Surface-coating binders containing blocked isocyanate groups, and their use in cathodic electrocoating

A surface-coating binder based on a copolymer which contains tertiary amino groups, blocked isocyanate groups, hydroxyl groups and ether groups and which, due to partial or complete salification with an acid, is water-soluble or water-dispersible, and wherein the copolymer contains, as copolymerized units,

• (A) from 6 to 22% by weight of one or more olefinically unsaturated compounds containing a tertiary amino group,
• (B) from 10 to 35% by weight of vinyl isocyanate or propenyl isocyanate blocked with a CH--, OH-- or NH-acidic blocking agent,
• (C) from 20 to 50% by weight of an adduct of an epoxy resin, based on bisphenol A and epichlorohydrin and having a molecular weight of from 380 to 3,500, with an olefinically unsaturated alcohol of 3 to 20 carbon atoms,
• (D) from 10 to 64% by weight of one or more copolymerizable olefinically unsaturated compounds not already mentioned under (A) to (C), with the proviso that the copolymer has a mean molecular weight of from 1,000 to 20,000 and that the sum of the percentages of (A) to (D) is 100.