Process of manufacturing a sheet of paper

Abstract

The present invention relates to a method for manufacturing a sheet of paper or cardboard comprising adding a mixture M and an amphoteric water-soluble polymer PA to a fibrous suspension.

Description

Title of the invention: Method for manufacturing a sheet of paper Technical field of the invention

[0001] The present invention relates to a method for manufacturing a sheet of paper or cardboard comprising the addition of a mixture M and an amphoteric water-soluble polymer to a fibrous suspension. Prior art

[0002] The paper industry is constantly seeking to improve its paper, cardboard or similar manufacturing processes, particularly with regard to cost reduction, yield, productivity or even the properties of the final product.

[0003] This is particularly the case for the packaging industry which is looking for paper, cardboard or similar materials with better dry strength performance in order, in particular, to meet current ecological challenges to replace plastic packaging.

[0004] The dry strength of paper is by definition the strength of the sheet, cardboard or similar in the dry state. Mechanical strength values ​​traditionally provide a measure of dry strength. These include burst strength, tensile strength, compression strength, delamination strength, etc.

[0005] It is well known to use water-soluble cationic polymers to improve the strength characteristics of paper. By their nature, these polymers can attach directly to the anionic cellulose, thereby improving the dry strength of the sheet.

[0006] The most commonly used cationic polymers are compounds of the cationic starch type, polyamide epichlorohydrin (PAE), polyamide amine epichlorohydrin (PAAE), cationic polyacrylamide optionally glyoxalated, polyvinylamine, polyethyleneimine (PEI), polyamine epichlorohydrin resins (PA).

[0007] It is also known to use a combination of cationic and anionic polymers, as in document FR 2880901 Bl, to improve the dry strength performance of the paper sheet.

[0008] The Applicant has discovered, surprisingly, that the combination between (1) a mixture comprising an aluminum salt and a water-soluble aldehyde polymer (2) in a precise ratio, and (3) an amphoteric water-soluble polymer obtained according to a particular process, added (4) in sequence to a fibrous cellulose suspension made it possible to improve the physical properties of the paper or cardboard, regardless of the source of the cellulose fibers used.

[0009] The method according to the invention is part of a principle of environmental awareness environmental and the impact of industries and humans on the planet. The synergistic effect of the combination resulting from the invention makes it possible to reduce the quantity of polymer required to obtain good mechanical performance of the final product, in particular dry strength, implying a reduction in the release of greenhouse gases such as carbon dioxide associated with the manufacture and use of synthetic polymers. Statement of the invention

[0010] The present invention relates to a method for manufacturing a sheet of paper (or cardboard) comprising the addition, in sequence, to a fibrous suspension of at least: 1) a mixture M comprising at least: (a) an aluminum salt; (b) a water-soluble cationic aldehyde polymer; the aluminum salt and the cationic aldehyde water-soluble polymer having a weight ratio of between 60:40 and 20:80; 2) an amphoteric water-soluble polymer PA comprising at least: a) a cationic hydrophilic monomer Apha; b) an anionic hydrophilic monomer BPHA; c) a hydrophilic non-ionic CPHA monomer; (d) a structuring system comprising at least: (i) a compound I, different from the anionic hydrophilic monomer BPHA, chosen from: allylsulfonic acid, methallylsulfonic acid, allyl disulfonic acid, methallyl disulfonic acid, their salts and their mixtures; (ii) a compound II of formula (2):

[0011] [Chem.l] Formula (2)

[0012] R1 and R2 being, independently of one another, a hydrogen atom, a methyl group, an ethyl group, an isopropyl group or a CH2-OH group; Ri and R2 not both being a hydrogen atom (Ri^H when R2=H; R2^H when Ri=H); the amphoteric water-soluble polymer PA being obtained according to the following steps: A) formation of a solution (SI) comprising at least a first fraction (Fl) comprising (1) at least one monomer selected from the monomers Apha, BPHA and CPHA and / or (2) at least one compound selected from compounds I and II; B) polymerization 1 (PO1) of the fraction Fl to form a solution of a first prepolymer PP1; C) adding, to the solution comprising PP1, a second fraction (F2) comprising (1) at least one monomer chosen from the monomers APHa, BPHa and CPHa and / or (2) at least one compound chosen from compounds I and II; D) polymerization 2 (PO2) of fraction F2 on PP1 to form a solution of a second prepolymer PP2; E) adding, to the solution comprising PP2, a third fraction (F3) comprising (1) at least one monomer chosen from the monomers Apha, BPHA and CPHa and / or (2) at least one compound chosen from compounds I and II; F) polymerization 3 (PO3) of the fraction F3 on PP2 to form a solution comprising the amphoteric water-soluble polymer PA; at least one of the fractions Fl, F2 or F3 comprising at least one Apha monomer, at least one of the fractions Fl, F2 or F3 comprising at least one BPHA monomer, at least one of the fractions Fl, F2 or F3 comprising at least one CPHa monomer, at least one of the fractions Fl, F2 or F3 comprising at least one compound I and at least one of the fractions Fl, F2 or F3 comprising at least one compound II. Description of the invention

[0013] By “polymer” is meant a copolymer prepared from at least two different monomers; it may optionally comprise more than two different monomers.

[0014] The term “paper” also includes cardboard.

[0015] By “hydrophilic monomer” is meant a monomer which has an octanol / water partition coefficient, Kow, less than or equal to 1, in which the partition coefficient Kow is determined at 25°C in an octanol / water mixture having a volume ratio of 1 / 1, at a pH between 6 and 8.

[0016] By "hydrophobic monomer" is meant a monomer which has an octanol / water partition coefficient, Kow, greater than 1, in which the partition coefficient Kow is determined at 25°C in an octanol / water mixture having a volume ratio of 1 / 1, at a pH between 6 and 8.

[0017] The octanol / water partition coefficient, Kow, represents the ratio of concentrations (g / L) of a monomer between the octanol phase and the aqueous phase. It is defined as follows:

[0018] [Math.l] I monomer] K_ L GW — ri % monomer l J water

[0019] By "water-soluble polymer" is meant a polymer which gives a solution aqueous without insoluble particles when dissolved under stirring at 25 °C and with a concentration of 10 g.l1 in deionized water.

[0020] Throughout the description, the Brookfield viscosities are measured with a Brookfield viscometer, at 25°C in aqueous solution, with an LV module.

[0021] In the present description, it is considered that a person skilled in the art is able to determine the modulus and speed of the Brookfield viscometer adapted according to the viscosity range to be measured. This type of measurement is in fact part of the general knowledge of a person skilled in the art.

[0022] According to the invention, “X and / or Y” means “X”, or “Y”, or “X and Y”.

[0023] Also part of the invention are all possible combinations between the various embodiments disclosed, whether preferred or exemplary. Furthermore, when ranges of values ​​are indicated, the limits are part of these ranges. The disclosure also includes all combinations between the limits of these ranges of values. For example, the ranges of values ​​"1-20, preferably 5-15", imply the disclosure of the ranges "1-5", "1-15", "5-20" and "15-20" and the values ​​1, 5, 15 and 20.

[0024] Method of manufacturing a sheet of paper or cardboard

[0025] The present invention relates to a method of manufacturing a sheet of paper or cardboard comprising the addition, in sequence, to a fibrous suspension of at least: 1) a mixture M comprising at least: (a) an aluminum salt; (b) a water-soluble cationic aldehyde polymer; the aluminum salt and the cationic water-soluble polymer having a weight ratio of between 60:40 and 20:80; 2) an amphoteric water-soluble polymer PA comprising at least: a) a cationic hydrophilic monomer Apha; b) an anionic hydrophilic monomer BPHA; c) a non-ionic hydrophilic monomer CPHA; (d) a structuring system comprising at least: (i) a compound I, different from the anionic hydrophilic monomer(s) BPHA, chosen from: allylsulfonic acid, methallylsulfonic acid, allyl disulfonic acid, methallyl disulfonic acid, their salts and their mixtures; (ii) a compound II of formula (2):

[0026] [Chem.2] Formula (2)

[0027] R1 and R2 being, independently of one another, a hydrogen atom, a methyl group, an ethyl group, an isopropyl group or a CH2-OH group; Ri and R2 not both being a hydrogen atom (Ri^H when R2=H; R24H when Ri=H); the amphoteric water-soluble polymer PA being obtained according to the following steps: A) formation of a solution (SI) comprising at least a first fraction (Fl) comprising (1) at least one monomer chosen from the monomers APHa, BPHa and CPHa and / or (2) at least one compound chosen from compounds I and II; B) polymerization 1 (PO1) of the fraction Fl to form a solution of a first prepolymer PP1; C) adding, to the solution comprising PP1, a second fraction (F2) comprising (1) at least one monomer chosen from the monomers Apha, BPHA and CPHa and / or (2) at least one compound chosen from compounds I and II; D) polymerization 2 (PO2) of fraction F2 on PP1 to form a solution of a second prepolymer PP2; E) adding, to the solution comprising PP2, a third fraction (F3) comprising (1) at least one monomer chosen from the monomers Apha, BPHA and CPHa and / or (2) at least one compound chosen from compounds I and II; F) polymerization 3 (PO3) of the fraction F3 on PP2 to form a solution comprising the amphoteric water-soluble polymer PA; and at least one of the fractions F1, F2 or F3 comprising at least one Apha monomer, at least one of the fractions F1, F2 or F3 comprising at least one BPHA monomer, at least one of the fractions F1, F2 or F3 comprising at least one CPHa monomer, at least one of the fractions F1, F2 or F3 comprising at least one compound I, and at least one of the fractions F1, F2 or F3 comprising at least one compound II.

[0028] The different stages of the process for manufacturing paper, cardboard or the like are known and conform to the techniques requiring the knowledge of those skilled in the art; the latter, if necessary, may refer to the document: Handbook for Pulp & Paper Technologists, 4th Edition, GASmook.

[0029] The fibrous suspension is typically a suspension of cellulose fibers in water.

[0030] In particular, it may be the thick stock or the thin stock in a papermaking process.

[0031] According to the invention, the mixture M and the amphoteric water-soluble polymer PA are added in the papermaking process, before forming the sheet of paper, cardboard or the like. Thus, bringing the cellulosic material into contact with the mixture M and the amphoteric water-soluble polymer PA can be carried out in different ways and in particular according to typical methods known to those skilled in the art.

[0032] The addition of the mixture M and the amphoteric water-soluble polymer PA is done in sequence, that is to say that the mixture M is added first, followed by the addition of the amphoteric water-soluble polymer PA.

[0033] Independently of each other, the mixture M and the amphoteric water-soluble polymer PA can be added to the fibrous suspension in the form of powder, diluted or undiluted aqueous solutions. Preferably, they are added in the form of dilute aqueous solutions.

[0034] Thus, the mixture M and the amphoteric water-soluble polymer PA can be introduced into the thick stock or into the thin stock. They can be added at the mixing pump, before the headbox or the filter screen. Preferably, the mixture M is added into the thick stock and the amphoteric water-soluble polymer PA is added into the thin stock.

[0035] In a preferred embodiment, the mixture M and the amphoteric water-soluble polymer PA are injected industrially into the fibrous suspension before its dilution with white water, i.e. into the thick paste whose consistency is of the order of 1 to 5% by mass of cellulose fibers.

[0036] The process for manufacturing a sheet of paper or cardboard can be implemented with any type of paper pulp, such as for example virgin fiber pulps (Kraft, Bisulfite), recycled fiber pulps, deinked pulps, chemical pulps, mechanical pulps and thermomechanical pulps.

[0037] The mixture M and the amphoteric water-soluble polymer PA can be added at a single point or at two injection points, preferably at two injection points.

[0038] The papermaking process according to the invention may also comprise the addition of other additives and / or polymers as required. By way of example and in a non-limiting manner, mention may be made of: biocides, coagulants, retention agents, flocculants, starch, etc.

[0039] The quantity of mixture M added to the fibrous suspension is advantageously between 0.1 and 5 kg / tonne of dry matter of the fibrous suspension, preferably primarily between 0.5 and 4 kg / tonne, more preferably between 1 and 3 kg / tonne.

[0040] The quantity of amphoteric water-soluble polymer PA added to the fibrous suspension is advantageously between 0.1 and 5 kg / tonne of dry matter of the fibrous suspension, preferably between 0.5 and 4 kg / tonne, more preferably between 1 and 3 kg / tonne.

[0041] The weight ratio between the mixture M and the amphoteric water-soluble polymer PA is advantageously between 1:50 and 50:1, preferably between 1:8 and 8:1, more preferably between 1:3 and 3:1. M Mix

[0042] The mixture M comprises at least: (a) an aluminum salt; b) a water-soluble cationic aldehyde polymer. Aluminum salt

[0043] The aluminum salt may be any aluminum compound. For example, and without limitation, it may be chosen from aluminum chlorohydrates, aluminum chloride, aluminum polychlorides, aluminum sulfate, aluminum polysulfates, aluminum potassium disulfate, hydrated aluminum potassium disulfate, and mixtures thereof. Preferably, the aluminum salt is a polyaluminum chloride or an aluminum chlorohydrate.

[0044] Examples of polyaluminum chloride (PAC) include PAC 18% or PAC 10HB. Aldehydic cationic water-soluble polymer

[0045] Advantageously, the cationic aldehyde water-soluble polymer comprises at least: a) a cationic hydrophilic monomer APCa; b) a non-ionic hydrophilic monomer CPCa-

[0046] The monomers APCa and CPCa of the cationic aldehyde water-soluble polymer are chosen independently of the hydrophilic cationic Apha and hydrophilic non-ionic CPHa monomers of the amphoteric water-soluble polymer PA.

[0047] Advantageously, the cationic hydrophilic monomer(s) APCa that can be used in the context of the invention (water-soluble cationic aldehyde polymer and water-soluble amphoteric polymer PA) are chosen, in particular, from monomers of the vinyl type, in particular acrylamide, acrylic, allyl or maleic having a protonatable amine or ammonium function, advantageously quaternary ammonium. Mention may be made, in particular and in a non-limiting manner, of diallyldialkyl ammonium salts such as dimethyldiallylammonium chloride (DADMAC); acidified or quaternized salts of dialkylaminoalkyl(meth)acrylamides, such as example (3-methacrylamidopropyl)trimethylammonium chloride (MAPTAC), (3-acrylamidopropyl)trimethylammonium chloride (APTAC); acidified or quaternized salts of dialkylaminoalkyl acrylate such as quaternized or salified dimethylaminoethyl acrylate (ADAME); acidified or quaternized salts of dialkylaminoalkyl methacrylate such as quaternized or salified dimethylaminoethyl methacrylate (MADAME); acidified or quaternized salts of N,N-dimethylallylamine; acidified or quaternized salts of diallylmethylamine; acidified or quaternized salts of diallylamine; vinylamine obtained by the hydrolysis (basic or acid) of an amide group -N(R2)-CO-R* with R1 and R2 being, independently, a hydrogen atom or an alkylated chain of 1 to 6 carbons, for example vinylamine resulting from the hydrolysis of vinylformamide; vinylamine obtained by Hofmann degradation; and mixtures thereof.Advantageously, the alkyl groups are C1-C7, preferably C1-C3 and can be linear, cyclic, saturated or unsaturated chains. Preferably, the cationic hydrophilic monomer APCa is dimethyldiallylammonium chloride.

[0048] The aldehyde cationic water-soluble polymer advantageously comprises between 1 and 60 mol% of cationic hydrophilic monomer(s) APCa, preferably between 2 and 50 mol%, more preferably between 3 and 40 mol%, more preferably between 4 and 30 mol%.

[0049] A person skilled in the art will know how to prepare the quaternized monomers, for example using a quaternizing agent of the RX type, R being an alkyl group and X being a halogen or a sulfate.

[0050] By “quaternizing agent” we mean a molecule capable of alkylating a tertiary amine.

[0051] The quaternizing agent may be chosen from dialkyl sulfates comprising from 1 to 6 carbon atoms or alkyl halides comprising from 1 to 6 carbon atoms. Preferably, the quaternizing agent is chosen from methyl chloride, benzyl chloride, dimethyl sulfate or diethyl sulfate.

[0052] Furthermore, the present invention also covers DADMAC, APTAC and MAPTAC type monomers whose counterion is a sulfate, a fluoride, a bromide or an iodide instead of chloride.

[0053] The non-ionic hydrophilic monomer(s) CPCa are chosen from acrylamide, methacrylamide, and mixtures thereof. Preferably, it is acrylamide.

[0054] The cationic aldehyde water-soluble polymer may optionally comprise a or several non-ionic hydrophilic monomers EPCa, advantageously chosen from: N-alkylacrylamides, N-alkylmethacrylamides, N,N-dialkyl acrylamides (for example N,N-dimethylacrylamide or N,N-diethylacrylamide), N,N-dialkylmethacrylamides, alkoxylated esters of acrylic acid, esters alkoxylated methacrylic acid, N-vinylpyrrolidone, N-methylol(meth)acrylamide, N-vinyl caprolactam, N-vinylformamide (NVF), N-vinyl acetamide, N-vinyl imidazole, N-vinyl succinimide, acryloyl morpholine (ACMO), glycidyl methacrylate, vinyl acetate, glyceryl methacrylate, diacetone acrylamide, methacrylic anyhydride, acrylonitrile, maleic anhydride, itaconic anhydride, itaconamide, hydroxyalkyl (meth)acrylate, thioalkyl (meth)acrylate, isoprenol and its alkoxylated derivatives, hydroxyethyl(meth)acrylates and their alkoxylated derivatives, hydroxypropyl(meth)acrylate and its derivatives alkoxylated, and mixtures thereof. Among these non-ionic monomers, the alkyl groups are advantageously C1-C5, more advantageously C1-C3.

[0055] The cationic aldehyde water-soluble polymer advantageously comprises between 40 and 99 mol% of non-ionic hydrophilic monomers (CPCa+EPCa), preferably between 50 and 98 mol%, more preferably between 60 and 97 mol% and even more preferably between 70 and 96 mol%.

[0056] The aldehyde cationic water-soluble polymer may optionally comprise one or more anionic hydrophilic monomers (referred to as “BPCa monomer(s)”)•

[0057] Advantageously, the other anionic hydrophilic monomer(s) BPCa that can be used in the context of the invention can be chosen from a broad group. These monomers can have a vinyl function, in particular acrylic, maleic, fumaric, malonic, itaconic, or allylic. They can also contain a carboxylate, phosphonate, phosphate, sulfonate, sulfate group, or another group with an anionic charge. Preferred monomers belonging to this class are, for example, acrylic acid; methacrylic acid; dimethylacrylic acid; itaconic acid; itaconic acid hemi-esters in C1-C3; acryloyl chloride; crotonic acid; maleic acid; fumaric acid; 3-acrylamido 3-methylbutanoic acid;strong acid monomers having for example a sulfonic acid or phosphonic acid function such as vinyl sulfonic acid, vinylphosphonic acid, allylsulfonic acid, methallyl sulfonic acid, 2-methylidenepropane-1,3-disulfonic acid, 2-sulfoethylmethacrylate, sulfopropylmethacrylate, sulfopropylacrylate, allylphosphonic acid, ethylene glycol methacrylate phosphate, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid (ATBS), 2-acrylamido-2-methylpropane disulfonic acid, 3-allyloxy-2-hydroxypropane sulfonic acid, diethylallylphosphonate, carboxyethyl acrylate; water-soluble salts of these monomers such as their alkali metal, alkaline earth metal or ammonium salts; and mixtures thereof. Preferably, it is acrylic acid and / or 2-acrylamido-2-methylpropane sulfonic acid (ATBS), more preferably it is acrylic acid. ;

[0058] In a particular embodiment of the invention, the anionic hydrophilic monomer(s) Bpca may be partially or totally salified.

[0059] By salified is meant the substitution of a proton of at least one acid function of the type -R(=O)-OH (with R representing P, S or C) of the anionic monomer by a metal or ammonium cation to form a salt of the type -R(=O)-OX (X being a metal cation or an organic cation). In other words, the non-salified form corresponds to the acid form of the monomer, for example RC(=O)-OH in the case of the carboxylic acid function, whereas the salified form of the monomer corresponds to the form RC(=O)-O X+, X+ corresponding to an alkali cation or an organic cation. The salification of the acid functions of the aldehyde cationic water-soluble polymer may be partial or total.

[0060] The salified form advantageously corresponds to the salts of alkali metals (Li, Na, K, etc.), alkaline earth metals (Ca, Mg, etc.) or ammonium (for example the ammonium ion or a tertiary ammonium), or their mixtures. The preferred salts are the sodium and lithium salts.

[0061] Salification can be done, partially or totally, before, during or after polymerization.

[0062] In a particular embodiment of the invention, the aldehyde cationic water-soluble polymer advantageously comprises between 1 and 100 mol% of its anionic hydrophilic monomers BPCa in salified form, preferably between 10 and 90 mol%.

[0063] The aldehyde cationic water-soluble polymer advantageously comprises less than 30 mol% of anionic hydrophilic monomers BPCa, preferably less than 10 mol%.

[0064] In a preferred embodiment, the cationic aldehyde water-soluble polymer is free of anionic BPCa water-soluble monomers.

[0065] The aldehyde cationic water-soluble polymer may optionally comprise one or more zwitterionic hydrophilic monomers (DPCa) and / or one or more hydrophobic monomers (FPCa)-

[0066] Advantageously, the hydrophilic zwitterionic monomer(s) DPCa which can be used in the context of the invention are chosen, in particular, from derivatives of a vinyl-type unit (advantageously acrylamide, acrylic, allyl or maleic), this monomer having an amine or quaternary ammonium function and an acid function of carboxylic (or carboxylate), sulfonic (or sulfonate) or phosphoric (or phosphate) type.

[0067] Preferably, this monomer comprises an amine or quaternary ammonium function and an acid function of the carboxylic (or carboxylate), sulfonic (or sulfonate) or phosphoric (or phosphate) type.

[0068] Dimethylaminoethyl acrylate derivatives, such as 2 - ((2-9 (acryloyloxy) ethyl) dimethylammonio) ethane-l-sulfonate, may be mentioned in particular and in a non-limiting manner, 3 - ((2- (acryloyloxy) ethyl) dimethylammonio) propane-1-sulfonate, 4 - ((2- (acryloyloxy) ethyl) dimethylammonio) butane-1-sulfonate, [2- (acryloyloxy) ethyl] (dimethylammonio) acetate, derivatives of dhné-thylaminoethyl methacrylate such as 2 - ((2- (methacryloyloxy) ethyl) dimethylammonio) ethane-l-sulfonate, 3 - ((2- (methacryloyloxy) ethyl) dimethylammonio) propane-1-sulfonate, 4 - ((2 - (methacryloyloxy) ethyl) dimethylammonio) butane-1-sulfonate, [2- (methacryloyloxy) ethyl] (dimethylammonio) acetate, dimethylamino propylacrylamide derivatives such as 2 - ((3-acrylamidopropyl) dimethylammonio) ethane-1-sulfonate, 3 - ((3-acrylamidopropyl) dimethylammonio) propane-1-sulfonate, 4 - ((3-acrylamidopropyl) dimethylammonio) butane -1-sulfonate, [3- (acryloyl) oxy) propyl] (dimethylammonio) acetate, dimethylamino propyl methylacrylamide,or derivatives such as 2-((3-methacrylamidopropyl) dimethylammonio) ethane-1-sulfonate, 3-(dimethylammonio) propane-1-sulfonate 4-((3-methacrylamidopropyl) dimethylammonio) butane-1-sulfonate and propyl[3-(methacryloyloxy)](dimethylammonio)acetate and mixtures thereof.

[0069] Other zwitterionic hydrophilic monomers may be used, in particular those described by the Applicant in document WO2021 / 123599.

[0070] The aldehyde cationic water-soluble polymer advantageously comprises less than 30 mol% of hydrophilic zwitterionic monomers DPCa, preferably less than 10 mol%.

[0071] In a preferred embodiment, the cationic aldehyde water-soluble polymer is free of zwitterionic DPCa- water-soluble monomers.

[0072] Advantageously, the FPCa monomer(s) having a hydrophobic character which can be used in the context of the invention can be chosen, in particular, from (meth)acrylic acid esters having a (i) C4-C30 alkyl, or (ii) arylalkyl (C4-C30 alkyl, C4-C30 aryl), or (iii) propoxylated, or (iv) ethoxylated, or (v) ethoxylated and propoxylated chain; alkyl aryl sulfonates (C4-C30 alkyl, C4-C30 aryl); mono- or di-substituted amides of (meth)acrylamide having a (i) C4-C30 alkyl, or (ii) arylalkyl (C4-C30 alkyl, C4-C30 aryl), or (iii) propoxylated, or (iv) ethoxylated, or (v) ethoxylated and propoxylated chain; anionic or cationic monomeric derivatives of (meth)acrylamide or (meth)acrylic acid bearing a hydrophobic chain; vinylpyridine, and mixtures thereof. The hydrophobic monomers may comprise halogen atoms, for example chlorine.

[0073] Among these hydrophobic FPCa monomers: - the alkyl groups are preferably C4-C2o, more preferably C4-C8. The C6-C2o alkyls are preferably linear alkyls while the C6-C2o alkyls are preferably linear alkyls. C4-C5 are preferably branched, - the arylalkyl groups are preferably C7-C25, more preferably C7-C

[0074]

[0075] 15, - the ethoxylated chains advantageously comprise between 1 and 200 -CH2 -CH2-0- groups, preferably between 6 and 100, more preferably between 10 and 40, - the propoxylated chains advantageously comprise between 1 and 50 -CH2 -CH2-CH2-O- groups, more preferably between 1 and 20. Preferred hydrophobic monomers belonging to these classes are, for example: - n-hexyl (meth)acrylate, n-octyl (meth)acrylate, octyl (meth)acrylamide, lauryl (meth)acrylate, lauryl (meth)acrylamide, myristyl (meth)acrylate, myristyl (meth)acrylamide, pentadecyl (meth)acrylate, pentadecyl (meth)acrylamide, cetyl (meth)acrylate, cetyl (meth)acrylamide, oleyl (meth)acrylate, oleyl (meth)acrylamide, erucyl (meth)acrylate, erucyl (meth)acrylamide, N-tert-Butyl(meth)acrylamide, 2-ethylhexyl acrylate, C4-C22 itaconic acid hemi-esters, acidified or quaternized salts of C4-C22 dialkylaminoalkyl (meth)acrylate, acidified or quaternized salts of C4-C22 dialkylaminoalkyl(meth)acrylamides, acrylamido undecanoic acid, and mixtures thereof, - cationic allyl derivatives of formula (I) or (II): [Chem. 3] 0) (IB

[0076] in which: R: independently an alkyl chain containing 1 to 4 carbons; Ri: an alkyl or arylalkyl chain comprising 8 to 30 carbons; X: a halide selected from the group consisting of bromides, chlorides, iodides, fluorides and any negatively charged counterion; and, preferably, hydrophobic cationic derivatives of the (meth)acryloyl type corresponding to formula (III):

[0077] [Chem.4]

[0078] in which: - A represents O or N-R5 (preferably A represents N-R5), - R2, R3, R4, R5, R6, R?: independently a hydrogen atom or an alkyl chain containing 1 to 4 carbons, - Q: an alkyl chain comprising 1 to 20 carbons, - R8: an alkyl or arylalkyl chain comprising 8 to 30 carbons, - X: a halide chosen from the group consisting of bromides, chlorides, iodides, fluorides, and any negatively charged counterion.

[0079] The aldehyde cationic water-soluble polymer advantageously comprises less than 1 mol% of hydrophobic monomers FPCa-

[0080] When the aldehyde cationic water-soluble polymer comprises hydrophobic FPCa monomers, they are present in such an amount that the polymer remains soluble in water.

[0081] In a preferred embodiment, the aldehyde cationic water-soluble polymer does not comprise a hydrophobic monomer FPCa-

[0082] The quantities of the different monomers will be adjusted by those skilled in the art so as not to exceed 100 mol% during the preparation of the cationic aldehyde water-soluble polymer.

[0083] In a preferred embodiment, the APCa and CPCa monomers represent 100 mol% of the monomers of the cationic aldehyde water-soluble polymer.

[0084] The aldehyde cationic water-soluble polymer may further comprise at least one crosslinking agent.

[0085] The crosslinking agent is advantageously chosen from: - structural agents, which may be chosen from the group comprising monomers with polyethylene unsaturation (having at least two unsaturated functions), such as for example vinyl functions, in particular allylic or acrylic, for example methylene bis acrylamide (MBA), triallyamine, or tetraallylammonium chloride or 1,2 dihydroxyethylene bis-(N-acrylamide), - monomers having at least two epoxy functions, - monomers having at least one unsaturated function and one epoxy function, - macroinitiators such as polyperoxides, polyazos and polytransfer agents such as polymercaptant polymers, and polyols, - functionalized polysaccharides, - water-soluble metal complexes composed of: * a metal with a valence greater than 3 such as, by way of example and without limitation, aluminum, boron, zirconium or titanium, and * of a ligand carrying a hydroxyl function.

[0086] The amount of crosslinking agent in the aldehyde cationic water-soluble polymer is advantageously between 5 and 5,000 ppm, relative to the total weight of the monomers constituting the aldehyde cationic water-soluble polymer, more preferably between 50 and 3,000 ppm.

[0087] When the cationic aldehyde water-soluble polymer according to the invention comprises a crosslinking agent, the polymer remains soluble in water. Those skilled in the art will know how to adjust the amount of crosslinking agent, and possibly the amount of transfer agent in order to achieve this result.

[0088] In a particular embodiment, the aldehyde cationic water-soluble polymer does not comprise a crosslinking agent.

[0089] The aldehyde cationic water-soluble polymer may further comprise at least one transfer agent, for example, selected from methanol; isopropyl alcohol; sodium hypophosphite; calcium hypophosphite; magnesium hypophosphite; potassium hypophosphite; ammonium hypophosphite; formic acid; sodium formate; calcium formate; magnesium formate; potassium formate; ammonium formate; 2-mercaptoethanol; 3-mercaptopropanol; dithiopropylene glycol; thioglycerol; thioglycolic acid; thiohydracrylic acid; thiolactic acid; thiomalic acid; cysteine; aminoethanethiol; thioglycolates; allyl phosphites; allyl mercaptans, such as n-dodecyl mercaptan; sodium methallysulfonate; calcium methallysulfonate; magnesium methallysulfonate; potassium methallysulfonate; ammonium methallysulfonate;alkyl phosphites such as trialkyl (C12-C15) phosphites, di-oleyl-hydrogen phosphites, dibutyl phosphite; dialkyldithiophosphates such as dioctyl phosphonate; tertiary nonyl mercaptan; 2-ethylhexyl thioglycolate; n-octyl mercaptan; n-dodecyl mercaptan; tert-dodecyl mercaptan; isooctylthioglycolate; 2-ethylhexyl thioglycolate; 2-ethylhexyl mercaptoacetate; polythiols; and mixtures thereof. Preferably, these are sodium hypophosphite or sodium formate.

[0090] The amount of transfer agent in the aldehyde cationic water-soluble polymer is advantageously between 10 and 10,000 ppm, relative to the total weight of the monomers constituting the aldehyde cationic water-soluble polymer, more preferably between 50 and 5,000 ppm.

[0091] In a particular embodiment, the cationic aldehyde water-soluble polymer does not comprise a transfer agent.

[0092] The aldehyde cationic water-soluble polymer is prepared from a base polymer on which a dialdehyde is reacted. It can be prepared according to different processes, such as for example that described in document US 2011 / 0056640, document FR2987375 of the Applicant, or in the patent application having the filing number FR2305149 of the Applicant. Preferably the aldehyde cationic water-soluble polymer is prepared according to document FR2305149 of the Applicant.

[0093] When the cationic aldehyde water-soluble polymer is prepared according to document FR2305149, the CPCa monomer does not include N-alkylacrylamides and N,N-dialkyl acrylamides while the BPCa monomer does not include allylsulfonic acid and methallylsulfonic acid.

[0094] Advantageously, the dialdehyde is chosen from glyoxal, glutaraldehyde, furan-dialdehyde, adipaldehyde, succinaldehyde, starch dialdehyde, 2,2-di-methoxyethanal and mixtures thereof. Preferably, it is glyoxal.

[0095] Advantageously, the concentration by weight of dialdehyde in the water-soluble aldehyde polymer is between 5 and 40% relative to the total weight of the monomers constituting the aldehyde-based polymer, preferably between 10 and 35%, more preferably between 15 and 30%. Physical characteristics of the base polymer

[0096] The base polymer has a weight-average molecular weight advantageously between 50,000 and 5,000,000 g / mol, preferably between 100,000 and 3,000,000 g / mol, more preferably between 150,000 and 2,000,000 g / mol, even more preferably between 200,000 and 1,000,000 g / mol, and even more preferably between 300,000 and 800,000 g / mol.

[0097] When the base polymer is obtained according to the process described in patent application FR2305149, its weight-average molecular weight is advantageously between 1,000,000 and 25,000,000 g / mol, preferably between 2,000,000 and 15,000,000 g / mol, more preferably between 3,000,000 and 10,000,000 g / mol

[0098] The weight average molecular weight is preferably measured by gel permeation chromatography coupled with a Malls detector.

[0099] The Brookfield viscosity of the solution comprising the base polymer is advantageously preferably between 1,000 and 50,000 cps, preferably between 5,000 and 20,000 cps.

[0100] The Brookfield viscosity of the solution comprising the cationic aldehyde water-soluble polymer is advantageously between 5 and 1,500 cps, preferably between 10 and 1,000 cps. Composition of the mixture M

[0101] The weight ratio between the aluminum salt and the aldehyde cationic water-soluble polymer is preferably between 50:50 and 25:75, more preferably between 35:65 and 30:70.

[0102] In a preferred embodiment, the mixture M comprises a quantity of cationic aldehyde water-soluble polymer greater than the quantity of aluminum salt.

[0103] The mixture M may be presented and / or used in liquid or solid form. Preferably, the mixture M is presented in liquid form. Amphoteric water-soluble polymer PA

[0104] The amphoteric water-soluble polymer PA comprises at least: a) a cationic hydrophilic monomer Apha; b) an anionic hydrophilic monomer BPHA; c) a hydrophilic non-ionic CPHA monomer; (d) a structuring system comprising at least: (i) a compound I, different from the anionic hydrophilic monomer(s) BPHA, chosen from: allylsulfonic acid, methallylsulfonic acid, allyl disulfonic acid, methallyl disulfonic acid, their salts and their mixtures; (ii) a compound II of formula (2):

[0105] [Chem.6] Formula (2)

[0106] R1 and R2 being, independently of one another, a hydrogen atom, a methyl group, an ethyl group, an isopropyl group or a CH2-OH group; Ri and R2 are not both hydrogen atoms (Ri^H when R2=H; R2^H when Ri=H).

[0107] Composition of the amphoteric water-soluble polymer PA

[0108] Advantageously, the cationic hydrophilic monomer(s) Apha are chosen from the same list as the cationic hydrophilic monomers Apca described above. previously for the cationic aldehyde water-soluble polymer.

[0109] The amphoteric water-soluble polymer PA advantageously comprises between 1 and 45 mol% of cationic hydrophilic monomer(s) Apha, preferably between 3 and 40 mol%, more preferably between 5 and 30 mol%.

[0110] Advantageously, the other anionic hydrophilic monomer(s) BPHA have a vinyl function, in particular acrylic, maleic, fumaric, malonic, itaconic, or allylic. They may also contain a carboxylate, phosphonate, phosphate, sulfonate, sulfate group or another group with an anionic charge. Preferred monomers belonging to this class are, for example, acrylic acid; methacrylic acid; dimethylacrylic acid; itaconic acid; C1-C3 itaconic acid hemiesters; acryloyl chloride; crotonic acid; maleic acid; fumaric acid; 3-acrylamido 3-methylbutanoic acid;strong acid monomers having for example a sulfonic acid or phosphonic acid function such as vinyl sulfonic acid, vinylphosphonic acid, 2-methylidenepropane-1,3-disulfonic acid, 2-sulfoethylmethacrylate, sulfopropylmethacrylate, sulfopropylacrylate, allylphosphonic acid, ethylene glycol methacrylate phosphate, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid (ATBS), 2-acrylamido-2-methylpropane disulfonic acid, 3-allyloxy-2-hydroxypropane sulfonic acid, diethylallylphosphonate, carboxyethyl acrylate; the water-soluble salts of these monomers such as their alkali metal, alkaline earth metal or ammonium salts; and mixtures thereof. ;

[0111] The amphoteric water-soluble polymer PA advantageously comprises between 0.1 and 30 mol% of anionic hydrophilic monomer(s) BPHA, preferably between 0.5 and 20 mol%, more preferably between 1 and 10 mol%.

[0112] In a particular embodiment, the anionic hydrophilic monomer(s) BPHA may be salified.

[0113] By salified is meant the substitution of a proton of at least one acid function of the type -Ra(=O)-OH (with Ra representing P, S or C) of the anionic monomer by a metal or ammonium cation to form a salt of the type -Ra(=O)-OX (X being a metal cation, an inorganic cation or an organic cation). In other words, the non-salified form corresponds to the acid form of the monomer, for example Rb -C(=O)-OH in the case of the carboxylic acid function, whereas the salified form of the monomer corresponds to the form Rb-C(=O)-0 X+, X+ corresponding to an alkali cation or an organic cation. The salification of the acid functions of the branched water-soluble polymer may be partial or total.

[0114] The salified form advantageously corresponds to the salts of alkali metals (Li, Na, K...), alkaline earth metals (Ca, Mg...) or ammonium (for example the ion ammonium or tertiary ammonium). The preferred salts are sodium salts.

[0115] Salification can be done before or after polymerization.

[0116] Advantageously, 0 to 100 mol% of the anionic hydrophilic monomer(s) BPHA can be in salified form, preferably 50 to 100 mol%. Thus, 50 mol% of anionic hydrophilic monomer(s) BPHA can be in salt form and 50 mol% in acid form.

[0117] In a preferred embodiment, in the amphoteric water-soluble polymer PA, the molar quantity of cationic monomer Apha is greater than the quantity of anionic monomer BPHA, in other words its overall charge is cationic.

[0118] Advantageously, the hydrophilic non-ionic CPHA monomer(s) is(are) chosen from acrylamide, methacrylamide, N-vinylformamide (NVF), and mixtures thereof. Preferably, it is acrylamide.

[0119] The amphoteric water-soluble polymer PA may optionally comprise one or more non-ionic hydrophilic monomers EPHA, advantageously chosen from N-alkylmethacrylamides, N,N-dialkylmethacrylamides, alkoxylated esters of acrylic acid, alkoxylated esters of methacrylic acid, N-vinylpyrrolidone, N-methylol(meth)acrylamide, N-vinyl caprolactam, N-vinyl acetamide, N-vinyl imidazole, N-vinyl succinimide, acryloyl morpholine (ACMO), glycidyl methacrylate, vinyl acetate, glyceryl methacrylate, diacetone acrylamide, methacrylic anhydride, acrylonitrile, maleic anhydride, anhydride itaconic acid, itaconamide, hydroxyalkyl (meth)acrylates, thioalkyl (meth)acrylates, isoprenol and its alkoxylated derivatives, hydroxyethyl (meth)acrylates and their alkoxylated derivatives, hydroxypropyl (meth)acrylate and its alkoxylated derivatives, and mixtures thereof.Among these non-ionic monomers, the alkyl groups are advantageously C1-C5, more advantageously C1-C3.

[0120] The amphoteric water-soluble polymer PA advantageously comprises between 35 and 89.9 mol% of non-ionic hydrophilic monomer(s) (CPHA+EPHA), preferably between 55 and 97.5 mol%, more preferably between 75 and 94 mol%.

[0121] The amphoteric water-soluble polymer PA may optionally comprise one or more zwitterionic hydrophilic monomers DPHA and / or one or more hydrophobic monomers FPHA.

[0122] Advantageously, the DPHA and FPHA monomer(s) are chosen from the same list as the DPCA and FPCA monomers described previously for the zwitterionic and hydrophobic hydrophilic monomers of the aldehyde cationic water-soluble polymer.

[0123] The amphoteric water-soluble polymer PA advantageously comprises less than 30 mol% of hydrophilic zwitterionic monomers DPHA, preferably less than 10 mol%.

[0124] In a preferred embodiment, the amphoteric water-soluble polymer PA is free of zwitterionic water-soluble monomers DPHa-

[0125] The amphoteric water-soluble polymer PA advantageously comprises less than 1 mol% of hydrophobic FPHA monomers.

[0126] When the amphoteric water-soluble polymer PA comprises hydrophobic monomers Fpha, they are present in such an amount that the polymer remains soluble in water.

[0127] In a preferred embodiment, the amphoteric water-soluble polymer PA does not comprise a hydrophobic monomer FPHA.

[0128] The quantities of the different monomers will be adjusted by those skilled in the art so as not to exceed 100 mol% during the preparation of the amphoteric water-soluble polymer PA.

[0129] In a preferred embodiment, the Apha, BPHA and CPHa monomers represent 100 mol% of the monomers of the amphoteric water-soluble polymer PA.

[0130] In a preferred embodiment, the amphoteric water-soluble polymer PA has a molar quantity of cationic hydrophilic monomer APHa greater than the molar quantity of anionic hydrophilic monomer BPHa-Structuring system

[0131] The structuring system of the amphoteric water-soluble polymer PA comprises at least: (i) a compound I; (ii) an IL compound

[0132] Compound I is chosen from: allylsulfonic acid, methallylsulfonic acid, allyl disulfonic acid, methallyl disulfonic acid, their salts and their mixtures. Preferably, it is methallylsulfonic acid, for example sodium methallylsulfonate.

[0133] The salified form advantageously corresponds to the salts of alkali metals (Li, Na, K, etc.), alkaline earth metals (Ca, Mg, etc.) or ammonium (for example the ammonium ion or a tertiary ammonium). The preferred salts are the sodium salts.

[0134] The amphoteric water-soluble polymer PA advantageously comprises between 500 and 100,000 ppm of compound I relative to the total weight of the monomers constituting the amphoteric water-soluble polymer PA, preferably between 1,000 and 80,000 ppm, more preferably between 2,000 and 70,000 ppm.

[0135] Compound II used in the context of the invention has the general formula:

[0136] [Chem.7] Formula (2)

[0137] R1 and R2 being, independently of one another, a hydrogen atom, a methyl group, an ethyl group, an isopropyl group or a CH2-OH group; Ri and R2 are not both hydrogen atoms (Ri^H when R2=H; R2^H when Ri=H).

[0138] Compound II is advantageously chosen from: N,N-dimethylacrylamide, N,N-diethylacrylamide, N-isopropylacrylamide, N-methylolacrylamide and mixtures thereof. Preferably, it is N,N-dimethylacrylamide.

[0139] The amphoteric water-soluble polymer PA advantageously comprises between 100 and 50,000 ppm of compound II relative to the total weight of the monomers constituting the amphoteric water-soluble polymer PA, preferably between 200 and 20,000 ppm, more preferably between 500 and 10,000 ppm.

[0140] In the amphoteric water-soluble polymer PA, the mass ratio between compound I and compound II is advantageously between 0.01 and 1000, preferably between 0.1 and 150.

[0141] In a preferred embodiment, in the amphoteric water-soluble polymer PA, the amount of compound I is greater than the amount of compound II. Thus, the mass ratio between compound I and compound II is advantageously greater than 1 and less than or equal to 150, preferably greater than 10 and less than or equal to 110.

[0142] The amphoteric water-soluble polymer PA may further comprise at least one crosslinking agent. Advantageously, the crosslinking agent is chosen from the list previously described for the cationic aldehyde water-soluble polymer.

[0143] The amount of crosslinking agent in the amphoteric water-soluble polymer PA is as described in the cationic aldehyde water-soluble polymer.

[0144] In a particular embodiment, the amphoteric water-soluble polymer PA does not comprise a crosslinking agent.

[0145] The amphoteric water-soluble polymer PA according to the invention may further comprise at least one transfer agent. The transfer agent and its quantity are as described previously for the cationic aldehyde water-soluble polymer.

[0146] In a particular embodiment, the amphoteric water-soluble polymer PA does not comprise a transfer agent.

[0147] Physical characteristics of the amphoteric water-soluble polymer PA

[0148] The amphoteric water-soluble polymer PA has a weight-average molecular weight advantageously between 1,000,000 and 25,000,000 g / mol, preferably between 2,000,000 and 15,000,000 g / mol, more preferably between 3,000,000 and 10,000,000 g / mol.

[0149] The weight average molecular weight is preferably measured by gel permeation chromatography coupled with a Malls detector.

[0150] The amphoteric water-soluble polymer PA is present and / or is used in liquid or solid form. Preferably, it is used in liquid form.

[0151] The Brookfield viscosity of the solution comprising the amphoteric water-soluble polymer PA is advantageously between 1,000 and 50,000 cps, preferably between 5,000 and 20,000 cps.

[0152] Process for the polymerization of amphoteric water-soluble polymer PA

[0153] The amphoteric water-soluble polymer PA is characterized by its method of production, it is obtained by polymerization of a first fraction (F1) and at least two additional fractions (F2 and F3). At least one of the fractions F1, F2 and F3 of the process is different from the other fractions. Preferably, the fractions F1, F2 and F3 are different from each other. By different fraction, we mean a fraction having a different composition in monomers (ratio and / or nature of the monomers) and / or in compounds I and II (ratio and / or nature of the compounds I and II).

[0154] The process for polymerizing the amphoteric water-soluble polymer PA comprises the following steps: A) formation of a solution (SI) comprising at least a first fraction (Fl) comprising (1) at least one monomer chosen from the monomers Apha, BPHA and CPHA and / or (2) at least one compound chosen from compounds I and II; B) polymerization 1 (PO1) of the fraction Fl to form a solution of a first prepolymer PP1; C) adding, to the solution comprising the first prepolymer PP1, a second fraction (F2) comprising (1) at least one monomer chosen from the monomers Apha, Bpha and Cpha and / or (2) at least one compound chosen from compounds I and II; D) polymerization 2 (PO2) of fraction F2 on the first prepolymer PP1 to form a solution of a second prepolymer PP2; E) adding, to the solution comprising the second prepolymer PP2, a third fraction (F3) comprising (1) at least one monomer chosen from the monomers Apha, Bpha and Cpha and / or (2) at least one compound chosen from compounds I and II; F) polymerization 3 (PO3) of the fraction F3 on the second prepolymer PP2 to form a solution comprising the amphoteric water-soluble polymer PA; at least one of the fractions Fl, F2 or F3 comprises at least one Apha monomer, at least one of the fractions Fl, F2 or F3 comprises at least one BPHA monomer, at least one of the fractions F1, F2 or F3 comprises at least one CPHA monomer at least one of the fractions F1, F2 or F3 comprises at least one compound I, and at least one of the fractions F1, F2 or F3 comprises at least one compound II.

[0155] In a preferred embodiment, at least one of the fractions F1, F2 or F3 comprises (1) at least one monomer chosen from the monomers Apha, BPHA and CPHA and (2) at least one compound chosen from compounds I and II, even more preferably the three fractions F1, F2 and F3 comprise (1) at least one monomer chosen from the monomers Apha, BPHA and CPHA and (2) at least one compound chosen from compounds I and II.

[0156] This method may comprise the addition of additional moieties prior to the formation of the amphoteric water-soluble polymer PA.

[0157] The polymerization process is advantageously carried out sequentially and continuously, i.e. without interruption.

[0158] By "in sequence", it is meant that the polymerization of the monomers of the amphoteric water-soluble polymer PA is carried out in several times by adding several fractions while not being interrupted, that is to say that the addition of the fractions is carried out continuously and that the polymerization does not stop. The different steps A) to F) are therefore carried out successively. In other words, a first fraction of monomers can be added during casting and polymerizes so as to form a first prepolymer PP1 which continues to polymerize with the fraction F2 to form the prepolymer PP2, which itself continues to polymerize with the fraction F3 to obtain, at the end of polymerization, the amphoteric water-soluble polymer PA. At least one of the fractions F1, F2 and F3 of the process is different from the other fractions. Preferably, the fractions F1, F2 and F3 are different.The addition of different fractions during the polymerization process allows obtaining a gradient in the composition of the amphoteric water-soluble polymer PA.

[0159] In a particular embodiment, the polymerization can be momentarily interrupted after PO1 and / or PO2 and continued in a different location. In this case, the monomers of the FX+1 fraction (X = 1 or 2) added to the PPX prepolymer formed during the previous steps, polymerize and interact with PPX to form PPX+1 and the process continues in the next step to finally obtain the amphoteric water-soluble polymer PA.

[0160] In the polymerization process according to the invention, the total sum of the molar percentages of the monomers of the different fractions is equal to the total sum of the molar percentages of the monomers of the amphoteric water-soluble polymer PA.

[0161] Step A), formation of a solution (SI) comprising a first fraction (Fl) Solution (SI)

[0162] The SI solution is generally composed of: - a solvent; - a primer; - of a first fraction Fl.

[0163] The solvent is advantageously water, or a solvent in which the monomers and prepolymers PP1 and PP2 and the amphoteric water-soluble polymer PA are soluble. Preferably, the solvent is water.

[0164] The polymerization initiators used can be any compounds that dissociate into radicals under polymerization conditions, for example: organic peroxides, hydroperoxides, hydrogen peroxide, persulfates, azo compounds and redox couples. The use of water-soluble initiators is preferred. In some cases, it is advantageous to use mixtures of various polymerization initiators, for example mixtures of redox catalysts and azo compounds. Preferably, these are persulfates.

[0165] In a particular embodiment, the SI solution is formed by mixing in a polymerization tank the solvent, the initiator and the FL fraction

[0166] In this particular embodiment, the fraction F1 can be added all at once, in several times or by pouring, i.e. progressively (for example drop by drop) into the solvent / initiator mixture. Preferably, the fraction F1 is added all at once into the polymerization tank.

[0167] In a particular embodiment, the initiator and the fraction F1 are added by casting into a polymerization tank comprising the solvent. They can be added separately or premixed. Preferably, they are added separately.

[0168] In a preferred embodiment, the initiator is added continuously throughout the polymerization process. In this case, the initiator is advantageously added in parallel with the different fractions, during the different polymerization steps and during any aging steps of the different prepolymers (PP1 and PP2) and the amphoteric water-soluble polymer PA.

[0169] In this preferred embodiment of the invention, the duration of the initiator casting is advantageously between 50 min and 560 min, preferably between 130 min and 430 min. First fraction (Fl)

[0170] Advantageously, the fraction F1 comprises between 10 and 45% by weight of monomer (Apha and / or BPHA and / or CPHA, + optionally EPHA and / or DPHA and / or FPHA) relative to the total weight of the monomers constituting the amphoteric water-soluble polymer PA, preferably between 15 and 40% by weight.

[0171] The fraction F1 advantageously comprises between 250 and 60,000 ppm of compounds I relative to the total weight of monomers constituting the amphoteric water-soluble polymer PA, preferably between 500 and 50,000 ppm, more preferably between 1,000 and 40,000 ppm.

[0172] The fraction F1 advantageously comprises between 50 and 30,000 ppm of compounds II relative to the total weight of monomers constituting the amphoteric water-soluble polymer PA, preferably between 100 and 10,000 ppm, more preferably between 200 and 5,000 ppm.

[0173] The various monomers and compounds comprising F1 are advantageously added in the form of solutions. These solutions can be added separately or as a mixture in the polymer tank, in one go, in several goes or by pouring, i.e. drop by drop, to form the solution SL. Preferably, the addition is done as a mixture and in one go.

[0174] When the fraction Fl is added during casting, the casting advantageously lasts between 10 min and 80 min, preferably between 40 min and 70 min.

[0175] In a preferred embodiment, the fraction F1 is prepared in the reactor (polymerization tank) before the addition of initiator.

[0176] In a preferred embodiment, the fraction F1 comprises at least one cationic hydrophilic monomer A, at least one non-ionic hydrophilic monomer C, at least one compound I and at least one compound IL.

[0177] Step B), polymerization of the F1 fraction to form a first prepolymer (PP1) Polymerization 1 (PO1)

[0178] Prior to the polymerization PO1, the atmosphere of the polymerization tank can be replaced by an inert gas such as for example nitrogen or argon.

[0179] The PO1 polymerization is generally a radical polymerization. One or more polymerization initiators may be used, in particular initiators which dissociate into radicals under the polymerization conditions.

[0180] The PO1 polymerization is generally initiated at a temperature between 70 and 90°C, preferably between 75 and 85°C, the polymerization temperature is then controlled using cooling means so as, preferably, not to exceed 95°C.

[0181] The PO1 polymerization generally lasts between 10 min and 80 min, preferably between 40 min and 70 min.

[0182] The polymerization advantageously begins at the moment when the first monomers, the solvent and the initiator are in contact, in other words, the polymerization duration PO1 advantageously corresponds to the duration of the casting of the FL fraction. Prepolymer (PP1)

[0183] At the end of the PO1 polymerization, a PP1 prepolymer is obtained.

[0184] In a particular embodiment, the prepolymer PP1 is left to age for between 5 min and 60 min, preferably between 10 min and 30 min.

[0185] By "left to age" we mean that the temperature of the medium is maintained between 80 and 90°C after the end of the polymerization to allow an increase in viscosity by internal branching phenomena of the polymer. This definition of aging concerns all stages of the polymerization process.

[0186] Step C), addition of a second fraction (F2) to the solution comprising PP1 Second fraction F2

[0187] Advantageously, fraction F2 comprises between 30 and 80% by weight of monomer (Apha and / or BPHA and / or CPHA, + optionally EPHA and / or DPHA and / or FPHa) relative to the total weight of the monomers constituting the amphoteric water-soluble polymer PA, preferably between 40 and 70%.

[0188] Fraction F2 advantageously comprises between 250 and 50,000 ppm of compounds I relative to the total weight of monomers constituting the amphoteric water-soluble polymer PA, preferably between 500 and 40,000 ppm, more preferably between 1,000 and 30,000 ppm.

[0189] Fraction F2 advantageously comprises between 0 and 30,000 ppm of compounds II relative to the total weight of monomers constituting the amphoteric water-soluble polymer PA, preferably between 0 and 10,000 ppm, more preferably between 0 and 5,000 ppm.

[0190] The various monomers and compounds comprising F2 are advantageously added in the form of solutions. These solutions can be added separately or as a mixture in the polymer tank, all at once, in several times or by pouring. Preferably, the addition is done by mixing and by pouring.

[0191] When fraction F2 is added during casting, the casting advantageously lasts between 10 min and 100 min, preferably between 30 min and 90 min.

[0192] In a preferred embodiment, fraction F2 comprises at least one anionic hydrophilic monomer BPHa, at least one non-ionic hydrophilic monomer CPHa and at least one compound I.

[0193] Step D), polymerization of fraction F2 on PP1 to form a second prepolymer (PP2) Polymerization (PO2)

[0194] The PO2 polymerization is carried out in the continuity of the PO1 polymerization, it is carried out under the same time and temperature conditions (advantageously 70 to 90°C).

[0195] The PO2 polymerization advantageously lasts between 10 min and 100 min, preferably between 30 min and 90 min.

[0196] PO2 polymerization begins with the addition of the first monomers of fraction F2.

[0197] Advantageously, the polymerization time PO2 corresponds to the duration of the casting of the fraction F2. In this case, the polymerization PO2 begins at the same time as the casting. Prepolymer (PP2)

[0198] At the end of the PO2 polymerization, a PP2 prepolymer is obtained.

[0199] In a particular embodiment, the PP2 prepolymer is left to age for between 5 and 60 min, preferably between 10 and 30 min.

[0200] Step E), addition of a third fraction (F3) to the solution comprising PP2 Fraction F3

[0201] Advantageously, fraction F3 comprises between 5 and 40% by weight of monomer (A PHA and / or Bpha and / or CPHa, + optionally EPHA and / or DPHA and / or FPHA) relative to the total weight of the monomers constituting the amphoteric water-soluble polymer PA, preferably between 10 and 30%.

[0202] Fraction F3 advantageously comprises between 0 and 20,000 ppm of compounds I relative to the total weight of monomers constituting the amphoteric water-soluble polymer PA, preferably between 10 and 15,000 ppm, more preferably between 20 and 10,000 ppm.

[0203] Fraction F3 advantageously comprises between 0 and 10,000 ppm of compounds II relative to the total weight of monomers constituting the amphoteric water-soluble polymer PA, preferably between 0 and 1,000 ppm.

[0204] The various monomers and compounds comprising F3 are advantageously added in the form of solutions. These solutions can be added separately or as a mixture in the polymer tank, in one go, in several goes or by pouring, i.e. drop by drop. Preferably, the addition is done by mixing and drop by drop.

[0205] When fraction F3 is added during casting, the casting advantageously lasts between 10 min and 100 min, preferably between 30 min and 90 min.

[0206] In a preferred embodiment, fraction F3 comprises at least one anionic hydrophilic monomer BPHA, at least one non-ionic hydrophilic monomer CPHa and at least one compound I.

[0207] Step F), polymerization of fraction F3 on PP2 to form the amphoteric water-soluble polymer PA Polymerization (PO3)

[0208] The PO3 polymerization is carried out in the continuity of the PO2 polymerization, it is carried out under the same time and temperature conditions as PO2 (advantageously 70 to 90°C for 10 min to 100 min, preferably between 30 min and 90 min).

[0209] PO3 polymerization begins with the addition of the first monomers of the F3 fraction.

[0210] Advantageously, the polymerization time PO3 corresponds to the duration of the casting of the fraction F3.

[0211] At the end of the PO3 polymerization, the amphoteric water-soluble polymer PA is obtained.

[0212] In a particular embodiment, the amphoteric water-soluble polymer PA is left to age for between 10 and 100 min before the elimination of the residual monomers, preferably between 30 and 90 min.

[0213] The reaction is stopped by adding an excess of initiator and / or water, this step is used to eliminate any residual monomers present in the solution comprising the amphoteric water-soluble polymer PA. Optional step(s)

[0214] The method according to the invention may further comprise additional steps and is not limited to the steps described previously.

[0215] In a particular embodiment, the polymerization process according to the invention may comprise the addition of additional monomer fractions constituting the amphoteric water-soluble polymer PA.

[0216] In a particular embodiment, a crosslinking agent and / or a transfer agent is added during at least one of the steps described above.

[0217] In a particular embodiment, a crosslinking agent is added to the fraction F1 and / or to the fraction F2.

[0218] When a crosslinking agent is added, it is advantageously chosen from the crosslinking agents previously mentioned.

[0219] When a crosslinking agent is added, its quantity is advantageously between 5 and 5,000 ppm relative to the total weight of monomer constituting the amphoteric water-soluble polymer PA, preferably between 50 and 3,000 ppm.

[0220] In a particular embodiment, a transfer agent is added to the fraction F1 and / or to the fraction F2.

[0221] When a transfer agent is added, it is advantageously chosen from the transfer agents previously mentioned.

[0222] When a transfer agent is added, its quantity is advantageously between 10 and 10,000 ppm relative to the total weight of monomers constituting the amphoteric water-soluble polymer PA, preferably between 50 and 5,000 ppm.

[0223] In a preferred embodiment, the Apha and BPHA monomers are added in fractions different. In this case, APHa and BPHa monomers can be added in several fractions, but they are not added in the same fraction, for example, APHa monomers can be added in fractions F1 and F2, BPHa monomers are then added in fraction F3; or BPHa monomers can be added in fractions F2 and F3, APHa monomers are then added in fraction F1; or BPHa monomers can be added in fractions F1 and F2, APHa monomers are then added in fraction F3; or Apha monomers can be added in fractions F2 and F3, BPHA monomers are then added in fraction F1

[0224] In a preferred embodiment, the Apha and BPHA monomers are added in different fractions and: (i) the fraction Fl comprises at least 50 mol% of the Apha monomers relative to the total amount of Apha monomers in the amphoteric water-soluble polymer PA, or at least 50 mol% of the BPHa monomers relative to the total amount of BPHa monomer in the amphoteric water-soluble polymer PA, and; (ii) fraction F3 comprises at least 50 mol% of the APHa monomers relative to the total amount of APHa monomers in the amphoteric water-soluble polymer PA, or at least 50 mol% of the BPHa monomers relative to the total amount of BPHa monomers in the amphoteric water-soluble polymer PA.

[0225] The invention and the advantages arising therefrom will become more apparent from the following examples given to illustrate the invention, and not in a limiting manner. Examples

[0226] DADMAC: Dimethyl diallyl ammonium chloride MBA: N,N'-methylenebisacrylamide AM: Acrylamide SPS: Sodium persulfate DMA: Dimethylacrylamide SMS: Sodium methallyl sulfonate MADAME: Dimethylaminoethyl methacrylate AI: Itaconic acid AA: Acrylic acid MADAME,ClBz: Dimethylaminoethyl methacrylate, chlorinated benzyl MBS: Sodium metabisulfite V-50: 2,2'-Azobis(2-methylpropionamidine)dihydrochloride PAC 18: Polyaluminium hydroxychloride (18% by weight in water) PAC 10 HB: High Basicity Polyaluminum Hydroxychloride (10% by weight in water) ACH: Aluminum Chlorohydrate (23% by weight in water)

[0227] Description of GPC-Malls molecular weight characterization

[0228] Gel permeation chromatography is a method for separating macromolecules according to their hydrodynamic volume. It is coupled with a Malls detector, allowing the measurement of light scattering at several angles. The products from the examples and counter-examples are characterized in detail as follows: - Instrument: GPC-2 - Columns: Shodex SB 807-G, Shodex SB 807-HQ, Shodex SB 805 custom - Method: * Temperature: 30°C * Mobile phase: 0.5 M NaNO3, HEPES (pH=8), 100 ppm NaN3 * Injection: 100 pL * Flow rate: 0.3 mL / min * Detection: (i) Light Scattering Detector (MALS): Absolute Molar Mass (ii) Refractometry (RI): Concentration

[0229] The viscosity is measured using a Brookfield viscometer, at 25°C with a Brookfield module of type LV (for example module LV1) and a speed of 60 rpm (rpm = rotations per minute). The Brookfield module chosen depends on the viscosity of the solution measured. The person skilled in the art knows and is accustomed to adjusting the module according to the viscosity of the solution to be measured, which is part of his general knowledge.

[0230] Example 1: Preparation of cationic water-soluble aldehyde polymers P CAI to PçA3

[0231] Aldehydic cationic water-soluble polymer 1 (PCai) composed of DADMAC / AM (30 mol% / 70 mol%))

[0232] Polymer base 1 (PB 1)

[0233] In a 1 liter reactor equipped with a mechanical stirrer, a thermometer, a condenser and a nitrogen gas immersion rod, 630.4 g of water, 154.3 g of DADMAC (64% by weight in water), 0.17 g of polyethyleneimine (Polymin HM BASF at 12% by weight in water) and 0.02 g of MBA are introduced. The pH is adjusted to 2.5 with H2SO4 (96% by weight in water). The medium is heated and maintained at a temperature between 79 and 81 °C using a water bath. Two solutions are poured in 90 min continuously and in parallel, a first comprising 202.5 g of AM (50% by weight in water) and a second comprising 7 g of SPS (6% by weight in water). After 30 min of aging, 0.6 g of sodium bisulfite (40% by weight in water) is added to react any residual monomers. A further 60-minute aging is applied before cooling. The resulting solution comprising polymer base 1 (PB1) has a pH of 5.0, an active ingredient of 20.1% by weight, and a viscosity of 4,500 cps. PB1 has a molecular weight (measured by GPC-Malls) of 610,000 g / mol.

[0234] Glyoxalation

[0235] In a 1 liter reactor equipped with a mechanical stirrer and a pH probe, 288 g of PB 1 and 478 g of water are introduced. After 10 min of stirring, the pH is adjusted to 10.4 with a sodium hydroxide solution (10% by weight in water). The temperature is maintained between 20 and 22 °C. 34 g of glyoxal (40% by weight in water) are added. When the desired viscosity is reached, the reaction is stopped by lowering the pH to less than 3.5 by adding H2SO4 (96% by weight in water), then the cationic water-soluble polymer 1 (PCai) is obtained. This pH control and viscosity monitoring make it possible to obtain a PCAi solution having a viscosity of 72 cps after 57 min of reaction.

[0236] Aldehydic cationic water-soluble polymer 2 (PCA2) composed of DADMAC / AM (30 mol% / 70 mol%)

[0237] The water-soluble cationic aldehyde polymer 2 (PCA2) is obtained according to the process described in patent application FR2305149 and described below: Polymer base 2 (PB2) First sequence: PP1 prepolymer

[0238] In a 1 liter reactor equipped with a mechanical stirrer, a thermometer, a condenser and a nitrogen gas immersion rod, a first fraction F1 composed of 146.9 g of water, 50.6 g of AM (50% by weight in water), 77.1 g of DADMAC (64% by weight in water), 1 g of citric acid, 0.5 g of DMA and 0.4 g of SMS is introduced. The medium is heated and maintained at a temperature between 79 and 81 °C using a water bath. An addition of 0.05 g of SPS makes it possible to initiate the polymerization of the monomers (PO1) to form a first prepolymer PPL Second sequence: Prepolymer PP2

[0239] When the exotherm is complete, 50 g of an SPS solution (0.33% by weight in water) is cast in 130 min (the casting of initiator lasts the time of the casting of F2, the aging of the PP2 prepolymer, the casting of F3 and the first aging of the base polymer 2), and simultaneously a second fraction F2 composed of 25.5 g of water, 101.3 g of AM (50% by weight in water), 77.1 g of DADMAC (64% by weight in water), 0.5 g of DMA and 0.19 g SMS in 50 min. Once the fraction F2 is cast, the PP2 prepolymer is left to age for 10 min (the PO2 polymerization to form the PP2 prepolymer takes place during the casting of the fraction F2 and during the aging). Third sequence: Polymer base 2 (PB2)

[0240] A third fraction F3, composed of 121.3 g of water, 50.6 g of AM (50% by weight in water), 0.01 g of SMS, is then poured in over 60 min. At the end of the addition of fraction F3, the polymer is left to age for 10 min (PO3 polymerization to form the base polymer takes place during the pouring of fraction F3 and during aging).

[0241] Once aging is complete, 146.9 g of water are added, as well as 0.15 g of SPS. A check of the viscosity evolution is carried out every 15 min. When the desired viscosity is reached, the reaction is stopped by the addition of 2.4 g of sodium bisulfite (40% by weight in water) and 146.9 g of water. A further aging of 60 min is applied before cooling. The solution comprising the polymer base 2 (PB2) has a pH of 3.5, an active material of 20% by weight and a viscosity of 3,500 cps. PB2 has a molecular weight (measured by GPC-Malls) of 2,650,000 g / mol.

[0242] Glyoxalation

[0243] In a 1 liter reactor equipped with a mechanical stirrer and a pH probe, 288 g of PB2 and 478 g of water are introduced. After 10 min of stirring, the pH is adjusted to 10.4 with a sodium hydroxide solution (10% by weight in water). The temperature is maintained between 20 and 22 °C. 34 g of glyoxal (40% by weight in water) are added. When the desired viscosity is reached, the reaction is stopped by lowering the pH to less than 3.5 by adding H2SO4 (92% by weight in water), then the cationic water-soluble polymer 2 (Pcai) is obtained. This pH control and viscosity monitoring make it possible to obtain a PCA2 solution having a viscosity of 69 cps after 51 min of reaction.

[0244] Aldehydic cationic water-soluble polymer 3 (Pcas) comprising DADMAC / AM (5 mol% / 95 mol%)

[0245] Polymer base 3 (PB3)

[0246] In a 1 liter reactor equipped with a mechanical stirrer, a thermometer, a condenser and a nitrogen gas immersion rod, 526 g of water, 33.1 g of DADMAC chloride (64% by weight in water) are introduced. The pH is adjusted to 2.5 with H 2SO4 (96% by weight in water). The medium is heated and maintained at a temperature between 79 and 81 °C using a water bath. Two solutions are poured in 90 min continuously and in parallel, a first of 357.8 g of AM (50% by weight in water) and a second of 7 g of SPS (6% by weight in water). After 30 min of aging, 0.6 g of sodium bisulfite (40% by weight in water) is added to react any residual monomers. A further aging of 60 min is applied before cooling. The solution comprising the polymer base 3 (PB3) obtained has a pH of 4.9, an active material of 20.05% and a viscosity of 4050 cps.PB3 has a molecular weight obtained by GPC-Malls of 435,000 g / mol.

[0247] Glyoxalation

[0248] In a 1 liter reactor equipped with a mechanical stirrer and a pH probe, 160 g of PB3 and 620 g of water are introduced. After 10 min of stirring, the pH is adjusted to 9.3 with a sodium hydroxide solution (10% by weight in water). The temperature is maintained between 20 and 22 °C. 20 g of glyoxal (40% by weight in water) are added. When the desired viscosity is reached, the reaction is stopped by lowering the pH to less than 3.5 by adding H2SO4 (96% by weight in water), then the cationic water-soluble polymer 3 (Pcas) is obtained. This pH control and viscosity monitoring make it possible to obtain a PCA3 solution having a viscosity of 53 cps after 50 min of reaction.

[0249] Example 2: Preparation of amphoteric water-soluble polymers according to the invention PA1 to PA3 and counter-example PA-CE1

[0250] Amphoteric water-soluble polymer 1 (PA1) comprising MADAME / AM / AI (4.4 mol% / 92.4 mol% / 3.2 mol%) according to the invention First sequence: Prepolymer PP1

[0251] In a 1 liter reactor equipped with a mechanical stirrer, a thermometer, a condenser and a nitrogen gas immersion rod, a first fraction F1 composed of 122.1 g of water, 75.1 g of AM (50% by weight in water), 19 g of MADAME, 1 g of citric acid, 6 g of H2SO4 (96% by weight in water), 0.03 g of DMA and 1.9 g of SMS is introduced. The medium is heated and maintained at a temperature between 79 and 81 °C using a water bath. An addition of 0.05 g of SPS makes it possible to initiate the polymerization of the monomers (PO1) to form a first prepolymer PPL Second sequence: Prepolymer PP2

[0252] When the exotherm is complete, 50 g of an SPS solution (0.33% by weight in water) are cast in 130 min (the casting of initiator lasts the time of the casting of F2, the aging of the prepolymer PP2, the casting of F3 and the first aging of the amphoteric water-soluble polymer PA1), and simultaneously a second fraction F2 composed of 15.2 g of water, 181.8 g of AM (50% by weight in water), 5.1 g of AI and 1.44 g SMS, in 60 min. Once the fraction F2 is cast, the prepolymer PP2 is left to age for 10 min (the PO2 polymerization to form the prepolymer PP2 takes place during the casting of the fraction F2 and during the aging).

[0253] Third sequence: Amphoteric water-soluble polymer PA1

[0254] A third fraction F3, composed of 15.2 g of water, 92.6 g of AM (50% by weight in water), 1.05 g of AI, 0.24 g of SMS, is then cast over 50 min. At the end of the addition of fraction F3, the polymer is left to age for 10 min (the PO3 polymerization to form the amphoteric water-soluble polymer PA1 takes place during the casting of fraction F3 and during aging).

[0255] Once aging is complete, 198.4 g of water are added as well as 0.15 g of SPS. A control of the evolution of the viscosity is carried out every 15 min. When the desired viscosity is reached, the reaction is stopped by the addition of 2.4 g of sodium bisulfite (40% by weight in water) and 213.4 g of water. A new aging of 60 min is applied before cooling, the amphoteric water-soluble polymer PAL is then obtained. The solution comprising the amphoteric water-soluble polymer PA1 has a pH of 3.6, an active material of 20% by weight and a viscosity of 8,900 cps. PA1 has a molecular weight (measured by GPC-Malls) of 4,580,000 g / mol.

[0256] Amphoteric water-soluble polymer counterexample 1 (PA-CE1) comprising MADAME / AM / AI (4.4 mol% / 92.4 mol% / 3.2 mol%) counterexample

[0257] Into a 1 liter reactor equipped with a mechanical stirrer, a thermometer, a condenser and a nitrogen gas dipstick, 606.1 g of water, 349.7 g of AM (50% by weight in water), 19 g of MADAME, 6.2 g of AI, 0.03 g of DMA and 3.58 g of SMS are introduced. The pH is adjusted to 7 with the addition of 4 g of H2SO4 (96% by weight in water). The medium is heated and maintained at a temperature of 25 °C. The reaction is initiated with the addition of 1.2 g of SPS, 1 g of MBS and 0.3 g of V-50.

[0258] When the exotherm is complete, the polymer is allowed to age for 60 min. Once the aging is complete, 2.4 g of sodium bisulfite (40% by weight in water) are added. A further aging of 60 min is applied before cooling. The pH is adjusted to 3 with the addition of 5 g of H2SO4 (96% by weight in water), and the amphoteric water-soluble polymer PA2 is then obtained. The solution comprising the amphoteric water-soluble polymer PA-CE1 has a pH of 3, an active material of 20% by weight and a viscosity of 7,100 cps. PA-CE1 has a molecular weight (measured by GPC-Malls) of 1,350,000 g / mol.

[0259] Amphoteric water-soluble polymer 2 (PA2) comprising DADMAC / AM / AA (5 mol% / 93 mol% / 2 mol%) according to the invention First sequence: PP1 prepolymer

[0260] In a 1 liter reactor equipped with a mechanical stirrer, a thermometer, a condenser and a nitrogen gas immersion rod, a first fraction F1 composed of 119.5 g of water, 76.0 g of AM (50% by weight in water), 30.9 g of DADMAC (64% by weight in water), 1 g of citric acid, 6 g of H2SO4 (96% by weight in water), 0.03 g of DMA and 1.7 g of SMS is introduced. The medium is heated and maintained at a temperature between 79 and 81 °C using a water bath. An addition of 0.05 g of SPS makes it possible to initiate the polymerization of the monomers (PO1) to form a first prepolymer PPL Second sequence: PP2 prepolymer

[0261] When the exotherm is complete, 50 g of an SPS solution (0.33% by weight in water) is poured in 130 min (the initiator pouring lasts the time of the F2 pouring, aging of the PP2 prepolymer, the casting of F3 and the first aging of the amphoteric water-soluble polymer PA3), and simultaneously a second fraction F2 composed of 14.9 g of water, 183.9 g of AM (50% by weight in water), 2.9 g of AA and 1.34 g SMS, in 60 min. Once the F2 fraction has been cast, the PP2 prepolymer is left to age for 10 min (the PO2 polymerization to form the PP2 prepolymer takes place during the casting of the F2 fraction and during aging).

[0262] Third sequence: Amphoteric water-soluble polymer PA2

[0263] A third fraction F3, composed of 14.9 g of water, 93.7 g of AM (50% by weight in water), 0.59 g of AA, 0.21 g of SMS, is then cast over 50 min. At the end of the addition of fraction F3, the polymer is left to age for 10 min (the PO3 polymerization to form the amphoteric water-soluble polymer PA3 takes place during the casting of fraction F3 and during aging).

[0264] Once aging is complete, 194.1 g of water are added as well as 0.15 g of SPS. A check of the change in viscosity is carried out every 15 min. When the desired viscosity is reached, the reaction is stopped by adding 2.4 g of sodium bisulfite (40% by weight in water) and 165.9 g of water. A further aging of 60 min is applied before cooling, then the amphoteric water-soluble polymer PA2 is obtained. The solution comprising the amphoteric water-soluble polymer PA2 has a pH of 3.4, an active material of 20% and a viscosity of 8,400 cps. PA2 has a molecular weight obtained by GPC-Malls of 4,460,000 g / mol.

[0265] Amphoteric water-soluble polymer 3 (PA3) comprising MADAME / MADAME,CIBz / AM / AI (15 mol% / 2 mol% / 70 mol% / 13 mol%) according to the invention First sequence: Prepolymer PP1

[0266] In a 1 liter reactor equipped with a mechanical stirrer, a thermometer, a condenser and a nitrogen gas immersion rod, a first fraction F1 composed of 136.8 g of water, 44.6 g of AM (50% by weight in water), 49.2 g of MADAME, 9.5 g of MADAME CIBz, 1 g of citric acid, 6 g of H2SO4 (96% by weight in water), 0.03 g of DMA and 1.1 g of SMS is introduced. The medium is heated and maintained at a temperature between 79 and 81 °C using a water bath. An addition of 0.05 g of SPS makes it possible to initiate the polymerization of the monomers (PO1) to form a first prepolymer PPL Second sequence: PP2 prepolymer

[0267] When the exotherm is finished, 50 g of a solution of SPS (0.33% by weight in water) is cast in 130 min (the casting of initiator lasts the time of the casting of F2, the aging of the prepolymer PP2, the casting of F3 and the first aging of the amphoteric water-soluble polymer PA4), and simultaneously a second fraction F2 composed of 17.1 g of water, 107.8 g of AM (50% by weight in water), 29.3 g of AI and 0.8 g SMS, in 60 min. Once the F2 fraction has been cast, the PP2 prepolymer is left to age for 10 min (PO2 polymerization to form the PP2 prepolymer takes place during the casting of the F2 fraction and during aging).

[0268] Third sequence: Amphoteric water-soluble polymer PA3

[0269] A third fraction F3, composed of 17.1 g of water, 54.9 g of AM (50% by weight in water), 6.0 g of AI (100% by weight in water), 0.1 g of SMS, is then started in 50 min. At the end of the addition of fraction F3, the polymer is left to age for 10 min (the polymerization PO3 to form the amphoteric water-soluble polymer PA3 takes place during the casting of fraction F3 and during the aging).

[0270] Once aging is complete, 222.3 g of water are added as well as 0.15 g of SPS. A check of the change in viscosity is carried out every 15 min. When the desired viscosity is reached, the reaction is stopped by adding 2.4 g of sodium bisulfite (40% by weight in water) and 189.8 g of water. A further aging of 60 min is applied before cooling, then the amphoteric water-soluble polymer PA4 is obtained. The solution comprising the amphoteric water-soluble polymer PA3 has a pH of 3.5, an active material of 20% and a viscosity of 9,100 cps. PA3 has a molecular weight obtained by GPC-Malls of 4,650,000 g / mol.

[0271] Example 3: Preparation of mixtures M1 to M-7 according to the invention and counter-examples M-CE1 to M-CE2:

[0272] The cationic water-soluble polymers PCAi to PcAs are mixed with an aluminum salt to form the mixtures according to the invention M1 to M-7 and counter-examples M-CE1 / CE2 in the ratios as presented in Table 1 below:

[0273] [Tables 1] Polymer mixture Aluminum salt Ratio by weight of aluminum salt / P CA M-CE1 PcAl PAC 10 HB 10 / 90 M-CE2 PcAl PAC 10 HB 75 / 25 Ml PcAl PAC 10 HB 60 / 40 M-2 PcAl PAC 10 HB 33 / 67 M-3 PcAl PAC 10 HB 25 / 75 M-4 PcAl PAC 18 33 / 67 M-5 PcAl ACH 33 / 67 M-6 PcA2 PAC 10 HB 33 / 67 M-7 PcA3 PAC 10 HB 33 / 67

[0274] Table 1 - Composition of the mixtures according to the invention M1 to M-7 and counter-examples M-CE1 / CE2. CE = counter-example Example 4: Application Testing

[0275] The wet pulp used in all application examples is obtained by disintegration of dry pulp in order to obtain a final aqueous concentration of 1% by mass of cellulose fibers and fillers in water. It is a neutral pH pulp composed of 100% recycled cardboard fibers.

[0276] Vacuum Drainage Performance Evaluation (DDA)

[0277] The DDA (Dynamic Drainage Analyzer) makes it possible to automatically determine the time (in seconds) required to drain a fibrous suspension under vacuum on a fabric. The polymers are added to the wet paste (0.6 liters of paste at 1.0% by mass) in the DDA cylinder with stirring at 1000 revolutions per minute: T = 0 seconds: stirring of the paste T= 10 seconds: addition of the cationic aldehyde water-soluble polymer mixture and / or the aluminum salt, or of the cationic aldehyde water-soluble polymer and the aluminum salt separately T= 20 seconds: addition of the amphoteric water-soluble polymer T= 30 seconds: stop stirring and drain under vacuum at 200 mBar for 60 seconds.

[0278] The pressure under the canvas is recorded as a function of time. When all the water is evacuated from the fibrous mat, the air passes through it, causing a break in slope to appear on the curve representing the pressure under the canvas as a function of time. The time, expressed in seconds, recorded at this break in slope corresponds to the draining time. The shorter the time, the better the vacuum draining.

[0279] Performance in dry strength application (Dry Strength Resin (DSR)), weight at 80 g.m2

[0280] The necessary quantity of pulp is taken so as to finally obtain a sheet with a weight of 80 g.m2.

[0281] The wet paste is introduced into the vat of the dynamic form and is kept stirring. The various components of the system are injected into this paste according to the predefined sequence. A contact time of 30 to 45 seconds is generally observed between each addition of polymer.

[0282] Paper forms are made with an automatic dynamic form: a blotter and the forming fabric are placed in the bowl of the dynamic form before starting the rotation of the bowl at 1000 rpm 1 and building the water wall. The treated pulp is distributed on the water wall to form the fibrous mat on the forming fabric.

[0283] Once the water is drained, the fibrous mat is recovered, pressed under a press delivering 4 bars, then dried at 117 °C. The resulting sheet is conditioned overnight in a room with controlled humidity and temperature (50% relative humidity and 23 °C). The dry strength properties of all the sheets obtained by this procedure are then measured.

[0284] Burst is measured with a Messmer Buchel M 405 burst tester according to TAPPI T403 om-02 standard. The result is expressed in kPa. The burst index, expressed in kPa.m2 / g, is determined by dividing this value by the grammage of the sheet tested. The results are expressed in Table 3 as a percentage improvement in the burst index compared to a blank (no additive).

[0285] The dry breaking length (DBL) in the dry state is measured in the machine direction with a Testometric AX tensile tester according to TAPPI T494 om-01 standard. The result is expressed in km. The results are expressed in Table 3 as a percentage improvement compared to a blank (no additive).

[0286] Different combinations were made to demonstrate the benefits of the invention and are summarized in Table 2. When the aluminum salt and the aldehyde cationic water-soluble polymer are added separately and not via mixture M, they are added in parallel (example CE3). In test CE9, polymer PA1 is added before mixture M-2. In test CE10, polymer PA1 and mixture M-2 are added in parallel.

[0287] [Tables2] Examples Mixtures Aluminum salt Aldehydic cationic water-soluble polymer Amphoteric water-soluble polymer CEI PAC 10 HB PA1 CE2 PcAl PA1 CE3 PAC 10 HB PcAl PA1 El Ml PA1 E2 M-2 PA1 E3 M-3 PA1 CE4 M-CE1 PA1 CE5 M-CE2 PA1 E5 M-4 PA1 E6 M-5 PA1 E7 M-6 PA1 CE6 M-2 PA-CE1 CE7 M-2 CE8 PA1 CE9 M-2 PA1 CE10 M-2 PA1 CE11 P CAI E8 M-7 PA1 E9 M-2 PA2 E10 M-2 PA3

[0288] Table 2 - Combinations made. E = invention and CE = counter-example

[0289] The application performances of the different examples are summarized in Table 3.

[0290] In the CE4 test, the prepared M-CE2 mixture is unstable and therefore did not allow application performance to be measured.

[0291] [Tables3] Example % DD A % DBL % burst IEC 39.8 21.5 26.2 CE2 16.4 20.3 28.2 CE3 55.4 23.7 32.6 El 59.6 28.1 39.9 E2 64.5 33.1 45.1 E3 60.5 32 40 CE4 - - - CE5 54.9 21.7 27.6 E5 63.7 32.9 44.9 E6 64.8 33.3 45.4 E7 65.2 34 45.9 CE6 33.1 22.4 29.1 CE7 32.4 15.1 22.0 CE8 1 14.1 20.1 CE9 25.8 18.4 20.9 CE10 22.6 15.8 18.7 CE11 40.5 17.5 25.8 E8 62.1 32.8 42.0 E9 65.1 32.7 44.3 E10 63.6 31.8 41.7

[0292] Table 3 - Application performance. E = invention and CE = counter-example

[0293] These results demonstrate that the combination between (1) a mixture M comprising an aluminum salt and a cationic aldehyde water-soluble polymer (2) in a precise ratio, and (3) an amphoteric water-soluble polymer obtained according to a particular process, added (4) in sequence to a fibrous cellulose suspension makes it possible to improve the physical properties of the paper or cardboard.

Claims

1. Claims A method of manufacturing a sheet of paper or cardboard comprising the addition, in sequence, to a fibrous suspension of at least: 1) a mixture M comprising at least: (a) an aluminum salt; (b) a water-soluble cationic aldehyde polymer; the aluminum salt and the cationic water-soluble polymer having a weight ratio of between 60:40 and 20:80; 2) an amphoteric water-soluble polymer PA comprising at least: a) a cationic hydrophilic monomer Apha; b) an anionic hydrophilic monomer BPHA; c) a non-ionic hydrophilic monomer CPHA; (d) a structuring system comprising at least: (i) a compound I, different from the anionic hydrophilic monomer BPHA, chosen from: allylsulfonic acid, methallylsulfonic acid, allyl disulfonic acid, methallyl disulfonic acid, their salts and their mixtures; (ii) a compound II of formula (2): [Chem. 8] Rf" Formula (2) R1 and R2 being, independently of each other, a hydrogen atom, a methyl group, an ethyl group, an isopropyl group or a CH2-OH group; Ri and R2 not both being a hydrogen atom; the amphoteric water-soluble polymer PA being obtained according to the following steps: A) formation of a solution (SI) comprising at least a first fraction (Fl) comprising (1) at least one monomer chosen from the monomers Apha, BPHA and CPHa and / or (2) at least one compound chosen from compounds I and II; B) polymerization 1 (PO1) of the fraction Fl to form a solution of a first prepolymer PP1; C) addition, to the solution comprising PP1, of a second fraction (F2) comprising (1) at least one monomer selected from monomers A PHA, Bpha and Cpha and / or (2) at least one compound selected from compounds I and II; D) polymerization 2 (PO2) of fraction F2 on PP1 to form a solution of a second prepolymer (PP2); E) addition, to the solution comprising PP2, of a third fraction (F3) comprising (1) at least one monomer selected from monomers A PHA, Bpha and Cpha and / or (2) at least one compound selected from compounds I and II; F) polymerization 3 (PO3) of fraction F3 on PP2 to form a solution comprising the amphoteric water-soluble polymer PA; at least one of the fractions Fl, F2 or F3 comprising at least one Apha monomer, at least one of the fractions Fl, F2 or F3 comprising at least one BPHa monomer, at least one of the fractions Fl, F2 or F3 comprising at least one CPHa monomer, at least one of the fractions Fl, F2 or F3 comprising at least one compound I, and at least one of the fractions Fl, F2 or F3 comprising at least one compound II.

2. Method according to claim 1, characterized in that the mixture M is added to a thick paste and in that the amphoteric water-soluble polymer PA is added to a diluted paste.

3. Method according to one of claims 1 or 2, characterized in that the mixture M and the amphoteric water-soluble polymer PA have a weight ratio of between 1:50 and 50:

1.

4. Method according to one of the preceding claims, characterized in that the aluminum salt is an aluminum polychloride or an aluminum chlorohydrate.

5. Method according to one of the preceding claims, characterized in that the mixture M comprises a quantity of cationic aldehyde water-soluble polymer greater than the quantity of aluminum salt.

6. Method according to one of the preceding claims, characterized in that compound II is chosen from: N,N-dimethylacrylamide, N,N-diethylacrylamide, N-isopropylacrylamide, N-methylolacrylamide and mixtures thereof.

7. Method according to one of the preceding claims, characterized in that that the monomers Apha, BPHA and CPHA represent 100 mol% of the monomers of the amphoteric water-soluble polymer PA.

8. Method according to one of the preceding claims, characterized in that the amphoteric water-soluble polymer PA has a molar quantity of cationic monomer Apha greater than the molar quantity of anionic monomer BPHA.

9. Method according to one of the preceding claims, characterized in that at least one of the fractions F1, F2 or F3 comprises (1) at least one monomer chosen from the monomers Apha, BPHA and CPHA and (2) at least one compound chosen from compounds I and II.

10. Process according to one of the preceding claims, characterized in that the three fractions F1, F2 and F3 comprise (1) at least one monomer chosen from the monomers Apha, BPHA and CPHA and (2) at least one compound chosen from compounds I and II.

11. Method according to one of the preceding claims, characterized in that the Apha and BPHA monomers are added in different fractions.

12. Method according to the preceding claim 11, characterized in that: (i) the fraction F1 comprises at least 50 mol% of the Apha monomers relative to the total quantity of Apha monomer in the amphoteric water-soluble polymer PA, or at least 50 mol% of the B pha monomers relative to the total quantity of BPHA monomer in the amphoteric water-soluble polymer PA, and; (ii) the fraction F3 comprises at least 50 mol% of the Apha monomers relative to the total quantity of Apha monomer in the amphoteric water-soluble polymer PA, or at least 50 mol% of the B pha monomers relative to the total quantity of BPHA monomer in the amphoteric water-soluble polymer PA.