Compositions comprising solid particles entrapped in collapsed polymeric microspheres, and methods of making the same

Abstract

A method for modifying or treating solid particles which includes the steps of: (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; and (c) coating the microspheres thus-produced with a film-forming material to form a liquid-impermeable membrane thereon.

What we claim is: 
     
         1 . A topical composition comprising a dispersion of microspheres in a cosmetically or pharmaceutically acceptable carrier, wherein each of said microspheres comprises a collapsed polymeric shell having entrapped therein one or more solid particles, wherein said collapsed polymeric shell is coated by a film-forming material resulting from reacting a siloxane resin with a diorganosiloxane. 
     
     
         2 . The composition of  claim 1 , wherein the microspheres have an average particle size ranging from about 1 micron to about 50 microns, and the solid particles have an average particle size ranging from about 0.001 micron to about 0.5 micron. 
     
     
         3 . The composition of  claim 1 , wherein the entrapped solid particles comprise one or more materials selected from the group consisting of talc, kaolin, mica, bismuth oxychloride, chromium hydroxide, barium sulfate, polymethylmethacrylates (PMMA), boron nitride, nylon beads, polymeric powders, silica, silica beads, lakes, metal oxides, iron oxide, chromium oxide, zinc oxide, titanium dioxide, and physical and chemical sunscreen agents. 
     
     
         4 . The composition of  claim 1 , wherein the entrapped solid particles comprise one or more materials capable of generating free oxygen radicals. 
     
     
         5 . The composition of  claim 1 , wherein the entrapped solid particles comprise one or more metal oxides. 
     
     
         6 . The composition of  claim 1 , wherein the entrapped solid particles comprises titanium dioxide, zinc oxide, or a combination thereof. 
     
     
         7 . The composition of  claim 1 , wherein the collapsed polymeric shell is further coated with a liquid-impermeable membrane. 
     
     
         8 . The composition of  claim 7 , wherein the liquid-impermeable membrane comprises one or more materials selected from the group consisting of acrylate homo- or co-polymers, methacrylate homo- or co-polymers, vinylpyrrolidone homo- or co-polymers, silicone gums, silicone waxes, silicone oils, silicone resins, esters, hydrocarbons, celluloses, fatty acids, fatty alcohols, and inorganic materials. 
     
     
         9 . The composition of  claim 7 , wherein the liquid-impermeable membrane comprises crosslinked dimethicone or trimethylated silica treated with dimethyl siloxane. 
     
     
         10 . The composition of  claim 4 , further comprising at least one organic compound susceptible to oxidative decomposition or degradation. 
     
     
         11 . The composition of  claim 10 , wherein said organic compound is an organic sunscreen agent susceptible to oxidative decomposition or degradation. 
     
     
         12 . The composition of  claim 10 , wherein said organic compound is an organic dye susceptible to oxidative decomposition or degradation.