Patent ID: 8859721

Claim:
A process for working up particulate crude polyoxymethylene, which comprises the following steps: (a) introduction of the particulate crude polyoxymethylene into an extraction column ( 13 ) operated at a pressure in the range from 1 to 6 bar, (b) introduction of a polar extractant into the extraction column ( 13 ) with a temperature in the range from 95 to 140° C. and a pressure in the range from 1 to 6 bar, wherein from 10 to 1000 ppm, based on the amount of polar extractant introduced, of a buffer substance which buffers in the pH range from 7.5 to 11.5 are introduced into the extraction column ( 13 ); wherein the buffer substance is selected from among sodium tetraborate, sodium glycerophosphate and mixtures thereof.