Aq. cationic coating compsn. prepn. - from amine-epoxy! adduct, partially blocked poly:isocyanate and polyamide forming films of excellent corrosion resistance

摘要

Prepn. of a cationic electrophoretic coating compsn. comprises (a) mixing or reacting (i) reaction product of an epoxy-amine adduct (I) and a partially blocked polyisocyanate (II) in wt. ratio of 95-5 (I) to 5-95 (II) and (ii) reaction prod. of a polyamide (III) and (II) in wt. ratio of 95-5 (III) to 5-95 (II) and (b) dissolving or dispersing the resluting mixt. or reaction prod. in an aq. medium by neutralisation with an acid. (III) has =1 basic amino gps. and (II) has is not 1 free NCO gp. Wt. ratio of reaction prod. (i):(ii) is 90:10 to 10:90. Coatings of excellent corrosion resistance, surface smoothness and impact resistance are formed on phosphate primed and uprimed steel sheets, Zn- and Sn plated steel sheets, Al and Cu (alloy) substrates.