Melamine cyanurate synthesis

Yield:37640-57-6 99.5%

Reaction Conditions:

Stage #1:isocyanuric acid for 0.166667 h;
Stage #2:2,4,6-triamino-s-triazine with K-SMA in water at 95 - 120; for 5 h;Product distribution / selectivity;Heating / reflux;

Steps:

5
Example 5; EPO In a 250 ml glass beaker equipped with a magnet stirrer and an electrical heater 83.6 g SMA 1000 P, obtainable from Cray Valley, are added with stirring to 54.7 g potassium hydroxide (85%) solution obtainable from Merck and diluted with 334.5 g water. The solution is heated to 50-60⁰C and stirred until it becomes clear. Evolution of heat resulting from an exothermal reaction is observed. 620 g cyanuric acid (1-1440) obtainable in big lumps from Nissan are loaded into a 1.5 I one-shaft kneader (LIST DTB 1.5) equipped with a reflux cooler and hea¬ ting. The lumps are crushed in the kneader within 10 minutes. 605.8 g Melamine obtainable from DSM are added with stirring. The reaction mass is heated to 95°C up to a maximum jacket temperature of 120°C. As soon as a temperature of 95°C is reached, a mixture of 47.3 g of the K-SMA solution described above, diluted with 138.1 g water, is added within 1 hour. This amounts to a concentration of 1% K-SMA in respect to melamine cyanurate. After the feed, the reaction mass is kept at reflux with a jacket temperature of 120⁰C during 4 hours. The reflux cooler is then replaced with a descending cooler and a receiver connected to a vacuum pump. The jacket temperature is increased to 150⁰C, and the vacuum reduced slowly to 20-30 mbar. As soon as a temperature of 120°C in the kneader is reached, the drying process is finished. The reaction mass is unloaded and analyzed. 1231.6 g product corresponding to 99.5% yield is obtained. The product is white, not dusty and free flowing. No crusts are observed in the kneader, the stirrer and or the inspection window. The conversion is analyzed by thermogravimetrical analysis (TGA), in which free melamine and cyanuric acid can be detected by weight loss between 200° and 245°C. The heating rate of the TGA equipment is 3°C per minute. The content of melamine and cyanuric acid is 0%. The puritiy of the melamine cyanurate is 98.8%. The particle size is determined in a 1% suspension in water by a Sympatex Helos (H0017) equipment. Ultrasonic radiation is applied for 3 minutes before the measurement. 90% of the particles have a diameter of less than 5.9 micron and 99% of the particles a diameter below 32.2 microns. Fine particles of melamine cyanurate can be produced even with unmilled starting materials at moderate temperatures and at high concentrations by using K-SMA as additive. The postassium content of the product amounted to 0.32%.

References:

CIBA SPECIALTY CHEMICALS HOLDING INC. WO2006/40289, 2006, A1 Location in patent:Page/Page column 14-15

FullText