PROCESS FOR THE PREPARATION OF BINDER DISPERSIONS CAPABLE OF BEING CATHODICALLY DEPOSITED USING CROSSLINKING AGENTS BASED ON POLYISOCYANATES BLOCKED BY AMINO GROUPS

摘要

AbstractProcess for the preparation of binder dispersions capableof being cathodically deposited using crosslinking agentsbased on polyisocyanates blocked by amino groupsThe invention relates to a process for the prepara-tion of aqueous dispersions to be further processed toelectrocoating paints with baking temperatures below 160°Cand baking times of ? 30 minutes, which dispersions containmodified epoxide-amine adducts as binders and polyiso-cyanates blocked by amino groups as crosslinking agents.In this process, polyepoxides and compounds whichcontain one or more, preferably 2, hydroxyl groups permolecule are converted at higher temperatures and in thepresence of catalysts to epoxide-containing intermediates.A solvent or a mixture of solvents is then addedwith external cooling and the solution is then caused toboil under reflux, if necessary by application of a vacuum,until the temperature of the solution drops to 95°C to20°C.Amines are then added onto the epoxide groups whichare still present in a free state in the epoxide resin andeither a dispersion is prepared after the addition of thecrosslinking agent by adding a water-acid mixture or theproducts are first dispersed and the crosslinking agent isadded subsequently.