Process for the extraction of pyrethrins from pyrethrum flowers

摘要

A method for recovering biologically-active pyrethrin substances for use as insecticides by extraction from fresh, undried or partially dehydrated pyrethrum flowers, in which the fresh flowers, which may be first coarsely divided, are brought into contact with a mixed extraction solvent preferably at p temperatures below 60 DEG C. consisting of a minor portion of a water miscible solvent, preferably acetone or dioxane and a major portion of a water-immiscible solvent preferably petroleum ether, hexane, heptane, solvent naptha or kerosene, preferably in the proportions of 5 to 35% by volume of the former to 95 to 65% of the latter, for a time sufficient to extract the biologically-active pyrethrin substances while extracting substantially none of the mixture from the flowers, separating the solvent from the exhausted flowers and evaporating the mixed solvent, preferably below 60 DEG C. to recover the biologically active pyrethin substances. Specified solvent mixture consists of 15% acetone and 85% petroleum ether. Specifications 559,735 and 596,187 are referred to.