Heat-curable powder coating composition

Abstract

The invention relates to a one component heat curable powder coating composition comprising a resin containing reactive unsaturations and wherein all said reactive unsaturations are carbon carbon double bonds connected directly to an electron withdrawing group, a thermal initiation system comprising a peroxide chosen from the group of compounds represented by formula (1), wherein R 1 and R 2 each independently stand for an optionally substituted alkyl of 1 to 30 C-atoms, wherein the 1 to 30 C-atoms do not include the C-atoms of the substituents or for an optionally substituted aryl of 6 to 18 C-atoms, wherein the 6 to 18 C-atoms do not include the C-atoms of the substituents, and a co-crosslinker chosen from the group of vinylethers, vinyletherurethanes, vinylesters, vinylamides, itaconates, enamines, vinylureas and mixtures thereof.

1 . One component heat curable powder coating composition comprising
 a resin containing reactive unsaturations and wherein all said reactive unsaturations are carbon carbon double bonds connected directly to an electron withdrawing group   a thermal initiation system comprising a peroxide chosen from the group of compounds represented by formula (1)   
       
         
           
           
               
               
           
         
       
       wherein R 1  and R 2  each independently stand for an optionally substituted alkyl of 1 to 30 C-atoms, wherein the 1 to 30 C-atoms do not include the C-atoms of the substituents or for an optionally substituted aryl of 6 to 18 C-atoms, wherein the 6 to 18 C-atoms do not include the C-atoms of the substituents, and
 a co-crosslinker chosen from the group of vinylethers, vinyletherurethanes, vinylesters, vinylamides, itaconates, enamines, vinylureas and mixtures thereof. 
 
     
     
         2 . Composition according to  claim 1 , wherein the peroxide is benzoyl peroxide or lauroyl peroxide. 
     
     
         3 . Composition according to  claim 1 , wherein the co-crosslinker is chosen from the group of vinylethers, vinylesters and mixtures thereof. 
     
     
         4 . Composition according to  claim 1 , wherein the composition further comprises an inhibitor. 
     
     
         5 . Composition according to  claim 4 , wherein the inhibitor is a hydroquinone or a catechol. 
     
     
         6 . Composition according to  claim 1 , wherein the amount of the peroxide is chosen such that when the powder coating composition is applied to a substrate and cured at a temperature of 130° C. for 20 minutes, the resulting coating resists at least 50 acetone double rubs. 
     
     
         7 . Composition according to  claim 1 , wherein the resin is a polyester. 
     
     
         8 . Composition according to  claim 1 , wherein the reactive unsaturations of the resin are based on maleic acid, fumaric acid, itaconic acid, acrylic acid and/or methacrylic acid. 
     
     
         9 . Process for the preparation of a powder coating composition according to  claim 1  comprising the steps of:
 a. mixing the components of the powder coating composition to obtain a premix 
 b. heating the premix to obtain an extrudate 
 c. cooling down the extrudate to obtain a solidified extrudate and 
 d. breaking the solidified extrudate into smaller particles to obtain the powder coating composition. 
 
     
     
         10 . Process for coating a substrate comprising the following steps:
 1) applying a powder coating composition according to  claim 1  to a substrate   2) heating the substrate.   
     
     
         11 . Substrate that is fully or partially coated with a powder coating composition according to  claim 1 . 
     
     
         12 . Use of a powder coating composition of  claim 1  to coat a heat-sensitive substrate. 
     
     
         13 . Use according to  claim 8 , wherein the heat-sensitive substrate is wood.