AbstractThe formation of diurea compounds containing methylene and dimethylene ether bridges, respectively, as well as the formation of more highly condensed compounds during the preparation of urea‐formaldehyde resins under different conditions have been investigated. The quantitative determination of each individual diurea compound was carried out by means of liquid chromatography. Identification of diurea compounds with a dimethylene ether bridge was made by1H‐NMR spectrosc