Coating composition comprising autoxidisable component

Abstract

An aqueous solution coating composition comprising an autoxidizable polyvinyl polymer having 20% of fatty acid residue by weight of polymer; T.sub.g from 60 to +15 C.; acid value of 15 to 75 mg KOH/g, M.sub.w from 2500 to 100000 g/mol; polydispersity 30, said composition having 25% co-solvent by weight of solids, 30% solids by weight of composition; said composition when in the form of a coating having a telegraphing value defined as the difference in gloss at a 20 angle of between a film cast on rough PVC and a film cast on smooth PVC of 10 gloss units.

Claims

1. An aqueous coating composition that comprises an autoxidisable polymer that comprises plurality of vinyl groups where: I) said autoxidisable polyvinyl polymer has: i) fatty acid residue in an amount greater than or equal to 20% by weight of said autoxidisable polyvinyl polymer ii) a glass transition temperature (Tg) from 60 C. to +20 C.; iii) an acid value from 5 to 75; iv) a weight average molecular weight (Mw) from 2500 to 100000 g/mol; and v) a polydispersity (PDi) less than or equal to 30; II) said composition comprises: a) a co solvent content less than 25% by weight of solids; b) a solids content greater than or equal to 30% by the total weight of said composition; c) 35% to 50% of the autoxidisable polyvinyl polymer by weight of the composition; d) 0 to 20% of co-solvent by weight of the composition; and e) 35% to 65% of water by weight of the composition; and III) said composition when in the form of a film has a telegraphing value of less than 10 gloss units, wherein the telegraphing value is a difference between an initial smooth gloss value of the film minus an initial rough gloss value of the film, where (1) the initial smooth gloss value is the gloss when the film is cast on a smooth PVC substrate with Rz=1 m0.25 m and the initial rough gloss value is the gloss when the film is cast on a rough PVC substrate with Rz=25 m5 m, wherein Rz is an average of five greatest peak-to-valley separations in a scanned surface area of 1.92.5 mm of the PVC substrate as analyzed with an optical profilometer at a magnification of 2.5; (2) each film has a dry film thickness of 52 m6 m; and (3) each initial gloss value is measured at a 20 angle, 24 hours after the film has been cast onto the PVC substrate.

2. The aqueous coating composition according to claim 1, wherein the autoxidisable polymer if carboxylic acid functional has an ND x AV value of >22 and <65; where ND=neutralization degree of the acid groups on the polymer and AV=acid value.

3. The aqueous coating composition according to claim 1, wherein the composition comprises <13% N methylpyrrolidone by weight of the composition.

4. The aqueous coating composition according to claim 1, wherein the coating composition comprises <13% by weight of polymer solids of nitrogen containing molecules with an evaporation rate <0.1 as determined by ASTM D3539 relative to the evaporation rate of n-butyl acetate=1.00 which are either aromatic, heterocyclic or which are aromatic and aliphatic primary and secondary (di)amines with the proviso that the weight % of nitrogen in such molecules is >5%.

5. The aqueous coating composition as claimed in claim 1, wherein the autoxidisable polyvinyl polymer has: i) fatty acid residue in an amount greater than or equal to 25% by weight of said autoxidisable polyvinyl polymer; ii) a glass transition temperature (Tg) from 40 C. to +10 C.; iii) an acid value from 5 to 50 mg KOH/g; iv) a weight average molecular weight (Mw) from 6000 to 40000 g/mol; and v) a polydispersity (PDi) less than or equal to 20; and wherein the composition has a co solvent content <6% by weight of solids.

6. The aqueous coating composition according to claim 1, comprising: i) 15% to 40% of TiO2; ii) 15% to 40% of polymer solids; iii) 0 to 10% of co solvent by weight of solids; iv) 0.1 to 3% of thickener; v) 0 to 5% dispersing agent; vi) 25% to 70% water; wherein unless indicated all percentages are by weight of the composition and i)+ii)+iii)+iv)+v)+vi)=100%.

7. The aqueous coating composition as claimed in claim 1, wherein the acid value of the autoxidisable polyvinyl polymer is from 15 to 75 mg KOH/g.

8. A method of coating a substrate comprising the steps of: i) applying a coating composition as claimed in claim 1 to a substrate; and ii) drying the substrate to form a coating thereon; wherein the coating has a telegraphing value of less than 10 gloss units.

Description

EXAMPLE 1

1a Preparation of an Epoxy Functional Vinyl Polymer

(1) A 2 L round bottom reactor, equipped with stirrer, baffle and cooler, was loaded with water (867.8 g), Na.sub.2SO.sub.4 (1.59 g) and PAA (0.79 g) under nitrogen. The mixture was neutralized with NaOH until pH>8 and brought to 60 C. A homogeneous mixture of MMA (190.17 g), BMA (127.19 g) and GMA (317.99 g), AIBN (4.77 g) and CoPhMeBF (0.064 g) was transferred to the reactor and the reaction temperature was brought to 80 C. After 90 minutes a mixture of FES993 (0.53 g) and water (79.5 g) was added to the reactor. After another 10 minutes, the temperature was raised to 85 C. and kept at that temperature for 60 minutes. Subsequently, the reactor was cooled to ambient temperature and the beads were washed and dried.

(2) The Mn was 1736 g/mol, Mw was 3589 g/mol and the PDi was 2.07. The Tg was 24 C. (midpoint) as measured by DSC.

1b Preparation of the Aqueous Autoxidisable Vinyl Polymer

(3) The vinyl polymer prepared as described in step 1a above (500.0 g) was dissolved in toluene (332.59 g). Sunflower fatty acid (492.85 g) and TRAP (4.93 g) were added to the resulting solution. The mixture was heated at 120 C. under nitrogen. The reaction was continued until the acid value reached 5.7 mg KOH/g.

(4) The M.sub.n was 2736 g/mol, M.sub.w was 7662 g/mol and the PDi was 2.8. The T.sub.g was 12 C. (midpoint) as measured by DSC.

1c Functionalisation and Dispersing

(5) HHPA (44.19 g) was added to the polymer solution resulting from step 1b above (340.0 g, 75% solids in toluene). The mixture was kept at 110 C. until virtually all anhydride was reacted as judged from the Infra Red spectrum of the reaction mixture (the anhydride groups typically show two absorptions at 1785 cm.sup.1 and 1865 cm.sup.1, which disappeared and were replaced by a new ester carbonyl absorption at 1740 cm.sup.1). Then the toluene was removed by distillation under reduced pressure to obtain a fatty acid functional acrylic with an acid value of 59.4 mg KOH/g. Dowanol PnP (75.0 g) and TEA (28.9 g) was added to the fatty acid functional acrylic (300.0 g) followed by water (453.0 g) to obtain an aqueous composition having a 35% solid content, pH of 7.8 and T.sub.g=1 C. (midpoint) as measured by DSC.

(6) TABLE-US-00001 TABLE 1 Properties example 1: Ex 1 Binder 100 Particle size [nm] <50 Additol VXW4940/water 1:1 1.4 DFT [hr] 2 TFT [hr] 2.5 G(s) 83.2 G(r) 79.0 Telg. 4.2 G decay (4 d) 6.7 G decay (7 d) 7.5 G decay (14 d) 8.9 Key DFT denotes dust free time defined and measured as described herein TFT denotes tack free time defined and measured as described herein G(r) denotes the initial rough gloss value as defined herein (measured in gloss units 1 day after film formation) G(s) denotes the initial smooth gloss value as defined herein (measured in gloss units 1 day after film formation) Telg. denotes the telegraphing value as defined herein in gloss units (i.e. G(s)G(r)) G decay (n d) denotes the gloss decay value as defined herein after n days (i.e. G(r) minus the rough gloss measured n days after film formation).