# US 7,745,566 B2 · Methods for the purification of polymers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,745,566 B2 - Document ID: US7745566B2 - Status: Granted - Kind: B2 - Application number: 12/017,399 - Filed: 2008-01-22 - Published: 2008-10-30 - Granted: 2010-06-29 - Earliest claimed: 2007-01-23 - Assignees: Ferro Corporation - Inventors: Pratibhash Chattopadhyay; Boris Y. Shekunov; K. Adam Gibson - Web page: https://patentgrep.com/patent/US7745566B2 ## CPC - C08G 63/90: Purification; Drying - C08G 65/30: Post-polymerisation treatment, e.g. recovery, purification, drying - C08G 63/08: Lactones or lactides - Y02P 20/54: using solvents, e.g. supercritical solvents or ionic liquids - C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract The present invention provides methods for purifying polymers. In each embodiment of the invention disclosed herein, a supercritical fluid is contacted with an organic solution that includes a polymer to be purified dissolved in an organic solvent. The supercritical fluid extracts the organic solvent from the organic solution. Impurities such as residual monomers and process solvents are removed with the organic solvent and supercritical fluid, thereby purifying the polymer. The methods of the invention are particularly suitable for use in the purification of biodegradable polymers for use in pharmaceutical applications. ## Claims ### Claim 1 A method of purifying a polymer containing impurities, the method comprising: dissolving the polymer containing impurities in an organic solvent to form an organic polymer solution; co-introducing the organic polymer solution and an aqueous solution into a homogenization device to form an emulsion, the emulsion having a discontinuous phase comprising the organic polymer solution and a continuous phase comprising the aqueous solution; contacting the emulsion with an extraction fluid in an extraction column while the extraction fluid is maintained in a supercritical state to extract the organic solvent and impurities from the discontinuous phase and thereby precipitate purified solid polymer particles into the aqueous continuous phase to form an aqueous suspension of solid polymer particles; and separating the aqueous suspension of purified solid polymer particles from the extraction fluid, organic solvent and impurities. ### Claim 2 (depends on 1) The method according to claim 1 wherein the precipitated purified solid polymer particles are substantially spherical. ### Claim 3 (depends on 1) The method according to claim 1 wherein the polymer is selected from the group consisting of poly(lactic-co-glycolic) acid, polylactic acid, polyethylene glycol, Eudragit polymers, PMMA polymers, ethylcellulose, and combinations thereof. ### Claim 4 (depends on 1) The method according to claim 1 wherein the organic solvent is selected from the group consisting of halogenated hydrocarbons, ketones, alcohols, and ethyl acetate. ### Claim 5 (depends on 1) The method according to claim 1 wherein the extraction fluid is selected from the group consisting of supercritical carbon dioxide, supercritical ethane, supercritical ethylene, supercritical propane, supercritical propylene and supercritical pentane. ### Claim 6 A method of purifying a polymer containing impurities, the method comprising: dissolving the polymer containing impurities in an organic solvent to form an organic polymer solution; simultaneously, but separately, co-introducing the organic polymer solution and an anti-solvent into an extraction vessel in concurrent flow streams while the anti-solvent is maintained in a supercritical state to extract the organic solvent and impurities from the organic solution and thereby form a plasticized polymer melt, the polymer being plasticized by the supercritical anti-solvent; and extruding the plasticized polymer melt from the extraction vessel into an accumulation vessel to separate the same from the anti-solvent containing the organic solvent and impurities. ### Claim 7 (depends on 6) The method according to claim 6 wherein the polymer is selected from the group consisting of poly(lactic-co-glycolic) acid, polylactic acid, polyethylene glycol, Eudragit polymers, PMMA polymers, ethylcellulose, and combinations thereof. ### Claim 8 (depends on 6) The method according to claim 6 wherein the organic solvent is selected from the group consisting of halogenated hydrocarbons, ketones, alcohols, and ethyl acetate. ### Claim 9 (depends on 6) The method according to claim 6 wherein the extraction fluid is selected from the group consisting of supercritical carbon dioxide, supercritical ethane, supercritical ethylene, supercritical propane, supercritical propylene and supercritical pentane. ### Claim 10 A method of purifying a polymer containing impurities, the method comprising: dissolving the polymer containing impurities in an organic solvent to form an organic polymer solution; simultaneously, but separately, co-introducing the organic polymer solution and an anti-solvent into an extraction vessel in counter-current flow streams while the anti-solvent is maintained in a supercritical state to extract the organic solvent and impurities from the organic solution and thereby form a plasticized polymer melt, the polymer being plasticized by the supercritical anti-solvent; venting the anti-solvent containing the organic solvent and impurities from the extraction vessel to allow the plasticized polymer melt to accumulate in the extraction vessel; and extruding the plasticized polymer melt from the extraction vessel. ### Claim 11 (depends on 10) The method according to claim 10 wherein the polymer is selected from the group consisting of poly(lactic-co-glycolic) acid, polylactic acid, polyethylene glycol, Eudragit polymers, PMMA polymers, ethylcellulose, and combinations thereof. ### Claim 12 (depends on 10) The method according to claim 10 wherein the organic solvent is selected from the group consisting of halogenated hydrocarbons, ketones, alcohols, and ethyl acetate. ### Claim 13 (depends on 10) The method according to claim 10 wherein the extraction fluid is selected from the group consisting of supercritical carbon dioxide, supercritical ethane, supercritical ethylene, supercritical propane, supercritical propylene and supercritical pentane. ### Claim 14 A method of purifying a polymer containing impurities, the method comprising: dissolving the polymer containing impurities in an organic solvent to form an organic polymer solution; simultaneously, but separately, introducing the organic polymer solution and an anti-solvent into an extraction vessel while the anti-solvent is maintained in a supercritical state to extract the organic solvent and impurities from the organic solution and thereby precipitate the polymer in the form of solid particles; collecting the solid particles of polymer on a filter in the extraction vessel as the anti-solvent, organic solvent and impurities are removed; and depressurizing the extraction chamber to recover the solid particles of purified polymer. ### Claim 15 (depends on 14) The method according to claim 14 wherein the polymer is selected from the group consisting of poly(lactic-co-glycolic) acid, polylactic acid, polyethylene glycol, Eudragit polymers, PMMA polymers, ethylcellulose, and combinations thereof. ### Claim 16 (depends on 14) The method according to claim 14 wherein the organic solvent is selected from the group consisting of halogenated hydrocarbons, ketones, alcohols, and ethyl acetate. ### Claim 17 (depends on 14) The method according to claim 14 wherein the extraction fluid is selected from the group consisting of supercritical carbon dioxide, supercritical ethane, supercritical ethylene, supercritical propane, supercritical propylene and supercritical pentane.