Patent ID: 8383160

Claim:
A method for modifying or treating solid particles, comprising: (a) forming a gelled mixture by mixing either simultaneously or sequentially in any order (1) hollow microspheres each comprising a deformable polymeric shell having entrapped therein an expandable fluid, (2) a polar organic solvent capable of swelling but not dissolving the polymeric shells of the hollow microspheres, and (3) solid particles, wherein micro-channels are formed in the swelled polymer shells to allow entry of the solid particles into the hollow microspheres and exit of the expandable fluid therefrom, thereby forming microspheres that each comprises a collapsed polymeric shell in a gelled state and has one or more of said solid particles entrapped therein; (b) removing the expandable fluid and the polar organic solvent from the gelled mixture; wherein the expandable fluid is first removed from the gelled mixture by de-gassing at a reduced pressure or under vacuum conditions, followed by a quenching step in which water is added to the gelled mixture to allow separation of the microspheres from one another before removal of the polar organic solvent; and (c) coating the microspheres thus-produced with a film-forming material to form a liquid-impermeable membrane thereon.