The invention concerns two-component polyurethane compositions of a polyol component and a polyisocyanate component, the polyol component including at least one reaction product of castor oil and ketone resins with an OH number of 110 to 200 mg KOH/g, and at least one aliphatic triol, and the polyisocyanate component including at least one aromatic polyisocyanate, the ratio in weight percent of being between 4 and 50 and the ratio of all NCO groups of the aromatic polyisocyanates to all the OH groups totaling (A1+A2)=1.15:1-85:1, the aliphatic triol being-1,2,3-propane triol and/or-1,1,1-trimethylol propane and/or polyether polyols based on 1,1,1-trimethylol propane with a molecular weight of 170-500 g/mol and an OH-number of 400-1100 mg KOH/g, and the total of all the OH groups of (A1+A2) being ≧90% of the total of all the OH groups of the two-component polyurethane composition.