Patent ID: 8884076

Claim:
A process for distilling an aqueous polymethylol mixture comprising a polymethylol of the formula (I) in which each R is independently a further methylol group or an alkyl group having 1 to 22 carbon atoms or an aryl or aralkyl group having 6 to 22 carbon atoms, a tertiary amine, water and the adduct of tertiary amine and formic acid (amine formate), wherein the aqueous polymethylol mixture is obtained in a multistage reaction involving, in stage a), condensing alkanals in an aldol reaction with formaldehyde in the presence of tertiary amines as a catalyst to give methylolalkanals of the formula (II) where each R is independently a further methylol group or an alkyl group having 1 to 22 carbon atoms or an aryl or aralkyl group having 6 to 22 carbon atoms and then, in stage b), distillatively separating the reaction mixture obtained from stage a) into bottoms comprising predominantly compounds of the formula (II), and a top stream comprising low boilers, and, in stage c hydrogenatingthe bottoms discharge from stage b), wherein the reaction discharge from the hydrogenation (stage c)) is an aqueous polymethylol mixture which comprises a polymethylol of the formula (I) and the aqueous polymethylol mixture is purified by removing low boilers from the polymethylol compound by distillation, wherein the distillation is performed in a distillation column which is connected at the bottom to an evaporator, the temperature at the bottom of the column being above the evaporation temperature of the monoester of formic acid and polymethylol (polymethylol formate) which forms during the distillation and wherein the reflux at the top of the column is adjusted such that the predominant amount of the polymethylol formate is retained in the column, and discharged from the bottom of the evaporator is a discharge which comprises predominantly the polymethylol compound.