| 摘要 |
The present invention provides a method for efficiently producing, at high yields, pyrophosphate, particularly melamine pyrophosphate, which is useful as a flame retardant. Specifically provided is a method for calcining orthophosphate, preferably melamine orthophosphate, in the presence of silicone oil, preferably methyl phenyl silicone oil, preferably in a temperature range of 120 to 350°C. A hot air dryer, a kneader, a Henschel mixer, a fluidized bed dryer, a rotary kiln, a paddle dryer, an extruder, a vibration dryer, a far-infrared conveyor oven, a microwave kiln, or the like, may be used as a calciner. |
