Aqueous emulsion coating composition comprising an autoxidisable fatty acid modified polyester

1. An aqueous coating composition comprising an autoxidisable fatty acid modified polyester resin, wherein

the autoxidisable fatty acid modified polyester resin has >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; and >5 wt % of ring structures; and wherein

the autoxidisable fatty acid modified polyester resin is obtained from components comprising:

i) 15 to 35 wt % of isophthalic acid and/or hexahydrophthalic anhydride (HHPAN);

ii) 0 to 2 wt % of glycerol;

iii) 45 to 63 wt % of fatty acid residues having an iodine value between 60 and 180 g I 2 /100 g; wherein

the fatty acid residues contain less than 10 wt % of linolenic acid; and wherein

part of the fatty acid residues is a short chain fatty acid residue derived from a short chain fatty acid of formula RCOOH, where R comprises a 1,3- or 1,4-dienyl carbon skeleton and wherein the longest carbon skeleton is C10; and wherein

the short chain fatty acid residue is present in an amount of 1 to 20 wt % based on the weight of the autoxidisable fatty acid modified polyester resin; and

iv) 0 to 5 wt % of trimellitic acid and/or trimellitic anhydride;

where components i)+ii)+iii+iv)=100%; and wherein the autoxidisable fatty acid modified polyester resin has a ND×AV value of <20 mgKOH/g, where ND is a neutralization degree of acid groups on the autoxidisable fatty acid modified polyester resin and AV is the acid value of the autoxidisable fatty acid modified polyester resin; and wherein

the composition has:

a) less than 20 wt % of a co-solvent based on the weight of solids content of the coating composition;

b) greater than 38 wt % of solids content of the coating composition; and

c) 4 to 8 wt % of a surfactant based on the weight of the autoxidisable fatty acid modified polyester resin, wherein the surfactant is a mixture of at least one anionic surfactant and at least one non-ionic surfactant, and wherein the at least one anionic surfactant is present in an amount of 2 to 5 wt % based on the total weight of the autoxidisable fatty acid modified polyester resin, and wherein

the composition when in the form of 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 <2 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 <1 wt % of glycerol.

6. An aqueous coating composition according to claim 1 wherein the fatty acid residues have an iodine number of at least 80 to 150 g I 2 /100 g fatty acid.

7. An aqueous coating composition according to claim 1 , wherein the short chain fatty acids comprising a 1,3- or 1,4-dienyl structure are selected from the group consisting of 2,4-hexadienoic acid, 2-methyl-5-isopropylhexa-2,5-dienoic acid, 2,3-octadienoic acid and mixtures thereof.

8. An aqueous coating composition according to claim 1 comprising at least:

i) 42 to 65 wt % of the autoxidisable fatty acid modified polyester resin;

ii) less than 20 wt % of the co-solvent based on the weight of solids content of the coating composition; 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 the 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 the weight of solids content of the coating composition.

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 the weight of solids content of the coating composition;

v) 0.1 to 4 wt % of a thickener based on the weight of solids content of the coating composition; and

vi) 0 to 9 wt % of a dispersing agent based on the weight of solids content of the coating composition.

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 .