ISSN:
0021-8995
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Maschinenbau
,
Physik
Notizen:
A commercial hexakis(methoxymethyl)melamine (HMMM) resin was fractionated (1) by crystallization of the hexane-soluble fraction from hexane and (2) by partitioning the hexane-soluble and hexane-Insoluble fractions between alumina and various solvents. Crystallization afforded hexakis(methoxymethyl)melamine (1) of 90 to 95% purity. Partitioning afforded 12 fractions with altered proportions of polar and nonpolar species; the least polar fraction was spectroscopically and chromatographically similar to the crystallized material. Relative reactivities of certain fractions were estimated by 1H NMR studies of the rates of reaction with neopentyl alcohol in the presence of catalytic amounts of p-toluenesulfonic acid (p-TSA). It was found that the reactivity of fractions, rich in less-polar species, was substantially greater than that of the commercial HMMM resin, whereas reactivity of fractions, rich in polar species, was less. Reactivity was especially enhanced by removal of all active hydrogen species, notably those containing NH groups. A practical consequence of this result was that fully formylated and alkylated melamine resins could crosslink with polyols at substantially lower temperatures than the commercial HMMM resin, which contained NH groups. Therefore, room-temperature crosslinking was feasible.
Zusätzliches Material:
1 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/app.1992.070451105
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