SYNTHESES AND STRUCTURAL-ANALYSES OF COCO NDENSED RESINS FROM UREA AND METHYLOLPHENOLS

The reactions of urea with polymethylolphenol mixtures in acidic state s were investigated by changing the reaction conditions such as the mo lar ratio and acidity. The cocondensates were analyzed with carbon 13 nuclear magnetic resonance (C-13-NMR) spectroscopy and gel permeation chromatography (GPC). The quantity of each chemical structure in the c ocondensates was normalized and represented to phenolic (P) nuclear as the molar ratio. The ratios of urea (U) incorporated into the coconde nsates, the ratios of cocondensation, and the degrees of condensations were determined as were the degrees of substitutions of phenol nuclea r and urea residues. The results were as follows: 1) The reactions wit h the larger molar ratios of U/P were found to decrease self-condensed units effectively. 2) A improved method, using the gradual addition o f a methylolphenol solution to that of urea saved in amount of urea to a great extent in attaining a larger incorporation ratio of urea. 3) A greater reactivity was recognized in p-methylol groups than in o-met hylol groups for the cocondensations with urea. 4) The less the reacti on pH, the cocondensations became faster. No significant differences c ould be observed in the structural compositions by differences of pH b etween 2.0 and 4.0. 5) In the water-soluble parts of the reactants, th e large amounts of sodium sulfate and low-molecular-weight cocondensed compounds were recognized as well as unreacted urea.