Coalescing agents are generally used in paints, varnishes and water-based adhesives. Coalescing agents act as a solvent and/or a plasticizer to the polymeric phase of paints, varnishes and adhesive formulations, diminishing the Tg thereof and favoring the formation of continuous and homogeneous films at several temperature and humidity conditions. Coalescing agents need to be stable in the presence of water and compatible with ingredients present in paints, varnishes and adhesive formulations. Specially, coalescing agents cannot destabilize polymer particles present in paints, varnishes and adhesive formulations. Coalescing agents should also be sufficiently volatile to be eliminated during drying of films, preferably after water evaporation.
The plasticization power of a coalescing agent, that is, the ability thereof in diminishing Tg of a polymer, depends on solubility parameters of the coalescent and the polymer. Usually, water-insoluble coalescing agents having solubility parameters that are compatible with those of the polymer to be plasticized are more effective in reducing MFFT than water-soluble coalescing agents.
Currently, there is an increasing need for coalescing agents that meet the environmental legislation that controls emission of volatile organic compounds (VOC) to the atmosphere. According to European Directive legislation 2004/42/CE coalescing agents having a boiling point of less than 250° C. are considered volatile organic compounds. Other features of coalescing agents that are valuable to manufacturers of paints, adhesives and varnishes and for the final consumer are: low odour, HAP-free, renewable raw material-derived coalescents having high vegetalization index and low CO2 emission during the manufacture process.
Several molecules having alcohol and/or ester functionality are used as a coalescing agent. Butyl glycol (Dow and Oxiteno), 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (Texanol from Eastman Kodak) monoethylene glycol phenyl ether (Dow, Oxiteno) are the molecules most used as coalescents. Due to its boiling point of 169-173° C. butyl glycol is considered a VOC by the European Legislation. Texanol, which has a boiling point of around 254° C. is not considered a VOC by the European Legislation. Nevertheless, Texanol is not derived from renewable raw material.
Patent literature contemplates only a few reports mentioning the use of fusel oil-derived esters as coalescing agents and/or plasticizers.
US patent application US2009/0198002 A1 to Rhodia INC entitled “Low VOC Coalescing Agents”, describes the use of diesters of adipic, glutaric and succinic acids and alcohols comprising a hydrocarbon chain having 4 to 8 carbon atoms, including alcohols from fusel oil. Diesters obtained from glycol ethers and diacids are also encompassed in the invention.
Based on the aforementioned patent example, one notes that the use of fusel oil-derived esters (US2009/0198002 A1) has been little explored. In addition, molecules described by Rhodia in application US2009/0198002 A1 are diesters from diacids and fusel oil. Accordingly, it is evident that monoesters of vegetable oil fatty acids and fusel oil alcohols have not been explored so far.