Oil-acrylic hybrid latexes as binders for waterborne coatings

The combination of the characteristics of oil, or alkyd, emulsions and acry lic latexes in a waterborne binder has been the object of various studies i n the past. Strategies for combining the positive properties of alkyds, e.g . autoxidative curing, gloss and penetration in wood, with the fast drying and gloss and color retention properties of acrylic latexes have mainly bee n directed towards the modification of the alkyd with an acrylate during al kyd synthesis followed by emulsification. This paper describes the preparat ion and application of oil-acrylic hybrid latexes as binders for waterborne coatings. The hybrid latexes were prepared using hydroperoxidized triglyce rides as initiators for the mini-emulsion polymerization of acrylates in an Fe(II)/EDTA/SFS redox system, The particle morphology of-hybrids initiated by fatty-acid hydroperoxides was compared with tert-butyl hydroperoxide-in itiated systems. Cryo-TEM analysis indicated that, whereas tert-butyl hydro peroxide initiation resulted in the formation of heterogeneous particles, f atty-acid hydroperoxide-initiated hybrid particles showed no intra-particle heterogeneity. an AFM study of the film formation process of the oil/alkyd -acrylic hybrid latexes showed that phase separation occurred between the o il and the acrylic phases upon drying, resulting in films that consist of d eformed acrylic particles embedded in a continuous matrix of oil. This resu lts in a very smooth surface of the film. (C) 1999 Elsevier Science S.A. Al l rights reserved.