GB927892A - Production of purified pyrethrum extract - Google Patents

Abstract

A process for the production of a purified pyrethrum containing composition comprises distilling a solution of a pyrethrum oleoresin extract, in a fraction of normally liquid paraffinic hydrocarbons, which distils between 200 DEG C. and 500 DEG C. at atmospheric pressure the distillation being carried out at a pressure which is sufficiently low substantially to avoid thermal decomposition and degradation of the pyrethrins present. The paraffinic hydrocarbons are paraffins and cycloparaffins e.g. kerosenes distilling above 200 DEG C., technical oils or medicinal oils which have been treated to remove unsaturated, hydrocarbons, waxy materials and colouring matter, such as white oils, Deobase liquid paraffin or light liquid paraffin. The pressure is preferably not greater than 1 mm. of Hg. and more specifically 10-2-10-5 mm. of Hg. The oleoresin extract is dissolved in less than 12 and preferably 2-10 times its volume of liquid paraffin hydrocarbons before distillation and the distillation is desirably carried out as a short parth distillation, which results in the oleoresin extract being freed from colouring matter; and by carrying out the process in a flash still in a plurality of stages with short path evaporators, the oleoresin extract may be separated into fractions which predominate in pyrethrins I or II respectively or alternatively such fractions may be obtained by fractional distillation in a pot still. By variation of the boiling point ranges of the paraffinic hydrocarbons the component which is rich in Pyrethrin II may be left undistilled or distilled as a separate fraction of higher boiling point than the component rich in Pyrethrin I. The distillates are clear pale yellow mobile liquids, which may be diluted with kerosene or other miscible organic liquids to form insecticidal sprays or solutions.