Conversion of mixtures of 2, 4-and 2, 6-toluene diisocyanates to other mixtures of different isomer ratio

Claim 1

A PROCESS FOR THE CONVERSION OF MIXTURES OF 2, 4AND 2, 6-TOLUENE DIISOCYANATES CONTAINING ABOUT 70-90% BY WEIGHT OF 2, 4-TOLUENE DIISOCYANATE, THE BALANCE BEING SUBSTANTIALLY 2, 6-TOLUENE DIISOCYANATE, TO A MIXTURE OF 65$3% BY WEIGHT OF 2, 4-TOLUNE DIISOCYANATE AND 35$3% BY WEIGHT OF 2, 6-TOLUNE DIISOCYANATE AND SUBSTANTIALLY PURE 2, 4-TOLUNE DIISOCYANATE CONTAINING LESS THAN ABOUT 2.5% BY WEIGHT OF THE 2, 6-ISOMER, WHICH COMPRISES (A) COOLING THE MIXTURE OF 2, 4- AND 2, 6-TOLUENE DIISOCYANATES CONTAINING 70-90% BY WEIGHT OF 2, 4TOLUENE DIISOCYANATE UNDER SUBSTANTIALLY STATIC CONDITIONS TO INDUCE CRYSTALLIZATION OF 2, 4-TOLUENE DIISOCYANATE, (B) CONTINUING COOLING UNDER SUBSTANTIALLY STATIC CONDITIONS TO DISSIPATE THE HEAT OF CRYSTALLIZATION OF THE 2, 4-ISOMER AND BRINGING THE TEMPERATURE OF THE MIXTURE TO ABOUT 5-8*C. UNDER SUBSTANTIALLY STATIC CONDITIONS TO FORM A MIXTURE OF MOTHER LIQUOR AND A COHERENT DEPOSIT OF CRYSTALS, (C) AT THIS TEMPERATURE SEPARATING MOTHER LIQUOR FROM THE COHERENT CRYSTALLINE MASS, (D) HEATING THE MIXTURE OF CRYSTALS AND ADHERENT MOTHER LIQUOR TO ABOUT 0.5-3*C. ABOVE THE TEMPERATURE AT THE COMMENCEMENT OF THE SEPARATION OF MOTHER LIQUOR AND SEPARATING ADHERENT LIQUID FROM THE CRYSTALLINE MASS DURING HEATING, THE COMBINED LIQUID FRACTIONS OF (C) AND (D) HAVING THE COMPOSITION OF 65$3% BY WEIGHT OF 2, 4-TOLUENE DISSOCYANATE AND 35$3% BY WEIGHT OF 2, 6-TOLUENE DIISOCYANATE, (E) HEATING THE RESIDUAL CRYSTALS TO A TEMPERATURE ABOVE THE MELTING POINT OF THE CRYSTALS, (F) COOLING THE MOLTEN MASS UNDER SUBSTANTIALLY STATIC CONDITIONS TO INDUCE CRYSTALLIZATION OF 2, 4-TOLUENE DIISOCYANATE, (G) CONTINUING COOLING UNDER SUBSTANTIALLY STATIC CONDITIONS TO DISSIPATE THE HEAT OF CRYSTALLIZATION OF THE 2, 4-ISOMER AND BRINGING THE TEMPERATURE OF THE MIXTURE TO ABOUT 8-11* C. UNDER SUBSTANTIALLY STATIC CONDITIONS TO FORM A MIXTURE OF MOTHER LIQUOR AND A COHERENT DEPOSIT OF CRYSTALS, (H) AT THIS TEMPERATURE SEPARATING MOTHER LIQUOR FROM THE COHERENT MASS OF CRYSTALS, (I) HEATING THE MIXTURE OF CRYSTALS AND ADHERENT MOTHER LIQUOR TO A TEMPERATURE OF ABOUT 18-21.5*C. AND SEPARATING ADHERENT LIQUID FROM THE CRYSTALLINE MASS DURING HEATING AND (J) RECOVERING SUBSTANTIALLY PURE 2, 4-TOLUENE DIISOCRYANATE REMAINING AS A CRYSTALLINE MASS.