METHOD FOR PRODUCING A MULTI-LAYER COATING

Claims

1. A process for producing a multilayer coating (M) on a metallic vehicle body (K) comprising body seams (Kn) comprising (1) producing a cured electrocoat layer (E.1) on the metallic substrate (S) by electrophoretic application of an electrocoat (e.1) to the substrate (S) and subsequent curing of the electrocoat (e.1), (2) producing a gelled PVC seal (P.2) in a region of the body seams (Kn) by application of a PVC sealing paste (p.2) to the cured electrocoat layer (E.1) in the region of the body seams (Kn) and subsequent thermally initiated gelling of the paste (p.2), (3) producing a basecoat layer (B.3.1) or (3.2) of two or more directly successive basecoat layers (B.3.2.x) directly on the surface obtained by step (2) by (3.1) application of an aqueous basecoat (b.3.1) directly to the surface or (3.2) directly successive application of two or more basecoats (b.3.2.x) to the surface, (4) producing a clearcoat layer (K) directly on (4.1) the basecoat layer (B.3.1) or (4.2) the uppermost basecoat layer (B.3.2.x) by application of a clearcoat (k) directly to (4.1) the basecoat layer (B.3.1) or (4.2) the uppermost basecoat layer (B.4.2.x), (5) jointly curing the (5.1) basecoat layer (B.3.1) and the clearcoat layer (K) or (5.2) the basecoat layers (B.3.2.x) and the clearcoat layer (K), wherein the basecoat (b.3.1) or the basecoats (b.3.2.x) are aqueous and contain at least one pigment and the basecoat (b.3.1) or at least one of the basecoats (b.3.2.x) - contains at least one aqueous dispersion of a polyurethane (PUR) as binder and has - a pigment to binder (P / B) ratio of more than 0.75 and - a solids content of at least 35%.

2. The process according to claim 1, wherein the solids content of the basecoat (b.3.1) or at least one of the basecoats (b.3.2.x) is a solids content of 35% to 62.5%.

3. The process according to claim 1 or 2, wherein the PVC sealing paste (p.2) used in step (2) has a gelation temperature of at least 145°C and the thermally initiated gelation is performed at a temperature of at least 145°C.

4. The process according to claims 1 to 3, wherein the process is performed in a plant configured for a standard process (5A process) and the gelation of the PVC paste is performed in the region for filler curing present in this plant.

5. The process according to claims 1 to 4, wherein step (3) comprises producing a basecoat layer (B.3.1) directly on the surface obtained by step (2) by (3.1) application of an aqueous basecoat (b.3.1) directly onto the surface.

6. The process according to claim 5, wherein the total layer thickness (dry layer thickness) of electrocoat layer (E.1), basecoat layer (B.3.1) and clearcoat layer (K) is from 70 to 110 micrometers.

7. The process according to claim 6, wherein the ratio of the layer thickness of the basecoat layer (B.3.1) to the total layer thickness of the aforementioned complete structure is from 0.25 to 0.5.

8. The process according to claims 5 to 7, wherein the basecoat (b.3.1) is a white basecoat and contains a white pigment.

9. The process according to claims 1 to 8, wherein at least one aqueous dispersion of a polyurethane (PUR) as binder is an aqueous polyurethane-polyurea dispersion (PD) comprising polyurethane-polyurea particles, wherein the polyurethane-polyurea particles present in this dispersion (PD) comprise anionic groups and / or groups which can be converted into anionic groups and have an average particle size of 40 to 2000 nm and a gel fraction of at least 50%.

10. The process according to claims 1 to 8, wherein at least one aqueous dispersion of a polyurethane (PUR) as binder is an aqueous secondary dispersion of an anionically or nonionically, preferably nonionically, stabilized polyurethane.

11. The process according to claim 3, wherein the PVC sealing paste (p.2) employed in step (2) has a gelation temperature of at least 155°C and the thermally initiated gelation is performed at a temperature of at least 155°C.

12. The process according to any of claims 1 to 11, wherein all curing steps of coating compositions which are performed after step (2) of the process are performed at temperatures of less than 150°C, preferably less than 145°C.

13. A multilayer coating (M) produced by a process according to claims 1 to 12.

14. The multilayer coating according to claim 13, wherein it has a transmittance in the wavelength range of 400 to 450 nm and at a basecoat layer thickness of 25 micrometers of less than 1%.

15. A vehicle body (K) comprising body seams (Kn) on which a multilayer coating according to claim 13 or 14 is arranged.