Novel polymers and methods for their preparation

Abstract

The present invention relates to a novel anionic water-soluble polymer, to a process for its preparation and to its use, in particular in the papermaking field.

Description

TECHNICAL FIELD

[0001] The present invention relates to a new anionic water-soluble polymer, to a process for its preparation and to its use, in particular in the papermaking field. BACKGROUND

[0002] The papermaking industry is always seeking to improve its method of producing paper, paperboard or similar, in particular in terms of cost reduction, yield, productivity and quality of the final product.

[0003] This is particularly true for the packaging industry which seeks paper, paperboard or similar with better dry strength properties, in particular in order to address current ecological problems and to replace plastic packaging. This improvement sought should not be at the expense of productivity.

[0004] By definition, the dry strength of paper is the strength of the sheet, paperboard or similar in the dry state. Conventionally, mechanical strength values provide a measure of the dry strength. One can cite in particular the burst strength, the tensile strength, the compressive strength, the delamination strength…

[0005] It is known to use water-soluble cationic polymers in order to improve the strength properties of paper. Due to their nature, these polymers can directly adhere to anionic cellulose and impart a cationic charge, making the anionic cellulose bind to anionic polymers which adhere to the cellulose fibers, thus improving the dry strength of the sheet.

[0006] JP 2012 251252 discloses a papermaking process involving an amphoteric polymer.

[0007] The most commonly used cationic polymers are compounds of the type of cationic starch, polyamide epichlorohydrin (PAE), polyamidoamine epichlorohydrin (PAAE), optionally glyoxalated cationic polyacrylamide, polyvinylamine, polyethyleneimine (PEI), polyamine epichlorohydrin resin (PA) or polymers obtained by Hofmann degradation.

[0008] This combination of cationic and anionic polymers for improving the dry strength is well known. In particular, it has been proposed in document FR 2880901 B1 to combine a cationic polymer with an anionic polymer, the aim of this combination being to provide an efficient system for the dry strength of the sheet.

[0009] The problem of this combination between the two polymers in solution is the loss of drainage properties of the paper. By reducing the drainage properties, the speed of the paper machine is reduced, which leads to a significant decrease in productivity.

[0010] This problem is mainly due to anionic polymers synthesized by liquid process and having a low molecular weight. In the liquid process, the increase of the molecular weight leads to an increase of the viscosity. Beyond a certain molecular weight, it is no longer possible to obtain a liquid.

[0011] To overcome this problem, manufacturers have to turn to other polymerization techniques, such as gel polymerization, in order to obtain higher molecular weights. The polymers obtained from these polymerization techniques are in solid form.

[0012] The use of polymers in solid form presents many drawbacks, such as:

[0013] - the obligation for the manufacturer to have an on-site powder dilution system;

[0014] - the increase of the size of the installation, thus increasing its footprint;

[0015] - the increase of the energy consumption and the maintenance;

[0016] - the management of the powder stock;

[0017] - the management of the preliminary dissolution of the powder;

[0018] - more frequent and complex maintenance.

[0019] The main problem remains the dissolution of the high molecular weight polymer powder. Indeed, the dissolution of this polymer is important and requires technical knowledge in order to avoid the risk of bad dissolution which would lead to the formation of aggregates on the paper, thus leading to the weakening of the paper or even worse, to the fouling of the machine which can lead to the complete stoppage and maintenance of the entire production unit. Moreover, this high molecular weight polymer in powder form leads to excessive flocculation and has a negative impact on the formation of the paper, which has a negative impact on the mechanical properties of the paper.

[0020] Manufacturers have been looking for a solution which would make it possible to obtain a paper with good dry strength properties, while maintaining satisfactory drainage properties and which would simplify their installation due to the use of a liquid form polymer.

[0021] The Applicant has surprisingly found that the synthesis of the polymer according to the process of the application makes it possible to meet the needs of the manufacturers, without being detrimental to the latter.

[0022] The use of the polymer resulting from the application is part of the general principle of improving the properties of the product, more particularly the dry strength and the drainage properties. The better performance of the polymer according to the application makes it possible to reduce the amount of product required for the application, which therefore means a reduction in the emissions of greenhouse gases (such as CO2) associated with the production and use of synthetic polymers. SUMMARY

[0023] The present invention relates to an anionic water-soluble polymer comprising:

[0024] - at least one anionic monomer A;

[0025] - at least one non-ionic monomer B;

[0026] - at least one structuring system comprising:

[0027] (i) at least one compound I different from the at least one monomer A, selected from the group consisting of allyl sulfonic acid, methylallyl sulfonic acid, allyl disulfonic acid, methylallyl disulfonic acid, salts thereof and mixtures thereof;

[0028] (ii) at least one compound II of formula II different from the at least one monomer B:

[0029]

[0030] R1and R2are, independently of each other, a hydrogen atom, a methyl group, an ethyl group, an isopropyl group or a CH2-OH group;

[0031] R1and R2are not both hydrogen atoms (R1≠ H when R2= H; R2≠ H when R1= H).

[0032] The anionic water-soluble polymer is obtained according to the following steps:

[0033] a) forming a solution (S1) comprising a first fraction (F1) containing (1) at least one monomer selected from monomers A and B and (2) at least one compound selected from compounds I and II;

[0034] b) subjecting fraction F1 to a polymerization 1 (PO1) so as to form a solution of a first gradient polymer (PG1);

[0035] c) adding to the solution comprising PG1 a second fraction (F2) containing (1) at least one monomer selected from monomers A and B and (2) at least one compound selected from compounds I and II;

[0036] d) subjecting fraction F2 to a polymerization 2 (PO2) on PG1 so as to form a solution of a second gradient polymer (PG2);

[0037] e) adding to the solution comprising PG2 a third fraction (F3) containing (1) at least one monomer selected from monomers A and B and (2) at least one compound selected from compounds I and II;

[0038] f) subjecting fraction F3 to a polymerization 3 (PO3) on PG2 so as to form a solution comprising an anionic water-soluble polymer and

[0039] At least one of the fractions F1, F2 or F3 contains at least one monomer A, at least one of the fractions F1, F2 or F3 contains at least one monomer B, at least one of the fractions F1, F2 or F3 contains at least one compound I and at least one of the fractions F1, F2 or F3 contains at least one compound II.

[0040] The anionic water-soluble polymer does not contain cationic monomers and zwitterionic monomers.

[0041] In the present invention, the first and second gradient polymers are prepolymers.

[0042] The present invention also relates to a process for the preparation of the anionic water-soluble polymer. It is a step-by-step polymerization process.

[0043] The present invention also relates to a process for the production of paper and paperboard using the anionic water-soluble polymer.

[0044] The present invention also relates to the use of the anionic water-soluble polymer in the recovery of hydrocarbons (oil and / or gas); in drilling or cementing; in the stimulation of hydrocarbon wells (oil and / or gas), for example, hydraulic fracturing, conformance, diversion; in water treatment in open, closed or semi-closed cycles; in the treatment of fermentation mash, in the treatment of sludges; in construction; in wood treatment; in the treatment of hydraulic compositions (concrete, cement, mortar and aggregates); in the mining industry; in the formulation of cosmetics; in the field of batteries; in the formulation of detergents; in the production of textiles; in geothermal technology; in the production of diapers; or in agriculture.

[0045] The present invention also relates to the use of the anionic water-soluble polymer as a flocculant, coagulant, binder, fixative, viscosity reducer, thickener, absorbent, friction reducer, drainage agent, filler retention agent, dewatering agent, conditioning agent, stabilizer, fixative, film former, sizing agent, superplasticizer, clay inhibitor or dispersant. DETAILED DESCRIPTION

[0046] "Polymer" means a copolymer prepared from at least two different monomers with at least one anionic monomer A and at least one non-ionic monomer B and from a structuring system comprising at least one compound I and at least one compound II. It can optionally comprise at least one hydrophobic monomer and / or crosslinker and / or transfer agent.

[0047] Water-soluble polymer is understood to mean a polymer which, when it is stirred and dissolved in deionized water at 25°C at a concentration of 10 g-L -1 of polymer gives rise to an aqueous solution free of insoluble particles.

[0048] Throughout the present specification, the viscosity is measured in aqueous solution at 25°C using a Brookfield viscometer with a Brookfield LV3 module.

[0049] In the present specification, the person skilled in the art is considered able to determine the appropriate module and speed of the Brookfield viscometer as a function of the viscosity range to be measured. This type of measurement is in fact part of the common general knowledge of the person skilled in the art.

[0050] According to the present application, "X and / or Y" is understood to mean "X" or "Y" or "X and Y".

[0051] Another part of the present application is all possible combinations between the different disclosed embodiments, whether they are preferred embodiments or embodiments given as examples. Furthermore, when a numerical range is indicated, the limits are part of these ranges. The present disclosure also includes all combinations of the limits of these numerical ranges. For example, the numerical range "1-20, preferably 5-15" means the disclosure of the ranges "1-5", "1-15", "5-20" and "15-20" as well as the numerical values 1, 5, 15 and 20.

[0052] Anionic water-soluble polymer

[0053] The anionic water-soluble polymer according to the present application comprises:

[0054] - at least one anionic monomer A;

[0055] - at least one non-ionic monomer B;

[0056] - at least one structuring system comprising:

[0057] (i) at least one compound I different from the at least one monomer A, selected from the following: allyl sulfonic acid, methylallyl sulfonic acid, allyl disulfonic acid, methylallyl disulfonic acid, salts thereof and mixtures thereof;

[0058] (ii) at least one compound II of formula II different from the at least one monomer B:

[0059]

[0060] R1and R2are, independently of each other, a hydrogen atom, a methyl group, an ethyl group, an isopropyl group or a CH2-OH group;

[0061] R1and R2are not both hydrogen atoms (R1≠ H when R2= H; R2≠ H when R1= H).

[0062] The polymer does not contain cationic monomers and zwitterionic monomers.

[0063] Monomer component

[0064] The anionic water-soluble polymer according to the application is a synthetic polymer. It can comprise one or more anionic monomers (referred to as "one or more monomers A").

[0065] Advantageously, the anionic monomer or the other anionic monomer(s) A can be chosen from a large group. These monomers can have a vinyl function, in particular acrylic, maleic, fumaric, malonic, itaconic or allyl function. They can also contain a carboxylate, phosphonate, phosphate, sulfonate or another anionic charge group. Preferred monomers belonging to this category are, for example, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, acrylamidoundecanoic acid, 3-acrylamido-3-methylbutanoic acid, maleic anhydride, 2-acrylamido-2-methylpropanesulfonic acid (ATBS), vinylsulfonic acid, vinylphosphonic acid, 2-sulfoethyl methacrylate, sulfopropyl methacrylate, sulfopropyl acrylate, allylphosphonic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanedisulfonic acid, salts thereof and mixtures thereof. Preferably, these monomers are acrylic acid or itaconic acid, even more preferably acrylic acid.

[0066] Thus, in a particular embodiment of the application, the one or more anionic monomers A can be salified.

[0067] Salification is understood to mean the replacement of the proton of at least one acid function of the anionic monomer A of the -R(O)-OH (R=P, S or C) type by a metal cation to form a salt of the -R(O)-OX (X is a metal cation) type. In other words, the non-salified form corresponds to the acid form of the monomer, for example R-C(=0)-OH in the case of a carboxylic function, while the salified form of the monomer corresponds to the R-C(=0)-O-X + form, X + corresponding to an alkali metal cation. The acid functions of the water-soluble polymer can be partially or totally salified.

[0068] The salified form advantageously corresponds to a salt of an alkali metal (Li, Na, K...), an alkaline earth metal (Ca, Mg...) or an ammonium (for example an ammonium ion or a tertiary ammonium). The preferred salt is a sodium salt.

[0069] Salification can be carried out before or after polymerization.

[0070] The anionic water-soluble polymer advantageously comprises from 1 to 99 mol%, preferably from 2 to 70 mol%, more preferentially from 3 to 50 mol%, even more preferentially from 5 to 35 mol% of one or more anionic monomers A.

[0071] In a particular embodiment of the application, when the anionic monomer A is 2-acrylamido-2-methylpropane sulfonic acid, the anionic monomer A is a hydrated form of 2-acrylamido-2-methylpropane sulfonic acid. The hydrated form of ATBS is a particular form of ATBS which can be obtained by controlled crystallization of ATBS monomer. The hydrated form of ATBS is described in document US 10,759,746.

[0072] The anionic water-soluble polymer can comprise one or more non-ionic monomers (referred to as “one or more monomers B”).

[0073] Advantageously, the one or more non-ionic monomers B can be chosen especially from the group comprising water-soluble vinyl monomers. Preferred monomers belonging to this class are, for example, acrylamide, methacrylamide, N-vinyl formamide (NVF), N-vinyl acetamide, N-vinyl pyrrolidone (NVP), N-vinyl imidazole, N-vinyl succinimide, acryloyl morpholide (ACMO), acryloyl chloride, glycidyl methacrylate, glyceryl methacrylate, bis-acetone acrylamide, (meth)acrylic acid hydroxyalkyl ester (C1-C3 alkyl), (meth)acrylic acid thioalkyl ester (C1-C3 alkyl), and mixtures thereof. Preferably, the monomer is acrylamide.

[0074] The anionic water-soluble polymer advantageously comprises from 1 to 99 mol%, preferably from 30 to 98 mol%, more preferably from 50 to 97 mol%, even more preferably from 65 to 95 mol% of non-ionic monomers B.

[0075] The anionic water-soluble polymer can optionally comprise one or more hydrophobic monomers (referred to as “one or more monomers C”).

[0076] Advantageously, the one or more hydrophobic monomers C can be chosen from the group consisting of propoxylated, ethoxylated or ethoxylated and propoxylated (meth)acrylic acid esters having a C4-C 30 alkyl, arylalkyl (C4-C 30 alkyl, C4-C 30 aryl) chain; propoxylated, ethoxylated or ethoxylated and propoxylated (meth)acrylamide derivatives having a C1-C3 alkyl, arylalkyl (C4-C 30 alkyl, C4-C 30 aryl) or dialkyl (C4-C 30 alkyl) chain; alkylaryl sulfonate salts (C4-C 30 alkyl, C4-C 30 aryl), or having a C4-C 30 alkyl, arylalkyl (C4-C 30 alkyl, C4-C 30Mono- or disubstituted amides of (meth)acrylic amides with propoxylated, ethoxylated, or ethoxylated and propoxylated (meth)acrylic amide chains; having a C4-C4 bond. 30 Alkyl, arylalkyl (C4-C) 30 Alkyl, C4-C 30 aryl), or C4-C 30 Derivatives of dialkyl chains propoxylated, ethoxylated, or ethoxylated and propoxylated (meth)acrylamides; alkyl aryl sulfonates (C4-C 30 Alkyl, C4-C 30 Aryl groups and their mixtures.

[0077] Anionic water-soluble polymers advantageously contain at least 1 mol% of a hydrophobic monomer C. Anionic water-soluble polymers may not contain the hydrophobic monomer C.

[0078] When the anionic water-soluble polymer according to the invention contains one or more hydrophobic monomers C, they are present in an amount that makes the polymer water-soluble.

[0079] The amounts of different monomers will be adjusted by those skilled in the art so as not to exceed 100 mol% during the preparation of the water-soluble polymer. Preferably, monomers A and B account for 100 mol% of the monomers in the anionic water-soluble polymer.

[0080] Structured system

[0081] The structured systems of anionic water-soluble polymers include:

[0082] (i) at least one compound I;

[0083] (ii) at least one compound II.

[0084] Compound I, as used in the context of this invention, is selected from the following: allyl sulfonic acid, methyl allyl sulfonic acid, allyl disulfonic acid, methyl allyl disulfonic acid, their salts, and mixtures thereof. Preferably, compound I is methyl allyl sulfonic acid, such as sodium methyl allyl sulfonate.

[0085] Salts are advantageously formed from salts of alkali metals (Li, Na, K, etc.), alkaline earth metals (Ca, Mg, etc.), or ammonium (e.g., ammonium ions or tertiary ammonium). Sodium salts are preferred.

[0086] The anionic water-soluble polymer advantageously contains 500 to 50,000 ppm, preferably 1,000 to 20,000 ppm, and more preferably 2,000 to 10,000 ppm of compound I relative to the total weight of monomers A and B (+optionally monomer C) of the anionic water-soluble polymer.

[0087] Compound II, as used in the context of this invention, has the general formula:

[0088]

[0089] R1and R2are independently of each other a hydrogen atom, a methyl group, an ethyl group, an isopropyl group or a CH2-OH group;

[0090] R1and R2are not both hydrogen atoms (R1≠ H when R2= H; R2≠ H when R1= H).

[0091] The compound II used in the context of the present application is advantageously selected from the group consisting of N,N-dimethylacrylamide, N,N-diethylacrylamide, N,N- isopropylacrylamide, N-hydroxymethylacrylamide and mixtures thereof. Preferably, the compound II is N,N-dimethylacrylamide.

[0092] The anionic water-soluble polymer according to the present application advantageously comprises 500 to 50,000 ppm, preferably 1000 to 20,000 ppm, more preferably 2000 to 10,000 ppm of compound II, relative to the total weight of monomers A and B (+ optional monomer C) of the anionic water-soluble polymer.

[0093] The mass ratio of compound I to compound II in the anionic water-soluble polymer is advantageously comprised between 0.01 and 100, preferably between 0.1 and 10.

[0094] In a preferred embodiment according to the present application, the amount of compound I is greater than the amount of compound II. Thus, the mass ratio of compound I to compound II is advantageously greater than 1 and less than or equal to 100, preferably greater than 1 and less than or equal to 10.

[0095] Optionally

[0096] The anionic water-soluble polymer can further comprise at least one cross-linking agent. The cross-linking agent can be selected from polyethylenically unsaturated monomers (having at least two unsaturated functional groups), such as vinyl functional groups, especially allyl, acrylic acid functional groups, or from monomers having at least two epoxy functional groups. The cross-linking agent can be mentioned, for example, methylenebisacrylamide (MBA), triallylamine, tetraallylammonium chloride, 1,2-dihydroxyethylenebis-(N- acrylamide) and mixtures thereof. Preferably, the cross-linking agent is methylenebisacrylamide (MBA).

[0097] The amount of cross-linking agent in the anionic water-soluble polymer is advantageously comprised between 5 and 5000 ppm, more preferably between 50 and 3000 ppm, relative to the total weight of monomers A and B (+ optional monomer C) of the anionic water-soluble polymer.

[0098] In a particular embodiment according to the present application, the anionic water-soluble polymer does not comprise a cross-linking agent.

[0099] The anionic water-soluble polymer according to the application can further comprise at least one transfer agent, for example chosen from methanol, isopropanol, sodium hypophosphite, 2-mercaptoethanol and mixtures thereof. We can also mention transfer agents of xanthate, dithiocarbonates, dithio carbamates and trithiocarbonates type and mixtures thereof. Preferably, the transfer agent is sodium hypophosphite.

[0100] The amount of transfer agent in the anionic water-soluble polymer is advantageously from 10 to 10,000 ppm, more preferably from 50 to 5000 ppm, relative to the total weight of monomers A and B (+ optional monomer C) of the anionic water-soluble polymer.

[0101] In a particular embodiment of the application, the anionic water-soluble polymer does not comprise a transfer agent.

[0102] Physical properties of the water-soluble polymer

[0103] The weight average molecular weight of the water-soluble polymer is advantageously from 1,000,000 to 25,000,000 Dalton, preferably from 2,000,000 to 15,000,000 Dalton, more preferably from 3,000,000 to 10,000,000 Dalton. This is the weight average molecular weight.

[0104] The weight average molecular weight is preferably measured by gel permeation chromatography.

[0105] The anionic water-soluble polymer is obtained and used in liquid form.

[0106] The viscosity of the solution comprising the anionic water-soluble polymer is advantageously from 1000 to 50,000 cps, preferably from 5000 to 20,000 cps.

[0107] Renewable origin

[0108] In a preferred embodiment according to the application, the anionic water-soluble polymer is prepared from compounds (monomers and / or compounds I and II) which are at least partially of renewable, non-fossil origin.

[0109] In the context of the present invention, the expression "renewable, non-fossil origin" means a source of a compound derived from biomass or synthesis gas, i.e. resulting from one or more chemical transformations of one or more raw materials having a natural, non-fossil origin. The expressions "biosourced" or "bioresourced" can also be used to characterize the renewable, non-fossil origin of a compound. The renewable, non-fossil origin of a compound includes renewable, non-fossil raw materials derived from a circular economy and which have previously been recycled one or more times in a process for recycling a material derived from biomass, for example resulting from depolymerization of a polymer or conversion of pyrolysis oil.

[0110] According to the present invention, "at least partially renewable, non-fossil origin" means that the carbon content of biological origin is preferably between 5% and 100% by weight, preferably at least 30%, more preferably at least 50%, even more preferably at least 70%, even more preferably at least 90% and even more preferably it consists of 100% of carbon of biological origin, relative to the total weight of carbon of the compound.

[0111] In the context of the present invention, the standard ASTM D6866-21, method B, is used to characterize the biosourced nature of a compound and to determine the biosourced carbon content of said compound. This value is expressed as a percentage by weight of carbon of biological origin relative to the total weight of carbon in the compound.

[0112] Gradient

[0113] The anionic water-soluble polymer according to the present invention is a gradient polymer.

[0114] A polymer having a gradient structure is a polymer comprising at least two monomers, wherein the composition of the monomers varies gradually, unlike a block polymer in which the composition varies abruptly, and unlike a random polymer in which the composition does not vary continuously. In a gradient polymer, the intra- and inter-chain repulsion is less due to the gradual variation of the composition over the length of the polymer chain.

[0115] The gradient can be formed by a spontaneous or forced gradient. Spontaneous gradient polymerization is due to the difference in reactivity of the monomers. Forced gradient polymerization includes varying the composition of the monomers introduced throughout the polymerization process.

[0116] The forced method includes (1) introducing a first portion of monomers into a reactor, (2) adding at least one additional portion of monomers, which is advantageously different from the first portion, and (3) polymerizing the monomers introduced into the reactor. The polymerization of the monomers begins upon introduction of the first portion.

[0117] The addition of the additional fractions of monomers can occur in parallel to the introduction of the first fraction of monomers into the reactor (so the introduction of the fractions can start and end at the same time). Thus, the fractions can have different flow rate addition profiles but the same total addition duration. In fact, the addition flow rate of the fractions can be continuous or discontinuous and constant or not constant throughout the addition. Alternatively, the start of the feeding of the first monomer (first fraction) into the reactor can precede the start of the addition of the second monomer fraction. Alternatively, the first and second fractions of monomers can be introduced simultaneously but the duration of the addition of the second fraction can be greater than the duration of the introduction of the first fraction into the reactor. This embodiment also applies to the process using at least 3 fractions of monomers.

[0118] According to the process of the application, the anionic water-soluble polymer obtained is formed by stepwise addition of monomers, in other words, it is preferably a forced gradient process.

[0119] The process according to the application comprises 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 others. Preferably, the fractions F1, F2 and F3 are different from each other (F1≠ F2≠ F3). By different fractions is meant fractions having different compositions in terms of monomers (ratio and / or nature of the monomers) and / or compounds I and II (ratio and / or nature of the compounds I and II).

[0120] Polymerization process

[0121] The process for the stepwise preparation of an anionic water-soluble polymer according to the application comprises the following steps:

[0122] a) forming a solution (S1) comprising at least one first fraction (F1) containing (1) at least one monomer chosen from monomers A and B and (2) at least one compound chosen from compounds I and II;

[0123] b) subjecting the fraction F1 to polymerization 1 (PO1) so as to form a solution of a first gradient polymer (PG1);

[0124] c) adding to the solution comprising PG1 a second fraction (F2) containing (1) at least one monomer chosen from monomers A and B and (2) at least one compound chosen from compounds I and II;

[0125] d) subjecting the fraction F2 to polymerization (PO2) on PG1 so as to form a solution of a second gradient polymer (PG2);

[0126] e) adding to the solution comprising PG2 a third fraction (F3) containing (1) at least one monomer chosen from monomers A and B and (2) at least one compound chosen from compounds I and II;

[0127] f) polymerizing (PO3) fraction F3 on PG2 so as to form an anionic water-soluble polymer and

[0128] at least one of fractions F1, F2 or F3 containing at least one monomer A, at least one of fractions F1, F2 or F3 containing at least one monomer B, at least one of fractions F1, F2 or F3 containing at least one compound I and at least one of fractions F1, F2 or F3 containing at least one compound II.

[0129] The method can comprise the addition of additional fractions.

[0130] The improved properties of the anionic water-soluble polymer according to the application can be due to the fact that the polymerization is carried out step by step and continuously, i.e. without interruption.

[0131] By "step by step" it is meant that the polymerization of the monomers of the anionic water-soluble polymer is carried out in several fractions, while not being interrupted, i.e. the addition of these fractions is carried out continuously and the polymerization does not stop. Thus, the different steps a) to f) are carried out continuously. In other words, the first fraction of monomers can be poured (in a flow form) and polymerized to form a first gradient polymer PG1 which continues to polymerize with fraction F2 so as to form a gradient polymer PG2 which itself continues to polymerize with fraction F3 so as to obtain the anionic water-soluble polymer at the end of the polymerization.

[0132] Preferably, at least one of fractions F1, F2 and F3 of the method is different from the others. Preferably, fractions F1, F2 and F3 are different from each other (F1 ≠ F2 ≠ F3). The addition of different fractions during the polymerization process allows obtaining a gradient of the composition of the anionic water-soluble polymer.

[0133] In the polymerization process according to the application, the sum of the molar percentages of the monomers of the different fractions is equal to the sum of the molar percentages of the monomers of the anionic water-soluble polymer.

[0134] Step a), forming a solution (S1 ) comprising a first fraction (F1 )

[0135] Solution (S1 )

[0136] Solution S1 advantageously consists of:

[0137] - a solvent;

[0138] - an initiator;

[0139] - a first fraction F1.

[0140] The solvent is advantageously water, or a solvent in which the monomers and the anionic water-soluble polymer are soluble. Preferably, the solvent is water.

[0141] The polymerization initiator used can be any compound that dissociates into free radicals under the polymerization conditions, for example: organic peroxides, hydroperoxides, hydrogen peroxide, persulfates, azo compounds and redox couples. It is preferable to use a water-soluble initiator. In certain cases, it is advantageous to use a mixture of various polymerization initiators, for example a mixture of a redox catalyst and an azo compound. Preferably, the polymerization initiator is a persulfate.

[0142] In a particular embodiment, the solution S1 is formed by mixing the solvent, the initiator and the fraction F1 in the polymerization vessel.

[0143] In this particular embodiment, the fraction F1 can be added to the solvent / initiator mixture all at once, in several portions or poured (in a flow) i.e. gradually (for example dropwise). Preferably, the fraction F1 is added all at once to the polymerization vessel.

[0144] In a particular embodiment of the application, the initiator and the fraction F1 are poured (in a flow) into the polymerization vessel containing the solvent. The initiator and the fraction F1 can be added separately or pre-mixed. Preferably, the initiator and the fraction F1 are added separately.

[0145] In a preferred embodiment of the application, the initiator is added continuously throughout the process (steps a) to f)). In this case, the initiator is advantageously added in parallel with the different fractions during the different polymerization steps and during possible aging steps of the different gradient polymers (PG1 and PG2) and the anionic water-soluble polymer.

[0146] In this preferred embodiment of the application, the duration of the pouring of the initiator is between 50 minutes and 560 minutes, preferably between 130 minutes and 430 minutes.

[0147] First fraction (F1)

[0148] Advantageously, the fraction F1 comprises between 10 and 40% by weight, preferably between 15 and 30% by weight of monomers (A and / or B, + optionally C) relative to the total weight of monomers (A + B + optionally C) of the anionic water-soluble polymer.

[0149] The fraction F1 advantageously comprises between 0 and 50 mol%, preferably between 0 and 35 mol% of anionic monomers A relative to the total number of moles of monomers in the fraction F1.

[0150] Part F1 advantageously contains 50 to 100 mol%, preferably 65 to 100 mol% of non-ionic monomers B, relative to the total number of moles of monomers in part F1.

[0151] Part F1 advantageously contains 250 to 30,000 ppm, preferably 500 to 10,000 ppm, more preferably 1000 to 7000 ppm of compound I, relative to the total weight of monomers A and B (+ optional monomers C) of the anionic water-soluble polymer.

[0152] Part F1 advantageously contains 250 to 30,000 ppm, preferably 500 to 10,000 ppm, more preferably 1000 to 5000 ppm of compound II, relative to the total weight of monomers A and B (+ optional monomers C) of the anionic water-soluble polymer.

[0153] The different monomers and compounds making up part F1 are advantageously added in the form of solutions. These solutions can be added all at once, in several portions or poured (in a flow) alone or in mixture to the polymerization vessel in order to form solution S1. Preferably, the addition is carried out all at once in mixture.

[0154] When part F1 is poured (in a flow), the pouring advantageously lasts from 10 minutes to 80 minutes, preferably from 40 minutes to 70 minutes.

[0155] In a preferred embodiment, part F1 is prepared in the reactor (polymerization vessel) before the addition of the initiator.

[0156] In a preferred embodiment, part F1 contains at least one monomer B, at least one compound I and at least one compound II.

[0157] Step b), polymerization of part F1 in order to form the first gradient polymer (PG1)

[0158] Polymerization PO1

[0159] Before the polymerization PO1, the air of the polymerization vessel can be replaced with an inert gas such as nitrogen or argon.

[0160] The polymerization PO1 is advantageously a free radical polymerization. A polymerization initiator can be used, in particular an initiator that dissociates into free radicals under the polymerization conditions.

[0161] The polymerization PO1 is advantageously initiated at a temperature of from 70 to 90°C, preferably from 75 to 85°C. A cooling device is advantageously used to control the polymerization temperature so as not to exceed 95°C.

[0162] The polymerization PO1 advantageously lasts from 10 minutes to 80 minutes, preferably from 40 minutes to 70 minutes.

[0163] The polymerization is advantageously initiated at the time of contact of the first monomers, the solvent and the initiator. That is to say, the duration of the polymerization PO1 advantageously corresponds to the duration of the pouring of the fraction F1.

[0164] Gradient polymer (PG1)

[0165] At the end of the polymerization PO1, a gradient polymer (or prepolymer) PG1 is obtained.

[0166] In a particular embodiment according to the application, the gradient polymer PG1 is allowed to age for 5 minutes to 60 minutes, preferably 10 minutes to 30 minutes.

[0167] By "allowed to age", it is meant that, after the end of the polymerization, the temperature of the solvent is maintained between 80 and 90°C, so as to allow the increase in viscosity by the internal branching phenomenon (branching) of the polymer. The definition of aging relates to all the steps of the polymerization process.

[0168] Step c), addition of the second fraction (F2) to the solution comprising PG1

[0169] Second fraction F2

[0170] Advantageously, the fraction F2 comprises 30 to 80% by weight, preferably 40 to 70% of monomers (A and / or B, + optionally C) relative to the total weight of the monomers (A + B + optionally C) of the anionic water-soluble polymer.

[0171] The fraction F2 advantageously comprises 0 to 70 mol%, preferably 0 to 50 mol% of anionic monomers A relative to the total number of moles of monomers in the fraction F2.

[0172] The fraction F2 advantageously comprises 30 to 100 mol%, preferably 65 to 100 mol% of non-ionic monomers B relative to the total number of moles of monomers in the fraction F2.

[0173] The fraction F2 advantageously comprises 250 to 30,000 ppm, preferably 500 to 10,000 ppm, more preferably 1000 to 5000 ppm of compound I relative to the total weight of the monomers A and B (+ optionally monomers C) of the anionic water-soluble polymer.

[0174] The fraction F2 advantageously comprises 250 to 30,000 ppm, preferably 500 to 10,000 ppm, more preferably 1000 to 5000 ppm of compound II relative to the total weight of the monomers A and B (+ optionally monomers C) of the anionic water-soluble polymer.

[0175] The different monomers and compounds constituting F2 are advantageously added in the form of a solution. This solution can be added all at once, in several portions or in the form of a flow to the polymerization vessel, alone or in mixture. Preferably, the addition is carried out in mixture and in the form of a flow.

[0176] The pouring of the fraction F2 is advantageously continued for 10 minutes to 100 minutes, preferably 30 minutes to 90 minutes.

[0177] In a preferred embodiment, the fraction F2 contains at least one monomer A and B, at least one compound I and at least one compound II.

[0178] Step d), polymerization of the fraction F2 on PG1 so as to form a second gradient polymer (PG2)

[0179] Polymerization (PO2)

[0180] The polymerization PO2 is carried out as a continuation of the polymerization PO1 ; the polymerization PO2 is carried out under the same temperature conditions, advantageously 70 to 90°C.

[0181] The polymerization PO2 is advantageously continued for 10 minutes to 100 minutes, preferably 30 minutes to 90 minutes.

[0182] The polymerization PO2 starts from the addition of the first monomer of the fraction F2.

[0183] Advantageously, the duration of the polymerization PO2 corresponds to the duration of the pouring of the fraction F2.

[0184] Gradient polymer (PG2)

[0185] At the end of the polymerization PO2, a gradient polymer (or prepolymer) PG2 is obtained.

[0186] In a particular embodiment according to the application, the gradient polymer PG2 is allowed to age for 5 to 60 min, preferably 10 to 30 min.

[0187] Step e), addition of a third fraction (F3) to the solution containing PG2

[0188] Fraction F3

[0189] Advantageously, the fraction F3 comprises 5 to 40% by weight, preferably 10 to 30% of monomers (A and / or B + optionally C) relative to the total weight of the monomers (A + B + optionally C) of the anionic water-soluble polymer.

[0190] The fraction F3 advantageously comprises 0 to 50 mol%, preferably 0 to 35 mol% of anionic monomers A relative to the total number of moles of monomers in the fraction F3.

[0191] Part F3 advantageously comprises 50 to 100 mol%, preferably 65 to 100 mol% of non-ionic monomers B, relative to the total number of moles of monomers in part F3.

[0192] Part F3 advantageously comprises 0 to 10,000 ppm, preferably 10 to 5000 ppm, more preferably 20 to 1000 ppm of compound I, relative to the total weight of monomers A and B (+ optional monomers C) of the anionic water-soluble polymer.

[0193] Part F3 advantageously comprises 0 to 10,000 ppm, preferably 0 to 1000 ppm of compound II, relative to the total weight of monomers A and B (+ optional monomers C) of the anionic water-soluble polymer.

[0194] The different monomers and compounds making up F3 are advantageously added in the form of solutions. These solutions can be added all at once, in several portions or in a flow (i.e. dropwise) either individually or in a mixture to the polymerization vessel. Preferably, the addition is carried out in a mixture and in a flow.

[0195] The pouring of part F3 is advantageously carried out for 10 minutes to 100 minutes, preferably 30 minutes to 90 minutes.

[0196] In a preferred embodiment, part F3 contains at least one monomer B and at least one compound I. Step f), the polymerization of part F3 is carried out in PG2 so as to form the anionic water-soluble polymer polymerization (PO3)

[0197] The polymerization PO3 is carried out as a continuation of the polymerization PO2; the polymerization PO3 is carried out under the same conditions of time and temperature as PO2 (advantageously at 70 to 90°C for 10 minutes to 100 minutes, preferably 30 minutes to 90 minutes).

[0198] The polymerization PO3 starts from the addition of the first monomer of part F3.

[0199] Advantageously, the duration of the polymerization PO3 corresponds to the duration of the pouring of part F3.

[0200] At the end of the polymerization PO3, the anionic water-soluble polymer is obtained.

[0201] In a particular embodiment according to the application, the anionic water-soluble polymer is allowed to age for 5 minutes to 60 minutes, preferably 10 minutes to 30 minutes, before removing the residual monomers.

[0202] The reaction is advantageously terminated by the addition of an excess of initiator and / or water; this step serves to eliminate the residual monomers that can be present in the solution comprising the anionic water-soluble polymer.

[0203] One or more optional steps

[0204] The process according to the application can also comprise additional steps and is not limited to the steps described above.

[0205] In a particular embodiment according to the application, the polymerization process according to the application can comprise the addition of additional fractions constituting the final anionic water-soluble polymer.

[0206] In a preferred embodiment according to the application, after step f) of polymerization of PO3, the anionic water-soluble polymer is allowed to age for 10 minutes to 100 minutes, preferably 30 minutes to 90 minutes. In the case of the addition of additional fractions, the aging occurs after the last polymerization step.

[0207] In a particular embodiment according to the application, a crosslinking agent and / or a transfer agent is added during at least one of the steps described above.

[0208] In a preferred embodiment according to the application, a crosslinking agent is added to fraction F1 and / or fraction F2.

[0209] When a crosslinking agent is added, it is advantageously chosen from the crosslinking agents described previously.

[0210] When a crosslinking agent is added, its amount is advantageously 5-5000 ppm, preferably 50-3000 ppm, relative to the total weight of the anionic water-soluble polymer (monomers A, B and optionally C).

[0211] In a preferred embodiment according to the application, a transfer agent is added to fraction F1 and / or fraction F2.

[0212] When a transfer agent is added, it is advantageously chosen from the transfer agents described previously.

[0213] When a transfer agent is added, its amount is advantageously 10-10,000 ppm, preferably 50-5000 ppm, relative to the total weight of the anionic water-soluble polymer (monomers A, B and optionally C).

[0214] Advantageously, the anionic water-soluble polymer obtained by the process according to the application can be used without post-treatment other than the salification of said polymer. The anionic water-soluble polymer can be used immediately after step f), or after one or more optional steps, in solution (without drying or prior purification), or after having been dried.

[0215] Papermaking process

[0216] The present invention also relates to a process for producing paper or paperboard comprising (1) adding the anionic water-soluble polymer according to the present invention to an aqueous suspension of fibres, advantageously cellulose fibres, and (2) forming the paper or paperboard. Thus, the present invention relates to the use of an anionic water-soluble polymer in a papermaking process.

[0217] The different steps of the process for producing paper, paperboard or the like are known and according to the techniques using the knowledge of the person skilled in the art; it is not necessary to describe these processes in more detail since they remain known and conventional as far as the knowledge of the person skilled in the art is concerned; if necessary, reference can be made to the following document: Handbook for Pulp & Paper Technologists, 3rd edition, G. A. Smook.

[0218] According to the present invention, the anionic water-soluble polymer is added in the papermaking process, before or after the formation of the paper, paperboard or the like. Thus, the contact of the cellulose material with the polymer of the present invention can be carried out in different ways, in particular according to the conventional methods known to the person skilled in the art.

[0219] The anionic water-soluble polymer can be added to the cellulose material in the form of a diluted or undiluted aqueous solution. The anionic water-soluble polymer can be applied by impregnation techniques or can be added directly to the fibre suspension at any point where dry strength agents are usually introduced in the papermaking process.

[0220] Thus, the polymer according to the present invention can be introduced into the thick stock (English "thick stock") or into the diluted stock (English "thin stock"). The polymer according to the present invention can be added at the mixing pump, before the headbox or the wire mesh. Preferably, the polymer is introduced before the headbox.

[0221] Preferably, the polymer according to the present invention is injected industrially into the fibre suspension, i.e. before it is diluted by the pulp water (thick stock). The consistency of the pulp is about 1-5% by weight of cellulose fibres.

[0222] The papermaking process according to the present invention can be used for any type of pulp, for example virgin fibre pulp (kraft, sulfite), recycled fibre pulp, deinked pulp, mechanical pulp and thermomechanical pulp.

[0223] In a preferred embodiment according to the present invention, the anionic water-soluble polymer according to the present invention is added together with a cationic water-soluble polymer in order to enhance the dry strength properties of the paper while maintaining good drainage properties.

[0224] The cationic water-soluble polymer is advantageously chosen from the following: PAE (polyamino polyamide epichlorohydrin), polyvinylamine, glyoxylated polyacrylamide, PEI (polyethyleneimine), PA (polyamine, epichlorohydrin-dimethylamine resin), polymer obtained by Hofmann degradation, polyacrylamide, starch and mixtures thereof. Preferably, the cationic water-soluble polymer is a polymer obtained by Hofmann degradation.

[0225] Advantageously, the mass ratio of the anionic water-soluble polymer to the cationic water-soluble polymer according to the application is between 1 / 10 and 10 / 1.

[0226] Advantageously, the anionic water-soluble polymer and the cationic water-soluble polymer are added directly to the fibrous suspension before the formation of the paper sheet.

[0227] The anionic water-soluble polymer and the cationic water-soluble polymer can be added, alone or in mixture, in any order of introduction, at a single injection point or at two injection points.

[0228] As desired, the papermaking process according to the application can also comprise the addition of other additives and / or polymers; as non-limiting examples, mention can be made of: biocides, coagulants, crosslinkers, flocculants, starches...

[0229] Use

[0230] The application also relates to the use of the anionic water-soluble polymer in the recovery of hydrocarbons (oil and / or gas); in drilling or cementing; in the stimulation of hydrocarbon wells (oil and / or gas), for example, hydraulic fracturing, conformance, diversion; in water treatment in open, closed or semi-closed cycles; in the treatment of fermentation broths, in the treatment of sludge; in construction; in wood treatment; in the treatment of hydraulic compositions (concrete, cement, mortar and aggregates); in the mining industry; in the formulation of cosmetics; in the field of batteries; in the formulation of detergents; in the production of textiles; in geothermal technology; in the production of diapers; or in agriculture.

[0231] The application also relates to the use of the anionic water-soluble polymer as a flocculant, coagulant, binder, fixative, viscosity reducer, thickener, absorbent, friction reducer, drainage agent, filler retention agent, dewatering agent, conditioning agent, stabilizer, fixative, film former, sizing agent, superplasticizer, clay inhibitor or dispersant.

[0232] In order to illustrate the application in a non-limiting manner, the application and its advantages will become more apparent in the examples given below.

[0233] Example

[0234] List of abbreviations:

[0235] AMD: Acrylamide (monomer B)

[0236] AA: Acrylic acid (monomer A)

[0237] DMAM: Dimethylacrylamide (compound II)

[0238] SMS: Sodium methylallyl sulfonate (compound I)

[0239] SPS: Sodium persulfate (polymerization initiator)

[0240] ATBS: 2-Acrylamido-2-methylpropanesulfonic acid (monomer A)

[0241] IA: Itaconic acid (monomer A)

[0242] DMAEMA: Dimethylaminoethyl methacrylate (cationic polymer)

[0243] Description of GPC-Malls characterization of the molecular weight

[0244] Gel permeation chromatography is a method that makes it possible to separate macromolecules as a function of their hydrodynamic volume; it is coupled with a Malls detector, which makes it possible to measure the scattering of light from multiple angles.

[0245] The synthesized polymers were analyzed under the following conditions:

[0246] - Instrument: GPC-2

[0247] - Columns: Shodex SB-807-HQ and SB-805 custom

[0248] - Method:

[0249] * Temperature: 30°C

[0250] * Mobile phase: 0.5 M NaNO3, HEPES (pH = 8), 100 ppm NaN3

[0251] * Injection: 100 μL

[0252] * Flow rate: 0.3 mL / min

[0253] * Detection:

[0254] (i) Light scattering detector (Malls): absolute molar mass

[0255] (ii) Refractometry (RI): concentration

[0256] The viscosity is measured at 25°C using a Brookfield viscometer with a Brookfield LV3 module at a speed of 6 rpm.

[0257] Preparation of polymers 1-5 (P1-P5(INV)) according to the application

[0258] Polymer 1 (P1)

[0259] First step: Gradient polymer or prepolymer PG1

[0260] In a 1 liter reactor equipped with a mechanical stirrer, a thermometer, a condenser and a gaseous nitrogen immersion bar, a first fraction F1 consisting of 165.6 g of water, 71.2 g of acrylamide (50% by weight aqueous solution), 1 g of citric acid, 0.5 g of dimethylacrylamide and 0.68 g of sodium methylallyl sulfonate is introduced as a starter. The medium is heated by a water bath and maintained at a temperature of 79-81 °C. The addition of 0.05 g of sodium persulfate makes it possible to initiate the starter and to initiate the polymerization of the monomers (PO1) in order to form a first gradient polymer PG1.

[0261] Second step: Gradient polymer or prepolymer PG2

[0262] When the exothermic reaction is finished, the flow is started: initiator (30 g of SPS, 0.33% by weight aqueous solution) 130 min, while the second fraction F2, consisting of 28.8 g of water, 124.9 g of acrylamide (50% by weight aqueous solution), 23 g of acrylic acid 100%, 0.5 g of dimethylacrylamide and 0.33 g of sodium methacryl sulfonate, 50 min above. After pouring fraction F2, the gradient polymer PG2 is allowed to age for 10 minutes (the polymerization PO2 for the formation of the gradient polymer PG2 is carried out during the pouring of fraction F2 and during the aging).

[0263] Third step: Polymer 1 (P1)

[0264] Then, a third fraction F3 consisting of 136.8 g of water, 61.1 g of acrylamide (50 wt% aqueous solution), 0.01 g of sodium methylallyl sulfonate was flowed for 60 minutes. At the end of the addition of fraction F3, the polymer was allowed to age for 10 minutes (polymerization PO3 to form the polymer was carried out during the pouring and aging of fraction F3). Once the aging was finished, 165.3 g of water and 0.15 g of sodium persulfate were added. When the desired viscosity was reached, the reaction was stopped by adding 2.4 g of sodium bisulfite (40 wt% aqueous solution) and 165.2 g of water. It was aged for another 60 minutes before cooling. The solution containing the polymer 1 (P1) had a pH of 3.5, 15 wt% of active substance, a viscosity of 8900 cps, and a molecular weight of 4,580,000 Da obtained by GPC-Malls.

[0265] Polymers 2-5 (P2 to P5 (INV)) according to the application

[0266] The protocol to prepare polymer 1 (P1) was replicated, while changing the composition of the different fractions, in order to produce polymers 2-5 (P2-P5); the composition of the different fractions used to obtain these polymers is summarized in Table 1.

[0267] Preparation of counterexample polymers 6 to 11 (CE1 to CE6)

[0268] Polymer 6 (CE1)

[0269] This polymer was prepared in one step.

[0270] In a 1 liter reactor equipped with a mechanical stirrer, a thermometer, a condenser and a gaseous nitrogen immersion bar, 663.7 g of water, 262.9 g of acrylamide (50 wt% aqueous solution), 23.5 g of acrylic acid 100%, 0.5 g of dimethylacrylamide and 0.65 g of sodium methylallyl sulfonate were introduced. The pH was adjusted to 6 by adding 23 g of NaOH (50 wt% aqueous solution). The reactor was heated to 35°C. The reaction was initiated by adding 0.16 g of VA 044.

[0271] When the maximum temperature was reached, 60 minutes of aging were allowed before adding 2.4 g of sodium bisulfite (40 wt% aqueous solution). It was aged for another 60 minutes before cooling. The solution containing the counterexample polymer 6 (CE1) had a pH of 7, 15 wt% of active substance, a viscosity of 7000 cps, and a molecular weight of 1,400,000 Da obtained by GPC-Malls.

[0272] Polymer 7 (CE2)

[0273] Polymer 7 was prepared according to the same protocol as polymer 6, while changing the monomer composition of the polymer.

[0274] Polymer 8 (CE3)

[0275] Polymer 8 was prepared according to the same scheme (i.e., 3 steps) as polymer 1, except that this polymer was obtained without compound II (DMAM).

[0276] Polymer 9 (CE4)

[0277] Polymer 9 (CE4) was prepared according to the same scheme (i.e., 3 steps) as polymer 1, except that this polymer was obtained in the absence of compound I (SMS) and compound II (DMAM) but in the presence of the transfer agent sodium hypophosphite (Hypo).

[0278] Polymer 10 (CE5)

[0279] Polymer 10 (CE5) was prepared according to the same scheme as polymer 1, but with only two steps.

[0280] Polymer 11 (CE6)

[0281] Polymer 11 (CE6) was prepared according to the same scheme (i.e., 3 steps) as polymer 1, while the monomer composition of the polymer was changed to obtain an amphoteric polymer.

[0282] The composition of the different parts of the preparation method of polymer 1-11 is summarized in Table 1a.

[0283] In Table 1a, the monomer content represents the molar weight percentage of the AMD (or AA, ATBS, or IA) monomer relative to the total molar weight of the corresponding monomer in the total portion. Therefore, for example, the sum of the percentages of AMD monomer in the three portions equals 100%.

[0284] The contents of Compound I (SMS) and Compound II (DMAM) are expressed in ppm by weight relative to the total weight of one or more monomers in the three parts.

[0285] [Table 1a]

[0286]

[0287]

[0288]

[0289] Table 1a: Composition of one or more polymerization methods for obtaining polymers P1 to P5 and counterexamples P6 to P11 (CE1 to CE6).

[0290] The physicochemical properties of the obtained polymers are shown in Table 1b below:

[0291] [Table 1b]

[0292]

[0293]

[0294] Table 1b: Physicochemical properties of polymers P1 to P5 and counterexamples CE1 to CE6 according to the present invention.

[0295] Table 2 summarizes the compositions of the different fractions (monomers A and B, compounds I and II) used to prepare polymers P1 to P5 (INV) and CE1 to CE6.

[0296]

[0297] Table 2: Composition of each part in the synthesis of polymers 1-9.

[0298] Application testing

[0299] Polymers 1 to 11 can be used in combination with the following cationic polymers:

[0300] HF 31: A polymer of SNF line, obtained by Hofmann degradation of polyvinylamine, cationic, with a viscosity of 200 cps and 21% by weight of dry extract.

[0301] VP 450: A polymer of SNF line, a cationic polyvinylamine obtained by hydrolysis of polyvinylformamide, with a viscosity of 1380 cps and a dry extract of 19.2 wt%.

[0302] The drainage and dry strength properties of polymer 1-11 in combination with HF 31 and VP 450 were evaluated under the following conditions.

[0303] The wet pulp used in all application examples was obtained by breaking down dry pulp to achieve a final moisture content of 1% by weight. This wet pulp is a neutral pH pulp composed of 100% recycled paperboard fibers.

[0304] Evaluation of vacuum drainage performance (DDA)

[0305] The DDA (“Dynamic Drainage Analyzer”) automatically determines, in seconds, the time required for vacuum drying of the fiber suspension on the fabric. The polymer is added to the wet pulp (0.6 liters of pulp, 1.0 wt%) in the cylinder of the DDA with stirring at 1000 rpm.

[0306] T=0s: Stirring the pulp

[0307] T = 10s: Add one or more polymers

[0308] T=30s: Stop stirring and vacuum dry for 60s at 200mbar.

[0309] The pressure under the fabric was recorded as a function of time. When all the water had been removed from the fiber pad, air passed through the pad, causing a sudden change in the slope of the curve representing the pressure under the fabric as a function of time. The time, expressed in seconds, was recorded at this point corresponding to the change in slope of the draining time. The shorter the time, the better the vacuum draining.

[0310] Performance in dry strength applications, basis weight 80 g.m -2

[0311] Collect the necessary amount of pulp to obtain a final weight of 80g.m. -2 The paper.

[0312] The wet pulp is introduced into the barrel of the dynamic paper forming machine and kept agitated. Different portions of the system are then injected into the pulp in a preset sequence. Generally, a contact time of 30-45 seconds should be maintained between each addition of polymer.

[0313] Paper forming is achieved by an automated dynamic paper forming machine: absorbent paper and forming fabric are placed in the drums of the dynamic paper forming machine before the drums begin to rotate at 1000 rpm and form a water wall. The treated pulp is distributed on the water wall to form a fibrous mat on the forming fabric.

[0314] Once the water was drained, the fiber pad was recovered, extruded under an output pressure of 4 bar, and then dried at 117°C. The resulting paper was conditioned overnight in a room with controlled humidity and temperature (50% relative humidity and 23°C). The dry strength properties of all the paper obtained through this step were then measured.

[0315] Bursting resistance was measured using a Messmer Buchel M 405 bursting resistance tester according to standard TAPPI T403 om-02.

[0316] According to standard TAPPI T494 om-01, the dry fracture length is measured in the machine direction using a Testometric AX traction device.

[0317]

[0318]

[0319] Table 3: Drainage and dry strength results of compositions containing cationic polymer HF 31 or VP 450 with polymers 1 to 5 (INV) according to the present invention and with comparative polymers 6 to 11 (CE).

[0320] Interestingly, it is noted that, compared to polymers prepared by conventional methods (polymers 6 and 7), polymers (1 to 5) of the present invention, which are combined with cationic polymers, have improved drainage performance (DDA) and mechanical properties (burst resistance; DBL: dry rupture) compared to polymers (polymers 8 and 9) which lack a structured system, lack a third part (polymer 10), or contain cationic monomers (polymer 11).

Claims

1. An anionic water-soluble polymer, comprising: - At least one anionic monomer A; - At least one nonionic monomer B; - At least one structured system comprising: (i) at least one compound I, which is different from at least one monomer A and is selected from: allyl sulfonic acid, methyl allyl sulfonic acid, allyl disulfonic acid, methyl allyl disulfonic acid, salts thereof, and mixtures thereof; (ii) At least one compound of formula II, which is different from at least one monomer B: ， R1 and R2 are independently hydrogen atoms, methyl, ethyl, isopropyl or CH2-OH groups; R1 and R2 are not both hydrogen atoms. The polymer contains neither cationic nor zwitterionic monomers; The anionic water-soluble polymer is obtained according to the following steps: a) Forming a solution (S1) comprising a first portion (F1), the first portion (F1) containing (1) at least one monomer selected from monomers A and B and (2) at least one compound selected from compounds I and II; b) A portion of F1 is polymerized to form a solution of the first gradient polymer (PG1); c) Add a second part (F2) to a solution containing PG1, the second part (F2) containing (1) at least one monomer selected from monomers A and B and (2) at least one compound selected from compounds I and II; d) A portion of F2 is polymerized on PG1 to form a solution of a second-gradient polymer (PG2); e) Add a third part (F3) to a solution containing PG2, said third part (F3) containing (1) at least one monomer selected from monomers A and B and (2) at least one compound selected from compounds I and II; f) A portion of F3 is polymerized on PG2 (PO3) to form a solution containing an anionic water-soluble polymer, wherein at least one of F1, F2, or F3 contains at least one monomer A, at least one of F1, F2, or F3 contains at least one monomer B, at least one of F1, F2, or F3 contains at least one compound I, and at least one of F1, F2, or F3 contains at least one compound II. The anionic water-soluble polymer does not contain a crosslinking agent.

2. The anionic water-soluble polymer according to claim 1, characterized in that... The at least one anionic monomer A is selected from the following: acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, acrylamidodecanoic acid, 3-acrylamido-3-methylbutyric acid, maleic anhydride, 2-acrylamido-2-methylpropanesulfonic acid (ATBS), vinyl sulfonic acid, vinyl phosphonic acid, 2-sulfoethyl methacrylate, sulfopropyl methacrylate, sulfopropyl acrylate, allyl phosphonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropanedisulfonic acid, their salts, and mixtures thereof.

3. The anionic water-soluble polymer according to claim 1 or 2, characterized in that... The at least one nonionic monomer B is selected from the following: acrylamide, methacrylamide, N-vinylformamide (NVF), N-vinylacetamide, N-vinylpyrrolidone (NVP), N-vinylimidazolium, N-vinylsuccinimide, acrylmorpholine (ACMO), acryloxychloride, glycidyl methacrylate, glyceryl methacrylate, diacetone acrylamide, hydroxyalkyl (meth)acrylate, thioalkyl (meth)acrylate, and mixtures thereof; wherein the alkyl group is C1-C3.

4. The anionic water-soluble polymer according to any one of the preceding claims, characterized in that, The anionic water-soluble polymer contains 500 to 50,000 ppm of compound I relative to the total weight of monomers A and B.

5. The anionic water-soluble polymer according to any one of the preceding claims, characterized in that, The anionic water-soluble polymer contains 500 to 50,000 ppm of compound II relative to the total weight of monomers A and B.

6. The anionic water-soluble polymer according to any one of the preceding claims, characterized in that... Compound II is selected from the following: N,N-dimethylacrylamide, N,N-diethylacrylamide, N,N-isopropylacrylamide, N-hydroxymethylacrylamide, and mixtures thereof.

7. The anionic water-soluble polymer according to any one of the preceding claims, characterized in that, The mass ratio of compound I to compound II is from 0.01 to 100.

8. A method for stepwise preparation of anionic water-soluble polymers, comprising: - At least one anionic monomer A; - At least one nonionic monomer B; - At least one structured system comprising: (i) at least one compound I, which is different from at least one monomer A and is selected from: allyl sulfonic acid, methyl allyl sulfonic acid, allyl disulfonic acid, methyl allyl disulfonic acid, salts thereof, and mixtures thereof; (ii) At least one compound of formula II, which is different from at least one monomer B: ， R1 and R2 are independently hydrogen atoms, methyl, ethyl, isopropyl or CH2-OH groups; R1 and R2 are not both hydrogen atoms; The polymer does not contain cationic monomers or zwitterionic monomers, and The anionic water-soluble polymer does not contain a crosslinking agent; The method includes the following steps: a) forming a solution (S1) comprising at least a first portion (F1), wherein the first portion (F1) contains (1) at least one monomer selected from monomers A and B and (2) at least one compound selected from compounds I and II; b) A portion of F1 is polymerized to form a solution of the first gradient polymer (PG1); c) Add a second part (F2) to a solution containing PG1, the second part (F2) containing (1) at least one monomer selected from monomers A and B and (2) at least one compound selected from compounds I and II; d) A portion of F2 is polymerized on PG1 (PO2) to form a solution of a second-gradient polymer (PG2); e) Add a third part (F3) to a solution containing PG2, said third part (F3) containing (1) at least one monomer selected from monomers A and B and (2) at least one compound selected from compounds I and II; f) A portion of F3 is polymerized on PG2 (PO3) to form a solution containing an anionic water-soluble polymer, wherein at least one of F1, F2 or F3 contains at least one monomer A, at least one of F1, F2 or F3 contains at least one monomer B, at least one of F1, F2 or F3 contains at least one compound I, and at least one of F1, F2 or F3 contains at least one compound II.

9. The method according to claim 8, characterized in that... The initiator is added continuously throughout the process.

10. The method according to claim 8 or 9, characterized in that, Following step f) of polymerization (PO3), the method includes an aging step of 10 to 100 minutes.

11. A method for producing paperboard, comprising adding an anionic water-soluble polymer according to any one of claims 1-7 to an aqueous suspension of fibers and forming paper or paperboard.

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