Polymer additives for powder coatings

Abstract

Comb polymers prepared by reacting an acrylic polyol or a siloxane polyol with a lactone are disclosed. These comb polymers find particular application as additives for powder coating compositions, to improve various performance properties thereof. Powder coating composition comprising the described comb polymers are also disclosed.

1 . A curable powder coating composition comprising: 
 (a) a compound that comprises the reaction product of a polyol having at least one hydroxyl group and a lactone, wherein the polyol comprises a siloxane polyol;    (b) a film-forming resin; and    (c) a crosslinker.    
     
     
         2 - 17 . (canceled)  
     
     
         18 . The composition of  claim 1 , wherein the siloxane polyol has a number average molecular weight of 500 to 5000.  
     
     
         19 . The composition of  claim 18 , wherein the siloxane polyol has a number average molecular weight of 750 to 3000.  
     
     
         20 . The composition of  claim 1 , wherein 1 to 100 percent of the hydroxyl functional groups on the siloxane polyol have a lactone grafted thereto.  
     
     
         21 . The composition of  claim 1 , wherein greater than 90 percent of the hydroxyl functional groups on the siloxane polyol have a lactone grafted thereto.  
     
     
         22 . The composition of  claim 1 , wherein the reaction product of the siloxane polyol and the lactone has a weight average molecular weight of 1,000 to 500,000.  
     
     
         23 . The composition of  claim 22 , wherein the reaction product of the siloxane polyol and the lactone has a weight average molecular weight of 20,000 to 140,000.  
     
     
         24 . The composition of  claim 1 , wherein the lactone comprises epsilon-caprolactone.  
     
     
         25 . The composition of  claim 1 , wherein the reaction product of the siloxane polyol and the lactone comprises lactone chains comprising 1 to 50 lactone derived units.  
     
     
         26 . The composition of  claim 1 , wherein the film-forming resin is hydroxy functional.  
     
     
         27 . The composition of  claim 26 , wherein the film-forming resin comprises polyester.  
     
     
         28 . The composition of  claim 1 , wherein the film-forming resin is present in an amount of 50 weight percent or greater, based on total weight of the composition.  
     
     
         29 . The composition of  claim 1 , wherein the reaction product of the siloxane polyol and the lactone is present in an amount of 0.1 to 20 weight percent.  
     
     
         30 . The composition of  claim 29 , wherein the reaction product of the siloxane polyol and the lactone is present in an amount of 0.1 to less than 10 weight percent.