Aqueous emulsion coating composition comprising an autoxidisable fatty acid modified polyester

Abstract

An aqueous coating composition comprising an autoxidisable fatty acid modified polyester resin having ≧40 wt % of fatty acid residues; a Tg in the range of from −70 to +20° C.; an acid value less than 40 mg KOH/g; a Mw in the range of from 5,000 to 125,000 g/mol; >5 wt % of ring structures; and said composition having a co-solvent content less than 20 wt % by weight of solids; a solids content >38 wt %; and when in the form of the film having a telegraphing value of less than 35 gloss units.

1 . An aqueous coating composition comprising an autoxidisable fatty acid modified polyester resin, wherein the resin has:
 i) >40 wt % of fatty acid residues;   ii) a Tg in the range of from −70 to +20° C.;   iii) an acid value less than 40 mg KOH/g;   iv) a Mw in the range of from 5,000 to 125,000 g/mol;   v) >5 wt % of ring structures; and wherein   the composition has:   a) less than 20 wt % of a co-solvent based on weight of solids;   b) less than 38 wt % of solids content; wherein   the composition when in the form of a film has a telegraphing value of less than 35 gloss units;   where the telegraphing value is a 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 68 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 fatty acid modified polyester resin comprises at least 10 wt % of ring structures. 
     
     
         3 . An aqueous coating composition according to  claim 1  wherein the autoxidisable fatty acid modified polyester resin comprises <5 wt % of trimellitic acid and/or trimellitic anhydride. 
     
     
         4 . An aqueous coating composition according to  claim 1  wherein the autoxidisable fatty acid modified polyester resin comprises <15 wt %, of phthalic acid, phthalic anhydride and/or benzoic acid. 
     
     
         5 . An aqueous coating composition according to  claim 1  wherein the autoxidisable fatty acid modified polyester resin comprises <6 wt % of glycerol. 
     
     
         6 . An aqueous coating composition according to  claim 1  wherein the fatty acid residues have an iodine number of at least 50 g I 2 /100 g fatty acid. 
     
     
         7 . An aqueous coating composition according to  claim 1  wherein the autoxidisable fatty acid modified polyester resin is obtained from components:
 i) 15 to 35 wt % of isophthalic acid and/or hexahydrophthalic anhydride (HHPAN); 
 ii) 0 to 2 wt % of glycerol; 
 iii) 45 to 80 wt % of fatty acid residues having an iodine value between 50 and 180 g I 2 /100 g; 
 wherein the fatty acid contains less than 10 wt % of fatty acids that contain 3 or more double bonds; 
 iv) 0 to 5 wt % of TMA (trimellitic acid and or trimellitic anhydride); 
 where i)+ii)+iii+iv)=100%; 
 wherein the resin has a ND×AV value of <20 mgKOH/g, where ND is a neutralization degree of acid groups on the resin and AV is the acid value of the resin; and 
 wherein the composition comprises: 
 4 to 8 wt % of a surfactant based on the weight of the total resin material, which is a mixture of at least one anionic and at least one non-ionic surfactant; 
 and wherein the anionic surfactant part is 2 to 5 wt % based on total weight of the resin. 
 
     
     
         8 . An aqueous coating composition according to  claim 1  comprising at least:
 i) 42 to 65 wt % of the autoxidisable fatty acid modified polyester; 
 ii) less than 20 wt % of the co-solvent based on the weight of solids; and 
 iii) 15 to 58 of water; 
 where i)+ii)+iii)=100%. 
 
     
     
         9 . An aqueous coating composition according to  claim 1  comprising resin solids comprising at least 50 wt %, based on the resin solids, of the autoxidisable fatty acid modified polyester resin. 
     
     
         10 . An aqueous coating composition according to  claim 1  comprising <13 wt %, based on solids content of the coating composition, of nitrogen containing compounds with an evaporation rate<0.1. 
     
     
         11 . An aqueous coating composition according to  claim 1  wherein the composition comprises N-methylpyrrolidone in an amount of <13 wt % based on weight of solids. 
     
     
         12 . An aqueous coating composition according to  claim 1  comprising at least:
 i) 20 to 45 wt % of the autoxidisable fatty acid modified polyester resin; 
 ii) 10 to 60 wt % of water; and 
 iii) 20 to 45 wt % of pigment; 
 where i)+ii)+iii)=100%; and 
 iv) less than 5 wt % of the co-solvent based on weight of solids; 
 v) 0.1 to 4 wt % of a thickener by-weight of solids; and 
 vi) 0 to 9 wt % of a dispersing agent by weight of solids. 
 
     
     
         13 . 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 14 gloss units. 
     
     
         14 . A substrate coated with the aqueous coating composition according to  claim 1 . 
     
     
         15 . A method for coating a substrate comprising applying the aqueous coating composition according to  claim 1  to the substrate, and then drying the aqueous coating composition to form a coated substrate. 
     
     
         16 . A paint comprising the aqueous coating composition according to  claim 1 .