| abstract |
The invention relates to a method for producing polyester alcohols by condensing polytetrahydrofuran with aromatic dicarboxylic acids and/or the anhydrides thereof and/or the esters thereof, preferably isophthalic acid, pthalic acid, and terephthalic acid, particularly preferably isophthalic acid, in the presence of a transesterification catalyst in a multistage operation at different pressure levels with at least one reaction stage at normal pressure and at least one reaction stage in a vacuum, wherein distillate is discharged from the reaction system. The method is characterized in that phosphoric acid is introduced in a molar ratio of the catalyst to the phosphoric acid of 1:1 to 1:3.5 after the polycondensation in order to deactivate the catalyst. |