Patent ID: 8629195

Claim:
A process for producing foamed articles comprising frothing and drying a composition comprising aqueous polyurethane dispersions (I) anionically hydrophilicized by means of sulphonate groups and a crosslinker (II); wherein said polyurethane dispersion (I) is prepared by A) producing a isocyanate-functional prepolymer from A1) organic polyisocyanates; A2) polymeric polyols having number-average molecular weights in the range from 400 to 8000 g/mol and OH functionalities in the range from 1.5 to 6; and A3) optionally hydroxyl-functional compounds having molecular weights in the range from 62 to 399 g/mol; and A4) optionally isocyanate-reactive, anionic or potentially anionic and optionally nonionic hydrophilicizing agents; and B) wholly or partly reacting the free NCO groups of said isocyanate-functional prepolymer B1) optionally with amino-functional compounds having molecular weights in the range from 32 to 400 g/mol; and B2) with an alkali metal salt of a mono- or diamino sulphonic acid by chain extension; wherein said isocyanate-functional prepolymer is dispersed in water before, during or after step B), wherein at least partial chemical crosslinking occurs during frothing and/or drying, and wherein said crosslinkers (II) are selected from the group consisting of unblocked, optionally hydrophilicized polyisocyanates; amide- and amine-formaldehyde resins; phenolic resins; aldehyde and ketone resins; resols; furan resins; urea resins; carbamidic ester resins; triazine resins; melamine resins; benzoguanamine resins; cyanamide resins; and aniline resins, and wherein the foamed article is a wound dressing.