Low-cure powder coatings and methods for using the same

Abstract

Low-cure powder coating compositions are disclosed. The compositions comprise a polyepoxide and a material having the structure wherein R 1 is an organic radical having 6 to 25 carbon atoms; R 2 is an organic radical having 1 to 20 carbon atoms; R 3 and R 4 are independently alkyl or phenyl groups having 1 to 8 carbon atoms; Z is oxygen or nitrogen, and when Z is oxygen R 5 is absent and when Z is nitrogen R 5 is hydrogen or is and n is 1 to 4. The material can optionally be reacted with an acidic hydrogen-containing compound. The compositions are curable without the use of crosslinking agents or accelerators. Methods for coating a substrate using these compositions, and substrates coated thereby, are also disclosed, as are additional catalysts useful for the same purpose.

Therefore, what is claimed is:  
     
         1 . A curable powder composition comprising: 
 (a) a material having the structure:                          wherein R 1  is an organic radical having 6 to 25 carbon atoms, R 2  is an organic radical having 1 to 20 carbon atoms; R 3  and R 4  are independently alkyl or phenyl groups having 1 to 8 carbon atoms; Z is oxygen or nitrogen and when Z is oxygen, R 5  is absent and when Z is nitrogen, R 5  is hydrogen or                          and when R 5  is                          each R 2 , each R 3  and each R 4  are the same or different; and n is 1 to 4; and    (b) a polyepoxide;    wherein the powder composition cures in the absence of any addition component.    
     
     
         2 . The powder composition of  claim 1 , wherein said composition cures at a temperature of between 80° C. and 125° C.  
     
     
         3 . The powder composition of  claim 2 , wherein said composition cures at a temperature of between 105° C. and 120° C.  
     
     
         4 . The powder composition of  claim 1 , wherein said composition cures at a temperature greater than 125° C.  
     
     
         5 . The powder composition of  claim 1 , wherein Z is nitrogen and R 5  is hydrogen.  
     
     
         6 . The composition of  claim 5 , wherein R 1  is 1,1,3,3-tetramethylcyclohexylene.  
     
     
         7 . The composition of  claim 5 , wherein R 2  is n-propylene.  
     
     
         8 . The composition of  claim 5 , wherein R 3  and R 4  are methyl.  
     
     
         9 . The composition of  claim 1 , wherein component (a) further comprises an acidic hydrogen-containing compound.  
     
     
         10 . The composition of  claim 9 , wherein the acidic hydrogen-containing compound is a phenolic compound.  
     
     
         11 . The composition of  claim 10 , wherein the phenolic compound is a polyphenol.  
     
     
         12 . The composition of  claim 11 , wherein the polyphenol is bis(4-hydroxyphenyl)-2,2-propane.  
     
     
         13 . The composition of  claim 1 , wherein (a) is present in an amount ranging from about 0.5 to 10 weight percent, and (b) is present in an amount ranging from about 20 to about 90 weight percent, with weight percent being based upon total weight of the composition.  
     
     
         14 . The composition of  claim 12 , wherein (a) is present in an amount ranging from about 3 to 5 weight percent, and (b) is present in an amount ranging from about 30 to about 60 weight percent, with weight percent being based upon total weight of the composition.  
     
     
         15 . A method for coating a substrate comprising: 
 (a) applying to said substrate the powder composition of  claim 1;  and    (b) curing said composition.    
     
     
         16 . The method of  claim 15 , wherein said composition is cured at a temperature of between 80° C. and 125° C.  
     
     
         17 . A substrate coated according to the method of  claim 15 .  
     
     
         18 . The substrate of  claim 17 , wherein said substrate is comprised of a thermoplastic polymer, a thermoset polymer, cardboard, paper, wood, particleboard, medium density fiberboard and/or metal.  
     
     
         19 . A powder coating composition that cures at a temperature of between 80° C. and 125° C., comprising a resin and curing agent therefor, wherein substantially all of the curing agent is extruded with the resin.  
     
     
         20 . The powder coating composition of  claim 19 , wherein said composition does not cure at a temperature below 70° C.  
     
     
         21 . A catalyst composition comprising: 
 the reaction product of: 
 i) a material having the structure  
                     
 wherein R 1  is an organic radical having 6 to 25 carbon atoms R 2  is an organic radical having 1 to 20 carbon atoms; R 3  and R 4  are independently alkyl or phenyl groups having 1 to 8 carbon atoms; Z is oxygen or nitrogen and when Z is oxygen R 5  is absent and when Z is nitrogen, R 5  is hydrogen or  
                     
 and when R 5  is  
                     
 each R 2 , each R 3  and each R 4  are the same or different, and n is 1 to 4, but when Z is nitrogen, R 2  is an alkylene having between 1 and 4 carbon atoms and R 3  and R 4  are both alkyl groups having between 1 and 4 carbons. R 5  is not hydrogen; and  
 (ii) an acidic hydrogen-containing compound;  
   
     
     
         22 . A powder composition comprising the catalyst of  claim 21 .  
     
     
         23 . A catalyst composition comprising: 
 a material having the structure:                          wherein R 1  is an organic radical having 6 to 25 carbon atoms, R 2  is an organic radical having 1 to 20 carbon atoms; R 3  and R 4  are independently alkyl or phenyl groups having 1 to 8 carbon atoms; Z is oxygen or nitrogen and when Z is oxygen R 5  is absent and when Z is nitrogen R 5  is hydrogen or                          and when R 5  is                          each R 2 , each R 3  and each R 4  are the same or different; and n is 1 to 4; wherein said composition does not include an acidic hydrogen-containing compound.    
     
     
         24 . A powder composition comprising the catalyst of  claim 23 , wherein said powder composition does not include an acidic hydrogen-containing compound.  
     
     
         25 . A cured coating layer comprising: 
 (a) a material having the structure:                          wherein R 1  is an organic radical having 6 to 25 carbon atoms, R 2  is an organic radical having 1 to 20 carbon atoms; R 3  and R 4  are independently alkyl or phenyl groups having 1 to 8 carbon atoms; Z is oxygen or nitrogen and when Z is oxygen, R 5  is absent and when Z is nitrogen, R 5  is hydrogen or                                                and when R 5  is    each R 2 , each R 3  and each R 4  are the same or different; and n is 1 to 4; and    (b) a polyepoxide;    wherein the polyepoxide has reacted with itself during cure.    
     
     
         26 . A method for initiating self cure of a polyepoxide resin comprising adding to a composition comprising said resin a catalyst having the structure  
       
         
           
           
               
               
           
         
       
       wherein R 1  is an organic radical having 6 to 25 carbon atoms, R 2  is an organic radical having 1 to 20 carbon atoms; R 3  and R 4  are independently alkyl or phenyl groups having 1 to 8 carbon atoms; Z is oxygen or nitrogen and when Z is oxygen R 5  is absent and when Z is nitrogen, R 5  is hydrogen or  
       
         
           
           
               
               
           
         
       
       and when R 5  is  
       
         
           
           
               
               
           
         
       
       each R 2 , each R 3  and each R 4  are the same or different; and n is 1 to 4.  
     
     
         27 . The method of  claim 26 , wherein said catalyst further comprises an acidic hydrogen-containing compound.  
     
     
         28 . The composition of  claim 1 , wherein R 2  is alkylene.  
     
     
         29 . The composition of  claim 1 , wherein R 3  and R 4  are alkyl.  
     
     
         30 . A curable powder composition comprising: 
 (a) a polyepoxide; and    (b) the reaction product of a polyisocyanate and either an amine comprising a primary or secondary amine group and a tertiary amine or an alcohol or polyol containing a tertiary amine.    
     
     
         31 . The composition of  claim 30 , wherein the reaction product is formed from a polyisocyanate and an amine comprising a primary or secondary amine group and a tertiary amine.  
     
     
         32 . The composition of  claim 31 , wherein the polyisocyanate is a diisocyanate.  
     
     
         33 . The composition of  claim 30 , wherein (b) is mixed with an acidic hydrogen-containing compound.