Aqueous polyester coating compositions

#The present invention relates to certain aqueous ambient temperature crosslinkable and shelf stable polyester polymer compositions which, inter alia, provide coatings having improved open and wet edge times as well as good tack-free times.

#A general need when applying a decorative or protective coating to a substrate is to be able to repair irregularities in the still-wet coating after some time has elapsed, for example by re-brushing over a freshly coated wet substrate, or by applying more of the coating composition over a previously coated substrate either over the main area of the coating or an edge of the coating or even blending a drop into the coating without vitiating the complete merging of any boundaries in the vicinity of the repaired irregularity. Traditionally compositions containing binder polymers dissolved in organic solvents are used and the organic solvents are employed to modify the drying characteristics of the coated composition. For example, organic solvent based alkyds with an open time of 30 to 45 minutes are available in the decorative “Do-it-yourself” DIY market. However the disadvantage of organic solvent based coatings is the toxic and flammable nature of such solvents and the pollution and odour caused on evaporation as well as the relatively high cost of organic solvents.

#Thus with the continuing concern about the use of organic solvent based coating compositions there has been a long felt need for an aqueous coating composition with comparable properties to those achievable using organic solvent based compositions. Unfortunately, aqueous polymer coating compositions currently known to the art do not offer a combination of drying properties which would make them fully comparable (or even superior to) solvent-based coatings, and in particular do not provide desirably long open and wet edge times (as discussed above and also later) together with desirably short tack-free times (discussed later).

#Pigmented Paint Composition Comprising Dispersion DE1:

#A 1-L 3-necked round bottom flask, equipped with a stirrer, was loaded with dispersion DE1 (130.00 g) and TiO2-based pigment paste (C830; 42.10 g; solids content of 74.9%) in a nitrogen atmosphere, and the mixture was stirred for 30 minutes at ambient temperature. The resulting paint formulation had a solids content of 36.8%. Then the wetting agent (Byk 344; 0.1-0.2% on paint solids) and finally a urethane thickener (Borchigel L75N, Trademark from Bayer, approximately 1.5 g) was added until a suitable paint-viscosity was obtained (4,000 to 6,000 mPa.s). The paint formulation was left is undisturbed for 24 h, then stirred up to mix the contents intimately, checked (and when necessary corrected) for its viscosity, and finally tested on drying and other properties.

#C830 is a pigment formulation comprising TiO2 (24.0 g), AMP-95 (0.2 g), water (3.3 g), Dehydran 1293 (0.5 g), Surfinol 104 E (0.4 g).