WO2006106108A1

WO2006106108A1 - Expansion-retarded super-absorbent foam, method for its production and use thereof

Info

Publication number: WO2006106108A1
Application number: PCT/EP2006/061317
Authority: WO
Inventors: Antje Ziemer; Andreas Popp; Anna Kowalski; Ernst Jürgen BAUER
Original assignee: Basf Aktiengesellschaft
Priority date: 2005-04-05
Filing date: 2006-04-05
Publication date: 2006-10-12

Abstract

The invention relates to a super-absorbent foam, which has been aftertreated with a complexation agent and/or expansion retarder. Said super-absorbent foam can be obtained by treating a known super-absorbent foam with complexation agents and/or expansion retarders. Said foams can be used as a storage layer in sanitary articles.

Description

Source-retarded superabsorbent foam, process for its preparation and its use

description

The invention relates to a superabsorbent foam which is delayed in swelling. This superabsorbent foam is obtainable by treating a known superabsorbent foam with source retardant. These foams can be used, for example, as "storage layers" in sanitary articles or generally to absorb, transfer or store aqueous liquids Superabsorbent materials are known For such materials, terms such as "high-swellable polymer" "hydrogel" (often also for the dry Form), "hydrogel-forming polymer", "water-absorbent polymer", "absorbent gelling material", "swellable resin", "water-absorbent resin" or the like.

Further embodiments of the present invention can be taken from the claims, the description and the examples. It goes without saying that the features mentioned above and those still to be explained below of the article according to the invention can be used not only in the respectively indicated combination but also in other combinations without departing from the scope of the invention.

Water-absorbing foams based on monomers containing crosslinked acid groups are known, cf. EP 858 478 B1, WO 97/31971 A1, WO 99/44648 A1 and WO 00/52087 A1. They are prepared, for example, by foaming a polymerizable aqueous mixture containing at least 50 mol% neutralized, monoethylenically unsaturated monomers containing acid groups, crosslinkers and at least one surfactant, and then polymerizing the foamed mixture. The foaming of the polymerizable mixture can be carried out, for example, by dispersing fine bubbles of a radical-inert gas or by dissolving such a gas under elevated pressure in the polymerizable mixture and depressurizing the mixture. The water content of the foams is adjusted to, for example, 1 to 60% by weight. Optionally, the foams may be subjected to surface postcrosslinking by spraying a crosslinking agent onto the foamed material or by dipping the foam therein and heating the crosslinker loaded foam to a higher temperature. The foams are used, for example, in hygiene articles for the acquisition, distribution and storage of body fluids. Carboxymethylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, hydroxypropylcellulose and cellulose mixed ethers are disclosed in these applications as thickeners. These thickeners are not fibers. In addition, superabsorbent fibers are known, which are obtainable, for example, by neutralizing the carboxyl groups of a hydrolyzed copolymer of isobutene and maleic anhydride with sodium hydroxide to 20 to 80%, adding a bifunctional compound which can react with the unneutralized carboxyl groups of the copolymer, for example propylene glycol or ethanolamine, then the water is largely removed from the solution so that the solids content of the solution is 45%. This solution is then spun into fibers. The fibers are then heated to a higher temperature, for example to 21O ⁰ C, the copolymers are cross-linked. The crosslinked copolymers have superabsorbent properties. They are used, for example, in baby diapers, tampons, sanitary napkins, surgical sponges, and body fluid absorption dressings. Such superabsorbent fibers are known, cf. For example, EP 264 208 A2, EP 272 072 A2, EP 436 514 A2 and US 4,813,945.

Foams of water-absorbing basic polymers are known from WO 03/066716 A1, which are obtainable by foaming an aqueous mixture containing at least one basic polymer such as polyvinylamine and at least one crosslinker such as glycidyl ether, and then crosslinking the foamed mixture. The polymerizable foams are added 25 to 200 wt .-% cellulose fibers. The CRC values, as well as the maximum extensibility and elongation at break of the dry, as well as wet, foams are dramatically reduced by the addition of 25 to 200% by weight of cellulose fibers.

WO 03/066717 A2 discloses a process by which the wet strength is increased and the residual monomer content is lowered in the case of superabsorbent foams by the addition of amino-containing polymers. The treatment with these polymers does not lead to a source delay.

WO 2004/007598 A1 discloses water-absorbing foams which have finely distributed hydrophilic silicon dioxide and / or a surface-active substance on the surface. The treatment of the foams leads to an increase in the absorption rate for liquids.

WO 2004/035668 A2 discloses water-absorbing foams which contain superabsorbent fibers or fruit fibers, in particular apple fibers.

German Patent and Trademark Office DE 102005011165.3 describes water-absorbing foams which contain wood fibers or waste paper fibers.

WO 2005/042 039 A2 describes hydrogels which have an increased blood absorption through the coating with hydrophobic compounds. The invention has for its object to improve the properties of water-absorbing foams, especially foams with good Flüssigkeitsabsorpti- ons-, good Flüssigkeitsretentions- and good Flüssigkeitsweiterleitenseigenschaften for aqueous liquids, also for saline aqueous liquids to find the stable, easy to handle, easy to process and easy to make.

The object is achieved according to the invention with superabsorbent foam whose surface has been treated with at least one complexing agent and / or at least one source delaying agent.

In the context of this invention, the "surface" of the foam is understood to be the surface of a foam molding which is accessible to external influences, for example by impregnation with a liquid, but in particular by spraying with a liquid, not the entire inner surface of all the pores of the foam as determined, for example, by the known methods of measuring adsorption isotherms.

In particular, the object is achieved with superabsorbent foams having a swelling time (as described in more detail below in the section on determination methods, the time in which 1.00 ± 0.009 g of foam absorb 20 g of water) greater than 10 seconds, a swelling time greater than 15 seconds, preferably one Swelling time greater than 20 seconds, more preferably a swelling time greater than 30 seconds, most preferably a swelling time greater than 60 seconds, and most preferably a swelling time greater than 120 seconds. This slow swelling property can also be expressed as a low swelling rate. The swelling rate is determined to be 20 [g] / (1 [g] * swelling time [s]), as described in more detail in the section "Methods of Determination." These superabsorbent foams thus have swelling rates of less than 2.0 s- \ less than 1.33 S " ¹ , preferably less than 1, 0 s ^{* 1} , more preferably less than 0.67 s ^~ \ very particularly preferably less than 0.33 s ^-1 and particularly preferably less than 0.17 s ^-1 on.

Superabsorbent foams are known in the art. By superabsorbent foam according to the present invention is meant a foam having a Centrifuge Retention Capacity ("CRC", measuring method described below in the section "Methods of Determination") of at least 3 g / g, preferably at least 4 g / g preferably at least 5 g / g, in particular at least 6 g / g.

The superabsorbent foams according to the invention are conveniently obtainable by foaming an aqueous mixture which, in addition to polymerizable and crosslinkable, acid group-containing monoethylenically unsaturated monomers which are optionally (partially) neutralized, crosslinker and at least one surfactant and optionally containing adjuvants or adjuvants such as solubilizers, thickeners, stabilizers, fillers, fibers and / or cell nucleating agents, and then polymerizing and / or crosslinking the foamed mixture and subsequent treatment with complexing and / or source retarding agents.

In addition, the superabsorbent foams can be conveniently prepared by foaming at least one crosslinkable basic polymer, crosslinker and at least one surfactant and optionally additives or auxiliaries such as solubilizers, thickeners, stabilizers, fillers, fibers and / or cell nucleating agents as a mixture, and then the basic polymers contained in the foamed mixture are crosslinked to form a foam-like hydrogel. Subsequently, the foam is treated with a complexing and / or source retardant. For convenience, when describing measures or properties that are not specific to mixtures containing crosslinkable basic polymers or polymerizable and crosslinkable monomers bearing acid groups, also for mixtures that are crosslinkable basic polymers but not polymerizable and crosslinkable, acid groups containing monomers, also used the term "polymerizable aqueous mixture".

In one embodiment of the invention, an aqueous mixture is foamed, for example

a) from 10 to 80% by weight of acid group-containing monoethylenically unsaturated monomers which have been neutralized to at least 50 mol%, or a basic crosslinkable polymer; b) when using acid groups-carrying monoethylenically unsaturated monomers, optionally additionally up to 50 wt .-% other monoethylenically unsaturated monomers, c) 0.001 to 5 wt .-% crosslinker, d) when using monoethylenically unsaturated monomers, in addition initiators, e) 0, 1 to 20% by weight of at least one surfactant, f) optionally a solubilizer and g) optionally thickeners, foam stabilizers, polymerization regulators, fillers, fibers and / or cell nucleating agents,

contains, in each case based on the total amount of the mixture.

The foaming of the aqueous mixtures can be carried out, for example, by dispersing fine bubbles of a gas which is inert toward free radicals in the mixture, or dissolving such a gas in the crosslinkable mixture under a pressure of from 2 to 400 bar and subsequently depressurizing them to atmospheric pressure. This gives a flowable foam which is filled in molds or cured on a belt can be. The curing takes place in the case of the use of acid group-containing monomers, optionally other monoethylenically unsaturated monomers and crosslinkers by polymerization and in the case of the use of basic polymers with crosslinking.

Foams based on crosslinked, acid group-containing polymers

Foams based on crosslinked, acid group-containing polymers are known from the cited references EP 858 478 B1, page 2, line 55 to page 18, line 22, WO 99/44 648 A1 and WO 00/52 087 A1, page 5, line 23 to page 41, line 18 known. Suitable monoethylenic unsaturated monomers are the monomers and monomer mixtures used to prepare granular superabsorbent. Preferred monomer is acrylic acid and its salts. Other monoethylenically unsaturated monomers are also known from the literature relating to the preparation of granular superabsorbent.

In one embodiment, foams of water-absorbent acidic polymers are used. As water-absorbing acidic polymers, which are also referred to below as acidic superabsorbers, it is possible to use all hydrogels, which are used, for example. in WO 00/63 295 A1, page 2, line 27 to page 9, line 16 are described. These are essentially weakly crosslinked polymers of acidic monomers which have a high water absorption capacity in at least partially neutralized form. Examples of such in each case slightly crosslinked polymers are crosslinked polyacrylic acids, crosslinked, hydrolyzed graft polymers of acrylonitrile on starch, crosslinked graft polymers of acrylic acid on starch, hydrolyzed, crosslinked copolymers of vinyl acetate and acrylic esters, crosslinked polyacrylamides, hydrolyzed, crosslinked polyacrylamides, crosslinked copolymers of ethylene and maleic anhydride , crosslinked copolymers of isobutylene and maleic anhydride, crosslinked polyvinylsulfonic acids, crosslinked polyvinylphosphonic acids and crosslinked sulfonated polystyrene. Preferably used as acidic superabsorbent polymers of (partially) neutralized, slightly crosslinked polyacrylic acids. The (partial) neutralization of the acid groups of the acidic superabsorber is preferably carried out with sodium hydroxide solution, sodium bicarbonate or sodium carbonate. However, the neutralization can also be carried out with potassium hydroxide solution, ammonia, amines or alkanolamines such as ethanolamine, diethanolamine or triethanolamine.

Acid superabsorbents are known from the abovementioned references, cf. in particular WO 00/63 295 A1, page 2, line 27 to page 9, line 16. They can optionally be surface-postcrosslinked, for example, slightly crosslinked polyacrylic acids are reacted with compounds which have at least two groups which are reactive toward carboxyl groups. These are known networks. Of particular interest for use as surface post-crosslinking are, for example, polyhydric alcohols such as propylene glycol, 1,4-butanediol or 1,6-hexanediol and glycidyl ethers of ethylene glycol and polyethylene glycols having molecular weights of 200 to 1500, preferably 300 to 400 daltons, and completely with acrylic acid or methacrylic acid esterified reaction products of trimethylolpropane , reaction products of trimethylolpropane and ethylene oxide in a molar ratio of 1: 1 to 25, preferably 1: 3 to 15 and of reaction products of pentaerythritol with ethylene oxide in a molar ratio of 1: 30, preferably 1: 4 to 20. The postcrosslinking of the surface of the anionic SAPs, if it is carried out, for example, at temperatures up to 22O ⁰ C, for example, preferably carried out at 120 to 19O ⁰ C. Non-surface-postcrosslinked superabsorbents are preferably treated according to the invention with complexing and / or source retarding agents.

Basic polymers

Suitable basic polymers are, for example, polymers containing vinylamine units, polymers containing vinylguanidine units, polymers comprising dialkylaminoalkyl (meth) acrylamide units, polyethyleneimines, polyamidoamines grafted with ethyleneimine and polydiallyldimethylammonium chlorides.

Vinylamine containing polymers are known, cf. US 4,421,602,

US 5,334,287, EP 216 387 A2, US 5,981,689, WO 00/63 295 A1 and US 6,121,409. They are prepared by hydrolysis of open-chain polymers containing N-vinylcarboxamide units. These polymers are e.g. obtainable by polymerizing N-vinylformamide, N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide and N-vinylpropionamide. The monomers mentioned can be polymerized either alone or together with other monomers.

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 ethers. Further suitable comonomers are esters, amides and nitriles of ethylenically unsaturated C 3 to C ₆ - carboxylic acids such as methyl acrylate, methyl methacrylate, ethyl methacrylate and e, acrylamide and methacrylamide, and acrylonitrile and methacrylonitrile.

Further suitable carboxylic acid esters are derived from glycols or polyalkylene glycols, in each case only one OH group esterified, for example hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate and acrylic acid monoesters of polyalkylene glycols having a molecular weight of 500 to 10,000 daltons. Further suitable comonomer esters of ethylenically unsaturated carboxylic acids with aminoalcohols, such as, for example, 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, such. 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, such as e.g. N-vinyl-2-methylimidazole, N-vinyl-4-methylimidazole, N-vinyl-5-methylimidazole, N-vinyl-2-ethylimidazole and N-vinylimidazolines such as N-vinylimidazoline, N-vinyl-2-methylimidazoline and N- vinyl-2-ethylimidazoline. N-vinylimidazoles and N-vinylimidazolines are used except in the form of the free bases also in mineral acids or organic acids neutralized or quaternized form, wherein the Qύaternisierung is preferably carried out with dimethyl sulfate, diethyl sulfate, methyl chloride or benzyl chloride. Also suitable are diallyldialkylammonium halides, e.g. Diallyldimethylammonium chloride.

The copolymers contain, for example

From 95 to 5 mol%, preferably from 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. 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-vinylurea, N-vinylpyrrolidone or Ci- to Cβ-alkyl vinyl ethers

and subsequent hydrolysis of the homo- or copolymers to form vinylamine units from the copolymerized N-vinylformamide units, the degree of hydrolysis being e.g. 5 to 100 mol%, 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 hydrolysis agents, the vinylamine units of the polymers are present as the ammonium salt, while free hydrolyses with bases result in free amino groups. ,

The homopolymers of the N-vinylcarboxamides and their copolymers may be hydrolyzed to 5 to 100, preferably 70 to 100 mol%. In most cases, the degree of hydrolysis of the homopolymers and copolymers is 80 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 homo- and copolymers containing vinylamine moieties may optionally contain up to 20 mole% of amidine units, e.g. by reaction of formic acid with two adjacent amino groups or by intramolecular reaction of an amino group with an adjacent amide group, e.g. of polymerized N-

Vinylformamide is formed. The molar masses of polymers containing vinylamine units are, for example, 500 to 10 million daltons, preferably 1000 to 5 million (determined by light scattering). This molar mass range corresponds, for example, to K values of 5 to 300, preferably 10 to 250 (determined according to H. Fikentscher in 5% aqueous common salt solution at 25 ^° C., pH 7 and a polymer concentration of 0.5% by weight, as in H Fikentscher, Cellulose Chemistry, Vol. 13, 52-63 and 71-74 (1932)).

The polymers containing vinylamine units are preferably used in salt-free form. Salt-free aqueous solutions of polymers comprising vinylamine units can be prepared, for example, from the salt-containing polymer solutions described above by means of ultrafiltration on suitable membranes at separation limits of, for example, 1000 to 500,000 daltons, preferably 10,000 to 300,000 daltons. The aqueous solutions of other polymers containing amino and / or ammonium groups described below can also be obtained by means of ultrafiltration in salt-free form.

Derivatives of polymers containing vinylamine units can also be used as basic hydrogel-forming polymers. It is thus possible, for example, to prepare a multiplicity of suitable hydrogel 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 context are uncrosslinked polyvinylguanidines which are obtained by reaction of polymers comprising vinylamine units, preferably polyvinylamines, with cyanamide (R ¹ R ² N-CN, where R ¹ , R ² = H, C ¹ to C ₄ -alkyl, C ₃ - to C ₆ -cycloalkyl, phenyl, benzyl, alkyl-substituted phenyl or naphthyl), cf. US 6,087,448, column 3, line 64 to column 5, line 14.

The polymers containing vinylamine units also include hydrolyzed graft polymers of, for example, N-vinylformamide on polyalkylene glycols, 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.

For the preparation of water-absorbing basic polymers are also polymers of dialkylaminoalkyl (meth) acrylamides into consideration. Suitable monomers for the preparation of such polymers are, for example, dimethylaminoethylacrylamide, dimethylaminoethylmethacrylamide, dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide, diethylaminoethylacrylamide, diethylaminoethylmethacrylamide and diethylaminopropylacrylamide. These monomers can be used in the form of the free bases, the salts with inorganic or organic acids or in quaternized form in the polymerization. They can be radically polymerized into homopolymers or together with other copolymerizable monomers to form copolymers. The polymers contain, for example, at least 30 mol%, preferably at least 70 mol% of the stated basic monomers in copolymerized form. Water-absorbing basic polymers based on poly (dimethylaminoalkylacrylamides) are known from US Pat. No. 5,962,578. Other suitable basic polymers are polyethyleneimines which can be prepared, for example, by polymerization of ethyleneimine in aqueous solution in the presence of acid-releasing compounds, acids or Lewis acids as catalyst. Polyethyleneimines have, for example, molar masses of up to 2 million daltons, preferably from 200 to 1,000,000. Particular preference is given to using polyethyleneimines having molar masses of from 500 to 750,000 daltons. The polyethyleneimines can be optionally modified, for example alkoxylated, alkylated or amidated. They may also be subjected to further reactions such as a Michael addition. The derivatives of polyethyleneimines which can be obtained are likewise suitable as basic polymers for the preparation of water-absorbing basic polymers.

Also contemplated are ethyleneimine-grafted polyamidoamines which are obtainable, for example, by condensing dicarboxylic acids with polyamines and then grafting ethyleneimine. Suitable polyamidoamines are obtained, for example, by reacting dicarboxylic acids having 4 to 10 carbon atoms with polyalkylenepolyamines which contain 3 to 10 basic nitrogen atoms in the molecule. Examples of dicarboxylic acids are succinic acid, maleic acid, adipic acid, glutaric acid, suberic acid, sebacic acid or terephthalic acid. In the preparation of the polyamidoamines it is also possible to use mixtures of dicarboxylic acids, as well as mixtures of several polyalkylenepolyamines. Suitable polyalkylenepolyamines are, for example, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenetriamine, tripropylenetetramine, dihexamethylenetriamine, aminopropylethylenediamine and bisaminopropylethylenediamine. The dicarboxylic acids and polyalkylenepolyamines are heated to higher temperatures, for example to temperatures in the range of 120 to 220, preferably 130 to 18O ⁰ C, to produce the polyamidoamines. The water formed during the condensation is removed from the system. In the condensation, it is also possible optionally to use lactones or lactams of carboxylic acids having 4 to 8 carbon atoms. For example, from 0.8 to 1.4 moles of a polyalkylenepolyamine are used per mole of a dicarboxylic acid. These polyamidoamines are grafted with ethyleneimine. The grafting reaction is carried out for example in the presence of acids or Lewis acids, such as sulfuric acid or boron trifluoride etherates at temperatures of for example 80 to 100 ⁰ C. Compounds of this type are described for example in DE 24 34 816 A1. Also optionally crosslinked polyamidoamines, which are optionally additionally grafted prior to crosslinking with ethyleneimine, are suitable as basic polymers. The crosslinked, with ethyleneimine grafted polyamidoamines are water-soluble and have, for example, an average molecular weight of 3000 to 2 million daltons. Typical crosslinkers are, for example, epichlorohydrin or bischlorohydrin ethers of alkylene glycols and polyalkylene glycols. As basic polymers are also polyallylamines into consideration. Polymers of this type are obtained by homopolymerization of allylamine, preferably in acid-neutralized form, or by copolymerizing allylamine with other monoethylenically unsaturated monomers described above as comonomers for N-vinylcarboxamides.

Also suitable are water-soluble crosslinked polyethyleneimines which are obtainable by reaction of polyethyleneimines with crosslinkers such as epichlorohydrin or bischlorohydrin ethers of polyalkylene glycols having 2 to 100 ethylene oxide and / or propylene oxide units and still have free primary and / or secondary amino groups. Amidic polyethyleneimines which are obtainable, for example, by amidation of polyethyleneimines with C 1 to C 22 monocarboxylic acids are also suitable. Further suitable cationic polymers are alkylated polyethyleneimines and alkoxylated polyethyleneimines. In the alkoxylation, e.g. per NH unit in the polyethyleneimine 1 to 5 ethylene oxide or propylene oxide units.

The above-mentioned basic polymers have e.g. K values of 8 to 300, preferably 15 to 180 (determined according to H. Fikentscher in 5% aqueous saline solution at 25% and a polymer concentration of 0.5 wt .-%). At a pH of 4.5, for example, they have a charge density of at least 1, preferably at least 4 meq / g polyelectrolyte.

Preferred basic polymers are polymers containing vinylamine units, polyvinylguanidines and polyethyleneimines. Examples for this are:

Vinylamine homopolymers, 10 to 100% hydrolyzed polyvinylformamides, partially or completely hydrolyzed copolymers of vinylformamide and vinyl acetate, vinyl alcohol, vinylpyrrolidone or acrylamide, each having molecular weights of 3,000 to 2,000,000 DaIton (= g / mol), and polyethyleneimines, crosslinked polyethyleneimines or amidated polyethyleneimines each having molecular weights of from 500 to 3,000,000 daltons.

The polymer content of the aqueous solution is for example 1 to 60, preferably 2 to 15 and usually 5 to 10 wt .-%.

Other monomers

A polymerizable aqueous mixture may contain other ethylenically unsaturated monomers in addition to monomers carrying acid groups. Suitable ethylenically unsaturated monomers are, for example, acrylamide, methacrylamide, crotonamide, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylamino-propyl acrylate, diethylaminopropyl acrylate, dimethylaminobutyl acrylate, dimethylamino noethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoneopentyl acrylate and dimethylaminoneopentyl methacrylate.

crosslinkers

In order to obtain water-absorbing basic polymers from the above-described basic polymers, they are reacted with at least one crosslinker. The basic polymers are mostly water-soluble or readily dispersible in water. The crosslinking therefore takes place mainly in an aqueous medium. Preference is given to using aqueous solutions of basic polymers which are desalinated, for example by means of ultrafiltration, or whose content of neutral salts is less than 1 or less than 0.5% by weight. In the production of foams by polymerization of monomers carrying acid groups, crosslinking takes place by copolymerization of the crosslinker added to the monomer solution. The crosslinkers have at least two reactive groups which react with the amino groups of the basic polymers or are incorporated into the polymer chains of the polymers formed from the acid group-carrying monomers to form insoluble products which are water-absorbing polymers. For 1 part by weight of the polymer, for example, 0.1 to 50, preferably 1 to 5 parts by weight and in particular 1, 5 to 3 parts by weight of a crosslinking agent. Suitable crosslinkers for both the preparation of crosslinked polymers from acid group-bearing and any other monomers, as well as for the crosslinking of basic polymers are known. Crosslinkers for basic polymers are described, for example, in WO 00/63 295 A1, page 14, line 43 to page 21, line 5.

Suitable bi- or polyfunctional crosslinkers are, for example

(1) Di- and polyepoxides, for example, di- and polyglycidyl compounds

(2) Di- and polyhalogen compounds (3) Compounds having two or more isocyanate groups which may be blocked

(4) polyaziridines

(5) carbonic acid derivatives

(6) compounds with two or more activated double bonds which can undergo a Michael addition (7) di- and polycarboxylic acids and their acid derivatives

(8) monoethylenically unsaturated carboxylic acids, their esters, amides and anhydrides

(9) di- and polyaldehydes and di- and polyketones.

Preferred crosslinkers (1) are, for example, the bischlorohydrin ethers of polyalkylene glycols described in US Pat. No. 4,144,123. Furthermore, phosphoric acid diglycidyl ether and ethylene glycol diglycidyl ether may be mentioned. Further crosslinkers are the reaction products of at least trihydric alcohols with epichlorohydrin to form reaction products which have at least two chlorohydrin units, for example glycerol, ethoxylated or propoxylated glycerols, polyglycerols with 2 to 15 glycerol units in the molecule and optionally ethoxylated alcohols as polyhydric alcohols and / or propoxylated polyglycerols. Crosslinking agents of this type are known, for example, from DE 29 16 356 A1.

Suitable crosslinkers (2) are α, ω or vicinal dichloroalkanes, for example 1, 2-dichloroethane, 1, 2-dichloropropane, 1, 3-dichlorobutane and 1,6-dichlorohexane.

Furthermore, EP 25 515 A1 discloses α, ω-dichloropolyalkylene glycols which preferably have 1 to 100, in particular 1 to 100, ethylene oxide units as crosslinkers.

Also useful are crosslinkers (3) containing blocked isocyanate groups, e.g. Trimethylhexamethylene diisocyanate blocked with 2,2,6,6-tetramethylpiperidin-4-one. Such crosslinkers are known, cf. for example from DE 40 28 285 A1.

Also preferred are aziridine-containing crosslinkers (4) based on polyethers or substituted hydrocarbons, e.g. 1, 6-bis-N-aziridinomethane, cf. US Pat. No. 3,977,923. This crosslinker class also includes at least two reaction products of dicarboxylic acid esters containing ethyleneimine containing aziridino groups and also mixtures of the crosslinkers mentioned.

Suitable halogen-free crosslinkers of group (4) are reaction products which are prepared by reacting dicarboxylic acid esters, which are completely esterified with monohydric alcohols having 1 to 5 carbon atoms, with ethyleneimine. Suitable dicarboxylic acid esters are, for example, dimethyl oxalate, diethyl oxalate, dimethyl succinate, diethyl succinate, dimethyl adipate, diethyl adipate and dimethyl glutarate. For example, in the reaction of diethyl oxalate with ethyleneimine, bis [β- (1-aziridino) ethyl] oxalic acid amide is obtained. The dicarboxylic acid esters are reacted with ethyleneimine, for example in a molar ratio of 1 to at least 4. Reactive groups of these crosslinkers are the terminal aziridine groups. These crosslinkers can be characterized, for example, with the aid of the formula: wherein n = 0 to 22.

As crosslinkers (5), ethylene carbonate, propylene carbonate, urea, thiourea, guanidine, dicyandiamide or 2-oxazolidinone and its derivatives may be mentioned by way of example. From this group of monomers it is preferred to use propylene carbonate, urea and guanidine.

Crosslinkers (6) are reaction products of polyether diamines, alkylenediamines, polyalkylenepolyamines, alkylene glycols, polyalkylene glycols or mixtures thereof with monoethylenically unsaturated carboxylic acids, esters, amides or anhydrides of monoethylenically unsaturated carboxylic acids, the reaction products having at least two ethylenically unsaturated double bonds, carboxylic acid amide, carboxyl or ester groups as functional groups, as well as methylenebisacrylamide and divinylsulfone.

Crosslinkers (6) are, for example, reaction products of polyether diamines having preferably 2 to 50 alkylene oxide units, alkylenediamines such as ethylenediamine, propylenediamine, 1,4-diaminobutane and 1,6-diaminohexane, polyalkylenepolyamines having molar masses <5000 daltons, e.g. Diethylenetriamine, triethylenetetramine, dipropylenetriamine, tripropylenetetramine, dihexamethylenetriamine and aminopropylethylenediamine, alkylene glycols, polyalkylene glycols or mixtures thereof with

monoethylenically unsaturated carboxylic acids,

Esters of monoethylenically unsaturated carboxylic acids,

Amides of monoethylenically unsaturated carboxylic acids and

Anhydrides of monoethylenically unsaturated carboxylic acids.

These reaction products and their preparation are described in EP 873 371 A2 and are expressly mentioned as crosslinkers.

Particularly preferred crosslinking agents are the reaction products of maleic anhydride with alpha-omega polyether diamines having a molecular weight of 400 to 5000 daltons, the reaction products of polyethyleneimines having a molecular weight of 129 to 50,000 daltons with maleic anhydride and the reaction products of ethylenediamine or triethylenetetramine with Maleic anhydride in a molar ratio of 1: at least 2.

As crosslinker (6) is preferably used the compounds of formula

in the X, Y, Z = independently of one another O or NH

and Y independently additionally CH ₂

m, n = 0 - 4

p, q = 0-45000

mean,

which are obtainable by reaction of polyether diamines, ethylenediamine and / or polyalkylenepolyamines with maleic anhydride.

Further halogen-free crosslinkers of group (7) are at least dibasic saturated carboxylic acids such as dicarboxylic acids and the salts, diesters and diamides derived therefrom. These compounds can be synthesized, for example, using the formula

X-CO- (CH ₂ ) n -CO-X

in which X = independently of one another OH, OR ¹ or N (R ² ) ₂

R ¹ = Ci to C ₂₂ alkyl,

R ² = H, C 1 -C ₂₂ -alkyl and

n = 0 to 22

mean, be characterized. In addition to the dicarboxylic acids of the abovementioned formula, for example, monoethylenically unsaturated dicarboxylic acids such as maleic acid or itaconic acid are suitable. The esters of the dicarboxylic acids in question are preferably derived from alcohols having 1 to 4 carbon atoms. Suitable dicarboxylic acid esters are, for example, dimethyl oxalate, diethyl oxalate, diisopropyl succinate, diisopropyl succinate, di-n-propyl succinate, succinate, dimethyl adipate, diethyl adipate and diisopropyl adipate or Michael addition products of polyether diamines, polyalkylene polyamines or at least 2 ester groups Ethylenediamine and esters of acrylic acid or methacrylic acid, each with monovalent 1 to 4 C Atoms containing alcohols. Suitable esters of ethylenically unsaturated dicarboxylic acids are, for example, dimethyl maleate, diethyl maleate, diisopropyl maleate, dimethyl itaconate and itaconic diisopropyl ester. Also suitable are substituted dicarboxylic acids and their esters such as tartaric acid (D, L-form and as racemate) and tartaric acid esters such as dimethyl tartrate and diethyl tartrate.

Suitable dicarboxylic acid anhydrides are, for example, maleic anhydride, itaconic anhydride and succinic anhydride. Further suitable crosslinkers (7) are dimethyl maleate, diethyl maleate and maleic acid, for example. The crosslinking of amino-containing compounds with the abovementioned Vernetzem takes place to form amide groups or amides such as adipamide by transamidation. Maleic acid esters, monoethylenically unsaturated dicarboxylic acids and their anhydrides can bring about crosslinking both by formation of carboxamide groups and by addition of NH groups of the component to be crosslinked (for example polyamidoamines) in the manner of a Michael addition.

The at least dibasic saturated carboxylic acids of crosslinker class (7) include, for example, tri- and tetracarboxylic acids such as citric acid, propanetricarboxylic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, butanetetracarboxylic acid and diethylenetriaminepentaacetic acid. Further, as the crosslinker of the group (7), there are derived the salts, esters, amides and anhydrides derived from the above-mentioned carboxylic acids. Dimethyl tartrate, diethyl tartrate, dimethyl adipate, diethyl adipate.

Suitable crosslinkers of group (7) are also polycarboxylic acids obtainable by polymerizing monoethylenically unsaturated carboxylic acids, anhydrides, esters or amides. As monoethylenically unsaturated carboxylic acids are e.g. Acrylic acid, methacrylic acid, fumaric acid, maleic acid and / or itaconic acid into consideration. Thus, as crosslinkers, e.g. Polyacrylic acids, copolymers of acrylic acid and methacrylic acid or copolymers of acrylic acid and maleic acid. As comonomers its vinyl ethers, vinyl formate, vinyl acetate and vinyl lactam exemplified.

Other suitable crosslinkers (7) are prepared, for example, by radical polymerization of anhydrides such as maleic anhydride in an inert solvent such as toluene, xylene, ethylbenzene, isopropylbenzene or solvent mixtures. In addition to the homopolymers, copolymers of maleic anhydride are suitable, for example copolymers of acrylic acid and maleic anhydride or copolymers of maleic anhydride and a C ₃ - to C ₃ -olefin. Preferred crosslinkers (7) are, for example, copolymers of maleic anhydride and isobutene or copolymers of maleic anhydride and diisobutene. The copolymers containing anhydride groups may optionally be modified by reaction with C 1 to C 20 alcohols or ammonia or amines and used in this form as crosslinking agent.

Preferred polymeric crosslinkers (7) are, for example, copolymers of acrylamide and acrylic esters, such as, for example, hydroxyethyl acrylate or methyl acrylate, wherein the molar ratio of acrylamide and acrylic ester may vary from 90:10 to 10:90. In addition to these copolymers terpolymers are also used, for example, combinations of acrylamide, methacrylamide, acrylic esters or methacrylic esters can be used.

The molecular weight M _{w of} the homopolymers and copolymers suitable as crosslinkers is, for example, up to 10,000, preferably 500 to 5,000 daltons. Polymers of the abovementioned type are described, for example, in EP 276 464 A2, US Pat. No. 3,810,834, GB 1 411 063 A and US Pat. No. 4,818,795. The at least dibasic saturated carboxylic acids and the polycarboxylic acids can also be used as crosslinkers in the form of the alkali metal or ammonium salts. Preferably, the sodium salts are used. The polycarboxylic acids may be partially, for example 10 to 50 mol% or completely neutralized.

Suitable halogen-free crosslinkers of group (8) are e.g. monoethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid and the amides, esters and anhydrides derived therefrom. The esters can be derived from alcohols having 1 to 22, preferably 1 to 18, carbon atoms. The amides are preferably unsubstituted, but may carry a C 1 -C 22 -alkyl radical as substituent.

Preferably used crosslinkers (8) are acrylic acid, methyl acrylate, ethyl acrylate, acrylamide and methacrylamide.

Suitable halogen-free crosslinkers of group (9) are, for example, dialdehydes or their semiesters or acetals as precursors, for example glyoxal, methylglyoxal, malondialdehyde, succinic dialdehyde, maleic and fumaric dialdehyde, tartaric dialdehyde, adipindialdehyde, 2-oxadipindialdehyde, furan-2 , 5-dipropionaldehyde, 2-formyl-2,3-dihydropyran, glutaric dialdehyde, pimelic acid aldehyde and aromatic dialdehydes such as terephthalaldehyde, o-phthalaldehyde, pyridine-2,6-dialdehyde or phenylglyoxal. However, it is also possible to use homopolymers or copolymers of acrolein and / or methacrolein with molar masses of from 114 to about 10,000 daltons. In principle, all water-soluble compounds can be used as comonomers, for example acrylamide, vinyl acetate and acrylic acid. Likewise suitable as crosslinkers are aldehyde starches. Examples of suitable halogen-free crosslinkers of group (9) are diketones or the corresponding halides or ketals as precursors, for example β-diketones, such as acetylacetone or cycloalkane-1, n-diones, for example cyclopentane-1, 3-dione and cyclohexane-1,4 -dione. But it can also be homopolymers or copolymers of

Methyl vinyl ketone having molecular weights of 140 to about 15,000 daltons can be used. In principle, all water-soluble monomers can be used as comonomers, for example acrylamide, vinyl acetate and acrylic acid.

It is of course also possible to use mixtures of two or more crosslinkers.

Preferred crosslinkers used are glycidyl ethers of alkylene glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol and polyalkylene glycols having molecular weights of up to 1,500 daltons, and the adducts of from 1 to 25 mols completely esterified with acrylic acid and / or methacrylic acid , preferably 2 to 15 moles of ethylene oxide with 1 mole of trimethylolpropane, glycerol or pentaerythritol.

initiators

Particularly suitable polymerization initiators are water-soluble azo initiators, e.g. B ..

As initiators of the polymerization reaction, all compounds decomposing into free radicals under the polymerization conditions can be used, e.g. As peroxides, hydroperoxides, hydrogen peroxide, persulfates, azo compounds and the so-called redox initiators, as well as any other known method for generating radicals, for example, high-energy radiation such as UV light. Preference is given to the use of water-soluble initiators or UV light. In some cases, it is advantageous to use mixtures of different polymerization initiators, for. B. mixtures of hydrogen peroxide and sodium or potassium peroxodisulfate. Mixtures of hydrogen peroxide and sodium peroxodisulfate can be used in any proportion. Suitable organic peroxides are, for example, acetylacetone peroxide, methyl ethyl ketone peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, tert-amyl perpivalate, tert-butyl perpivalate, tert-butylpemeohexanoate, tert-butyl perisobutyrate, tert-butyl per-2-ethylhexanoate, tert-butyl perisononanoate , tert.

Butyl permaleate, tert-butyl perbenzoate, di- (2-ethylhexyl) peroxydicarbonate, dicyclohexyl peroxydicarbonate, di- (4-tert-butylcyclohexyl) peroxydicarbonate, dimyristil peroxydicarbonate, diacetyl peroxydicarbonate, allyl perester, cumyl peroxyneodecanoate, tert-butyl peroxide carbonate. 3,5,5-tri-methylhexanoate, acetylcyclohexylsulfonyl peroxide, dilauryl peroxide, dibenzoyl peroxide and tert-amylperneodecanoate. Other suitable polymerization initiators are azo initiators, e.g. 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis (N, N-dimethylene) isobutyramidine dihydrochloride, 2- (carbamoylazo) isobutyronitrile, 2,2'- Azobis [2- (2'-imidazoirn-2-yl) propane] dihydrochloride and 4,4'-azobis (4-cyanovaleric acid). The polymerization initiators mentioned are used in conventional amounts, for. B. in amounts of generally at least 0.01 mol%, preferably at least 0.05 and more preferably at least 1 mol% and generally at most 5, preferably at most 2 mol%, based on the monomers to be polymerized.

The redox initiators contain as oxidizing component at least one of the abovementioned per compounds and a reducing component, for example ascorbic acid, glucose, sorbose, ammonium or alkali metal hydrogen sulfite, sulfite, thiosulfate, hyposulfite, pyrosulfite or sulfide, metal salts such as iron-I Honing or silver ions or sodium hydroxymethyl sulfoxylate. Preferably used as the reducing component of the redox initiator ascorbic acid, sodium sulfite or sodium pyrosulfite. Relative to the employed in the polymerization amount of monomers used is generally at least 3 ^• 1O ^-6, at least 1 ^• 10 ⁵ preferably up to 1 mol% of the reducing component of the redox initiator and generally at least 1 ^■ 10 ^"5, preferably at least 1 ^• 10- ³ to 5 mol% of the oxidizing component. Instead of the oxidizing component or in addition one can also use one or more water-soluble azo initiators.

In one embodiment of the invention, a redox initiator consisting of hydrogen peroxide, sodium peroxodisulfate and ascorbic acid is used. For example, these components are used in the concentrations 1 ^× 10 ² mol% of hydrogen peroxide, 0.084 mol% of sodium peroxodisulfate and 2.5 ^× 10 ^-3 mol% of ascorbic acid, based on the monomers.

However, the polymerization can also be triggered in the absence of initiators of the abovementioned type by the action of high-energy radiation in the presence of photoinitiators. These may be, for example, so-called α-splitters, H-abstracting systems or azides. Examples of such initiators are benzophenone derivatives such as Michler's ketone, phenanthrene derivatives, fluorene derivatives, anthraquinone derivatives, thioxanthone derivatives, coumarin derivatives, benzoin ethers and their derivatives, azo compounds such as the abovementioned radical formers, substituted hexaarylbisimidazoles or acylphosphine oxides. Examples of azides are: 2- (N, N-dimethylamino) ethyl-4-azidocinnamate, 2- (N, N-dimethyl-amino) -ethyl-4-azidonaphthyl ketone, 2- (N, N-dimethylamino) -ethyl 4-azidobenzoate, 5-azido-1-naphthyl-2 '- (N, N-dimethylamino) ethylsulfone, N- (4-sulfonylazidophenyl) maleimide, N-acetyl-4-sulfonylazidoaniline, 4-sulfonylazidoaniline, 4-azidoaniline, 4-azidophenacyl bromide, p-azidobenzoic acid, 2,6-bis (p-azidobenzylidene) cyclohexanone and 2,6-bis (p-azidobenzylidene) -4-methylcyclohexanone. The photoinitiators, if used, are usually used in amounts of 0.01 to 5 wt .-% based on the monomers to be polymerized. The aqueous monomer solution may contain the initiator dissolved or dispersed. However, the initiators can also be fed to the polymerization reactor separately from the monomer solution.

surfactants

The polymerisable or crosslinkable aqueous mixtures contain as further component 0.1 to 20 wt .-% of at least one surfactant. The surfactants are crucial for the production and stabilization of the foam. One can use anionic, cationic or nonionic surfactants or surfactant mixtures that are compatible with each other. It is possible to use low molecular weight or else polymeric surfactants, with combinations of different or also identical types of surfactants having proven advantageous. Usable nonionic surfactants are, for example, addition products of alkylene oxides, in particular ethylene oxide, propylene oxide and / or butylene oxide with alcohols, amines, phenols, naphthols or carboxylic acids. The surfactants used are advantageously addition products of ethylene oxide and / or propylene oxide with alcohols containing at least 10 carbon atoms, the addition products containing 3 to 200 moles of ethylene oxide and / or propylene oxide per mole of alcohol. The addition products contain the alkylene oxide units in the form of blocks or in random distribution. Examples of nonionic surfactants which can be used are the addition products of 7 mol of ethylene oxide and 1 mol of tallow fatty alcohol, reaction products of 9 mol of ethylene oxide with 1 mol of tallow fatty alcohol and addition products of 80 mol of ethylene oxide and 1 mol of tallow fatty alcohol. Other useful commercial nonionic surfactants consist of reaction products of oxo alcohols or Ziegler alcohols with 5 to 12 moles of ethylene oxide per mole of alcohol, especially with 7 moles of ethylene oxide. Other useful commercial nonionic surfactants are obtained by ethoxylation of castor oil. For example, 12 to 80 moles of ethylene oxide are added per mole of castor oil. Further commercial products which can be used are, for example, the reaction products of 18 mol of ethylene oxide with 1 mol of tallow fatty alcohol, the addition products of 10 mol of ethylene oxide with 1 mol of a C 13 / C 20 oxalcohol, or the reaction products of 7 to 8 mol of ethylene oxide with 1 mol of a C 13 / Ci5 oxo alcohol. Other suitable nonionic surfactants are phenol alkoxylates such as p-tert-butylphenol, which is reacted with 9 moles of ethylene oxide, or methyl ethers of reaction products of 1 mole of a Ci ₂ - to Ciβ alcohol and 7.5 moles of ethylene oxide.

The nonionic surfactants described above can be converted, for example, by esterification with sulfuric acid into the corresponding sulfuric acid half esters. The sulfuric acid half esters are used in the form of the alkali metal or ammonium salts as anionic surfactants. Suitable anionic surfactants are, for example, alkali metal or ammonium salts of sulfuric monoesters of reaction products of ethylene oxide and / or propylene oxide with fatty alcohols, alkali metal or ammonium salts of alkylbenzenesulfonic acid or of alkylphenol ether sulfates. Products of the type mentioned are commercially available. For example, the sodium salt of a sulfuric monoester of a Ci3 / Ci5-oxoalcohol reacted with 106 moles of ethylene oxide, the triethanolamine salt of dodecylbenzenesulfonic acid, the sodium salt of alkylphenol ether sulfates and the sodium salt of the sulfuric acid half ester of a reaction product of 106 moles of ethylene oxide with 1 mole of tallow fatty alcohol are commercially available anionic surfactants. Other suitable anionic surfactants are Schwefelsäurehalbester of Ci3 / C ₅ oxo-alcohols, paraffin sulfonic acids, such as C15 alkyl sulfonate, alkyl-substituted benzene sulfonic acids and alkyl-substituted naphthalene sulfonic acids such as dodecylbenzenesulfonic acid, and di-n-butylnaphthalenesulfonic acid and fatty alcohol phosphates such as cis / Ciβ fatty alcohol phosphate. The polymerizable aqueous mixture may contain combinations of a nonionic surfactant and an anionic surfactant or combinations of nonionic surfactants or combinations of anionic surfactants. Also cationic surfactants are suitable. Examples of these are the dimethyl sulfate-quaternized reaction products of 6.5 mol of ethylene oxide with 1 mol of oleylamine, distearyldimethylammonium chloride, lauryltrimethylammonium chloride, cetylpyridinium bromide and dimethyl sulfate-quaternized stearic acid triethanolamine ester, which is preferably used as cationic surfactant.

The surfactant content of the aqueous mixture is preferably 0.5 to 10 wt .-%. In most cases, the aqueous mixtures have a surfactant content of 1, 5 to 8 wt .-%.

solubilizers

The crosslinkable aqueous mixtures may optionally contain, as further component, at least one solubilizer. By this is meant water-miscible organic solvents, e.g. Dimethyl sulfoxide, dimethylformamide, N-methylpyrrolidone, monohydric alcohols, glycols, polyethylene glycols or monoethers derived therefrom, the monoethers containing no double bonds in the molecule. Suitable ethers are methyl glycol, butyl glycol, butyl diglycol, methyl diglycol, butyl triglycol, 3-ethoxy-1-propanol and glycerol monomethyl ether.

The aqueous mixtures contain 0 to 50 wt .-% of at least one solubilizer. If solubilizers are used, their content in the aqueous mixture is preferably 1 to 25% by weight.

Thickeners, foam stabilizers, fillers, fibers, cell nucleating agents

The crosslinkable aqueous mixture may optionally contain thickeners, foam stabilizers, fillers, fibers and / or cell nucleating agents. Thickeners, for example used to optimize the foam structure and to improve foam stability. This ensures that the foam shrinks only slightly during the polymerization. Suitable thickeners are all known natural and synthetic polymers which greatly increase the viscosity of an aqueous system and do not react with the amino groups of the basic polymers. These may be water-swellable or water-soluble synthetic and natural polymers. For a detailed review of thickeners, see, for example, the publications of RY Lochhead and WR Fron, Cosmetics & Toiletries, 108, 95-135 (May, 1993) and MT. Clarke, "Rheological Additives" in D. Laba (ed.) "Rheological Properties of Cosmetics and Toiletries", Cosmetic Science and Technology Series, Vol. 13, Marcel Dekker Inc., New York 1993.

Examples of suitable thickener water-swellable or water-soluble synthetic polymers are high molecular weight polyethylene glycols or copolymers of ethylene glycol and propylene glycol and high molecular weight polysaccharides such

Starch, guar gum, locust bean gum or derivatives of natural substances such as carboxymethylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, hydroxypropylcellulose and cellulose mixed ethers. Another group of thickeners are water-insoluble products, such as finely divided silica, zeolites, bentonite, cellulose powder or other finely divided powders of crosslinked polymers. The aqueous mixtures may contain the thickeners in amounts of up to 30% by weight. If such thickening agents are used at all, they are contained in amounts of 0.1, preferably 0.5 to 20 wt .-% in the aqueous mixture.

In order to optimize the foam structure, it is optionally possible to add hydrocarbons having at least 5 C atoms in the molecule to the aqueous reaction mixture. Suitable hydrocarbons are, for example, pentane, cyclopentane, hexane, cyclohexane, heptane, octane, isooctane, decane and dodecane. The aliphatic hydrocarbons contemplated may be straight chain, branched or cyclic and have a boiling temperature which is above the temperature of the aqueous mixture during foaming. The aliphatic hydrocarbons increase the service life of the not yet polymerized foamed aqueous reaction mixture. This facilitates the handling of the not yet polymerized foams and increases process reliability. The hydrocarbons, for example, act as cell nucleators and at the same time stabilize the already formed foam. In addition, they can cause further foaming of the mixture when polymerizing the monomer foam. You can then also have the function of a propellant. Instead of hydrocarbons or in mixture with it, one can optionally also use chlorinated or fluorinated hydrocarbons as cell nucleating agents and / or foam stabilizers, for example dichloromethane, trichloromethane, 1,2-dichloroethane, trichlorofluoromethane or 1,1,2-trichlorotrifluoroethane. If hydrocarbons are used, they are used, for example, in amounts of from 0.1 to 20% by weight, They are used for example in amounts of 0.1 to 20 wt .-%, preferably 0.1 to 10 wt .-%, based on the polymerizable aqueous mixture.

In order to modify the properties of the foams, one or more fillers may be added to the crosslinkable aqueous mixture, e.g. Chalk, talc, clay, titanium dioxide, magnesium oxide, aluminum oxide, precipitated silicas in hydrophilic or hydrophobic modifications, dolomite and / or calcium sulfate The particle size of the fillers is, for example, 10 to 1000 μm, preferably 50 to 850 μm in amounts up to 30 wt .-% in the crosslinkable aqueous mixture.

Optionally, the properties of the foams can also be modified with the aid of further fibers. These may be natural or synthetic fibers or mixtures of fibers, e.g. Fibers of cellulose, wool, polyethylene, polypropylene, polyesters or polyamides. If fibers are used, they may be present in the aqueous mixture, for example, in an amount of up to 200% by weight, preferably up to 25% by weight. Fillers and fibers can optionally also be added to the already foamed mixture. The concomitant use of fibers leads to an increase in the strength properties such as wet strength of the finished foam.

Pulp fibers, in particular wood pulp or waste paper, fruit fibers and superabsorbent fibers

The invention further relates to fibers containing superabsorbent foam, in particular fibers of wood pulp, in particular of wood pulp or waste paper, fruit fibers and / or foam containing superabsorbent fibers. In a preferred form, the fibers are distributed in such a way that in a foam body, which is divided along its shortest axis, the number of fibers in two equal volume elements in the two outer thirds, each containing at least 100 fibers, no longer than 50%, preferably not more than 25%, in particular not more than 10% from each other. Shortest axis is the shortest possible connecting line of two opposite points on the surface of the foam body.

Wood pulp fibers are preferably used as wood sulfates or wood sulfites. Fibers made by other wood pulping methods are also usable. Particularly preferred are wood sulfites, especially those produced by the acid sulfite process. As woods, beech and softwood are preferred. Among the softwoods especially birch, spruce and pine. The wood species could also be present in mixtures, for example in the form of additions of spruce or pine wood to beech wood. Waste paper is understood to mean the papers, cartons and cardboard covered by DIN 6730. Particularly suitable according to the invention are those fibers from waste paper which correspond in fiber length and fiber property to the preferred wood pulps. The waste paper fibers can also be used in blends with the wood pulp fibers.

Other pulp fibers can be obtained from annual plants. An example of this are fibers of straw.

Fruit fibers are fibers derived from fruits or grains. The preferred fibers are mentioned in WO 2004/35 668 A2.

According to the invention, the foams may comprise superabsorbent fibers, which are preferably added to the aqueous polymerizable solution before foaming or the foam. Superabsorbent fibers are known from the prior art references EP 264 208 A2, EP 272 072 A2, EP 436 514 A2 and US 4,813,945. These are preferably fibers of a hydrolyzed and then crosslinked copolymer of isobutene and maleic anhydride. Instead of isobutene, the copolymers may also contain copolymerized other 1-olefins such as ethylene, propylene, diisobutylene or styrene. The olefins and styrene mentioned are readily copolymerizable with maleic anhydride. The copolymers are hydrolyzed in an aqueous medium, for example, 20 to 80 mol% neutralized with sodium hydroxide or potassium hydroxide, mixed with crosslinkers that can react with the carboxyl groups of the copolymers (eg polyhydric alcohols Ie, polyhydric amines or amino alcohols) and after substantial removal the water spun into fibers. The fibers are crosslinked by heating to temperatures of for example 170 to 24O ⁰ C, whereby they become superabsorbers. The diameter of the fibers is for example 5 to 500 .mu.m, preferably 10 to 300 .mu.m, the length of the fibers is for example in the range of 2 to 60 mm, preferably 6 to 12 mm. The fibers are preferably added to the aqueous polymerizable mixture, but may also be added to the foamed mixture prior to curing by polymerizing the monomers or by crosslinking the basic polymers.

The wood fibers preferably have an average length of more than 0.3 mm or 0.5 mm, preferably lengths greater than 0.8 or 1.0 mm, particularly preferably more than 1.2 mm. The upper value for the average fiber length is usually less than 5 cm or 4 cm, preferably less than 3 cm or 2.5 cm, in particular less than 2 cm. The fibers of wood pulp, waste paper and also the superabsorbent fibers are used, for example, in amounts of from 0.05 to 10% by weight, preferably 0.1 to 5% by weight, in particular between 0.4 and 1, 2% by weight. used.

For example, the superabsorbent synthetic fibers have a Free Swell Capacity of at least 30 g / g, preferably at least 40 g / g.

Foams especially for the absorption of saline aqueous solutions

In order to produce foams which also have a high absorption capacity compared with saline aqueous solutions, the basic and acidic superabsorbents are preferably used in unneutralized form. The degree of neutralization of the acidic water-absorbing polymers is for example 0 to 100, preferably 0 to 75 and usually 0 to 50 mol%. The water-absorbing basic polymers in the form of the free bases have a higher absorption capacity for saline aqueous solutions and in particular acidic aqueous solutions than in the acid-neutralized form. When basic polymers are used as the sole water-absorbing polymers, the degree of neutralization is, for example, 0 to 100, preferably 0 to 60, mol%.

Production of foams

The crosslinkable aqueous mixtures described above, which comprise the monomers or the basic polymer, crosslinker, and surfactant, as well as optionally superabsorbent fibers and / or at least one further component, are first foamed. For example, it is possible to dissolve an inert gas in the crosslinkable aqueous mixture under a pressure of, for example, 2 to 400 bar and connect it to atmospheric pressure. When relaxing from a nozzle creates a flowable foam. It is also possible to foam the crosslinkable aqueous mixture by another method by dispersing therein fine bubbles of an inert gas. The foaming of the crosslinkable aqueous mixture can be carried out in the laboratory, for example, by foaming the aqueous mixture in a food processor equipped with a whisk. The generation of foam is preferably carried out in an inert gas atmosphere and with inert gases, for example by adding nitrogen or noble gases under normal pressure or elevated pressure, for example up to 25 bar, and then releasing. The consistency of the foams, the size of the gas bubbles and the distribution of the gas bubbles in the foam can be varied within a wide range, for example by the choice of surfactants, solubilizers, foam stabilizers, cell nucleating agents, thickeners and fillers. This allows you to easily adjust the density, the degree of the open-cell foam and wall thickness of the foam. The aqueous mixture is preferred foamed at temperatures below the boiling point of the constituents of the aqueous mixture, for example at room temperature up to 10O ⁰ C, preferably at 20 to 5O ⁰ C. However, you can also work at temperatures above the boiling point of the component with the lowest boiling point, by foaming the mixture in a pressure-tight container. Crosslinkable, foam-like mixtures are obtained which are flowable and stable over a relatively long period of time. The density of the foamed mixture is crosslinked at a temperature of 2O ⁰ C, for example, 0.01 to 0.9 g / cm ^3.

Polymerization and / or crosslinking of the foamed mixture

In the second stage of the process, the polymerization of the monomers or the crosslinking of the basic polymer takes place to form a water-absorbing basic polymer. In the polymerization, e.g. at least two ethylenically unsaturated double bonds containing compounds used as crosslinking agents. The polymerization is carried out in the presence of customary radical-forming initiators. Crosslinked polymers are then obtained which are superabsorbent.

The originally water-soluble basic polymer becomes water-insoluble due to the crosslinking. A hydrogel of a basic polymer is obtained. The crosslinkable foam-like mixtures are, for example, transferred into suitable molds and heated therein so that the monomers polymerize or the crosslinkers react with the basic polymer. The foamed material can be applied, for example, in the desired thickness to a temporary carrier material, which is advantageously provided with a non-stick coating. For example, it is possible to doctor the foam onto a base. Another possibility is to fill the foamy aqueous mixture in molds which are also non-stick coated.

Since the foamed aqueous mixture has a long service life, this mixture is also suitable for the production of composite materials. It can for example be applied to a permanent carrier material, for example films of polymers (for example films of polyethylene, polypropylene or polyamide) or metals such as aluminum. It is also possible to apply the foamed aqueous mixture to nonwovens, fluff, tissues, fabrics, natural or synthetic fibers, or to other foams. In the production of composite materials, it may be advantageous to apply the foam in the form of certain structures or in different thickness on a substrate. However, it is also possible to apply the foam to fluff layers or nonwovens and to impregnate these materials so that the fluff after crosslinking is an integral part of the foam. The foamed aqueous mixture obtainable in the first process step can also be formed into large blocks and crosslinked. The blocks can become linked after networking smaller shaped bodies are cut or sawn. It is also possible to produce sandwich-like structures by applying a foamed aqueous mixture to a substrate, covering the foam-like layer with a film or nonwovens, tissues, fabrics, fibers or other foams, and crosslinking the sandwich-type structure by heating. However, it is also possible, before or after crosslinking, to apply at least one further layer of a foamed, crosslinkable layer and optionally to cover it with another film, nonwovens, tissues, fabrics, fibers or other materials. The composite is then subjected to crosslinking in the second process stage. However, it is also possible to produce sandwich-like structures with further foam layers of the same or different density.

Foaming layers according to the invention with a layer thickness of up to about 1 millimeter are produced, for example, by one-sided heating or, in particular, by irradiation of the foamed polymerized or crosslinkable aqueous mixture on one side. If thicker layers of a foam are to be produced, for example foams with thicknesses of several centimeters, the heating of the crosslinkable foamed material with the aid of microwaves is particularly advantageous, because in this way a relatively uniform heating can be achieved. The crosslinking takes place, for example, at temperatures of 20 to 18O ⁰ C, preferably in the range of 40 ⁰ C to 16O ⁰ C, in particular at temperatures of 65 to 140 ⁰ C. For thicker foam layers to be crosslinked, the foamed mixture treated on both sides with heat, for example by means of contact heating or by irradiation. The density of the foam-like hydrogel essentially corresponds to the density of the crosslinkable aqueous mixture. Thus, foams of water-absorbing polymers having a density of, for example, 0.01 to 0.9 g / cm ³ , preferably 0.1 to 0.7 g / cm ^{3 are obtained} . The foam-like polymers are open-celled. The proportion of open cells is for example at least 80%, preferably it is above 90%. Foams having an open-cell content of 100% are particularly preferred. The proportion of open cells in the foam is determined, for example, by means of scanning electron microscopy (Scanning Electron Microscopy).

Foams which are obtainable by starting from a polymerizable aqueous mixture which comprises at least 50% of acrylic acid neutralized with sodium hydroxide or potassium hydroxide, a crosslinker containing at least two ethylenically unsaturated double bonds, an initiator, superabsorbent fibers of a hydrolyzed and then crosslinked copolymer of isobutene and maleic anhydride and at least one surfactant. Further examples of superabsorbent foams are obtainable by foaming a polymerizable aqueous mixture comprising at least one basic polymer from the group of polymers containing vinylamine units, polymers containing vinylguanidine units and polyisocyanates containing dialkylaminoalkyl (meth) acrylamide units. mers, polyethyleneimines, ethyleneimine-grafted polyamidoamines and polydiallyldimethylammoniumchloriden contains.

Foams having a particularly high water absorption capacity and improved absorption capacity for electrolyte-containing aqueous solutions can be obtained by crosslinking foamed aqueous mixtures of basic polymers which, based on the polymer mixture, contain from 10 to 90% by weight of a finely divided, water-absorbing, acidic polymer. The acidic hydrogel can be present as a solid particulate polymer or as a foamed particulate polymer having particle sizes of, for example, 10 to 2000 μm in the foams according to the invention.

After crosslinking of the foamed mixture or during crosslinking, drying of the foam-like hydrogel takes place. In doing so, water and other volatiles are removed from the crosslinked foam hydrogel. Drying preferably takes place after crosslinking of the foam-like hydrogel. Examples of suitable drying methods are thermal convection drying such as, for example, tray, chamber, channel, flat web, plate, rotary drum, trickle bed, screen belt, current, fluidized bed, fluidized bed, paddle and ball bed drying, thermal contact drying such as Heizteller-, roller, belt, drum screen, screw, tumble and contact disk drying, radiation drying such as infrared drying, dielectric drying such as microwave drying and freeze-drying. In order to avoid undesirable decomposition and crosslinking reactions, it may be advantageous to dry under reduced pressure, under an inert gas atmosphere and / or under mild thermal conditions in de- the product temperature NEN 12O ⁰ C, preferably from 100 ⁰ C, does not exceed perform , Particularly suitable drying methods are the (vacuum) belt drying and the paddle drying.

After the drying step, the foamy hydrogel mostly contains no more water. However, the water content of the foamed material can be arbitrarily adjusted by wetting the foam with water or steam. In most cases, the water content of the foam-like gel is 1 to 60 wt .-%, preferably 2 to 10 wt .-%. With the help of the water content, the flexibility of the foam-like hydrogel can be adjusted. Fully dried foam hydrogels are hard and brittle, while foamed materials having a water content of, for example, 5 to 20 wt% are flexible. The foamed hydrogels can either be used directly in the form of films or granules or individual sheets or foils are cut from thicker foam blocks.

However, the foam hydrogels described above may still be modified by postcrosslinking the surface of the foamed materials. As a result, the gel stability of the shaped bodies from the foamed hydrogel be improved. In order to carry out a surface postcrosslinking, the surface of the shaped bodies of the foamed hydrogels is treated with at least one crosslinking agent and the shaped bodies treated in this way are heated to a temperature at which the crosslinkers react with the hydrogels. Suitable crosslinkers are described above. These compounds can also be used for post-crosslinking the surface of the foam hydrogels. Preferred crosslinkers used are the above-mentioned glycidyl ethers and esters of acrylic acid and / or methacrylic acid with the reaction products of 1 mole of trimethylolpropane and 6 to 15 moles of ethylene oxide or polyhydric alcohols which are used, for example, for the post-crosslinking of foam-containing superabsorbents containing carboxyl groups.

The crosslinkers for the surface postcrosslinking are preferably applied to the foam surface in the form of a water-containing solution. The aqueous solution may contain water-miscible organic solvents, for example alcohols such as methanol, ethanol and / or i-propanol or ketones such as acetone. The amount of crosslinker that is applied to the surface of the foam-form hydrogels is, for example, 0.1 to 5 wt .-%, preferably 1 to 2 wt .-%. If the surface postcrosslinking of the hydrogel foams by heating the treated with at least egg nem crosslinking hydrogel foams at a temperature of, for example, 60 to 12O ⁰ C, preferably at 70 to 100 ⁰ C. After surface crosslinking, the water content of the foamed post-crosslinked at the surface Hydrogels can also be adjusted to values of 1 to 60% by weight.

Post-treatment of the foams with complexing agent and / or source retarding agent

complexing

In one embodiment of the invention, the stability of the foam, preferably a foam, formed from a polymerizable mixture containing acid group-bearing monomers is increased by forming complexes on the foam surface. The formation of the complexes on the foam takes place by treatment with at least one complexing agent. A complexing agent is an agent containing complexing cations. Preferably, this is accomplished by spraying solutions of di- or polyvalent cations, which cations may react with functional groups, such as the acid groups of the polymeric foam to form complexes. Examples of divalent or polyvalent cations are polymers which are formally wholly or partially composed of vinylamine monomers, such as partially or completely hydrolyzed polyvinylamide (so-called "polyvinylamine"), whose amine groups are always partially protonated to ammonium groups, even at very high pH values or metal cations such as Mg ²⁺ , Ca ²⁺ , Al ³⁺ , Sc ³⁺ , Ti ⁴⁺ , Mn ²⁺ , Fe ²⁺ ^/ ³⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Zn ²⁺ , Y ³⁺ , Zr ⁴⁺ , La ³⁺ , Ce ⁴⁺ , Hf ⁴⁺ , and Au ³⁺ . Preferred metal cations are Mg ²⁺ , Ca ²⁺ , Al ³⁺ , Ti ⁴⁺ , Zr ⁴⁺ and La ³⁺ , and particularly preferred metal cations are Al ³⁺ , Ti ⁴⁺ and Zr ⁴⁺ . The metal cations can be used both alone and in a mixture with each other. The anions are not subject to any significant restriction, of the said metal cations, all such metal salts are suitable which have sufficient solubility in the solvent to be used. Particularly suitable are metal salts with weakly complexing anions such as chloride, nitrate and sulfate, hydrogen sulfate, carbonate, bicarbonate, nitrate, phosphate, hydrogen phosphate, dihydrogen phosphate and carboxylate, such as acetate and lactate. In a particularly preferred form, aluminum sulfate Ab (SO _{4) is} used as the solvent for the metal salts, water, alcohols, DMF, DMSO and mixtures of these components are particularly preferably water and water / alcohol mixtures such as water / methanol, Water / 1,2-propanediol and water / 1,3-propanediol. Very particular preference is given to water.

The concentration of the polyvalent metal ion in the aqueous solution is generally at least 1 wt%, preferably at least 2 wt%, and generally at most 20 wt%, preferably at most 10 wt%. In general, at least 0.05% by weight, preferably at least 0.1% by weight, more preferably at least 0.2% by weight, for example at least 0.8% by weight and generally at most 10, are used Wt .-%, preferably at most 8 wt .-% and more preferably at most 5 wt .-%, for example at most 3.2 wt .-%, of the polyvalent metal ion based on the dry foam prior to application of complexing or Quellverzögerungsmittel. "Dry" in the context of this invention is a foam which contains 5% by weight of water. When aluminum sulfate is used, a content of 0.8% by weight of the cation corresponds to a content of Ab (SO ₄ ) 5 of 5% by weight. -% and a content of 3.2 wt .-% of the cation a content of Ab (SO ₄ ) 3 of 20 wt .-%.

Source retardants

In one embodiment of the invention, the foam is treated with at least one source retardant. By source retardants is meant substances which are applied to the surface of the superabsorbent foam in a wet or dry state (<10% by weight of water in the foam) resulting in a delay in liquid uptake, which is a decrease in swelling rate or increase in swelling time of the treated foam in comparison with the untreated foam.

The time required to take up liquid is increased by the treatment according to the invention of the foams. The swelling rate is generally about at least 25%, preferably more than 50%, more preferably more than 100%, in particular more than 200% is lowered.

As a source retardants, for example, water repellents are used or applied water-soluble polymers that slow down the fluid intake.

waterproofing

The terms "hydrophobic" and "hydrophilic" describe the wetting behavior of a surface with water. On hydrophobic surfaces, the edge or contact angle of a water droplet is less than 90 °, preferably less than 80 °, more preferably less than 70 °, particularly preferably less than 60 °, in particular less than 50 °, and on hydrophilic surfaces is the edge or contact angle of one Water droplet greater than 90 °, preferably greater than 100 °, more preferably greater than 110 °, particularly preferably greater than 120 °, in particular greater than 130 °. The edge or contact angle is for example in CoIloid Polym. Sci., Vol. 259 (1981), pages 391-394. For rough surfaces, the apparent contact angle is measured. With powders, the surface is smoothed with a smooth punch and a pressure of 0.5 bar.

For example, there are free hydroxyl groups on the particle surface of pyrogenic silicas. Hydrogen bonds are possible via these hydroxy groups. As a result, pyrogenic silicas are hydrophilic.

By reacting pyrogenic silicic acids with, for example, trimethylchlorosilane, the free hydroxyl groups can be converted into silyl ether groups. The silyl ether groups can no longer form hydrogen bonds. The fumed silica was rendered hydrophobic.

The swelling rate is lowered, for example, by hydrophobing the surface of the foam. Hydrophobing is the increase of the edge or contact angle of water on the foam to a value of at least 90 °, preferably at least 100 °, more preferably at least 110 °, more preferably at least 120 °, in particular at least 130 °. Methods for hydrophobing are known, usually water repellents are applied to the surface. One way to hydrophobize the foam is to post-treat (eg, by powdering or applying a slurry or dispersion) with hydrophobic particles. The amount of hydrophobic particles used is set individually, with the swelling rate of the superabsorbent foam thus treated dropping as the content of hydrophobic particles increases. The hydrophobicity of the surface can optionally also be adjusted by applying a mixture of hydrophobic and hydrophilic particles. Will the superabsorbent foam in this way also with aftertreatment of hydrophilic substances, the amount of hydrophobic particles is typically to be increased.

By combining hydrophilic and hydrophobic particles, superabsorbent foams can be produced with individually adjustable swelling rates. The amounts of hydrophilic and hydrophobic particles are advantageously chosen so that the desired delay of the swelling rate is achieved.

Hydrophobic or hydrophobicized compounds are known and common commercial products. Hydrophobed aluminas and / or silicic acids can be obtained, for example, by reacting hydrophilic aluminum oxides and / or silicas with hexamethyldisilazane or dimethyldichlorosilane. Such silica, for example, under the names Aerosil ^® R 812, Aerosil ^® R 974 or Aerosil ^® R 8200 from Degussa AG, Dusseldorf, Germany, available. Hydrophilic compounds are also known and common commercial goods. Such silica is, for example, under the name Aerosil ^® 200 of Degussa AG, Dusseldorf, Germany, available. Preferably, fumed aluminas, fumed silicas or mixtures thereof are used. Particular preference is given to mixtures of pyrogenic silicic acids with more than 0 to 20% by weight of pyrogenic aluminum oxide and pyrogenic silicic acids.

Preferably, the hydrophobic and hydrophilic compounds are used as particles. The mean particle size is generally at least 0.001 μm, preferably at least 0.002 μm, in a particularly preferred form at least 0.005 μm and in a very particularly preferred form at least 0.01 μm and generally at most 10 μm, preferably at most 5 μm, particularly preferably at most 1 μm and most preferably at most 0.1 microns. The average primary particle size (one particle contains several primary particles) is generally at least 5 nm and preferably at least 10 nm and generally at most 50 nm, preferably at most 20 nm. The specific surface area ("BET surface area") of the particles is generally at least 10 m ² / g, preferably at least 80 m ² / g and generally at most 1000 m7g, preferably at most 380 m ² / g The measurement method for the particle size distribution is based on the analysis of the diffraction spectra according to Fraunhofer The analyzes are carried out as standard with a Mastersizer S In general, at least 0.005% by weight, preferably at least 0.05% by weight, more preferably at least 0.1% by weight, and most preferably at least 1, are used Wt .-% and generally at most 50 wt .-%, preferably at most 20 wt .-%, in a particularly preferred form highest 5% by weight, and in a most preferred form at most 5% by weight, of hydrophobic, hydrophobized or hydrophilic compound based on the superabsorbent dry foam having a water content of 5%. The hydrophobic and hydrophilic compounds are preferably added to the non-wet foam. Non-humid means a water content of less than 20% by weight, more preferably less than 10% by weight. The type of bonus is not restricted.

Water-soluble polymers

Another alternative source retarding agent is water-soluble polymers which may be used alone or in combination with the above-mentioned source retarders and in the same manner as described above for these.

Water-soluble refers to those polymers which are at least 50 mg / l soluble in water at 20 ^° C. If the water solubility is pH-dependent, solubility is achieved at a pH range of 4 to 8, preferably 5 to 7.

The polymers preferably contain (meth) acrylic acid or salts thereof as the monomer component. By (meth) acrylic acid is meant acrylic acid, methacrylic acid and their mixtures.

Further preferably, the polymers contain as the monomer component alkyl esters of (meth) acrylic acid.

The polymer can also be crosslinked.

Applicable water-soluble polymers are described, for example, in EP 88 951 B1, column 2 line 14 ff. Suitable water soluble polymers are also available commercially available goods and, for example, under the name Kollicoat ^® from BASF Aktiengesellschaft, Ludwigshafen, Germany.

As source retardants, copolymers can be used

A) 20-85% by weight of at least one alkyl ester of acrylic and / or methacrylic acid,

B) 80-15% by weight of at least one salt-capable, free-radically polymerizable monomer

C) optionally up to 30% by weight of one or more ethylenically unsaturated monomers

be used. The copolymers are preferably film formers of an emulsion polymer. Preferred ranges for A are 40-70% by weight and for B 60-30% by weight.

Alternatively, coplymers can only be made

B) at least one salt-capable, free-radically polymerizable monomer

be used.

Suitable monomer components (A) are alkyl esters of acrylic or methacrylic acid with alkyl radicals consisting of 1 to 30, preferably 1 to 8, carbon atoms, with methyl acrylate, methyl methacrylate, ethyl acrylate and ethyl methacrylate being preferred.

The monomer component (B) which is capable of salt formation preferably contains carboxyl groups which are capable of forming salts with bases. Suitable acidic group-containing monomers are preferably monoethylenically unsaturated carboxylic acids such as acrylic acid and methacrylic acid and, for example, maleic acid, fumaric acid, itaconic acid, mesaconic acid, methylenemalonic acid or citraconic acid. Alternatively, this component may contain primary, secondary or tertiary amino groups, which is then capable of salt formation with acids. Suitable monomers having amino groups are vinylimidazole, vinylimidazoline, vinylimidazolidine, vinylpyridine, monoalkyl or dialkylaminoalkyl esters or monoalkyl or dialkylaminoalkylamides of unsaturated, copolymerizable carboxylic acids, such as e.g. Cyclohexylaminoethyl acrylate, cyclohexylaminoethyl methacrylate, morpholinoethyl acrylate, morpholinoethyl methacrylate, piperidinoethyl acrylate, piperidinoethyl methacrylate, 4-dimethylamino-butyl acrylate, 4-dimethylamino-butyl methacrylate, dimethylaminoneopentyl acrylate, dimethylaminoneopentyl methacrylate, N-dimethylaminoethylacrylamide and dimethylaminoethylmethacrylamide. Preference is given to methacrylic acid.

In addition, optionally further comonomers (C) may be involved in the construction of the polymer. Acrylic or methacrylamide, hydroxyalkyl esters of acrylic acid or methacrylic acid, glycerol monoacrylate, glycerol monomethacrylate, N-vinylformamide, vinylpyrrolidone, acrylonitrile, methacrylonitrile, vinylaromatics such as styrene or vinyltoluene or lower olefins such as ethylene or propylene are mentioned as examples. Furthermore, n-butyl, 2-ethylhexyl, n-octyl, n-hexyl, cyclohexyl, benzyl and dodecyl esters of unsaturated polymerizable carboxylic acids, especially of acrylic and methacrylic acid, and the higher N are Alkylamides of these acids, vinyl esters of higher fatty acids such as butyric acid or valeric acid called. For example, in addition to the described comonomers (C), a bifunctional vinyl compound, such as, for example, divinylbenzene or glycol dimethacrylate, can be copolymerized in small amounts, resulting in poor crosslinking. Thus, the active substance is released diffusion-controlled.

The preferred polymer according to the invention is either a (meth) acrylate copolymer of from 1 to 60% by weight of methacrylic acid and from 40 to 99% by weight of ethyl acrylate. Preference is given to copolymers of from 10 to 40% by weight of methacrylic acid and from 60 to 90% by weight of ethyl acrylate. Also preferred are copolymers with 40-70% by weight of ethyl acrylate and 60-30% by weight of methacrylic acid. The pH at which the copolymer dissolves can be adjusted by the ratio of the monomers. For example, in the case of a copolymer of ethyl acrylate with methacrylic acid having a monomer ratio of 49:51, the pH at which the polymer dissolves is> 5.5. However, particularly preferred in the present invention is a ratio of ethyl acrylate to methacrylic acid of 60:40. This product dissolves at a pH of about> 6.6.

production:

The claimed copolymer is prepared by free radical emulsion polymerization of the monomer dispersion with the addition of sodium lauryl sulfate from and / or Tween ^® 80 as emulsifiers.

The polymerization is initiated as usual by an initiator. Initiators are used to prepare the water-soluble polymer as described above for the polymerization of acid group-carrying and other monomers. Likewise, as is the case there, initiation of the polymerization by the action of electromagnetic radiation on the polymerizable, aqueous mixture is possible.

The aftertreatment agents to be used-complexing agents, swelling retardants or complexing and swelling retardants-are applied to the foam as described, preferably as a solution or as far as insoluble, as a dispersion or solid. When both complexing and source retarding agents are applied, they are preferably sprayed together in a solution onto the dried water-absorbent foam or, in the case of a particulate source retardant, applied to the complexing agent pretreated foam.

Further process variants for the application of complexing and / or Quellverzögerungsmittel A further process according to the invention for the aftertreatment of foams for the production of superabsorbent foams according to the invention comprises the following steps:

Aftertreatment of a superabsorbent foam as described above with at least one hydrophobic compound, preferably with at least one hydrophobic and / or hydrophobized clay mineral, hydrophobicized aluminum oxide and / or hydrophobicized silica, particularly preferably at least one hydrophobicized aluminum oxide and / or one hydrophobicized silica.

optionally after-treatment with at least one hydrophilic compound, preferably at least one hydrophilic clay mineral, aluminum oxide and / or silicic acid, particularly preferably alumina and / or silicic acid.

Yet another process according to the invention for the after-treatment of superabsorbent foams comprises the following steps:

Post-treatment with at least one polyvalent metal ion, solutions of polyvalent metal ions, water-soluble cationic polymers and / or solutions of water-soluble polymers, preferably polyvalent metal ions, such as Al ³⁺ , Fe ²⁺ , Fe ³⁺ , Ti ³⁺ , Ti ⁴⁺ , Co ^{2 +} , Ni ²⁺ , Cr ³⁺ , Mn ²⁺ , Zn ²⁺ , Mg ²⁺ , Ca ²⁺ , Zr ³⁺ , Zr ⁴⁺ , more preferably Al ³⁺ .

Post-treatment with at least one hydrophobic compound, preferably hydrophobic and / or hydrophobized clay minerals, hydrophobicized aluminum oxides and / or hydrophobized silicic acids, particularly preferably hydrophobicized aluminum oxides and / or hydrophobized silicic acids.

optionally aftertreatment with at least one hydrophilic compound, preferably hydrophilic clay minerals, aluminum oxides and / or silicic acids, more preferably aluminum oxides and / or silicic acids.

optionally post-treatment with at least one anionic, cationic and / or nonionic surfactant, preferably a nonionic surfactant, for example sorbitan ester having an HLB value of from 2 to 18, tightening about 80 ^® (Uniqema, NL).

Preferably, the surfactants are dosed as a solution. Particularly preferred as a solvent is diethylene glycol monobutyl ether. The concentration of the surfactant in the solution is typically from 5 to 70 wt .-%, preferably 10 to 60 wt .-%, particularly preferably 20 to 50 wt .-%. Typically, 0.01 to 4 are used Wt .-%, preferably 0.05 to 2 wt .-%, particularly preferably 0.1 to 1 wt .-%, of the surfactant based on the dry foam.

The order in which the aftertreatment agents are dosed is not limited, the order is preferred

polyvalent metal ions, solutions of polyvalent metal ions, water-soluble cationic polymers and / or solutions of water-soluble polymers,

- hydrophilic and hydrophobic compounds together or separately in any order

Surface-active compounds, such as surfactants, and their solutions,

preferably only polyvalent metal ions and hydrophobic compounds to

Post-treatment can be used.

Drying after application of complexing and / or retarding agents

After the last step is optionally dried. The drying can be carried out in a customary manner, for example by heating the jacket of the reactor or blowing hot air. Also suitable is a downstream dryer, as it is used in the drying of not yet treated foam. Preferred drying temperatures are in the range from 50 to 250 ^° C., preferably from 50 to 200 ^° C., more preferably from 50 to 150 ° C. The residence time at this temperature in the reaction mixer or dryer is advantageously less than 30 minutes, preferably less than 20 minutes.

The drying is preferably carried out at reduced pressure, preferably at less than 500 mbar, more preferably at less than 200 mbar, and optionally by a dry gas stream, preferably nitrogen, in an amount of 20 to 1000 l / kgh, preferably 100 to 250 l / kgh, supported.

Post-treatment after application of complexing and / or swelling retardant or drying

Preferably, the absorbent foams in the process according to the invention are additionally treated with a hydrophilic organic compound. In particular, the hydrophilic organic compounds improve the fixation of particulate aftertreatment agents on the superabsorbent foam. Suitable hydrophilic organic compounds are, for example, lower water-soluble polyols having a average molecular weight of 100 to 6,000 daltons, preferably 200 to 3,000 daltons, more preferably from 250 to 2,000 daltons.

Preferred hydrophilic organic compounds are dendritic polymers, highly branched polymers such as polyglycerols, polyethylene glycols, polypropylene glycols, random or block copolymers of ethylene oxide and propylene oxide. Further suitable compounds for this purpose are the polyethoxylates or polypropoxylates of polyhydroxy compounds, such as glycerol, sorbitol, trimethylolpropane, trimethylolethane, pentaerythritol. Examples of these are n-times ethoxylated trimethylolpropane or glycerol where n is an integer between 1 and 100. Further examples are block copolymers such as n-times ethoxylated and then m-fold propoxylated trimethylolpropane or glycerol where n is an integer between 1 and 40 and m is an integer between 1 and 40. The order of the blocks can also be reversed.

The hydrophilic organic compound may be added before, during or after each of the post-treatment steps, preferably before the post-treatment with the hydrophobic organic compound, more preferably together with the polyvalent metal ion.

The hydrophilic organic compound is liquid at 23 ° C and has at 23 ° C a viscosity of less than 3000 mPas, preferably less than 1500 mPas, preferably less than 1000 mPas, more preferably less than 500 mPas, most preferably less than 300 mPas , on.

The hydrophilic organic compound is usually used in an amount of from 0.01 to 2% by weight, preferably from 0.025 to 1% by weight, more preferably from 0.05 to 0.75% by weight, based on the superabsorbent foam used.

Use of the foams

The foam-like hydrogels according to the invention, which are optionally postcrosslinked on the surface, can be used for all purposes for which, for example, the water-absorbing foam-like hydrogels known from EP 858 478 B1 are used based on acid group-containing polymers such as crosslinked polyacrylates. The foamy hydrogels of the invention are suitable, for example, for use in hygiene articles for absorption of body fluids, in dressings for covering wounds, as a sealing material, as a packaging material, as a soil conditioner, as a soil substitute, for dewatering sludges, for absorbing acidic aqueous wastes, for thickening aqueous ones Paints in the disposal of residual amounts of paints, for drainage of hydrous oils or hydrocarbons or as a filter material in ventilation systems.

A further subject of the invention are hygiene articles which contain the foams according to the invention, such as baby diapers, sanitary napkins, incontinence articles and dressings. The foams according to the invention fulfill, for example, in hygiene articles several functions, namely acquisition, distribution and / or storage of body fluids. In particular, they are suitable for storing body fluids as a storage layer in a diaper or a feminine hygiene article. Due to the delay of the liquid intake, the liquid to be absorbed is distributed evenly in the hygiene article. Thus, in a staggered second or repeated exposure to liquid, the entire surface of the foam can continue to be available to a better extent.

Structures of sanitary articles containing absorbent foam layers are known, as is their manufacture. The absorbent foams of the present invention in these sanitary articles as well as known absorbent foams. Foam layers of the foamy hydrogels of the present invention may be used, for example, in a thickness of 1 to 5 mm in one of the above-mentioned sanitary articles as an absorbent core between an upper liquid-permeable cover and a lower liquid-impermeable layer of a film of e.g. Polyethylene or polypropylene may be arranged. The liquid-permeable layer of the hygiene article is in direct contact with the skin of the user during use. This material usually consists of a fleece of natural fibers such as cellulose fibers or fluff. Optionally, a tissue layer is disposed above and / or below the absorbent core. Optionally, a storage layer of a conventional particulate anionic superabsorber may alternatively be present between the lower layer of the hygiene article and the absorbent core. When the foamed basic hydrogels are used as the absorbent core in diapers, due to the open-cell structure of the foamed basic hydrogels, the bodily fluid, which is normally applied in individual quantities at once, can be rapidly removed. This gives the user a pleasant feeling of surface dryness of the diaper.

Positioning methods

density

Any suitable gravimetric method can be used to determine the density of the multi-component foam system. The mass of solid multi-component foam system per unit volume of foam structure is determined. A method of determining the density of the multi-component foam system is described in ASTM Method No. D 3574-86, Test A. This method was originally developed for the density determination of urethane foams, but can also be used for this purpose. Thereafter, at a preconditioned sample, as described in the method, the dry matter mass and volume are determined at 22 ± 2 ^° C. Volume determinations of larger sample dimensions are carried out under normal pressure.

Free swell capacity ("FSC")

In this method, the free swellability of the multi-component foam system is determined in a tea bag. To determine the FSC, 0.2000 +/- 0.0050 g of dried foam (i.e., residual moisture content of 5%) is introduced into a 60 x 85 mm teabag, which is then sealed. The teaspoon is placed in an excess of test solution for 30 minutes (at least 0.83 L 0.9 wt% NaCl solution / 1 g of polymer). The tea bag is then drained for 10 minutes by hanging it on a corner. The determination of the amount of liquid is done by weighing the tea bag.

Centrifuge Retention Capacity ("CRC")

In this method, the retention capacity of the multi-component foam system in the tea bag is determined against gravity. To determine the CRC, 0.2000 +/- 0.0050 g of dried multi-component foam is introduced into a 60 × 85 mm tea bag, which is subsequently welded. The teabag is placed in an excess of 0.9% by weight saline for 30 minutes (at least 0.83 L saline solution / 1 g polymer). The teabag is then centrifuged for 3 minutes at 250G. The determination of the amount of liquid is done by weighing the centrifuged teabag.

Free Swell Rate (FSR)

To determine the free swell rate, 0.50 g (WH) multi-component foam system is placed on the bottom of a plastic dish with a round bottom of approx. 6 cm. The plastic bowl has a height of about 2.5 cm. Using a funnel, 10 g (wu) of a 0.9% NaCl solution are added to the center of the plastic dish. As soon as the liquid has contact with the multicomponent foam system, the time measurement is started and only stopped when the multicomponent foam system has completely absorbed the entire liquid, ie until no more free liquid is recognizable. This time is noted as tA. The free swell rate is then calculated according to FSR = Wu / (WH X t _A ).

dry weight

The dry weight is determined by heating the foam at 105 ° C for 3 hours. The exact procedure is described in EDANA Method 430.2-02. EDANA is the EUROPEAN DISPOSABLES AND NONWOVENS ASSOCIATION, Avenue Eugene Plasky, 157 - 1030 Brussels - Belgium, www.edana.org.

dry strength

Dry strength is the force required to controllably load a dried superabsorbent foam test article in the apparatus described below.

The dry strength is measured in a commercial texture analyzer (TA-XT2) from Stable Micro Systems, Surrey, UK. The measuring device is the same as in the determination of the wet fracture value (WO 2004/035668 p. 30 line 29ff and FIG. 1). On a measuring arm (1) is mounted a ball (2) of stainless steel with a diameter of 1 inch (2.54 cm), which is movable against a fixed between two metal plates sample of the superabsorbent foam (3). Both metal plates have a bore in the middle with a diameter (M) = 5.1 cm and a diameter (r2) = 3.5 cm, cf. WO 2004/035668 Figure 2. As can be seen from Figure 3 in WO 2004/035668, the side of the pierced plate with the diameter (r1) has a rounding, which corresponds to a quarter segment of a circle with a diameter of 0.8 cm. Only this side of the plates comes into contact with the foamy superabsorber to be examined. The rounding is important so that the test foam is not damaged by sharp corners during testing. The surface of the panels that come in contact with the foam is roughened to hold the foam in place during the test.

The plates each have a wall thickness of 0.8 cm and edge lengths a = 10 cm and b = 9 cm. The foam sample is placed between both plates as indicated above. The load of the device is set to 5000 g. In order to determine the dry strength, the ball (2) connected to the measuring arm (1) is then lowered at a speed of 0.5 mm / s and the force required to destroy the foam sample is measured. If the foam sample is not destroyed, the force necessary to reach the maximum distance of 30 mm passed through the ball (2) during the measurement is measured. From each foam, 3 samples were prepared and measured as described above. Here it is important that the foam samples to be examined do not contain any holes or larger air pockets, because this falsifies the measurement results. The following measurement specifications are described in detail in WO 2004/035668 to which reference is hereby made.

Wet failure value of superabsorbent foams (WFV): WO 2004/035668 p. 30, line 29ff.

Determination of the thickness of the swollen foam: WO 2004/035668 p. 31 line 28ff.

Cross-sectional area (CSA): WO 2004/035668 p. 31 line 34ff.

Wet break point: WO 2004/035668 p. 32 line 1ff.

swelling rate

The swelling rate is determined as follows: Using a sharp knife made of a foam (thickness 3 mm) with 5% by weight of moisture, a rectangular sample weighing 1.00 ± 0.009 g (which is typical foam densities and 3 mm thick Samples of about 3 x 3 cm pieces correspond, so that the required accuracy is easily achievable) cut out. The sample is placed in a Petri dish and charged with 20 g of a 0.9 wt .-% NaCl solution. It measures the swelling time, ie the time until the solution is completely absorbed by the foam. The swelling rate is determined to be 20g / [1g * swelling time in seconds].

Examples

Preparation of the foam used in the examples

The following components were mixed in a beaker using a magnetic stirrer.

209.13 g of acrylic acid

81, 31 g of a 37.3% sodium acrylate solution in water 16.8 g of polyethylene glycol diacrylate 400 25.60 g of a 15% aqueous solution of an addition product of 80 moles of ethylene oxide with 1 mol of a linear, saturated C16-C ₁ 8 fatty alcohols 26.62 g water

240.54 g of triethanolamine were slowly added to this solution while cooling with ice and then allowed to cool to 15 ° C. The resulting solution was transferred to a pressure vessel and saturated there with carbon dioxide for 25 minutes at a pressure of 12 bar by passing a carbon dioxide stream of 300 l / h. Vacuum 16 g of a 3% strength by weight aqueous solution of 2,2'-azobis (2-amidinopropane) dihydrochloride were added and then carbon dioxide was passed through the reaction mixture for a further 5 minutes. The reaction mixture was then forced out through a nozzle with a diameter of 1.0 mm at a pressure of 12 bar, forming a fine-cell, readily flowable foam.

The monomer foam obtained was applied to a DIN A3-sized glass plate with 3 mm high edges and covered with a second glass plate. The foam sample was irradiated synchronously from both sides over 4 minutes with UV light, from the top with a UV / VIS UVASPOT spotlight 1000 / T from Dr. Ing. Hönle AG, Gräfelfing, Germany, from below with 2 UV / VIS-Strahlem UVASPOT 4007T from the same manufacturer.

The foam layer obtained was completely dried in a vacuum drying oven at 80 ^° C. under a stream of nitrogen and then adjusted to a moisture content of 5% by weight by spraying with water.

Solids content of the reaction mixture: 81, 35% degree of neutralization: 60 mol% monomer foam density: 0.24 like " ³

Polymer foam density: 0,20 - ³

Foam structure: homogeneous, completely open-celled, none

skinning

Further properties of the open-cell foam are given in Table 1.

Examples 1-21

14 x 14 cm pieces of foam obtained as described were weighed and then treated with the source retardants listed in Table 1 in the form of aqueous solutions. The dispersions were sprayed on in the form of an aqueous solution of the stated concentration, and the powders were applied by powdering. Thereafter, the sample was each dried at 80 ⁰ C in a vacuum oven under a stream of nitrogen and weighed. The weight difference corresponds to the applied quantity. The results obtained are shown in Table 1. These examples show that treatment of the foam with source retardant slows water uptake as desired.

Examples 22-25

14 x 14 cm pieces of the foam obtained as described were sprayed with aqueous aluminum sulphate solution, so that the concentrates listed in Table 2 ones of aluminum sulfate were applied. Thereafter, the sample was in each case dried at 80 ^° C. in a vacuum drying oven under a stream of nitrogen and then adjusted to a moisture content of 5% by weight by spraying with water. The results obtained are shown in Table 2.

In addition, the dry strength of post-treated foams was measured. While untreated foam is destroyed at a force of 750 N, all post-treated foams resist this action.

The examples show that the treatment with complexing agent increases the stability of the foam in a desired manner.

Table 1

CJL

EA means ethyl acrylate, MAS means methacrylic acid

n

Claims

claims

1. Superabsorbent foam, the surface of which has been treated with at least one complexing agent and / or at least one source delaying agent.

2. A complexing agent-treated superabsorbent foam according to claim 1, characterized in that the complexing agent is a polyvalent cation.

3. Superabsorbent foam according to claim 2, characterized in that the complexing agent is a polyvalent metal cation.

4. Superabsorbent foam according to claim 3, characterized in that the polyvalent metal cation is Al ³⁺ .

5. A source-retarded superabsorbent foam according to claim 1, wherein the swelling rate is reduced by at least 50% by the source retardant.

The superabsorbent foam of claim 1 or 5 wherein the source retardant is a hydrophobic compound and optionally a hydrophilic compound.

7. Superabsorbent foam according to claim 6, wherein the hydrophobic and optionally hydrophilic compounds are particles having an average diameter of 0.001 to 10 microns.

8. Superabsorbent foam according to claims 6 or 7, wherein the hydrophobic compounds ben hydrophobic silicas or hydrophobic mixtures of silicas and alumina are.

9. superabsorbent foam according to any one of claims 6 to 8, characterized in that the hydrophilic compounds are silicas or mixtures of silicas and aluminas.

The superabsorbent foam of claim 1 or 5, wherein the source retardant is a water-soluble polymer.

11. Superabsorbent foam according to any one of claims 6 to 9, wherein the

In addition to hydrophobic and hydrophilic compounds, the source-delaying agent additionally comprises a water-soluble polymer.

12. A superabsorbent foam according to claim 10 or 11, wherein the polymer includes as the monomer component (meth) acrylic acid or its salts.

13. A superabsorbent foam according to any one of claims 10 to 12, wherein the polymer includes as the monomer component alkyl esters of (meth) acrylic acid.

The superabsorbent foam of any one of claims 10 to 13, wherein the polymer is crosslinked.

15. A superabsorbent foam according to any one of claims 2 to 11, characterized in that the foam has been post-treated with both a source retardant and with a polyvalent cation and optionally with a surfactant.

Superabsorbent foam according to claim 15, characterized in that the polyvalent cation is Al ³⁺ .

17. Superabsorbent foam according to claim 15 or 16, characterized in that it has been aftertreated with a sorbitan ester as a surfactant.

18. A superabsorbent foam according to any one of claims 15 to 17, characterized in that the polyvalent cation was metered as an aqueous solution and the surfactant has an HLB value of less than 18.

19. Superabsorbent foam according to one of claims 1 to 18, characterized in that the foam additionally contains fibers.

20. Superabsorbent foam according to claim 19, characterized in that the fibers are selected from one or more members of the group containing pulp fibers, in particular wood pulp or waste paper fibers, fruit fibers or superabsorbent fibers.

A superabsorbent foam according to claim 19 or 20, containing fibers at 0.01% to 10% by weight, based on the dry weight of the foam.

22. Superabsorbent foam according to any one of claims 1 to 21, obtainable by foaming an aqueous mixture containing polymerisable and crosslinkable, optionally (partially) neutralized, acid group-containing monoethylenically unsaturated monomers or at least one basic polymer, and crosslinker and at least one surfactant, and subsequent polymerization and / or crosslinking the foamed mixture and subsequent treatment with complexing and / or source retarding agents.

23. Superabsorbent foam according to one of claims 1 to 22, character- ized in that the surface of the foam is postcrosslinked.

24. Superabsorbent foam according to one of claims 22 to 23, characterized in that the aqueous mixture contains at least one crosslinkable basic polymer from the group of vinylamine units containing polymers, vinylguanidine units containing polymers, Dialkylaminoal- kyl (meth) acrylamideinheiten containing polymers, polyethylene imines, with E - Methylene grafted Polyamidoaminen and Polydiallaldimethylammoniumchlo- riden contains.

25. Use of the superabsorbent foams according to claims 1 to 24 in hygiene articles for absorption of body fluids, in particular as a storage component, in dressing material for covering wounds, as a sealing material, as a packaging material, as a soil conditioner, as a soil substitute, for dewatering sludges , for thickening aqueous paints when disposing of remaining paint quantities, for

Drainage of hydrous oils or hydrocarbons or as a filter material in ventilation systems.

26. A process for producing a superabsorbent foam as defined in claims 1 to 25, comprising the steps of foaming an aqueous mixture, the polymerizable and crosslinkable, optionally (partially) neutralized, acid group-containing monoethylenically unsaturated monomers or at least one crosslinkable basic polymer , as well as crosslinker and at least one surfactant, subsequent polymerization and / or crosslinking of the foamed mixture and subsequent treatment with complexing and / or

Source retardant.

27. Process according to claim 26, characterized in that the surface of the foam is postcrosslinked before treatment with complexing and / or swelling retardants.

28. The method according to claims 26 and 27, characterized in that one comprises an aqueous mixture with at least one crosslinkable basic polymer from the group of polymers comprising vinylamine units, polymers containing vinylguanidine n, polymers containing dialkylaminoalkyl (meth) acrylamide units, polyethyleneimines, with ethyleneimine grafted polyamidoamines and Polydiallaldimethylammoniumchloriden uses.