Waterborne, radiation-curable coating compositions and related methods

Abstract

Disclosed are waterborne, radiation-curable coating compositions. These coating compositions include a water-dispersible polymer and a hydrophobic multi-functional ethylenically unsaturated compound. The compositions are characterized by being viscosity stable at elevated temperatures and alkaline conditions.

1 . A waterborne coating composition comprising:
 a water-dispersible, acid-functional polymer neutralized by a neutralizing agent comprising a monofunctional tertiary amine having a pK a  of no more than 9.5, wherein the neutralizing agent comprises at least 50 percent by weight of total amine in the composition; and   a hydrophobic multi-functional ethylenically unsaturated compound;   wherein the composition has an initial viscosity of 100 to 300 centipoises at 77° F. and a final viscosity of 100 to 450 centipoises at 77° F. after exposure to a temperature of 120° F. for a period of 28 days; and   wherein the composition is curable by exposure to ultraviolet radiation or electron beam radiation.   
     
     
         2 . The waterborne coating composition of  claim 1 , wherein the composition comprises a carrier fluid comprising at least 80 weight percent water. 
     
     
         3 . The waterborne coating composition of  claim 1 , wherein the water-dispersible, acid-functional polymer comprises a vinyl polymer, acrylic polymer, polyolefin, epoxy, polyamide, and/or polyurethane. 
     
     
         4 . The waterborne coating composition of  claim 1 , wherein the water-dispersible, acid-functional polymer comprises a carboxylic acid-functional polymer. 
     
     
         5 . The waterborne coating composition of  claim 1 , wherein the water-dispersible, acid-functional polymer comprises a vinyl polymer. 
     
     
         6 . The waterborne coating composition of  claim 1 , wherein the water-dispersible, acid-functional polymer comprises a carboxylic acid-functional vinyl polymer. 
     
     
         7 . The waterborne coating composition of  claim 1 , wherein the water-dispersible, acid-functional polymer comprises an acrylic polymer. 
     
     
         8 . The waterborne coating composition of  claim 1 , wherein the water-dispersible, acid-functional polymer comprises a carboxylic acid-functional acrylic polymer. 
     
     
         9 . The waterborne coating composition of  claim 1 , wherein the water-dispersible, acid-functional polymer has an acid number of 15 to 50. 
     
     
         10 . The waterborne coating composition of  claim 1 , wherein the composition comprises from 5 percent to 50 percent of the water-dispersible, acid-functional polymer by weight based on the total weight of the composition. 
     
     
         11 . The waterborne coating composition of  claim 1 , wherein the hydrophobic multi-functional ethylenically unsaturated compound comprises three or more sites of ethylenic unsaturation per molecule. 
     
     
         12 . The waterborne coating composition of  claim 10 , wherein the hydrophobic multi-functional ethylenically unsaturated compound comprises trimethylolpropane tri(meth)acrylate. 
     
     
         13 . The waterborne coating composition of  claim 1 , wherein the composition comprises from 2 percent to 30 percent of the hydrophobic multi-functional ethylenically unsaturated compound by weight based on the total weight of the composition. 
     
     
         14 . The waterborne coating composition of  claim 1 , wherein the coating composition has a pH of 7 to 9. 
     
     
         15 . The waterborne coating composition of  claim 1 , wherein the monofunctional tertiary amine has a pK a  of no more than 8.0. 
     
     
         16 . A waterborne coating composition comprising:
 (a) a carrier fluid comprising at least 80 weight percent water;   (b) 5 percent to 50 percent by weight based on the total weight of the composition of a carboxylic acid-functional acrylic polymer;   (c) a neutralizing agent comprising a monofunctional tertiary amine having a pK a  of no more than 9.5, wherein the neutralizing agent comprises at least 50 percent by weight of total amine in the composition, and wherein the carboxylic acid-functional acrylic polymer is neutralized by the monofunctional tertiary amine; and   (d) 2 percent to 30 percent by weight based on the total weight of the composition of a hydrophobic multi-functional ethylenically unsaturated compound comprising three or more sites of ethylenic unsaturation per molecule;   wherein the composition has an initial viscosity of 100 to 300 centipoises at 77° F. and a final viscosity of 100 to 450 centipoises at 77° F. after exposure to a temperature of 120° F. for a period of 28 days;   wherein the coating composition has a pH of 7 to 9; and   wherein the composition is curable by exposure to ultraviolet radiation or electron beam radiation.