Water-soluble coating compositions and process for their preparation

A coating composition for cathode-precipitating electrodeposition consisting essentially of

• (1) a curable resinous film-forming component capable of being rendered water-soluble, said component consisting of an unsaturated organic compound having a molecular weight of 300 to 30,000 containing a carbon-carbon double bond in an amount corrresponding to an iodine number of 50 to 500, said unsaturated organic compound being selected from the group consisting of (a) a homopolymer of a conjugated diolefin containing 4 to 8 carbon atoms, (b) a copolymer of at least two conjugated diolefins containing 4 to 8 carbon atoms, (c) a copolymer of at least one conjugated diolefin containing 4 to 8 carbon atoms and a vinyl monomer having an ethylenic unsaturation containing 2 to 20 carbon atoms, (d) a natural oil, (e) a natural fat and (f) a petroleum resin produced by cationic polymerization of petroleum cracking fractions containing 4 to 10 carbon atoms with a Friedel-Crafts catalyst, said unsaturated organic compound having bonded thereto, through a carbon-carbon bond, organic basic groups of the following formula in aqueous solutions when rendered water-soluble ##STR12## wherein R.sub.1 is hydrogen, halogen or a hydrocarbon residue containing 1 to 3 carbon atoms, R.sub.2, R.sub.3 and R.sub.4 are identical or different and each represents a hydrocarbon residue containing 1 to 20 carbon atoms, R.sub.5 is hydrogen, and X represents hydrogen or a bond, the amount of said organic basic groups being 0.05 to 0.5 mole per 100 g of the film-forming component, and
• (2) an aqueous or organic liquid medium, said film-forming component being rendered water-soluble by neutralization with a water-soluble inorganic or organic acid.