| 摘要 |
A melamine polymetaphosphate having a solubility of from 0.01 to 0.10 g/100 ml in water at 25 ~C, a pH of from 2.5 to 4.5 in the form of a 10 wt.% aqueous slurry at 25 ~C and a melamine content of from 1.0 to 1.1 mol per mol of phosphorus atom. A process for producing such a melamine polymetaphosphate, which comprises the following steps (a) and (b): (a) a step of mixing melamine, urea and an aqueous orthophosphoric acid solution containing at least 40 wt.% of orthophosphoric acid, in such a ratio that melamine is from 1.0 to 1.5 mol per mol of orthophosphoric acid and urea is from 0.1 to 1.5 mol per mol of orthophosphoric acid, at a temperature of from 0 to 140 ~C, to form a reaction mixture, and stirring the reaction mixture at a temperature of from 0 to 140 ~C, while removing water, to obtain a powdery product of a double salt of orthophosphoric acid with melamine and urea; and (b) a step of calcining the powdery product obtained in step (a) at a temperature of from 240 to 340 ~C for from 0.1 to 30 hours, while preventing agglomeration, to obtain a melamine polymetaphosphate.
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