Patent ID: 7537803

Claim:
A method for coating ultrafine particles with a polymer, comprising: preparing a solution of a polymer in an organic solvent; suspending a quantity of insoluble ultrafine particles in said solution to form a suspension; and combining a supercritical fluid as an antisolvent with said suspension in a high pressure vessel to cause the polymer to precipitate from said solution and coat the surface of at least a portion of said quantity of suspended ultrafine particles to produce polymer-coated ultrafine particles; providing a suspension delivery system and an antisolvent supply system; wherein no vibrational force is applied to the high pressure vessel while the antisolvent and suspension are combined in the high pressure vessel; wherein said insoluble ultrafine particles are nanoparticles or submicron particles having a particle size of about 16 nm to about 500 nm; wherein the polymer concentration of said polymer with respect to said solvent in said solution is less than about 4.0 mg/ml so as to minimize agglomeration of said polymer-coated ultrafine particles; wherein the insoluble ultrafine particles are substantially insoluble in the organic solvent; wherein the polymer-coated ultrafine particles are in the form of loose agglomerates or individual particles; wherein the thickness of the polymer coating on the surface of the polymer-coated ultrafine particles is less than about 75 nm; and wherein the antisolvent is combined with the suspension by: (i) supplying the antisolvent to the high pressure vessel using the antisolvent supply system; and (ii) delivering the suspension into the antisolvent using the suspension delivery system.