CA2213314C - Aqueous alkyl diketene dispersions and the use thereof as glue for paper - Google Patents

Abstract

Aqueous alkyldiketene dispersions which contain a C14-C22-alkyldi-ketene and from 1 to 10% by weight of a polymeric protective col-loid contain, as the protective colloid (a) copolymers of (1) N-vinylpyrrolidone and (2) at least one quaternized N-vinylimidazole or a substi-tuted quaternized N-vinylimidazole as polymerized units in a molar ratio of from 80:20 to 5:95 and have a K value of at least 20 (according to H. Fiken-tscher in 0.5 M aqueous sodium chloride solution at a polymer concentration of 0.1% by weight and at 25°C) or (b) condensates which are obtainable by (1) partial amidation of polyethyleneimines with monocarbox-ylic acids and, if required (2) condensation of the partially amidated polyethyleneimines with at least bifunctional crosslinking agents Which have a halohydrin, glycidyl, aziridine or isocyanate unit or a halogen atom as a functional group to give crosslinked, amidated polyethyleneimines which have a viscosity of at least 100 mPa.s in 20% strength by weight aqueous solution at 20°C, or mixtures of (a) and (b) and are used as engine size in the production of paper, board and cardboard and for rendering cellu-losic fibers water-repellent.

Description

Aqueous alkyl diketene dispersions and the use thereof as glue for paper The present invention relates to aqueous alkyldiketene disper sions which contain a C14-C22-alkyldiketene and from 1 to 10% by weight of a polymeric protective colloid and the use of the aqueous alkyldiketene dispersions as engine size in the produc-tion of paper, board and cardboard and for rendering cellulosic fibers water-repellent.
Alkyldiketenes are used in the form of aqueous dispersions as size for paper. They are emulsified in water in the presence of emulsifiers or organic thickeners (cf. US-A 2 627 477 and US-A 3 130 118). The last-mentioned publication discloses the preparation of aqueous alkyldiketene dispersions with cationic starch. The low-concentration alkyldiketene dispersions described therein have a sufficiently long shelf life for use as size, but aqueous alkyldiketene dispersions having fatty alkyldiketene con-centrations of more than 12% become solid relatively rapidly.
various substances have already been used for stabilizing aqueous dispersions of fatty alkyldiketenes. For example, US-A-2 901 371 and US-A-3 311 532 disclose the use of higher fatty acids, their anhydrides, amides, aldehydes and acyl chlorides. The concentra-tions of fatty alkyldiketenes in the aqueous dispersions is, however, always below 10% by weight.
DE-A-2 514 128 discloses aqueous dispersions of ketene dimers which contain from 1 to 30% by weight, based on ketene dimers, of polyvinylpyrrolidone and/or polyvinylcaprolactam. They may fur-thermore contain an emulsifier, such as a fatty alcohol sulfate or a salt of a sulfonic acid which is obtained by sulfonation of an ethoxylated fatty alcohol or a cationic emulsifier which is prepared, for example, by reaction of oleylamine with ethylene oxide and quaternization with dimethyl sulfate. For the prepara-tion of aqueous alkyldiketene dispersions having a particularly long shelf life, according to this publication an inert solvent, such as toluene or cyclohexane, is additionally used in dispers-ing the alkyldiketenes.
According to DE-A 3 316 179, from 4 to 12% strength aqueous alkyldiketene dispersions are obtained if alkyldiketenes are dis-persed in water in the presence of cationic starch and a cationic protective colloid, the protective colloid being a water-soluble condensate which is obtainable by grafting polyamidoamines with ethyleneimine and crosslinking the polyami.doamines grafted with ethyleneimine with at least difunctional crosslinking agents. In BASF Aktiengesellschaft 940656 O.Z. 0050/45641 order to increase the stability of the aqueous dispersion, water-soluble dicyandiamide/formaldehyde condensates must be added.
According to the examples, the alkyldiketene concentration in the aqueous dispersions is 6% by weight.
EP-B-0 341 509 discloses a size mixture which contains, as essen-tial components, an alkyldiketene and a hydrophilic polymer which is obtainable by polymerizing at least one hydrophilic vinyl monomer in the presence of from 0.01 to 10 mol% of an alkyl mer-captan having 6 to 22 carbon atoms in the molecule. According to Example 5, a copolymer of 97% of acrylamide and 3% of dimethyl-aminoethyl methacrylate is used as a hydrophilic vinyl polymer.
EP-B 0 437 764 discloses stable aqueous alkyldiketene dispersions which contain a protective colloid and an ester of a long-chain carboxylic acid and a long-chain alcohol in addition to an alkyl-diketene. Preferred protective colloids are cationic starches.
Sorbitan esters, soaps, synthetic detergents and thickeners, such as polymers of acrylamide, vinylpyrrolidone and N-vinyl-2-methylimidazoline, may also be used.
WO-A 94/12560 discloses condensates of polyalkylenepolyamines which are obtainable by 25 (a) partial amidation of polyalkylenepolyamines with monocarb-oxylic acids and (b) condensation of the partially amidated polyalkylenepolyamines with at least bifunctional crosslinking agents which have a 30 halohydrin, glycidyl, aziridine or isocyanate unit or a halo-gen atom as a functional group to give crosslinked polyalkylenepolyamines which have a viscosity of at least 100 mPa.s in 20% strength by weight aqueous solution 35 at 20'C. The condensates are used as drainage aids, flocculants, retention aids and fixing agents in papermaking.
The stability of the aqueous diketene dispersions described above is still unsatisfactory.
It is an object of the present invention to provide novel aqueous alkyldiketene dispersions which have a long shelf life and, when used as engine size, give sized paper in which the sizing effect is substantially displayed immediately after production of the paper.

BASF Aktiengesellschaft 940656 O.Z. 0050/45641 We have found that this object is achieved, according to the in-vention, by aqueous alkyldiketene dispersions which contain a Ci4-Cz2-alkyldiketene and from 1 to 10% by weight of a polymeric protective colloid if said dispersions contain, as the protective colloid, (a) copolymers of (1) N-vinylpyrrolidone and (2) at least one quaternized N-vinylimidazole of the formula R
H2C = CH- N ~~N-R3 Rz ~ Ri where R, R1 and Rz are each H, C1-C4-alkyl or phenyl, R3 is H, C1-C18-alkyl or benzyl and Xe is an anion, the copolymers containing the monomers (1) and (2) as poly-merized units in a molar ratio of from 80:20 to 5:95 and hav-ing a K value of at least 20 (determined according to H. Fikentscher in 0.5 M aqueous sodium chloride solution at a polymer concentration of 0.1% by weight and at 25°C), or (b) condensates which are obtainable by (1) partial amidation of polyethyleneimines with monocarb-oxylic acids and (2} condensation of the partially amidated polyethyleneimines with at least bifunctional crosslinking agents which have a halohydrin, glycidyl; aziridine or isocyanate unit or a halogen atom as a functional group to give crosslinked amidated polyethyleneimines which have a viscosity of at least 100 mPa.s in 20% strength by weight aqueous solution at 20°C, or a mixture of (a) and (b).

BASF Aktiengesellschaft 940656 O.Z. 0050/45641 The present invntion furthermore relates to the use of the aqueous alkyldiketene dispersions as engine size in the produc-tion of paper, board and cardboard and for rendering cellulosic fibers water-repellent.
For example, C14-C22-alkyldiketenes or mixtures of such alkyldi-ketenes are suitable for the preparation of the aqueous alkyl-diketene dispersions. Alkyldiketenes are known and are commer-cially available. They are prepared, for example, from the cor-responding acyl chlorides by elimination of hydrogen chloride with tertiary amines. The fatty alkyldiketenes can be character-ized, for example, by the formula R1-CH = C- O
I (II).
RZ-CH-C= O
where R1 and R2 are identical or different C14-Cz2-alkyl groups.
Examples of suitable fatty alkyldiketenes are tetradecyldiketene, hexadecyldiketene, octadecyldiketene, eicosyldiketene, docosyl-diketene, palmityldiketene, stearyldiketene and behenyldiketene.
Examples of compounds of the formula II where R1 and R2 have dif-ferent meanings are stearylpalmityldiketene, behenylstearyldi-ketene, behenyloleyldiketene and palmitylbehenyldiketene. Among the compounds of the formula II, stearyldiketene, palmityldi-ketene or mixtures of stearyldiketene and palmityldiketene are preferably used. The diketenes are present in the aqueous emul-sions in concentrations of from 5 to 60, preferably from 10 to 40, % by weight. Particularly preferred aqueous alkyldiketene emulsions are those which have concentrations of from 10 to 20%
by weight of a C14-C22-alkyldiketene.
Dialkyldiketenes are emulsified in water in the presence of the abovementioned protective colloids (a) and/or (b). Suitable pro-tective colloids (a) are copolymers of N-vinylpyrrolidone and at least one quaternized N-imidazole of the abovementioned formula I. In the formula I, the anion may be, for example, a halide ion, an alkylsulfate ion or a radical of an inorganic or organic acid.
Examples of quaternized 1-vinylimidazoles of the formula I are 1-vinylimidazole quaternized with C1-C18-alkyl halides, salts of 1-imidazole with mineral acids, such as sulfuric acid or hydro-chloric acid, 2-methyl-1-vinylimidazole quaternized with C1-C18-alkyl halides, 3-methyl-1-vinylimidazolinium chloride, 3-benzyl-1-vinylimidazolium chloride, 3-ethyl-1-vinylimidazolium methosulfate and 2-methyl-1-vinylimidazolium methosulfate. The BASF Aktieagesellschaft 940656 O.Z. 0050/45641 copolymers of N-vinylpyrrolidone may also contain a plurality of different quaternized N-vinylimidazole as polymerized units, for example 1-vinylimidazolium chloride and 2-methyl-1-vinylimidazo-lium methosulfate.
Copolymers of N-vinylpyrrolidone and vinylimidazole quaternized with methyl chloride and copolymers of N-vinylpyrrolidone and 2-methyl-1-vinylimidazole quaternized with methyl chloride are preferably used.
The copolymers preferably contain from 80 to 5 mol% of N-vinyl-pyrrolidone and from 20 to 95 mol% of a quaternized vinylimid-azole of the formula I. The K value of the copolymers is at least 20, preferably from 40 to 80. The K values are determined accord-ing to H. Fikentscher in 0.5 M aqueous sodium chloride solution at a polymer concentration of 0.1% and at 25'C.
Suitable protective colloids (b) are condensates which are de-scribed in WO-A 94/12560 cited at the outset. These are amidated polyalkylenepolyamines or the crosslinked products thereof. Among the amidated polyalkylenepolyamines, amidated polyethyleneimines are preferred. They are prepared, for example, by a 2-stage reac-tion in which polyethyleneimines are partially amidated with monocarboxylic acids in the first stage of the reaction. For ex-ample, monocarboxylic acids of 1 to 28, preferably 1 to 18, car-bon atoms are used in the amidation. The monocarboxylic acids may be saturated or may have one ethylenically unsaturated double bond or a plurality of ethylenically unsaturated nonconjugated double bonds. Suitable carboxylic acids are, for example, formic acid, acetic acid, propionic acid, butyric acid, capric acid, 2-ethylhexanoic acid, benzoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, arachidic acid, erucic acid, behenic acid, valeric acid, decanoic acid, en-anthic acid, caprylic acid and fatty acid mixtures which are ob-tained, for example, from naturally occurring fatty esters, for example from coconut fat, tallow, soybean oil, linseed oil, rapeseed oil and mixed oil. For the preparation of the amidated polyethyleneimines, it is also possible to use, for example, al-kyldiketenes such as stearyldiketene, palmityldiketene, lauryldi-ketene, oleyldiketene, behenyldiketene or mixtures of the stated diketenes. The polyethyleneimines are partially amidated in pro-cess step (1) so that, for example, from 0.1 to 90%, preferably from 1 to 30%, of those nitrogen atoms of the polyethyleneimines which are capable of amidation are present as amido groups. No linkage of polyethyleneimine molecules occurs during the amid-ation. Such a linkage is achieved only in the case of any BASF Aktieagesellschaft 940656 O.Z. 0050/45641 reaction of the partially amidated polyethyleneimines with at least bifunctional crosslinking agents.
Examples of suitable crosslinking agents are epihalohydrins, in particular epichlorohydrin, and a,w-bis(chlorohydrin)polyalkylene glycol ethers and the a,w-bisepoxides of polyalkylene glycol ethers, which bisepoxides are obtainable from said ethers by treatment with bases. The chlorohydrin ethers are prepared, for example, by reacting polyalkylene glycols with epichlorohydrin in a molar ratio of 1 to at least 2-5. Suitable polyalkylene glycols are, for example, polyethylene glycol, polypropylene glycol and polybutylene glycols and block copolymers of C2-C4-alkylene ox-ides. The average molecular weights (MW) of the polyalkylene gly-cols are, for example, from 200 to 6000, preferably from 300 to.
2000, g/mol. a,w-Bis(chlorohydrin)polyalkylene glycol ethers of this type are described, for example, in DE-C-2 434 816, stated in connection with the prior art. As also stated therein, the corresponding bisglycidyl ethers are formed from the dichlorohy-drin ethers by treatment with bases. a,w-Dichloropolyalkylene glycols which, for example, are disclosed as crosslinking agents in EP-B-0 025 515 are also suitable. Other suitable crosslinking agents are a,w- dichloroalkanes or vicinal dichloroalkanes, for example 1,2-dichloroethane, 1,2-dichloropropane, 1,3-dichloropro-pane, 1,4-dichlorobutane and 1,6-dichlorohexane. Examples of fur-ther crosslinking agents are the reaction products of at least trihydric alcohols with epichlorohydrin, which reaction products have at least two chlorohydrin units; for example, the polyhydric alcohols used are glycerol, ethoxylated or propoxylated gly-cerols, polyglycerols having from 2 to 15 glycerol units in the molecule and polyglycerols which may be. ethoxylated and/or pro-poxylated. Crosslinking agents of this type are disclosed, for example, in the abovementioned DE-C-2 916 356. Crosslinking agents which contain blocked isocyanate groups, for example tri-methylhexamethylene diisocyanate blocked with 2,2,3,6-tetra-methylpiperidin-4-one, are also suitable. Such crosslinking agents are those disclosed, for example, in DE-A-4 028 285 and crosslinking agents containing aziridine units and based on poly-ethers or substituted hydrocarbons, eg. 1,6-bis-N-aziridino-hexane, cf. US-A-3 977 923. It is of course also possible to use mixtures of two or more crosslinking agents for increasing the molecular weight of the amidated polyalkylenepolyamines.
For the preparation of the condensates preferably to be used as protective colloid (b), BASF Aktiengesellschaft 940656 O.Z. 0050/45641 (1) the amidated polyalkylenepolyamines are reacted with (2) bifunctional or polyfunctional crosslinking agents in a weight ratio (a):(b) of from 1:0.001 to 1:10, preferably from 1:0.01 to-1:3.
The crosslinking of the amidated polyalkylenepolyamines described under (1) with the crosslinking agents stated under (2) is car-ried out at from 0 to 200°C, preferably from 50 to 80°C. The reac-tion can be carried out in the presence or absence of a solvent.
A preferred solvent is water. Alcohols, for example C1-C12-alcohols, such as methanol, ethanol, n-propanol, isopropanol and butanols, and ethers, eg. polyethylene glycol dimethyl ether and tetrahydrofuran, and mixtures of these solvents with one another or (and) with water, are also suitable. The reaction of the com-ponents (1) and (2) is preferably carried out in an aqueous medium. The pH in the reaction is usually from 10 to 14, prefer-ably from 10 to 12. For this purpose, it may be necessary to add a base or a mixture of bases during the condensation reaction.
Examples of suitable bases are sodium hydroxide solution, potas-sium hydroxide solution, calcium hydroxide, barium hydroxide and tertiary amines, eg. triethylamine, triethanolamine or tri-n-propylamine. A preferably used base is sodium hydroxide. The con-densation can be carried out continuously or batchwise. In order to prepare particularly high molecular weight condensates, for example, relatively high molecular weight polyethyleneimines, for example those having average molecular weights (Mw) of from 1000 to 10,000, are reacted with bischlorohydrin ethers of poly-alkylene glycols having a molecular weight of from 300 to 6000, preferably from 800 to 1500. Very high molecular weight conden sates are also formed, for example, in the condensation of par tially amidated polyethyleneimines having a molecular weight of at least 500,000 with epichlorohydrin.
Condensates which are obtainable by (1) partial amidation of polyethyleneimines having from 10 to 50,000 ethyleneimine units with monocarboxylic acids and (2) condensation of the partially amidated polyethyleneimines with epichlorohydrin, a,w-bis(chlorohydrin)polyalkylene gly-col ethers, a,w-(glycidyl)ethers of polyalkylene glycols, a,w-dichloropolyalkylene glycols, a,w- dichloroalkanes or vicinal dichloroalkanes or mixtures thereof BASF Aktiengesellschaft 940656 O.Z. 0050/45641 in a weight ratio (1):(2) of from 1:0.01 to 1:3 are particularly preferred. Acetic acid, propionic acid, valeric acid, decanoic acid, benzoic acid, enanthic acid, caprylic acid or distearyl-diketene is preferably used for the amidation of the poly-ethyleneimines.
The protective colloids (a) and (b) are used, for example, in amounts of from 1 to 20% by weight, based on alkyldiketene. The aqueous alkyldiketene dispersions are prepared in a manner known per se in the conventional apparatuses by emulsifying the hydro-phobic components in an aqueous solution of the protective col-loids. Suitable apparatuses are, for example, homogenizers which operate according to the high-pressure flash principle, eg.
LAB 100 from APV Gaulin.
In general, the procedure is such that the solid alkyldiketene is melted and is added to an aqueous solution of the protective col-loids (a) and/or (b) heated to 80-85°C, and the mixture is homo-genized under the action of shear forces. The aqueous solution of the protective colloids is preferably brought to a pH below 7, for example pH 3.5. After homogenization, the emulsion obtained is cooled to ambient temperature so that solid particles of alkyldiketene are present in the form of a dispersion in water.
The pH of the alkyldiketene dispersions is then, for example, from 2 to 4.5. The aqueous alkyldiketene dispersions contain, for example, from 6 to 30, preferably from 10 to 20, % by weight of a C14-Cz2-alkyldiketene and from 1 to 10, preferably from 1 to 3, %
by weight of a protective colloid (a) and/or (b).
In the preparation of the alkyldiketene dispersion, the assis-tants usually used in the preparation of such dispersions may be present, for example conventional protective colloids, such as cationic starch, sorbitan esters, anionic or nonionic emulsi-fiers, naphthalene/formaldehyde/sulfonic acid condensates and carboxylic acids. These assistants, which are usually present in alkyldiketene dispersions, are used in the novel dispersions only in amounts such that the stability of the dispersion is not ad-versely affected as a result.
The novel aqueous alkyldiketene dispersions have particular ad-vantages with respect to the shelf life and stability to. shearing compared with the known starch-containing alkyldiketene disper-sions. They also have the advantage that the papers sized with the novel alkyldiketene dispersions display virtually the com-plete sizing effect immediately after production and require virtually no maturing time as is the case with the known alkyldi-ketene dispersions. Rapid development of the sizing effect is BASF Aktiengesellschaft 940656 O.Z. 0050/45641 particularly important for paper machines having an integrated coating unit because immediate sizing of the paper is required before the application of the paper coating slip. The novel aqueous alkyl-di.ketene dispersions are used as engine sizes in the production of paper, board and carboard and for rendering cellulosic fibers water-repellent. Compared with the known alkyl-diketene dispersions, the novel aqueous alkyldiketene dispersions exhibit virtually quantitative retention to the paper fibers.
They also have an excellent sizing effect even in paper stocks which contain considerable amounts of interfering substances.
Such interfering substances originate partly from recycled waste paper.
The novel alkyldiketene dispersion can be used for the production of all paper, board and cardboard qualities, for example liners, papers for letterpress/offset printing, medium writing and print-ing papers, natural gravure papers and light-weight coating papers. The main raw materials used for the production of such papers are sulfite and sulfate pulp, each of which may be short-fiber or long-fiber, groundwood, thermomechanical pulp (TMP), chemothermomechanical pulp (CTMP) and pressure groundwood (PGW).
It is also possible to use various waste paper qualities, alone or as a mixture with one or more of the abovementioned raw mate-rials. Other suitable raw materials for the preparation of the pulp are chemical pulp and mechanical pulp which is further pro-cessed to paper in the integrated mills in a more or less moist form directly without prior thickening or drying and, owing to the impurities from the digestion which have not been completely removed, still contains substances which greatly interfere with the conventional papermaking process. The aqueous alkyldiketene dispersions can be used as engine size in the production of both filler-free papers and filler-containing papers. The filler con-tent of the paper may be up to 30% by weight and, if filler-con-taining papers are produced, preferably from 5 to 25% by weight.
Suitable fillers are, for example, clay, kaolin, chalk, talc, ti-tanium dioxide, calcium sulfate, barium sulfate, alumina, satin white and mixtures of the stated fillers.
In the examples which follow, parts and percentages are by weight. The K values of the polymers were determined according to H. Fikentscher, Cellulose-Chemie 13 (1932) 58-64 and 71-74, in 0.5 M aqueous sodium chloride solution at a polymer concentration of 0.1% by weight and at 25°C.

BASF Aktiengesellschaft 940656 O.Z. 0050/45641 Example 1 215 g of an anhydrous polyethyleneimine which contains 460 ethyleneimine units is reacted with 6.1 g of benzoic acid at 5 from 150 to 180°C in the course of 10 hours. The reaction mixture is then cooled and taken up in water. A 2% strength aqueous solu tion of the polyethyleneimine amidated with benzoic acid is pre pared, the solution is heated to 80°C and the pH is brought to 4 by adding acetic acid. A stearyldiketene melt is added to the 10 solution so that the stearyldiketene content of the prepared dis-persion is 10%, and the mixture is homogenized by the action of high shear forces in a homogenizer. The homogenizer used is an apparatus from APV Gaulin. After 2 cycles, the resulting aqueous stearyldiketene dispersion is cooled to room temperature in the course of about 2 minutes.
Example 2 172 g of an anhydrous polyethyleneimine which contains 500 ethyleneimine units is mixed with 48.2 g of decanoic acid and heated at from 150 to 180°C for 10 hours. A polyethyleneimine par-tially amidated with decanoic acid is obtained. This is converted into a 2% strength aqueous solution. 1275 g of the 2% solution of the polyethyleneimine partially amidated with decan-oic acid are heated to 80°C. Acetic acid is then added in an amount such that the solution has a pH of 4. A stearyldiketene melt is then added to the solution in an amount such that the stearyldiketene con-tent of the mixture is 15%. The hot mixture is then processed to a stearyldiketene dispersion in the homogenizer described in Ex-ample 1, by the action of high shear forces. After 2 cycles, the stearyldiketene dispersion is cooled to room temperature in the course of 1 minute.
Example 3 220 g of an anhydrous polyethyleneimine which contains 35 ethyl-eneimine units is partially amidated with 38 g of propionic acid at from 150 to 180°C in the course of 24 hours. The reaction mix-ture is then cooled, taken up in water and thus processed to a solution having a solids content of 25%.
1350 g of a 2.5% strength aqueous solution of the polyethylenei-mine partially amidated with propionic acid are heated to 80°C.
Acetic acid is added in an amount such that the pH of the solu-tion is 4. A stearyldiketene melt which is at 85°C is then added to the aqueous solution in an amount such that the mixture con-tains 10% of stearyldiketene. This mixture is processed to an BASF Aktiengesellschaft 940656 O.Z. 0050/45641 aqueous stearyldiketene emulsion in the apparatus described in Example 1 by the action of high shear forces. After 2 cycles; the resulting emulsion is cooled to room temperature in the course of minutes. A stable, aqueous stearyldiketene dispersion is ob-5 tained.
Example 4 172 g of an anhydrous polyethyleneimine which contains 500 poly-merized ethyleneimine units is circulated with 34.2 g of benzoic acid at from 150 to 180°C in the course of 8 hours. The reaction mixture is then cooled, taken up in water and brought to a solids content of 24.1%. 81 ml of a 22% strength aqueous solution of the bis(chlorohydrin)polyethylene oxide having 10 ethylene oxide units are then added and the reaction mixture is heated to 70°C
while continuously monitoring the viscosity. As soon as the reac-tion mixture has a viscosity of 416 mPa.s (determined at 20°C and at a concentration of 19.1%), the crosslinking reaction is ter-minated. The crosslinked, amidated polyethyleneimine is then pro-cessed to a 2% strength aqueous solution.
1320 g of the 2% strength aqueous solution of the amidated, crosslinked polyethyleneimine are heated to 80°C and brought to a pH of 4 by adding acetic acid. An alkyldiketene melt heated to 85°C is then added in an amount such that a mixture containing 12%
of alkyldiketene is formed. This mixture is processed to a dis-persion by the action of high shear forces. After 2 cycles, the resulting dispersion is cooled to room temperature in the course of 4 minutes.
Example 5 1350 g of a 2.5% strength aqueous solution of a copolymer of 70%
of vinylpyrrolidone and 30% of vinylimidazole quaternized with methyl chloride are heated to 80°C and brought to a pH of 4 by ad-ding acetic acid. The copolymer has a K value of 45 and a charge density of about 2 meq/g. An alkyldiketene melt heated to 85°C is then added in an amount such that a mixture which contains 10% of alkyldiketene is formed. This mixture is then processed to a ho-mogeneous dispersion by the action of high shear forces by allow-ing it to run twice through a homogenizer and, after the final cycle, is cooled to room temperature in the course of 3 minutes.

BASF Aktiengesellschaft 940656 O.Z. 0050/45641 Example 6 1320 g of a 2% strength aqueous solution of a copolymer of 55% of N-vinylpyrrolidone and 45% of vinylimidazole quaternized with methyl chloride are heated to 80°C and brought to a pH of 4 by ad-ding acetic acid. The copolymer has a K value of 75 and a charge density of about 3 meq/g. An alkyldiketene melt heated to 85°C is then added to the aqueous solution in an amount such that a mix-ture which contains 12% of alkyldiketene is formed. This mixture is then homogenized by the action of high shear forces by allow-ing it to run twice through a homogenizer. After the second cycle, the resulting finely divided dispersion is cooled to room temperature in the course of 5 minutes.
Example 7 258 g of an anhydrous polyethyleneimine which contains 420 ethyleneimine units is mixed with 43.7 g of valeric acid and heated at 150-180°C for 8 hours, water being continuously dis-tilled off from the reaction mixture. After cooling, the reaction product is taken up in water and the solids content of the solu-tion is brought to 25%. 75 g of a 22% strength aqueous solution of a bis(chlorohydrin)polyethylene oxide having 10 ethylene oxide units are then added and the reaction mixture is heated until the viscosity (measured at 20°C and 21.6% concentration) is 790 mPa.s.
A 2% strength aqueous solution of the crosslinked condensate de-scribed above is heated to 80°C and brought to a pH of 4 by adding acetic acid. A stearyldiketene melt is then added to the aqueous solution in an amount such that the stearyldiketene content of the mixture is 12%. The mixture is then homogenized, as described in Example 1, by the action of high shear forces and is cooled in the course of 2 minutes.
The efficiency of the novel alkyldiketene dispersions as engine size is tested in Examples 8 and 9 on two different stock models.
The Cobb water absorption according to DIN 53 132 and the ink floatation time (minutes) according to DIN 53 126 are determined.
Stock model I
40 parts of chalk are used per 100 parts of wood-free birch sul-fate pulp. The concentration of birch sulfate pulp in the paper stock is 1.0%, based on dry fiber. The pH of the stock suspension is brought to 7Ø The stock mixture is beaten to a freeness of 35°SR (Schopper-Riegler), and 0.025%, based on dry fiber, of a BASF Aktiengesellschaft 940656 O.Z. 0050/45641 commercial retention aid based on a high molecular weight acryl-amide is added.
Stock model II
Waste paper stock comprising a mixture of 50 parts of newsprint and 50 parts of cardboard waste. The waste paper stock is only disintegrated but not beaten. The stock concentration is 1.0%, based on dry fiber. The pH of the paper stock is 7Ø 0.025%, based on dry fiber, of a commercial retention aid based on a high molecular weight polyacrylamide is added to the stock suspension.
Example 8 Sheets having a basis weight of 80 g/m2 are produced on a Rapid Kothen sheet former, using in each case the amounts, stated in Table 1, of stearyldiketene dispersion obtained according to Ex-ample 3.
The sizing effect is measured after conditioning of the sheets at 23'C and 50% relative humidity, 24 hours after production. The re-sults are shown in Table 1.
Sheets having a basis weight of 80 g/m2 are produced for compari-son, a commercial stearyldiketene dispersion which contains 2% of cationic starch as a protective colloid being added to the two stock suspensions I and II, in the amounts stated in Table 1. The sheets are then conditioned and tested as described above. The size values found are shown in Table 1.

BASF Aktiengesellschaft 940656 O.Z. 0050/45641 Table 1 Ex. Stock Stearyl- Paper sized 8 with model diketene, Stearyldiketene dispersion according used based on to dry fiber [%] Ex. 3 Comparison Ex. 3 Comparison Cobb values [g/m2]
Ink floatation time [min]

a) I 0.07 31 29 6 2 b) I 0.085 30 27 26 11 c) I 0.1 27 27 60 60 d) II 0.1 104 112 0 0 e) II 0.15 34 58 23 19 f) II 0.2 27 25 47 37 Example 9 A paper having a basis weight of 80 g/m2 is produced on an exper-imental paper machine having a working width of 75 cm at a speed of 80 m/min. The stock is composed of 40 parts of TMP, 30 parts of bleached birch sulfate pulp, 30 parts of bleached pine sulfate pulp, 15 parts of chalk, 0.8% of starch soluble in cold water and 0.02%, based on dry fiber, of a commercial high molecular weight polyacrylamide. The increasing amounts, stated in Table 2, of 12%
strength stearyldiketene dispersion obtained according to Example 7 are added to the paper stock.
Examples a) to g) are repeated for comparison with a commercial 12% strength stearyldiketene dispersion which contains 3% of ca-tionic starch as a protective colloid. Samples of the paper are tested directly after production and after conditioning for 24 hours under the conditions stated in Example 8. The results are shown in Table 2.

BASF Aktiengesellschaft 940656 O.Z. 0050/45641 Table 2 Ex. 12% strength Cobb [g/m2]
9 values stearyldiketene directly 24 h 5 dispersion, based after of production the paper with on dry fiber stearyldiketene dispersion according [%] to Ex. 7 Ex. 7 Comparison. Comparison.

a) 0.5 53 122 29 95 b) 0.75 33 116 23 41 c) 1.0 32 103 22 25 d) 1.25 27 103 21 23 15 e) 1.5 25 102 20 23 f) 1.75 24 90 20 22, g) 2.0 26 73 21 21

Claims (4)

We claim:

1. An aqueous alkyldiketene dispersion which contains a C14-C22-alkyldiketene and from 1 to 10% by weight of a poly-meric protective colloid, wherein said dispersion contains, as the protective colloid, (a) copolymers of (1) N-vinylpyrrolidone and (2) at least one quaternized N-vinylimidazole of the for-mina where R, R1 and R2 are each H, C1-C4-alkyl or phenyl, R3 is H, C1-C18-alkyl or benzyl and X~ is an anion, the copolymers containing the monomers (1) and (2) as polymerized units in a molar ratio of from 80:20 to 5:95 and having a K value of at least 20 (determined according to H. Fikentscher in 0.5 M aqueous sodium chloride solu-tion at a polymer concentration of 0.1% by weight and at 25°C), or (b) condensates which are obtained by (1) partial amidation of polyethyieneimines with mono-carboxylic acids and (2) condensation of the partially amidated polyethylene-imines with at least bifunctional crosslinking agents which have a halohydrin, glycidiyl, aziridine or iso-cyanate unit or a halogen atom as a functional group to give crosslinked amidated polyethyleneimines which nave a viscosity of at least 100 mPa.s in 20%
strength by weight aqueous solution at 20°C, or mixtures of (a) and (b).

2. An aqueous alkyldiketene dispersion as claimed in claim 1, which contains, as protective colloid (a), copolymers of (1) N-vinylpyrrolidone and (2) quaternized N-vinylimidazole or quaternized 2-meth-yl-1-vinylimidazole.

3. An aqueous alkyldiketene dispersion as claimed in claim 1, which contains, as protective colloid (b), condensates which are obtained by (1) partial amidation of polyethyleneimines having 10 to 50,000 ethyleneimine units with monocarboxylic acids and, if required (2) condensation of the partially amidated polyethyleneimines with epichlorohydrin, .alpha.,.omega.-bis(chlorohydrin)polyalkylene glycol ethers, .alpha.,.omega.-bis(glycidyl) ethers of polyalkylene glycols, .alpha.,.omega.-dichloropolyalkylene glycols, .alpha.,.omega.-di-chloroalkanes or vicinal dichloroalkanes or mixtures thereof in a weight ratio (1):(2) of from 1:0.01 to 1:3.

4. Use of an aqueous alkyldiketene dispersion as claimed in any one of claims 1 to 3 as engine size in the production of paper, board and cardboard and for rendering cellulosic fibers water-repellent.