COMPOSITION FOR COLOURING BY CATIONIC ELECTRODEPOSITION, SUITABLE FOR COLOURING EVEN PARTS OF NARROW GAPS AND ELECTRODEPOSITED COATING FILM USING SAME

摘要

FIELD: chemistry.SUBSTANCE: invention relates to a composition for colouring by cationic electrodeposition. The composition contains an amine-modified cationic epoxy resin (A), a blocked isocyanate curing agent (B), a hydrophobic agent (C) which is a non-crosslinked acrylic resin, a viscosity modifier (D) which is particles of a crosslinked resin with mean particle diameter of 50-200 nm, and a neutralising acid in an aqueous medium, wherein the weight ratio (A)/(B) ranges from 60/40 to 80/20, the solubility parameter (SP) of the hydrophobic agent (C) is 10.2 or greater and less than 10.6, and 0.6-1.0 less than the SP of the cationic epoxy resin (A), content of the hydrophobic agent (C) is equal to 0.2-5 wt % with respect to the total amount of the cationic epoxy resin (A) and the blocked polyisocyanate curing agent (B). Content of the viscosity modifier (D) is equal to 3-10 wt % with respect to the total amount of the cationic epoxy resin (A), the blocked polyisocyanate curing agent (B) and the hydrophobic agent (C). The Coulombic efficiency of the composition for colouring by electrodeposition is equal to 2.0-2.5 mg/(mcm·C). Also disclosed is a method of producing an electrodeposited coating film of said composition, where the rate of raising voltage when colouring is equal to 30-70 V/10 s.EFFECT: invention provides high quality of the deposited coating film, as well as rust resistance, even on parts of gaps of the coloured articles.8 cl, 6 tbl, 18 ex