Isosorbide mono- and di-alkyl ethers, a new class of sustainable coalescents for water-borne paints

The performances of new biosourced solvents, the short mono- and di-alkyl isosorbide ethers have been assessed and compared with benchmark coalescents, namely Texanol and DBE-IB. Firstly, the influence of various coalescents and co-solvents on the glass transition temperature and viscosity of a styrene acrylic latex, Craymul 2423, has been determined. In a second time, application tests and MS-DWS (multispeckle diffusing wave spectroscopy) have been performed on a formulated paint to determine the kinetics of film formation and the quality of the coating. Moreover, this technique allows characterizing the coalescent influence on the water-borne paint drying kinetics. Particular attention has been paid to the influence of coalescent on the “open time” of the water-borne paint. At the same time, the quality of the coalesced film has been quantified by image analysis of the film crackles. Dialkyl isosorbide ethers, such as DMI and DEI (respectively dimethyl- and diethyl-isosorbide ether), show good coalescing properties at room temperature, while monomethylisosorbide (MMI) appears to act as a mere co-solvent. DMI exhibits a unique balance affinity for the aqueous dispersing phase and for the latex particles. It acts as a co-solvent during the water loss phase and as a coalescing agent during the film formation.