| 摘要 |
<p>An aqueous water-dilutable composition for use as a cathodic coating material is prepared by partially epoxidizing a liquid polydiene, all or a major proportion of which is derived from a 1,4-conjugated diene, such as butediene, aminating the epoxidized polydiene at a temperature of at least 120 DEG C. and, optionally in the presence of an organic hydroxy-group-containing catalyst, with at least polyamine reactant which contains not more than one primary amino group and/or at least one secondary amine group with the or any remaining amine group(s) being selected from secondary and tertiary amine groups and thereafter partially neutralizing the aminated polymeric material with acid to yield a water-dilutable material containing residual unsaturation. The liquid polydiene has a molecular weight such that cathodically deposited material will not run off a vertical surface; the minimum molecular weight is preferably 1500 for a liquid polybutadiene homopolymer but may be as low as 1000 for a butadiene/styrene copolymer. A metal substrate is made a cathode while immersed in a bath of the aqueous water-dilutable composition using an anode as a counter-electrode and passage of an electric current deposits a layer of the polymeric material on the substrate. The electro-deposited polymeric material is subjected to oxidative cross-linking by reaction of the said residual unsaturation with atmospheric oxygen at elevated temperature to form a coating of improved toughness and flexibility.</p> |
