Preparation of biuret polyisocyanates

摘要

Biuret polyisocyanates are prepared by reacting an organic di- or polyisocyanate with an organic primary monoamine in such proportions that the ratio -NCO to -NH2 is at least 3 and heating the reaction mixture to an elevated temperature while continuously removing the organic monoisocyanate resulting from said reaction as rapidly as it is formed. The reaction may be completed in one step or with the formation and isolation of intermediate products.ALSO:Biuret polyisocyanates are prepared by reacting an organic di- or polyisocyanate with an organic primary monoamine in such proportions that the ratio -NCO to -NH2 is at least 3 and heating the reaction mixture to an elevated temperature while continuously removing the organic monoisocyanate resulting from said reaction as rapidly as it is formed. The solution of the final product in excess polyisocyanate starting material may be reacted with a polyalkylene glycol (prepared, e.g. from trimethylolpropane and propylene oxide) and the product blown with water to give a semi-rigid foam. The biuret polyisocyanates may also be reacted with polyesters (prepared, e.g. from phthalic acid and trimethylolpropane) and the product used to form coatings.