Polyurethane-based pressure-sensitive adhesive, characterized in that the polyurethane is composed of the following starting materials which are reacted catalytically with one another in the stated proportions: a) at least one aliphatic or alicyclic polyisocyanate having a functionality of in each case less than or equal to three, b) a combination of at least one triol A based on polypropylene glycol and having an average number-averaged molecular weight M.sub.n of less than or equal to 1000 and a triol B based on polypropylene glycol and having an average number-averaged molecular weight M.sub.n of greater than or equal to 1000, preferably greater than or equal to 3000, the ratio of the number of hydroxyl groups of the triol component A to the number of hydroxyl groups of the triol component B being between greater than 0 and 12, the ratio of the number of isocyanate groups to the total number of hydroxyl groups being between 0.8 and 1.15, preferably between 0.95 and 1.05, the catalyst for the reaction to the polyurethane consisting of or comprising a compound comprising bismuth and carbon, preferably a bismuth carboxylate or a bismuth carboxylate derivative.