Substrate having a multilayer coat and method for its production

Abstract

The invention relates to a process, in which a body to be coated passes via the entry 1 into the pretreatment stage 2. This is followed by electrodeposition coating 3 and the baking 4 of the electrodeposition coat. In stage 5 preparation takes place for coating with powder coating material (stage 6 ). In stage 7 drying is carried out with IR irradiation. This is followed by the cooling stage 7. The powder coating material is applied to the powder coat in stage 9. Following passage through the intermediate drying stage 10 a protective coat is applied in stage 11 and then is baked in stage 12. The body is transported out of the unit via the exit 13.

1 . A process for preparing a substrate provided with a multilayer coating, wherein the substrate is selected from the group consisting of a motor vehicle bodywork panel and a motor vehicle plastics moulding, comprising the following process steps: 
 a) applying a surfacer layer comprising a crosslinkable powder coating material to the substrate, wherein the surfacer layer has a layer thickness in the range from 30 μm to 250 μm;    b) drying the powder coating material and precrosslinking by means of irradiation or heating from 1 minute to 10 minutes at a temperature in the range from 130° C. to 240° C.;    c) applying an aqueous decorative coating material to the dried and precrosslinked powder coating material and drying the aqueous decorative coating material, wherein the aqueous decorative coating material comprises a binder selected from the group consisting of acrylate resins, carboxyl-,epoxy-, and hydroxyl-containing binders and mixtures thereof and comprising a crosslinker selected from the group consisting of isocyanates, amino resins, tris(alkoxy carbonylamino) triazine, and mixtures thereof;    d) applying an aqueous protective coating material to the decorative coating material, wherein the aqueous protective coating is selected from the group consisting of one-component clearcoats, two-component clearcoats, and transparent powder coating materials; and    e) baking and crosslinking the assembly of the surfacer layer, the decorative coating material, and the protective coating material at a temperature in the range from 120° C. to 180° C.    
     
     
         2 . The process of  claim 1 , wherein the surfacer layer is dried and precrosslinked from 2 minutes to 6 minutes at a temperature of from 180° C. to 220° C.  
     
     
         3 . The process of  claim 1 , wherein the assembly of surfacer layer, decorative coating material, and protective coating material is baked and crosslinked at a temperature in the range from 130° C. to 150° C.  
     
     
         4 . The process of  claim 2 , wherein the assembly of surfacer layer, decorative coating material, and protective coating material is baked and crosslinked at a temperature in the range from 130° C. to 150° C.  
     
     
         5 . The process of  claim 1 , wherein the aqueous decorative coating material is virtually free from organic solvents; the aqueous protective coating is selected from the group consisting of an aqueous protective coating material that is virtually free from organic solvents and an aqueous transparent powder coating dispersion; and wherein the surfacer layer the decorative coating material, and the protective coating material are applied and baked in a coating unit that is operated with circulating air.  
     
     
         6 . The process of  claim 1 , wherein the surfacer layer is dried and precrosslinked for from 2 minutes to 6 minutes, at a temperature of from 180° C. to 220° C., by the passage of the substrate that has been provided with a powder coating material through an IR irradiation zone.  
     
     
         7 . The process of  claim 1 , wherein the decorative layer has a layer thickness in the range of 10 μm to 100 μm and in the protective layer has a layer thickness in the range from 20 μm to 150 μm.  
     
     
         8 . The process of  claim 1 , wherein the surfacer layer has a layer thickness in the range of 50 μm to 80 μm, the decorative layer has a layer thickness in the range of 15 μm to 17 μm, and the protective layer has a layer thickness in the range from 35 μm to 50 μm.  
     
     
         9 . The process of  claim 1 , wherein the surfacer layer lies directly on the substrate material.  
     
     
         10 . The process of  claim 1 , wherein the substrate is a metal panel.  
     
     
         11 . The process of  claim 1 , wherein the substrate is a plastics moulding.  
     
     
         12 . The process of  claim 1 , wherein the surfacer layer has a layer thickness in the range from 60 μm to 70 μm, the decorative layer has a layer thickness in the range from 15 μm to 16 μm, and the protective layer has a layer thickness in the range from 40 μm 45 μm.  
     
     
         13 . The process of  claim 1 , wherein the substrate is a motor vehicle bodywork panel.  
     
     
         14 . The process of  claim 1 , wherein the substrate is a motor vehicle plastics moulding based on sheet molded compound.