Polyharnstoffe aus Diiesocyanaten und Verfahren zu deren Herstellung

摘要

A method for increasing the yield of diisocyanate and decreasing non-volatile by-products produced at elevated temperature when reacting phosgene and a hydrochloride of an ester of formula wherein R is H or C1- 21 alkyl, x is 0 or 1 and 2 to 10, comprises heating the reactants at such elevated temperature that the corresponding dicarbamoyl chloride derivative of at least 90% by weight of the esters is produced before 20% by weight of said derivative has been converted to its diisocyanate and then at higher temperature heating the dicarbamoyl chloride derivative to convert it into its corresponding diisocyanate. The preferred temperature for the first stage is no greater than 65 DEG C. and the second stage at least 75 DEG C. In examples the preparation of L-lysine diisocyanate octyl, octadecyl and decyl esters and L-ornithine diisocyanate octyl ester is described. The preparation of the diisocyanate esters by prior art processes is also described.