Abstract
Initial-stage kinetics for the condensation of di- and trimethylolmelamine (M2F and M3F respectively) have been studied in an aqueous dimethylsufoxide media with pH ca. 1—9. The main results were as follows.(1) Regardless of pH, the initial rate was given by R0=k[MnF]2 (n=2 or 3) and k is the overall rate constant. The values of k in the pH range of ca. 1—9 were obtained.(2) The observed curves (k vs. pH, logk vs. pH, and k vs. [H+]) were compared with the corresponding calculated curves based on the rate equation. Consequently, in the presence of the acid, it was revealed that for an S≡[hydrochloric acid]0/[M2F]0 or [M3F]0 ratio less than 1.0 (pH ca. 2—7) the main reaction at the early stage of the condensation is the reaction between the methylolmelamine molecule and the conjugate acid; furthermore for S>1.0—1.2 (pH<ca. 2) the main condensation would be the reaction between the conjugate acid themselves.(3) At equal S, the k for M3F is remarkably larger than that for M2F. This is opposite to the rates of mono- and dimethylolurea. The mechanism was interpreted.
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Sato, K., Naito, T. Studies on Melamine Resin. VII. Kinetics of the Acid-Catalyzed Condensation of Di- and Trimethylolmelamine. Polym J 5, 144–157 (1973). https://doi.org/10.1295/polymj.5.144
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DOI: https://doi.org/10.1295/polymj.5.144
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