Synthesis and properties of hybrid alkyd–acrylic dispersions and their use in VOC-free waterborne coatings

• Waterborne hybrid alkyd–acrylic dispersions were synthesized and characterized.
• Spontaneous emulsification of the hybrid resin was achieved by neutralization with aqueous base.
• Particle size in the range of 60–200 nm could be obtained according to the carboxyl content.
• Stable coating with good gloss and accepted drying time was obtained using the hybrid dispersion as a binder.

Hybrid waterborne alkyd–acrylic dispersions with solid content of 40%, free from any surfactant and exempt of any organic solvent, were successfully synthesized by a melt co-condensation reaction between an acrylic prepolymer bearing carboxylic groups and a long-oil alkyd resin. Spontaneous emulsification of the ensuing hybrid resin was achieved by the addition of an aqueous ammonia solution that neutralized the carboxylic functions. The key role of the carboxylic groups on the stabilization process and on the storage stability of the dispersion was assessed and it was shown that the insertion of anhydride moieties within the acrylic prepolymer ensured the efficient coupling between the acrylic and the alkyd resin and prevented the phase separation. These dispersions are easy to implement and might be used to prepare high quality zero VOC coatings in terms of drying time, stability and gloss. The most stable dispersion was also used in the formulation of air-drying waterborne lacquers and their coating properties were evaluated.

Figure optionsDownload as PowerPoint slide