Process for preparing heat-curable, water-dilutable coating compositions and their use as coatings

In a process for preparing heat-curable, water-dilutable coating compositions based on

• (A) 1-90% by weight of at least one epoxy resin which is solid at ambient temperature and free from amino groups,
• (B) 10-90% by weight of at least one synthetic resin having functional groups, which is in the form of a solution or dispersion with a solids content of 10 to 70% by weight,
• (C) 0.05-40% by weight of at least one organic cross-linking agent which is solid or liquid at ambient temperature and
• (D) 0-75% by weight of at least one component selected from the group consisting of pigments and conventional adjuvants,
• in which the sum of components (A) to (D) is always 100% by weight and the percentages are referred to the substances free from solvents and water, and the components (A) to (D) are conjointly processed together in at least one stage while reducing the original particle size so far to form a homogeneous coating composition having a particle size of less than 100 .mu.m and wherein there is, or is not, subsequently water added to adjust the solids content to that required for application, the improvement which consists in using as component (B) an aqueous dispersion or solution of saturated polyester resins having carboxyl groups and consisting of carbon, hydrogen and oxygen, or of modification products obtained therefrom by ester oils, the said polyester resin being at least partially neutralized with amines and having an acid number in the range from 30 to 120 and an OH number of 10 to 150 and the sum of acid number and hydroxy number being at least as high that the polyester resin which is at least partially neutralized forms a stable aqueous dispersion or solution.