EP1828481A2

EP1828481A2 - Papers with a high filler material content and high dry strength

Info

Publication number: EP1828481A2
Application number: EP05819674A
Authority: EP
Inventors: Anton Esser; Hans-Joachim HÄHNLE; Tibor Adalbert Von Vadkerthy
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2004-12-17
Filing date: 2005-12-14
Publication date: 2007-09-05
Anticipated expiration: 2025-12-14
Also published as: CA2590489C; US8778139B2; US20090272506A1; EP1828481B1; PT1828481E; ES2554691T3; JP5130049B2; WO2006066769A2; WO2006066769A3; JP2008524452A; PL1828481T3; CA2590489A1

Abstract

The invention relates to a method for producing paper, paperboard and cardboard in the presence of an aqueous suspension of components containing fine-particles of filler material. The fine-particle filler materials are covered at least partially with water-soluble amphoteric copolymers. Said method consists in adding to the fibre suspension, prior to the formation of the sheet, and in addition to the aqueous suspension of components containing fine-particles filler material, at least one cationic and/or amphoteric polymer which, as a structural element, does not contain any ester unsaturated carboxylic acids with quaternised amino alcohols.

Description

Papers with high filler content and high dry strength

description

The present invention relates to a process for the production of papers with high filler content and high dry strength and the papers produced by this method.

In papermaking, numerous paper auxiliaries are added to the fiber suspension. For example, fillers are added to the fiber suspension, which is particularly advantageous when the filler is cheaper than the pulp. In this case, the addition or increased addition of filler can lead to a reduction of the fiber content and thus to a reduction in the production costs of the paper. Filler-containing papers or papers with a particularly high filler content are easier to dry than non-filler papers or papers with a lower filler content. As a result, the paper machine can be operated faster and with lower steam consumption, which both increases productivity and lowers costs.

In the production of filler-containing papers, the filler slurry is added to the fiber suspension prior to passing it to the former of the paper machine. A retention aid or retention aid system is typically added to the filler / pulp suspension to retain as much filler as possible in the paper sheet. The addition of the filler to the paper gives the papermaker the opportunity to achieve numerous improvements in sheet properties. These include properties such as opacity, whiteness, feel and printability.

However, the filler addition to the fiber suspension also entails disadvantages which can only be partially compensated by the addition of further paper auxiliaries. For a given basis weight, there are limits to the amount of filler that can be used. The strength properties of the paper are usually the most important parameters that limit the amount of filler in the paper. Other factors, such as filler retention, dewatering of the pulp suspension, and possibly increased need for chemicals in retention and sizing may also play a role here.

The loss of strength properties of papers can in some cases be compensated in whole or in part by the use of dry and wet strength agents. A common procedure is the addition of cationic starch as dry strength in the pulp. Likewise, synthetic dry and wet strength agents are used, for example, based on cationic or anionic polyacrylamides. However, the amount of addition and the strengthening effect are limited in most cases. To the same extent is the compensating effect in relation to the loss of strength due to an increase in the filler and thus also the realizable limited filler increase. In addition, not all strength properties are increased to the same extent and in some cases only insufficiently by the use of dry strength. An important example of this is the on-going work, which is only slightly influenced by the use of starch or synthetic dry strength compared to other strength parameters. The increase in the filler content in paper, on the other hand, usually has a very strong negative impact on continuing work.

Other important properties are the thickness and stiffness of the paper. The increase in the filler content leads to a decrease in the paper density and the thickness of the paper sheet at the same basis weight. The latter leads to a significant decrease in paper stiffness. In many cases, this decrease in paper stiffness can not be compensated for solely by the use of dry strength. Frequently, additional measures such as the reduction of mechanical pressure in the press section in the calenders, in calenders or in the dryer section of the paper machine are necessary. The latter compensates the thickness loss by increasing the filler in whole or in part.

Some filler systems are described in the literature. From WO 01/86067 the modification of fillers with hydrophobic polymers is known, wherein the filler particles are coated with the hydrophobic polymer. The hydrophobic polymers according to WO 01/86067 are starchy. The papers produced therewith have improved properties such as wet strength.

It is known from JP-A 08059740 that amphoteric water-soluble polymers are added to aqueous suspensions of inorganic particles, wherein at least some of the polymers are adsorbed on the filler surface. The amphoteric polymers are preferably prepared by hydrolyzing copolymers of N-vinylformamide, acrylonitrile and acrylic acid in the presence of acids. They contain 20 to 90 mol% amidine units of the structure

in which R ¹ and R ² each denote H or a methyl group and X ^" denotes an anion The filler slurries treated with such polymers are added to the paper stock in the preparation of filler-containing papers The filler treatment leads to an improvement in the dewatering of the paper stock and results In addition, an improvement of various strength properties of the dried paper and an improvement in the filler retention.

US-A 2002/0088579 describes the pretreatment of inorganic fillers with cationic, anionic and amphoteric (zwitterionic) polymers. The treatment consists in each case of at least two stages. It is recommended to first treat with a cationic polymer followed by treatment with an anionic polymer. In further steps, other cationic and anionic polymers can be adsorbed alternately again. The aqueous suspensions containing the pretreated filler particles are added to the stock in the production of filler-containing paper. The filler treatment leads to an improvement in various strength properties of the dried paper.

WO 04/087818 describes aqueous slurries of finely divided fillers which are at least partially coated with polymers and which are obtainable by treating aqueous slurries of finely divided fillers with at least one water-soluble amphoteric copolymer which is obtainable by copolymerizing

a) at least one N-vinylcarboxamide of the formula

in which R ¹ , R ² = H or C ₁ - to C ₆ -alkyl,

b) at least one monoethylenically unsaturated carboxylic acid having 3 to 8 C atoms in the molecule and / or their alkali metal, alkaline earth metal or ammonium salts and optionally

c) other monoethylenically unsaturated monomers which are free of nitrile groups, and optionally

d) compounds which have at least two ethylenically unsaturated double bonds in the molecule,

and subsequent partial or complete removal of the groups -CO-R ¹ from the monomers II copolymerized in the copolymer.

DE 103 34 133 A1 discloses aqueous compositions comprising at least one finely divided filler and at least one water-soluble amphoteric copolymer. polymerizate obtainable by copolymerizing a monomer mixture containing

a) at least one N-vinylcarboxamide of the general formula

in which R ¹ and R ² independently of one another are H or C ₁ - to C ₆ -alkyl,

b) at least one monomer selected from monoethylenically unsaturated sulfonic acids, phosphonic acids, phosphoric acid esters and derivatives thereof,

c) if appropriate at least one monomer which is selected from monoethylenically unsaturated mono- and dicarboxylic acids, their salts and dicarboxylic anhydrides,

d) optionally at least one of the components a) to c) different monoethylenically unsaturated monomer which is free of nitrile groups, and

e) optionally at least one compound which has at least two ethylenically unsaturated double bonds in the molecule,

with the proviso that the monomer mixture contains at least one monomer b) or c) with at least one free acid group and / or one acid group in salt form,

and subsequent partial or complete hydrolysis of the groups -CO-R ¹ from the monomers II copolymerized in the copolymer.

All filler systems known in the literature have in common that papers with a limited filler content can be produced therewith. Furthermore, the typical paper properties such as dry strength are in need of improvement.

It was therefore an object to provide a process for the production of paper with high filler content and high dry strength. The resulting papers should be distinguished by improved performance properties, especially good strength properties of the dried paper. These include, in particular, good dry tear lengths, tear propagation, flexural rigidity and internal strength. Furthermore, the papers produced should have a higher filler content than known from the prior art. The object was achieved by a process for the production of paper, paperboard and cardboard in the presence of an aqueous slurry of components containing finely divided fillers, wherein the finely divided fillers are at least partially coated with water-soluble amphoteric copolymers, wherein in addition to the aqueous slurry of finely divided fillers Components at least one cationic and / or amphoteric polymer containing as structural element no esters of unsaturated carboxylic acids with quaternized amino alcohols, the fiber suspension added before sheet formation.

For the purposes of the present invention, components comprising finely divided fillers are both finely divided fillers alone, i. in pure form or as a so-called fresh filler, as well as finely divided fillers containing raw materials such as the so-called Committee of coated paper, as well as mixtures in any composition thereof understood.

In general, the metering of the aqueous slurry of components containing finely divided fillers to the fiber suspension, before it is passed to the former of the paper machine.

The dosage of the cationic and / or amphoteric polymers may be at various points in the papermaking process. Conceivable is a dosage in the thick matter range, but also a dosage in the thin material of the fiber suspension. A split addition at different points in the manufacturing process is also possible.

Preferably, however, the at least one cationic and / or amphoteric polymer is added to the fiber suspension immediately after the addition of the aqueous slurry of components containing finely divided fillers. Immediately means that between the dosages of the components no further process step, i. no dosage of other paper auxiliaries or, for example, the action of shear forces on the suspension is.

The cationic and / or amphoteric polymer contains no structural elements of esters of unsaturated carboxylic acids, for example C ₃ -C ₈ -carboxylic acids, with quaternized amino alcohols, for example N, N, N-trimethyl-ammonium-methanol.

The cationic and / or amphoteric polymer is selected from

Homopolymers and copolymers of vinylimidazoles, diallylalkylamines and allyldialkyamines, these monomers being used in neutral form, as salts of acids or in quaternized form, Homo- and copolymers of esters of unsaturated carboxylic acids with N ₁ N- dialkylamino or N-Alkylaminalkoholen, these monomers are used in neutral form or as salts of acids, homo- and copolymers of amides of unsaturated carboxylic acids with N ₁ N- Dialkyldiaminen or N- Alkyldiaminen, these monomers are used in neutral form, as salts of acids or in quaternized form, condensation products of epichlorohydrin or bisepoxides with dialkylamines or polyamidoamines, polyethyleneimines, - graft products of ethyleneimines on amidoamines or polyamines, cationic starches and / or vinylamine units containing polymers.

Homo- and copolymers of vinylimidazoles, diallylalkylamines having alkyl groups of Ci - C _10, preferably C ₁ - C _6, and Allyldialkyaminen having alkyl groups of C ₁ - C _10, preferably C ₁ - C _6, where the alkyl groups may be the same or different, and wherein these monomers are used in neutral form, as salts of acids or in quaternized form, are typically based on the monomers N-vinylimidazole, dimethyldiallylammonium chloride and dimethylallylamine.

Homo- and copolymers of esters of unsaturated carboxylic acids having 3 to 8 carbon atoms with N, N-dialkylamino alcohols having alkyl groups of C ₁ - C ₁₀ , preferably Ci - C ₆ , wherein the alkyl groups may be identical or different, or N-alkylamino with alkyl groups of C _t - C _10, preferably Ci - C _6, wherein said Mo nomere be used in neutral form or as salts of acids, for example, based on esters of acrylic acid or methacrylic acid with ₁ N N- dimethylaminoethylamine.

Homopolymers and copolymers of amides of unsaturated carboxylic acids having 3 to 8 carbon atoms with N, N-dialkyldiamines having alkyl groups of C ₁ -C ₁₀ , preferably C ₁ -C ₆ , where the alkyl groups may be identical or different, or N-alkyldiamines with alkyl groups of C ₁ -C ₁₀ , preferably C ₁ -C ₆ , these monomers being used in neutral form, as salts of acids or in quaternized form, are based, for example, on amides of acrylic acid and methacrylic acid with N, N-dimethylaminoethylene - amine, 3- (N, N-dimethylamino) propylamine or 3- (N, N, N-trimethylammonium) propylamine.

Condensation products of epichlorohydrin or bisepoxides with dialkylamines with alkyl groups of C ₁ - C _0, preferably C ₁ - C _6, where the alkyl groups may be the same or comparable be secreted, or polyamidoamines can also be used. Typical representatives are, for example Catiofast® ^® PR 8153 and PR 8154 ^® Catiofast® the BASF Aktiengesellschaft, which are commonly used as fixatives in the paper industry.

Polyethyleneimines are disclosed, for example, in WO 97/25367 and the literature cited therein.

Graft products of ethyleneimines on amidoamines or polyamines are, for example, the nitrogen-containing condensation products described in German Offenlegungsschrift DE 24 34 816. Cationic starches are disclosed, for example, in Günther Tegge, Stärke und Stärkederivate, Behr's Verlag, Hamburg, 1984. These are, for example, potato starch, corn starch, wheat starch, rice starch, tapioca starch, sago starch, manioc starch and rye starch. These starches are e.g. reacted with 2,3- (epoxy) -propyltrimethyl ammonium chloride.

Polymers containing vinylamine units, as used in the context of the present invention, are known, cf. US 4,421,602, US 5,334,287, EP-A 216,387, US 5,981,689, WO 00/63295, US 6,121,409 and US 6,132,558. They are prepared by hydrolysis of open-chain N-vinylcarboxylic acid amide units containing polymers. These polymers are e.g. obtainable by polymerizing N-vinylformamide, N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide and N-vinylpropionamide. The monomers mentioned can be polymerized either alone or together with other monomers. Preference is given to N-vinylformamide.

Suitable monoethylenically unsaturated monomers which are copolymerized with the N-vinylcarboxamides are all compounds which can be copolymerized therewith. Examples of these are vinyl esters of saturated carboxylic acids of 1 to 6 carbon atoms such as vinyl formate, vinyl acetate, N-vinylpyrrolidone, vinyl propionate and vinyl butyrate and vinyl ethers such as C ₁ to C ₆ alkyl vinyl ethers, for example methyl or ethyl vinyl ether. Further suitable comonomers are esters of alcohols having, for example, 1 to 6 carbon atoms, amides and nitriles of ethylenically unsaturated C ₃ - to C ₆ -carboxylic acids, for example methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate and dimethyl maleate, acrylamide and methacrylamide and acrylonitrile and methacrylonitrile.

Further suitable carboxylic acid esters are derived from glycols or polyalkylene glycols, in each case only one OH group esterified, for example hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate and acrylic acid monoesters of polyalkylene glycols having a molecular weight of 500 to 10,000. Further suitable comonomers are esters of ethylenically unsaturated carboxylic acids with amino alcohols, such as dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminopropyl acrylate, dimethylaminopropyl methacrylate, diethylaminopropyl acrylate, dimethylaminobutyl acrylate and diethylaminobutyl acrylate. The basic acrylates can be used in the form of the free bases, the salts with mineral acids such as hydrochloric acid, sulfuric acid or nitric acid, the salts with organic acids such as formic acid, acetic acid, propionic acid or the sulfonic acids or in quaternized form. Suitable quaternizing agents are, for example, dimethyl sulfate, diethyl sulfate, methyl chloride, ethyl chloride or benzyl chloride.

Further suitable comonomers are amides of ethylenically unsaturated carboxylic acids such as acrylamide, methacrylamide and N-alkyl mono- and diamides of monoethylenically unsaturated carboxylic acids having alkyl radicals of 1 to 6 carbon atoms, e.g. N-methylacrylamide, N, N-dimethylacrylamide, N-methylmethacrylamide, N-ethylacrylamide, N-propylacrylamide and tert-butylacrylamide and basic (meth) acrylamides, such as e.g. Dimethylaminoethylacrylamide, dimethylaminoethylmethacrylamide, diethylaminoethylacryloamide, diethylaminoethylmethacrylamide, dimethylaminopropylacrylamide, diethylaminopropylacrylamide, dimethylaminopropylmethacrylamide and diethylaminopropylmethacrylamide.

Further suitable comonomers are N-vinylpyrrolidone, N-vinylcaprolactam, acrylonitrile, methacrylonitrile, N-vinylimidazole and substituted N-vinylimidazoles, such as e.g. N-vinyl-2-methylimidazole, N-vinyl-4-methylimidazole, N-vinyl-5-methylimidazole, N-vinyl-2-ethylimidazole and N-vinylimidazolines such as N-vinylimidazoline, N-vinyl-2-methylimidazo-Hn and N-vinyl-2-ethylimidazoline. N-vinylimidazoles and N-vinylimidazolines are used except in the form of the free bases also in mineral acids or organic acids neutralized or in quaternized form, the quaternization is preferably carried out with dimethyl sulfate, diethyl sulfate, methyl chloride or benzyl chloride. Also suitable are diallyldialkylammonium halides, e.g. Diallyldimethylammonium chloride.

The copolymers contain, for example

95 to 5 mol%, preferably 90 to 10 mol% of at least one N-vinylcarboxylic acid amide, preferably N-vinylformamide, and

From 5 to 95 mol%, preferably from 10 to 90 mol% of monoethylenically unsaturated monomers,

in copolymerized form. The comonomers are preferably free of acid groups. The polymerization of the monomers is usually carried out in the presence of radical-forming polymerization initiators. The homopolymers and copolymers can be obtained by all known processes, for example by solution polymerization in water, alcohols, ethers or dimethylformamide or in mixtures of various solvents, by precipitation polymerization, reverse suspension polymerization (polymerizing an emulsion of a monomeric aqueous solution) Phase in an oil phase) and polymerizing a water-in-water emulsion, for example, in which one dissolves or emulsifies an aqueous monomer solution in an aqueous phase and polymerizes to form an aqueous dispersion of a water-soluble polymer, as described, for example, in WO 00/27893. Following the polymerization, the homopolymers and copolymers which contain copolymerized N-vinylcarboxamide units are partially or completely hydrolyzed as described below.

In order to prepare polymers containing vinylamine units, preference is given to homopolymers of N-vinylformamide or of copolymers obtained by copolymerizing

N-vinylformamide with

Vinyl formate, vinyl acetate, vinyl propionate, acrylonitrile, methyl acrylate, ethyl acrylate and / or methyl methacrylate

and subsequent hydrolysis of the homo- or copolymers to form vinylamine units from the copolymerized N-vinylformamide units, the degree of hydrolysis being e.g. 1 to 100 mol%, preferably 25 to 100 mol%, particularly preferably 50 to 100 mol% and particularly preferably 70 to 100 mol%. The degree of hydrolysis corresponds to the content of the polymers of vinylamine groups in mol%. The hydrolysis of the above-described polymers is carried out by known methods by the action of acids (eg mineral acids such as sulfuric acid, hydrochloric acid or phosphoric acid, carboxylic acids such as formic acid or acetic acid, or sulfonic acids or Phsophonsäuren), bases or enzymes, such as in DE-A 31 28 478 and US 6,132,558. When acids are used as hydrolyzing agents, the vinylamine units of the polymers are present as the ammonium salt, while hydrolysis with bases gives rise to the free amino groups.

In most cases, the degree of hydrolysis of the homopolymers and copolymers used is 85 to 95 mol%. The degree of hydrolysis of the homopolymers is synonymous with the content of the polymers of vinylamine units. For copolymers containing vinyl esters in copolymerized form, in addition to the hydrolysis of the N-vinylformamide units, hydrolysis of the ester groups to form vinyl alcohol units may occur. This is especially the case when the hydrolysis of the copolymers risate in the presence of sodium hydroxide solution. Polymerized acrylonitrile is also chemically altered upon hydrolysis. In this case, for example, arise a-mid groups or carboxyl groups. The vinylamine units containing homo- and copolymers may optionally contain up to 20 mol% of amidine units, for example by reaction of formic acid with two adjacent amino groups or by intramolecular reaction of an amino group with an adjacent Amidgrup- example of copolymerized N-vinylformamide.

The average molecular weights M _{w of} the polymers containing vinylamine units are, for example, 500 to 10 million, preferably 750 to 5 million and particularly preferably 1 000 to 2 million g / mol (determined by light scattering). This molar mass range corresponds, for example, to K values of 30 to 150, preferably 60 to 100 (determined according to H. Fikentscher in 5% strength aqueous sodium chloride solution at 25 ^° C., a pH of 7 and a polymer concentration of 0.5% by weight. ). Particular preference is given to using polymers comprising vinylamine units which have K values of from 85 to 95.

The polymers containing vinylamine units have for example a charge density (determined at pH 7) of 0 to 18 meq / g, preferably of 5 to 18 meq / g and especially of 10 to 16 meq / g.

The polymers containing vinylamine units are preferably used in salt-free form. Salt-free aqueous solutions of polymers comprising vinylamine units can be prepared, for example, from the above-described salt-containing polymer solutions by means of ultrafiltration on suitable membranes at separation limits of, for example, 1,000 to 500,000 daltons, preferably 10,000 to 300,000 daltons.

Derivatives of polymers containing vinylamine units can also be used. It is thus possible, for example, to prepare a large number of suitable derivatives from the vinylamine units by amidation, alkylation, sulfonamide formation, urea formation, thiourea formation, carbamate formation, acylation, carboxymethylation, phosphonylation or Michael addition of the amino groups of the polymer. Of particular interest in this context are uncrosslinked polyvinylguanidines which are obtained by reaction of polymers comprising vinylamine units, preferably polyvinylamines, with cyanamide (R ¹ R ² N-CN, where R ¹ , R ² = H, C ¹ to C ₄ -alkyl, C ₃ - to C ₆ -cycloalkyl, phenyl, benzyl, alkyl-substituted phenyl or naphthyl), cf. US 6,087,448, column 3, line 64 to column 5, line 14.

The polymers containing vinylamine units also include hydrolyzed graft polymers of, for example, N-vinylformamide on polyalkylene glycols, polyisocyanates vinyl acetate, polyvinyl alcohol, polyvinylformamides, polysaccharides such as starch, oligosaccharides or monosaccharides. The graft polymers can be obtained by free-radically polymerizing, for example, N-vinylformamide in aqueous medium in the presence of at least one of the stated grafting bases together with copolymerizable other monomers and then hydrolyzing the grafted vinylformamide units in a known manner to give vinylamine units.

Preferred polymers containing vinylamine units are vinylamine homopolymers of N-vinylformamide having a degree of hydrolysis of from 1 to

100 mol%, preferably 25 to 100 mol%, and from 1 to 100 mol%, preferably from 25 to 100 mol%, of hydrolyzed copolymers of N-vinylformamide and vinyl formate, vinyl acetate, vinyl propionate, acrylonitrile, methyl acrylate, ethyl acrylate and / or methyl methacrylate having K values of 30 to 150, in particular 60 to 100. Particularly preferred in the process according to the invention are the aforementioned homopolymers of N-vinylformamide.

Typical representatives of these homopolymers of N-vinylformamide are company known under the trade name Catiofast® ^® VFH, Catiofast® ^® VSH and Catiofast® ^® VMP of BASF share.

Of course, it is also possible to use mixtures of the stated cationic and / or amphoteric polymers in the process according to the invention. However, preference is given to using representatives of a polymer class. In particular, polymers containing vinylamine units are used in the process according to the invention.

The cationic and / or amphoteric polymers to be used in the process according to the invention are particularly preferred in an amount of from 0.0001 to 1% by weight, based on the solids content of the paper stock suspension, preferably from 0.0005 to 0.5% by weight in an amount of 0.001 to 0.2 wt .-% and in particular in an amount of 0.005 to 0.1 wt .-%, each based on the solids content of the pulp suspension, added to the fiber suspension.

By adding at least one cationic and / or amphoteric polymer to the fiber suspension, enormously increased filler retention is achieved compared to the prior art, i. It can be prepared by the novel process papers with a high filler content. As a result, the pulp content is reduced in the production, which leads to a reduction in the production cost of the paper.

Furthermore, they have papers prepared by the process according to the invention, in addition to the increased filler content improved dry strength. This is especially characterized by properties such as dry breaking length, tear propagation, internal strength and bending stiffness.

In addition to the increase in filler with constant strength properties, the paper gloss can also be significantly increased by the treatment according to the invention of the fillers. This is especially true for woody papers such as e.g. SC-paper. Here, the gloss increase means an increase in paper quality, which allows the paper manufacturer to obtain a higher selling price.

The finely divided fillers to be used in the process according to the invention are known from the literature. These are finely divided fillers which are at least partially coated with water-soluble amphoteric copolymers. Such aqueous slurries are known from JP-A 08059740, WO 04/087818 and the file reference DE 103 34 133 A1. These references are hereby incorporated by reference. The water-soluble amphoteric copolymers disclosed in these references have as common structural feature that they contain amide units, both five- and six-membered.

As previously described, both finely divided fillers alone, i. in pure form or as a so-called fresh filler, as well as finely divided fillers containing raw materials such as the so-called committee of coated paper, as well as mixtures in any composition thereof understood by the term finely divided fillers components.

For example, aqueous slurries of 100% fresh filler, based on the filler content, are used in the process according to the invention.

Alternatively, aqueous slurries can be used in the process according to the invention, the filler content is obtained to 100% from the Committee of coated paper. It does not matter whether it is the Committee of one or two sides coated paper.

In a third variant of the process according to the invention, aqueous slurries of mixtures in any desired composition of fresh filler and scrap of coated paper are used. For example, such a blend may consist of 90% fresh filler and 10% filler from the coated paper broke, each based on the filler content of the aqueous slurry. The ratio can also be reversed, namely fresh filler: filler from the coated paper broke of 10%: 90%. Examples of possible mixtures of fresh filler to filler from the coated paper committee are 15%: 85%, 20%: 80%, 30%: 70%, 40%: 60%, 50%: 50%, 60%: 40% , 70%: 30%, 80%: 20% and 85%: 15%. As described above, however, mixtures in any composition are possible.

Preference is given to using mixtures which have a mixing ratio in the range from 10% (fresh filler) to 90% (filler from the committee of coated paper) to 90% (fresh filler) to 10% (filler from the committee of coated paper).

More preferably, the mixing ratio is in the range of 15% (fresh filler) to 85% (filler of the coated paper broke) to 60% (fresh filler) of 40% (filler of the coated paper broke).

The percentages in each case relate to the total filler content in the aqueous slurry.

As the filler base, e.g. Calcium carbonates, which are present in the form of ground lime (GCC), lime, chalk, marble or in the form of precipitated calcium carbonate (PCC). Talc, kaolin, bentonite, satin white, calcium sulfate, barium sulfate and titanium dioxide can likewise be used as fillers. Of course, it is also possible to use mixtures of two or more of the stated fillers. The particle diameter of the fillers is preferably less than 2 μm, for example between 40 and 90% of the filler particles have a particle diameter of <2 μm.

In the processes described in JP-A 08059740, WO 04/087818 and DE 103 34 133 A1, the fillers are present as aqueous slurries. Precipitated calcium carbonate is usually present as an aqueous slurry in the absence of dispersants. In order to prepare aqueous slurries of the other fillers (eg GCC), an anionic dispersant, for example polyacrylic acid with an average molecular weight M _w of, for example, 1,000 to 40,000 daltons, is generally used. If the fillers contain a high solids content (eg 60% or more), the fillers are milled in the presence of an anionic dispersant. If an anionic dispersant is used, it is used, for example, from 0.01 to 0.6% by weight, preferably from 0.2 to 0.5% by weight, for the preparation of aqueous filler slurries. The slurries dispersed in water in the presence of anionic dispersants contain, for example, 10-60% by weight, usually 15-50% by weight, of at least one filler.

The water-soluble amphoteric polymers described in JP-A 08059740, WO 04/087818 and DE 103 34 133 A1 are added to the aqueous slurries. mixed. For example, from 0.1 to 5% by weight, based on fillers, of a water-soluble amphoteric polymer according to JP-A 08059740, WO 04/087818, and up to 1 to 60% by weight of at least one fine-particle filler containing aqueous slurry DE 103 34 133 A1 or enter an aqueous Anschläm- tion of a finely divided filler in an aqueous solution of an amphoteric polymer and mix the components each.

This treatment of the aqueous slurry of particulate fillers with the amphoteric polymers can be carried out continuously or batchwise. Preferably, the treatment of the fillers with the amphoteric polymer takes place in a continuous mode. For this example, the amphoteric polymer can be added as a dilute solution between the filler tank and the filler pump. The dilution and the shear forces in the filler pump guarantee a thorough mixing of the filler with the polymer. As a result, the finely divided fillers are at least partially coated or impregnated with the water-soluble amphoteric polymers. The solid content of the dilute polymer solution of the water-soluble amphoteric polymers may be between 20% by weight and 0.01% by weight.

When using finely divided fillers obtained from the coated paper committee, the treatment with the water-soluble amphoteric copolymers can be carried out, for example, by dissolving the broke of coated paper in the presence of the water-soluble amphoteric copolymers.

Alternatively, the treatment with water-soluble amphoteric copolymers is carried out after dissolution of the coated paper committee.

Regardless of the type of treatment of the filler from the committee also finely divided fillers are obtained, which are at least partially coated or impregnated with water-soluble amphoteric copolymers.

From the filler pump, the filler sludge treated with the polymer passes directly into the thick material or the thin material of the paper machine. It is also conceivable that the treated filler be metered in both the thick and in the thin paper machine.

The process according to the invention is suitable both for the production of wood-free papers and wood-containing papers. In all cases, the process according to the invention leads to a significant increase in the filler content in the paper, without causing any significant losses in the paper properties, such as dry strength. The filler Content is increased without loss of strength by the addition of at least one cationic and / or amphoteric polymer.

The production of paper, paperboard and cardboard by the process according to the invention is usually carried out by dewatering a slurry of cellulose fibers. Suitable cellulose fibers are any of the common types, e.g. Cellulosic fibers of wood pulp and all annual plants obtained fibers. Wood pulp includes, for example, groundwood, thermo-mechanical pulp (TMP), chemo-thermo-mechanical pulp (CTMP), pressure groundwood, semi-pulp, high-yield pulp and refiner mechanical pulp (RMP) and waste paper. Also suitable are pulps that can be used in bleached or unbleached form. Examples include sulphate, sulphite and soda pulps. Bleached pulps, also referred to as bleached kraft pulp, are preferably used. The fibers mentioned can be used alone or in a mixture.

The present invention also provides papers coated in the presence of an aqueous slurry of finely divided fillers, wherein the finely divided fillers are at least partially coated with water-soluble amphoteric Copoly-, wherein in addition to the aqueous slurry of finely divided fillers containing components at least one cationic and / or amphoteric polymer are added to the fiber suspension prior to sheet formation.

These papers are characterized in particular by a high filler content and a high dry strength. For the purposes of the present invention, papers having a high filler content are understood in particular to be papers having a filler content of from 3 to 45% by weight, based on the solids content of the paper stock suspension, preferably from 10 to 45% by weight, more preferably from 15 to 40 wt .-% and particularly preferably from 20 to 35 wt .-%, each based on the solids content of the paper stock suspension having.

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

The percentages in the examples are by weight unless otherwise indicated in the context. The electrophoretic mobility and the zeta potential were determined by laser optics. For electrophoresis measurements, the samples were diluted with an aqueous KCl solution (eg 10 mmoles) to a concentration for the measurement of 1% by volume. The measuring instrument used was the Zetasizer 3000 HS from Malvern Instruments Ltd .. The molecular weights M _{w of} the polymers were determined by means of static light scattering. The measurements were carried out at pH 7.6 in a 10 mmol aqueous saline solution.

K values were determined according to H. Fikentscher, Cellulose Chemistry, Vol. 13, 48-64 and 71-74 (1932) in 1.0% aqueous brine at 25 ° C, pH 7, and polymer concentration of 0 , 1 wt .-% determined.

The fillers used were precipitated chalk, precipitated calcium carbonate (PCC), ground chalk (GCC), kaolin or mixtures of the stated fillers. Five different copolymer-pretreated fillers were used in the examples of this invention.

The structural composition of these copolymers was determined from the monomer mixture used, the degree of hydrolysis and using the calculation disclosed in the earlier German patent application with the file 103 34 133.1 and in WO 04/087818 based on the ¹³ C NMR spectroscopy. For this purpose, the signals of the C atoms were integrated. The solvent used was D ₂ O.

I. Use of so-called fresh filler

Filler 1

6 g of a 12% aqueous solution of an amphoteric copolymer containing 40 mol% of vinylformamide units, 30 mol% of acrylic acid units and 30 mol% of vinylamine and amidine units and a molecular weight M _w of about 500,000 were in a beaker submitted and then diluted with 30 g of water. Subsequently, 150 g of a 20% slurry of precipitated calcium carbonate (PCC) in water was added. During the addition of the PCC slurry and then the mixture was stirred using a Heiltof stirrer at 1000 rpm. The pH of the mixture was then adjusted to 8.5. The mobility of the filler particles at pH 8.5 and at pH 7 was measured by microelectrophoresis. Electrophoretic mobility took a slightly negative value at both pH settings.

Filler 2

6 g of a 12% aqueous solution of an amphoteric copolymer containing 40 mol% of vinylformamide units, 30 mol% of acrylic acid units and 30 mol% vinylamine and amidine units and a molecular weight M _w of about 500,000 were placed in a beaker and then diluted with 30 g of water. Subsequently, 150 g of a 20% slurry of ground calcium carbinate (GCC) in water. Grinding of the GCC was carried out in a laboratory pigment mill in the presence of a sodium acrylate-containing dispersant. After grinding, approximately 75% of the GCC particles had a particle size <2 μm. During the addition of the GCC slurry and then the mixture was stirred by means of a Heiltof stirrer at 1000 rpm. The pH of the mixture was then adjusted to 8.5. The mobility of the filler particles at pH 8.5 and at pH 7 was measured by microelectrophoresis. Electrophoretic mobility took a slightly negative value at both pH settings.

Filler 3

5.4 g of a 13.5% aqueous solution of an amphoteric copolymer, which was prepared according to Example 1 of the prior German patent application with the file number 103 34 133.1, containing 35 mol% vinylformamide units, 30 mol% vinylamine and Amidine units, 11 mol% of sodium vinyl sulfonate units and 27 mol% of sodium acrylate units and a molecular weight M _w of about 500,000 were placed in a beaker and then diluted with 30 g of water. Subsequently 150 g of a 20% slurry of ground Calciumcarbi- nat (GCC, Hydrocarb® ^® 60 GU from Omya) in water were. During the addition of the GCC slurry and then the mixture was added using a Heiltof stirrer

Stirred 1000 rpm. The pH of the mixture was then adjusted to 8.5. The mobility of the filler particles at pH 8.5 and at pH 7 was measured by microelectrophoresis. Electrophoretic mobility took a slightly negative value at both pH settings.

Filler 4

6 g of a 12% aqueous solution of an amphoteric copolymer containing 40 mol% of vinylformamide units, 30 mol% of acrylic acid units and 30 mol% vinylamine and amidine units and a molecular weight M _w of about 500,000 were placed in a beaker and then diluted with 30 g of water. Then, 150 g of a 20% slurry of kaolin-clay mixture in water was added. During the addition of this slurry and then the mixture was stirred by means of a Heiltof stirrer at 1000 rpm. The pH of the mixture was then adjusted to 8.5. The mobility of the filler particles at pH 8.5 and at pH 7 was measured by microelectrophoresis. Electrophoretic mobility took a slightly negative value at both pH settings.

Filler 5 (according to Example 1 of JP-A 08059740)

6 g of a 12% aqueous solution of an amphoteric copolymer containing 35 mol% of amidine units of structure (I), 20 mol% of vinylformamide units, 10 mol% of vinylamine units, 5 mol% of acrylic acid units and 30 mol% of nitrile units and a molar mass M _w of 300,000 daltons were placed in a beaker and then diluted with 30 g of water. The intrinsic viscosity of the polymers was 2.7 dl / g (measured with an Oswald viscometer in an aqueous NaCl solution at a NaCl content of 0.1 g / dl and a temperature of 25 ° C. Subsequently, 150 g of a 20% slurry of precipitated calcium carbonate (PCC) in water was added during the addition of the slurry and then the mixture was stirred by means of a Heiltof stirrer at 1000 rpm and the pH of the mixture was then adjusted to 8.5 the mobility of the filler particles was measured by means of microelectrophoresis at pH 8.5 and at pH 7. The electrophoretic mobility assumed a slightly negative value at both pH settings.

Production of paper sheets of type A.

Examples 1 to 5

A mixture of TMP (Thermo-Mechanical Pulp) and groundwood was whisk-free in a ratio of 70/30 at a solids concentration of 4% in the laboratory pulper until a grinding degree of 60-65 was reached. The pH of the substance was in the range between 7 and 8. The milled substance was then diluted by the addition of water to a solids concentration of 0.35%.

In order to determine the behavior of the above-described aqueous filler slurries of the pretreated fillers in combination with polymers containing vinylamine units in the production of filler-containing paper, in each case 500 ml of the paper stock suspension were added and the slurries of the pretreated fillers and a vinylamine units were metered into this pulp containing polymer (Catio- fast® VMP). The metered amount of the polymers containing vinylamine units was in each case 0.1% of polymer, based on the solids content of the paper stock suspension. Immediately thereafter, the metered addition, a cationic polyacrylamide retention aid (Polymin ^® KE 2020) in this mixture. The metered amount of the retention agent was in each case 0.01% polymer, based on the solids content of the paper stock suspension.

The amount of slurry was adjusted by means of several preliminary tests so that the amount of pretreated filler was about 20%.

The paper sheets were each produced on a Rapid-Köthen sheet former according to ISO 5269/2 with a sheet weight of 80 g / m ² and then dried for 7 minutes at 9O ⁰ C and then calendered with a line pressure of 200 N / cm.

Comparative Examples 6 to 10 Paper sheets were prepared analogously to Examples 1 to 5 with the corresponding pretreated fillers. However, the addition of vinylamine-containing polymers was omitted.

Comparative Examples 11 to 14

It paper sheets were prepared analogously to Comparative Examples 6 to 9, however, in addition, the corresponding fillers were untreated, that is free of amphoteric copolymers used. However, the addition amount of the filler slurry in the sheet formation was increased so much that the equivalent filler content of the respective filler type was obtained from Examples 1 to 4.

Testing of type A paper sheets

After a storage time in a climate chamber at a constant 23 ° C and 50% humidity for 12 hours, the dry breaking length of the sheets were determined according to DIN 54540, the tear propagation to Brecht-Imset (DIN 53115) and the flexural strength according to DIN 53121. The results are shown in Table 1.

Table 1

Production of paper sheets of type B

Examples 15 to 18

A mixture of bleached birch sulphate and bleached pine sulphite was blotted open in a ratio of 70/30 at a solids concentration of 4% in the laboratory pulper until a freeness of 55-60 was reached. The opened substance is an optical brightener (Blankophor ^® PSG) and a cationic starch (HICAT ^® 5163 A) were then added. The digestion of the cationic starch was carried out as a 10% starch slurry in a jet cooker at 130 ⁰ C and 1 minute residence time. The metered amount of the optical brightener was 0.5% commercial goods, based on the solids content of the paper stock suspension. The dosage of cationic starch was 0.5% starch, based on the solids content of the stock suspension. The pH of the substance was in the range between 7 and 8. The milled substance was then diluted by the addition of water to a solids concentration of 0.35%.

In order to determine the behavior of the above-described aqueous filler slurries of the pretreated fillers in combination with polymers containing vinylamine units in the production of filler-containing paper, in each case 500 ml of the paper stock suspension were added and the slurries of the pretreated fillers and a vinylamine units were metered into this pulp containing polymer (Catio- fast® VFH). The metered amount of the polymers containing vinylamine units was in each case 0.1% of polymer, based on the solids content of the paper stock suspension. Immediately thereafter, the metered addition, a cationic polyacrylamide retention aid (Polymin ^® KE 2020) in this mixture. The metered amount of the retention agent was in each case 0.01% polymer, based on the solids content of the paper stock suspension.

The amount of slurry was adjusted by means of several preliminary tests so that the amount of pretreated filler was about 16%. 2

The paper sheets were each produced on a Rapid-Köthen sheet former according to ISO 5269/2 with a sheet weight of 80 g / m ² and then dried for 7 minutes at 90 ⁰ C and then calendered with a line pressure of 200 N / cm.

Comparative Examples 19 to 22

Paper sheets were prepared analogously to Examples 15 to 18 with the corresponding pretreated fillers. However, the addition of vinylamine-containing polymers has been omitted.

Comparative Examples 23 to 25

It paper sheets were prepared analogously to Comparative Examples 19 to 21, however, in addition, the corresponding fillers were untreated, that is free of amphoteric copolymers used. However, the addition amount of the filler slurry in the sheet formation was increased so much that the equivalent filler content of the respective filler type was obtained from Examples 15 to 17.

Testing of type B paper sheets

After a storage time in a climate chamber at a constant 23 ° C and 50% humidity for 12 hours, the internal strength according to DIN 54516 and the dry tear length of the sheets were determined according to DIN 54540. The tear propagation was determined according to Brecht-Imset (DIN 53115) and the bending stiffness according to DIN 53121. The results are shown in Table 2.

Table 2

Production of paper sheets of type C

Example 26

A mixture of bleached chemical pulp and groundwood was blotted open in a ratio of 20/80 at a solids concentration of 4% in the laboratory pulper until a freeness of 55-60 was reached. The pH of the substance was in the range between 7 and 8. The milled substance was then diluted by the addition of water to a solids concentration of 0.35%.

Subsequently, 500 ml of the paper stock suspension were introduced and the one filler slurry of the filler 2 was metered into this pulp. In addition, a 20% by weight slurry of an untreated kaolin / clay mixture was metered in. Immediately thereafter, the metered addition, a cationic polyacrylamide retention aid (poly mϊn ^® KE 2020) in this mixture. The metered amount of the retention agent was 0.01% polymer, based on the solids content of the paper stock suspension.

The amount of dosed filler slurry of the filler 2 and the untreated kaolin clay mixture was adjusted by means of several preliminary experiments so that the amount of filler 2 and untreated kaolin clay was about 20%. The total filler content was thus about 40%.

The paper sheets were produced on a Rapid-Köthen sheet former according to ISO 5269/2 with a sheet weight of 80 g / m ² and then dried for 7 minutes at 90 ⁰ C and then calendered with a line pressure of 200 N / cm. Comparative Example 27

Paper sheets were produced analogously to Example 26. The corresponding filler was untreated, ie free of amphoteric copolymers. However, the addition amount of the filler slurry in the sheet formation was increased so much that the equivalent filler content of the respective filler type of Example 26 was achieved.

Testing of type C paper sheets

After a storage time in a climate chamber at a constant 23 ° C. and 50% relative humidity for 12 hours, the dry breaking length of the sheets to DIN 54540 and the gloss of the paper sheets according to Lehmann were determined at an angle of 75 ° (DIN EN ISO 8254-2). The dry pick resistance of the paper sheets was confirmed by the ITG

Printability tester (ISO 3783) determined. The results are shown in Table 3.

Table 3

II. Use of filler from the Committee of coated paper

The double-coated woodfree paper having a basis weight of 104 g / m 2 used in the examples contained a total of 38.4% of filler according to analysis of the ashing data (500 ^° C. for 2 hours in the ashing furnace). According to the paper manufacturer, the raw paper used for the production of the coated grade was produced with a filler content of about 23% (ground calcium carbonate, GCC). The weight on each side was 12 gsm. The coating pigment used was precipitated calcium carbonate. Examples 28-31

Production of the painted committee

In a 30 liter container 500 grams of the coated paper were softened with 12 liters of water for 5 minutes. Subsequently, 5 g of a 12% strength aqueous solution of an amphoteric copolymer containing 40 mol% vinyl formamide units, 30 mol% acrylic acid units and 30 mol% vinylamine and amidine units and a molecular weight M _w of approx 500,000 too. Thereafter, the mixture was pitched in a laboratory pulper (Escher Wyss) for 10 minutes without specks. The freeness of the whipped stock suspension was then 65 Schopper Riegler.

Production of type D paper sheets

A mixture of bleached birch sulphate and bleached pine sulphite was blotted open in a ratio of 70/30 at a solids concentration of 4% in the laboratory pulper until a freeness of 55-60 was reached. The whisker and the coated broke spread in the presence of the amphoteric copolymer were mixed in a 1: 1 ratio. The total material, an optical brightener (Blankophor ^® PSG) and a cationic starch (HICAT ^® 5163 A) were then added. The digestion of the cationic starch was carried out as a 10% strength starch in a jet cooker at 130 ⁰ C and 1 minute residence time. The metered amount of the optical brightener was 0.5% commercial product, based on the solids content of the paper stock suspension. The dosage of cationic starch was 0.5% starch, based on the solids content of the stock suspension. The pH of the substance was in the range between 7 and 8. The total material was then diluted by the addition of water to a solids concentration of 0.35%.

For the preparation of paper containing filler, 500 ml of the stock suspension were placed in each case and each metered 1.5 g (Example 28), 2 g (Example 29), 2.5 g (Example 30) and 3 g (Example 31) of a 20% sodium GCC slurry (Hydrocarb ^® 60 GU from Omya) and in each case 0.05% of a polymer containing vinylamine units (Catiofast VFH ^®), based on the solids content of the paper stock suspension. Immediately thereafter, the metered addition, a cationic polyacrylamide retention aid (Polymin ^® KE 2020) in this mixture. The metered amount of the retention agent was in each case in each case 0.01% polymer, based on the solids content of the paper stock suspension. The paper sheets were each produced on a Rapid-Köthen sheet former according to ISO 5269/2 with a sheet weight of 80 g / m ² and then dried for 7 minutes at 90 ⁰ C and then calendered with a line pressure of about 200 N / cm.

Examples 32-35

Production of the painted committee

500 g of the coated paper were pitched in a laboratory pulper (Escher Wyss) with 12 liters of water (consistency 4%) for 10 minutes without stippings. The degree of grinding of the stock suspension was 65 Schopper Riegler. 5 g of a 12% strength aqueous solution of an amphoteric copolymer containing 40 mol% of vinylformamide units, 30 mol% of acrylic acid units and 30 mol% of vinylamine and amidine units having a molecular weight M _w of approx. 500,000 too.

Production of paper sheets type E

A mixture of bleached birch sulphate and bleached pine sulphite was blasted in a ratio of 70/30 at a solids concentration of 4% in the laboratory pulper until a freeness of 55-60 was reached. The whisker and the coated broke spread in the presence of the amphoteric copolymer were mixed in a 1: 1 ratio. The total material, an optical brightener (Blankophor ^® PSG) and a cationic starch (HICAT ^® 5163 A) were then added. The digestion of the cationic starch was carried out as a 10% strength starch in a jet cooker at 130 ⁰ C and 1 minute residence time. The metered amount of the optical brightener was 0.5% commercial goods, based on the solids content of the paper stock suspension. The dosage of cationic starch was 0.5% starch, based on the solids content of the stock suspension. The pH of the substance was in the range between 7 and 8. The total material was then diluted by addition of water to a solids concentration of 0.35%. For the preparation of paper containing filler, in each case 500 ml of the stock suspension were added and each metered 1, 5 g (Example 32), 2 g (Example 33), 2.5 g (Example 34) and 3 g (Example 35) a 20% sodium GCC slurry (Hydrocarb ^® 60 GU from Omya) and in each case 0.05% of a polymer containing vinylamine units (Catiofast VFH ^®), based on the solids content of the paper stock suspension. Immediately thereafter, the metered addition, a cationic polyacrylamide retention aid (Polymin ^® KE 2020) in this mixture. The metered amount of the retention agent was in each case in each case 0.01% polymer, based on the solids content of the paper stock suspension.

The paper sheets were each produced on a Rapid-Köthen sheet former according to ISO 5269/2 with a sheet weight of 80 g / m ² and then dried for 7 minutes at 90 ⁰ C and then calendered with a line pressure of about 200 N / cm.

Comparative Examples 36-39

Production of the painted committee

500 g of the coated paper were pitched in a laboratory pulper (Escher Wyss) with 12 liters of water (consistency 4%) for 10 minutes without stippings. The freeness of the whipped stock suspension was then 65 Schopper Riegler.

Production of paper sheets of type F

A mixture of bleached birch sulphate and bleached pine sulphite was blotted open in a ratio of 70/30 at a solids concentration of 4% in the laboratory pulper until a freeness of 55-60 was reached. The whipped material was then mixed with the coated broke in the ratio 1: 1. The total material, an optical brightener (Blankophor ^® PSG) was then added as a so-cationic starch (HICAT ^® 5163 A). The digestion of the cationic starch was carried out as a 10% starch slurry in a jet cooker at 13O ⁰ C and 1 minute residence time. The metered amount of the optical brightener was 0.5% strength, based on the solids content of the paper stock suspension. The dosage of cationic starch was 0.5% starch, based on the solids content of the pulp suspension. The pH of the substance was in the range between 7 and 8. The total material was then diluted by the addition of water to a solids concentration of 0.35%.

For the preparation of paper containing filler, 500 ml of the stock suspension were placed in each case and each metered into this pulp 1.5 g (Comparative Example 36), 2 g (Comparative Example 37), 2.5 g (Comparative Example 38) and 3 g (Comparative Example 39) a 20% GCC slurry (Hydrocarb ^® 60 GU from Omya) and 0.05% each a vinylamine-containing polymer (Catiofast VFH ^®), based on the dry content of the paper stock suspension. Immediately thereafter, one doosierte a cationic polyacrylamide retention aid (Polymin ^® KE 2020) in this mixture. The metered amount of the retention agent was in each case in each case 0.01% polymer, based on the solids content of the paper stock suspension.

Testing of paper sheets of type D, E, F

After a storage time in a climate chamber at a constant 23 ⁰ C and 50% humidity for 12 hours, the dry breaking length of the sheets were determined according to DIN 54540 and the internal strength according to DIN 54516. The results are shown in Table 4.

Table 4

Claims

claims

1. A process for the production of paper, paperboard and cardboard in the presence of an aqueous slurry of finely divided fillers containing components, wherein the finely divided fillers are at least partially coated with water-soluble amphoteric copolymers, characterized in that in addition to the aqueous slurry of finely divided fillers components containing at least one cationic and / or amphoteric polymer containing as structural element no esters of unsaturated carboxylic acids with quaternized amino alcohols, the fiber suspension added before sheet formation.

2. The method according to claim 1, characterized in that the cationic and / or amphoteric polymers is selected from

- homo- and copolymers of vinylimidazoles, diallylalkylamines and allyl dialkyaminen, these monomers are used in neutral form, as salts of acids or in quaternized form, homo- and copolymers of unsaturated esters of carboxylic acids with N ₁ N- dialkylamino or N-Alkylaminalkoholen these monomers being used in neutral form or as salts of acids,

Homo- and copolymers of unsaturated carboxylic acids with amides of N ₁ N- Dialkyldiaminen or N-alkyl diamines, these monomers are used in neutral form, as salts of acids or in quaternized form, lamins condensation products of epichlorohydrin or bisepoxides with dialkyl or polyamidoamines,

polyethyleneimines,

Graft products of ethyleneimines on amidoamines or polyamines, cationic starches and / or vinylamine units containing polymers.

3. The method according to any one of claims 1 or 2, characterized in that it is a polymer containing vinylamine units.

4. The method according to claim 3, characterized in that it is hydrolyzed in the vinylamine units containing polymers to 1 to 100 mol%

Homopolymers and copolymers of N-vinylformamide is.

5. The method according to claim 4, characterized in that it is homopolymers of N-vinylformamide.

6. The method according to claim 4, characterized in that it contains copolymerisates

95 to 5 mol% of N-vinylformamide and - 5 to 95 mol% of monoethylenically unsaturated monomers

is.

7. The method according to claim 6, characterized in that the monoethylenically unsaturated monomers are selected from vinyl formate, vinyl acetate, acrylonitrile, methyl acrylate, ethyl acrylate and methyl methacrylate.

8. The method according to any one of claims 1 to 7, characterized in that the at least one cationic and / or amphoteric polymer immediately after the addition of the aqueous slurry of finely divided fillers

Components of the fiber suspension is added.

9. The method according to any one of claims 1 to 8, characterized in that the at least one cationic and / or amphoteric polymer in an amount of 0.0001 to 1 wt .-%, based on the solids content of the paper stock suspension, is added to the fiber suspension ,

10. The method according to any one of claims 1 to 9, characterized in that the water-soluble amphoteric copolymers contain amidine units.

11. Paper produced by a process of claims 1 to 10.

12. Paper according to claim 11, characterized in that the filler content is 3 to 45 wt .-%, based on the solids content of the paper stock suspension.