Ciba-Geigy Corporation

Michael Marky

Werner Schreiber

A very pure, dust-free commercial form of 4,2',4'-trichloro-2-hydroxydiphenyl ether with little odor is prepared by diazotizing 4,2'4'-trichloro-2-aminodiphenyl ether, boiling the diazonium salt and purifying the reaction product. The pure, dust-free and odor-free commercial form is obtained by separating off the acid aqueous phase of the reaction mixture, rendering the mixture containing 4,2'4'-trichloro-2-hydroxydiphenyl ether and 2,4,8-trichlorodibenzofuran alkaline, extracting it several times with an inert water-immiscible solvent, either after removal of the organic solvent by steam distillation and precipitation of the by-product 2,4,8-trichlorodibenzofuran or directly, and then adjusting the pH to 3 to 10; subsequently, the highly volatile constituents are removed from the 4,2',4'-trichloro-2-hydroxydiphenyl ether melt which has separated out, the melt is subjected to molecular distillation and the distilled melt is introduced into an aqueous dispersion of crystalline 4,2',4'-trichloro-2-hydroxydiphenyl ether, this dispersion simultaneously being subjected to wet grinding. Filtration and drying gives a granular-like ready-to-use commercial form.

Growing community of inventors

Binningen, Switzerland

Michael Marky