Patent ID: 7420077

Claim:
A process for preparing oligocarbonate diols, comprising: reacting dimethyl carbonate with a diol component in the presence of a titanium tetraisopropoxide transesterification catalyst at a pressure of 3 to 6 bar and at temperatures of 100 to 200° C., by continuously introducing the DMC into the liquid phase of the reaction mixture and continuously removing from the reaction mixture by distillation the methanol which forms as a gaseous methanol/dimethyl carbonate mixture, and, reducing the temperature of the reaction mixture on completion of the continuous metered addition of dimethyl carbonate, to ≦190° C., and reducing the pressure to atmospheric pressure, such that further methanol/dimethyl carbonate mixture is distilled off in parallel, further reducing the pressure after atmospheric pressure has been attained and, after a pressure of ≦100 mbar has been attained, introducing an inert gas stream into the reaction mixture, wherein the oligocarbonate diols have an OH-functionality of at least 1.9.