Continuous method of preparing aromatic isocyanates

Claim 1

A CONTINUOUS METHOD OF PREPARING AROMATIC ISOCYANATES BY REACTING IN AN INERT ORGANIC SOLVENT PHOSGENE AND AN AMINE FROM THE GROUP CONSISTING OF AROMATIC PRIMARY MONO-, DI- AND POLYAMINES WHICH PROCESS COMPRISES: (A) CONTINUOUSLY FLOWING A STREAM OF PHOSGENE IN THE LIQUID PHASE THROUGH A TUBULAR REACTOR UNDER SUPERATMOSPHERIC PRESSURE; (B) CONTINUOUSLY INTRODUCING A STREAM OF SAID AMINE IN SOLUTION IN SAID ORGANIC SOLVENT INTO SAID STREAM OF PHOSGENE UNDER A PRESSURE AT LEAST EQUAL TO THAT IN THE TUBULAR REACTOR TO DISPERSE THE AMINE SOLUTION UPON ITS INTRODUCTION INTO THE TUBULAR REACTOR THROUGHOUT THE FLOWING STREAM OF PHOSGENE; (C) INTRODUCING SAID STREAMS IN AMOUNTS SUCH THAT THE RESULTANT MIXTURE CONTAINS AT LEAST 1 MOL OF PHOSGENE AND NOT EXCEEDING ABOUT 12 MOLS OF PHOSGENE PER MOL OF AMINE INTRODUCED INTO ADMIXTURE WITH THE PHOSGENE AND SO AS TO EFFECT FORWARD FLOW IN SAID TUBULAR REACTOR OF SAID AMINE SOLUTION, PHOSGENE AND THE REACTION PRODUCTS, THUS MINIMIZING BACK MIXING THEREOF INSAID TUBULAR REACTOR; (D) CONDUCTING THE INTRODUCTION OF SAID SOLUTION AND THE FLOW OF THE RESULTANT MIXTURE THROUGH SAID TUBULAR REACTOR SO THAT THE SAID FLOW TAKES PLACE AT A REYNOLDS NUMBER OF AT LEAST 2,100, WHILE MAINTAINING THE TEMPERATURE OF THE RESULTANT MIXTURE IN SAID TUBULAR REACTOR AT NOT EXCEEDING ABOUT90*C. TO PRODUCE AN INTERMEDIATE REACTION PRODUCT CONTAINING AROMATIC ISOCYANATE; (E) CONTINUOUSLY INTRODUCIG THE INTERMEDIATE REACTION PRODUCT PRODUCED INSAID TUBULAR REACTOR INTO A SECOND REACTION ZONE MAINTAINED AT A TEMPERATURE OF FROM 110* TO 135*C. AND MAINTAINING THE INTERMEDIATE REACTION PRODUCT THEREIN UNTIL THE REACTION HAS GONE TO SUBSTANTIAL COMPLETION TO FORM THE DESIRED ISOCYANATE REACTION PRODUCT; AND (F) CONTINUOUSLY REMOVING FROM SAID SECOND REACTION ZONE A LIQUID STREAM OF REACTION MIXTURE CONSISTING ESSENTIALLY OF THE ORGANIC SOLVENT AND THE AROMATIC ISOCYANATE REACTION PRODUCT AND A VAPOR STREAM CONSISTING ESSENTIALLY OF UNREACTED PHOSGENE, SOLVENT AND HYDROCHLORIC ACID.