| abstract |
The invention discloses a process for preparing a chemically cross-linked polyurethane film, which comprises (a) chemically reacting a mixture comprising many polyols with one or more polyisocyanates,where at least one of the polyols or at least one of the polyisocyanates contains tri- or higher functional molecules and the ratio of the total number of the isocyanate groups to the total number ofthe hydroxyl groups is less than 1, to a hydroxyl-functionalized, meltable reaction product, also called hydroxyl-functionalized polyurethane-hotmelt-prepolymer, (b) introducing the polyurethane-hotmelt-prepolymer and one or more polyisocyanates in a continuously operating mixer for chemical reaction and (c) coating the melt on a tapered sheet-like material or between two tapered sheet-like material, and continuously performing the reaction begining with the (b). |