Chemical Engineering Research & Design, Vol.135, 1-20, 2018
Formation of alkoxy groups in the synthesis of butylated urea formaldehyde resins: Reaction mechanism and kinetic model
Water-resistant amino resins have found diverse applications in the paint and coatings industry. Butylated urea formaldehyde (BUF) amino resins exhibit excellent water-resistant properties due to the presence of butyl groups in its molecular structure. BUF resins are typically synthesized in two steps via addition and condensation reactions. Here, we develop detailed reaction mechanism for the BUF synthesis and develop the kinetic model for the addition reactions. The species in the mechanism are represented in a generic fashion and thus, our mechanism can be utilized not only for the BUF condensation reactions but also for the synthesis of other amino resins. The mechanism incorporates species containing, -CH2-O-CH2- linkages and the new -CH2-O-C4H9 end group, the presence of which have been confirmed experimentally. Further, the kinetic model for the addition reactions is developed and the values of the rate constants are determined from the isothermal experiments conducted at different temperatures. We demonstrate that the predictions from our kinetic model match the experimental observations for reaction synthesis under non isothermal conditions. In addition, we also predict the transient behavior of intermediate species including -CH2-O-CH2- linkages and -CH2-O-C4H9 end groups, which qualitatively matches our experimental findings. The presence of these linkages opens up new possibilities to design resin-based composite materials, where functionality of oxygen can be utilized to graft nanomaterials onto the oligomers in subsequent steps. Our mechanism and the kinetic model can also be utilized for the optimization of the process conditions required for synthesis of resin with tailor-made properties. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.