WO2006122934A2

WO2006122934A2 - Method for producing paper, paperboard and cardboard in the presence of water-swellable polymers

Info

Publication number: WO2006122934A2
Application number: PCT/EP2006/062346
Authority: WO
Inventors: Simon Champ; Roland Ettl; Samantha Champ
Original assignee: Basf Aktiengesellschaft
Priority date: 2005-05-18
Filing date: 2006-05-16
Publication date: 2006-11-23
Also published as: CA2608428A1; CN101180436A; US20080190576A1; WO2006122934A3; EP1883733A2; DE102005023608A1; JP2008540866A

Abstract

The invention relates to a method for producing paper, paperboard and cardboard in the presence of a water-swellable polymer by adding the latter to a fibre suspension. According to said method, the fibre suspension containing water-swellable polymers is milled.

Description

Process for the production of paper, paperboard and cardboard in the presence of water-swellable polymers

description

The present invention describes a process for the production of paper, paperboard and cardboard in the presence of water-swellable polymers. Furthermore, the invention relates to the use of water-swellable polymers in the production of paper, board and cardboard and paper products with water-swellable polymers.

Water-swellable polymers according to the invention are polymers which can absorb at least 1% of their own weight of water. Preferably, they absorb at least 10% of their own weight, more preferably at least 25% of their own weight, and most preferably at least 50% of their own weight in water. Water-swellable polymers in the context of the present invention are in particular so-called superabsorbent polymers which can absorb at least 100% of their own weight in water. These are, for example, polymers of (co) polymerized hydrophilic monomers, graft (co) polymers of one or more hydrophilic monomers on a suitable graft base, crosslinked cellulose or starch ethers, crosslinked carboxymethylcellulose, partially crosslinked polyalkylene oxide or aqueous products swellable natural products such as guar derivatives. Such hydrogels are commonly used as a gel-like suspension of absorbent products for making diapers, tampons, sanitary napkins and other personal care products, but also as water-retaining agents in agricultural horticulture.

However, the use of water-swellable polymers may also be of interest in other areas. Up to now, polyurethane foams and so-called airlaid cellulose matts have been used to increase the water absorption capacity of tissue papers while maintaining wet strength. These are also used in the production of packaging material, the packaging material should also retain the strength while absorbing liquids. These are, for example, packaging material for frozen foods. In papermaking, an increase in bulk (so-called bulk) is desired without sacrificing the strength of the paper. These could also be potential applications for water-swellable polymers.

EP 0 437 816 A1 describes a superabsorbent wet laid nonwoven material which is obtained by a process comprising the following steps: mixing the superabsorbent polymer particles with a liquid to form a slurry, mixing the resulting slurry with fibers, filtering the superabsorbent polymer Fiber mixture and then drying to obtain a highly absorbent wet-laid nonwoven material. The materials thus obtained are used, inter alia, in diapers, incontinence articles, packaging papers for foodstuffs and dressing materials such as patches.

EP 1 068 392 B1 discloses an improved wet process for producing an absorbent structure. Accordingly, in a device for web formation by the wet process, a fiber suspension is processed, which additionally contains water-swellable, water-insoluble superabsorbent particles. A wetted superabsorbent particle-containing wet web is formed, deprived of water and then transported to the dryer section. It is crucial that the contact between superabsorbent and suspension to fleece inlet into the dryer section is at most 45 seconds, which does not give the superabsorbent sufficient time to swell.

US 5,997,690 and US 6,290,813 B1 disclose a process for making superabsorbent wet-laid nonwoven material wherein a slurry of water-swellable, water-insoluble superabsorbent particles with fibers is first prepared, the superabsorbent particles having a particle size of less than 250 microns prior to addition. This slurry is then added to a saline solution. Thereafter, a wet web is formed, which is washed with water and then dried. The wet laid nonwoven materials thus obtained have a residual salt content of less than 40% in the dry state.

US 2002/0060013 A1 relates to a method for producing wet-laid

Nonwoven materials containing at least 1% by weight of an absorbent polymer having a thermo-reversible liquid holding capacity.

US 2003/0014038 A1 discloses superabsorbent articles which contain a core with swellable branched superabsorbent particles which is in a liquid-permeable shell. The articles disclosed in this document can be added with effective amounts of an antibiotic or antibacterial agent so that the end products can be used in the medical field.

A disadvantage of the methods of the prior art is that the aforementioned problems are not sufficiently solved or eliminated.

The object of the present invention was therefore to find a process for the production of paper, paperboard and cardboard in the presence of a water-swellable polymer, which solves the aforementioned problems, namely the size of the swollen polymer in the Compared to the paper thickness and on the other hand, the high water content of the swollen polymer, which is usually up to 99.9 wt .-%, eliminated.

The object was achieved by a process for the production of paper, paperboard and cardboard in the presence of a water-swellable polymer by adding the water-swellable polymer to a fiber suspension, wherein the water-swellable polymers contained fiber suspension is ground.

For the purposes of the present invention, a water-swellable polymer is understood as meaning water-absorbing polymers which can absorb at least 1% of their own weight of water. Preferably, they take up at least 10% of their own weight, more preferably at least 25% of their own weight, and most preferably at least 50% of their own weight in water. Water-swellable polymers for the purposes of the present invention are in particular so-called superabsorbent polymers which can absorb at least 100% of their own weight of water. These are, for example, polymers of (co) polymerized hydrophilic monomers, graft (co) polymers of one or more hydrophilic monomers on a suitable graft base, crosslinked cellulose or starch ethers, crosslinked carboxymethylcellulose, partially crosslinked polyalkylene oxide or in aqueous liquids swellable natural products, such as guar derivatives. Such hydrogels are commonly used as aqueous solutions of absorbent products for the manufacture of diapers, tampons, sanitary napkins, and other personal care products.

According to the method of the invention, the water-swellable polymers contained fiber suspension is ground. This grinding is usually carried out to a degree of beating by Schopper-Riegler of 10, preferably 25, more preferably 35, most preferably 50 and more preferably 70. The milling can be carried out, for example, in a conventional pulper.

Subsequently, the fiber-containing polymer suspension is subjected to the usual papermaking process. Preferably, after the milling, paper process chemicals are added. Of course, paper pulps may also be added to the fiber suspension prior to addition of the water-swellable polymer.

The mixture containing water-swellable polymers can pass through one or more shear stages, both prior to the addition of the paper processing chemicals and thereafter. Subsequently, the mixture is dewatered with foliar formation on a sieve and drying of the leaves. As paper process chemicals, the additives customarily used in papermaking are added in the customary amounts, for example fixing agents, retention aids, including microparticle systems, dry and wet strength agents, massagers, biocides and / or dyes.

In the process according to the invention, 0.1 to 20% by weight of a water-swellable polymer is added to the fiber suspension. The amount of water-swellable polymers in the fiber suspension is preferably between 0.5 and 10% by weight, more preferably between 0.8 and 5% by weight and very particularly preferably between 1 and 2.5% by weight, based in each case on the dry content of the suspension.

The fiber suspension to which the water-swellable polymer is added usually contains from 0.5 to 4% by weight of fibers, preferably from 0.5 to 2.5% by weight of fibers and most preferably from 0.8 to 1.5 % By weight of fibers, in each case based on the dry content of the suspension. In particular, the suspension preferably has a fraction of about 1% by weight of fibers, based on the solids content of the suspension.

The water-swellable polymers may have any particle size before swelling in aqueous solution, preferably the particle size is in the range of 10 nm to 10 mm, more preferably in the range of 50 nm to 5 mm and particularly preferably in the range of 100 nm to 1 mm. After swelling, the water-swellable polymers usually have particle sizes in the range of 100 nm to 100 mm, preferably in the range of 0.5 mm to 25 mm and particularly preferably in the range of 0.1 mm to 10 mm.

The form of addition of the water-swellable polymer to the fiber suspension is irrelevant. Thus, for example, a solid mixture of the fiber with a solid mixture of the water-swellable polymer in the above-mentioned quantitative ranges of the individual components are mixed together. Subsequently, the mixture is mixed with sufficient water to form a water-swellable polymer-containing fiber suspension. The water-swellable polymer is given in this way the possibility to swell in the presence of the fibers.

It is likewise possible to prepare a gel-like suspension of a water-swellable polymer in water in which the water-swellable polymer swells, this gel-like suspension then being added to the fiber suspension. In this embodiment of the process according to the invention, it is possible for the gelatinous suspension to be exposed to a shear stage with swollen water-swellable polymer. The duration and shear rate depend on the water-swellable polymer used. The optimum duration and shear rate will be determined by one skilled in the art within the scope of his usual experiments. In another embodiment of the method according to the invention, the water-swellable polymer is introduced by spraying into the fiber suspension.

Of course, several water-swellable polymers can also be used in the process according to the invention. These can be added to the fiber suspension both as a mixture at the same time as well as separately from one another. Preferably, however, a water-swellable polymer is used.

Production processes for superabsorbent polymers are described in "Modern Superabsorbed Polymer Technology", F.L. Buchholz and A.T. Graham, Wiley-VCH, 1998, pages 69 to 118. A monomer solution is polymerized into a base polymer, for example in a kneader or a belt reactor.

The superabsorbent polymer particles which can be used in the process according to the invention can be obtained by polymerization of a monomer solution comprising

i) at least one ethylenically unsaturated, acid group-carrying monomer, ii) at least one crosslinker, iii) optionally one or more ethylenically and / or allylically unsaturated monomers copolymerizable with i) and iv) optionally one or more water-soluble polymers to which the

Monomers i), ii) and optionally iii) can be grafted at least partially,

wherein the base polymer thereby obtained dried, classified,

v) optionally post-treated with at least one Nachvemetzer, dried and thermally postcrosslinked

will be produced.

Suitable monomers i) are, for example, ethylenically unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, or derivatives thereof, such as acrylamide, methacrylamide, acrylic esters and methacrylic acid esters. Particularly preferred monomers are acrylic acid and methacrylic acid. Very particular preference is given to acrylic acid.

The monomers i), in particular acrylic acid, preferably contain up to 0.025 wt .-% of a Hydrochinonhalbethers. Preferred hydroquinone half ethers are hydroquinone monomethyl ether (MEHQ) and / or tocopherols.

Tocopherol is understood as meaning compounds of the following formula

wherein R ^{1 is} hydrogen or methyl, R ^{2 is} hydrogen or methyl, R ^{3 is} hydrogen or methyl and R ^{4 is} hydrogen or an acid radical having 1 to 20 carbon atoms.

Preferred radicals for R ⁴ are acetyl, ascorbyl, succinyl, nicotinyl and other physiologically acceptable carboxylic acids. The carboxylic acids can be mono-, di- or tricarboxylic acids.

Preferred is alpha-tocopherol with R ¹ = R ² = R ³ = methyl, in particular racemic alpha-tocopherol. R ⁴ is particularly preferably hydrogen or acetyl. Especially preferred is RRR-alpha-tocopherol.

The monomer solution preferably contains at most 130 ppm by weight, more preferably at most 70 ppm by weight, preferably at least 10 ppm by weight, particularly preferably at least 30 ppm by weight, particularly preferably by 50 ppm by weight, hydroquinone halide, in each case based on acrylic acid, wherein acrylic acid salts are taken into account arithmetically as acrylic acid. For example, to prepare the monomer solution, an acrylic acid having a corresponding content of hydroquinone half-ether can be used.

The superabsorbent polymers are crosslinked, ie the polymerization is carried out in the presence of compounds having at least two polymerisable groups which can be radically copolymerized into the polymer network. Suitable crosslinkers ii) are, for example, ethylene glycol dimethacrylate, diethylene glycol diacrylate, allyl methacrylate, trimethylolpropane triacrylate, triallylamine, tetraallyloxyethane, as described in EP-A-0 530 438, di- and triacrylates, as in EP-A 547 847, EP-A 559 476, EP-A 632 068, WO 93/21237, WO 03/104299, WO 03/104300, WO 03/104301 and described in the German patent application with the file number DE 103 31 450.4, mixed acrylates containing in addition to acrylate groups further ethylenically unsaturated groups, such as in German patent applications DE 103 31 456.3 and DE 103 55 401.7, or crosslinker mixtures, as described, for example, in DE-A-195 43 368, DE-A-196 46 484, WO-A-90/15830 and WO-A- 02/32962. Useful crosslinkers ii) include in particular N ₁ N '- methylenebisacrylamide and N ₁ N' - diacrylate methylenebismethacrylamide, esters of unsaturated mono- or polycarboxylic acids of polyols, such as diacrylate or triacrylate, for example butanediol or ethylene glycol or - methacrylate and trimethylolpropane triacrylate and allyl compounds, such as allyl (meth) acrylate, triallyl cyanurate, maleic acid diallyl esters, polyallyl esters, tetraallyloxyethane, triallylamine, tetraallylethylenediamine, allyl esters of phosphoric acid and vinylphosphonic acid derivatives, as described, for example, in EP-A-0 343 427. Further suitable crosslinkers ii) are pentaerythritol di-, pentaerythritol tri- and pentaerythritol tetraallyl ethers, polyethylene glycol diallyl ether, ethylene glycol diallyl ether, glycerol and glycerol triallyl ethers, polyallyl ethers based on sorbitol, and ethoxylated variants thereof. Useful in the process according to the invention are di (meth) acrylates of polyethylene glycols, wherein the polyethylene glycol used has a molecular weight between 300 and 1000.

However, particularly advantageous crosslinkers ii) are di- and triacrylates of 3 to 20 times ethoxylated glycerol, 3 to 20 times ethoxylated trimethylolpropane, 3 to 20 times ethoxylated trimethylolethane, in particular di- and triacrylates of 2 to 6-fold ethoxylated glycerol or trimethylolpropane, the 3-fold propoxylated glycerol or trimethylolpropane, and the 3-times mixed ethoxylated or propoxylated glycerol or trimethylolpropane, the 15-times ethoxylated glycerol or trimethylolpropane, and at least 40-times ethoxylated glycerol, Trimethylolethane or trimethylolpropane.

Very particularly preferred crosslinkers ii) are the polyethoxylated and / or propoxylated glycerols esterified with acrylic acid or methacrylic acid to form di- or triacrylates, as described, for example, in German Patent Application DE 103 19 462.2. Particularly advantageous are di- and / or triacrylates of 3- to 10-fold ethoxylated glycerol. Very particular preference is given to diacrylates or triacrylates of 1 to 5 times ethoxylated and / or propoxylated glycerol. Most preferred are the triacrylates of 3 to 5 times ethoxylated and / or propoxylated glycerin. These are characterized by particularly low residual contents (typically below 10 ppm by weight) in the superabsorbent polymer and the aqueous extracts of the superabsorbent polymers produced therewith have an almost unchanged surface tension (typically at least 0.068 N / m) compared to water same temperature.

For example, acrylamide, methacrylamide, crotonic acid amide, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylaminopropyl acrylate, dimethylaminobutyl acrylate, dimethylaminoethyl methacrylate, diethylamine are copolymerizable with the monomers i). minoethyl methacrylate, dimethylaminoneopentyl acrylate and dimethylaminoneopentyl methacrylate.

As water-soluble polymers iv) it is possible to use polyvinyl alcohol, polyvinylpyrrolidone, starch, starch derivatives, polyglycols or polyacrylic acids, preferably polyvinyl alcohol and starch.

The preparation of a suitable base polymer and further suitable hydrophilic ethylenically unsaturated monomers i) are described in DE-A 199 41 423, EP-A 686 650, WO 01/45758 and WO 03/104300.

The reaction is preferably carried out in a kneader, as described, for example, in WO 01/38402, or on a belt reactor, as described, for example, in EP-A 955 086.

The hydrogel after leaving the polymerization reactor at a higher temperature, preferably at least 5O ⁰ C is advantageous, particularly preferably at least 70 ⁰ C, most preferably at least 80 ⁰ C, and preferably less than 100 ⁰ C ₁ mounted, for example, in insulated containers. By storage, usually 2 to 12 hours, the monomer conversion is further increased.

The acid groups of the hydrogels obtained are usually partially neutralized, preferably from 25 to 95 mol%, preferably from 27 to 80 mol%, particularly preferably from 27 to 30 mol% or from 40 to 75 mol%, using the customary neutralizing agents may be, preferably alkali metal hydroxides, alkali metal oxides, alkali metal carbonates or Alkalimetallhydrogencarbonate and mixtures thereof. Instead of alkali metal salts and ammonium salts can be used. Sodium and potassium are particularly preferred as alkali metals, but most preferred are sodium hydroxide, sodium carbonate or sodium bicarbonate and mixtures thereof. Usually, the neutralization is achieved by mixing the neutralizing agent as an aqueous solution, as a melt, or preferably as a solid. For example, sodium hydroxide with a water content well below 50 wt .-% may be present as a waxy mass with a melting point above 23 ° C. In this case, a dosage as general cargo or melt at elevated temperature is possible.

The neutralization can be carried out after the polymerization at the hydrogel stage. However, it is also possible to neutralize up to 40 mol%, preferably 10 to 30 mol%, particularly preferably 15 to 25 mol%, of the acid groups prior to the polymerization by adding a part of the neutralizing agent to the monomer solution and the desired final degree of neutralization after the polymerization is adjusted at the level of the hydrogel. The monomer solution can be neutralized by mixing in the neutralizing agent. The hydrogel can be mechanically comminuted, for example by means of a meat grinder, wherein the neutralizing agent can be sprayed, sprinkled or poured on and then carefully mixed in. For this purpose, the gel mass obtained can be further gewolfft for homogenization. Neutralization of the monomer solution directly to the final degree of neutralization is preferred.

The neutralized hydrogel is then dried with a belt or roller dryer until the residual moisture content is preferably less than 15% by weight, in particular less than 10% by weight, the water content being in accordance with that recommended by EDANA (European Disposables and Nonwovens Association) Test Method No. 430.2-02 "Moisture content" is determined. Alternatively, a fluidized bed dryer or a heated ploughshare mixer can be used for drying.

The dried hydrogel is thereafter ground and classified, wherein for grinding usually one- or multi-stage roller mills, preferably two- or three-stage roller mills, pin mills, hammer mills or vibratory mills can be used.

To improve application properties, such as diaper fluid conductivity (SFC) and absorption under pressure (AUL), superabsorbent polymer particles are generally postcrosslinked. This postcrosslinking can be carried out in aqueous gel phase. Preferably, however, ground and sieved polymer particles (base polymer) are coated on the surface with a post-crosslinker, dried and postcrosslinked thermally. Crosslinking agents suitable for this purpose are compounds which contain at least two groups which can form covalent bonds with the carboxylate groups of the hydrophilic polymer or which can crosslink at least two carboxyl groups or other functional groups of at least two different polymer chains of the base polymer.

Suitable postcrosslinkers v) are compounds which contain at least two groups which can form covalent bonds with the carboxylate groups of the polymers. Suitable compounds are, for example, alkoxysilyl compounds, polyaziridines, polyamines, polyamidoamines, di- or polyglycidyl compounds, as described in EP-A 083 022, EP-A 543 303 and EP-A 937 736, polyhydric alcohols, as described in DE-C 33 14 019, DE-C 35 23 617 and EP-A 450 922, or IJ-hydroxyalkylamides, as described in DE-A 102 04 938 and US Pat. No. 6,239,230. Also suitable are compounds having mixed functionality, such as glycidol, 3-ethyl-3-oxetanemethanol (trimethylolpropane oxetane), as described in EP-A 1 199 327, noethanol, diethanolamine, triethanolamine or compounds which form a further functionality after the first reaction, such as ethylene oxide, propylene oxide, isobutylene oxide, aziridine, azetidine or oxetane.

Furthermore, in DE-A 40 20 780 cyclic carbonates, in DE-A 198 07 502 2-oxazolidone and its derivatives, such as N- (2-hydroxyethyl) -2-oxazolidone, in DE-A 198 07 992 Bis- and Poly-2-oxazolidinone, in DE-A 198 54 573 2-oxotetrahydro-1, 3-oxazine and its derivatives, in DE-A 198 54 574 N-acyl-2-oxazolidone, in DE-A 102 04 937 cyclic ureas , German Patent Application DE 103 34 584.1 describes bicyclic amide acetals, EP-A1 199 327 oxetanes and cyclic ureas, and WO 03/031482 describes morpholine-2,3-dione and its derivatives as suitable post-crosslinking agents v).

The postcrosslinking is usually carried out so that a solution of the postcrosslinker is sprayed onto the hydrogel or the dry base polymer particles. Subsequent to the spraying, it is thermally dried, whereby the postcrosslinking reaction can take place both before and during the drying.

The spraying of a solution of the crosslinker is preferably carried out in mixers with moving mixing tools, such as screw mixers, paddle mixers, disk mixers, plowshare mixers and paddle mixers. Vertical mixers are particularly preferred, plowshare mixers and paddle mixers are very particularly preferred. Suitable mixers are, for example, Lödige ^® mixers, Bepex ^® mixers, Nauta ^® mixer, Processall mixers and Schugi ^® ^® mixer.

The thermal drying is preferably carried out in contact dryers, more preferably paddle dryers, very particularly preferably disk dryers. Suitable dryers include for example Bepex ^® dryers and Nara ^® dryers. Moreover, fluidized bed dryers can also be used.

The drying can take place in the mixer itself, by heating the jacket or blowing hot air. Also suitable is a downstream dryer, such as a hopper dryer, a rotary kiln or a heatable screw. However, it is also possible, for example, to use an azeotropic distillation as the drying process.

Preferred drying temperatures are in the range 50 to 25O ⁰ C, preferably at 50 to 200 ⁰ C, and particularly preferably at 50 to 15O ⁰ C. The preferred residence time at this temperature in the reaction mixer or dryer is below 30 minutes and more preferably below 10 minutes. The papers, boards and cardboards produced by the process according to the invention have an increased water absorption capacity compared to conventional paper qualities without loss of strength. The papers can absorb water and also hold under heat, such as when used in laser printers.

By the method according to the invention, all paper qualities can be produced, e.g. Cardboard, single / multi-layer carton, single / multi-layer liner, corrugated medium, papers for newspaper printing, so-called medium-fine writing and printing papers, natural gravure papers and lightweight base papers. For example, wood pulp, thermomechanical pulp (TMP), chemo-thermo-mechanical pulp (CTMP), pressure pulp (PGW), wood pulp and sulphite and sulphate pulp can be used to produce such papers. The pulps can be short fiber as well as long fiber.

According to the method of the invention, so-called tissue papers such as toilet paper, paper handkerchiefs and facial tissues as well as kitchen paper, furthermore hygiene or sanitary papers, packaging papers, for example for foodstuffs or multilayer papers which can be used in hygiene articles or packaging materials, are preferably produced. The last-mentioned multilayer papers consist of several different paper layers, the paper layer produced by the process according to the invention being incorporated either above a conventional paper layer or between two conventional paper layers.

The present invention furthermore relates to the use of water-swellable polymers in the production of paper, paperboard and cardboard in the process according to the invention.

Another object of the present invention are also paper, cardboard and

Cardboard produced by the process according to the invention. In particular, the invention relates to so-called tissue papers, such as toilet paper, paper handkerchiefs and facial tissues and kitchen paper, further hygiene or sanitary papers, packaging papers, for example, for food, or even multi-layer paper, which can be used in hygiene articles or packaging materials.

The invention will be further illustrated by the following non-limiting examples.

Examples The percentages in the examples are by weight unless otherwise indicated in the context.

The dry breaking length of the dried paper sheets was determined according to the test method according to DIN EN ISO 1924-2.

Water swellable polymer 1

At room temperature, 1280 of BASF Aktiengesellschaft in a slight excess of water was swollen for one hour as a water-swellable polymer Luquasorb ^®.

example 1

A mixture of bleached birch sulphate and bleached pine sulphite in the ratio of 70/30 at a solids concentration of 1% was admixed with 1% by weight, based on the solids content of the paper stock suspension, of the previously swollen water-swellable polymer 1. This mixture was added to the laboratory pulper without specking until a Schopper-Riegler freeness of 35 was reached.

Example 2

Example 1 was repeated except that 2.5% by weight, based on the solids content of the pulp suspension, of the previously swollen water-swellable polymer 1 was added to the bleached birch sulphate bleach bleached pine sulphite blend.

Example 3

A mixture of bleached birch sulphate and bleached pine sulphite in a ratio of 70/30 at a solids concentration of 1% was admixed with 1% by weight, based on the solids content of the paper stock suspension, of the previously swollen water-swellable polymer 1. This mixture was added to the laboratory pulper without specking until a Schopper-Riegler freeness of 35 was reached. Immediately thereafter, the metered addition, a cationic polyacrylamide retention aid (poly min ^® KE 2020, BASF Aktiengesellschaft) in this mixture. The metered amount of the retention agent was 0.03% polymer, based on the solids content of the paper stock suspension.

Example 4

Example 3 was repeated except that 2.5% by weight, based on the solids content of the pulp suspension, of the previously swollen water-swellable polymer 1 was added to the bleached birch sulphate bleached pine sulphite blend.

Example 5

A mixture of bleached birch sulphate and bleached pine sulphite in a ratio of 70/30 at a solids concentration of 1% was admixed with 1% by weight, based on the solids content of the pulp suspension, of the previously swollen water-swellable polymer 1. This mixture was tapped in the laboratory pulper until it reached a grinding degree of 35 according to Schopper-Riegler. Immediately thereafter, the metered addition, a cationic polyacrylamide retention aid (poly min ^® KE 2020, BASF Aktiengesellschaft) and a filler (Hydrocarb ^® OG from Omya) in this mixture. The metered amount of the retention agent and the filler was 0.03% polymer or 20% filler, based on the solids content of the paper stock suspension.

Example 6

Example 5 was repeated except that 2.5% by weight, based on the solids content of the paper stock suspension, of the previously swollen water-swellable polymer 1 was added to the mixture of bleached birch sulphate and bleached pine sulphite. Comparative Example 1

A mixture of bleached birch sulphate and bleached pine sulphite in a ratio of 70/30 at a solids concentration of 1% was added without specks in the laboratory pulper until a Schopper-Riegler freeness of 35 was reached. Subsequently, a cationic starch (Solvitose BKN ^®) in an amount of 0.06 wt .-%, based on the dry content of the paper stock suspension.

Comparative Example 2

A mixture of bleached birch sulphate and bleached pine sulphite in a ratio of 70/30 at a solids concentration of 1% was beaten without specks in the laboratory pulper until a Schopper-Riegler freeness of 35 was reached. Subsequently, a cationic starch (Solvitose BKN ^®) in an amount of 0.06 wt .-%, based on the dry content of the paper stock suspension. Immediately thereafter, the metered addition, a cationic polyacrylamide retention aid (Polymin ^® KE 2020, BASF Aktiengesellschaft) and a filler (Hydrocarb ^® OG from Omya) in this mixture. The metered amount of the retention agent and the filler was 0.03% polymer or 20% filler, based on the solids content of the paper stock suspension.

Production of paper sheets

The paper sheets were each made on a Rapid-Köthen sheet former according to ISO 5269/2 with a sheet weight of 80 g / m ² and then dried for 5 minutes at 100 ⁰ C. Subsequently, the dry break length of the paper sheets was checked. The results are summarized in Table 1.

Table 1

Testing the water absorption after the wicking test

The paper sheets were each cut to a size of 200 mm x 15 mm. These cut paper strips were each hung in a beaker filled with water, with the upper end of the paper strip being clamped to the edge of the beaker. At the beginning of the test, the paper strips dipped about 10 to 20 mm into the water, marking the place of immersion (lower limit). After 10 minutes, the paper strips were pulled out of the water. The upper limit to which the water had run was also marked. Then the distance between the lower and upper limit, ie the distance that the water traveled, was measured. The results are summarized in Table 2.

Table 2

Claims

claims

1. A process for the production of paper, paperboard and cardboard in the presence of water-swellable polymers by adding the water-swellable polymer to a fiber suspension, characterized in that the water-swellable polymers contained fiber suspension is ground.

2. The method according to claim 1, characterized in that the water-swellable polymer can absorb at least 1% of its own weight of water.

3. The method according to claim 1 or 2, characterized in that it is superabsorbent polymers in the water-swellable polymers.

4. The method according to any one of claims 1 to 3, characterized in that after the grinding of the water-swellable polymers contained fiber suspension paper process chemicals are added.

5. The method according to any one of claims 1 to 4, characterized in that the water-swellable polymer is added as a gel-like suspension of the fiber suspension.

6. The method according to any one of claims 1 to 4, characterized in that the water-swellable polymer is introduced by spraying into the fiber suspension.

7. The method according to any one of claims 1 to 6, characterized in that the fiber suspension is added to 0.1 to 20 wt .-% of a water-swellable polymer.

8. Use of water-swellable polymers in the production of paper, paperboard and cardboard by a process according to claims 1 to 7.

9. paper, board and board produced by a method according to claim 1 to 7.

10. Paper according to claim 9, characterized in that it is tissue paper, hygiene or sanitary papers, packaging papers or multilayer papers.