FI119481B - Cellulose particles modified with cationic polyelectrolytes, process for making them and use in the manufacture of paper and paperboard - Google Patents

Description

119481

Cellulose particles modified by cationic polyelectrolytes, process for their preparation and use in paper and board production

The present invention relates to improving dewatering and retention in the manufacture of paper and board. The present invention relates to cationic polyelectrolyte modified cellulose particles useful for this purpose, which are regenerated cellulose and have an outer surface comprising low and high molecular weight cationic polyelectrolytes. The invention further relates to a process for the production of polyelectrolyte modified cellulose particles, their use in the manufacture of paper or board and to a process for the production of paper or board.

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State of the art

The pulp for paper and paperboard consists mainly of cellulose fibers, fine pulp and fillers. Typically, high molecular weight charged polymers are added to the pulp as dewatering and retention aids to adsorb the fines and fillers to the fibers so that they are not leached with the water removed from the web. Further, the mass comprises a quantity of * * * algae so-called. interfering substances, which generally refer to soluble or co-anionic oligomers or polymers and non-ionic hydrocolloids.

.. 25 These substances increase the cationic need of the pulp and diminish the effectiveness of the retention aids and the paper strength agents. The result is e.g.

• · ** formation of deposits in the paper machine, disruption of web formation and dewatering, and deterioration of paper strength and opacity. Special-. "it is highly interfering with recycled fiber and mechanical ***** 30 masses. The effect of anionic interfering agents can be counteracted by the addition of low molecular weight cationic polymers to the pulp, 2 119481, whereby the efficacy of the subsequent dewatering and retention aids is improved.

EP 0 752 496 B1 describes an improved papermaking process for dewatering and retention, wherein a low molecular weight (LMW) cationic polymer, a high molecular weight (HMW) cationic or amphoteric polymer and anionic inorganic particles are added to the papermaking pulp. The HMW polymer has a molecular weight of more than 1,000,000 and the LMW polymer has a molecular weight of less than 700,000. The HMW polymer may be exemplary of cationic starch, cationic guar gum or cationic acrylamide based polymer. The LMW cationic polymer may be, for example, a homo- or copolymer based on starch, polyamine, polyethyleneimine or diallyl dimethylammonium chloride, vinylamine, (meth) acrylamide, (meth) acrylate monomers or mixtures thereof. Anionic inorganic particles include silica-based particles, smectite-type clays and titanyl sulfate salts. The polymers are added to the pulp substantially simultaneously and in the same place, for example as a mixture, preferably before the addition of the inorganic particles.

Particularly when high cationic polymers are added to the pulp, it is difficult to dispense properly. Overdose leads to excessive cationization and cationic dispersion of the web and the water leaving it. Excessive dosing of cationic polymers is more easily avoided when cationic groups are bound to · · · · * * * pulp conditions on an insoluble carrier such as inorganic and organic particles. An additional benefit is the simplification of the paper and board manufacturing process and the easier flow control of the chemical, when the benefits of dewatering and retention of cationic polymers are achieved by | by massing a single component into the mass.

US 6,184,302 B1 describes a substantially water-insoluble and cationic polymer containing a cationic polymer 3 119481 or a copolymer containing lyl and / or vinyl double bonds and nitrogen, a process for their preparation and a papermaking process using them. The cationized solid particles are prepared by crosslinking an aqueous cationic polymer or copolymer in the presence of solid particles with a free radical initiator itself and / or solid particles, with reaction times varying from 1 to 12 hours. particles while stirring vigorously and heating. The cationizable solids are at least 80% water-insoluble, for example, particulate forms of cellulose or mineral, or even fibers, films, or textiles. Cationic polymers and copolymers include linear polyethyleneimines, polyallylamines, polydiallylamines, hydrolyzed poly-N-vinylpyrrolidones, hydrolyzed polyvinylcaprolactams, amino-containing peptides, and chitosan. The cationized solid particles can be used as a retention aid and as a binder in papermaking.

Published Patent Application EP 0 845 495 A2 discloses cellulose particles which are substantially insoluble in water and have cationic · · ♦ groups on their surface, a process for making such cellulosic particles, and their use in the manufacture of paper and board interfering substances. • · • · ·: and as a flocculant in waste water treatment. The particles may be prepared, for example, by bonding a polymer containing cationic or subsequently cationic groups to the cellulose surface by means of a catalyst or initiator under near dry conditions and at elevated temperature. Alternatively, at least one. 25 types of reagents, which may be copolymerized or crosslinked, of which at least one contains cationic or later cationizable groups, · * "impregnated on the surface of the carrier cellulose particles and polymerized [under suitable conditions in the presence of cellulose, polymer formation and cross-linking form mechanical bonds with the cellulose surface 30. The cationizable material may be bleached, unsubstituted cellulose or a cellulose derivative such as an ether or ester, chitin and derivatives thereof.

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For example, low molecular weight polyDADMAC as concentrated aqueous solutions or other water-soluble cationic or cationizable group-containing polymers that are capable of further reacting with the use of a free radical initiator as catalyst may be used as the cationizer.

The cationized cellulose particles can be prepared by spraying an aqueous solution of the free radical initiator acting as a catalyst into the substantially dry, finely divided cellulose powder in the mixer. A solution of a cationic polymer such as polyDADMAC is slowly added to the moist powder thus obtained. The catalyst and cationic polymer may also be pre-mixed and added together. The water content of the powder is kept low. In the reaction vessel, air is replaced with nitrogen and the temperature is raised to at least 65 ° C with stirring, with reaction times of several hours. The resulting cationized cellulose particles are added to the pulp prior to the retention aids in the manufacture of paper and board, whereby the particles bind interfering Union substances to the paper, improving the effect of retention agents such as polyacrylamides and fillers. The cationized cellulose particles may also be mixed with an aqueous solution of a water-soluble polymer such as polyethyleneimine or polyacrylamide before use.

The published patent application WO 96/26220 discloses cationized cellulosic particles, wherein preferably at least 50% of the cationic groups are present in the particles. »'I in the interior of the pile, where cationic groups are bound throughout the particle cross-sectional area of the particle. The cellulose may be unsubstituted pulp, substituted cellulose such as an ester or ether of cellulose, or alkaline cellulose. The cationization reaction can be carried out between the solids by trituration or dissolving the cellulose into the solution to which the cationization agents are added and precipitating the cationized cellulose into particles. Highly substituted soluble cellulose, e.g. carboxymethyl cellulose, can also be precipitated as particles in an aqueous solution of cationic polyelectrolytes to form cationized cellulose particles. The cationization agent may be an aluminum salt, a cationic poly ·, electrolyte and a reactive monomer. The cationized cellulose particles may be spherical or fibrous. The cationized cellulose particles can be used in papermaking, whereby a fibrous structure is preferred, or as flocculants, for example in waste water treatment. When used in papermaking, particles are said to improve paper strength and fines retained from the web. The particles can be used as a solid or suspension alone or in combination with water-soluble polymers such as cationic polyacrylamide, polyethyleneimine and water-soluble cellulose derivatives, whereby in papermaking the particles are advantageously added to the pulp and the polymer just prior to web formation and water purification. preferably added as a mixture.

EP 1 047 813 B1 describes cationic cellulose fibrils having more than 10% to 50% by weight of a cellulose polymeric amine having a weight average molecular weight in the range of 100,000 to 1,000,000 and comprising monomer units -XCR3 of the formula (CH2) ) nNR 1 R 2) (CH 2) m-9 wherein X is selected from a chemical bond, O and NR 4; R1 and R2 are the same, ···. different or different, and are selected from H, C 1 -C 4 alkyl, phenyl, and one selected from the group consisting of: •. or three of C 1 -C 4 -alkyl, C 1 -C 4 -alkoxy, F, Cl and Br with an intermediate •.

: 20 is a substituent substituted phenyl; R and R are independently selected

· * · I

: H, methyl and ethyl; m is a variable from 1 to 4; and n is an initial • I ·; · * · The variable in 0-4. Also described is the process of cationic cellulosic fibrils: by adding an aqueous solution of said polymeric amine to a viscous solution, mixing the resulting solution with a coagulation and regeneration solution in a vortex flow and collecting the cationic cellulose fibrils. .

»• t By using just certain types of polymeric amines for cationization, the dissolution of the cationic polymer in the regeneration agent and the polymer release are prevented; · · · From the surface of the cellulose particle, when the particles are washed with water. Cationic cellulosic fibrils can be used as an additive in the manufacture of paper and board, especially to improve web formation and dewatering.

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The unmodified particles of regenerated cellulose resemble in many respects the chemical and mechanical pulps of the pulp contained in the chemical pulp. Compared to cellulosic fibers, both have a small particle size with a large hydrodynamic surface area. In addition, they bind more water than fibers and are somewhat anionic. Both the particles and the fines in the regenerated cellulose increase the strength and density of the paper and reduce the light scattering by reducing the number of optical interfaces between solid and air. The particles of regenerated cellulose differ from the pulp fines in that they are clearly spherical in shape and have a somewhat colloidal surface whereas the pulp fines are filamentous. Another significant difference is in particle size distribution, which is of particular importance in terms of light scattering properties. The fines are defined as all particles that pass through a 200 mesh sieve, so that the fines are a very heterogeneous set of particles that vary in size over a wide range from nanometers to 76 µm. The average particle size of the regenerated cellulose is usually in the order of a few micrometers and has a relatively narrow particle size distribution. Thus, the structure of the particles of regenerated cellulose is more favorable for light scattering.

The use of particles of regenerated cellulose modified by cationic polyelectrolytes according to the invention in the manufacture of paper and board has several advantages. Modification with cationic polyelectrolytes significantly improves the retention of J · · cellulose particles in the web, so that when used as filler for paper or cardboard, the particles of regenerated cellulose may be partially or completely replaced by the modified admixtures of the invention. • ·· * ... with lulose particles. The addition of the cellulose particles of the invention to the pulp also improves the retention of other components used in the manufacture of paper and board. Modified cellulose particles according to the invention *. * provides better dewatering than the use of corresponding ***** unmodified or modified with only one cationic polymer.

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In the modified cellulose particles of the present invention, the canonical groups are located on the outer surface of the particles, whereby they can more effectively bind the interfering substances as compared to the solution in which the cationization agent is added to the cellulose solution. In this solution, a large part of the cationic groups remain inside the particles 5 when the cellulose solution is regenerated. In addition, a significant amount of cationization agent may remain in the regeneration solution.

Compared to solutions in which the cationic groups are bound to the support by polymerization by a starter, the modification carried out in the process of the present invention is considerably faster, even though the process involves the modification of the particles with two different polyelectrolytes. duaalipolymeerisysteemi.

It is also preferred that the modified particles according to the invention carry organic particles which carry cationic groups. The higher the organic content of the paper and board components, the less ash is formed when the paper or board is burned. The modified cellulose particles of the invention have the added advantage of being lightweight and non-abrasive in relation to the mineral components used in paper and board making the use of the modified cellulose particles of the invention. ! reduces the basis weight of paper and board and reduces machine wear.

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OBJECTIVE OF THE INVENTION It is an object of the invention to provide cellulose particles modified by cationic polyelectrolytes.

It is also an object of the invention to provide a process for preparing cellulose particles modified with cationic polyelectrolytes.

·: · *: 30 • · • · · • M • ». 119481

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A further object of the invention is the use of modified cellulose particles in the manufacture of paper or board.

It is a further object of the invention to provide a process for making paper or board 5.

The cationic polyelectrolyte modified cellulose particles of the invention, the process for their manufacture, their use in the production of paper and board and the process for the production of paper or board are characterized in what is claimed.

Summary of the Invention

The invention relates to cationic polyelectrolyte modified cellulose particles, wherein the cellulose particles are particles of regenerated cellulose and have an outer surface of molecular weight in the range of 20,000 to 500,000 g / mol and a charge density of more than 3 meq / g in mol and charge · *** of the moiety of the second cationic polyelectrolyte in the range of 0.5 to 3 meq / g • · J ·! : 20 leeches.

The invention also relates to a process for the preparation of cationic polyelectrolyte modified "t" · * cellulose particles. In process (a), the cellulose solution is passed to: *** a regenerating solution to precipitate the cellulose particles; (b) the formed cellulose particles are washed with water until the pH is no longer substantially changed, and then with a basic solution until the pH is basic; (c) modifying the outer surface * · · * of the cellulose particles with a molecular weight in the range of 20,000 to 500,000 g / mol and charge | comprising a first cationic polyelectrolyte of greater than 3 meq / g. aqueous solution; followed by (d) modifying the outer surface of the cellulose particles with a molecular weight in the range of 2 to 10 million g / mol and a charge density of 9 119,481 in the range of 0.5 to 3 meq / g. in an aqueous solution comprising a second cationic polyelectrolyte, wherein steps (c) and (d) are carried out sequentially in the same aqueous solution.

The cationic polyelectrolyte modified cellulose particles according to the invention can be added to the pulp in the manufacture of paper or board, whereby the combination of retention and dewatering is improved compared to the addition of the corresponding unmodified or single cation polyelectrolyte modified cellulose.

In the following, the invention will be illustrated by means of figures and detailed description, and by way of example but not intended to be limited thereto.

DRAWINGS Figure 1 is a graph showing the dewatering time, in seconds, of pulps containing 6 and 14% by weight of cellulose particles comprising cationic polyDADMAC and polyacrylamide (C-PAM) molecules prepared according to Example 1, with particles added to one mass. ** continued to precipitate sodium dodecyl sulfate (SDS). Comparisons were made of zeta- • i ·· · 20 cellulose modified with potentials of -10 mV and +20 mV polyDADMAC. Particulate matter and unmodified cellulose particles 6 and 14% by weight. The cellulose particles used in the comparisons were prepared by regeneration as in Example 1. A portion of the particles were washed and modified at 1.0 g / L in polyDADMAC solutions containing 0.6 mg / L (zeta-. 25 potential -10 mv) and 1.8 mg / l (zeta potential +20 mV).

Fig. 2 shows a graph of unmodified and one cationic | sheet metal retention retention of polyelectrolyte modified cellulose particles at target sheet contents of 6 and 14% by weight, as well as retention values of sheet * modified particles of two * · ** · 30 cationic polymers. * *: at a target concentration of 6.14 and 22% by weight.

119481 ίο

Detailed Description of the Invention

Surprisingly, it has been found that the problems encountered in the prior art solutions can be avoided or at least substantially reduced by the process of the invention. The invention is based on the discovery that modifying the regenerated cellulose particles with low and high molecular weight cationic polyelectrolytes and adding the resulting modified cellulose particles in the manufacture of paper or board to the pulp can clearly improve the combination of retention and dewatering, cellulose particles modified with a single cationic polymer.

The invention relates to cellulose particles modified by cationic polyelectrolytes, wherein the cellulose particles are particles of regenerated cellulose and their outer surface comprises low molecular weight first cationic polyelectrolyte molecules and high molecular weight second cationic polyelectrolyte. "Regenerated cellulose particles" refers to particles regenerated from dissolved cellulose in a known manner, whereby the raw material may be, for example, cellulose xanthate, i.e. viscose, or in time. • 20% cellulose, and precipitation may have been effected, for example, by spraying with cellulose. saline to acid solution. The particles may be spherical, needle-shaped, fibrous, granular or the like and may have some porosity. The outer surface of the cellulose particles herein refers to the area with which the molecules of the cationic polyelectrolyte may come into contact when the cellulosic particles are cationized in an aqueous polyelectrolyte solution. Low molecular weight in this range refers to an average molecular weight of 20,000 to 500,000 g / mol, preferably 100,000 to 500,000 g / mol. The charge density of the low molecular weight * cationic polyelectrolyte should be greater than 3 meq / g, preferably *. * added 5-8 meq / g. By high molecular weight is meant in this range 2-10 ***** 30 million g / mol, preferably in the range 5-10 million. g / mol average mo- • · *. *: Weight of leech. The charge density of the high molecular weight cationic polyelectrolyte 11,119,481 should be in the range of 0.5 to 3 meq / g, preferably in the range of 0.5 to 1.5 meq / g. All water-soluble cationic poly-electrolytes that meet the above criteria can be used as polyelectrolytes. Useful polyelectrolytes can be either straight-chain or branched. Thus, for example, starch 5 can be used.

Preferably, the zeta potential of the first and second cationic polyelectrolyte modified cellulose particles, which describes the electric field mobility of the charged particles, is at least + 5 mV, measured at pH 8. The first cationic polyelectrolyte is preferably polydiallyl dimethylammonium chloride (polyDADMAC) and the second cationic polyelectrolyte is preferably a cationic polyacrylamide. The first cationic polyelectrolyte is polyDADMAC preferably having a molecular weight of 100,000 to 500,000 g / mol, and the second cationic polyelectrolyte having a cationic polyacrylamide preferably has a molecular weight of 5-10 million g / mol.

The modified cellulose particles of the invention may, in principle, be of any shape and size. Depending on the application, the particles may be, for example, spheres, fibers, grains or the like. When used in paper and board making: the modified cellulose particles of the invention are • · • · * ·· *! for example, spherical and having an average particle size in the range 0.05: * · γ -10 µm.

The outer surface of the cellulose particles may have been further modified with an anionic surfactant to provide hydrophobicity to the cellulose particles. In addition to the first and second cationic polyelectrolytes, the outer surface of the cellulosic particles comprises any anionic surfactant, for example [oleate, stearate or SDS. Preferably, the anionic surfactant is SDS.

The invention also relates to a process modified with cationic polyelectrolytes. *: for the preparation of cellulose particles. In process (a), a cellulose solution is introduced into 12,119,481 regenerating solutions to precipitate cellulose particles; (b) washing the formed cellulose particles with water until the pH is no longer substantially changed, and then with the alkaline solution until the pH is basic; (c) modifying the outer surface of the cellulosic particles in an aqueous solution comprising a first cationic polyelectrolyte having a molecular weight in the range of 20,000 to 500,000 g / mol and having a charge content greater than 3 meq / g; followed by (d) modifying the outer surface of the cellulose particles in an aqueous solution of a second cationic polyelectrolyte having a molecular weight in the range of 2 to 10 million g / mol and having a charge density of 0.5 to 3 meq / g, wherein steps (c) and (d) are performed sequentially in . After modification, the cellulose particles are recovered, for example by filtration, and used immediately. Optionally, the modified cellulose particles can be stored in a cool place, for example at + 5 ° C, before use.

The cellulose solution used in step (a) of the process of the invention may be any regenerable dissolved cellulose, for example a viscose solution or an alkaline cellulose solution. A suitable concentration range for the cellulose solution is 0.5 to 7%. Regeneration of the dissolved cellulose into cellulose particles is most easily accomplished, for example, by spraying or mixing the cellulose solution with a regenerating solution. When regeneration is carried out by mixing, for example • · • · ·! ·! ! By gradually adding the cellulose solution in a burette, the regenerating solution must be agitated effectively, for example, with a magnetic stirrer at 600 to 1000 rpm. When • · * · * “i regeneration is accomplished by spraying, it is possible, for example, to use steplessly • i *

Hl of spray bottle with adjustable fan nozzle, or equivalent.

• «• · *** The nozzle spreading angle can be selected, for example, from 10 ° to 150 °. A suitable spreading angle depends, e.g. distance of the nozzle to the regenerating solution. The farther the spraying occurs, the smaller the application angle can be. When spraying the regenerative solution at a distance of 20 - 30 cm, a suitable application • ·. the angle is from 20 ° to 60 °. The regenerating solution is preferably acid, more preferably diluted. honey sulfuric acid solution such as 1 M sulfuric acid solution. Other options include * ·· # ♦] * 30 other strong acids such as HCl as well as HC104, HI, HBr and HNO3 can be used. When modified cellulose particles produced by the process of the invention are to be used in paper and board production, the average particle size of the cellulose particles is preferably in the range of 0.05 to 10 µm. The particle size of the cellulose particles to be precipitated is obtained in a desired range by selecting parameters of the manufacturing process, such as the cellulose content of the cellulose solution and the droplet size when the cellulose solution is sprayed into the regenerating solution.

The cellulose particles formed in step (b) of the process of the invention are first washed with water until the pH is no longer substantially changed, and then with a basic solution until the pH is basic. Suitable alkaline solutions are, for example, aqueous solutions of alkali metal hydroxides and hydrogen carbonates or mixtures thereof. Washing with water and a basic solution is carried out, for example, on a filter, whereby the pH change can be monitored from the pH of the filtrate. Preferably, the regenerated cellulose lozenge particles are washed with water until the pH of the filtrate reaches at least about 4. Thereafter, the cellulose particles are preferably washed with a NaOH / NaHCO 3 solution, each having a concentration of, for example, about 1 mmol / l. Washing with the alkaline solution is continued until the pH of the filtrate is> 7, preferably until about 8. After washing, the moist cellulosic particles are transferred directly to the modification step.

In step (c) of the process of the invention, the outer surface of the cellulosic particles is modified in a molecular weight range of 20,000 to 500,000 g / mol and a charge. In a 25% aqueous solution of the first cationic polyelectrolyte having a density greater than 3 meq / g followed by a modification of the outer surface of the cellulosic particles in step (d) having a molecular weight in the range of 2 to 10 million g / mol and in an aqueous solution comprising a second cationic polyelectrolyte having a charge density in the range of 0.5 to 3 meq / g, wherein steps (c) and (d) are carried out sequentially in the same aqueous solution. surface area of the suspended cellulose particles with which the polyelectrolyte molecules can come into contact.

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Preferably, the outer surface of the cellulose particles is modified in an aqueous solution of the first cationic polyelectrolyte, to which a second cationic polyelectrolyte is then added. However, steps (c) and (d) may also be carried out in the reverse order, in which the outer surface of the cellulose particles is first modified in an aqueous solution of a second cationic polyelectrolyte to which the first cationic polyelectrolyte is added. Each modification step lasts 1 to 30 minutes, preferably 1 to 5 minutes. By successively carrying out each of the modification steps in the same aqueous solution, the collection and washing of the cellulose particles between the modifications is avoided, and the modified cellulose particles can be prepared in the shortest possible time.

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In the process of the invention, it is preferable to select the concentrations of the first and second cationic polyelectrolytes such that the modified cellulose particles have a zeta potential of -10 to -5 mV after the first modification step and at least +5 mV after the second modification step measured at pH 8. .

The concentration of cationic polyelectrolyte required to effect a certain amount of zeta potential change in the cellulosic particles is determined as a precursor to the following. From the cationic polyelectrolyte, a dilution is made of: • 20 ppm to a suitable concentration range, each dilution is modified • ·: a small amount of regenerated cellulose, washed as described above! particles and the zeta potential of the modified cellulose particles are measured on a Coulter • · · '· * · * Delsa 440 instrument. Because pH affects the value of the zeta potential, the measurement is performed at the same pH at which the cellulose particles to be modified are washed, for example, at pH 8. The measurement results are plotted for the zeta of the cellulose particles. potential curve as a function of cationic polyelectrolyte concentration. Aiming to · · • «*! ' read the curve for the polyelectrolyte content required to obtain the zeta potential value.

The first cationic polyelectrolyte preferably has a molecular weight in the range of 100,000 to 500,000 g / mol and the second cationic polyelectrolyte has a molecular weight of 15,119,481 in a range of 5-10 million g / mol. The charge density of the first cationic polyelectrolyte is preferably in the range of 5-8 meq / g and the charge density of the second cationic polyelectrolyte is in the range of 0.5 to 1.5 meq / g.

In the process of the invention, the first cationic polyelectrolyte is preferably polyDADMAC and the second cationic polyelectrolyte is a cationic polyacrylamide. The first cationic polyelectrolyte is polyDADMAC preferably having a molecular weight of 100,000 to 500,000 g / mol, and the second cationic polyelectrolyte having a cationic polyacrylamide preferably having a molecular weight of 10 to 10 million g / mol.

The process of the invention may further comprise the step of modifying the outer surface of the cellulose particles with an anionic surfactant, preferably SDS. Preferably, the anionic surfactant modification is effected by mixing the surfactant with the first or second cationic polyelectrolyte, depending on which of the latter modification is carried out, wherein the surfactant modification is carried out simultaneously with the latter cationic polyelectrolyte. Alternatively, the modification with an anionic surfactant can be carried out in 20 separate steps with the first and second cationic polyelectrolyte modi · ·: After ringing, the surfactant is added to an appropriate concentration of solvent. · Jossa ϊ where the latter cationic polyelectrolyte modification is more effective 1 1 * ·: · 1, or by collecting cellulose particles modified by cationic polyelectrolytes, for example by filtration and slurrying in a Union surfactant. aqueous solution.

In order to ensure the homogeneity of the cationic polyelectrolyte modified cellulose particles to be prepared, the aqueous suspension of the cationic polyelectrolyte and the * cellulose particles may be mixed or shaken during the modification. The modification can be carried out at a temperature of 5 to 95 ° C, preferably at a temperature of 20 to 50 ° C. Further, the modification is preferably carried out at an ionic strength of less than 0.1 M.

After modification, the cellulose particles are recovered, for example, by filtration and added to the pulp of paper or board. Optionally, the modified cellulose particles can be stored in a cool place, for example at + 5 ° C, before use.

When using the modified cellulose particles of the invention in the manufacture of paper and cardboard, the particles are added to the pulp at a convenient point in the system prior to the press section, preferably in a short rotation and or board containing 0.01% to 50% by weight. The modified cellulose particles of the invention used in the manufacture of paper and board preferably have a particle size in the range of 0.05 to 10 µm. The modified cellulose particles of the invention are suitable for use in both fine and mechanical pulp papers, such as LWC, ULWC, MWC and SC.

·· *! 20 •: Examples • · · · · · · · · · · · · · · · · · · ·

Example 1. Preparation of Cationic Polyelectrolyte Modified Cellulose Particle Particles 25,800 g of viscose was diluted to 6.6% and the solution was dropped from the burette 1. M batches of large quantities of sulfuric acid with a magnetic stirrer. Meyer flask to precipitate cellulose particles (about 252 g total). Here • ·. with the amount of viscose used, the consumption of sulfuric acid was 4 kg. The regenerated cellulose * 30 lozenge particles were then washed with water on the filter until the filtrate pH reached 4, four times in total. Thereafter, the cellulose particles were washed with a solution of 11,119,481 containing 1 mM NaOH and NaHCO 3 until the pH of the filtrate reached 8. The average particle size of the particles was measured to be 3.7 µm.

Next, the isoelectric point and zeta-5 potential curve of the cellulose particles as a function of the concentration of the cationic polyelectrolyte used in the modification were determined. Dilution formulations were prepared from the repentant polyacrylamide (Fennopol K3400R, mp 6-7x106 g / mol, charge 1.1 meq / g) and polyDADMAC (Salcare SC30, mp> 300,000 g / mol) to modify a small amount of cellulose particles , and the zeta potentials of the modified cellulose particles were determined. The cellulose particles washed prior to modification had a zeta potential of -19.2 mV. Based on the curve, suitable concentrations of cationic polyelectrolytes were selected to achieve the target zeta potential of +5 mV.

For the preparation of cationic polyelectrolyte modified cellulose particles, the above prepared and washed cellulose particles were suspended in 5.08 g (dry weight) of a 1.0 g / L polyDADMAC solution at 0.9 mg / L with stirring. In this treatment for up to 30 min, the cellulosic particles reached a value of 70% of the isoelectric point. Subsequently, to the polyDADMAC solution containing the cellulose particles was added cationic polyacrylamide to a concentration of 1.6 mg / l and the treatment was continued with further stirring.

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j * ·: until the zeta potential of the cellulose particles reached the target value of +5 mV. Processing time * * * · * ·: up to 30 min.

* A similar batch of cationic polyelectrolytes and SDS was also prepared .. 25 modified cellulose particles. The cellulose particles prepared and washed above were suspended in 5.08 g (dry weight) of a 1.0 g / L polyDADMAC solution in 0.9 mg / L solution with stirring. In this reading, the | the lulose particles reached 70% of the isoelectric point as above. The cationic polyacrylamide and SDS were mixed and the mixture was added to the polyDADMAC solution containing the cellulosic particles so that the cationic * · * · * polyacrylamide content was the same as above, i.e. 1.6 mg / L, and 18 119481 SDS the amount was 0.1% relative to the dry weight of the cellulose particles. The treatment of the first cationic polyelectrolyte modified cellulose particles in this solution was continued with stirring for up to 30 min. The zeta potential of the finished modified cellulose particles was measured at -15 mV.

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Example 2. Use of cationic polyelectrolyte modified cellulose particles in papermaking

Pulp containing 70% dried birch pulp and 30% dried coniferous pulp was milled in a Valley Hollander until a tensile strength of 50 Nm / g was achieved. Sheets weighing 60 g / m 2 were prepared using SCAN-C26: 76. The sheets included cationic polyelectrolyte-modified cellulose particles as well as cationic polyelectrolyte and SDS-modified cellulose particles, and control sheets were unmodified and non-cellulose-containing particles. In the wet pressing of the sheets, drying sheets and two-step pressing at a pressure of 400 + 10 kPa were used. Drying was performed under standard conditions at 23 ° C with a relative humidity of 50%. The light scattering coefficients of the sheets, the peel strengths a a * a: 20 as Scott Bond values and the tensile indices were determined by the methods SCAN-P 8:93, I *: 'TAPPI T 569 and SCAN-P 67:93.

The dewatering times from the pulp were determined on a Dynamic Drainage Analyzer using the following parameters: wire M 0.15 mesh, pre-treatment time 30 s, agitation speed 500 rpm, pressure 0 , 25 kPa, sample density 1 g / l, sample volume 600 ml.

* · ·, · · ·, Retention was calculated from data from sheet making.

* · • · · Φ φ | Figure 1 graphically illustrates the dewatering time, in seconds, of the mass containing 6 and 14% by weight of the inventive cationic polyDADMAC and C-PAM molecules prepared according to Example 1 a * * 30. · '· "Loose particles, the particles added to one mass still comprising 119481 19 SDS, and comparisons to zeta potentials of -10 mV and +20 mV with poly-DADMAC-modified cellulose particles alone and unmodified cellulose particles can be observed. that the dewatering of the pulps containing the modified cellulose particles of the invention is clearly faster than that of the pulp containing unmodified cellulosic particles. when the outer surface of the cellulosic particles comprises both low and high molecular weight cationic polyelectrolytes.

Figure 2 shows the retention of graphically unmodified as well as one cationic polyelectrolyte modified cellulose particles in sheet production at target sheet contents of 6 and 14% by weight, and two 15 cationic . Figure 2 shows that modifying cellulose particles with polyD AD MAC alone to a zeta potential value of +20 mV does little to improve the retention of the cellulose particles, but retention of the unmodified cellulose particles is in fact 10: 20 percentage points better. Reduced cationic * · Mization with polyDADMAC alone to -10 mV zeta potential significantly improves the retention of cellulosic particles. However, the best retention is achieved by incorporating into the sheets the cationic polyelectrolyte modified low and high molecular weight cationic polyelectrolyte particles of the invention. The best retention of almost 100% is achieved by using the inventive Modified cellulose particles according to the invention have a filler content of 14% by weight, wherein the outer surface of the particles comprises SDS in addition to low and high molecular weight cationic polyelectrolytes.

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Claims (16)

1. Cellulose particles modified with cationic polyelectrolytes, characterized in that the cellulose particles are particles of regenerated cellulose and their outer surface comprises molecules of a first cationic polyelectrolyte having a molecular weight in the range of 20,000 - 500,000 g / mol. over 3 meq / g and molecules of a second cationic polyelectrolyte having a molecular weight in the range of 2 to 10 million g / mol and a charge density in the range of 0.5 to 3 meq / g. 10 2. Modified cellulose particles according to claim 1, characterized in that the zeta potential of the cellulose modified cellulose modified particles is at least +5 mV measured at pH 8. Modified cellulose particles according to claim 1 or 2, characterized in that the molecular weight of the first cationic polyelectrolyte is in the range 100,000 - 500,000 g / mol and the molecular weight of the second cationic polyelectrolyte is in the range 5-10 million g / mol. • m «# • · • · · • 1:.: · 20 4. Modified cellulose particles according to any of claims 1-3, characterized in that the charge density of the first cationic polyelectrolyte lies within the range 5-8 meq / g and the charge density. of the second cationic polyethylene: 1 electrolyte is in the range of 0.5-1.5 meq / g. · • · 5. Modified cellulose particles according to any one of claims 1 to 4, characterized in that the first cationic polyelectrolyte is a polyDADMAC and the second cationic polyelectrolyte is a cationic polyacrylamide. · «T · • · · • · '··· 1 6. Modified cellulose particles according to any one of claims 1-5, characterized by surfactant, advantageous SDS. The outer surface of the cellulose particles further comprises an anionic polymer. Modified cellulose particles according to any one of claims 1-6, characterized in that the cellulose particles are spherical and their average particle size is in the range 0.05 to 10 μηι. 5 A process for preparing cellulose particles modified with cationic polyelectrolytes, characterized in that (a) a cellulose solution is led to a regenerating solution for precipitation of cellulose particles, (b) the cellulose particles formed are no longer washed with the water (c) the outer surface of the cellulose particles is modified in an aqueous solution comprising a first cationic polyelectrolyte having a molecular weight in the range 20,000 - 500,000 g / mol and a charge density above 3 (d) the outer surface of the cellulose particles is modified in an aqueous solution comprising a second cationic polyelectrolyte having a molecular weight in the range of 2-10 million g / mol and a charge density in the range of 0.5 - 3 meq / g , wherein steps (c) and (d) are performed successively in the same aqueous solution. • «*« ··: 20 9. A method according to claim 8, characterized in that steps (c) and (d) · Is carried out in the opposite order. • · • · · • Process according to claim 8 or 9, characterized in that the contents of the ··· first and second cationic polyelectrolytes in the aqueous solution are selected in such a way that the zeta potential of the modified cellulose particles after the steps * * a * ·: * ( c) and (d) are at least +5 mV measured at pH 8. t *** · • · »·· ·· i: Method according to any one of claims 8 to 10, characterized in that the molecular weight of the first cationic polyelectrolyte is in the range 100,000 ····· 30 - 500,000 g / mol and the molecular weight of the second cationic polyelectrolyte is equal. : * ·, · Gives in the range 5-10 million g / mol. • · 119481 Method according to any of claims 8-11, characterized in that the charge density of the first cationic polyelectrolyte is in the range 5-8 meq / g and the charge density of the second cationic polyelectrolyte is in the range 0.5 - 1.5. meq / g. Process according to any of claims 8 to 12, characterized in that the first cationic polyelectrolyte is a polyDADMAC and the second cationic polyelectrolyte is a cationic polyacrylamide. 10 14. A method according to any one of claims 8-13, characterized in that the method further comprises a step in which the outer surface of the cellulose particles is modified with an anionic surfactant, advantageously SDS. Use of cellulose particles modified with cationic polyelectrolytes according to any one of claims 1-7 or prepared by a method according to any of claims 8-14 in the manufacture of paper or paperboard. »M ϊ ϊ 16. A process for making paper or paperboard, characterized in that cellulose particles modified with cationic polyelectrolytes according to any one of claims 1-7 or prepared by a process according to any of the preceding claims. of the claims • ·: 8-14 is added to the pulp at a suitable point in the system in such a way that the amount of modified cellulose particles in the paper or carton is 0.01 - 50% by weight ··· • · * ··· 1 %, and the paper or carton is manufactured in the usual manner. • · · • 1 • · · a ··· »·· · · · · 1 · ··· * 1 • · ·· · n · • · · * ·· • ·