Process for the preparation of binder dispersions capable of being cathodically deposited using crosslinking agents based on polyisocyanates blocked by amino groups

摘要

The invention relates to a process for the preparation of aqueous dispersions to be further processed to electrocoating paints with baking temperatures below 160° C. and baking times of <=30 minutes, which dispersions contain modified epoxide-amine adducts as binders and polyisocyanates blocked by amino groups as crosslinking agents. In this process, polyepoxides and compounds which contain one or more, preferably 2, hydroxyl groups per molecule are converted at higher temperatures and in the presence of catalysts to epoxide-containing intermediates. A solvent or a mixture of solvents is then added with external cooling and the solution is then caused to boil under reflux, if necessary by application of a vacuum, until the temperature of the solution drops to 95° C. to 20° C. Amines are then added onto the epoxide groups which are still present in a free state in the epoxide resin and either a dispersion is prepared after the addition of the crosslinking agent by adding a water-acid mixture or the products are first dispersed and the crosslinking agent is added subsequently.