Process for the multilayer coating of substrates with electrodeposition and powder coating materials

Abstract

The present invention relates to a process for the multilayer coating of substrates with electrodeposition and powder coating materials, in which electrodeposition is used to apply at least one coat ( 2 ) of electrodeposition coating material to the substrate ( 1 ), after deposition the substrate ( 1 ) is, if desired, wholly or partially air-dried, a coat of powder coating material ( 3 ) is then applied, and finally electrodeposition coating material and powder coating material are jointly baked.

1 . A process for the multilayer coating of substrates with electrodeposition and powder coating materials, in which 
 a) to a substrate ( 1 ) made preferably of metal, especially iron or zinc, at least one coat ( 2 ) of a liquid coating material, preferably an electrodeposition coating material, is applied,    b) after deposition the substrate ( 1 ) is, if desired, wholly or partially dried,    c) at least one coat of powder coating material ( 3 ) is applied, and    d) electrodeposition coating material and powder coating material are jointly baked,    wherein drying takes place at temperatures of ≦100° C., preferably ≦40° C.    
     
     
         2 . The process as claimed in    claim 1   , wherein the predrying of the electrodeposition coat takes place by blowing with air and/or at elevated temperatures, preferably up to 40° C.  
     
     
         3 . The process as claimed in    claim 2   , wherein predrying is carried out until the content of solvents has fallen such that the loss of substance when baking the electrodeposition coat, by gaseous expulsion of solvents and volatile elimination products, is less than 20%, preferably 13%.  
     
     
         4 . The process as claimed in one of    claims 1    to    3   , wherein drying lasts ≦60 minutes, preferably ≦30 minutes.  
     
     
         5 . The process as claimed in one of    claims 1    to    4   , wherein the joint baking of electrodeposition coating material and powder coating material takes place at temperatures from 150 to 220° C., preferably from 160 to 200° C.  
     
     
         6 . The process as claimed in    claim 5   , wherein the joint baking takes place for a duration of from 10 to 40 minutes, preferably from 15 to 30 minutes.  
     
     
         7 . The process as claimed in one of    claims 1    to    6   , wherein the application of the powder coating material takes place by electrostatic adhesion, preferably by high voltage or frictional charging.  
     
     
         8 . The process as claimed in one of    claims 1    to    7   , wherein the electrodeposition coating material employed in step a) crosslinks at less than 170° C., preferably from 140° C. to 160° C.  
     
     
         9 . The process as claimed in one of    claims 1    to    8   , wherein a powder coating material is employed whose crosslinking temperature lies from 10 to 60° C., preferably from 10 to 40° C. above the crosslinking temperature of the electrodeposition coating material.  
     
     
         10 . The process as claimed in one of    claims 1    to    9   , wherein a powder coating material is employed which comprises degassing agent(s) in a concentration of up to 2% by weight, with very particular preference 0.4% by weight.  
     
     
         11 . The process as claimed in one of    claims 1    to    10   , wherein the powder coating material comprises as degassing agents compounds of the formula  
                 
 
       in which R is an alkanol having 1-6 carbon atoms and R 1  and R 2  are benzoyl- or phenyl groups, and where R 1  and R 2  can be identical or different.  
     
     
         12 . A layered material comprising at least two coats on a substrate, which is prepared in a process as claimed in one of    claims 1    to    10   .  
     
     
         13 . The layered material as claimed in    claim 12   , wherein the thickness of the electrodeposition coat is from 5 to 35 μm, preferably from 10 to 25 μm.  
     
     
         14 . The layered material as claimed in one of claims  12  and  13 , wherein the thickness of the powder coat is from 30 to 200 μm, preferably from 50 to 120 μm.  
     
     
         15 . The use of the layered material as claimed in one of    claims 10    to    14    to produce radiators, car bodies and automotive accessories, machine components, compressors, shelving units, office furniture and comparable industrial products.