Extract from Ind. Eng. Chem: 33(6); 770
<b>Methylolmelamines</b>. Melamine reacts with alcohols, simple sugars such as glucose (66), and phenol (6). But of greater importance to
the resin chemist is the reaction of both alkyl and aromatic aldehydes and ketones with melamine. These condensations are so extensively used that
they warrant particular consideration.
The most important of this large group of condensation products are the methylol compounds. They are produced in good yields when melamine is reacted
with neutral or slightly alkaline formaldehyde, or with some substance producing formaldehyde. Of the six products possible from the condensation of
these two compounds, the most stable and readily isolated is hexamethylolmelamine (10, 82). This compound may be produced either by heating melamine
with an excess of neutral formaldehyde to 90" C. (194" F.), or by allowing the melamine to react with neutral formaldehyde at room temperature over a
period of 15 to 18 hours. Elemental analysis indicates that the product formed in both cases is the same and contains one molecule of water of
crystallization per molecule of hexamethylolmelamine.
Though the trimethylol compound is not so stable as the hexamethylol compound, it has also been prepared. If one mole of melamine is reacted with
three moles of neutral or slightly alkaline formaldehyde in the cold for 15 hours, the trimethylol compound is obtained. The entire separation and
purification of this material must be carried out with extreme rapidity and at very low temperatures to prevent further reaction. Elemental analysis
shows that under these conditions the compound crystallizes from aqueous solution with two molecules of water of crystallization. Owing to its extreme
reactivity, the material has no definite melting point and is not stable on standing. |
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