PREPARATION OF ALIPHATIC OLIGOCARBONATE POLYOLS

摘要

Provided is a method for preparing an aliphatic oligocarbonate polyol having a theoretical OH functionality number by the ester exchange reaction of dimethyl carbonate and an aliphatic polyol. The method comprises the steps of reacting dimethyl carbonate and a polyol component in the presence of a ytterbium compound as an ester exchange reaction catalyst at a pressure of atmospheric pressure to 6 bar and at a temperature of 100-170 deg.C, wherein this step comprises a continuous sub-step Ai having i of 1-n and n of 2 or more, at each sub-step Ai, a pressure ^1pi of 3-6 bar is obtained in a reactor, the fraction xi of the total amount of dimethyl carbonate is added to a liquid phase reaction mixture, the methanol during the reaction is removed from the reaction mixture by distillation in a form of a gas phase mixture of methanol and methyl carbonate at a temperature Ti after the reaction time t_i, and the pressure is lowered from ^1pi to ^2pi at a constant temperature T1 during the process, and at final step An, the still deficient fraction x_n to the total amount is added, and the pressure ^2p_n is atmospheric pressure at the end part of the sub-step; and lowering further the pressure until it reaches a pressure of 100 mbar or less, and passing an inert gas stream through the reaction mixture to remove further the mixture of methanol and methyl carbonate by distillation with maintaining the temperature of the reaction mixture to be 195 deg.C or less.