Method for producing a multicoat paint system on plastics substrates

A method for producing a paint system on a plastics substrate, the method comprising:

• (1) producing a basecoat film or a plurality of directly successive basecoat films on the plastics substrate by applying an aqueous basecoat material to the substrate or directly successively applying a plurality of basecoat materials to the substrate;
• (2) producing a clearcoat film directly on the basecoat film or a topmost basecoat film by applying a clearcoat material directly to the basecoat film or the topmost basecoat film;
• and
• (3) jointly curing the basecoat film and the clearcoat film or the basecoat films and the clearcoat film,
• wherein:
• the aqueous basecoat material or at least one of the basecoat materials comprises at least one aqueous polyurethane-polyurea dispersion comprising polyurethane-polyurea particles;
• the polyurethane-polyurea particles in the dispersion comprise anionic groups, groups which can be converted into anionic groups, or both;
• the polyurethane-polyurea particles comprise, in each case in reacted form:
• at least one polyurethane prepolymer containing isocyanate groups and comprising the anionic groups, the groups which can be converted into anionic groups, or both;
• and
• at least one polyamine comprising two primary amino groups and one or two secondary amino groups;
• the polyurethane prepolymer does not contain subunits formed from a monoalcohol;
• the polyurethane-polyurea particles present in the dispersion have an average particle size of 40 to 2000 nm;
• and
• a gel fraction of the polyurethane-polyurea particles present in the dispersion is at least 50%.