Water-borne thermoplastic polyhydroxyether compositions

Method of protecting metallic substrates which comprises depositing a colloidal dispersion of a thermoplastic polyhydroxyether on said substrates followed by baking at elevated temperatures until a clear, continuous, tough film adheres to said substrates, said colloidal dispersion being prepared by:

• (1) grafting onto normally solid thermoplastic polyhydroxyether one or more ethylenically unsaturated hydrocarbon monomers having 3 to about 8 carbons at least one of said monomers containing sufficient carboxyl, --COOH, groups to provide from about 1 carboxyl group per 10 monomeric units of thermoplastic polyhydroxyether to about 10 carboxy groups per each monomeric unit of polyhydroxyether;
• and
• (2) blending said grafted thermoplastic polyhydroxyether in a high turbulence field with:
• (a) water,
• (b) a water-miscible base, and
• (c) a water-miscible organic solvent in which said thermoplastic polyhydroxyether is soluble until an ionomer of the grafted thermoplastic polyhydroxyether is obtained as colloidal dispersion, said thermoplastic polyhydroxyether having the general formula:
• --D-O-E-O--.sub.n
• wherein D is the radical residuum of a dihydric phenol, E is an hydroxyl containing radical residuum of an epoxide and n represents the degree of polymerization and is at least 30.