Formaldehyde → (Hydroxymethyl)melamine

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

In this version of the synthesis of the benzoxazine polymer composition, 462.4 grams of 50% formalin and 0.59 grams of 25% sodium hydroxide solution were added to the reaction flask so that the pH after mixing was 8.59. Then, 157 grams of the resole of example 1 and 141 grams of melamine were added. Under mixing, the contents of the reaction flask were heated to 70° C. and allowed to exotherm to 80° C. The flask contents were clear when 80° C. was reached. When the temperature dropped to 79° C. further heating was used to bring the flask contents to 103.5° C. and atmospheric reflux was established. The flask contents were then allowed to react under atmospheric reflux until an HPC time of 83 seconds was reached. The time under atmospheric reflux was 54 minutes. The free formaldehyde of the flask contents at this point was measured at 9.2% by the hydroxylamine method. To further reduce the free formaldehyde, 40 grams of urea was added. Next, water and volatile components were removed by vacuum distillation at a reduced pressure of about 22 inches of mercury and a temperature of about 65° C. The vacuum distillation was continued until the second HPC time of 54 seconds was reached. The free formaldehyde at this point was 1.0 percent.

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