# US 5,703,193 A · Removal of unreacted diisocyanate monomer from polyurethane prepolymers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,703,193 A - Document ID: US5703193A - Status: Granted - Kind: A - Application number: 08/657,135 - Filed: 1996-06-03 - Granted: 1997-12-30 - Earliest claimed: 1996-06-03 - Assignees: Uniroyal Chemical Company, Inc. - Inventors: Ronald Owen Rosenberg; Ajaib Singh; Christopher James Maupin; Brian Scott Lombardo - Web page: https://patentgrep.com/patent/US5703193A ## CPC - C08G 18/10: Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step - C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS ## Abstract A process for reducing the amount of residual organic diisocyanate monomer in a polyurethane prepolymer reaction product mixture which comprises distilling the polyurethane prepolymer reaction product mixture in the presence of a combination of at least one inert first solvent with a boiling point below the boiling point of the residual organic diisocyanate monomer and at least one inert second solvent with a boiling point above the boiling point of the residual organic diisocyanate monomer, at a temperature which exceeds the vaporization temperature of the residual organic diisocyanate monomer and which is below the decomposition temperature of the polyurethane prepolymer. ## Claims ### Claim 1 A process for reducing the amount of residual organic diisocyanate monomer in a polyurethane prepolymer reaction product mixture which comprises heating the polyurethane prepolymer reaction product mixture in the presence of a combination of at least one inert first solvent with a boiling point below the boiling point of the residual organic diisocyanate monomer selected from the group consisting of dimethyl glutarate, dimethyl adipate, diethyl adipate, diisopropyl adipate, ortho-, meta-, or para-dichlorobenzene. 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, .gamma.-butyrolactone, and dimethyl succinate, and at least one inert second solvent with a boiling point above the boiling point of the residual organic diisocyanate monomer selected from the group consisting of dimethylphthalate, diethylphthalate, and an isomer of dibutyladipate, at a temperature which exceeds the vaporization temperature of the residual organic diisocyanate monomer and which is below the decomposition temperature of the polyurethane prepolymer, wherein the combination of the first solvent and the second solvent comprises about 5 to about 85 percent by weight of the total weight of the polyurethane prepolymer reaction product mixture plus the solvents, and wherein the ratio of the first solvent to the second solvent is from about 20:1 to about 1:20. ### Claim 2 (depends on 1) A process as recited in claim 1 wherein the melting point of the residual organic diisocyanate monomer is greater than 50.degree. C. ### Claim 3 (depends on 2) A process as recited in claim 2 wherein the boiling point of the second solvent is between about 1.degree. C. and about 50.degree. C. above the boiling point of the residual organic diisocyanate monomer. ### Claim 4 (depends on 2) A process as recited in claim 2 wherein the residual organic diisocyanate monomer is para-phenylene diisocyanate. ### Claim 5 (depends on 1) A process as recited in claim 1 wherein the residual organic diisocyanate monomer is reduced below about 0.5% by weight of the polyurethane prepolymer reaction product mixture. ### Claim 6 (depends on 5) A process as recited in claim 5 wherein the residual organic diisocyanate monomer is reduced below about 0.1% by weight of the polyurethane prepolymer reaction product mixture. ### Claim 7 (depends on 6) A process as recited in claim 6 wherein the residual organic diisocyanate monomer is reduced below about 0.05% by weight of the polyurethane prepolymer reaction product mixture. ### Claim 8 (depends on 1) A process as recited in claim 1 wherein the combination of first solvent and second solvent comprises about 10 to about 70 percent by weight based on the total weight of the polyurethane prepolymer reaction product mixture plus the solvents. ### Claim 9 (depends on 1) A process as recited in claim 1 wherein the ratio of the first solvent to the second solvent is from about 5:1 to about 1:5. ### Claim 10 (depends on 9) A process as recited in claim 9 wherein the ratio of the first solvent to the second solvent is about 2:1. ### Claim 11 (depends on 1) A prepolymer prepared in accordance with the process recited in claim 1. ### Claim 12 (depends on 11) A prepolymer as recited in claim 11 wherein the organic diisocyanate monomer is a PPDI monomer. ### Claim 13 A prepolymer prepared by reacting a polyol with a stoichiometric excess of para-phenylene diisocyanate (PPDI) monomer and subsequently removing unreacted PPDI monomer, which prepolymer comprises less than 0.5% by weight of unreacted PPDI monomer. ### Claim 14 (depends on 13) A prepolymer as recited in claim 13 which comprises less than 0.1% by weight of unreacted PPDI monomer. ### Claim 15 (depends on 14) A prepolymer as recited in claim 14 which comprises less than 0.05% by weight of unreacted PPDI monomer.