Diamine recovery process

An improved process for recovering unreacted diamine vapor in the form of a diamine dicarboxylic acid salt from water vapor continuously being separated from a reaction zone in which an aqueous solution of a polyamide-forming salt prepared from at least one diamine and at least one dicarboxylic acid is being heated and partially reacted to form water vapor containing a vapor of said diamine and a polyamide prepolymer, said process consisting essentially of one in which a portion of the water vapor is continuously separated from the reaction zone through a rectifying zone having an upper portion and a lower portion and in which rectifying zone the water vapor is partially condensed as reflux water containing unreacted diamine which diamine is recovered by returning the reflux water from said lower portion to the reaction zone, wherein the improvement comprises continuously adding a pre-determined amount of said dicarboxylic acid or acids to the reflux water in an upper portion of said rectifying zone to form a water-soluble polyamide-forming salt with unreacted diamine contained therein.