WO2013000910A1 - Composite foam for wound dressings - Google Patents

Abstract

The present invention relates to a composite foam comprising an absorption layer and a storage layer bonded directly to the absorption layer at least in some regions, the absorption layer comprising a polyurethane foam A) obtainable by mechanical foaming of an aqueous polyurethane dispersion a) and subsequent drying, and the storage layer comprising a polyurethane foam B) obtainable by reactive conversion of a least the following components: b) an isocyanate-functional prepolymer, c) water. The invention further provides a process for producing the inventive composite foam and a wound dressing comprising the inventive composite foam.

Description

 Composite foam for wound dressings

The present invention relates to a composite foam comprising an absorption layer and a storage layer connected at least in regions to the absorption layer. Further objects of the invention are a process for producing the composite foam according to the invention and a wound dressing comprising the composite foam according to the invention.

European Patent Application EP 2 143 744 A1 describes hydrophilic aliphatic polyurethane foams which are obtainable by reacting monomer-poor prepolymers with water. The absorbency of these foams for liquids such as water is high, i. they can store large quantities of liquid, but the absorption rate is relatively low, so that only relatively small amounts of liquid per time can be absorbed. For products such as e.g. This is disadvantageous for sanitary napkins, diapers or wound dressings, since it is of decisive importance here that the liquid is absorbed quickly and transported away from the receiving location into the interior of the foam. This is especially true in the treatment of open wounds such as ulcers during the exudative phase of wound healing. In this case, the excess moisture released by the wound must be absorbed, otherwise a secretion may cause a wound infection.

EP 2 028 223 A1 again discloses polyurethane foams which can be produced by mechanical foaming of aqueous polyurethane dispersions. These foams are intended, inter alia, for use in wound dressings and are characterized by a high absorption rate for liquids. However, their absorption capacity is limited.

EP 2 140 888 A1 discloses a composite foam which can be used in particular as part of a wound dressing. The composite foam comprises a storage layer, an absorption layer and a cover layer. The storage layer consists of a superabsorbent and the absorption layer of a polyurethane foam, which is obtained by mechanical impact of an aqueous polyurethane dispersion. The composite foam is an island composite in which the storage layer is completely enclosed by the absorption layer and the cover layer. The composite foam is produced by applying the polyurethane foam of the absorption layer to a substrate and using a superabsorbent material. bervlies is placed in the still wet foam. After drying the polyurethane foam, the cover layer is then applied to the absorption layer over the superabsorbent web. For example, a further polyurethane foam or a thermoplastic film can be used as the cover layer, which are then bonded to the absorption layer either by drying the polyurethane foam or by thermolamination of the thermoplastic film. Composite foams for wound dressings without a cover layer are not disclosed in EP 2 140 888 A1. Thus, the top layer is also required because the superabsorbent fleece on the one hand on the access of liquid from the outside must be protected and on the other hand its direct contact with tissue, such as by accidental contact, should be prevented. For this reason, the design options with respect to the spatial arrangement and connection of the individual layers are limited in the known composite foam. Another disadvantage of this composite foam is the extremely high absorption capacity of the superabsorbent, which can cause excessive drying of the wound, although a slightly moist environment of fresh wound exudate is optimal for wound healing. The object of the present invention was therefore to provide a composite foam which has a high absorbency and a high absorption rate while allowing great flexibility in the arrangement and connection of the individual layers.

This object is achieved by a composite foam comprising an absorption layer and a storage layer connected at least in regions directly to the absorption layer, in which the absorption layer comprises a polyurethane foam A) which is obtainable by mechanical foaming of an aqueous polyurethane dispersion a) and subsequent drying and the storage layer comprises a polyurethane foam B) obtainable by reacting at least the following components: b) an isocyanate-functional prepolymer, c) water.

Thus, it has surprisingly been found that the composite foam according to the invention is both capable of quickly absorbing liquids such as water and of storing them in large quantities. It thus has both a high absorption rate and a high absorption capacity, the absorption capacity is not so great that it when used in a wound dressing can lead to excessive drying of the wound. In addition, the absorption layer and the storage layer can be spatially arranged in a variety of ways and directly connected to each other, wherein it additionally does not necessarily require an additional cover layer. Finally, due to the direct connection of the absorption layer with the storage layer, the transfer of liquids from the absorption layer into the storage layer takes place particularly efficiently. This advantage is particularly evident in comparison with prior art composite foams in which the absorption layer and the storage layer are connected, for example, by an adhesive between the layers. Thus, the adhesive may interfere with the transfer of fluid between the layers.

According to a first preferred embodiment of the composite foam according to the invention, it is provided that the polyurethane dispersion a) is obtainable by reacting at least the following components: a) an isocyanate-functional prepolymer, a2) optionally an isocyanate-reactive, preferably amino-functional, anionic or potentially anionic hydrophobic agent, a3) optionally an amino-functional compound, in particular having a molecular weight of from 32 to 400 g / mol, a4) water, wherein the hydrophobic agent a2) is obligatory if the prepolymer al) itself does not have any hydrophilicizing groups.

In the present case, preference is given to anionic and potentially anionic groups as hydrophilicizing groups. Polyurethane foams, which are obtainable by foaming such an aqueous polyurethane dispersion, are distinguished by a particularly high absorption rate.

Particularly preferred is an isocyanate-functional prepolymer al) obtainable by reacting at least the following components: aa) an organic polyisocyanate, aa2) a polymeric polyol, in particular having a number-average molecular weight of 400 to 8000 g / mol and / or an average OH functionality of 1.5 to 6, aa3) optionally a hydroxy-functional compound, in particular having a molecular weight of 62 to 399 g / mol, aa4) optionally an isocyanate-reactive, anionic or potentially anionic and / or optionally nonionic hydrophilicizing agent.

Suitable polyisocyanates of component aal) are the aromatic, araliphatic, aliphatic or cycloaliphatic polyisocyanates having an NCO functionality of> 2 known to the person skilled in the art. Examples of such polyisocyanates are 1,4-butylene diisocyanate, 1,6-hexamethylene diisocyanate

(HDI), isophorone diisocyanate (IPDI), 2,2,4 and / or 2,4,4-trimethylhexamethylene diisocyanate, the isomeric bis (4,4'-isocyanatocyclohexyl) methanes or mixtures thereof of any isomer content, 1,4-cyclohexylene diisocyanate, 1 , 4-phenylene diisocyanate, 2,4- and / or 2,6-toluene diisocyanate, 1,5-naphthylene diisocyanate, 2,2'- and / or 2,4'- and / or 4,4'-di-phenylmethane diisocyanate, 1 , 3- and / or 1,4-bis (2-isocyanato-prop-2-yl) -benzene (TMXDI), 1,3-bis (isocyanatomethyl) benzene (XDI), alkyl 2,6-diisocyanatohexanoate ( Lysindiisocyanate) with C l -C 8 -alkyl groups, and 4-isocyanatomethyl-l, 8-octane diisocyanate (Nonantriisocyana- nat) and triphenylmethane-4,4 ', 4 "triisocyanate.

In addition to the abovementioned polyisocyanates, it is also possible proportionally to use modified diisocyanates or triisocyanates having uretdione, isocyanurate, urethane, allophanate, biuret, iminooxadiazinedione and / or oxadiazinetrione structures.

Preference is given to polyisocyanates or polyisocyanate mixtures of the abovementioned type with exclusively aliphatically and / or cycloaliphatically bonded isocyanate groups and an average NCO functionality of the mixture of 2 to 4, preferably 2 to 2.6 and particularly preferably 2 to 2.4 ,

Particularly preferred are in aal) 1,6-hexamethylene diisocyanate, isophorone diisocyanate, the isomeric bis (4,4'-isocyanatocyclohexyl) methanes and mixtures thereof.

In aa2) it is preferred to use polymeric polyols having a number average molecular weight Mn of from 400 to 8000 g / mol and more preferably from 600 to 3000 g / mol. These preferably have an OH functionality of from 1.8 to 3, particularly preferably from 1.9 to 2.1.

Suitable polymeric polyols are the polyester polyols known per se in polyurethane coating technology, polyacrylate polyols, polyurethane polyols, polycarbonate polyols, polyether polyols, polyester polyacrylate polyols, polyurethane polyacrylate polyols, polyurethane polyester polyols, polyurethane polyether polyols, polyurethane polycarbonate polyols and polyester polycarbonate polyols. These can be used in aa2) individually or in any mixtures with each other.

Examples of suitable polyester polyols are the known polycondensates of di- and optionally tri- and tetraols and di- and optionally tri- and tetracarboxylic acids or hydroxycarboxylic acids or lactones. Instead of the free polycarboxylic acids, it is also possible to use the corresponding polycarboxylic acid anhydrides or corresponding polycarboxylic acid esters of lower alcohols to prepare the polyesters.

Suitable diols for the preparation are ethylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycols such as polyethylene glycol, furthermore 1,2-propanediol, 1,3-propanediol, butanediol (1,3), butanediol (1,4), hexanediol (1,6 and isomers, neopentyl glycol or hydroxypivalic acid neopentyl glycol esters, with hexanediol (1,6) and isomers, neopentyl glycol and neopentyl glycol hydroxypivalate being preferred. In addition, it is also possible to use polyols, such as trimethylolpropane, glycerol, erythritol, pentaerythritol, trimethylolbenzene or trishydroxyethyl isocyanurate.

Suitable dicarboxylic acids are phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, glutaric acid, tetrachlorophthalic acid, maleic acid, fumaric acid, itaconic acid, malonic acid, suberic acid, 2-methylsuccinic acid, 3,3-diethylglutaric acid and / or 2,2-dimethylsuccinic acid. The acid source used may also be the corresponding anhydrides.

If the mean functionality of the polyol to be esterified is greater than 2, monocarboxylic acids, such as benzoic acid and hexanecarboxylic acid may additionally be used.

Preferred acids are aliphatic or aromatic acids of the abovementioned type. Particular preference is given to adipic acid, isophthalic acid and, if appropriate, trimellitic acid. Hydroxycarboxylic acids which can be used as reactants in the preparation of a hydroxyl-terminated polyester polyol include hydroxycaproic acid, hydroxybutyric acid, hydroxydecanoic acid, hydroxystearic acid and the like. Suitable lactones are caprolactone, butyrolactone and homologs. Preference is given to caprolactone.

It is likewise possible in aa2) to use hydroxyl-containing polycarbonates, preferably polycarbonatediols, particularly preferably having number-average molecular weights M _{n of} from 400 to 8000 g / mol and very particularly preferably from 600 to 3000 g / mol. These are obtainable by reaction of carbonic acid derivatives, such as diphenyl carbonate, dimethyl carbonate or phosgene, with polyols, preferably diols. Examples of suitable diols are ethylene glycol, 1, 2 and 1, 3-propanediol, 1,3- and 1, 4-butanediol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, 1, 4-bishydroxymethylcyclohexane, 2 Methyl-1,3-propanediol, 2,2,4-trimethylpentanediol-1,3-dipropylene glycol, polypropylene glycols, dibutylene glycol, polybutylene glycols, bisphenol A and lactone-modified diols of the abovementioned type. The polycarbonate diol preferably contains from 40 to 100% by weight. % Hexane diol, especially 1,6-

Hexanediol and / or hexanediol derivatives, based on the underlying diols. These hexanediol derivatives are based on hexanediol and have ester or ether groups in addition to terminal OH groups. Such derivatives are obtainable by reaction of hexanediol with excess caprolactone or by etherification of hexanediol with itself to give di- or trihexylene glycol.

Instead of or in addition to pure polycarbonate diols, it is also possible to use polyether-polycarbonate diols in aa2).

The hydroxyl-containing polycarbonates are preferably built linear.

Also in aa2) polyether polyols can be used. Suitable examples are the polytetramethylene glycol polyethers known per se in polyurethane chemistry, such as are obtainable by polymerization of tetrahydrofuran by means of cationic ring opening.

Also suitable polyether polyols are the per se known addition products of styrene oxide, ethylene oxide, propylene oxide, butylene oxides and / or epichlorohydrin to di- or polyfunctional starter molecules. As suitable starter molecules, it is possible to use all known compounds according to the prior art. These are, for example, water, butyldiglycol, glycerol, diethylene glycol, trimethylolpropane, propylene glycol, sorbitol, ethylenediamine, triethanolamine, 1,4-butanediol. Preferred starter molecules are water, ethylene glycol, propylene glycol, 1,4-butanediol, diethylene glycol and butyl diglycol.

Particularly preferred components aa2) used are a mixture of polycarbonate polyols and polytetramethylene glycol polyols, in which mixture the proportion of polycarbonate polyols may preferably be from 20 to 80% by weight and the proportion of polytetramethylene glycol polyols may preferably be from 80 to 20% by weight. More preferred is a proportion of 30 to 75 wt .-% of polytetramethylene glycol polyols and a proportion of 25 to 70 wt .-% of polycarbonate polyols. Very particular preference is given to a fraction of from 35 to 70% by weight of polytetramethylene glycol polyols and a fraction of from 30 to 65% by weight of polycarbonate polyols, in each case with the proviso that the sum of the percentages by weight of the polycarbonate and polytetramethylene glycol polyols gives 100% and Proportion of the sum of the polycarbonate and Polytetramethylenglykolpolyetherpolyole to the component J2) is at least 50 wt .-%, preferably 60% by weight and particularly preferably at least 70% by weight.

In aa3) may optionally hydroxy-functional compounds such as polyols of said molecular weight range having up to 20 carbon atoms, such as ethylene glycol, diethylene glycol, triethylene glycol, 1, 2-propanediol, 1,3-propanediol, 1, 4-butanediol, 1,3-butylene glycol, cyclohexanediol , 1,4-cyclohexanedimethanol, 1,6-hexanediol, neopentyl glycol, hydroquinone dihydroxyethyl ether, bisphenol A (2,2-bis (4-hydroxyphenyl) propane), hydrogenated bisphenol A, (2,2-bis (4-hydroxycyclohexyl) propane), trimethylolpropane, glycerol, pentaerythritol and any mixtures thereof.

Also suitable are ester diols of the stated molecular weight range, such as α-hydroxybutyl-ε-hydroxycaproic acid ester, ro-hydroxyhexyl-γ-hydroxybutyric acid ester, adipic acid- (β-hydroxyethyl) ester or terephthalic acid bis (β-hydroxyethyl) ester.

Furthermore, it is also possible to use monofunctional, hydroxyl-containing compounds in aa3). Examples of such monofunctional compounds are ethanol, n-butanol, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether,

Dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, 2-ethylhexanol, 1-octanol, 1-dodecanol, 1-hexadecanol.

Particularly preferred compounds of component aa3) are 1,6-hexanediol. 1, 4-butanediol, neopentyl glycol and trimethylolpropane. By anionically or potentially anionically hydrophilizing compounds of component aa4) is meant all compounds which have at least one isocyanate-reactive group such as a hydroxyl group and at least one functionality such as -COCTM ⁺ , -SO3 M ⁺ , -PO (OTVI ⁺ ) ₂ with M ⁺ for example, metal cation, H ⁺ , NH ₄ ⁺ , NHR ₃ ⁺ , where R may each be a C ₁ -C 12 -alkyl radical, C 5 -C ₆ -cycloalkyl radical and / or a C ₂ -C ₄ -hydroxyalkyl radical which, upon interaction with aqueous media, has a pH - Value-dependent dissociation equilibrium is received and can be loaded in this way negative or neutral. Suitable anionic or potentially anionic hydrophilizing compounds are mono- and dihydroxycarboxylic acids, mono- and dihydroxysulfonic acids, as well as mono- and dihydroxyphosphonic acids and their salts. Examples of such anionic or potentially anionic hydrophobic agents are dimethylolpropionic acid, dimethylolbutyric acid, hydroxypivalic acid, malic acid, citric acid, glycolic acid, lactic acid and the propoxylated adduct of 2-butenediol and NaHSOs, as described in DE-A 2 446 440, page 5-9, Formula I-III is described. Preferred anionic or potentially anionic hydrophobic agents of component aa4) are those of the abovementioned type which have carboxylate or carboxylic acid groups and / or sulfonate groups.

Particularly preferred anionic or potentially anionic hydrophobic agents of component aa4) are those which contain carboxylate or carboxylic acid groups as ionic or potentially ionic groups, such as dimethylolpropionic acid, dimethylolbutyric acid and hydroxypivalic acid or salts thereof. Suitable nonionically hydrophilicizing compounds of component aa4) are e.g. Polyoxyalkylenether containing at least one hydroxy or amino group, preferably at least one hydroxy group.

Examples are the monohydroxy-functional, on average 5 to 70, preferably 7 to 55 ethylene oxide units per molecule having Polyalkylenoxidpolyetheralkohole, as they are accessible in a conventional manner by alkoxylation of suitable starter molecules (eg in Ullmann's Encyclopedia of Industrial Chemistry, 4th Edition, Volume 19, Verlag Chemie, Weinheim pp. 31-38).

These compounds are either pure polyethylene oxide ethers or mixed polyalkyleneoxides, in which case they then preferably contain at least 30 mol% and more preferably at least 40 mol%, based on all the alkylene oxide units present, of ethylene oxide units.

Very particularly preferred nonionic compounds are monofunctional mixed polyalkylene oxide polyethers which have 40 to 100 mol% of ethylene oxide and 0 to 60 mol% of> propylene oxide units.

Suitable starter molecules for such nonionic hydrophilicizing agents are saturated monoalcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-

Butanol, the isomers pentanols, hexanols, octanols and nonanols, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol, n-octadecanol, cyclohexanol, the isomeric methylcyclohexanols or hydroxymethylcyclohexane, 3-ethyl-3-hydroxymethyloxetane or Tetrahydrofurfuryl alcohol, diethylene glycol monoalkyl ethers such as diethylene glycol monobutyl ether, unsaturated alcohols such as allyl alcohol, 1,1-dimethylallyl alcohol or oleic alcohol, aromatic alcohols such as phenol, the isomeric cresols or methoxyphenols, araliphatic alcohols such as benzyl alcohol, anisalcohol or cinnamyl alcohol, secondary mono- amines such as dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, bis (2-ethylhexyl) amine, N-methyl- and N-ethylcyclohexylamine or dicyclohexylamine and heterocyclic secondary amines such as morpholine, pyrrolidine, piperidine or 1H-pyrazole. Preferred starter molecules are saturated monoalcohols of the abovementioned type. Particular preference is given to using diethylene glycol monobutyl ether or n-butanol as starter molecules.

Alkylene oxides which are suitable for the alkoxylation reaction are, in particular, ethylene oxide and propylene oxide, which can be used in any desired order or even as a mixture in the alkoxylation reaction.

In the preparation of the polyurethane prepolymer a) from aal) to aa4), the molar ratio of isocyanate groups to isocyanate-reactive groups may be 1.05 to 3.5, preferably 1.2 to 3.0, particularly preferably 1.3 to 2.5. The reaction of components aal) to aa44) to the prepolymer takes place partially or completely, but preferably completely. In this way, polyurethane prepolymers which contain free isocyanate groups are obtained in bulk or in solution.

In the neutralization step for the partial or complete conversion of potentially anionic groups to anionic groups, bases such as tertiary amines, e.g. Trialkylamines having 1 to 12, preferably 1 to 6 carbon atoms, particularly preferably 2 to 3 carbon atoms in each alkyl radical or alkali metal bases used as the corresponding hydroxides.

Examples of these are trimethylamine, triethylamine, methyldiethylamine, tripropylamine, N-methylmorpholine, methyldiisopropylamine, ethyldiisopropylamine and diisopropylethylamine. The alkyl radicals can also carry, for example, hydroxyl groups, as in the case of the dialkylmonoalkanol, alkyldialkanol and trialkanolamines. If appropriate, inorganic bases such as aqueous ammonia solution or sodium or potassium hydroxide can also be used as neutralizing agents.

Preference is given to ammonia, triethylamine, triethanolamine, dimethylethanolamine or diisopropylethylamine and also sodium hydroxide and potassium hydroxide, particular preference to sodium hydroxide and potassium hydroxide.

The molar amount of the bases is in particular 50 and 125 mol%, preferably between 70 and 100 mol% of the molar amount of the acid groups to be neutralized. The neutralization can also take place simultaneously with the dispersion in which the dispersing water already contains the neutralizing agent.

Subsequently, in a further process step, if not yet or only partially done, the resulting prepolymer with the aid of aliphatic ketones such as acetone or 2-butanone dissolved.

Isocyanate-reactive, anionic or potentially anionic hydrophilicizing agents a2) are understood as meaning all compounds which have at least one isocyanate-reactive group, preferably an amino group, and at least one hydrophilizing group such as -COO M ⁺ , -SO ₃ TVT, -PO (OTVI ⁺ ) ₂ with M ^+, for example, the same metal cation, H ⁺ , NH ₄ ⁺ , NHR ₃ ⁺ , where R may each be a C ₁ -C 12 -alkyl radical, C 5 -C 6 -cycloalkyl radical and / or a C ₂ -C ₄ -hydroxyalkyl radical which may be present at Interaction with aqueous media, a pH value dependent dissociation equilibrium is received and can be charged in this way negative or neutral.

 Suitable compounds a2) are mono- and diaminocarboxylic acids, mono- and diaminosulfonic acids and also mono- and diaminophosphonic acids and their salts. Examples of such anionic or potentially anionic hydrophilicizing agents are N- (2-aminoethyl) -β-alanine, 2-

(2-aminoethylamino) ethanesulfonic acid, ethylenediamine propyl or butylsulfonic acid, 1,2- or 1,3-propylenediamine-.beta.-ethylsulfonic acid, glycine, alanine, taurine, lysine, 3,5-diaminobenzoic acid and the addition product of IPDA and acrylic acid (EP-A 0 916 647, Example 1). Furthermore, cyclohexylaminopropanesulfonic acid (CAPS) from WO-A 01/88006 can be used as anionic or potentially anionic hydrophilicizing agent.

 Preferred hydrophilicizing agents a2) are those of the abovementioned type which have carboxylate or carobonic acid groups and / or sulfonate groups such as the salts of N- (2-aminoethyl) -β-alanine, of 2- (2-aminoethylamino) ethanesulfonic acid or of Addition product of IPDA and acrylic acid (EP-A 0 916 647, Example 1).

For hydrophilization, mixtures of anionic or potentially anionic

Hydrophilic and nonionic hydrophilicizing agents are used.

As component a3) can di- or polyamines such as 1, 2-ethylenediamine, 1,2- and 1, 3-diaminopropane, 1, 4-diaminobutane, 1, 6-diaminohexane, isophoronediamine, isomer mixture of 2,2,4- and 2,4,4-trimethylhexamethylenediamine, 2-methylpentamethylenediamine, diethylenetriamine, triaminononane, 1,3- and 1,4-xylylenediamine, a, a, a ', a'-tetramethyl-l, 3- and -1,4 -xylylenediamine and 4,4-diaminodicyclohexylmethane and / or Dimethylethylendiamm be used. Also possible, but less preferred, is the use of hydrazine or hydrazides such as adipic dihydrazide.

In addition, it is also possible to use as component a3) compounds which, in addition to a primary amino group, also have secondary amino groups or, in addition to an amino group (primary or secondary), OH groups. Examples thereof are primary / secondary amines, such as diethanolamine, 3-amino-1-methylaminopropane, 3-amino-1-ethylaminopropane, 3-amino-1-cyclohexylaminopropane, 3-amino-1-methylaminobutane, alkanolamines, such as N-aminoethylethanolamine , Ethanolamine, 3-aminopropanol, neopentanolamine. Furthermore, as component a3) it is also possible to use monofunctional isocyanate-reactive amine compounds such as methylamine, ethylamine, propylamine, butylamine, octylamine, laurylamine, stearylamine, isononyloxypropylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, N-methylaminopropylamine, diethyl (methyl) aminopropylamine, morpholine, piperidine, or suitable substituted derivatives thereof, amide amines from diprimary amines and monocarboxylic acids, monoketime of diprimary amines, primary / tertiary amines, such as N, N-dimethylaminopropylamine,

 Preferred compounds of component a3) are 1, 2-ethylenediamine, 1, 4-diaminobutane and isophoronediamine.

The preparation of the polyurethane dispersion a) can be carried out in one or more stages in homogeneous or multistage reaction, partly in disperse phase. After completely or partially carried out polyaddition of aal) to aa4) can follow a dispersing, emulsifying or dissolving step. Subsequently, if appropriate, a further polyaddition or modification in disperse or dissolved (homogeneous) phase can be carried out. For this purpose, all known from the prior art methods such. Example, prepolymer mixing method, acetone method or Schmelzdispergierverfahren can be used. Preference is given to working by the acetone process.

In chain extension, NH ₂ - and / or NH-f ional components with the remaining isocyanate groups of the prepolymer can be partially or completely implemented. Preferably, chain extension / termination is performed prior to dispersion in water.

If anionic or potentially anionic hydrophilicizing agents corresponding to the definition a2) with NH 2 or NH groups are used for the partial or complete chain extension, the chain extension of the prepolymers preferably takes place before the dispersion. The aminic components a2) and a3) can optionally be used individually or in mixtures in water-diluted or solvent-diluted form, it being possible in principle for any order of addition to be possible.

The dispersion preferably takes place after the chain extension. For this purpose, the dissolved and chain-extended polyurethane polymer a) is optionally either added to the dispersing water under high shear, such as vigorous stirring, or it is reacted. The dispersing water is stirred to the chain-extended polyurethane polymer solutions. Preferably, the water is added to the dissolved chain-extended polyurethane polymer.

The organic solvent still present in the dispersions after the dispersing step is then usually removed by distillation. A distance already during the dispersion is also possible.

The residual content of organic solvents in the polyurethane dispersion a) is typically less than 1.0 wt .-%, preferably less than 0.5 wt .-%, based on the total dispersion.

The pH of the polyurethane dispersion a) is typically less than 9.0, preferably less than 8.5, more preferably less than 8.0, and most preferably 6.0 to 7.5.

The solids content of the polyurethane dispersion a) is typically 40 to 70, preferably 50 to 65, particularly preferably 55 to 65 wt .-%. Further dilution of the dispersion with water before use is also possible, as is the use of the dispersion and water as an independent constituent of the composition.

To improve the foaming, foam stability or the properties of the polyurethane foam A), all known anionic, cationic, amphoteric and nonionic surfactants and mixtures thereof may be added to the dispersion a). Alkyl polyglycosides, EO / PO block copolymers, alkyl or aryl alkoxylates, siloxane alkoxylates, esters of sulfosuccinic acid and / or alkali metal or alkaline earth metal alkanoates are preferably used. Particular preference is given to using EO / PO block copolymers. Very particular preference is given to using EO / PO block copolymers alone as component C).

It is likewise preferred if an isocyanate-functional prepolymer b) obtainable by reacting at least the following components: bl) an aliphatic diisocyanate having a molar mass of 140 to 278 g / mol, b2) a di- to hexafunctional, is preferred a tri- to hexafunctional polyalkylene oxide having an OH number of 22.5 to 1 12 and an ethylene oxide content of 50 to 100 mol%, based on the total amount of oxyalkylene groups contained. The prepolymers b) preferably have a residual monomer content of less than 0.5% by weight, based on the prepolymer. This content can be achieved by appropriately selected amounts of the diisocyanates bl) and the polyalkylene oxides b2). However, preference is given to using the diisocyanate bl) in excess and then, preferably by distillation, separation of unreacted monomers.

In the preparation of the isocyanate-functional prepolymers b), the ratio of the polyalkylene oxides b2) to the diisocyanates b1) can typically be adjusted so that 2 to 20 mol, preferably 2 to 10 mol and more preferably 5 to 1 mol of OH groups of the polyalkylene oxides A2) to 10 moles of NCO groups of the diisocyanate bl) come. The reaction of components bl) and b2) can be carried out in the presence of urethanization catalysts such as tin compounds, zinc compounds, amines, guanidines or amidines, or in the presence of allophanatization catalysts such as zinc compounds.

It is typically carried out at 25 to 140 ° C, but preferably 60 to 100 ° C.

Was worked in the preparation of the prepolymer b) with excess isocyanate, then the removal of the excess of diisocyanate is preferably carried out by thin film distillation.

Acidic or alkylating stabilizers, such as benzoyl chloride, isophthaloyl chloride, methyl tosylate, chloropropionic acid, HCl or antioxidants, such as di-tert-butylcresol or tocopherol, can be added before, during and after the reaction or distillative removal of the diisocyanate excess.

The NCO content of the isocyanate-functional prepolymer b) is preferably from 1.5 to 4.5% by weight, more preferably from 1.5 to 3.5% by weight and very particularly preferably from 1.5 to 3.0% by weight. %.

Examples of the aliphatic diisocyanate bl) are hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), butylene diisocyanate (BDI), bisisocyanatocyclohexylmethane (HMDI), 2,2,4-trimethylhexamethylene diisocyanate, bisisocyanatomethylcyclohexane, bisisocyanoatomethyltricyclodecane, xylene diisocyanate, tetramethylxylylene diisocyanate, bornane diisocyanate, cyclohexane diisocyanate or diisocyanatododecane, wherein hexamethylene diisocyanate, isophorone diisocyanate, butylene diisocyanate and bis (isocyanatocyclohexyl) methane are preferred. Particularly preferred are butylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, very particularly preferably hexamethylene diisocyanate and isophorone diisocyanate.

The polyalkylene oxides b2) are preferably copolymers of ethylene oxide and propylene oxide having an ethylene oxide content, based on the total amount of the oxyalkylene groups, of from 50 to 100 mol%, preferably from 60 to 85 mol%, started on polyols or amines. Suitable initiators of this type are glycerol, trimethylolpropane (TMP), sorbitol, pentaerythritol, triethanolamine, ammonia or ethylenediamine.

The polyalkylene oxides b2) typically have number-average molecular weights of from 1000 to 15000 g / mol, preferably from 3000 to 8500 g / mol.

Furthermore, the polyalkylene oxides b2) preferably have OH functionalities of 2 to 6, more preferably of 3 to 6 and particularly preferably of 3 to 4.

Heterocyclic, 4-ring or 6-membered oligomers d) of aliphatic diisocyanates, in particular having a molar mass of 140 to 278 g / mol such as isocyanurates, iminooxadiazinediones or uretdiones of the abovementioned aliphatic diisocyanates, can be used as further components in the preparation of the polyurethane foam B) Diisocyanates bl) can be used. Preference is given to using heterocyclic 4-ring oligomers, such as uretdiones. The increased by the use of component d) content of isocyanate groups provides for a better foaming, as in the isocyanate-water reaction more CO _{2 is} formed. It is also possible that in the production of the polyurethane foam B) additionally catalysts e) are used. These are typically the compounds known to those skilled in polyurethane technology. Preference is given here to compounds of the group consisting of catalytically active metal salts, amines, amidines and guanidines. Examples include tin dibutyl dilaurate (DBTL), tin acetate, 1, 8-diazabicyclo [5.4.0] undecene-7 (DBU), 1, 5-diazabicyclo [4.3.0] nonene-5 (DBN), 1,4 Diazabicyclo [3.3.0] octene-4 (DBO), N-ethylmorpholine (NEM), triethylenediamine (DABCO), pentamethylguanidine (PMG), tetramethylguanidine (TMG), cyclotetramethylguanidine (TMGC), n-decyl-tetramethylguanidine (TMGD ), n-dodecyltetramethylguanidine (TMGDO), dimethylaminoethyltetramethylguanidine (TMGN), 1,1,4,4,5,5-hexamethylisobiguanidine (HMIB), phenyltetramethylguanidine (TMGP) and hexamethylenoctamethylbiguanidine (HOBG).

Preference is given to the use of amines, amidines, guanidines or mixtures thereof as catalysts of component e). Preference is also given to the use of 1,8-diazabicyclo [5.4.0] undecene-7 (DBU).

In a particularly preferred embodiment of the invention, however, catalysts e) are dispensed with completely.

Furthermore, in the preparation of the polyurethane foam B) Cs to C22 monocarboxylic acids or their ammonium or alkali metal salts or C12 to C44 dicarboxylic acids or their ammonium or alkali metal salts f) can be reacted with.

Examples of suitable compounds of component f) are the ammonium, Na, Li or K salts of ethylhexanoic, octanoic, decanoic, dodecanoic, palmitic, stearic, octadecenoic, octadecadienoic, octadecatrienoic, isostearic, erucic, abietic and their acids hydrogenation. Examples of C 12 to C 44 dicarboxylic acids and the ammonium and alkali salts derived therefrom are dodecanedioic, dodecenyl, tetradecenyl, hexadecenyl and octadecenyl succinic acid, C 36 and C 44 dimer fatty acids and their hydrogenation products and the corresponding ammonium, Na, Li or K salts of these dicarboxylic acids.

In order to improve the foam formation, foam stability or the properties of the resulting polyurethane foam B), compounds of component g) can be used, wherein such additives may in principle be all anionic, cationic, amphoteric and nonionic surfactants known per se and mixtures thereof. Alkyl polyglycosides, EO / PO block copolymers, alkyl or aryl alkoxylates, siloxane alkoxylates, esters of sulfosuccinic acid and / or alkali metal or alkaline earth metal alkanoates are preferably used. It is particularly preferable to use EO / PO block copolymers. Preferably, only the EO / PO block copolymers are used as component g).

In addition, to improve the foam properties of the polyurethane foam B) compounds of component h) can be used. These are in principle all monohydric and polyhydric alcohols known to the person skilled in the art and mixtures thereof. These are mono- or polyhydric alcohols or polyols, such as ethanol, propanol, buta- nol, decanol, tridecanol, hexadecanol, ethylene glycol, neopentyl glycol, butanediol, hexanediol, decanediol, trimethylolpropane, glycerol, pentaerythritol, monofunctional polyether alcohols and polyester alcohols, polyether diols and polyester diols.

As a further component in the preparation of the polyurethane foam B) hydrophilic polyisocyanates i) can be used, which by reaction of

11) aliphatic diisocyanates having a molecular weight of 140 to 278 g / mol and / or polyisocyanates obtainable therefrom with an isocyanate functionality of 2 to 6 with

12) monofunctional polyalkylene oxides having an OH number of from 10 to 250 and an ethylene oxide content of from 50 to 100 mol%, based on the total amount of the oxyalkylene groups present. are available.

In the preparation of the hydrophilic polyisocyanates i) the ratio of the monofunctional polyalkylene oxides i2) to the aliphatic diisocyanates 1) is typically adjusted so that for 1 mol of OH groups of the monofunctional polyalkylene oxides from 1.25 to 15 mol, preferably with 2 to 10 mol and more preferably 2 to 6 moles of NCO groups of the aliphatic diisocyanate il) come. Subsequently, the allophanatization or biurization and / or isocyanurate formation or uretdione formation takes place. If the polyalkylene oxides i2) are bound via urethane groups to the aliphatic diisocyanates II), allophanatization preferably takes place subsequently. It is further preferred that isocyanurate structural units are formed.

An alternative preparation of the hydrophilic polyisocyanates i) is typically carried out by reacting 1 mol of OH groups of the monofunctional polyalkylene oxide component i2) with 1, 25 to 15 mol, preferably with 2 to 10 mol and particularly preferably 2 to 6 moles NCO groups of a polyisocyanate il) with an isocyanate functionality of 2 to 6, based on aliphatic disocyanates. Exemplary of such polyisocyanates II) are biuret

Structures, isocyanurates or uretdiones based on aliphatic diisocyanates. In this case, the polyisocyanate II) and the polyalkylene oxide i2) are preferably linked to one another via a urethane group or a urea group, the linking via urethane groups in particular being preferred. The reaction of the components II) and II) can be carried out in the presence of urethanization catalysts such as tin compounds, zinc compounds, amines, guanidines or amidines, or in the presence of allophanatization catalysts such as zinc compounds.

The reaction of il) and i2) is typically carried out at 25 to 140 ° C, preferably at 60 to 100 ° C.

Was worked in the implementation of il) and i2) with excess diisocyanate il), then the removal of the excess can be done by thin film distillation.

Acidic or alkylating stabilizers, such as benzoyl chloride, isophthaloyl chloride, methyl tosylate, chloropropionic acid, HCl or antioxidants, such as di-tert-butylcresol or tocopherol, can be added before, during and after the reaction or the distillative removal of the diisocyanate excess.

The NCO content of the hydrophilic polyisocyanates i) is preferably 0.3 to 20 wt .-%, more preferably 2 to 10 wt .-% and most preferably 3 to 6 wt .-%.

Examples of aliphatic diisocyanates of component II) are hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), butylene diisocyanate (BDI), bisisocyanatocyclohexylmethane (HMDI), 2,2,4-trimethylhexamethylene diisocyanate, bisisocyanatomethylcyclohexane, bisisocyanatomethyltricyclodecane, xylene diisocyanate, tetramethylxylylene diisocyanate, norbornene diisocyanate , Cyclohexane diisocyanate or diisocyanatododecane, with hexamethylene diisocyanate, isophorone diisocyanate, butylene diisocyanate and bis (isocyanatocyclohexyl) methane being preferred. Particularly preferred are butylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, most preferably hexamethylene diisocyanate and isophorone diisocyanate.

Further examples of polyisocyanates II) are polyisocyanates having an isocyanate functionality of 2 to 6 with isocyanurate, urethane, allophanate, biuret, iminooxadiazinetrione, oxadiazinetrione and / or uretdione groups based on the aliphatic and / or aliphatic groups mentioned in the preceding paragraph cycloaliphatic diisocyanates.

Compounds with biuret, iminooxadiazinedione, isocyanurate and / or uretdione groups based on hexamethylene diisocyanate, isophorone diisocyanate and / or 4,4'-diisocyanatodicyclohexylmethane are preferably used as component II). Further preferred are iso- cyanurates. Very particular preference is given to structures based on hexamethylene diisocyanate.

The monofunctional polyalkylene oxides i2) have an OH number of from 15 to 250, preferably from 28 to 112, and an ethylene oxide content of from 50 to 100 mol%, preferably from 60 to 100 mol%, based on the total amount of the oxyalkylene groups present.

By monofunctional polyalkylene oxides in the context of the invention are meant compounds which are only one isocyanate-reactive group, i. a group capable of reacting with an NCO group.

The preparation of polyalkylene oxides i2) by alkoxylation of suitable starter molecules is known from the literature (for example Ullmanns Encyclopadie der technischen Chemie, 4th Edition, Volume 19,

Verlag Chemie, Weinheim pp. 31-38). Suitable starter molecules are, in particular, saturated monoalcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, diethylene glycol monobutyl ether and aromatic alcohols, such as phenol or monoamines, such as diethylamine. Preferred starter molecules are saturated monoalcohols of the aforementioned type. Particular preference is given to using diethylene glycol monobutyl ether or n-butanol as starter molecules.

The monofunctional polyalkylene oxides i2) typically have number average molecular weights of from 220 to 3700 g / mol, preferably from 500 to 2800 g / mol.

The monofunctional polyalkylene oxides i2) preferably have an OH group as the isocyanate-reactive group.

Typically, to prepare the polyurethane foam B), the components b) to i) are used in the following amounts:

100 parts by weight of isocyanate-functional prepolymer b)

0.1 to 200 parts by weight of water c) 0 to 30 parts by weight of heterocyclic oligomer d)

0 to 1 parts by weight of catalyst e) 0 to 5 parts by weight of C 1 to C 12 monocarboxylic acid or its ammonium or alkali metal salt or C 12 to C 44 dicarboxylic acid or its ammonium or alkali metal salt f)

0 to 10 parts by weight of surfactant g)

0 to 20 parts by weight of alcohol h) 0 to 250 parts by weight of hydrophilic polyisocyanate component i).

The polyurethane foam B) is preferably produced by mixing the components, with water preferably being added as the last component, foaming the resulting mixture, applying the foamed mixture to a substrate by means of a doctor blade and then curing, preferably by chemical crosslinking. The substrate may be, for example, a release paper or also the polyurethane foam A).

After curing, residual moisture which is still present may optionally be removed by means of conventional methods, such as e.g. be removed by convective air or microwave drying.

According to a further preferred embodiment of the composite foam according to the invention it is provided that the absorption layer is directly connected to the storage layer. In this case, for example, no additional adhesive layer is necessary to bond the layers together. In addition, the transition of liquid from the absorption layer into the storage layer takes place particularly quickly here.

The direct connection of the absorption layer with the storage layer can be realized according to a particularly preferred embodiment by either the polyurethane foam A) on the already finished polyurethane foam B) or the polyurethane foam B) on the already finished polyurethane foam A) is applied. In the case of the first variant, the foamed polyurethane dispersion a) can be applied to the polyurethane foam B) and dried there. In the second variant, the mixture of components b), c) and optionally d) -i) can be applied to the polyurethane foam A).

It is also particularly preferred if the absorption layer and the storage layer are connected to one another in a flat manner. The absorption layer may have a thickness in the range from 0.3 to 6 mm, preferably from 0.5 to 5 mm and more preferably from 0.7 to 3 mm. At the same time or independently, the storage layer may have a thickness in the range of 0.5 to 10 mm, preferably 1 to 8 mm, and more preferably 1.5 to 6 mm.

The invention further provides a process for producing a composite foam according to the invention, in which the polyurethane foam A) of the absorption layer is produced by mechanical foaming of the aqueous polyurethane dispersion a) and subsequent drying and the polyurethane foam B) of the storage layer by reacting at least the following components: b) an isocyanate-functional prepolymer, c) water and the absorption layer and the storage layer are at least partially connected directly.

Particularly preferred is a process in which the polyurethane dispersion a) is prepared by reacting at least the following components: al) an isocyanate-functional prepolymer, a2) optionally an isocyanate-reactive, preferably amino-functional, anionic or potentially anionic hydrophilicizing agent, a3) optionally an amino-functional compound, in particular having a molecular weight of 32 to 400 g / mol, a4) water, wherein the hydrophilicizing agent a2) is obligatory if the prepolymer al) does not have hydrophilicizing groups.

It is likewise preferred if the isocyanate-functional prepolymer al) is prepared by reacting at least the following components: aa) an organic polyisocyanate, aa2) a polymeric polyol, in particular having a number average molecular weight of 400 to 8000 g / mol and / or an OH functionality of 1.5 to 6, aa3) optionally a hydroxy-functional compound, in particular having a molecular weight of 62 to 399 g / mol and aa4) optionally an isocyanate-reactive, anionic or potentially anionic and / or optionally nonionic hydrophilicizing agent.

According to a further preferred embodiment of the process according to the invention, it is provided that the isocyanate-functional prepolymer b) is prepared by reacting at least one of the following components: bl) a low molecular weight, aliphatic diisocyanate having a molecular weight of 140 to 278 g / mol, b2) a di- to hexafunctional, preferably a tri- to hexafunctional polyalkylene oxide having an OH number of 22.5 to 1 12 and an ethylene oxide content of 50 to 100 mol%, based on the total amount of oxyalkylene groups contained. In a further development of the method according to the invention, it is provided that the absorption layer is connected directly to the storage layer.

Yet another subject of the invention is a wound dressing comprising a composite foam according to the invention or a composite foam obtainable according to a method according to the invention. Preferably, the wound dressing may additionally have a covering layer, which may in particular be connected to the storage layer.

Suitable cover layers are, for example, films, films, foams or membranes.

The cover layer can be made water vapor permeable according to DIN 53333 or DIN 54101. The cover layer may preferably contain a thermoplastic polymer, for example in the form of a coating, or consist thereof. A thermoplastic polymer is first understood to mean a polymer which, when used in the material for processing and Application typical temperature range repeatedly heated and cooled, remains thermoplastic. By thermoplastic is meant the property of a plastic to soften in a typical temperature range for him repeatedly in the heat and harden on cooling and be repeatedly formed in the softened state by flow, for example as a molded part, extrudate or forming part to semifinished or articles.

Preferred thermoplastic polymers are polyurethane, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyether, polyester, polyamide, polycarbonate, polyether-polyamide copolymers, polyacrylate, polymethacrylate and / or polymaleate. Advantageously, the thermoplastic polymers are elastomeric. Most preferably, the carrier film contains thermoplastic polyurethane (TPU) or consists thereof. Particularly suitable are thermoplastic polyurethanes which are selected from the group comprising aliphatic polyester polyurethanes, aromatic polyester polyurethanes, aliphatic polyether polyurethanes and / or aromatic polyether polyurethanes. With these polymers, cover layers in the form of breathable elastic membrane films can be obtained. These are characterized by high flexibility and elasticity over a wide temperature range, a good seal for liquid water with high water vapor permeability, low noise, good textile feel, washing and cleaning resistance, very good chemical and mechanical resistance and freedom from plasticizers.

Particularly preferred is also a cover layer, which acts as a barrier for germs and / has over the exudate exiting from the wound a high density with simultaneous permeability to water vapor. For this purpose, the cover layer may be designed, for example, as a semipermeable membrane.

Furthermore, it is advantageous if the cover layer has a thickness in the range of> 5 μιη to <80 μιη, particularly preferably from> 5 μιη to <60 μιη and very particularly preferably from> 10 μιη to <30 μιη and / or an elongation at break of over 450%.

The wound dressing may additionally have an adhesive layer. This may preferably be connected to the absorption layer.

Suitable adhesive layers include, for example, polyurethane, silicone or acrylate-based pressure-sensitive adhesives. Examples of such polyurethane-based adhesives are hydrophilic polyurethane elastomers, as described, for example, in EP 1 923 077 and in EP 1 815 875 A1. Also suitable are the self-adhesive hydrophilic polyurethane gel foams known from WO 94/07935. The wound dressing may also have a covering layer which is detachably connected to the adhesive layer and can be removed before application. Suitable cover layers contain or consist of materials which have low adhesion to the adhesive of the adhesive layer when brought into contact therewith. Examples of such cover layers are release papers provided with a non-adhesive silicone or polyolefin layer.

The invention will be explained in more detail below with reference to examples.

Examples Methods:

Unless otherwise indicated, all percentages are by weight.

The solids contents were determined according to DIN-EN ISO 3251. The viscosities were determined at 23 ° C. and were carried out in accordance with DIN 53019.

The NCO contents were determined volumetrically according to DIN-EN ISO 11909.

To determine the bulk density, the width (B), height (H) and thickness (D) of a piece of foam were first measured and its mass (M) was determined. Subsequently, the bulk density was calculated according to the formula: apparent density = M / (B * H * D).

The determination of the free suction power was carried out by absorption of physiological saline solution according to DIN EN 13726-1, part 3.2.

Retention was determined on the basis of the determination of the absorption of physiological saline solution according to DIN EN 13726-1, Part 3.2, whereby the foam, soaked with physiological saline solution, was drained off for 30 s and then squeezed for 20 s with a 6 kg sample. Retention in% is the amount of residual moisture divided by the maximum absorption.

The absorption rate was determined by placing with a Eppendorfpippette a 30 μl drop of a physiological saline solution (conditioned at 37 ° C.) on the surface of the foam and measuring the time until the drop had been completely absorbed in the foam.

The determination of the average particle sizes (indicated by the number average) was carried out by means of laser correlation spectroscopy (instrument: Malvern Zetasizer 1000, Malver Inst. Limited).

The molecular weights were determined by gel permeation chromatography (GPC) as follows: The calibration was carried out with polystyrene standards having a molecular weight of Mp 1,000,000 to 162. The eluent used was tetrahydrofuran pA. The following parameters were observed during the double measurement: Degassing: Online - Degasser; By- flow: 1 ml / min; Analysis time: 45 minutes; Detectors: refractometer and UV detector; Injection volume: 100 μΐ - 200 μΐ. The calculation of the molar mass averages M _w ; M _n and M _p and the polydispersity M _w / M _n was software-based. Baseline points and evaluation limits were determined in accordance with DIN 55672 Part 1. The Zehntner Universal Applicator ZUA 2000 with a film width of 200 mm and a gap height adjustable from 0 to 3 mm (Zehntner GmbH, Sissach, Switzerland) was used as the doctor blade.

Substances and Abbreviations: Diaminosulphonate: NH ₂ -CH ₂ CH ₂ -NH-CH ₂ CH ₂ -SO 3 Na (45% in water)

Desmophen ^® C2200: polycarbonate polyol, OH number 56 mg KOH / g, number average molecular weight 2000 g / mol (Bayer MaterialScience AG, Leverkusen, DE)

PolyTHF ^® 2000: Polytetramethylenglykolpolyol, OH number 56 mg KOH / g, number average molecular weight 2000 g / mol (BASF AG, Ludwigshafen, DE) PolyTHF ^® 1000: Polytetramethylenglykolpolyol, OH number 112 mg KOH / g, number-average number average molecular weight 1000 g / mol (BASF AG, Ludwigshafen, DE)

Polyether LB 25: mono-functional polyether based on ethylene oxide / propylene oxide, number average molecular weight 2250 g / mol, OH number 25 mg KOH / g (Bayer MaterialScience AG, Leverkusen, DE) Desmodur® N 3400: Aliphatic polyisocyanate (HDI uretdione), NCO Content 21, 8%, Bayer MaterialScience AG, Leverkusen, Germany

Desmodur® N 3300: Aliphatic polyisocyanate (HDI isocyanurate), NCO content 21.8%, Bayer MaterialScience AG, Leverkusen, Germany

Pluronic PE6800 block polymer of propylene oxide and ethylene oxide, BASF, Ludwigshafen, Germany Preparation of the aqueous polyurethane dispersion a

1077.2 g PolyTHF ^® 2000, 409.7 g of PolyTHF ^® 1000, 830.9 g Desmophen ^® C2200 and 48.3 g of polyether LB 25 were heated in a standard stirred apparatus at 70 ° C. Subsequently, a mixture of 258.7 g of hexamethylene diisocyanate and 341.9 g of isophorone diisocyanate was added at 70 ° C within 5 min and stirred at 120 ° C until the theoretical NCO value was reached or slightly below. The finished prepolymer was dissolved with 4840 g of acetone while cooled to 50 ° C and then a solution of 27.4 g of ethylenediamine, 127.1 g of isophoronediamine, 67.3 g of diaminosulfonate and 1200 g of water was added within 10 min , The stirring time was 10 min. It was then dispersed by adding 654 g of water. This was followed by removal of the solvent by distillation in vacuo.

The polyurethane dispersion obtained had the following properties:

Solids content: 61.6%

Average particle size: 528 nm pH (23 ° C): 7.5

Preparation of Polyurethane Prepolymer 1 al

To a mixture of 1000 g of hexamethylene diisocyanate (HDI) and lg benzoyl chloride at 80 ° C within 3 h 1000 g of a polyalkylene oxide having a molecular weight of 4680 g / mol, based on glycerol, an ethylene oxide of 72% and a propylene oxide weight fraction of 28%, which was previously dried at 100 ° C for 6 h at a pressure of 0.1 mbar, added dropwise and stirred for 12 h. The excess HDI was removed by thin film distillation at 130 ° C and 0.1 mbar, stabilizing the non-volatiles with 1 g of chloropropionic acid. This gave a prepolymer having an NCO content of 2.77% and a viscosity of 3500 mPas. Preparation of the hydrophilic polyisocyanate i)

A mixture of 282.5 g of Desmodur N 3300 and 843.8 g of an ethylene oxide / propylene oxide based monohydroxy-functional polyether (having an ethylene oxide content of 80 moles based on the total amount of the oxyalkylene groups present), number average molecular weight 2250 g / mol (OH number 25 mg KOH / g) was stirred in a glass apparatus at 80 ° C until the tritrimetrically determined content of NCO groups (according to DIN-EN ISO 11909) was constant. A liquid having an NCO content of 4.04% and a viscosity of 3330 mPas was obtained.

Composite foams 1, 2 and 3: polyurethane foam B) on polyurethane foam A)

Preparation of polyurethane foam A):

10 kg of the above-described aqueous polyurethane dispersion a) were mixed with 775 g of a 40% aqueous Pluronic PE6800 solution. The mixture was then whipped in a Hansamixer Topmix type 100 to a density of 200 g / l. The blended mixture was then laced onto a 30 cm wide polyethylene coated release paper. The gap height was 0.7 or 2 mm. It was then dried at 120 ° C for 3 or 5 minutes. Foams having a thickness of 0.6 and 1.9 mm and a density of 149 and 122 g / 1, respectively, were obtained.

Preparation of Polyurethane Foam B):

The polyurethane prepolymer al), the hydrophilic polyisocyanate i) and the oligomer B were homogenized for 15 seconds at a stirrer speed of 1200 rpm and then the other components in the amounts indicated in Table 1 were added. After mixing all the components, the mixture was stirred for a further 10 seconds at 1200 rpm and finally the finished composition was applied to the polyurethane foam A) using a doctor blade (gap height 0.7 or 1.5 mm). Here then formed the polyurethane foam B). The determination of the bulk density, absorption, retention and absorption rate was then carried out as described in the section "Methods." The results are shown in Table 1.

Composite foam 4: polyurethane foam A) on polyurethane foam B) Preparation of polyurethane foam B):

The polyurethane prepolymer al), the hydrophilic polyisocyanate i) and Desmodur N3400 were homogenized for 15 seconds at a stirrer speed of 1200 rpm and then the other components in the amounts indicated in Table 1 were added. After mixing all the components, the mixture was stirred at 1200 rpm for a further 10 seconds and finally the finished composition was applied with a doctor blade (gap height 0.7 or 1.5 mm) to a siliconized release paper. Here, the polyurethane foam B) formed.

Preparation of polyurethane foam A):

10 kg of the above-described aqueous polyurethane dispersion a) were mixed with 775 g of a 40% aqueous Pluronic PE6800 solution. The mixture was then whipped in a Hansamixer Topmix type 100 to a density of 200 g / l. The whipped mixture was then laced onto the polyurethane foam B). The gap height was 0.4 mm. It was then dried at 120 ° C for 3 minutes. A composite foam having a thickness of 5.6 mm and a density of 139 g / 1 was obtained.

Comparative foams 5 and 6:

The polyurethane prepolymer al), the hydrophilic polyisocyanate i) and Desmodur N3400 were homogenized for 15 seconds at a stirrer speed of 1200 rpm and then the other components in the amounts indicated in Table 1 were added. After mixing all the components, the mixture was stirred for a further 10 seconds at 1200 rpm and the finished composition was finally applied with a doctor blade (gap height 1.5 mm) to a siliconized release paper. Here, the comparison foam 5 or 6 formed. 1 2 3 4 5 6

Vergl

Prepolymer 1 al) (g) 90 90 90 90 90 90

Desmodur N3400) (g) 12.5 12.5 12.5 12.5 12.5 12.5

Hydrophilic polyisocyanate i) 22.5 22.5 22.5 22.5 22.5 22.5 (g)

DBU (g) (component e)) 0.075 0.075 0.075 0.075 0.075 0.075

Sodium oleate 5% in water 17 17 17 17 17 17 (g) (component f))

PU foam A) Thickness (mm) 0.6 1.9 0.6 0.4 without

Gap height squeegee for PU 1.5 1.5 0.7 1.5 0.7 1.5 foam B) (mm)

Type of foam B) on B) on A) B) on A) A) on B) only B) only B)

 A)

Thickness of the composite foam 4.1 5.2 2.2 5.6 1.6 4.2 or the comparative foam

(Mm)

Density of the composite foam 148 139 175 139 157 131 or the comparative foam

 (g i)

Suction power (g / 100 cm ² ) 45 63 29 98 31 52

Retention (%) 82 63 67 70 75 75 Absorption rate (s) 12 15

Table 1: Components of the foams and properties

The composite foams of Examples 1, 2 and 4 correspond in terms of foam thickness, density, absorbency (suction) and retention of the foam of Comparative Example 6. At the same time, however, they have a significantly higher absorption rate.

The composite foam of Example 3 has a significantly higher absorption rate with comparable foam thickness, density, suction power and retention compared to Comparative Example 5.

Claims

Composite foam comprising an absorption layer and a storage layer directly connected at least in regions to the absorption layer, characterized in that the absorption layer comprises a polyurethane foam A) which is obtainable by mechanical foaming of an aqueous polyurethane dispersion a) and subsequent drying and the storage layer comprises a polyurethane foam B), the component obtainable by reactive conversion of at least the following components: b) an isocyanate-functional prepolymer, c) water.

Composite foam according to claim 1, characterized in that the polyurethane dispersion a) is obtainable by reacting at least the following components: al) an isocyanate-functional prepolymer, a2) optionally an isocyanate-reactive, preferably amino-functional, anionic or potentially anionic hydrophilicizing agent, a3) optionally an amino-functional Compound, in particular having a molecular weight of 32 to 400 g / mol, a4) water, wherein the hydrophilizing agent a2) is obligatory if the prepolymer al) has no hydrophilicizing groups.

Composite foam according to claim 2, characterized in that the isocyanate-functional prepolymer al) is obtainable by reacting at least the following components: aal) an organic polyisocyanate, aa2) a polymeric polyol, in particular having a number-average molecular weight of from 400 to 8000 g / mol and / or an average OH functionality of from 1.5 to 6, aa3) optionally a hydroxy-functional compound, in particular having a molecular weight of from 62 to 399 g / mol, aa4) optionally an isocyanate-reactive, anionic or potentially anionic and / or optionally nonionic hydrophilicizing agent.

Composite foam according to one of claims 1 to 3, characterized in that the isocyanate-functional prepolymer b) is obtainable by reacting at least the following components: bl) a low molecular weight, aliphatic diisocyanate having a molecular weight of 140 to 278 g / mol, b2) a di- to hexafunctional, preferably a tri- to hexafunctional polyalkylene oxide having an OH number of 22.5 to 112 and an ethylene oxide content of 50 to 100 mol%, based on the total amount of oxyalkylene groups contained.

Composite foam according to one of claims 1 to 4, characterized in that the absorption layer has a thickness in the range of 0.3 to 6 mm, preferably from 0.5 to 5 mm and particularly preferably from 0.7 to 3 mm and / or the storage layer a thickness in the range of 0.5 to 10 mm, preferably from 1 to 8 mm and more preferably from 1.5 to 6 mm.

Composite foam according to one of claims 1 to 5 for the treatment of wounds.

Process for the preparation of a composite foam according to one of claims 1 to 6, in which the polyurethane foam A) of the absorption layer is produced by mechanical foaming of the aqueous polyurethane dispersion a) and subsequent drying and the polyurethane foam B) of the storage layer by reacting at least the following components: b) an isocyanate-functional prepolymer, c) water and the absorption layer and the storage layer are at least partially connected directly.

A method according to claim 7, characterized in that the polyurethane dispersion a) is prepared by reacting at least the following components: al) an isocyanate-functional prepolymer, a2) optionally an isocyanate-reactive, preferably amino-functional, anionic or potentially anionic hydrophilicizing agent, a3) optionally an amino-functional compound, in particular with a molecular weight of 32 to 400 g / mol, a4) water, wherein the hydrophilicizing agent a2) is obligatory if the prepolymer al) has no hydrophilicizing groups.

A method according to claim 8, characterized in that the isocyanate-functional prepolymer al) is prepared by reacting at least the following components: aal) an organic polyisocyanate, aa2) a polymeric polyol, in particular having a number average molecular weight of 400 to 8000 g / mo l and / or an OH functionality of 1, 5 to 6, aa3) optionally a hydroxy-functional compound, in particular having a molecular weight of 62 to 399 g / mol and aa4) optionally an isocyanate-reactive, anionic or potentially anionic and / or optionally nonionic hydrophilicizing agent , Method according to one of claims 7 to 9, characterized in that the isocyanate-functional prepolymer b) is prepared by reacting at least the following components: bl) a low molecular weight, aliphatic diisocyanate having a molecular weight of 140 to 278 g / mol, b2) a di- to hexafunctional, preferably a tri- to hexafunctional polyalkylene oxide having an OH number of 22.5 to 112 and an ethylene oxide content of 50 to 100 mol%, based on the total amount of oxyalkylene groups contained.

Method according to one of claims 7 to 10, characterized in that the polyurethane foam A) on the already finished polyurethane foam B) or the polyurethane foam B) on the already finished polyurethane foam A) is applied.

A method according to claim 11, characterized in that the foamed polyurethane dispersion a) applied to the polyurethane foam B) and dried there or the mixture of components b), c) and optionally d) -i) are applied to the polyurethane foam A).

 A wound dressing comprising a composite foam according to any one of claims 1 to 6 or a composite foam obtainable according to a method according to any one of claims 7 to 12.

Wound dressing according to claim 11, characterized in that it additionally comprises a cover layer, which may in particular be connected to the storage layer.

15. Wound dressing according to claim 12, characterized in that the cover layer comprises or consists of a thermoplastic polyurethane and / or a thermoplastic polyethylene.