A multi-layer paint film satisfies 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. The method comprises coating an aqueous first base paint (A) over an electrodeposited cured paint film to form a first base paint film, and then coating an aqueous second base paint (B) over the first base paint film without carrying out preliminary drying by heating after forming the first base paint film to form a second base paint film, preliminary drying by heating is carried out after forming the second base paint film, coating a single-liquid type clear paint (C) over the second base paint film to form a clear coat paint film. These three paint film layers are heated and cured at the same time.

The present invention aims to provide a method for forming a multilayer coating film having good coating film smoothness. A method for forming a multilayer coating film, comprising a first aqueous coating composition application step of applying a first aqueous coating composition (A) to form an uncured first aqueous coating film; a second aqueous coating composition application step of applying a second aqueous coating composition (B) onto the uncured first aqueous coating film to form an uncured second aqueous coating film; a clear coating step of applying a clear coating composition (C) onto the uncured second aqueous coating film to form an uncured clear coating film; and a curing step of heat-curing at once these coating films to form a multilayer coating film, wherein the first aqueous coating composition (A) contains a water-dispersible polyurethane resin (a1) and a viscosity modifier (a2), and the second aqueous coating composition (B) contains water and an organic solvent as diluent components besides solid matters in a state of dilution to a coating viscosity.

The present invention relates to a method for producing a multicoat paint system by producing a basecoat or a plurality of directly successive basecoats directly on a substrate coated with a first coat, producing a clearcoat directly on the one or the topmost of the plurality of basecoats, and subsequently jointly curing the one or the plurality of basecoats and the clearcoat. At least one of the basecoat materials is admixed, directly before application, either with an aqueous dispersion (D1) comprising a polyamide (PA) having an acid number of 15 to 60 mg KOH/g or with an aqueous dispersion (D2) comprising a polyamide (PA) and an amide wax (AW).

This invention relates to a multilayer coating film sequentially comprising, on a substrate, a colored coating film, an effect coating film, and a clear coating film, wherein the multilayer coating film has a lightness L*110 within a range of 60 to 90, the lightness L*110 being based on a spectral reflectance of light illuminated at an angle of 45 degrees with respect to the coating surface and received at an angle of 110 degrees with respect to the specularly reflected light; a 60-degree specular gloss within a range of 105 to 180, a graininess HG within a range of 10 to 40; and a flip-flop value within a range of 1.0 to 1.8.

Provided is a method for forming a multilayer coating film, the method being capable of forming a high-brightness white multilayer coating film which is excellent in terms of brilliant feeling, smoothness, and weather resistance and with which white stains are suppressed. In this method for forming a multilayer coating film to form a brilliant coating film, a white multilayer coating film is formed by: sequentially applying a first coloring paint (P1), a second aqueous coloring paint (P2), a third aqueous coloring paint (P3), and a clear coat paint (P4) on a cured electrodeposition coating film formed on a steel sheet; and forming a first colored coating film, a second colored coating film, a third colored coating film, and a clear coat coating film which each have a particular composition, brightness, film thickness, and the like.

Provided is a method for forming a multilayer coating film, comprising simultaneously curing an uncured base coating film, an uncured effect coating film, and an uncured clear coating film. In this method, an effect pigment dispersion (Y) that forms the effect coating film contains water, a surface adjusting agent (A), a flake-effect pigment (B), and a rheology control agent (C), and has a solids content of 0.5 to 10 mass %.

Described herein are aqueous coating compositions including at least one dispersion of core/shell particles containing a polyurethane resin as core portion and a crosslinked acrylic resin as shell portion and at least one aqueous polyurethane-polyurea dispersion containing crosslinked polyurethane-polyurea particles. Also described herein is a method for forming a multilayer coating on a substrate using the aqueous coating compositions as basecoat compositions. Also described herein is a multicoat paint system produced by the method.

Provided is a multilayer coating film comprising a colored base coating film and an effect base coating film formed on the colored base coating film, wherein the hue angle h in the L*C*h color space diagram is within the range of 30° to 70°, and when the following formulas hold: X=[(C*45).sup.2+(C*75) .sup.2].sup.1/2, and Y=[(L*15).sup.2+(C*15).sup.2].sup.1/2+[(L*25).sup.2+(C*25).sup.2].sup.1/2, X is 80 or more and Y is 140 or more; provided that C*15, C*25, C*45, and C*75 represent the chroma of the multilayer coating film when light is illuminated at an angle of 45 degrees and received at angles of 15 degrees, 25 degrees, 45 degrees, and 75 degrees deviated from the specular reflection light in the incident light direction, and L*15 and L*25 similarly represent the lightness of the multilayer coating film.

Provided is a water-based coating composition capable of forming a multilayer coating film having an excellent finished appearance and having excellent storage stability. A water-based coating composition to be used as a water-based first colored coating (X) in a 3-coat-1-bake multilayer coating formation method which sequentially applies a water-based first colored coating (X), a water-based second colored coating (Y), and a clear coating (Z) and heats and cures the obtained three-layer multilayer coating film simultaneously, wherein the water-based coating composition contains at least one resin selected from acrylic resins (A) and polyester resins (B), a curing agent (C), and urethane resin particles (D) obtained from structural components including a polyisocyanate component (d1) containing at least one diisocyanate (d1-1) selected from xylylene diisocyanate and hydrogenated xylylene diisocyanate and a polyol component (d2).

The present invention provides a coating composition capable of forming a coating film having a good appearance and design of a coating film and having coating film properties such as scratch resistance with a good balance. Furthermore, the present invention provides a method for forming a multilayer coating film including forming a coating film using the coating composition of the present invention.