EP2585506A1

EP2585506A1 - Method for producing flat, hydrophilic, aliphatic polyurethane foams

Info

Publication number: EP2585506A1
Application number: EP11726770.8A
Authority: EP
Inventors: Meike Niesten; Sebastian Dörr; Thorsten KRÄMER
Original assignee: Bayer Intellectual Property GmbH
Current assignee: Bayer Intellectual Property GmbH
Priority date: 2010-06-22
Filing date: 2011-06-20
Publication date: 2013-05-01
Also published as: CN103080172A; WO2011161033A1; JP2013532216A; US20130131206A1

Abstract

The invention relates to a method for producing flat, hydrophilic, aliphatic polyurethane foams. The invention also relates to a flat, hydrophilic, aliphatic polyurethane foam obtained according to said method and to the use thereof as a wound dressing, incontinence product or cosmetic article. According to the invention, a prepolymer-component and a carbonic acid or carboxylate component containing water is produced, said components are combined and mixed, and the obtained mixture is applied to a flat substrate as a layer which has an even thickness. Directly after application, a perforated separation element is applied in a flat manner to the layer. Said applied layer then expands with the applied perforated separation element to form the flat polyurethane foam.

Description

Process for the production of flat, hydrophilic, aliphatic polyurethane foams

The invention relates to a process for the production of flat, hydrophilic, aliphatic polyurethane foams. Furthermore, a surface-available, hydrophilic, aliphatic polyurethane foam obtainable by the process and its use as a wound dressing, incontinence product or as a cosmetic article are objects of the invention.

European Patent Application EP 2 143 744 discloses a process by means of which hydrophilic aliphatic polyurethane foams can be produced. In this process, isocyanate-functional prepolymers with Cg to C22 monocarboxylic acids or their ammonium or alkali metal salts or C12 to C44 dicarboxylic acids or their ammonium or alkali metal salts and water are reacted. The prepolymers are obtainable by reacting low molecular weight aliphatic diisocyanates with polyalkylene oxides. The components are mixed and placed in a beaker in which the foaming reaction then takes place. In this case, a polyurethane block foam is obtained. This is, if it is to be used, for example, as a wound dressing, cut to the desired thickness of typically 10 μ to 5 cm. Disadvantage of this method is that significant amounts of waste arise, which must be disposed of. Furthermore, the implementation of the cutting process in this class of materials is associated with considerable practical difficulties. For example, the foam breaks quickly when sheathed. In addition, it is difficult to obtain a uniform layer thickness.

In the non-prepublished European patent application with the application number EP 09009202.4 a process for the preparation of flat, hydrophilic, aliphatic polyurethane foams is described in which foam mixtures of the type described above are strung onto a substrate to obtain foams having a uniform layer thickness.

Disadvantage of this method is that it forms a skin on the foam on the air side. This skin stiffens the foam, thereby affecting its drapability, i. his ability to adapt to certain areas of the body. Drapability, however, is an important property especially for wound dressings and incontinence products.

It was therefore an object of the invention to provide a rapid, simple and material-efficient process for the production of flat, hydrophilic, aliphatic polyurethane foams having a constant thickness in the range from 1 to 20 mm, in which foams having a homogeneous, skin-free surface are obtained become.

This object is achieved by the method of claim 1, wherein I) isocyanate-functional prepolymers A), are prepared by reacting low molecular weight, aliphatic diisocyanates AI) of a molecular weight of 140 to 278 g / mol with di- to hexafunctional polyalkylene oxides A2) an OH number of 22.5 to 112 mg KOH / g and an ethylene oxide content of 50 to 100 mol%, based on the total amount of the oxyalkylene groups present,

II) C8 to C22 monocarboxylic acids or their ammonium or alkali metal salts or C12 to C44 dicarboxylic acids or their ammonium or alkali metal salts B) are mixed with water C), III) the mixtures of steps I) and II) are combined and mixed become,

IV) the mixture of step III) is applied to a flat substrate as a layer of constant thickness,

V) a perforated separating element is applied flatly to the layer of step IV) so that the surface of the layer facing away from the substrate is covered, VI) the layer of step V) is expanded to form the foam to be formed.

The preparation of the isocyanate-functional prepolymers A) is typically carried out by reacting one equivalent of the polyol component A2) with 1 to 20 mol, preferably with 1 to 10 mol, particularly preferably with 5 to 10 mol, of the low molecular weight, aliphatic diisocyanate AI).

The reaction 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 is typically carried out at 25 to 140 ° C, preferably at 60 to 100 ° C.

Was worked with excess isocyanate, then the removal of the excess of low molecular weight, aliphatic 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 the distillative removal of the excess of diisocyanate. Examples of low molecular weight aliphatic diisocyanates of component AI) 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 (HDI), isophorone diisocyanate (IPDI), biphenyl endii so cyanate (BDI) and bis (isocyanatocyclohexyl) methane (HMDI) being preferred , Particularly preferred are hexamethylene diisocyanate, isophorone diisocyanate, butylene diisocyanate, and very particularly preferred are hexamethylene diisocyanate and isophorone diisocyanate. It is also preferred if exclusively diisocyanate AI) hexamethylene diisocyanate and isophorone diisocyanate or mixtures thereof are used with each other.

The polyalkylene oxides A2) are preferably copolymers of ethylene oxide and propylene oxide which are started on polyols or amines and have 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%. Suitable initiators of this type are glycerol, trimethylolpropane (TMP), sorbitol, pentaerythritol, triethanolamine, ammonia or ethylenediamine.

The polyalkylene oxides A2) typically have number average molecular weights of from 1000 to 15000 g / mol, preferably from 3000 to 8500 g / mol.

Furthermore, the polyalkylene oxides A2) OH functionalities of 2 to 6, preferably from 3 to 6, more preferably from 3 to 4 have.

In a further development of the invention is provided as polyalkylene oxides A2) copolymers of ethylene oxide and propylene oxide having an ethylene oxide content, based on the total amount of oxyalkylene groups contained, of 60 to 85 mol%, started on polyols or amines.

The prepolymers A) used preferably have a residual monomer content of less than 1.0% by weight, more preferably less than 0.5% by weight, based on the prepolymer. This content can be achieved by appropriately selected amounts of Al) and A2). However, the use of the isocyanate AI) in excess and the subsequent, preferably distillative, separation of unreacted monomers is preferred.

The NCO content of the isocyanate-functional prepolymers A) is preferably 1.5 to 4.5% by weight, more preferably 1.5 to 3.5% by weight and very particularly preferably 1.5 to 3.0% by weight. %. As component B) ammonium and alkali salts of Cg to C22 monocarboxylates or their free carboxylic acids or ammonium and alkali metal salts of C12 to C44 dicarboxylates or their free dicarboxylic acids, preferably potassium or sodium salts of Cg to C22 mono- carboxylates or C12 to C44 dicarboxylates and more preferably sodium salts of Cg to C22 monocarboxylates used.

Examples of suitable compounds of component B) 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 or the ammonium and alkali salts derived therefrom are dodecanedioic acid, dodecenyl, tetradecenyl, hexadecenyl and octadecenyl succinic acid, C 36 and C 44 dimer fatty acids and their hydrogenation products, and the corresponding ammonium, alkali metal , Li or K salts of these dicarboxylic acids.

The water C) to be used can be used as such, as the water of crystallization of a salt, as a solution in a dipolar aprotic solvent or as an emulsion. Preferably, the water is used as such or in a dipolar aprotic solvent.

According to a preferred embodiment of the invention, it is provided that the prepolymers A) in step I) with heterocyclic 4-membered or 6-membered oligomers D) of low molecular weight, aliphatic diisocyanates having a molecular weight of 140 to 278 g / mol and / or hydrophilic Polyisocyanates E) obtainable by reacting low molecular weight, aliphatic diisocyanates El) having a molecular weight of 140 to 278 g / mol and / or polyisocyanates obtainable therefrom having an isocyanate functionality of 2 to 6 with monofunctional polyalkylene oxides E2) having an OH number of 10 to 250 and an ethylene oxide content of 50 to 100 mol%, based on the total amount of the contained oxyalkylene groups.

The use of component D) and / or E) increased content of isocyanate groups provides for a better Schäumungsergebnis, since in the isocyanate-water reaction, a larger amount of acting as a blowing agent CO2 is formed. It is also preferred if only heterocyclic 4-membered oligomers are mixed with the prepolymers.

Optionally to be used compounds of component D) are heterocyclic 4-membered ring or 6-membered oligomers of low molecular weight aliphatic diisocyanates having a molecular weight of 140 to 278 g / mol such as isocyanurates, iminooxadiazinediones or uretdiones of the aforementioned low molecular weight aliphatic diisocyanates. Preference is given to heterocyclic 4-membered oligomers, such as uretdiones.

The preparation of the hydrophilic polyisocyanates E) is typically carried out by reacting 1 mol of OH groups of the monofunctional polyalkylene oxide component E2) with 1.25 to 15 mol, preferably with 2 to 10 mol and more preferably with 2 to 6 mol of NCO groups Polyisocyanates El) with an isocyanate functionality of 2 to 6, based on aliphatic disocyanates. Exemplary of such polyisocyanates El) are biuret structures, isocyanurates or uretdiones based on aliphatic diisocyanates. In this case, the polyisocyanate E1) and the polyalkylene oxide E2) 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 is typically carried out at 25 to 140 ° C, preferably at 60 to 100 ° C. Was worked with excess low molecular weight diisocyanate, then the removal of the excess of low molecular weight, aliphatic 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 the distillative removal of the excess of diisocyanate.

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

Examples of low molecular weight, aliphatic diisocyanates of component El) are hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), butylene diisocyanate (BDI), bisisocyanatocyclohexyl xylmethane (HMDI), 2,2,4-trimethylhexamethylene diisocyanate, bisisocyanatomethylcyclohexane, bisisocyanatomethyltricyclodecane, xylene diisocyanate, tetramethylxylylene diisocyanate, norbornene diisocyanate, cyclohexane diisocyanate or diisocyanatododecane, with hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), butylene thiiocyanate (BDI) and Bis (isocyanatocyclohexyl) methane (HMDI) are preferred. Particularly preferred are hexamethylene diisocyanate, isophorone diisocyanate, butylene diisocyanate, most preferably hexamethylene diisocyanate and isophorone diisocyanate.

Examples of relatively high molecular weight polyisocyanates E2) 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 aliphatic polyisocyanates E2) or cycloaliphatic diisocyanates.

As component E2), relatively high molecular weight compounds with biuret, iminooxadiazinedione, isocyanurate and / or uretdione groups based on hexamethylene diisocyanate, isophorone diisocyanate and / or 4,4'-diisocyanatodicyclohexylmethane are preferably used. Further preferred are isocyanurates. Very particular preference is given to structures based on hexamethylene diisocyanate.

The monofunctional polyalkylene oxides E2) 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 E2) 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, pages 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 abovementioned type. Particular preference is given to using diethylene glycol monobutyl ether or n-butanol as starter molecules.

The monofunctional polyalkylene oxides E2) typically have number-average molecular weights of from 220 to 3700 g / mol, preferably from 500 to 2800 g / mol. The monofunctional polyalkylene oxides E2) preferably have an OH group as the isocyanate-reactive group.

It is also possible that the mixture of step III) optionally contains catalysts F), surfactants G) alcohols H) and / or blowing agent J). Thus, catalysts F) can be used to accelerate the formation of urethane. 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 octoate (SO), tin acetate, zinc octoate (ZO), l, 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-dodecyltetra methylguanidine (TMGDO), dimethylaminoethyltetramethylguanidine (TMGN), 1,1,4,4,5,5-hexamethylisobiguanidine (HMIB), phenyltetramethylguanidine (TMGP) and hexamethylenoctahamine. thylbiguanidine (HOBG).

As catalysts F), in particular, individually or in combination, metal salts, amines, amidines and guanidines can be used.

To improve the foaming, foam stability or the properties of the resulting polyurethane foam, the compounds of component G) can be used, wherein such additives may in principle be any known anionic, cationic, amphoteric and nonionic surfactants and mixtures thereof. Alkyl polyglycosides, EO / PO block copolymers, alkyl or aryl alkoxylates, siloxane alkoxylates, esters of sulfosuccinic acid and / or are preferably used. Particular preference is given to using EO / PO block copolymers. Preferably, only the EO / PO block copolymers are used as component G). In addition, compounds of component H) can be used to improve the foam properties of the resulting polyurethane foam. These are in principle all monohydric and polyhydric alcohols known to the person skilled in the art and mixtures thereof. These are monohydric or polyhydric alcohols or polyols, such as ethanol, propanol, butanol, decanol, tridecanol, hexadecanol, ethylene glycol, neopentyl glycol, butanediol, hexanediol, decanediol, trimethylolpropane, glycerol, pentaerythritol, monofunctional polyether alcohols and polyester alcohols, polyethylenes herdiols and polyester diols. The foaming can in principle be carried out by the carbon dioxide formed in the reaction of the isocyanate groups with water, but the use of further blowing agents J) is likewise possible. Thus, in principle, blowing agents from the class of hydrocarbons such as C ₃ -C 6 alkanes, for example, butanes, n-pentane, z o-pentane, cyc / o-pentane, hexanes, or the like. or halogenated hydrocarbons, such as dichloromethane, dichloromonofluoromethane, chlorodifluoroethanes, 1,1-dichloro-2,2,2-trifluoroethane, 2,2-dichloro-2-fluoroethane, in particular chlorine-free fluorohydrocarbons, such as difluoromethane, trifluoromethane, difluoroethane, 1, 1, 1, 2-tetrafluoroethane, tetrafluoroethane (R 134 or R 134a), 1,1,1,3,3-pentafluoropropane (R 245 fa), 1,1,1,3,3,3-hexafluoropropane (R 256 ), 1,1,1,3,3-pentafluorobutane (R 365 mfc), heptafluoropropane or sulfur hexafluoride. It is also possible to use mixtures of these blowing agents.

According to a preferred embodiment of the invention, it is provided that the components A) to H) are used in the following amounts:

Typically, components A) to H) are used in the following amounts:

100 parts by weight of isocyanate-functional prepolymers A)

0.1 to 5 parts by weight of C8 to C22 monocarboxylic acids or their ammonium or alkali metal salts or C12 to C44 dicarboxylic acids or their ammonium or alkali metal salts B)

1 to 200 parts by weight of water C)

0 to 100 parts by weight of heterocyclic oligomers D)

0 to 250 parts by weight of hydrophilic polyisocyanate component E)

0 to 1 parts by weight of catalysts F)

0 to 10 parts by weight of surfactants G)

0 to 20 parts by weight of alcohols H).

The components A) to H) are particularly preferably used in the following amounts:

100 parts by weight of isocyanate-functional prepolymers A)

2 to 100 parts by weight of water C) 0 to 100 parts by weight of heterocyclic oligomers D) 5 to 250 parts by weight of hydrophilic polyisocyanate component E) 0 to 1 parts by weight of catalysts F) 0 to 10 parts by weight of surfactants G) 0 to 20 parts by weight of alcohols H).

Very particular preference is given to using components A) to H) in the following amounts: 100 parts by weight of isocyanate-functional prepolymers A)

0.1 to 5 parts by weight of C8 to C22 monocarboxylic acids or their ammonium or alkali metal salts or C12 to C44 dicarboxylic acids or their ammonium or alkali metal salts B) 5 to 50 parts by weight of water C)

5 to 50 parts by weight of heterocyclic oligomers D)

10 to 50 parts by weight of hydrophilic polyisocyanate component E)

0 to 1 parts by weight of catalysts F)

0 to 10 parts by weight of surfactants G) 0 to 20 parts by weight of alcohols H).

When mixing the components and / or mixtures and during the Schäumungsreaktion can be carried out at temperatures from 0 to 100 ° C, preferably at 15 to 70 ° C, most preferably at 20 to 50 ° C.

After mixing the component, the mixture is applied to a flat substrate as a layer of constant thickness. Suitable substrates are, for example, release films or release papers, which may also be perforated.

Preferably, the mixture can be knife-coated onto the substrate. For this purpose, the mixture can be poured into a doctor box and in a certain thickness horizontal in flat mats on a suitable substrate such as a release film or a release paper are geräkelt. The gap height of the doctor blade is generally in the range of 0.2 to 20 mm, preferably from 0.2 to 5 and most preferably from 0.2 to 2 mm. The film width of the doctor blade to be used can be adapted to the respective intended use. Examples are film widths between 10 and 5000 mm, preferably between 10 and 4000 mm. As a doctor, all known types such as air knife, roller blade, doctor blade, box doctor, knife blade or magnetic doctor blade can be used. As a material for the doctor blade all the usual materials come into consideration, such as metals such as stainless steel or plastics. A combination of several materials for the production of the doctor blade is possible. Both hand wringer and machine squeegee can be used; preference is given to the use of machine squeegees, incorporated in suitable coating systems. The application between rollers is possible.

Directly after application, a perforated separating element is placed flat on the layer of the mixture so that it covers the surface of the layer facing away from the substrate.

Under perforated is understood in the present case a separating element that has a plurality of, the separating element from the support surface passing through recesses. The recesses preferably have a circular diameter.

It is also preferable if the recesses are distributed uniformly over the separating element.

The recesses may preferably have a diameter of 20 to 300 μιη. In this case, foams are obtained in which no elevations in the form of the gaps of the separating element on the foam surface are visible. The foams have a smooth surface, which is particularly advantageous when used as a wound dressing, since they should be as flat as possible on the body.

The distance between two adjacent recesses is preferably between 0.1 to 5 mm, more preferably between 0.5 to 3 mm and most preferably between 0.8 and 2.5 mm.

The perforated separating element can be, for example, a perforated separating paper or a perforated separating film. The release paper may e.g. be siliconized paper, polyolefin coated paper or fluorocarbon coated paper. Likewise, the release film may consist of silicone, polyolefins and / or fluorocarbon, or be coated with such materials.

Preferably, after application, the separating element can be pressed in particular still with a defined pressure on the layer of the mixture of step III). To accelerate the curing of the polyurethane foam after completion of the expansion, this can be heated. Preferably, the polyurethane foam may be heated to a temperature of from 40 to 140 ° C, more preferably from 60 to 120 ° C, and most preferably from 60 to 110 ° C. Also particularly preferred is a process in which a wound dressing is produced from the polyurethane foam according to the invention.

Further objects of the invention are a polyurethane foam which can be produced by the process according to the invention.

The polyurethane foams obtained have a porous, at least partially open-cell structure with cells which communicate with each other. The density of the polyurethane foams is typically from 0.01 to 0.6 g / cm ³ , preferably from 0.02 to 0.85 g / cm ³ , particularly preferably from 0.05 to 0.4 g / cm ³ and most preferably at 0.1 to 0.3 g / cm ³ (determined according to DIN 53420).

The polyurethane foams can be bonded, laminated or coated with other materials, for example based on hydrogels, (semi-) permeable films, foam films, coatings, hydrocolloids or other foams.

The polyurethane foams according to the invention are particularly suitable for the production of wound dressings. The polyurethane foams may be in direct or indirect contact with the wound. However, the polyurethane foams are preferably used in direct contact with the wound in order, for example, to ensure optimum absorption of wound fluid. The polyurethane foams show no cell toxicity (determination according to ISO 10993-5 and ISO 10993-12).

The polyurethane foams which are used as a wound dressing can additionally be sterilized in a further process step. For sterilization, the processes known per se to those skilled in the art are used in which sterilization by thermal treatment, chemical substances such as ethylene oxide or irradiation, for example by gamma radiation, takes place. The irradiation may optionally take place under a protective gas atmosphere. The polyurethane foams according to the invention have the great advantage that they do not discolor during irradiation, in particular when irradiated with gamma rays.

Also possible is the addition, incorporation or coating of or with antimicrobial or biological agents, which have a positive effect, for example, in terms of wound healing and the avoidance of bacterial load. Finally, the subject matter of the invention is also a planar, hydrophilic, aliphatic polyurethane foam according to the invention for use as a wound dressing. Incontinence product or cosmetic article.

Examples

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 in accordance with DIN-EN ISO 11909.

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 used and abbreviations:

Desmodur ^® N 3400: Aliphatic polyisocyanate (HDI uretdione), NCO content 21.8% Desmodur ^® N 3300: Aliphatic polyisocyanate (HDI isocyanurate), NCO content

21.8%, Bayer MaterialScience AG, Leverkusen, Germany

Example 1: Preparation of the polyurethane prepolymer 1

1000 g of a polyalkylene oxide having a molecular weight of 4680 g / mol were started at 80 ° C. over 3 hours on a mixture of 1000 g of hexamethylene diisocyanate (HDI) and 1 g of benzoyl chloride on glycerol, an ethylene oxide weight fraction of 72% and a propylene oxide weight fraction of 28%, previously at 100 ° C was dried for 6 h at a pressure of 0.1 mbar, added dropwise and stirred for 12 h. Excess HDI was removed by thin-film distillation at 130 ° C and 0.1 mbar, stabilizing the nonvolatile components with 1 g of chloropropionic acid. This gave a prepolymer having an NCO content of 2.77% and a viscosity of 3500 mPas

Example 2: Preparation of the hydrophilized polyisocyanates

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 mol, based on the total amount of 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 according to DIN-EN ISO 11909 content of NCO groups was constant. A liquid having an NCO content of 4.04% and a viscosity of 3330 mPas was obtained. Examples 3-10, Comparative Examples 11-15: Preparation of Foams from the Polyurethane

Prepolymers 1

The isocyanate components, the prepolymer, Desmodur N3400 and the hydrophilized polyisocyanate were homogenized in a 250 ml beaker for 15 seconds at a stirrer speed of 1200 rpm. The other components were weighed in a second beaker and stirred together for 10 seconds. Then the contents of the two cups would be combined and mixed. The mixture thus obtained was surface-coated on a release paper with a squeegee ZUA 2000 with a gap height of 1.5 mm. Immediately after the doctoring a perforated release paper was placed on the layer of the still wet area reaction mixture. The foam was then cured within 5 minutes at 100 ° C.

Overview of the used release papers:

A: perforated siliconized separation paper K900 natural Matt, 51BU / 51B4, (manufacturer Laufenberg), hole size ΙΟμηι, hole spacing 1 mm

B: perforated PE-coated release paper Y5200 (manufacturer Felix Schöller), hole size 120 μηι, hole spacing 2 mm

C: perforated siliconized release paper KS 1200 white 51B (manufacturer Laufenberg), hole size 235 μηι, hole spacing 2 mm D: perforated siliconized release paper 2CC 130/1 (manufacturer Cotek), hole size 100 μιη, hole spacing 2 mm

E: perforated siliconized release paper 2CC 130/1 (manufacturer Cotek), hole size 265 μιη, hole spacing 2 mm

F: perforated PE-coated release paper Y5200 (manufacturer Felix Schöller), hole size 1000 μηι, hole spacing 10 mm

G: perforated PE-coated release paper Y5200 (manufacturer Felix Schöller), hole size 400 μm, hole spacing 10 mm H: perforated PE-coated release paper Y5200 (manufacturer Felix Schöller), hole size 400 μηι, hole spacing 5 mm

I: siliconized release paper K900 natural Matt, 51BU / 51B4, (manufacturer Laufenberg) without perforation J: PE-coated release paper Y5200 (manufacturer Felix Schöller) without perforation

K: siliconized release paper KS 1200 white 51B (manufacturer Laufenberg) without perforation L: siliconized release paper 2CC 130/1 (manufacturer Cotek) without perforation M: siliconized release paper 2CC 130/1 (manufacturer Cotek) without perforation.

COMPOISE EXAMPLE 3 Example 4 Example 5 Example 6 Example 7 nente [g]

Präpoly100 100 100 100 100

mer

Hydrophilic 25 25 25 25 25

lated PIC

Desmodur 11.1 11.1 11.1 11.1 11.1

N3400

11,1 11,1 11,1 11,1 11,1 umoleate

5% in

water

Water 4.7 4.7 4.7 4.7 4.7

Squeegee gap 1.5 1.5 1.5 1.5 1.5

(Mm)

TrennpaA B C D E

pier COMPOICE EXAMPLE 8 Example 9 Example 10

parent [g]

Präpoly100 100 100

mer

Hydrophilic 25 25 25

lated PIC

Desmodur 11,1 11,1 11,1

N3400

Na- 11,1 11,1 11,1

umoleat

5% in

water

Water 4.7 4.7 4.7

Squeegee gap 1.5 1.5 1.5

(Mm)

TrennpaF G H

pier

Comparedcomparisoncomparisoncomparisoncomponent [g] game 11 example 12 example 13 example 14 example 15

Präpoly100 100 100 100 100 mer

Hydrophilic PIC

Desmodur 11,1 11,1 11,1 11,1 11,1 N3400

11,1 11,1 11,1 11,1 11,1 umoleate

5% in

water

Water 4.7 4.7 4.7 4.7 4.7

Squeegee gap 1.5 1.5 1.5 1.5 1.5 (mm)

In Examples 3 to 10 according to the invention, foams with a homogeneous, skin-free, smooth surface are obtained, which feel very soft and have good drapability on the skin. In the foams of Examples 8 to 10, however, elevations in the form of the perforations of the release paper were visible on the foam surface. As a result, the surfaces of the foams were not quite smooth.

In Comparative Examples 11 to 15 (covering with non-perforated release papers), foams having an inhomogeneous surface having many large holes and voids and a stiff skin were obtained.

Claims

claims

1. A process for the production of flat, hydrophilic, aliphatic polyurethane foams, in which

I) isocyanate-functional prepolymers A), are prepared by reacting low molecular weight, aliphatic diisocyanates AI) having a molecular weight of 140 to 278 g / mol with di- to hexafunctional polyalkylene oxides A2) an OH number of 22.5 to 112 mg KOH / g and an ethylene oxide content of 50 to 100 mol%, based on the total amount of oxyalkylene groups contained, II) C8 to C22 monocarboxylic acids or their ammonium or alkali metal salts or C12 to C44 dicarboxylic acids or their ammonium or alkali metal salts B) with water C) to be mixed

III) the mixtures of steps I) and II) are combined and mixed,

IV) the mixture of step III) is applied to a flat substrate as a layer with constant thickness,

V) a perforated separating element is applied flatly to the layer of step IV) so that the surface of the layer facing away from the substrate is covered,

VI) the layer of step V) is expanded to the foam to be formed.

2. The method according to claim 1, characterized in that the prepolymers A) in step I) with heterocyclic 4-ring or 6-membered ring oligomers D) of low molecular weight, aliphatic

Diisocyanates having a molecular weight of 140 to 278 g / mol and / or hydrophilic polyisocyanates E) obtainable by reacting low molecular weight, aliphatic diisocyanates El) having a molecular weight of 140 to 278 g / mol and / or polyisocyanates thereof having an isocyanate functionality of 2 to 6 with monofunctional polyalkylene oxides E2) 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, be mixed.

3. The method according to any one of claims 1 or 2, characterized in that the perforated separating element is a release paper or a release film, which preferably consists of silicone, polyolefin, fluorocarbon and / or paper or contains one or more of these constituents.

4. The method according to any one of claims 1 to 3, characterized in that the perforated separating element has circular recesses, which in particular have a diameter of 20 to 300 μιη.

5. The method according to any one of claims 1 to 4, characterized in that the distance between two adjacent recesses preferably between 0, 1 to 5 mm, more preferably between 0.5 to 3 mm and most preferably between 0.8 and 2, 5 mm.

6. The method according to any one of claims 1 to 5, characterized in that the NCO content of the isocyanate-functional prepolymers A) is 1.5 to 3.0 wt .-%.

7. The method according to any one of claims 1 to 6, characterized in that as diisocyanate AI) exclusively hexamethylene diisocyanate, isophorone diisocyanate or mixtures thereof are used below each other.

8. The method according to any one of claims 1 to 7, characterized in that as polyalkylene oxides A2) copolymers of ethylene oxide and propylene oxide with an ethylene oxide, based on the total amount of oxyalkylene groups contained, from 60 to 85 mol%, started on polyols or amines be used.

9. The method according to any one of claims 1 to 8, characterized in that the polyalkylene oxides A2) have number average molecular weights of 3000 to 8500 g / mol.

10. The method according to any one of claims 1 to 9, characterized in that the polyalkylene oxides A2) have OH functionalities of 3 to 4.

11. The method according to any one of claims 1 to 10, characterized in that the mixture of step III) optionally catalysts F), surfactants G), alcohols H) and / or propellant I).

12. The method according to claim 11, characterized in that are used as catalysts F) individually or in combination metal salts, amines, amidines and guanidines.

13. The method according to any one of claims 11 or 12, characterized in that the components A) to H) are used in the following amounts:

100 parts by weight of isocyanate-functional prepolymers A)

0.1 to 5 parts by weight of C8 to C22 monocarboxylic acids or their ammonium or alkali salts or C12 to C44 dicarboxylic acids or their ammonium or alkali metal salts B)

1 to 200 parts by weight of water C)

0 to 100 parts by weight of heterocyclic oligomers D)

0 to 250 parts by weight of hydrophilic polyisocyanate component E)

0 to 1 parts by weight of catalysts F) 0 to 10 parts by weight of surfactants G)

0 to 20 parts by weight of alcohols H).

14. The method according to any one of claims 1 to 13, characterized in that the polyurethane foam is heated after completion of the expansion to accelerate the curing, preferably to a temperature of 40 and 140 ° C, more preferably from 60 to 120 ° C and more preferably from 60 to 110 ° C.

15. The method according to any one of claims 1 to 14, characterized in that from the polyurethane foam, a wound dressing is produced.

16. A flat, hydrophilic, aliphatic polyurethane foam, obtainable by a process according to one of claims 1 to 14.

17. Areal, hydrophilic, aliphatic polyurethane foam according to claim 15 for use as a wound dressing, incontinence product or cosmetic article.