GB616463A - An improved process for preparing urea formaldehyde lacquer compositions - Google Patents

Abstract

Coating compositions are prepared by reacting urea with at least 2.7 mols. of formaldehyde per mol. of urea in an aqueous alkaline solution, distilling off most of the water under reduced pressure, then acidifying the mixture and adding a monohydric aliphatic alcohol having four or more carbon atoms or benzyl alcohol or a lower homologue thereof and a solvent inert to the reactants, but which on distillation will entrain alcohol and water to give a two-phase condensate, the amounts added being no more than will yield a product of the desired concentration, then distilling at atmospheric pressure, with separation of the aqueous and solvent phases of the condensate and recycling of the solvent only, until substantially all water is removed. Urea may be partly replaced by thiourea, melamine and their derivatives. Formaldehyde may be used as aqueous solution or as substances which will liberate formaldehyde under the reaction conditions, e.g. paraformaldehyde or hexamethylenetetramine. There are also specified: alkalis-ammonium, sodium and potassium hydroxides and sodium carbonate; alcohols-butyl, amyl, hexyl, octyl, benzyl and mixtures thereof; inert solvents-benzene, toluene, xylene; acids-phthalic anhydride and oxalic, sulphuric and phosphoric acids. There may also be added during the etherification stage minor proportions of methanol, ethanol or n- or iso-propanol or of other resins or resin-forming ingredients, e.g. alkyd resins.