Dialdehyde polymer production process

Abstract

The invention relates to a production process of dialdehyde polymer and its use in the paper industry and particularly in papermaking.

Description

[0001] DIALDEHYDE POLYMER PRODUCTION PROCESS

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The invention relates to a production process of dialdehyde polymer and its use in the paper industry and particularly in papermaking.

[0004] TECHNICAL BACKGROUND

[0005] The paper industry is in constant search for improvements of its manufacturing processes for paper, cardboard or the like, in particular with regard to costs reduction, yield, productivity and even the end-product properties.

[0006] The papermaking process typically involves the dispersion of dry market pulp obtained from cellulosic material to form a thick stock corresponding to a suspension of a cellulosic fibers having a concentration generally comprised between 2 and 5% by weight. The thick stock is then diluted to form a thin stock, with a fiber concentration comprised between 0.5 and 1% by weight before passing through the headbox and being homogeneously placed on a wire in the form of a fiber mat corresponding to the paper sheet before water removal. The water elimination is made through three successive steps, i) natural drainage of the water on the wire during transport to the mechanical pressing area, ii) mechanical pressing of the sheet by roller and iii) drying of the paper sheet to obtain the final product, all this water constitutes the white water.

[0007] During the preparation of the thick stock and the thin stock, various additives and polymers are added to the pulp suspension in order to give to the final product the desired properties, for example fillers which impart opacity, brightness, surface smoothness and printability.

[0008] One problem faced by papermakers is that some of the additives, in particular fillers, are removed from the paper sheet during the water elimination steps and end up in the white water. The white water also contains some cellulose fibers and cellulose fines (short cellulose fibers).

[0009] To minimize the cost and wastes generated, papermakers generally recycle these white water to form the thick and the thin stock and complete with fresh water. Glyoxalated polyacrylamides have been used for many years in the paper industry to impart wet and dry strength to the final papers. They are prepared by addition of glyoxal to a polyacrylamide. The double functionality of the glyoxal allows the polyacrylamide to create covalent bonds with cellulose fibers and the reversibility of the reaction make glyoxalated polyacrylamides perfect for temporary wet strength applications.

[0010] EP 2 820 188 Bl and US 9,873,986 B2 disclose aldehyde modified polyacrylamide-type polymers.

[0011] The Applicant has found a new way to reduce water consumption by preparing directly glyoxalated polyacrylamide using process water. The quantity of fresh water needed to produce the glyoxalated polyacrylamide is thus reduced without negatively impacting the wet and dry strength. It was unexpected to not negatively impact the properties of glyoxalated polyacrylamide as process water is known to contain large amount of dissolved compound and colloidal substances, for example fillers, which have been shown to interfere with many added chemicals.

[0012] The invention is especially interesting, when the glyoxalated polyacrylamides are prepared on site. The emission of greenhouse gases, such as CO2, is significantly reduced as glyoxalated polyacrylamide are transported in diluted solution due to its instability. With the process of the invention, there is a double ecological benefit in reducing the quantity of fresh water used and the greenhouse gas emissions linked to the preparation and transport of the glyoxalated polyacrylamides .

[0013] The new glyoxalated polyacrylamide production process of the invention is in line with the principle of environmental consciousness and the impact of industry and man on the planet. The new glyoxalated polyacrylamide production process optimizes the use of compounds during papermaking, allowing a reduction of the wastes generated, a reduction of the fresh water consumption, improve the quality of the wastewater rejected by paper production and reduce CO2 emissions linked to the transport of glyoxalated polyacrylamides.

[0014] The present invention is advantageously carried out using materials of biological origin, such as biomass, or recycled materials. The synthesis of the monomer used in the invention are advantageously a biological synthesis, for example, by enzymatic catalysis or extracted from renewable raw material. The energy used to carry out the process according to the invention is advantageously derived from a heat pump or of renewable origin, for example wind power, photovoltaic s, or, in particular for mobile installations, from fuel cells or lithium batteries.

[0015] SUMMARY OF THE INVENTION

[0016] The invention relates to a production process of dialdehyde polymer and its use in the paper industry and particularly in papermaking.

[0017] More particularly, the invention relates to a process for preparing a dialdehyde polymer comprising at least the following successive steps:

[0018] 1) mixing a base polymer with an aqueous solution comprising at least 10% by weight of process water, in order to form a solution SI of the base polymer; the base polymer comprising at least one non-ionic hydrophilic monomer selected from the group consisting of: acrylamide, methacrylamide, dimethylaminopropyl acrylamide, dimethylaminopropyl methacrylamide and mixture thereof and the amount of base polymer in the solution SI is comprised between 0.5 and 15% by weight wherein the process water is any one of the following, or a mixture thereof:

[0019] - white water,

[0020] - clarified water which corresponds to white water that has been filtered to remove solid particles having a particle size above 1 000 pm;

[0021] 2) mixing at least one dialdehyde with the solution SI, at a temperature of between 17 and 40°C, to form a solution S2; the dialdehyde is selected from the group consisting of: glyoxal, glutaraldehyde, 2,5- furandicarboxaldehyde, adipaldehyde, succinaldehyde, starch dialdehyde, 2,2 dimethoxyethanal and mixtures thereof and the solution S2 has an amount of dialdehyde of between 5 and 40% by weight relative to the weight of the base polymer

[0022] 3) adjusting the pH of the solution S2 to at least 8 and reacting the base polymer with the at least one dialdehyde, for between 2 minutes and 90 minutes, to form a solution S3 comprising a dialdehyde polymer;

[0023] 4) optionally, acidifying the solution S3 to a pH of between 2 and 4.

[0024] DESCRIPTION OF THE INVENTION

[0025] The process water is any one of the followings, or a mixture thereof: - white water,

[0026] - clarified water which corresponds to white water that has been filtered to remove solid particles having a particle size above 1 000 pm, preferably above 500 pm, more preferably above 100 pm. For example, the filtration can be carried out with a poly disc filter or a DAF (Dissolved Air Flotation).

[0027] The “particle size”, refers to the size of particles measured by conventional techniques, preferably with a laser measuring device, for instance a Zetasizer® Nano by Malvern®. Regardless of the shape of a particle, the particle size corresponds to the diameter of the sphere scattering in the same way as the particle. In the present invention, the “particle size” refers to the particle sizer distribution based on number distribution.

[0028] The solid particles are essentially aggregated cellulosic material (fiber fragments and fines), together with mineral fillers such as calcium carbonate, talc, and kaolin. They also include colloidal hydrophobic residues called pitch which originate from wood and recycled fibers

[0029] White water generally contains water, cellulose fibers and cellulose fines (short cellulose fibers), mineral fillers (for instance CaCO , talc, kaolin and pitch).

[0030] Preferably, process water is white water.

[0031] By “paper” is meant paper, cardboard and the like.

[0032] By “polymer” is meant a homopolymer or a copolymer. A homopolymer is a polymer composed of a single identical repeating unit, while a copolymer is composed of two or more different repeating units. Repeating units are chosen from: non-ionic hydrophilic monomers, cationic hydrophilic monomers, anionic hydrophilic monomers, zwitterionic hydrophilic monomers and hydrophobic monomers.

[0033] “Water-soluble polymer” is meant a polymer that yields an aqueous solution without insoluble particles when it is dissolved under stirring at 25°C and with a concentration of 10 g.L'1in deionized water.

[0034] By "hydrophilic monomer" is meant a monomer which has its coefficient, log(Kow), less than or equal to 1, wherein Kow is the n-octanol / water partition and is determined at 25 °C in an n- octanol / water mixture having a volume ratio of 1 / 1, at a pH of between 6 and 8. By "hydrophobic monomer" is meant a monomer which has its coefficient, log(Kow), greater to 1, wherein Kow is the n-octanol / water partition and is determined at 25 °C in an n- octanol / water mixture having a volume ratio of 1 / 1, at a pH of between 6 and 8.

[0035] The n-octanol-water partition coefficient, Kow, represents the ratio of concentrations (g / L) of a monomer between the n-octanol phase and the aqueous phase.

[0036] The n-octanol / water partition coefficient, Kow, is defined as follows:

[0037] Kow = [monomer]n-octonoi

[0038] [monomer]waterwith:

[0039] [monomer] n-octanoi = equilibrium concentration of the monomer in g / L in n-octanol

[0040] [monomer] water = equilibrium concentration of the monomer in g / L in deionized water.

[0041] In the entire specification, viscosities are measured with a Brookfield viscometer, at 25°C in aqueous solution.

[0042] In this specification, it is considered that the person skilled in the art is able to determine the Brookfield viscometer module and speed suitable according to the viscosity range to be measured. Indeed, this type of measurement is part of the general knowledge of the person skilled in the art.

[0043] As used herein, the expression "A and / or B" means "A, or B, or A and B".

[0044] The invention also includes all possible combinations of the various embodiments disclosed, whether they are preferred or exemplary embodiments when they are not mutually exclusive. Furthermore, where ranges of values are indicated, the end- values are part of these ranges. The disclosure also includes all combinations between the end-values of these ranges. For example, ranges "1-20, preferably 5-15", imply disclosure of the ranges "1-5", "1-15", "5-20" and "15-20".

[0045] All the particular and / or preferred embodiments described in the invention are combinable, provided they are not incompatible.

[0046] By “base polymer” is meant the polymer on which the dialdehyde is reacted. Process for preparing the dialdehyde polymer

[0047] The invention relates to a process for preparing a dialdehyde polymer comprising at least the following successive steps:

[0048] 1) mixing a base polymer with an aqueous solution comprising at least 10% by weight of process water, in order to form a solution SI of the base polymer; the base polymer comprising at least one non-ionic hydrophilic monomer selected from the group consisting of: acrylamide, methacrylamide, dimethylaminopropyl acrylamide, dimethylaminopropyl methacrylamide and mixtures thereof; the amount of base polymer in the solution SI is comprised between 0.5 and 15% by weight wherein the process water is any one of the followings, or a mixture thereof:

[0049] - white water,

[0050] - clarified water which corresponds to white water that has been filtered to remove solid particles having a particle size above 1 000 pm;

[0051] 2) mixing at least one dialdehyde with the solution SI, at a temperature of between 17 and 40°C, to form a solution S2; the dialdehyde is selected from the group consisting of: glyoxal, glutaraldehyde, 2,5- furandicarboxaldehyde, adipaldehyde, succinaldehyde, starch dialdehyde, 2,2- dimethoxyethanal and mixtures thereof and the solution S2 has an amount of dialdehyde of between 5 and 40% by weight relative to the weight of the base polymer

[0052] 3) adjusting the pH of the solution S2 to at least 8 and reacting the base polymer with the at least one dialdehyde, for between 2 minutes and 90 minutes, to form a solution S3 comprising a dialdehyde polymer;

[0053] 4) optionally, acidifying the solution S3 to a pH of between 2 and 4.

[0054] In step 1), the aqueous solution comprises at least 10 % by weight of process water, preferably at least 15% by weight of process water, more preferably at least 20 % by weight, more preferably at least 30% by weight, more preferably at least 50% by weight, more preferably at least 70% by weight, more preferably at least 90% by weight and even more preferably 100% by weight.

[0055] Preferably, the aqueous solution consists of process water and fresh water. Preferably, the process water is white water.

[0056] The amount of base polymer in the solution SI is comprised between 0.5 and 15% by weight, preferably between 1 and 13% by weight.

[0057] Step 2 )

[0058] By “dialdehyde” is meant a compound having 2 aldehyde groups or a compound wherein one or both of the aldehyde group(s) are protected with a protecting group (for example an acetal) and the aldehyde function is generated in situ in step 2).

[0059] The dialdehyde is selected from the group consisting of glyoxal, glutaraldehyde, 2,5- furandicarboxaldehyde, adipaldehyde, succinaldehyde, starch dialdehyde, 2,2 dimethoxyethanal, and mixtures thereof. Preferably the dialdehyde is glyoxal.

[0060] The weight concentration of dialdehyde is comprised between 5 and 40 % by weight relative to the weight of the base polymer, preferably between 10 and 35% by weight, more preferably between 15 and 30% by weight.

[0061] Step 2) is carried out at a temperature comprised between 17 and 40°C, preferably between 19 and 26 °C, in a reactor under stirring.

[0062] Step 2) preferably lasts between 2 minutes and 90 minutes, more preferably, between 5 minutes and 75 minutes.

[0063] In step 3), the pH is adjusted to at least 8, preferably 10 and even more preferably between 10 and 12 to obtain a solution S3 comprising a dialdehyde polymer. The pH adjustment can be carried out for example, using 10% by weight of a soda solution in water.

[0064] Step 3) lasts between 2 minutes and 90 minutes, preferably, between 5 and 75 minutes.

[0065] Step 3) is carried out at a temperature of between 17 and 40°C, preferably between 19 and 26°C, in a reactor under stirring.

[0066] The reaction between the dialdehyde and the base polymer is followed by an increase in the viscosity of the aqueous solution. In a particular embodiment of the invention, the solution S3 is directly used and injected into a paper pulp.

[0067] Once the desired viscosity is reached (0.1 to 20 000 cPs), step 4) may be carried out. The Brookfield viscosity is preferably measured for an aqueous solution containing 2 weight% of polymer, by weight of the solution.

[0068] Advantageously, the dialdehyde reaction is monitored via the measure of viscosity, turbidity, delta P... etc.

[0069] Preferably, the dialdehyde reaction is monitored via the measure of delta P, according to the following steps, preferably at a temperature maintained between 20 and 22°C during the reaction process prior to step 4): measuring the pressure of the solution S3 as a function of time after the solution S3 has passed through a tube calibrated in length (2.2 m) and diameter (2 mm), ending the reaction when a delta pressure increase of +300% is reached.

[0070] Step 4)

[0071] This step is preferably carried out at a temperature comprised between 10 and 40°C in a reactor, preferably under stirring and with the addition of acid. The acid may be, for example, concentrated sulfuric acid, and may preferably be added between 15 and 35°C.

[0072] At the end of step 3) or 4), an aqueous solution of dialdehyde polymer is obtained.

[0073] Additional step

[0074] The dialdehyde reaction can eventually comprise an additional step 5) comprising the addition of at least one dialdehyde to the aqueous solution obtained in step 4).

[0075] Advantageously the dialdehyde is selected from the group previously described. Preferably, the dialdehyde is the same as in step 2).

[0076] In a particular embodiment the weight concentration of dialdehyde added in step 5) is comprised between 5 and 40% by weight relative to the weight of the dialdehyde polymer, preferably between 10 and 35% by weight, more preferably between 15 and 30% by weight. Advantageously, the weight concentration of the dialdehyde added in step 5) is the same as in step 2).

[0077] The Brookfield viscosity of the solution comprising the dialdehyde polymer (from step 3), 4) or 5)) is advantageously between 0.1 and 20 000 cPs, preferably between 10 and 10000 cPs.

[0078] The Brookfield viscosity is preferably measured for an aqueous solution containing 2 weight% of polymer, by weight of the solution.

[0079] Base polymer composition

[0080] The base polymer comprises at least one non-ionic hydrophilic monomer selected from the group consisting of acrylamide, methacrylamide, dimethylaminopropyl acrylamide, dimethylaminopropyl methacrylamide and mixture thereof. Preferably, it comprises at least acrylamide.

[0081] The base polymer can optionally comprise additional monomer chosen from cationic hydrophilic monomers, anionic hydrophilic monomers, non-ionic hydrophilic monomers (different from acrylamide, methacrylamide, dimethylaminopropyl acrylamide and dimethylaminopropyl methacrylamide), zwitterionic hydrophilic monomers, hydrophobic monomers.

[0082] In a preferred embodiment, the base polymer comprises at least:

[0083] - one non-ionic hydrophilic monomer chosen from acrylamide, methacrylamide, dimethylaminopropyl acrylamide, dimethylaminopropyl methacrylamide and mixture thereof;

[0084] - one cationic hydrophilic monomer.

[0085] The base polymer advantageously comprises between 40 and 99 mol% of non-ionic hydrophilic monomer(s), preferably between 50 and 98 mol%, more preferably between 60 and 97 mol%, and even more preferably between 70 and 96 mol%.

[0086] The cationic hydrophilic monomer(s) used in the invention are chosen, in particular, from vinyl-type monomers, notably acrylamide, acrylic, allylic or maleic monomers possessing a protonable amine or ammonium function, advantageously quaternary ammonium.

[0087] Advantageously, the cationic hydrophilic monomer(s) used in the context of the invention are chosen from: diallyldialkyl ammonium salts such as diallyldimethylammonium chloride (DADMAC); acidified or quaternized salts of dialkyl-aminoalkyl(meth)acrylamides, such as (3-methacrylamidopropyl)trimethylammonium chloride (MAPTAC), (3- acrylamidopropyl)trirnethylarnmonium chloride (APTAC); acidified or quaternized salts of dialkylaminoalkyl acrylate, such as quaternized or salified dimethylaminoethyl acrylate (DMAEA); acidified or quaternized salts of dialkylaminoalkyl methacrylate, such as quaternized or salified dimethylaminoethyl methacrylate (DMAEMA); acidified or quaternized salts of N,N-dimethylallylamine; acidified or quaternized salts of diallylmethylamine; acidified or quaternized salts of diallylamine; acidified or quaternized salts of vinylamine obtained by the hydrolysis (basic or acid) of an amide group -N(R2)-CO- Ri with Ri and R2 being, independently, a hydrogen atom or an alkylated chain of 1 to 6 carbons, for example acidified or quaternized salts of vinylamine obtained by the hydrolysis of vinylformamide; acidified or quaternized salts of vinylamine obtained by Hofmann degradation; and mixtures thereof. Advantageously, the alkyl groups are C1-C5, preferably Ci- C3, and can be linear, cyclic, saturated or unsaturated chains. Preferably, the hydrophilic cationic monomer is diallyldimethylammonium chloride.

[0088] The base polymer advantageously comprises between 1 and 60 mol% of hydrophilic cationic monomer(s), preferably between 2 and 50 mol%, more preferably between 3 and 40 mol%, most preferably between 4 and 30 mol%.

[0089] Those skilled in the art will know how to prepare quaternized monomers, for example using a quaternizing agent of the R-X type, where R is an alkyl group and X is a halogen or sulfate.

[0090] The term “quaternizing agent” designates a molecule capable of alkylating a tertiary amine.

[0091] The quaternizing agent may be chosen from dialkyl sulfates containing from 1 to 6 carbon atoms or alkyl halides containing from 1 to 6 carbon atoms. Preferably, the quaternizing agent is chosen from methyl chloride, benzyl chloride, dimethyl sulfate or diethyl sulfate.

[0092] In addition, the present invention also covers DADMAC, APTAC and MAPTAC monomers whose counterion is a sulfate, fluoride, bromide or iodide instead of chloride.

[0093] In a particular embodiment, the base polymer comprises at least:

[0094] - between 40 and 99 mol% of non-ionic hydrophilic monomer(s), and;

[0095] - between 1 and 60 mol% of hydrophilic cationic monomer(s).

[0096] The anionic hydrophilic monomer(s) used in the invention can be selected from a wide group. These monomers may have a vinyl function, in particular acrylic, maleic, fumaric, malonic, itaconic or allylic. They may also contain a carboxylate, phosphonate, phosphate, sulfonate, sulfate or other anionically charged group. Advantageously, the anionic hydrophilic monomer(s) used in the context of the invention are chosen from: acrylic acid; methacrylic acid; dimethylacrylic acid; crotonic acid; maleic acid; fumaric acid; 3-acrylamido 3- methylbutanoic acid; strong acid monomers with, for example, a sulfonic acid or phosphonic acid function, such as vinyl sulfonic acid, vinyl phosphonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-methylidenepropane-l,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, the hydrophilic anionic monomer is acrylic acid or 2-acrylamido-2- methylpropane sulfonic acid and mixture thereof.

[0097] The base polymer advantageously comprises between 1 and 40 mol% of anionic hydrophilic monomer(s), preferably between 2 and 35 mol%, more preferably between 5 and 30 mol%.

[0098] In a particular embodiment, the anionic hydrophilic monomer(s) may be salified. It may also be a mixture of acid and salified forms, for example a mixture of acrylic acid and acrylate.

[0099] By salified, we mean the substitution of a proton of at least one acid function of the-Ra(=O)- OH type (with Rarepresenting P, S or C) of the anionic monomer by a metal cation or organic cation to form a salt of the -Ra(=O)-O-A+type (A+being a metal cation or an organic cation). In other words, the non-salified form corresponds to the acid form of the monomer, e.g. Rb- C(=O)-OH in the case of the carboxylic acid function, while the salified form of the monomer corresponds to the Rb-C(=O)-O- A+form, A+being a metal or organic cation, Rbbeing a vinylic group.

[0100] The salified form advantageously corresponds to alkali metal salts (Li+, Na+, K+...), to alkaline earth metal salts (Ca2+, Mg2+...) or to ammonium salts (for example, the ammonium ion or a tertiary ammonium). The preferred salts are sodium salts.

[0101] The salification can be carried out before or after the polymerization. Advantageously between 1 and 100 mol% of the anionic hydrophilic monomer(s) of the base polymer are salified, preferably between 30 and 100 mol%, more preferably between 50 and 100 mol%.

[0102] In a preferred embodiment, the base polymer is free of anionic hydrophilic monomer(s).

[0103] The base polymer may optionally comprise one or more non-ionic hydrophilic monomer(s) different from acrylamide and methacrylamide, dimethylaminopropyl acrylamide and dimethylaminopropyl methacrylamide .

[0104] The one or more non-ionic hydrophilic monomer(s) may substitute partially or totally the non-ionic monomer(s) chosen from acrylamide, methacrylamide, dimethylaminopropyl acrylamide, dimethylaminopropyl methacrylamide and mixtures thereof.

[0105] The non-ionic hydrophilic monomer(s) different from acrylamide, methacrylamide, dimethylaminopropyl acrylamide or dimethylaminopropyl methacrylamide is advantageously selected from: N-alkylacrylamides, N-alkylmethacrylamides, N,N-dialkyl acrylamides (e.g. N,N-dimethylacrylamide or N,N-diethylacrylamide), N,N-dialkylmethacrylamides, alkoxylated esters of acrylic acid, alkoxylated methacrylic acid esters, N-vinylpyrrolidone, N- methylol(meth)acrylamide, N-vinyl caprolactam, N-vinylformamide (NVF), N-vinyl acetamide, N-vinyl imidazole, N-vinyl succinimide, acryloyl morpholine (ACMO), acryloyl chloride, glycidyl methacrylate, vinyl acetate, glyceryl methacrylate, diacetone acrylamide, methacrylic anyhydride, acrylonitrile, maleic anydride, itaconamide, vinylpyridine, hydroxyalkyl (meth)acrylate, thioalkyl (meth)acrylate, 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.

[0106] The base polymer advantageously comprises at most 50 mol% of non-ionic hydrophilic monomer(s) different from acrylamide, methacrylamide, dimethylaminopropyl acrylamide or dimethylaminopropyl methacrylamide, preferably at most 40 mol%, more preferably at most 30 mol% and more preferably at most 20 mol%.

[0107] The base polymer may comprise one or more zwitterionic hydrophilic monomers, or hydrophobic monomers. A zwitterionic monomer is an ionic monomer with a zero overall charge. A zwitterionic monomer has an identical cationic charge number and anionic charge number.

[0108] Zwitterionic hydrophilic monomer(s) that can be used in the context of the invention are advantageously selected from derivatives of a vinyl pattern, specifically derivatives of acrylamide, acrylic, allylic or maleic monomers. Preferably, this monomer comprises an amine or an ammonium function and one of more of the followings: a carboxylic (or carboxylate) acid-type function, a sulfonic (or sulfonate) acid-type function or a phosphoric (or phosphate) acid-type function. Preferred zwitterionic hydrophilic monomer(s) are selected from the group consisting of: dimethylaminoethyl acrylate derivatives, such as 2-[(2-(acryloyloxy)ethyl) dimethylammonio] ethane- 1- sulfonate, 3-[[2-(acryloyloxy)ethyl]dimethylammonio]propane-l- sulfonate, 4-[[2-(acryloyloxy)ethyl]dimethylammonio]butane-l-sulfonate, [2- (acryloyloxy) ethyl] (dimethylammonio)acetate; derivatives of dimethylaminoethyl methacrylate such as 2- [[2-(methacryloyloxy) ethyl]dimethylammonio]ethane- 1-sulfonate, 3-[[2-(methacryloyloxy) ethyl] dimethylammonio]propane-l -sulfonate, 4-[[2-(methacryloyloxy)ethyl] dimethylammonio]butane- 1-sulfonate, [2-(methacryloyloxy)ethyl](dimethylammonio)acetate; derivatives of N-(3-dimethylaminopropyl)acrylamide such as 2-[3-acrylamidopropyl) dimethylammonio] ethane- 1-sulfonate, 3-[(3-acrylamidopropyl)dimethylammonio]propane-l- sulfonate, 4-[(3-acrylamidopropyl)dimethylammonio]butane- 1-sulfonate, [3-(acryloyloxy) propyl](dimethylammonio)acetate, N-[3-(dimethylamino)propyl]methacrylamide; derivatives such as 2-[(3-methacrylamidopropyl)dimethylammonio]ethane- 1-sulfonate, 3-(dimethyl ammonio)propane- 1-sulfonate, 4-[(3-(methacrylamido)propyl](dimethyl)ammoniobutane- 1- sulfonate and propyl[3-(methacryloyloxy)](dimethylammonio)acetate; and mixtures thereof.

[0109] Other zwitterionic monomers are described by the Applicant in document WO2021123599.

[0110] The base polymer according to the invention advantageously comprises between 0.001 and 30 mol% of zwitterionic hydrophilic monomer(s), preferably between 0.01 and 20 mol%, more preferably between 0.1 and 15 mol%.

[0111] Hydrophobic monomer(s) are advantageously selected from the group consisting of:

[0112] - anionic, cationic or non-ionic (meth)acrylic acid ester comprising:

[0113] (i) a C4-C30 alkyl group, or a C6-C30 aryl group, or

[0114] (ii) an arylalkyl constituted of a C4-C30 alkyl group and a C6-C30 aryl group, or

[0115] (iii) a propoxylated chain, or (iv) an ethoxylated chain, or

[0116] (v) a propoxylated and ethoxylated chain comprising both ethoxylated units and propoxylated units;

[0117] - sulfonated monomer having an unsaturated double bond and comprising:

[0118] (i) a C4-C30 alkyl group, or a C6-C30 aryl group, or

[0119] (ii) an arylalkyl constituted of a C4-C30 alkyl group and a C6-C30 aryl group, or

[0120] (iii) a propoxylated chain, or

[0121] (iv) an ethoxylated chain, or

[0122] (v) a propoxylated and ethoxylated chain comprising both ethoxylated units and propoxylated units;

[0123] - anionic, cationic or non-ionic mono-substituted or di-substituted (meth)acrylamide comprising:

[0124] (i) a C4-C30 alkyl group, or a C6-C30 aryl group, or

[0125] (ii) an arylalkyl constituted of a C4-C30 alkyl group and a C6-C30 aryl group, or

[0126] (iii) a propoxylated chain, or

[0127] (iv) an ethoxylated chain, or

[0128] (v) a propoxylated and ethoxylated chain comprising both ethoxylated units and propoxylated units; and

[0129] - mixtures thereof.

[0130] Among these hydrophobic monomers:

[0131] - alkyl groups are C4-C20, preferably C4-C8. The C6-C20 alkyls are preferably linear, while the C4-C5 alkyls are preferably branched,

[0132] - arylalkyl groups are preferably C7-C25, more preferably C7-C15,

[0133] - the ethoxylated chains advantageously comprise between 1 and 200 -CH2-CH2-O- groups, preferably between 6 and 100, more preferably between 10 and 40,

[0134] - the propoxylated chains advantageously comprise between 1 and 50 -CH2-CH2-CH2-O- groups, more preferably between 1 and 20.

[0135] Preferred hydrophobic monomers belonging to these classes are advantageously:

[0136] - 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, vinylpyridine, 2-ethylhexyl acrylate, C4-C22 itaconic acid hemiesters, acidified or quatemized salts of C4-C22 dialkylaminoalkyl (meth)acrylate, acidified or quatemized salts of C4-C22 dialkylaminoalkyl (meth)acrylamides, acrylamido undecanoic acid, and mixtures thereof,

[0137] - cationic allyl derivatives of formula (I) or (II): in which:

[0138] R: independently an alkyl chain containing 1 to 4 carbons ;

[0139] Ri: an alkyl or arylalkyl chain containing 8 to 30 carbons;

[0140] X: a halide selected from the group consisting of bromides, chlorides, iodides, fluorides and any negatively charged counterion; and

[0141] - preferably cationic derivatives of the (meth) acryloyl type corresponding to formula (III): in which:

[0142] * A represents O or N-R5 (preferably A represents N-R5),

[0143] *R2, R3, R4, Rs, Re, R7: independently hydrogen or an alkyl chain containing 1 to 4 carbons,

[0144] * Q: an alkyl chain containing 1 to 20 carbons,

[0145] * Rs: an alkyl or arylalkyl chain containing 8 to 30 carbons,

[0146] * X: a halide selected from the group consisting of bromides, chlorides, iodides, fluorides and any negatively charged counterion. The base polymer generally comprises less than 1 mol% of hydrophobic monomer(s). In a preferred embodiment, the base polymer is free of hydrophobic monomer.

[0147] When the base polymer comprises one or more hydrophobic monomers, they are present in a quantity such that the base polymer remains water-soluble.

[0148] The quantities of the different monomers will be adjusted by the person skilled in the art so as not to exceed 100 mol% during the preparation of the base polymer.

[0149] In a preferred embodiment, the base polymer consists of:

[0150] - hydrophilic monomer(s) chosen from acrylamide, methacrylamide and mixture thereof, and;

[0151] - hydrophilic monomer(s).

[0152] Base polymer structure

[0153] The base polymer can have a linear, branched, star-shaped or comb-shaped structure. This structure can be obtained, according to the general knowledge of the person skilled in the art, for example by selecting the initiator, the transfer agent, the polymerization technique such as Reversible Addition Fragmentation chain Transfer Polymerization (RAFT), Nitroxide Mediated Polymerization (NMP), Atom Transfer Radical Polymerization (ATRP), incorporation of structural monomers, or concentration.

[0154] The base polymer may further comprise at least one crosslinking agent. The crosslinking agent is advantageously selected from:

[0155] - structural agents, which may be chosen from the group comprising polyethylenically unsaturated compounds (having at least two unsaturated functions) different from cationic hydrophilic monomer(s), such as vinyl functions, in particular allyl or acrylic functions, and may include, for example, methylene bis acrylamide (MBA), trially amine, or tetraallylammonium chloride or 1,2 dihydroxyethylene bis-(N-acrylamide),

[0156] - compounds with at least two epoxy functions,

[0157] - compounds with at least one unsaturated and one epoxy function,

[0158] - macroinitiators such as polyperoxides, polyazoids and transfer agents such as polymercaptant polymers, and polyols,

[0159] - functionalized polysaccharides,

[0160] - water-soluble metal complexes composed of:

[0161] * a metal with a valence greater than 3, such as, by way of example and non-limitation, aluminum, boron, zirconium or titanium, and

[0162] * a ligand bearing a hydroxyl function.

[0163] The quantity of crosslinker in the base polymer is advantageously comprised between 5 and 5 000 ppm, based on to the total weight of monomers constituting the base polymer, preferably between 50 and 3 000 ppm.

[0164] When the base polymer comprises a crosslinking agent, the base polymer remains water- soluble. The person skilled in the art will know how to adjust the amount of crosslinking agent, and possibly the amount of chain transfer agent, to achieve this result.

[0165] In a particular embodiment, the base polymer is free of crosslinker.

[0166] The base polymer may further comprise at least one chain transfer agent, for example, selected from the group consisting of: 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; 2- aminoethanethiol; thioglycolates; allyl phosphites; methallyl mercaptans, such as sodium methallyl sulfonate; calcium methallyl sulfonate; magnesium methallyl sulfonate; potassium methallyl sulfonate; ammonium methallyl sulfonate; alkyl mercaptans, such as such as n- dodecyl mercaptan, n-octyl mercaptan, tert-dodecyl mercaptan; alkyl phosphites (C4-C18), such as trialkyl (C4-C18) phosphites, di-oleyl-hydrogen phosphites, dibutyl phosphite; dialkyldithiophosphates (alkyl = C4-C15) such as dioctyl dithiophosphate; tertiary nonylmercaptan; 2-ethylhexyl thioglycolate; ; iso-octylthioglycolate; 2-ethylhexyl mercaptoacetate; polythiols; and mixtures thereof. Preferably, it is selected from sodium hypophosphite, sodium formate and mixtures thereof.

[0167] The quantity of transfer agent in the base polymer is advantageously comprised between 10 and 10000 ppm, based on to the total weight of monomers constituting the base polymer, preferably between 50 and 5 000 ppm.

[0168] The base polymer can be prepared by various processes, such as that described in US 2011 / 0056640, FR 2987375, or FR 2206322, preferably the base polymer is prepared in accordance with FR 2206322. When the base polymer is prepared according to FR2206322, the non-ionic hydrophilic monomer different from acrylamide and methacrylamide, dimethylaminopropyl acrylamide and dimethylaminopropyl methacrylamide does not include N-alkylacrylamides and N,N- dialkyl acrylamides.

[0169] In a particular embodiment, the base polymer is being modified with at least one polyfunctional compound comprising at least three heteroatoms chosen from N, S, O and P, in which at least three of these heteroatoms each have at least one mobile hydrogen as in document FR2987375.

[0170] Physical properties of the base polymer

[0171] The base polymer has a weight- average molecular weight advantageously of between 50 000 and 5 000 000 g / mol, preferably between 100 000 and 3 000000 g / mol, more preferably between 150 000 and 2000000 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.

[0172] When the base polymer is obtained using the process described in patent application FR 2206322, its weight-average molecular weight is advantageously of between 1 000 000 and 25 000 000 g / mol, preferably between 2000 000 and 15 000 000 g / mol, more preferably between 3 000000 and 10000 000 g / mol.

[0173] The weight- average molecular weight is preferably measured by Gel Permeation Chromatography using a Malls detector.

[0174] The Brookfield viscosity of the solution comprising the base polymer is advantageously between 100 and 20 000 cPs, preferably between 1 000 and 10000 cPs.

[0175] The Brookfield viscosity is preferably measured for an aqueous solution containing 20 weight% of base polymer, by weight of the solution.

[0176] When the base polymer is obtained using the process described in patent application FR 2206322, the Brookfield viscosity of the solution comprising the base polymer is advantageously between 1 000 and 50000 cPs, preferably between 2 000 and 20 000 cPs, more preferably between 5 000 and 20 000 cPs. Renewable origin

[0177] In a preferred embodiment according to the invention, the base polymer is prepared using monomers of at least partially renewable and non-fossil origin.

[0178] In the context of the invention, the terms “of renewable and non-fossil origin” designate the origin of a chemical compound issuing from biomass or synthetic gas (syngas), namely, one that is the result of one or more chemical transformations performed on one or more raw materials of natural, and non-fossil, origin. The terms “bio-sourced” or “bio-resourced” can also be used to characterize the renewable and non-fossil origin of a chemical compound. The renewable and non-fossil origin of a compound includes renewable and non-fossil raw materials coming from the circular economy, and which have been previously recycled, one or more times, during a recycling process of material coming from biomass, such as, for example, material coming from polymer depolymerization or from the transformation of pyrolysis oil.

[0179] According to the invention, “at least partially of renewable and non-fossil origin” means a content of bio- sourced carbon comprised between 5% by weight and 100% by weight based on to the total carbon weight of said compound, preferably at least 30%, more preferably at least 50%, even more preferably at least 70%, more preferably at least 90% and even more preferably, at least 100% bio-sourced carbon.

[0180] In the context of the invention, the standard ASTM D6866-21, method B, is used to characterize the bio- sourced nature of a chemical compound, and to determine the bio- sourced content of said compound. The value is expressed in percent by weight of bio-sourced carbon based on to the total weight of carbon in said compound.

[0181] In a preferred embodiment, the base polymer has a carbon content from renewable and non- fossil origin of between 5% by weight and 100% by weight, based on the total carbon weight of the base polymer, preferably between 30% by weight and 100% by weight, more preferably between 50% by weight and 100% by weight, more preferably between 70% by weight and 100% by weight, more preferably between 90% by weight and 100% by weight and even more preferably 100% by weight.

[0182] The dialdehyde polymer obtained by the process described above can be used for manufacturing a sheet of paper, cardboard or the like. The process of manufacturing a sheet of paper, cardboard or the like comprises the following successive steps:

[0183] (1) adding a dialdehyde polymer, prepared according to the invention, to an aqueous suspension of cellulosic fibers and;

[0184] (2) forming a sheet of paper, cardboard or the like.

[0185] The different steps in a process of manufacturing paper, cardboard or the like are known and comply with techniques that are part of the knowledge of the skilled person in the art, it is not necessary to describe them in further detail, because they remain known and classic of what the person skilled in the art knows. If necessary, they can refer to the document: Handbook for Pulp & Paper Technologists, 4thEdition, G.A. Smook.

[0186] The addition of the dialdehyde polymer of the invention to the aqueous suspension of cellulosic fibers can be done in different ways and in particular according to the typical methods known to the person skilled in the art.

[0187] The dialdehyde polymer can be added to the cellulose material in the form of a diluted or undiluted aqueous solution. It can be applied by an impregnation technic, or it can be added directly to the fibrous suspension at any point of the process of producing paper where dry strength agents are usually introduced.

[0188] Thus, the dialdehyde polymer can be introduced into the thick stock or into the thin stock. It can be added at the mixing pump, before the headbox or filter sieve. Preferably, the dialdehyde polymer is introduced before the headbox.

[0189] Preferably, the dialdehyde polymer is industrially injected into the fibrous suspension, i.e., before its dilution by the pulp water (thick stock). The consistency of the pulp is on the order of 1 to 5% by weight of the cellulose fibers.

[0190] The papermaking method can be implemented with any type of paper pulp, such as, for example, virgin fiber pulp (Kraft, Bisulfite), recycled fibers, de-inked pulps, mechanical and thermo-mechanical pulps.

[0191] The dialdehyde polymer is advantageously added before the formation of the sheet, directly into the fibrous suspension. It can be added at a single injection point, or at two injection points.

[0192] In particular embodiments, the process comprises, prior to step (1) the preparation on site of the dialdehyde polymer described above.

[0193] By “on site” is meant that the dialdehyde reaction is carried out in the industrial papermaking process site and the dialdehyde polymer can subsequently be directly injected into the papermaking process.

[0194] In a particular embodiment, a micro-cellulose compound is reacted with the dialdehyde polymer before the addition of the latter to cellulose fibers.

[0195] The micro-cellulose / dialdehyde polymer mixture can then be added as an additive to the paper pulp in place of the dialdehyde polymer alone according to the invention in all of the particular embodiments herein described.

[0196] Advantageously, the micro-cellulose compound is selected from nano-fibrillated cellulose, micro-fibrillated cellulose, nano-crystalline cellulose, nano cellulose.

[0197] Advantageously between 10% and 100% by weight of the micro-cellulose compound are added to the dialdehyde polymer, relative to the weight of the dialdehyde polymer, preferably between 10 and 50% by weight.

[0198] The process of manufacturing a sheet of paper may also include the addition of other additives and / or polymers, according to needs; by way of example and not as limitations, we can cite biocides, coagulants, retention agents, flocculants, starch...

[0199] EXAMPLES

[0200] White water solution parameters pH measurement was carried out using a pH meter from Mettler Toledo, SEVENGO. The PCD is the cationic demand measured with PCD 06 from Mutek.

[0201] 10 mL of white water are added into PCD. Cationic demand is achieved by neutralizing the anionic particles with a polydiallyldimethylammonium chloride (polyDADMAC) solution at 10'3mol / L. The result is in peq / L.

[0202] The turbidity was measured with a turbidimeter from Hanna Instrument, HI 88713.

[0203] The conductivity was measured with a conductivity meter from Eutech Instrument, CON 150.

[0204] Description of the characterization of the GPC- MALSof the molecular weight

[0205] Gel permeation chromatography is a method that allows separation of the macromolecules according to their hydrodynamic volume; it is coupled to a MALS detector, making it possible to measure the diffusion of the light at multiple angles.

[0206] The synthetized polymers are analyzed under the following conditions:

[0207] - Instrument: GPC-2

[0208] - Columns: Shodex SB-807-HQ & SB-805 custom

[0209] - Method:

[0210] * Temperature: 30°C

[0211] * Mobile phase: 0.5M NaNO3, HEPES (pH=8), 100 ppm NaN3

[0212] * Injection: lOOpL

[0213] * Flow: 0.3mL / min

[0214] * Detection:

[0215] (i) Light diffusion detector (MALS): Absolute molar mass

[0216] (ii) Refractometry (RI): Concentration

[0217] The viscosity is measured using a Brookfield viscometer, at 25 °C, with a Brookfield LVI module, speed 60 rpm.

[0218] 582.2 g of water and 33.4 g of DADMAC (64% by weight in water) were introduced in a 1 litre reactor equipped with a mechanical stirrer, a thermometer, a cooler and a nitrogen inlet. The pH was adjusted to 2.5 with H2SO4 (96% by weight in water).

[0219] The solution was heated and maintained at a temperature comprised between 79 and 81 °C using a water bath.

[0220] Through two continuous additions, a solution of 357.2 g of acrylamide (AM) (50% by weight in water) and a solution of 1.4 g of sodium persulphate (5.9% by weight in water) were added in 90 minutes.

[0221] After 30 minutes of aging, 0.25 g of sodium bisulphite (40% by weight in water) was added to react any residual monomers.

[0222] Another aging step is applied to the polymer solution for 60 minutes before cooling, the base polymer Bl was obtained.

[0223] The solution comprising Bl has a pH of 5.0, an active matter of 20.1%, a viscosity of 3 000 cPs and the polymer Bl has a molecular weight of 401 000 g / mol.

[0224] By “aging” is meant that the polymer solution formed after the polymerization is maintained at a temperature comprised between 80 and 90°C in order to increase the viscosity of the polymer solution.

[0225] The same protocol was reproduced by varying the composition of the different monomers in order to obtain a base polymer B2. The compositions of the polymers are presented in Table 1.

[0226] Table 1 - Compositions and properties of base polymers Bl and B2

[0227] Example 2: Dialdehyde polymer preparation

[0228] 69.6 g of base polymer Bl, 652.68 g of fresh water and 72.52 g of white water were introduced in a 1 litre reactor equipped with a mechanical stirrer and a pH meter to form a solution SI. The solution conductivity was measured to be of 0.5 mS / cm.

[0229] After stirring for 10 minutes, 5.22 g of glyoxal (40% by weight in water) were introduced in the reactor to give a solution S2 and the pH was adjusted to 10.2 using a sodium hydroxide solution (10% by weight in water) affording a solution S3.

[0230] The temperature was maintained between 20 and 22°C during the reaction process. Completion of the reaction was monitored by measuring a delta pressure increase until a value of +300% was reached.

[0231] The pressure was measured as a function of time through a tube calibrated in length (2.2 m) and diameter (2 mm).

[0232] When the fixed pressure delta was reached, the reaction was stopped by lowering the pH to less than 3.5 by addition of a H2SO4 concentrated solution (96% by weight in water) to give a solution of polymer Pl. The viscosity of the resulting solution of glyoxalated polymer (GPAM) Pl was then measured.

[0233] A Delta P of 500 mbar gives a viscosity of 35 cPs at a concentration of 2% of the polymer by weight in water.

[0234] The same protocol was reproduced by varying the base polymer used, the quantity of glyoxal and the percentage by weight of white water.

[0235] The results are presented in Table 2.

[0236] Table 2 : Dialdehyde polymers compositions. CE = comparative example

[0237] Example 3: Application testing

[0238] The wet pulp used in all of the application examples is obtained by disintegration of the dry pulp in order to obtain a final aqueous mass concentration of 1%. This is a pH neutral pulp with 100% recycled cardboard fibers. under vacuum (DDA)

[0239] The DDA (Dynamic Drainage Analyzer) makes it possible to determine, automatically, the time (in seconds) necessary to vacuum dewater a fibrous suspension on a fabric. The polymers are added to the wet pulp (0.6 liters of pulp to 1.0% mass) in the cylinder of the DDA under stirring at 1 000 rotations per minute:

[0240] T=0 s: stirring of the pulp

[0241] T=10 s: addition of the polymer(s)

[0242] T=30 s: stop of the stirring and vacuum drainage at 200 mBar for 60 s.

[0243] The pressure under the fabric is recorded as a function of time. When the water is evacuated from the fibrous mat, air passes through it which causes a slope break on the curve representing the pressure under the fabric as a function of time. The time, expressed in seconds, related to this slope break on the curve corresponds to the drainage time. The shorter the time, the better is the vacuum drainage.

[0244] 3B: Performances in dry resistance , basis weight at 80 g.nT2

[0245] The quantity of pulp necessary is sampled in order to ultimately obtain a sheet representing a basis weight of 80 g.nT2.

[0246] The wet pulp is introduced into the dynamic hand sheet former tank and kept under stirring. Different compounds are injected into this pulp, according to a pre-defined sequence. In general, there is a contact time of 30 to 45 seconds between additions of polymer.

[0247] Paper hand sheets are made with an automatic dynamic hand sheet former: a blotter and a forming fabric are placed in the tank of the dynamic hand sheet former before starting the rotation of the tank at 1 000 rotations per minute and building the water wall. The treated pulp is distributed on the water wall to form the fibrous mat on the forming fabric.

[0248] Once the water is drained, the fibrous mat is recovered, pressed under a press that delivers 4 bars, then dried at 117 °C. The obtained sheet is packaged for one night in a room with controlled humidity and temperature (50% relative humidity and 23 °C). The dry resistance properties of all of the sheets obtained by this procedure are then measured.

[0249] Bursting strength is measured with a Messmer Buchel M 405 burst tester according to the TAPPI T403 om-02 standard.

[0250] The quantity of the polymer added is expressed in kg of active polymer per ton of dry fiber. Trials at 2.5 kg / t. The results are expressed as a percentage of increase compared to a blank (no polymer) and are summarized in Table 3. The dry breaking length is measured in the machine direction with a Testometric AX tensile tester in accordance with TAPPI standard T494 om-01. The results are expressed as a percentage of increase compared to a blank (no polymer) and are summarized in Table 3.

[0251] Table 3 : Results of of the drainage and dry strength performances of the dialdehyde polymers 1 to 16 (Pl to P16). As can be seen in table 3, the dialdehyde polymers prepared in aqueous solution containing white water are as efficient as dialdehyde polymers prepared with only fresh water, in terms of dry resistance and drainage performances than dialdehyde polymers prepared with fresh water.

[0252] These results are surprising and unexpected with regard to the prior art’s teaching. Example 3C: Calculating the amount of fresh water saved with the process of the invention

[0253] Each tonne of paper is treated with 2.5 kg of dry dialdehyde polymer P3 per tonne of pulp, i.e. a solution of 125 kg / t at 2%. From this 125 kg / t needs to be subtracted the quantity of water provided by the base polymer 30% active matter representing 85% in weight of the dialdehyde polymer (7.1 kg / t) and the quantity of water provided by the dialdehyde in solution, for example for Pl, glyoxal at 40% in weight in water and representing 15% in weight of the glyoxalated polymer (0.9 kg / t). This gives a fresh water saving of 117 kg / t of paper produced.

[0254] A small paper machine produces in average 10 t / h of paper, a medium one 25 t / h and a large one 50 t / h. The total world paper production is estimated to be 47 260 t / h.

[0255] Table 4 presents the quantity of water saved over a year using the process of paper manufacturing according to the invention.

[0256] Table 4 : Equivalents with regard to savings of water when using the paper manufacturing process of the invention

[0257] The savings in water obtained when replacing the actual paper manufacturing process with the paper manufacturing process according to the invention would allow, for example, to have 2 Oktoberfests per month.

Claims

CLAIMS1. Process for preparing a dialdehyde polymer comprising at least the following successive steps:1) mixing a base polymer with an aqueous solution comprising at least 10% by weight of process water, in order to form a solution SI of the base polymer; the base polymer comprising at least one non-ionic hydrophilic monomer selected from the group consisting of: acrylamide, methacrylamide, dimethylaminopropyl acrylamide, dimethylaminopropyl methacrylamide and mixture thereof; wherein the amount of base polymer in the solution SI is between 0.5 and 15% by weight; wherein the process water is any one of the followings, or a mixture thereof:- white water,- clarified water which corresponds to white water that has been filtered to remove solid particles having a particle size above 1 000 pm;2) mixing at least one dialdehyde with the solution SI to form a solution S2; wherein the dialdehyde is selected from the group consisting of: glyoxal, glutaraldehyde, 2,5-furandicarboxaldehyde, adipaldehyde, succinaldehyde, starch dialdehyde, 2,2 dimethoxy ethanal and mixtures thereof; wherein the solution S2 has an amount of dialdehyde of between 5 and 40% by weight relative to the weight of the base polymer;3) adjusting the pH of the solution S2 to at least 8 and reacting the base polymer with the at least one dialdehyde, for between 2 minutes and 90 minutes at a temperature comprised between 17°C and 40°C, to form a solution S3 comprising a dialdehyde polymer;4) optionally, acidifying the solution S3 to a pH of between 2 and 4.

2. Process according to claim 1, wherein the base polymer comprises at least one cationic hydrophilic monomer.

3. Process according to any of the preceding claims, wherein the base polymer comprises at least:- between 40 and 99 mol% of non-ionic hydrophilic monomer(s), and;- between 1 and 60 mol% of hydrophilic cationic monomer(s).

4. Process according to any of the preceding claims, wherein the aqueous solution of step 1) consists of process water and fresh water.

5. Process according to any of the preceding claims, wherein the base polymer has a carbon content from renewable and non-fossil origin of between 5% by weight and 100% by weight, based on the total carbon weight of the base polymer.

6. Process according to any of the preceding claims, wherein the base polymer is a polymer of acrylamide and D ADM AC.

7. Process according to any of the preceding claims, wherein the base polymer is a polymer of 40 to 99 mol% acrylamide and 1 to 60 mol% DADMAC.

8. Process according to any of the preceding claims, wherein the dialdehyde is glyoxal.

9. Process according to any of the preceding claims, wherein the aqueous solution of step 1) comprises at least 10 % by weight of process water.

10. Process according to any of the preceding claims, wherein the aqueous solution of step 1) comprises at least 20 % by weight of process water.

11. Process according to any of the preceding claims, wherein the aqueous solution of step 1) comprises at least 50 % by weight of process water.

12. Process according to any of the preceding claims, wherein the aqueous solution of step 1) comprises at least 70 % by weight of process water.

13. Process according to any of the preceding claims, wherein the aqueous solution of step 1) comprises at least 90 % by weight of process water.

14. Process according to any of the preceding claims without claim 4, wherein the aqueous solution of step 1) consists of process water.

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