Curable coating composition and coating film forming method

Abstract

The present invention is to provide a curable coating composition having much less of a volatile organic component, and being excellent in coating film performance such as durability and scratch resistance, and a coating film forming method using the above curable coating composition capable of suppressing generation of sagging and so on. The present invention is a curable coating composition which comprises (a) a component having an active methylene group and/or an active methine group, (b) a component having a methacrylate group and/or an acrylate group, (c) a Michael reaction catalyst and (d) a photo-polymerization initiator. The present invention also provides a coating film forming method which comprises a step (1) of applying a curable coating on a substrate to be coated and a step (2) including a stage of irradiating with ultraviolet ray and a stage of heating, said curable coating comprising the above curable coating composition.

1 . A curable coating composition 
 which comprises (a) a component having an active methylene group and/or an active methine group,    (b) a component having a methacrylate group and/or an acrylate group,    (c) a Michael reaction catalyst and    (d) a photo-polymerization initiator.    
     
     
         2 . The curable coating composition according to  claim 1 , 
 wherein said component (a) is at least one species selected from the group consisting of reaction products of polyol with a carboxylic acid compound containing an active methylene group and/or an active methine group and/or a carboxylic acid ester containing an active methylene group and/or an active methine group, reaction products of a polyamine compound with diketene, acrylic resins containing an active methylene group and/or an active methine group and reaction products of an isocyanate compound with a carboxylic acid compound containing an active methylene group and/or a carboxylic acid ester containing an active methylene group.    
     
     
         3 . The curable coating composition according to  claim 1  or  2 , 
 wherein said component (b) is at least one species selected from the group consisting of (meth)acrylate esters of polyol, unsaturated polyester resins, epoxy(meth)acrylate resins, urethane(meth)acrylate resins, acrylic resins containing an α,β-unsaturated carbonyl group, polyether (meth) acrylate resins and silicone oligomers containing a (meth)acryloyl group.  
 
     
     
         4 . The curable coating composition according to any of  claims 1  to  3 , 
 wherein said component (c) comprises at least one selected from the group consisting of alkaline metal hydroxides, alkaline metal alkoxides, quaternary ammonium hydroxides, quaternary ammonium carbonates, tertiary amines, guanidine, amidine, and tertiary phosphines.  
 
     
     
         5 . The curable coating composition according to any of  claims 1  to  3 , 
 wherein said component (c) comprises a component (i) having an onium salt.  
 
     
     
         6 . The curable coating composition according to  claim 5 , 
 wherein a cation of said onium salt is at least one selected from the group consisting of quaternary ammonium cations, quaternary phosphonium cations and tertiary sulfonium cations, and    an anion of said onium salt is at least one selected from the group consisting of halide anions except for an fluoride anion, carboxylate anions, sulfonate anions, sulfate anions, nitrate anions and phosphate anions.    
     
     
         7 . The curable coating composition according to  claim 5  or  6 , 
 wherein said component (i) having the onium salt is a resin obtainable by copolymerization of at least one monomer selected from the group consisting of quaternized aminoalkyl (meth)acrylates, quaternized amonoalkyl (meth)acrylamides, quaternary ammonium (meth) acrylates, quaternary phosphinoalkyl (meth)acrylates and quaternary phosphonium (meth)acrylates.  
 
     
     
         8 . The curable coating composition according to any of  claims 5  to  7 , 
 wherein said component (c) comprises a component (ii) having an epoxy group.  
 
     
     
         9 . The curable coating composition according to  claim 8 , 
 wherein said component (ii) having the epoxy group is a glycidyl compound, an alicyclic epoxy compound or an α-olefin epoxide.    
     
     
         10 . The curable coating composition according to  claim 8 , 
 wherein said component (ii) having the epoxy group is a resin obtainable by copolymerization of at least one monomer selected from the group consisting of glycidyl (meth) acrylates, β-methylglycidyl (meth)acrylates, glycidyl ether of 4-hydroxybutyl(meth)acrylate and (meth)acrylate of 3,4-epoxycyclohexanemethanol.    
     
     
         11 . A coating film forming method 
 which comprises a step (1) of applying a curable coating on a substrate to be coated and    a step (2) including a stage of irradiating with ultraviolet ray and a stage of heating,    said curable coating comprising the curable coating composition according to any of  claims 1  to  10 .    
     
     
         12 . The coating film forming method according to  claim 11 , 
 wherein said curable coating is a clear coating.    
     
     
         13 . The coating film forming method according to  claim 12 , 
 wherein the substrate in said step (1) is formed with an uncured base coating film thereon in advance.