| 摘要 |
<p>Multicrystalline melamine powder having the following properties : d90: 50-150 νm; d50 < 50 νm; bulk density (loose) 430-570 kg/m3; color APHA less than 17; melamine: > 98.5 wt.%; melam: < 1 wt.%. Multicrystalline melamine powder obtainable via a high-pressure process in which solid melamine is obtained by the melamine melt coming from the reactor being transferred to a vessel where the melamine melt is cooled with an evaporating cooling medium, characterized in that the melamine melt which comes from the melamine reactor and has a temperature between the melting point of melamine and 450 °C is sprayed via spraying means and cooled with an evaporating cooling medium within a vessel in an ammonia environment at an ammonia pressure of 4.5-25 MPa, the melamine melt being converted into melamine powder having a temperature between 200 °C and the solidification point of melamine, the melamine powder then being cooled to a temperature below 50 °C, the powder being agitated mechanically over at least part of the cooling range and being cooled directly or indirectly, and the ammonia pressure being released at a temperature below 270 °C.</p> |
