Recovery of solvents employed in the production of isocyanates from esters of carbamic acids

Claim 1

IN A METHOD FOR THE PRODUCTION OF ISOCYNATES FROM ESTERS OF CARBAMIC ACIDS BY THERMALLY DECOMPOSING SAID ESTER WHILE SAID ESTER IS DISSOLVED IN AN REACTION MEDIUM SOLVENT TO PRODUCE THE ISOCYANATE AND CORRESPONDING ALCOHOL, REMOVING THE ISOCYANATE AND ALCOHOL AS OVERHEAD IN THE VAPOR PHASE WITH A CARRIER AGENT AND SEPARATELY RECOVERING THE ISOCYANATE AND ALCOHOL AND CARRIER AGENT, LEAVING INERT REACTION MEDIUM SOLVENT CONTAINING ISOCYANATE AND URETHANE VALUES DISSOLVED THEREIN AND BY-PRODUCT RESIDUE AS BOTTOMS, THE IMPROVEMENT WHICH COMPRISES RECOVERING SAID INERT REACTION MEDIUM SOLVENT SAID SOLVENT BEING A HIGHER MOLECULAR WEIGHT COMPOUND OR MIXTURE OF COMPOUNDS SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC, CYCLOALIPHATIC OR AROMATIC HYDRICARBONS, SUBSTITUTED HYDROCARBONS, OXYGENATED COMPOUNDS SELECTED FROM THE GROUP CONSISTING OF ETHERS, KETONES AND ESTERS AND THE SULFUR ANALOGUES OF SAID OXYGENATED COMPOUNDS, TOGETHER WITH ISOCYNATE AND URETHANE VALUES CONTAINED THEREIN BY STRIPPING SAID INERT SOLVENT AND THE ISOCYANATE/ URETHANE VALUES FROM THE THERMAL REACTOR BOTTOMS AND THE BYPRODUCT RESIDUE PRESENT IN SAID REACTOR BOTTOMS AT TEMPERATURE IN THE RANGE OF 175*C. TO 350*C. WITH AN INERT STRIPPING AGENT SELECTED FROM INERT SOLVENTS, WHICH ARE LOWER BOILING INERT COMPOUNDS OR MIXTURE OF COMPOUNDS SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC OR AROMATIC HYDROCARBONS, SUBSTITUTED AROMATIC HYDROCARBONS, CYCLOALLIPHATIC HYDROCARBONS, OXYGENATED COMPOUNDS SELECTED FROM THE GROUP CONSISTING OF ETHERS AND KETONES AND THE SULFUR ANALOGUES OF SAID OXYGENATED COMPOUNDS, INERT GASES SELECTED FROM THE GROUP CONSISTING OF NITROGEN, HELIUM, ARGON CARBON DIOXIDE, METHANE, ETHANE AND PROPANE AND MIXTURES OF SOLVENTS AND GASES.