Production of dry powders of substances which are sensitive to oxidation

Claim 1

A process for converting an oxygen-sensitive, oil soluble substance into a dry, free-flowing, oxygen-insensitive powder, which comprises: (a) dispersing said oxygen-sensitive, oil soluble substance in an aqueous solution which contains a film-forming colloid and one or more compounds selected from the group consisting of a mono-, di-, and poly-saccharide to form a dispersion wherein said colloid constitutes the continuous phase; (b) atomizing said dispersion within the spraying zone of a spray tower to form discrete particles therefrom; (c) causing said particles, as they form, to contact a hydrophobic spray assistant selected from the group consisting of silanized silica, a metal salt of a higher fatty acid and mixtures thereof in the absence of significant amounts of starch powder, with the newly formed particles being at a temperature during such contact which precludes solidification; said contact being effected by maintaining a uniform distribution of said spray assistant in the spraying zone of said spray tower during atomization of said dispersion therein to form said particles, with the spray assistant being supplied to the spraying zone in an amount of from about 0.02 to 0.15 parts by weight based on the weight of said dispersion; (d) collecting said particles laden with said hydrophobic spray assistant in a fluidized bed downstream from the spraying zone of said spray tower with said bed being maintained in a fluidized state by an upwardly directed flow of dry air; and (e) causing said particles to solidify and dry in said fluidized bed by means of the upward flow of dry air through the bed.