Method of manufacturing paper or paperboard

Abstract

This invention relates to a method for manufacturing paper or paperboard from a fiber suspension, the method comprising the following steps: a) injecting a P3 polymer into a cellulose fiber suspension; b) forming paper or paperboard; c) drying the paper or paperboard. Prior to step a), a P3 polymer is prepared from a water-soluble P1 polymer of at least one nonionic monomer selected from acrylamide, methacrylamide, N,N-dimethylacrylamide, and acrylonitrile. The P1 polymer is subjected to a Re1 reaction to obtain a P2 polymer, which is then subjected to a Re2 reaction to obtain the P3 polymer. The P3 polymer is then subjected to a Re2 reaction. The e1 reaction is injected into the fiber suspension within 24 hours of the start of the reaction; the -Re1 reaction comprises the preparation of a P2 polymer containing an isocyanate functional group by reacting (i) an alkali metal hydroxide and / or an alkaline earth metal hydroxide, (ii) an alkali metal hypohalide and / or an alkaline earth metal hypohalide and (iii) a P1 polymer for 10 seconds to 60 minutes; the -Re2 reaction comprises the preparation of a P3 polymer by reacting (iv) a compound containing at least one aldehyde functional group or a compound capable of generating at least one aldehyde functional group with (v) a P2 polymer containing an isocyanate functional group.

Description

Technical Field

[0001] This invention relates to a method for manufacturing paper or paperboard with improved drainage and processability properties. More specifically, the subject of this invention is a method comprising preparing a polymer by isocyanate functionalization and addition of a compound containing at least one aldehyde functional group prior to adding the polymer to a fiber suspension used for manufacturing paper or paperboard.

[0002] The present invention also includes subject paper and paperboard with improved physical properties obtained by the method. Background Technology

[0003] The paper industry has been seeking to optimize its manufacturing processes, particularly in terms of output, productivity, cost reduction, and finished product quality.

[0004] The uses of polymers as dry strength agents, drainage agents, and machinability agents are described extensively.

[0005] Drainage performance refers to the ability of a fiber mat to evacuate or drain as much water as possible before it dries.

[0006] Improved drainage performance refers to energy conservation and increased production capacity.

[0007] Processability refers to optimizing the operation of a paper machine by improving productivity through better drainage on the table, better drying in the press section, reducing breakage through greater loop cleanliness, and reducing deposits.

[0008] Polyvinylamine is known to improve drainage in the papermaking process.

[0009] U.S. Patent 8,262,859 describes the reaction of polyethyleneamine with at least one dialdehyde to produce functionalized polyethyleneamine, which imparts improved wet and / or dry strength to paper or paperboard. However, this reaction is very rapid, difficult to control, and takes place in a very diluted medium, which requires costly transportation of the product from the production site to the paper mill. The reaction also causes the reaction medium to freeze. Therefore, the reaction cannot be carried out directly on the papermaking site, upstream of where the polymer is injected into the cellulose fibers, due to the risk of altering processability from deposits generated on the paper machine. Summary of the Invention

[0010] Surprisingly, the applicant discovered a papermaking method using a polymer obtained by isocyanate functionalization and the addition of a compound containing at least one aldehyde functional group upstream of the fiber suspension (advantageously a cellulose fiber suspension), which improves drainage and dry strength properties. Furthermore, no polymer gel formation was observed during this process, which does not alter processability.

[0011] More specifically, the present invention relates to a method for manufacturing paper or paperboard from a fiber suspension (advantageously a suspension of cellulose fibers), wherein a water-soluble P1 polymer comprising at least one nonionic monomer selected from acrylamide, methacrylamide, N,N-dimethylacrylamide and acrylonitrile is subjected to a Re1 reaction to obtain a P2 polymer, and then the P2 polymer is subjected to a Re2 reaction to obtain a P3 polymer, wherein the P3 polymer is injected into the fiber suspension within 24 hours (less than or equal to 24 hours) of the start of the Re1 reaction;

[0012] The Re1 reaction involves adding alkali metal and / or alkaline earth metal hydroxides and alkali metal and / or alkaline earth metal hypohalides to the P1 polymer to obtain an isocyanate-functionalized P2 polymer after 10 seconds to 60 minutes.

[0013] The Re2 reaction involves adding a compound that is functionalized with at least one aldehyde or capable of generating at least one aldehyde functional group to the P2 polymer to obtain the P3 polymer.

[0014] In other words, the method for manufacturing a sheet of paper or paperboard from a fiber suspension according to the present invention includes the following steps:

[0015] a) Inject the P3 polymer into the cellulose fiber suspension.

[0016] b) Forming paper or paperboard.

[0017] c) Dry the paper or cardboard.

[0018] Prior to step a), polymer P3 is prepared from a water-soluble polymer P1 containing at least one nonionic monomer selected from acrylamide, methacrylamide, N,N-dimethylacrylamide, and acrylonitrile, according to Re1 to Re2 reactions:

[0019] -Re1: A P2 polymer containing isocyanate functional groups was prepared by reacting (i) alkali metal hydroxides and / or alkaline earth metal hydroxides, (ii) alkali metal hypohalides and / or alkaline earth metal hypohalides, and (iii) a P1 polymer for 10 seconds to 60 minutes.

[0020] -Re2: P3 polymer is prepared by reacting (iv) a compound containing at least one aldehyde functional group or a compound capable of generating at least one aldehyde functional group with (v) a P2 polymer containing an isocyanate functional group.

[0021] -P3 polymer is injected into the fiber suspension in step a) within 24 hours of the start of the Re1 reaction.

[0022] This method advantageously eliminates the decarboxylation step (CO2 removal) after the Re1 reaction. In fact, this would consume the isocyanate functional groups necessary for the Re2 reaction. This method is advantageously advantageous in that it eliminates the decarboxylation step (CO2 removal) after the Re2 reaction, especially when the Re2 reaction is partial (a partial reaction of the isocyanate functional groups).

[0023] In the following description and claims, all terms beginning with gt -1 or kg.t -1 The polymer measurements are given as the weight of the active polymer per tonne of dry matter. Dry matter is a dry extract obtained by evaporating water from a fiber suspension used in the manufacture of paper or paperboard. Dry matter is typically based on cellulose fibers and fillers, and advantageously consists of cellulose fibers and fillers. The term "cellulose fiber" includes any cellulose entity, including fibers, fine fibers, microfibers, or nanofibers. Cellulose fiber refers to a stock or slurry based on water and cellulose fibers. Stocks, with a dry matter concentration (by weight) greater than 1% or even greater than 3%, are located upstream of the dilution pump. Slurries, with a dry matter concentration typically less than 1% by weight, are located downstream of the dilution pump.

[0024] The term "polymer" refers to homopolymers and copolymers.

[0025] Amphoteric polymers are polymers containing both cationic and anionic charges, preferably with anionic charges being equal to cationic charges.

[0026] As used herein, the term "water-soluble polymer" refers to a polymer that, when stirred at 25°C for 4 hours, yields a product at a concentration of 20 g / L. -1 When dissolved in water at a concentration of [specific concentration], it produces an aqueous solution of the polymer without insoluble particles.

[0027] This numerical range includes a lower limit and an upper limit. Therefore, the numerical ranges “0.1 to 1.0” and “0.1 to 1” include the values ​​0.1 and 1.0.

[0028] The water-soluble P1 polymer contains at least one nonionic monomer selected from acrylamide, methacrylamide, N,N-dimethylacrylamide, and acrylonitrile. Optionally, the water-soluble P1 polymer may also contain anionic and / or cationic and / or zwitterionic monomers.

[0029] The anionic monomer is preferably selected from the group consisting of: monomers having a carboxyl functional group and their salts, including acrylic acid, methacrylic acid, itaconic acid, and maleic acid; monomers having a sulfonic acid functional group and their salts, including acrylamide tert-butyl sulfonic acid (ATBS), allyl sulfonic acid, and methyl allyl sulfonic acid and their salts; and monomers having a phosphonic acid functional group and their salts.

[0030] Generally, the anionic monomers of P1 to P5 polymers are salts of alkali metals, alkaline earth metals, or ammonium (preferably quaternary ammonium).

[0031] The cationic monomer is preferably selected from the group consisting of: quaternized or salted dimethylaminoethyl acrylate (ADAME), quaternized or salted dimethylaminoethyl methacrylate (MADAME), diallyl dimethyl ammonium chloride (DADMAC), acrylamide propyltrimethylammonium chloride (APTAC), and methacrylamide propyltrimethylammonium chloride (MAPTAC).

[0032] Advantageously, the salts of the cationic monomers of the P1 to P5 polymers are salts of halides, preferably chlorides.

[0033] The zwitterionic monomers are preferably selected from the group consisting of: sulfobetaine monomers, such as sulfopropyl dimethylammonium ethyl methacrylate, sulfopropyl dimethylammonium propyl methacrylamide, or sulfopropyl 2-vinylpyridine; phosphate betaine monomers, such as ethyl trimethylammonium phosphate ethyl methacrylate; and carboxybetaine monomers.

[0034] Preferably, the water-soluble P1 polymer is nonionic. In other words, the water-soluble P1 polymer preferably contains only nonionic monomers. Even more preferably, P1 is a homopolymer of acrylamide or methacrylamide.

[0035] The P1 polymer can be linear, structured, or crosslinked. The crosslinking agent used for structured crosslinking can be selected from sodium allyl sulfonate, sodium methyl allyl sulfonate, sodium methyl allyl disulfonate, methylenebisacrylamide, triallylamine, and triallyl ammonium chloride.

[0036] The structuring of P1 polymers can also be achieved using at least one polyfunctional compound containing at least three heteroatoms selected from N, S, O, and P, and each heteroatom having at least one mobile hydrogen atom. In particular, such a polyfunctional compound can be polyethyleneimine or polyamine.

[0037] The weight-average molecular weight of the P1 polymer is advantageously from 100,000 to 20,000,000, preferably from 250,000 to 5,000,000 Daltons.

[0038] According to the present invention, the weight-average molecular weight of the P1 polymer is determined by measuring its intrinsic viscosity. Intrinsic viscosity can be measured by methods known to those skilled in the art, and can be calculated, in particular, graphically from specific viscosity values ​​at different concentrations. This graphical method involves plotting the specific viscosity value (on the y-axis) as a function of concentration (on the x-axis) and extrapolating the curve to zero concentration. The intrinsic viscosity value is read on the y-axis, or using the least squares method. The weight-average molecular weight can then be determined using the well-known Mark-Houwink equation:

[0039] [η]=KM α

[0040] [η] represents the intrinsic viscosity of the polymer as determined by solution viscosity measurement.

[0041] K represents an empirical constant, and M represents the molecular weight of the polymer.

[0042] α represents the Mark-Houwink coefficient.

[0043] α and K depend on the specific polymer-solvent system. Tables known to those skilled in the art provide values ​​for α and K based on the polymer-solvent system.

[0044] The Re1 reaction involves adding (i) an alkali metal hydroxide and / or an alkaline earth metal hydroxide and (ii) an alkali metal hypohalide and / or an alkaline earth metal hypohalide to the P1 polymer to obtain an isocyanate-functionalized P2 polymer.

[0045] Advantageously, the alkali metal hydroxide is soda (sodium hydroxide), and the alkali metal hypohalide is sodium hypochlorite.

[0046] The Re1 reaction is advantageously carried out in an aqueous solution at a mass concentration of 0.5 to 20%, preferably 1 to 10%, of the P1 polymer.

[0047] Preferably, for the Re1 reaction, the coefficient α = the number of moles of hypohalides (alkali and / or alkaline earth) / the number of moles of nonionic monomers of the P1 polymer is 0.1 to 1.0, and the coefficient β = the number of moles of hydroxides (alkali and / or alkaline earth) / the number of moles of hypohalides (alkali and / or alkaline earth) is 0.5 to 4.0.

[0048] The α coefficient is used to determine the amount of isocyanate functionality formed from the nonionic monomers (acrylamide, methacrylamide, N,N-dimethylacrylamide, and acrylonitrile) of the P1 polymer during the Re1 reaction. It is not the Mark-Houwink coefficient expressed in α.

[0049] The Re1 reaction is advantageously carried out at temperatures between 30°C and 60°C.

[0050] Therefore, according to one specific embodiment, the Re1 reaction can be carried out at a temperature of 30°C to 60°C in the presence of an α coefficient of 0.1 to 1.0, using an aqueous solution of P1 polymer with a mass concentration of 0.5% to 20%, where the α coefficient is the ratio of the molar number of the hypohalide to the molar number of the nonionic monomer of the P1 polymer.

[0051] The Re2 reaction involves adding a compound containing at least one aldehyde functional group or a compound capable of generating at least one aldehyde functional group to the P2 polymer to obtain the P3 polymer.

[0052] The Re2 reaction is advantageously carried out in an aqueous solution at a mass concentration of 0.5% to 20%, preferably 1% to 5%, of the P2 polymer.

[0053] Advantageously, the Re2 reaction is carried out by directly adding a compound containing at least one aldehyde functional group or a compound capable of generating at least one aldehyde functional group to the reaction medium (aqueous solution) produced by the Re1 reaction.

[0054] The Re2 reaction is advantageously carried out at temperatures between 10°C and 60°C, and advantageously between 20°C and 40°C.

[0055] Without being bound by any theory, it appears that during the Re2 reaction, the isocyanate functional groups of the P2 polymer react with the aldehyde functional groups, for example, to form -N=C(HR). 1 ) type imine functional group.

[0056] The molecular weight of compounds containing at least one aldehyde functional group is preferably less than or equal to 200 g·mol⁻¹. -1 Preferably, the compound containing at least one aldehyde functional group is selected from glyoxal, glutaraldehyde, furanyl dialdehyde, 2-hydroxyhexanedialdehyde, succinal, starch dialdehyde, 2,2-dimethoxyacetaldehyde, and combinations thereof. Even more preferably, the compound containing at least one aldehyde functional group is glyoxal.

[0057] The molecular weight of compounds that can produce at least one aldehyde functional group is advantageously less than or equal to 500,000 g.mol. -1 More advantageously less than or equal to 100,000 g·mol⁻¹ -1 For example, less than or equal to 50,000 g·mol⁻¹ -1 The molecular weight of this compound is advantageously greater than or equal to 500 g·mol⁻¹. -1 For example, greater than or equal to 1000 g·mol -1 .

[0058] According to one embodiment, the compound that can produce at least one aldehyde functional group is a polyepoxide, such as polyethylene glycol diepoxide or polyethylene glycol triepoxide. In this case, the polyepoxide is a precursor to a compound containing at least one aldehyde functional group.

[0059] According to another embodiment, the compound capable of generating at least one aldehyde functional group is preferably a nonionic, cationic, anionic, or amphoteric P5 polymer, which is derived from the reaction between at least one compound containing at least one aldehyde functional group and at least one base P4 polymer selected from a nonionic monomer of acrylamide, methacrylamide, N,N-dimethylacrylamide, and acrylonitrile.

[0060] The base P4 polymer can be nonionic, cationic, anionic, or amphoteric. Advantageously, the base P4 polymer is water-soluble.

[0061] The P4 polymer may contain cationic monomers preferably selected from the group consisting of: quaternized or salted dimethylaminoethyl acrylate (ADAME), quaternized or salted dimethylaminoethyl methacrylate (MADAME), dimethyl diallyl ammonium chloride (DADMAC), acrylamidopropyltrimethylammonium chloride (APTAC), and methacrylamidopropyltrimethylammonium chloride (MAPTAC).

[0062] The P4 polymer may contain anionic monomers preferably selected from the following: 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, methacrylic acid, itaconic acid and / or their salts.

[0063] The compound containing at least one aldehyde functional group that reacts at P4 to form P5 is advantageously selected from glyoxal, glutaraldehyde, furanyl dialdehyde, 2-hydroxyhexanedialdehyde, succinal, starch dialdehyde, 2,2-dimethoxyacetaldehyde, and combinations thereof. Even more preferably, the compound containing at least one aldehyde functional group is glyoxal.

[0064] The molecular weight of the P5 polymer is advantageously 100,000 g.mol. -1 Up to 2,000,000 g.mol -1 For example, 120,000 g / mol -1 Up to 1,000,000 g.mol -1 .

[0065] According to a preferred embodiment, the P5 polymer is obtained by reacting a compound containing at least one aldehyde functional group with at least one base P4 polymer within a maximum of 12 hours before being added to the P2 polymer. This is the time between the start of the reaction and the addition of P2.

[0066] Preferably, for reaction Re2 of the method of the present invention, 2 to 50%, more preferably 5 to 30%, of a compound containing at least one aldehyde functional group or a compound capable of generating at least one aldehyde functional group is added to polymer P2, the percentage being expressed by weight relative to the weight of polymer P2.

[0067] Therefore, some or all of the isocyanate functional groups of the P2 polymer can be functionalized.

[0068] According to one specific embodiment, an excess of a compound containing at least one aldehyde functional group or a compound capable of generating at least one aldehyde functional group may be added. In this case, the molar amount of the aldehyde functional group is higher than the molar amount of the isocyanate functional group during the Re2 reaction.

[0069] The P3 polymer can be used immediately after the Re2 reaction without purification.

[0070] In a preferred embodiment, after homogenizing the fiber suspension in the fan pump, polymer P3 is introduced into white water and / or slurry and / or a mixture formed from white water and slurry.

[0071] Advantageously, P3 polymers can also be introduced into the papermaking process at the forming wire or size press, for example by spraying.

[0072] Add 0.25 to 15 kg / t to the fiber suspension. -1 Preferably 0.5 to 5 kg / t -1 P3 polymer.

[0073] Fiber suspensions may include various cellulose fibers that can be used: virgin fibers, regenerated fibers, chemical pulps, mechanical pulps, microfibrillated cellulose, or nanofibrillated cellulose. Fiber suspensions also include the use of these different cellulose fibers and all types of fillers, such as TiO2, CaCO3 (ground or precipitated), kaolin, organic fillers, and mixtures thereof.

[0074] P3 polymers can be combined with other products for use in papermaking processes, such as inorganic or organic coagulants, dry strength agents, wet strength agents, natural polymers such as starch or carboxymethyl cellulose (CMC), inorganic microparticles such as bentonite microparticles and colloidal silica microparticles, and any ionic (nonionic, cationic, anionic, or amphoteric) organic polymers that can be (but are not limited to) linear, branched, crosslinked, hydrophobic, or associated.

[0075] The following examples illustrate the present invention, but do not limit its scope. Detailed Implementation

[0076] Programs used for application testing:

[0077] a) Type of slurry used

[0078] Virgin fiber pulp:

[0079] Wet pulp is obtained by disintegrating the dry pulp to achieve a final water concentration of 1% by weight. This is a pH-neutral pulp consisting of 90% bleached virgin grown fibers, 10% bleached virgin short fibers, and 30% additional GCC (Hydrocal 55 from Omya).

[0080] Regenerated fiber pulp:

[0081] Wet pulp is obtained by breaking down the dry pulp to achieve a final water concentration of 1% by weight. This is a pH-neutral pulp made from 100% recycled paperboard fiber.

[0082] b) Drainage performance assessment (DDA)

[0083] The DDA (“Dynamic Drainage Analyzer”) automatically determines the time (in seconds) required to drain the fiber suspension under vacuum. The polymer is added to the wet slurry (0.6 L of 1.0 wt% slurry) in the DDA cylinder with stirring at 1,000 rpm.

[0084] -T=0s: Stirring slurry

[0085] -T=20s: Add polymer

[0086] -T = 30s: Stop stirring at 200mbar (1 bar = 10). 5 Vacuum drainage for 70 seconds under pressure (Pa).

[0087] The pressure under the fabric is recorded as a function of time. When all the water has drained from the fiber pad, air passes 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 (in seconds) taken for this slope change corresponds to the drainage time. The shorter the time, the better the vacuum drainage effect.

[0088] c) Performance (dry strength) under DSR application, basis weight 90 gm - 2

[0089] Take the required amount of slurry to obtain a weight of 90g.m -2 A piece of paper (sheet).

[0090] A wet slurry is introduced into the barrel of the dynamic formette and agitation is maintained. The various components of the system are then injected into the slurry in a predetermined sequence. Typically, a contact time of 30 to 45 seconds is observed between each addition of the polymer.

[0091] The paper formette is made by an automated dynamic formmaker: absorbent paper and forming fabric are placed in the tank of the dynamic formmaker before the tank is started rotating at 1000 rpm and a water wall is built. The treated pulp is spread on the water wall to form a fiber mat on the forming fabric.

[0092] Once the water is drained, the fiber pad is collected, pressed under a provided pressure of 4 bar, and then dried at 117°C. The resulting paper sheets are left overnight in a humidity- and temperature-controlled chamber (50% relative humidity and 23°C). The dry strength properties of all paper sheets obtained through this procedure are then measured.

[0093] Fracture measurements were performed using a Messier Buchel M 405 fracture gauge according to the TAPPI T403 om-02 standard. Results are expressed in kPa. Fracture index, expressed in kPa·m. 2 / g indicates that the value is determined by dividing the weight of the test paper.

[0094] Dry fracture length was measured longitudinally using a Testometric AX tensile testing machine according to TAPPI T494 om-01. Results are expressed in km.

[0095] Test products in application testing:

[0096] P1 polymer

[0097] In a 1-liter reactor equipped with a mechanical stirrer, thermometer, refrigerant, and nitrogen immersion tube, 310 g of water was introduced. The pH of the reaction medium was adjusted to 3.3 using a pH buffer solution (30 wt% NaOH aqueous solution and 75 wt% H3PO4 aqueous solution). The medium was heated using a water bath and maintained at a temperature of 79–81 °C. Using two consecutive pours, 400 g of 50% acrylamide aqueous solution, 0.28 g of 100% N,N-methylenebisacrylamide, 237.8 g of water, and 2.40 g of 100% sodium methyl allyl sulfonate were added (Pour 1) over 180 minutes. In Pour 2, 0.48 g of 100% sodium persulfate and 48 g of water were added over 180 minutes. After the pouring process, the polymer was placed at 80 °C for 120 minutes.

[0098] The resulting P1 polymer solution had a pH of 5.7, a polymer weight concentration of 20%, and a viscosity of 6000 cps.

[0099] P2 polymer

[0100] A 10% by weight P1 aqueous solution was prepared by diluting 20g of a 20% by weight P1 aqueous solution with 20g of water.

[0101] The polymer solution was heated to 50°C.

[0102] Based on the α and β coefficients of the Re1 reaction, a mixture of 14.6% sodium hypochlorite (by weight in water) and 30% soda ash (by weight in water) was prepared. The mixture of sodium hypochlorite and soda ash was added to the P1 polymer solution while it was at 50°C. After reacting for 30 seconds, water was added. The result was polymer P2 (Table 1: List of P2 polymers).

[0103] α coefficient β coefficient Sodium hypochlorite soda water P2-A 0.35 2 10.05 5.25 144.70 P2-B 0.5 2 14.35 7.5 138.15 P2-C 0.7 2 20.10 10.50 129.40 P2-D 0.05 2 1.44 0.75 157.81 P2-E 0.35 6 10.05 15.75 134.20

[0104] Table 1: P2 polymers

[0105] P3 polymer

[0106] • Three minutes after obtaining the P2 polymer, 1.7 g of glyoxal (40% by weight aqueous solution) was added to carry out the Re2 reaction, based on a polymer content of 17% by weight. Polymers P3-A1, P3-B1, and P3-C1 were obtained.

[0107] • Three minutes after obtaining the P2-B polymer, 6.5 g of P5 polymer and 25 g of water were added to carry out the Re2 reaction, wherein the P5 polymer was 11% by weight. The P3-B3 polymer was obtained.

[0108] • Three minutes after obtaining the P2 polymer, the pH was adjusted to 10, and 0.67 g of glycerol triglycidyl ether (E-100) was added to carry out the Re2 reaction, based on a polymer weight of 17%. P3-A5 and P3-B5 polymers were obtained.

[0109] • Three minutes after obtaining the P2 polymer, the pH was adjusted to 10, and 0.67 g of pentaerythritol tetraglycidyl ether (GE-500) was added to carry out the Re2 reaction, based on a polymer weight of 17%. P3-A6 and P3-B6 polymers were obtained.

[0110] P4 polymer

[0111] In a 1-liter reactor equipped with a mechanical stirrer, thermometer, refrigerant, and nitrogen immersion tube, 153 g of water, 67 g of 64% diallyldimethylammonium chloride, and 5.0 g of sodium hypophosphite were introduced. The pH of the reaction medium was adjusted to 2.5 using 96% sulfuric acid. The medium was heated using a water bath and maintained at a temperature of 79–81°C. 715 g of a 50% (wt) acrylamide aqueous solution was added in two consecutive pours over 135 minutes (Pour 1). In Pour 2, 4.0 g of 100% sodium persulfate and 56 g of water were added over 160 minutes. After the pouring process, the polymer was placed at 80°C for 30 minutes. Before aging at 80°C, 1 g of a 40% (wt) sodium bisulfite aqueous solution was added over 60 minutes.

[0112] The resulting P4 polymer solution had a pH of 5.2, a concentration of 40% by weight, and a viscosity of 2300 cps.

[0113] P5 polymer

[0114] In a 1000 ml stirred reactor, 211 g of P4 polymer and 745 g of deionized water were introduced. The reactor was equipped with a pH measuring probe. After stirring for 10 minutes, the pH was adjusted to 11.2 with a 30% by weight sodium bicarbonate solution. The temperature was maintained between 19 and 26 °C.

[0115] Add 42 g of a 40 wt% glyoxal aqueous solution. pH control and viscosity monitoring allowed for a product viscosity of 20 cps (viscosity at the end of the reaction). When this viscosity was reached, the reaction was stopped by lowering the pH to less than 3.5 with the addition of 92 wt% H2SO4 aqueous solution. Record the final viscosity and pH. A P5 polymer with a concentration of 7.5 wt% was obtained.

[0116] For all viscosity measurements, the viscometer was a Brookfield type, with a modulus of LV1 and a speed of 60 rpm.

[0117] P3-CE polymer (counterexample)

[0118] • Three minutes after obtaining the P2-D polymer, 1.7 g of glyoxal (40% by weight aqueous solution) was added to carry out the Re2 reaction, based on a polymer content of 17% by weight. This yielded the P3-CE-1 polymer. This polymer was unstable and formed a solid gel.

[0119] • Three minutes after obtaining the P2-E polymer, 1.7 g of glyoxal (40% by weight aqueous solution) was added to carry out the Re2 reaction, based on a polymer content of 17% by weight. The P3-CE-2 polymer was obtained.

[0120] Application testing

[0121] Drainage performance (DDA)

[0122] Observation: The tests were conducted in series; a blank test was performed each time.

[0123] Series 1

[0124]

[0125] Table 2: Drainage properties based on P2 or P3 polymers

[0126] An improvement in drainage was observed as the α coefficient increased. For the same α coefficient, polymer P3 exhibited better performance than polymer P2. This demonstrates the benefits of the Re2 reaction.

[0127] Series 2

[0128]

[0129]

[0130] Table 3: Based on the drainage properties of polymers

[0131] CE-3: During the drainage sequence, P2 and P5 polymers are added simultaneously without prior mixing in the pulp.

[0132] Glyoxal-modified P5 polymer alone has no effect on drainage performance. Compared with P2 polymer, improved drainage performance was observed in P3 polymer. The addition of P5 polymer to P2 polymer during the Re2 reaction resulted in a polymer with better performance.

[0133] Series 3

[0134]

[0135]

[0136] Table 4: Based on the drainage properties of polymers

[0137] It was observed that the drainage properties of the P3 polymer obtained by adding an epoxide to the P2 polymer were improved during the Re2 reaction.

[0138] Series 4

[0139]

[0140] Table 5: Based on the drainage properties of the polymer

[0141] PA: A copolymer of acrylamide and acrylic acid in an aqueous dispersion (70 / 30, mol%)

[0142] The polymers of this invention, with the addition of anionic PA polymers, improve drainage performance. P3-CE-2 polymers with a β coefficient greater than 4 do not provide DDA properties. P3-CE-1 polymers with an α coefficient of 0.05 are unusable.

[0143] Series 5

[0144]

[0145]

[0146] Table 6. Based on the drainage properties of the polymer

[0147] CE-5-3 and CE-6-5 are derived from U.S. Patent 8,262,859 (Examples 3 and 5).

[0148] Glyoxalized CE-5-3 and CE-6-5 polyethyleneamines exhibited inferior drainage performance compared to P3 polymers.

[0149] Performance (dry strength) in DSR applications

[0150] pH 6.5 slurry

[0151] % burst index %DBL SM %DBL ST blank Reference Reference Reference P2-B 15％ 9％ 14％ P3-B-1 18％ 12％ 26％ P3-B-5 19％ 10％ 18％ P3-B-6 19％ 17％ 18％ CE-5-3 9％ 9％ 19％ CE-6-5 2％ 4％ 9％

[0152] Table 7: Based on the dry strength of the polymer

[0153] Compared to P2 polymers and their CE counterparts (counterparts), the use of P3 polymers improved bursting strength. The same trend was observed in fracture length measurements in both the forward (DBL SM) and transverse (DBL ST) directions.

Claims

1. A method for producing paper or paperboard from a fiber suspension, comprising the following steps: a) Inject the P3 polymer into the cellulose fiber suspension. b) Forming paper or paperboard, c) Dry paper or cardboard. Prior to step a), polymer P3 is prepared from a water-soluble polymer P1 composed of at least one nonionic monomer selected from acrylamide, methacrylamide, N,N-dimethylacrylamide, and acrylonitrile. The P1 polymer is subjected to a Re1 reaction to obtain the P2 polymer, and then the P2 polymer is subjected to a Re2 reaction to obtain the P3 polymer. The P3 polymer is injected into the fiber suspension within 24 hours after the start of the Re1 reaction. - The Re1 reaction comprises preparing a P2 polymer containing isocyanate functional groups by reacting (i) an alkali metal hydroxide and / or an alkaline earth metal hydroxide, (ii) an alkali metal hypohalide and / or an alkaline earth metal hypohalide, and (iii) a P1 polymer for 10 seconds to 60 minutes. The Re1 reaction is carried out at a temperature of 30°C to 60°C, with coefficient α = moles of hypohalide / moles of nonionic monomer of water-soluble P1 polymer ranging from 0.1 to 1.0, and coefficient β = moles of hydroxide / moles of hypohalide ranging from 0.5 to 4.

0. The weight-average molecular weight of the P1 polymer is between 100,000 and 20,000,000 Daltons. - The Re2 reaction comprises the preparation of a P3 polymer by reacting (iv) a compound containing at least one aldehyde functional group or a compound capable of generating at least one aldehyde functional group with (v) the P2 polymer containing an isocyanate functional group, wherein the Re2 reaction is carried out at a temperature of 10°C to 60°C by adding 2% to 50% of the compound containing at least one aldehyde functional group or a compound capable of generating at least one aldehyde functional group to the P2 polymer, where % is by weight relative to the weight of the P2 polymer. The method described there is no decarboxylation step after the Re1 reaction.

2. The method according to claim 1, characterized in that... The P1 polymer is nonionic.

3. The method according to claim 1 or 2, characterized in that... The P1 polymer is a homopolymer of acrylamide or methacrylamide.

4. The method according to claim 1 or 2, characterized in that... For the Re2 reaction, the compound containing at least one aldehyde functional group is selected from glyoxal, glutaraldehyde, furanaldehyde, 2-hydroxyhexanedialdehyde, succinal, starch dialdehyde, 2,2-dimethoxyacetaldehyde, and combinations thereof.

5. The method according to claim 1 or 2, characterized in that... For the Re2 reaction, the compound containing at least one aldehyde functional group is glyoxal.

6. The method according to claim 1 or 2, characterized in that... For the Re2 reaction, the compound capable of producing at least one aldehyde functional group is a polyepoxide.

7. The method according to claim 1 or 2, characterized in that... For the Re2 reaction, the compound capable of generating at least one aldehyde functional group is a nonionic, cationic, anionic, or amphoteric P5 polymer, which is obtained by reacting a compound containing at least one aldehyde functional group with at least one base polymer P4 containing at least one nonionic monomer selected from acrylamide, methacrylamide, N,N-dimethylacrylamide, and acrylonitrile.

8. The method according to claim 7, characterized in that The base polymer P4 further comprises a cationic monomer selected from the group consisting of: quaternized or salted dimethylaminoethyl acrylate (ADAME), quaternized or salted dimethylaminoethyl methacrylate (MADAME), dimethyl diallyl ammonium chloride (DADMAC), acrylamidopropyltrimethylammonium chloride (APTAC), and methacrylamidopropyltrimethylammonium chloride (MAPTAC).

9. The method according to claim 7, characterized in that... The base polymer P4 further comprises anionic monomers selected from the following: 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, methacrylic acid, itaconic acid and / or their salts.

10. The method according to claim 7, characterized in that... The P5 polymer is obtained within a maximum of 12 hours prior to its addition to the P2 polymer by reacting a compound containing at least one aldehyde functional group with at least one base P4 polymer.

11. The method according to claim 1, characterized in that... After homogenizing the fiber suspension in a dilution pump, the P3 polymer is introduced into white water and / or slurry and / or a mixture formed from white water and slurry.

12. The method according to claim 1, characterized in that... The weight-average molecular weight of the P1 polymer is between 250,000 and 5,000,000 Daltons.

13. The method according to claim 1, characterized in that: - The Re1 reaction is carried out in an aqueous solution of P1 polymer with a mass concentration of 0.5% to 20%; - The Re2 reaction is carried out in the presence of a P2 polymer and 10 to 100% by weight of a compound containing at least one aldehyde functional group or a compound capable of generating at least one aldehyde functional group relative to the P2 polymer.

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