Process for the preparation of condensation products of melamine

摘要

The invention relates to a process for the purification of a melamine condensation product, comprising the steps of a) making a diluted slurry of a reaction product mixture comprising the melamine condensation product in a solution of a base in water with a pH of at least 9, b) keeping the diluted slurry for a period of at least 1 hour, c) concentrating the diluted slurry, thereby obtaining a concentrated slurry and an eluent, and d) washing the concentrated slurry by diluting the concentrated slurry with aqueous liquid and repeating step c, wherein the washing is performed by counterflow washing wherein eluents of downstream concentration steps are used to wash the slurry in upstream concentration steps.

主权项

1. A process for the purification of a melamine condensation product obtained by a process comprising the step of heating a starting material comprising melamine or a melamine salt in the presence of:
(i) at least one organic or inorganic acid, or (ii) at least one ammonia or melamine salt of the acid, or (iii) a combination of (i) and (ii), under reaction conditions effective for the formation of a melamine condensation product, resulting in a reaction product mixture comprising melamine condensation product and the organic or inorganic acid and/or salts or other residues thereof, wherein the purification process comprises the steps of: (a) making a diluted slurry of the reaction product mixture in a solution of a base in water with a pH of at least 9, (b) keeping the diluted slurry for a period of at least 1 hour, (c) concentrating the diluted slurry, thereby obtaining a concentrated slurry and an eluent, and (d) washing the concentrated slurry by diluting the concentrated slurry with aquous liquid and repeating step c, wherein the washing step (d) is performed by counterflow washing using eluents of downstream concentration steps to wash the slurry in upstream concentration steps.