EP1819876A2

EP1819876A2 - Paper sizing agent

Info

Publication number: EP1819876A2
Application number: EP05816209A
Authority: EP
Inventors: Markus Schmid; Roland Ettl; Klaus Lorenz; Rainer Dyllick-Brenzinger; Andreas Brockmeyer
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2004-11-29
Filing date: 2005-11-29
Publication date: 2007-08-22
Anticipated expiration: 2025-11-29
Also published as: CN101068986A; CN101068986B; DE502005010891D1; ES2359072T3; EP1819876B1; CA2587527A1; WO2006058711A3; CA2587527C; ATE496172T1; US20080041546A1; WO2006058711A2; US8512520B2; PT1819876E

Abstract

A paper size which comprises a stable aqueous dispersion of a reactive size, from 5 to 100% by weight, based on the reactive size, of a substantially linear nitrogen-comprising polymer having at least 3 mmol/g of basic nitrogen atoms, and from 1 to 50% by weight of cationic starch having a degree of substitution of at least 0.05 is described. The paper size has a good sizing effect and a stable viscosity.

Description

paper size

description

The invention relates to a paper sizing agent comprising a stable aqueous dispersion of a reactive sizing agent, a process for its preparation and its use for sizing paper, board and cardboard.

Reactive sizing agents, such as alkylketene dimers, are widely used for massaging paper, board and board. Reactive sizing agents are usually sold as ready-to-use dispersions. They usually contain cationic polymers such as cationic starch or synthetic cationic polymers which impart substantivity to cellulose to the reactive sizing agents and / or act as protective colloids.

In order for the sizing dispersions to be suitable for use, they must be sufficiently stable to viscosity so that they remain pumpable and dilutable until they are added to the paper machine. In practice, the dispersions often have to remain thin for several weeks at temperatures up to 40 ^° C. These requirements are difficult to meet due to the inherent instability of colloidal systems. In many cases, the viscosity of the dispersions increases sharply until they can no longer be pumped or the dispersions coagulate. The higher the content of the reactive size dispersions, the more pronounced are the problems.

From US-A-3,223,544 alkyl diketene (AKD) dispersions with cationic starch as protective colloid and an anionic dispersant as stabilizer are known.

From WO-A-96/26318 AKD dispersions are known which contain a protective colloid in the form of a copolymer of N-vinylpyrrolidone and N-vinylimidazole or a condensate condensation product based on polyethyleneimines.

WO 2004/022847 discloses the use of polyvinylamines as promoters for engine sizing in starch-containing AKD dispersions.

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

The earlier German patent application with the file reference DE 102004010447.6 discloses the use of polyvinylamines as protective colloids in aqueous dispersions. on reactive sizing agents. The dispersions should preferably be free of cationic starch.

The object of the invention is to provide paper sizing agents based on aqueous dispersions of reactive sizing agents which have a good sizing effect and sufficient viscosity stability.

The object is achieved according to the invention by a paper sizing agent which comprises:

(a) a stable aqueous dispersion of a reactive sizing agent,

(b) from 5 to 100% by weight, preferably from 10 to 100% by weight, in particular from 20 to 50% by weight, based on the reactive size, of a substantially linear nitrogen-containing polymer having at least 5 mmol / g of basic nitrogen atoms ( c) 1 to 50 wt .-%, preferably 3 to 25 wt .-%, in particular 10 to 20% by weight, based on the reactive sizing agent, cationic starch having a degree of substitution of at least 0.05, preferably 0.05 to 0 , 5, especially 0.08 to 0.3 and most preferably 0.1 to 0.2.

Usually, the paper sizing agents according to the invention contain from 1 to 50% by weight of reactive sizing agent, based on the total weight of the paper sizing agent.

The term "stable dispersion" is intended to mean that the dispersion remains liquid at 40 ^° C. for 4 weeks and does not coagulate.

By "linear polymer" is meant a polymer that is substantially free of branching and crosslinking. Polyalkyleneimines, in particular polyethylenimines, are not considered to be "linear polymers" because of their structure branched over by tertiary amino groups.

By "basic nitrogen atoms" is meant those nitrogen atoms which can be protonated in aqueous solution by a Bronsted acid. Basic nitrogen atoms are in particular primary, secondary and tertiary amino groups, of which primary amino groups are preferred. The basic nitrogen atoms in the nitrogen-containing polymer are preferably at least 90 mol%, in particular substantially quantitatively protonated. The protonation can be carried out by reaction with a mineral acid, such as hydrochloric acid, sulfuric acid or phosphoric acid, but is preferably carried out by reaction with a carboxylic acid. Suitable carboxylic acids are, above all, formic acid, acetic acid, propionic acid, oxalic acid, tartaric acid, citric acid and the like. Substantially quantitative protonation is obtained when the nitrogen-containing polymer is adjusted to a pH of less than 5 with the chosen acid. The nitrogen-containing polymer used in the invention contains at least 3 mmol / g, preferably at least 5 mmol / g basic nitrogen atoms, especially 7.5 to 23 mmol / g, and most preferably 12 to 18 mmol / g. The content p of a polymer of basic nitrogen atoms can be calculated according to the following equation:

wherein x is _N for the molar ratio of a monomer having a basic nitrogen atom (such as vinylamine), X ₀ for the molar fraction of a monomer without (basic) nitrogen atoms (such as vinylformamide), M _N for the molecular weight of the monomer with basic nitrogen atom and M ₀ for the Molecular weight of the monomer without (basic) nitrogen atoms. The term "molar fraction" refers to the monomer composition of the polymer.

The average molecular weight Mw of the nitrogen-containing polymer is e.g. 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 after

H. Fikentscher in 5% aqueous saline solution at 25 ^° C., a pH of 7 and a polymer concentration of 0.5% by weight).

Suitable nitrogen-containing polymers include hydrolysis products of homopolymers and copolymers of N-vinylcarboxamides and / or N-vinylcarboximides. In the hydrolysis of a part or all of the copolymerized N-vinylcarboxamide or N-vinylcarboximide units, the acyl group (s) is cleaved off by the action of acids, bases or enzymes to form vinylamine units.

Suitable N-vinylcarboxamides are generally open-chain and cyclic N-vinylcarboxamides. Preferred N-vinylcarboxamides are open-chain N-vinylcarboxamides, in particular those open-chain N-vinylcarboxamides whose hydrolysis yields a primary amine. Examples of particularly suitable N-vinylcarboxamides are N-vinylformamide, N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide and N-vinylpropionamide, in particular N -Vinylformamid. Examples of suitable N-vinylimides are N-vinylsuccinimide and N-vinylphthalimide. The stated monomers can be polymerized either alone or in a mixture with one another or together with other monomers. Vinylamine containing polymers are z. From 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.

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, wherein in each case only one OH group is esterified, e.g. 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 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.

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-methylimidazo-Nn and N-vinyl-2-ethylimidazoline.

Such copolymers preferably contain at least 50 mol% of at least one N-vinylcarboxamide in copolymerized form. The comonomers are preferably free of acid groups.

In order to prepare suitable polyvinylamines, preference is given to using N-vinylformamide homopolymers or N-vinylformamide copolymers, for example vinyl formate, vinyl acetate, vinyl propionate, acrylonitrile, N-vinylcaprolactam, N-vinylurea, N-vinylpyrrolidone or C ₁ - bis C ₆ alkyl vinyl ethers whose N-vinylformamide units are then hydrolyzed to N-Vinylamineinheiten to a degree of hydrolysis of preferably 25 to 100 mol%, particularly preferably 50 to 100 mol% and particularly preferably 70 to 100 mol%. The hydrolysis of the above-described polymer merisate is carried out by known methods by the action of acids, bases or enzymes. When acids are used as hydrolysis 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 polymers are preferably used in salt-free form. Salt-free aqueous solutions can be prepared, for example, from the salt-containing polymer solutions described above 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.

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

Alternatively, as the nitrogen-containing polymer, it is possible to use polymers which contain polymerized units of monomers having side groups comprising basic nitrogen atoms or their copolymers with monomers without (basic) nitrogen atoms in a suitable ratio.

Suitable monomers having side groups comprising basic nitrogen atoms are e.g. Allylamine, basic acrylates, e.g. Dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethyaminopropyl acrylate, dimethylaminopropyl methacrylate, diethylaminopropyl acrylate, dimethylaminobutyl acrylate and diethylaminobutyl acrylate; basic (meth) acrylamides, e.g. Dimethylaminoethylacrylamide, dimethylaminoethylmethacrylamide, diethylaminoethylacrylamide, diethylaminoethylmethacrylamide, dimethylaminopropylacrylamide, diethylaminopropylacrylamide, dimethylaminopropylmethacrylamide and diethylaminopropylmethacrylamide.

Suitable monomers without (basic) nitrogen atoms are those mentioned above.

The terms "cationic starch" and "cationically modified starch" are used interchangeably herein. Suitable cationic starches are commercially available. The starting starch can be any type of starch, such as. Potato starch, corn starch, wheat starch, waxy maize starch and tapioca starch. Starches having an amylopectin content of more than 50% by weight, preferably 80 to 100% by weight, are preferred, with those having an amylopectin content of at least 90% by weight being particularly preferred. Part of the free hydroxyl groups of the starch are coupled by means of a chemical reaction to protonatable or cationically charged groups, in particular dialkylamino or trialkylammonium groups. Particularly suitable cationizing agents are dialkylaminoalkyl epoxides and dialkylaminoalkyl halides. Instead of the alkyl groups, the cationizing agents may also contain aryl groups.

Preferred cationizing agents are, for example, N, N-dimethylaminoethyl chloride, N, N-diethylaminoethyl chloride, N, N-dimethylaminopropyl chloride, 3-dibutylamino-1, 2-epoxypropane, 2-bromo-5-diethylaminopentane hydrobromide, N- (2,3-epoxypropyl ) - piperidine, 2,3-epoxypropyltrimethylammonium chloride and N, N- (2,3-epoxypropyl) -methylaniline. Instead of the free amines, hydrochloric acid or other salts can also be used.

The reaction between the starting starch and the cationizing reagent is preferably carried out in an alkaline medium. The proportion of reagent to be used depends on the desired degree of substitution. The degree of substitution is the ratio of cationic group to carbohydrate unit (i.e., glucose unit). He can assume a maximum value of 3.

Suitable reactive sizing agents for the paper sizing agents according to the invention are, for example, C ₁₂ -C ₂₂ -alkyl ketene dimers, C ₅ -C ₂₂ -alklyl or C ₅ -C ₂₂ -alkenylsuccinic anhydrides, C ₁₂ -C ₃₆ -alkyl isocyanates and / or organic isocyanates. cyanates such as dodecyl isocyanate, octadecyl isocyanate, tetradecyl isocyanate, hexadecylsiocyanate, eicosyl isocyanate and decyl isocyanate. Preferably used mass modifiers 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 with different alkyl groups such as stearyl palmitate diketene, benzyl stearyl diketene, behenyl enyl diketene or palmityl behenyl diketene. Stearyldiketen, Palmityldiketen, Behenyldiketen or mixtures of Behenyldiketen and Stearyldiketen are preferably used. Substituted succinic anhydrides suitable as reactive sizes are, for example, 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 The content of succinic anhydrides is, for example, from 1 to 25% by weight, preferably from 2 to 10% by weight, based on the total weight of the dispersion.

In order to stabilize the dispersed reactive sizing agents in the aqueous phase, the sizing agents of the present invention typically contain an anionic dispersant. 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 0.1 to 1 wt .-%, based on the reactive.

Preferred anionic dispersants are selected from condensation products

(a) naphthalenesulfonic acid and formaldehyde

(b) phenol, phenolsulfonic acid and formaldehyde,

(c) naphthalenesulfonic acid, formaldehyde and urea, as well

(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 from primary, secondary and tertiary amines, for example 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. substance 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.

Also suitable as anionic dispersants are amphiphilic copolymers

(i) hydrophobic monoethylenically unsaturated monomers and

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

Suitable hydrophobic monoethylenically unsaturated monomers

(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 C atoms, diesters of maleic acid or fumaric acid with monohydric C ₁ - to C ₂₄ -alcohols, vinyl ethers of alcohols having 3 to 24 C- 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.

Particularly preferred are aqueous sizing agent dispersions containing as anionic dispersant amphiphilic copolymers (a) α-olefins having 4 to 12 C atoms, styrene or mixtures thereof as hydrophobic monomers and

(b) maleic acid, acrylic acid, methacrylic acid, monoesters of maleic acid and alcohols having 1 to 25 carbon atoms or alkoxylation products of such alcohols,

Halides 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 of 1 500 to 100 000 have.

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 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 solution or dispersions, wherein the anhydride group is present open and the carboxyl groups are preferably partially or completely neutralized. The following bases are used for neutralization: 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 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 are described, for example, in EP-A-437 764 and EP-A-658 228. Suitable non-cellulose-reactive substances are, for example, fatty acids, amides and esters as well as waxes. Examples thereof without any claim to completeness are stearic acid behenyl ester, myristic acid stearyl ester, stearic acid isododecyl ester, carbonic acid oleyl ester, carbonic acid oleylstearyl ester, oleyl N, N-distearyl urethane, parrafin, di-oleic acid glycerol ester, tris-oleic acid glycerol ester and tris-stearic acid glycerol ester. 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 known, for example, from EP-B-0 051 144, EP-B-0 257 412, EP-B 276 770, EP-B 0 058 313 and EP-B 150 003. 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

(a) styrene, acrylonitrile and / or methacrylonitrile,

(b) acrylic acid and / or methacrylic acid esters of C 1 -C ₁₈ -alcohols and / or vinyl esters of saturated C ₂ -C ₄ -carboxylic acids and optionally

(c) other monoethylenically unsaturated copolymerizable monomers

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

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 -C ₅ -monoethylenically unsaturated carboxylic acids, acrylamidomethylpropanesulfonic acid, sodium vinylsulfonate, vinylimidazole, N-vinylformamide, acrylamide, methacrylamide, N-vinylimidazoline and cationic polymers such as dimethylaminopropylmethacrylamide or dimethylaminoethyl 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 WO-A-96/31650 and the literature cited therein.

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 from 25 to 300% by weight, preferably from 50 to 250% by weight and more preferably from 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.

To prepare 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 shearing forces. The liquid alkenyl succinic anhydride can be emulsified already at room temperature. By adding lipophilic substances such as fatty acids, waxes, resin acids and resins, fatty acid amides or esters, the melting point of the reactive sizing agent may optionally be lowered, thereby improving the stability of the resulting dispersion.

In this case, it is possible, for example, to submit an aqueous solution of the cationic starch and of the anionic dispersant, then to add the sizing agent and the nitrogen-containing polymer in any desired sequence and to subject the resulting mixture to a dispersing step. The dispersing step is preferably carried out at temperatures of, for example, 20 to 100, preferably 40 to 90 ^° C. The sizing agent is preferably added in the form of a melt. It has not been proven to provide the nitrogen-containing polymer and to provide it with an anionic dispersant. In the dispersing step, apparatuses known to the person skilled in the art are used, for example high-pressure homogenizers, colloid mills and ultrasound dispersants. The resulting dispersion is cooled in each case.

The paper sizing agent according to the invention has a viscosity, for example, in the range from 20 to 1,000 mPas, preferably 100 to 500 mPas (measured using a Brookfield viscometer and a temperature of 22 ^° C.). The viscosity increases during storage for 4 weeks at 4O ⁰ C, preferably to a maximum of less than twice the value of initial viscosity immediately after preparation to. In the preparation of the aqueous dispersions, the pH is preferably in the range from 3 to 4. As a rule, aqueous sizing agent dispersions having an average particle size of the sizing agents are obtained in the range from 100 to 3,000 nm, preferably 250 to 2,000 nm.

The dispersions according to the invention are used as engine size agents in the production of paper, board and cardboard. Paper, board and board are usually made by dewatering a slurry of cellulosic fibers. Suitable cellulosic fibers are all types customary for this purpose, for example cellulose fibers from mechanical pulp and fibers derived from annual plants. costume. 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 recovered 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 paper stock may 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 are obtained, which have a weight per unit area of, for example, 20 to 400 g / m ² , preferably 40 to 220 g / m ² .

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, polyvinyltetrahydropyrines, poly (dialkylaminoalkylvinylethers), poly (dialkylaminoalkyl (meth) acrylates) in protonated or in quaternized form as well as polyamidoamines from a dicarboxylic acid such as adipic acid and polyalkylenepolyamines such as diethylenetriamine grafted with ethyleneimine and crosslinked with Polyethylenglykoldichlorhydrinethern according to the teaching of DE-B-24 34 816 or polyamidoamines, which are reacted with epichlorohydrin to water-soluble condensation onsprodukten and copolymers of acrylamide or methacrylamide and Dialkylaminoethylacrylates 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, K-values according to Fikentscher of more than 150 (as determined in 5% wässri- ger sodium chloride solution at a polymer concentration of 0.5 wt .-%, a temperature of 25 ⁰ C and a pH 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 paper sizing agent according to the invention as a sizing agent 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 determined according to H. Fikentscher, Cellulose-Chemie, Vol. 13, 58-64 and 71-74 (1932) in 5% aqueous common salt solution at a temperature of 25 ^° C. and a pH of 7 determined at a polymer concentration of 0.5 wt .-%. The average 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 using 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 53 132 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 50 to a degree of hydrolysis of 95 mol%, d. H. it was a polymer containing about 95 mole% vinylamine units and about 5 mole% vinylformamide units. The polymer was adjusted to pH 3.7 with formic acid.

Polyvinylamine 2

Cationic polymer obtained by hydrolysis of poly-N-vinylformamide having a K value of 45 to a degree of hydrolysis of 75 mol%, d. H. it was a polymer containing about 75 mole% vinylamine units and about 25 mole% vinylformamide units). The polymer was adjusted to pH 3.7 with formic acid.

example 1

The mixture was heated 30 parts by weight of a 5 wt .-% solution of a cationic starch (with N, N-dimethylaminoethyl modified starch, DS 0.1) at 95 ⁰ C, stirred for 5.7 parts by weight of a 5 wt. -% solution of naphthalenesulfonic acid-formaldehyde condensate sodium salt, mixed with 19.3 parts by weight of water and then added with 20 parts by weight of a melt of C ₁₆ -C ₁₈ -Alkylketendimer with a temperature of 90 ⁰ C. . to the resulting emulsion were added 25 parts by weight of a 12 wt .-% aqueous solution of polyvinylamine 1 at 90 ⁰ C.

The mixture was homogenized by means of a high-pressure homogenizer at 100 bar and 75 ⁰ C in two passes and cooled rapidly with ice.

The dispersion obtained had a viscosity of 80 mPas (22 ⁰ C) and an average particle size of 1, 3 .mu.m. After storage for 4 weeks at 40 ^° C., the dispersion had a viscosity of 120 mPas.

Example 2 Example 1 was repeated except that the solution of the naphthalenesulfonic acid-formaldehyde condensate sodium salt and then the polyvinylamine 1 was added first to the cationic starch solution initially charged. The mixture was mixed with the melt of the alkyl ketene dimer.

Then emulsified with a high speed stirrer and homogenized in two passes in the high pressure homogenizer as described.

The dispersion obtained had a viscosity of 100 mPas (22 ⁰ C) and an average particle size of 1, 5 .mu.m. After storage for 4 weeks at 40 ^° C., the dispersion had a viscosity of 180 mPas.

Comparative Example 3

Example 1 was repeated except that the solution of the cationic starch initially introduced was first the solution of the polyvinylamine 1 and then the naphthalenesulfonic acid-formaldehyde condensate sodium salt. The mixture was mixed with the melt of the alkyl ketene dimer.

The dispersion obtained had a viscosity of 250 mPas (22 ⁰ C) and an average particle size of 2.5 microns. After 4 weeks of storage at 40 ⁰ C, the dispersion was coagulated and solid.

Example 4

Example 1 was repeated except that 22 parts by weight of an 18% strength by weight solution of polyvinylamine 2 was used instead of polyvinylamine 1.

The dispersion obtained had a viscosity of 150 mPas (22 ⁰ C) and an average particle size of 1, 4 .mu.m. After storage for 4 weeks at 40 ^° C., the dispersion had a viscosity of 300 mPas.

Comparative Example 5

Example 4 was repeated, but adding the solution of polyvinylamine 2 after homogenization and cooling. The dispersion obtained had a viscosity of 250 mPas (22 ⁰ C) and a mean particle size of 2.8 microns. After 4 weeks of storage at 40 ⁰ C, the dispersion was solid.

Comparative Example 6

It heated 50 parts by weight of a 5 wt .-% solution of a cationic starch (DS 0.1) to 95 ° C, stirred 5.7 parts by weight of a 5 wt .-% solution of naphthalenesulfonic acid Formaldehyde condensate sodium salt, mixed with 24.3 parts by weight of water and then added with 20 parts by weight of a melt of C ₁₆ -C ₁₈ - Alkylketendimer at a temperature of 90 ° C and emulsified with a high speed stirrer.

The dispersion obtained had a viscosity of 50 mPas (22 ⁰ C) and an average particle size of 1, 4 .mu.m. After storage for 4 weeks at 40 ^° C., the dispersion had a viscosity of 130 mPas.

Comparative Example 7

The mixture was heated, 52.3 parts by weight of deionized water at 90 ⁰ C, stirred for 5.7 parts by weight of a 5 wt .-% solution of naphthalenesulfonic acid Formaldehydkondensat- sodium salt, and then mixed with 22 parts by weight of a 18 Wt .-% solution of polyvinylamine 2. In the 90 ⁰ C hot mixture was added 20 parts by weight of a melt of C ₁₆ -C ₁₈ -Alkylketendimer with a temperature of 90 ⁰ C and emulsified with a high speed stirrer.

The dispersion obtained had a viscosity of 40 mPas (22 ⁰ C) and an average particle size of 0.9 .mu.m. After storage for 4 weeks at 40 ^° C., the dispersion had a viscosity of 900 mPas.

Comparative Examples 3 and 5 show that no stable dispersion is obtained when the nitrogen-containing polymer is charged (Comparative Example 3) or added after the dispersing step (Comparative Example 5). Comparative Examples 6 and 7 show the viscosity increase of dispersions which are not nitrogen-containing polymer (Comparative Example 6) or contain no cationic starch (Comparative Example 7) at 4 weeks storage at 40 ° C.

Application examples

Application example 1

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 Table 1 listed amounts of the above dispersions, 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 ⁰ C to a water content of 7%. Immediately after drying, the Cobb value of the leaves was determined. 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 1.

Table 1

Application 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 the above dispersions shown in Table 2, 0.6 wt .-% of a cationic corn starch and 0.04 wt .-% of a cationic polyacrylamide (Polymin ^® KE2020) as a retention agent. 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 ⁰ C to a water content of 7%. The leaves were then stored for 24 hours at 25 ⁰ C and a relative humidity of 50%. The measurements were then repeated. The results obtained are shown in Table 2.

Table 2

Application 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 the above dispersions, 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 ⁰ 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 placed in a 30% hydrogen peroxide bath at 70 ° C. The edge penetration was de determined by differential weighing. The results obtained are shown in Table 3.

Table 3

Claims

claims

A paper sizing agent comprising a) a stable aqueous dispersion of a reactive sizing agent, b) 5 to 100% by weight, based on the reactive sizing agent, of a substantially linear nitrogen-containing polymer having at least 3 mmol / g basic nitrogen atoms, c) 1 to 50% by weight %, based on the reactive sizing agent, of cationic starch having a degree of substitution of at least 0.05.

2. Paper sizing agent according to claim 1, characterized in that the basic nitrogen atoms in the nitrogen-containing polymer are at least 90 mol% protonated.

3. paper sizing agent according to claim 2, characterized in that the basic nitrogen atoms are protonated by reaction with a carboxylic acid.

4. Paper sizing agent according to one of claims 1 to 3, characterized in that the nitrogen-containing polymer is a vinylamine polymer.

5. The paper sizing agent according to claim 4, wherein the vinylamine polymer is a homo- or copolymer of N-vinylformamide whose N-vinylformamide units are hydrolyzed to from 25 to 100 mol%.

Paper sizing agent according to any one of Claims 1 to 5, characterized in that it additionally comprises an anionic dispersant.

7. Paper sizing agent according to one of claims 1 to 6, characterized in that the reactive sizing agent under

(i) C ₂ - to C ₂₂ -alkylketene,

(ii) C ₅ - to C ₂₂ alkyl or C ₅ - to C ₃₆ is selected -Alkylisocyanaten and / or organic isocyanates - to C ₂₂ -Alkenylbernsteinsäureanhydriden and (iii) Ci. ₂

8. Paper sizing agent according to one of claims 1 to 7, characterized in that it comprises 1 to 50 wt .-% reactive sizing agent.

9. A process for producing a paper sizing agent according to any one of claims 6 to 8, wherein a) introducing an aqueous solution of the cationic starch and the anionic dispersant, b) adding the reactive sizing agent and the nitrogen-containing polymer in any order, and c) subjecting the resulting mixture to a dispersing step.

10. A process for producing paper, paperboard or paperboard comprising adding to an aqueous slurry of cellulosic fibers a paper sizing agent as claimed in any one of claims 1 to 8 and dewatering the stock.

11. Use of the paper sizing agent according to one of claims 1 to 8 as a sizing agent in the production of paper, cardboard, cardboard and liquid cardboard.