Cathodic electrocoat having a carbamate functional resin

Abstract

The invention provides a polymer (a) having a polymer backbone having appended thereto at least one carbamate functional group, the polymer represented by randomly-repeating units according to the formula: R 1 represents H or CH 3 , R 2 represents H, alkyl, or cycloalkyl, L represents a divalent linking group, A represents repeat units comprising at least one repeat unit having a pendant cationic salting group, x represents 10 to 90 weight %, and y represents 90 to 10 weight %. The invention further provides a cathodic electrocoat coating composition comprising an aqueous dispersion of a polymer (a) and (b) a compound having a plurality of functional groups that are reactive with said carbamate groups, wherein the repeat units A of polymer (a) having a pendant cationic salting group are salted with an acid. Finally, the invention provides a cathodic electrodeposition method requiring 1 ) immersing a conductive substrate in a coating composition comprising, in an aqueous medium, a polymer (a) and (b) a compound having a plurality of functional groups that are reactive with said carbamate groups, 2 ) applying a voltage between an anode and the conductive substrate, and 3 ) removing the substrate from the coating composition.

I claim:  
     
         1 . A polymer composition comprising: 
 a polymer (a) having a polymer backbone having appended thereto at least one carbamate functional group, said polymer represented by randomly repeating units according to the formula:                        R 1  represents H or CH 3 ,    R 2  represents H, alkyl, or cycloalkyl,    L represents a divalent linking group,    A represents repeat units comprising at least one repeat unit having a pendent cationic salting site,    x represents 10 to 90 weight %, and    y represents 90 to 10 weight %.      
     
     
         2 . The polymer composition of  claim 1  wherein the cationic salting site comprises an amine functional group.  
     
     
         3 . The polymer composition of  claim 1  wherein A comprises repeat units having a cationic salting site which are derived from at least one ethylenically unsaturated monomer having a cationic salting site.  
     
     
         4 . The polymer composition of  claim 1 , wherein the pendant cationic salting sites of repeat units A are salted with an acid.  
     
     
         5 . The polymer composition of  claim 2  wherein the pendent cationic salting sites are a tertiary amine group.  
     
     
         6 . The polymer composition of  claim 5  wherein the tertiary amine group is dimethylaminoethyl.  
     
     
         7 . The polymer composition of  claim 1  having a number average molecular weight of from about 2000 to 100,000.  
     
     
         8 . The polymer composition of  claim 7  having a number average molecular weight of from about 10,000 to 60,000.  
     
     
         9 . The polymer composition of  claim 1  having a meq range of from 0.5 to 2.0.  
     
     
         10 . The polymer composition of  claim 9  having a meq range of from 0.8 to 1.5.  
     
     
         11 . A cathodic electrocoat coating composition comprising an aqueous dispersion of 
 (a) a polymer comprising a polymer backbone having appended thereto at least one carbamate functional group, said first component represented by randomly repeating units according to the formula:                        R 1  represents H or CH 3 ,    R 2  represents H, alkyl, or cycloalkyl,    L represents a divalent linking group,    A represents repeat units comprising at least one repeat unit having a pendent cationic salting site,    x represents 10 to 90 weight %, and    y represents 90 to 10 weight %, and      (b) a compound having a plurality of functional groups that are reactive with said carbamate groups,    wherein the repeat units A having a pendant cationic salting site are reacted with an acid.    
     
     
         12 . The cathodic electrocoat coating composition of  claim 11  wherein A further comprises repeat units derived from one or more ethylenically unsaturated monomers.  
     
     
         13 . The cathodic electrocoat coating composition of  claim 11  wherein A comprises repeat units having a pendent cationic salting site which are derived from at least one ethylenically unsaturated monomer having a pendent cationic salting site.  
     
     
         14 . The cathodic electrocoat coating composition of  claim 11  wherein the pendent cationic salting sites are salted with an acid.  
     
     
         15 . The cathodic electrocoat coating composition of  claim 14  wherein the cationic salting site is a tertiary amine.  
     
     
         16 . The anodic electrocoat coating composition of  claim 11  wherein polymer (a) has a number average molecular weight of from about 10,000 to 60,000.  
     
     
         17 . The anodic electrocoat coating composition of  claim 11  wherein polymer (a) has a meq value of from 0.5 to 2.0.  
     
     
         18 . A cathodic electrodeposition method, comprising 
 1) immersing a conductive substrate in a coating composition comprising, in an aqueous medium: 
 (a) a polymer backbone having appended thereto at least one carbamate functional group, said first component represented by randomly repeating units according to the formula:  
                     R 1  represents H or CH 3 ,    R 2  represents H, alkyl, or cycloalkyl,    L represents a divalent linking group,    A represents repeat units comprising at least one repeat unit having a pendent cationic salting site which is salted with an acid,    x represents 10 to 90 weight %, and    y represents 90 to 10 weight %, and    
 (b) a compound having a plurality of functional groups that are reactive with said carbamate groups,  
   2) applying a voltage between an anode and the conductive substrate, and    3) removing the substrate from the coating composition.    
     
     
         19 . The method of  claim 18  further comprising rinsing the substrate.  
     
     
         20 . The method of  claim 18  further comprising baking the substrate at a temperature of from 200° to 300° F.  
     
     
         21 . The method of  claim 18  wherein the conductive substrate comprises metal.  
     
     
         22 . The method of  claim 21  wherein the metal is selected from the group consisting of aluminum and steel.