| 摘要 |
<p>An aqueous aminoplast resin containing 10-60 wt.% melamine and having a specified formaldehyde to primary amine ratio is prepared by reacting formaldehyde, urea and melamine in a specified molar ratio, terminating the reaction and adjusting the pH of the mixture by adding a base and borax, adding urea, and cooling. Preparation of an aqueous melamine/urea/formaldehyde resin with a formaldehyde to primary amine ratio (F/NH2) of 0.3-0.6 and containing 10-60 wt.% melamine. The preparation comprises reacting an aqueous mixture of formaldehyde, urea and melamine in a F/NH2 molar ratio of 0.9-1.2 at a pH of 6-6.8, terminating the condensation by adding a base to adjust the pH to 7-7.4 and borax to adjust the pH to 8-8.6, adding urea over 20-60 minutes at 50-80 degrees C to give the final ratio, and cooling. The amount of borax added is such that the pH does not fall below 7.8 during the addition of the urea. The final pH is optionally adjusted to 8.6-9.2. Independent claims are included for the obtained resin and a material derived from wood and obtained using the resin.</p> |
