Stabilised mineral suspension

Abstract

The invention provides an aqueous suspension of a mineral material, for example calcium carbonate, which is prepared by wet grinding in the presence of an aqueous dispersion of (meth)acrylic polymer neutralised by a combination of at least one monovalent ion and at least one divalent ion, and post-grinding concentration. The particle size distribution and the viscosity and stability of the suspension according to the invention are particularly well controlled. The invention also relates to an agent for facilitating grinding and to the use of said mineral suspension for preparing a mass filler for paper production, for preparing a paper coating slip, or for preparing a coating composition, for example a paint composition.

Description

[0001] STABILIZED MINERAL SUSPENSION

[0002] The invention provides an aqueous suspension of a mineral material, for example calcium carbonate, which is prepared by wet grinding in the presence of an aqueous dispersion of (meth)acrylic polymer neutralized by means of a combination of at least one monovalent ion and at least one divalent ion, followed by concentration after grinding. The particle size distribution and viscosity of the suspension according to the invention are particularly well controlled. The invention also relates to a grinding aid agent 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 materials are known. In particular, methods are known which use grinding aids, in particular 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 controlling the particle size of the particles obtained, in particular so that the resulting suspension has a narrow particle size distribution characterized by a high slope factor. 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 of a particular particle size, a reduced operating time of the grinding plants allows for an improvement in the overall efficiency of the grinding method.

[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, grinding aids should be able to be prepared in the absence of compounds that may be considered environmentally harmful or in the absence of compounds whose use is restricted by regulatory provisions. In particular, the preparation of these agents in the absence of compounds 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 should 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 the coated paper. Improving the uniformity of the particle size distribution should therefore be sought.

[0009] Improving the compatibility of the various compounds used in paper preparation should also be sought. WO2012066308 relates to compositions for preparing filled and coated paper that comprise microfibrillated cellulose and a particulate mineral material. WO2010131016 describes the preparation of an aqueous suspension of microfibrillated cellulose in the presence of a particulate mineral material. WO2016115393 relates to a method for treating a sulfur-containing fluid to form gypsum and magnesium carbonate. WO2014062476 describes a coating composition comprising calcium carbonate particles and kaolin having an aspect ratio of less than 70. CA2403878 describes acrylic copolymers prepared in the presence of a sulfur-containing compound and then modified by reaction with a polyalkylene glycol.Document CA2518622 describes the use of polyacrylic acids with sulfur end groups for the wet grinding of calcium carbonate.

[0010] Thus, although there are methods for wet grinding of mineral matter which 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.

[0011] Thus, the invention provides an aqueous suspension S of mineral particles whose concentration ranges from 65 to 80% by weight and whose slope factor E of the mass distribution of particle sizes [(d30 / d70)xl00], measured by sedimentometry, is greater than 30, which is prepared:

[0012] - by grinding in water at a concentration ranging from 30 to 60% by weight of an aqueous suspension Sd of at least one particulate mineral material M in the presence of an aqueous dispersion D comprising at least one a-sulfonated polymer P with a molecular weight by weight (Mw), measured by CES, of between 4,000 and 20,000 g / mol and o 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 (sulfur IV or S IV ), and o totally or partially neutralized by means of a combination of at least one monovalent ion and at least one divalent ion, then

[0013] - concentration of the ground Sd suspension.

[0014] Sedimentometry is a method of measuring the rate at which solid particles fall in a less dense liquid. Using Stokes' law, the grain size is determined.

[0015] • v: sedimentation rate (m / s)

[0016] • g: acceleration of gravity (m / s 2 )

[0017] • Ay: difference in density between the particles and the suspending liquid (kg / m 3 )

[0018] • p: viscosity of the suspending liquid (Pa.s).

[0019] The particle diameter or its Stokes diameter is then determined according to formula I:

[0020] 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. For the suspensions according to the invention, sedimentometry makes it possible to determine the slope factor E which is representative of the slope of a particle size distribution curve of the suspension in which the particle diameter is represented on the abscissa and the cumulative mass percentage of the particles is represented on the ordinate. Thus, the slope factor is high when the particle size distribution is narrow.

[0021] According to the invention, the slope factor E of the mass distribution of particle sizes [(d30 / d70)xl00] of the suspension S, measured by sedimentometry, is greater than 30. According to the invention, the diameters d30 and d70 respectively define the diameters of the particles for which 30% and 70% of the particles by weight have a diameter smaller than the value of d30 and the value of d70; d30 and d70 are measured using a sedimentometer, for example a Sedi Graph 5100 sedimentometer. When the values ​​d30 and d70 are close, the slope factor E is high, the particle size distribution is narrow.

[0022] Preferably for the suspension S according to the invention, the slope factor E is greater than 35, preferably greater than 40.

[0023] Preferably according to the invention, the suspension S has a Brookfield viscosity at 25°C, at 100 rpm, measured 1 hour after 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 8 days after preparation, 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 8 days after preparation, 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.

[0024] 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, dolomite, kaolin, titanium dioxide, talc, lime, calcium sulfate, barium sulfate. 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.

[0025] 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 in dry matter of 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 less than 75% by weight.

[0026] 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. Preferably according to the invention, the concentration of the suspension Sd is less than 55% by weight. Also preferably according to the invention, the concentration of the suspension Sd is greater than 40% by weight, preferably greater than 45% by weight. More preferably, the concentration of the suspension Sd ranges from 30% to 55% by weight or from 40% to 60% by weight. The concentration of the suspensions S and Sd is measured by weighing a quantity of 100 g of suspension from which the water and the volatile substances at room temperature are separated, for example by heating.

[0027] Preferably according to the invention, the polymer P is used in an amount ranging from 0.05% to 5% by dry weight, preferably from 0.3% to 1.0% by dry weight, relative to the dry weight of particulate mineral matter M.

[0028] According to the invention, the particles of dispersed material M have a median size 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. Also preferably for the suspension S according to the invention, the material M is ground in water in the presence of the aqueous dispersion D. Preferably, the particles of ground material M then have a median size 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. According to the invention, the median size of the particles of matter M is measured by sedimentometry, for example by means of a sedimentometer.

[0029] Essentially according to the invention, the suspension S is prepared in the presence of an aqueous dispersion D which comprises the α-sulfonated polymer P. Preferably according to the invention, the polymer P is chosen from an α-co-disulfonated polymer P1, an α-monosulfonated polymer P2 and combinations thereof. According to the invention, the polymer P is prepared using the monomer A. Preferably, the monomer A is chosen from acrylic acid, an acrylic acid salt and combinations thereof. Advantageously, the monomer A can be combined with at least one other monomer chosen from vinyl acetate, methyl acrylate, ethyl acrylate, hydroxyethylmethacrylate, hydroxyethylacrylate, hydroxypropylmethacrylate, hydroxypropylacrylate, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), maleic acid, maleic anhydride, itaconic acid and combinations thereof.More preferably, monomer A is selected from acrylic acid, an acid salt and combinations thereof, combined with at least one other monomer selected from vinyl acetate, methyl acrylate, ethyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), maleic acid, maleic anhydride, itaconic acid and combinations thereof.

[0030] Essentially according to the invention, the polymer P is prepared in the presence of at least one compound T comprising sulfur IV. Preferably, the 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.

[0031] 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.

[0032] According to the invention, polymer A 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. Advantageously, polymer P may be partially non-neutralized, preferably non-neutralized from 2 mol% to 35 mol%, more preferably from 5 mol% to 30 mol%, relative to the number of carboxylic groups. Essentially according to the invention, the polymer P is 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 P may be partially neutralized at a rate of 70 to 97 mol%, preferably at a rate of 90 to 95 mol%. Preferably, the polymer P is partially neutralized.

[0033] According to the invention, the total or partial neutralization of the polymer P 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, 60 / 40 or 50 / 50.

[0034] 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 and ammonium derivatives. 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 P can be neutralized by means of at least one compound chosen from CaO, Ca(OH)2, MgO, Mg(OH)2 and their combinations.

[0035] Preferably, the polymer P can be totally or partially neutralized by means of a combination of Na + and of Ca 2+ .

[0036] Preferably, the polymer P 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 9,500 g / mol or less than 8,000 g / mol. The polymer P 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 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 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 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.

[0037] 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.

[0038] According to the invention, the molecular weight or mass of the polymer P is determined by Size Exclusion Chromatography (SEC). A test sample 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 line consists of a Waters 510 isocratic pump with a flow rate set at 0.8 mL / min, a Waters 717+ autosampler, an oven containing a 6 cm long, 40 mm inner diameter Waters Guard Column Ultrahydrogel precolumn, followed by a 30 cm long, 7.8 mm inner diameter Waters Ultrahydrogel linear column.Detection is carried out using a differential refractometer type RI Waters 410. The oven is heated to a temperature of 60°C and the refractometer is heated to a 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 linear and takes into account the correction obtained using the flow marker: dimethylformamide (DMF). The acquisition and processing of the chromatogram are carried out using the PSS WinGPC Scientific v 4.02 software. The chromatogram obtained is integrated in the zone corresponding to molecular weights greater than 250 g / mol.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 of the monomers used.

[0039] According to the invention, the suspension S comprises at least one compound B chosen from a sulfocarboxylic acid, a sulfocarboxylic acid salt and combinations thereof. According to the invention, the compound B is chosen from sulfoarylcarboxylic acids and sulfoalkylcarboxylic acids, in particular 3-sulfopropionic acid, 3-sulfo-2-methylpropionic acid, sulfosuccinic acid, their salts and combinations thereof. The salts of the compound B are generally the sodium salt, the potassium salt, the lithium salt, the calcium salt, the magnesium salt or the ammonium salt.

[0040] According to the invention, the molar quantity of compound B present in the suspension S is generally less than 25% relative to the molar quantity of sulfur IV. Preferably, the molar quantity of compound B is less than 20% or more preferably less than 15% or 12% relative to the molar quantity of sulfur IV. Generally according to the invention, the molar quantity of compound B present in the suspension S is greater than 0.2% relative to the molar quantity of sulfur IV. 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%.

[0041] 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.

[0042] The suspension S according to the invention is prepared by grinding the suspension Sd and then 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 95°C. Preferably according to the invention, the concentration step is carried out in the presence of a dispersing agent which is known as such. The dispersing agent according to the invention may comprise a polymer chosen from (meth)acrylic homopolymers or (meth)acrylic copolymers. It may be totally or partially neutralized, for example by means of Na + , Li + , That 2+ or Mg 2+. The molecular mass Mw, measured by CES, of the polymer of the dispersing agent is generally between 2,000 g / mol and 20,000 g / mol, preferably between 5,000 g / mol and 12,000 g / mol. The dispersing agent may also comprise an acid, for example phosphoric acid.

[0043] The invention also relates to the preparation of suspension S.Thus, the invention provides a method for preparing an aqueous suspension S comprising the grinding in water of at least one mineral material M in the presence of an aqueous dispersion D comprising: a) 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 solely by means of a combination of at least one monovalent ion and at least one divalent ion, b) at least one compound B chosen from a sulfocarboxylic acid, a sulfocarboxylic acid salt and combinations thereof, present in a molar amount of less than 25% relative to the molar amount of sulfur IV.The preparation of the suspension S according to the invention uses the aqueous dispersion D of a-sulfonated polymer P as a grinding aid agent for the mineral material M. The invention also relates to this agent.Thus, the invention provides a grinding aid agent comprising an aqueous dispersion D comprising: a) 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 solely by means of a combination of at least one monovalent ion and at least one divalent ion, b) at least one compound B chosen from a sulfocarboxylic acid, a sulfocarboxylic acid salt and combinations thereof, present in a molar amount of less than 25% relative to the molar amount of sulfur IV.

[0044] This grinding aid agent makes it possible to particularly effectively improve the grinding of the mineral material M. Thus, the invention also provides a method for improving the efficiency of the grinding in water of at least one mineral material M comprising the use, during the grinding, of an aqueous dispersion D comprising 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 solely by means of a combination of at least one monovalent ion and at least one divalent ion, having a reduced level of compound B chosen from a sulfocarboxylic acid,a sulfocarboxylic acid salt and combinations thereof, preferably comprising compound B in a molar amount of less than 25% relative to the molar amount of sulfur IV.,

[0045] The aqueous suspension S obtained by 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 color composition comprising the preparation of an aqueous suspension S of mineral particles prepared by grinding in water at least one mineral material M in the presence of an aqueous dispersion D comprising: a) 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 solely by means of a combination of at least one monovalent ion and at least one divalent ion, b) at least one compound B chosen from a sulfocarboxylic acid, a sulfocarboxylic acid salt and combinations thereof, present in a molar quantity of less than 25% relative to the molar quantity of sulfur IV.,

[0046] 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.

[0047] 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:

[0048] • the preparation of an aqueous suspension S of mineral particles prepared by grinding in water at least one mineral material M in the presence of an aqueous dispersion D comprising: a) 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 a combination of at least one monovalent ion and at least one divalent ion, b) at least one compound B chosen from a sulfocarboxylic acid, a sulfocarboxylic acid salt and combinations thereof, present in a molar quantity of less than 25% relative to the molar quantity of sulfur IV,

[0049] • mixing the suspension S with at least one binder compound, optionally with at least one compound chosen from a rheology modifying compound and an organic or mineral pigment.

[0050] The coating composition according to the invention comprises:

[0051] • an aqueous suspension S of mineral particles prepared by grinding in water at least one mineral material M in the presence of an aqueous dispersion D comprising: a) 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 a combination of at least one monovalent ion and at least one divalent ion, b) at least one compound B chosen from a sulfocarboxylic acid, a sulfocarboxylic acid salt and combinations thereof, present in a molar quantity of less than 25% relative to the molar quantity of sulfur IV,

[0052] • at least one binding compound, optionally with at least one compound chosen from a rheology modifying compound and an organic or mineral pigment.

[0053] The invention also provides a method of preparing a coating comprising applying to a substrate a coating composition according to the invention.

[0054] The invention also provides a method for controlling, preferably improving or increasing the slope factor E of the mass distribution of particle sizes [(d30 / d70)xl00] measured by sedimentometry, of an aqueous suspension S of mineral particles whose particle concentration ranges from 65 to 80% by weight, comprising:

[0055] - grinding in water at a concentration ranging from 30 to 60% by weight of an aqueous suspension Sd of at least one particulate mineral material M in the presence of an aqueous dispersion D comprising at least one a-sulfonated polymer P with a molecular weight by weight (Mw), measured by CES, of between 4,000 and 20,000 g / mol and o 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 (sulfur IV or S IV ), and o totally or partially neutralized by means of a combination of at least one monovalent ion and at least one divalent ion, then

[0056] - the concentration of the ground Sd suspension.

[0057] 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 grinding agents which are also particular, advantageous or preferred.

[0058] The following examples illustrate the various aspects of the invention.

[0059] Preparation and characterization of the PI polymer according to the invention:

[0060] In a 1 liter glass reactor equipped with stirring, a thermometer and a cooling system, a charge comprising 0.006 g of iron sulfate heptahydrate and 380 g of water is prepared at room temperature. Then, 3 charges are prepared to be introduced separately and in parallel over three hours. 623.5 g of acrylic acid are introduced into a first beaker, 3.74 g of sodium persulfate and 46.6 g of water into a second beaker and 90.43 g of a 40% by mass aqueous solution of sodium bisulfite into a third beaker. After three hours of addition at 73°C, a clear dispersion of PI polymer is obtained. This polymer is then partially neutralized by adding milk of lime and sodium hydroxide (pH = 5.1) (45Na, 30Ca). The dry matter concentration of the PI polymer dispersion is 39.6%. The PI polymer has a Mw of 6600 g / mol and a PI of 2.4.

[0061] Compound B and the amount of compound B (molar % relative to the molar amount of sulfur IV of compound T used) included in the polymer dispersion are determined by dosage of sulfate ions and by 'H NMR and NMR analysis. 13 C of the sulfonated groups of polymer P and compound B.

[0062] Sulfate ion levels in polymer dispersions are determined by ion chromatography. A sample of the polymer dispersion of approximately 80 mg is placed in a 15 mL flask. 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 consists 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 standard solutions. 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. Chromatogram acquisition and processing are carried out using Chromeleon 7.2.10 software.

[0063] H NMR and NMR analyses 13 C were 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.

[0064] The polymer dispersion D PI according to the invention comprises 3-sulfopropionic acid as compound B in an amount of 8 mol% relative to the molar amount of sodium bisulfite.

[0065] Preparation and characterization of aqueous suspensions S according to the invention:

[0066] 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 PL polymer. Stirring is maintained for 20 minutes.

[0067] 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 Sdl suspension to be ground is 50% ± 1%. After 75 min of grinding, the desired particle size is reached (75% ± 1% by weight of particles with an equivalent spherical diameter < 1 μm). The particle size characteristics are determined using a SediGraph III 5120 sedimentometer (Micromeritics, USA).

[0068] 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.

[0069] The slope factor E of the mass distribution of particle sizes [(d30 / d70)xl00] is measured, which is equal to 43.

[0070] This 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 a known dispersing agent comprising phosphoric acid and a sodium polyacrylate, the molecular mass Mw of which measured by CES is 10,000 g / mol.

[0071] The suspension S 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 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 8 days of storage of the suspension S in a climatic chamber at 25°C. The viscosity of this suspension S noted VB8 (in mPa.s) is measured at 25°C and before stirring at 100 rpm using the Brookfield DV3T rheometer equipped with a module 5.

[0072] The suspension S is stirred using a Rayneri type mechanical motor for 1 min at 2,000 rpm before measuring its Brookfield viscosity at 100 rpm noted VB8a (in mPa.s). The results obtained are presented in Table 1.

[0073] Table 1

[0074] The use of a PI polymer according to the invention comprising a controlled quantity of compound B makes it possible to effectively control the particle size of the suspension, its slope factor as well as its viscosity and stability.

Claims

DEMANDS 1. Aqueous suspension S of mineral particles whose concentration ranges from 65 to 80% by weight and whose slope factor E of the mass particle size distribution [(d30 / d70)xl00], measured by sedimentation, is greater than 30, which is prepared: - by grinding in water at a concentration of 30 to 60 wt% of an aqueous suspension Sd of at least one particulate mineral material M in the presence of an aqueous dispersion D comprising at least one α-sulfonated polymer P of weight molecular mass (Mw), measured by CES, between 4,000 and 20,000 g / mol, prepared in water and in the absence of phosphorus compounds, by a polymerization reaction of at least one monomer A selected from acrylic acid, methacrylic acid, a salt of acrylic acid, a salt of methacrylic acid and their combinations, in the presence of at least one initiating compound and at least one sulfur compound T comprising sulfur in oxidation state IV (sulfur IV or S IV ), and o totally or partially neutralized by means of a combination of at least one monovalent ion and at least one divalent ion, then - concentration of the crushed Sd suspension.

2. Suspension S according to claim 1 having a slope factor E greater than 35, preferably greater than 40.

3. Suspension S according to claim 1 or 2, of which: - the Brookfield viscosity at 25°C, at 100 rpm, measured 1 hour after preparation, is less than 1000 mPa.s, preferably less than 800 mPa.s, or of which - the Brookfield viscosity at 25°C, at 100 rpm and after stirring, measured 8 days after preparation, 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 8 days after preparation 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.

4. Suspension S according to any one of claims 1 to 3, wherein: • only one material M or two or three materials M are implemented; or for which • the 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, calcium sulfate, barium sulfate; or of which • the concentration of suspension S is greater than 70% by weight or less than 78% by weight or less than 75% by weight, preferably with a concentration ranging from 70% by weight to 78% by weight or from 70% by weight to 75% by weight; or which • Polymer P is used in an amount ranging from 0.05% to 5% by dry weight, preferably from 0.3% to 1.0% by dry weight, relative to the dry weight of particulate mineral matter M.

5. Suspension S according to any one of claims 1 to 4, wherein: • the particles of ground material M have a median size, measured by sedimentation, 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 40% by weight, preferably greater than 45% by weight; or for which • the concentration of the suspension Sd is less than 55% by weight, preferably the concentration of the suspension Sd is from 30% to 55% by weight or from 40% to 60% by weight.

6. Suspension S according to any one of claims 1 to 5 wherein the polymer P is selected from an α-co-disulfonated PI polymer, an α-monosulfonated P2 polymer and combinations thereof.

7. Suspension S according to any one of claims 1 to 6, wherein: • Monomer A is chosen from acrylic acid, a salt of acrylic acid, and combinations thereof; preferably monomer A is acrylic acid, or • Monomer A is combined with at least one other monomer selected from vinyl acetate, ethyl acrylate, methyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, 2- acid acrylamido-2-methylpropane sulfonic acid (AMPS), maleic acid, maleic anhydride, itaconic acid, their salts and combinations, or • Monomer A is selected from acrylic acid, an acid salt and their combinations, combined with at least one other monomer selected from 2-acrylamido-2-methylpropanesulfonic acid (AMPS), maleic acid, maleic anhydride, itaconic acid, their salts and their combinations, 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 their combinations, 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 selected from a peroxide (e.g. hydrogen peroxide, zer-butyl hydroperoxide), a persulfate (e.g. sodium persulfate, ammonium persulfate, potassium persulfate), their combinations and their associations with a metal salt, preferably a metal salt selected from an iron salt (e.g. Fe II or Fe III), a copper salt (e.g. Cu I or Cu II) and their combinations, or • the polymer P is partially non-neutralized, preferably non-neutralized from 2 mol% to 35 mol%, more preferably from 5 mol% to 30 mol%, with respect to the number of carboxylic groups, or the polymer P is totally neutralized, or • The polymer P is totally or partially neutralized by means of a combination of a monovalent ion chosen from K + , N / A + , Li + NF + and their combinations and a divalent ion chosen from Mg 2+ , That 2+ and their combinations, preferably totally or partially neutralized by means of a combination of Na + and Ca 2+ , more preferably partially neutralized by means of a combination of Na + and Ca 2+ , Or • the polymer P has a weight-average molecular mass Mw, measured by CES, of less than 15,000 g / mol, preferably 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 • 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 1.9 to 2.

9.

8. Suspension S according to any one of claims 1 to 7, wherein: • 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 of the monomers used.

9. Suspension S according to any one of claims 1 to 8 wherein the dispersion D also comprises a compound B selected from a sulfocarboxylic acid, a salt of a sulfocarboxylic acid and combinations thereof, present in a molar quantity less than 25% relative to the molar quantity of sulfur IV, preferably a compound B selected from sulfoarylcarboxylic acids and sulfoalkylcarboxylic acids, more preferably a compound B selected from 3-sulfopropionic acid, 3-sulfo-2-methylpropionic acid, sulfosuccinic acid, their salts and combinations thereof.

10. Suspension S according to claim 9, wherein: • 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 in the suspension Sd is greater than 0.2%, in particular greater than 2% or 5%, relative to the molar quantity of sulfur IV.

11. Method for preparing an aqueous suspension S according to any one of claims 1 to 10 comprising: - the grinding in water at a concentration of 30 to 60 wt% of an aqueous suspension Sd of at least one particulate mineral material M in the presence of an aqueous dispersion D comprising at least one α-sulfonated polymer P of weight molecular mass (Mw) measured by CES of between 4,000 and 20,000 g / mol, prepared in water and in the absence of phosphorus compounds, by a polymerization reaction of at least one monomer A selected from acrylic acid, methacrylic acid, a salt of acrylic acid, a salt of methacrylic acid and their combinations, in the presence of at least one initiating compound and at least one sulfur compound T comprising sulfur in oxidation state IV (sulfur IV or S IV ), and o totally or partially neutralized by means of a combination of at least one monovalent ion and at least one divalent ion, then - the concentration of the crushed Sd suspension at a particle concentration ranging from 65 to 80% by weight and a slope factor E of the mass distribution of particle sizes [(d30 / d70)xl00], measured by sedimentometry, greater than 30.

12. A grinding agent comprising an aqueous dispersion D comprising at least one α-sulfonated polymer P of weight molecular mass (Mw) measured by CES of between 4,000 and 20,000 g / mol - prepared in water and in the absence of phosphorus compounds, by a polymerization reaction of at least one monomer A selected from acrylic acid, methacrylic acid, a salt of acrylic acid, a salt of methacrylic acid and their combinations, in the presence of at least one initiating compound and at least one sulfur compound T comprising sulfur in oxidation state IV (sulfur IV or S IV ), And - totally or partially neutralized by means of a combination of at least one monovalent ion and at least one divalent ion.

13. Method for preparing a paper mass filler composition or a paper coating sauce composition comprising: • the preparation of an aqueous suspension S of mineral particles whose particle concentration ranges from 65 to 80% by weight and whose slope factor E of the mass particle size distribution [(d30 / d70)xl00], measured by sedimentation, is greater than 30, which is prepared - by grinding in water at a concentration ranging from 30 to 60% by weight of an aqueous suspension Sd of at least one particulate mineral substance M in the presence of an aqueous dispersion D comprising at least one α-sulfonated polymer P with a weight molecular mass (Mw), measured by CES, between 4,000 and 20,000 g / mol, prepared in water and in the absence of phosphorus compounds, by a polymerization reaction of at least one monomer A selected from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt, and their combinations, in the presence of at least one initiating compound and at least one sulfur compound T comprising sulfur in oxidation state IV (sulfur IV or S IV ), and o totally or partially neutralized by means of a combination of at least one monovalent ion and at least one divalent ion, then - concentration of the crushed Sd suspension • the mixing of the aqueous suspension S with at least one binding compound, possibly with at least one compound chosen from among a rheology modifier compound, a water retaining agent, an optical brightening agent and an organic or mineral pigment.

14. Paper preparation method comprising the use of a suspension S according to any one of claims 1 to 10.

15. Method for preparing a coating composition comprising: • the preparation of an aqueous suspension S of mineral particles whose particle concentration ranges from 65 to 80% by weight and whose slope factor E of the mass particle size distribution [(d30 / d70)xl00], measured by sedimentation, is greater than 30, which is prepared - by grinding in water at a concentration of 30 to 60 wt% of an aqueous suspension Sd of at least one particulate mineral material M in the presence of an aqueous dispersion D comprising at least one α-sulfonated polymer P of weight molecular mass (Mw) measured by CES between 4,000 and 20,000 g / mol, prepared in water and in the absence of phosphorus compounds, by a polymerization reaction of at least one monomer A selected from acrylic acid, methacrylic acid, a salt of acrylic acid, a salt of methacrylic acid and their combinations, in the presence of at least one initiating compound and at least one sulfur compound T comprising sulfur in oxidation state IV (sulfur IV or S IV ), and o totally or partially neutralized by means of a combination of at least one monovalent ion and at least one divalent ion, then - concentration of the crushed Sd suspension, then • the mixing of the aqueous suspension S with at least one binding compound, possibly with at least one compound chosen from a rheology modifying compound and an organic or mineral pigment.

16. Coating composition comprising: • an aqueous suspension S of mineral particles with a particle concentration of 65 to 80% by weight and a slope factor E of the mass particle size distribution [(d30 / d70)xl00] measured by sedimentation analysis greater than 30, which is prepared - by grinding in water at a concentration of 30 to 60 wt% of an aqueous suspension Sd of at least one particulate mineral material M in the presence of an aqueous dispersion D comprising at least one α-sulfonated polymer P of weight molecular mass (Mw) measured by CES between 4,000 and 20,000 g / mol, prepared in water and in the absence of phosphorus compounds, by a polymerization reaction of at least one monomer A selected from acrylic acid, methacrylic acid, a salt of acrylic acid, a salt of methacrylic acid and their combinations, in the presence of at least one initiating compound and at least one sulfur compound T comprising sulfur in oxidation state IV (sulfur IV or S IV ), and o totally or partially neutralized by means of a combination of at least one monovalent ion and at least one divalent ion, then - concentration of the crushed Sd suspension, and • at least one binding compound, possibly at least one compound chosen from a rheology modifying compound and an organic or mineral pigment.

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

18. Method for controlling, preferably improving or increasing, the slope factor E of the mass particle size distribution [(d30 / d70)xl00], measured by sedimentation analysis, of an aqueous suspension S of mineral particles having a particle concentration of 65 to 80% by weight, comprising: - grinding in water at a concentration ranging from 30 to 60% by weight of an aqueous suspension Sd of at least one particulate mineral substance M in the presence of an aqueous dispersion D comprising at least one α-sulfonated polymer P of weight molecular mass (Mw) measured by CES between 4,000 and 20,000 g / mol, prepared in water and in the absence of phosphorus compounds, by a polymerization reaction of at least one monomer A selected from acrylic acid, methacrylic acid, a salt of acrylic acid, a salt of methacrylic acid and their combinations, in the presence of at least one initiating compound and at least one sulfur compound T comprising sulfur in oxidation state IV (sulfur IV or S IV ), and o totally or partially neutralized by means of a combination of at least one monovalent ion and at least one divalent ion, then - the concentration of the ground Sd suspension.

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