Dispersion of mineral particles

Abstract

The invention relates to a method for preparing a concentrated aqueous mineral composition, which method comprises thermally or mechanically concentrating a composition of mineral material previously ground in a wet environment at medium or low concentration. A particular poly(itaconate) is used when concentrating or dispersing the composition of mineral material. The invention also provides an aqueous concentration or dispersion agent comprising this particular poly(itaconate) and the use of the aqueous mineral composition for preparing paper.

Description

[0001] DISPERSION OF MINERAL PARTICLES

[0002] The invention relates to a method for preparing a concentrated aqueous mineral composition comprising the thermal or mechanical concentration of a previously ground mineral composition in a humid medium at medium or low concentration. A particular poly(itaconate) is used during the concentration or dispersion of this mineral composition. The invention also provides an aqueous concentrating or dispersing agent comprising this particular poly(itaconate) and the use of the aqueous mineral composition for papermaking.

[0003] Methods exist for preparing aqueous compositions of ground mineral material in a humid environment at medium or low concentrations, followed by mechanical or thermal concentration. These methods generally employ concentrating or dispersing agents, particularly to control the rheology of the aqueous composition during its preparation or storage. In general, methods for preparing mineral material compositions must be efficient and allow for good viscosity control. Viscosity drift must be controlled because it can lead to gelation of the prepared compositions, making them difficult or even impossible to handle. Similarly, sedimentation of mineral particles must be avoided or significantly slowed.In addition to stability control, viscosity control of aqueous compositions of ground mineral particles is also essential. Therefore, the stability of mineral compositions is a key characteristic not only during their preparation but also during their transport and storage.

[0004] Another desirable property for mineral compositions is their high mineral concentration. Therefore, it is important to be able to prepare aqueous compositions of mineral particles with a high dry extract. A high dry extract in these compositions allows for increased productivity of the methods that utilize them, as well as reduced costs and resources required for their preparation and transport.

[0005] Mineral compositions can be used alone, but they can also be combined with other mineral compositions. Thus, in addition to the problems encountered with each individual mineral composition, combining several of these compositions can generate further issues. Therefore, preparing concentrated mineral compositions becomes even more complex when multiple compositions must be combined. The compatibility of concentrated aqueous mineral compositions is thus a particularly desirable property. In particular, controlling the viscosity and stability of concentrated compositions containing multiple minerals is especially challenging.

[0006] To address these problems, various agents are used during one or more stages of preparing concentrated aqueous mineral compositions, particularly during grinding, mechanical or thermal concentration, or dispersion. Most often, the agents used are selected from grinding aids and concentration or dispersion agents. For example, there are polymeric agents prepared using carboxylic acid, notably (meth)acrylic polymers. However, it is important to have alternative agents available to improve the methods for preparing these compositions, as well as the methods for preparing the polymers themselves.

[0007] Within aqueous compositions of mineral matter, grinding aids and concentrating agents are expected to develop significant interactions with the mineral particles. In particular, these interactions should reduce the amount of free agent, that is, the amount of agent not adsorbed onto the mineral matter.

[0008] Finally, from an environmental point of view, it is important to have access to polymers prepared from reagents of renewable or natural origin, in particular reagents of plant origin.

[0009] Furthermore, during papermaking, aqueous mineral filler compositions are used either as a coating on the paper or to add mineral content to the pulp, which comprises water and plant-based fibers, particularly cellulosic fibers. In these compositions, the mineral matter is in particulate form. The use of such mineral fillers allows for improvements to the paper's physical properties, especially its optical properties, or for reducing the relative amount of cellulosic material compared to the amount of mineral filler, or for enhancing the optical properties of coated paper.

[0010] Improving the efficiency of papermaking processes is also possible through the use of these mineral fillers. To enhance the use of these mineral filler compositions in papermaking, and more specifically to retain these mineral fillers within the fibrous mat during paper sheet production, cationic compounds, particularly cationic starches or cationic acrylamide copolymers, are commonly used. These cationic compounds, or cationic mineral filler retention agents, increase the retention of mineral fillers on plant fibers or fibrils during papermaking. Specifically, by neutralizing the charges carried by the mineral filler particles, these cationic retention agents allow the formation of cationic coagulates retained by the plant fibers or fibrils.These cationic compounds also improve the drainage phase during papermaking, during which the greatest possible amount of mineral filler must be retained in the fibrous mat of the paper sheet. These compounds also help limit the loss of cellulosic material in the form of fine particles. Thus, cationic compounds are commonly used in papermaking, including cationic agents such as cationic binders, cationic coagulants, and cationic agents for retaining mineral or cellulosic material.

[0011] The reduction of the absolute value of the "Mütek" charge or the cationic demand of a composition of mineral matter particles in water should also be sought.

[0012] The cationic demand can be determined using a streaming current detector. This streaming current measurement can be performed using a Mütek apparatus by pouring polyDADMAC until the electrical charges of the mineral filler are neutralized. The Mütek charge value of the mineral filler is then obtained.

[0013] Document WO 2011147922 describes the preparation of aqueous calcium carbonate suspensions, including dispersion followed by high-concentration grinding of the mineral in the presence of two sodium polyacrylates of different molar masses. Document WO 2024009009 describes the preparation of an aqueous mineral suspension, including a grinding step followed by a mechanical or thermal concentration step in the presence of a rheological control agent combining phosphoric acid and an α-sulfonated poly(meth)acrylate. Document WO 2018087469 describes a method for grinding mineral material in the presence of a partially decarboxylated sodium polyitaconate. Document EP 0079165 describes copolymers of itaconic acid and (meth)acrylic acid used as antiscalants.

[0014] Thus, although methods exist for preparing concentrated aqueous compositions of mineral matter that utilize polymers as concentration or dispersion aids, prior art methods do not always provide satisfactory solutions to the problems encountered. Therefore, there is a need for improved methods for preparing concentrated aqueous compositions of mineral matter. The invention provides a solution to all or part of the problems with prior art methods.

[0015] Thus, the invention provides a method for preparing an aqueous composition C of mineral particles, in the presence of at least one water-soluble polymer P, having a molecular mass Mw, measured by CES, ranging from 1,500 g / mol to 50,000 g / mol, and prepared by a radical polymerization reaction in water, of at least one compound Ml selected from itaconic anhydride, itaconic acid, sodium itaconate, potassium itaconate, lithium itaconate, ammonium itaconate, calcium itaconate, magnesium itaconate and their combinations, comprising:

[0016] A- the grinding in water of an aqueous composition Cd comprising at least one particulate mineral material M in a concentration ranging from 15% by weight to 60% by weight of the composition Cd resulting in a composition Cb, then

[0017] Bl- the mechanical concentration of the aqueous composition Cb in the absence of polymer P resulting in the composition Ce followed by its dispersion in the presence of polymer P or its thermal concentration in the presence of polymer P, or

[0018] B2- the thermal concentration of the composition Cb in the presence of the polymer P. Before being concentrated, the composition according to the invention includes the essential step A of grinding in a wet medium of the mineral matter M.

[0019] During grinding, the starting composition Cd has a mineral content M ranging from 15% to 60% by weight. Preferably, according to the invention, the concentration of composition Cd is greater than 20% by weight, preferably greater than 25% by weight. Also preferably, according to the invention, the concentration of composition Cd is less than 55% by weight, preferably ranging from 15% to 50% by weight or from 20% to 55% by weight. Preferably, according to the invention, grinding, mechanical concentration, dispersion, and thermal concentration are carried out at atmospheric pressure.

[0020] According to the invention, the grinding can be carried out in the presence of a grinding aid. Generally, this is a polycarboxylic acid, in particular a (meth)acrylic polymer. Preferably for the method according to the invention, the aqueous composition Cd is ground in the absence of a grinding aid, preferably in the absence of a polycarboxylic acid, in particular in the absence of a (meth)acrylic polymer or in the absence of polyitaconic acid or in the absence of polymer P.

[0021] For the preparation method according to the invention, the aqueous composition Cb from the grinding step A can therefore have a concentration of particulate mineral matter M ranging from 15% by weight to 60% by weight, preferably a concentration ranging from 15% by weight to 30% by weight or a concentration ranging from more than 30% by weight to 60% by weight.

[0022] Also preferably, the aqueous composition Cb from the grinding step A, the concentration of particulate mineral matter M of which ranges from 15% by weight to 30% by weight, can be obtained by grinding in the absence of a grinding aid.

[0023] Also preferably, the aqueous composition Cb from the grinding step A, the concentration of particulate mineral matter M of which ranges from more than 30% by weight to 60% by weight, can be obtained by grinding in the presence of a grinding aid, preferably in the absence of polycarboxylic acid, in particular a (meth)acrylic polymer or a polyitaconic acid or the polymer P.

[0024] Essentially, according to the invention, the aqueous composition of ground mineral matter Cb is treated to remove some of the water it contains. The concentration of the composition Cb then increases its mineral matter concentration M.

[0025] In step B1, composition Cb is mechanically concentrated to obtain the more concentrated composition Ce, which can be dispersed in the presence of polymer P to form composition C according to the invention. According to the invention, composition Ce can subsequently be thermally concentrated in the presence of polymer P to form composition C according to the invention.

[0026] In step B2, composition Cb is treated by thermal concentration in the presence of polymer P to form composition C according to the invention.

[0027] Thus, the aqueous composition Ce has a concentration of particulate mineral matter M which is greater than the concentration of the composition Cb. Preferably according to the invention, the aqueous composition Ce has a concentration of particulate mineral matter M ranging from 35% by weight to 65% by weight, preferably ranging from 40% by weight to 65% by weight or from 50% by weight to 65% by weight.

[0028] Finally, the aqueous composition C generally has a concentration of particulate mineral matter M that is greater than the concentration of the composition Ce. Preferably, the composition C has a concentration ranging from 40% by weight to 72% by weight, preferably ranging from 40% by weight to 76% by weight, more preferably ranging from 40% by weight to 78% by weight.

[0029] According to the invention, the thermal concentration B2 is carried out in the presence of the polymer P. It can also be carried out in the presence of phosphoric acid, in particular in an amount of phosphoric acid ranging from 0.05% to 1% by dry weight of phosphoric acid relative to the dry weight of mineral matter M.

[0030] According to the invention, phosphoric acid can be implemented separately, simultaneously or in combination with polymer P, preferably in an amount from 0.05% to 1%, preferably from 0.1% to 0.6%, in dry weight of phosphoric acid relative to the dry weight of mineral matter M.

[0031] According to the invention, it is also possible that phosphoric acid is not used at all.

[0032] The invention allows for the preparation of an aqueous composition C of mineral particles by grinding a composition Cd of particulate mineral matter M in water. Generally, according to the invention, the mineral matter M used is not soluble in water at room temperature. Preferably, for the method according to the invention, a single material M, or two or three materials M, are used.

[0033] According to the invention, the mineral material M can be synthetic or of natural origin. Preferably, it is selected from alkaline earth metal carbonates, more preferably calcium carbonate (natural calcium carbonate or precipitated calcium carbonate), strontium carbonate, magnesium carbonate, barium carbonate, dolomite, kaolin, titanium dioxide, talc, lime, magnesium hydroxide, calcium sulfate, and barium sulfate. Calcium carbonate and kaolin are particularly preferred.

[0034] According to the invention, the ground mineral material particles M have a median size, measured by sedimentation, of less than 50 µm, or a median size ranging from 0.05 µm to 50 µm, or a median size of less than 10 µm. Preferably, this size is less than 5 µm or 2 µm, and more preferably less than 1 µm or 0.5 µm. Essentially, according to the invention, the method for preparing composition C involves at least one polymer P during at least one thermal concentration or dispersion step.

[0035] Preferably for the preparation method according to the invention, the polymer P has a molecular mass Mw, measured by CES, ranging from 2,000 g / mol to 50,000 g / mol or

[0036] 1,500 g / mol to 40,000 g / mol. Preferably, the molecular weight Mw of polymer P ranges from 2,000 g / mol to 25,000 g / mol or from 1,500 g / mol to 20,000 g / mol. More preferably, it ranges from 2,000 g / mol to 20,000 g / mol, even more preferably from 2,000 g / mol to 15,000 g / mol, much more preferably from 3,000 g / mol to 13,000 g / mol, or from

[0037] 2,500 g / mol to 15,000 g / mol, particularly preferably from 3,500 g / mol to 20,000 g / mol or from 3,000 g / mol to 15,000 g / mol, most preferably from 3,500 g / mol to 15,000 g / mol and much more preferably from 3,500 g / mol to 13,000 g / mol.

[0038] Also preferably for the preparation method according to the invention, the polymer P has a polymolecularity index IP, measured by CES, of less than 5.5, preferably less than 4.5. More preferably, the polymolecularity index IP is less than 4. Also more preferably, this polymolecularity index IP, measured by CES, ranges from 1.6 to 5.5, preferably from 1.6 to 4.5, more preferably from 1.6 to 4.

[0039] According to the invention, the molecular weight or mass of polymer P is determined by Size Exclusion Chromatography (SEC). A test portion of the polymer solution, corresponding to 90 mg of dry matter, is introduced into a 10 mL bottle. Mobile phase, supplemented with 0.04% dimethylformamide (DMF), is added up to a total mass of 10 g. The composition of this mobile phase is as follows: NaHCO3: 0.05 mol / L, NaNO3: 0.1 mol / L, triethanolamine: 0.02 mol / L, NaN3: 0.03 wt%. The CES chain consists of a Waters 510 type isocratic pump, with a flow rate set at 0.8 mL / min, a Waters 717+ sample changer, a furnace containing a 6 cm long and 40 mm internal diameter Waters Guard Column Ultrahydrogel pre-column, followed by a 30 cm long and 7.8 mm internal diameter Waters Ultrahydrogel linear column.Detection is performed using a Waters 410 type RI differential refractometer. The oven is heated to 60°C and the refractometer to 45°C. The CES device is calibrated with a series of sodium polyacrylate standards supplied by Polymer Standard Service, with peak molecular weights ranging from 1200 g / mol to 1390,000 g / mol and polymolecularity indices between 1.4 and 1.7. The calibration curve is linear and incorporates the correction obtained using the flow marker dimethylformamide (DMF). Chromatogram acquisition and processing are performed using NTeqGPC v.5.1.5 software. The resulting chromatogram is integrated into the region corresponding to molecular weights greater than 250 g / mol.

[0040] According to the invention, polymer P is prepared by a radical polymerization reaction of compound Ml selected from itaconic anhydride, itaconic acid, sodium itaconate, potassium itaconate, lithium itaconate, ammonium itaconate, calcium itaconate, magnesium itaconate and their combinations.

[0041] Preferably, the polymerization reaction involves a combination of itaconic acid and at least one itaconate, preferably an itaconate selected from sodium itaconate, potassium itaconate, lithium itaconate, ammonium itaconate.

[0042] Preferably according to the invention, the polymer P is totally or partially neutralized, preferably by means of an ion selected from a monovalent ion, a divalent ion and combinations thereof, more preferably by means of an ion selected from K + , N / A + , Li + , NHÉ, Mg 2+ , That 2+ and their combinations.

[0043] Also preferably, polymer P is totally or partially neutralized by means of at least one compound selected from LiOH, NaOH, KOH, Zn(OH)2, Mg(OH)2, Ca(OH)2, ZnO, MgO, CaO, ammonium derivatives, ammonia, ammonia, amino bases, for example triethanolamine, aminomethylpropanol, diethanolisopropylamine or 2-amino-2-methylpropanol (AMP) and their combinations, more preferably NaOH, Ca(OH)2, CaO and their combinations.

[0044] According to the invention, polymer P is prepared by a radical polymerization reaction in water of at least one compound ML. Preferably, for the method according to the invention, the polymerization reaction involves a combination of itaconic acid and an itaconate, preferably a combination of itaconic acid and an itaconate selected from sodium itaconate, potassium itaconate, lithium itaconate, and ammonium itaconate. Also preferably, the polymerization reaction involves a combination of itaconic acid and an itaconate in a molar ratio of itaconic acid / itaconate ranging from 80 / 20 to 20 / 80, more preferably ranging from 45 / 55 to 55 / 45.

[0045] Preferably according to the invention, compound Ml does not comprise an ester group; in particular, compound Ml is not an itaconic acid ester, especially an itaconic acid diester. Even if, preferably according to the invention, polymer P is a homopolymer, in addition to compound Ml, polymer P can also be prepared using at least one other compound different from compound Ml, preferably from 0.5% by weight to 30% by weight of another compound relative to the total weight of monomers.

[0046] Thus, polymer P can also be prepared using another compound chosen from:

[0047] • a compound M2 selected from acrylic acid, methacrylic acid, an acrylic acid oligomer, a methacrylic acid oligomer, an acrylic acid salt, a methacrylic acid salt, an acrylic acid oligomer salt, a methacrylic acid oligomer salt, maleic acid, maleic anhydride, crotonic acid, 2-acrylamido-2-methylpropane sulfonic acid, a salt of 2-acrylamido-2-methylpropane sulfonic acid, ethoxymethacrylate sulfonic acid, sodium methallyl sulfonate, styrene sulfonate, phosphated hydroxyethyl acrylate, phosphated hydroxyethyl methacrylate, phosphated hydroxypropyl acrylate, phosphated hydroxypropyl methacrylate, phosphated hydroxybutyl acrylate, phosphated hydroxybutyl methacrylate and their combinations;

[0048] • a compound M3 independently selected from C1-C12 esters of methacrylic acid, C1-C12 esters of acrylic acid, acrylamide, N-Zc / V-butyl acrylamide, alkylacrylamides, N-methylolacrylamide, acrylonitrile, vinyl-lactam, N-vinylpyrrolidone, ureidomethacrylate, hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropylacrylate, hydroxypropylmethacrylate, hydroxybutylmethacrylate, hydroxybutylacrylate, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactame methacrylate, lactame acrylate, polycaprolactame methacrylate, polycaprolactame acrylate, vinyl acetate and combinations thereof; preferably Ci-Cs esters of methacrylic acid, Ci-Cs esters of acrylic acid and their combinations;preferably, N- / c77-butyl acrylamide, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, more preferably, methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate and their combinations.;

[0049] For the method according to the invention, the polymerization reaction is carried out in the presence of an initiating compound, preferably an initiating compound selected from a peroxide (e.g., hydrogen peroxide, tert-butyl hydroperoxide), a persalt, preferably a persulfate (e.g., sodium persulfate, ammonium persulfate, potassium persulfate), combinations thereof, and optionally a metal salt, preferably a metal salt selected from an iron salt (e.g., Fe 11 or Fe 111 ), a copper salt (for example Cu 1 or Cu 11 ) and their combinations.

[0050] Also, the polymerization reaction can be carried out in the presence of at least one sulfur compound Tl comprising sulfur in oxidation state IV (sulfur IV or S IV Preferably, compound Tl is selected 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, compound Tl is used in an amount of 0.5% by weight to 15% by weight, preferably 1% by weight to 10% by weight, and more preferably 1.5% by weight to 8% by weight, relative to the total dry weight amount of monomers used in the polymerization reaction.

[0051] The polymerization reaction can also be carried out in the presence of at least one phosphorus compound T2 comprising phosphorus in oxidation state I (phosphorus I or P 1) or containing phosphorus in oxidation state III (phosphorus III or P 111 Preferably, compound T2 is selected from hypophosphorous acid, sodium hypophosphite, ammonium hypophosphite, phosphorous acid, sodium phosphite, and ammonium phosphite. Preferably, compound T2 is used in an amount of 0.5% by weight to 15% by weight, preferably 1% by weight to 10% by weight, and more preferably 1.5% by weight to 8% by weight, relative to the total dry weight amount of monomers used in the polymerization reaction.

[0052] During the polymerization reaction, the reaction conditions may vary. Preferably, compound Ml is present during the polymerization reaction in an amount by weight greater than 30%, preferably greater than 35% or 40%, more preferably greater than 45% or 50%, relative to all the compounds present in the reaction medium.

[0053] Preferably according to the invention, the polymerization reaction comprises:

[0054] • the preparation of a reaction medium comprising at least one compound M1 in a weight quantity greater than 35%, preferably greater than 50% or 60%, more preferably greater than 65% or 70%, relative to all the reactants in that reaction medium, then • the addition of the initiating compound, possibly a separate addition of compound T1 or possibly compound T2, and possibly a separate addition of compound M1 and

[0055] • heating the reaction medium.

[0056] Essentially, the method for preparing composition C according to the invention uses polymer P. For this method of preparation, the quantity of polymer P can vary but it preferably ranges from 0.05% to 5% by dry weight, preferably from 0.3% to 2.0% by dry weight, relative to the dry weight of particulate mineral matter M.

[0057] Preferably according to the invention, thermal concentration is achieved by heating, preferably at a heating temperature above 80°C or at a heating temperature below 95°C.

[0058] Also preferably according to the invention, mechanical concentration is carried out by centrifugation or by means of a filter press or a rotary filter.

[0059] The preparation method according to the invention makes it possible to obtain a composition C highly concentrated in mineral matter M. Preferably according to the invention, the concentration of composition C in mineral matter M is greater than 60% by weight or greater than 65% by weight or greater than 70% by weight or is less than 78% by weight or is less than 75% by weight, preferably from 70% by weight to 78% by weight or from 70% by weight to 75% by weight of composition C.

[0060] The polymer P implemented according to the invention favorably influences the properties of composition C according to the invention when used according to the preparation method of the invention. In particular, the polymer P according to the invention allows control of the viscosity of composition C. Preferably according to the invention, the Brookfield viscosity of composition C, measured at 25°C, at 100 rpm 1 hour after preparation, can be less than 800 mPa·s, preferably less than 000 mPa·s, and more preferably less than 400 mPa·s.

[0061] Also preferably according to the invention, the Brookfield viscosity of composition C measured at 25 °C, at 100 rpm before stirring, measured 8 days after preparation may be less than 2,500 mPa.s, preferably less than 2,000 mPa.s, more preferably less than 1,500 mPa.s or 1,000 mPa.s, much more preferably less than 800 mPa.s.

[0062] The interaction of polymer P with mineral matter M also limits the amount of free polymer in composition C according to the invention. Preferably, the amount of free polymer P not adsorbed onto mineral matter M, measured by determining the total organic carbon by weight present in the water of composition C, is less than 45% by weight, preferably less than 35% by weight, relative to the total organic carbon of polymer P introduced during concentration. Furthermore, the use of polymer P during the preparation of composition C according to the invention allows for control of the cation demand of composition C. Preferably, according to the invention, the cation demand of composition C, measured using a Mütek apparatus, is less than -25 peq / g of composition C.

[0063] The use of polymer P in the preparation of composition C according to the invention makes it possible to prepare a concentrated aqueous composition C possessing properties useful in many technical fields. Thus, the invention also provides an aqueous composition C obtained according to the preparation method of the invention.

[0064] The polymer P according to the invention can be used directly or it can be combined with water. Thus, the invention provides an aqueous agent D with a concentration of composition Cb according to the invention comprising at least one polymer P defined according to the invention.

[0065] The polymer P imparts particular properties to the composition C according to the invention and allows its use in combination with other mineral compositions having different characteristics or obtained by preparation methods different from the method of preparing composition C according to the invention. Thus, the invention also provides a method for preparing an aqueous composition Cm of mineral particles comprising: i. the preparation of an aqueous composition C according to the invention; ii. the preparation of an aqueous composition Cg comprising a mineral material Q in a concentration ranging from 65% by weight to 78% by weight of composition Cg, and obtained by grinding a mineral material Q in water in the presence of a grinding aid, preferably a (meth)acrylic polymer R; iii. the mixing, under stirring, of the aqueous composition C with the aqueous composition Cg.

[0066] Preferably according to the invention, the composition Cg is prepared by a method which includes grinding in water, at a high concentration of mineral matter Q and in the presence of a grinding aid comprising at least one polymer R. Preferably, the polymer R is generally a polyacrylate, for example a sodium polyacrylate or a sodium and calcium polyacrylate.

[0067] In a highly advantageous manner, the presence of polymer P in composition C mixed with composition Cg improves the compatibility of composition C with composition Cg to obtain composition Cm according to the invention.

[0068] According to the invention, the mineral material Q can be synthetic or of natural origin. Preferably, it is selected from alkaline earth metal carbonates, more preferably calcium carbonate (natural calcium carbonate or precipitated calcium carbonate), strontium carbonate, magnesium carbonate, barium carbonate, dolomite, kaolin, titanium dioxide, talc, lime, magnesium hydroxide, calcium sulfate, and barium sulfate. Calcium carbonate and kaolin are particularly preferred.

[0069] Preferably according to the invention, the method of preparing composition Cm makes it possible to obtain a composition Cm which comprises from 60% to 90% by dry weight of composition C and from 10% to 40% by dry weight of composition Cg, relative to the dry weight of composition Cm.

[0070] Also preferably according to the invention, the concentration of the composition Cm in mineral matter M and Q is greater than 45% by weight or 50% by weight or 70% by weight or is less than 78% by weight or is less than 75% by weight, preferably goes from 70% by weight to 78% by weight or from 70% by weight to 75% by weight of the composition Cm.

[0071] Preferably, the Brookfield viscosity of the composition Cm measured at 25°C, at 100 rpm 1 hour after preparation, is less than 800 mPa.s, preferably less than 600 mPa.s.

[0072] Preferably, the Brookfield viscosity of the composition Cm measured at 25°C, at 100 rpm before stirring, measured 8 days after preparation is less than 2,500 mPa.s, preferably less than 2,000 mPa.s, more preferably less than 2,000 mPa.s or 1,000 mPa.s.

[0073] The invention also provides an aqueous composition Cm obtained according to the preparation method of the invention. According to the invention, the use of polymer P allows for good control of the rheology of the composition Cm according to the invention. Thus, the invention provides a method for controlling the viscosity of a composition Cm according to the invention, comprising the use of at least one polymer P according to the invention or an aqueous concentrating or dispersing agent according to the invention. The use of the compositions C and Cm according to the invention for papermaking is particularly advantageous, especially for the preparation of a paper mass filler composition or for the preparation of a paper coating slurry composition.

[0074] Thus, the invention provides an aqueous paper preparation composition selected from a paper mass filler composition and a paper coating slurry composition comprising:

[0075] - a composition C according to the invention or a composition Cm according to the invention and possibly

[0076] - at least one binding compound, and possibly at least one compound selected from a rheology modifier compound, a water-retaining agent and an optical brightening agent.

[0077] According to the invention, the paper mass filler composition and the paper coating sauce composition are prepared by mixing their different ingredients, in particular by mixing these ingredients in water.

[0078] The invention also provides a method of paper preparation comprising the application of a composition C according to the invention or a composition Cm according to the invention.

[0079] According to the invention, the particular, advantageous or preferred characteristics of composition C according to the invention and of its method of preparation define methods for its use, compositions Cm and paper preparation compositions, methods for their preparation or using them, as well as concentrating agents according to the invention which are also particular, advantageous or preferred.

[0080] The various aspects of the invention can be illustrated by the following examples. The methods or techniques implemented are known or described.

[0081] EXAMPLES

[0082] Preparation and characterization of polymers P according to the invention

[0083] Preparation of the PI polymer according to the invention

[0084] In a glass reactor, 207 g of itaconic acid (compound Ml) are introduced, followed by 127.38 g of a 50 wt% aqueous sodium hydroxide solution. The reaction is exothermic, the reactor temperature is maintained at 90°C ± 2°C, and then 21 g of deionized water are introduced.

[0085] In a first beaker, 10.3 g of sodium persulfate and 21 g of deionized water are weighed out. The reagents from the beaker are introduced all at once into the reactor, and the temperature is maintained at 90°C ± 2°C for 2 hours. Then, 150 g of deionized water is added, and the mixture is allowed to cool to room temperature. The PI polymer solution is neutralized to pH 7.4 by adding 50 wt% sodium hydroxide to the water. The resulting composition, CPI, comprises the PI polymer according to the invention at 47.0 wt% dry extract, the composition and characteristics of which are detailed in Table 1.

[0086] Preparation of polymer P2 according to the invention

[0087] In a glass reactor, 207 g of itaconic acid (compound Ml) are introduced, followed by 127.38 g of a 50 wt% aqueous sodium hydroxide solution. The reaction is exothermic, the reactor temperature is maintained at 90°C ± 2°C, and then 0.008 g of iron(II) sulfate heptahydrate diluted in 10 g of deionized water is added all at once.

[0088] In the first beaker, 27.3 g of hydrogen peroxide solution (35 wt.) and 27 g of deionized water are weighed out. In the second beaker, 25 g of sodium bisulfite solution (40 wt.) are weighed out.

[0089] The reagents from the two beakers are introduced in parallel into the reactor for 2 hours, and the temperature is maintained at 90°C ± 2°C for 1 hour. Then, 150 g of deionized water is added, and the mixture is allowed to cool to room temperature.

[0090] The polymer P2 solution is neutralized to pH 7.9 by adding 50% (w / m) sodium hydroxide to water. The resulting composition, CP2, comprises polymer P2 according to the invention at 44.4% (w / m) dry extract, the composition and characteristics of which are detailed in Table 1.

[0091] Table 1

[0092] Measurement of the charge of polymer P according to the invention

[0093] In a 1 L volumetric flask, approximately 1 g dry of neutralized polymer is introduced. The mass (mO) of polymer (P) dry extract (ESp) is precisely recorded in grams. Deoxygenated water is added to dilute the polymer, and the volume is adjusted to the calibration mark with deoxygenated water. The volumetric flask is thoroughly shaken to obtain a homogeneous solution. Using a pre-calibrated micropipette, approximately 0.5 g of the previously prepared neutralized polymer solution is introduced into the measuring cell of a Mütek PCD 03 instrument equipped with an automatic titrator (PCD titrator two). The mass (ml) of this solution is precisely recorded in grams. Approximately 20 mL of deoxygenated water is also introduced into this measuring cell. The piston of the measuring cell is activated for approximately 1 minute before starting the titration.The titration is then automatically initiated by introducing a titrant solution into the measuring cell. This solution is a polyDADMAC (poly(diallyldimethyl ammonium chloride)) solution with molecular masses ranging from 10,000 g / mol to 400,000 g / mol. A certified solution of this polymer titrant at a concentration of 0.001 N is commercially available. In our case, it is supplied by the company "NOVIPROFIBRE" (France). The titration stops when the charge neutralization point is reached. The volume of titrant solution dispensed, V, is then recorded in mL. The polymer charge is given by the following expression:

[0094] V charge = —96485 X 1.0

[0095] This polymer charge is expressed in Coulombs per gram of dry polymer. Preparation and characterization of aqueous compositions C according to the invention

[0096] An aqueous composition Cdl containing calcium carbonate (Carrara marble "Omyacarb" 10 AV) is ground in water using a horizontal "DYNO" mill, type KDL-Pilot A ("W AB Group", Switzerland), to a concentration of 18% by mass. This yields the aqueous composition Cbl, in which 75% by mass of the calcium carbonate particle population has an equivalent spherical diameter of less than 1 µm. Composition Cbl is mechanically concentrated by centrifugation to obtain composition Ccl, which has a concentration of 55% by dry weight of mineral matter M.

[0097] Then, at room temperature and with stirring, 2800 g of composition Ccl and composition CPI, providing 0.60 g of dry PI polymer per 100 g of dry calcium carbonate, are mixed in the bowl of a mixer (Vorwerk). The Ccl composition is thermally concentrated by heating to 90°C while adding, every 30 minutes, composition CPI, providing 3 x 0.45 g of dry PI polymer per 100 g of dry calcium carbonate.

[0098] Composition Cl according to the invention is obtained, having a concentration of 72.0% by dry weight of mineral matter M. Similarly, by replacing composition CPI comprising polymer PI with composition CP2 comprising polymer P2, composition C2 according to the invention is prepared, having a concentration of 71.7% by dry weight of mineral matter M.

[0099] After cooling to room temperature, the Cl and C2 compositions were characterized by measurements of pH, dry extract (SE), free polymer content (P), calcium carbonate particle size, viscosity, and Mütek charge. The stability of the Cl and C2 compositions was also evaluated. The results are presented in Table 2.

[0100] Measurement of the free polymer content in Cl and C2 compositions

[0101] For a diluted CPI composition comprising the PI polymer at a PI polymer concentration in water by dry weight identical to that of the Cl composition, the TOC1 (Total Organic Carbon) value is determined by measuring the amount of organic carbon using an Xpert-COT / TNb TOC analyzer “HACH”.

[0102] Then, after separation by filtration of the calcium carbonate from composition Cl, the TOC2 value is determined by measuring the amount of organic carbon in the filtrate of composition Cl.

[0103] The amount of free PI polymer in composition Cl is calculated according to the equation:

[0104] % free dispersant = TOC2

[0105] TOC 1 x 100

[0106] Similarly, the amount of free polymer P2 in composition C2 is determined.

[0107] Particle size measurement of Cl and C2 compositions

[0108] The particle size distribution of calcium carbonate particles of compositions Cl and C2 is measured using a particle size analyzer (“Sedi graph” 5100 “Micromeritics”) by determining the value of the mass percentage of the particle population whose equivalent spherical diameter is less than 1 pm (esd < 1 pm).

[0109] These measurements are performed using Cl and C2 compositions dispersed at a concentration of 33 g of dry matter per liter in a solution of sodium polyacrylate with a molecular weight of 4000 g / mol and a concentration of 1.6 g of dry sodium polyacrylate per liter of solution. Each sample is subjected to ultrasonic testing before measurement.

[0110] Measurement of Brookfield viscosity and stability of Cl and C2 compositions

[0111] One hour after their preparation, the Brookfield viscosity (VB0 - in mPa·s) of the Cl and C2 compositions according to the invention is measured at 25°C ± 1°C and at a rotation speed of 100 rpm using a Brookfield DVIII viscometer equipped with a module 2 to 5 adapted to the particular viscosity. After 8 days in a climate-controlled chamber at 25°C, and in a similar manner, the Brookfield viscosity (VB8 - in mPa·s) of the Cl and C2 compositions is measured.

[0112] Measurement of the cationic demand ("Mütek" charge) of the Cl and C2 compositions

[0113] The cationic demand of the Cl and C2 compositions is measured using a titrator (“Mütek” PCD 03) equipped with an automatic titrator PCD titrator two, by titration using a cationic polymer of known titer and until neutralization of the charges contained in the sample of each of the Cl and C2 compositions.

[0114] The titrant solution is a 0.001 N solution of polyDADMAC (poly(diallyldimethyl ammonium chloride) from "NOVIPROFIBRE" (France)) with molecular masses between 10,000 g / mol and 400,000 g / mol.

[0115] Weigh out 0.8 g of Cl or C2 composition and add 20 mL of diperized water. Place the piston in the cell and start the motor that drives the piston's reciprocating motion. After 2 to 3 minutes, the titration begins. At the end of the titration, the instrument displays the measurement result (in eq / g of composition).

[0116] Table 2

[0117] PI and P2 polymers allow the preparation of highly concentrated Cl and C2 compositions with well-controlled viscosity. These compositions are stable, contain very little free polymer, and exhibit low cation demand.

[0118] Preparation and characterization of Cm compositions according to the invention

[0119] Compositions Cml and Cm2 are prepared by mixing compositions Cl and C2, respectively, with an aqueous composition Cgi comprising calcium carbonate ground in water at a high concentration (74.6 wt.) in the presence of a grinding aid (poly(acrylic acid) partially neutralized with sodium - Mw of 4700 g / mol), and of which 82.8 wt. have an equivalent spherical diameter of less than 1 µm. Composition Cgi has a dry extract of 74.6 wt., a pH of 9.4, and a Brookfield viscosity measured at 100 rpm at 25°C of 188 mPa·s. Composition Cg is mixed, under mechanical stirring for approximately 20 minutes, in a weight ratio of 20 / 80 dry / dry with compositions Cl and C2, respectively. The resulting compositions Cml and Cm2 according to the invention are characterized in the same way as compositions Cl and C2 according to the invention. The results are presented in Table 3.

[0120] Table 3

[0121] The PI and P2 polymers allow the preparation of highly concentrated and stable Cml and Cm2 compositions. The Cl and C2 compositions according to the invention exhibit very good compatibility with the known aqueous calcium carbonate composition Cgi. Preparation and characterization of an aqueous bread preparation composition according to the invention

[0122] The mixture is stirred using a "VMI Turbotest" dispersion device:

[0123] - 100 parts by mass of composition C2 according to the invention,

[0124] - 9 parts of a binding compound (DL1066 "Trinseo") at 55% by weight in water,

[0125] - 0.4 part of polyvinyl alcohol (“Mowiol” 5-98 “Chang Chung Petrochemical”) at 25% by weight in water,

[0126] - 0.6 part of an optical brightening compound (“Blankophor” TP 4900 “Indulor”),

[0127] - 0.135 part of a thickening compound ("Rheocoat" 93 "Coatex") at 31% by weight in water,

[0128] - water qsp for a dry extract of 69% by mass.

[0129] The pH of the aqueous composition of paper preparation according to the invention is adjusted to 8.8 by adding sodium hydroxide in aqueous solution at 20% by weight.

[0130] The dry extract of the resulting composition is measured using a microwave balance (MMB) by depositing between 1 g and 4 g of the composition onto a piece of fiberglass paper of a predetermined mass. The balance then dries the composition by microwave irradiation until its weight remains constant for 10 seconds. The weight loss allows the dry extract (% by weight) of the papermaking composition according to the invention to be determined. The pH is measured at 25°C using a pH meter (WTW) equipped with a conventional electrode coupled to a temperature probe. The Brookfield viscosity (in mPa·s) of the papermaking composition according to the invention is measured at 100 rpm and 25°C using an analog viscometer equipped with a spindle adapted to the viscosity range of the composition.

[0131] The capillary viscosity (in mPa.s) of the papermaking preparation composition according to the invention is measured at a high shear gradient (500,000 s' 1 ) and at 25°C using a capillary viscometer (AX100 ACA) equipped with a capillary 10 mm long and 0.5 mm in inner diameter.

[0132] The water retention of the papermaking composition according to the invention is determined using a water retention measuring apparatus (AAGWR "Gradek") comprising a measuring chamber in which a test paper (Test Blotter Paper "Gradek") covered by a perforated plastic film (Test Filter PCTE "Gradek" - 2 µm) is placed. 10 mL of the papermaking composition according to the invention is introduced into the chamber. A pressure (1.5 bar for 90 seconds) is applied to the composition, causing all or part of the water and water-soluble substances to pass through the perforated plastic film and migrate into the test paper.

[0133] The increase in paper mass (between pO weighed before measurement and pl weighed at the end of measurement) corresponds to the quantity of water and water-soluble substances that migrated from the papermaking composition according to the invention to the test paper during the measurement. The relative value of the increase in water retention is equal to 1250 x (pl - pO) / pO.

[0134] The results are presented in Table 4.

[0135] Table 4

[0136] The polymers according to the invention make it possible to prepare papermaking compositions which are stable and whose viscosity and water retention are well controlled.

[0137] Preparation and characterization of paper according to the invention

[0138] We have a sheet of wood-free paper measuring 21 x 29.7 cm with a specific weight of 78 g / m² 2The paper is coated with the coating solution to be tested using a laboratory coating machine with a scraper blade. Each sheet of paper is coated at 11-12 g / m². 2 and dried in a non-ventilated oven for 5 minutes at 50°C. Each sheet is then calendered on each side using a laboratory calender at 80°C and 25 bars.

[0139] The optical properties of the coated paper were measured using a spectrophotometer (“Elrepho” 3000 “Data Color”): - whiteness W(CIE) according to ISO 11475,

[0140] - Opacity according to standard NFQ-03040,

[0141] - reflectance in the blue (wavelength equal to 457 nm) according to the TAPPI T 452 om-08 standard, ISO 2470,

[0142] - Opacity is measured according to TAPPI T 519 om-06, ISO 2471. Gloss is measured according to TAPPI T 480 om-09 using a glossmeter.

[0143] (coordinate: m / «Lehmann»). Contact angles were measured with bipermuted water and rapeseed oil using a contact angle goniometer (“Digidrop” OCE 15EC «DataPhysics»).

[0144] The results are presented in Table 5.

[0145] Table 5

[0146] The P polymers according to the invention make it possible to prepare coated paper having very good optical properties.

Claims

DEMANDS 1. Method for preparing an aqueous composition C of mineral particles, in the presence of at least one water-soluble polymer P, having a molecular mass Mw, measured by CES, ranging from 1500 g / mol to 50000 g / mol, and prepared by a radical polymerization reaction in water, of at least one compound Ml selected from itaconic anhydride, itaconic acid, sodium itaconate, potassium itaconate, lithium itaconate, ammonium itaconate, calcium itaconate, magnesium itaconate and their combinations, comprising: A- the grinding in water of an aqueous composition Cd comprising at least one particulate mineral material M in a concentration ranging from 15% by weight to 60% by weight of the composition Cd resulting in a composition Cb, then Bl- the mechanical concentration of the aqueous composition Cb in the absence of polymer P resulting in the composition Ce followed by its dispersion in the presence of polymer P or its thermal concentration in the presence of polymer P, or B2- the thermal concentration of the composition Cb in the presence of the polymer P.

2. Method according to claim 1 wherein: - grinding, mechanical concentration, dispersion and thermal concentration are carried out at atmospheric pressure; or - the aqueous composition Cd is ground in the absence of a grinding aid, preferably in the absence of polycarboxylic acid, in particular in the absence of (meth)acrylic polymer or in the absence of polyitaconic acid or in the absence of polymer P; or - the thermal concentration B2 is carried out in the presence of phosphoric acid, preferably in an amount of phosphoric acid ranging from 0.05% to 1% by dry weight of phosphoric acid relative to the dry weight of mineral matter M; or - Phosphoric acid is used separately, simultaneously or in combination with polymer P, preferably in an amount from 0.05% to 1%, preferably from 0.1% to 0.6%, in dry weight of phosphoric acid relative to the dry weight of mineral matter M, or no phosphoric acid is used.

3. A method according to claim 1 or 2, wherein: - the concentration of the Cd composition is greater than 20% by weight, preferably greater than 25% by weight of the Cd composition; or - the concentration of the Cd composition is less than 55% by weight, preferably the concentration of the Cd composition ranges from 15% by weight to 50% by weight or from 20% by weight to 55% by weight of the Cd composition; or for which: - the aqueous composition Cb has a concentration of particulate mineral matter M ranging from 15% by weight to 60% by weight, preferably a concentration ranging from 15% by weight to 30% by weight or a concentration ranging from more than 30% by weight to 60% by weight, or - the aqueous composition Ce has a concentration of particulate mineral matter M which is greater than the concentration of the composition Cb or the aqueous composition Ce has a concentration of particulate mineral matter M ranging from 35% by weight to 65% by weight, preferably ranging from 40% by weight to 65% by weight or from 50% by weight to 65% by weight, or - the aqueous composition C has a concentration of particulate mineral matter M which is greater than the concentration of the composition Ce or the composition C has a concentration ranging from 40% by weight to 72% by weight, preferably ranging from 40% by weight to 76% by weight, more preferably ranging from 40% by weight to 78% by weight.

4. A method according to any one of claims 1 to 3, wherein: - only one material M, or two or three materials M are used; or - the mineral material M is synthetic or of natural origin, preferably selected from alkaline earth metal carbonate, preferably calcium carbonate (natural calcium carbonate or precipitated calcium carbonate), strontium carbonate, magnesium carbonate, barium carbonate, dolomite, kaolin, titanium dioxide, talc, lime, magnesium hydroxide, calcium sulfate, barium sulfate; or - the particles of crushed mineral matter M have a median size, measured by sedimentometry, of less than 50 pm or a median size ranging from 0.05 pm 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.

5. A method according to any one of claims 1 to 4, wherein: - the polymer P has a molecular mass Mw, measured by CES, ranging from 2,000 g / mol to 50,000 g / mol or from 1,500 g / mol to 40,000 g / mol, preferably 2,000 g / mol to 25,000 g / mol or from 1,500 g / mol to 20,000 g / mol, more preferably from 2,000 g / mol to 20,000 g / mol, even more preferably from 2,000 g / mol to 15,000 g / mol, much more preferably from 3,000 g / mol to 13,000 g / mol or from 2,500 g / mol to 15,000 g / mol, particularly preferably from 3,500 g / mol to 20,000 g / mol or from 3,000 g / mol to 15,000 g / mol, most preferably from 3,500 g / mol to 15,000 g / mol and much more preferably from 3,500 g / mol to 13,000 g / mol; or - polymer P has a polymolecularity index (PI), measured by CES, of less than 5.5, preferably less than 4.5, more preferably less than 4; or - polymer P has a polymolecularity index (PI), measured by CES, ranging from 1.6 to 5.5, preferably ranging from 1.6 to 4.5, more preferably ranging from 1.6 to 4; or - the polymer P is totally or partially neutralized, preferably by means of an ion chosen from a monovalent ion, a divalent ion and their combinations, more preferably by means of an ion chosen from K + , N / A + , Li + , NÜ4 + , Mg 2+ , That 2+ and their combinations; also preferably, polymer P is totally or partially neutralized by means of at least one compound selected from LiOH, NaOH, KOH, Zn(OH)2, Mg(OH)2, Ca(OH)2, ZnO, MgO, CaO, ammonium derivatives, ammonia, ammonia, amino bases, for example triethanolamine, aminomethylpropanol, diethanolisopropylamine or 2-amino-2-methylpropanol (AMP) and their combinations, more preferably NaOH, Ca(OH)2, CaO and their combinations.

6. A method according to any one of claims 1 to 5, wherein: - the polymerization reaction involves a combination of itaconic acid and an itaconate, preferably a combination of itaconic acid and an itaconate selected from sodium itaconate, potassium itaconate, lithium itaconate, ammonium itaconate; also preferably a combination of itaconic acid and an itaconate in a molar ratio of itaconic acid / itaconate ranging from 80 / 20 to 20 / 80, preferably ranging from 45 / 55 to 55 / 45; or - polymer P is a homopolymer or polymer P is also prepared using at least one other compound different from compound M1, preferably from 0.5% by weight to 30% by weight of another compound relative to the total weight of monomers; or - Polymer P is also prepared using another compound selected from: • a compound M2 selected from acrylic acid, methacrylic acid, an acrylic acid oligomer, a methacrylic acid oligomer, an acrylic acid salt, a methacrylic acid salt, an acrylic acid oligomer salt, a methacrylic acid oligomer salt, maleic acid, maleic anhydride, crotonic acid, 2-acrylamido-2-methylpropane sulfonic acid, a salt of 2-acrylamido-2-methylpropane sulfonic acid, ethoxymethacrylate sulfonic acid, sodium methallyl sulfonate, styrene sulfonate, phosphated hydroxyethyl acrylate, phosphated hydroxyethyl methacrylate, phosphated hydroxypropyl acrylate, phosphated hydroxypropyl methacrylate, phosphated hydroxybutyl acrylate, phosphated hydroxybutyl methacrylate and their combinations; • a compound M3 independently selected from C1-C12 esters of methacrylic acid, C1-C12 esters of acrylic acid, acrylamide, N-Zc / V-butylacrylamide, alkylacrylamides, N-methylolacrylamide, acrylonitrile, vinyl-lactam, N-vinylpyrrolidone, ureidomethacrylate, hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropylacrylate, hydroxypropylmethacrylate, hydroxybutylmethacrylate, hydroxybutylacrylate, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactame methacrylate, lactame acrylate, polycaprolactame methacrylate, polycaprolactame acrylate, vinyl acetate and combinations thereof; preferably Ci-Cs esters of methacrylic acid, Ci-Cs esters of acrylic acid and their combinations;preferably, N-tert-butylacrylamide, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, more preferably, methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate and their combinations.; 7. A method according to any one of claims 1 to 6, wherein: - The polymerization reaction is carried out in the presence of an initiating compound chosen from a peroxide (for example, hydrogen peroxide, hydroperoxide) tert-butyl), a persalt, preferably a persulfate (e.g., sodium persulfate, ammonium persulfate, potassium persulfate), their combinations and associations with possibly a metallic salt, preferably a metallic salt selected from an iron salt (e.g., Fe 11 or Fe 111 ), a copper salt (for example Cu 1 or Cu 11 ) and their combinations; or - The polymerization reaction is carried out in the presence of at least one sulfur compound Tl comprising sulfur in oxidation state IV (sulfur IV or S IV ), preferably the compound Tl is selected from lithium hydrogen sulfite, sodium hydrogen sulfite, potassium hydrogen sulfite, ammonium hydrogen sulfite, calcium di(hydrogen sulfite), magnesium di(hydrogen sulfite) and combinations thereof; also preferably, the compound Tl is used in an amount of 0.5% by weight to 15% by weight, preferably 1% by weight to 10% by weight, more preferably 1.5% by weight to 8% by weight, relative to the total dry weight amount of monomers used in the polymerization reaction; or - The polymerization reaction is carried out in the presence of at least one phosphorus compound T2 comprising phosphorus in oxidation state I (phosphorus I or P 1) or containing phosphorus in oxidation state III (phosphorus III or P 111 ), preferably the compound T2 is chosen from hypophosphorous acid, sodium hypophosphite, ammonium hypophosphite, phosphorous acid, sodium phosphite, ammonium phosphite, also preferably the compound T2 is used in an amount of 0.5% by weight to 15% by weight, preferably 1% by weight to 10% by weight, more preferably 1.5% by weight to 8% by weight, relative to the total dry weight amount of monomers used in the polymerization reaction.

8. A method according to any one of claims 1 to 7, wherein: - compound Ml is present during the polymerization reaction in a quantity by weight greater than 30%, preferably greater than 35% or 40%, more preferably greater than 45% or 50%, relative to all the compounds present in the reaction medium; or for which: - The polymerization reaction includes: • the preparation of a reaction medium comprising at least one compound Ml in a weight quantity greater than 35%, preferably greater at 50% or 60%, more preferably greater than 65% or 70%, relative to all the reactants in this reaction medium, then • the addition of the initiating compound, possibly separate addition of compound T1 or possibly compound T2, and possibly separate addition of compound M1 and • heating the reaction medium.

9. Method according to one of claims 1 to 8, wherein: - the polymer P is used in an amount ranging from 0.05% to 5% by dry weight, preferably from 0.3% to 2.0% by dry weight, relative to the dry weight of particulate mineral matter M; or - thermal concentration is achieved by heating, preferably at a heating temperature above 80°C or below 95°C; or - Mechanical concentration is achieved by centrifugation or by means of a filter press or a rotary filter.

10. Method according to one of claims 1 to 9, wherein: - the concentration of composition C in mineral matter M is greater than 60% by weight or greater than 65% by weight or greater than 70% by weight or is less than 78% by weight or is less than 75% by weight, preferably ranging from 70% by weight to 78% by weight or from 70% by weight to 75% by weight of composition C; or for which: - the Brookfield viscosity of composition C, measured at 25°C, at 100 rpm 1 hour after preparation, is less than 800 mPa.s, preferably less than 600 mPa.s, more preferably less than 400 mPa.s; or of which - the Brookfield viscosity of composition C measured at 25°C, at 100 rpm before stirring, measured 8 days after preparation, is less than 2,500 mPa.s, preferably less than 2,000 mPa.s, more preferably less than 1,500 mPa.s or 1,000 mPa.s, much more preferably less than 800 mPa.s; or - the quantity of free polymer P not adsorbed onto the mineral matter M, measured by determining the quantity of total organic carbon by weight present in the water of composition C, is less than 45% by weight, preferably less than 35% by weight, relative to the total amount of organic carbon from polymer P introduced during concentration; or - the cationic demand of composition C measured using a "Mütek" device is less in absolute value than -25 peq / g of composition C.

11. Aqueous composition C obtained according to the preparation method according to any one of claims 1 to 10.

12. Aqueous concentration agent D of a composition Cb according to any one of claims 1 to 10 comprising at least one polymer P defined according to any one of claims 1 to 8.

13. Method of preparing an aqueous composition Cm of mineral particles comprising: i. the preparation of an aqueous composition C according to any one of claims 1 to H; ii. the preparation of an aqueous composition Cg comprising a mineral material Q in a concentration from 65 wt% to 78 wt% of composition Cg, and obtained by grinding in water of a mineral material Q in the presence of a grinding aid, preferably a (meth)acrylic polymer R; iii. the mixing under stirring of the aqueous composition C with the aqueous composition Cg.

14. Preparation method according to claim 13, wherein: - the Cm composition comprises 60% to 90% by dry weight of composition C and 10% to 40% by dry weight of composition Cg, relative to the dry weight of composition Cm; or - the concentration of the composition Cm in mineral matter M and Q is greater than 45% by weight or 50% by weight or 70% by weight or is less than 78% by weight or is less than 75% by weight, preferably ranging from 70% by weight to 78% by weight or from 70% by weight to 75% by weight of the composition Cm; or for which: - the Brookfield viscosity of the composition Cm, measured at 25°C, at 100 rpm 1 hour after preparation, is less than 800 mPa.s, preferably less than 600 mPa.s; or whose - the Brookfield viscosity of the composition Cm measured at 25°C, at 100 rpm before stirring, measured 8 days after preparation is less than 2,500 mPa.s, preferably less than 2,000 mPa.s, more preferably less than 2,000 mPa.s or 1,000 mPa.s.

15. Aqueous composition Cm obtained according to the preparation method according to one of claims 13 or 14.

16. Method for controlling the viscosity of a composition Cm according to claim 15 comprising the implementation of at least one polymer P according to any one of claims 1 to 8 or of an aqueous concentration or dispersion agent according to claim 12.

17. Aqueous composition of paper preparation selected from a paper mass filler composition and a paper coating slurry composition comprising: - a composition C according to claim 11 or a composition Cm according to claim 15 and possibly - at least one binding compound, and possibly at least one compound selected from a rheology modifier compound, a water-retaining agent and an optical brightening agent.

18. Paper preparation method comprising the application of a composition C according to claim 11 or a composition Cm according to claim 15.

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