No abstract

The molecular weight distributions of resins produced by reaction of formaldehyde with phenols, melamine, or urea have been studied by gel permeation chromatography.

SynopsisDeviations occur from the classical postulate that all pairs of functionalities in a condensation reaction have equal rates of engaging in bond formation or bond breakage. In so-called first-shell substitution effects, which can be treated most readily, the rates involving functionalities X and Yare influenced at most by the existence or absence of other links borne by the two units to which X and Yare directly attached. Quantitative analyses are made of data on melamine and urea-formaldehyde systems in terms of first-shell substitution effects. 4567

Gel permeation chromatography (GPC) waa used to investigate the course of the sodium hydroxide catalysed methylolation of phenol in dilute aqueous solution. At low concentrations, the initial rate of methylolation was directly proportional to the concentrations of sodium hydroxide and of formaldehyde.By computer integration of the rate equations for the methylolation of phenol, of 2-methyl01 phenol and of 4-methyl01 phenol, the experimental rate curves were simulated and optimal values for the rate constants of all the methylolation steps were obtained. ZUSAMMENFASSUNG :Die durch Natriumhydroxid katalysierte Hydroxymethylierung des Phenols in verdiinnter wgl3riger Losung wurde mit Hilfe der Gelchromatographie untersucht. Bei niedriger Konzentration war die Anfangsgeschwindigkeit der Hydroxymethylierung direkt proportional der Konzentration von Natriumhydroxid und von Formaldehyd.Die experimentell erlangten Geschwindigkeitskurven der Hydroxymethylierung des Phenols, des 2-Methylolphenols und des 4-Methylolphenols wurden durch Integrieren mittels Computer reproduziert, und Optimalwerte fiir die Geschwindigkeitskonstanten aller Hydroxymethylierungsstufen wurden bestimmt.