Preparation of an ester copolymer

Abstract

The invention relates to a method for preparing an ester copolymer using an unsaturated carboxylic acid and a cycloacetalketene (cyclic ketene acetal or CKA) by a radical ring-opening polymerization reaction in a neutral or basic aqueous medium. The copolymer according to the invention is biodegradable and can be used as a dispersing agent for particles of a mineral material in an aqueous composition.

Description

Title of the invention: Preparation of an ester copolymer

[0001] The invention relates to a method for preparing an ester copolymer using an unsaturated carboxylic acid and a cycloacetalketene (cyclic ketene acetal or CKA) by a radical ring-opening polymerization reaction in a neutral or basic aqueous medium. The copolymer according to the invention is degradable and can be used as a dispersing agent for particles of a mineral material in an aqueous composition.

[0002] Many technical fields require the use of polymers chosen for their specific properties. In particular, the field of mineral processing, especially the dispersion or grinding of mineral matter, uses dispersing agents or grinding aids. Similarly, the fields of water treatment and detergents use polymers capable of developing interactions with mineral materials.

[0003] The methods of preparing these polymers play an essential role for their effectiveness but also for their implementation conditions, in particular when it comes to limiting or banning the use of polluting or hazardous substances.

[0004] Numerous methods for preparing polymers are known, including methods for preparing ester copolymers. Organic solvents are commonly used in these methods. Therefore, there is a significant need for efficient polymers that can be prepared using improved methods. Control of the molecular mass of the polymers is also a desirable feature.

[0005] In addition to their functional properties, these polymers must be able to degrade once they have been used. Preferably, they must be able to degrade in a controlled manner or in a natural manner.

[0006] State-of-the-art polymers and their preparation methods are not always satisfactory in providing a solution to all or part of the problems encountered.

[0007] Thus, the invention provides a method for preparing a P ester copolymer comprising a radical ring-opening polymerization reaction, in a neutral or basic aqueous medium and at a temperature above 50°C: - of at least one anionic compound (a) comprising at least one polymerizable olefinic unsaturation and at least one carboxylic acid function or one of its salts; - of at least one compound (b) cycloacetalketene (cyclic ketene acetal or CKA), in presence of at least one radical-generating compound.

[0008] Essentially, according to the invention, the radical ring-opening polymerization reaction is carried out in a neutral or basic medium. Preferably, the polymerization reaction is carried out at a pH greater than 6. Advantageously, the pH of the reaction medium is less than 14. More preferably, the polymerization reaction is carried out at a pH ranging from 6 to 12 or from 7 to 9. Also preferably, the pH is controlled by means of a compound selected from sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydroxide, magnesium oxide, magnesium hydroxide, and combinations thereof. The preferred compound is sodium hydroxide.

[0009] According to the invention, the quantities of compounds (a) and (b) used can vary. Preferably, the method according to the invention uses from 70 mol% to 98 mol% of compound (a), preferably from 70 mol% to 95 mol% of compound (a) or from 75 mol% to 95 mol% of compound (a), or more preferably from 80 mol% to 90 mol% of compound (a) or from 85 mol% to 90 mol% of compound (a), relative to the mol% of compounds (a) and (b).

[0010] Also preferably, the method according to the invention employs 2 mol% to 30 mol% of compound (b), preferably 5 mol% to 30 mol% of compound (b) or 5 mol% to 25 mol% of compound (b), more preferably 10 mol% to 20 mol% of compound (b) or 10 mol% to 15 mol% of compound (b), relative to the molar amount of compounds (a) and (b).

[0011] More preferably, the method according to the invention implements: - from 70 mol% to 98 mol% of compound (a) and from 2 mol% to 30 mol% of compound (b), preferably: - from 70 mol% to 95 mol% of compound (a) and from 5 mol% to 30 mol% of compound (b) or - from 75 mol% to 95 mol% of compound (a) and from 5 mol% to 25 mol% of compound (b), more preferably: - from 80 mol% to 90 mol% of compound (a) and from 10 mol% to 20 mol% of compound (b) or - from 85% molar to 90% molar of compound (a) and from 10% molar to 15% molar of compound (b), compared to the molar quantity of compounds (a) and (b).

[0012] Essentially according to the invention, the copolymer P is prepared by means of at least one anionic compound (a) comprising at least one polymerizable olefinic unsaturation and at least one carboxylic acid function or one of its salts. Preferred method for the copolymer P according to the invention, the compound (a) comprises one or two carboxylic acid functions, preferably it comprises a single carboxylic acid function.

[0013] More preferably for the copolymer P according to the invention, the compound (a) is chosen from acrylic acid, methacrylic acid, a salt of acrylic acid, a salt of methacrylic acid and their combinations, more preferably acrylic acid.

[0014] For the preparation of the copolymer P according to the invention, the polymerization reaction may involve at least one other compound selected from: * another anionic compound (c), preferably a compound (c) selected from itaconic acid, maleic acid, maleic anhydride and their combinations; * a compound (d) selected from 2-acrylamido-2-methylpropane sulfonic acid, a salt of 2-acrylamido-2-methylpropane sulfonic acid, 2-(methacryloyloxy)ethanesulfonic acid, a salt of 2-(methacryloyloxy)ethanesulfonic acid, sodium methallyl sulfonate, styrene sulfonate and combinations thereof; * a non-ionic compound (e) comprising at least one polymerizable olefinic unsaturation, preferably at least one polymerizable ethylenic unsaturation, and in particular a polymerizable vinyl function, more preferably a non-ionic compound (e) selected from styrene, vinylcaprolactam, esters of an acid comprising at least one monocarboxylic acid function, in particular an ester of an acid selected from acrylic acid, methacrylic acid, and combinations thereof, for example hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, alkyl acrylate, in particular Ci-CiO-alkyl acrylate, preferably Ci-C4-alkyl acrylate, more preferably methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, isobutyl acrylate, n-butyl acrylate, alkyl methacrylate, in particular methacrylate Ci-Cio-alkyl, preferably Ci-C4-alkyl methacrylate,more preferably methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, aryl acrylate, preferably phenyl acrylate, benzyl acrylate, phenoxyethyl acrylate, aryl methacrylate, preferably phenyl methacrylate, benzyl methacrylate, phenoxyethyl methacrylate; , * a compound (f) of formula I: [Chem I] R1 in which: - R1 and R2, whether identical or different, independently represent H or CH3. - L1 independently represents a grouping chosen from C(0), CH2, CH2-CH2 and o-ch2-ch2-ch2-ch2, - L2 independently represents a group chosen from (CH2-CH2O)X, (CH2 CH(CH3)O)y, (CH(CH3)CH2O)z and their combinations and - x, y and z, identical or different, independently represent 0 or an integer or decimal number between 1 and 150 and the sum x+y+z is between 10 and 150; * a crosslinking compound (g) or a compound (g) comprising at least two olefinic unsaturations; preferably in an amount of less than 5% by weight, also preferably from 0.01 to 4% by weight, in particular from 0.02 to 4% by weight or from 0.02 to 2% by weight, in particular from 0.02 to 1% by weight, of compound (g) relative to the total amount by weight of monomers; * a compound (h) selected from the thionolactones, preferably a cyclic thionolactone, more preferably a cyclic thionolactone comprising at least 5 to 16 ring members, much more preferably comprising at least 5 to 10 ring members, in particular a cyclic thionolactone comprising 5, 6 or 7 ring members, much more preferably a thionolactone selected from dibenzo[c,e]oxepane-5-thione (DOT, CAS number 4445-34-5), γ-thionobutyrolactone (TBL), β-thionovalerolactone (TVL), co-thionopentadecalactone (TPDL), ε-thionocaprolactone (TCL), substituted ε-thionocaprolactone (thCL), 3,3-dimethyl-2,3-dihydro-5H-benzo[e][l,4]dioxepine-5-thione (DBT), thionoiso-chromanone (TIC), 3,6-dimethyl-5-thioxo-l,4-dioxan-2-one (TLD), 5-phenyloxolane-2-thione, 2-benzofuran- l(3H)-thione, l-sulfanylidene-l,3-dihydro-2-benzofuran-5-carbonitrile, 6-nitro-2-benzofuran-1(3H)-thione, 3-ethyl-2-benzofuran-1(3H)-thione, dibenzo[c,e]oxepine-5(7H)-thione and their combinations. ,

[0015] The compound (h) implemented according to the invention can be used as a complement to or as a partial replacement for a fraction of the compound (b).

[0016] Essentially according to the invention, the copolymer P is prepared using at least one compound (b) cycloacetalketene. Preferably, for the copolymer P according to the invention, compound (b) is a cycloacetalcetene compound comprising at least 5 to 16 ring members, in particular a cycloacetalcetene compound comprising at least 5 to 10 ring members, in particular a cycloacetalcetene compound comprising 5, 6, or 7 ring members, preferably a cycloacetalcetene compound selected from 2-methylene-1,3-dioxepane (MDO, CAS No. 497-26-7), 2-methylene-4-phenyl-1,3-dioxolane (MPDL, CAS No. 82613-73-8), 5,6-benzo-2-methylene-1,3-dioxepane (BMDO), 2-methylene-1,3-dioxane (MD, CAS No. 497-26-7), 3-methylene-dioxepane (MDP, CAS No. 82613-73-8). 69814-56-8), 2-methylene-4-phenyl-l,3-dioxane (MPD, CAS number 103612-87-9), 4,7-dimethyl-2-methylene-1,3-dioxepane (DMMDO), 2-isopropyl-4-methylene-l,3-dioxolan (I4MDO), 2-methoxy-4-methylene-l,3-dioxolan (MOMDO) and their combinations.

[0017] During the polymerization reaction, the reaction conditions may vary. Preferably for the copolymer P according to the invention, the polymerization reaction is carried out at a temperature below 120°C, preferably below 100°C.

[0018] Also preferably for the copolymer P according to the invention, the polymerization reaction is carried out in water, alone or in a mixture with at least one polar, protic solvent, preferably an alcohol, more preferably isopropanol. Preferably according to the invention, a mixture of water and organic solvent may respectively comprise equal weight proportions of water and organic solvent or comprise a majority of water, for example 60% by weight, 70% by weight, or 80% by weight of water. Preferably according to the invention, the polymerization reaction is carried out in water and in the absence of organic solvent.

[0019] According to the invention, the P ester copolymer is prepared by a polymerization reaction in the presence of at least one radical-generating compound. The polymerization reaction may be an electrochemical polymerization reaction, an ultrasonic polymerization reaction, or an irradiation polymerization reaction, particularly under UV irradiation.

[0020] Preferably according to the invention, the radical-generating compound is selected from 4,4'-azobis-4-cyanopentanoic acid (ACPA or 4,4'-azobis-(4-cyanovaleric acid or AZDN or 2,2'-azobisisobutyronitrile), hydrogen peroxide, benzoyl peroxide, acetyl peroxide, lauryl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, ammonium persulfate, an alkali metal persulfate (in particular sodium persulfate, potassium persulfate), an azo compound and their respective combinations or associations with an ion selected from Fe11, Fe111, Cu1, Cu11 and their combinations.According to the invention, the Fe11, Fe111, Cu1, Cu11 ions can be implemented by means of at least one compound selected from iron sulfate, hydrated iron sulfate, hemihydrated iron sulfate, heptahydrated iron sulfate, iron carbonate, hydrated iron carbonate, hemihydrated iron carbonate, iron chloride, copper carbonate, hydrated copper carbonate, hemihydrated copper carbonate, copper acetate, copper sulfate, pentahydrated copper sulfate, copper hydroxide, copper halide.

[0021] Also preferably according to the invention, the radical-generating compound is selected from 4,4'-azobis-4-cyanopentanoic acid (ACPA), sodium persulfate, 2,2'-azobis(2-(4,5-dihydroimidazolyl)propane, dihydrochloride of 2,2'-azobis(2-methylpropionamidine), diazovalero-nitrile.

[0022] According to the invention, the radical-generating compound is more preferably chosen from 4,4'-azobis-4-cyanopentanoic acid (ACPA), hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, particularly sodium persulfate.

[0023] According to the invention, the polymerization reaction can be carried out in the presence of a compound comprising phosphorus in oxidation state I, in particular hy-pophosphorous acid (H3PO2) or a derivative of hypophosphorous acid (H3PO2), such as compounds comprising at least one hypophosphite ion (H2PO2), in particular a compound selected from sodium hypophosphite (H2PO2Na), potassium hypophosphite (H2PO2K), calcium hypophosphite ([H2PO2]2Ca).

[0024] According to the invention, the polymerization reaction can be carried out in the presence of a compound comprising phosphorus in oxidation state III, in particular phosphorous acid or a derivative of phosphorous acid.

[0025] According to the invention, the polymerization reaction can also be carried out in the presence of a compound comprising a bisulfite ion, preferably sodium bisulfite or potassium bisulfite,

[0026] According to the invention, the radical-generating compound can also be associated with at least one radical-controlled polymerization transfer agent, in particular a RAFT (reversible addition-fragmentation chain transfer) type transfer agent. The polymerization reaction can be carried out in the presence of a mercaptan compound, in particular a mercaptan compound comprising at least 4 carbon atoms such as butylmercaptan, n-octylmercaptan, n-dodecylmercaptan, tert-dodecylmercaptan, isooctyl 3-mercaptopropionate, or a trithiocarbonate compound. Preferably, according to the invention, the trithiocarbonate compound is a compound of formula II: [chem II] 1 f in which X independently represents H, Na or K and R independently represents a Ci-C5-alkyl group, preferably a Ci-C3-alkyl group, more preferably a methyl group; the preferred compound of formula II is disodium trithiocarbonate dipropionate (DPTTC - CAS No. 86470-33-2) or dipropyl trithiocarbonate (DPTTC, CAS No. 6332-91-8).

[0027] The copolymer P according to the invention is particularly advantageous. Thus, the invention also provides a copolymer P obtained according to the preparation method according to the invention.

[0028] Preferably according to the invention, the molecular mass in weight Mw of the copolymer P, measured by CES, ranges from 800 g / mol to 100,000 g / mol; preferably from 800 g / mol to 80,000 g / mol or from 800 g / mol to 60,000 g / mol; more preferably from 1,000 g / mol to 80,000 g / mol or from 1,000 g / mol to 60,000 g / mol; much more preferably, from 1,000 g / mol to 30,000 g / mol or from 1,000 g / mol to 20,000 g / mol.

[0029] According to the invention, the molecular weight Mw is determined by Size Exclusion Chromatography (SEC), also known as Gel Permeation Chromatography (GPC). This technique employs a Waters brand liquid chromatography instrument equipped with a detector. This detector is a Waters brand refractometric concentration detector. This liquid chromatography apparatus is equipped with a size exclusion column to separate the different molecular weights of the copolymers studied. The elution liquid phase is an aqueous phase adjusted to pH 9.00 using 1 N sodium hydroxide containing 0.05 M NaHCO3, 0.1 M NaNO3, 0.02 M triethanolamine, and 0.03% NaN3.

[0030] According to a first step, the copolymer solution is diluted to 0.9% dry in the solubilizing solvent of the CES, which corresponds to the liquid elution phase of the CES, to which 0.04% dimethylformamide is added, which acts as a flow marker or internal standard. Then, it is filtered at 0.2 µm. 100 pL are then injected into the chromatography apparatus (eluent: an aqueous phase adjusted to pH 9.00 with sodium hydroxide (IN) containing 0.05 M NaHCO3, 0.1 M NaNO3, 0.02 M triethanolamine and 0.03% NaN3).

[0031] The liquid chromatography apparatus includes an isocratic pump (“Waters” 515) with a flow rate set at 0.8 mL / min. The chromatography apparatus also includes a furnace which itself comprises, in series, the following column system: a 6 cm long, 40 mm internal diameter “Guard Column Ultrahydrogel Waters” pre-column and a 30 cm long, 7.8 mm internal diameter “Ultrahydrogel Waters” linear column. The detection system consists of a “RI Waters” 410 refractometer detector. The furnace is heated to 60°C and the refractometer to 45°C.The chromatography apparatus is calibrated using powdered sodium polyacrylate standards of different molecular weights certified by the supplier: Polymer Standards Service or American Polymers Standards Corporation (molecular weight ranging from 900 to 2,250,000 g / mol and polydispersity index ranging from 1.4 to 1.7).

[0032] Also preferably, the copolymer P according to the invention comprises from 70 mol% to 98 mol% of residue of compound (a), preferably from 70 mol% to 95 mol% of residue of compound (a) or from 75 mol% to 95 mol% of residue of compound (a), more preferably 80 mol% to 90 mol% of residue of compound (a) or 85 mol% to 90 mol% of residue of compound (a), compared to the molar amount of residues of compounds (a) and (b).

[0033] Also preferably, the copolymer P according to the invention comprises 2 mol% to 30 mol% of residue of compound (b), preferably 5 mol% to 30 mol% of residue of compound (b) or 5 mol% to 25 mol% of residue of compound (b), more preferably 10 mol% to 20 mol% of residue of compound (b) or 10 mol% to 15 mol% of residue of compound (b), relative to the molar amount of residues of compounds (a) and (b).

[0034] More preferably, the copolymer P according to the invention comprises: - from 70 mol% to 98 mol% of compound residue (a) and from 2 mol% to 30 mol% of compound residue (b), preferably - from 70 mol% to 95 mol% of compound residue (a) and from 5 mol% to 30 mol% of compound residue (b) or - from 75 mol% to 95 mol% of compound residue (a) and from 5 mol% to 25 mol% of compound residue (b), more preferably - from 80 mol% to 90 mol% of compound residue (a) and from 10 mol% to 20 mol% of compound residue (b) or - from 85% molar to 90% molar of compound residue (a) and from 10% molar to 15% molar of compound residue (b), compared to the molar quantity of residues of compounds (a) and (b).

[0035] Preferably according to the invention, the copolymer P is water-soluble. Advantageously, a water-soluble polymer is a polymer capable of forming a solution in water. Generally, the solubility of polymers in water arises from the presence of hydrophilic groups.

[0036] The properties of the copolymer P according to the invention make it particularly useful in many technical fields, in particular in the fields of preparation or use of suspensions of mineral particles, especially aqueous suspensions of mineral particles.

[0037] Thus, the invention also provides a dispersing agent comprising at least one copolymer P according to the invention and at least one solid or liquid support, preferably water, alone or in combination with at least one other substance, for example at least one surfactant compound.

[0038] The use of the copolymer P or the dispersing agent according to the invention makes it possible to provide a method for dispersing a mineral material comprising the introduction of at least one copolymer P according to the invention or at least one dispersing agent according to the invention into a composition, preferably an aqueous composition, comprising particles of a mineral material. Preferably according to the invention, it It is a synthetic or naturally occurring mineral material, preferably selected from alkaline earth metal carbonate, preferably calcium carbonate (natural calcium carbonate or precipitated calcium carbonate), strontium carbonate, magnesium carbonate, barium carbonate and their combinations, dolomite, kaolin, titanium dioxide, talc, lime, calcium sulfate, barium sulfate, tartar and their combinations.

[0039] Preferably, for the dispersion method according to the invention, the copolymer P is degradable, preferably degradable in a controlled manner or naturally, more preferably biodegradable. More preferably according to the invention, the copolymer P is degradable in a basic or acidic medium.

[0040] The method for preparing copolymer P according to the invention comprises the polymerization reaction of the anionic compound (a) with the compound (b) which is selected from among the cycloacetalketens. The resulting copolymer P is degradable. Thus, the invention also provides a method for degrading an ester copolymer P comprising treating the prepared copolymer P in a neutral or basic aqueous medium, at a temperature above 50°C, with at least one basic compound or with at least one acidic compound, by a radical ring-opening polymerization reaction: - of at least one anionic compound (a) comprising at least one polymerizable olefinic unsaturation and at least one carboxylic acid function or one of its salts; - of at least one compound (b) cycloacetalketene (cyclic ketene acetal, CKA), in the presence of at least one radical-generating compound.

[0041] Preferably according to the invention, the method of degrading the copolymer P leads to a degraded polymer Pd. Thus, the invention also provides a method for preparing a polymer Pd by acid degradation or by basic degradation of an ester copolymer P prepared in a neutral or basic aqueous medium, at a temperature above 50°C, by a radical ring-opening polymerization reaction: - of at least one anionic compound (a) comprising at least one polymerizable olefinic unsaturation and at least one carboxylic acid function or one of its salts; - of at least one compound (b) cycloacetalketene (cyclic ketene acetal, CKA), in the presence of at least one radical-generating compound.

[0042] Preferably for the degradation method according to the invention, the degraded polymer, respectively the Pd polymer, has a molecular weight in weight Mw, measured by CES, reduced by 10%, preferably reduced by 25% or reduced by 40%, more preferably reduced by 50% or reduced by 60%, much more preferably reduced by 75% or reduced by 90%, compared to the weight molecular mass Mw of the P copolymer.

[0043] The particular, advantageous or preferred characteristics of the method for preparing copolymer P according to the invention define copolymers P, a dispersing agent, a method for dispersing a mineral material, a method for degrading an ester copolymer P and a method for preparing a polymer Pd which are also particular, advantageous or preferred.

[0044] The following examples illustrate the different aspects of the invention, in particular the preparation and characterization of P ester copolymers according to the invention.

[0045] EXAMPLES

[0046] PI polymer according to the invention

[0047] In a glass IL reactor, 390 g of water, 50.2 g of 50% sodium hydroxide solution in water, 6.4 g of sodium hypophosphite, 5 g of 2-methylene-1,3-dioxepane (MDO), and 45 g of acrylic acid are successively introduced. The reaction mixture is heated to 75°C with stirring. Then, 0.83 g of sodium persulfate in 10 g of water is added. The reaction is continued for 2 hours at 84°C. The mixture is cooled to room temperature. The dry extract is measured at 13.5% and the pH at 7. The resulting PI polymer has a molecular weight Mw of 2850 g / mol and an Ip of 2, as measured by size-exclusion chromatography.

[0048] P2 polymer according to the invention

[0049] In a IL glass reactor, 390 g of water, 50.2 g of 50% sodium hydroxide solution in water, 3.2 g of sodium hypophosphite, 5 g of MDO, and 45 g of acrylic acid are successively introduced. The reaction mixture is heated to 75°C with stirring. Then, 0.83 g of sodium persulfate in 10 g of water is added. The reaction is continued for 2 hours at 84°C. The mixture is cooled to room temperature. The dry extract is measured at 13.5% and the pH at 7. The resulting P2 polymer has a molecular weight Mw of 4950 g / mol and an Ip of 2.5, as measured by size-exclusion chromatography.

[0050] P3 polymer according to the invention

[0051] In a glass IL reactor, 390 g of water, 50.2 g of 50% sodium hydroxide solution in water, 5 g of MDO, and 45 g of acrylic acid are introduced successively. The reaction mixture is heated to 75°C with stirring. Then, 0.83 g of sodium persulfate in 10 g of water is added. The reaction is continued for 2 hours at 84°C. The mixture is cooled to room temperature. The dry extract is measured at 13.5% and the pH at 7. The resulting P3 polymer has a molecular weight Mw of 19,500 g / mol and an Ip of 5.4, as measured by size-exclusion chromatography.

[0052] The degradation of the polymers according to the invention can be evaluated by weighing 20 mg of polymer P to be dissolved in 1 mL of water and then adding propylamine (20 mg) in now under agitation for 24 hours at room temperature and finally by drying the degraded polymer Pd under a hood and then analyzing it by CES to measure its molecular mass Mw and its polydispersity index; the decrease in mass confirming that the polymer P according to the invention is degradable in a controlled manner.

Claims

Claims

1. Method for preparing an ester copolymer P comprising a radical ring-opening polymerization reaction, in a neutral or basic aqueous medium and at a temperature above 50°C: - of at least one anionic compound (a) comprising at least one polymerizable olefinic unsaturation and at least one carboxylic acid function or one of its salts; - of at least one cycloacetalketene (cyclic ketene acetal or CKA) compound (b), in the presence of at least one radical-generating compound.

2. Method according to claim 1 for which the polymerization reaction uses: - from 70 mol% to 98 mol% of compound (a), preferably: from 70 mol% to 95 mol% of compound (a) or from 75 mol% to 95 mol% of compound (a), more preferably: from 80 mol% to 90 mol% of compound (a) or from 85 mol% to 90 mol% of compound (a), or - from 2 mol% to 30 mol% of compound (b), preferably: from 5 mol% to 30 mol% of compound (b) or from 5 mol% to 25 mol% of compound (b), more preferably: from 10 mol% to 20 mol% of compound (b) or from 10 mol% to 15 mol% of compound (b), relative to the molar quantity of compounds (a) and (b).

3. Method of one of claims 1 or 2 for which: - compound (a) comprises one or two carboxylic acid functions, preferably it comprises a single carboxylic acid function, - preferably, compound (a) is chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, more preferably acrylic acid; or for which: - the polymerization reaction also uses at least one other compound chosen from: * another anionic compound (c), preferably a compound (c) chosen from itaconic acid, maleic acid, maleic anhydride and combinations thereof; * a compound (d) chosen from 2-acrylamido-2-methylpropane acid sulfonic acid, a salt of 2-acrylamido-2-methylpropane sulfonic acid, 2-(methacryloyloxy)ethanesulfonic acid, a salt of 2-(methacryloyloxy)ethanesulfonic acid, sodium methallyl sulfonate, styrene sulfonate and combinations thereof;* a non-ionic compound (e) comprising at least one polymerizable olefinic unsaturation, preferably at least one polymerizable ethylenic unsaturation and in particular a polymerizable vinyl function, more preferably a non-ionic compound (e) chosen from styrene, vinylcaprolactam, esters of an acid comprising at least one monocarboxylic acid function, in particular an ester of an acid chosen from acrylic acid, methacrylic acid, and combinations thereof, for example hydroxyethylacrylate, hydroxypropylacrylate, hydroxyethylmethacrylate, hydroxypropylmethacrylate, alkyl acrylate, in particular C1-C10-alkyl acrylate, preferably C1-C4-alkyl acrylate, more preferably methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, isobutyl acrylate, n-butyl acrylate, alkyl methacrylate, in particular C1-C10-alkyl acrylate, preferably C1-C4-alkyl acrylate, more preferably methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, isobutyl acrylate, n-butyl acrylate, alkyl methacrylate, in particular C1-C10-alkyl methacrylate, Ci-Cio-alkyl, preferably C1-C4-alkyl methacrylate,more preferably methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, aryl acrylate, preferably phenylacrylate, benzylacrylate, phenoxyethylacrylate, aryl methacrylate, preferably phenylmethacrylate, benzylmethacrylate, phenoxyethylmethacrylate;, * a compound (f) of formula I: [Chem I] R1 in which: - R1 and R2, identical or different, independently represent H or CH3, - L1 independently represents a group chosen from C(O), CH2, CH2-CH2 and O-CH2-CH2-CH2-CH2, - L2 independently represents a group chosen from (CH2-CH2 O)x, (CH2CH(CH3)O)y, (CH(CH3)CH2O)z and their combinations and - x, y and z, identical or different, independently represent 0 or an integer or decimal number between 1 and 150 and the sum x+y+z is between 10 and 150; * a crosslinking compound (g) or a compound (g) comprising at least two olefinic unsaturations; preferably in an amount of less than 5% by weight, also preferably from 0.01 to 4% by weight, in particular from 0.02 to 4% by weight or from 0.02 to 2% by weight, in particular from 0.02 to 1% by weight, of compound (g) relative to the total amount by weight of monomers; * a compound (h) chosen from thionolactones, preferably a cyclic thionolactone, more preferably a cyclic thionolactone comprising at least 5 to 16 members in the ring, much more preferably a cyclic thionolactone comprising at least 5 to 10 members in the ring, in particular a cyclic thionolactone comprising 5, 6 or 7 members in the ring, much more preferably a thionolactone chosen from dibenzo[c,e]oxepane-5-thione (DOT, CAS number 4445-34-5), y-thionobutyrolactone (TBL), 6-thionovalerolactone (TVL), co-thionopentadecalactone (TPDL), e-thionocaprolactone (TCL), substituted e-thionocaprolactone (thCL), 3,3-dimethyl-2,3-dihydro-5H-benzo[e][l,4]dioxepine-5-thione (DBT), thionoisochromanone (TIC), 3,6-dimethyl-5-thioxo-1,4-dioxan-2-one (TLD), 5-phenyloxolane-2-thione, 2-benzofuran-l(3H)-thione, l-sulfanylidene-l,3-dihydro-2-benzofuran-5-carbonitrile, 6-nitro-2-benzofuran-l(3H)-thione, 3-ethyl-2-benzofuran-l(3H)-thione, dibenzo[c,e]oxepine-5(7H)-thione and their combinations.,

4. Method according to one of claims 1 to 3 for which the compound (b) is a cycloacetalketene compound, preferably a cycloa-ketalketene compound comprising at least 5 to 16 members in the ring, more preferably a cycloacetalketene compound comprising at least 5 to 10 members in the ring, in particular a cycloacetalketene compound comprising 5, 6 or 7 members in the ring, preferably a cycloacetalketene compound chosen from 2-methylene-1,3-dioxepane (MDO, CAS number 497-26-7), 2-methylene-4-phenyl-1,3-dioxolane (MPDL, CAS number 82613-73-8), 5,6-benzo-2-methylene-1,3-dioxepane (BMDO), 2-methylene-1,3-dioxane (MD, CAS number 497-26-7), 3-methylene-dioxepane (MDP, CAS number 69814-56-8), 2-methylene-4-phenyl-1,3-dioxane (MPD, CAS number 103612-87-9), 4,7-dimethyl-2-methylene-1,3-dioxepane (DMMDO),

5.

6.

7. 2-isopropyl-4-methylene-l,3-dioxolan (I4MD0), 2-methoxy-4-methylene-l,3-dioxolan (MOMDO) and combinations thereof. Method according to one of claims 1 to 4 for which the copolymer P is water-soluble or for which: - the polymerization reaction is carried out at a pH above 6, advantageously at a pH below 14, more preferably at a pH ranging from 6 to 12 or from 7 to 9, also preferably, the pH is controlled by means of a compound chosen from sodium hydroxide, potassium hydroxide, ammonia, ammonia, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydroxide, magnesium oxide, magnesium hydroxide and combinations thereof; or - the polymerization reaction is carried out at a temperature below 120°C, preferably below 100°C; or - the polymerization reaction is carried out in water, alone or in a mixture with at least one polar, protic solvent, preferably an alcohol, more preferably isopropanol; or for which: - the radical-generating compound is chosen from 4,4'-azobis-4-cyanopentanoic acid (ACPA), hydrogen peroxide, benzoyl peroxide, acetyl peroxide, lauryl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, ammonium persulfate, an alkali metal persulfate (in particular sodium persulfate, potassium persulfate), an azo compound and their combinations or their respective associations with an ion chosen from Fe11, Fe111, Cu1, Cu11 and their combinations. Copolymer P obtained according to the method defined according to one of claims 1 to 5. Copolymer P according to claim 6 which is water-soluble or whose molecular mass by weight Mw, measured by CES, ranges from 800 g / mol to 100,000 g / mol; preferably from 800 g / mol to 80,000 g / mol or from 800 g / mol to 60,000 g / mol; more preferably from 1,000 g / mol to 80,000 g / mol or from 1,000 g / mol to 60,000 g / mol; even more preferably, from 1,000 g / mol to 30,000 g / mol or from 1,000 g / mol to 20,000 g / mol; or comprising: - from 70 mol% to 98 mol% of residue of compound (a), preferably: from 70 mol% to 95 mol% of residue of compound (a) or from 75 mol% to 95 mol% of residue of compound (a), so as to more preferably: from 80 mol% to 90 mol% of residue of compound (a) or from 85 mol% to 90 mol% of residue of compound (a), or - from 2 mol% to 30 mol% of residue of compound (b), preferably: from 5 mol% to 30 mol% of residue of compound (b) or from 5 mol% to 25 mol% of residue of compound (b), more preferably: from 10 mol% to 20 mol% of residue of compound (b) or from 10 mol% to 15 mol% of residue of compound (b), relative to the molar quantity of residues of compounds (a) and (b).

8. Dispersing agent comprising at least one copolymer P according to one of claims 6 or 7 and at least one solid or liquid support, preferably water, alone or in combination with at least one other substance, for example at least one surfactant compound

9. A method of dispersing a mineral material comprising the introduction of at least one copolymer P according to one of claims 6 or 7 or at least one dispersing agent according to claim 8 into a composition, preferably into an aqueous composition, comprising particles of a mineral material, preferably a synthetic or naturally occurring mineral material, preferably chosen from alkaline earth metal carbonate, preferably calcium carbonate (natural calcium carbonate or precipitated calcium carbonate), strontium carbonate, magnesium carbonate, barium carbonate and combinations thereof, dolomite, kaolin, titanium dioxide, talc, lime, calcium sulfate, barium sulfate, tartar and combinations thereof.

10. Method according to claim 9 for which the copolymer P is degradable, preferably degradable in a controlled manner or in a natural manner, more preferably biodegradable, in particular in a basic medium or in an acidic medium.

11. Method for degrading an ester copolymer P prepared in a neutral or basic aqueous medium, at a temperature above 50°C, by a radical ring-opening polymerization reaction: - of at least one anionic compound (a) comprising at least one polymerizable olefinic unsaturation and at least one carboxylic acid function or one of its salts; - of at least one compound (b) cycloacetalketene (cyclic ketene acetal, CKA), in the presence of at least one radical-generating compound; comprising treating the copolymer P with at least one basic compound or with at least one acidic compound.

12. Method for preparing a Pd polymer by acid degradation or by basic degradation of an ester copolymer P prepared in a neutral or basic aqueous medium, at a temperature above 50°C, by a radical ring-opening polymerization reaction: - of at least one anionic compound (a) comprising at least one polymerizable olefinic unsaturation and at least one carboxylic acid function or one of its salts; - of at least one compound (b) cycloacetalketene (cyclic ketene acetal, CKA), in the presence of at least one radical-generating compound.

13. Method according to one of claims 11 or 12 for which the degraded polymer, respectively the Pd polymer, has a molecular mass by weight Mw, measured by CES, reduced by 10%, preferably reduced by 25% or reduced by 40%, more preferably reduced by 50% or reduced by 60%, much more preferably reduced by 75% or reduced by 90%, relative to the molecular mass by weight Mw of the copolymer P.