EP1727937B1 - Aqueous dispersions of reactive gluing agents, method for the production and the use thereof - Google Patents

Description

The invention relates to aqueous dispersions of reactive sizing agents which comprise polymers containing protective vinylamine units as a protective colloid, the protective colloid containing less than 0.0001% by weight, based on the protective colloid, of diketene. Furthermore, the invention relates to a process for preparing the aqueous dispersions, their use for sizing of paper, cardboard and cardboard, and a method for sizing paper, cardboard and cardboard.

Aqueous alkyldiketene dispersions stabilized with cationic starch or with anionic emulsifiers are commercially available engine sizing agents for paper. The full sizing effect of papers sized with alkyldiketene dispersions develops only when the sized papers are stored. Thus, such papers can not be further processed immediately following papermaking, e.g. finished with coating colors, or printed. Instead, they must be stored for at least 24 hours until sufficient sizing effect is achieved. However, it is known from the literature that cationic polymers increase the speed of sizing.

Although the usual sizing dispersions containing cationic polymers increase the speed of sizing, they are often not storage stable for extended periods of time.

DE-A-3 316 179 describes AKD dispersions containing ethyleneimine units-containing polymers and a water-soluble dicyandiamide-formaldehyde condensation product. Although the latter increases the rate of sizing formation (so-called promoter effect), it does not contribute to the stabilization of the dispersion.

From the US-A-3,223,544 are as well as from the EP-A-0 353 212 Alkyldiketen (AKD) dispersions with cationic starch as a protective colloid and an anionic dispersant known as a stabilizer.

From the WO-A-96/26318 AKD dispersions are known which contain as protective colloids either copolymers of N-vinylpyrrolidone and N-vinylimidazole or condensation products based on polyethyleneimines. The preparation of these AKD dispersions is very complicated by the copolymerization or condensation of the protective colloids.

From the older German patent application with the file number 10 237 911.4 the use of polymers containing vinylamine units as promoters for engine sizing in starch-containing AKD dispersions is known.

The older German patent application with the file number 10 237 912.2 discloses a method for sizing paper in which a reactive sizing agent, a retention agent and a cationic polymer selected from polymers containing vinylamine units, polymers containing vinylguanadine units, polyethyleneimines, ethyleneimine grafted polyamidoamines and polydiallyldimethylammonium chlorides are added to the aqueous slurry of cellulosic fibers. In this case, the cationic polymers are added separately from the reactive sizes, or the components are metered together, but without a dispersion of the components is prepared beforehand.

From the WO-A-98/41565 AKD dispersions are known which contain as protective colloid reaction products of polymers containing amino groups from the group of polymers containing vinylamine units, polyamidoamines and polymaidoamines grafted with polyethyleneimine with diketenes in a weight ratio of polymer to diketene of 10,000: 1 to 1: 3. However, the preparation of the protective colloid is very expensive.

It is an object of the present invention to provide aqueous dispersions of reactive sizing agents which are improved over the prior art and which are easy to prepare and which have both an increased sizing speed and a sufficient storage stability.

The object is achieved according to the invention with aqueous dispersions of reactive sizes which contain cationic vinylamine units as protective colloid polymers, wherein the protective colloid contains less than 0.0001 wt .-%, based on the protective colloid, of diketenes. Diketenes in this sense are understood to mean the C ₁₂ -C ₂₂ -alkyl ketene dimers described in more detail below.

Preference is given to aqueous dispersions whose protective colloids are essentially free of diketenes, and those whose protective colloids are completely free of diketenes are particularly preferred.

Also preferred are those aqueous dispersions which generally contain less than 0.0001% by weight of reactive sizing agent. Reactive sizing agents, in addition to the C ₁₂ - to C ₂₂ -Alkketendimere also described in more detail below C ₅ - to C ₂₂ alkyl or C ₅ - to C ₂₂ -Alkenylbernsteinsäureanhydride, C _{12 to} C ₃₆ alkyl isocyanates, organic isocyanates and / or their mixtures understood.

Preference is given to aqueous dispersions whose protective colloids are substantially free of reactive sizes, and those whose protective colloids are completely free of reactive sizes are particularly preferred.

Furthermore, preference is given to those aqueous dispersions which contain less than 1% by weight, based on the aqueous dispersion, of cationic starch.

Particularly preferred are those aqueous dispersions which are substantially free of cationic starch, and particularly preferred are those which are entirely free of cationic starch.

According to the invention, at least one polymer comprising vinylamine units is used as protective colloid for the reactive sizing agent in the aqueous dispersions according to the invention. The amount of cationic polymers is for example 10 to 100 wt .-%, preferably 15 to 75 wt .-%, particularly preferably 20 to 50 wt .-%, based on the reactive size.

Vinylamine containing polymers are known, cf. US-A-4,421,602 . US-A-5,334,287 . EP-A-0 216 387 . US-A-5,981,689 . WO-A-00/63295 and US-A-6,121,409 , They are prepared by hydrolysis of open-chain polymers containing N-vinylcarboxamide units. These polymers are obtainable, for example, 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.

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, 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, amides and nitriles of ethylenically unsaturated C ₃ - to C ₆ -carboxylic acids, for example methyl acrylate, methyl methacrylate, ethyl acrylate and ethyl methacrylate, acrylamide and methacrylamide and also acrylonitrile and methacrylonitrile.

Further suitable carboxylic acid esters are derived from glycols or polyalkylene glycols, in each case only one OH group being 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 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, e.g. Dimethylaminoethylacrylamide, dimethylaminoethylmethacrylamide, diethylaminoethylacrylamide, diethylaminoethylmethacrylamide, dimethylaminopropylacrylamide, diethylaminopropylacrylamide, dimethylaminopropylmethacrylamide and diethylaminopropylmethacrylamide.

Further suitable comonomers are N-vinylpyrrolidone, N-vinylcaprolactam, acrylonitrile, methacrylonitrile, N-vinylimidazole and substituted N-vinylimidazoles, 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-methylimidazoline and N- vinyl-2-ethylimidazoline. N-vinylimidazoles and N-vinylimidazolines are also used, except in the form of the free bases, in neutralized or quaternized form with mineral acids or organic acids, the quaternization preferably being carried out with dimethyl sulfate, diethyl sulfate, methyl chloride or benzyl chloride. Also suitable are diallyldialkylammonium halides, e.g. Diallyl dimethyl ammonium chloride.

• 95 bis 5 mol-%, vorzugsweise 90 bis 10 mol% mindestens eines N-Vinylcarbonsäureamids und
• 5 bis 95 mol-%, vorzugsweise 10 bis 90 mol% andere, damit copolymerisierbare monoethylenisch ungesättigte Monomere

in einpolymerisierter Form. Die Comonomeren sind vorzugsweise frei von Säuregruppen.The copolymers contain, for example

• 95 to 5 mol%, preferably 90 to 10 mol% of at least one N-vinylcarboxamide and
• 5 to 95 mol%, preferably 10 to 90 mol% of other monoethylenically unsaturated monomers copolymerizable therewith

in copolymerized form. The comonomers are preferably free of acid groups.

• N-Vinylformamid mit
• Vinylformiat, Vinylacetat, Vinylpropionat, Acrylnitril, N-Vinylcaprolactam, N-Vinylharnstoff, N-Vinylpyrrolidon oder C₁- bis C₆-Alkylvinylethern

und anschließende Hydrolyse der Homo- oder der Copolymerisate unter Bildung von Vinylamineinheiten aus den einpolymerisierten N-Vinylformamideinheiten erhältlich sind, wobei der Hydrolysegrad z.B. 1 bis 100 mol%, vorzugsweise 25 bis 100 mol%, besonders bevorzugt 50 bis 100 mol-% und insbesondere bevorzugt 70 bis 100 mol% beträgt. Die Hydrolyse der oben beschriebenen Polymerisate erfolgt nach bekannten Verfahren durch Einwirkung von Säuren, Basen oder Enzymen. Bei Verwendung von Säuren als Hydrolysemittel liegen die Vinylamineinheiten der Polymerisate als Ammoniumsalz vor, während bei der Hydrolyse mit Basen die freie Aminogruppen entstehen. Die Vinylamineinheiten enthaltenden Polymere können in Form der freien Basen, der Ammoniumsalze oder auch in quaternierter Form als Promotor eingesetzt werden.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, N-vinylcaprolactam, N-vinyl urea, N-vinylpyrrolidone or C ₁ - to C ₆ alkyl vinyl ethers

and subsequent hydrolysis of the homo- or copolymers to form vinylamine units from the copolymerized N-vinylformamide units are available, the degree of hydrolysis, for example 1 to 100 mol%, preferably 25 to 100 mol%, particularly preferably 50 to 100 mol% and particularly preferably 70 to 100 mol%. The hydrolysis of the above-described polymers is carried out by known methods by the action of acids, bases or enzymes. 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. The vinylamine containing polymers can be used in the form of the free bases, the ammonium salts or in quaternized form as a promoter.

In most cases, the degree of hydrolysis of the homo- and copolymers used is 90 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 carrying out the hydrolysis of the copolymers in the presence of sodium hydroxide solution. Polymerized acrylonitrile is also chemically altered upon hydrolysis. This produces, for example, amide 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 amide group, for 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 (determined by light scattering). This molar mass range corresponds, for example, to K values of 30 to 150, preferably 60 to 90 (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 cationic polymers which have K values of from 85 to 90.

The polymers containing vinylamine units are preferably used in salt-free form. Salt-free aqueous solutions of polymers containing 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 as cationic polymers. 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, phosphonomethylation or Michael addition of the amino groups of the polymer. Of particular interest in this case 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 - C ₆ -Cycloalkyl, phenyl, benzyl, alkyl-substituted phenyl or naphthyl mean), cf. US-A-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, 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.

Preferred polymers containing vinylamine units are vinylamine homopolymers having a degree of hydrolysis of from 1 to 100 mol%, preferably from 25 to 100 mol%, and from 1 to 100 mol%, preferably from 25 to 100 mol%, of hydrolyzed copolymers of vinylformamide and vinyl acetate, vinyl alcohol, vinyl pyrrolidone or acrylamide each having K values of 30 to 150, especially 60 to 90.

The polymers containing vinylamine units are used in the aqueous dispersions according to the invention as protective colloids for reactive sizes, in order to obtain aqueous sizing dispersions which have both an increased rate of sizing formation and a sufficient storage stability.

Suitable reactive sizes for the dispersions according to the invention are, for example, C ₁₂ -C ₂₂ -alkyl ketene dimers, C ₅ -C ₂₂ -alkyl or C ₅ -C ₂₂ -alkenylsuccinic anhydrides, C ₁₂ to C ₃₆ alkyl isocyanates and / or organic isocyanates such as dodecyl isocyanate, octadecyl isocyanate, tetradecyl isocyanate, hexadecyl isocyanate, eicosyl isocyanate and decyl isocyanate. Preferably used engine sizing agents are alkyl ketene dimers and long-chain alkyl or alkenylsuccinic anhydrides.

Examples of alkylketene dimers are tetradecyldiketene, stearydikethene, lauryldiketen, palmityldiketen, oleyldiketen, Behenyldiketen or mixtures thereof. Also suitable are alkyldiketenes having different alkyl groups, such as stearyl palmitate diketene, behenylstearyl diketene, behenylenyldiketene or palmitylbehenyldiketene. Stearyldiketen, Palmityldiketen, Behenyldiketen or mixtures of Behenyldiketen and Stearyldiketen are preferably used. Examples of substituted succinic anhydrides suitable as reactive sizes are decenylsuccinic anhydride, n-octadecenylsuccinic anhydride, dodecenylsuccinic anhydride and n-hexadecenylsuccinic anhydride.

The aqueous dispersions according to the invention usually have a content of reactive sizes of from 1 to 50% by weight, based on the total weight of the dispersion. For example, the dispersions have a content of 1 to 50 wt .-%, preferably 5 to 35 wt .-%, based on the total weight of the dispersion, of C _{12 to} C ₂₂ alkyldiketenes. When using C ₅ - to C ₂₂ -alkyl or C ₅ - to C ₂₂ -alkenyl succinic anhydrides whose content is, for example, 1 to 25 wt .-%, preferably 2 to 10 wt .-%, based on the total weight of the dispersion.

1. (a) Naphthalinsulfonsäure und Formaldehyd
2. (b) Phenol, Phenolsulfonsäure und Formaldehyd,
3. (c) Naphthalinsulfonsäure, Formaldehyd und Harnstoff sowie
4. (d) Phenol, Phenolsulfonsäure, Formaldehyd und Harnstoff.

The preferred sizing agent alkyldiketenes and long-chain alkenyl or alkyl succinic anhydrides and methods for preparing anionically adjusted aqueous dispersions of such reactive sizing agents are known from WO-A-00/23651 known, cf. Pages 2-12. For sizing dispersions, the reactive sizing agents are usually heated to a temperature above their melting point and emulsified in molten form in water under the action of shear forces. The liquid alkenyl succinic anhydride can be emulsified already at room temperature. For this you use eg homogenizers. In order to stabilize the dispersed sizing agents in the aqueous phase, at least one anionic dispersant is used from the group of condensation products

1. (a) naphthalenesulfonic acid and formaldehyde
2. (b) phenol, phenolsulfonic acid and formaldehyde,
3. (c) naphthalenesulfonic acid, formaldehyde and urea, as well
4. (d) phenol, phenolsulfonic acid, formaldehyde and urea.

The anionic dispersants may be in the form of the free acids, the alkali metal, alkaline earth metal and / or ammonium salts. The ammonium salts can be derived from both ammonia and primary, secondary and tertiary amines, e.g. The ammonium salts of dimethylamine, trimethylamine, hexylamine, cyclohexylamine, dicyclohexylamine, ethanolamine, diethanolamine and triethanolamine are suitable. The condensation products described above are known and commercially available. They are prepared by condensing said components, it being possible to use the corresponding alkali metal, alkaline earth metal or ammonium salts instead of the free acids. Suitable catalysts for the condensation are, for example, acids such as sulfuric acid, p-toluenesulfonic acid and phosphoric acid. Naphthalenesulfonic acid or its alkali metal salts are condensed with formaldehyde preferably in a molar ratio of 1: 0.1 to 1: 2 and usually in a molar ratio of 1: 0.5 to 1: 1. The molar ratio for the production of condensates of phenol, phenolsulfonic acid and formaldehyde is also in the range given above, using any mixtures of phenol and phenolsulfonic acid instead of naphthalenesulfonic acid in the condensation with formaldehyde. Instead of phenolsulfonic acid, it is also possible to use the alkali metal and ammonium salts of phenolsulfonic acid. The condensation of the abovementioned starting materials may optionally be carried out additionally in the presence of urea. For example, based on naphthalenesulfonic acid or on the mixture of phenol and phenolsulfonic acid, 0.1 to 5 mol of urea are used per mole of naphthalenesulfonic acid or per mole of the mixture of phenol and phenolsulfonic acid.

The condensation products have, for example, molar masses in the range from 800 to 100,000, preferably 1,000 to 30,000 and in particular from 4,000 to 25,000. Preferably used as anionic dispersants are salts which are obtained, for example, by neutralizing the condensation products with lithium hydroxide, sodium hydroxide, Potassium hydroxide or ammonia receives. The pH of the salts is, for example, in the range of 7 to 10.

Further suitable anionic dispersants are lignosulfonic acid and its alkali metal, alkaline earth metal or ammonium salts.

1. (i) hydrophoben monoethylenisch ungesättigten Monomeren und
2. (ii) hydrophilen Monomeren mit einer anionischen Gruppe wie monoethylenisch ungesättigten Carbonsäuren, monoethylenisch ungesättigten Sulfonsäuren, monoethylenisch ungesättigten Phosphonsäuren oder deren Mischungen.

Also suitable as anionic dispersants are amphiphilic copolymers

1. (i) hydrophobic monoethylenically unsaturated monomers and
2. (Ii) hydrophilic monomers having an anionic group such as monoethylenically unsaturated carboxylic acids, monoethylenically unsaturated sulfonic acids, monoethylenically unsaturated phosphonic acids or mixtures thereof.

1. (a) sind beispielsweise Olefine mit 2 bis 150 C-Atomen, Styrol, α-Methylstyrol, Ethylstyrol, 4-Methylstyrol, Acrylnitril, Methacrylnitril, Ester aus monoethylenisch ungesättigten C₃- bis C₅-Carbonsäuren und einwertigen Alkoholen, Amide der Acrylsäure oder Methacrylsäure mit C₁- bis C₂₄-Alkylaminen, Vinylester von gesättigten Monocarbonsäuren mit 2 bis 24 C-Atomen, Diester der Maleinsäure oder Fumarsäure mit einwertigen C₁- bis C₂₄-Alkoholen, Vinylether von Alkoholen mit 3 bis 24 C-Atomen oder Mischungen der genannten Verbindungen.

Suitable hydrophobic monoethylenically unsaturated monomers

1. (a) are, for example, olefins having 2 to 150 carbon atoms, styrene, α-methylstyrene, ethylstyrene, 4-methylstyrene, acrylonitrile, methacrylonitrile, esters of monoethylenically unsaturated C ₃ - to C ₅ -carboxylic acids and monohydric alcohols, amides of acrylic acid or Methacrylic acid with C ₁ - to C ₂₄ -alkylamines, vinyl esters of saturated monocarboxylic acids having 2 to 24 carbon atoms, diesters of maleic acid or fumaric acid with monohydric C ₁ - to C ₂₄ -alcohols, vinyl ethers of alcohols having 3 to 24 carbon atoms or Mixtures of the compounds mentioned.

The amphiphilic copolymers contain as hydrophilic monomers (b), for example, C ₃ - to C ₁₀ - monoethylenically unsaturated carboxylic acids or their anhydrides, 2-acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, styrenesulfonic acid, vinylphosphonic acid, salts of said monomers or mixtures thereof as hydrophilic monomers polymerized in an anionic group.

1. (a) α-Olefinen mit 4 bis 12 C-Atomen, Styrol oder deren Mischungen als hydrophobe Monomere und
2. (b) Maleinsäure, Acrylsäure, Methacrylsäure, Halbester aus Maleinsäure und Alkoholen mit 1 bis 25 C-Atomen oder Alkoxylierungsprodukten solcher Alkohole, Halbamide der Maleinsäure, Salze der genannten Monomeren oder Mischungen dieser Verbindungen als hydrophile Monomere mit einer anionischen Gruppe

einpolymerisiert enthalten und eine Molmasse Mw von 1 500 bis 100 000 halben.Particularly preferred are aqueous sizing agent dispersions containing as anionic dispersant amphiphilic copolymers

1. (a) α-olefins having 4 to 12 C atoms, styrene or mixtures thereof as hydrophobic monomers and
2. (B) maleic acid, acrylic acid, methacrylic acid, half esters of maleic acid and alcohols having 1 to 25 carbon atoms or alkoxylation of such alcohols, hemiamides of maleic acid, salts of said monomers or mixtures of these compounds as hydrophilic monomers having an anionic group

polymerized and have a molecular weight Mw from 1,500 to 100,000 half.

Preferred anionic dispersants are copolymers of maleic anhydride with C ₄ to C ₁₂ olefins, more preferably C ₈ olefins, such as octene-1 and diisobutene. Most preferred is diisobutene. The molar ratio between maleic anhydride and olefin is, for example, in the range from 0.9: 1 to 3: 1, preferably from 0.95: 1 to 1.5: 1. These copolymers are preferably used in hydrolyzed form as aqueous solutions or dispersions, where the anhydride group is present open and the carboxyl groups are preferably partially or completely neutralized. For neutralization, the following bases are used: alkali metal bases such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, alkaline earth salts such as calcium hydroxide, calcium carbonate, magnesium hydroxide, ammonia, primary, secondary or tertiary amines such as triethylamine, triethanolamine, diethanolamine, ethanolamine, morpholine etc.

If the amphiphilic free acid-based copolymers are not sufficiently water-soluble, they are used in the form of water-soluble salts, e.g. the corresponding alkali metal, alkaline earth metal and ammonium salts are used. The molecular weight Mw of the amphiphilic copolymers is, for example, 800 to 250,000, usually 1,000 to 100,000 and is preferably in the range from 3,000 to 20,000, in particular from 1,500 to 10,000. The acid numbers of the amphiphilic copolymers are, for example, 50 to 500 , preferably 150 to 300 mg KOH / g polymer.

The amphiphilic copolymers are e.g. in amounts of 0.05 to 20, preferably 0.5 to 10 wt .-%, based on the reactive sizing agent, used as an anionic dispersant for the preparation of sizing dispersions. Preferably, the amphiphilic copolymers are used in amounts of 0.1 to 2, in particular 0.6 to 1 wt .-%, based on the sizing agent to be dispersed.

The content of anionic dispersants in the aqueous dispersion is for example 0.01 to 5 wt .-%, preferably 0.01 to 2.5 wt .-% and most preferably 0.01 to 1 wt .-%.

The aqueous dispersions according to the invention may contain further components, such as, for example, non-cellulose-reactive hydrophobic substances which contribute to improving the stability and, for example, in US Pat EP-A-437 764 and EP-A-658,228 are described. Suitable non-cellulosic-reactive substances are, for example, fatty acids, amides and esters as well as waxes. Examples thereof, but not exhaustive, are stearyl behenyl ester, myristate stearylate, isododecyl stearate, dioleyl carbonate, oleic acid stearylate, oleyl N, N-distearyl urethane, paraffin, di-oleic acid glycerol ester, glycerol tris-oleic acid ester and glyceryl tris-stearate.

1. (a) Styrol, Acrylnitril und/oder Methacrylnitril,
2. (b) Acrylsäure- und/oder Methacrylsäureester von C₁- bis C₁₈-Alkoholen und/oder Vinylester von gesättigtem C₂- bis C₄-Carbonsäuren und gegebenenfalls
3. (c) anderen monoethylenisch ungesättigten copolymerisierbaren Monomeren

in wässriger Lösung in Gegenwart von 1 Gew.-Teil eines Lösungscopolymerisats wie in der WO-A-96/31650 und der darin zitierten Literatur beschrieben polymerisiert.In addition, finely divided, aqueous polymer dispersions which are a sizing agent for paper may additionally be present in the dispersions according to the invention. Such polymer dispersions are for example from EP-B-0 051 144 , of the EP-B-0 257 412 , of the EP-B-0 276 770 , of the EP-B-0 058 313 and the EP-B-0 150 003 known. Such polymer dispersions acting as a paper sizing agent are obtainable for example by reacting 1 to 32 parts by weight of a mixture of

1. (a) styrene, acrylonitrile and / or methacrylonitrile,
2. (B) acrylic acid and / or methacrylic acid esters of C ₁ - to C ₁₈ -alcohols and / or vinyl esters of saturated C ₂ - to C ₄ -carboxylic acids and optionally
3. (c) other monoethylenically unsaturated copolymerizable monomers

in aqueous solution in the presence of 1 part by weight of a Lösungscopolymerisats as in WO-A-96/31650 and the literature cited therein polymerized.

Suitable monomers of group (a) are styrene, acrylonitrile, methacrylonitrile or mixtures of styrene and acrylonitrile or of styrene and methacrylonitrile. As monomers of group (b) are used acrylic acid and / or methacrylic acid esters of C ₁ - to C ₁₈ -alcohols and / or vinyl esters of saturated C ₂ - to C ₄ -carboxylic acids. Preferably used as monomer of group (b) butyl acrylate and butyl methacrylate, for example, acrylic acid isobutyl acrylate, acrylic acid n-butyl acrylate and methacrylic acid isobutyl acrylate. Examples of monomers of group (c) are butadiene, isoprene, C ₃ to C ₅ monoethylenically unsaturated carboxylic acids, acrylamidomethylpropanesulfonic acid, sodium vinylsulfonate, vinylimidazole, N-vinylformamide, acrylamide, methacrylamide, N-vinylimidazoline and cationic polymers such as dimethylaminopropylmethacrylamide or dimethylaminoethylacrylate-methochloride. From 1 to 32 parts by weight of a monomer mixture of components (a) to (c) are used per 1 part by weight of the copolymer. The monomers of components (a) and (b) can be copolymerized in any ratio, for example in a molar ratio of 0.1: 1 to 1: 0.1.

If necessary, the monomers of group (c) are used to modify the properties of the copolymers.

Details on the preparation of these additional polymer dispersions can be found in the WO-A-96/31650 and the literature quoted there.

If these polymer dispersions are used in the aqueous dispersions of reactive sizes according to the invention, preference is given to those which contain cationic polymers such as dimethylaminopropylmethacrylamide and / or dimethylaminoethyl acrylate in combination with styrene, acrylonitrile, butadiene and / or acrylic acid esters.

When such polymer dispersions are used, their content is generally 25 to 300% by weight, preferably 50 to 250% by weight and more preferably 75 to 200% by weight, based on the reactive sizing agent.

The invention further provides a process for the preparation of the aqueous dispersions of reactive sizes according to the invention.

In this case, for example, an aqueous solution of polymers comprising vinylamine units, at least one anionic dispersant and optionally other components such as non-cellulose-reactive hydrophobic substances and the polymer dispersions mentioned and therein at temperatures of for example 20 to 100, preferably 40 to 90 ° C, the reactive sizing agent disperse. The sizing agent is preferably added in the form of a melt and dispersed with vigorous stirring or shearing. In another variant, first the sizing agent with the anionic dispersant is converted into an emulsion. Then, an aqueous solution of a polymer containing vinylamine units is added, and the emulsifying step is repeated. The preparation of the dispersions is carried out in apparatuses known to the person skilled in the art, for example high-pressure homogenizers, colloid mills and ultrasonic dispersants. The resulting dispersion is cooled in each case. In this way it is possible, for example, to prepare aqueous sizing agent dispersions which contain 0.1 to 65% by weight, preferably 1 to 50% by weight and more preferably 5 to 35% by weight, of an alkyldiketene or 0.1 to 65% by weight. -%, preferably 1 to 50 wt .-%, more preferably 1 to 25 wt .-% and in particular 2 to 10 wt .-% of an alkenylsuccinic anhydride as sizing agent dispersed.

Such highly concentrated sizing dispersions have a relatively low viscosity, eg in the range of 20 to 1,000 mPas (measured with a Brookfield viscometer and a temperature of 20 ° C). In the preparation of the aqueous dispersions, the pH is, for example, from 2 to 8, and is preferably in the range of from 3 to 4. As a rule, aqueous sizing agent dispersions having a mean particle size of the sizing agents in the range from 100 to 3,000 nm are obtained However, depending on the choice of the protective colloid and the anionic dispersant, the average particle sizes may also be less than 100 nm, for example between 50 and 100 nm, or greater than 3000 nm, for example up to 4 μm .

The dispersions according to the invention are used as engine size agents in the production of paper, board and cardboard. The production of paper, paperboard and cardboard is usually done by dewatering a slurry of cellulosic fibers. Suitable cellulosic fibers are all conventional types, for example cellulosic fibers from wood pulp and all fibers obtained from 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 well as waste paper. Also suitable are pulps that can be used in bleached or unbleached form. Examples include sulphate, sulphite and soda pulps. Preferably, unbleached pulps, also referred to as unbleached kraft pulp, are used. The fibers mentioned can be used alone or in a mixture.

The pH of the cellulose fiber slurry is, for example, 4 to 8, preferably 6 to 8. The dewatering of the stock can be carried out batchwise or continuously on a paper machine.

After dewatering the paper stock and drying the paper product, paper products sized as paper, paperboard or cardboard with a weight per unit area of, for example, 20 to 400 g / m ² , preferably 40 to 220 g / m ^{2, are obtained} .

The dewatering of the paper stock is preferably carried out additionally in the presence of a retention agent. In addition to anionic retention aids or nonionic retention aids such as polyacrylamides, cationic polymers are preferably used as retention aids and as drainage aids. This achieves a significant improvement in the runnability of the paper machines.

As cationic retention agents one can use all commercially available products. These are, for example, cationic polyacrylamides, polydiallyldimethylammonium chlorides, high molecular weight polyvinylamines, high molecular weight polyvinylamines having K values of more than 150, polyethyleneimines, polyamines having a molecular weight of more than 50,000, modified polyamines grafted with ethyleneimine and optionally crosslinked, polyetheramides Polyvinylimidazoles, polyvinylpyrrolidines, polyvinylimidazolines, polyvinyltetrahydropyrins, poly (dialkylaminoalkylvinylethers), poly (dialkylaminoalkyl (meth) acrylates) in protonated or quaternized form and polyamidoamines of a dicarboxylic acid such as adipic acid and polyalkylenepolyamines such as diethylenetriamine grafted with ethyleneimine and with polyethylene glycol dichlorohydrin ethers according to the Teaching the DE-B-24 34 816 or polyamidoamines which are reacted with epichlorohydrin to give water-soluble condensation products and copolymers of acrylamide or methacrylamide and dialkylaminoethyl acrylates or methacrylates, for example copolymers of acrylamide and dimethylaminoethyl acrylate in the form of the salt with hydrochloric acid or in methyl chloride quaternized form. Further suitable retention aids are so-called microparticle systems of cationic polymers such as cationic starch and finely divided silica or of cationic polymers such as cationic polyacrylamide and bentonite.

The cationic polymers used as retention aids have, for example, Fikentscher K values of greater than 150 (determined in 5% aqueous common salt solution at a polymer concentration of 0.5% by weight, a temperature of 25 ° C. and a pH Value of 7). They are preferably used in amounts of from 0.01 to 0.3% by weight, based on dry cellulose fibers.

If necessary, other adjuvants known to those skilled in the literature may be added to the stock prior to sheet formation. These are, for example, fixing agents, solidifiers and defoamers.

Furthermore, the present invention relates to the use of the inventive aqueous dispersions described above as engine size for the production of paper, cardboard and cardboard.

The following examples are intended to illustrate the invention without, however, limiting it.

Unless otherwise indicated in the context, the percentages in the examples are percent by weight. The K values were after H. Fikentscher, Cellulosic Chemistry, Vol. 13, 58-64 and 71-74 (1932 ) in 5% aqueous saline solution at a temperature of 25 ° C and a pH of 7 at a polymer concentration of 0.5% by weight. The molecular weights Mw of the polymers were measured by light scattering. The mean particle diameter of the dispersed particles of the polymer dispersions was determined both by Fraunhofer diffraction with a Coulter device of the type LS 230 with a small volume module and by electron microscopy. The viscosities were determined with a Brookfield viscometer at a temperature of 22 ° C.

Examples Ink flotation time

The ink buoyancy time (measured in minutes) is the time required for a test ink according to DIN 53 126 to 50% penetration through a test sheet.

Cobb value

The determination was carried out according to DIN 53132 by storage of the paper sheets for a period of 60 seconds in water. The water absorption is given in g / m ² .

edge penetration

The paper sheet is coated on both sides with an adhesive tape streak-free. Then strips are cut with the dimensions 25 x 75 mm. These test strips are immersed in a 30% hydrogen peroxide bath at 70 ° C or in a 3% lactic acid bath at 25 ° C. The edge penetration is determined by differential weighing of the dry test strips and the dip in the bath test strip.

Polyvinylamine 1

Cationic polymer obtained by hydrolysis of poly-N-vinylformamide having a K value of 90 with a degree of hydrolysis of 95 mol% (polymer containing 95 mol% of vinylamine units and 5 mol% of vinylformamide units).

Polyvinylamine 2

Cationic polymer obtained by hydrolysis of poly-N-vinylformamide having a K value of 75 with a degree of hydrolysis of 65 mol% (polymer containing 65 mol% of vinylamine units and 35 mol% of vinylformamide units).

Polyvinylamine 3

Cationic polymer obtained by hydrolysis of poly-N-vinylformamide having a K value of 110 with a degree of hydrolysis of 95 mol% (polymer containing 95 mol% of vinylamine units and 5 mol% of vinylformamide units).

Dispersion 1

76 g of an aqueous 8 wt .-% solution of polyvinylamine 1, adjusted to a pH of 3.7, were heated to a temperature of 75 ° C. With a high-speed stirrer, 3 g of a 5% strength by weight sodium salt of the condensation product of naphthalenesulfonic acid with formaldehyde in a molar ratio of 1: 0.8 and a molecular weight Mw of 7,000 were stirred in as anionic dispersant. Subsequently, 12 g of stearyldiketen were also added with a high-speed stirrer. The resulting emulsion was homogenized by means of a high-pressure homogenizer at 170 bar and 75 ° C and then rapidly cooled with ice. The dispersion had a viscosity of 120 mPas at 22 ° C. and an average particle size of 1.6 μm .

Dispersion 2

89 g of an aqueous 3 wt .-% solution of polyvinylamine 2, adjusted to a pH of 3.4, were heated to 75 ° C. With a high-speed stirrer, 1.78 g of a 5% by weight lignosulfonate sodium salt were stirred in as an anionic dispersant. Subsequently, 7 g of stearyl diketene were added with a high-speed stirrer. The resulting emulsion was homogenized by means of a high-pressure homogenizer at 190 bar and 75 ° C and then rapidly cooled with ice. The dispersion had a viscosity of 20 mPas at 22 ° C. and an average particle size of 0.98 μm .

Dispersion 3

68 g of an aqueous 8% strength by weight solution of polyvinylamine 3, adjusted to a pH of 3.6, were heated to a temperature of 75 ° C. 2 g of a 5% strength by weight lignosulfonate sodium salt were stirred in as an anionic dispersant with a high-speed stirrer. Subsequently, 15 g Stearyldiketen were also added with a high-speed stirrer. The resulting emulsion was homogenized by means of a high-pressure homogenizer at 170 bar and 75 ° C and then rapidly cooled with ice. The dispersion had a viscosity of 120 mPas at 22 ° C. and an average particle size of 1.6 μm .

Dispersion 4

20 g of dispersion 1 were mixed by means of an intensive stirrer with 12 g of a 30 wt .-% polymer dispersion prepared from the monomers styrene, butyl acrylate and a cationic acrylamide (Basoplast ^® 270D), having an average particle size of 45 nm. The resulting dispersion had a viscosity of 700 mPas at 22 ° C. and a mean particle size of 1.7 μm .

Comparative dispersion 1

Example 1 from WO 6/26318

Comparative dispersion 2

Sizing agent 2 off WO 98/41565

Application examples example 1

To a paper stock having a consistency of 8 g / l of a fully bleached mixture of 70% pine and 30% birch sulphate pulp with a freeness of 35 ° (Schopper-Riegler) was added, based in each case on dry cellulose fiber mixture, in Table 1 stated amounts of dispersions 1 to 4 and comparative dispersions 1 and 2, 20 wt .-% calcium carbonate, 0.6 wt .-% of a cationic corn starch and 0.04 wt .-% of a cationic polyacrylamide (Polymin ^® KE2020) as a retention aid. The pH of the mixtures was adjusted to 7. The mixtures were then processed in a Rapid-Kothen sheet former into a sheet having a basis weight of 80 g / m ^2. The sheet was then dried on a steam-heated drying cylinder at a temperature of 90 ° C to a water content of 7%. Immediately after drying, the Cobb value of the leaves was determined. The leaves were then kept at 25 ° C for 24 hours stored at a relative humidity of 50%. The measurements were then repeated. The results obtained are shown in Table 1. Table 1 Test no. dispersion [% By weight] stearyl diketene, bez. on dry paper stock Cobb 60 in g / m ² immediately Cobb 60 in g / m ² after 24 h Ink floats after 24 h in min 1 Comparative dispersion 1 0.9 48 25 45 2 Comparative dispersion 2 0.9 45 25 46 3 Dispersion 1 0.9 32 24 50 4 Dispersion 2 0.9 34 23 55 5 Dispersion 3 0.9 37 24 55 6 Dispersion 4 0.9 30 22 60 Test Nos. 1 and 2 are comparative examples, and Tests 3 to 6 are examples according to the invention.

Example 2

To a paper stock having a consistency of 8 g / l of 100% waste paper was added, in each case based on dry cellulose fiber mixture, the amounts of dispersions 1 to 4 and comparative dispersions 1 and 2 shown in Table 2, 0.6 wt .-% cationic corn starch and 0.04 wt .-% of a cationic polyacrylamide (Polymin ^® KE2020) as a retention aid. The pH of the mixtures was adjusted to 7. The blends were then processed on a Rapid-Kothen sheet former into a sheet having a basis weight of 100 g / m ² . The sheet was then dried on a steam-heated drying cylinder at a temperature of 90 ° C to a water content of 7%. The leaves were then stored for 24 hours at 25 ° C and a relative humidity of 50%. The measurements were then repeated. The results obtained are shown in Table 2. Table 2 Test no. dispersion [Wt.%] Stearyldiketen, bez. on dry paper stock Cobb 60 in g / m ² after 24 h Ink floating time after 24 h in min 7 Comparative dispersion 1 1.3 42 33 8th Comparative dispersion 2 1.3 39 37 9 Dispersion 1 1.3 29 55 10 Dispersion 2 1.3 30 52 11 Dispersion 3 1.3 26 60 12 Dispersion 4 1.3 30 53 Test Nos. 7 and 8 are comparative examples, and tests 9 to 12 are examples according to the invention.

Example 3

To a paper stock with a consistency of 8 g / l of a fully bleached mixture of 70% pine and 30% birch sulphate pulp with a freeness of 35 ° (Schopper-Riegler) was given, based in each case on dry cellulose fiber mixture, in Table 3 stated amounts of dispersions 1 to 4 and comparative dispersions 1 and 2, 20 wt .-% calcium carbonate, 0.75 wt .-% of a cationic corn starch and 0.04 wt .-% of a cationic polyacrylamide (Polymin ^® KE2020) as a retention aid. The pH of the mixtures was adjusted to 7. The blends were then processed on a Rapid-Kothen sheet former into a sheet having a basis weight of 150 g / m ² . The sheet was then dried on a steam-heated drying cylinder at a temperature of 90 ° C to a water content of 7%. Subsequently, the leaves were coated from both sides with an adhesive tape streak-free. From the leaves strips were cut with the dimensions 25 x 75 mm. The test strips were immersed in a 30% hydrogen peroxide bath at 70 ° C or in a 3% lactic acid bath at 25 ° C. The edge penetration was determined by differential weighing. The results obtained are shown in Table 3. Table 3 Test no. dispersion [% By weight] stearyl diketene, bez. on dry paper stock Edge penetration peroxide in kg / m ² Edge penetration lactic acid in kg / m ² 13 Comparative dispersion 1 2.0 2.45 0.76 14 Comparative dispersion 2 2.0 1.98 0.76 15 Dispersion 1 2.0 1.23 0.54 16 Dispersion 2 2.0 1.42 0.44 17 Dispersion 3 2.0 1.34 0.51 18 Dispersion 4 2.0 1.51 0.49 Test Nos. 13 and 14 are comparative examples, and Tests 15 to 18 are examples according to the invention.

Claims (12)

1. An aqueous dispersion of a reactive size which comprises a cationic polymer comprising vinylamine units as a protective colloid, wherein the protective colloid comprises less than 0.0001% by weight, based on the protective colloid, of diketenes.
2. The aqueous dispersion according to claim 1, wherein the protective colloid is substantially free of diketenes.
3. The aqueous dispersion according to claim 1 or 2, which comprises less than 1% by weight, based on the aqueous dispersion, of a cationic starch.
4. The aqueous dispersion according to claim 3, which is substantially free of cationic starch.
5. The aqueous dispersion according to any of claims 1 to 4, wherein the cationic polymer comprising vinylamine units comprises from 1 to 100 mol% of hydrolyzed homo- or copolymers of N-vinylformamide.
6. The aqueous dispersion according to any of claims 1 to 5, wherein the cationic polymer comprising vinylamine units has an average molecular weight Mw of from 1000 to 2 million.
7. The aqueous dispersion according to any of claims 1 to 6, wherein the content of protective colloid is from 10 to 100% by weight, based on the reactive size.
8. The aqueous dispersion according to any of claims 1 to 7, wherein C₁₂- to C₂₂-alkylketene dimers, C₅- to C₂₂-alkyl- or C₅- to C₂₂-alkenylsuccinic anhydrides and/or C₁₂- to C₃₆-alkyl isocyanates are used as reactive sizes.
9. The aqueous dispersion according to claim 8, wherein the content of reactive size is from 1 to 50% by weight, based on the total weight of the dispersion.
10. A process for the preparation of an aqueous dispersion according to any of claims 1 to 9, wherein the reactive size and the cationic polymer comprising vinylamine units are homogenized in an aqueous mixture in the presence of an anionic dispersant at from 20 to 100°C under the action of shear forces.
11. A process for the engine sizing of paper, board and cardboard by adding an aqueous dispersion according to any of claims 1 to 9 to an aqueous slurry of cellulose fibers and draining the paper stock.
12. The use of an aqueous dispersion according to any of claims 1 to 9 as an engine size in the production of paper, board, cardboard and liquid packaging cardboard.