VERFAHREN ZUR ABTRENNUNG VON TECHNISCH REINEM 2,4-DIISOCYANATOTOLUOL ODER VON, EINEN ERHOEHTEN GEHALT AN 2,4-DIISOCYANATOTOLUOL AUFWEISENDEN, ISOMERENGEMISCHEN VON, IM WESENTLICHEN AUS 2,4- UND 2,6-DIISOCYANATOTOLUOL BESTEHENDEN, ISOMERENGEMISCHEN

摘要

Technically pure 2,4-diisocyanatotoluene or an isomer mixture having an increased 2,4-diisocyanatotoluene content is obtained from an isomer mixture of 2,4- and 2,6-diisocyanatotoluene. The 2,4- and 2,6-diisocyanatotoluene mixture is first cooled to a temperature of from 4 DEG to 9 DEG C. and further cooled to between -2 DEG to -6 DEG C. at a rate of 0.5 DEG to 3 DEG C. per hour. The temperature of the mixture is maintained at that temperature for at least 30 minutes. Any liquid present is removed and the solid remaining is then melted. Melting is preferably carried out by heating the solid at a rate of 0.5 DEG to 3 DEG C. per hour until the remaining solid has a 2,4-diisocyanatotoluene content of at least 98%. The liquid melt is removed and the solid having the desired 2,4-diisocyanatotoluene content is then melted.