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J. Lubczak

Addition reaction of oxiranes to hydroxymethyl derivatives of melamine.

Part V. Restriction of the participation of the crosslinking reaction

Polimery 1995, No 9, 509

DOI: dx.doi.org/10.14314/polimery.1995.509


To restrict the undesirable condensation reactions of hydroxymethyl groups, accompanying the addition of ethylene and propylene oxides to the hydroxymethyl derivatives of melamine and yielding products similar to crosslinked melamine-formaldehyde resins, oxirane was used in the initial step of the reaction, in a large molar excess (>11.5-fold) over the hydroxymethyl groups (to rapidly block the groups). With a melamine derivative carrying many (>4) hydroxymethyl groups it was possible to restrict substantially the crosslinking reactions and to prepare liquid and very well watersoluble polyetherols of the general formula (I). Temperature is crucial: it should not exceed the condensation temperature of hydroxymethyl groups; the best range is 45—70°C. The formaldehyde blocked in the hydroxymethyl groups by only one molecule of oxirane is labile and, at temperatures >70°C, it is shifted toward the chain end. A stable structure is obtained with formaldehyde blocked by two or more oxirane molecules. Instrumental (1HNMR) and classical methods gave the approximate composition of the resulting polyetherols; density, viscosity, surface tension, and refractive index were determined over 20—80°C.

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