ALIPHATIC DIAMINE ISOMERIZATION METHOD, DIISOCYANATE PRODUCTION METHOD, POLYURETHANE PRODUCTION METHOD, AND POLYURETHANE

The present invention relates to a method for isomerizing an aliphatic diamine, the method including isomerizing an aliphatic diamine represented by Formula (1) below in the presence of: an imine compound obtained by dehydration condensation of an aliphatic diamine represented by Formula (1) below and an aldehyde and/or a ketone; and at least one selected from the group consisting of an alkali metal and the like, wherein a ratio of a total amount of the alkali metal and the like used to a total amount of the aliphatic diamine used is 0.5 mol% or greater and 6.0 mol% or less,wherein R represents a single bond or an unsubstituted aliphatic or alicyclic alkylene group having 1 to 8 carbon atoms, and n represents an integer from 0 to 5.