MANUFACTURE OF POLYISOCYANATE HAVING BULLET GROUP AND*OR POLYURET GROUP*COMPOUND OBTAINED BY SAID MANUFACTURE AND ITS USE AS SYNTHETIC COMPONENT IN POLYURETHANE PLASTIC MANUFACTURE

摘要

A process for the preparation of polyisocyanates containing biuret and/or higher polyuret groups by reacting secondary diamines with diisocyanates characterized in that the reaction is carried out in the presence of catalytic quantities of strong acids which form mixed carbamic acid anhydrides with isocyanates. Alternatively, the secondary diamines may be reacted with organic diisocyanates in the absence of catalysts to form a urea diisocyanate which is then reacted in the presence of catalytic quantities of strong acids which form mixed carbamic acid anhydrides either with the same diisocyanate used in the first step or a second diisocyanate. The invention also relates to the polyisocyanates containing biuret and/or higher polyuret groups obtainable by this process.