Novel latent curing agent and moisture-curable epoxy resin composition

Abstract

An oxazolidine compound which can be used as a latent curing agent for a moisture-curable resin composition and which is capable of improving storage stability and depth curability of the compositions is provided. Also provided is a moisture-curable epoxy resin composition which contains an oxazolidine compound of predetermined type as its latent curing agent, which is excellent in storage stability and depth curability and capable of attaining desired cured film thickness, and which is well adapted for such use as adhesive, sealant, and coating composition. Also provided is a latent curing agent which is capable of imparting a satisfactory storage stability and a good depth curability with the composition, or in addition, capable of improving curing speed of the composition. Also provided is a moisture-curable epoxy resin composition which has excellent storage stability and high curing speed and which is well adapted for such use as adhesive, sealant and primer. Also provided is a moisture-curable epoxy resin composition which exhibits excellent depth curability simultaneously with sufficient surface curability, and which is well adapted for use in such application as adhesive, sealing material, capping agent, and coating composition.

1 . An oxazolidine compound represented by formula (1):  
       
         
           
           
               
               
           
         
       
       wherein 
 R 1  is methyl group or ethyl group;  
 R 2  is an alkyl group containing 1 to 6 carbon atoms;  
 R 3  is methyl group or ethyl group;  
 R 4  is hydrogen atom, methyl group or ethyl group; and  
 R 5  is a hydrogen atom or a hydrocarbon group containing 1 to 6 carbon atoms;  
 with the proviso that R 2 , R 3  and R 4  may together represent an alicyclic ring or an aromatic ring; and that R 3  and R 5  may together represent an alicyclic ring or an aromatic ring:  
 
     
     
         2 . An oxazolidine compound according to    claim 1    wherein R 1  is methyl group.  
     
     
         3 . A moisture-curable epoxy resin composition comprising a polyepoxy compound having two or more epoxy groups in the molecule, and the oxazolidine compound of    claim 1    or    2   .  
     
     
         4 . A moisture-curable epoxy resin composition according to    claim 3    further comprising a ketimine compound synthesized from a ketone or an aldehyde represented by formula (2):  
       
         
           
           
               
               
           
         
       
       wherein 
 R 6  is hydrogen atom or methyl group;  
 R 7  is an alkyl group containing 1 to 6 carbon atoms;  
 R 8  is methyl group or ethyl group; and  
 R 9  is hydrogen atom, methyl group or ethyl group; with the proviso that R 7 , R 8  and R 9  may together represent an alicyclic ring or an aromatic ring; and that R 6  and R 7  may together represent an alicyclic ring or an aromatic ring; and  
 a polyamine.  
 
     
     
         5 . A moisture-curable epoxy resin composition according to    claim 3    or    4    wherein the skeleton of said polyepoxy compound contains up to 10% by mole of hydroxyl group.  
     
     
         6 . A latent curing agent containing the oxazolidine compound of    claim 1    or    2   , or the oxazolidine compound and the ketimine compound of    claim 4   .  
     
     
         7 . A moisture-curable epoxy resin composition comprising 
 a polyepoxy compound having at least two epoxy groups in the molecule;    an oxazolidine compound and/or ketimine compound; and    a silyl phosphate ester and/or acidic phosphoric acid.    
     
     
         8 . A moisture-curable epoxy resin composition according to    claim 7    wherein said silyl phosphate ester is a compound represented by formula (8):  
       
         
           
           
               
               
           
         
       
       wherein 
 R 2-1  is an alkyl group containing 1 to 6 carbon atoms;  
 X is an organic group which may contain a hetero atom; and  
 n is an integer of from 1 to 3.  
 
     
     
         9 . A moisture-curable epoxy resin composition according to    claim 7    wherein said acidic phosphoric acid is a compound represented by formula (9):  
       
         
           
           
               
               
           
         
       
       wherein 
 Y is an organic group which may contain a hetero atom or hydroxyl group; and  
 n is an integer of from 1 to 3.  
 
     
     
         10 . A moisture-curable epoxy resin composition according to any one of    claims 7    to    9    wherein said oxazolidine compound or said ketimine compound is a compound produced from a ketone represented by formula (10):  
       
         
           
           
               
               
           
         
       
       wherein 
 R 11  is hydrogen atom or an alkyl group containing 1 to 6 carbon atoms;  
 R 12  is methyl group or ethyl group;  
 R 13  is hydrogen atom or an alkyl group containing 1 to 6 carbon atoms; and  
 R 14  is an alkyl group containing 1 to 6 carbon atoms; with the proviso that R 12 , R 13 and R 14  may together represent an alicyclic ring or an aromatic ring, and that R 11  and R 12  may together represent an alicyclic ring or an aromatic ring.  
 
     
     
         11 . A moisture-curable epoxy resin composition comprising 
 a polyepoxy compound having at least two epoxy groups in the molecule; and    an oxazolidine compound represented by formula (16):                          wherein    R 17  is a hydrocarbon group containing 1 to 6 carbon atoms; and    R 18  and R 19  are either independently hydrogen atom or a hydrocarbon group containing 1 to 15 carbon atoms, or forming together an alicyclic ring or an aromatic ring.    
     
     
         12 . A moisture-curable epoxy resin composition according to    claim 11    wherein said R 17  is methyl group or ethyl group.  
     
     
         13 . A moisture-curable epoxy resin composition according to    claim 11    or    12    wherein first positioned carbon atom of said R 18  is a branched carbon or a ring member carbon.  
     
     
         14 . A moisture-curable epoxy resin composition according to any one of    claims 11    to    13    further comprising a ketimine compound.  
     
     
         15 . A moisture-curable epoxy resin composition according to    claim 14    wherein carbon atom and/or nitrogen atom in the ketimine bond of said ketimine compound has tertiary or quaternary carbon at its α position.