Aqueous anticorrosion primers based on polyvinylbutyral

摘要

Water-dilutable polyvinylbutyral dispersions obtainable by a two-stage reaction in the first stage of which at least one tertiary alkanolamine A and at least one diisocyanate B are reacted to the theoretically calculated NCO content and the amounts of components A and B are chosen such that the amount of substance of the diisocyanates B is from 0.8 to 1.3 times the amount of substance of the reactive hydroxyl groups in A and thereafter in the second stage a polyvinylbutyral C dissolved in a solvent which is inert towards isocyanates is reacted with the adduct AB from the first step to form the product ABC until all of the isocyanate groups have undergone complete reaction, the number of hydroxyl groups in C being at least ten times the number of isocyanate groups in the reaction product AB.