METHOD OF FORMING A MULTI-LAYER PAINT FILM

摘要

To provide a method of forming a multi-layer paint film with which a multi-layer paint film which satisfies the paint film performance, such as water resistance, impact resistance and the like, required of an automobile paint film and which has excellent paint film appearance is obtained even in the case where an aqueous first base paint is coated and a first base paint film is formed and then an aqueous second base paint is coated over the aforementioned first base coat film without carrying out preliminary drying. [Means of Resolution] A method of forming a multi-layer paint film in which an aqueous first base paint (A) i's coated over an electrodeposited cured paint film and a first base paint film is formed and then an aqueous second base paint (B) is coated over the aforementioned first base paint film without carrying out preliminary drying by heating after forming said first base paint film and a second base paint film is formed, preliminary drying by heating is carried out after said second base paint ' film forming process, a single-liquid type clear paint (C) is coated over the aforementioned second base paint film and a clear coat paint film is formed and these three paint film layers are heated and cured at the same time wherein the aforementioned first base paint (A) includes water-soluble or water-dispersible polyurethane resin (A1) of acid value of less than 15 mgKOH/g and hydroxyl group value from 10 to 100 mgKOH/g and titanium oxide (A2) of specific surface area not more than 13 m2/g, the aforementioned water- soluble or water-dispersible polyurethane resin (A1) includes from 4 to 15 mass% with respect to the resin solid fraction of the aforementioned water-soluble or water-dispersible polyurethane resin (A1) of at least one of ethylene oxide units and propylene oxide units, and the mass content ratio of the aforementioned titanium oxide (A2) is from 40 to 60 mass% with respect to the paint solid fraction of aforementioned aqueous first base paint (A).