Transetherification of melamine–formaldehyde resin methyl ethers and competing reaction of self‐condensation

Abstract

AbstractTransetherification of methyl ethers of melamine‐formaldehide resins (MER) with monophenyl ethers of ethylene glycol or propylene glycol (ROH) and competing reaction of self‐condensation are studied depending on MER composition (amounts of CH3O, CH2OH, and NH2 groups), ROH type, MER/ROH molar ratio, presence or absence of acid catalysts, and temperature. High rates of self‐condensation processes prevent a complete conversion of CH3O into RO‐groups. It turned out MER free of methylol groups were not able to be transetherified with high yields due to a premature gelation taking place prior to attaining 50% conversion of methoxy groups (∼4 mol/kg) even at low MER/ROH ratios. In contrast, transetherification of MER with methylol groups content up to 3 mol/kg affords the incorporation of RO‐groups into the resin up to 8 mol/kg owing to direct etherification of CH2OH groups. The following factors are responsible for the growth of etherified product yield: presence of methylol groups in MER in some amounts without deterioration of MER–ROH compatibilization; CH3O/ROH molar ratio no higher than 1; primary alcohols (ROH) is more preferable compared to secondary ones; thermal activation of the process is more efficient in comparison with acidic catalysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2977–2985, 2006