Powder coating compositions for low temperature curing and high flow

Abstract

The present invention relates to powder coating compositions and to components and ingredients for incorporation therein, suitable for low temperature curing schedule and with excellent resistance to outside aging. The powder coating composition can be cured at a temperature from 140° C. to lead to a coating with excellent flow and high gloss.

1 . A powder coating composition comprising a polyester resin which comprises
 (1) Polyols,   (2) Diacids,   (3) Fatty acids.   and from 4 to 65 weight percent of a curative and additives, wherein the weight percent is based on the total weight of the polyester resin and curative.   
     
     
         2 . The powder coating composition of  claim 1  wherein the polyester resin comprises
 (1) 0.1 to 60 weight percent of mono or poly-functional saturated or unsaturated fatty acids or mixtures thereof, 
 (2) 30 to 60 weight percent of an aromatic diacid or cycloalkyl diacids or anhydrides thereof, 
 (3) 20 to 30 weight percent of aliphatic diol, 
 (4) 0 to 6 weight percent of aliphatic triol, 
 (5) 0 to 10 weight percent of isosorbide and isomers or cycloalkyl diol, 
 (6) 0 to 10 weight percent of C 3 -C 12  aliphatic diacid, and 
 with total weight percent of the monomers equal to 100. 
 
     
     
         3 . The powder coating composition of  claim 1  wherein an acid/alcohol mole ratio is higher than 1 and with an acid value of higher than 15 mg KOH/g. 
     
     
         4 . The powder coating composition of  claim 3  wherein the acid/alcohol mole ratio in lower that 1 and with a hydroxyl value of higher than 25 mg KOH/g. 
     
     
         5 . The powder coating composition of  claim 1  wherein the polyester resin comprises:
 (1) 0.5 to 30 weight percent of mono or poly-functional saturated or unsaturated fatty acids of mixtures of them, 
 (2) 30 to 60 weight percent of an aromatic diacid or cycloalkyl diacid or anhydride, 
 (3) 20 to 30 weight percent of aliphatic diol, 
 (4) 0 to 6 weight percent of aliphatic triol, 
 (5) 0 to 10 weight percent of isosorbide and isomers or cycloalkyl diol, 
 (6) 0 to 10 weight percent of C 3 -C 12  aliphatic diacid, and 
 with total weight percent of the monomers equal to 100. 
 
     
     
         6 . The powder coating composition of  claim 2  wherein the aromatic diacid, cycloalkyl diacid or anhydride thereof is selected from the group consisting of isophthalic acid (IPA), terephthalic acid (TPA), phthalic anhydride (PA), trimellitic anhydride (TMA), furandicarboxylic acid (FDCA), cyclohexandicarboxilic acid (CHDA), hexahydrophtalic anhydride (HHPA) and combinations thereof. 
     
     
         7 . The powder coating composition of  claim 1  wherein the melt viscosity (ICI) at 200° C. of the polyester resin is from 1500 to 12000 mPa·s and a Tg of above 44° C. but lower than 70° C. 
     
     
         8 . The powder coating composition of  claim 3  wherein the curative is selected from a non-isocyanurate polyepoxide or beta-hydroxyalkylamide or triglycidyl-isocyanurate or epoxy resins (glycidyl ethers of Bisphenol A & F or epoxy novolac resins, glycidyl esters and mixtures thereof) in a weight percent (on total polyester resin and curative) of 2.5-50. 
     
     
         9 . The powder coating composition of  claim 4  wherein the curative is selected from trimer of isophorone diisocyanate, trimer of hexamethylene diisocyanate, caprolactam-blocked polyisocyanate or self blocked uretdiones in a weight percent (on total polyester resin and curative) of 10 to 65. 
     
     
         10 . The powder coating composition of  claim 7  wherein the cure temperature is lower than 180° C. and higher than 100° C. 
     
     
         11 . A coated article comprising the polymeric composition of  claim 10  in a cured film.