EP1347790A1

EP1347790A1 - Absorbent compositions

Info

Publication number: EP1347790A1
Application number: EP01272659A
Authority: EP
Inventors: Volker Frenz; Norbert Herfert; Ulrich Riegel; William E. Volz; Thomas H. Majette; James M. Hill
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2000-12-29
Filing date: 2001-12-20
Publication date: 2003-10-01
Also published as: WO2002053198A1; JP4315680B2; JP2004522491A; US20020128618A1; US6849665B2; US20020165288A1

Abstract

The invention relates to a water-absorbent composition containing, in relation to its weight, between 30 and 100 wt. % of non-water soluble hydrogels which can swell in water. Said hydrogels comprises the following characteristics: a centrifuge retention capacity (CRC) of at least 24 g/g; a saline flow conductivity (SFC) of at least 80 x 10<-7> cm<3>s/g; and a free swell rate (FSR) of at least 0,15 g/g and/or a maximum vortex time of 160s.

Description

Absorbent compositions

The invention relates to water-absorbent compositions with increased permeability, capacity and swelling rate, hygiene articles containing them and methods for improving the property profile of such hygiene articles.

By using hydrophilic, highly swellable hydrogels in hygiene articles, it was possible to significantly reduce the volume of the hygiene articles while maintaining the water absorption capacity. The hydrogels were selected primarily on the basis of their water absorption capacity.

The current trend in diaper construction is towards producing even thinner constructions with a reduced cellulose fiber content and an increased hydrogel content. The advantage of thinner constructions is not only evident in improved wearing comfort, but also in reduced packaging and storage costs. With the trend towards ever thinner diaper constructions, the requirement profile for the water-swellable hydrophilic polymers has changed significantly. The ability of the hydrogel to transfer and distribute fluids is now critical. Due to the higher loading of the hygiene article (polymer per unit area), the polymer in the swollen state must not form a barrier layer for subsequent liquid (gel blocking). If the product has good transport properties, optimal utilization of the entire hygiene article can be guaranteed.

In general, the effect of gel blocking is usually avoided by providing additional acquisition layers in the hygiene article from the outset, which absorb the liquid that hits it as a kind of intermediate buffer and distribute it within the absorption layer in order to then discharge it to the hydrogels. WO 91/11162 describes a hygiene article which has an additional liquid distribution layer made from chemically crosslinked cellulose fibers.

By incorporating an additional acquisition layer, the liquid is drained off from the point of impact, buffered and then absorbed by the hydrogel material at the rate set by long optimization work has been. The only path that was followed was to generate optimal absorption values (PAI), especially with regard to absorption values under pressure load (AUL), or in the latest studies on a whole range of different pressure loads and the effect of gel blocking, which primarily affects large ones The amount of highly swellable hydrogel particles used can be observed as given and compensated for by incorporating additional acquisition layers in the hygiene article.

According to WO 95/26209, an improved permeability of the absorption layer is achieved if the highly swellable hydrogels have a saline flow conductivity (SFC) of at least 30 x 10 ^"7 cm ³ s / g. The SFC measures the ability of the hydrogel layer formed to transmit liquid under one In addition, the high swellable hydrogels must have performance under pressure (PUP) values of at least 23 g / g to achieve the above objective, and are expressed as 60 minute absorbance values for synthetic urine weighing less than 0.7 psi (5 kPa) determined Finally, the extractable content must not exceed 15% of the total polymer content.

However, hygiene articles with thin absorbent compositions which are highly loaded with highly swellable hydrogels still show increased leakage rates in practice. It is still required to provide absorbent compositions which, when used in hygiene articles, have good transport properties, rapid fluid absorption with a high final absorption capacity and do not have the disadvantages of the prior art.

The object of the present invention is to provide absorbent compositions which have excellent permeability, a high absorption capacity and a high swelling rate, so that the effect of gel blocking can be avoided. This circumstance allows a higher loading with highly swellable hydrogels, which in turn enables the production of thinner hygiene articles with clear advantages in terms of wearing comfort and logistics.

The object is achieved according to the invention by a water-absorbing composition containing 30 to 100% by weight, based on the water-absorbing composition, of non-water-soluble water-swellable hydrogels, the hydrogels having the following features: centrifuge retention capacity (CRC) of at least 24 g / g, saline flow Conductivity (SFC) of at least 80 x 10 ^"7 cm ³ s / g and Free swell rate (FSR) of at least 0.15 g / gs and / or vortex time of maximum 160 s.

In addition, the object is achieved according to the invention by a method for improving the performance profile of water-absorbing compositions by increasing the permeability, capacity and swelling rate of the water-absorbing compositions by using non-water-soluble, water-swellable hydrogels which have the following property spectrum: centrifuge retention capacity (CRC) of at least 24 g / g, Saline Flow Conductivity (SFC) of at least 80 x 10 ^"7 cm s / g and Free Swell Rate (FSR) of at least 0.15 g / gs and / or Vortex Time of maximum 160 s, in the water-absorbing compositions.

In addition, the object is achieved according to the invention by a method for determining water-absorbing compositions with high permeability, capacity and swelling rate by measuring the centrifuge retention capacity (CRC), saline flow conductivity (SFC), free swell rate (FSR) and / or vortex time for all Given water-absorbing composition, contains water-insoluble, water-swellable hydrogels and determination of the water-absorbing compositions whose hydrogels show the following property spectrum: CRC of at least 24 g / g, SFC of at least 80 x 10 ^"7 cm ³ s / g and of at least 0.15 g / gs and / or vortex time of maximum 160 s.

Furthermore, the object is achieved according to the invention by using water-absorbing compositions which contain water-insoluble, water-swellable hydrogels which have the following features:

Centrifuge retention capacity (CRC) of at least 24 g / g, Saline Flow Conductivity (SFC) of at least 80 x 10 ^"7 cm ³ s / g and Free Swell Rate (FSR) of at least 0.15 g / gs and / or vortex time of maximum 160 s, in hygiene articles or other articles that serve to absorb aqueous liquids, to increase permeability, capacity and swelling speed.

It has been found that the use of highly swellable hydrogels with a special spectrum of characteristics of absorption capacity, absorption rate and permeability enables the production of absorbent compositions with a high hydrogel content, the highly swellable polymer particles of which are distinguished by high absorption capacity and good liquid distribution. When using highly swellable hydrogels with the combination of properties according to the invention an absorbent composition with improved permeability and high capacity can be generated. As a result of the increased proportion of highly swellable hydrogels with high capacity which is made possible, the absorbent composition has enormous absorption capacities, so that the problem of leakage is also avoided. At the same time, the high absorption capacity is fully exploited.

The term "water-absorbent" refers to water and aqueous systems which can contain dissolved organic and inorganic compounds, in particular to body fluids such as urine, blood or fluids containing them.

The absorbent composition is suitable for use in hygiene articles, such as diapers, sanitary napkins and incontinence pads, which are intended for single use.

The absorbent composition can preferably have a high proportion of highly swellable hydrogels, so that their proportion in the absorbent composition is at least 30% by weight, better at least 50% by weight, preferably at least 60%, more preferably at least 70%, particularly preferably 80 % and extremely preferably at least 90%.

According to the invention, hydrogels with the following combinations of properties are used:

CRC> 24 g / g, preferably> 26 g / g, more preferably> 28 g / g, even more preferably> 30 g / g, particularly preferably CRC> 32 g / g and most preferably> 35 g / g and

SFC> 80 x 10 ^"7 cm ³ s / g, preferably> 100 x 10 ^{" 7} cm ³ s / g, more preferably> 120 x 10 ^"7 cm ³ s / g, even more preferably> 150 x 10 ^{" 7} cm ³ s / g, particularly preferably> 200 x 10 ^"7 cm ³ s / g, most preferably> 300 x 10 ^{" 7} cm ³ s / g and - free swell rate> 0.15 g / gs, preferably> 0, 20 g / gs, more preferably> 0.30 g / gs, even more preferably> 0.50 g / gs, particularly preferably> 0.70 g / gs, most preferably> 1.00 g / gs and / or vortex Time> 160 s, preferably vortex time> 120 s, more preferably vortex time> 90 s, particularly preferably vortex time> 60 s, most preferably vortex time> 30 s.

The water-swellable hydrogels can be present in connection with a carrier material for the hydrogels. They can preferably be in the form of particles in a polymer fiber matrix or are embedded in an open-pore polymer foam, but they can also be fixed to a flat carrier material or be present as particles in chambers formed from a carrier material.

In addition, the hydrogels can be coated with a steric or electrostatic spacer.

The water-absorbent compositions according to the invention can by

- production of water-swellable hydrogels,

- If necessary, coating the hydrogels with a steric or electrostatic spacer and

- Connecting the hydrogels with the carrier material, preferably introducing the hydrogels into a polymer fiber matrix or an open-pore polymer foam or in chambers formed from a fiber material or fixing them to a flat carrier material

getting produced.

The water-absorbing compositions are used in particular for the production of hygiene articles or other articles which serve to absorb aqueous liquids. Such hygiene articles preferably contain a water-absorbing composition as defined above between a liquid-permeable cover sheet and a liquid-impermeable back sheet. They can be in the form of diapers, sanitary napkins and incontinence products such as pads.

The structure of the water-swellable hydrogels and their use is explained in more detail below.

Water-swellable hydrogels

Hydrogel-forming polymers are, in particular, polymers of (co) polymerized hydrophilic monomers, graft (co) polymers of one or more hydrophilic monomers on a suitable graft base, crosslinked cellulose or starch ethers, crosslinked carboxymethyl cellulose, partially crosslinked polyalkylene oxide or natural products swellable in aqueous liquids, such as guar derivatives, alginates and carrageenans. Suitable graft bases can be of natural or synthetic origin. Examples are starch, cellulose or cellulose derivatives and other polysaccharides and oligosaccharides, polyvinyl alcohol, polyalkylene oxides, in particular polyethylene oxides and polypropylene oxides, polyamines, polyamides and hydrophilic polyesters. Suitable polyalkylene oxides have, for example, the formula

X

R ^{1 ~} O ^~ (CH_ ^{~ "} CH ^_ O) _n ^~ R ²

R and R independently of one another are hydrogen, alkyl, alkenyl or aryl,

X is hydrogen or methyl and n is an (integer) number from 1 to 10,000.

R ¹ and R ² are preferably hydrogen, (C _\ - C ₄₎ alkyl, (C ₂ - C ₆₎ alkenyl or phenyl.

Preferred hydrogel-forming polymers are crosslinked polymers having acid groups which are predominantly in the form of their salts, generally alkali metal or ammonium salts. Such polymers swell particularly strongly into gels on contact with aqueous liquids.

Preferred are polymers which are obtained by crosslinking polymerization or copolymerization of monoethylenically unsaturated monomers bearing acid groups or their salts. It is also possible to (co) polymerize these monomers without crosslinking agents and to subsequently crosslink them.

Monomers bearing such acid groups are, for example, monoethylenically unsaturated C ₃ to C ₅ carboxylic acids or anhydrides such as acrylic acid, methacrylic acid, ethacrylic acid, α-chloroacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, aconitic acid and fumaric acid. Also suitable are monoethylenically unsaturated sulfonic or phosphonic acids, for example vinylsulfonic acid, allylsulfonic acid, sulfoethyl acrylate, sulfomethacrylate, sulfopropyl acrylate, sulfopropyl methacrylate, 2-hydroxy-3-acryloxypropylsulfonic acid, 2-hydroxy-3-methacrylic-oxypropylsulfonic acid,

Vinylphosphonic acid, allylphosphonic acid, styrene sulfonic acid and 2-acrylamido-2- methylpropanesulfonic. The monomers can be used alone or as a mixture with one another.

Preferred monomers are acrylic acid, methacrylic acid, vinyl sulfonic acid, acrylamidopropanesulfonic acid or mixtures of these acids, e.g. B. mixtures of acrylic acid and methacrylic acid, mixtures of acrylic acid and acrylamidopropanesulfonic acid or mixtures of acrylic acid and vinylsulfonic acid.

To optimize properties, it can be useful to use additional monoethylenically unsaturated compounds which do not carry any acid groups but can be copolymerized with the monomers bearing acid groups. These include, for example, the amides and nitriles of monoethylenically unsaturated carboxylic acids, e.g. As acrylamide, methacrylamide and N-vinylformamide, N-vinyl acetamide, N-methyl vinyl acetamide, acrylonitrile and methacrylonitrile. Other suitable compounds are, for example, vinyl esters of saturated C 1 -C ₄ -carboxylic acids such as vinyl formate, vinyl acetate or vinyl propionate, alkyl vinyl ethers having at least 2 C atoms in the alkyl group, such as ethyl vinyl ether or butyl vinyl ether, esters of monoethylenically unsaturated C ₃ -C ₆ -carboxylic acids , e.g. B. esters of monohydric - to C ₁₈ - alcohols and acrylic acid, methacrylic acid or maleic acid, half esters of maleic acid, for. B. maleic acid monomethyl ester, N-vinyl lactams such as N-vinyl pyrrolidone or N-vinyl caprolactam, acrylic acid and methacrylic acid esters of alkoxylated monohydric, saturated alcohols, for. B. of alcohols with 10 to 25 carbon atoms, which have been reacted with 2 to 200 moles of ethylene oxide and / or propylene oxide per mole of alcohol, and monoacrylic acid esters and monomethacrylic acid esters of polyethylene glycol or polypropylene glycol, the molecular weights (M _n ) of the polyalkylene glycols, for example, up to can be up to 2000. Other suitable monomers are styrene and alkyl-substituted styrenes such as ethylstyrene or tert-butylstyrene.

These monomers bearing no acid groups can also be used in a mixture with other monomers, for. B. Mixtures of vinyl acetate and 2-hydroxyethyl acrylate in any ratio. These monomers not carrying acid groups are added to the reaction mixture in amounts between 0 and 50% by weight, preferably less than 20% by weight.

Crosslinked polymers from monoethylenically unsaturated monomers bearing acid groups, which are optionally converted into their alkali metal or ammonium salts before or after the polymerization, and from 0 to 40% by weight, based on them, are preferred Total weight, no monoethylenically unsaturated monomers bearing acid groups.

Crosslinked polymers of monoethylenically unsaturated C ₃ to C ₁₂ carboxylic acids and / or their alkali metal or ammonium salts are preferred. In particular, crosslinked polyacrylic acids are preferred, the acid groups of which are 25-100% in the form of alkali or ammonium salts.

Compounds which have at least two ethylenically unsaturated double bonds can function as crosslinkers. Examples of compounds of this type are N, N ^C -methylene bisacrylamide, polyethylene glycol diacrylates and

Polyethylene glycol dimethacrylates which are each derived from polyethylene glycols having a molecular weight of from 106 to 8500, preferably 400 to 2000, derived, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate propylene glycol dimethacrylate, butanediol diacrylate, butanediol dimethacrylate, hexanediol diacrylate, hexanediol dimethacrylate, allyl methacrylate, diacrylates and dimethacrylates of block copolymers of ethylene oxide and Propylene oxide, polyhydric alcohols esterified two or more times with acrylic acid or methacrylic acid, such as glycerol or pentaerythritol, triallylamine, dialkyldiallylammonium halides such as dimethyldiallylammonium chloride and diethyldiallylammonium chloride. Tetraallylethylenediamine, divinylbenzene, diallyl phthalate, polyethylene glycol divinyl ether of polyethylene glycols with a molecular weight of 106 to 4000, trimethylol propane diallyl ether, butanediol divinyl ether, pentaerythritol triallyl ether, reaction products of 1 mole of ethylene glycol diglycidyl ether or pentylene glycol ether or polyethylene glycol trihydric ether or polyethylene glycol trihydric ether or polyethylene glycol trihydric ether or polyethylene glycol trihydric ether or polyethylene glycol trihydric ether or polyethylene glycol trihydric ether or pentyl glycol ether or polyethylene glycol trihydric ether or polyethylene glycol trihydric ether or polyethylene glycol trichlorodiacetyl or ethylene glycol trihydric ether or polyethylene glycol trihydric ether or methyl pentyl ether or methyl pentyl ether, Preferably, water-soluble crosslinking agents are used, e.g. B. N, N'-methylene bisacrylamide, polyethylene glycol diacrylates and

Polyethylene glycol dimethacrylates derived from addition products of 2 to 400 moles of ethylene oxide to 1 mole of a diol or polyol, vinyl ethers of addition products of 2 to 400 moles of ethylene oxide to 1 mole of a diol or polyol, ethylene glycol diacrylate, ethylene glycol dimethacrylate or triacrylates and trimethacrylates from addition products 20 moles of ethylene oxide with 1 mole of glycerol, pentaerythritol triallyl ether and / or divinyl urea.

Also suitable as crosslinkers are compounds which contain at least one polymerizable ethylenically unsaturated group and at least one further functional group. The functional group of these crosslinkers must be able to use the functional groups, essentially the acid groups, of the monomers. Suitable functional groups are, for example, hydroxyl, amino, epoxy and aziridino groups. Can be used for. B. hydroxyalkyl esters of the above monoethylenically unsaturated carboxylic acids, e.g. B. 2-hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate,

Hydroxypropyl methacrylate and hydroxybutyl methacrylate, allylpiperidinium bromide, N-vinylimidazoles such as N-vinylimidazole, l-vinyl-2-methylimidazole and Ν-vinylimidazolines such as Ν-vinylimidazoline, l-vinyl-2-methylimidazoline, l-vinyl-2-ethylimidazoline 2-propylimidazoline, which can be used in the form of the free bases, in quaternized form or as a salt in the polymerization. Dialkylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate and diethylaminoethyl methacrylate are also suitable. The basic esters are preferably used in quaternized form or as a salt. Furthermore, e.g. B. Glycidyl (meth) acrylate can also be used.

Also suitable as crosslinkers are compounds which contain at least two functional groups which are able to react with the functional groups, essentially the acid groups of the monomers. The functional groups suitable for this have already been mentioned above, ie hydroxyl, amino, epoxy, isocyanate, ester, amido and aziridino groups. Examples of such crosslinking agents are ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerin, polyglycerol, triethanolamine, propylene glycol, polypropylene glycol, block copolymers of ethylene oxide and propylene oxide, ethanolamine, sorbitan fatty acid ester, ethoxylated sorbitan fatty acid panitole, 1-pentaerytol fatty acid ester, trimethylphenol fatty acid, pentaethylene fatty acid, penta-adenol fatty acid, penta-ethylenediphenol, penta-ethane-1-propanol, penta-1-ethylenediol, penta-1-ethanediol, penta-1-olefanediol, penta-1-olefanediol, penta-1-ethanediol, penta-1-ethanediol, penta-1-olefin, 4-butanediol, polyvinyl alcohol, sorbitol, starch, polyglycidyl ethers such as ethylene glycol, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, propylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether, polyaziridine compounds such as 2,2-bishydroxymethylbutanol-tris [3- (l-aziridinyl ) - propionate], 1, 6-hexamethylene diethylene urea, diphenylmetharι-bis-4,4 '-Ν, Ν' -diethylene, haloepoxy compounds such as epichlorohydrin and α-methyl epifluorohydrin, polyisocyanates such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate, alkylene carbonates such as l, 3-dioxolan-2-one and 4-methyl-l, 3-dioxolan-2-one, further bisoxazolines and oxazolidones, polyamidoamines and their reaction products Epichlorohydrin, also polyquaternary amines such as condensation products of dimethylamine with epichlorohydrin, homo- and copolymers of diallyldimemylammonium chloride and homo- and copolymers of dimethylaminoethyl (meth) acrylate, which are optionally quaternized with, for example, methyl chloride.

Other suitable crosslinkers are polyvalent metal ions, which are able to form ionic crosslinks. Examples of such crosslinkers are magnesium, calcium, barium and aluminum ions. These crosslinkers are used, for example, as hydroxides, carbonates or bicarbonates. Other suitable crosslinkers are multifunctional bases which are also able to form ionic crosslinks, for example polyamines or their quaternized salts. Examples of polyamines are ethylenediamine, diethylenetriamine, triethylenetetramine,

Tetraethylene pentamine, pentaethylene hexamine and polyethylene imines as well as polyamines with molecular weights of up to 4000000 each.

The crosslinkers are present in the reaction mixture, for example from 0.001 to 20% by weight and preferably from 0.01 to 14% by weight.

The polymerization is initiated as usual by an initiator. It is also possible to initiate the polymerization by the action of electron beams on the polymerizable, aqueous mixture. However, the polymerization can also be initiated in the absence of initiators of the type mentioned above by exposure to high-energy radiation in the presence of photoinitiators. All compounds which decompose into free radicals under the polymerization conditions can be used as polymerization initiators, e.g. B. peroxides, hydroperoxides, hydrogen peroxides, persulfates, azo compounds and the so-called redox catalysts. The use of water-soluble initiators is preferred. In some cases it is advantageous to use mixtures of different polymerization initiators, e.g. B. mixtures of hydrogen peroxide and sodium or potassium peroxodisulfate. Mixtures of hydrogen peroxide and sodium peroxodisulfate can be used in any ratio. Suitable organic peroxides are, for example, acetylacetone peroxide, methyl ethyl ketone peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, tert-amyl perpivalate, tert-butyl perpivalate, tert-butyl perneohexanoate, tert-butyl perisobutyrate, tert-butyl per-2-ethylhexanoate, tert-butyl-peranoate , tert-butyl permaleate, tert-butyl perbenzoate, di- (2-ethylhexyl) peroxidicarbonate, dicyclohexyl peroxidicarbonate, di- (4-tert-butylcyclohexyl) peroxidicarbonate, dimyristilperoxidicarbonate, diacetylperoxydicarbonate, allylperodecylperyl, cumper 5,5-trimethylhexanoate, acetylcyclohexylsulfonyl peroxide, dilauryl peroxide, dibenzoyl peroxide and tertiary amyl perneodecanoate. Particularly suitable polymerization initiators are water-soluble azo starters, e.g. B. 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis (N, N'-dimethylene) isobutyramidine dihydrochloride, 2- (carbamoylazo) isobutyronitrile, 2,2 ' -Azobis [2- (2'-imidazolin-2-yl) propane] dihydrochloride and 4,4'-azo bis- (4-cyanovaleric acid). The polymerization initiators mentioned are used in conventional amounts, e.g. B. in amounts of 0.01 to 5, preferably 0.05 to 2.0 wt .-%, based on the monomers to be polymerized.

Redox catalysts are also suitable as initiators. The redox catalysts contain at least one of the above-mentioned per compounds as the oxidizing component and as reducing component, for example, ascorbic acid, glucose, sorbose, ammonium or alkali metal bisulfite, sulfite, thiosulfate, hyposulfite, pyro-sulfite or sulfide, metal salts, such as iron ( II) ions or sodium hydroxymethyl sulfoxylate. Ascorbic acid or sodium sulfite is preferably used as the reducing component of the redox catalyst. Based on the amount of monomers used in the polymerization, for example 3 × 10 ^"6 to 1 mol% of the reducing component of the redox catalyst system and 0.001 to 5.0 mol% of the oxidizing component of the redox catalyst are used.

If the polymerization is triggered by exposure to high-energy radiation, so-called photoinitiators are usually used as initiators. These can be, for example, so-called α-splitters, H-abstracting systems or also azides. Examples of such initiators are benzophenone derivatives such as Michler's ketone, phenanthrene derivatives, fluorene derivatives, anthraquinone derivatives, thioxanone derivatives, coumarin derivatives, benzoin ethers and their derivatives, azo compounds such as the radical formers mentioned above, substituted hexaarylbisimidazoles or acylphosphine oxides. Examples of azides are: 2- (N, N-dimethylamino) ethyl 4-azidocinnamate, 2- (N, N-dimethylamino) 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. If used, the photoinitiators are usually used in amounts of from 0.01 to 5% by weight, based on the monomers to be polymerized. In the subsequent crosslinking, polymers which have been prepared by the polymerization of the abovementioned monoethylenically unsaturated acids and, if appropriate, monoethylenically unsaturated comonomers and which have a molecular weight greater than 5000, preferably greater than 50,000, are reacted with compounds which have at least two groups reactive towards acid groups. This reaction can take place at room temperature or at elevated temperatures up to 220 ° C.

The suitable functional groups have already been mentioned above, i.e. Hydroxyl, amino, epoxy, isocyanate, ester, amido and aziridino groups, as well as examples of such crosslinkers.

Other suitable crosslinkers for postcrosslinking are polyvalent metal ions, which are able to form ionic crosslinks. Examples of such crosslinkers have already been listed above. Other suitable crosslinkers are multifunctional bases, which are also able to form ionic crosslinks; here too, examples of such compounds have already been mentioned above.

The crosslinking agents are added to the acid-bearing polymers or salts in amounts of 0.5 to 25% by weight, preferably 1 to 15% by weight, based on the amount of the polymer used.

The crosslinked polymers are preferably used in neutralized form. However, the neutralization can also have been carried out only partially. The degree of neutralization is preferably 25 to 100%, in particular 50 to 100%. Possible neutralizing agents are: alkali metal bases or ammonia or amines. Sodium hydroxide solution or potassium hydroxide solution is preferably used. However, the neutralization can also be carried out with the aid of sodium carbonate, sodium hydrogen carbonate, potassium carbonate or potassium hydrogen carbonate or other carbonates or hydrogen carbonates or ammonia. In addition, primary, secondary and tertiary amines can be used.

As a technical process for the production of these products, all processes can be used which are usually used in the production of superabsorbers, such as those used for. B. in Chapter 3 in "Modern Superabsorbent Polymer Technology", F.L. Buchholz and A.T. Graham, Wiley-VCH, 1998.

Polymerization in aqueous solution is preferred as so-called gel polymerization. 10 to 70% by weight aqueous solutions of the monomers and optionally a suitable graft base polymerized in the presence of a radical initiator using the Trommsdorff-Norrish effect.

The polymerization reaction can be carried out in the temperature range between 0 ° C. and 150 ° C., preferably between 10 ° C. and 100 ° C., both under normal pressure and under elevated or reduced pressure. As usual, the polymerization can also be carried out in a protective gas atmosphere, preferably under nitrogen.

By reheating the polymer gels for several hours, e.g. in the temperature range 50 to 130 ° C, preferably 70 to 100 ° C, the quality properties of the polymers can be improved even further.

Hydrogel-forming polymers which are post-crosslinked on the surface are preferred. The surface postcrosslinking can take place in a manner known per se with dried, ground and sieved polymer particles.

For this purpose, compounds which can react with the functional groups of the polymers with crosslinking are preferably applied to the surface of the hydrogel particles in the form of a water-containing solution. The water-containing solution can contain water-miscible organic solvents. Suitable solvents are alcohols such as methanol, ethanol, i-propanol or acetone.

Suitable post-crosslinking agents are, for example

Di- or polyglycidyl compounds such as phosphonic acid diglycidyl ether or ethylene glycol diglycidyl ether, bischlorohydrin ether of polyalkylene glycols,

alkoxysilyl

Polyaziridines, compounds containing aziridine units based on polyethers or substituted hydrocarbons, for example bis-N-aziridinomethane,

- Polyamines or polyamidoamines and their reaction products with

epichlorohydrin, Polyols such as ethylene glycol, 1,2-propanediol, 1,4-butanediol, glycerol, methyltriglycol, polyethylene glycols with an average molecular weight M _w of 200-10000, di- and polyglycerol, pentaerythritol, sorbitol, the oxyethylates of these polyols and their esters with carboxylic acids or carbonic acid such as ethylene carbonate or propylene carbonate.

Carbonic acid derivatives such as urea, thiourea, guanidine, dicyandiamide, 2-oxazolidinone and its derivatives, bisoxazoline, polyoxazolines, di- and polyisocyanates,

Di- and poly-N-methylol compounds such as methylenebis (N-methylol-methacrylamide) or melamine-formaldehyde resins,

Compounds with two or more blocked isocyanate groups such as trimethylhexamethylene diisocyanate blocked with 2,2,3,6-

Tetramethyl l-piperidinone-4.

If necessary, acidic catalysts such as p-toluenesulfonic acid, phosphoric acid, boric acid or ammonium dihydrogen phosphate can be added.

Particularly suitable post-crosslinking agents are di- or polyglycidyl compounds such as ethylene glycol diglycidyl ether, the reaction products of polyamidoamines with epichlorohydrin and 2-oxazolidinone.

The crosslinker solution is preferably applied by spraying on a solution of the crosslinker in conventional reaction mixers or mixing and drying systems such as Patterson-Kelly mixers, DRAIS turbulence mixers, Lödige mixers, screw mixers, plate mixers, fluidized bed mixers and Schugi mix. After spraying on the crosslinking agent solution, a temperature treatment step can follow, preferably in a downstream dryer, at a temperature between 80 and 230 ° C, preferably 80-190 ° C, and particularly preferably between 100 and 160 ° C, over a period of 5 minutes to 6 hours, preferably 10 minutes to 2 hours and particularly preferably 10 minutes to 1 hour, it being possible for both cleavage products and solvent fractions to be removed. However, drying can also take place in the mixer itself, by heating the jacket or by blowing in a preheated carrier gas. In a particularly preferred embodiment of the invention, the hydrogel-forming polymer is then coated with a steric or electrostatic spacer. Inert powders, such as, for example, silicates with a band, chain or leaf structure (montmorillonite, kaolinite, talc), zeolites, activated carbons or polysilicic acids, can act as steric spacers. Other inorganic inert spacers are, for example, magnesium carbonate, calcium carbonate, barium sulfate, aluminum oxide, titanium dioxide and iron (II) oxide. For example, polyalkyl methacrylates or thermoplastics such as polyvinyl chloride can function as inert organic-based spacers. Polysilicic acids are preferably used which, depending on the type of production, differentiate between precipitated silica and pyrogenic silicas. Both variants are commercially available under the names AEROSIL ^® (pyrogenic silicas) or Silica FK, Sipernat ^® , Wessalon ^® (precipitated silicas). The use of precipitated silicas is particularly preferred. The coating of the hydrogel-forming polymers with inert spacer material can be carried out by applying the inert spacers in an aqueous or water-miscible medium or else by applying the inert spacers in powder form to powdered hydrogel-forming polymer. The aqueous or water-miscible media are preferably applied by spraying onto dry polymer powder. In a particularly preferred production variant, pure powder / powder mixtures are produced from powdery inert spacer material and hydrogel-forming polymer. The inert spacer material is used in a proportion of 0.05 to 5% by weight, preferably 0.1 to 1.5% by weight, particularly preferably 0.3 to 1% by weight, based on the total weight of the coated hydrogel, applied to the surface of the hydrogel-forming polymer.

Cationic components can be used as electrostatic spacers. In general, it is possible to add cationic polymers for the purpose of electrostatic repulsion. This is possible, for example, with polyalkylene polyamines, cationic derivatives of polyacrylamides, polyethyleneimines, polyquaternary amines, such as. B. condensation products from hexamethylenediamine, dimethylamine and epichlorohydrin, condensation products from dimethylamine and epichlorohydrin, copolymers from hydroxyethylcellulose and diallyldimethylammonium chloride, copolymers from acrylamide and β-methaciylyloxyethyltrimethylammonium chloride, hydroxycellulose reacted with epichlorohydrin or ethylamine aminodimidophenium imidium imidium chloride, then quaternium aminidium imidium imidium imidium imidium imidonium imidium aminidium imidonium imidium aminidium imidonium aminomethyl imidonium imidium aminomethyl imidonium aminomethylchloride, then quaternium aminidium dimethyl aminophenyl imidium aminomethylchloride, then quaternyl aminodichlorohydrin amidium aminodichlorohydrin, then quaternium ammonium amide with aminodichlorohydrin, then quaternium aminium dehydrochloride; Polyquaternary amines can also by reacting Dimethyl sulfate can be synthesized with polymers such as polyethyleneimines, copolymers of vinylpyrrolidone and dimethylaminoethyl methacrylate or copolymers of ethyl methacrylate and diethylaminoethyl methacrylate. The polyquaternary amines are available in a wide range of molecular weights.

Electrostatic spacers are also generated by applying a cross-linked, cationic shell, either by reagents that can network with themselves, such as addition products of epichlorohydrin to polyamidoamines, or by applying cationic polymers that can react with an added crosslinker, e.g. B. polyamines or polyimines in combination with polyepoxides, multifunctional esters, multifunctional acids or multifunctional (meth) acrylates. All multifunctional amines with primary or secondary amino groups such as: polyethyleneimine, polyallylamine, polylysine, preferably polyvinylamine can be used. Further examples of polyamines are ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine and polyethyleneimines, and polyamines with molecular weights of up to 4,000,000 each.

Electrostatic spacers can also be applied by adding solutions of di- or polyvalent metal salt solutions. Examples of divalent or polyvalent metal cations are 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⁺ , Ag ⁺ , La ³⁺ , Ce ⁴⁺ , Hf ⁴⁺ , and Au ^{+ / 3 +} , preferred metal cations are Mg ⁺ , 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 either alone or in a mixture with one another. Of the metal cations mentioned, all metal salts are suitable which have sufficient solubility in the solvent to be used. Metal salts with weakly complexing anions such as chloride, nitrate and sulfate are particularly suitable. Water, alcohols, DMF, DMSO and mixtures of these components can be used as solvents for the metal salts. Water and water / alcohol mixtures such as water / methanol or water / 1,2-propanediol are particularly preferred.

In the manufacturing process, as in the case of the inert spacers, the electrostatic spacers can be applied by application in an aqueous or water-miscible medium. This is the preferred production variant when adding metal salts. Cationic polymers are made by applying an aqueous solution or in a water-miscible solvent, optionally also as a dispersion, or by applying in powder form to powdered hydrogel-forming polymer applied. The aqueous or water-miscible media are preferably applied by spraying onto dry polymer powder. The polymer powder can then optionally be dried. The cationic spacers are used in a proportion of 0.05 to 5% by weight, preferably 0.1 to 1.5% by weight, particularly preferably 0.1 to 1% by weight, based on the total weight of the coated hydrogel, applied to the surface of the hydrogel-forming polymer.

The highly swellable (water swellable) hydrogels can form the water-absorbing composition together with structure formers (carrier materials). This can e.g. B. be a fiber matrix, which consists of a cellulose fiber mixture (airlaid web, wet laid web) or synthetic polymer fibers (meltblown web, spunbonded web), or else consists of a mixed fiber structure made of cellulose fibers and synthetic fibers. Furthermore, open-pore foams or the like can be used for the installation of highly swellable hydrogels.

Alternatively, such a composition can result from the fusion of two individual layers, one or better a plurality of chambers being formed which contain the highly swellable hydrogels. In this case, at least one of the two layers should be permeable to water. The second layer can be either water permeable or water impermeable. Tissues or other fabrics, closed or open-cell foams, perforated films, elastomers or fabrics made of fiber material can be used as layer material. If the absorbent composition consists of a composition of layers, the layer material should have a pore structure whose pore dimensions are small enough to retain the highly swellable hydrogel particles. The above examples for the composition of the absorbent composition also include laminates of at least two layers, between which the highly swellable hydrogels are installed and fixed.

Furthermore, the absorbent composition can consist of a carrier material, such as. B. consist of a polymer film on which the highly swellable hydrogel particles are fixed. The fixation can be done on one or both sides. The carrier material can be water-permeable or water-impermeable.

In the absorbent compositions above, the highly swellable hydrogels are used in a weight fraction of 30 to 100% by weight, more preferably 50 to 100% by weight, preferably 60 to 100% by weight, more preferably 70 to 100% by weight. , in particular preferably from 80 to 100% by weight and extremely preferably from 90 to 100% by weight based on the total weight of the composition.

If the above composition of the absorbent composition is a fiber matrix, the absorbent composition results from a mixture of fiber materials and highly swellable hydrogels. The highly swellable hydrogels are incorporated in this fiber mixture in a weight fraction of preferably at least 30% by weight, better at least 50% by weight, preferably at least 60% by weight, based on the total weight of the absorbent composition.

The structure of the present absorbent composition according to the invention can be based on a variety of fiber materials which are used as fiber networks or matrices. Included in the present invention are both fibers of natural origin (modified or unmodified) and synthetic fibers.

Examples of cellulosic fibers include those commonly used in absorption products such as fleece pulp and cotton-type pulp. The materials (softwood or hardwood), manufacturing processes such as chemical pulp, semi-chemical pulp, chemothermal mechanical pulp (CTMP) and bleaching processes are not particularly limited. For example, natural cellulose fibers such as cotton, flax, silk, wool, jute, ethyl cellulose and cellulose acetate are used.

Suitable synthetic fibers are made from polyvinyl chloride, polyvinyl fluoride, polytetrafluoroethylene, polyvinylidene chloride, polyacrylics such as ORLON ^®, polyvinyl acetate, polyethylvinyl acetate, polyvinyl alcohol soluble or insoluble. Examples of synthetic fibers include thermoplastic polyolefin fibers, such as polyethylene fibers (PULPEX ^® ), polypropylene fibers and polyethylene-polypropylene two-component fibers, polyester fibers, such as polyethylene terephthalate fibers (DACRON ^® or KODEL ^® ), copolyesters, polyvinyl acetate, polyethyl vinyl acetate, polyvinyl polyamide, copolyamides, polyvinyl chloride , Polystyrene and copolymers of the abovementioned polymers, and also two-component fibers made from polyethylene terephthalate-polyethylene-isophthalate copolymer,

Polyethyl vinyl acetate / polypropylene, polyethylene / polyester, polypropylene / polyester, copolyester / polyester, polyamide fibers (nylon), polyurethane fibers, polystyrene fibers and

Polyacrylonitrile fibers. Polyolefin fibers, polyester fibers and their are preferred

Two-component fibers. Also preferred are those adhering to heat Bicomponent sheath-core and side-by-side polyolefin fibers because of their excellent shape retention after liquid absorption.

The synthetic fibers mentioned are preferably used in combination with thermoplastic fibers. During heat treatment, the latter partially migrate into the matrix of the existing fiber material and thus represent connection points and renewed stiffening elements when cooling. In addition, the addition of thermoplastic fibers means an expansion of the existing pore dimensions after the heat treatment has taken place. In this way it is possible to continuously increase the proportion of thermoplastic fibers to the cover sheet by continuously metering in thermoplastic fibers during the formation of the absorption layer, which results in an equally continuous increase in pore sizes. Thermoplastic fibers can be formed from a large number of thermoplastic polymers which have a melting point of less than 190 ° C., preferably between 75 ° C. and 175 ° C. At these temperatures, no damage to the cellulose fibers is yet to be expected.

The lengths and diameters of the synthetic fibers described above are not particularly limited, and in general, any fiber with a length of 1 to 200 mm and a diameter of 0.1 to 100 denier (grams per 9,000 meters) can be preferably used. Preferred thermoplastic fibers have a length of 3 to 50 mm, particularly preferred a length of 6 to 12 mm. The preferred diameter of the thermoplastic fiber is between 1.4 and 10 decitex, particularly preferably between 1.7 and 3.3 decitex (grams per 10,000 meters). The shape is not particularly limited, and examples include fabric-like, narrow cylinder-like, cut / split yarn-like, staple fiber-like and continuous fiber-like.

The fibers in the absorbent composition of the invention can be hydrophilic, hydrophobic, or a combination of both. According to the definition by Robert F. Gould in the publication "Contact Angle, Wettability and Adhesion", American Chemical Society (1964), a fiber is said to be hydrophilic if the contact angle between the liquid and the fiber (or its surface) is less than 90 ° or if the liquid tends to spread spontaneously on the same surface. As a rule, both processes are coexistent. Conversely, a fiber is said to be hydrophobic if a contact angle of greater than 90 ° is formed and no spreading is observed. Hydrophilic fiber material is preferably used. It is particularly preferred to use fiber material that is weakly hydrophilic on the body side and most hydrophilic in the region around the highly swellable hydrogels. In the manufacturing process, the use of layers of different hydrophilicity creates a gradient that channels the impinging liquid to the hydrogel, where the absorption ultimately takes place.

Suitable hydrophilic fibers for use in the absorbent composition according to the invention are, for example, cellulose fibers, modified cellulose fibers, rayon, polyester fibers such as, for. B. polyethylene terephthalate (DACRON ^® ), and hydrophilic nylon (HYDROFIL ¹ ). Suitable hydrophilic fibers can also be obtained by hydrophilizing hydrophobic fibers, such as treating thermoplastic fibers obtained from polyolefins (such as polyethylene or polypropylene, polyamides, polystyrenes, polyurethanes, etc.) with surfactants or silica. However, cellulose fibers are preferred for reasons of cost and availability.

The highly swellable hydrogel particles are embedded in the fiber material described. This can be done in a variety of ways, e.g. B. builds up an absorption layer in the form of a matrix with the hydrogel material and the fibers, or by embedding highly swellable hydrogels in layers of fiber mixture, where they are ultimately fixed, whether by adhesive or lamination of the layers.

The liquid-absorbing and -distributing fiber matrix can consist of synthetic fiber or cellulose fiber or a mixture of synthetic fiber and cellulose fiber, whereby the mixing ratio of (100 to 0) synthetic fiber: (0 to 100) cellulose fiber can vary. The cellulose fibers used can additionally be chemically stiffened to increase the dimensional stability of the hygiene article.

The chemical stiffening of cellulose fibers can be achieved in different ways. On the one hand, fiber stiffening can be achieved by adding suitable coatings to the fiber material. Such additives include for example polyamide-epichlorohydrin coatings (Kymene ^® 557H, Hercoles, Inc. Wilmington, Delaware, USA), polyacrylamide coatings (described in US 3,556,932 or as a product of Parez ^® 631 NC trademark, American Cyanamid Co., Stamford, CT, USA), melamine-formaldehyde coatings and polyethyleneimine coatings. The chemical stiffening of cellulose fibers can also be done by chemical reaction. So z. B. the addition of suitable crosslinking substances bring about a crosslinking that takes place within the fiber. Suitable crosslinking substances are typical substances that are used to crosslink monomers. Included, but not limited to, are C ₂ -C ₈ dialdehydes, C ₂ -C ₈ monoaldehydes with acidic functionality, and in particular C ₂ -C polycarboxylic acids. Specific substances from this series are, for example, glutaraldehyde, glyoxal, glyoxylic acid, formaldehyde and citric acid. These substances react with at least 2 hydroxyl groups within a single cellulose chain or between two adjacent cellulose chains within a single cellulose fiber. The crosslinking stiffens the fibers, which are given greater dimensional stability through this treatment. In addition to their hydrophilic character, these fibers have uniform combinations of stiffening and elasticity. This physical property makes it possible to maintain the capillary structure even with simultaneous contact with liquid and compression forces and to prevent premature collapse.

Chemically crosslinked cellulose fibers are known and are described in WO 91/11162, US 3,224,926, US 3,440,135, US 3,932,209, US 4,035,147, US 4,822,453, US 4,888,093, US 4,898,642 and US 5,137,537. The chemical crosslinking stiffens the fiber material, which is ultimately reflected in the improved dimensional stability of the entire hygiene article. The individual layers are by methods known to those skilled in the art, such as. B. fused together by heat treatment, adding hot melt adhesives, latex binders, etc.

Examples of processes with which an absorbent composition is obtained which consists, for example, of highly swellable hydrogels (c) embedded in a fiber material mixture of synthetic fibers (a) and cellulose fibers (b), the mixing ratio of (100 to 0) synthetic fibers : (0 to 100) cellulose fiber may vary include (1) a process in which (a), (b) and (c) are mixed simultaneously, (2) a process in which a mixture of (a) and ( b) is mixed into (c), (3) a process in which a mixture of (b) and (c) is mixed with (a), (4) a process in which a mixture of (a) and ( c) is mixed into (b), (5) a process in which (b) and (c) are mixed and (a) is metered in continuously, (6) a process in which (a) and (c) are mixed and (b) is metered in continuously, and (7) a process in which (b) and (c) are mixed separately into (a). Of these examples, methods (1) and (5) are preferred. The device in this The method used is not particularly restricted and a conventional device known to the person skilled in the art can be used.

The correspondingly produced absorbent composition can optionally be subjected to a heat treatment, so that an absorption layer with excellent dimensional stability in the moist state results. The heat treatment process is not particularly limited. Examples include heat treatment by supplying hot air or infrared radiation. The temperature during the heat treatment is in the range from 60 ° C. to 230 ° C., preferably between 100 ° C. and 200 ° C., particularly preferably between 100 ° C. and 180 ° C.

The duration of the heat treatment depends on the type of synthetic fiber, its quantity and the manufacturing speed of the hygiene article. In general, the duration of the heat treatment is between 0.5 seconds to 3 minutes, preferably 1 second to 1 minute.

The absorbent composition is generally provided, for example, with a liquid pervious top layer and a liquid impervious bottom layer. Leg cuffs and adhesive tapes are also attached, thus completing the hygiene article. The materials and types of the permeable top layer and impermeable bottom layer, as well as the leg ends and adhesive tapes are known to the person skilled in the art and are not particularly restricted.

Description of the test methods

Centrifuge Retention Capacity (CRC Centrifuge Retention Capacity)

This method determines the free swellability of the hydrogel in the tea bag. To determine the CRC, 0.2000 ± 0.0050 g of dried hydrogel (comfraction 106 - 850 μm) are weighed into a 60 x 85 mm tea bag, which is then sealed. The tea bag is placed in an excess of 0.9% by weight saline solution (at least 0.83 1 saline solution / lg polymer powder) for 30 minutes. The tea bag is then centrifuged at 250 g for 3 minutes. The amount of liquid is determined by weighing the centrifuged tea bag. Free Swell Rate (FSR)

To determine the free swell rate, 1.00 g (W _H ) hydrogel is spread evenly on the bottom of a plastic dish with a round bottom of approx. 6 cm. The plastic bowl has a height of approx. 2.5 cm and has a square opening of approx. 7.5 cm x 7.5 cm. With the aid of a funnel, 20 g (WTJ) of a synthetic urine replacement solution can now be prepared by dissolving 2.0 g KC1, 2.0 g Na ₂ SO, 0.85 g NH ₄ H ₂ PO ₄ , 0.15 g (NH ₄ ) Add ₂ HPO ₄ , 0.19 g CaCl ₂ and 0.23 g MgCl ₂ in 1 liter distilled water to the center of the plastic dish. As soon as the liquid comes into contact with the hydrogel, the time measurement is started and only stopped when the hydrogel has completely absorbed all the liquid, ie until no free liquid can be seen. This time is noted as _A. The free swell rate is then calculated according to

FSR = Wu / (W _H xt _A ).

Saline Flow Conductivity (SFC)

The test method for determining the SFC is described in WO 95/26209.

Vortex test

50 ml of 0.9% strength by weight NaCl solution are placed in a 100 ml beaker and, while stirring at 600 rpm, 2.00 g of hydrogel are quickly added using a magnetic stirrer in such a way that clumping is avoided. The time is measured in seconds until the vortex created by the stirring of the liquid is closed and a smooth surface is created.

Acquisition Time / Rewet under pressure

The examination is carried out on so-called laboratory pads. To produce these laboratory pads, 11.2 g of cellulose fluff and 23.7 g of hydrogel are swirled homogeneously in an air chamber and placed on a 12 x 26 cm mold by applying a slight negative pressure. This composition is then wrapped in tissue paper and pressed twice at 15 bar at a pressure of 200 bar. A laboratory pad manufactured in this way is attached to a horizontal surface. The center of the pad is determined and marked. The task of synthetic Urine replacement is done using a plastic plate with a ring in the middle (inner diameter of the ring 6.0 cm, height 4.0 cm). The plate is loaded with additional weights so that the total load on the pad is 13.6 g / cm ² . The plastic plate is placed on the pad so that the center of the pad is also the center of the feed ring. 100 ml of 0.9% by weight sodium chloride solution are applied three times. The saline solution is measured in a measuring cylinder and applied to the pad in one shot through the ring in the plate. Simultaneously with the task, the time is measured which is necessary for the solution to penetrate completely into the pad. The measured time is noted as Acquisition Time 1. The pad is then loaded with a plate for 20 minutes, the load being kept at 13.6 g / cm ² . After this time the plate is removed, 10 g ± 0.5 g of the filter paper (Schleicher & Schuell, 1450 CV) are placed on the center and with a weight (area 10 x 10 cm, weight 3.5 kg) for 15 s loaded. After this time, the weight is removed and the filter paper is weighed back. The difference in weight is noted as Rewet 1. Then the plastic plate with the feed ring is placed on the pad again and the second application of the liquid takes place. The measured time is noted as Acquisition Time 2. The procedure is repeated as described, but 45g ± 0.5g filter paper is used for the Rewet examination. Rewet 2 is noted. The same procedure is followed when determining acquisition time 3. When determining Rewet 3, 50 g ± 0.5 g filter paper are used.

The following examples are intended to explain the invention in more detail.

Examples

Highly swellable hydrogels were investigated, which were designated with the letters A to K in the following tables.

Samples C, F, I and J are comparative samples which do not meet the selection criteria according to the invention and therefore cannot meet the absorbent compositions according to the invention.

It can be seen very clearly that these products in the tests of the Acquisition Time and Rewet, especially in the third task of the urine replacement solution (Acquisition Time 3, Rewet 3) deviate enormously from the products which correspond to the selection criteria according to the invention. Examples:

Examined hydrogels:

Results of the acquisition time / rewet test:

Claims

claims

1. Water-absorbing composition containing 30 to 100 wt .-%, based on the water-absorbing composition, non-water-soluble water-swellable hydrogels, characterized in that the hydrogels follow

Features:

- centrifuge retention capacity (CRC) of at least 24 g / g,

- Saline Flow Conductivity (SFC) of at least 80 x 10 ^"7 cm ³ s / g and - Free Swell Rate (FSR) of at least 0.15 g / gs and / or Vortex Time of maximum 160 s.

2. Water-absorbing composition according to claim 1, characterized in that the water-swellable hydrogels are present in connection with a carrier material for the hydrogels.

3. Water-absorbing composition according to claim 2, characterized in that the water-swellable hydrogels are present as particles embedded in a polymer fiber matrix or an open-pore polymer foam, are fixed to a flat carrier material or are present as particles in chambers formed from a carrier material.

4. Water-absorbing composition according to one of claims 1 to 3, characterized in that the hydrogels are coated with a steric or electrostatic spacer.

5. A process for the preparation of water-absorbent compositions according to any one of claims 2 to 4

- production of water-swellable hydrogels,

optionally coating the hydrogels with a steric or electrostatic spacer,

- Connecting the hydrogels with the carrier material, preferably introducing the hydrogels into a polymer fiber matrix or an open-pore polymer foam or in chambers formed from a carrier material or fixing them to a flat carrier material.

6. Use of water-absorbent compositions according to any one of claims 1 to 4 for the production of hygiene articles or other articles which serve for the absorption of aqueous liquids.

7. hygiene article containing a water-absorbing composition according to any one of claims 1 to 4 between a liquid-permeable cover sheet and a liquid-impermeable back sheet.

8. Hygiene article according to claim 7 in the form of diapers, sanitary napkins or incontinence products.

9. A method for improving the performance profile of water-absorbent compositions by increasing the permeability, capacity and swelling rate of the water-absorbent compositions by using non-water-soluble water-swellable hydrogels, the following

Show property spectrum:

- centrifuge retention capacity (CRC) of at least 24 g / g,

- Saline Flow Conductivity (SFC) of at least 80 x 10 ^" cm s / g and - Free Swell Rate (FSR) of at least 0.15 g / gs and / or Vortex Time of maximum 160 s,

in the water absorbing compositions.

10. Method for determining water-absorbent compositions with high permeability, capacity and swelling rate by measuring the centrifuge retention capacity (CRC), saline flow conductivity (SFC), free swell rate (FSR) and / or vortex time for non-water-soluble ones contained in a given water-absorbing composition , water-swellable hydrogels and determination of the water-absorbing compositions, the hydrogels of which show the following range of properties:

- CRC of at least 24 g / g,

- SFC of at least 80 x 10 ^"7 cm ³ s / g and - FSR of at least 0.15 g / gs and / or vortex time of maximum 160 s.

1. Use of water-absorbent compositions which contain non-water-soluble, water-swellable hydrogels which have the following features:

- centrifuge retention capacity (CRC) of at least 24 g / g,

- Saline Flow Conductivity (SFC) of at least 80 x 10 ^"7 cm ³ s / g and

- Free Swell Rate (FSR) of at least 0.15 g / g s and / or vortex time of 160 s,

in hygiene articles or other articles that are designed to absorb watery

Liquids are used to increase permeability, capacity and swelling rate.