-AH, P4-CEANa2c, P4-CEANa2d and P4-CEANa2e are prepared according to the preparation process described in Example 16a.

Polymers P5-ANa2a, P5-AH, P5-CEANa2c, P5-CEANa2d and P5-CEANa2e are prepared according to the preparation process described in Example 16a.

The reduced viscosity of the polymers prepared in examples <NUM> to <NUM> is measured at <NUM> in a <NUM> aqueous sodium chloride solution using a Brookfield LVT viscometer fitted with a UL adapter at <NUM> rpm.

<NUM> of dried polymers are dissolved in a beaker containing <NUM> of deionized water at a stirring speed of <NUM> rpm.

<NUM> of sodium chloride are added to the prepared solutions.

The solutions are left to stir for <NUM> at <NUM> rpm to dissolve the salt completely.

The prepared solutions are filtered through a <NUM> mesh.

<NUM> of the prepared solutions is transferred to a cylindrical tube and used to carry out a viscosity measurement.

Claim 1:
Crystaline form of <NUM>-acrylamido-<NUM>-methylpropanesulphonic acid sodium salt ATBS.Na having an X-ray powder diffraction pattern comprising peaks at <NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>°; <NUM>,<NUM>° <NUM>-theta angles (+/- <NUM>°).