GB887868A - Conversion of plastic organic substances into granular form - Google Patents

Abstract

A water-insoluble cellulose derivative or a water-insoluble synthetic resin is formed into spherical particles by dissolving it in an organic solvent which is substantially immiscible with water to form a viscous lacquer, suspending bodies of the lacquer in an aqueous liquid suspending medium, said bodies having a minimum average diameter in excess of 0,070 inch such that, after they have subsequently been rounded and the solvent has been removed from them, the resulting spherical particles will have a minimum average diameter of at least 0,070 inch, maintaining said bodies in suspension until they assume a spherical shape, removing the solvent from the suspended bodies, and separating the particles from the suspending medium. A solute is initially dissolved in the aqueous medium to provide a solution having substantially the same density as the lacquer and, during the solvent removal stage, additional solute is added to the aqueous medium continuously or at intervals at a rate sufficient to maintain the density of the aqueous medium substantially equal to that of the lacquer globules while the latter are continuously increasing in density due to the removal of solvent therefrom. The solute may be sodium sulphate, magnesium sulphate, barium nitrate, sodium nitrate, aluminium sulphate, sodium chloride or sugar. The solvent may be removed from the lacquer globules by heating the suspension, or by bubbling air through it, or by adding a considerable excess of water to the suspension. A protective colloid such as glue, gum arabic, gum tragacanth or starch is preferably present in the aqueous medium. The synthetic resin may be polyvinyl chloride, polyvinyl acetate, a vinyl chloride-acetate copolymer or polystyrene, and the cellulose derivative may be nitrocellulose, cellulose acetate butyrate or ethyl cellulose. Specification 815,788 and U.S.A. Specification 2,160,626 are referred to.