Stabilised concentrated mineral suspension

Abstract

The invention provides an aqueous suspension of a mineral material, for example calcium carbonate, which suspension is prepared by wet grinding step followed by a concentration step in the presence of at least one rheological agent R comprising phosphoric acid and an α-sulfonated polymer P which is completely or partially neutralised by means of a monovalent ion. The invention also relates to the rheological agent R and to the use of this mineral suspension for preparing a mass filler for paper, for preparing a paper coating slip, or for preparing a coating composition, for example a paint composition.

Description

[0001] STABILIZED CONCENTRATED MINERAL SUSPENSION

[0002] The invention provides an aqueous suspension of a mineral material, for example calcium carbonate, which is prepared by wet grinding and then concentration after grinding in the presence of at least one rheological agent R comprising phosphoric acid and an a-sulfonated polymer P which is totally or partially neutralized by means of a monovalent ion. The invention also relates to the rheological agent R as well as to the use of this mineral suspension for the preparation of a paper mass filler or a paper coating slip or for the preparation of a coating composition, for example a paint composition.

[0003] Methods for preparing suspensions of mineral matter are known. In particular, methods are known which use additives during the various stages of these methods, in particular additives to control the rheology of the suspension during its preparation or during its storage.

[0004] In general, mineral grinding methods must be efficient and allow for control of the particle size of the particles obtained. In addition, mineral grinding methods must have a high efficiency in terms of grinding time for a particular particle size and for a defined quantity of mineral material. Indeed, for the preparation of a defined quantity of mineral particles, a reduced operating time of the grinding plants allows for an improvement in the overall efficiency of the method for preparing an aqueous suspension of mineral material.

[0005] Similarly, it is important to have mineral grinding methods that allow the preparation of aqueous suspensions of mineral particles that are stable shortly after their preparation but also for several hours or days after. Viscosity drift phenomena must be controlled because they can lead to gelation of the prepared suspensions, which would make handling difficult or even impossible. Similarly, particle sedimentation phenomena must be avoided or significantly slowed down. In addition to stability control, viscosity control of aqueous suspensions of ground mineral particles is also essential.

[0006] It is also important to be able to prepare aqueous suspensions of mineral particles with a high dry extract. A high dry extract of these aqueous suspensions of mineral particles makes it possible, in particular, to increase the productivity of methods that use these suspensions as well as to limit the costs and resources for transporting these suspensions.

[0007] Furthermore, rheological control agents should be able to be prepared in the absence of any compound that may be considered environmentally harmful or in the absence of any compound whose use is restricted by regulatory provisions. In particular, the preparation of these agents in the absence of any compound containing phosphorus should be preferred, in particular the absence of phosphorus in oxidation states I, III or V.

[0008] Furthermore, during papermaking, aqueous mineral filler compositions are used to provide a mineral filler within the pulp comprising water and plant-based fibers, in particular cellulosic fibers. Within these compositions, the mineral filler is in the form of particles. The use of such mineral fillers makes it possible in particular to improve the physical properties of the paper, in particular to improve its optical properties, or to reduce the relative quantity of cellulosic material compared to the quantity of mineral filler. Improving the efficiency of papermaking methods is also made possible by the use of these mineral fillers. The formation of flocs of mineral filler particles or fibers that disrupt the quality of the paper must be limited.The ability to prepare particle suspensions with a narrow size distribution must also be sought to improve the quality of coated paper using these suspensions. In particular, limiting the fraction of very fine particles then makes it possible to improve the opacity of coated paper.

[0009] Improving the compatibility of the different compounds used in paper preparation should also be sought.

[0010] WO 02070571 describes the preparation of polyacrylic acid in ethanol in the presence of compounds comprising sulfur. These polymers are used to disperse ground calcium carbonate. FR 2846972 discloses an aqueous mineral suspension prepared in the presence of an acrylic polymer as a grinding aid. JP 2014105224 relates to a method for producing a suspension of mineral particles which uses an aqueous solution of poly(meth)acrylic acid polymer during the grinding of the mineral. WO 2014021345 describes a (meth)acrylic acid polymer prepared in the presence of a mercapto-carboxylic compound and usable as a dispersant for mineral particles. EP 2583984 describes the preparation of an aqueous mineral suspension in the presence of a partially neutralized phosphino-carboxylic polymer and used as a grinding agent for mineral particles.

[0011] Thus, although there are methods for wet grinding of mineral matter, some of which can use polymers as grinding aids, the methods of the prior art do not always provide a satisfactory solution to the problems encountered with the aqueous mineral suspensions obtained. There is therefore a need to have improved aqueous suspensions of mineral matter. The invention makes it possible to provide a solution to all or part of the problems of the suspensions of the prior art.

[0012] Thus, the invention provides an aqueous suspension S of particles of at least one mineral material M prepared:

[0013] * by grinding in water at a concentration ranging from 10% by weight to 60% by weight of an aqueous suspension Sd of at least one particulate mineral material M, then

[0014] * by concentration to a concentration ranging from 65% by weight to 80% by weight, by a treatment chosen from mechanical treatment, heat treatment and their combinations, of the ground suspension Sd, in the presence of at least one rheological agent R comprising phosphoric acid and at least one a-sulfonated polymer P prepared in water and in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer A chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and their combinations, in the presence of at least one initiator compound and at least one sulfur compound T comprising sulfur in oxidation state IV, and totally or partially neutralized by means of at least one monovalent ion.

[0015] Preferably according to the invention, the suspension S has a Brookfield viscosity at 25°C, at 100 rpm, measured 1 hour after its preparation, of less than 1,000 mPa.s, preferably less than 800 mPa.s. Also preferably according to the invention, the suspension S has a Brookfield viscosity at 25°C, at 100 rpm and after stirring, measured 24 hours after preparation and storage at 60°C, of ​​less than 800 mPa.s, preferably less than 600 mPa.s. Also preferably according to the invention, the suspension S has a Brookfield viscosity at 25°C, at 100 rpm and before stirring, measured 24 hours after preparation and storage at 60°C, of ​​less than 3,000 mPa.s, preferably less than 2,500 mPa.s, more preferably less than 2,000 mPa.s or 1,900 mPa.s.

[0016] Preferably, the suspension S uses a single material M or two or three materials M. According to the invention, the material M is synthetic or of natural origin. Preferably, the material M is chosen from alkaline earth metal carbonate, more preferably calcium carbonate (natural calcium carbonate or precipitated calcium carbonate), strontium carbonate, magnesium carbonate, barium carbonate and combinations thereof, dolomite, kaolin, titanium dioxide, talc, lime, calcium sulfate, barium sulfate and combinations thereof. Most preferably, the material M is chosen from natural calcium carbonate, precipitated calcium carbonate, magnesium carbonate, dolomite, kaolin, titanium dioxide, talc, lime. Even more preferably, the material M is calcium carbonate.

[0017] Thus, essentially according to the invention, the aqueous suspension S and the suspension Sd comprise particles of at least one mineral material M. According to the invention, the concentration of the suspension S or the suspension Sd is its concentration by weight of dry matter particles of material M. Preferably according to the invention, the concentration of the suspension S is greater than 70% by weight. Also preferably according to the invention, the concentration of the suspension S is less than 78% by weight or less than 75% by weight. More preferably according to the invention, the concentration of the suspension S ranges from 70% by weight to 78% by weight or from 70% by weight to 75% by weight.

[0018] According to the invention, the particles of ground material M have a median size, measured by sedimentometry, of less than 50 pm or a median size ranging from 0.05 to 50 pm or a median size of less than 10 pm, preferably less than 5 pm or 2 pm, more preferably less than 1 pm or less than 0.5 pm.

[0019] Sedimentometry is a method of measuring the rate at which solid particles fall into a less dense liquid. Using Stokes' law, the grain size is determined according to:

[0020] • v: sedimentation rate (m / s)

[0021] • g: acceleration of gravity (m / s 2 )

[0022] • Ay: difference in density between the particles and the suspending liquid (kg / m 3 )

[0023] • p: viscosity of the suspending liquid (Pa.s).

[0024] The particle diameter or its Stokes diameter is then determined according to formula I:

[0025] 18 pvd = ( According to the invention, sedimentometry is carried out by X-rays which measure the absorption of radiation by the suspension at a given height and a given time depending on the concentration.

[0026] Preferably according to the invention, the concentration of the Sd suspension is greater than 10% by weight. Also preferably according to the invention, the concentration of the Sd suspension is less than 60% by weight. More preferably, the concentration of the Sd suspension ranges from 10% by weight to 60% by weight.

[0027] Essentially according to the invention, the concentration of the ground Sd suspension is carried out by a treatment chosen from mechanical treatment, heat treatment and their combinations, in the presence of a rheological agent R comprising phosphoric acid and at least one a-sulfonated polymer P.

[0028] Phosphoric acid is a compound of formula H3PO4. According to the invention, the concentration of the ground suspension Sd uses from 0.05% by weight to 3% by weight of phosphoric acid relative to the quantity by weight of mineral matter M. Preferably, the phosphoric acid is used from 0.1% by weight to 3% by weight or from 0.1% by weight to 2% by weight of phosphoric acid relative to the quantity by weight of mineral matter M.

[0029] More preferably, the phosphoric acid is used from 0.1% by weight to 1% by weight or from 0.1% by weight to 0.6% by weight of phosphoric acid relative to the quantity by weight of mineral matter M.

[0030] Preferably according to the invention, the rheological agent R comprises at least one polymer P chosen from an a-co-disulfonated polymer P1, an a-monosulfonated polymer P2 and combinations thereof.

[0031] According to the invention, polymer P is prepared using monomer A. Preferably, monomer A is selected from acrylic acid, an acrylic acid salt and combinations thereof. The preferred monomer A is acrylic acid. Also preferably, monomer A may be combined with at least one other monomer selected from vinyl acetate, ethyl acrylate, methyl acrylate, hydroxy ethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), maleic acid, maleic anhydride, itaconic acid, their salts and combinations thereof. More preferably, monomer A is selected from acrylic acid, an acrylic acid salt and combinations thereof, combined with at least one other monomer selected from 2-acrylamido-2-methylpropane sulfonic acid, maleic acid, maleic anhydride, itaconic acid, their salts and combinations thereof.

[0032] Essentially according to the invention, the polymer P is prepared in the presence of at least one compound T comprising sulfur IV, sulfur in oxidation state IV (sulfur IV, S IV or S IV). Preferably, the sulfur compound T is chosen from lithium hydrogen sulfite, sodium hydrogen sulfite, potassium hydrogen sulfite, ammonium hydrogen sulfite, calcium di(hydrogen sulfite), magnesium di(hydrogen sulfite) and combinations thereof. Preferably according to the invention, the compound T is a mono-hydrogen sulfite. Sodium hydrogen sulfite or sodium bisulfite is very particularly preferred. Preferably according to the invention, the compound T is a mineral derivative.

[0033] Preferably according to the invention, the polymerization reaction is carried out at a temperature above 30°C and below 100°C, preferably below 90°C, more preferably below 80°C or 75°C.

[0034] According to the invention, the polymer P is prepared in the presence of at least one initiator compound. Preferably, the initiator compound is chosen from a peroxide (for example hydrogen peroxide, / c / V-butyl hydroperoxide), a persulfate (for example sodium persulfate, ammonium persulfate, potassium persulfate), their combinations and their associations with a metal salt, preferably a metal salt chosen from an iron salt (for example Fe II or Fe III), a copper salt (for example Cu I or Cu II) and their combinations.

[0035] Advantageously, the polymer P may be partially non-neutralized, preferably non-neutralized from 2 mol% to 65 mol%, more preferably non-neutralized from 25 mol% to 60 mol%, relative to the number of carboxylic groups. Essentially according to the invention, the polymer P is partially or totally neutralized by means of at least one monovalent ion. According to the invention, the carboxylic groups of the polymer P may be partially neutralized at a rate of 35 mol% to 98 mol%, preferably at a rate of 40 mol% to 75 mol%. Preferably, the polymer P is partially neutralized. Preferably according to the invention, the monovalent ion is chosen from K + , N / A + , Li + , NH4 + and their combinations. The particularly preferred ion is Na +. According to the invention, the polymer P can be neutralized by means of at least one compound chosen from NaOH, KOH, LiOH, ammonium derivatives and combinations thereof. Preferably, the polymer P has a weight-average molecular mass Mw, measured by CES, of less than 20,000 g / mol, preferably less than 15,000 g / mol, less than 10,000 g / mol, more preferably less than 9,500 g / mol or less than 8,000 g / mol. The polymer P generally has a weight-average molecular mass Mw, measured by CES, of greater than 4,500 g / mol or greater than 5,000 g / mol, preferably greater than 5,500 g / mol or greater than 6,000 g / mol. According to the invention, the weight-average molecular mass Mw of the polymer P therefore advantageously ranges from

[0036] 4,500 g / mol to 15,000 g / mol, from 4,500 g / mol to 10,000 g / mol, from 4,500 g / mol to 9,500 g / mol or from 4,500 g / mol to 8,000 g / mol. Also advantageously according to the invention, the weight-average molecular mass Mw of the polymer P ranges from 5,000 g / mol to 15,000 g / mol, from

[0037] 5,000 g / mol to 10,000 g / mol, from 5,000 g / mol to 9,500 g / mol or from 5,000 g / mol to 8,000 g / mol. More advantageously according to the invention, the weight-average molecular mass Mw of the polymer P ranges from 5,500 g / mol to 15,000 g / mol, from 5,500 g / mol to 10,000 g / mol, from 5,500 g / mol to 9,500 g / mol or from 5,500 g / mol to 8,000 g / mol.

[0038] Preferably, the polymer P has a polymolecularity index IP, measured by CES, of less than 4 or ranging from 1.9 to 4; from 1.9 to 3 or from 1.5 to 3; from 1.2 to 2.5 or even from 1.9 to 2.9.

[0039] According to the invention, the molecular weight or mass of the polymer P is determined by Size Exclusion Chromatography (SEC). A test portion of the polymer dispersion corresponding to 90 mg of dry matter is introduced into a 10 mL flask. Mobile phase, containing 0.04% dimethylformamide (DMF), is added to a total mass of 10 g. The composition of this mobile phase is as follows: NaHCCU 0.05 mol / L, NaNCU 0.1 mol / L, triethanolamine: 0.02 mol / L, NaNi 0.03% by mass. The CES chain is composed of a “Waters” 510 isocratic pump, whose flow rate is set at 0.8 mL / min, a “Waters” 717+ sample changer, an oven containing a “Guard Column Ultrahydrogel Waters” precolumn of 6 cm length and 40 mm inner diameter, followed by a linear “Ultrahydrogel Waters” column of 30 cm length and 7.8 mm inner diameter.Detection is ensured by means of a differential refractometer type RI “Waters” 410. The oven is brought to the temperature of 60°C and the refractometer is brought to the temperature of 45°C. The CES device is calibrated with a series of sodium polyacrylate standards supplied by “Polymer Standard Service” with a peak molecular weight between 900 g / mol and 2,250,000 g / mol and a polydispersity index between 1.4 and 1.7. The calibration curve is of the linear type and takes into account the correction obtained thanks to the flow marker: dimethylformamide (DMF). The acquisition and processing of the chromatogram are carried out using the PSS software “WinGPC Scientific v 4.02”. The chromatogram obtained is integrated in the zone corresponding to molecular weights greater than 250 g / mol.

[0040] Preferably according to the invention, the molar quantity of sulfur compound T present in the suspension S, preferably the molar quantity of sulfur IV, is between 1% and 15%, preferably between 1.5% and 12%, relative to the total molar quantity of monomers used. More preferably according to the invention, the molar quantity of sulfur compound T present in the suspension S, preferably the molar quantity of sulfur IV, is between 1% and 15%, preferably between 1.5% and 12%, relative to the total molar quantity of unsaturated groups, preferably unsaturated ethylenic groups, of the monomers used.

[0041] When preparing the suspension S, the agent R according to the invention can be used in different ways.

[0042] Preferably according to the invention, the rheological agent R is introduced after grinding. It can also be introduced during the concentration of the suspension Sd. It can also be introduced in a sequenced manner, a fraction being introduced after grinding and before the concentration of the suspension Sd, another fraction being introduced during the concentration of the suspension Sd.

[0043] According to the invention, the agent R can be introduced directly in the form of a combination of phosphoric acid and polymer P. According to the invention, the agent R can also be implemented by separate introductions of the phosphoric acid and the polymer P, for example by the prior introduction of one and then the introduction of the other. The phosphoric acid and the polymer P can also be introduced separately and sequentially. Thus, the separate introduction of the phosphoric acid and the polymer P can be carried out after grinding for one and during concentration for the other. The phosphoric acid can be introduced after grinding and before concentration and the polymer P can be introduced during concentration; the introduction of the phosphoric acid can continue during concentration.Also, the polymer P can be introduced after grinding and before concentration and the phosphoric acid can be introduced during concentration; the introduction of the polymer P can continue during concentration. Also preferably according to the invention, the rheological agent R is used in an amount by dry weight ranging from 0.05% by weight to 5% by weight relative to the amount by dry weight of mineral matter M.

[0044] Within the agent R according to the invention, the quantities of phosphoric acid and polymer P can vary. Preferably, the rheological agent R comprises:

[0045] * from 5% by weight to 95% by weight of phosphoric acid and

[0046] * from 5% by weight to 95% by weight of polymer P, relative to the total quantity by dry weight of agent R.

[0047] More preferably, the rheological agent R comprises:

[0048] * from 15% by weight to 45% by weight of phosphoric acid and

[0049] * from 55% by weight to 85% by weight of polymer P, relative to the total quantity by dry weight of agent R.

[0050] Advantageously according to the invention, the rheological agent R may also comprise a compound B chosen from a sulfocarboxylic acid, a sulfocarboxylic acid salt and combinations thereof, preferably present in a molar amount of less than 25% relative to the molar amount of sulfur IV, preferably a compound B chosen from sulfoarylcarboxylic acids and sulfoalkylcarboxylic acids. More preferably, compound B is chosen from 3-sulfopropionic acid, 3-sulfo-2-methylpropionic acid, sulfosuccinic acid, their salts and combinations thereof. The salts of compound B are generally the sodium salt, the potassium salt, the lithium salt, the calcium salt, the magnesium salt or the ammonium salt.

[0051] Also preferably according to the invention, the molar quantity of compound B is less than 20%, preferably less than 15% or 12%, relative to the molar quantity of sulfur IV, or the molar quantity of compound B present within the suspension Sd is greater than 0.2%, in particular greater than 2% or 5%, relative to the molar quantity of sulfur IV.

[0052] In particular, the molar quantity of compound B is greater than 2% or 5% relative to the molar quantity of sulfur IV. According to the invention, the molar quantity of compound B present in the suspension S, relative to the molar quantity of sulfur IV, is therefore generally within the ranges of 0.2% to 25%, 2% to 25%, 5% to 25%, 0.2% to 20%, 2% to 20%, 5% to 20%, 0.2% to 15%, 2% to 15%, 5% to 15%, 0.2% to 12%, 2% to 12%, 5% to 12%.

[0053] According to the invention, the polymer P is prepared in the absence of a phosphorus compound. In particular, the polymer P is prepared in the absence of a compound comprising phosphorus in oxidation state I, in particular in the absence of hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, lithium hypophosphite, ammonium hypophosphite, calcium hypophosphite and magnesium hypophosphite; or in the absence of a compound comprising phosphorus in oxidation state III, in particular in the absence of phosphorous acid and phosphorous acid salt.

[0054] The suspension S according to the invention is prepared by grinding the suspension Sd and by concentrating the suspension resulting from the grinding. Preferably according to the invention, the concentration step is carried out by thermal concentration, generally by heating. The heating temperature is generally greater than 80°C. Preferably, the heating temperature is generally less than 110°C.

[0055] According to the invention, the concentration step can also be carried out by mechanical concentration, in particular by means of a device chosen from a decanter, a centrifuge, a cyclone, a rotary filter and combinations thereof. According to the invention, the concentration step can also be carried out by combining thermal concentration and mechanical concentration.

[0056] Essentially according to the invention, the suspension S is prepared by grinding in water the suspension Sd of at least one particulate mineral material M. According to the invention, the grinding can be carried out in the absence of a grinding aid agent or in the presence of at least one grinding aid agent.

[0057] Preferably according to the invention, the grinding is carried out in water in the absence of a grinding aid agent and at a concentration ranging from 10% by weight to 40% by weight, preferably from 10% by weight to 30% by weight, of the aqueous suspension Sd.

[0058] Also preferably according to the invention, the grinding is carried out in water in the presence of an aqueous grinding aid dispersion D comprising at least one polymer Q and at a concentration ranging from 30% by weight to 60% by weight, preferably from 40% by weight to 60% by weight, of the aqueous suspension Sd.According to the invention, the suspension S then results from grinding in water in the presence of an aqueous grinding aid dispersion D comprising at least one polymer Q with a molecular weight by weight (Mw), measured by CES, of between 4,000 g / mol and 20,000 g / mol and prepared in water or in an organic solvent, optionally in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer G chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, in the presence of at least one initiator compound and at least one chain transfer compound H during the polymerization reaction, and totally or partially neutralized by means of at least one ion chosen from a monovalent ion, a divalent ion and combinations thereof.

[0059] Preferably according to the invention during grinding, the quantity of aqueous dispersion D used ranges from 0.05% by weight to 5% by weight, preferably from 0.2% by weight to 1.5% by weight or from 0.2% by weight to 1% by weight, relative to the quantity of mineral matter M.

[0060] Advantageously according to the invention, the polymer Q can be partially or completely neutralized by means of a combination of at least one monovalent ion and at least one divalent ion. According to the invention, the carboxylic groups of the polymer Q can be partially neutralized at a rate of 50 mol% to 97 mol%, preferably at a rate of 65 mol% to 90 mol%. Preferably, the polymer P is partially neutralized.

[0061] According to the invention, the total or partial neutralization of the polymer Q can be carried out in variable relative molar proportions of the monovalent and divalent ions. Preferably according to the invention, the monovalent ion / divalent ion molar proportions are between 90 / 10 and 10 / 90 or between 80 / 20 and 20 / 80, preferably between 80 / 20 and 60 / 40, for example 70 / 30 or 50 / 50.

[0062] Preferably according to the invention, the monovalent ion is chosen from K + , N / A + , Li + , NH4 + and their combinations. The particularly preferred monovalent ion is Na + . According to the invention, the polymer Q can be neutralized by means of at least one compound chosen from NaOH, KOH, LiOH, ammonium derivatives and their combinations. Also preferably according to the invention, the divalent ion is chosen from Ca 2+ , Mg 2+ and their combinations. The particularly preferred ion is Ca 2+. According to the invention, the polymer Q can be neutralized by means of at least one compound chosen from CaO, Ca(OH)2, MgO, Mg(OH)2 and their combinations. Preferably, the polymer Q can be totally or partially neutralized by means of a combination of Na + and of Ca 2+ or a combination of Na + , of Ca 2+ and Mg 2+ .

[0063] Preferably according to the invention, the aqueous grinding aid dispersion D comprises at least one polymer Q chosen from:

[0064] - an a-sulfonated polymer Q1 with a molecular weight (Mw), measured by CES, of between 4,000 g / mol and 20,000 g / mol and prepared in water, optionally in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer G chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, in the presence of at least one initiator compound and at least one sulfur compound H1 comprising sulfur in oxidation state IV (sulfur IV or S IV ), and totally or partially neutralized by means of at least one ion chosen from a monovalent ion, a divalent ion and their combinations,

[0065] - a polymer Q2 with a molecular mass by weight (Mw), measured by CES, of between 4,000 g / mol and 20,000 g / mol and prepared in water or in an organic solvent, optionally in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer G chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, in the presence of at least one initiator compound and a compound H2 chosen from secondary alcohols, and totally or partially neutralized by means of at least one ion chosen from a monovalent ion, a divalent ion and combinations thereof,

[0066] - a polymer Q3 with a molecular weight by weight (Mw), measured by CES, of between 4,000 g / mol and 20,000 g / mol and prepared in water, by a polymerization reaction of at least one monomer G chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, in the presence of at least one initiator compound and at least one compound H3 comprising phosphorus and chosen from a compound comprising phosphorus in oxidation state I, a compound comprising phosphorus in oxidation state III and combinations thereof, and totally or partially neutralized by means of at least one ion chosen from a monovalent ion, a divalent ion and combinations thereof and

[0067] - a polymer Q4 with a molecular mass by weight (Mw), measured by CES, of between 4,000 g / mol and 20,000 g / mol and prepared in water, by a polymerization reaction of at least one monomer G chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, in the presence of at least one initiator compound and at least one compound H4 of formula II: coox

[0068] II in which X represents Na, K or H and R represents a Ci-Cs-alkyl group, preferably a methyl group; and totally or partially neutralized by means of at least one ion chosen from a monovalent ion, a divalent ion and their combinations.

[0069] According to the invention, the chain transfer compound H is used during the polymerization reaction making it possible to obtain the polymer Q. Preferably according to the invention, the compound H is chosen from a compound H1, a compound H2, a compound H3 and a compound H4.

[0070] Preferably, the compound Hl is chosen from lithium hydrogen sulfite, sodium hydrogen sulfite, potassium hydrogen sulfite, ammonium hydrogen sulfite, calcium di(hydrogen sulfite), magnesium di(hydrogen sulfite) and combinations thereof. Preferably according to the invention, the compound Hl is a mono-hydrogen sulfite. Sodium hydrogen sulfite or sodium bisulfite is particularly preferred.

[0071] Preferably, the compound H2 is isopropyl alcohol.

[0072] Preferably, the compound H3 is chosen from hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, lithium hypophosphite, ammonium hypophosphite, calcium hypophosphite, magnesium hypophosphite, phosphorous acid, a phosphorous acid salt and combinations thereof. Preferably according to the invention, the compound H3 is sodium hypophosphite.

[0073] Preferably, compound H4 is dipropyl trithiocarbonate (CAS No. 6332-91-8) or one of its salts, for example its disodium salt, sodium dipropionate trithiocarbonate (CAS No. 86470-33-2).

[0074] According to the invention, polymer Q is prepared using monomer G. Preferably, monomer G is selected from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof. Advantageously, monomer G may be combined with at least one other monomer selected from vinyl acetate, methyl acrylate, ethyl acrylate, hydroxy ethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), maleic acid, maleic anhydride, itaconic acid and combinations thereof.More preferably, monomer G is selected from acrylic acid, methacrylic acid, a salt of acrylic acid, a salt of methacrylic acid and combinations thereof, combined with at least one other monomer selected from vinyl acetate, methyl acrylate, ethyl acrylate, hydroxy ethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), maleic acid, maleic anhydride, itaconic acid and combinations thereof.

[0075] Preferably, the polymer Q has a weight-average molecular weight Mw (measured by CES) of less than 20,000 g / mol, preferably less than 15,000 g / mol, less than 10,000 g / mol, more preferably less than 7,000 g / mol or less than 6,000 g / mol. The polymer Q generally has a weight-average molecular weight Mw (measured by CES) of greater than 4,500 g / mol or greater than 5,000 g / mol. Preferably, the polymer Q has a polydispersity index IP (measured by CES) of less than 4 or ranging from 1.2 to 4 or from 1.5 to 4; from 1.2 to 3.5 or from 1.5 to 3.5; from 1.2 to 3 or even from 1.5 to 3.

[0076] According to the invention, the temperature and initiator compound used during the polymerization reaction to prepare the polymer Q are similar to the temperature and initiator compound for preparing the polymer P.

[0077] The invention also relates to the preparation of the suspension S according to the invention. Thus, the invention provides a method for preparing an aqueous suspension S comprising:

[0078] * grinding in water at a concentration ranging from 10% by weight to 60% by weight of an aqueous suspension Sd of at least one particulate mineral material M, then

[0079] * the concentration to a concentration ranging from 65% by weight to 80% by weight, by a treatment chosen from mechanical treatment, heat treatment and their combinations, of the ground suspension Sd, in the presence of at least one rheological agent R comprising phosphoric acid and at least one a-sulfonated polymer P prepared in water and in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer A chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and their combinations, in the presence of at least one initiator compound and at least one sulfur compound T comprising sulfur in oxidation state IV, and totally or partially neutralized by means of at least one monovalent ion.

[0080] Essentially, the preparation of the suspension S according to the invention uses the rheological agent R. The invention also relates to this agent. Thus, the invention provides a rheological agent R comprising phosphoric acid and at least one a-sulfonated polymer P prepared in water and in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer A chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, in the presence of at least one initiator compound and at least one sulfur compound T comprising sulfur in oxidation state IV, and totally or partially neutralized by means of at least one monovalent ion, and optionally a compound B chosen from a sulfocarboxylic acid, a sulfocarboxylic acid salt and combinations thereof, preferably present in a molar amount of less than 25% relative to the molar amount of sulfur IV.

[0081] The rheological agent R according to the invention is particularly effective when it is implemented within an aqueous suspension S of particles according to the invention. The invention therefore also provides a method for controlling the rheology of an aqueous suspension S of particles of at least one mineral material M prepared:

[0082] * by grinding in water at a concentration ranging from 10% by weight to 60% by weight of an aqueous suspension Sd of at least one particulate mineral material M, then

[0083] * by concentration to a concentration ranging from 65% by weight to 80% by weight, by a treatment chosen from mechanical treatment, heat treatment and their combinations, of the ground suspension Sd, comprising the use during the concentration of at least one rheological agent R comprising phosphoric acid and at least one a-sulfonated polymer P prepared in water and in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer A chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and their combinations, in the presence of at least one initiator compound and at least one sulfur compound T comprising sulfur in oxidation state IV, and totally or partially neutralized by means of at least one monovalent ion.

[0084] The aqueous suspension S obtained by means of the invention has particularly advantageous properties and can be used in many technical fields, in particular for the preparation of paper. Thus, the invention provides a method for preparing a papermaking mass filler composition or a papermaking coating slip composition comprising:

[0085] * the preparation of an aqueous suspension S according to the invention comprising:

[0086] - grinding in water at a concentration ranging from 10% by weight to 60% by weight of an aqueous suspension Sd of at least one particulate mineral material M, then

[0087] - the concentration to a concentration ranging from 65% by weight to 80% by weight, by a treatment chosen from mechanical treatment, heat treatment and their combinations, of the ground suspension Sd, in the presence of at least one rheological agent R comprising phosphoric acid and at least one a-sulfonated polymer P prepared in water and in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer A chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and their combinations, in the presence of at least one initiator compound and at least one sulfur compound T comprising sulfur in oxidation state IV, and totally or partially neutralized by means of at least one monovalent ion, then

[0088] * mixing the aqueous suspension S with at least one binder compound, and optionally with at least one compound chosen from a rheology modifying compound, a water-retaining agent, an optical brightening agent, an organic pigment, a mineral pigment and combinations thereof.

[0089] This method of preparing paper comprises the use of a suspension S according to the invention, in particular when applying a paper coating sauce or when adding a filler composition.

[0090] The aqueous suspension S obtained by the invention can also be used for the preparation of a coating composition, in particular a varnish or a paint. Thus, the invention provides a method for preparing a coating composition comprising:

[0091] * the preparation of an aqueous suspension S according to the invention comprising:

[0092] - grinding in water at a concentration ranging from 10% by weight to 60% by weight of an aqueous suspension Sd of at least one particulate mineral material M, then

[0093] - the concentration to a concentration ranging from 65% by weight to 80% by weight, by a treatment chosen from mechanical treatment, heat treatment and their combinations, of the ground suspension Sd, in the presence of at least one rheological agent R comprising phosphoric acid and at least one a-sulfonated polymer P prepared in water and in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer A chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and their combinations, in the presence of at least one initiator compound and at least one sulfur compound T comprising sulfur in oxidation state IV, and totally or partially neutralized by means of at least one monovalent ion, then

[0094] * mixing the aqueous suspension S with at least one binder compound, and optionally with at least one compound chosen from a rheology modifying compound, an organic pigment, a mineral pigment and their combinations.

[0095] The coating composition according to the invention comprises:

[0096] * at least one aqueous suspension S according to the invention prepared:

[0097] - by grinding in water at a concentration ranging from 10% by weight to 60% by weight of an aqueous suspension Sd of at least one particulate mineral material M, then

[0098] - by concentration to a concentration ranging from 65% by weight to 80% by weight, by a treatment chosen from mechanical treatment, heat treatment and combinations thereof, of the ground suspension Sd, in the presence of at least one rheological agent R comprising phosphoric acid and at least one a-sulfonated polymer P prepared in water and in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer A chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, in the presence of at least one initiator compound and at least one sulfur compound T comprising sulfur in oxidation state IV, and totally or partially neutralized by means of at least one monovalent ion, and

[0099] * at least one binder compound, and optionally at least one compound chosen from a rheology modifying compound, a mineral pigment, an organic pigment and their combinations.

[0100] The invention also provides a method of preparing a coating comprising applying to a substrate a coating composition according to the invention.

[0101] According to the invention, the particular, advantageous or preferred characteristics of the suspension S according to the invention define methods for its preparation, methods which use it as well as rheological agents R which are also particular, advantageous or preferred.

[0102] The following examples illustrate the various aspects of the invention. EXAMPLES

[0103] Preparation and characterization of a dispersion of the Pla polymer according to the invention

[0104] In a 1 L glass reactor equipped with stirring, a thermometer, a glass condenser and a heating system, a charge comprising 0.003 g of iron sulfate heptahydrate and 226.7 g of water is prepared at room temperature. Then, 3 charges are prepared to be introduced separately and in parallel over 3 hours. 254 g of acrylic acid (monomer A) are introduced into a first beaker, 1.54 g of sodium persulfate and 40.8 g of water into a second beaker and 36.84 g of an aqueous solution of sodium bisulfite (compound T) at 40% by mass into a third beaker. After 3 hours of addition at 73°C, a clear polymer dispersion is obtained. The dry matter concentration of the polymer dispersion is 50.9%. The obtained Pla polymer has a Mw of 6,485 g / mol and an IP of 2.5.

[0105] Compound B and the quantity of compound B (molar % relative to the molar quantity of sulfur IV of compound T used) included in the Pla polymer dispersion are determined by determination of sulfate ions by ion chromatography, of 3-sulfopropionic ions, by NMR analysis 3 H and NMR 13 C of the sulfonated groups of the polymer Pla and of compound B.

[0106] The sulfate ion content in the Pla polymer dispersion is determined by ion chromatography. A sample of the polymer dispersion of approximately 80 mg is introduced into a 15 mL bottle. Mobile phase is added to a total mass of 15 g. The composition of the mobile phase is as follows: sodium carbonate: 0.009 mol / L. The ion chromatography system for anion determination is composed of a "Dionex Aquion" ion chromatography system with integrated degasser, whose flow rate is set at 1 mL / min, containing a chemical suppressor, an AG9-HC precolumn, a CG3 metal trap precolumn, an NG1 precolumn and an AG9-HC column. Detection is ensured by means of a conductometric detector. The ion chromatography device is calibrated with a series of sodium sulfate solution standards. The calibration range is between 0.5 and 100 ppm. The calibration curve is linear.Automatic dilution of samples by the device allows to be within the calibration range. The acquisition and processing of the chromatogram are carried out using the “Chromeleon” 7.2.10 software.

[0107] NMR analyses 3 H and NMR 13 C are carried out using a “Bruker” AV III HD 500 spectrometer equipped with a 5 mm BBI probe. The polymer samples were dissolved in deuterated water and examined by 'H NMR and NMR 13 C via 2D experiments: 'H / ' correlations 13 C at single and long distance.

[0108] The Pla polymer dispersion according to the invention comprises 3-sulfopropionic acid as compound B in an amount of 15 mol% relative to the molar amount of sodium bisulfite used (compound T).

[0109] Preparation and characterization of an aqueous dispersion D2 of the polymer O2a according to the invention

[0110] In a 1 L glass reactor equipped with stirring, a thermometer, a glass condenser and a heating system, a charge comprising 0.19 g of iron sulfate heptahydrate, 0.58 g of hydroxylamine sulfate, 121 g of isopropyl alcohol (compound H2) and 110 g of water is prepared at room temperature. Then, 3 charges are prepared to be introduced separately and in parallel over 2 hours. 276.52 g of acrylic acid (monomer A) are introduced into a first beaker, 3.6 g of dihydrogen peroxide 130 volume and 100 g of water into a second beaker and 0.63 g of hydroxylamine sulfate and 100 g of water into a third beaker.

[0111] After 2 hours of reflux addition, the isopropyl alcohol (compound H2) is separated by distillation and the polymer is diluted with water. After rinsing the injection systems, the product of the polymerization reaction is neutralized. For this, two charges are prepared to be introduced successively. 21.96 g of hydrated lime and 82.5 g of water are introduced into a first beaker, and 17.06 g of magnesium hydroxide and 31.10 g of water into a second beaker. After rinsing the injection systems, 138.26 g of 50% sodium hydroxide are added to the reactor. The mixture is left to react at a temperature between 80°C and 85°C for 45 minutes. A clear aqueous dispersion D2 is obtained comprising at least one polymer Q2a whose carboxylic groups are partially neutralized at a rate of 45 mol% with the sodium ion, 15 mol% with the calcium ion and 15 mol% with the magnesium ion.

[0112] The dry matter concentration of the aqueous dispersion D2 is 37%. The resulting polymer Q2a has a Mw of 9,760 g / mol and an IP of 3.

[0113] Preparation and characterization of a rheological agent RI according to the invention

[0114] 85.5 g of an aqueous sodium hydroxide solution (50% by weight), 109.5 g of an aqueous phosphoric acid solution at 85% by weight, 344.7 g of the previously obtained Pla polymer dispersion and 109.8 g of water are mixed together under stirring while maintaining the temperature at room temperature. The rheological agent RI according to the invention (ES = 46.4%) is obtained. Preparation and characterization of a suspension SI according to the invention

[0115] Under mechanical stirring using a “Rayneri” type motor, 1,425 g of calcium carbonate (BL 200 “Omya”) are dispersed in 4,275 g of water. Stirring is maintained for 20 minutes.

[0116] Then, grinding is carried out using a mill (“Wab Dyno Mill” type KDL pilot 1.4 L) containing 2,850 g of ceramic balls (ER 120 S of 0.6 mm to 1.0 mm diameter - “Saint Gobain”). The grinding conditions are adjusted to obtain a suspension of mineral matter particles of the desired particle size. The concentration of the Sdl suspension to be ground is 25% ± 1%. Grinding is continued to achieve the desired particle size (75% ± 1% by weight of particles with an equivalent spherical diameter < 1 μm). The particle size characteristics are determined using a sedimentometer (“SediGraph” III 5120 “Micromeritics”, USA).

[0117] The particle size distribution of suspensions of mineral matter particles is measured. It allows the determination of the percentage mass fraction of a population of particles whose equivalent spherical diameter is less than 1 pm (esd < 1 pm, expressed in %). These measurements are carried out for an aqueous suspension of mineral matter particles diluted to a concentration of approximately 37 g of dry matter per liter of solution and comprising a standard sodium polyacrylate of Mw 4,000 g / mol at a concentration of 2.25 g dry / L. Each sample is dispersed and sonicated before particle size measurement.

[0118] This Sdl suspension is then thermally concentrated to a concentration of 71% ± 1% by evaporation of water using a “Vorwerk” device in the presence of 0.8% dry weight relative to the dry weight of dry calcium carbonate of rheological agent RI according to the invention added in 3 equal portions during the thermal concentration.

[0119] The obtained SI suspension is then characterized by controlling its pH at 25°C, its dry extract (SE, % by weight) measured using a “Précisa” balance. Its Brookfield viscosity at 100 rpm noted VB0 (in mPa.s) is measured at 25°C using a “Brookfield” DV3T rheometer equipped with a module 3. A stability study is carried out after 24 hours of storage of the SI suspension in a climatic chamber at 60°C. The Brookfield viscosity of this SI suspension noted VB24 (in mPa.s) is measured at 25°C and before stirring at 100 rpm using the “Brookfield” DV3T rheometer equipped with a module 5. The SI suspension is stirred using a “Rayneri” type mechanical motor for 1 minute at 2,000 rpm before measuring its Brookfield viscosity noted VB24a (in mPa.s) at 100 rpm at 25°C using the Brookfield rheometer equipped with a module 3. The results obtained are presented in Table 1.

[0120] Table 1

[0121] The use of a Pla polymer according to the invention makes it possible to prepare a highly concentrated mineral suspension and to effectively control its viscosity and stability.

[0122] Preparation and characterization of a suspension S2 according to the invention

[0123] With mechanical stirring using a “Rayneri” type motor, 4,000 g of calcium carbonate (“Omyacarb” 10 AV “Omya”) are dispersed in 4,000 g of water in the presence of 0.45% by dry weight relative to the dry weight of dry calcium carbonate of aqueous dispersion D2. Stirring is maintained for 20 minutes.

[0124] Then, grinding is carried out using a mill (“Wab Dyno Mill” type KDL pilot 1.4 L) containing 2,800 g of ceramic balls (ER 120 S of 0.6 mm to 1.0 mm diameter - “Saint Gobain”). The grinding conditions are adjusted to obtain a suspension of mineral matter particles of the desired particle size. The concentration of the Sd2 suspension to be ground is 50% ± 1%. Grinding is continued to achieve the desired particle size (75% ± 1% by weight of particles with an equivalent spherical diameter < 1 μm). The particle size characteristics are determined using a sedimentometer “SediGraph” III 5120 “Micromeritics”, USA).

[0125] The particle size distribution of suspensions of mineral matter particles is measured. It allows the determination of the percentage mass fraction of a population of particles whose equivalent spherical diameter is less than 1 pm (esd < 1 pm, expressed in %). These measurements are carried out for an aqueous suspension of mineral matter particles diluted to a concentration of approximately 37 g of dry matter per liter of solution and comprising a standard sodium polyacrylate of Mw 4,000 g / mol at a concentration of 2.25 g dry / L. Each sample is dispersed and sonicated before particle size measurement.

[0126] This Sd2 suspension is then thermally concentrated to a concentration of 71% ± 1% by evaporation of water using a “Vorwerk” device in the presence of 0.25% dry weight relative to the dry weight of dry calcium carbonate of rheological agent RI according to the invention. The S2 suspension obtained is then characterized by controlling its pH at 25°C, its dry extract (SE, % by weight) measured using a “Précisa” balance. Its Brookfield viscosity at 100 rpm noted VBO (in mPa.s) is measured at 25°C using a “Brookfield” DV3T rheometer equipped with a module 3. A stability study is carried out after 24 hours of storage of the S2 suspension in a climatic chamber at 60°C. The Brookfield viscosity of this S2 suspension noted VB24 (in mPa.s) is measured at 25°C and before stirring at 100 rpm using the “Brookfield” DV3T rheometer equipped with a module 5.The S2 suspension is stirred using a “Rayneri” type mechanical motor for 1 minute at 2,000 rpm before measuring its Brookfield viscosity, noted VB24a (in mPa.s), at 100 rpm at 25°C using the Brookfield DV3T rheometer equipped with a module 3. The results obtained are presented in Table 2.

[0127] Table 2

[0128] The use of a Pla polymer after grinding in the presence of an aqueous dispersion D2 of the polymer Q2a according to the invention makes it possible to prepare a highly concentrated mineral suspension and to effectively control its viscosity and stability.

Claims

CLAIMS aqueous suspension S of particles of at least one mineral material M prepared: * by grinding in water at a concentration ranging from 10% by weight to 60% by weight of an aqueous suspension Sd of at least one particulate mineral material M, then * by concentration to a concentration ranging from 65% by weight to 80% by weight, by a treatment chosen from mechanical treatment, heat treatment and their combinations, of the ground suspension Sd, in the presence of at least one rheological agent R comprising phosphoric acid and at least one a-sulfonated polymer P prepared in water and in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer A chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and their combinations, in the presence of at least one initiator compound and at least one sulfur compound T comprising sulfur in oxidation state IV, and totally or partially neutralized by means of at least one monovalent ion. suspension S according to claim 1 including: - the Brookfield viscosity at 25°C, at 100 rpm, measured 1 hour after its preparation, is less than 1,000 mPa.s, preferably less than 800 mPa.s, or of which - the Brookfield viscosity at 25°C, at 100 rpm and after stirring, measured 24 hours after preparation and storage at 60°C, is less than 800 mPa.s, preferably less than 600 mPa.s, or of which - the Brookfield viscosity at 25°C, at 100 rpm and before stirring, measured 24 hours after preparation and storage at 60°C, is less than 3,000 mPa.s, preferably less than 2,500 mPa.s, more preferably less than 2,000 mPa.s or 1,900 mPa.s. suspension S according to one of claims 1 or 2 for which: - only one material M or two or three materials M are used; or for which - the material M is synthetic or of natural origin, preferably chosen from alkaline earth metal carbonate, preferably calcium carbonate (natural calcium carbonate or precipitated calcium carbonate), strontium carbonate, magnesium carbonate, barium carbonate and combinations thereof, dolomite, kaolin, titanium dioxide, talc, lime, calcium sulfate, barium sulfate and combinations thereof; or of which - the concentration of suspension S is greater than 70% by weight or is less than 78% by weight or less than 75% by weight, preferably the concentration of which ranges from 70% by weight to 78% by weight or from 70% by weight to 75% by weight. Suspension S according to one of claims 1 to 3 for which: - the particles of ground material M have a median size, measured by sedimentometry, of less than 50 pm or a median size ranging from 0.05 to 50 pm or a median size of less than 10 pm, preferably less than 5 pm or 2 pm, more preferably less than 1 pm or less than 0.5 pm; or for which: - the concentration of the suspension Sd is greater than 10% by weight or the concentration of the suspension Sd is less than 60% by weight, preferably the concentration of the suspension Sd ranges from 10% by weight to 60% by weight. Suspension S according to one of claims 1 to 4 for which the polymer P is chosen from an a-co-disulfonated polymer P1, an a-monosulfonated polymer P2 and their combinations. Suspension S according to one of claims 1 to 5 for which: - monomer A is chosen from acrylic acid, an acrylic acid salt and combinations thereof, preferably monomer A is acrylic acid, or - monomer A is combined with at least one other monomer chosen from vinyl acetate, ethyl acrylate, methyl acrylate, hydroxy ethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), maleic acid, maleic anhydride, itaconic acid, their salts and their combinations, or - monomer A is chosen from acrylic acid, an acrylic acid salt and combinations thereof, combined with at least one other monomer chosen from 2-acrylamido-2-methylpropane sulfonic acid, maleic acid, maleic anhydride, itaconic acid, their salts and combinations thereof, or - the sulfur compound T is chosen from lithium hydrogen sulfite, sodium hydrogen sulfite, potassium hydrogen sulfite, ammonium hydrogen sulfite, calcium di(hydrogen sulfite), magnesium di(hydrogen sulfite) and combinations thereof, or - the polymerization reaction is carried out at a temperature above 30°C and below 100°C, preferably below 90°C, more preferably below 80°C or 75°C, or for which: - the polymer P is prepared in the presence of at least one initiator compound chosen from a peroxide (for example hydrogen peroxide, / c / V-butyl hydroperoxide), a persulfate (for example sodium persulfate, ammonium persulfate, potassium persulfate), their combinations and their associations with a metal salt, preferably a metal salt chosen from an iron salt (for example Fe II or Fe III), a copper salt (for example Cu I or Cu II) and their combinations, or - the polymer P is partially non-neutralized, preferably non-neutralized from 2 mol% to 65 mol%, more preferably from 25 mol% to 60 mol%, relative to the number of carboxylic groups, or the polymer P is partially or totally neutralized, or - the polymer P is totally or partially neutralized by means of at least one monovalent ion chosen from K + , N / A + , Li + , NH4 + and their combinations, preferentially Na + , Or - the polymer P has a weight-average molecular mass Mw, measured by CES, of less than 20,000 g / mol, preferably less than 15,000 g / mol, less than 10,000 g / mol, less than 9,500 g / mol or less than 8,000 g / mol, or - the polymer P has a weight-average molecular mass Mw, measured by CES, greater than 4,500 g / mol or greater than 5,000 g / mol, preferably greater than 5,500 g / mol or greater than 6,000 g / mol, or - the polymer P has a polymolecularity index IP, measured by CES, less than 4 or ranging from 1.9 to 4; from 1.9 to 3 or from 1.5 to 3; from 1.2 to 2.5 or from 1.9 to 2.

9. suspension S according to one of claims 1 to 6 for which: - the molar quantity of sulfur compound T, preferably the molar quantity of sulfur IV, is between 1% and 15%, preferably between 1.5% and 12%, relative to the total molar quantity of monomers used, preferably: - the molar quantity of sulfur compound T, preferably the molar quantity of sulfur IV, is between 1% and 15%, preferably between 1.5% and 12%, relative to the total molar quantity of unsaturated groups, preferably unsaturated ethylenic groups, of the monomers used. Suspension S according to one of claims 1 to 7 for which: * the rheological agent R is introduced after grinding, or * the rheological agent R is used in a quantity by dry weight ranging from 0.05% by weight to 5% by weight relative to the quantity by dry weight of mineral matter M, or * the rheological agent R includes: - from 5% by weight to 95% by weight of phosphoric acid and - from 5% by weight to 95% by weight of polymer P, relative to the total quantity by dry weight of agent R, or * the rheological agent R also comprises a compound B chosen from a sulfocarboxylic acid, a sulfocarboxylic acid salt and combinations thereof, preferably present in a molar amount of less than 25% relative to the molar amount of sulfur IV, preferably a compound B chosen from sulfoarylcarboxylic acids and sulfoalkylcarboxylic acids, more preferably a compound B chosen from 3-sulfopropionic acid, 3-sulfo-2-methylpropionic acid, sulfosuccinic acid, salts thereof and combinations thereof; preferably the molar amount of compound B is less than 20%, preferably less than 15% or 12%, relative to the molar amount of sulfur IV, or the molar amount of compound B present in the suspension Sd is greater than 0.2%, in particular greater than 2% or 5%, relative to the molar amount of sulfur IV.Suspension S according to one of claims 1 to 8 for which the grinding is carried out in water in the absence of a grinding aid agent or is carried out in the presence of an aqueous grinding aid dispersion D comprising at least one polymer Q with a molecular mass by weight (Mw), measured by CES, of between 4,000 g / mol and 20,000 g / mol and prepared in water or in an organic solvent, optionally in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer G chosen from acrylic acid, methacrylic acid, an acid salt. acrylic, a methacrylic acid salt and combinations thereof, in the presence of at least one initiator compound and at least one chain transfer compound H during the polymerization reaction, and totally or partially neutralized by means of at least one ion chosen from a monovalent ion, a divalent ion and combinations thereof, preferably in the presence of an aqueous grinding aid dispersion D comprising at least one polymer Q chosen from: - an a-sulfonated polymer Q1 with a molecular weight (Mw), measured by CES, of between 4,000 g / mol and 20,000 g / mol and prepared in water, optionally in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer G chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, in the presence of at least one initiator compound and at least one sulfur compound H1 comprising sulfur in oxidation state IV (sulfur IV or SIV ), and totally or partially neutralized by means of at least one ion chosen from a monovalent ion, a divalent ion and their combinations, - a polymer Q2 with a molecular mass by weight (Mw), measured by CES, of between 4,000 g / mol and 20,000 g / mol and prepared in water or in an organic solvent, optionally in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer G chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, in the presence of at least one initiator compound and a compound H2 chosen from secondary alcohols, preferably isopropyl alcohol, and totally or partially neutralized by means of at least one ion chosen from a monovalent ion, a divalent ion and combinations thereof, - a polymer Q3 with a molecular weight by weight (Mw), measured by CES, of between 4,000 g / mol and 20,000 g / mol and prepared in water, by a polymerization reaction of at least one monomer G chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, in the presence of at least one initiator compound and at least one compound H3 comprising phosphorus and chosen from a compound comprising phosphorus in oxidation state I, a compound comprising phosphorus in oxidation state III and combinations thereof, preferably at least one compound H3 chosen from hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, lithium hypophosphite, ammonium hypophosphite, hypophosphite calcium, magnesium hypophosphite, phosphorous acid, a phosphorous acid salt and combinations thereof, and totally or partially neutralized by means of at least one ion selected from a monovalent ion, a divalent ion and combinations thereof and - a polymer Q4 with a molecular mass by weight (Mw), measured by CES, of between 4,000 g / mol and 20,000 g / mol and prepared in water, by a polymerization reaction of at least one monomer G chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, in the presence of at least one initiator compound and at least one compound H4 of formula II: coox II in which X represents Na, K or H and R represents a Ci-Cs-alkyl group, preferably a methyl group; and totally or partially neutralized by means of at least one ion chosen from a monovalent ion, a divalent ion and their combinations. Suspension S according to claim 9 for which: * the grinding is carried out in water in the absence of a grinding aid agent and at a concentration ranging from 10% by weight to 40% by weight, preferably from 10% by weight to 30% by weight, of the aqueous suspension Sd or * the grinding is carried out in water in the presence of an aqueous grinding aid dispersion D comprising at least one polymer Q and at a concentration ranging from 30% by weight to 60% by weight, preferably from 40% by weight to 60% by weight, of the aqueous suspension Sd. Method for preparing an aqueous suspension S according to one of claims 1 to 10 comprising: * grinding in water at a concentration ranging from 10% by weight to 60% by weight of an aqueous suspension Sd of at least one particulate mineral material M, then * concentration at a concentration ranging from 65% by weight to 80% by weight, by a treatment chosen from mechanical treatment, heat treatment and their combinations, of the ground suspension Sd, in the presence of at least one rheological agent R comprising phosphoric acid and at least one a-sulfonated polymer P prepared in water and in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer A chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, in the presence of at least one initiator compound and at least one sulfur compound T comprising sulfur in oxidation state IV, and totally or partially neutralized by means of at least one monovalent ion.

12. Rheological agent R comprising phosphoric acid and at least one a-sulfonated polymer P prepared in water and in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer A chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, in the presence of at least one initiator compound and at least one sulfur compound T comprising sulfur in oxidation state IV, and totally or partially neutralized by means of at least one monovalent ion, and optionally a compound B chosen from a sulfocarboxylic acid, a sulfocarboxylic acid salt and combinations thereof, preferably present in a molar amount of less than 25% relative to the molar amount of sulfur IV.

13. Method of preparing a papermaking mass filler composition or a papermaking coating slip composition comprising: * the preparation of an aqueous suspension S according to one of claims 1 to 10 comprising: - grinding in water at a concentration ranging from 10% by weight to 60% by weight of an aqueous suspension Sd of at least one particulate mineral material M, then - the concentration to a concentration ranging from 65% by weight to 80% by weight, by a treatment chosen from mechanical treatment, heat treatment and their combinations, of the ground Sd suspension, in the presence of at least one rheological agent R comprising phosphoric acid and at least one a-sulfonated polymer P prepared in water and in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer A chosen from acrylic acid, methacrylic acid, an acrylic acid salt, an acid salt methacrylic and their combinations, in the presence of at least one initiator compound and at least one sulfur compound T comprising sulfur in oxidation state IV, and totally or partially neutralized by means of at least one monovalent ion, then * mixing the aqueous suspension S with at least one binder compound, and optionally with at least one compound chosen from a rheology modifying compound, a water-retaining agent, an optical brightening agent, an organic pigment, a mineral pigment and combinations thereof.

14. Method of preparing paper comprising the use of a suspension S according to one of claims 1 to 10.

15. Method of preparing a coating composition comprising: * the preparation of an aqueous suspension S according to one of claims 1 to 10 comprising: - grinding in water at a concentration ranging from 10% by weight to 60% by weight of an aqueous suspension Sd of at least one particulate mineral material M, then - the concentration to a concentration ranging from 65% by weight to 80% by weight, by a treatment chosen from mechanical treatment, heat treatment and their combinations, of the ground suspension Sd, in the presence of at least one rheological agent R comprising phosphoric acid and at least one a-sulfonated polymer P prepared in water and in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer A chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and their combinations, in the presence of at least one initiator compound and at least one sulfur compound T comprising sulfur in oxidation state IV, and totally or partially neutralized by means of at least one monovalent ion, then * mixing the aqueous suspension S with at least one binder compound, and optionally with at least one compound chosen from a rheology modifying compound, an organic pigment, a mineral pigment and their combinations.

16. Coating composition comprising: * at least one aqueous suspension S according to one of claims 1 to 10 prepared: - by grinding in water at a concentration ranging from 10% by weight to 60% by weight of an aqueous suspension Sd of at least one particulate mineral material M, then - by concentration to a concentration ranging from 65% by weight to 80% by weight, by a treatment chosen from mechanical treatment, heat treatment and combinations thereof, of the ground suspension Sd, in the presence of at least one rheological agent R comprising phosphoric acid and at least one a-sulfonated polymer P prepared in water and in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer A chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, in the presence of at least one initiator compound and at least one sulfur compound T comprising sulfur in oxidation state IV, and totally or partially neutralized by means of at least one monovalent ion, and * at least one binder compound, and optionally at least one compound chosen from a rheology modifying compound, an organic pigment, a mineral pigment and their combinations.

17. A method of preparing a coating comprising applying to a substrate a coating composition according to claim 16.

18. Method for controlling the rheology of an aqueous suspension S of particles of at least one mineral material M prepared: * by grinding in water at a concentration ranging from 10% by weight to 60% by weight of an aqueous suspension Sd of at least one particulate mineral material M, then * by concentration to a concentration ranging from 65% by weight to 80% by weight, by a treatment chosen from mechanical treatment, heat treatment and their combinations, of the ground suspension Sd, comprising the use during the concentration of at least one rheological agent R comprising phosphoric acid and at least one a-sulfonated polymer P prepared in water and in the absence of a phosphorus compound, by a polymerization reaction of at least one monomer A chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and their combinations, in the presence of at least one compound initiator and at least one sulfur compound T comprising sulfur in oxidation state IV, and totally or partially neutralized by means of at least one monovalent ion.

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