A process for purifying formaldehyde, its use and thus produced plastics

The invention relates to a method for purifying formaldehyde, whereby the formaldehyde is rinsed with alcohol in an absorption unit and almost entirely converted to hemiformal while gaseous impurities are separated in a first purification step. The remaining impurities are transformed into a gaseous state in a desorption unit and are separated from the liquid hemiformal, whereupon the purified hemiformal is thermally cleaved into alcohol and formaldehyde in a pyrolysis unit. The formaldehyde thus produced is suitable, for instance, for use in the production of oligomers, polymers, dyes and fertilisers, in addition to seed treatment.