The invention relates to a process for preparing polymethylol compounds of
the formula (I) ##STR00001## where the radicals R are each,
independently of one another, a further methylol group or an alkyl group
having from 1 to 22 carbon atoms or an aryl or aralkyl group having from
6 to 22 carbon atoms, by condensation of aldehydes having from 2 to 24
carbon atoms with formaldehyde in an aldol reaction using tertiary amines
as catalyst to form alkanals of the formula (II) ##STR00002## where the
radicals R each independently have one of the abovementioned meanings,
and subsequent hydrogenation of the latter. The particular inventive
feature of this process is that the aldol reaction is carried out using
an aqueous formaldehyde solution having a formic acid content of <150
ppm and preferably <100 ppm.In this way of carrying out the process,
the formation of by-products can advantageously be prevented in a
targeted manner and the yield of the desired polymethylol compound can
thereby be increased.