| 摘要 |
PROBLEM TO BE SOLVED: To obtain a melamine resin markedly having a reduced tendency toward emitting formaldehyde by consecutively performing the methylol addition reaction of melamine with formaldehyde, the etherification reaction in the presence of added methanol, and vacuum concentration, reacting the remaining formaldehyde by adding melamine, etherifying the product with methanol, and finally concentrating the reaction mixture in a vacuum. SOLUTION: A mixture of 1 mol of melamine with 6-10 mol of formaldehyde is adjusted to a pH of 9-11, and subjected to a methylol addition reaction. After the addition of 10-40 mol of methanol to the reaction mixture, and the adjustment to a pH of 5-7, the reaction mixture is reacted until the water becomes turbid. After the adjustment to a pH of 8-10, the reaction mixture is concentrated in a vacuum until the nonvolatiles concentration of the resin is increased to at least 70 wt.%. After the addition of 1-30 wt.%, based on the amount of the initially used melamine, melamine, the concentrated product is subjected to an addition reaction at a pH of 9-11. After the addition of methanol in an amount half of that of the initially used methanol, the mixture is subjected to condensation and etherification until the water becomes turbid, and it is concentrated in a vacuum until the nonvolatiles concentration is increased to at least 70 wt.%.
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