Patent ID: 7497931

Claim:
A process for recovering 3-aminomethyl-3,5,5-trimethylcyclohexylamine (isophoronediamine, IPDA) having a fractionally distilled cis/tran isomer ratio of at least 73/27, which comprises the following steps: a. providing IPDA in a cis/tran isomer ratio of <73/27; and b. feeding IPDA into the middle region of a distillation column having internals and distilling the IPDA in this distillation column at a temperature of from 5 to 300° C. and a pressure of from 10 to 2000 mbar; and c. optionally further distilling the IPDA obtained by step b) in at least one further column, and thus further purifying the IPDA; where steps b) and optionally c) separate the IPDA used in step a) into at least five fractions ia) to iv): ia) an organic proportion of a fraction of impurities having lower boiling points than trans-IPDA, ib) an aqueous proportion of a fraction of impurities having lower boiling points than trans-IPDA, ii) a fraction of impurities having higher boiling points than cis-IPDA, iii) an IPDA fraction having a cis/trans isomer ratio of ≧73/27 and iv) a depleted IPDA fraction having a cis/trans isomer ratio of ≦66/34.