Cationic coating composition and coating film-forming method

Abstract

A cationic coating composition containing (A) an unsaturated group-modified blocked polyisocyanate crosslinking agent obtained by reacting a hydroxyl group-containing unsaturated compound (a), a blocking agent (b) and a polyisocyanate compound (c), (B) a cationic epoxy resin, and (C) a photopolymerization initiator, preferably further containing a polymerizable unsaturated group-containing compound (D).

1 . A cationic coating composition containing (A) an unsaturated group-modified blocked polyisocyanate crosslinking agent obtained by reacting a hydroxyl group-containing unsaturated comound (a), a blocking agent (b) and a polyisocyanate compound (c), (B) a cationic epoxy resin, and (C) a photopolymerization initiator.  
     
     
         2 . A cationic coating composition as claimed in  claim 1 , wherein an unsaturated group concentration of the unsaturated group-modified blocked polyisocyanate crosslinking agent (A) is in the range of 0.25 to 4.5 moles/kg on the basis of the solid content of the crosslinking agent (A).  
     
     
         3 . A cationic coating composition as claimed in  claim 1 , wherein the cationic coating composition further contains a polymerizable unsaturated group-containing compound (D).  
     
     
         4 . A mono-layer coating film-forming method, which comprises subjecting a cationic electrodeposition coating composition as the cationic coating composition as claimed in  claim 1  to an electrodeposition coating to form an electrodeposition coating film, followed by subjecting the electrodeposition coating film to both irradiation and heating to form a cured mono-layer coating film.  
     
     
         5 . A multi-layer coating film-forming method which comprises the following successive steps (1) to (4): a step (1) of coating the cationic coating composition as claimed in  claim 1  onto a coating substrate to form a cationic coating film, 
 a step (2) of subjecting the cationic coating film formed in the step (1) to irradiation,    a step (3) of coating an intercoat coating composition and/or a topcoat coating composition to form an intercoat coating film and/or a topcoat coating film, and    a step (4) of simultaneously heating and curing the cationic coating film, and the intercoat coating film and/or the topcoating film.    
     
     
         6 . A multi-layer coating film-forming method as claimed in  claim 5 , wherein the cationic coating film formed by the step (1) in  claim 5  is preheated at a temperature of 60 to 120° C.  
     
     
         7 . A multi-layer coating film-forming method as claimed in  claim 5 , wherein the cationic coating composition is a cationic electrodeposition coating composition.  
     
     
         8 . A coated product obtained by the method as claimed in  claim 4 .  
     
     
         9 . A cationic coating composition as claimed in  claim 2 , wherein the cationic coating composition further contains a polymerizable unsaturated group-containing compound (D).  
     
     
         10 . A mono-layer coating film-forming method, which comprises subjecting a cationic electrodeposition coating composition as the cationic coating composition as claimed in  claim 2  to an electrodeposition coating to form an electrodeposition coating film, followed by subjecting the electrodeposition coating film to both irradiation and heating to form a cured mono-layer coating film.  
     
     
         11 . A mono-layer coating film-forming method, which comprises subjecting a cationic electrodeposition coating composition as the cationic coating composition as claimed in  claim 3  to an electrodeposition coating to form an electrodeposition coating film, followed by subjecting the electrodeposition coating film to both irradiation and heating to form a cured mono-layer coating film.  
     
     
         12 . A multi-layer coating film-forming method which comprises the following successive steps (1) to (4): a step (1) of coating the cationic coating composition as claimed in  claim 2  onto a coating substrate to form a cationic coating film, 
 a step (2) of subjecting the cationic coating film formed in the step (1) to irradiation,    a step (3) of coating an intercoat coating composition and/or a topcoat coating composition to form an intercoat coating film and/or a topcoat coating film, and    a step (4) of simultaneously heating and curing the cationic coating film, and the intercoat coating film and/or the topcoating film.    
     
     
         13 . A multi-layer coating film-forming method which comprises the following successive steps (1) to (4): a step (1) of coating the cationic coating composition as claimed in  claim 3  onto a coating substrate to form a cationic coating film, 
 a step (2) of subjecting the cationic coating film formed in the step (1) to irradiation,    a step (3) of coating an intercoat coating composition and/or a topcoat coating composition to form an intercoat coating film and/or a topcoat coating film, and    a step (4) of simultaneously heating and curing the cationic coating film, and the intercoat coating film and/or the topcoating film.    
     
     
         14 . A coated product obtained by any one of the methods as claimed in  claim 5 .  
     
     
         15 . A coated product obtained by any one of the methods as claimed in  claim 6 .  
     
     
         16 . A coated product obtained by any one of the methods as claimed in  claim 7.