One-component, dual-cure conformal coating compositions

Abstract

Disclosed are one-component compositions that include: (1) an isocyanate-functional urethane acrylate and (2) a polyisocyanate containing allophanate and/or uretdione groups, wherein the one-component composition has a viscosity of less than or equal to about 500 mPas and an isocyanate content of greater than about 5% by weight, based on the weight of the one-component composition. Also disclosed are circuit boards and electronic components that are coated with such compositions.

What is claimed is: 
     
         1 . A one-component composition comprising:
 1) an isocyanate functional urethane (meth)acrylate and   2) a polyisocyanate containing allophanate and/or uretdione groups,   
       wherein the one-component composition has:
 (i) a viscosity of less than or equal to about 500 mPas according to ASTM Standard D 7395-07 using a Brookfield R/S Rheometer at 25° C., 100 s-1 shear rate for 2 minutes with a C-50-1 spindle, and 
 (ii) an isocyanate content of greater than about 5% by weight, based on the weight of the one-component composition. 
 
     
     
         2 . The one-component composition of  claim 1 , wherein the solids content of the composition is at least 90 percent by weight, based on the total weight of the one-component composition. 
     
     
         3 . The one-component composition of  claim 1 , wherein the solids content of the composition is at least 95 percent by weight, based on the total weight of the one-component composition. 
     
     
         4 . The one-component composition of  claim 1 , wherein component 1) is a reaction product of a composition comprising: (a) a monohydric alcohol comprising (meth)acryloyl groups; and (b) a di- or polyisocyanate. 
     
     
         5 . The one-component composition of  claim 4 , wherein the monohydric alcohol containing (meth)acryloyl groups comprises hydroxmethyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, trimethylol propane di(meth)acrylate, pentaerythritol tri(meth)acrylate, a (meth)acrylic acid adduct of glycidyl (meth)acrylate, and/or a polycaprolactone hydroxy ethyl (meth)acrylate. 
     
     
         6 . The one-component composition of  claim 4 , wherein the monohydric alcohol containing (meth)acryloyl groups comprises a polycaprolactone hydroxy ethyl (meth)acrylate. 
     
     
         7 . The one-component composition of  claim 6 , wherein the polycaprolactone hydroxy ethyl (meth)acrylate comprises a poly(ε-caprolactone) ester of 2-hydroxyethyl acrylate. 
     
     
         8 . The one-component composition of  claim 1 , wherein component 1) is present in an amount of at least 40 percent by weight, based on the total weight of the coating composition. 
     
     
         9 . The one-component composition of  claim 1 , wherein component 1) is present in an amount of no more than 60 percent by weight, based on the total weight of the coating composition. 
     
     
         10 . The one-component composition of  claim 1 , wherein component 2) comprises a polyisocyanate containing uretdione groups. 
     
     
         11 . The one-component composition of  claim 1 , wherein component 2) is present in an amount of at least 10 percent by weight and no more than no more than 30 percent by weight, based on the total weight of the coating composition. 
     
     
         12 . The one-component composition of  claim 1 , further comprising a reactive diluent comprising a mono-functional (meth)acrylate monomer containing at least 6 carbon atoms in the alkyl moiety that is present in an amount of up to 50 percent by weight, based on the total weight of the composition. 
     
     
         13 . The one-component composition of  claim 1 , wherein the composition has an isocyanate content of greater than about 6% by weight and a solids content of at least 95 percent by weight, based on the total weight of the composition. 
     
     
         14 . A method comprising depositing the composition of  claim 1  over at least a portion of a substrate and exposing the coated substrate to actinic radiation. 
     
     
         15 . The method of  claim 14 , wherein the substrate comprises a circuit board or electronic component.