MELAMINE-FORMALDEHYDE COMPOUNDS .I. ALKALINE DECOMPOSITION OF METHYLOL MELAMINES AND METHOXYMETHYL MELAMINES

The decomposition of trimethylol melamine TMM, methylated trimethylol melamine TMM-Me, hexamethylol melamine HMM and hexamethoxymethyl melamine HMM-Me in alkaline solutions has been investigated kinetically. The decomposition of TMM shows general base catalysis. The hydrolysis of TMM-Me, containing primary ether groups, is found to be specifically catalyzed by OH- ions. In the range where the rate of splitting of both TMM and TMM-Me is proportional to the OH- concentration, the specific catalytic constant for the OH- ions is about 400 times higher for TMM than for TMM-Me. At high alkalinities this ratio is reduced. HMM-Me, which contains only secondary methoxymethyl groups, appeared to be completely stable towards alkali. It is postulated that, for an ether group to hydrolyze in alkaline solution, it is necessary to have, or to get from initial reactions, a free hydrogen atom on the nitrogen atom to which the methoxy methyl group is attached. Melamine formaldehyd resins therefore may contain two kinds of ether groups which behave quite differently towards alkali treatment. This fact has been overlooked in the literature. © 1969.