Aqueous autoxidisable coating composition

Abstract

An aqueous coating composition comprising an autoxidisable polyester resin having ≧30 wt % of fatty acid residues; a Tg in the range of from −60° C. to +35° C.; an acid value greater than 15 mg KOH/g and less than 75 mg KOH/g; a Mw in the range of from 2,500 to 100,000 g/mol; said composition having a co-solvent content less that 15 wt % by weight of total composition; a solids content >30 wt %; and when a film, a telegraphing value of less than 20 gloss units.

1 . An aqueous coating composition comprising an autoxidisable polyester resin, said autoxidisable polyester resin having:
 i) >30 wt % of fatty acid residues;   ii) a Tg in the range of from −60° C. to +35° C.;   iii) an acid value greater than 15 mg KOH/g and less than 75 mg KOH/g; and   iv) a Mw in the range of from 2,500 to 100,000 g/mol;   said composition having:   a) a co-solvent content 15 wt % by weight of total composition;   b) a solids content >30 wt %; and   said composition when in the form of the film having a telegraphing value of less than 20 gloss units;   where the telegraphing value is the difference between an initial smooth gloss value minus an initial rough gloss value of the film, where   the initial smooth gloss value is the gloss when the film is cast on smooth PVC (R z =1 μm [±0.25 μm]);   the initial rough gloss value is the gloss when the film is cast on rough PVC (R z =25 μm [±5 μm]); and where   each film has a dry film thickness of 52 μm [±6 μm]; and   each initial gloss value is measured at a 20° angle, one day (24 h) after the film has been cast.   
     
     
         2 . An aqueous coating composition according to  claim 1  wherein the autoxidisable polyester resin has an ND×AV value of >22 and <65 mgKOH/g. 
     
     
         3 . An aqueous coating composition according to  claim 1  comprising <13 wt % N-methylpyrrolidone by weight of resins solids. 
     
     
         4 . An aqueous coating autoxidisable composition according to  claim 1 , wherein the autoxidisable polyester resin comprises at least 5 wt % of ring structures. 
     
     
         5 . An aqueous coating composition according to  claim 1 , wherein the autoxidisable polyester resin comprises <5 wt % of TMA (trimellitic acid and or trimellitic anhydride). 
     
     
         6 . An aqueous coating composition according to  claim 1 , wherein the autoxidisable polyester resin comprises <15 wt %, of phthalic acid, phthalic anhydride and or benzoic acid. 
     
     
         7 . An aqueous coating composition according to  claim 1 , wherein the fatty acid residues have an iodine number of at least 50 g l 2 /100 g fatty acid. 
     
     
         8 . An aqueous coating composition according to  claim 1 , wherein the autoxidisabie polyester resin is selected from the group consisting of pure polyester resin, polyesteramide resin, urethanised polyester resin, urethanised polyesteramide resin and mixtures thereof. 
     
     
         9 . An aqueous coating composition according to  claim 1  comprising at least an autoxidisable pure polyester resin obtained from components comprising:
 i) 15 to 40 wt % of isophthalic acid and or hexahydrophthalic anhydride (HHPAN); 
 ii) 0 to 2 wt % of glycerol; 
 iii) 30 to 70 wt % of fatty acid residues having an iodine value between 50 and 180 g l 2 /100 g; 
 wherein i)+ii)+iii)=100%; 
 wherein the fatty acid contains less than 10 wt % of fatty acids that contain 3 or more double bonds; 
 wherein the ND×AV value of the pure autoxidisabie polyester resin is in the range of from 22 to 65 mg KOH/g; 
 wherein the autoxidisable pure polyester resin comprises <5 wt % of TMA (trimellitic acid and or trimellitic anhydride); 
 wherein the composition comprises <13 wt % N-methylpyrrolidone on solids; and 
 wherein the composition has a pH in the range of from 5.1 to 9.2. 
 
     
     
         10 . An aqueous coating composition according to  claim 1 , wherein the autoxidisable polyester resin is an autoxidisable urethanised polyester(-amide) resin. 
     
     
         11 . An aqueous coating composition according to  claim 10  wherein the autoxidiable urethanised polyester(-amide) resin comprises 1 to 20 wt % on resin solids of isocyanates. 
     
     
         12 . An aqueous coating composition according  claim 10  wherein the autoxidisable urethanised polyester(-amide) resin is obtained from components comprising:
 i) 10 to 45 wt % of a cyclic anhydride; 
 iii) 33 to 65 wt % of fatty acid residues having an iodine value between 80 and 155 g l 2 /100 g; 
 wherein the fatty acid residue contains less than 10 wt % of fatty acid residues that contain 3 or more double bonds; 
 iv) 10 to 35 wt % of a hydroxyl functional amine; 
 v) 0.5 to 7 wt %, of a polyisocyanate; 
 wherein i)+ii)+iii)+iv)+v)=100%; 
 wherein the ND×AV value of the autoxidisable urethanised polyester(-amide) resin is in the range of from 22 to 65 mg KOH/g; 
 wherein the autoxidisable urethanised polyester(-amide) resin comprises <5 wt % of TMA (trimellitic acid and or trimellitic anhydride). 
 
     
     
         13 . An aqueous coating composition according to  claim 1 , wherein the autoxidisable resin has an amide group content of at least 15 mmoles/100 g solid resin. 
     
     
         14 . An aqueous coating composition according to  claim 1  comprising:
 i) 35 to 65 wt % of the autoxidisable polyester resin; 
 ii) 0 to 20 wt % of co-solvent; and 
 iii) 35 to 65 wt % of water; 
 where i)+ii)+iii)=100%. 
 
     
     
         15 . An aqueous coating composition according to  claim 1 , comprising:
 i) 10 to 40 of pigment;   ii) 10 to 40 of the autoxidisable polyester resin;   iii) 20 to 70 wt % of water; and   iv) 0 to 15 wt % of co-solvent;   where i)+ii)+iii)+iv)=100%; and   v) 0 to 2.5 wt % of thickener by weight of solids; and   vi) 0 to 5 wt % of dispersing agent by weight of solids.   
     
     
         16 . An aqueous coating composition according to  claim 1 , comprising resin solids comprising at least 50 wt % of the autoxidisable polyester resin on total resin solids. 
     
     
         17 . An aqueous coating composition according to  claim 1 , wherein the initial rough gloss value minus the rough gloss value measured at 4 days after film formation is less than 10 gloss units. 
     
     
         18 . A substrate coated with an aqueous coating composition according to  claim 1 . 
     
     
         19 . A method for coating a substrate comprising applying the aqueous coating composition according to  claim 1  to the substrate and then drying the aqueous composition to form a coated substrate. 
     
     
         20 . A paint comprising an aqueous coating composition according to  claim 1 .