EP2315875B1 - Method for increasing the dry strength of paper, paperboard and cardboard - Google Patents

Description

The invention relates to a process for the production of paper, paperboard and cardboard with high dry strength by adding at least one cationic polymer and a polymeric anionic compound to a pulp, dewatering of the pulp under sheet formation and drying of the paper products.

From the CA patent 1 110 019 discloses a process for the production of paper with high dry strength, in which one adds to the paper material first a water-soluble cationic polymer, then dosed a water-soluble anionic polymer, then dewatered the paper stock on the paper machine with sheet formation and the paper products dried. Suitable anionic polymers are, for example, hydrolyzed polyacrylamides which may have up to 30 mol% of acrylic acid units. As cationic polymers, for example, water-soluble homo- and copolymers of cationic monomers such as vinylpyridine, vinylimidazolidine, diallylamines, ethyleneimine and basic acrylates and basic methacrylates are used. The basic (meth) acrylates can each be copolymerized with acrylamide or methacrylamide. These cationic polymers and also polyacrylamides can be modified to form other cationic polymers which are suitable for the process described, for example they can be subjected to a Mannich reaction or Hofmann degradation.

From the DE-A 35 06 832 discloses a process for the production of paper with high dry strength, in which one adds to the stock first a water-soluble cationic polymer and then a water-soluble anionic polymer. Suitable anionic polymers are, for example, homopolymers or copolymers of ethylenically unsaturated C ₃ -C ₅ -carboxylic acids. The copolymers contain at least 35 wt .-% of an ethylenically unsaturated C ₃ - C ₅ carboxylic acid (eg acrylic acid) in copolymerized form. As cationic polymers in the examples polyethyleneimine, polyvinylamine, polydiallyldimethylammonium chloride and epichlorohydrin crosslinked condensation products of adipic acid and diethylenetriamine are described. The use of partially hydrolyzed homo- and copolymers of N-vinylformamide has also been considered.

The JP-A 1999-140787 relates to a process for the production of corrugated board, wherein to improve the strength properties of a paper product to the pulp 0.05 to 0.5 wt .-%, based on dry pulp, of a polyvinylamine obtained by hydrolysis of polyvinylformamide having a degree of hydrolysis of 25 to 100 %, is added in combination with an anionic polyacrylamide, the stock is then dewatered to form sheets and the paper is dried.

From the WO 03/052206 For example, there is known a paper product having improved strength properties obtainable by applying to the surface of a paper product a polyvinylamine and a polymeric anionic compound which can form a polyelectrolyte complex with polyvinylamine, or a polymeric compound having aldehyde functions such as aldehyde group-containing polysaccharides. Not only does the paper improve its dry and wet strength, it also observes a sizing effect of the treating agents.

From the WO 2004/061235 discloses a process for the production of paper, especially tissue, with particularly high wet and / or dry strengths, in which the paper stock is first added a water-soluble cationic polymer containing at least 1.5 meq / g of polymer to primary amino functionalities and a molecular weight of at least 10,000 daltons. Particular emphasis is placed here partially and fully hydrolyzed homopolymers of N-vinylformamide. Subsequently, a water-soluble anionic polymer is added which contains anionic and / or aldehydic groups.

1. (a) mindestens eines N-Vinylcarbonsäureamids der Formel
   
   in der R¹, R² = H oder C₁- bis C₆-Alkyl bedeuten,
2. (b) mindestens eines Säuregruppen enthaltenden monoethylenisch ungesättigten Monomeren und/oder deren Alkalimetall-, Erdalkalimetall- oder Ammoniumsalzen und gegebenenfalls
3. (c) anderen monoethylenisch ungesättigten Monomeren, und gegebenenfalls
4. (d) Verbindungen, die mindestens zwei ethylenisch ungesättigte Doppelbindungen im Molekül aufweisen.

In the DE-A 10 2004 056 551 Another method of improving the dry strength of paper is described. In this process, a separate addition of a Vinylamineinheiten polymers and a polymeric anionic compound to a pulp, dewatering of the pulp and drying of the paper products, wherein the polymeric anionic compound is at least one copolymer obtained by copolymerizing

1. (a) at least one N-vinylcarboxamide of the formula
   
   in which R ¹ , R ² = H or C ₁ - to C ₆ -alkyl,
2. (B) at least one acid group-containing monoethylenically unsaturated monomer and / or their alkali metal, alkaline earth metal or ammonium salts and optionally
3. (c) other monoethylenically unsaturated monomers, and optionally
4. (d) compounds having at least two ethylenically unsaturated double bonds in the molecule.

From the WO 2006/075115 the use of Hofmann degradation products of copolymers of acrylamide or methacrylamide in combination with anionic polymers having an anionic charge density of> 0.1 meq / g for the production of paper and cardboard with a high dry strength is known.

In WO 2006/120235 describes a process for producing papers having a filler content of at least 15% by weight, in which filler and fibers are treated together with cationic and anionic polymers, the treatment taking place alternately with cationic and anionic polymers and comprising at least 3 steps.

1. a) ein Polymer mit primären Aminogruppen und einer Ladungsdichte von > 1,0 meq/g
2. b) ein zweites, anderes kationisches Polymer mit einer Ladungsdichte von > 0,1 meq/g, das durch radikalische Polymerisation von kationischen Monomeren erhältlich ist, und
3. c) ein anionisches Polymer mit einer Ladungsdichte von > 0,1 meq/g.

The WO 2006/090076 also relates to a process for the production of paper and paperboard having a high dry strength, wherein 3 components are added to the paper stock:

1. a) a polymer with primary amino groups and a charge density of> 1.0 meq / g
2. b) a second, different cationic polymer with a charge density of> 0.1 meq / g, which is obtainable by free-radical polymerization of cationic monomers, and
3. c) an anionic polymer with a charge density of> 0.1 meq / g.

The invention has for its object to provide a further process for the production of paper, paperboard and cardboard with high dry strength available, the dry strength properties of the paper products compared to those of known products are further improved as possible. Another object of the invention is to achieve faster dewatering of the stock compared to known methods.

1. (a) Vinylamineinheiten enthaltende Polymere und
2. (b) Ethylenimineinheiten enthaltende Polymere

in beliebiger Reihenfolge oder als Mischung zu einem Papierstoff dosiert und wobei das Gewichtsverhältnis von (a) Vinylamineinheiten enthaltenden Polymeren zu (b) Ethylenimineinheiten enthaltenden Polymeren 10 : 1 bis 1 : 10 beträgt und man als (a) Vinylamineinheiten enthaltende Polymere die Reaktionsprodukte einsetzt, die erhältlich sind

• durch Polymerisieren mindestens eines Monomeren der Formel
  
  in der R¹, R² = H oder C₁- bis C₆-Alkyl bedeuten,
  und anschließende teilweise oder vollständige Abspaltung der Gruppen -CO-R¹ aus den in das Polymerisat einpolymerisierten Einheiten der Monomeren (I) unter Bildung von Aminogruppen
  und/oder
• durch Hofmann-Abbau von Polymeren, die Acrylamid- und/oder Methacrylamideinheiten aufweisen.

The objects are achieved according to the invention with a process for the production of paper, paperboard and cardboard with high dry strength by adding at least one water-soluble cationic polymer and at least one water-soluble polymeric anionic compound to a pulp, dewatering the pulp under sheet formation and drying the paper products, if water-soluble cationic polymers

1. (a) polymers containing vinylamine units and
2. (b) polymers containing ethyleneimine units

dosed in any order or as a mixture to form a pulp and wherein the weight ratio of (a) polymers containing vinylamine units to (b) polymers containing ethyleneimine units is from 10: 1 to 1:10 and the polymers containing (a) vinylamine units are the reaction products which are available

• by polymerizing at least one monomer of the formula
  
  in which R ¹ , R ² = H or C ₁ - to C ₆ -alkyl,
  and subsequent partial or complete cleavage of the groups -CO-R ¹ from the polymerized in the polymer units of the monomers (I) to form amino groups
  and or
• by Hofmann degradation of polymers having acrylamide and / or methacrylamide units.

• durch Polymerisieren mindestens eines Monomeren der Formel
  
  in der R¹, R² = H oder C₁- bis C₆-Alkyl bedeuten,
  und anschließende teilweise oder vollständige Abspaltung der Gruppen -CO-R¹ aus den in das Polymerisat einpolymerisierten Einheiten der Monomeren (I) unter Bildung von Aminogruppen
  und/oder
• durch Hofmann-Abbau von Polymeren, die Acrylamid- und/oder Methacrylamideinheiten aufweisen.

Polymers containing vinylamine units are known, cf. those mentioned in the prior art DE-A 35 06 832 and DE-A 10 2004 056551 , In the inventive Methods are used as (a) vinylamine units containing polymers, for example, the reaction products that are available

• by polymerizing at least one monomer of the formula
  
  in which R ¹ , R ² = H or C ₁ - to C ₆ -alkyl,
  and subsequent partial or complete cleavage of the groups -CO-R ¹ from the polymerized in the polymer units of the monomers (I) to form amino groups
  and or
• by Hofmann degradation of polymers having acrylamide and / or methacrylamide units.

1. (i) mindestens eines Monomeren der Formel
   
   in der R¹, R² = H oder C₁- bis C₆-Alkyl bedeuten,
2. (ii) mindestens eines anderen monoethylenisch ungesättigten Monomeren und gegebenenfalls
3. (iii) mindestens eines vernetzend wirkenden Monomeren mit mindestens zwei Doppelbindungen im Molekül

und anschließende teilweise oder vollständige Abspaltung der Gruppen -CO-R¹ aus den in das Polymerisat einpolymerisierten Einheiten der Monomeren (I) unter Bildung von Aminogruppen.As (a) polymers containing vinylamine units, for example, the reaction products obtainable by polymerizing

1. (i) at least one monomer of the formula
   
   in which R ¹ , R ² = H or C ₁ - to C ₆ -alkyl,
2. (ii) at least one other monoethylenically unsaturated monomer and optionally
3. (Iii) at least one crosslinking monomer having at least two double bonds in the molecule

and subsequent partial or complete cleavage of the groups -CO-R ¹ from the polymerized in the polymer units of the monomers (I) to form amino groups.

• (i) mindestens eines Monomeren der Formel
  
  in der R¹, R² = H oder C₁- bis C₆-Alkyl bedeuten,
• (ii,a) mindestens jeweils einer monoethylenisch ungesättigten Sulfonsäure, einer monoethylenisch ungesättigten Phosphonsäure, einer monoethylenisch ungesättigten Carbonsäure mit 3 bis 8 C-Atomen im Molekül und/oder deren Alkalimetall-, Erdalkalimetall- oder Ammoniumsalzen und gegebenenfalls
• (ii,b) mindestens eines anderen neutralen und/oder eines kationischen Monomeren und gegebenenfalls
• (iii) mindestens eines vernetzend wirkenden Monomeren mit mindestens zwei Doppelbindungen im Molekül

und anschließende teilweise oder vollständige Abspaltung von Gruppen -CO-R¹ aus den in das Polymerisat einpolymerisierten Monomeren der Formel I unter Bildung von Aminogruppen, wobei der Gehalt an Aminogruppen im Copolymerisat mindestens 5 Mol-% über dem Gehalt an einpolymerisierten Säuregruppen der Monomere (ii,a) beträgt.The polymers containing vinylamine units may also be amphoteric if they have a total cationic charge. The content of cationic groups in the polymer should be at least 5 mol%, preferably at least 10 mol% the content of anionic groups. Such polymers are obtainable, for example, by polymerizing

• (i) at least one monomer of the formula
  
  in which R ¹ , R ² = H or C ₁ - to C ₆ -alkyl,
• (ii, a) at least one monoethylenically unsaturated sulfonic acid, one monoethylenically unsaturated phosphonic acid, 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
• (ii, b) at least one other neutral and / or cationic monomer and optionally
• (Iii) at least one crosslinking monomer having at least two double bonds in the molecule

and subsequent partial or complete cleavage of groups -CO-R ¹ from the copolymerized in the polymer monomers of formula I to form amino groups, wherein the content of amino groups in the copolymer at least 5 mol% above the content of copolymerized acid groups of the monomers (ii , a) is.

1. (i) N-Vinylformamid und
2. (ii) Acrylnitril

und anschließende Abspaltung von Formylgruppen aus den in das Copolymerisat einpolymerisierten Vinylformamideinheiten unter Bildung von Aminogruppen erhältlich sind.Preferably used as (a) vinylamine units containing the reaction products, which are obtainable by polymerizing N-vinylformamide and subsequent cleavage of formyl groups from the copolymerized in the polymer vinylformamide units to form amino groups or one uses the reaction products by copolymerizing

1. (i) N-vinylformamide and
2. (ii) acrylonitrile

and subsequent cleavage of formyl groups from the copolymerized in the copolymer vinylformamide units to form amino groups are available.

• (i) N-Vinylformamid,
• (ii,a) Acrylsäure, Methacrylsäure und/oder deren Alkalimetall-, Erdalkalimetall- oder Ammoniumsalzen und gegebenenfalls
• (ii,b) Acrylnitril und/oder Methacrylnitril

und anschließende teilweise oder vollständige Abspaltung von Formylgruppen aus dem in das Polymerisat einpolymerisierten N-Vinylformamid unter Bildung von Aminogruppen erhältlich sind, wobei der Gehalt an Aminogruppen im Copolymerisat mindestens 5 Mol-% über dem Gehalt an einpolymerisierten Säuregruppen der Monomere (ii,a) beträgt.Also of interest are amphoteric Vinylamineinheiten containing polymers that carry a total cationic charge and, for example, by copolymerizing

• (i) N-vinylformamide,
• (ii, a) acrylic acid, methacrylic acid and / or their alkali metal, alkaline earth metal or ammonium salts and optionally
• (ii, b) acrylonitrile and / or methacrylonitrile

and subsequent partial or complete cleavage of formyl groups from the N-vinylformamide polymerized into the polymer to form amino groups are obtainable, wherein the content of amino groups in the copolymer at least 5 mol% above the content of copolymerized acid groups of the monomers (ii, a) ,

Examples of monomers of the formula I are N-vinylformamide, N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide, N-vinylpropionamide and N-vinyl-N-methylpropionamide and N-vinylbutyramide. The monomers of group (i) can be used alone or mixed in the copolymerization with the monomers of the other groups. Preferably used monomer of this group is N-vinylformamide.

These polymers may optionally be modified by copolymerizing the N-vinylcarboxamides (i) together with (ii) at least one other monoethylenically unsaturated monomer and then hydrolyzing the copolymers to form amino groups. If anionic monomers are used in the copolymerization, the hydrolysis of the copolymerized vinylcarboxamide units is carried out so far that the molar excess of amine units compared to the anionic units in the polymer is at least 5 mol%.

Examples of monomers of group (ii) are esters of α, β-ethylenically unsaturated mono- and dicarboxylic acids with C ₁ -C ₃₀ -alkanols, C ₂ -C ₃₀ -alkanediols and C ₂ -C ₃₀ -aminoalcohols, amides of α, β-ethylenically unsaturated monocarboxylic acids and their N-alkyl and N, N-dialkyl derivatives, nitriles of α, β-ethylenically unsaturated mono- and dicarboxylic acids, esters of vinyl alcohol and allyl alcohol with C ₁ -C ₃₀ monocarboxylic acids, N-vinyl lactams, nitrogen-containing Heterocycles with α, β-ethylenically unsaturated double bonds, vinyl aromatics, vinyl halides, vinylidene halides, C ₂ -C ₈ monoolefins and mixtures thereof.

Suitable representatives are, for example, methyl (meth) acrylate (this notation symbolizes both "acrylates" and "methacrylates" here as well as in the following text), methyl methacrylate, Ethyl (meth) acrylate, ethyl ethacrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, tert-butyl methacrylate, n-o-cytriethyl (meth) acrylate, 1,1,3, 3-Tetramethylbutyl (meth) acrylate, ethylhexyl (meth) acrylate and mixtures thereof. Suitable additional monomers of group (ii) are furthermore the esters of α, β-ethylenically unsaturated mono- and dicarboxylic acids with aminoalcohols, preferably C ₂ -C ₁₂ -aminoalcohols. These may be C ₁ -C ₈ -monoalkylated or -dialkylated on the amine nitrogen. As the acid component of these esters are z. For example, acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, crotonic acid, maleic anhydride, monobutyl maleate and mixtures thereof. Preference is given to using acrylic acid, methacrylic acid and mixtures thereof. These include, for example, N-methylaminomethyl (meth) acrylate, N-methylaminoethyl (meth) acrylate, N, N-dimethylaminomethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N , N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminopropyl (meth) acrylate and N, N-dimethylaminocyclohexyl (meth) acrylate.

Further suitable monomers of group (ii) are 2-hydroxyethyl (meth) acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl ( meth) acrylate, 6-hydroxyhexyl (meth) acrylate and mixtures thereof.

Further suitable monomers of group (ii) are acrylamide, methacrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, n-propyl (meth) acrylamide, N- (n-butyl) (meth) acrylamide, tert-butyl (meth) acrylamide, n-octyl (meth) acrylamide, 1,1,3,3-tetramethylbutyl (meth) acrylamide, ethylhexyl (meth) acrylamide and mixtures thereof.

In addition, as further monomers of group (ii) N- [2- (dimethylamino) ethyl] acrylamide, N- [2- (dimethylamino) ethyl] methacrylamide, N- [3- (dimethylamino) propyl] acrylamide, N- [ 3- (dimethylamino) propyl] methacrylamide, N- [4- (dimethylamino) butyl] acrylamide, N- [4- (dimethylamino) butyl] methacrylamide, N- [2- (diethylamino) ethyl] acrylamide, N- [2-] (Diethylamino) ethyl] methacrylamide and mixtures thereof.

Further examples of monomers of group (ii) are nitriles of α, β-ethylenically unsaturated mono- and dicarboxylic acids such as, for example, acrylonitrile and methacrylonitrile. The presence of units of these monomers in the copolymer leads during or after the hydrolysis to products which have amidine units, cf. eg EP-A 0 528 409 or DE-A 43 28 975 , Namely, in the hydrolysis of N-vinylcarboxylic acid amide polymers, amidine units are formed in a secondary reaction by reacting vinylamine units with an adjacent vinylformamide unit or, if a nitrile group is present as an adjacent group in the polymer. In the following means the indication of vinylamine units in the amphoteric Copolymers or in unmodified homo- or copolymers always the sum of vinylamine and amidine units.

Suitable monomers of group (ii) are furthermore N-vinyllactams and derivatives thereof which, for. B. one or more C ₁ -C ₆ alkyl substituents (as defined above) may have. These include N-vinylpyrrolidone, N-vinylpiperidone, N-vinylcaprolactam, N-vinyl-5-methyl-2-pyrrolidone, N-vinyl-5-ethyl-2-pyrrolidone, N-vinyl-6-methyl-2-piperidone, N-vinyl-6-ethyl-2-piperidone, N-vinyl-7-methyl-2-caprolactam, N-vinyl-7-ethyl-2-caprolactam and mixtures thereof.

Further suitable monomers of group (ii) are N-vinylimidazoles and alkylvinylimidazoles, in particular methylvinylimidazoles such as 1-vinyl-2-methylimidazole, 3-vinylimidazoleN-oxide, 2- and 4-vinylpyridine N-oxides and betaine derivatives and quaternization products of these monomers and ethylene, propylene, isobutylene, butadiene, styrene, α-methylstyrene, vinyl acetate, vinyl propionate, vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride and mixtures thereof.

The aforementioned monomers can be used individually or in the form of any mixtures. Typically, they are used in amounts of 1 to 90 mol%, preferably 10 to 80 mol% and particularly preferably 10 to 60 mol%.

For the preparation of amphoteric Copoylmerisaten come as other monoethylenically unsaturated monomers of group (ii) also anionic monomers into consideration, which are referred to above as monomers (ii, a). They may optionally be copolymerized with the neutral and / or cationic monomers (ii, b) described above. However, the amounts of anionic monomers (ii, a) is at most 45 mol%, so that the resulting amphoteric copolymer has a total cationic charge.

Examples of anionic monomers of group (ii, a) are ethylenically unsaturated C _{3 to} C ₈ carboxylic acids such as acrylic acid, methacrylic acid, dimethacrylic acid, ethacrylic acid, maleic acid, fumaric acid, itoconic acid, mesaconic acid, citraconic acid, methylenemalonic acid, allylacetic acid, vinylacetic acid and crotonic acid. Also suitable as monomers of this group are monomers containing sulfo groups, such as vinylsulfonic acid, acrylamido-2-methylpropanesulfonic acid and styrenesulfonic acid, and monomers containing phosphono groups, such as vinylphosphonic acid. The monomers of this group can be used alone or in admixture with each other, in partially or completely neutralized form in the copolymerization. For neutralization, for example, alkali metal or alkaline earth metal bases, ammonia, amines and / or alkanolamines are used. Examples of these are sodium hydroxide solution, potassium hydroxide solution, soda, potash, sodium bicarbonate, magnesium oxide, calcium hydroxide, calcium oxide, Triethanolamine, ethanolamine, morpholine, diethylenetriamine or tetraethylenepentamine.

A further modification of the copolymers is possible by using in the copolymerization monomers of group (iii) which contain at least two double bonds in the molecule, for. B. triallylamine, methylenebisacrylamide, glycol diacrylate, glycol dimethacrylate, glycerol triacrylate, pentaerythritol triallyl ether, at least two times with acrylic acid and / or methacrylic acid esterified polyalkylene glycols or polyols such as pentaerythritol, Sobit or glucose. If at least one monomer of the above group is used in the polymerization, the amounts used are up to 2 mol%, e.g. B. 0.001 to 1 mol%.

Furthermore, it may be useful for modifying the polymers to combine the use of the above crosslinked with the addition of regulators are typically used 0.001 to 5 mol%. All regulators known in the literature can be used, eg. For example, sulfur compounds such as mercaptoethanol, 2-Ethylhexylthioglycolat, thioglycolic acid and dodecyl mercaptan and sodium hypophosphite, formic acid or Tribromchlormethan.

The polymers containing vinylamine units also include hydrolyzed graft polymers of, for example, N-vinylformamide on polyalkylene glycols, polyvinyl acetate, polyvinyl alcohol, polyvinylformamides, polysaccharides such as starch, oligosaccharides or monosaccharides. The graft polymers are obtainable 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.

The hydrolysis of the copolymers can be carried out in the presence of acids or bases or else enzymatically. In the case of hydrolysis with acids, the vinylamine groups formed from the vinylcarboxamide units are present in salt form. The hydrolysis of vinylcarboxylic acid amide copolymers is described in U.S. Pat EP-A 0 438 744 , Page 8, line 20 to page 10, line 3, described in detail. The explanations made there apply correspondingly to the preparation of the cationic and / or amphoteric polymers containing vinylamine units to be used according to the invention and having a total cationic charge. The polymers containing vinylamine units can also be used in the form of the free bases in the process according to the invention. Such polymers are useful, for example, in the hydrolysis of polymers containing vinylcarboxylic acid units with bases.

The polymers containing vinylamine units have, for example, K values (determined according to H. Fikentscher in 5% strength aqueous sodium chloride solution at pH 7, a polymer concentration of 0.5% by weight and a temperature of 25 ° C.) in the range from 20 to 250 , preferably 50 to 150.

The preparation of the homopolymers and copolymers containing vinylamine units described above can be carried out by solution, precipitation, suspension or emulsion polymerization. Preference is given to solution polymerization in aqueous media. Suitable aqueous media are water and mixtures of water and at least one water-miscible solvent, e.g. As an alcohol such as methanol, ethanol, n-propanol or isopropanol. The cationic polymers are water-soluble. The solubility in water at a temperature of 20 ° C, 1013 mbar and a pH of 7.0, for example, at least 5 wt .-%, preferably at least 10 wt .-%.

The charge density of the cationic polymers (without counterions) is for example at least 1.0 meq / g and is preferably in the range of 4 to 10 meq / g.

As (a) polymers containing vinylamine units, the reaction products which are obtainable by Hofmann degradation of homopolymers or copolymers of acrylamide or methacrylamide in an aqueous medium in the presence of sodium hydroxide solution and sodium hypochlorite and subsequent decarboxylation of the carbamate groups of the reaction products in the presence of an acid are also suitable , Such polymers are for example made EP-A 0 377 313 and WO 2006/075115 known. The preparation of polymers containing vinylamine groups is described, for example, in WO 2006/075115 , Page 4, line 25 to page 10, line 22 and in the examples on pages 13 and 14 are treated in detail. The information given there applies to the characterization of the polymers containing vinylamine units prepared by Hofmann degradation.

It is based on polymers containing acrylamide and / or methacrylamide units. These are homopolymers or copolymers of acrylamide and methacrylamide. Suitable comonomers are, for example, dialkylaminoalkyl (meth) acrylamides, diallylamine, methyldiallylamine and also the salts of the amines and the quaternized amines. Also suitable as comonomers Dimethyldiallylammonium salts, acrylamidopropyltrimethylammonium chloride and / or Methacrylamidopropyltrimethylammoniumchlorid, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, vinyl acetate and acrylic and methacrylic acid esters. As comonomers are optionally also anionic monomers such as acrylic acid, methacrylic acid, maleic anhydride, maleic acid, itaconic acid, acrylamidomethylpropanesulfonic acid, methallylsulfonic acid and vinylsulfonic acid and the alkali metal, Erdalkylimetall- and Ammonium salts of said acidic monomers into consideration, wherein not more than 5 mol% of these monomers are used in the polymerization. The amount of water-insoluble monomers is chosen in the polymerization so that the resulting polymers are soluble in water.

If appropriate, comonomers may also be used crosslinkers, for. B. ethylenically unsaturated monomers containing at least two double bonds in the molecule such as triallylamine, methylenebisacrylamide, ethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, triallylamine and trimethylol trimethacrylate. If a crosslinker is used, the amounts used are, for example, 5 to 5000 ppm. The polymerization of the monomers can be carried out by any known method, for. B. by free-radical initiated solution, precipitation or suspension polymerization. If appropriate, it is possible to work in the presence of customary polymerization regulators.

When Hofmann degradation is for example from 20 to 40 wt .-% aqueous solutions of at least one acrylamide and / or methacrylamide units containing polymers. The ratio of alkali metal hypochlorite to (meth) acrylamide units in the polymer is decisive for the resulting content of amine groups in the polymer. The molar ratio of alkyl metal hydroxide to alkyl metal hypochlorite is, for example, 2 to 6, preferably 2 to 5. For a certain amine group content in the degraded polymer, the amount of alkali metal hydroxide required for the degradation of the polymer is calculated.

The Hofmann degradation of the polymer takes place z. In the temperature range of 0 to 45 ° C, preferably 10 to 20 ° C in the presence of quaternary ammonium salts as a stabilizer to prevent side reaction of the resulting amino groups with the amide groups of the starting polymer. After completion of the reaction with alkyllauge / alkali metal hypochlorite, the aqueous reaction solution is passed into a reactor in which an acid is introduced for the decarboxylation of the reaction product. The pH of the reaction product containing vinylamine units is adjusted to a value of 2 to 7. The concentration of the decomposition products containing vinylamine units is, for example, more than 3.5% by weight, in most cases above 4.5% by weight. The aqueous polymer solutions can be concentrated for example by means of ultrafiltration.

The polymers containing ethyleneimine units include all polymers obtainable by polymerization of ethyleneimine in the presence of acids, Lewis acids or haloalkanes, such as homopolymers of ethyleneimine or graft polymers of ethyleneimine, cf. US 2,182,306 or in US 3,203,910 , If desired, these polymers can subsequently be subjected to crosslinking. As crosslinkers z. B. all multifunctional compounds into consideration, the opposite For example, multifunctional epoxides such as bisglycol ethers of oligo- or polyethyleneoxides or other multifunctional alcohols such as glycerol or sugars, multifunctional carboxylic acid esters, mulifunctional isocyanates, polyfunctional acrylic or methacrylic acid esters, multifunctional acrylic or methacrylic acid amides, epichlorohydrin, multifunctional acid halides, multifunctional nitriles, α, ω-chlorohydrin ethers of oligo- or polyethylene oxides or of other multifunctional alcohols such as glycerol or sugars, divinyl sulfone, maleic anhydride or ω-halocarboxylic acid chlorides, multifunctional haloalkanes in particular α, ω-dichloroalkanes. Other crosslinkers are in WO 97/25367 , Pages 8 to 16 described.

For example, polymers containing ethyleneimine units are made EP-A-0411400 . DE 2434816 and US 4,066,494 known.

• Homopolymerisate des Ethylenimins,
• mit mindestens bifunktionellen Vernetzern umgesetzten Polyethylenimine,
• mit Ethylenimin gepfropften Polyamidoamine, die mit mindestens bifunktionellenVernetzern umgesetzt sind,
• Umsetzungsprodukte von Polyethyleniminen mit einbasischen Carbonsäuren zu amidierten Polyethyleniminen,
• Michaeladditionsprodukte von Polyethyleniminenen an ethylenisch ungesättigte Säuren, Salze, Ester, Amide oder Nitrile von monoethylenisch ungesätitgten Carbonsäuren,
• phosphonomethylierten Polyethylenimine,
• carboxylierten Polyethylenimine und
• alkoxylierten Polyethylenimine.

As (b) ethyleneimine units containing polymers used z. B. in the inventive method, at least one water-soluble cationic polymer from the group of

• Homopolymers of ethyleneimine,
• polyethyleneimines reacted with at least bifunctional crosslinkers,
• ethyleneimine grafted polyamidoamines reacted with at least bifunctional crosslinkers,
• Reaction products of polyethylenimines with monobasic carboxylic acids to amidated polyethylenimines,
• Michael addition products of polyethyleneimines to ethylenically unsaturated acids, salts, esters, amides or nitriles of monoethylenically unsaturated carboxylic acids,
• phosphonomethylated polyethyleneimines,
• carboxylated polyethyleneimines and
• alkoxylated polyethyleneimines.

Polymers which are obtained by first condensing at least one polycarboxylic acid with at least one polyamine to form polyamidoamines, then grafting with ethyleneimine and then crosslinking the reaction products with one of the abovementioned compounds belong to the compounds preferably containing E-thylenimine units. A method for producing such compounds is, for example, in DE-A-2434816 wherein α, ω-chlorohydrin ethers of oligo- or polyethylene oxides are used as crosslinkers application.

Particularly preferred are products of the two above types which have been subjected to ultrafiltration and thus optimized in their molecular weight distribution. Such ultrafiltered products are extensively in WO 00/67884 and WO 97/25367 described.

Reaction products of polyethylenimines with monobasic carboxylic acids to amidated polyethylenimines are known from the WO 94/12560 known. Michael addition products of polyethyleneimines with ethylenically unsaturated acids, salts, esters, amides or nitriles of monoethylenically unsaturated carboxylic acids are the subject of WO 94/14873 , Phosphonomethylated polyethylenimines are described in detail in U.S. Pat WO 97/25367 described. Carboxylated polyethyleneimines are obtainable, for example, by means of a plug synthesis by reacting polyethyleneimines with formaldehyde and ammonia / hydrogen cyanide and hydrolysing the reaction products. Alkoxylated polyethyleneimines can be prepared by reacting Polyethyleiminen with alkylene oxides such as ethylene oxide and / or propylene oxide.

The polymers containing ethyleneimine units have, for example, molecular weights of from 10,000 to 3,000,000. The cationic charge of the polymers containing ethyleneimine units is e.g. at least 4 meq / g. It is usually in the range of 8 to 20 meq / g.

The weight ratio of polymers containing (a) vinylamine units to polymers containing (b) ethyleneimine units in the process of the present invention is, for example, 10: 1 to 1:10, preferably 5: 1 to 1: 5. The combination of polymers containing ethyleneimine units and polymers containing vinylamine units used in the inventive method for producing paper, for example in an amount of 0.01 to 2.0 wt .-%, preferably 0.1 to 1.0 wt .-%, based on dry pulp.

1. (1) wenigstens einem Monomer, das ausgewählt ist aus der Gruppe bestehend aus
   • (1.1) monoethylenisch ungesättigten Sulfonsäuren, Phosphonsäuren, Phosphorsäureestern und Derivaten davon, und
   • (1.2) monoethylenisch ungesättigten Mono- und Dicarbonsäuren, deren Salzen und Dicarbonsäureanhydriden,
2. (2) gegebenenfalls wenigstens einem von den Komponenten (1.1) und (1.2) verschiedenen monoethylenisch ungesättigten Monomer, und
3. (3) gegebenenfalls wenigstens eine Verbindung, die mindestens zwei ethylenisch ungesättigte Doppelbindungen im Molekül aufweist,

mit der Maßgabe, dass das Monomerengemisch mindestens ein Monomer (1) mit mindestens einer freien Säuregruppe und/oder einer Säuregruppe in Salzform enthält.The water-soluble polymeric anionic compounds include all polymers which carry acid groups or their salts and have a charge density of> 0.5 meq / g. The acid groups may be carboxyl groups, sulfonic acid groups and phosphonic acid groups. Also esters of phosphoric acid belong to this, wherein at least one acid function of the phosphoric acid is not esterified. In principle, it is possible to use polymers, polycondensates, for example polyaspartic acid, polyaddition compounds and also compounds prepared by ring-opening polymerization with a charge density of> 0.5 meq / g in each case. Also applicable are polymers which have been modified by polymer-analogous reactions such as Strecker reaction or by phosphonomethylation with acidic groups. However, preference is given to polymers of the following composition:

1. (1) at least one monomer selected from the group consisting of
   • (1.1) monoethylenically unsaturated sulfonic acids, phosphonic acids, phosphoric acid esters and derivatives thereof, and
   • (1.2) monoethylenically unsaturated mono- and dicarboxylic acids, their salts and dicarboxylic acid anhydrides,
2. (2) optionally at least one monoethylenically unsaturated monomer other than components (1.1) and (1.2), and
3. (3) if appropriate, 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 (1) with at least one free acid group and / or one acid group in salt form.

Suitable monomers of group (1.1) are compounds which have an organic radical having a polymerizable, α, β-ethylenically unsaturated double bond and at least one sulfonic acid or phosphonic acid group per molecule. Also suitable are the salts and esters of the aforementioned compounds. The esters of phosphonic acids may be mono- or diesters. Suitable monomers (1.1) are furthermore esters of phosphoric acid with alcohols having a polymerizable, α, β-ethylenically unsaturated double bond. In this case, a proton of the phosphoric acid group or the other two protons of the phosphoric acid group can be neutralized by suitable bases or esterified with alcohols which have no polymerizable double bonds.

Suitable bases for the partial or complete neutralization of the acid groups of the monomers (1.1) are, for example, alkali metal or alkaline earth metal bases, ammonia, amines and / or alkanolamines. Examples of these are sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, magnesium hydroxide, magnesium oxide, calcium hydroxide, calcium oxide, triethanolamine, ethanolamine, morpholine, diethylenetriamine or tetraethylenepentamine. Suitable alcohols for the esterification of phosphoric acid are, for example, C ₁ -C ₆ -alkanols, such as, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, n-pentanol, n-hexanol and their isomers.

The monomers (1.1) include, for example, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, sulfoethyl acrylate, sulfoethyl methacrylate, sulfopropyl acrylate, sulfopropyl methacrylate, 2-hydroxy-3-acryloxypropylsulfonic acid, 2-hydroxy-3-methacryloxypropylsulfonic acid, styrenesulfonic acid, acrylamidomethylenephosphonic acid, 2-acrylamido-2-methylpropanesulfonic acid, Vinylphosphonic acid, CH ₂ = CH-NH-CH ₂ -PO ₃ H, monomethyl vinylphosphonate, dimethyl vinylphosphonate, allylphosphonic acid, monomethyl allylphosphonate, dimethyl allylphosphonate, acrylamidomethylpropylphosphonic acid, (meth) acrylethylene glycol phosphate and monoesters of phosphoric acid.

Are used as component (1.1) exclusively monomers in which all protons of the acid groups are esterified, such as. As Vinylphosphonsäuredimethylester or Allylphosphonsäuredimethylester, so at least one monoethylenically unsaturated mono- and / or dicarboxylic acid or a salt thereof is used for the polymerization, as described below as component (1.2). This ensures that the copolymers used according to the invention have anionic groups.

The abovementioned monomers (1.1) can be used individually or in the form of any desired mixtures in the preparation of the anionic polymers.

Suitable monomers of group (1.2) are monoethylenically unsaturated carboxylic acids having 3 to 8 carbon atoms and the water-soluble salts such as alkali metal, alkaline earth metal or ammonium salts of these carboxylic acids and the monoethylenically unsaturated carboxylic acid anhydrides. This group of monomers includes, for example, acrylic acid, methacrylic acid, dimethacrylic acid, ethacrylic acid, α-chloroacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, mesaconic acid, citraconic acid, glutaconic acid, aconitic acid, methylenemalonic acid, allylacetic acid, vinylacetic acid and crotonic acid. The monomers of group (1.2) can be used alone or mixed with each other, in partially or completely neutralized form in the homo- or copolymerization. Suitable bases for neutralization are the compounds mentioned above in component (1.1).

The water-soluble anionic polymer contains at least one monomer from the group (1) which is selected from the subgroups (1.1) and / or (1.2). Of course, the water-soluble copolymer may also contain mixtures of monomers from subgroups (1.1) and (1.2) in copolymerized form.

If appropriate, the copolymers may contain at least one further monomer of group (2) in copolymerized form for modification. These monomers are preferably selected from esters of α, β-ethylenically unsaturated mono- and dicarboxylic acids with C ₁ -C ₃₀ -alkanols, C ₂ -C ₃₀ -alkanediols and C ₂ -C ₃₀ -aminoalcohols, amides of α, β-ethylenically unsaturated monocarboxylic acids and their N-alkyl and N, N-dialkyl derivatives, esters of vinyl alcohol and allyl alcohol with C ₁ -C ₃₀ monocarboxylic acids, N-vinyl lactams, nitrogen-containing heterocycles having α, β-ethylenically unsaturated double bonds, vinyl aromatics, vinyl halides, vinylidene halides, C ₂ C ₈ monoolefins and mixtures thereof.

Suitable representatives of group (2) are z. Methyl (meth) acrylate, methyl methacrylate, ethyl (meth) acrylate, ethyl methacrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, tert-butyl methacrylate, n-ocytl ( meth) acrylate, 1,1,3,3-tetramethylbutyl (meth) acrylate, ethylhexyl (meth) acrylate and mixtures thereof. Suitable additional monomers (2) are furthermore acrylic acid amide, methacrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, n-propyl (meth) acrylamide, N- (n-butyl) (meth) acrylamide, tert. Butyl (meth) acrylamide, n-octyl (meth) acrylamide, 1,1,3,3-tetramethylbutyl (meth) acrylamide, ethylhexyl (meth) acrylamide and mixtures thereof.

Further, as monomers (2), 2-hydroxyethyl (meth) acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) are suitable. acrylate, 6-hydroxyhexyl (meth) acrylate and mixtures thereof.

Further suitable monomers of group (2) are nitriles of α, β-ethylenically unsaturated mono- and dicarboxylic acids, such as, for example, acrylonitrile and methacrylonitrile.

Suitable monomers of group (2) are also N-vinyl lactams and derivatives thereof, the z. B. one or more C ₁ -C ₆ alkyl substituents (as defined above) may have. These include N-vinylpyrrolidone, N-vinylpiperidone, N-vinylcaprolactam, N-vinyl-5-methyl-2-pyrrolidone, N-vinyl-5-ethyl-2-pyrrolidone, N-vinyl-6-methyl-2-piperidone, N-vinyl-6-ethyl-2-piperidone, N-vinyl-7-methyl-2-caprolactam, N-vinyl-7-ethyl-2-caprolactam and mixtures thereof.

Further suitable monomers of group (2) are ethylene, propylene, isobutylene, butadiene, styrene, α-methylstyrene, vinyl acetate, vinyl propionate, vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride and mixtures thereof.

The aforementioned monomers of group (2) can be used in the copolymerization with at least one anionic monomer, individually or in the form of any mixtures.

A further modification of the copolymers is possible by using in the copolymerization monomers of group (3) which contain at least two double bonds in the molecule, for. As methylenebisacrylamide, glycol diacrylate, glycol dimethacrylate, glycerol triacrylate, pentaerythritol triallyl ether, at least two times with acrylic acid and / or methacrylic acid esterified polyalkylene glycols or polyols such as pentaerythritol, soba or glucose. If at least one monomer of group (3) is used in the copolymerization, the amounts used are up to 2 mol%, z. B. 0.001 to 1 mol%.

Furthermore, it may be useful to combine the use of the above crosslinked with the addition of regulators in the polymerization. Typically, from 0.001 to 5 mole percent of at least one regulator is employed. All known literature can be used Regulators such as mercaptoethanol, 2-ethylhexyl thioglycolate, thioglycolic acid, dodecyl mercaptan, sodium hypophosphite, formic acid and / or tribromochloromethane.

The anionic polymeric compound used is preferably homopolymers of ethylenically unsaturated C ₃ - to C ₅ -carboxylic acids, in particular polyacrylic acid and polymethacrylic acid, and also hydrolyzed homopolymers of maleic anhydride and of itaconic anhydride. Preferred anionic copolymers comprise, for example, (1) 10 to 99% by weight of at least one ethylenically unsaturated C ₃ to C ₅ carboxylic acid and (2) 90 to 1% by weight of at least one amide, nitrile and / or one Esters of an ethylenically unsaturated C ₃ - to C ₅ -carboxylic acid in copolymerized form. The sum of the percentages by weight of components (1) and (2) is always 100. Particularly preferred are copolymers of acrylic acid and acrylamide, Copoylmerisate of acrylic acid and acrylonitrile, copolymers of acrylic acid and N-vinylformamide, copolymers of methacrylic acid and methacrylamide, copolymers of Methacrylic acid and N-vinylformamide, copolymers of acrylic acid and methacrylamide, copolymers of acrylic acid and methacrylonitrile, copolymers of methacrylic acid and methacrylonitrile and copolymers of acrylic acid, acrylamide and acrylonitrile.

The anionic polymers are water-soluble. They can be used in the form of the free acids and / or as alkali metal, alkaline earth metal or ammonium salt in the process according to the invention. They have, for example, a K value of 50 to 250 (determined according to H. Fikentscher in 5% strength by weight aqueous sodium chloride solution at 25 ° C. and pH 7).

The water-soluble anionic polymer is used in the process according to the invention in an amount of, for example, from 0.01 to 2.0% by weight, preferably from 0.05 to 1.0% by weight, in particular from 0.1 to 0.5% by weight. %, based on dry pulp, used. The weight ratio of cationic polymers (a) polymers containing vinylamine units and (b) polymers containing ethyleneimine units to the water-soluble polymeric anionic compounds is for example 3: 1 to 1: 3 and is preferably 1: 1.

For papermaking, the pulps used for producing the pulps are all grades which are customary for this purpose, for example wood pulp, bleached and unbleached pulp and paper pulp from all annual plants. Wood pulp includes, for example, groundwood, thermomechanical pulp (TMP), chemothermomechanical pulp (CTMP), pressure groundwood, semi-pulp, high yield pulp, and refiner mechanical pulp (RMP). As pulp, for example, sulphate, sulphite and soda pulps come into consideration. For example, unbleached pulp, also referred to as unbleached kraft pulp, is used. Suitable annual plants For example, rice, wheat, sugar cane and kenaf are used to make paper stocks.

The inventive method is particularly suitable for the production of dry-proof papers from waste paper (comprising deinked waste paper), which is used either alone or in admixture with other fibers. It is also possible to start with fiber blends of a primary material and recycled coated broke, e.g. B. bleached pine sulfate in admixture with recycled coated broke. The inventive method is for the production of paper, cardboard and cardboard from waste paper and in special cases from deinked waste paper of technical interest, because it significantly increases the strength properties of the recycled fibers. It is of particular importance for improving the strength properties of graphic papers and packaging papers.

The pH of the stock suspension is, for example, in the range of 4.5 to 8, most 6 to 7.5. To adjust the pH, it is possible to use, for example, an acid, such as sulfuric acid or aluminum sulphate.

In the process according to the invention, the cationic polymers, namely (a) polymers comprising vinylamine units and polymers containing ethyleneimine units, are preferably first metered into the pulp. The cationic polymers can be added to the thick material (fiber concentration> 15 g / l, for example in the range from 25 to 40 g / l up to 60 g / l) or preferably to a thin material (fiber concentration <15 g / l, eg in in the range of 5 to 12 g / l). The point of addition is preferably in front of the screens, but it can also be between a shearing stage and a screen or afterwards. The dosage of the cationic polymers (a) and (b) to the paper stock can be carried out, for example, successively, simultaneously or else as a mixture of (a) and (b).

The anionic component is usually added only after the addition of the cationic polymers (a) and (b) to the paper stock, but can also be metered simultaneously to the stock, but separately from the cationic polymers. Furthermore, it is also possible first to add the anionic and subsequently the cationic component or first to meter one of the cationic components (a) or (b) to the paper stock, then to add the anionic polymer and then to add the other cationic component.

In the method according to the invention, the process chemicals commonly used in papermaking can be used in the usual amounts, for. As retention aids, dehydrating agents, other dry strength such as Starch, pigments, fillers, optical brighteners, defoamers, biocides and paper dyes.

The process according to the invention gives dry-proof papers whose dry strength relative to papers produced by known processes has an increased dry strength. In addition, in the method according to the invention, the dewatering rate is improved in comparison with known methods.

The percentages in the examples are by weight unless otherwise specified. The K value of the polymers was after Fikentscher, Cellulose Chemie, Vol. 13, 58-64 and 71-74 (1932 ) at a temperature of 25 ° C in 5 wt .-% aqueous saline solutions at a pH of 7 and a polymer concentration of 0.5%.

• Berstdruck nach DIN ISO 2758 (bis 600 kPa), DIN ISO 2759 (ab 600 kPa)
• SCT nach DIN 54518 (Bestimmung des Streifenstauchwiderstandes)
• CMT nach DIN EN 23035 (Bestimmung des Flachstauchwiderstandes)
• DIN EN ISO 7263 (Bestimmung des Flachstauchwiderstandes an labormäßig gewellter Wellpappe)

For the individual tests, sheets were produced in laboratory tests in a Rapid-Köthen laboratory sheet former. The leaves were stored for 24 hours at 23 ° C and a 50% Luftfeutchtigkeit. Thereafter, the following strength tests were carried out:

• Bursting pressure according to DIN ISO 2758 (up to 600 kPa), DIN ISO 2759 (from 600 kPa)
• SCT according to DIN 54518 (determination of the strip crush resistance)
• CMT according to DIN EN 23035 (determination of the flat crush resistance)
• DIN EN ISO 7263 (Determination of the flat crush resistance on laboratory-corrugated corrugated board)

Examples

• Polymer KA
  Polyethylenimin (Polymin® P, BASF SE, D-67056 Ludwigshafen)
• Polymer KB
  Verwendet wurde ein mit Ethylenimin gepropftes und mit einem Dichlorhydrinether von Polyethylenglykol vernetztes Polyamidoamin, wie in DE-A 2434816 , Beispiel 13 beschrieben.
• Polymer KC
  Verwendet wurde ein mit Ethylenimin gepropftes und vernetztes Polyamidoamin, das zusätzlich noch einer Ultrafiltration unterworfen wurde, vgl. WO 00/67884 , Seite 23, Beispiel B1 b.
• Polymer KD
  Verwendet wurde ein zu 30 % teilhydrolysiertes Polyvinylformamid mit einem K-Wert von 90, wie in DE-A 10 2004 056551 , Seite 9, letzter Abschnitt als PVAm 4 beschrieben.
• Polymer KE
  Verwendet wurde ein Polymer, das durch saure Hydrolyse eines Copolymers aus 30 Mol-% N-Vinylformamid und 70 Mol-% Acrylnitril hergestellt wurde, wie in DE 4328975 als Beispiel P auf den Seiten 8 und 9 beschrieben.
• Polymer KF
  Verwendet wurde ein handelsübliches Hofmann-Abbau Produkt der Firrma SNF mit der Bezeichnung RSL HF 70D. Das Produkt hatte einen Festgehalt von 24,2 %, eine Viskosität von 19 mPas (Brookfield, LVT, Spindel 1, 60 Upm, 20°C) und eine Ladungsdichte von 57,2 meq/100 g Produkt (Polyelektrolyttitration).
• Polymer KG
  Das verwendete Polymer war identisch mit dem in WO 2006/075115 auf Seite 13 in der Tabelle als C8 beta 2 bezeichnete Hofmann-Abbauprodukt. Es wurde hergestellt durch Umsetzung von Polyacrylamid mit Natriumhypochlorit im Molverhältnis 1 : 1, und Natronlauge, wobei das Molverhältnis von Natriumhydroxid zu Natriumhypochlorit 2 : 1 betrug.
• Polymer KH
  Das verwendete Polymer war identisch mit dem in WO 2006/090076 auf Seite 15, Zeile 23 als C2 bezeichneten glyoxylierten Copolymer aus 95 Mol-% Acrylamid und 5 Mol-% Diallyldimethylammoniumchlorid (DADMAC).
• Polymer AA
  Copolymer aus 70 % N-Vinylformamid und 30 % Acrylsäure in Form des Na-Salzes mit einem K-Wert von 85, wie in DE 10 2004 056551 auf Seite 9, letzter Abschnitt als Copolymerisat 4 beschrieben.
• Polymer AB
  Das verwendete Polymer war identisch mit dem in WO 2006/075115 auf Seite 14 in der Tabelle als A1 bezeichneten Copolymer aus 70 % Acrylamid und 30 % Acrylsäure in Form des Na-Salzes.
• Polymer AC
  Das verwendete Polymer war identisch mit dem in WO 2006/075115 auf Seite 14 in der Tabelle als A2 bezeichneten Copolymer aus 70 Mol-% Acrylamid und 30 Mol-% Acrylsäure, vernetzt mit Methylenbisacrylamid (MBA) in Form des Na-Salzes. Das Copolymer hatte eine anionische Ladung von 3,85 meq/g.
• Polymer AD
  Das verwendete Polymer war identisch mit dem in WO 2006/090076 auf Seite 16 in der Tabelle als A2 bezeichneten Copolymer aus 70 Mol-% Acrylamid und 30 Mol-% Acrylsäure, vernetzt mit Methylenbisacrylamid (MBA) in Form des Na-Salzes. Das Copolymer hatte eine anionische Ladung von 3,85 meq/g.

In the examples and in the comparative examples, the following polymers were used:

• Polymer KA
  Polyethyleneimine (Polymin® P, BASF SE, D-67056 Ludwigshafen)
• Polymer KB
  A polyamidoamine grafted with ethyleneimine and crosslinked with a dichlorohydrin ether of polyethylene glycol was used as in DE-A 2434816 Example 13.
• Polymer KC
  A polyamidoamine grafted with ethyleneimine and cross-linked, which was additionally subjected to ultrafiltration, was used, cf. WO 00/67884 , Page 23, example B1 b.
• Polymer KD
  A 30% partially hydrolyzed polyvinylformamide having a K value of 90 was used as in DE-A 10 2004 056551 , Page 9, last section described as PVAm 4.
• Polymer KE
  A polymer prepared by acid hydrolysis of a copolymer of 30 mole% N-vinylformamide and 70 mole% acrylonitrile was used as in DE 4328975 described as Example P on pages 8 and 9.
• Polymer KF
  A commercially available Hofmann degradation product of the Firrma SNF with the designation RSL HF 70D was used. The product had a solids content of 24.2%, a viscosity of 19 mPas (Brookfield, LVT, Spindle 1, 60 rpm, 20 ° C) and a charge density of 57.2 meq / 100 g product (polyelectrolyte titration).
• Polymer KG
  The polymer used was identical to that in WO 2006/075115 on page 13 in the table referred to as C8 beta 2 Hofmann degradation product. It was prepared by reacting polyacrylamide with sodium hypochlorite in a molar ratio of 1: 1, and sodium hydroxide solution, the molar ratio of sodium hydroxide to sodium hypochlorite being 2: 1.
• Polymer KH
  The polymer used was identical to that in WO 2006/090076 on page 15, line 23, designated C2, glyoxylated copolymer of 95 mole% acrylamide and 5 mole% diallyldimethylammonium chloride (DADMAC).
• Polymer AA
  Copolymer of 70% N-vinylformamide and 30% acrylic acid in the form of the Na salt with a K value of 85, as in DE 10 2004 056551 on page 9, last section described as copolymer 4.
• Polymer AB
  The polymer used was identical to that in WO 2006/075115 on page 14 in the table as A1 designated copolymer of 70% acrylamide and 30% acrylic acid in the form of the Na salt.
• Polymer AC
  The polymer used was identical to that in WO 2006/075115 on page 14 in the table referred to as A2 copolymer of 70 mol% of acrylamide and 30 mol% of acrylic acid, crosslinked with methylenebisacrylamide (MBA) in the form of the Na salt. The copolymer had an anionic charge of 3.85 meq / g.
• Polymer AD
  The polymer used was identical to that in WO 2006/090076 on page 16 in the table referred to as A2 copolymer of 70 mol% of acrylamide and 30 mol% of acrylic acid, crosslinked with methylenebisacrylamide (MBA) in the form of the Na salt. The copolymer had an anionic charge of 3.85 meq / g.

Preparation of the paper stock for the examples and comparative examples

A paper made of 100% waste paper (mixture of the grades: 1.02, 1.04,4.01) was pitched with drinking water at a consistency of 4% in a laboratory pulper without specks and ground in a laboratory refiner to a freeness of 40 ° SR. This substance was then diluted with drinking water to a consistency of 0.7%.

drainage test

In the examples and comparative examples, in each case 1 liter of the paper stock described above was used and in each case successively mixed with the water-soluble polymers indicated in the table with stirring and then dewatered using a Schopper-Riegler dewatering tester, wherein the time in seconds for a flow rate (Filtrate) of 600 ml. The concentration of water-soluble cationic and anionic polymers each tested as a dry strength agent for paper was 1% each. The measurement results are given in the table.

sheet formation

In the examples and comparative examples, the polymers listed in the table were added successively to the above-described paper stock with stirring. The polymer concentration of the aqueous solutions of cationic and anionic polymers was 1% each. In the table, the amounts of polymers used in each case are given in percent by weight, based on the solids content of the paper stock. After the last addition of a water-soluble polymer to the stock, as much stock was removed (approximately 500 mL) to produce a sheet having a basis weight of 120 g / m ² (3.2 g otro = oven-dry) on a Rapid-Kothen sheet former. The leaves were, as usual in Rapid-Köthen method, abgegautscht and dried for 8 minutes at 110 ° C in a drying cylinder. The results are given in the table. Table 1 Examples Cationic Polymer 1 Dosage [%] Cationic Polymer 2 Dosage [%] anionic polymer Dosage [%] Drainage time for 600 ml [s] Burst pressure [kPa] SCT [kN] CMT 30 [N] Comparison 1 without without without 87 291 1.37 137 Comparison 2 Polymer KD 0.3 without Polymer AA 0.3 72 375 2.04 180 Comparison 3 Polymer KG 0.3 without Polymer AB 0.3 79 345 1.59 163 Comparison 4 Polymer KG 0.3 without Polymer AC 0.3 76 358 1.61 170 Comparison 5 Polymer KH 0.16 Polymer KG 0.14 Polymer AD 0.3 76 359 1.6 171 example 1 Polymer KA 0.1 Polymer KD 0.2 Polymer AA 0.3 69 376 2.06 180 Example 2 Polymer KB 0.1 Polymer KD 0.2 Polymer AA 0.3 56 380 2.11 181 Example 3 Polymer KC 0.1 Polymer KD 0.2 Polymer AA 0.3 50 385 2.17 186 Example 4 Polymer KC 0.15 Polymer KD 0.15 Polymer AA 0.3 53 379 2.1 182 Example 5 Polymer KC 0.2 Polymer KD 0.1 Polymer AA 0.3 60 377 2.05 181 Example 6 Polymer KC 0.1 Polymer KD 0.2 Polymer AB 0.3 51 386 2.12 182 Example 7 Polymer KC 0.1 Polymer KD 0.2 Polymer AC 0.3 50 388 2.16 185 Example 8 Polymer KC 0.1 Polymer KE 0.2 Polymer AA 0.3 51 386 2.14 183 Example 9 Polymer KF 0.2 Polymer KA 0.1 Polymer AA 0.3 77 358 1.6 170 Example 10 Polymer KF 0.2 Polymer KB 0.1 Polymer AA 0.3 73 361 1.63 174 Example 11 Polymer KF 0.2 Polymer KC 0.1 Polymer AA 0.3 67 368 1.67 177 Example 12 Polymer KF 0.15 Polymer KC 0.15 Polymer AA 0.3 69 362 1.63 173 Example 13 Polymer KF 0.1 Polymer KC 0.2 Polymer AA 0.3 74 359 1.6 173 Example 14 Polymer KF 0.2 Polymer KC 0.1 Polymer AB 0.3 66 363 1.64 174 Example 15 Polymer KF 0.2 Polymer KC 0.1 Polymer AC 0.3 64 365 1.68 177 Comparison 2 according to Example 6 of DE-A-10 2004 056551
Comparison 3 according to Example 17 of WO-A-2006/075115
Comparison 4 according to Example 1 of WO-A-2006/075115
Comparison 5 according to Example 5 of WO-A-2006/090076

Claims (11)

1. A process for the production of paper, board and cardboard having high dry strength by addition of at least one water-soluble cationic polymer and at least one water-soluble polymeric anionic compound to a paper stock, draining of the paper stock with sheet formation and drying of the paper products, wherein

   (a) polymers comprising vinylamine units and

   (b) polymers comprising ethylenimine units

   are metered as water-soluble cationic polymers in any sequence or as a mixture into a paper stock and the weight ratio of (a) polymers comprising vinylamine units to (b) polymers comprising ethylenimine units being from 10 : 1 to 1 : 10 and the reaction products which are obtainable

   - by polymerization of at least one monomer of the formula

   

   in which R¹, R² are H or C₁- to C₆-alkyl,
   and subsequent partial or complete elimination of the groups -CO-R¹ from the units of the monomers (I) incorporated in the form of polymerized units into the polymer with formation of amino groups
   and/or

   - by Hofmann degradation of polymers which have acrylamide and/or methacrylamide units

   are used as (a) polymers comprising vinylamine units.
2. The process according to claim 1, wherein the reaction products which are obtainable by polymerization of

   (i) at least one monomer of the formula

   

   in which R¹, R² are H or C₁- to C₆-alkyl,

   (ii) at least one other monoethylenically unsaturated monomer and, if appropriate,

   (iii) at least one crosslinking monomer having at least two double bonds in the molecule

   and subsequent partial or complete elimination of the groups -CO-R¹ from the units of the monomers (I) incorporated in the form of polymerized units into the polymer with formation of amino groups are used as (a) polymers comprising vinylamine units.
3. The process according to claim 1 or 2, wherein the reaction products which are obtainable by polymerization of

   (i) at least one monomer of the formula

   

   in which R¹, R² are H or C₁- to C₆-alkyl,

   (ii,a) at least in each case one monoethylenically unsaturated sulfonic acid, one monoethylenically unsaturated phosphonic acid, one monoethylenically unsaturated carboxylic acid having 3 to 8 carbon atoms in the molecule and/or the alkali metal, alkaline earth metal or ammonium salts thereof and optionally

   (ii,b) at least one other neutral and/or one cationic monomer and optionally

   (iii) at least one crosslinking monomer having at least two double bonds in the molecule

   and subsequent partial or complete elimination of groups -CO-R¹ from the monomers of the formula (I) which are incorporated in the form of polymerized units into the polymer with formation of amino groups, the content of amino groups in the copolymer being at least 5 mol% above the content of acid groups of the monomers (ii,a) which are incorporated in the form of polymerized units, are used as (a) polymers comprising vinylamine units.
4. The process according to any of claims 1 to 3, wherein the reaction products which are obtainable by polymerization of N-vinylformamide and subsequent elimination of formyl groups from the vinylformamide units incorporated in the form of polymerized units into the polymer with formation of amino groups are used as (a) polymers comprising vinylamine units.
5. The process according to any of claims 1 to 4, wherein the reaction products which are obtainable by copolymerization of

   (i) vinylformamide and

   (ii) acrylonitrile

   and subsequent elimination of formyl groups from the vinylformamide units incorporated in the form of polymerized units into the copolymer with formation of amino groups are used as (a) polymers comprising vinylamine units.
6. The process according to claim 3, wherein the reaction products which are obtainable by copolymerization of

   (i) N-vinylformamide,

   (ii,a) acrylic acid, methacrylic acid and/or the alkali metal, alkaline earth metal or ammonium salts thereof and optionally

   (ii,b) acrylonitrile and/or methacrylonitrile

   and subsequent partial or complete elimination of formyl groups from the N-vinylformamide incorporated in the form of polymerized units into the polymer with formation of amino groups, the content of amino groups in the copolymer being at least 5 mol% above the content of acid groups of the monomers (ii,a) which are incorporated in the form of polymerized units, are used as (a) reaction products comprising vinylamine units.
7. The process according to claim 1, wherein the reaction products which are obtainable by Hofmann degradation of homo- or copolymers of acrylamide or of methacrylamide in an aqueous medium in the presence of sodium hydroxide solution and sodium hypochlorite and subsequent decarboxylation of the carbamate groups of the reaction product in the presence of an acid are used as (a) polymers comprising vinylamine units.
8. The process according to any of claims 1 to 7, wherein at least one water-soluble cationic polymer from the group consisting of the

   - homopolymers of ethylenimine,

   - polyethylenimines reacted with at least bifunctional crosslinking agents,

   - polyamidoamines which have been grafted with ethylenimine and reacted with at least bifunctional crosslinking agents,

   - reaction products of polyethylenimines with monobasic carboxylic acids to give amidated polyethylenimines,

   - Michael adducts of polyethylenimines with ethylenically unsaturated acids, salts, esters, amides or nitriles of monoethylenically unsaturated carboxylic acids,

   - phosphonomethylated polyethylenimines,

   - carboxylated polyethylenimines and

   - alkoxylated polyethylenimines

   is used as (b) polymers comprising ethylenimine units.
9. The process according to claim 8, wherein homopolymers of ethylenimine and/or polyamidoamines grafted with ethylenimine and subsequently reacted with at least bifunctional crosslinking agents are used as (b) polymers comprising ethylenimine units.
10. The process according to any of claims 1 to 9, wherein a water-soluble polymer having acid groups and having a charge density of >0.5 meq/g or salts thereof is or are used as the polymeric anionic compound.
11. The process according to claim 10, wherein at least one water-soluble compound from the group consisting of polyacrylic acid, polymethacrylic acid, copolymers of acrylamide and acrylic acid, copolymers of N-vinylformamide and acrylic acid, hydrolyzed copolymers of N-vinylformamide and acrylic acid and in each case the salts thereof is used as the polymeric anionic compound.