Process for reducing the hydrolyzable chlorine content of organic isocyanates

Claim 1

IN THE PROCESS FOR PURIFYING A CRUDE ORGANIC ISOCYANATE BY PASSING AN INERT GAS THROUGH SAID ISOCYANATE TO REMOVE HYDROGEN CHLORIDE AND PHOSGENE CONTAINED THEREIN, DISTILLING, IN A FIRST DISTILLATION STEP, THE RESULTING DEGASSED MATERIAL TO REMOVE SOLVENT CONTAINED THEREIN, AND DISTILLING, IN A SECOND DISTILLATION STEP, THE RESIDUE OF THE FIRST DISTILLATION STEP TO REMOVE THE ORGANIC ISOCYANATE FROM RESIDUAL IMPURITIES, THE IMPROVEMENT WHICH COMPRISES HEATING THE RESIDUE OF THE FIRST DISTILLATION STEP TO A TEMPERATURE IN THE RANGE BETWEEN ABOUT 150* AND ABOUT 300*C. PRIOR TO SAID SECOND DISTILLATION STEP, WHEREBY THE CONCENTRATION OF THE HYDROLYZABLE CHLORIDE IS SUBSTANTIALLY REDUCED.