Method for Refinishing A Vehicle Using a Multi-Layer Coating System Including a Hydroxyl Modified Polyurethane Dispersion Binder

Abstract

A method for refinishing a vehicle using a multi-layer coating system is provided. The multi-layer coating system comprises a hydroxyl-functional polyurethane dispersion. The hydroxyl-functional polyurethane comprises the reaction product of a pre-polymer intermediate formed from the reaction of an isocyanate with an active hydrogen containing compound, such as a polyester polyol, with a compound having at least two amine groups and one hydroxyl group, such as a diamino alcohol.

1 . A method for refinishing a vehicle comprising:
 (1) applying a primer coat to the vehicle surface;   (2) applying a basecoat over the primer coat, wherein the basecoat comprises a polyurethane dispersion and at least one pigment, wherein the polyurethane dispersion comprises the reaction product of:
 (a) a hydroxyl-functional polyurethane resin comprising the reaction product of
 (i) an isocyanate pre-polymer intermediate, which comprises the reaction product of an isocyanate and a compound comprising at least one active hydrogen and 
 (ii) a chain extender compound comprising at least two primary amine groups and one hydroxyl group; 
 
  wherein the hydroxyl-functional polyurethane resin is substantially free of terminal hydroxyl groups; and 
 (b) water; and 
   (3) applying a clear coat over the applied basecoat.   
     
     
         2 . The multi-layer automotive coating system of  claim 1 , wherein the compound comprising at least one active hydrogen is a polyhydroxy compound. 
     
     
         3 . The multi-layer automotive coating system of  claim 1  wherein the polyhydroxy compound is selected from polyhydroxylated polyethers, polyhydroxylated polyesters, polyhydroxylated polyesteramides, polyhydroxylated polycarbonates, polyhydroxylated hydrocarbons and polyhydroxylated acrylics. 
     
     
         4 . The multi-layer automotive coating system of  claim 1  wherein the chain extender compound is selected from 1,3-diamino-2-propanol and aminoethylethanolamine. 
     
     
         5 . The multi-layer automotive coating system of  claim 1 , wherein the hydroxyl-functional polyurethane resin has a hydroxyl value of about 0.62 to about 62.3. 
     
     
         6 . The multi-layer automotive coating system of  claim 1  wherein the hydroxyl-functional polyurethane resin has a hydroxyl value of about 10 to about 20. 
     
     
         7 . The multi-layer automotive coating system of  claim 1  wherein the hydroxyl-functional polyurethane resin has an Mn of about 20,000 as measured by gel permeation chromoatography based on a polystyrene standard. 
     
     
         8 . The multi-layer automotive coating system of  claim 1  wherein the hydroxyl-functional polyurethane dispersion has a viscosity that is less than about 5000 cPs. 
     
     
         9 . The multi-layer automotive coating system of  claim 1  wherein the hydroxyl-functional polyurethane dispersion has a viscosity that is less than or equal to about 500 cP. 
     
     
         10 . The multi-layer automotive coating system of  claim 1  wherein the hydroxyl-functional polyurethane dispersion has a solids content of about 33% to about 35%.