Electrodepositable coating compositions and related methods

Abstract

An electrodepositable coating composition is provided including a resinous phase and catalyst nanoparticles dispersed in an aqueous medium, the resinous phase including (a) at least one active hydrogen-containing, ionic salt group-containing resin; and (b) at least one curing agent; and the catalyst nanoparticles for effecting cure between the resin (a) and the curing agent (b). The catalyst nanoparticles have an average BET specific surface area greater than 20 square meters per gram (m 2 /g). Methods of preparing and using the composition also are provided.

1 . An electrodepositable coating composition comprising a resinous phase and catalyst nanoparticles dispersed in an aqueous medium, 
 the resinous phase comprising: 
 (a) a active hydrogen-containing, ionic salt group-containing resin; and  
 (b) a curing agent; and  
   the catalyst nanoparticles for effecting cure between the resin (a) and the curing agent (b), the catalyst nanoparticles being selected from the group consisting of bismuth oxide; bismuth silicate; bismuth titanate; molybdenum oxide; molybdenum silicate; molybdenum titanate; tungsten oxide; tungsten silicate; tungsten titanate; a combination of cerium oxide, zinc oxide and silicon dioxide; a combination of cerium oxide and silicon dioxide; and combinations thereof, wherein the catalyst nanoparticles have an average B.E.T. specific surface area greater than 20 square meters per gram (m 2 /g).    
   
   
       2 . The electrodepositable coating composition according to  claim 1 , wherein at least a portion of the catalyst nanoparticles are dispersed in one or both of the resin (a) and the curing agent (b) prior to dispersing the resinous phase in the aqueous medium.  
   
   
       3 . The electrodepositable coating composition according to  claim 1 , wherein the catalyst nanoparticles comprise bismuth oxide.  
   
   
       4 . The electrodepositable coating composition according to  claim 1 , wherein the catalyst nanoparticles comprise bismuth oxide and bismuth silicate.  
   
   
       5 . The electrodepositable coating composition according to  claim 1 , wherein the catalyst nanoparticles further comprise silica.  
   
   
       6 . The electrodepositable coating composition according to  claim 1 , wherein the catalyst nanoparticles have an average B.E.T. specific surface area greater than 25 square meters per gram (m 2 /g).  
   
   
       7 . The electrodepositable coating composition according to  claim 6 , wherein the catalyst nanoparticles have an average B.E.T. specific surface area greater than 30 square meters per gram (m 2 /g).  
   
   
       8 . The electrodepositable coating composition according to  claim 1 , wherein the catalyst nanoparticles have an average primary particle size of less than 500 nanometers.  
   
   
       9 . The electrodepositable coating composition according to  claim 1 , wherein the catalyst nanoparticles are present in the electrodepositable coating composition in an amount sufficient to effect cure of the electrodepositable composition at a temperature at or below 360° F. (182.2° C.).  
   
   
       10 . The electrodepositable coating composition according to  claim 1 , wherein the catalyst nanoparticles are present in the electrodepositable coating composition in an amount sufficient to effect cure of the electrodepositable composition at a temperature at or below 340° F. (171.1° C.).  
   
   
       11 . The electrodepositable coating composition according to  claim 1 , wherein the catalyst nanoparticles are present in the coating composition in an amount sufficient to effect cure of the coating composition at or below a temperature of 320° F. (160° C.).  
   
   
       12 . The electrodepositable coating composition according to  claim 1 , wherein the catalyst nanoparticles are present in the coating composition in an amount ranging from 0.1 to 5.0 percent by weight of metal based on weight of total resin solids present in the electrodepositable coating composition.  
   
   
       13 . The electrodepositable coating composition according to  claim 1 , wherein the catalyst further comprises dioctyltin oxide and/or its derivatives.  
   
   
       14 . The electrodepositable coating composition according to  claim 1 , wherein the catalyst is substantially non-volatile at a temperature at or below 360° F. (182.2° C.).  
   
   
       15 . The electrodepositable coating composition according to  claim 1 , wherein the resin (a) comprises active hydrogens derived from reactive hydroxyl groups and/or primary amine groups.  
   
   
       16 . The electrodepositable coating composition according to  claim 1 , wherein the resin (a) compresses the reaction product of a polyepoxide and a diglycidyl ether of a polyhydric phenol.  
   
   
       17 . The electrodepositable coating composition according to  claim 1 , wherein at least a portion of the active hydrogens present in the resin (a) comprise primary amine groups derived from the reaction of a ketimine-containing compound and an epoxy group-containing material.  
   
   
       18 . The electrodepositable coating composition according to  claim 1 , wherein the curing agent (b) is at least partially blocked with a blocking agent.  
   
   
       19 . The electrodepositable coating composition according to  claim 1 , which is free of lead-containing compounds.  
   
   
       20 . A method for electrocoating a conductive substrate serving as a cathode in an electrical circuit comprising the cathode and an anode, the cathode and anode being immersed in an aqueous electrocoating composition, 
 the method comprising passing electric current between the cathode and anode to cause deposition of the electrocoating composition onto the substrate as a substantially continuous film, the aqueous electrocoating composition comprising a resinous phase and catalyst nanoparticles dispersed in an aqueous medium,    the resinous phase comprising: 
 (a) a active hydrogen-containing, ionic salt group-containing resin; and  
 (b) a curing agent; and  
   the catalyst nanoparticles for effecting cure between the resin (a) and the curing agent (b), the catalyst nanoparticles being selected from the group consisting of bismuth oxide; bismuth silicate; bismuth titanate; molybdenum oxide; molybdenum silicate; molybdenum titanate; tungsten oxide; tungsten silicate; tungsten titanate; a combination of cerium oxide, zinc oxide and silicon dioxide; a combination of cerium oxide and silicon dioxide; and combinations thereof, wherein the catalyst nanoparticles have an average B.E.T. specific surface area greater than 20 square meters per gram (m 2 /g).